METHOD AND APPARATUS FOR HEAT TREATING METAL CASTINGS

APPAREIL SERVANT AU TRAITEMENT THERMIQUE DES PIECES COULEES, ET METHODE CONNEXE

English Abstract

An improved method and apparatus for heat treating a metal casting having a sand core comprising a heat treating furnace
(11), with fans (44) for directing a flow of air over the casting to dislodge the sand core. The dislodged sand falls into a trough
(50) where it is collected and conveyed to a central collection bin (60) for reuse.

French Abstract

La présente invention vise une méthode améliorée de traitement thermique d'une pièce de fonte à noyau de sable. L'invention vise également l'appareil connexe qui comprend un four de traitement thermique (11) et des ventilateurs (44) servant à diriger l'air sur la pièce pour faire décoller le noyau de sable. Le noyau délogé tombe dans une goulotte (50) puis est acheminé vers un bac de récupération central (60).

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for heat treating a casting having a sand core,
the sand core comprising, at least, sand particles bound
together by a binder material, and the sand core defining
a cavity within the casting, the method comprising the
steps of:
introducing the metal casting, with the sand core
therein, into a furnace;
heating the furnace to a temperature in excess of the
combustion temperature of the binder material;
providing an oxygenated atmosphere within the heated
furnace;
containing the metal casting, with the sand core
therein, within the heated furnace in the
oxygenated atmosphere to permit the binder material
to combust, whereby sand particles of the sand core
are loosened from the sand core;
removing the loosened sand particles from the cavity;
capturing clumps of sand core material which become
dislodged from the casting prior to the binder
material being combusted therefrom; and retaining
the dislodged clumps of sand core material within
the furnace to permit the binder material to be
combusted therefrom.
2. The method of claim 1, wherein the step of removing the
loosened sand particles from the cavity includes, at least,
continuously removing the loosened sand particles from the
cavity as the binder material is combusted.

3. The method of claim 1, wherein the step of removing the
loosened sand particles from the cavity includes, at least,
directing a flow of air against the casting as the casting is
contained within the furnace such that the flow of air
dislodges loosened sand particles from the cavity.



4. The method of claim 3, wherein the step of directing a
flow of air against the casting as the casting is contained
within the furnace includes, at least, a step of directing a
flow of air against the casting at an airflow velocity in
excess of 3,000 feet per minute.


5. The method of claim 1, further comprising a step of
collecting the portion of the sand particles dislodged from
the casting and conveying it out of the furnace.

6. The method of claim 5, wherein the step of collecting the
portion of the sand particles dislodged from the casting
includes, at least, the step of continuously collecting
portions of the sand particles as the portions of the sand
particles are dislodged from the casting and conveying the
portions of the sand particles out of the furnace.

7. The method of claim 1, wherein the step of heating the
furnace includes, at least, heating the furnace to a
temperature in excess of approximately 850°F.

8. The method of claim 1, wherein the steps of capturing and
retaining the dislodged clumps of sand core material include,
at least, a step of providing a screen disposed beneath the
casting, the screen having openings therein which are not
sufficiently large to pass clumps of sand core material of
predetermined size.

9. The method of claim 8, further comprising a step of
causing clumps of sand core material smaller than the
predetermined size which pass through the screen to impact
upon a surface so as to break up the clumps.

10. A method for heat treating a casting having a sand core



which comprises, at least, sand particles bound together by a
binder material, the sand core defining a cavity within the
casting, and the method comprising the following steps:
introducing the casting with at least a portion of sand
core therein into a furnace;
heating the furnace to a temperature in excess of the
combustion temperature of the binder material;
providing an oxygenated atmosphere within the furnace;
containing the casting, with the sand core therein,
within the oxygenated atmosphere in the heated
furnace to permit the binder material to combust,
whereby portions of the sand core are loosened from the
sand core and fall from the cavity while the casting
is in the furnace; and
suspending, within the oxygenated atmosphere in the
furnace, portions of the sand core which become
dislodged from the casting prior to the binder being
combusted therefrom; and
releasing the suspended portions of the sand core once
the binder is combusted therefrom.

11. A method for heat treating a casting having a sand core
which comprises, at least, sand particles bound together by a
binder material, the sand core defining a cavity within the
casting, and the method comprising the following steps:
introducing the casting with at least a portion of sand
core therein into a furnace;
heating the furnace to a temperature in excess of the
combustion temperature of the binder material;
providing an oxygenated atmosphere within the furnace;
containing the casting, with the sand core therein,
within the oxygenated atmosphere in the heated
furnace to permit the binder material to combust,
whereby portions of the sand core are loosened from the
sand core and fall from the cavity while the casting
is in the furnace; and



providing a screen disposed beneath the casting and
within the oxygenated atmosphere of the furnace,
wherein the screen has openings therein which are
not sufficiently large to pass portions of the sand
core of a predetermined size, and wherein the
openings are sufficiently large to pass portions of
the sand core which are less than the predetermined
size; and
suspending on the screen portions of the sand core
which are larger than the predetermined size, to
allow further combustion of binder material
therefrom.

12. The method of claim 11, further comprising the step of
releasing the suspended portions of the sand core once the
binder is combusted therefrom.

13. The method of claim 11, further comprising, at least, a
step of causing portions of the sand core which pass through
the screen to impact upon a surface so as to break up the
portions of the sand core which pass through the screen.

14. The method of claim 11, further comprising a step of
directing airflow against the casting, while the casting is in
the furnace, so as to dislodge portions of the sand core from
the casting.

15. The method of claim 14, wherein the step of directing
airflow against the casting, while the casting is in the
furnace, includes, at least, directing, from a plurality of
directions, airflow against the casting so as to dislodge
portions of the sand core from the casting.

16. The method of claim 14, wherein the step of directing
airflow against the casting, while the casting is in the
furnace, includes, at least, directing airflow against the



casting at an airflow velocity in excess of 3,000 feet per
minute.

17. The method of claim 11, wherein the step of providing an
oxygenated atmosphere within the furnace comprises, at least,
the step of controlling the oxygen content in the furnace so
that a higher percent of oxygen is maintained where a higher
percentage of the binder material combusts.

18. The method of claim 17, wherein the step of providing an
oxygenated atmosphere within the furnace includes, at least,
conveying the casting through a plurality of zones
within the furnace,
controlling the oxygen content within the furnace to
provide 13-17% oxygen in zones of the plurality of
zones in which a major portion of binder combustion
takes place, and
controlling the oxygen content within the furnace to
provide 10-13% oxygen in zones of the plurality of
zones in which a major portion of binder combustion
does not take place.

19. The method of claim 11, further comprising the steps of
collecting and conveying the loosened portions of sand core
out of the furnace.

20. The method of claim 11, wherein the step of heating the
furnace includes, at least, heating the furnace to a
temperature of approximately 980°F.

21. A method for manufacturing a casting comprising the
following steps:
producing a casting having a sand core,
wherein the sand core includes, at least, sand
particles bound together by a combustible
binder material, and



wherein the sand core defines a cavity within
the casting;
introducing the casting into a furnace prior to any
substantial destruction to the sand core, wherein
the furnace is heated to a temperature in excess of
the combustion temperature of the binder material;
providing an oxygenated atmosphere within the furnace;
containing the casting, with the sand core therein,
within the furnace to permit the binder material to
combust, whereby sand particles of the sand core
are loosened from the sand core and fall from the
cavity while the casting is in the furnace; and
suspending, within the oxygenated atmosphere in the
furnace, portions of the sand core which become
dislodged from the casting prior to the binder being
combusted therefrom; and
releasing the suspended portions of the sand core once
the binder is combusted therefrom.

22. The method of claim 21, wherein the step of
introducing the casting into the furnace is performed prior to
any mechanical shaking intended to remove meaningful portions
of the sand core, whereby mechanical shaking for core removal
is avoided.

23. A method for heat treating a casting having a sand core
which comprises, at least, sand particles bound together by a
binder material, the sand core defining a cavity within the
casting, and the method comprising the following steps:
introducing the casting with at least a portion of sand
core therein into a furnace, wherein the furnace
defines a plurality of zones that are spatially
displaced from one another;
heating the furnace to a temperature in excess of the
combustion temperature of the binder material;
providing an oxygenated atmosphere in at least one zone



of the plurality of zones;
conveying the casting along a path through the
plurality of zones,
whereby the casting, with the sand core therein, is
exposed to the oxygenated atmosphere within the
heated furnace to permit the binder material to
combust,
whereby portions of the sand core are loosened from the
sand core and fall from the cavity while the casting
is in the furnace;
suspending, within the oxygenated atmosphere in the
furnace, portions of the sand core which become
dislodged from the casting prior to the binder being
combusted therefrom; and
releasing the suspended portions of the sand core once
the binder is combusted therefrom.

24. The method of claim 23, wherein the step of introducing
the casting into the furnace is performed prior to any
mechanical shaking intended to remove substantial portions of
the sand core, whereby mechanical shaking for core removal is
avoided.

25. The method of claim 24, further comprising the steps of:
providing a screen disposed beneath the casting and
within the oxygenated atmosphere of the furnace,
wherein the screen has openings therein which are
not sufficiently large to pass portions of the sand
core of a predetermined size, and wherein the
openings are sufficiently large to pass portions of
the sand core which are less than the predetermined
size; and
suspending on the screen portions of the sand core
which are larger than the predetermined size, to
allow further combustion of binder material
therefrom.


26. The method of claim 23, further comprising the steps of:
providing a screen disposed beneath the casting and
within the oxygenated atmosphere of the furnace,
wherein the screen has openings therein which are
not sufficiently large to pass portions of the sand
core of a predetermined size, and wherein the
openings are sufficiently large to pass portions of
the sand core which are less than the predetermined
size; and
suspending on the screen portions of the sand core
which are larger than the
predetermined size, to allow further
combustion of binder material
therefrom.

27. The method of claim 26, further comprising, at least, a
step of causing portions of the sand core which pass through
the screen to impact upon a surface so as to break up the
portions of the sand core which pass through the screen.

28. The method of claim 23, further comprising a step of
directing airflow against the casting, while the casting is in
the furnace, so as to dislodge portions of the sand core from
the casting.

29. The method of claim 28, wherein the step of directing
airflow against the
casting, while the casting is in the furnace, includes, at
least, directing, from a plurality of directions, airflow
against the casting so as to dislodge portions of the sand
core from the casting.


30. The method of claim 23, wherein the step of providing an
oxygenated atmosphere further includes, at least,


controlling the oxygen content within the furnace to
provide 13-17% oxygen in the zones of the plurality
of zones in which a higher percentage of the binder
material combusts, and
controlling the oxygen content within the furnace to
provide 10-13% oxygen in the zones of the plurality
of zones in which a lesser percentage of the binder
material combusts.

31. The method of claim 23, further comprising the step of
angling the casting within the furnace such that at least a
portion of the loosened portions of the sand core will fall
out of the casting under the force of gravity.

32. The method of claim 23, further comprising the steps of
collecting and conveying the loosened portions of sand core
out of the furnace.

33. The method of claim 23, wherein the step of heating the
furnace includes, at least, heating the furnace to a
temperature of approximately 980°F.

34. A method for manufacturing a casting comprising the
following steps:
producing a casting having a sand core,
wherein the sand core includes, at least, sand
particles bound together by a combustible
binder material, and
wherein the sand core defines a cavity within
the casting;
introducing the casting with at least a portion of
sand core therein into a furnace,
wherein the furnace is heated to a temperature
in excess of the combustion temperature of
the binder material, and



wherein the furnace defines a plurality of zones
that are spatially displaced from one
another;
providing an oxygenated atmosphere in at least one
zone of the plurality of zones;
conveying the casting along a path through the
plurality of zones,
whereby the casting, with the sand core therein, is
exposed to the oxygenated atmosphere within the
heated furnace to permit the binder material to
combust,
whereby portions of the sand core are loosened from
the sand core and fall from the cavity while the
casting is in the furnace; and
suspending, within the oxygenated atmosphere in the
furnace, portions of the sand core which become
dislodged from the casting prior to the binder being
combusted therefrom; and
releasing the suspended portions of the sand core once
the binder is combusted therefrom.

35. The method of claim 34, wherein the step of introducing
the casting into the furnace is performed prior to any
mechanical shaking intended to remove substantial portions of
the sand core, whereby mechanical shaking for core removal is
avoided.

36. The method of claim 34, further comprising the steps of:
providing a screen disposed beneath the casting and
within the oxygenated atmosphere of the furnace,
wherein the screen has openings therein which are
not sufficiently large to pass portions of the sand
core of a predetermined size, and wherein the
openings are sufficiently large to pass portions of
the sand core which are less than the predetermined
size; and



suspending on the screen portions of the sand core
which are larger than the predetermined size, to
allow further combustion of binder material
therefrom.

37. The method of claim 36, further comprising a step of
causing portions of the sand core which pass through the
screen to impact upon a surface so as to break up the portions
of the sand core which pass through the screen.

38. The method of claim 34, further comprising a step of
directing airflow against the casting, while the casting is in
the furnace, so as to dislodge portions of the sand core from
the casting.

39. The method of claim 38, wherein the step of directing
airflow against the casting, while the casting is in the
furnace, includes, at least, directing, from a plurality of
directions, airflow against the casting so as to dislodge
portions of the sand core from the casting.

40. The method of claim 38, wherein the step of directing
airflow against the casting, while the casting is in the
furnace, includes, at least, directing airflow against the
casting at an airflow velocity in excess of 3,000 feet per
minute.

41. The method of claim 34, wherein the step of providing an
oxygenated atmosphere further includes, at least,
controlling the oxygen content within the furnace to
provide 13-17% oxygen in the zones of the plurality
of zones in which a higher percentage of the binder
material combusts , and
controlling the oxygen content within the furnace to
provide 10-13% oxygen in the zones of the plurality
of zones in which a lesser percentage of the binder



material combusts.
42. The method of claim 34, further comprising steps of
collecting and conveying the loosened portions of sand core
out of the furnace.

43. The method of claim 34, wherein the step of heating the
furnace includes, at least, heating the furnace to a
temperature of approximately 980°F.

44. A method for heat treating a casting having a sand core
which comprises, at least, sand particles bound together by a
binder material, the sand core defining a cavity within the
casting, and the method comprising the following steps:
introducing the casting, with the sand core therein,
into a furnace;
heating the furnace to a temperature in excess of the
combustion temperature of the binder material;
providing an oxygenated atmosphere within the furnace;
containing the casting, with the sand core therein,
within the oxygenated atmosphere in the heated
furnace to permit binder material to combust,
whereby portions of the sand core are loosened from
the sand core and fall from the cavity while the
casting is in the furnace; and
suspending within the oxygenated atmosphere in the
furnace portions of the sand core that have fallen
from the casting.

45. The method of claim 44, wherein the step of suspending
includes, at least,
capturing at least some of the portions of the sand
core that have fallen from the casting,
retaining the captured portions of the sand core
within the furnace in a manner that permits binder
material to be combusted therefrom, and
releasing the retained portions of the sand core



subsequent to the combustion of binder material
therefrom.

46. The method of claim 45,
wherein the furnace defines a plurality of zones that
are spatially displaced from one another, and
wherein the method further comprises the step of
conveying the casting along a path through the
plurality of zones.

47. An apparatus for heat treating a metal casting having a
sand core comprising sand bound by a binder, wherein the
sand core defines a cavity within the casting, and
wherein the apparatus comprises:
a work chamber for receiving the casting therewithin;
a heating means for heating an atmosphere within said
work chamber such that the casting and the sand
core are heated to a temperature sufficient to
combust the binder of the sand core, whereby the
binder is burned off, so as to dislodge
portions of the sand core from the casting; and
retaining means operatively associated within said
work chamber
for capturing portions of the sand core which
become dislodged from the casting prior to the
binder being combusted therefrom, and retaining
the captured portions of the sand core within
said work chamber atmosphere, until the binder
has been substantially combusted therefrom.

48. The apparatus of claim 47, further comprising collection
means formed in a lower portion of said work chamber for
collecting the portion of the sand dislodged from the casting,
where said retaining means is disposed above said collection
means.


49. The apparatus of claim 47 or 48, wherein said retaining
means includes, at least, a screen.

50. The apparatus of claim 47 or 48, wherein said retaining
means is a broad member defining a plurality of apertures
therethrough.

51. The apparatus of claim 48, further comprising hearth
means for supporting the casting within said work chamber,
wherein said hearth means is disposed above said collection
means.

52. The apparatus of one of claims 47-51, wherein said
retaining means is constructed and arranged to release
captured and retained portions of the sand core once the
binder has been substantially combusted therefrom, wherein the
released portions of the sand core are reduced to a size
smaller than one-quarter inch.

53. The apparatus of claim 48, wherein said collection means
includes, at least, a trough.

54. The apparatus of claim 47, further comprising baffle means
disposed beneath said retaining means for contacting portions
of sand core released from said capturing means.

55. The apparatus of claim 47, further comprising a discharge
means for discharging the sand from said collection means and
said work chamber.

56. An apparatus for heat treating a casting having a sand
core comprising sand bound by a binder, wherein the sand core
defines a cavity within the casting, and wherein the apparatus
comprises:
a work chamber for receiving the casting therewithin;
a heating means for heating said work chamber such that



the casting and the sand core are heated to a
temperature sufficient to combust the binder of the
sand core, whereby binder is burned and portions of
the sand core are dislodged from the costing; and
suspension means in heat and gaseous communication with
said work
chamber fosuspending portions of the sand core and
substantially
promoting further combustion of the binder of the
suspended portions of the sand core.

57. The apparatus of claim 56, wherein said suspension means
includes, at least, a screen.

58. The apparatus of claim 56, further comprising baffle means
disposed beneath said suspension means for contacting portions
of sand core released from said suspension means.

59. The apparatus of claim 58, wherein said suspension means
is constructed and arranged to release suspended portions of
the sand core once the binder has been substantially combusted
therefrom.

60. The apparatus of claim 59, wherein the released portions
of the sand core are reduced to a size smaller than
one-quarter inch.

61. The apparatus of claim 60, further comprising means for
directing airflow over the suspended portions of the sand core
so as to promote combustion of the binder therefrom.

62. The apparatus of any one of claims 56-61, further
comprising:
hearth means for supporting the casting within said
work chamber, wherein said suspension means is
disposed below said hearth means.


63. The apparatus of claim 56, wherein said suspension means
is disposed within said work chamber.

64. The apparatus of claim 63, further comprising collection
means formed in a lower portion of said work chamber for
collecting portions of the sand core dislodged from the
casting, wherein said suspension means is disposed above said
collection means.

65. The apparatus of claim 64, further comprising a hearth
means for supporting the casting within said work chamber,
wherein said hearth means is disposed above said collection
means and said suspension means is interposed between said
hearth means and said collection means.

66. The apparatus of claim 65, wherein said suspension means,
said hearth means, and said collection means are vertically
aligned.

67. The apparatus of claim 66, further comprising a discharge
means for discharging the sand from said collection means and
said work chamber.

68. A method for heat treating a casting having a sand core
which comprises, at least, sand particles bound together by a
binder material, the sand core defining a cavity within the
casting, and the method comprising the following steps:
providing a flow of oxygenated air;
heating the flow of oxygenated air to a temperature in
excess of the combustion temperature of the binder
material;
introducing the casting into a furnace, wherein the
casting is exposed within the furnace to the flow
of oxygenated and heated air to permit binder
material to combust, whereby portions of the sand
core are loosened from and fall from the cavity of


the casting while the casting is within the
furnace;
collecting, distant from the casting, the portions of
the sand core which fall from the cavity of the
casting prior to the binder being combusted
therefrom;
maintaining the collected portions of the sand core
within the flow of oxygenated air to permit binder
to be combusted therefrom, whereby the flow of
oxygenated air is heated and sand is at least
partially reclaimed from the collected portions of
the sand core; and
conveying the at least partially reclaimed sand away
from the furnace.

69. The method of claim 68, wherein the step of
maintaining the collected portions of sand core within the
flow of oxygenated air includes, at least, suspending the
collected portions of sand core within the flow of oxygenated
air to permit binder to be combusted therefrom.

70. The method of claim 69, wherein any clumps of portions of
sand core transported away from the furnace with the at least
partially reclaimed sand have been disintegrated to a size
smaller than one-quarter inch.

71. The method of claim 69, wherein the step of suspending the
collected portions of sand core is carried out within the
furnace.

72. The method of claim 71, wherein the step of suspending
includes, at least,
providing a screen disposed beneath the casting and
within the furnace,suspending on the screen portions
of the sand core which are larger than a predetermined
size, to allow further combustion of binder material





therefrom, and
releasing the suspended portions of the sand core
subsequent to the combustion of binder therefrom.

73. The method of claim 69,
wherein the furnace defines a plurality of zones that
are spatially displaced from one another, and
wherein the method further comprises the steps of,
conveying the casting along a path through the
plurality of zones, and
directing the flow of oxygenated air from a
plurality of directions against the casting,
while the casting is in the furnace, so as to
dislodge portions of the sand core from the
casting, wherein the step of directing
airflow includes, at least,
directing a flow of air in a first
direction in a first zone of the
plurality of zones, and
directing a flow of air in a second
direction in a second zone of the
plurality of zones, and
wherein the step of conveying includes, at least,
conveying the casting sequentially through the
first zone and the second zone.

74. A method for heat treating a casting having a sand core
which comprises, at least, sand particles bound together by a
binder material, the sand core defining a cavity within the
casting, and the method comprising the following steps:
introducing the casting into a furnace, wherein the
furnace defines a plurality of zones that are
spatially displaced from one another;
heating the furnace to a temperature in excess of the
combustion temperature of the binder material;
providing an oxygenated atmosphere in at least one zone


of the plurality of zones;
conveying the casting along a path through the
plurality of zones, whereby the casting, with the
sand core therein, is exposed to the oxygenated
atmosphere within the heated furnace to permit the
binder material to combust;
directing airflow at the casting while the casting is
in the furnace so as to dislodge portions of the
sand core from the casting, wherein the step of
directing airflow includes, at least, varying the
direction from which airflow is directed at the
casting as the casting is conveyed through the
furnace; and
suspending, within the oxygenated atmosphere in the
furnace, portions of the sand core which become
dislodged from the casting prior to the binder being
combusted therefrom such that binder is combusted
from the suspended portions of the sand core.

75. The method of claim 74, Wherein the step of varying the
direction from which airflow is directed at the casting
includes, at least,
directing a flow of air in a first direction in
a first zone of the plurality of zones, and
directing a flow of air in a second direction in
a second zone of the plurality of zones, and
wherein the step of conveying includes, at least,
conveying the casting sequentially through the
first zone and the second zone.

76. The method of claim 75, wherein the step of varying the
direction from which airflow is directed at the casting
includes, at least, operating a fan in each of the first zone
and the second zone, and providing ductwork in each of the
first zone and the second zone such that the direction of
airflow in the first zone differs from the direction of





airflow in the second zone.

77. The method of claim 75, wherein the step of directing a
flow of air against the casting as the casting is contained
within the furnace includes, at least, a step of directing a
flow of air against the casting at an airflow velocity in
excess of 3,000 feet per minute.

78. The method of claim 75,
wherein the step of varying the direction from which
airflow is directed at the casting further
includes, at least, directing a flow of air
horizontally through a third zone of the plurality
of zones,
wherein the step of conveying further includes, at
least, conveying the casting through the third
zone, and
wherein the first direction and the second direction
are vertical directions.

79. A method of processing a casting having a sand core, which
sand core comprises, at least, sand particles bound together
by a binder material, which sand core defines a cavity within
the casting, the method comprising the steps of:
introducing a casting with at least some sand core
therein into a furnace;
heating the furnace to a temperature sufficient to
heat treat the casting and sufficient to combust
the binder of the sand core;
burning binder of the sand core within the furnace to
release core portions of varying sizes from the
casting;
reducing the size of at least larger portions of the
released sand core portion within the furnace,
which reducing is accomplished through additional
burning of binder in the larger portions of the


released sand core portions; and
thereafter conveying sand and any attached binder away
from the furnace,
thereby accomplishing heat treatment, core removal,
and at least partial sand reclamation in an
integrated process associated with a single
furnace.

80. The method of claim 79, wherein the step of introducing
the casting into the furnace is performed prior to any
mechanical shaking intended to remove substantial portions of
the sand core, whereby mechanical shaking for core removal is
avoided.

81. The method of claim 79, further comprising the steps of:
conveying the casting along an elongated path through
a plurality of adjacent zones, wherein the path and
the plurality of adjacent zones are defined by the
furnace; and
cooling the casting at some point in time after the
casting has been conveyed through the plurality of
adjacent zones; and
wherein the heating step includes, at least, the step
of heating all zones of the plurality of adjacent
zones; and
wherein the burning step includes, at least, the steps
of introducing oxygen to zones of the plurality of
adjacent zones and controlling the introduction of
oxygen to introduce larger amounts of oxygen in
certain zones encountered by the casting and
smaller amounts of oxygen in the zones encountered
by the casting later than said certain zones,
whereby core portions in varying amounts and varying
sizes are released in more than one zone of the
plurality of adjacent zones.


82. The method of claim 81, wherein the reducing step
includes, at least, the step of reexposing the larger portions
of the released sand core portions to heated and oxygenated
air associated with at least one of the zones of the plurality
of adjacent zones.

83. The method of claim 81,
wherein the method further comprises a step of
directing airflow from a plurality of directions
against the casting, while the casting is in the
furnace, so as to dislodge portions of the sand
core from the casting, wherein the step of
directing airflow includes, at least,
directing a flow of air in a first direction in
a first zone of the plurality of zones, and
directing a flow of air in a second direction in
a second zone of the plurality of zones, and
wherein the step of conveying includes, at least,
conveying the casting sequentially through the
first zone and the second zone.

84. A method for heat treating a casting having a sand core
which comprises, at least, sand particles bound together by a
binder material, the sand core defining a cavity within the
casting, and the method comprising the following steps:
providing an oxygenated atmosphere;
heating the oxygenated atmosphere to a temperature in
excess of the combustion temperature of the binder
material;
introducing the casting, with at least a portion of
the sand core therein, into a furnace,
wherein the furnace includes a support assembly
for supporting the casting within the
furnace,
wherein the introducing step includes a step of
placing the casting upon the support


assembly,
wherein the casting is exposed within the
furnace to the oxygenated and heated
atmosphere to permit binder material to
combust, and
wherein portions of the sand core are loosened
from and fall from the cavity of the casting
and the support assembly while the casting is
within the furnace;
collecting, distant from the casting and the support
assembly, the portions of the sand core which fall
from the support assembly prior to the binder being
combusted therefrom;
maintaining the collected portions of the sand core
within the oxygenated atmosphere in a manner that
permits binder to be combusted therefrom such that
sand is at least partially reclaimed from the
collected portions of the sand core; and
conveying the at least partially reclaimed sand away
from the furnace.

85. The method of claim 84, wherein the step of
maintaining the collected portions of the sand core within the
oxygenated atmosphere includes a step of suspending the
collected portions of the sand core within the oxygenated
atmosphere to permit binder to be combusted therefrom.

86. The method of claim 85, wherein the maintaining step
includes a step of sizing the collected portions of the sand
core and any clumps of portions of the sand core transported
away from the furnace with the at least partially reclaimed
sand have been disintegrated to a size smaller than
one-quarter inch.

87. The method of claim 85 or 86, wherein the step of
suspending the collected portions of the sand core is carried


out within the furnace.

88. The method of claim 85, wherein the step of suspending
includes steps of
providing a screen disposed beneath the casting and
within the furnace,
suspending on the screen portions of the sand core
which are larger than apertures defined by the
screen, to allow further combustion of binder
material therefrom, and
releasing the suspended portions of the sand core
subsequent to the combustion of binder therefrom.

89. The method of claim 88, wherein the released portions of
the sand core fall into a hopper disposed within the furnace.

90. The method of claim 85,
wherein the furnace defines a plurality of zones that
are spatially displaced from one another, and
wherein the method further comprises a step of
conveying the casting along a path through the
plurality of zones

91. The method of claim 90,
wherein the method further comprises a step of
directing the oxygenated atmosphere from a
plurality of directions against the casting, while
the casting is in the furnace, so as to dislodge
portions of the sand core from the casting, wherein
the directing step includes steps of
directing a flow of air in a first direction in
a first zone of the plurality of zones, and
directing a flow of air in a second direction in
a second zone of the plurality of zones, and
wherein the step of conveying includes a step of
conveying the casting sequentially through the


first zone and the second zone.

92. A method of processing a casting having a sand core,
which sand core comprises, at least, sand particles bound
together by a binder material, which sand core defines a
cavity within the casting, the method comprising steps of:
introducing a casting with at least some sand core
therein into a furnace,
wherein the furnace includes a support assembly
for supporting the casting within the
furnace, and
wherein the introducing step includes a step of
placing the casting upon the support
assembly;
heating the furnace to a temperature sufficient to
heat treat the casting and sufficient to combust
the binder of the sand core;
burning binder of the sand core within the furnace to
release core portions of varying sizes from the
casting, wherein the released sand core portions
fall from the cavity of the casting and the support
assembly while the casting is within the furnace;
reducing, at a reclaiming region distant from the
casting and the support assembly, the size of at
least larger portions of the fallen sand core
portions to at least partially reclaim sand from
larger portions of the fallen sand core portions,
which reducing is accomplished through
additional burning of binder in the larger
portions of the released sand core portions,
and
wherein the reclaiming region and the furnace
are proximately located such that heat passes
between the reclaiming region and the
furnace; and
thereafter conveying sand and any attached binder away





from the furnace,
thereby accomplishing heat treatment, core removal,
and at least partial sand reclamation in an
integrated process associated with a single
furnace.

93. The method of claim 92, wherein gasses are transferred
between the reclaiming region and the furnace.

94. The method of claim 92, wherein the method further
comprises a step of maintaining the larger portions of the
released sand core portions in a heated state during the time
between the step of burning binder and the step of reducing.

95. The method of claim 92, wherein the step of reducing is
carried out prior to any activity intended to substantially
cool the larger portions of the released sand core portions.

96. The method of claim 92, wherein the reclaiming region is
below the support assembly such that the released sand core
potions fall, under the force of gravity, from the support
assembly to the reclaiming region.

97. The method of claim 96, wherein the reclaiming region is
disposed within the furnace.

98. The method of claim 97, wherein the reducing step includes
a step of suspending upon a screen disposed within the heated
atmosphere of the furnace at least the larger portions of the
fallen sand core portions.

99. The method of claim 92, further comprising steps of:
conveying the casting along an elongated path through
a plurality of adjacent zones, wherein the path and
the plurality of adjacent zones are defined by the
furnace; and





cooling the casting at some point in time after the
casting has been conveyed through the plurality of
adjacent zones; and
wherein the heating step includes a step of heating
all zones of the plurality of adjacent zones; and
wherein the burning step includes steps of
introducing oxygen to zones of the plurality of
adjacent zones, and
controlling the introduction of oxygen to
introduce larger amounts of oxygen in certain
zones, and smaller amounts of oxygen in those
zones encountered by the casting later than
said certain zones,
whereby core portions in varying amounts and varying
sizes are released in more than one zone of the
plurality of adjacent zones.

100. The method of claim 99, wherein the reducing step
includes a step of reexposing the larger portions of the
released sand core portions to heated and oxygenated air
associated with at least one of the zones of the plurality of
adjacent zones.

101. The method of claim 91,
wherein the method further comprises a step of
directing airflow from a plurality of directions
against the casting, while the casting is in the
furnace, so as to dislodge portions of the sand
core from the casting, wherein the step of
directing airflow includes steps of
directing a flow of air in a first direction in
a first zone of the plurality of zones, and
directing a flow of air in a second direction in
a second zone of the plurality of zones, and
wherein the step of conveying includes a step of
conveying the casting sequentially through the





first zone and the second zone.
102. A method for heat treating a casting having a sand core
and reclaiming sand from the sand core, wherein the sand
core comprises sand particles bound together by a binder
material, the sand core defining a cavity within the
casting, and the method comprising the following steps:
introducing the casting, with at least a portion of
the sand core therein, into a furnace system
containing an oxygenated and heated atmosphere,
wherein the furnace system defines
a heat treating region, and
a reclaiming region disposed below the
heat treating region and in heat and
gaseous communication with the heat
treating region,
wherein the furnace system includes a support
assembly for supporting the casting within
the heat treating region, and
wherein the introducing step includes a step of
placing the casting upon the support
assembly;
heat treating the casting while the casting is
disposed within the heat treating region;
dislodging portions of the sand core from the casting
while the casting is disposed within the heat
treating region,
wherein the dislodging step includes a step of
combusting binder material of the portions of
the sand core, and
wherein the dislodged portions of the sand core
fall from the casting and the support
assembly into the reclaiming region;
reclaiming, at least partially and within the
reclaiming region, sand from the fallen portions of
the sand core, wherein the reclaiming step includes
a step of further combusting binder material of the


fallen portions of the sand core; and
conveying the reclaimed sand away from the furnace
system,
thereby accomplishing heat treatment, core removal,
and at least partial sand reclamation in an
integrated process associated with a single furnace
system.

103. The method of claim 102, wherein the method further
comprises a step of maintaining the released sand core
portions in a heated state during the time between the
dislodging step and the reclaiming step.

104. The method of claim 102, wherein the step of reclaiming
is carried out prior to any activity intended to substantially
cool the dislodged portions of the sand core.

105. The method of claim 102, wherein the heat treating region
and the reclaiming region are vertically aligned.

106. The method of claim 102, wherein the dislodged portions
of the sand core free fall from casting and the support
assembly into the reclaiming region.


107. The method of claim 102, wherein the heat treating region
and the reclaiming region are both disposed within a single
furnace.

108. The method of claim 102, wherein the combusting step of
the dislodging step includes a step of exposing the casting
and at least a portion of the sand core therein to the
oxygenated and heated atmosphere.

109. The method of one of the claims 102-108, wherein the
further combusting step of the reclaiming step includes a step


of suspending, within the oxygenated and heated atmosphere, at
least some of the fallen portions of the sand core such that
binder is combusted from the suspended portions of the sand
core.

110. A method for heat treating a casting having a sand core
which comprises sand particles bound together by a combustible
binder material, the sand core defining a cavity within the
casting, and the method comprising steps of:
introducing the casting, with at least a portion of the
sand core therein, into a furnace;
heating the furnace to a temperature sufficient to heat
treat the casting and in excess of the combustion
temperature of the binder material;
providing an oxygenated atmosphere in the furnace,
whereby the casting and the sand core therein are
exposed to the oxygenated atmosphere within the
heated furnace to permit binder material of the sand
core to combust;
directing airflow at the casting while the casting is
in the furnace so as to dislodge portions of the
sand core from the casting, wherein the directing
step includes a step of varying the direction from
which airflow is directed at the casting while the
casting is in the furnace; and
suspending, within the oxygenated atmosphere of the
furnace, the fallen portions of the sand core.

111. The method of claim 110, further comprising steps of
supporting the casting upon a support assembly within
the furnace, wherein the dislodged portions of the
sand core fall from the casting and the support
assembly, and
forcing the oxygenated atmosphere to flow across the
suspended portions of the sand core, whereby
combustion of the binder material of the suspended


portions of the sand core is enhanced.


112. The method of claim 111, further comprising a step of
releasing the suspended portions of the sand core subsequent
to the combustion of binder material therefrom.

113. The method of claim 110,
wherein the furnace defines a plurality of zones that
are spatially displaced from one another, and
wherein the method further comprises a step of
conveying the casting along a path through the
plurality of zones.

114. The method of claim 113,
wherein the step of varying the direction from which
airflow is directed at the casting includes steps
of
directing a flow of air in a first direction in
a first zone of the plurality of zones, and
directing a flow of air in a second direction in
a second zone of the plurality of zones, and
wherein the step of conveying includes a step of
conveying the casting sequentially through the
first zone and the second zone.

115. The method of claim 114,
wherein the step of varying the direction from which
airflow is directed at the casting further includes
a step of directing a flow of air horizontally
through a third zone of the plurality of zones,
wherein the step of conveying further includes a step
of conveying the casting through the third zone,
and
wherein the first direction and the second direction
are vertical directions.



116. The method of claim 114, wherein the step of varying
the direction from which airflow is directed at the casting
includes a step of operating a fan in each of the first zone
and the second zone of the plurality of zones.

117. The method of claim 114, wherein the step of varying the
direction from which airflow is directed at the casting
further includes a step providing ductwork in each of the
first zone and the second zone.

118. The method of claim 114, further comprising a step of
suspending, within the oxygenated atmosphere in the furnace,
portions of the sand core which become dislodged from the
casting prior to the binder being combusted therefrom such
that binder material is combusted from the suspended portions
of the sand core.

119. The method of claim 114, including a step of sizing the
suspended portions of the sand core and releasing portions of
the sand core smaller than one-quarter inch.

120. The method of claim 114, wherein the step of suspending
includes steps of
providing a screen disposed beneath the casting and
within the oxygenated atmosphere of the furnace,
wherein the screen has openings therein which are
not sufficiently large to pass portions of the sand
core of a predetermined size, and wherein the
openings are sufficiently large to pass portions of
the sand core which are less than the predetermined
size, and
suspending on the screen portions of the sand core
which are larger than the predetermined size, to
allow further combustion of binder material
therefrom.


121. The method of claim 110, wherein the predetermined size
is one-quarter inch.

122. A method for heat treating a casting having a sand core
which comprises sand particles bound together by a binder
material, the sand core defining a cavity within the casting,
and the method comprising steps of:
introducing the casting, with at least a portion of
the sand core therein, into a furnace that defines
a plurality of zones that are spatially displaced
from one another;
heating at least a plurality of zones of the plurality
of zones to a temperature sufficient to heat treat
the casting and in excess of the combustion
temperature of the binder material;
conveying the casting along a path through the
plurality of zones;
providing an oxygenated atmosphere including steps of
introducing a larger amount of oxygen into
certain zones of the heated plurality of
zones, and
introducing a smaller amount of oxygen into
zones of the heated plurality of zones
encountered by the casting later than said
certain zones,
whereby the casting and the sand core therein are
exposed to the oxygenated atmosphere within the
heated furnace to permit binder material of the
sand core to combust so that portions of the sand
core are loosened from the sand core and fall from
the cavity while the casting is in the furnace; and
suspending within the oxygenated atmosphere of the
furnace, the fallen portions of the sand core.
123. The method of claim 112, wherein the step of providing an
oxygenated atmosphere further includes steps of
controlling the oxygen content within the furnace to
provide 13-17% oxygen in the zones of the plurality


of zones in which a higher percentage of the binder
material combusts , and
controlling the oxygen content within the furnace to
provide 10-13% oxygen in the zones of the plurality
of zones in which a lesser percentage of the binder
material combusts.

124. A method for heat treating a casting having a sand core
which comprises sand particles bound together by a combustible
binder material, the sand core defining a cavity within the
casting, and the method comprising steps of:
introducing the casting, with at least a portion of
the sand core therein, into a furnace, and placing
the casting upon a support assembly within the
furnace;
providing an oxygenated atmosphere in the furnace;
heating the oxygenated atmosphere in the furnace to a
temperature sufficient to heat treat the casting
and in excess of the combustion temperature of the
binder material, wherein the casting and the sand
core therein are exposed to the heated and
oxygenated atmosphere within the furnace so that
binder material of the sand core combusts and
portions of the sand core fall from the casting and
the support assembly; and
further reclaiming sand from the fallen portions of
the sand core, by further exposing the fallen
portions of the sand core to the heated and
oxygenated atmosphere, wherein the further
reclaiming step includes a step of sizing the
fallen portions of the sand core so that any clumps
of portions of sand core that are with the
reclaimed sand have been disintegrated to a size
smaller than one-quarter inch.

25. The method of claim 114, wherein the reclaiming step
includes a step of suspending the fallen portions of the sand
core within the heated and oxygenated atmosphere.

126. The method of claim 114, wherein the reclaiming step is
carried out within the furance.

127. The method of claim 114, further comprising a step of
conveying the reclaimed sand away from the furnace, wherein
the reclaiming step is carried out such that any clumps of
portions of sand core that are conveyed away from the furnace
with the reclaimed sand have been disintegrated to a size
smaller than one-quarter inch.

128. A method for heat treating a casting having a sand core
which comprises sand particiles bound together by a
combustible binder material, the sand core defining a cavity
within the casting, and the method comprising steps of:
introducing the casting, with at least a portion of the
sand core therein, into a furnace;
heating the furnace to a temperature sufficient to
heat treat the casting and in excess of the
combustion temperature of the binder material;
providing an oxygenated atmosphere in the furnace,
whereby the casting and the sand core therein are
exposed to the oxygenated atmosphere within the
heated furnace to permit binder material of the sand
core to combust;
directing airflow, at an airflow velocity in excess of
3,000 feet per minute, at the casting while the
casting is in the furnace, whereby portions of the
sand core are dislodged from the casting; and
suspending, within the oxygenated atmosphere of the
furnace, the fallen portions of the sand core.

129. A method for heat treating a casting having a sand core
which comprises sand particles bound together by a binder
material, the sand core defining a cavity within the casting,


and the method comprising steps of:
providing a flow of oxygenated air;
heating the flow of oxygenated air to a temperature in
excess of the combustion temperature of the binder
material;
introducing the casting into a furnace, wherein the
casting is exposed within the furnace to the flow
of oxygenated and heated air to permit binder
material to combust, whereby portions of the sand
core are loosened from and fall from the cavity of
the casting while the casting is within the
furnace;
collecting, distant from the casting, the portions of
the sand core which fall from the cavity of the
casting prior to the binder being combusted
therefrom;
maintaining the collected portions of the sand core
within the flow of oxygenated air to permit binder
to be combusted therefrom, whereby sand is at least
partially reclaimed from the collected portions of
the sand core; and
conveying the at least partially reclaimed sand away
from the furnace, wherein the maintaining step
includes a step of sizing the collected portions of
the sand core so that any clumps of portions of
sand core transported away from the furnace with
the at least partially reclaimed sand have been
disintegrated to a size smaller than one-quarter
inch.


130. An apparatus for heat treating a casting having a sand
core comprising sand bound by a binder, wherein the sand core
defines a cavity within the casting, and wherein the apparatus
comprises:
a furnace defining a work chamber for receiving the


casting therewithin;
a support assembly for supporting the casting within
said work chamber;
a heating means for heating said work chamber to a
temperature sufficient to combust the binder of the
sand core, whereby binder material is burned and
portions of the sand core fall from both the
casting and the support assembly;
suspension means for suspending within said work
chamber portions of the sand core that fall from
the casting and the support assembly prior to the
binder being combusted therefrom, wherein said
suspension means includes a broad member defining
apertures therethrough; and
airflow means for directing airflow through said
apertures and over the suspended portions of the
sand core so as to promote combustion of the binder
therefrom.

Description

lo




METEIOD AND APPARATUS FOR H~AT
TREATING METAL CASTINGS

Technical Field
The present invention relates generally to methods and
apparatus for heat treating hollow metal c~ting~, and relates more specifically
to an improved method and apparatus for heat treating metal castings with
sand cores which provides for removal of the sand core and for recovery of the
sand core material for reuse.

B~ckground of the Invention
Methods and apparatus for manufacturing hollow metal castings such
as cylinder heads, engine blocks, and the like are well known. Conventional prior art
processes ~or manufacturing aluminum castings ~ypically employ a cast iron "flask-
typel' mold having the exterior features ofthe block forrned on the interior walls ofthe
mold A sand core, pre-molded from a mixture of sand and an organic binder and


. s,
,, i

WO 92J2047~ PC'r/US92/03079 ~
~l 03136


having interior features of the casting formed on by it~
exterior surface, is placed within the mold. The mold is ~hen
filled with molten aluminum alloy.
After the aluminum alloy has solidified, the
casting is removed from the mold. Because untreated
aluminum alloys may be softer or less strong than desired, it is
often necessary to heat treat the casting to strengthen or
harden the metal. According to conventional manufacturing
processes, before the casting is heat treated, the sand is
o removed from the interior of the casting. An operator chisels
the sand out of the interior of the wor}~piece wi~h a pneumatic
chisel. The casting may then be fed into a "sh~keout" system,
a vibrating table which agitates the casting to further brea~; up
dle sand and dislodge it from the interior of the casting. When
the sand has been removed, the casting is heat-treated in a
conventional m~nner by heating the casting to a high
temperature and then quenching the casting. Optionally, the
casting may further be heated at a lower temperature to "age"
the al~lmimlm alloy.
If it is then desired to recover the sand removed
from the interior of the casting for subsequent reuse,
additional steps must be taken to process the sand. l'he sand
removed by chiseling and shaking the casting is fed into a sand
burnout unit to bum off the binders.
Prior art processes for manufacturing aluminum
alloy castings suffer a number of disadvantages. The steps of
removing the sand from the interior of the casting by chiseling
and sh~ing not infrequently result in damage or scarring to
the as-then unhardened alunlinum alloy. Further, the shakeoul
process must be carried out manually and is thus labor-
intensive, thereby increasing the expense of the manufacturing
process. Also, the additional steps required to salvage the sand
for reuse are time-consuming and require additional labor and
equipment expense. The sand recovery process is costly and

WO 92/2047X 2 1 0 3 1 3 S PCr/~lS92/03079




presents certain environmental problems concerning the
handling of the binder was~e products.
Efforts have been made to overcome some of the
disadvantages associated with prior art methods and apparatus
for sand-casting metal objects. One exarnple is disclosed in
U.S. Patent No. 4,41 1,709, wherein a method for the
manufaclure of aluminum alloy castings comprises pouring a
molten ~ nninllm alloy into a mold having therein a sand core
forrned from sand and an organic resin binder. After the
o alloy solidifies, the casting is shaken or vibrated to destroy the
core, and appro~ tely half of the sand used to form the core
can readily be removed from the casting. Subsequently, the
casting is he~te~, and Ihe organic resin binder in the remaining
portion of the sand core is burned off. The sand is thus
unbonded such that about 80% of the remaining sand
(approxirn~tely io% of the total core sand) falls from the
casting by force of gravity. Thereafter, the casting is
quenched in a water bath, and the rem~ining sand in the
c~stin~ is removed by flowing water ~rough the casting.
While ~e method disclosed in the aforementioned
U.S. Patent No. 4,411,709 af~ords certain benefits over the
prior art by eli~in~ting the process of vibrating the sand core
from the casting, it still suffers certain disadvantages in that i
does not climin~te the requirement for s~ ing or agitating the
2s casting prior to heat treating, nor does it eliminate the
additional processing steps needed to recover the sand for
subsequent reuse. The aforementioned patent also does not
include an age hardening process for increasing the hardness
of the metal. Further, since the method disclosed in the
aforementioned U.S. Palent No. 4,411,709 relies upon force of
gravity to remove the sand from the casting, sand will remain
on flat and upwardly concave surfaces after the binder has
bumed off.

~0 92/20478 PCr/US92/03079
.~ ' ~
21i)313~ 4


Summary of the Invention
As will be seen, the present invention overcomes
~hese and other disadvantages associated with prior art casting
processes. Stated generally, the present invention provides an
improved method and apparatus for heat treating metal
castings with sand cores which provides for removal of the
sand core and recovery of the sand core material for reuse.
The method and apparatus of the present invention elin~linates
the need for chiseling or sh~king the casting prior to hea~
o treating, thereby eliminating the possibility of damage
associated with those steps. In addition, the present invention
recovers the sand in a clean state.
Stated more specifically, the present invention
comprises an apparatus for heat treating a metal casting having
a sand core comprising sand bound by a binder. A furnace
includes a work ~n~ber for ~eceiving the casting ~erewithin.
A ~ti~lg me~ns heats the work cl arrlber such that the casting
and its sand core are heated to a temperature sufficient to
combust the binder of the sand core. Thus, the binder is
burned off, leaving only the sand of the sand core. The
apparatus further includes an air~ow means for directing a
flow of air over the casting so-as to dislodge a portion of the
sand from the casting. A me~ns, for example a screen,
disposed within the work ch~r~ber retains portions of the sand
core which may become dislodged from said casting prior to
the binder being combusted therefrom. A means operativel~
associated with the furnace collects the sand which is dislodged
from the casting. lhe sand thus collec~ed is free of binder
material and is suitable for reuse.
3() In another aspect, the apparatus of the present
invention comprises a quench tank for containing water into
which the lle~teA c~stin& is submerged. The tank includes an
agitation me~ns for agitating the water so as to dislodge sand
remaining in the càsting. A collection means operatively
3s associated with the tank removes the dislodged sand and a

wo 92/20478 2 i 3 3 1 3 ~ Pcr/~lsg2/03079




portion of the water from the tan~ and separates a major
portion of the water from the sand.
Another aspect of the invention comprises a
method for heat treating a metal casting having a sand core
s comprising sand bound by a binder. The casling with sand
core therewithin is heated to a temperature sufficient to
combust the binder of the sand core. Thus, the binder is
burned off, leaving only the sand of the sand core. Next, a
flow of air is directed over the casting so as to dislodge a
o portion of the sand from the casting. Clumps of sanld core
material which become dislodged from said casting prior to
the binder material being combusted therefrom are captured
and retained within the fumace to permit the binder material
to be combusted therefrom. The sand dislodged from the
casting is dlen collçc~e~ e sand thus ~ollected being free of
binder material arid suitable for reuse.
Thus, it is an objec~ of the present invention to
provide an improved method and apparatus for heat trealing
metal castings.
It is another object of the present invention to
provide an improved method and apparatus for removing the
sand cores from metal castings.
Another object of the present invention is to
provide a method and apparatus which removes the sand core
from a metal ~asting which rrinimizes the risl~ of damage
resl-ltirl& to the casting.
It is a further obiect of the present invention to
provide a method and apparatus for removing the sand core
from a metal casting which requires less labor and expense
than conve-~tiorl~l methods and apparatus.
Yet another object of the present invention is to
provide a method and apparatus for removing a sand core
from a casting which recovers the core material in a state
suitable for reuse, thereby elilnin~ting the need for additional
3s ~rocessing of the recovered sand.

WO 92/20478 PCI /US92/03079
~ ) t, 13 G 6



Other objects, features, and advantages of the
present invention will become apparenl upon reading the
following specification, when taken in conjunction with the
drawings and the appended claims.




Brief Description of lhe Drawings
Fig. 1 is a top plan view of a first embodiment of
an apparatus for heat treating, quenching, and aging metal
castings according to the present invention.
o Fig. 2 is a side cut-away view of the heat treating
furnace of the apparatus of Fig. 1.
Fig. 3 is an end cut-away view of the heat
treating fumace of Fig. 2.
Fig. 4 is a side cut-away view of the quench tank
of the apparatus of Fig. 1.
Fig. 5 is an end cut-away view of the aging oven
of the apparatus of Fig. 1.
Fig. 6 is a side cut-away view of an alternate
embodirnent of an apparatus for heat treating, quenching, and
aging metal castings according to the present invention.

Detailed Description~ of the Disclosed Embodiment
Referring now to the drawings, in which like
nllmerals indicate like ele~ne~ts throughout the several views,
Fig. 1 shows an apparatus 10 for heat-treating and aging
metal castings according to the present invention. In the
disclosed embodiment, the metal castings are cylinder heads
which are cast from an aluminum alloy in a conventional
manner. The casting process is well known to those skilled in
~he art and comprises no part of the present invention.
Accordingly, the casting process will be described only
briefly.
The casting process employs a cast iron flask-type
mold having the exterior features of the cylinder head fo~ned
on its interior surfaces. A sand core comprised of sand and a

WO 9~/20478 PCI /US92/03079
~iO31~




suitable binder material and defining the interior features of
the casting is placed within the mold. Depending upon the
applica~ion, the binder may comprise a phenolic resin binder,
a phenolic urethane "cold box" binder, or other suitable
s organic binder material. The mold is then filled with a molten
al.~ ..., alloy. When the alloy has solidified, the c~s~ing is
removed from the mold and is now ready for heat tre, ~g and
aging.
The heat treating and aging apparatus comprises a
o heat treating furnace 11, a quench tanlc 12, and an aging oven
13. ln the disclosed embo~ nent, these three components are
laid out in a "U" s~ ell configuration, with the heat treating
fumace 11 comprising one leg of the "U", the quench tank 12
comprising the base of the "U", and the aging oven 13
s comprising the other leg of the "U". However, other
con~lgurations, such as an in-line configuration or an L-shaped
aligtl~Gn~, may be employed as spase constraults may dictate.
Referring now to Figs. 2 and 3, the heat treating
furnace 11 defines a work chamber lS therewilhin. The
furnace 11 comprises a number of different zones 16, the
nature and purpose of which will become apparent. In the
disclosed embodiment, the furnace comprises eight ~ones,
designated by the re~erence numerals 16AoH. However, the
number of zones 16 is not crucial, and the furnace may be
zs divided into a greater or lesser number of zones as the
individual application may require.
Wi~hin each zone of the fumace 11, a pair of
burners 18 are mounted in the vertical side walls 19 and are
diagonally disposed to fire in opposi~e directions to heat the
work chamber 15 of the furnace. The burners l8 are
conventional me(liuln velocity, tempered air burners which are
commercially available from a number of different
manufactu~ers. As can be seen in ~ig. 3, each bumer 18
includes a fuel line 20 for supplying natural gas to the bumer.
3s A combustion air blower 21 in communication with the

WO 92/20478 PCI /US92/03079




burner by means of an air line 22 supplies combustion air to
the bumer. A butterfly valve 23 located within the air line 22
is adjustable to control the volume of air delivered to the
bu~ner 18.
s The burners 18 are designed to heat the wor};
chamber I S of the furnace 11 to a temperature of
approximately 850~-1000~F. In the disclosed embodiment, the
work chamber lS is heated to a temperature of approxinnately
. .
980~P. The butterfly valves 23 for the first zone 16A and the
o fourth through eighth zones 16D-H are adjusted to introduce
1~13% oxygen to their respective burners 18. The butterfly
valves 23 for the second and third zones 16B, 16C are
adjusted to introduce 13-17% oxygen to their respective
burners 18. The function and purpose of controlling the
~s amount of oxygen delivered to the various zones 16 will be
explained below.
The fumace 11 further includes a prehea~
ch~rnber 24 disposed upline of the heating zones 16. Exhaus~
gases from the heating ~ones 16 are directed through the
preheat chamber 24 and heat the chamber to a temperature of
approximately ~00~-700~F. By utilizing waste gases rather
than burners to heat the preheat chamber 24, considerable
energy saYings are rea!ized. The fun~ace 11 has an input door
25 at i~s upper end 26 and a discharge door 27 at its lower
end 28. Another door 29 separates the preheat chamber 24
from the heating zones 16. To inhibit the loss of heat through
the furnace walls, a layer of ceramic fiber insulation 30 is
disposed just inside the outer fumace walls 31. A me~al liner
32 is disposed on the inner side of the ceramic fiber
insulation. The pwpose of the metal liner 32 is to protect the
jns~ tjon 31 from the abrasive effects of flying sand, as will
be more fully explained below.
Within the work chamber lS of the fumace 11 is
a roller hearth 34 comprising a plurality of driven roller~ 36
3s for supporting and conveying workpieces through the f~mace

WO 92/20478 PC'r/US92/03079
~ ~ ~' 3 1 :,~




in a direction of travel indicated by the arrow 38. The roller
hearth 34 and drive mech~nism for driving the rollers 36 are
of conventional design well known to those skilled in the art.
At the entry and exit locations of the furnace 11, the roller
s hearth 34 comprises high speed clutch actuated rollers for
transporting the workpieces rapidly into and out of the
furnace. In addition, the portion of the roller hearth 34 which
transports the workpieces from the preheat chamber 24 into
the heating zones 16 of the fumace also comprises high speed,
o clutch actuated rollers. The major portion of the roller hearth
34 disposed within the furnace 11 is driven at a constant
speed.
To facilitate 1Q~ of castings into the furnace
11 and transport of the c~ctin~s through the furnace, the
castings are lo~de~ into b~c~pts 40 which, in tum, are loaded
onto the roller hearth 34 to be conveyed through the furnace.
In the disclosed embodiment, each basket 40 holds forty to
fifty workpieces. The ~sl~ets 40 are of open construction to
perrnit sand dislodged from the workpieces to fall freely out
of tbe basket. To facilitate removal of the sand from the
workpieces, the workpieces may advantageously be angled
within the bPc~ets 40 so that the sand ~,vill more easily fall out.
With further reference ~o the roller hearth 34,
the speed with which the roller hearth conveys ~e wor}~pieces
through the furnace 11 is a f!~nction of ~he production capacity
of the apparatus 10. Thus, in the disclosed embodiment where
the furnace 11 must accommodate a new basket of workpieces
every thirty-five minutes, ~he roller hear~h 34 must have
conveyed the previous basket of workpieces within thirty-five
3~ minutes by a dist~nce at least suf~lcient to permit the next
basket of workpieces to be introduced into the fumace. In the
disclosed embor1irne~ based upon the size of the baske~s and
the production requirerne-~ts of the apparatus, the roller hear~h
34 conveys the workpieces through the fumace 11 a~ a speed
3s of approxiln~tely six feet per hour.

WO 92/2W78 PCI'/US92/03079 ,~

210313G lO


It will be appreciated by those skilled in the art
that given the speed of ~he roller hearth 34, the dwell time,
that is, the time for which the workpieces are exposed within
the work chamber lS of the fwnace ll, is a function of the
s length of the furnace. For a roller hearth 34 which moves at
six feet per hour, where it is desired to heat lreat the
workpieces for six hours, the furnace ll must be at least
thirty-six feet in length plus the length of one baslcet 40 and
door end clearance space.
o At the vertical center line of each zone, an axial
fan 44 is mo1~n~ed in the top 45 of the fumace ll. The fan
44 circ~ tes the air within the c~--csl,onding zone to provide
an airflow of 3000-5000 feet per mirllltc~ In the first five
zones 16A-E of the fumace ll, the fan 44 directs its airflow
lS downward into the work ch~rnber 15 by meanc of ductwork
46. In the sixth zone lCF, the airflow is directed hori70nt~11y
over the workpieces by side-flow ductwork (not shown). In
- the ~eventh zone 16G, the fan 44 draws air upwardly through
the work çh~nber lS. In the eighth zone 16H, the fan 44
once again directs its airflow downward into the work
ch~mber lS by me~n~ of ductwork 46 in a manner similar to
the first ~lve zones 16A-E. The reason for the varying
airflow patterns within.the various zones 16 will be more
fully explained below.
2s Disposed within the furnace ll beneath the roller
hearth 34 are a plurality of st~in1ess steel troughs 50 whose
pu~pose is to collect sand which falls from the castings within
- the work chamber 15. The interior walls of the troughs 50
are smooth and are disposed at a 45~ angle with respect to
horizontal. The walls are sufficiently angled that sand will
scttle into the bottom of the trough 50 without "bridging."
While conventional troughs for h~ndling wet sand typically
havc walls angled as much as 60~, it will be appreciated that
lhc troughs 50 within the furnace 11 will be handling only
3S CA~ICUIC1Y dry sand, and walls angled at even less than 45~ will

WO !~/20478 2 1 ~ 3 1 3 1'~ PCr/US92/03079




collect the sand without permitting the sand to bridge the
trough.
A one-quarter inch screen 52 is positioned
beneath the roller hearth 34 and over the troughs 50 in each
of the first three zones 16A-C. The screens 52 capture
particles larger than one-quarter inch which are dislodged
from the castings and prevent these larger particles from
passing into the trough 50. Any clumps of core material
which may becorl~e dislodged from the workpieces before the
o phenolic resin binder fusing the core together has been
complelely bumed off will be ret~ined on the screens 52. The
clumps of core material collected on the screens 52 will
contin-le to be exposed to the heat and oxygen-rich airflow
within the fumace 11 until the binders have burned off, at
which time the clumps will ~isintegrate. When the clumps
have ~ ntegrated to a size m ~11er than one-quarter inch, the
sand will fall through thc screcns 52.
It has been found that a screen size of sm~ller than
one-quarter inch is not practical, since flashings.which are
dislodged from the castings will tend to clog a finer screen.
Also, while screens 52 may be pssitioned across the troughs
50 in all of the zones 16A-H if desired, it has been found that
by far the greatest risk of clumps of core material becoming
dislodged from d~e castings occurs within the first three zones
16A-C. Thus, in the disclosed embodiment, screens are
provided only over the troughs in zones 16A-C, and screens
o~.rer the ~roughs in the remaining zones 16D-H are not
necess~ry.
The disclosed embodiment further comprises a
plurality of inverted V-shaped baffles 53 disposed over the
troughs 50 and belle~t1l the screens 52. Sand passing through
the screens 52 will strike the baMes 53 and tumble down the
sloped sides of the baffles. Tbus, any remaining small clumps
of sand will be broken up further before falling into the
3s troughs 50. ln the disclosed embodiment, the baffles 53 have

WO 92/20478 PCT/I_'S92/03079 ,<. .

2io3136 12


upturned flanges at their lower ends which provide structural
rigidity to the bafnes and also comprise another surface for
sand particles to impact before falling into the trou~hs ~0.
Referring in more detail to the ductwork 46
illustrated in FIG. 3, the ductwork includes vertical walls 5~
which tenninate at a lower end 55. A narrow gap ~6 is
fo~ned between the lower end SS of the ductwork 46 and the
roller hearth 34. The dimensions of the gap 56 are closely
controlled so as not to provide a retum airflow path above the
roller hearth 34. Instead~ the airflow is forced between the
rollers 36 and sweeps over the screen52 and the baffles 53
before returning upwardly outside the vertical walls 54 of the
ductwork 46. The importance of this airflow pattern will be
explained below.
s One end of a screw conveyer or auger 58 is in
communication with the bottom of each trough j0 and is
ad~pted to remove the sand which collects in the respective
trough. ln the ~isclosed embo~i~ent, it has been determined
that the screw conveyers ~8 need run only periodically in
order to keep the troughs 50 emptied. Because the major
portion of the sand will be collected within the troughs in the
first three heating zones 16A-C, the augers 58 associated with
those troughs run for two minutes out of every fifteen minute
period. The remaining screw conveyers 58 run for two
2s minutes out of every twenty-~lve minute period. All of the
screw conveycrs 58 empty onto a steel vibratory sand
conveyer 59 which comprises a reciprocating steel bed capable
of accommodating material as hot as 900~F. without being
damaged. The conveyer 59 transports the reclaimed sand to a
central collection bin 60 to await reuse.
Referring now to Fig. 4, at the downline end of
the heat treating fumace is the quench tank 12. The capacity
of the quench tank 12 is a function of the size and number of
workpieces being immersed at a single time, the specific heat
3s of the alloy comprising the workpieces, and the temperature to

W092/204~X f~ 1 ~ 3 1 3 S PCI/US92/03079

13


which the workpieces have been heated. Preferably, the
quench tank 12 should hold sufficient water that the
immersion of a load of workpieces into the tank will raise the
temperature of the water by no more than 10~F. In the
s ~lisclo~ed embodiment, this requirement is met by a quench
tank 12 having a capacity of 4,000 gallons of water.
The quench tank 12 includes a conven~ional rack
arr~-lE~..,c..t 62 for immersing tbe ~cket of workpieces in the
tank. The rack 62 has a plurality of driven rollers 64 for
drawing the workpieces onto the rack. The basket of
workpieces is l~q~e~ onto the rack 62 while the rack is in its
niscd position, ir.~ic~d by ~e solid lines in Fig. 4. At that
point, thc rollcr drive ~nech~lis~n is disengaged, and the rack
62 with workpieces thereon is lowered into the tank 12 by
lS means of a pn~m~iC cylinder (not shown) until the basket of
workpieces rescl~es the lowennost position, shown by the
dotted lines in Fig. 4. The ~ çnGh tank 12 is fully automatic
and is designed to submerge a load fully within ten seconds
af~er the furnace discharge door 27 begins to open. The
quench tank 12 preheats the water to a suitab~e quench
temperature and includes cooling plates 66 to restore the
preq-lenching temperature after each cycle. The quench tanlc
12 also is proYided with twin propeller agitators 68 and
direction vanes to agitate thé water in the tank. After the
2S workpieces have been submerged for approximately eight
minl~tes~ thé pneumatic cylinder is actuated to raise the rack
62 and lift the workpieces out of the tank 12. As will be
appreciated by those skilled in the art, all of the
aforementioned features of the quench tank 12 are
conventi~
In addition to the foregoing conventional
characteristics, the guench tank 12 includes certain other
fcatures for recovcring sand which may be loosened from the
workpieces during the quenchirlg process. The tank 12
includes a trough 72 within its base such that any sand which

WO g2/2047X PCl ~US92/03079
~ iO~13G 14


becomes dislodged from the castings and setlles out of the
water will be collected in the bottom of the trough. A
watertight screw auger 74 is disposed within the bottom of the
trough 72, and the auger communicates with a holding area
s 76. A double-diaphragm slurTy pump 78 is operative to draw
material out of the bottom of the holding area 76 and to
convey it to a vibratory sand dryer 80. The vibral~ sand
dryer 80 is of conventional design and therefore is s ~vn in
the drawings only schematically. l'he sand dryer 80 includes
o a vibrating, rotating 150 mesh screen which pennits water but
not partic~ te matter larger than 150 mesh to pass through the
screen. Particulate mar~ter too hrge to pass through the screen
openings is vibrated off onto the sand conveyor 59. Water
which passes dlrough the screen falls into a collector beneath
IS the screen. The collector in tum is in fluid communica~ion
with a 30 gallon holding tank, which is periodically emptied
into the quench tank 12.
Workpieces removed from the quench tank 12
are introduced into the aging oven 13 for precipitation
hardening to increase the hardness of the castings. The aging
oven is of conventional design and will therefore be described
only brietly. Wi~h reference to Fig. 5, the aging oven 13 of
the disclosed embodiment is a four z~ne oven and comprises a
work ch~mber 85. The oven 13 includes outer oven walls 86,
an insulating blanket of ceramic fiber 88, and a metal liner
90. A fan 92 located along the longitudinal centerline of the
oven 13 circulates hea~ed air throughout the work chamber 85
of the oven. To transport workpieces through the work
chamber 85, the oven 13 includes a roller hearth 9~ for
conveying workpieces through the oven. As is the case with
the roller heanh ~4 of the furnace 11, the sections of the
roller heanh 94 which transport the wor}~pieces into and oul
of the oven 13 comprise high speed, clutch actuated rollers.
The major portion of the roller hearth 94 which is disposed
3s within the oven 13 transports ~he workpieces at a constant

wo 92/2047X 2 i ~ 3 1 ~ ~ PCI~/US92/03079




speed. As hereinabove explained with respect to the speed of
the roller hearth 34 of the furnace 11, the minimum speed of
the roller hearth 94 is determined by the production
requirements of ~he apparatus 10. Given the constraints thus
s imposed by the minim~ required speed of the roller hear~h
94, the maximum dwell time of the workpieces within the
oven 13 is a function of the length of the oven. In the
disclosed embodiment, the dwell time is approximately four
hours, though longer ovens for aging periods of up to twenly
o hours may be desirable, depending upon the alloy used in the
ca,stin~ and the characteristics required of the casting.
The oven 13 includes a number of burners 96 for
heating the interior of the ovcn. In the disclosed embodimer~t,
the burners 96 heat the interior of the oven to a temperature
lS of 450~ + 5~F. However, depen~ling upon the alloy being aged
and the hardness desired, the temperature in the oven may
range from 250~-500~F.
The aging oven 13 includes a series of troughs 98
located in its lower portion. However, since the vast majority
of the sand is removed during the heat treating and quenching
steps, the amount of sand reln~ining on the wor}ipieces upon
their introduction into Ihe aging oven 13 is, at most, minimal.
Since so little sand is dislodged within the oven 13, no
provision is made for automatically collecting and conveying
2~ the sand to a central recl~m~tion location. Instead, th~e troughs
98 may be emptied at relatively long intervals during routine
rn~intenance of the oven.
The operalion of the appara~us 10 will now be
described. When the molten ~ minum alloy of the castings
has solidified, the castings are removed from their respective
molds and transferred into one of the baskets 40. Each of the
~sl~ets 40 is large enough to hold forty to fifty workpieces
and, as previously mentioned, is of open construction to
pe~mit sand to pass freely there~hrough. To fur~her facilitate
3s removal of the sand from the cavities of the workpieces, the

WO 92~20478 PCI /US92/03079

~ia313~' 16


wor~;pieces may advantageously be angled within the basliet 40
so that the s~nd will more easily fall out of lhe wor};pieces.
The basket 40 of workpieces is placed on the
roller hearth 34 at the upper end 26 of the furnace 11. The
input door 25 of the fumace 11 is opened, and the high speed,
clutch actuated rollers transport the basket 40 of worl~pieces
into the preheat chamber 24. E~haust gases from the fumace
11 are directed through the preheat chamber 24 and bring the
workpieces up to a temperature of about 380~F. The
o workpieces are exposed wilhin the preheat chamber 48 until
the preceding basket has moved far enough through the
fumace to perimit introduction of another basket. Thus, in the
disclosed embodiment, the workpieces soak in the preheat
ch~n~ber for approximately thirty-five minutes. When the
1S preceAing b~c~el has moved far enough into the furnace to
pennit another basket to enter, the door 29 between the
preheat ct~ ber 24 and~the work ch~mber lS opens, and high
speed, clutch ~ct~l~t~(l rollers transport the bas};et 40 into the
work eh~mber.
The natural gas fired burners 18 heat the interior
of the furnace 11 to a temperature of approximately 980~F.
This temperature is sufficient not only to heat treat the castings
but also to burn off the organic binders fusing the core sand
together. Thus, as the castings are heated within the wor}~
chamber 15 of the furnace 11, the binders are burned off of
the sand core material. As the binder burns off, the sand
comprising the core loosens. The sand is dislodged from the
castings by force of gravity and by the 3000-5000 feet per
minute airflow within the fumace generated by ~e fans 44.
As previously described, the second and third
16B, 16C of the eight zones 16 are provided wilh 13-17%
oxygcn, while the remaining zones 16A and 16D-H are
provided wilh only 1(~13% oxygen. It has been found thal
the major ponion of such combustion occurs in the second and
3s ~hird zones; in the first zone 16A, the casting and core are

wo 92/20478 ;~ 1 0 3 1 ~3 ~ PCI /US92/03079




being brought up to the combustion temperature of 980~~, and
in the later zones 16D-H the combustion has been substan~ially
completed. Further, it has been found that, in those zones
where the major ponion of ~he combustion occurs, combuslion
of the organic binder material will consume approximately 4-
S% oxygen. Accordingly, the burners 18 in zones 16B and
16C are adjusted to provide approximately 4-5% more
oxygen than the other zones to compensate for lhe oxygen
consumed by combustion of the binder material and lo
o facilitate the combustion process. ln the remaining zones 16A
and 16D-F, however, the burners 18 are not adjusted to
provide the excessive amount of air required by zones 16B
and 16C. Since there is not the excessive amount of air which
must be healed, the burners in those zones where less
combustion occurs can operate more efficiently than if the
higher volume of air were provided to all zones of the
fumace.
The workpieces and the sand cores within the
workpieces are heated to a temperature of 980~F. over the
course of approYim~tely one hour. After the workpieces have
reached the "soak" temperature of 980~F., ~hey remain in the
fumace for an additional five hours, for six total hours of
exposure within the fumace. In other applications, depending
upon the alloy used and the metalurgical characteristics
desired, the soak time may be as long as twelve hours or as
short as four hours.
As the workpieces are conveyed through the first
five zones 16A-E, they are subjected tO a downward directed
flow of turbulent air. As the workpieces pass into the sixth
zone 1 6F, the side-flow ductwork redirec~s the airflow
horizontally over the workpieces. Then, as the wor~ipieces
pass into the seventh zone 16G of the fumace 11, they are
subjected to an upwardly directed turbulent airflow, caused by
the respective one of the fans 44 drawing air upwardly
3s tbrougb the wor}; ~h~rnber 15. Finally, as the workpieces pass

WO 92/2047X PCT/IIS92/03079 .
~10313~ '
18


through the eighth zone 1 6H, the workpieces are again
exposed to a downward directed airflow. This succession of
downward, sideways, upward, and downward turbulent
airflows is successful in dislodging about ~5% of the sand
s from the workpieces.
As will be clear to those skilled in the art, sand
panicles being blown about inside the furnace by the 3000-
5000 feet per minute airflow have a significant potential for
ab~asion to the interior surfaces of the fumace 11. The metal
~oliner 32 can thus be appreciated for the protection it affords
against damage to the fumace's ceramic fiber insulation 31.
The sand dislodged from the castings falls through
the basket 40, passes through the s~ce~ between the rollers 36
of the roller hearth 34, falls through the screens 52, strikes
ISthe baffles ~3, and falls into the troughs 50 beneath the
heanh. Any ~huil~ of sand still bound by the organic resin
which may become dislodged from the worlcpieces over the
rst third of ~he fumace are captured on the screens ~2 over
the troughs 50, where they will remain until the heat of the
20furnace burns off uhe rem~inir~ binder. When the remaining
binder is bumed off, the clumps of sand will fall apart, and the
sand will fall throllgh~the screen 52, impact upon the baffles
53 to further break up the clumps, and fall in~o the trough 50.
The sand which falls into the troughs 5 0 is
25conveyed by the screw conveyers 58 to the common sand
conveyer 59, whereby it is transponed to the collection bin 60
for reuse. It will be appreciated that the sand thus recovered
is substantially pure, the organic resin having been bumed off
during the heat treating process.
30As Ihe workpieces exit the lower end 9~ of the
heat treating furnace 11, they are ready for quenching. The
water in the quench tank 12 is preheated to a suitable
q-lenching temperature. The basket 40 of castings is driven
on~o the rack 62 by the powered rollers 64, and the racli is
35submerged in the water within ten seconds after the furnace

WO 92/20478 2 i ~ 3 1 ~ ~i PCr/US92/03079

19


discharge door begins to open. While Ihe wor~;pieces are
submerged, the twin propellers 68 agitate the water in the
tan};, ~nd the direction vanes direct the flow of water over the
workpieces. The turbulent water washes any sand remaining
s in the cavity of the workpieces out of the worlcpieces and into
the tank 12. The workpieces remain submerged for
approximately eight minutes, at the end of which time the
pneumatic cylinder is actuated to lift the racl; 62 out of the
tank 12. When the workpieces are removed from the quench
o tank, subst~rlti~lly all of the rem~ining sand has been removed
from the castings. The c~ctin~ are now ready for aging.
Meanwhile, the sand which was washed out of the
c~sti~s in the quench tanlc 12 settles into the trough 72 in the
bottom of the tank. The screw auger 74 conveys the sand-
water slur~ to dle hold~ng area 76, and the double-diaphragm
pump 78 moves the slurry onto the vibratory sand unit 80.
The water in the slu~ry p~Cse~ through the vibrating screen
and falls into the collector adjacent to the screen. The water
thus separated from the sand is conveyed to the holding tank
82 and from there is returned to the quench tank 12. The
sand which remains on top of the vibrating screen is
tlisch~rged from the screen onto the sand conveyer 59, where
it joins sand from the troughs 50 of the furnace ll in route to
the reclamation bin 60.
Upon completion of the quenching process, the
workpieces are introduced into the aging oven 13. The
burners 96 heat the work chamber 8~ of the oven 13 to
approximately 450~F. The roller hearth 94 conveys the bas~;et
40 of workpieces slowly through the work chamber 8~ of the
oven 13 such that the workpieces are subjected tO the 450~F.
heat of the oven of the disclosed embodiment for a period of
about four hours. As previously suggested, the dwell time
within the aging oven 13 may range from four to twenty
hours, depending upon the particular alloy being used and the
3s metallurgical characteristics desired of the casting. The

WO 92~20~8 PCI /US92/03079 ,

21031~

circulation of the air within the wor~; chamber 85 by the f~n
92 facilitates uniform heating of the wor};pieces. Any sand
which becomes dislodged from the workpieces d~lring the
aging procedure will settle into the troughs 98 in the boltom
of the oven 13. The emergence of the workpieces from the
aging oven 13 signals the end of the heat treating and aging
process.
As will be appreciated from tl~e foregoing
description of the operation of the apparatus 10, a primary
feature of the present invention is the combustion of the
phenolic resin binding the sand core by exposing the casting
and core to the heat of the furnace 11. It has been found that
the major portion of such combustion occurs in lhe second and
third of the eight 7O'~S; in ~e ~lrst zone 16A, the casting and
lS core are being brought up to combustion temperature of
980~F, and in the later zones 16D~H the combustion is
subst~nti~lly complete. Accordingly, the burners 1g in zones
16B and 16C are adjusted to provide air in excess of the
amounlt required by the burners to ensure that there is
suf~lcient oxygen in those zones to facilitate the combustion
process. In the disclosed embodiment, the burners 18 in zones
16B and 16C are adjusted to provide 13-17% oxygen. ln the
remaining zones 16A and 16D-F, however, the burners 18
are adjusted ~o provide only lO-13% oxygen. Since there is
2s not the extent of excess air which must be heated, the bumers
in those zones where less combustion occurs can operate more
efficiently than if the same extent of excess air were provided
to all zones of the furnace.
The foregoing embodiment has been disclosed
with respect to a continuous process, that is, workpieces are
continuously being introduced into the apparatus 10, some
workpieces thus being in one stage of processing ~ hile other
workpieces are at other stages of the process. In this
continuous process, some workpieces will be undergoing he:~
3s treating at the same ~ime that other workpieces are being

WO 92/2047X PCI /US92/03079
213313~


quenched and still other wor};pieces are being aged. ln fi~ict, al
any given time, there may be baskets of wor~pieces al ~ilrious
poin~s within the fumace 11, some only just beginninn the heat
treating process while others are further along in the process,
s all continuously advancing through thie apparalus. However, it
will be appreciated that the present invention is equally well
suited for batch processing, where only a single b~tch of
materials is undergoing processing at any given timie.
Fig. 6 discloses a batch-type heat t~ tin~
o apparatus 110 according to the present invention. Cer.~ o~
the components of the batch apparatus 110 are i(iientical to
components previously described and will be designat~d by th~
same reference numerals previously used. Thus, con pollenls
previously described can be reco~ni7e~1 from their design~tioll
lS by a reference numeral less thian 100. Thiose components not
previously described with reference to the continuous h~a~
tre~tin~ furnace will be designated with reference numer;31s
higher than 100.
The apparatus 110 includes an ele~ate~i drop-
bottom furnace 111 elevated on legs 114. A lift mechainism
116 powered by pneumatic, hydraulic, or mech~nic~l po~er,
is operative to raise and lower workpieces into and out of the
furnace 111. In the disclosed embodiment, the lift mechilnisn~
116 includes hooks 1 18 for engaging a bas~et ~0 of
workpieces, whereby the entire basket is lifted inlo the
furnace. A sliding door 120 in the bottom of the fumace has
a pair of sand collection troughs 122 formied therein. Screells
52 positioned over the troughs 122 prevent p~irticles l.lrp~er
than one-quarter inch from falling into th~ troughs.
Pneumatically operated high temperature slide gat~s al e
selectively operable to discharge sand collected in ~lle trou~h~
122.
As with the continuous furnace 11, the batcll
furnace 110 has a ceramic fiber insulating blanket 12~ lo
3s retain heat within the furnace and a metal liner 126 to protec~

WO 92/20478 PCI /US92~03079

21G313~ 22


the ceramic fiber insulation from flying sand. A fan 44
mounted in the top of the furnace circulates the air within the
furnace at 3000-5000 feet per minute. Burners 18 mounted in
the side walls of the fumace 110 heat the work chamber 130
s of the furnace. The bumers 1~ once again comprise means
for introducing 120-160% excess air into the burners, with the
result that the environrnent within the furnace comprises 10-
12% oxygen.
A pair of tracks 140 runs beneath lhe elevated
o furnace 110. A quench tank and transfer car 145 runs along
the tracks 140 on wheels 146 and comprises a quench tan~;
148, a sand collection bin 150, and a basket transfer area
152. The car 14S is selectively operable to position eilher the
basket transfer area 152, the quench tank 148, or the sand
IS collection bin lS0 bene~ the drop-bottom furnace worl~
chq~nber 130.
The quench tank 148 includes a heater for
preh~ting the water in the tank to a suitable quenching
temperature. A pair of propeller agitators 68 circulate the
water in the quench tank. A header 156 in the bottom of the
tank has a plurality of openin~s for placing the interior of the
tank in ~luid connrnllnication with a vibratory sand dryer ~0.
A double diaphragm pump 78 is selectively operable to pump
sand out of the bottom of the q!ler-ch tank 148 and convey i~ to
the vibratory sand dryer 80. The operation of the vibratory
sand dryer has previously been explained. After the water has
been remoYed from the sand by the vibra~ory sand dryer 80,
the water is pumped into a holding tank 82, and the sand is
conveyed into the sand bin lS0.
The operation of the batch-type fumace 110 will
now ~e explained. Castings are formed as previously
described and removed from their respective molds. The
castings are placed in a basket 4 0, and the basket of
workpieces is placed on the basket transfer area 1~2 of the
3s quench tank and transfer car 145. The car 14~ is then moved

wo 92/20478 ~ 1 0 3 1 ~ 6 PCI /US92/03079




along its trac~s 140 to position its basket transfer area 152
directly beneath the heated fumace 111. The bot~om door
120 of the fumace is opened, and the lift mechanism 116 is
lowered so that the hooks 118 of the lift mechanism enga~e
s the basket 40. The lift mech~-lism 116 is then actuated to
raise the basket 40 of workpieces in~o the work chamber 130
of the furnace 111, and the bottom 120 of the furnace is
closed.
The burners 18 heat the load in the work
o chamber 130 of the fumace 111 to a temperature of
approximately 980~F. Again, however, depending up~n the
alloy used and the metallurgical characteristics desired, the
workpieces may be heated over a range o~' 850~-1000~F. 120-
160% excess air is introduced into the bumers 18 so that the
IS resulting atmosphere within the fumace comprises 10-12%
oxygen. The fans 44 operate to circulate the air within the
fumace to achieve an airflow of 3000-5000 feet per minute.
As the castings and the cores are heated, the resin
binder begins to burn off. Loosened sand is dislodged from
the workpieces by the airflow and by force of gravity, and the
dislodged sand falls into the troughs 122. Clumps of core
mateAal from which the binder component has not completely
bumed off will be captured on the screens 52 over the troughs
12~ and retained there until the binder has burned off, at
which time the unbonded sand will fall through the screen,
tumble down the inverted V-shaped baffles 53, and fall into
the troughs. The metal liner 126 protects the interior of the
furnace 111 from the abrasive effects of flying sand.
When the workpieces have been heat trea~ed for
the desired length of time (six hours in the disclosed
embodiment), the burners 18 are shut down. The transfer car
145 is positioned along itS tracks 140 so that the quench tanl;
148 is directly beneath the work chamber 130 of the furnace
111, and the bottom 120 of ~he furnace is opened. The lift
3s mechanism 116 is then actuated to lower the basket 40 of

wo 92120478 Pcr/us92/03079 .

~ 1 O,~ ; 24


workpieces into the quench tank 148. The wor};pieces are
submerged for the desired length of time, during which period
the water in the tank is agitated by the tWih propellers 68 to
loosen the rem~ining sand from the castings. Sand thus
dislodged from the wor~pieces settles to the bottom of the tan};
148. At the end of the quench sequence, the lift mechanism
116 is again actuated to lift the workpieces out of the tanl;
148. If aging is desired, the furnace 111 is cooled tO abou~ -
450~F., the basket is again lihed inlo the work chamber 130,
o and the fumace door 120 is closed. The workpieces are then
aged for the desired length of time.
Upon completion of the quenching sequence, the
transfer car 145 is positioned such ~at the sand collection bin
150 is directly bene~th the slide gates of the sand troughs 122.
The gates are opened, and the collected sand is discharged
from the troughs into the sand collection bin. Again, the sand
thus recovered is in a clean, reusable state, all of the binder
material having been burned of~ by the heat of the furnace.
It will be appreciated by those skilled in the art
tbat the provision of a high speed airflow within the wor}~
chamber 1~ of the fumace 11 will result in abrasive particles
of sand being blown about the interior of the furnace at high
velocities. The disclosed embodiments therefore include
special precautions for preventing excessive abrasion and
dama~e to the interior of the fumace. The interior walls of
the furnace, for example, are provided with l l gauge liners
comprised of a 4l30 alloy to resist abrasion~ Also, the fans 4
include features designed to withstand the abrasive
~nvironment wilhin the work chambers 15. For example, the
blades of the fans 4 4 are of solid, rather than hollow,
construction, as it has been found that flying sand particles can
wear holes in hollow blades, especially along seams, and
acc~ te within the blades. Even a small accumulation of
sand within the hollow blades can throw the fan 44 out of
b~l~nce and cause catastropkic damage to the fan drive

wo 92/20478 ~ 1 0 3 1 3 6 PC'r/US92/03079




mechanism. As another precaution, the leading edges of the
blades of the fans 44 are tapered to deflect sand particles.
It will be appreciated that the present invention
offers significant advantages over prior art methods and
s apparatus for processing sand castings. First, the requirement
of removing a subst~ti~l portion of the core material prior to
heat treating the casting has been elimin~ted. Consequently,
the labor, equipment, expense, and risk of damage or scarring
to the workpiece associated with manually chiseling out ~he
o sand core or subjecting the workpiece to agitation and
vibration have been elin in~te~
Funher, by subjecting the sand core material to
the heat and airflow within the furnace, the resin binder fusing,
the core sand is bumed off. To cnsure that substantially all of
IS d e binder is comb~lsted, the screens 52 prevent chunlcs of core
material larger than a predetennine~l size from falling out of
the furnace and retain such ch~mks within the wor~; chamber
15 until a sufficient amount of binder has burned off that the
chunk can disintegrate and pass through the screen. Chunks of
material which are sufficiently srnall to pass through the
screen 52 will impact upon the inverted V-shaped baffles 53
and tumble down the sloped walls of the baffles, further
rlisintegrating the material into its individual particles of sand.
Thus, the sand is recovered ir~ a clean, reusable state.
While the recovered sand is clean in the sense that
the binder materials have been bumed off, the requirements of
a parlicular installation may dictate certain additional
processing of the sand before it can be reused. For example, i~
may be desirable to screen the reclaimed sand to reclassify the
sand and tO remove any debris which may have become
in~elmixed with the sand.
To facilitate combu~tion of binder material from
chunks of sand retained on the screens 52, the fumace 11 of
the disclosed embodirnent ensures a continuous airflow of
3s oxygenated air over the screens, as indicated by the arrows in



~"::, "", ~ ~",.

W O 92/20478 P ~ /US92/03079 .

- 2 1 0 3 1 3 ~ 26


FIG. 3. To accomplish the desired airflow pattern, the
dimension of the gap 56 between the lower end 55 of the
walls 54 of the duct 46 is kept to a minimum so as not to
provide an airflow path around the lower end of the wall and
s above the roller hearth 34. The air flowing downwardly
through the ducts 46 must therefore follow a path downward
between the rollers 36 and across the screens 52 before it can
retum upward between the outer surface of the duct and the
liner 32 of the fumace.
A further advantage of the present invention is
that since the binder component is combusted, the ecological
problems associated with disposal of solid waste material are
avoided. If the exhaust gases include ar~ unacceptable quantity
of organics or phenils, additional incineration of the exhaust
IS gases may be n~cess~ry. In such an inst~rlce~ the exhaust gases
upon exiting the preheat ch~mber can be delivered to an inline
incinerator operating at a temperature of 1400~-1450~F. to
incinerate the free organics or phenils.
The control of the oxygen content of the fumace
atmosphere in the disclosed embodiment also affords certain
adYantages wi~h respect ~o buming off the resin binder. By
introducing excess air into the bumers ~ only those zones of
the fumace where the ma~or ponion of the combustion proeess
occurs, a 10-12% oxygen level within those zo.~es of the
furnace i~ maintained. This level of oxygen facilitates the
combustion of the organic resin binder which fuses the core,
thereby accelerating the breakdown of the binder and
promoting effeclive combustion of the waste products.
However, since the burners in the remaining zones are not
adjusted to deliver the extreme amount of excess air required
in those zones where the major portion of the combustion
process takes place, the bumers are able to operate at
increased efficiency.
The invention hereinabove described has been
3s disclosed with respect to a furnace utilizing natural gas

WO 92/20418 PCI /US92/03079
~i~3136
27


bumers as the heat source. However, it will be understood
that the nature of the heating means is not crilical, and other
types of heating systems, such as propane burners, indirect
gas-fired radiant heaters, electric heaters, oil-fired bumers, or
s coal-fired burners, may be employed. ~t will be appreciated
that when indirect gas-fired radiant heaters or electric heat are
employed, an air injection system should be used to maintain
the oxygen level within the fumace at the desired 10-12%
level.
Also, while the disclosed embodiment is an eight
zone furnace, the major portion of the binder combustion
occurring in the second and third zones, it will be understood
that a greater or sn~ller number of zones may be defined
within the furnace. In such an instance, the precise zones
s within which the major portion of the binder combustion
occurs may vary according to a variely of factors, including
without li~it~ion the temperature within the fumace, ~he size
and confilguration of dle c~tirl~s and cores, the speed at which
the castings are moved through the furnace, and the
te~ e-ature of the castings when they are introduced into the
fumace.
Finally, it will be understood that the preferred
embodiment has been disclosed by way of example, and Ihat
other modifications may occur tO those skilled in the art
2s without departing from the scope and spirit of the appended
claims.

Representative Drawing