Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED ~OTAR~ RETORT FURNACE
Background o'f t~e 'Invention
Rotary retort furnaces have long been used for
the continuous heat treatment of a variety of small parts,
such as screws~, nuts, bolts, studs, nails and washers.
These furnaces ? even those without an internal auger
flight, are particularly well suited for the processing
of such small parts as, in addition, to providing con-
tinuous operation, the rotary conveying action tends to
tumble the parts breaking up any jams or tangled clumps
of parts thereby facilitating better and more thorough
heat treatment of each of the individual parts. Unfor-
tunately, the cost of manufacturing and maintaining the
prior art rotary retort furnaces is not always commen-
surate with the economy of heat treating such small parts.Furthermore, the manner of loading of the prior art rotary
retort furnaces often defeats the advantageous conveying
mechanism of the rotary retort in that because of improper
and uneven loading, jams of parts are formed at the charge
end which cannot be broken up by the continuous tumbling
in the rotary retort,
It has long been the practice in the prior art
to support a retort for rotation within a heated shell at
both ends of the retort or along the entire length of the
retort. Such support in the heat treating ~urnace
environment has significant economic disadvantages not
only with respect to the original manufacture of it but
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also in connection with its maintenance. If the retort
is supported at ~oth ends outside of the furnace shell to
facilitate maintenance then two heat and atmosphere seals
will be reguired. Aside from the initial expense of such
duplicate seals> in order to keep the seals effective they
must be frequently repaired or replaced. If the support
is within the heated shell, it presents serious mainten-
ance problems.
Since rotary retort furnaces are often used in
a controlled atmosphere heat treating operation, it is
important to minimize any loss of the atmosphere within
the furnace. In addition to losses of atmosphere and
heat through the seals between the shell and the rotary
retort, significant amounts of the atmosphere are lost in
lS prior art furnaces during the charging of the retort.
Manufacture of the internal helical auger flight
for a rotary retort furnace can prove to be an expensive
aspect of the cost of construction of such a furnace. In-
asmuch as rotary retort furnaces are usually used for
handling small parts such as screws and nuts, the outer
edges of the auger flight must be kept in close contact
with the walls of the retort, otherwise parts will tend to
become lodged between the auger flight and the wall. If
parts heat treated in one operation become lodged in the
spaces between an auger f'ight and the walls of a retort
and subsequently drop into a different set of parts being
heat treated in a subsequent operation, it can prove to
be a burdensome and expensive task for the heat treater
to have to separate such parts. Prior art means of form-
ing an auger contiguous with the walls of the retort, suchas machining, casting, or continuous welding of the auger
flight edge, are very expensive.
Summary of the Invention
The present invention involves a rotary retort
furnace for small parts wherein the retort is supported
for rotation at only one end outside of the shell such
that the retort is cantilevered into the shell. A
charging door mechanism on the rotary retort cooperates
with a parts loading mechanism to provide ch~rges of the
parts to be heat treated that are of a uniform si~e and
are introduced into the retort in a manner which minimizes
the loss of any controlled atmosphere. The loading
mechanism comprises a vibrating feed hopper which dis-
penses a weight controlled charge into a skip hoist
bucket. The skip hoist bucket, after receiving the pre-
determined charge of parts to be heat treated, is held ina ready position until such time as a cam mechanism
controlling the opening and closing of a door on the
charge end of the retort causes the door to open and the
skip bucket to be moved to a position wherein the parts
are du~ped into the retort for heat treating.
The retort is provided with an internal auger
flight that is made by forming a number of toroids from
a resilient material, radially cutting each of the toroids
and deforming them to form individual flights, and
connecting one of the split edges resulting from the
cutting to the opposite edge of an adjacent flight such
that an axially compressed helical subassem~ly is obtained~
The helical subassembly is then screwed onto the shaft
having a number of guide pins axially on the shaft at pre-
determi~ed spacings. In screwing the helical subassemblyonto the shaft, the subassembly is both axially extended
; and radially compressed, the helical subassembly and
shaft are inserted into a retort shell and one free end
of the subassembly is welded to one end of the retort.
The shaft is then unscrewed while at the same time being
forced axially into the retort such that the edges of
the helic~l subassembly fit tightly against the inside of
the retort. After the shaft has been removed, the
remaining end of the helical subassembly is welded to
the end of the re~ort.
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Accordingly, it is an object of the present
invention to provide a rotary retort-furnace for small
parts wherein the retort is supported for rotation outside
of the furnace shell at one end with the free end extend-
ing into the furnace shell.
It is a further object of the present inventionto provide a rotary retort furnace having an internal
auger flight which is economical to assemble yet results
in an assembly wherein the edges of the auger flight are
in tight contact with the inside wall of the retort.
It is an additional object of the present
invention to provide a door means on the charging end of
the retort which will seal the charging opening except
for the actual times the retort is being charged.
It is yet another object of the present
invention to provide loading means for a rotary retort
furnace which will automatically supply charges of the
parts to be heat treated of a controlled preselected
weight.
It is still another object of the present
invention to provide control means on the furnace which
will coordinate the final dumping of the charge of parts
to be heat treated with the opening of the door means on
; the charging end of the rotary retort furnace.
Further objects and advantages of the present
invention will become apparent as the following descrip-
tion proceeds, and the features of novelty which char-
acterize the invention will be particularly pointed out
in the claims annexed to and forming a part of the spec-
ification.
Brief Description of the Drawings
For a better understanding of the present
invention, reference may be had to the accompanying
drawings in which:
Fig. 1 is a longitudinal view, partly in
section, of a rotary retort furnace embodying our
invention;
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~ig, 2 is an enlarged side elevation of the
loading mechanism shown in Fig, 1;
Fig, 3 is an enlarged elevational view of the
loading mechanism from the end adjacent the furnace;
Fig. 4 is an enlarged fragmentary sectional view
of the charging end of the retort showing the details of
the mounting and door mechanisms not included in Fig. 1;
Fig. 5 is an enlarged sectional view of the seal
for the retort;
Fig. 6 is a perspective view showing the helical
subassembly being inserted into the retort; and
Fig. 7 is a side elevation showing the helical
subassembly screwed onto the shaft prior to insertion into
the retort,
Description of the Prererrea Embodiment
Referring now to the drawings in which like parts
are designated by like reference numerals in the various
views, there is shown in Fig. 1 a rotary retort furnace
generally designated by the reference numeral 20. As
indicated in Fig. 1, the rotary retort furnace of the
present invention may be used with a liquid quenching
system such as that designated by the reference numeral 25
which is disclosed in greater detail in Canadian Letters
Patent No. 1,038,1~9, issued September 12, 1978 and
; 25 assigned to the same assignee as the instant application.
The furnace has a heated refractory shell 30 of
any conventional design with a floor 31, side walls, one
of which is shown in Fig. 1 designated by reference
numeral 32, end walls 34 and 35, and a roof 37 which
prelerably is removable to facilitate access for any
necessary ~aintenance required within the shell, Suitable
heating means are provided within the shell. The heating
means may either be electric or gas fired, such as the
burner 40 with the radiant tube 41 extending through end
wall 35~
; l'he shell 30 is supported above the ground by
means of a structural metal frame assembly 45. The frame
45 also provides support for the drive mechanism for the
rotary retort including the motor 47. Part of the frame
assembly also supports the cantilevered retort 50 for
rotation. The retort has a cantilevered or free arm 51
and a supported end 52. The supported end 52 is mounted
for rotation by means of the bearing plate 55 which is
supported on the frame assembly 45 or more particularly to
the portion of the frame assembly comprising the platform
56 and bracing arm 57. Attached to the bearing plate 55
by welding or other suitable assembly means is an annular
water cooled collar 58. Also secured to the plate 55
wi~-hin the collar 58 is a stationary bearing race 59.
Retort 50 has a drive and bearing assembly 60 including
flange 62 which is attached to the retort for rotation
therewith or may be formed as an integral part of the
retort. Drive sprocket 63 is secured to flange 62 as is
- the rotating bearing race 64. The retort 50 is supported
for rotation by the bearing assembly, such as Rotex~
bearing model number L7-33PlZ Series 2000 with steel
spacers or Rotex bearing model number L7-22DlZ Series 2000
with steel spacers, which include the stationary race 59,
the rotating race 64 and the ball bearings 65. A drive
chain 66 driven by the motor 47 through a gear arrangement
(not shown) engages the drive sprocket 63 to rotate the
retort S0.
The retort 50 extends through an opening in the
end wall 34 of the shell. The free or cantilevered end 51
of the retort is unsupported within the shell and is spaced
from the end wall 35. A controlled atmosphere for heat
treating is admitted into the shell 30 under pressure by
means of inlet 68. A seal assembly 70 which is shown in
greater detail in Fig. 5 is provided for the opening in the
end wall 34. It includes a plate 71 which is affixed to
the outside surface of the end wall 34. The plate carries
an annular water cooling jacket 73 having an inlet 74 and
an outlet (not shown). Within the area circumscribed by
the annular water cooled jacket is a packing flange 75.
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Between the Elange 75 and the outside rim of the water
cooled jacket 73 heat resistance packing materials such as
asbestos ring seals 77 are secured. The seaLs 77 are in
contact with the rotating retort 50 and prevent the escape
of heat and a~mosphere from the shell 30. It is preferred
to machine a smooth bond on the part of the outside wall
of the retort that will be in contact with the ring seals
77 to minimize the wear on the seals. Adjustable clamping
means 78 are provided to keep the ring seals 77 compressed
as required to maintain them in effective sealing engage-
ment with the retort.
In order to minimize the loss of heat and
atmosphere seal at the charging end of the retort itself,
the charging end of the retort is generally closed by an
end cover plate 80 having a small charging opening 81.
~he door 83 closes the charging opening except for the
period during which products to be heat treated are
actually fed into the furnace. The door 83 has a lever
arm 85 which is pivotally mounted to the cover plate 80.
The arm 85 pivots about the pin 87 which is carried by a
bracket member 88 that is attached to the cover plate 80.
The end of the arm 85 opposite the end which is secured
to the door 83 carries a cam roller 90. A cam 91 is
at~ached to the stationary bearing plate 55. The door 83
is inside the retort 50 and is larger than the charging
opening 81. A spring 93 which is secured at one end to
the arm 85 and at the other end to a projection 94
attached to the rotating reto9r~t biases the door to a
closed position. The spring ~ extends through the
flange 62, the sprocket 63 and the rotating bearing brace
64. As the retort rotates, the door 83 is biased to its
closed position, except for the short interval during
which the roller 90 rides upon the cam member 91 to pivot
the arm 85 overcoming the biasing force of spring 93 and
pushing in the door 83 to open the charging opening 81.
As will be discussed in greater detail laLer in this
specification, the opening of the charging door 83 is
timed ~o cooperate with the dumping of a charge of parts to
be treated into the charging chute 96.
Parts dumped into the chute 96 for heat treat-
ing are admitted into the rotating retort at the pre-
determined time determined by the s~&ed of rotation of theretort, the size of the cam roller ~ and the length of the
camming surface on cam member ~, The retort is provided
with an internal helical auger 100 which conveys the parts
to be heat treated through the rotating retort. The parts
are discharged at the cantilevered or free end of the~retort
51. Disposed below the discharge end of the retort is a
quench chute 101 which extends through the floor 31 of the
furnace shell into a quenching system 25 such as thatdes-
cribed in Canadian Letters Patent No. 1,038,159, issued
September 12, 1978.
The internal helical auger which extends
through the length of the rotating retort 50 is fabricated
in a manner which is economical but still insures a tight
fit between the outside edges of the auger and the inside
wall of the retort. The helical auger 100 is formed from
a number of toroids, one of which is designated by
reference numeral 105 in Fig. 7. The individual toroids
which are of a resilient material are cut radially as is
indicated by reference numeral 106 and slightly deformed
to form one flight of the helical auger 100. Each flight
is then secu~ed to another flight by welding one edge of
the radial cut to an opposite edge on another flight.
After so joining a number of flights, a compressed helical
auger with two free ends is formed~ This helical auger
subassembly is then axially extended while being compressed
in the radial direction by screwing it onto a shaft 108
having a number of guide pins 109. The pins 109 are
spaced both radially and axially at predetermined distances
such that, when the helical subassembly is screwed onto
the shaft, it is longer and has an outside diameter less
than the inside of the rotary retort 50. The helical sub-
assembly and the shaft 108 are then inserted into the
retort 50, and one free end of the helical subassembly is
welded to the adjacent end of the retort. The shaft 108
is then screwed in a reverse direction to remove it from
the helical subassembly while, at the same time, the shaft
is driven axially into the retort 50 by means of impact
blows. The simultaneous forcing of the helical subassembly
and the shaft axially into the retort and the removal of
the shaft by unscrewing it from the helical subassembly
results in the subassembly returning to its former greater
diameter to some degree thereby causing the subassembly to
fit tightly against the inside walls of the retort 50. A
tight fit of the outside edges of the helical subassembly
to the inside walls of the retort 50 may be further
enhanced by preheating the retort to approximately 200
to 300 F. in~ediately prior to inserting the helical
subassembly. The resulting contraction of the retort 50
as it cools from the elevated temperat~lre will result in
a tighter fit.
Turning now to the parts loading mechanism 115
shown in Figs. l, 2 and 3, there is a hopper 116 into which
parts to be heat treated are conveyed by any suitable means
such as a forklift truck, conveyor belt, or hand loading.
The hopper has an inclined floor 117 leading to a chute
119. As is best shown in Fig. 3, the floor 117 also con-
verges downwardly from the sides of the hopper leading to
the chute 119. The hopper is provided with at least one
vertical.ly positioned pin 121 which serves to break up
a load of parts to be heat treated such as screws or the
like. Also provided to control the discharge of the parts
is pivotally adjustable damper 123 which is secured to
; horizontal shaft 124. The sides of the hopper rotatably
; support horizontal shaft 124 thereby permitting the
~ damper 123 to be pivoted about the axis of the shaft 124.
; 35 The damper may be locked in any particular angular orien-
tation with respect to the floor 117 by means of the
control member 125 or by a turnbuckle secured between
the damper 123 and a stationary member.
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The incline of floor 117 of the hopper is
slight, approximately 7 1/2, such that most parts of the
type which will be handled by the rotary retort furnace
will not, particularly with the control damper 123, feed
through the chute 119 solely by force of gravity. To
control the feeding of the parts from the hopper, a
vibrator 127 is attached to the inclined floor 117. Parts
emerging from the chute 119 drop into a skip hoist bucket
130 which dumps the parts into the retort charging chute
96. It has been found desirable to control the size of
each charge of parts by weight in order to permit proper
spacing of the parts within the rotary retort as they are
being conveyed through the retort during heat treating.
The weight of the charge is controlled by the operation
of the vibrator 127. When the skip hoist bucket 130
reaches its lowermost position, it trips a switch (not
shown) which completes an electrical circuit activating
the vibrator 127.
Upon receiving the preselected weigh~ of parts,
the skip hoist bucket 130 tips the balance beam 132 which
has been set by positioning the counterweight 133. The
counterweight 133 is slidable along the balance beam and
may be locked into position by the locking mechanism 134.
Alternatively, a series of weights may be used to set the
balance beam 132. Tipping of the balance beam by the
skip hoist bucket actuates another switch (not shown)
which interrupts the circuit and shuts off the vibrator
127. After the vibrator is shut off, a skip hoist motor
~36 is automatically energized. It has been found to
be preferable to have a time delay in the magnitude of
two seconds for allowing the vibrator to stop before
starting the skip hoist motor 136. The skip hoist motor,
in turn, drives the winch 137 which moves the bucket 130
up the guide rails 140. Ascent of the skip hoist bucket
is momentarily halted just before it reaches the outwardly
turned ends of the guide rails at 141 wnich could cause
the bucket to dump the parts into the charging chute 96.
This momentary halting of the ascent is accomplished by
the bucket tripping a delay switch (not shown) on the guide
rails just prior to the bucket reaching the portion of the
rails designated by reference numeral 141.
Coordinated with the previously discussed
charging door 83 opening mechanism is another switch (not
shown) which reactivates the skip hoist motor 136 for
dumping the parts into the charging chute 96 at the time
that the door 83 is opened. After dumping the parts, the
skip hoist bucket descends to its lowermost point again
tripping the switch which actuates the vibrator.
While the specific embodiments of the present
invention have been shown and described, it will be
apparent to those skilled in the art that various changes
and modifications may be made without departing from the
invention in its broader aspects, and it is, thereiore,
contemplated in the appended claims to cover all such
changes and modifications as fall within the true spirit
and scope of the present invention.
