Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Background of the Invention
The present invention relates to vacuum
furnaces and has particular application in the vacuum
heat treating of work parts, wherein the work parts are
introduced and processed in a subatmospheric environment
and are thereafter removed from the furnace without
closlng down the operation of the furnace.
Prior to the instant invention, vacuum furnaces
for heat treating and processing of metal articles
have become generally accepted for commercial use; but,
heretofore batch processing has been the generally accepted
technique for use with vacuum furnaces; and, as a result,
furnaces using the batch process have been somewhat
limited in the use and application thereof. In this
connection batch heat treating requires that the furnace
be shut down after each heat treating cycle for removal
of the processed work parts from the furnace; and, although
the results as obtained from such heat treating have been
acceptable, it is understood that considerable time and
labor is e~pended in shutting down the furnace, removing
the parts therefrom, loading the furnace again, and then
heat treating the new batch. Obviously, this technique
is inefficient, since the furnace operation must be
completely closed down during removal of the processed
work parts and the introduction of the new parts therein.
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Some efforts have been made heretofore to
utilize continuously operated heat treating furnaces
employing conveyor belts; but such furnaces have normally
been usable in atmosphere environments, wherein an
atmosphere has been introduced into the furnace heating
chamber under pressure. In U.S. Patent ~3,782,705, a
continuously operated vacuum furnace is disclosed; and,
although the furnace as illustrated therein is capable
of heat treating work parts without breaking the vacuum
within the furnace, the door assemblies and conveyor
mechanisms are somewhat complicated; and, therefore, the
manufacture of such a furnace is relatively costly.
Other attempts have been made to heat treat under vacuum ;'
in a continuously operated furnace, but problems have
always been encountered in the :loading of the work parts
in the furnace and the unloading thereof without contaminat-
ing the furnace heating chamber,.
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Summary of the Inventlon
The present invention relates to a vacuum
furnace for continuously introducing and processing
work parts through a heating chamber of the furnace for
the heat treatment thereof without breaking the vacuum
in the heating chamber, and wherein the heating chamber
is operated at a predetermined subatmospherlc pressure
and temperature as the work parts are conveyed therethrough.
In order to provide for continuous operation of the vacuum
furnace embodied herein, a loading vestibule is provided
with a unique vacuum sealed door assembly that is operable
to move from a sealed vertical position to a substantially
horizontal open position, whereupon a work load is
directed into the loading vestibule in preparation for
introduction into the heating chamber. Additional
vacuum sealed door assemblies are provided in the system
for protecting the heating chamber and enabling work
loads to be removed from the cooling station of the
furnace without discontinuing the operation of the heating
chamber or breaking the vacuum therein.
The vacuum sealed door assemblies are so con-
structed and arranged as to avoid the usual elevated
lifting unit that normally increases the overall height
of the furnace and instead include an operating mechanism
that provides for a combination lifting and pivotal action
as each door member is moved to and from the sealed position.
The furnace as embodied herein further includes
a unique load transfer mechanism that provides for the
longitudinal movement of a flexible coil spring that is
operable to transfer a work load through the various
stations in the furnace. As the coil spring is moved
by a motor in a longitudinal direction for transferring
the work load, a reversing mechanism is actuated for
effecting a retracting movement of the coil spring in
preparation for the next transfer operation. An unload
transfer mechanism that is located at -the cooling station
of the furnace also includes a longitudinally movable coil
spring that is operable to withdraw a work load from the
heating chamber into the cooling station following a
heat treating operation, and following the cooling
operation withdraws the work load from the cooling
station to a discharge station~
Another feature of the invention provides for
the cooling of the hydraulic fLuid that is used in the
operation of the various motors fox operating the door
assemblies and the like, the hydraulic fluid being
circulated in a chamber that is adjacent to the cooling
jacket of the furnace heating chamber wherein the heating
; chamber cooling jacket defines a heat exchanger for the
hydraulic fluid for the effective cooling thereof.
Accordingly, it is an object of the present
invention to provide a continuously operated vacuum
furnace for heat treating metal articles in a subatmospheric
environment therein, wherein a work load is periodically
advanced through the various stations of the furnace for
the heat treating thereof and without breaking the vacuum
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in the Eurnace heating chamber. Additional work loads
are periodically introduced into the furnace and moved
therethrough for the processing thereof in the subatmos-
pheric environment, the work load being cooled and removed
from the furnace without discontinuing the operation of
the furnace heating chamber or breaking the vacuum therein.
Other objects, features and advantages of the
invention shall become apparent as the description
thereof proceeds when considered in connection with the
accompanying illustrative drawings.
Description of the Drawings
In the drawings which illustrate the best
mode presently contemplated for carrying out the
present invention;
Fig. 1 is a side elevational view of the
continuous heat treating vacuum furnace as embodied in
the present invention;
Fig. 2 is a top plan view thereof;
Fig. 3 is a sectional view taken along line 3-3
in Fig. 2, and showing the loading station including
the loading vestibule and work cart transfer mechanism;
Fig. 4 is a sectional view taken along line 4-4
in Fig. 2,and showing the heating chamber;
Fig. 5 is a sectional view taken along line 5-5
in Fig. 2, and showing the quench and discharge stations
including the unload mechanism for retracting a work
cart from the heatin~ chamber and quench station;
Fig. 6 is a front eIevational view of the
vacuum furnace embodied herein and taken along line 6-6
in Fig. l;
Fig. 7 is a sectional view through the furnace
heating chamber taken along line 7-7 in Fig. 1,
Fig. 8 is a sectional view of the quench tank
taken along line 8-8 in Fig. l;
Fig. 9 is a perspective view of the door assembly
and operating mechanism therefor as located at the loading
station;
Fig. 10 is a sectional view with parts shown
in elevation of the loading station door assembly and
illustrating the sequential movement of the door member
from the closed to the open positions;
Fig. 11 is a top plan view of the work cart
transfer mechanism and -the pressure roll device for
the drive spring and the tilting mechanism therefor;
Fiy. 12 is a sec-tional view taken along line
12-12 in Fig. 11;
Fig. 13 is a sectional view taken along line ~ ~-
13-13 in Fig. 11;
Fig. 13a is an end view of the drive pulley as
used in the transfer mechanism;
Fig. 14 is a side elevational view of a portion
of the heating chamber track on which work carts are
transferred;
Fig. 15 is a sectional view taken along line
15 15 in Fig. 14;
Fig. 16 is a top plan view with portions broken
away of the reversing mechanism that is utilized to return
the work load transfer mechanism to its original position
`~ following a transfer operation;
Fig. 17 is a sectional view taken along line
17-17 in Fig. 16; and
Fig. 18 is a sectional view taken along line
18-18 in Fig. 7 and illustrating the hydraulic fluid
cooling system.
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Description of the Invention
Referring now to the drawings and particularly
to Figs. 1 and 2, the continuously operated vacuum furnace
embodied in the present invention is illustrated and is
generally indicated at 10. As will be described, the
vacuum furnace 10 is used for the heat treating of
metal parts under subatmospheric conditions and continuously
receives and processes the work paxts without the require-
ment of discontinuing the operation of the furnace heating
chamber or breaking the vacuum therein. The furnace 10
may be employed for a variety of heat treating operations
that also include sintering and brazing and has particular
application in the continuous carburizing of metal parts
under vacuum.
Referring to Figs. 3, 4 and 5, the vacuum
furnace 10 as illustrated includes a loading station
generally indicated at 12 (Fig. 3), a heating chamber
generally indicated at 14 (Fig. 4), a quench station
generally indicated at 16 (Fig. 5), and an unloading
2~ station generally indicated at 18 (Fig. 5). As will be
described, the loading station 12, heating chamber 14,
quench station 16 and the discharge station 13 are all
interconnected end--to-end to define the complete furnace
construction 10. However, the various units are so con-
structed that they are easily assembled and are somewhat
modular in arrangement for modifying the location of the
units as required and as will be described.
Referring now to Fig. 3, the loading station 12
is illustra-ted in detail and is mounted on a base generally
indicated at 20 that includes spaced beams 22 having
casters 24 located at the lower end thereon for facilitating
the assembly of the loading station 12 with the other
furnace units. As further shown in Fig. 6, supports 26
are mounted on the spaced beams 22 for supporting a
shell 28 in which the loading vestibule of the loading
station 12 is defined. The shell 28 includes a front
wall 30 having a generally convex configuration in which
a central openin~ is formed for receiving a tubular door
frame 32 therein. Mounted on the rearmost end of the
shell is a flange 34. Secured to the flange 34 of the
shell 28 by a rear flange 36 is a separable intermediate
connecting section generally indicated at 38. The con-
necting section 38 further includes a forward flange 40
that is sealed to a flange of the heating chamber 14 as
will be described (Fig. 4). Formed as part of the con-
necting section 38 is a convex wall 42 that cooperates
with the front wall 30 to complete the shell construction.
A wall 43 is also formed as part of the connecting section
38 and defines the forward wall of the heating chamber 14.
Secured to the walls 42 and 43 is an interior door frame 44
that provides for communication between the shell loading
vestibule with the heating chamber 14. Suitable bolts
secure the flanges 34 and 36 together, and the shell 28
and connecting section 38 are formed in modular relation
so as to be interchanged in different positions depending
on the end use of the furnace.
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Located exteriorly of the loading vestibule
as defined by the shell 28 and formed as a part of the
loading station 12 is a loading platform generally
indicated at ~2 that includes spaced inclined supports
45 that are joined to the base 20 and to which horizontal
supports 46 are secured at the outermost end thereof.
The innermost ends of the supports 46 are locked on
sleeves 47 that are secured to the underside of the door
fralne 32. Vertical struts 48 are mounted on the horizontal
supports 46 and support spaced loading tracks 50 that
are formed in the spaced-apart sections between which
a plurality of rollers 52 are mounted for receiving a work
cart 53 on which a work load 5~ diagrammatically illustrated
in Fig. 3 is mounted.
One of the unique features of the present
invention is the door assemb]y that sea~ the various
stations and that i5 operable to provide communication
therebetween. As will be desc:ribed, each of the door
assemblies is movable in a manner that not only provides
complete access to the station with which it communicates,
but also avoids the use of a mechanism that extends
upwardly above the furnace construction as heretofore
known, which construction materially reduce~ the overall
vertical dimension of the apparatus with which it was
employed.
Referring now to Figs. 9 and 10, one of the
door constructions is illustrated and is generally
indicated at 56. The door assembly 56 as shown is located
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at the loading station and seals communication between
-the loading platform 42 and the interior of the loading
vestibule in the shell 28; although, it will be under-
stood that the constructional arrangement and the opera~
tion of the other vacuum sealing door assemblies is the
same as that illustrated in Figs. 9 and 10. The door
assembly 56 includes a door member 58 that is generally
square in configuration and that is designed to seal
the opening as formed in the frame 32 mounted in the
opening in the front wall 30 of the shell 28. For this
purpose a marginal groove is formed on the inner face of
the door member 58 for receiving an O-ring seal 60 as
illustrated in Fig. 10. The seal 60 normally engages the
adjacent edges of the door frame 32 in sealing engagement
therewith when the door assembly 56 is located in the
closed position thereof. Formed in the door member 5~
is an opening for receiving a frame having a sight por-t
62 mounted therein that enables the interior or vestibule
of the shell 28 -to be observed after the door member 58
has been moved to the closed position thereof. Fixed to
the outer surface of the door member 58 are spaced trunions
64 that receive a rod 66 in rotatable relation therewith.
A bearing block 68 is also secured to the outer surface
of the door member 58 and acts to suppor-t a sprocket gear
as will hereinafter be described.
Secured to the door frame 32 at the sides thereof
are spaced brackets 69 and 70 on which bearings 72 and 74
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are mounted. Journalled for rotation in the bearings 72 and
74 is a dxive shaft 76, the outermost end of which is engage-
able by a hydraulically operated motor 78. Fixed to the drive
shaft 76 in spaced relation beyond the sides of the door mem-
ber 58 are links 80, the other ends of which are fixed to the
outer ends of the rod 66. Thus, upon rotation of the drive
shaft 76, the links 80 are movable therewith to pivotally
move the door member 58 in a corresponding motion.
The operation of the door assembly 56 is also
unique in that the door member 58 is reversely rotated on
the axis of the rod 66 as it is pivotally moved to and from
the closed and open positions. B~ providing for the movement
i of the door member 58 in this :manner, less space is required
for movement thereof, thereby enabling the loading platform
42 to be located closely adjacent to the loading shell 28.
Referring again to Figs. 9 and 10, a sprocket gear 82 is
shown that is fixed to a hub that is, in turn, mounted on the
; front wall 30 of the Ioading shell 28. A smaller sprocket
gear 84 is mounted on a hub that is secured to the block 68,
the block 68 as described hereinabove being secured to the
door member 58. Interconnected to the sprocket gears 82 and
` 84 is a nonrotating sprocke-t chain 86, and, as will be de-
scribed, the sprocket chain 86 is provided Eor effecting a
rotating movement of the rod 66 and door member 58 fixed
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thereto relative to the shaft 76. As shown, the ratio of the
gear 82 to the gear 84 is 2:1, which provides that radial
movement of the door member 58 joined to the sprocket chain
86 through the block 68 and gear 84 is twice that
of the drive shaft 76. ~lence, as
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the drive shaft 76 pivots the links 80 and door member
~ 58 joined thereto, the interconnection of the gears 82
; and 84 by the sprocket chain 86 produces a 2:1 counter
rotating movement of the door member 58. As more clearly
illustrated in Fig. lO, when the links 80 secured to the
shaft 76 are moved to the upper horizontal position,
the door member 58 is simultaneously , reversely or counter-
rotated relative to the shaft 76 and links 80 to a sub-
stantially, horizontal upper position. It is seen from
the movement of the door member as illustrated in Fig. lO
in phantom that the counterrotating movement of the
door member 58 is accomplished in a relatively small space
and that the reverse rotation of the door member 58 not
only accomplishes the purpose of effectively locating
the door member in the open position as indicated, but
that the seal 60 is disposed in an upper protected
position. As will be described hereinafter, the door
assemblies that are located interiorly of the furnace
and adjacent to the heating chamber are operated in
substantially the same manner, and by locating the seal
; 60 in protected relation behind the door member when
the door member is open the seals in the interior door
assemblies are protected from the heat emanating from
the heating chamber.
~ounted in the loading shell 2æ and in alignment
with the track sections 50 of the loading platform 42
are longitudinally spaced track
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sections 88 and 90, both of which are comprised of pairs
of spaced-apart track members between which rollers
similar to rollers 52 are mounted for rotation. A
cart 53 carrying a work load 54 is receivable on the
rollers 52 of the track sections 88 and 90 for transfer
through the shell 28 and into the heating chamber 14,
as will be described.
Another unique feature of the invention embodied
herein is the load and unload transfer mechanisms for
moving the work cart 53 through the loading shell 28
and into the heating chamber, and thereafter to the quench
and unloading stations. Referring now to Figs. 3, 11
and 12, the load transfer mechanism is illustrated and
is generally indicated at 92; and as later described,
the unload transfer mechanism is substantially similar
thereto in structure and in operation. The load -transfer
mechanism 92 includes an elongated flexible drive
spring 94 which is a con~entional coil spring, and, as
illustrated in Fig. 3~ projects from the interior of
the shell 28 to the outside thereof, and then extends
beneath the shell within a tubular housing, as will be
described. In order to effect a longitudinal or linear
movement of the flexible drive spring 94, the drive
mechanism 92 includes a drive shaft 96, which as
illustrated in Fig. 13 is coupled to a motor 98 mounted
on a bracket support 100 by bolts 101. The bracket
support 100 is mounted on a base 102 that is, in turn,
secured to a plate 104 fixed to the interior of the shell 28.
Also supported by the base 102 are spaced brackets 106
in which appropriate bushings 107 are mounted for receiving
the shaft 96 in bearing relation therein. Spaced pillow
blocks 108 are mounted on the brackets 106 and carry
bearings 110 therein in which the shaft 96 is rotatably
- mounted. Fixed -to the shaft 96 intermedia-te the brackets
106 is a drive pulley 114 that is formed with a concave
groove 116 therein, in which spaced teeth 117 are formed.
As shown in Fig. 13a, the teeth 117 are formed only in
the bo-ttommost portion of the groove 116 and are pitched
to accommodate the spirally extending coils of the
spring 94. sy locating the teeth 117 in -this manner
the coils of the spring 94 remain in driving contact
with the -teeth 117 and do not tend to ride out of the
groove 116 as the spring is moved longitudinally during
a loading or retracting operation.
In order to effectively retain the teeth 117
of the drive pulley 114 in engaging relation with the
coils of -the spring 94 for producing the linear movement
of the spring, a retainingroller 118 is provided; and
as illustrated in Figs. 11 and 13, the retainin-groller
118 is also formed with a groove 120 that conforms to the
configura-tion of the coils of the spring 94 and fits there-
over to urge the spring into the groove 116 of the
drive pulley 114. Fixed in the roller 118 are needle
bearings 122 which receive the reduced end 124 of theshaft 126 therein and thereby rotatably moun-t the
roller 118 on the shaft 126. As will be described, the
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roller 118 must be pivoted relative to the drive spring
94 to a position that will permit transfer of the work
cart 53 inwardly of the forwardmost end of the drive
spring 94 so that the cart will be located in a position
to permit the transfer movement thereof into the heating
chamber 16. For this purpose, the roller 118 is pivoted
relative to the drive spring 94 and the drive shaft 96
; on which the drive pulley 114 is mounted by securing a
swivel bracket generally indicated at 128 on the
shaft 126. As shown in Fig. ll, the swivel bracket 128
includes spaced plates 130 having upper openings 132
formed therein for receiving the reduced shaft 124 and
shaft 126. Larger lower openings 134 are also formed
in the plates 130 for receiving appropriate bushings 136
in which the shaft 96 is mounted for rotation. A guide
tube 138 (Fig. 11) having a slot 139 formed therein is
secured between the plates 130 and ex~ends forwardly
thereof and receives the spring 94 therein. In order
to produce the pivotal or swivel movement oE the swivel
bracket 128 that carries theretaini~ng roller 118, a lever
140 is provided and is secured to an end of the shaft 126
as shown in Fig. 13. The lever 140 is secured to a motor
shaft 142 that is operatively interconnected to a hydrau-
lically operated motor that is sequentially actuated to
25pivotally move the lever 140 and thereby produces the
swivel movement of the swivel bracket 128 and the pressure
roller 118 carried thereon. As further illustrated in
Fig. 12, a pusher bar 144 is secured to the interior end
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of the spring 94, the pusher bar 144 extending beyond the
guide tube 138 and terminating in a slot 146 (Fig. 11).
Secured in the slot 146 by a pin 148 is a pusher element
150 that cooperates with the pusher rod 144 to produce
a feeding movement of a work cart with which it has been
engaged during a transfer operation. Extending through
the slot 139 of the tubular guide 138 and outwardly
thereof for engagement with the pusher arm 144 is a
keystock 151 that prevents the pusher arm from turning,
and thus orients the pusher element 150 for the entry
thereof into a tubular guide in the shell 28 as will
be described. It is seen that the drive spring 94 is
longitudinally driven by the rotation of the drive
pulley 114, the pusher bar 144 and pusher element 150
secured thereto being movable with the spring 94 in its
linear travel. As further shown in Figs. 11 and 12, an
eIongated tubular guide member 152 is mounted within the
shell 28 between the track sections 90 and is formed with
a central slot 154 therein for receiving the pusher element
150. As the drive spring 94 directs the pusher bar 144 -~
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.
interiorly of the sheIl 28 and the pusher element 150
is received in the slot 154, the pusher bar 144 and
spring 94 enter the tubular guide member 152. As will
be described, the pusher element 150 is engageable with
a rear cross bar of a work cart 53;and,as the drive spring
94 continues its longitudinal rnovernent interiorly of the
shell 28, the work cart is moved through the shell 28
and door fxame 44 and into the heating chamber 16 during
a work load transfer operation.
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As illustrated in Fig. 3, the rear portion of
- the drive spring 94 projects outwardly of the loading
shell 28 and extends into a sealed tube 156 that projects
beneath the loading shell in curved relation and then
extends thereunder in parallel relation. Thus, the spring
94 is movable within the sealed tube 156 in a forwardly
direction within the loading shell 28 during a feeding
movement and rearwardly of the shell 28 as it is retracted
in the tube 156. In order to effect the reverse movement
of the drive spring 94 to re~ract the- pusher bar 1~4,
it is necessary to reverse the operation of the motor 98
in accordance with a predetermined movement of the spring,
and for this purpose a spring reversing assembly is pro-
vided. Referring now to Figs. 16 and 17, the spring
reversing assembly is illustrated and as shown includes
a bustle 158 that is mounted on the base 20 and receives
the tube 156 therein. ~paced from the bustle 158 is
a second bustle 160 that is also mounted on the base
;` 20, and joining the bustles in sealed relation is a
i:
cylinder 162. Projecting through the bustle 158,
cylinder 162 and into the bustle 160 in sealed relation
is the tube 156 through which the spring 94 extends.
~s shown in Fig. 17, the spring 94 as it is
received within the inner tube 156 has a tab 166 joined
to the end thereof, the tab 166 extending upwardly through
a slot 168 as formed in the portion of the tube 156
that is located in the cylinder 162. The tab is located
between arms 170 and 172 that are mounted for pivotal
movement in the bustles 158 and 160, respectively, the
tab 166 being movable by the spring 94 the distance that
is defined between the arms 170 and 172 as the spring 94
is moved in a feeding operation by the motor 98. As
shown in Fig. 16, the arms 172 extend outwardly of the
bustles 158 and 160, respectively, through vacuum seals
173 and 174 and are interconnected by linkages to an
elongated connecting rod 175. Mounted on the elongated
connecting rod 174 intermediate the ends thereof are
limit stops 176 and 178, and extending between the limit
stops 176 and 178 is a roller 180 that is secured to a
switch arm 182 of a limit switch 184. The limit switch
184 is eIectrically interconnected to the motor 98 and
is operative to control the direction of rotation of the
motor 98 for producing either forwardly or rearwardly
:Eeeding of the drive spring 94. It is seen that as the
drive spring 9a is moved to the endmost position in a
transfer or feeding operation, the tab 166 will strike
the arm 170 to produce a corresponding longitudinal move-
ment of the rod 174 thereby reversing the operation of
the switch 184. The operation of the switch 184 then
reverses the operation of the motor 98 to immediately
retract the drive spring 94 to the original position
thereof and to place the pusher arm 144 in position for
the next transfer operation. As the tab 166 is returned
to the original position thereof it engages the arm 172,
thereby moving the rod 175 to again reverse the operation
of the motor 98. A time delay may be utilized to delay
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the operation of the motor for the next feeding movement
of the drive spring.
As already described, the retainingroller 118
is provided for positively urging the drive spring 94
into engagement with the drive pulley 114. When a
work cart 53 is introduced into the loading shell 28,
; the roller 118 would normally restrict the inward
movement of the work cart. In order to allow free move-
ment of the work cart into the loading shell 28, the
pressure roller 118 is pivotally moved forwardly of its
normal position by the swivel bracket 128 from the
` full line position shown in Fig. 12 to the dotted line ;~
position thereof, thereby depressing the roller 118,
the guide tube 138, pusher bar 144 and pusher element 150.
~fter the work cart 54 has entered into the loading
; shell 28 forwardly of the pusher element 150, the swivel
bracket 128 is thereafter returned to the normal position
thereof by pivotal movement of the lever 140, the pusher
element 150 moving into engagement with the rearmost
cross bar of the work cart 54, and the retainingroller
118 once again en~ages the drive spring 94 to urge it
into driving relation with the drive pulley 114.
When a work cart 53 is introduced into the
loading shell 28, an interior door assembly generally
indicated at 186 that is disposed in a vacuum sealed
position relative to the door frame 44 seals communication
between the loading shell 28 and the heating chamber 16.
The door assembly 186 which includes a door member 188
is moved to and from a vacuum sealed position in the
manner as previously described with respect to the door
member 58 of the door assembly 56. In this connection,
the door member 188 is usually disposed in a sealed
position when the door member 58 is open to receive a
work cart 53 for introduction of a work load into the
loading shell 28. As will be described, the heating
chamber 14 is at all times maintained under a predetermined
vacuum and temperature, so that the operation of the
furnace is substantially continuous, in that a vacuum and
a predetermined temperature is maintained in the heating
chamber 14 during all phases of the operation of the .
furnace.
Prior to introduction of the work load into the
loading shell 28, the door assembly 186 is moved to the
sealed position, whereafter an atmosphere is introduced
into the loading shell 28 until atmospheric pressure is
obtained. In accordance with the cycle of operation, the
door assembly 56 is operated to move the door member 58 to
the open position thereof. A-Eter the work load has been
~: moved into the loading shell 28, and with the door
member 188 still in the sealed position, the door member 58
is sealed and the loading shell 28 is evacuated until
the vacuum therein is substan-tially the same as that
of the heating chamber 1~. Thereafter, the door member
188 is moved to the open position and the work load S4
is transferred through the door frame 44 into the heating
chamber by the longitudinal feeding movement of the drive
spring 94.
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Referring now to Figs. 4 and 7, the heating
chamber 14 is illustrated and as shown includes an inner
shell 190 having substantially a circular cross-sectional
configuration and that is mounted within an outer shell
192, which as shown in Fig. 7 has substantially a square
cross^sectional configuration. Suitable supports are
provided for locating the inner shell 190 within the
outer shell 192l the outer shell being supported by the
spaced beams 24 that extend longitudinally of the furnace.
; 10 The inner shell 190 is water cooled, the space that is
defined by the inner and outer shells forming a water
jacket through which water is circulated for effectively
cooling the inner shell 190 during the operation of the
furnace. As will be further described, an inner inclined
wall 194 (Fig. 7) extends the length of the outer shell 192
and defines an interior chamber 196 in which hydraulic
fluid i5 circulated, the chamber 196 acting as a cooling
chamber for the hydraulic fluid utili~ed in the various
hydraulic motors used throughout the system.
The forward end of the inner shell 190 has an
annular flange 197 secured thereto that is fixed in
mating relation to the flange 40 for interconnecting the
connecting section 38 and the heating chamber in sealed
relation. The other end of the inner shell 190 also
has an annular flange ]98 secured thereto that is fixed
to a flange 199 of an intermediate connecting section
generally indicated at 200 and that includes a domed
wall 201 in which an opening is formed for receiving a
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door frame 202. ~ounted on the door frame 202 is a vacuum
sealed door assembly 203 that includes a door member 204,
the door assembly being constructed and operated similar
to the door assembly 56 and controlling access from the
heating chamber 14 to the quench station 16.
Located interiorly of the shell 190 of the
heating chamber 14 is a heating area that is defined by a
cage generally indicated at 205. Located exteriorly of
the cage 205 are supports 206 therefor that are mounted on
the interior of the inner shell 190. Defining the exterior
of the cage 205 is a mild steel wire mesh 207 to which
; exterior layers 208, 210 and 214 of alumina-silica fibers
and interor layers 209, 211 and 212 of graphite fi~rsare æcured
; therebetween, the exterior and interior layers de~ining
lS the heating area. Projecting t:hrough the side layers 212
and 214 and the wire mesh 207 of the cage 205 are terminal
portions of a plurality of heating elements 216 which
are tubular in construction and which are also formed of
a woven graphite material of the type described in
,; ,
U.S~ Patent ~3,525,795. Joined to the terminal por-
tions of -the heating elements 216 are bars 217 that
are electrically connected to terminals 218 , the
terminals 218 extending outwardly of the heating chamber
14 and being connected to appropriate electrical connectors
that are interconnected to a source of power located
exteriorly of the furnace. As shown more clearly in
Fig. 4, thermal doors generally indicated at 220 and 222
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are mounted exteriorly of the cage 205 adjacent to the
ends thereof. The thermal door 220 controls access
through a forward opening 223 of the cage 205, while
the thermal door 222 controls access through a rear
; 5 opening 224. Both of the doors 220 and 222 are operatively
interconnected to the adjacent vacuum sealed door assembly
so that operation of the door assembly 186 produces a
corresponding movement of the thermal door 220. Similarly,
the thermal door 222 is moved to an open and closed
position in accordance with the operation of the vacuum
sealed door assembly 203 that controls access between
the heating chamber 14 and quench station 16. As further
illustrated in Figs. 3 and 4, a track section 228 extends
; from the door frame 40 to the thermal door assembly 220.
Located intermediate the track elements of the track
section 228 is a tubular guide member 229 that is
aligned with the guide member 152 and receives the
pusher bar 144 and drlve spring 194 therein during a work
load transfer operation. An independently mounted track
- 20 section 230 is located within the heating area interiorly
of the cage 205, while a track section 232 is mounted
downstream and exteriorly of the cage 205 and extends
into the tubular door frame 207 disposed at the discharge
side of the heating chamber 14. A tubular guide member
233 is located intermediate the track elements of the
track section 232 and receives a puller bar and retract
spring therein as will be described. The longitudinal
dimension of the cage 198 is constructed such that three
of the work carts 53 located in end to-end relation
may be accommodated therein. Thus, as each cart 53
is introduced into the loading shell 28 and thereafter
moved into the heating chamber 14, the last cart
loaded engages the cart in front and subsequent operation
of the transfer mechanism causes the drive spring 94
to advance the carts and loads therein forwardly to
the next position. As will be described, a retract or
unload mechanism is utilized to remove the forwardmost
load from the heating chamber for location at the quench
station 16, the load and unload mechanisms cooperating
to continuously advance the work loads thr~ugh the
various stations. As will also be described, a load
will be located within the heating chamber 14 for at
least three feeding operations, and the heat treating
`; operàtion of the work load as contained on a cart in the
; heating chamber is controlled accordingly. If desired
~ a fan 23~ may be mounted in the heating chamber lg for
,~ communication with ducting for circulating a carburizing
gas within the hea-ting chamber duringthecarburizing operation.
Following the heat treating operation, a work
load is moved from the heating chamber 14 into the quench
station 16, access into the quench station being controlled
by the vacuum sealed door assembly 203. The operation
of the door assembly 203 is substantially identical to
that described above in connection with the door assembly
- 56, the movement of the door member 204 of the door
assembly 203 effecting the same movement as the door
member 58 described hereinabove. The door frame 202
which extends into the quench station 16 provides for
communication of the heating chamber 14 and the quench
station 16, and as illustrated in Fig. 5, the door
assembly 203 is operable to seal communication between
the heating chamber 14 and the quench station 16 as required.
As shown in Fig. 5, the quench tank 16
includes an inner shell 240, the axis of which is sub-
stantially vertical as contrasted with the loading shell
28 and the heating chamber 14. The inner shell of the
quench tank 16 is mounted in spaced relation relative to
an outer shell 242 that engages the surface on which the
furnace 10 is located. The inner and outer shells 240
and 242 define a cooling space 244 therebetween, in which
a cooling liquid is circulated for effectively cooling
the quench tank as is well known in the art. A dome 246
is mounted on the inner and outer shells 240 and 242
and also includes a cooling space therein for effectively
cooling the dome 246. Joined to the cuter shell 242 is
the connecting section 200 that cooperates therewith to
form a part of the cooling jacket in which a cooling liquid
is circulated. Also formed on the wall of the inner
shell 2A0 is an opening through which the door frame 202
extends for sealing engagement therein. Mounted on a
support 248 located at the bottom of the inner shell 242
is a hydraulic ram 250. Mounted for vertical reciprocating
movement in the hydraulic ram 250 is a piston 252 on the
uppermost end of which a pulley 254 i5 secured. Located
a-t the uppermost end of the quench tank 16 are cross beams
2S6 between which idler pulleys 258 and 260 are rotatably
mounted. Fixed to suitable supports and extending substan-
tially the height of the quench tank 16 are spaced track
members 262 between which an elevator 264 is mounted for
vertical movement. The elevator 264 includes a frame 266
o~ the lowermost end of which a track section is mounted as
defined by spaced track elements 268. The track sections
268 have rollers 269 mounted thereon that receive a work cart
53, the elevator 264 being vertically movable together
with the work cart 53 as mounted on the track section to
and from the bottom of the quench tank for quenching of
the work load 54 as located on the cart 53. For this purpo~ a
cable or chain 270 is provided and extends around the pulley
254 for securement at one end to a fixed point in the
quench tank and at the other end to the uppermost end of
; the elevator 264. Thus, as the hydraulic ram 250 vertically
moves the pulley 254 to that position illustrated in phantom
in Fig. 8, the elevator 264 with the work cart and load
thereon descends to the bottom of the quench tank for
immersion of the work cart and the work load thereon within
the quench liquid indicated at 272. A motor 274 is mounted
at the bottommost end of thequench tank and operates a
circulating fan 271 for effectively circulating the quench
liquid 272 as indicated by the arrows in Fig. 5 during
the quenching operation. As indicated in Figs. 5 and 8,
spring actuated lock elements 275 are mounted on the ends
of the elevator adjacent to the track section thereof, the
lock elements 275 being urged upwardly on descent of the
-28-
elevator to form end barriers for capturing the cart on
the elevator.
Also mounted on a suitable support in the quench
tank is a track section 274 that is located between the door
assembly 203 and the elevator 264, the track section 274
directing the work carts 53 from the door frame 202 onto the
track section of the elevator 264. A track section 276 is
located downstream of the elevator 264 and receives the work
cart 54 thereon following the quench operation. A tubular
; 10 guide member 277 is also mounted on the track section 274
intermediate the track elements and is aligned with the
tubular guide member 232. A tubular guide member 278 is
further carried by the elevator 264 intermediate the track
elements 268 as shown in Fig. 8 and is aligned with the
guide members 232 and 274 when the elevator is in the
elevated position. A yuide member 279 is mounted between
the track elements of the track sections 276, all of the
aligned guide elements receiving an unload bar and retract
spring of an unload mechanism generally indicated at 281.
The unload mechanism 281 operates in substantially the
same manner as described hereinabove in connection with
the loading mechanism and includes a retract spring 282
that is received over a drive pulley 283 similar to
drive pulley 114. The drive pulley 283 is mounted for
rotation on a drive shaft and is rotatably driven by a
drive motor similar to the drive motor 98. A retaining
roller 284 engages the drive pulley 283 and is tiltable
inwardly toward the quench tank by an unloading tilt
assembly that is similar to the loading tilt assembly 128
-29-
if~
illustrated in Fig. 13~ A secondary retaining roller 286 is
located adjacent to the drive pulley 283 but downstream
thereof, and urges the drive spring 282 downwardly into a
sealed tube 288 that is disposed in a generally vertical posi-
tion. Secured to the innermost end of the drive spring 282
is an unloading bar 290 on the end of which a pivotal retract
element 292 is mounted. The retaining roller 284 is movable
by the unloading tilt assembly to depress the unloading bar
290 and retract element 292 in a downward direction during
the unloading operation of a cart 53 from the elevator 264
following a quenching operation, wherein the cart is retracted
from the elevator track section onto the track section 276.
It is understood that the normal operation tension on both
springs 94 and 282 is less than the break-away tension thereof,
so that the springs never extend in the operation of the load
and unload mechanisms.
As further shown in Fig. 5, a door frame 294 is
mounted in the inner and outer shells 240 and 242 of the quench
tank and has the unload mechanism 281 mounted therein. ~ounted
on the outermost end of the door frame 294 is a door assembly
generally indicated at 296 that includes a door member 298
that controls access through an opening 300 formed in the door
frame 29A. The door assembly 296 includes the same structure
and is moved in the same manner as described above in
connection with the door assembly 56. The door member 298
is movable to and from a closed position for vacuum
sealing the opening 300 in the door frame 294, and
located exteriorly of the door assembly 296 is a track
- section 302 that forms the discharge station 18 for
-30-
receiving the carts 53 as they are removed from the
furnace following a quench operation.
; As previously described, the work carts 53
with the loads 54 thereon are moved through the loading
shell 28 and into the heating chamber by a drive
spring 94 and the pusher bar 144 to which the pusher
element 150 is secured. The cart loaded into the loading
shell 28 i5 moved forwardly by the drive spring 94 until
it engages the next cart in the heating chamber~ Thus
it is the last cart loaded that provides for successive
movement of the previously loaded carts. In this con-
nection the last cart loaded is conveyed into the heating
chamber 14 by the drive spring 94 and the pusher bar
144, the drive spring and pusher bar extending through
the guide members 152 and 229 during the transfer move-
ment thereof~ However the work carts 53 are discharged
from the heating chamber 14 by extending the puller
bar 290 and unload spring 282 through the guide members
276, 278, 277 and 233 into the heating chamber 14. The
retract element 292 pivots upon engagement with a cross
bar of the work cart and is movable therebehind, where-
upon it latches behind the cart cross bar. A retract
movement of the drive spring then pulls the forwardmost
cart in the heating chamber by the open thermal door
222 through the door frame 202 and by the open door
assembly 203 for positioning on the track section of the
elevator 264. At this point the tilt mechanism for the
spring 232 and puller bar 290 is operated to depress
the puller bar and move the retract element 292 out of
engagement with the cart cross bar. Continued rearward
movement of the spring 282 by its drive motor retracts
the puller bar from the elevator which is now free to
descend into the quench liquid. Following the quench
operation and elevation of the work load to the upper
position, the unload mechanism again operates to advance
the puller bar 290 and the retract element 292 toward
the cart until the retract element once more engages
the cross bar of the work cart. A reverse movement
of the retract spring 282 pulls the cart from the
elevator onto the track section in the door frame 294
for unloading onto the track section 302 at the dis-
charge station 18.
As described hereinabove, the various track
sections as located at the stations of the furnace are
all constructed substantially similar; and, in order to
illustrate the construction of the track sections and the
rollers as mounted thereon, reference is made to Figs. 14
and 15. In this connection, reference is made to the
track section 230 and the rollers as mounted thereon,
since this track sectlon is located in the heating chamber
14 and is constructed of special materials to withstand
the high temperatures experienced during the heat treating
operation. The track section 230 includes pairs of spaced-
apart members 304 which are supported by a series of
notched pier supports 306. The material from which the
track members 304 and pier supports 306 are constructed
-32-
~2~
is preferably molybdenum, since this material is capable
; of withstanding relatively high temperatures that are ex-
perienced during the heat treating operation of the furnace.
Spacing the track members 304 apart are a plurality of spacer
elements 308 through which a bolt 310 extends, the ends of
the bolt 310 projecting through suitable openings formed in
the members 304 and receiving nuts 312 thereon. The spacers
308, bolts 310 and nuts 312 are also formed of molybdenum
materlal. Rollers 313 which are mounted between the members
304 are formed of a graphite material and are thus heat
resistent and are rotatably mounted on tungsten pins 314. In
order to fix the pins 314 in the members 304, the members are
recessed as indicated at 316, the ends of the pins 314 being
received therein in frictional relation. As previously
described, the side frame of the carts 53 are received on the
rollers 313, the rollers 313 having free rotation on the pins :~
314 thereby providing for movement of the carts 53 on the tra~
section 230 through the heating station 14. Track section 232
which is also located in the heating chamber 14 would be con-
structed similarly to track section 230, and those track
sections not exposed to excessively high temperatures would
; also be constructed similarly, but the materials from which t~e
component parts of these latter track sections are constructed
is mild steel. Further, the rollers of these latter track
sections are provided with interior bearings to promote the
rotation thereof.
As previously described~ a chamber 196 is formed
in the outer shell 192 of the heating chamber 14 by
locating a plate 194 withln the outer shell 192 in
angular relationt~ereto. The chamber 196 which is further
illustrated in Fig. 18 is provided for circulation of the
hydraulic fluid therein that is used to operate the
various hydraulic motors of the system. An inlet 318
that communicates with the hydraulic system extends into
the chamber 196 and directs the hydraulic fluid therein.
A filter 320 is also located in the chamber 196 and
communicates with a suction pump 322, the suction pump
3Z2 directing the hydraulic fluid to the hydraulic
system. It is seen that the cooling chamber as defined
between the inner shell 190 and outer shell 192 of the
heating chamber 14 is effective to withdraw heat from
the hydraulic fluid that circulates through the chamber
196. The cooling chamber 196 thus avoids the use of an
external heat exchanger unit for the hydraulic system
and that would normally be employed in furnaces of the
; type embodied in the subject invention.
In the operation of the device, it is under-
s-tood that the loading shell 28 at the loading station 12,
the heating chamber 14 and the quench station 16 are all
operated under vacuum conditions during various phases
of the operation of the furnace and for this purpose
communicate with a vacuum pump indicated at 324 in Fig. 1.
A vacuum line 326 is interconnected to vacuum lines 328,
333 and 332 for evacuating the various stations of the
furnace at the required intervals. Al-though not shown,
conventional valves are utilized to control the evacuation
-34-
3L~
of the sta-tions, and the usual purge lines are also
provided for the loading and quench stations for intro-
ducing an a-tmosphere therein.
OP~RATION
In describing the operation of the furnace 10,
it will be assumed that the heating chamber 14 and the
quench station 16 are normally operating and have been
evacuated to a predetermined vacuum pressure. In this
connection the heating chamber has been evacuated to less
-than 500 microns and the quench station has been backfilled
with nitrogen and is operating at ten inches of mercury
; 15 vacuum. All of the doors are closed and sealed, and the
pressure in the loading shell is atmospheric. It is further
assumed that a load i5 on the elevator 264 and is disposed
` in the quench liquid undergoing a quench cycle. A load is
in the loading vestibule within the shell 28 and three loads
are disposed end-to-end in the heating chamber 14. A load
is also located on the loading platform 42 ready for entry
into the loading chamber. Maintaining the conditions as
described, the elevator 264 ascends with the load thereon
to the unload position. The quench station 16 is then ;
purged with nitrogen and brought to atmospheric conditions,
whereafter the door assembly 296 is operated to open the
door member 300. The quench load now completely heat
-35-
5`~
treated is manually withdrawn onto the track sections 302
at the discharge station for removal. Thereaf-ter~ the door
assembly 296 closes the door member 298 and the quench tank
is evacuated to approximately 500 mircons for removing con-
taminants that reslllted when the last load was quenched and
then removed from the quench station. Thereafter the
quench tank is backfilled with nitrogen to 10" hg vac.
and maintained thereat for a predetermined soak period.
The heating chamber 14 is then backfilled with nitrogen to
10" hg vac. With both the heating chamber and quench station
at 10" hg vac., the door assembly 203 is operated to open
the door member 204 which simultaneously opens the thermal
door 222. The unload mechanism is operated to remove the
next load onto the elevator 264 which immediately descends
into the quench liquid to begin the quench cycle. The
door assembly 203 seals the door member 204 and the thermal
door 222 is also closed. The heating chamber is then
again evacuated to approximately 500 microns.
In preparation of moving the load in the loading
vestibule into the heating chamber, the loading shell 28
is evacuated to 500 microns and the door assembly 186
is then operated to open the door member 188 which simul-
taneously opens the thermal door 220. The l-oad mechanism:~
is operated to -transfer the load~from the`loading ~
vestibule into the heating c-hamber, the t`ransfer operation
stepping the two remaining loads in the heatlng chamber
-36-
forwardly. The door assembly 186 then seals the door
member 188, which closes the thermal door 220, and the
loading shell 28 is backfilled with nitrogen to 5" hg vac.
Thereafter the loading shell is brought to atmospheric
condition and the loading door 56 is operated to open
the door member 58 for entry of the load on the platform
into the loading shell 28. The door member 58 is then
closed and the cycle is repeated.
It is understood that the vacuum pressures
referred to in the description of the operating cycle
hereinabove are only representative of one cycle of
operation, and the operating conditions employed will
be predetermined by the heat treating requirements of
the work load. The temperature in the heating chamber
is also varled in accordance with the work load to be
heat treated and time intervals for the cycle will again
be predetermineld in accordance with the heat treating
requirements.
~ecause of the modular cons-truction of the
loading shell 28 and the connecting sections 38 and 200,
it is also contemplated to include an atmosphere cooling
chamber in place of the liquid quench station or in
conjunction therewith. Various heat treating operations '
can be carried out by the furnace and carburizing,
sintering, brazing and other conventional procedures may
be accomplished by the furnace without any alteration
of the structure thereof.
.
-37-
$'~
It is also understood that all of the operations
of the various motors that control the load and unload
mechanisms, the door assemblies, the evacuation and
purging of the loading shell 28 and quench station 16,
and movement of the quench elevator are all automatic
and are timed in accordance with the characteristics
of the metal parts being heat treated. ~n appropriate
console is located adjacent to the furnace 10 and is
electrically connected to the various operating mechanisms
so that -the system is preset and upon operation of the
starting motor the cycle begins and is carried out
automatically. It is understood of course that loading
of a cart into the loading shell 28 and withdrawal at
the discharge station is carried out manually, although
this also may be accomplished automatically if required.
While there is shown and described herein
certain specific structure embodying the inven-tion, it
will be manifest to those skilled in the art that various
modifications and rearrangements of the parts may be made
without departing from the spirit and scope of the under-
lying inventive concept and that the same is not limited
to the paxticular forms herein shown and described
except insofar as indicated by the scope of the appended
; claims.
-38-
