JP6053864B2 - Workload lifting system for vertical vacuum furnace - Google Patents

Description

  The present invention relates to a vacuum heat treatment furnace, and more particularly to a vertically disposed vacuum furnace and a lifting device for raising a work load (member to be treated) into the vacuum heat treatment furnace and lowering the work from the inside. .

  Industrial vacuum heat treatment furnaces having a horizontal configuration or a vertical configuration are known. In a vacuum furnace having a horizontal configuration, a workload of a part to be heat-treated is carried into a heat-treating furnace chamber using an apparatus that translates the part. In a vacuum furnace having a vertical configuration, a lifting device is used to lift a workload from a factory floor to a heat treatment furnace chamber at a high position.

  A known structure of a lifting system for a vertical vacuum furnace employs a four-point lifting device. The device typically has four ball screws that operate synchronously so that the workload is lifted flat. In order to operate the ball screws in synchronism with each other, a connecting shaft including a plurality of gearboxes and connecting parts is used. Known designs for such lifts are made up of a number of parts that need to be assembled, aligned, and disassembled for transport at the manufacturing site. Once the vacuum furnace is delivered to the customer site, the lift device must again be assembled and aligned. This is a time consuming task and typically adds days to the delivery time schedule.

  Gearboxes, drive shafts, and connecting components used in known lifting mechanisms generate significant noise when operating to raise and lower the workload. The connecting parts that connect the drive shaft, motor shaft, gearbox shaft, and ball screw shaft loosen over time. In this case, one or more ball screws do not operate in synchronization with the other ball screws. Such asynchronous operation can cause fatal damage to the lifting mechanism. If the asynchronous operation of the ball screw becomes too severe, the workload itself and even the hot zone in the vacuum furnace can be damaged.

  A known lifting mechanism for a vertical vacuum furnace has a lifting point that abuts against the bottom lifting structure of the vacuum furnace via a coil spring. The lift mechanism lifts the bottom door toward the furnace until the mechanical limit switch is activated, indicating that the lift structure is in the fully lifted final position. At the final lifted position, the bottom lift structure is in contact with the top of the furnace vessel, so the amount of compression of the spring is small. If the mechanical switch is not properly adjusted or if an adjustment failure occurs, the spring may be over-compressed and the lifting structure and door may be damaged.

  In view of the above problems with known lifting systems for vertical vacuum furnaces, it is desirable to provide a lifting apparatus for vertical vacuum furnaces that solves problems with known lifting systems.

  A system for raising and lowering a workload in a vertical vacuum furnace according to the present invention has two ball screws, and each ball screw is driven by a servo motor and uses an encoder and / or resolver that feeds back position information. And driven synchronously by an electric servo drive system. Each ball screw has a configuration and a structure for raising and lowering a lifting part guided in the track. A lifting system having a ball screw and a motor is incorporated into the leg structure of the vertical furnace. The leg / elevator / ball screw / motor complex is a modular assembly that is maintained in perfect condition for shipping and assembly at the end user site.

  Since the gearbox, shaft and connecting parts are not provided, the raising / lowering movement of the raising / lowering parts is extremely quiet. Each servo motor is directly connected to a respective ball screw. The acceleration and deceleration of the up and down movement near the end point of the movement stroke can be programmed into the servo drive system. Thereby, the spring provided between the raising / lowering structure and the taking-out point of raising / lowering components can be excluded. By accurately feeding back with the encoder, the elevating part can be arranged at the fully raised position or the completely lowered position.

  Another advantageous feature of the lifting system according to the invention is that the fixing point of the ball screw on the lifting mechanism has a joint connection that eliminates misalignment with little or no stress on the ball screw. In the point.

  A better understanding will be obtained by reading the following detailed description and the summary of the invention described above with reference to the accompanying drawings.

1 is a perspective view of a vertical vacuum furnace assembly according to the present invention. It is a front view of the vertical type vacuum furnace assembly shown in FIG. It is a perspective view of the leg assembly used for the vertical type vacuum furnace assembly shown in FIG. FIG. 4 is a rear view of the leg assembly shown in FIG. 3. It is a perspective view of the bottom head assembly used for the vertical type vacuum furnace shown in FIG. FIG. 6 is a plan view of the bottom head assembly shown in FIG. 5. FIG. 6 is a front view of the bottom head assembly shown in FIG. 5. FIG. 4 is a front perspective view of an elevating carriage used in the leg assembly shown in FIG. 3. It is a back perspective view of the raising / lowering cart shown in FIG. FIG. 4 is a perspective view of a ball screw jack used in the leg assembly shown in FIG. 3. It is a front view of the ball screw jack shown in FIG. It is a block diagram of the servomotor control system used for the vertical type vacuum furnace shown in FIG.

  Referring now to the accompanying drawings, and more particularly to FIGS. 1 and 2, a vacuum furnace 10 according to the present invention is shown. The vacuum furnace 10 has a vertical configuration and is lifted with respect to a floor of a facility where the vacuum furnace is disposed. The vacuum furnace 10 includes a pressurized or vacuum container (pressurized / vacuum container) 12 and a vacuum pump 14. The pressurization / vacuum container 12 is supported by a pair of leg assemblies including a first leg assembly 16 and a second leg assembly 18. A work table 20 is attached to the upper ends of the leg assemblies 16 and 18. A control cabinet 22 and a control console 24 are preferably provided adjacent to the vacuum furnace 10.

  The pressurization / vacuum container 12 has a main body 26, and the main body has an opening 28 at the lower end thereof. The pressurization / vacuum vessel 12 has a bottom head assembly 30 that is movable to close the opening 28 when the vacuum furnace is operated to heat treat a metal component workload. The body portion 26 of the pressurization / vacuum vessel 12 is mounted on the leg assemblies 16 and 18 by a plurality of support arms. Support arms 40a, 40b, 40c, 40d are provided to attach the forward portion of the pressure-type container body 26 to the forward portion of the leg assemblies 16,18. A similar series of support arms (not shown) are provided to attach the rear portion of the pressure-type container body 26 to the rear portions of the leg assemblies 16,18.

  With reference now to FIGS. 3 and 4, the construction of the leg assembly 16 is shown in greater detail. Leg assembly 18 is constructed and arranged in substantially the same manner as leg assembly 16. Therefore, only the leg assembly 16 will be described.

  The leg assembly 16 has a pair of support columns 32a and 32b. The support columns 32 a and 32 b are integrally connected to the cross beam 34 and the floor plate 35. The floor plate 35 is fixed to the bottoms of the support columns 32a and 32b, and is preferably fixed by welding. The cross beam 34 is attached between the columns 32a and 32b at a position intermediate between the lower ends and the upper ends of the columns 32a and 32b.

The leg assembly 16 also includes an elevator mechanism 46 configured to raise and lower the bottom head assembly 30 relative to the pressurized container body. The elevator mechanism 46 includes a mechanical lifting device, preferably a ball screw jack 50, and a lifting carriage (lifting trolley) 52 operably connected to the lifting device. Guide channels 42a and 42b are formed or provided on the opposing surfaces of the columns 32a and 32b, respectively. The guide channels 42 a and 42 b form a track that allows the lifting carriage to move along the leg assembly 16. As shown in more detail in FIGS. 10 and 11, the ball screw jack 50 has a threaded shaft 58 and a ball nut 59 having a known structure. A drive gearbox 60 is connected at one end to a threaded shaft 58. The drive gear box 60 has a motor mounting portion 61 for attaching the electric motor 51 thereto. It will be appreciated by those skilled in the art that mechanical screw jacks may be used in place of the ball screw jacks shown in FIGS.

  8 and 9, the lifting carriage 52 has a pair of L-shaped side plates 70a and 70b. The side plates are integrally connected to the upper lateral beam 72 and the lower lateral beam 74. In the illustrated embodiment, the lower lateral beam 74 is composed of a pair of lateral plates (bars) 74 ′ and 74 ″ spaced in parallel to each other. The upper transverse beam 72 preferably has an opening 88 formed at an intermediate position between the side plates 70a, 70b. The opening 88 is dimensioned and arranged so that the threaded shaft 58 of the ball screw jack 50 can pass therethrough. The lifting carriage 52 has a ball screw fixing assembly 76 for connecting the ball screw jack 50 to the lifting carriage 52. Lift plates (lift bars) 80 a and 80 b are attached between the horizontal plates 74 ′ and 74 ″ of the lower horizontal beam 74. A bracket 78 is provided to connect the ball screw jack 50 to the lifting carriage 52. As shown in the embodiment of FIGS. 8 and 9, the bracket 78 has a mounting plate 79 that includes a central opening 89 and a plurality of bolt holes. The central opening has dimensions such that the threaded shaft 58 of the ball screw jack 50 can penetrate the lift carriage 52. In order to attach the ball nut 59 of the ball screw jack 50 to the mounting bracket 78, a bolt hole is provided.

  The mounting bracket 78 is connected to the lift plates 80a and 80b via connecting plates (link bars) 82a, 82b, 82c, and 82d. The coupling plates 82a and 82b are pivotally coupled between the elevating plate 80a and the mounting bracket 76 by pivot pins 84a and 84b. The coupling plates 82c and 82d are pivotally coupled between the elevating plate 80b and the mounting bracket 76 by pivot pins 84c and 84d. Even when there is a slight misalignment between the lifting carriage and the ball screw shaft, the joint connection realized by the connecting plate between the lifting plate and the mounting bracket will result in substantial lateral stress on the ball screw jack. Can be prevented.

  Guide wheels or guide bearings 180a and 180b are provided on the outward face of the end wall plate 70a. Similarly, guide wheels or guide bearings 180c and 180d are provided on the outward face of the end wall plate 70b. Guide wheels 180a and 180b are mounted on mounting pads 182a and 182b, respectively. Similarly, guide wheels 180c and 180d are mounted on mounting pads 182c and 182d, respectively. Guide wheels 180a-180d are dimensioned and arranged to fit within guide channels 42a, 42b of leg assembly 16 and move therethrough.

  The end wall plates 70a and 70b have an L-shape and have leg portions 86a and 86b extending in the horizontal direction. The legs 86a, 86b are arranged and configured to engage the support structure of the bottom head assembly of the pressure / vacuum vessel, as will be described in detail below.

  As will be apparent to those skilled in the art, the structural features of the leg assemblies 16, 18 have the advantage that the leg assemblies can be shipped with the vacuum furnace after being preassembled as a module. Since the leg assembly can be shipped as a pre-assembled module, the time required to ship the vacuum furnace and assemble the vacuum furnace in the user's factory can be greatly reduced. Further, as is apparent from the above description, no mechanical connection is required between the lifting mechanisms above each leg assembly. That is, since the leg assemblies 16 and 18 have a modular structure, there is no need to mechanically connect the lifting mechanisms, and the plurality of lifting mechanisms and the connecting parts necessary for the known lifting mechanisms are accurately aligned. No need to re-align. In addition, by omitting a plurality of gearboxes, drive shafts, and connecting parts, which are usually mechanically connected parts, a considerably quieter operation can be realized.

  Referring now to FIGS. 5, 6 and 7, there is shown a bottom head of a pressurized / vacuum vessel 12 according to a preferred embodiment. The bottom head assembly 102 has a substantially flat outer shape (profile) for simplicity. The bottom head 102 has a generally circular steel plate 104 dimensioned to cover (cover) an opening in the bottom of the pressure vessel body. The plate 104 is preferably formed with a peripheral groove for receiving the sealing ring 107. A flange 106 is formed around the periphery of the plate 104 and is dimensioned and arranged to engage a corresponding mating flange around the opening 28 in the body 26 of the pressurized / vacuum vessel. . If gas quenching pressures higher than about 2 bar are not used in the vacuum furnace, a flat bottom head device is appropriate. That is, if a gas quenching pressure higher than about 2 bar is used, a conventional dished or dome shaped bottom head must be used to meet the requirements of a pressurized container standard.

  A pair of support beams (support beams) 108a and 108b are fixed to the outside of the plate 104, and extend parallel to each other so as to cross the plate. These support beams have portions that protrude beyond the plate 104. In particular, the support beam 108a has extensions 110a and 110b, and the support beam 108b has extensions 112a and 112b. The extension portions 110a and 110b are configured to engage with the foot portions 86a and 86b of the elevating carriage 52. Similarly, the extensions 112a, 112b are configured to engage corresponding feet of the lift carriage on the leg assembly 18. As shown in FIG. 7, support legs 114 a and 114 b extend from the outer surface of the plate 104 in the vertical direction. Although not shown in FIG. 7, the pair of second support legs are disposed behind the support legs 114 a and 114 b so as to be separated from each other. These support legs are configured and arranged to add rigidity to the plate 104 and support the bottom head assembly 102 when the bottom head assembly 102 is placed on the floor. Also, these support legs are dimensioned to provide sufficient height above the floor so that the lift carriage can be easily engaged with the extensions 110a, 110b, 112a, 112b of the support beams 108a, 108b. Yes.

  A plurality of sockets or receptacles 118 are disposed and fixed in the central region of the inner surface of the plate 104. These receptacles 118 extend in the vertical direction and are dimensioned to receive struts (posts, see eg, FIG. 1) that support the hearth rail. The cover plate 122 is fixed on the inner surface of the plate 104 and covers the central area of the plate 104. The cover plate 122 is placed and fixed on the spacer ring 124, and the spacer ring is fixed on the inner surface of the plate 104. Cover plate 122 has an opening, and receptacle 118 extends through the opening. The bottom head assembly 102 preferably has means for cooling the head assembly from the enormous heat generated in the furnace during the heat treatment cycle. Preferably, the cooling means is realized by a composite consisting of a spacer ring 124 and a cover plate 122, which defines a sealed space that functions as a coolant cover (coolant coating). Preferably, the coolant cover has channels (not shown) for controlling the flow of coolant, such as water, and the channels extend across the inner surface of the plate 104. Preferably, the channels are arranged so that substantially the entire central region of the plate 104 can contact the coolant. Those skilled in the art can easily design the channel arrangement so that the plate 104 is sufficiently cooled so that no stagnant spots or vortices are formed. When the bottom head assembly 102 is closed relative to the body 26 of the pressurized / vacuum vessel, the cover plate isolates the cooling channel from the interior of the vacuum furnace.

  Referring now to FIG. 12, an apparatus suitable for controlling the operation of the lifting apparatus according to the present invention is illustrated. The control system 90 is configured to realize a fail-safe operation of the lifting device, and moves the bottom head assembly in a horizontal state by providing means for synchronizing the movement of the ball screw drive and synchronizing the operation of the lifting motor. Thus, damage to the bottom head and / or the lifting mechanism can be avoided. The control system 90 includes a programmable logic controller (PLC) 100, a master servo drive circuit 92, and a follower servo drive circuit 94. A lift motor 50 is connected to the master servo drive circuit 92. An encoder 96 is mechanically coupled to the drive shaft of the motor 50. Similarly, the lift motor 55 is connected to the follower servo drive circuit 94, and the resolver 98 is mechanically coupled to the drive shaft of the motor 55.

The PLC 100 has a processor programmed to provide electrical command signals for operating the lift motors 50, 55 to raise and lower the bottom head assembly in response to commands entered by the furnace operator. Operator instructions can be entered into the PLC using convenient means such as push buttons or a keyboard. The PLC 100 is programmed to receive status information from the master servo drive circuit and the follower servo drive circuit indicating whether the bottom head assembly 102 is in the raised position or the lowered position. When the position of the bottom head assembly is specified, the PLC 100 transmits an interlock signal indicating that the interlock operation can be executed to the servo drive circuit. The master servo drive circuit 92 is connected to the PLC 100, receives a command signal, and outputs a first feedback signal to the PLC. The follower servo drive circuit 94 is connected to the master servo drive circuit 92, receives a command signal, and outputs a feedback signal to the PLC via the master servo drive circuit 92. The PLC is programmed to monitor feedback signals from the master servo drive circuit and the follower servo drive circuit and to output updated command signals to maintain the synchronized operation of the lifting motors 50 and 55. The feedback signal may be an indicator that indicates position and / or velocity. The encoder 96 is configured to generate a first feedback signal based on the rotation of the drive shaft of the lift motor 50. The encoder 96 is connected to the master servo drive circuit 92 and transmits a first feedback signal to the master servo drive circuit. Similarly, the resolver 98 is configured to generate a second feedback signal based on the rotation of the drive shaft of the lift motor 55. The resolver 98 is connected to the follower servo drive circuit 94 and outputs a second feedback signal to the follower servo drive circuit. Preferably, the system has a feedback limit switch (not shown) connected to the lift controller. The feedback limit switch is arranged to detect that the lift carriage has reached the fully lowered position, and outputs a signal to the lift controller so that the system itself sets the position index to zero.

  The servo drive control system according to the present invention eliminates the need for a mechanical coupling device including a plurality of gearboxes, shafts, and coupling components between the lifting mechanisms on each leg assembly, and on each leg assembly. The lifting mechanism is moved up and down in synchronization. By omitting the mechanical coupling device, the time required to assemble the vacuum furnace at the customer's factory can be greatly reduced. The elevating mechanism has a considerably quieter operation sound than the known elevating mechanism used in a vertical vacuum furnace. Further, by omitting the mechanical coupling device, the problem of misalignment caused by long-term use can be avoided. In addition, the control system according to the present invention can be programmed to realize an accurate lifting cycle and to prevent accidental damage to any lifting component by self-regulating the torque or lifting force generated by the drive mechanism. . In order to substantially avoid accidental damage to the lifting components, the driving force of the lifting mechanism is such that the torque or lifting force generated thereby is self-controlled.

  The terms and expressions used in this specification are merely used to describe the present invention, and do not limit the present invention in any way. The use of such terms and expressions is not intended to exclude any equivalents of the features and steps illustrated and described or portions thereof. Accordingly, it will be appreciated that various modifications can be made that fall within the scope and spirit of the invention. Therefore, the present invention includes modifications that belong to the above-described category of the invention.

Claims (12)

A vertical vacuum furnace assembly comprising:
A vacuum vessel (12) having an opening (28) at the lower end;
A bottom head assembly (30) sized to close the opening of the vacuum vessel and configured to support a workload;
A support structure comprising first and second support modules (16, 18), which are attached to support arms (40a to 40d) fixed to the vacuum vessel, arranged on opposite sides of the vacuum vessel, and assembled in advance; ,
A control system (90),
Each of the pre-assembled support modules
First and second struts (32a, 32b);
Fixing means (35) connected to the bottom of the first and second struts for securing the first and second struts to the surface;
A transverse beam (34) connecting the first and second struts spaced apart from each other, the transverse beam disposed above the fixing means by a first distance;
First and second guide channels (42a, 42b) formed longitudinally on opposing surfaces of the first and second struts between the fixing means and the cross beam;
An elevator mechanism (46),
The elevator mechanism (46)
An elevating carriage (52) having feet (86a, 86b) movably disposed in the first and second guide channels and configured to engage the bottom head assembly (30);
Elevating mechanism (50, 51, 60, 61) supported by a cross beam, fixed to the elevating carriage for raising or lowering the elevating carriage, electrically connected to the control system, and raising or lowering the elevating carriage And a vertical vacuum furnace assembly characterized by having an elevating mechanism operable to operate. The fixing means includes a floor board (35),
The lifting mechanism is
A threaded shaft (58) rotatably attached to the floorboard at one end;
A drive mechanism (51, 60) mounted on the transverse beam and connected to the other end of the threaded shaft;
The vertical vacuum furnace assembly according to claim 1, further comprising a conveying part (59) which is mounted on a threaded shaft so as to be movable up and down and connected to a lifting carriage.   The vertical vacuum furnace assembly according to claim 2, wherein the driving mechanism includes a gear box (60) mounted on the cross beam and a driving motor (51) connected to the gear box. The elevating carriage includes first and second side plates (70a, 70b) that are spaced apart from each other and arranged in parallel, and a horizontal beam (72) that connects them at the upper ends of the first and second side plates. And a lifting plate including a lateral plate (74) connecting them at the lower ends of the first and second side plates,
The vertical vacuum furnace assembly according to claim 2 or 3, wherein the lift carriage further comprises a fixed assembly (76) connected to the conveying part (59). The fixing assembly (76) has first and second lifting plates (80a, 80b) fixed to the horizontal plate of the lifting assembly at the lower end thereof, a bracket (78), first and second lifting plates, The vertical vacuum furnace assembly according to claim 4, further comprising first and second connecting parts (82a, 82d) pivotably connected to the bracket. The transverse plate has a first transverse plate component (74 ′) and a second transverse plate component (74 ″) which are spaced parallel to each other on either side of the fixed assembly (76). The vertical vacuum furnace assembly according to claim 4.   The bottom head assembly includes a circular steel plate (104), a flange (106) formed around the periphery of the steel plate, and first and second support beams (108) secured to the outer surface of the steel plate. 108b) and means for supporting a workload on the steel plate secured to the inner surface of the steel plate.   8. A vertical vacuum furnace assembly according to claim 7, wherein the bottom head assembly has cooling means (122, 124) for circulating a coolant along the inner surface of the steel plate.   The cooling means includes a channel for guiding the coolant along the inner surface of the steel plate therein, an inlet formed in the steel plate for allowing the coolant to be introduced into the channel, and for letting the coolant out of the channel. 9. The vertical vacuum furnace assembly according to claim 8, further comprising an outlet formed in the steel plate. The control system
A first sensor (96) connected to a drive motor provided in the first support module and generating an electrical signal indicating a vertical position of the lifting carriage (52) provided in the first support module;
A second sensor (96) connected to a drive motor provided in the second support module and generating an electrical signal indicating a vertical position of the elevating carriage (52) provided in the second support module;
Drive circuits (92, 94) connected to these drive motors and the first and second sensors;
A processor (100) connected to the drive circuit and receiving the position signal generated by the first and second sensors;
The processor is configured to receive an operation command and is programmed to generate a command signal in response to the position signal and the operation command and send the command signal to the drive circuit so that the drive motor can operate synchronously. The vertical vacuum furnace assembly according to claim 1, wherein the vertical vacuum furnace assembly is provided. The drive circuit of the control system is
A drive motor provided in the first support module, a first sensor, and a master drive circuit (92) connected to the programmable logic controller;
11. A vertical vacuum furnace assembly according to claim 10, comprising a drive motor provided in the second support module, a second sensor, and a follower drive circuit (94) connected to the programmable logic controller.   12. The vertical vacuum furnace assembly of claim 11, wherein the follower drive circuit is connected to the programmable logic controller via a master drive circuit.

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