JP2014122719A - Workload lifting system for vertical vacuum furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lifting device for a vertical vacuum furnace capable of being reassembled and positioned on a customer site in short time.SOLUTION: A vertical vacuum furnace assembly 10 includes: first and second support modules 16 and 18 arranged to be distanced from each other and aligned in parallel; first and second reciprocating lifting mechanisms attached to the first and second support modules 16 and 18, respectively; and motive power means, coupled to the reciprocating lifting mechanisms, for driving the reciprocating lifting mechanisms, respectively. First and second trolleys are operatively connected to the first and second reciprocating lifting mechanisms, respectively so as to be engaged with payload. The vertical vacuum furnace assembly 10 also includes control systems 22 and 24, connected to the first and second motive power means, for enabling the first and second trolleys to reciprocate by controlling the first and second reciprocating lifting mechanisms connected to operate, respectively. In addition to the vertical vacuum furnace assembly 10 including the lifting device, the support modules and a bottom head assembly 30 are provided for the lifting device.

Description

  The present invention relates to a vacuum heat treatment furnace, and more particularly to a vertically oriented vacuum furnace and an apparatus for lifting a work load into and lowering a workload from the vacuum furnace. is there.

  Industrial vacuum heat treatment furnaces having a horizontal structure or a vertical structure are known. In a vacuum furnace having a horizontal structure, a work load of parts to be heat-treated is carried into the furnace chamber by a device that translates the one throughput part horizontally. In a vacuum furnace having a vertical structure, a lifting device is used to lift a throughput of parts from the factory floor to a higher furnace chamber.

  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 in synchronism so that a single throughput part is lifted uniformly. In order to keep these ball screws operating in synchronization with each other, a multi-gearbox and a connecting shaft with a coupling are used. The known structure of such lifts consists of a number of parts that must be assembled and aligned at the factory and then disassembled for transport. When the furnace arrives at the customer site, the lift device must be reassembled and realigned. This is a time consuming work and usually adds an extra number of days to the delivery time schedule.

  Gearboxes, drive shafts and couplings used in known lift mechanisms generate a significant amount of noise when operating to raise and lower a throughput amount of parts. The coupling that connects the drive shaft, the motor shaft, the gear box shaft, and the ball screw shaft becomes loose over time. When that happens, one or more ball screws will not synchronize with the other ball screws. Such asynchronous operation can cause catastrophic damage to the lifting mechanism. If the ball screw is extremely unsynchronized, the single throughput part itself, even the hot zone in the furnace, can be damaged.

  Known lift mechanisms for vertical vacuum furnaces have a lifting point that contacts the furnace bottom lifting structure via a coil spring. The lift mechanism operates to lift the bottom door toward the furnace until the mechanical limit switch is turned off, indicating that the lifting structure is in its fully lifted final position. In this final lifted position, the bottom lifting structure is in contact with the top of the furnace vessel so that the spring is compressed a small amount. If the mechanical switch is not properly adjusted, or if it is misadjusted, the spring can shrink too much and the lifting structure and door can be bent.

  In view of the above-mentioned problems associated with known lifting systems for vertical vacuum furnaces, it is desirable to ensure a lifting device for vertical vacuum furnaces that overcomes the problems associated with known lifting systems.

  A lifting system for lifting a throughput part in a vertical vacuum furnace according to the present invention has two ball screws, each of which is driven by a servo-type motor and has an encoder and / or resolver. The movements are synchronized with each other via an electrical servo drive system that uses position feedback. Each ball screw is constructed and arranged to raise and lower an elevator guided in the track. The elevator system along with the ball screw and motor is integrated into the leg structure of the vertical furnace. This leg / elevator / ball screw / motor combination is a modular assembly that remains intact for transport and installation at the end user site.

  Since there are no gearboxes, shafts or couplings, the movement of the lifting elevator is very quiet. A servo motor is directly connected to each ball screw. The servo drive system can be programmed to accelerate and decelerate the movement of the elevator near the traveling end of the elevator. This makes it possible to remove the spring between the lifting structure and the pickup point of the elevator. With the feedback of the encoder, the elevator is accurately positioned in the fully raised or fully lowered position.

  Another advantage of the lift system according to the invention is that the ball screw mounting point on the elevator mechanism has a connected linkage that allows a misalignment with little or no stress on the ball screw. It is that.

  The foregoing summary, as well as the following detailed description, will be clearly understood by reference to the accompanying drawings.

FIG. 1 is a perspective view of a vertical vacuum furnace assembly according to the present invention. FIG. 2 is a front view of the vertical vacuum furnace assembly shown in FIG. FIG. 3 is a perspective view of a leg assembly used in the vertical vacuum furnace assembly shown in FIG. FIG. 4 is a rear view of the leg assembly shown in FIG. FIG. 5 is a perspective view of a bottom head assembly used in the vertical vacuum furnace shown in FIG. FIG. 6 is a plan view of the bottom head assembly shown in FIG. FIG. 7 is a front view of the bottom head assembly shown in FIG. FIG. 8 is a front perspective view of an elevator trolley used in the leg assembly shown in FIG. 3. FIG. 9 is a rear perspective view of the elevator trolley shown in FIG. FIG. 10 is a perspective view of a ball screw jack used in the leg assembly shown in FIG. FIG. 11 is a front view of the ball screw jack shown in FIG. 12 is a block diagram of a servo motor control system used in the vertical vacuum furnace shown in FIG.

  Referring 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 orientation and is lifted with respect to the floor of the facility where the vacuum furnace is located. The vacuum furnace 10 has a pressure / vacuum vessel 12 and a vacuum pump 14. The pressure / vacuum vessel 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 close to the vacuum furnace 10.

  The pressure / vacuum vessel 12 has a body 26 with an opening 28 at the lower end. The pressure / vacuum vessel 12 also has a bottom head assembly 30 that is movable to close the opening 28 when the vacuum furnace is operated to heat treat a throughput metal part. The body 26 of the pressure / vacuum vessel 12 is attached to the leg assemblies 16, 18 by a plurality of support arms. The support arms 40a, 40b, 40c, and 40d are provided to attach the front portion of the pressure vessel body 26 to the front portions of the leg assemblies 16 and 18. A similar group of support arms (not shown) are provided to attach the rear portion of the pressure vessel body 26 to the rear portions of the leg assemblies 16,18.

  3 and 4, the construction of the leg assembly 16 is shown in more detail. Leg assembly 18 is constructed and arranged in substantially the same manner as leg assembly 16. Accordingly, only the leg assembly 16 will be described.

  The leg assembly 16 includes a pair of support columns 32a and 32b. The columns 32 a and 32 b are integrally connected to a cross beam 34 and a floor plate 35. The floor plate 35 is preferably attached to the lower part of the columns 32a and 32b 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 pressure vessel body. The elevator mechanism 46 includes a mechanical lifting device, preferably a ball screw jack 50, and a lifting trolley 52 operatively coupled to the lifting device. Guide channels 42a and 42b are formed or attached to the opposing surfaces of the columns 32a and 32b, respectively. Guide channels 42 a, 42 b provide a track for a lifting trolley that moves along the leg assembly 16. The ball screw jack 50 illustrated in more detail in FIG. 10 has a screw shaft 58 and a ball nut 59 according to a known configuration. A drive gear box 60 is connected to the screw shaft 58 at one end thereof. The drive gearbox 60 includes a motor attachment 61 for attaching the electric drive motor 51 to the gearbox. It will be appreciated by those skilled in the art that a machine-screw jack can be used in place of the ball screw jack shown in FIGS.

  8 and 9, the lifting trolley 52 includes a pair of L-shaped side plates 70a and 70b. The side plate is integrally connected to the upper cross beam 72 and the lower cross bar 74. In the illustrated embodiment, the lower cross bar 74 is composed of a pair of bars 74 ′ and 74 ″ spaced apart from each other in parallel. The upper cross beam 72 preferably has an opening 88 formed at an intermediate position between the side plates 70a and 70b. The opening 88 is dimensioned and aligned so that the screw shaft 58 of the ball screw jack 50 can pass therethrough. The lifting trolley 52 has a ball screw attachment assembly 76 for connecting the ball screw jack 50 to the trolley 52. Between the bars 74 ′ and 74 ″ of the lower cross bar 74, lift bars 80 a and 80 b are attached. A bracket 78 for connecting the ball screw jack 50 to the lifting trolley 52 is provided. As shown in the embodiment of FIGS. 8 and 9, the bracket 78 has a mounting plate 79 having a central opening 89 and a plurality of bolt holes. The central opening is dimensioned to allow the screw shaft 58 of the ball screw jack 50 to pass through the lifting trolley 52. The bolt hole is provided to attach the ball nut 59 of the ball screw jack 50 to the mounting bracket 78.

  The mounting bracket 78 is connected to the lift bars 80a and 80b by link bars 82a, 82b, 82c and 82d. The link bars 82a and 82b are pivotally connected between the lift bar 80a and the mounting bracket 78 by pivot pins 84a and 84b. The connection linkage provided by the link bar between the lift bar and the mounting bracket ensures that significant lateral stress is applied to the ball screw jack in the event of minor misalignment between the elevator trolley and the ball screw shaft. To prevent.

  Guide wheels or bearings 180a and 180b are provided on the outward face of the end plate 70a. Similarly, guide wheels 180c and 180d are provided on the outward face of the end plate 70b. The guide wheels 180a and 180b are attached to the end plate 70a in contact with the attachment pads 182a and 182b, respectively. Similarly, the guide wheels 180c and 180d are attached to the end plate 70b in contact with the attachment pads 182c and 182d, respectively. The guide wheels 180a-180d are sized and arranged to run snugly against the guide channels 42a, 42b of the leg assembly 16.

  The end plates 70a and 70b are formed in an L shape and have side portions 86a and 86b extending laterally. The feet 86a, 86b are constructed and arranged to engage a support structure for the pressure / vacuum vessel bottom head assembly, which 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 provide the advantage that they can be preassembled as a module before they are transported with the vacuum furnace. The ability to transport the leg assembly as a pre-assembled module significantly reduces the time required to transport the vacuum furnace and assemble the vacuum furnace at the user's facility. Furthermore, it is clear from the above that the required mechanical linkage does not exist between the lifting mechanisms for each leg assembly. Thus, the modular construction of the leg assemblies 16, 18 avoids the need for such linkage attachment and the need for proper alignment and realignment of the lifting mechanism and linkage required in known lift mechanisms. Is done. Omitting the multi-gearbox, drive shaft and coupling, which are usually part of the mechanical linkage between the lifting mechanisms, results in a fairly quiet operation.

  Referring now to FIGS. 5, 6 and 7, a preferred embodiment of the bottom head for the pressure / vacuum furnace 12 is shown. The bottom head assembly 102 has a substantially flat outer shape for making it compact. The bottom head 102 has a generally circular plate 104 that is dimensioned to close an opening formed in the bottom of the pressure vessel body. The plate 104 is preferably formed with a circumferential groove for receiving the seal ring 107. A flange 106 is formed around the circumference of the plate 104 and is dimensioned to be engaged with a corresponding mating flange around the opening 28 formed in the pressure / vacuum vessel body 26 and Has been placed. A flat bottom head structure is preferred when high gas quenching pressures, eg, gas pressures greater than about 2 bar, are not used in a vacuum furnace. Thus, if a gas quenching pressure greater than about 2 bar is used, a conventional dished or dome shaped bottom head must be used to meet pressure vessel standard requirements.

  A pair of support beams 108a, 108b are attached to the outside of the plate 104 and extend across the plate in parallel and spaced apart from each other. The support beams have portions that extend beyond the plate 104. More specifically, the support beam 108a has extended portions 110a and 110b, and the support beam 108b has extended portions 112a and 112b. The extending portions 110 a and 110 b are configured to engage with the feet 86 a and 86 b of the lifting trolley 52. Similarly, the extensions 112a, 112b are configured to engage corresponding feet of the lifting trolley associated with the leg assembly 18. As shown in FIG. 7, support legs 114 a and 114 b extend from the outside of the plate 104 in the vertical direction. A second pair of support legs is provided behind the support legs 114a, 114b and spaced from the support legs 114a, 114b, which are not shown in FIG. These support legs are constructed and arranged to provide rigidity to the plate 104 and support the bottom head assembly 102 when the bottom head assembly 102 is placed on the floor. These support legs also provide a sufficient height above the floor so that the lifting trolley can easily engage the extensions 110a, 110b, 112a, 112b of the support beams 108a, 108b. Dimensioned.

  A plurality of sockets or receptacles 118 are disposed and attached to the central region inside the plate 104. These receptacles 118 are dimensioned to extend vertically and receive struts that support furnace heart rails (see, for example, FIG. 1). A cover plate 122 is attached inside the plate 104 to cover the central area plate. The cover plate 122 is positioned on the spacer ring 124 fixed to the inner surface of the plate 104 and attached to the spacer ring 124. Cover plate 122 has an opening that allows receptacle 118 to extend therethrough. Preferably, the bottom head assembly 102 includes means for cooling the head assembly from the unusually high temperatures generated in the furnace during the heat treatment cycle. The cooling means is preferably realized by a combination of a spacer ring 124 and a cover plate 122 defining a closed space that functions as a coolant jacket. The coolant jacket preferably has channels (not shown) for directing a flow of coolant, such as water, across the inner surface of the plate 104. The channels are preferably arranged such that substantially the entire surface of the central region of the plate 104 can contact the coolant. Those skilled in the art will know that the channel arrangement is free of dead-flow spots or vortices that adversely affect the cooling of the bottom head assembly 102 to ensure that the plate 104 is sufficiently cooled. It can be designed easily. The cover plate separates the cooling channel from the interior of the vacuum furnace when the bottom head assembly 102 is in a closed position relative to the pressure / vacuum vessel body 26.

  Referring now to FIG. 12, a preferred arrangement for controlling the operation of the lift device according to the present invention is shown. The control system 90 interlocks the movement of the ball screw drive and synchronizes the operation of the lift motor so that the bottom head assembly can be raised and lowered at a level that avoids damage to the bottom head and / or lifting mechanism. By providing the means for making it, it is comprised so that the fail safe operation (failsafe operation) of a lift apparatus may be heeded. 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 connected to the drive shaft of the motor 50. Similarly, a lift motor 55 is connected to a follower servo drive circuit 94, and a resolver 98 is mechanically coupled to the drive shaft of the motor 55.

  The PLC 100 includes 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 output by the furnace operator. Yes. Operator commands can be entered into the PCL by typical means such as push buttons or by 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 its raised or lowered position. When the PLC determines the position of the bottom head assembly, the PLC sends an interlock signal to the servo drive circuit indicating that it can move. The master servo drive circuit 92 is connected to the PLC 100 to receive a command signal and send a first feedback signal to the PLC. The follower servo drive circuit 94 is connected to the master servo drive circuit 92 for receiving a command signal and providing a feedback signal to the PLC via the master servo drive circuit 92. The PLC is also programmed to monitor the feedback signals from the master servo drive circuit and the follower servo drive circuit and to provide the latest command signal to maintain the synchronism between the lift motors 50,55. The feedback signal may be indicative of 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 in order to transmit the first feedback signal to the master servo drive circuit 92. 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 to transmit a second feedback signal to the follower servo drive circuit 94. Preferably, the system includes a homing limit switch (not shown) connected to the lift controller. The homing limit switch is positioned to detect that the lifting mechanism is in a fully lowered position, so that the system signals the lift controller to set the system itself to zero for position indication. Operate.

  The servo drive control system of the present invention allows for the synchronous motion of the lifting mechanism for each leg assembly without the need for mechanical linkage including a multi-gearbox, shaft and coupling between the lifting mechanisms. Omitting such mechanical linkage results in a considerable reduction in the time required in the assembly of the vacuum furnace at the customer's facility. The lifting mechanism is much quieter in operation than known lifting mechanisms for vertical vacuum furnaces. Further, by omitting the mechanical linkage, the misalignment problem that is discouraged from long-term use is avoided. The control system according to the invention also relates to the torque or lifting force generated by the drive mechanism so as to ensure an accurate lifting cycle and avoid accidental damage to any of the elevator parts. Programmable to self-control. The drive for the lifting mechanism is self-regulated in relation to the torque or lifting force generated by the lifting mechanism to substantially avoid accidental damage to the elevator parts.

  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 or portions of the features or processes described above. Accordingly, it will be appreciated that various modifications can be made within the scope and spirit of the invention. Accordingly, the present invention includes modifications that fall within the scope of the invention described above.

Claims (10)

A pressure / vacuum vessel having an opening at the lower end;
A bottom head assembly dimensioned to close the opening of the pressure / vacuum vessel;
First and second support modules spaced apart and aligned in parallel to support the pressure / vacuum vessel in a vertical orientation;
First and second reciprocating lifting mechanisms attached to each of the first and second support modules;
First and second power means coupled to the first and second reciprocating lifting mechanisms for driving the reciprocating lifting mechanism;
First and second trolleys operatively connected to the first and second reciprocating lifting mechanisms and configured to engage the bottom head assembly;
A vertical system having a control system connected to the first and second power means and enabling the first and second trolleys to move up and down by controlling the operations of the first and second reciprocating lifting mechanisms. Type vacuum furnace assembly. First and second support legs spaced apart and aligned in parallel;
A reciprocating lifting mechanism attached between the first and second support legs;
A trolley operatively connected to the reciprocating lifting mechanism;
A support module for a vertical vacuum furnace, having power means connected to the reciprocating lifting mechanism to drive the reciprocating lifting mechanism.   The support module according to claim 2, wherein the power means is directly connected to the reciprocating lifting mechanism. A substantially circular steel plate;
A flange formed around the steel plate;
First and second lifting beams attached to the outer surface of the steel plate;
A bottom head assembly for a vertical vacuum furnace attached to the inner surface of the steel plate and having means for supporting a workload on the steel plate.   The bottom head assembly according to claim 3, further comprising a coolant jacket for circulating coolant along an inner surface of the steel plate. The coolant jacket is
A channel for inducing a coolant along the inner surface of the steel plate within the coolant jacket;
An inlet formed in the steel panel to allow coolant to flow into the channel;
6. The bottom head assembly of claim 5, having an outlet formed in the steel plate distally from the inlet to allow the coolant to flow out of the channel. A control system for operating a lifting device for a vertical vacuum furnace,
A first motor connected to the first reciprocating workload lifting device to drive the first reciprocating lifting device;
A first sensor connected to the first motor for generating an electrical signal indicating a longitudinal position of the first reciprocating workload lifting device;
A second motor connected to a second reciprocating workload lifting device to drive the second reciprocating lifting device;
A second sensor connected to the second motor for generating an electrical signal indicative of a longitudinal position of the second reciprocating workload lifting device;
A drive circuit connected to the first and second motors and the first and second sensors;
A processor connected to the drive circuit for receiving a position signal emitted by the first and second sensors;
The processor is configured to receive an operation command from an operator, generates a command signal in response to the position signal and the operation command, and sends the command signal to the drive circuit, thereby the first and second motors. Control system for operating a lifting device for a vertical vacuum furnace, programmed to operate in sync with each other. The drive circuit is
A master drive circuit connected to the first motor, the first sensor and a programmable logic controller;
The control system according to claim 7, further comprising a follower drive circuit connected to the second motor, the second sensor, and the programmable logic controller. First and second support modules spaced apart and aligned in parallel;
First and second reciprocating lifting mechanisms attached to each of the first and second support modules;
First and second power means connected to the first and second reciprocating lifting mechanisms for driving the first and second reciprocating lifting mechanisms;
First and second trolleys operatively connected to the first and second reciprocating lifting mechanisms and configured to engage a payload;
A control system connected to the first and second power means for controlling the operation of the first and second reciprocating lifting mechanisms to enable the first and second trolleys to move up and down; Lifting device for vertical vacuum furnace. Providing a payload that is moved longitudinally;
Engaging the payload with the first and second trolleys;
10. The method of lifting the payload with a lifting device according to claim 9, further comprising actuating the lifting device to move the payload longitudinally.

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