Servo-driven workpiece supporting device

Abstract

The invention relates to a servo-driven workpiece supporting device which is provided with a double-output worm and gear mechanism, an upper supporting mechanism and a lower supporting mechanism, the upper supporting mechanism is provided with an upper supporting screw mechanism, and the front end of an upper supporting guide sleeve of the upper supporting screw mechanism is connected with an upper supporting block used for laterally supporting a workpiece. The lower supporting mechanism comprises a lower supporting screw mechanism and a lower supporting lever mechanism, the middle of a lower supporting seat of the lower supporting lever mechanism is rotationally connected to the rack, and the rear end of the lower supporting seat of the lower supporting lever mechanism is in transmission connection with a lower supporting guide sleeve of the lower supporting screw mechanism; and a lower supporting block for supporting the lower part of the workpiece is arranged at the front end. Synchronous automatic adjustment of the upper supporting block and the lower supporting block can be achieved, and the supporting device is suitable for supporting workpieces, especially long and thin workpieces, of machining equipment such as a numerical control grinding machine.

Description

TECHNICAL FIELD

[0001] The present application relates to a servo-driven workpiece holding device, which is suitable for the holding of workpieces during the machining process of a machine tool such as a numerical control grinding machine, in particular the holding of elongated workpieces, and belongs to the technical field of machining. BACKGROUND

[0002] In the process of machining elongated rod parts, the existing machining equipment, especially numerical control grinding machines, mostly use manually adjusted holding devices, which cannot be adjusted during the grinding process, affecting the machining accuracy. In addition, some equipment uses a three-point centering device driven by hydraulic pressure to lock the workpiece, but since the three-point holding position of the workpiece contacted by the three-point centering device driven by hydraulic pressure uses hard and wear-resistant materials such as hard alloy, the holding position of the workpiece will have grinding marks during the rotation of the workpiece, which are difficult to eliminate. SUMMARY

[0003] The purpose of the present application is to provide a servo-driven workpiece holding device to realize the holding of workpieces during the machining process under the cooperation of a control system.

[0004] The technical solution of the present application is: a servo-driven workpiece holding device, which is provided with a double-output worm gear mechanism, an upper holding mechanism and a lower holding mechanism. The double-output worm gear mechanism is provided with a vertical worm shaft and an upper gear (also referred to as a worm wheel) and a lower gear meshing with the worm shaft. The upper holding mechanism is provided with an upper support screw mechanism, which includes a longitudinal upper support screw shaft and an upper support guide sleeve threadedly connected with the upper support screw shaft. The front end of the upper support guide sleeve is connected with an upper support block for lateral holding of the workpiece. The upper gear is in transmission connection (for example, coaxial connection through a shaft coupling) with the rear end of the upper support screw shaft. The lower holding mechanism includes a lower support screw mechanism and a lower support lever mechanism. The lower support screw mechanism includes a longitudinal lower support screw shaft and a lower support guide sleeve threadedly connected with the lower support screw shaft. The lower support lever mechanism includes a lower support base (which can be regarded as a lever). The middle part of the lower support base is rotationally connected (for example, connected through a rotating shaft and a bearing for mounting the rotating shaft, the specific position of the rotating shaft being determined according to actual needs) to a machine frame (a fixed member). The lower support base is arranged obliquely with the front end higher than the rear end. The rear end (or lower end) of the lower support base is in transmission connection with the lower support guide sleeve, and the front end (or upper end) of the lower support base is provided with a lower support block for holding below the workpiece. By reasonably setting the sizes and transmission ratios of the parts of the upper holding mechanism and the lower holding mechanism, the longitudinal movement distance of the upper support block and the vertical movement distance of the lower support block in the working process can meet the required proportional requirements. For example, in the process of grinding the lateral surface (peripheral surface) of the workpiece using a numerical control grinding machine, the longitudinal movement distance of the upper support block and the vertical movement distance of the lower support block can be made the same (within the allowable range of difference), so as to adapt to the change in diameter of the workpiece during the grinding process.

[0005] The double-output worm gear mechanism (worm shaft and gear shafts) can be installed on the servo support seat of the frame through bearings.

[0006] The double-output worm gear mechanism can use a servo motor as a driving device. The servo motor is installed on the servo support seat, and its output (for example, the output shaft of the servo motor reducer) drives and connects (for example, coaxially connects through a shaft coupling) the upper end of the worm shaft to drive the worm shaft to rotate.

[0007] Preferably, the number of teeth of the upper gear and the lower gear can be the same or different to achieve the same or different rotational speed between the upper gear and the lower gear. According to actual needs or specific design, it can be used as one of the means to adjust the ratio between the longitudinal movement distance of the upper support seat and the vertical movement distance of the lower support seat.

[0008] Preferably, the pitch of the upper support screw mechanism and the lower support screw mechanism can be the same or different. According to actual needs or specific design, it can be used as one of the means to adjust the ratio between the longitudinal movement distance of the upper support seat and the vertical movement distance of the lower support seat.

[0009] Preferably, the upper support fixed sleeve is fixedly installed on the frame (for example, fixed to the side plates on both sides through brackets or connecting pieces), the upper support guide sleeve is sleeved in the upper support fixed sleeve and is in sliding fit with the upper support fixed sleeve, and an upper support linear guide structure is arranged between the upper support fixed sleeve and the upper support guide sleeve to limit the upper support guide sleeve to be able to only linearly slide in the upper support fixed sleeve.

[0010] Preferably, the upper support seat is fixedly installed at the front end of the upper support guide sleeve; or the upper support seat is threadedly connected with the upper support guide sleeve through the upper support fine adjustment sleeve sleeved outside the upper support seat.

[0011] Preferably, the upper support block, at least the supporting surface (the surface directly contacting the workpiece) of the upper support block, adopts a material with a hardness suitable for supporting.

[0012] Preferably, the front end surface of the upper support block is a plane, constituting a side supporting surface contacting the workpiece.

[0013] According to actual needs, the edge portion (edge corners) of the front end surface of the upper support block can be rounded.

[0014] Preferably, the lower support fixed sleeve is fixedly installed on the frame (for example, fixed to the side plates on both sides through brackets or connecting pieces), the lower support guide sleeve is sleeved in the lower support fixed sleeve and is in sliding fit with the lower support fixed sleeve, and a lower support linear guide structure is arranged between the lower support fixed sleeve and the lower support guide sleeve to limit the lower support guide sleeve to be able to only linearly slide in the lower support fixed sleeve.

[0015] Preferably, the front end of the lower support guiding sleeve is fixedly provided with a top block, and the front end of the top block is a smooth curved surface (for example, a spherical cap surface) abutting against the rear end surface of the lower support base to push the lower support base to rotate. The rear end surface of the lower support base is preferably a plane, thereby allowing the front end of the top block to slide on the rear end surface of the lower support base. The lower support base (including the lower support block mounted on the lower support base) can rely on its own weight to have a rotating trend with the front end downward, so as to maintain the pressure contact between the rear end surface of the lower support base and the front end of the top block.

[0016] Preferably, the front arm (the part located on the front side of the rotating shaft) of the lower support base can be close to the horizontal state (the included angle between the horizontal plane is less than 45 degrees, for example, 5-30 degrees), so that the displacement (the displacement in the actual working process) of the lower support block is mainly vertical displacement; the rear arm (the part located on the rear side of the rotating shaft) of the lower support base can be close to the vertical state (the included angle between the vertical line is less than 45 degrees, for example, 5-30 degrees), so that the longitudinal movement of the top block is effectively converted into the rotation of the lower support base. By reasonably setting the position of the rotating shaft of the lower support base and the initial angle and length of the front arm, and setting the moving track of the upper support block (the supporting surface of the upper support block) to meet the supporting requirements. By reasonably setting the length and initial angle of the front and rear arms of the lower support base, and setting the relationship between the displacement of the front end and the rear end of the lower support base, according to the actual needs or specific design, it can be used as one of the means to adjust the proportion between the longitudinal movement distance of the upper support base and the vertical movement distance of the lower support base.

[0017] Preferably, the lower support block, at least the supporting surface of the lower support block, is made of a material with a hardness suitable for supporting.

[0018] Preferably, the front end surface of the lower support block is a plane, constituting the lower supporting surface in contact with the workpiece.

[0019] The beneficial effects of the present application are: due to the setting of the upper supporting mechanism and the lower supporting mechanism, the workpiece is supported from the horizontal side and the lower side, and the workpiece is clamped together with the grinding wheel, so as to realize and maintain the centering, which is suitable for supporting various workpieces, especially long and thin workpieces; since the supporting blocks of each supporting mechanism abut against the surface of the workpiece, and the supporting blocks or their surface layers can be made of soft and wear-resistant materials, it is beneficial to avoid forming grinding marks on the surface of the workpiece; since the double-output worm gear mechanism is used to drive the upper and lower supporting mechanisms to move synchronously, and each part of the upper and lower supporting mechanisms can adopt appropriate size and transmission ratio, the upper supporting block and the lower supporting block move synchronously according to the set movement distance relationship (proportion) in the whole machining process, and are always kept in the appropriate supporting position, thereby meeting the supporting requirements of the workpiece from the lateral side and the lower side in the machining process, which is beneficial to simplify the mechanical structure, reduce the data acquisition and processing amount of the control system, and is beneficial to ensure the accuracy and reliability of the supporting. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a schematic diagram of the structure of the present application; Figure 2 is a schematic diagram of the structure of the present application; Figure 1 is a schematic diagram of the structure of the present application; Figure 3 is a schematic diagram of the structure of the present application; Figure 4 is a schematic diagram of the structure of the present application; Figure 3 is a schematic diagram of the structure of the present application; Figure 5 is a schematic diagram of the structure of the present application; Figure 6 is a schematic diagram of the structure of the present application;

[0021] Marked in the figure: 1, servo motor; 2, thrust bearing; 3, worm shaft; 4, self-lubricating bearing; 5, servo support seat; 6, upper gear; 7, lower gear; 8, support base; 9, upper support threaded screw; 10, upper support guide screw; 11, upper support guide sleeve; 12, upper support positioning snap spring; 13, upper support fine adjustment sleeve; 14, upper support seat; 15, upper support block; 16, lower support threaded screw; 17, lower support guide sleeve; 18, lower support guide screw; 19, lower support pin; 20, lower support seat; 21, lower support shaft; 22, lower support block. DETAILED DESCRIPTION

[0022] Referring to Figures 1 to 5 , the workpiece holding device mainly consists of a double-output worm gear mechanism, an upper holding mechanism (upper holding part) and a lower holding mechanism (lower holding part). The double-output worm gear mechanism is provided with two worm gear (or gear) outputs, which respectively drive the upper holding mechanism and the lower holding mechanism to act. Among them, the servo support seat 5 and the support base 8 are fixed as a whole by screws, together constituting the frame of the device. The shape of the support base is set according to the installation requirements of the related parts, and is provided with two side plates for installing the lower support shaft and other related parts. The servo motor 1 (motor seat) is fixed on the servo support seat 5 by screws. The worm shaft (or worm) 3 is vertically arranged and is rotatably installed on the servo support seat 5 through the thrust bearing 2 located at the upper part and the self-lubricating bearing 4 located at the lower part. The servo motor 1 can also be vertically arranged and coaxially connected with the driving worm shaft 3, which can drive the worm shaft 3 to rotate. The upper gear (or upper support worm gear) 6 located at the upper part and the lower gear (or lower support worm gear) 7 located at the lower part are all meshed with the worm shaft 3. When the worm shaft 3 rotates, it drives the upper gear 6 and the lower gear 7 to rotate at the same time. The rotation axes of the upper gear 6 and the lower gear 7 are both longitudinal (corresponding to the left-right direction in Figure 1 , which can be located on the same side of the worm shaft 3, , the rear end of the upper support threaded screw 9 (corresponding to the left-right direction in Figure 1The left end, or inner end, of the upper support guiding sleeve 11 is fixedly connected to the upper gear 6. When the upper gear 6 rotates, it drives the upper support threaded screw 9 to rotate. The front part of the upper support threaded screw 9 is threadedly connected to the upper support guiding sleeve 11. The upper support guiding sleeve 11 is sleeved on the upper support fixed sleeve and is in sliding fit with the upper support fixed sleeve. An upper support linear guiding structure is arranged between the upper support fixed sleeve and the upper support guiding sleeve 11. The upper support fixed sleeve is fixedly connected to the support base 8. The rear part of the upper support fixed sleeve can be connected to the upper support threaded screw 9 through a bearing to realize the rotary support of the upper support threaded screw. The upper support linear guiding structure includes the upper support guiding screw 10 which is threadedly connected to the upper support fixed sleeve and the upper support guiding straight slot (referred to as guiding slot) on the side of the upper support guiding sleeve 11 which cooperates with the upper support guiding screw 10. The upper support guiding screw 10 penetrates the side wall of the upper support fixed sleeve and extends into the upper support guiding straight slot and is in sliding fit with the upper support guiding straight slot. Thus, the upper support guiding screw 10 can limit the upper support guiding sleeve 11 from rotating. When the upper support threaded screw 9 rotates, the upper support guiding sleeve 11 moves longitudinally (advances or retreats) under the guidance of the corresponding linear guiding structure through the threaded transmission between the upper support threaded screw 9 and the upper support guiding sleeve 11.

[0023] The front end of the upper support guiding sleeve 11 is provided with the upper support seat 14. The upper support block 15 is fixedly installed at the front end of the upper support seat 14. The upper support block 15 can be a separate piece which is fixedly installed on the upper support seat 14 or can be integrated with the upper support seat 14 (prepared as one piece). The outer side of the upper support seat 14 is provided with the upper support fine adjustment sleeve 13. The upper support positioning snap spring 12 for fixing the upper support fine adjustment sleeve 13 on the upper support seat is arranged. When the upper support guiding sleeve 11 moves longitudinally, the upper support fine adjustment sleeve 13, the upper support seat 14 and the upper support block 15 advance or retreat integrally. The upper support fine adjustment sleeve 13 is threadedly connected to the front face of the upper support guiding sleeve 11, thereby realizing the threaded connection of the upper support seat 14 on the upper support guiding sleeve 11. In use, the longitudinal position of the upper support fine adjustment sleeve 13 can be adjusted according to actual needs to realize the fine adjustment of the position of the upper support block, so that the upper and lower support blocks of the holding device can simultaneously abut / hold the corresponding surfaces of the corresponding parts of the workpiece.

[0024] The rear end of the lower support threaded screw 16 is coaxially fixedly connected to the lower gear 7. When the lower gear 7 rotates, it drives the lower support threaded screw 16 to rotate together. The front part of the lower support threaded screw 16 is threadedly connected to the lower support guide sleeve 17. The lower support guide sleeve 17 is fitted inside the lower support fixed sleeve and slides with it. A lower support linear guide structure is provided between the two. The lower support fixed sleeve is fixedly connected to the support base 8. Its rear part can be connected to the lower support threaded screw 16 through a bearing to achieve rotational support for the lower support threaded screw. The lower support linear guide mechanism includes a threaded connection to the lower support fixed sleeve. The lower support guide screw 18 and the lower support guide sleeve 17 have a lower support guide groove (hereinafter referred to as guide groove) on their sides that mates with the lower support guide screw 18. The lower support guide screw 18 passes through the side wall of the lower support fixed sleeve, and its inner end extends into the lower support guide groove and slides with it. This allows the lower support guide screw 18 to restrict the lower support guide sleeve 17 from rotating. When the lower support threaded screw 16 rotates, it transmits power to the lower support guide sleeve 17 through the thread between the two. The lower support guide sleeve 17 moves longitudinally (forward or backward) under the guidance and restriction of the corresponding linear guide mechanism.

[0025] The lower support 20 is connected to the support base 8 via a lower support shaft 21. The lower support shaft 21 is mounted on the side plates of the support base 8 via bearings at both ends, thereby allowing the lower support 20 to swing / rotate around the axis of the lower support shaft 21. The lower support block 22 is fixed to the supporting end (or upper end, or front end) of the lower support 20 with screws, and its upper end face supports the workpiece below. When appropriate, the lower support block 15 and the upper support 14 can also be integrated (manufactured as a single part).

[0026] The front end of the lower support pin 19, used as a top block, abuts against the rear end of the lower support seat 20, thereby supporting the lower support seat 20 and keeping it stable. It can also rotate the lower support seat 20 around the axis of the lower support shaft 21 by pushing its rear end. The front end of the lower support pin 19 can be round (the head surface is a smooth convex curved surface). The rear end face of the lower support seat 20 that contacts the front end of the lower support pin can be flat and can have a certain inclination to facilitate the stability of the transmission between the lower support pin 19 and the lower support seat 20. The inclination of the rear end face of the lower support seat 20 can be determined by the movement trajectory of the front end of the lower support pin 19 and the movement trajectory of the rear end of the lower support seat 20. The tilt angle can also be set based on experience to adjust the tilt angle of the rear end face of the lower support seat 20, so that the two can transmit power effectively and stably during relative movement. The lower support pin 19 is threaded or fixedly connected to the front end of the lower support guide sleeve 17. When the lower support guide sleeve 17 moves forward, the lower support pin 19 pushes the lower support seat 20 to rotate around the lower support shaft 21. When the lower support pin 19 is connected to the front end of the lower support guide sleeve 17 by a threaded connection, the screw depth of the lower support pin 19 can be adjusted according to actual needs during assembly or use, thereby changing the posture of the lower support seat 20 and the position of the top surface (upper end face) of the lower support block 22.

[0027] The lower support block 22 can be fixedly installed at the front end of the lower support seat 20 by means of threaded connection, and the two are fixed as one, so that the lower support block 22 rotates together with the lower support seat 20 around the lower support shaft 21 under the drive of the lower support seat 20.

[0028] As mentioned above, the upper support portion is constrained to have only one degree of freedom in the forward and backward directions, and the lower support portion is constrained to have only one degree of freedom in rotation relative to the lower support base 20. The servo motor 1 synchronously drives the upper and lower support portions to move according to their respective motion modes via the worm shaft, so that the upper support block 15 and the lower support block 22 maintain their respective appropriate support (support) positions as the workpiece is being ground. Figure 5As shown, when the workpiece diameter changes, the lower support block (upper end face) 22 moves from point A to point B, the upper support block (front end face) 15 moves from point C to point D, and the lower support pin (top end) 19 moves from point E to point F. Let the movement distance from point E to point F be X, requiring the lower support threaded screw 16 to helically drive the lower support pin 19 to move a distance of X; let the movement distance from point C to point D be Y, requiring the upper support threaded screw 9 to helically drive the upper support block 15 to move a distance of Y. Since X and Y are not equal, the upper support threaded screw 9 and the lower support threaded screw 16 need to be set to two threaded screws with different pitches to ensure that the lower support portion moves a distance X and the side support portion moves a distance Y under the same rotation of the upper gear 6 and the lower gear 7. Alternatively, by adjusting the number of teeth on the upper gear 6 and the lower gear 7, and matching the different pitches of the upper support threaded screw 9 and the lower support threaded screw 16, a precise ratio of the X and Y movement distances can be achieved. The upper support threaded screw 9 and the lower support threaded screw 16 are two threaded screws with different pitches. By setting the ratio and coordinating it with the structural ratio of the lower support seat 20 relative to the front and rear (or up and down) sides of the lower support shaft, the upper support block 15 and the lower support block 22 can be simultaneously in contact with the workpiece support position throughout the entire processing under the driving action of the upper gear 6 and the lower gear 7.

[0029] The fine-tuning of the upper support section is achieved by connecting the upper support fine-tuning sleeve 13 and the upper support guide sleeve 11 via a threaded connection. The upper support fine-tuning sleeve 13 rotates within the upper support guide sleeve 11, allowing it to move forward or backward relative to the upper support guide sleeve 11. The upper support seat 14 and the upper support positioning snap ring 12 combine to constrain the upper support fine-tuning sleeve 13 onto the upper support seat 14. The upper support fine-tuning sleeve 13 can only rotate on the upper support seat 14. The upper support guide sleeve 11 has a guide groove, and the upper support seat 14 can only slide horizontally (longitudinally) under the linear guidance constraint of the upper support guide sleeve 11 (guide groove and guide screw). This ensures that the contact position between the upper support block 15 and the workpiece remains unchanged during the fine-tuning process of the upper support fine-tuning sleeve 13. Thus, by adjusting the rotation of the upper support fine-tuning sleeve 13 to push the upper support block 15, the upper support block 15 can be moved forward or backward.

[0030] The upper support base 14 and the upper support block 15 are connected by threads, which facilitates the replacement of the upper support block 15 after it has reached its limit. The lower support base 20 and the lower support block 22 are connected by threads, which facilitates the replacement of the lower support block 22 after it has reached its limit.

[0031] The thread distribution area of ​​each threaded component (a component with threads) can be set according to actual needs. For example, for the part of each guide screw (upper support guide screw and lower support guide screw) that extends into the guide groove, a smooth rod suitable for sliding fit with the guide groove wall should be used, and it is not necessary and should not have threads. Each threaded screw can also have external threads only at the part that fits with the thread of its corresponding guide sleeve.

[0032] This invention can be used in CNC grinding machines and other machining equipment to support workpieces, especially slender workpieces. Under the control of the machine tool control system, a servo motor drives the upper and lower support blocks to move in tandem, meeting the lateral and bottom support requirements of the workpiece during continuous grinding. The control system can be implemented based on the existing photoelectric sensing device and external diameter measuring device configured on the CNC grinding machine. If necessary, a separate matching photoelectric sensing device and diameter measuring device can also be configured. The photoelectric sensing device monitors the size of the grinding sparks during grinding and compares it in real time with the size range set by the diameter measuring device. By comparing the grinding diameter and the size of the grinding sparks, the system comprehensively judges the program feed or retraction amount and the stop feed time sequence, and sends the feed amount to the servo drive, realizing adjustable feed during the grinding process. After grinding, the machine returns to the initial position set by the servo.

[0033] Unless otherwise specified, the preferred and optional technical means disclosed in this invention can be arbitrarily combined to form several different specific embodiments when one preferred or optional technical means is a further limitation of another technical means.

Claims

1. A servo-driven workpiece holding device, characterized in that... The device is equipped with a dual-output worm gear mechanism, an upper support mechanism, and a lower support mechanism. The dual-output worm gear mechanism has a vertical worm shaft and an upper gear and a lower gear meshing with the worm shaft. The upper support mechanism has an upper support screw mechanism, which includes a longitudinal upper support screw shaft and an upper support guide sleeve threaded to the upper support screw shaft. The front end of the upper support guide sleeve is connected to an upper support block for lateral support of the workpiece. The upper gear is driven to the rear end of the upper support screw shaft. The lower support mechanism includes a lower support screw mechanism and a lower support lever mechanism. The lower support screw mechanism includes a longitudinal lower support screw shaft and a lower support guide sleeve threaded to the lower support screw shaft. The lower support lever mechanism includes a lower support seat, the middle of which is rotatably connected to the frame. The lower support seat is slanted with a higher front end and a lower rear end. Its rear end is driven to the lower support guide sleeve, and its front end has a lower support block for supporting the workpiece from below.

2. The workpiece holding device as described in claim 1, characterized in that... The upper gear and the lower gear may have the same or different number of teeth.

3. The workpiece holding device as described in claim 1, characterized in that... The pitches of the upper support screw mechanism and the lower support screw mechanism may be the same or different.

4. The workpiece holding device as described in any one of claims 1-3, characterized in that... An upper support fixed sleeve is fixedly installed on the frame, and an upper support guide sleeve is fitted inside the upper support fixed sleeve and slides with the upper support fixed sleeve. An upper support linear guide structure is provided between the upper support fixed sleeve and the upper support guide sleeve to limit the upper support guide sleeve to slide only in a straight line inside the upper support fixed sleeve.

5. The workpiece holding device as described in any one of claims 1-3, characterized in that... The upper support seat is fixedly installed at the front end of the upper support guide sleeve; or, the upper support seat is threadedly connected to the upper support guide sleeve through an upper support fine-tuning sleeve sleeved on its outer side.

6. The workpiece holding device as described in any one of claims 1-3, characterized in that... The front end face of the upper support block is flat.

7. The workpiece holding device as described in any one of claims 1-3, characterized in that... A lower support fixed sleeve is fixedly installed on the frame, and a lower support guide sleeve is fitted inside the lower support fixed sleeve and slides with the lower support fixed sleeve. A lower support linear guide structure is provided between the lower support fixed sleeve and the lower support guide sleeve to limit the lower support guide sleeve to slide only in a straight line inside the lower support fixed sleeve.

8. The workpiece holding device as described in claim 7, characterized in that... A top block is fixedly installed at the front end of the lower support guide sleeve. The front end of the top block is a smooth curved surface that abuts against the rear end face of the lower support seat. The rear end face of the lower support seat is a flat surface.

9. The workpiece holding device as described in any one of claims 1-3, characterized in that... The forearm of the lower support is nearly horizontal; the rear arm of the lower support is nearly vertical.

10. The workpiece holding device as described in any one of claims 1-3, characterized in that... The front end face of the lower support block is flat.

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