Chip breaking turning device

Abstract

The invention discloses a chip breaking turning device, which comprises: a middle drag plate; a turning tool with an arc plate at the tail, and an inclined groove on the arc plate; the turning tool can rotate around the turning tool axis; a handle axis and a handle rotating around it; a pressure head; a lever rotatably arranged through a lever axis; a first roller rotatably arranged at the tail end of the lever; a second roller rotatably arranged at the head end of the lever; a connecting rod, the tail end of the lower part of which is connected to the first roller through a first connecting rod axis eccentrically arranged on the first roller, and the head end of the lower part of which is connected to the second roller through a second connecting rod axis eccentrically arranged on the second roller, and the upper part of the connecting rod is provided with a connecting rod slot; a turning tool slider, which can slide up and down in the height direction, and the turning tool slider has a first pin shaft and a second pin shaft, wherein the first pin shaft is inserted in the inclined groove, and the second pin shaft is inserted in the connecting rod slot. The chip breaking turning device converts the rotational motion of the workpiece into the reciprocating swing of the turning tool, thereby achieving the purpose of chip breaking.

Description

Technical Field

[0001] The invention relates to a mechanical processing device, in particular to a turning device. Background Art

[0002] Turning is a common machining method.

[0003] In the turning process of many parts, such as the turning process of automobile engine crankshafts, the turning process will produce continuous strip chips, which are easily entangled on the crankshaft processing surface, which often causes damage to the blade. In addition, the long iron chips entangled on the crankshaft will also cause the inductor of the subsequent induction hardening process to short-circuit and catch fire, causing major production safety problems. In addition, the long chips will also entangle the chip chain of the machine tool, causing the chip chain to get stuck and damaged.

[0004] In the prior art, the following solutions are usually adopted to solve this problem:

[0005] One is to change the workpiece material to increase hardness and reduce plasticity. However, the workpiece material cannot be changed in all situations. In addition, changing the workpiece material will also affect the mechanical properties of the workpiece and the structural performance of the product design.

[0006] Another method is to change the cutting parameters, for example, using low cutting speed and high feed rate to increase chip deformation to reach the fracture strain. However, this method will increase the cutting force and cause excessive wear on the machine tool feed system. In addition, this method is complicated to operate and has poor adaptability to different machine models.

[0007] Another method is to change the blade form, reduce the rake angle, aggravate chip deformation, and increase the width of the chip breaker. This method will lead to a decrease in blade cutting performance and shorten tool life.

[0008] Based on this, it is desired to provide a simple and feasible solution, which can achieve the purpose of chip breaking without changing the cutting edge of the tool. Summary of the invention

[0009] The object of the present invention is to provide a chip breaking turning device which can realize the swing of the turning tool by using the rotational motion of the workpiece as a power source without changing the cutting edge of the tool, thereby achieving the purpose of chip breaking.

[0010] In order to achieve the above object, the present invention proposes a chip breaking turning device, which comprises:

[0011] A middle carriage, which is provided as a base of a chip breaking and turning device;

[0012] The turning tool has a tool head for turning a workpiece at its head, and an arc-shaped plate is provided at the tail of the turning tool, and an inclined groove extending in both the width direction and the height direction of the middle carriage is provided on the arc-shaped plate; the turning tool can rotate around the turning tool axis;

[0013] A handle assembly, which is arranged on the middle drag board, the handle assembly comprises a handle and a handle shaft, and the handle can rotate around the handle shaft;

[0014] A pressure head assembly connected to the handle, the pressure head assembly can slide along the length direction of the middle drag plate, and the pressure head assembly includes a pressure head;

[0015] A lever is rotatably arranged through a lever shaft, the length direction of the lever is consistent with the length direction of the middle drag plate, the lever is arranged below the pressure head, and the part of the lever below the pressure head has an inclined portion;

[0016] A first roller, which is rotatably disposed at the tail end of the lever via a first roller shaft;

[0017] a second roller, which is rotatably disposed at the head end of the lever via a second roller shaft;

[0018] A connecting rod, the tail end of which is connected to the first roller via a first connecting rod shaft eccentrically arranged on the first roller, and the head end of which is connected to the second roller via a second connecting rod shaft eccentrically arranged on the second roller, and a connecting rod sliding groove is arranged on the upper part of the connecting rod;

[0019] A turning tool slider, which can slide up and down in the height direction along the vertically arranged guide rod, the turning tool slider having a first pin shaft and a second pin shaft, wherein the first pin shaft is inserted in the inclined groove, and the second pin shaft is inserted in the connecting rod sliding groove;

[0020] The rotation of the handle around the handle axis drives the pressure head to slide along the length direction of the chip breaking and turning device. The pressure head pushes the lever through the inclined portion, so that the tail end of the lever is lifted upward to make the first roller contact the workpiece. The rotation of the workpiece is converted into reciprocating motion of the tool slider in the height direction through the first roller, the connecting rod and the second roller, and then converted into reciprocating swing of the tool with the tool shaft as the rotation axis through the arc plate.

[0021] Furthermore, in the chip breaking turning device of the present invention, the handle is provided with a first handle groove; the handle assembly further comprises:

[0022] A locking slider seat, which is arranged on the middle carriage;

[0023] A locking slider is slidably connected to the locking slider seat, and the locking slider can slide along the locking slider seat in the width direction of the middle drag plate; a locking slider pin is provided on the locking slider, and is inserted into the first handle groove; the head of the locking slider is fork-shaped;

[0024] The rotation of the handle around the handle shaft drives the locking slider to slide in the width direction of the middle slide to a locking position or an unlocking position, wherein at the locking position, the locking slider prevents the turning tool from swinging back and forth.

[0025] Furthermore, in the chip breaking turning device of the present invention, the handle is provided with a second handle groove; the middle carriage is also provided with a guide rail extending along its length direction; the pressure head assembly further includes:

[0026] A pressure head slider is slidably connected to the guide rail, and a pressure head slider pin is provided on the pressure head slider and inserted into the second handle groove;

[0027] A spring seat, which is arranged on the pressure head slider;

[0028] The pressing head is arranged on a spring seat; a spring is arranged on the outer sleeve of the shaft portion of the pressing head, and the spring applies elastic force to the pressing head in the height direction.

[0029] Furthermore, in the chip breaking turning device described in the present invention, a lever sleeve is also provided on the lever shaft.

[0030] In this embodiment, the lever sleeve is used to limit the axial position of the lever.

[0031] Furthermore, the chip breaking turning device described in the present invention also includes: a small carriage, which is slidably connected to the guide rail to slide along the length direction of the middle carriage, and the turning tool shaft and the guide rod are both arranged on the small carriage.

[0032] Furthermore, in the chip breaking turning device described in the present invention, a turning tool support column is also provided on the small carriage, which vertically supports the turning tool.

[0033] Furthermore, the chip breaking turning device of the present invention further comprises:

[0034] A joystick, which is rotatably arranged on the middle carriage via a joystick rotating shaft, and a joystick slot is provided on the joystick;

[0035] The small carriage connecting pin is inserted into the operating rod slot and the connecting pin hole on the small carriage.

[0036] In this embodiment, the rotation of the joystick around the joystick shaft can drive the small carriage to move in the length direction of the middle carriage, thereby realizing the advance and retreat of the turning tool.

[0037] Furthermore, the chip breaking turning device of the present invention further comprises:

[0038] A small carriage limiting pin extending from the small carriage in a width direction;

[0039] The small carriage limit stopper is arranged on the middle carriage and cooperates with the small carriage limit pin to limit the displacement of the small carriage in the length direction.

[0040] The chip breaking turning device of the present invention can use the rotational motion of the workpiece as a power source without changing the tool blade structure and the workpiece material, and achieves the purpose of chip breaking by converting the rotation of the workpiece into the swing of the turning tool.

[0041] The chip breaking turning device of the present invention has an ingenious design, is simple to manufacture and maintain, has good reliability, is easy to use and operate, and effectively solves the chip breaking problem of plastic materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in the present invention is shown at a viewing angle in one embodiment.

[0043] Figure 2 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in the present invention is shown in another perspective under one embodiment.

[0044] Figure 3 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in an embodiment of the present invention is shown from another viewing angle.

[0045] Figure 4 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in the present invention is shown from a bottom perspective in one embodiment.

[0046] Figure 5 A top view of a chip breaking turning device according to the present invention is shown in one embodiment.

[0047] Figure 6 for Figure 5 Cross-sectional view at BB.

[0048] Figure 7 for Figure 6 Cross-sectional view at CC.

[0049] Figure 8 A schematic structural diagram of the chip breaking turning device of the present invention in one embodiment is shown in a coordinate system.

[0050] Fig. 9 The figure shows the state of the lower pressure head pushing the lever of the chip breaking turning device according to one embodiment of the present invention.

[0051] Fig.10 for Fig. 9 Enlarged view of point I in the middle.

[0052] Fig.11 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in one embodiment of the present invention is shown from another viewing angle. DETAILED DESCRIPTION

[0053] The chip breaking turning device of the present invention will be further explained and illustrated below in conjunction with the accompanying drawings and specific embodiments of the specification. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0054] Figure 1 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in the present invention is shown at a viewing angle in one embodiment.

[0055] like Figure 1 As shown, the chip breaking turning device of the present invention converts the rotation of the workpiece 7 into the reciprocating swing of the turning tool during the turning process of the workpiece 7 to achieve chip breaking.

[0056] Figure 2 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in the present invention is shown in another perspective under one embodiment.

[0057] Figure 3 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in an embodiment of the present invention is shown from another viewing angle.

[0058] Figure 4 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in the present invention is shown from a bottom perspective in one embodiment.

[0059] like Figure 2 , Figure 3 and Figure 4 As shown, in one embodiment, in one embodiment of the present invention, the chip breaking turning device includes:

[0060] The middle carriage 2 is fixed on the saddle of the lathe and serves as the base of the chip breaking and turning device. The head of the turning tool 8 has a tool head for turning the workpiece 7, and the workpiece 7 is clamped by the lathe chuck. The hole in the middle of the turning tool 8 is clearance-matched with the turning tool shaft 15. The nut is connected to the turning tool shaft 15 through a thread pair, and the end face of the nut is in contact with the end face of the turning tool shaft 15. A gap is left between the end face of the nut and the end face of the turning tool 8 so that the turning tool 8 can rotate around the turning tool shaft 15. An arc plate 9 is provided at the tail of the turning tool 8, and an inclined groove 91 (such as ) extending in the width direction and the height direction of the middle carriage is provided on the arc plate 9. Figure 8 shown).

[0061] The handle assembly is arranged on the middle carriage 2, and includes a handle 3 and a handle shaft 4. The hole in the middle of the handle 3 is in clearance with the handle shaft 4, and a nut 33 (such as Figure 8 The nut 33 is connected to one end of the handle shaft 4 by a thread, and the end face of the nut 33 contacts the step of the handle shaft. There is a gap between the end face of the handle 3 and the nut 33 so that the handle 3 can rotate around the handle shaft 4.

[0062] The pressure head assembly includes a pressure head 24 , and the pressure head assembly is connected to the handle 3 so that the pressure head assembly can be driven to slide along the length direction of the middle drag plate when the handle 3 is rotated.

[0063] The lever 26 is rotatably arranged via a lever shaft 27 , the length direction of the lever 26 is consistent with the length direction of the middle drag plate 2 , the lever 26 is arranged below the pressure head 24 , and the portion of the lever 26 below the pressure head 24 has an inclined portion.

[0064] like Figure 7 As shown, the lever shaft 27 is inserted into two lug holes at the bottom of the middle carriage 2 , that is, the lever 26 is rotatably arranged on the middle carriage 2 via the lever shaft 27 .

[0065] In some embodiments, Figure 4 As shown, a lever sleeve 28 is also provided on the lever shaft 27 for axially limiting the lever.

[0066] Figure 5 A top view of a chip breaking turning device according to the present invention is shown in one embodiment. Figure 6 for Figure 5 Cross-sectional view at BB in the middle.

[0067] like Figure 5 and Figure 6 As shown, the chip breaking turning device further comprises: a first roller 13 is rotatably disposed at the tail end of a lever 26 via a first roller shaft, and the first roller 13 contacts the workpiece 7. A second roller 20 is rotatably disposed at the head end of the lever 26 via a second roller shaft.

[0068] The connecting rod 12 is L-shaped, and the tail end of the lower horizontal rod is connected to the first roller 13 through a first connecting rod shaft 121 eccentrically arranged on the first roller, and the head end of the lower part is connected to the second roller 20 through a second connecting rod shaft 122 eccentrically arranged on the second roller. The tail end and the head end of the connecting rod 12 are both matched with the first connecting rod shaft and the second connecting rod shaft by the shaft hole clearance, so that they can rotate relatively. A connecting rod slide groove is provided on the upper part of the connecting rod 12.

[0069] The tool slide block 11 can slide up and down in the height direction along the vertically arranged guide rod 10. Fig.11As shown, the turning tool slider has a first pin shaft 111 and a second pin shaft 112, wherein the first pin shaft 111 is inserted into the inclined groove of the arc plate, and the second pin shaft 112 is inserted into the connecting rod sliding groove.

[0070] This means that the handle 3 rotates around the handle shaft 4, driving the pressure head 24 to slide along the length direction of the chip breaking and turning device. During the sliding process, the pressure head 24 will push the lever through the inclined portion of the lever 26, so that the tail end of the lever 26 is lifted upward to allow the first roller 13 to contact the workpiece 7. In this case, the rotation of the workpiece 7 will drive the first roller 13 to rotate through the friction force, and then be converted into a reciprocating motion of the tool slide 11 along the guide rod 10 in the height direction through the connecting rod 12 and the second roller 20, and then be converted into a reciprocating swing of the tool 8 with the tool shaft 15 as the rotation axis through the arc plate 9.

[0071] like Figure 2 As shown, in some embodiments of the present invention, the chip breaking turning device also includes: a locking slider seat 5 fixedly arranged on the middle slide plate 2, a locking slider 6 is slidably connected to the locking slider seat 5 through a guide rail pair, the head of the locking slider 6 is fork-shaped, and the locking slider 6 can slide along the locking slider seat 5 in the width direction of the middle slide plate, and a locking slider pin is provided on the locking slider 6, which is inserted into the first handle groove 31 set on the handle 3 and can slide along the first handle groove 31.

[0072] In this way, when the handle 3 rotates around the handle shaft 4, the locking slider 6 is driven to slide along the locking slider seat 5 in the width direction of the middle carriage. When sliding to the locking position, the fork shape of the head prevents the turning tool 8 from swinging repeatedly. When sliding in the opposite direction to the unlocking position, the turning tool is unlocked and can swing back and forth.

[0073] like Figure 2 and Figure 3 As shown, in some embodiments of the present invention, the chip breaking turning device further includes: a guide rail 1 arranged on the middle carriage 2 and extending along the length direction thereof, a pressure head slider 21 being slidably connected to the guide rail 1, and a pressure head slider pin 211 (such as Figure 8 As shown in the figure, it is inserted into the second handle groove 32 of the handle 3 and can slide along the second handle groove 32. The spring seat 22 is arranged on the pressure head slider 21, and the pressure head 24 is arranged on the spring seat 22. The shaft of the pressure head 24 is covered with a spring 23, and the two ends of the spring 23 respectively abut against the step surface of the pressure head 24 and the spring seat 22 to apply elastic force to the pressure head 24 in the height direction. The pressure head nut 25 is threadedly fastened to the upper end of the pressure head 24.

[0074] like Figure 3As shown, in some embodiments, the chip breaking turning device of the present invention further includes: a small carriage 14, which is slidably connected to the guide rail 1 to slide along the length direction of the middle carriage, and the turning tool shaft 15 and the guide rod 10 are both arranged on the small carriage 14. The small carriage 14 is also provided with a turning tool support column 19, which contacts the end surface of the arc plate 9 to vertically support the turning tool 8.

[0075] Continue reading Figure 3 In some embodiments, the chip breaking turning device of the present invention further comprises:

[0076] The joystick 18 is rotatably arranged on the middle carriage 2 through the joystick shaft 16, and a joystick groove is arranged on the joystick 18; the small carriage connecting pin 17 is inserted in the joystick groove and can slide along the joystick groove, and the small carriage connecting pin 17 is also inserted in the connecting pin hole on the small carriage 14, so as to realize the linkage between the small carriage 14 and the joystick 18.

[0077] In this embodiment, the rotation of the joystick 18 around the joystick shaft 16 can drive the small carriage 14 to move in the length direction of the middle carriage 2, thereby realizing the advance and retreat of the turning tool 8.

[0078] Fig.11 A schematic diagram of the three-dimensional structure of the chip breaking and turning device described in one embodiment of the present invention is shown from another viewing angle.

[0079] like Figure 3 and Fig.11 As shown, in some embodiments, the chip breaking turning device also includes: a small slide plate limit pin 30, which extends from the small slide plate 14 in the width direction; a small slide plate limit block 29, which is arranged on the middle slide plate 2 and cooperates with the small slide plate limit pin 30 to limit the displacement of the small slide plate 14 in the length direction.

[0080] Figure 8 A schematic structural diagram of the chip breaking turning device of the present invention in one embodiment is shown in a coordinate system.

[0081] like Figure 8 As shown, in some embodiments, the chip breaking and turning device is in operation:

[0082] First, the handle 3 is moved along the positive x direction, so that the handle 3 rotates counterclockwise around the handle axis 4 along the Z axis.

[0083] The first handle groove 31 on the handle 3 enables the locking slider 6 to move in the negative direction of the X-axis through the locking slider pin, so that the locking slider 6 is disengaged from the turning tool 8, thereby unlocking the turning tool 8.

[0084] At the same time, the second handle groove 32 on the handle 3 causes the pressure head slider 21 to move along the negative Y direction. In this case, Fig. 9 and Fig.10 As shown, the pressing head 24 performs a pressing action P on the lever 26 along the inclined surface of the lever 26 to overcome the elastic force of the spring 23, so that the tail end of the lever 26 with the first roller 13 is lifted toward the positive direction of the Z axis, so that the first roller 13 contacts the workpiece 7.

[0085] As a result, the rotational movement of the workpiece 7 is transmitted to the second roller 20 via the connecting rod 12 by friction force.

[0086] The second pin shaft 112 of the turning tool slide block 11 cooperates with the connecting rod sliding groove of the connecting rod 12, so that the turning tool slide block 11 slides reciprocatingly up and down along the Z axis along the guide rod 10.

[0087] The first pin shaft 111 of the turning tool slider 11 cooperates with the inclined groove 91 on the arc plate 9 to convert the reciprocating up and down sliding of the turning tool slider 11 along the Z axis into reciprocating rotational motion of the turning tool around the turning tool shaft 15 around the z axis, that is, swinging, thereby achieving the purpose of chip breaking through the reciprocating swinging of the turning tool 8.

[0088] When the handle 3 is moved along the negative x direction, the locking slider 6 slides toward the turning tool 8, the pressure head slider 21 moves along the positive y direction, the pressure head 24 disengages from the inclined portion of the lever 26, and the turning tool is locked. At this time, the turning tool no longer swings back and forth for chip breaking.

[0089] Move the joystick 18 along the negative x direction, the small carriage 14 can slide along the guide rail through the small support plate connecting pin 17, so as to realize the lathe tool feed. The lathe tool feed limit is realized by the small support plate limit block 29 and the small support plate limit pin 30.

[0090] By moving the operating lever 18 in the x direction, the small carriage 14 can slide along the guide rail through the small support plate connecting pin 17, so that the turning tool can be retracted.

[0091] It can be seen that the chip breaking turning device of the present invention uses the rotational motion of the workpiece as a power source, and achieves the purpose of chip breaking by converting the rotation of the workpiece into the reciprocating swing of the turning tool. The chip breaking turning device of the present invention is ingenious in conception, simple in manufacturing and maintenance, good in reliability, easy in use and operation, and effectively solves the chip breaking problem of plastic materials.

[0092] The combination of the various technical features in this case is not limited to the combination described in the claims of this case or the combination described in the specific embodiments. All technical features recorded in this case can be freely combined or combined in any way unless there is a contradiction between them.

[0093] It should also be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with by those skilled in the art from the contents disclosed in the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A chip breaking turning device, characterized in that: include: A middle carriage, which is provided as a base of the chip breaking and turning device; the middle carriage is also provided with a guide rail extending along its length direction; A turning tool, the head of which has a tool head for turning a workpiece, the tail of the turning tool is provided with an arc plate, the arc plate is provided with an oblique groove extending in both the width direction and the height direction of the middle carriage; the turning tool can rotate around the turning tool axis; A handle assembly, which is arranged on the middle carriage, and the handle assembly comprises: a handle, wherein the handle is provided with a first handle groove and a second handle groove; a handle shaft, and the handle can rotate around the handle shaft; a locking slider seat, which is arranged on the middle carriage; a locking slider, which is slidably connected with the locking slider seat, and the locking slider can slide along the locking slider seat in the width direction of the middle carriage; a locking slider pin is provided on the locking slider, which is inserted into the first handle groove; the head of the locking slider is fork-shaped; wherein the rotation of the handle around the handle shaft drives the locking slider to slide in the width direction of the middle carriage to a locking position or an unlocking position, wherein in the locking position, the locking slider prevents the turning tool from reciprocatingly swinging; A pressure head assembly is connected to the handle, and the pressure head assembly can slide along the length direction of the middle drag plate. The pressure head assembly includes: a pressure head; a pressure head slider, which is slidably connected to the guide rail, and a pressure head slider pin is provided on the pressure head slider, which is inserted into the second handle groove; a spring seat, which is provided on the pressure head slider; the pressure head is arranged on the spring seat; a spring is provided on the outer sleeve of the shaft of the pressure head, and the spring applies elastic force to the pressure head in the height direction; A lever is rotatably arranged through a lever shaft, the length direction of the lever is consistent with the length direction of the middle drag plate, the lever is arranged below the pressure head, and the part of the lever below the pressure head has an inclined portion; A first roller, which is rotatably disposed at the tail end of the lever via a first roller shaft; a second roller, which is rotatably disposed at the head end of the lever via a second roller shaft; A connecting rod, the tail end of which is connected to the first roller via a first connecting rod shaft eccentrically arranged on the first roller, and the head end of which is connected to the second roller via a second connecting rod shaft eccentrically arranged on the second roller, and a connecting rod sliding groove is arranged on the upper part of the connecting rod; A turning tool slider, which can slide up and down in the height direction along the vertically arranged guide rod, the turning tool slider having a first pin shaft and a second pin shaft, wherein the first pin shaft is inserted in the inclined groove, and the second pin shaft is inserted in the connecting rod sliding groove; The rotation of the handle around the handle axis drives the pressure head to slide along the length direction of the chip breaking and turning device. The pressure head pushes the lever through the inclined portion, so that the tail end of the lever is lifted upward to make the first roller contact the workpiece. The rotation of the workpiece is converted into reciprocating motion of the tool slider in the height direction through the first roller, the connecting rod and the second roller, and then converted into reciprocating swing of the tool with the tool shaft as the rotation axis through the arc plate.

2. The chip breaking turning device according to claim 1, characterized in that: A lever shaft sleeve is also provided on the lever shaft.

3. The chip breaking turning device according to claim 1, characterized in that: The chip breaking turning device also includes: a small carriage, which is slidably connected to the guide rail so as to slide along the length direction of the middle carriage, and the turning tool shaft and the guide rod are both arranged on the small carriage.

4. The chip breaking turning device according to claim 3, characterized in that: The small carriage is also provided with a turning tool support column, which vertically supports the turning tool.

5. The chip breaking turning device according to claim 3 or 4, characterized in that: Also includes: A joystick, which is rotatably arranged on the middle carriage via a joystick rotating shaft, and a joystick slot is provided on the joystick; The small carriage connecting pin is inserted into the operating rod slot and the connecting pin hole on the small carriage.

6. The chip breaking turning device according to claim 3 or 4, characterized in that: Also includes: A small carriage limiting pin extending from the small carriage in a width direction; The small carriage limit stopper is arranged on the middle carriage and cooperates with the small carriage limit pin.

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