Rivet posture adjustment and conveying device

Abstract

The utility model discloses a rivet posture adjustment and conveying device, comprising a rivet selection section and a selected rivet A transfer transition section, wherein the rivet A selected by the rivet selection section is in the form of a rivet head A1 obliquely facing upward and a rivet rod A2 obliquely facing downward; the rivets A sequentially supplied by a barrel-shaped vibrating feeder arrive at the rivet selection section in forms of different postures, and only the rivet A with the rivet head A1 obliquely facing upward and the rivet rod A2 obliquely facing downward is selected and collected in the form of sequential arrangement, and the rivets A with other postures slide from the rivet selection section, and the selected rivets A arriving at the selected rivet A transfer transition section are gradually transformed into a vertical posture with the rivet head A1 obliquely facing upward and the rivet rod A2 obliquely facing downward under the constraint guidance of the rivet A transfer transition section, and continue to be conveyed downstream in this posture, thereby providing rivets with determined postures one by one for the riveting of a pot body and a handle.

Description

Technical Field

[0001] The utility model relates to a posture adjustment and conveying scheme of rivets during the riveting operation of a pot body and a handle, and in particular to a rivet posture adjustment and conveying device. Background Art

[0002] Small-volume kitchenware such as non-stick pans are particularly suitable for processing small amounts of food at home. For easy operation, a rod-shaped handle or an earring-shaped handle needs to be installed on the outer wall of the pan near the edge. There are common ways to connect the handle or ear with the pan, such as welding, screws, and riveting. Riveting is the preferred method for non-stick pans.

[0003] In order to improve the riveting efficiency, a corresponding solution is disclosed in the name of "Continuous automatic riveting equipment for pot body and pot handle docking processing" (CN216705826U, hereinafter referred to as document 1), in which a riveter 15 is fixedly installed at the telescopic end of the second hydraulic cylinder 14, which is responsible for riveting the through hole on the side wall of the pot body 1 and the rivet hole on the front end of the pot handle 2, and the solution does not involve the specific content of how the riveter 15 constrains the rivet.

[0004] The solution disclosed in the name of "an adjustable riveting device" (CN108526376A, hereinafter referred to as Document 2) can only solve the riveting operations of two rivets at the same time. This solution also involves first processing rivet holes on the cookware body and the handle, and then using the riveting device provided to perform riveting.

[0005] Both Documents 1 and 2 mentioned above can realize the automated riveting process, and Document 2 also solves the problem of completing two rivet riveting operations at one time, effectively improving the riveting quality and efficiency. However, if the pot body punching process is established as an independent process, it is necessary to add a set of pot body punching equipment, and the pot body needs to be transferred and re-positioned during riveting. In Document 2, the rivet constraint scheme during riveting is complicated, and Document 2 has not yet involved how to adjust and constrain the posture during the rivet supply process. In Document 1, the posture of the rivet during riveting is that the nail core is horizontal, which further increases the difficulty of constraining the rivet when it is inserted into the riveting hole.

[0006] Rivets are commonly used parts. In order to improve the riveting efficiency, the posture of the rivets when they are transported to the riveting position is directly related to the structural scheme of the riveting equipment, which in turn affects the riveting efficiency and quality. The document is named "A feeding device for slender screw rivet parts" (CN208560640U, hereinafter referred to as document 3). The screws or rivets are placed in the material tray of the disc vibrating feeder 1. Under the action of the disc vibrating feeder 1, these parts will move to the material channel 2 through the spiral material channel in a fixed posture with the nut part facing upward, and randomly enter a certain material channel 2. In this way, after working for a period of time, there are multiple parts in each material channel 2. Document 3 does not specifically explain how the rivet or screw is positioned with its head facing upward and its push rod facing downward; secondly, maintaining the position of the nail head facing upward and its push rod facing downward requires constraints provided by supporting and restraining components, which is not conducive to inserting the screw or rivet into the connecting hole; thirdly, once the constraints provided by the supporting and restraining components that maintain the position of the nail head facing upward and its push rod facing downward are released, the position of the nail head facing upward and its push rod facing downward cannot be maintained, making it difficult for the rivet to be inserted into the riveting hole in a timely and accurate manner. Utility Model Content

[0007] The utility model aims to provide a rivet posture adjustment and conveying device, which can adjust rivets with disordered postures to stable and determined postures, and provide rivets for riveting a pot body and a handle.

[0008] To achieve the above-mentioned purpose, the utility model adopts the following technical scheme: a rivet posture adjustment and conveying device, comprising a rivet selection section and a selected rivet rotation transition section, the rivet A selected by the rivet selection section is in a state where the rivet head A1 is obliquely facing upward and the rivet rod A2 is obliquely facing downward, and the selected rivet rotation transition section guides the selected rivet A to transition from a posture in which the rivet head A1 is obliquely facing upward and the rivet rod A2 is obliquely facing downward in an upstream position to a posture in which the rivet head A1 is facing upward and the rivet rod A2 is facing downward.

[0009] According to the technical solution provided by the utility model, the rivets A supplied sequentially by the barrel-shaped vibrating feeder arrive at the rivet selection section in various postures, and only the rivet A with the rivet head A1 obliquely facing upward and the rivet rod A2 obliquely facing downward are selected and collected in a sequentially arranged form, while the rivets A with other postures slide down from the rivet selection section, and the selected rivets A arriving at the selected rivet A transfer transition section are gradually transformed into a vertical posture with the rivet head A1 facing upward and the rivet rod A2 facing downward under the constraint and guidance of the rivet A transfer transition section, and continue to be conveyed downstream in this posture, thereby providing rivets with determined postures one by one for the riveting of the pot body and the handle. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a three-dimensional structural schematic diagram of the present application;

[0011] Figure 2It is a three-dimensional structural schematic diagram of the rivet selection section and the transfer transition section of the present application;

[0012] Figure 3 It is a three-dimensional structural schematic diagram of a single nail transfer device of the present application;

[0013] Figure 4 It is a three-dimensional structural schematic diagram of a single nail transfer device transferring rivets. DETAILED DESCRIPTION

[0014] Combination Figure 1 , 2 As shown, the rivet posture adjustment and conveying device includes a rivet selection section and a selected rivet rotation transition section. The rivet A selected by the rivet selection section is in a state where the rivet head A1 is obliquely facing upward and the rivet rod A2 is obliquely facing downward. The selected rivet rotation transition section guides the selected rivet A to transition from a posture in which the rivet head A1 is obliquely facing upward and the rivet rod A2 is obliquely facing downward in an upstream position to a posture in which the rivet head A1 is facing upward and the rivet rod A2 is facing downward.

[0015] In the above scheme, the rivets A arriving at the top discharge position of the barrel-shaped vibrating feeder 10 present a relatively messy posture. The rivet selection section selects and collects the rivet A with the rivet head A1 obliquely facing upward and the rivet rod A2 obliquely facing downward, and the rivets A in other postures will slide and leave the rivet selection section. The rivets A selected by the rivet selection section are successively shifted to the downstream selected rivet transfer transition section. Under the guidance of the selected rivet transfer transition section, the posture of the rivet head A1 obliquely facing upward and the rivet rod A2 obliquely facing downward is gradually transitioned to the posture of the rivet head A1 facing upward and the rivet rod A2 facing downward, thereby obtaining a rivet array with a stable sequence arrangement of the postures of the rivet head A1 facing upward and the rivet rod A2 facing downward.

[0016] like Figure 1 , 2 As shown, the rivet selection section includes a strip plate 12 connected to the discharge plate belt 11 of the notch of the upper end wall of the vibrating feeder 10, one side of the plate edge of the strip plate 12 is low and the other side is high, and the low side is far away from the wall of the vibrating feeder 10, and a stopper 20 is arranged above the low side of the strip plate 12, and the extension direction of the stopper 20 is consistent with the extension direction of the low side of the strip plate 12, and the downstream end of the stopper 20 is located at the downstream position of the downstream end of the strip plate 12, and the stopper 20 and the strip plate 12 are arranged with the upstream end high and the downstream end low, and the distance between the stopper 20 and the low side of the strip plate 12 is less than the diameter of the rivet head A1 of the rivet A and greater than the diameter of the rivet rod A2.

[0017] like Figure 2As shown, in the overlapped section of the extension direction of the stopper 20 and the strip plate 12, only the rivet head A1 of the rivet A2 is obliquely upward and the rivet rod A2 is inserted into the narrow gap area between the stopper 20 and the strip plate 12. With the vibration of the vibrating feeder 10, the stopper 20 and the strip plate 12 also vibrate, and the selected rivet A moves downstream. The rivet rod A2 of the rivet A in other postures cannot reach the narrow gap area between the stopper 20 and the strip plate 12, and will naturally fall off during the process of continuing to move downstream.

[0018] like Figure 2 As shown, the selected rivet transfer transition section includes a torsion strip plate 30 connected to the downstream section of the low side of the strip plate 12, the plate surface of the torsion strip upstream section 31 of the torsion strip plate 30 is flush with the plate surface of the downstream section of the strip plate 12, the plate surface of the torsion strip downstream section 33 of the torsion strip plate 30 gradually approaches the plumb plane and the downstream end is located on the plumb plane, and the plate surface of the torsion strip midstream section 32 of the torsion strip plate 30 gradually transitions and twists from the torsion strip upstream section 31 to the torsion strip downstream section 33.

[0019] like Figure 2 As shown, in the overlapped section of the upstream section 31 of the torsion band and the strip plate 12, the lower section of the rivet rod A2 is placed on the upstream section 31 of the torsion band, the low side edge of the rivet head A1 is placed on the strip plate 12, and the bottom surface of the rivet head A1 at the high position is placed on the stop bar 20. When the rivet A moves to the downstream end away from the strip plate 12, the back of the rivet head A1 is placed on the plate edge and the stop bar 20 at the high side of the upstream section 31 of the torsion band; when the rivet A continues to move to the downstream end away from the stop bar 20, the rivet rod A2 is placed on the plate surface of the upstream section 31 of the torsion band, and the rivet head A1 is hung on the plate edge of the high side of the upstream section 31 of the torsion band. At this time, the plate surface of the upstream section 31 of the torsion band is still arranged in an inclined shape. It should be noted that rivet A in other postures other than the selected posture will fall off at the downstream end of the strip plate 12.

[0020] When rivet A passes through the upstream section 31, the midstream section 32 and the downstream section 33 of the torsion band plate 30 in sequence, the rivet rod A2 gradually shifts from an inclined state to a vertical state. In addition, the friction force applied to rivet A by the torsion band plate 30 cannot maintain the vertical posture of rivet A, and rivet A tends to tip over and fall. To prevent it from falling, the present application provides the following solution, namely, a clamping plate 40 extending from upstream to downstream is provided on the upper plate surface side of the midstream section 32 of the torsion band, and the torsion extension direction of the clamping plate 40 is consistent with that of the midstream section 32 and the downstream section 33 of the torsion band. The clamping plate 40 is parallel to the upper plate edge of the downstream section 33 of the torsion band, and the distance between the upper plate edges of the two is less than the diameter of the rivet head A1 of the rivet A and greater than the diameter of the rivet rod A2. The selected rivet A is located between the clamping plate 40 and the downstream section 33 of the torsion band, and the rivet head A1 is placed on the upper plate edge of the clamping plate 40 and the downstream section 33 of the torsion band.

[0021] Under the constraint of the channel formed by the spacing arrangement between the clamping plate 40 and the midstream section 32 and the downstream section 33 of the torsion band, during the displacement of rivet A from a high position to a low position, the rod body of the rivet rod A2 gradually shifts from the original inclined state in contact with the midstream section 32 of the torsion band to a posture parallel to the plate surface of the clamping plate 40 and the downstream section 33 of the torsion band. In order to ensure the smooth displacement of rivet A in the downstream section where the clamping plate 40 and the downstream section 33 of the torsion band cooperate, the upper edge of the clamping plate 40 and the downstream section 33 of the torsion band changes between high and low positions gradually and smoothly until the end of its downstream section extends horizontally.

[0022] In order to meet the riveting requirements, it is hoped that the rivet A is supplied as a single nail during riveting. For this purpose, the present application provides the following solution: the clamping plate 40 is parallel to the upper section of the torsion belt downstream section 33.

[0023] A guide rod 50 is provided and the guide rod 50 is close to the side where the downstream section 33 of the torsion band is located. The guide rod 50 is a corrugated rod and the extension direction of the rod length is consistent with the upper plate edge of the downstream section 33 of the torsion band. The distance between the wave crest on the guide rod 50 and the supporting surface formed by the holding plate 40 and the upper half plate edge of the downstream section 33 of the torsion band is greater than the thickness of the rivet head A1 and less than the thickness of the two rivet heads A1 in the superimposed state. It should be noted that the wave crest on the guide rod 50 appropriately crosses the wave crest to the midline position between the holding plate 40 and the downstream section 33 of the torsion band, and a spacing of about 0.5 mm is reserved between the top surface of a single running rivet head A1, so that the normal displacement of a single rivet A can be ensured, and the rivets pressed together by the rivet heads A1 can be separated.

[0024] The above scheme solves the problem that the rivet heads A1 arrive at the downstream single nail transfer device 60 in a state of overlapping each other. A guide rod 50 is set in the downstream section of the constraint area jointly constructed by the clamping plate 40 and the downstream section 33 of the torsion belt. Due to the corrugated rod shape of the guide rod 50, the rivets A with the rivet heads A1 overlapping each other will be separated from each other, so that the rivets A are discretely arranged and transported downstream, avoiding the rivets A from gathering and overlapping in large quantities, and ensuring that the rivets A gather at the nail entry port 61 on the side wall of the single nail transfer device 60, making it difficult to enter the nail entry port 61 accurately and timely.

[0025] The downstream end of the selected rivet transfer transition section is connected to the nail entry port 61 on the side wall of the single nail transfer device 60. The single nail transfer device 60 is connected to the pressure air pipe 70 at the bottom and the guide pipe 80 at the top. The rivet A located between the pressure air pipe 70 and the guide pipe 80 enters the guide pipe 80 with the rivet head A1 facing upward and the rivet rod A2 facing downward. The nail exit end of the guide pipe 80 faces downward and is connected to the nail receiving position of the rivet pushing mechanism. The above scheme only requires that the end section of the guide pipe 80, that is, the downstream end, faces downward to realize the conversion of the rivet head A1 from facing upward to facing downward, so that the rivet A can be inserted into the riveting hole from bottom to top for riveting.

[0026] The task of the above-mentioned single nail transfer device 60 is to transport a single rivet A. The nail entry port 61 is only for one rivet A to enter. The shape of the nail entry port 61 also corresponds to the posture of the delivered rivet A. The single rivet A entering the single nail transfer device 60 from the nail entry port 61 arrives at the setting position of the pressure air pipe 70 and the guide pipe 80. Under the blowing of pressurized gas, the rivet head A1 is transported to the riveting station with the rivet rod A2 facing upward, thereby releasing all possible constraints on the rivet rod A2, making the rivet rod A2 fully exposed, and inserted into the rivet hole from bottom to top to implement riveting, which significantly improves the riveting efficiency.

[0027] like Figure 3 , 4 As shown, the downstream section 33 of the torsion band constituting the transition section for the selected rivet transfer is flush with the clamping plate 40 and connected to the nail entry opening 61 on the side wall of the single nail transfer device 60. The nail entry opening 61 is T-shaped with a large upper portion and a small lower portion. The large and small diameter portions of the nail entry opening 61 respectively accommodate the rivet head A1 and the rivet rod A2 of the rivet A.

[0028] After rivet A is detached from the end of the constraint area formed by the downstream section 33 of the torsion band and the clamping plate 40, it can enter the nail entry port 61 and wait. In order to reliably transfer the rivet A to the setting position of the pressure air pipe 70 and the guide pipe 80, the present application provides a sliding shoe 62 to perform the transfer operation on the rivet A, that is, the position of the nail entry port 61 and the setting position of the pressure air pipe 70 and the guide pipe 80 are arranged at a distance. In this way, it can be avoided that when the nail entry port 61 is arranged close to the pressure air pipe 70 and the guide pipe 80, the nail entry port 61 will become a discharge path for the pressurized gas, resulting in energy waste and the possibility that the rivet A is transferred slowly or paused or even blown out from the nail entry port 51.

[0029] See also Figure 3 , 4 A sliding shoe 62 is provided in the chamber 631 of the single nail transfer device 60. When the sliding shoe 62 is displaced, the nail receiving notch 621 on the sliding shoe 62 is aligned with or avoids the nail entry port 61. The nail receiving notch 621 is U-shaped and its opening is smaller than the diameter of the rivet head A1 and larger than the diameter of the rivet rod A2. The height of the upper end of the nail receiving notch 621 is equal to or lower than the height of the upper end of the small diameter of the nail entry port 61. The rivet A arriving at the nail entry port 61 is pushed by the rivet A on the upstream side and arrives at the nail receiving notch 621. The sliding shoe 62 is displaced to transfer the rivet A to the setting position of the pressure air pipe 70 and the guide pipe 80.

[0030] Figure 3 , 4In the figure, a baffle 622 is provided beside the nail receiving notch 621 on the sliding shoe 62. When the nail receiving notch 621 is in a position to avoid the nail entry opening 61, the baffle 622 blocks the inner edge of the nail entry opening 61. The baffle 622 can store a rivet at the nail entry opening 61, so that a rivet A can be obtained in time when the nail receiving notch 621 reaches the nail entry opening 61, thereby improving work efficiency and preventing the rivet A from squeezing into the chamber of the single nail transfer device 60 when the sliding shoe 62 is displaced, thereby affecting the normal displacement movement of the sliding shoe 62.

[0031] The guide pipe 80 and the pressure air pipe 70 are connected to the chamber 631 in the sliding shoe 62 in an opposed manner, and the nail receiving notch 621 is vertically opposite to the guide pipe 80 and the pressure air pipe 70 when it is in a position to avoid the nail entry opening 61. This solution achieves accurate positioning and is easy to implement.

[0032] The single nail indexer 60 includes a chamber 631 for accommodating the sliding shoe 62. The chamber 631 is a groove-shaped cavity of the housing 63 of the single nail indexer. One end of the housing 63 of the single nail indexer is connected to the cylinder 64. The rod end of the piston rod 641 of the cylinder 64 is connected to one end of the sliding shoe 62. The extended position and the retracted position of the piston rod 641 correspond to the position where the nail receiving notch 621 on the sliding shoe 62 is aligned with or avoids the nail entry port 61. The extreme stroke position of the piston rod 641 is directly used as the positioning reference, and there is no need to set up a complex solution such as a position sensor combined with a controller, which simplifies the structure and ensures accurate positioning.

Claims

1. A rivet posture adjustment and conveying device, characterized in that: The invention comprises a rivet selection section and a selected rivet transfer transition section, wherein the rivet (A) selected by the rivet selection section is in a state where the rivet head (A1) is obliquely facing upward and the rivet rod (A2) is obliquely facing downward, and the selected rivet transfer transition section guides the selected rivet (A) to transfer from a state in which the rivet head (A1) is in an upstream position and the rivet rod (A2) is obliquely facing downward to a state in which the rivet head (A1) is facing upward and the rivet rod (A2) is facing downward.

2. The rivet posture adjustment and conveying device according to claim 1 is characterized in that: The rivet selection section comprises a strip plate (12) connected to a discharge plate belt (11) at a notch of an upper end wall of a vibrating feeder (10); one side of the strip plate (12) is low and the other side is high, and the low side is away from the wall of the vibrating feeder (10); a stopper rod (20) is arranged above the low side of the strip plate (12); the extension direction of the stopper rod (20) is consistent with the extension direction of the low side of the strip plate (12); the downstream end of the stopper rod (20) is located at a downstream position of the downstream end of the strip plate (12); the stopper rod (20) and the strip plate (12) are arranged with the upstream end high and the downstream end low; the distance between the stopper rod (20) and the low side of the strip plate (12) is smaller than the diameter of the rivet head (A1) of the rivet A and larger than the diameter of the rivet rod (A2).

3. The rivet posture adjustment and conveying device according to claim 1 or 2, characterized in that: The selected rivet transfer transition section includes a downstream section of the lower side of the strip plate (12) connected to a torsion strip plate (30), the plate surface of the torsion strip upstream section (31) of the torsion strip plate (30) is flush with the plate surface of the downstream section of the strip plate (12), the plate surface of the torsion strip downstream section (33) of the torsion strip plate (30) gradually approaches the plumb line and the downstream end is located on the plumb line, and the plate surface of the torsion strip midstream section (32) of the torsion strip plate (30) gradually transitions from the torsion strip upstream section (31) to the torsion strip downstream section (33).

4. The rivet posture adjustment and conveying device according to claim 3 is characterized in that: A clamping plate (40) extending from upstream to downstream is provided on the upper plate surface side of the midstream section (32) of the torsion band. The clamping plate (40) has the same torsion extension direction as the midstream section (32) of the torsion band and the downstream section (33) of the torsion band. The upper plate edges of the clamping plate (40) and the downstream section (33) of the torsion band are parallel, and the spacing between the upper plate edges of the clamping plate (40) and the downstream section (33) of the torsion band is smaller than the diameter of the rivet head (A1) of the rivet A and larger than the diameter of the rivet rod (A2). The selected rivet (A) is located between the clamping plate (40) and the downstream section (33) of the torsion band, and the rivet head (A1) is placed on the upper plate edges of the clamping plate (40) and the downstream section (33) of the torsion band.

5. The rivet posture adjustment and conveying device according to claim 4 is characterized in that: A guide rod (50) is arranged above the parallel section of the clamping plate (40) and the downstream section (33) of the torsion band, and the guide rod (50) is close to the side where the downstream section (33) of the torsion band is located. The guide rod (50) is a corrugated rod, and the extension direction of the rod length is consistent with the upper plate edge of the downstream section (33) of the torsion band. The distance from the wave crest on the guide rod (50) to the supporting surface formed by the clamping plate (40) and the upper half plate edge of the downstream section (33) of the torsion band is greater than the thickness of the rivet head (A1) and less than the thickness of the two rivet heads (A1) in a superimposed state.

6. The rivet posture adjustment and conveying device according to claim 1, characterized in that: The downstream end of the selected rivet transfer transition section is connected to a nail entry opening (61) on the side wall of the single nail transfer device (60). The single nail transfer device (60) is connected to a pressure air pipe (70) at the bottom and a guide pipe (80) at the top. The rivet (A) located between the pressure air pipe (70) and the guide pipe (80) enters the guide pipe (80) with the rivet head (A1) facing upward and the rivet rod (A2) facing downward. The nail exit end of the guide pipe (80) is connected to the nail receiving position of the rivet pushing mechanism with the rivet head (A1) facing upward and the rivet rod (A2) facing downward.

7. The rivet posture adjustment and conveying device according to claim 6, characterized in that: The downstream section (33) of the torsion belt constituting the transition section for the selected rivet transfer is flush with the clamping plate (40) and connected to the nail entry opening (61) on the side wall of the single nail transfer device (60). The nail entry opening (61) is T-shaped with a large upper portion and a small lower portion. The large and small diameter portions of the nail entry opening (61) respectively accommodate the rivet head (A1) and the rivet rod (A2) of the rivet (A).

8. The rivet posture adjustment and conveying device according to claim 7, characterized in that: A sliding shoe (62) is arranged in the chamber (631) of the single nail transfer device (60). When the sliding shoe (62) is displaced, the nail receiving notch (621) on the sliding shoe (62) is aligned with or avoids the nail entry opening (61). The nail receiving notch (621) is U-shaped and its opening is smaller than the diameter of the rivet head (A1) and larger than the diameter of the rivet rod (A2). The height of the upper end of the nail receiving notch (621) is equal to or lower than the height of the upper end of the small diameter of the nail entry opening (61).

9. The rivet posture adjustment and conveying device according to claim 7, characterized in that: A baffle plate (622) is provided beside the nail receiving notch (621) on the sliding shoe (62). When the nail receiving notch (621) is in a position to avoid the nail entry opening (61), the baffle plate (622) blocks the inner edge of the nail entry opening (61).

10. The rivet posture adjustment and conveying device according to claim 8 or 9, characterized in that: The guide pipe (80) and the pressure air pipe (70) are connected to the chamber in the sliding shoe (62) in an opposed manner, and the nail receiving notch (621) is directly opposite to the guide pipe (80) and the pressure air pipe (70) in the vertical direction when the nail receiving notch (621) is in a position to avoid the nail entry opening (61).

11. The rivet posture adjustment and conveying device according to claim 10, characterized in that: The single nail transfer device (60) comprises a chamber (631) for accommodating a sliding shoe (62), the chamber (631) being a groove-shaped cavity of a housing (63) of the single nail transfer device, one end of the housing (63) of the single nail transfer device being connected to a cylinder (64), a rod end of a piston rod (641) of the cylinder (64) being connected to one end of the sliding shoe (62), and an extended position and a retracted position of the piston rod (641) respectively corresponding to a position where a nail accommodating notch (621) on the sliding shoe (62) is aligned with or avoids a nail entry opening (61).

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