A pull-back self-positioning hydraulic clamp

Abstract

This invention relates to the field of hydraulic clamping technology, specifically to a pull-back self-positioning hydraulic clamp; it includes a connecting body and a supporting body arranged coaxially; one end of the supporting body near the connecting body is tightly fitted to the end face of the connecting body, forming a sealed space with the middle of the end face of the connecting body; an expansion sleeve assembly is fitted on the end of the supporting body away from the connecting body, and the expansion sleeve assembly is connected to the supporting body by a guide key; a first oil circuit system connects the sealed space and the oil chamber in the expansion sleeve assembly; a piston unit and an intermediate connecting member are arranged in the sealed space; a pull rod is fitted in the connecting body, one end of the pull rod passes into the sealed space and connects the piston unit and the intermediate connecting member; one end of the intermediate connecting member passes out of the sealed space and is fixedly connected to the expansion sleeve assembly; by pulling the pull rod backward, the piston unit is driven to cause the expansion sleeve assembly to tighten the workpiece, and at the same time, the intermediate connecting member and the expansion sleeve assembly move towards the connecting body, pulling the positioning end face of the workpiece tight onto the positioning block, thereby achieving self-positioning.

Description

Technical Field

[0001] This invention relates to the field of hydraulic clamping technology, specifically to a pull-back self-positioning hydraulic clamp. Background Technology

[0002] Currently, many hydraulic clamps have their main body connected to a connecting body. The clamp is installed on the machine tool spindle by connecting the connecting body to the machine tool spindle. The main method used is to expand the inner hole and fix the end face. The piston is pushed by the pull rod to compress the hydraulic oil inside the clamp and enter the expansion sleeve, thereby tightening the workpiece. The positioning end face of the workpiece is positioned by the clamp positioning block.

[0003] Existing hydraulic clamps can achieve workpiece clamping (centering) through expansion sleeves. However, during manual clamping, axial displacement of the workpiece is easily caused by operational errors, resulting in the workpiece's positioning end face not being able to tightly fit the positioning surface of the positioning block. Currently, the solution to this problem is usually to incorporate an airtight channel into the hydraulic clamp, using airtightness testing to check the fit between the workpiece's end face and the positioning surface of the positioning block, thereby determining whether the workpiece's positioning end face is accurate. However, this method has the following problems:

[0004] 1. When the machine tool's airtightness detection function fails, the machine tool's airtightness detection accuracy decreases, or the machining accuracy requirements of the workpiece are high, the accuracy of the machine tool's airtightness detection system cannot meet the corresponding requirements of the workpiece's machining accuracy; it cannot guarantee that the fit between the workpiece's positioning end face and the positioning surface of the positioning block meets the workpiece's machining accuracy requirements.

[0005] 2. Existing hydraulic clamps do not have end face self-positioning function (i.e., they cannot automatically fit the positioning end face of the workpiece tightly with the positioning surface of the positioning block). When the air tightness test fails, it is necessary to manually disassemble, inspect, clamp, and test the air tightness repeatedly until the air tightness test passes, resulting in low workpiece processing efficiency. Summary of the Invention

[0006] This invention provides a pull-back self-positioning hydraulic clamp to solve the technical problems in the prior art where the machine tool's airtightness detection system cannot meet the corresponding requirements of the workpiece's machining accuracy when the machine tool's airtightness detection function fails, the machine tool's airtightness detection accuracy decreases, or the machining accuracy requirements of the workpiece are high; it cannot guarantee that the fit between the workpiece's positioning end face and the positioning surface of the positioning block meets the workpiece's machining accuracy requirements; and the existing hydraulic clamps themselves do not have end face self-positioning function (i.e., they cannot automatically fit the workpiece's positioning end face tightly with the positioning surface of the positioning block). When the airtightness detection fails, manual repeated disassembly, inspection, clamping, and airtightness detection are required until the airtightness detection passes, resulting in low workpiece machining efficiency.

[0007] The technical solution adopted in this invention is: a pull-back self-positioning hydraulic clamp, comprising a connecting body and a support body arranged coaxially; one end of the support body near the connecting body is tightly connected to the end face of the connecting body, and forms a sealed space with the middle part of the end face of the connecting body;

[0008] An expansion sleeve assembly is fitted at one end of the support body away from the connecting body. The expansion sleeve assembly can slide back and forth along its axial direction on the support body. A first oil circuit system is provided in both the support body and the expansion sleeve assembly. The first oil circuit system connects the sealed space and the oil cavity in the expansion sleeve assembly.

[0009] The sealed space is equipped with a piston unit and an intermediate connector. A pull rod is sleeved in the connector. One end of the pull rod passes through the connector from the end away from the support and connects the piston unit and the intermediate connector.

[0010] The intermediate connector is capable of reciprocating along the axial direction within the sealed space. The intermediate connector is fixedly connected to the pull rod. One end of the intermediate connector extends out of the sealed space and is fixedly connected to the expansion sleeve assembly. A positioning block is sleeved on one end of the expansion sleeve assembly near the connector. The positioning block is fixedly connected to the support body and is used to mate with the positioning end face of the workpiece.

[0011] The pull rod is used to move away from the support body to drive the piston unit to deliver hydraulic oil through the first oil circuit system to the oil chamber in the expansion sleeve assembly, while driving the intermediate connector and the expansion sleeve assembly to move along the axial direction towards the connector body.

[0012] This allows the expansion sleeve assembly to tighten the workpiece while simultaneously pulling the positioning end face of the workpiece to the positioning surface of the positioning block.

[0013] The expansion sleeve assembly can slide back and forth along its axial direction on the support body, which can be achieved through various key connection methods, including but not limited to: spline connection, guide key connection, etc.

[0014] By fitting the expansion sleeve assembly onto the end of the support body away from the connecting body, and allowing the expansion sleeve assembly to slide axially back and forth on the support body; simultaneously, an intermediate connector and a piston unit are arranged in the sealed space, and a pull rod connects the intermediate connector and the piston unit, so that when the pull rod moves away from the support body, it can drive the piston unit to deliver hydraulic oil through the first oil circuit system to the oil chamber in the expansion sleeve assembly, and at the same time drive the intermediate connector and the expansion sleeve assembly to move axially towards the connecting body, so that the expansion sleeve assembly tightens the workpiece while pulling the positioning end face of the workpiece to the positioning surface of the positioning block; thus, a self-positioning function for the positioning end face of the workpiece is achieved, and because the positioning end face of the workpiece is pulled to the positioning surface of the positioning block, the self-positioning function for the positioning end face of the workpiece is realized. On the positioning surface, a tight fit is ensured between the positioning end face of the workpiece and the positioning surface of the positioning block, so that the fit between the positioning end face of the workpiece and the positioning surface of the positioning block can meet the machining accuracy requirements of the workpiece. This solves the technical problems in the existing technology where the machine tool airtightness detection system cannot meet the corresponding requirements of the workpiece machining accuracy when the machine tool airtightness detection function fails, the machine tool airtightness detection accuracy decreases, or the machining accuracy requirements of the workpiece are high; it cannot guarantee that the fit between the positioning end face of the workpiece and the positioning surface of the positioning block can meet the machining accuracy requirements of the workpiece; and the existing hydraulic fixture itself does not have an end face self-positioning function (i.e., it cannot automatically fit the positioning end face of the workpiece and the positioning surface of the positioning block tightly), so when the airtightness detection fails, it is necessary to manually repeatedly disassemble, inspect, clamp, and perform airtightness detection until the airtightness detection passes, resulting in low workpiece machining efficiency.

[0015] Furthermore, the expansion sleeve assembly is connected to the support body via a guide key.

[0016] Furthermore, the piston unit includes a first piston assembly and a second piston assembly. The pull rod is fixedly connected to the input end of the first piston assembly. The first piston assembly is used to drive the second piston assembly. The pull rod is used to move away from the support body to drive the first piston assembly, thereby driving the second piston assembly to deliver hydraulic oil through the first oil circuit system to the oil chamber in the expansion sleeve assembly.

[0017] Furthermore, a first piston hole is formed in the central region of one end of the connector near the support body along the axial direction;

[0018] The first piston assembly includes a first piston fitted inside a first piston bore. A first oil chamber is formed between the first piston and the bottom of the first piston bore. The piston rod of the first piston passes through the bottom of the first piston bore and is fixedly connected to the pull rod. A third piston bore is formed at the center of the end of the first piston body facing outward from the first piston bore. A piston pusher is fitted in the third piston bore. A second oil chamber is formed between the piston pusher and the bottom of the third piston bore. A second oil passage system is provided in the first piston, and the second oil passage system connects the first oil chamber and the second oil chamber. The radial cross-sectional area of ​​the first oil chamber is larger than the radial cross-sectional area of ​​the second oil chamber. The piston pusher is used to drive the second piston assembly.

[0019] The piston body of the first piston has a plurality of first columns arranged circumferentially around the third piston hole at one end facing the first piston hole. One end of each first column extends out of the first piston hole along the axial direction and is fixedly connected to the intermediate connecting member.

[0020] Furthermore, a second piston hole is formed in the central region of one end of the support near the connector along the axial direction;

[0021] The second piston assembly includes a second piston fitted inside the second piston bore, a third oil chamber formed between the second piston and the bottom of the second piston bore, the third oil chamber being connected to the first oil circuit system; the piston rod of the second piston passes through the intermediate connector along the axial direction and abuts against the piston push block.

[0022] With the above technical solution, as the pull rod moves away from the support and drives the first piston to move away from the support, the volume of the first oil chamber is compressed, causing the hydraulic oil in the first oil chamber to be transported to the second oil chamber through the second oil circuit system. The volume of the second oil chamber increases, and since the radial cross-sectional area of ​​the first oil chamber is larger than that of the second oil chamber, the hydraulic oil in the second oil chamber will push the piston pusher block to move closer to the support, thereby pushing the second piston assembly and transporting the hydraulic oil to the expansion sleeve assembly through the first oil circuit system.

[0023] Provided that the radial cross-sectional area of ​​the first oil chamber is greater than that of the second oil chamber, the ratio between the radial cross-sectional areas of the first and second oil chambers can be adjusted to regulate the ratio of the speed at which the pull rod moves away from the support to the speed at which the piston push block moves towards the support. This is different from the technical solution of directly installing a pull-back piston in the sealed space, fixing the piston rod of the pull-back piston to the pull rod, and fixing the intermediate connecting piece to the piston rod of the pull-back piston or directly to the pull rod, and directly supplying hydraulic oil to the oil chamber of the expansion sleeve assembly through the pull-back piston. This solution eliminates the need to adjust the machine tool to adjust the movement speed of the pull rod, thus achieving the adjustment of the expansion speed of the expansion sleeve assembly. This ensures that when the pull rod moves away from the support, the expansion action of the expansion sleeve assembly and the movement of the expansion sleeve assembly towards the connecting body achieve optimal coordination.

[0024] The ratio between the radial cross-sectional area of ​​the first oil chamber and the radial cross-sectional area of ​​the second oil chamber can be adjusted by changing the diameter of the first piston hole, the diameter of the third piston hole, and the diameter of the piston rod of the first piston.

[0025] Furthermore, the radial cross-sectional area of ​​the first oil cavity is greater than twice the radial cross-sectional area of ​​the second oil cavity.

[0026] By making the radial cross-sectional area of ​​the first oil chamber greater than twice the radial cross-sectional area of ​​the second oil chamber, when the pull rod moves away from the support, the piston push block moves towards the support at a speed greater than the pull rod moves away from the support. This allows the hydraulic oil to be delivered to the expansion sleeve assembly more quickly compared to traditional pull-back hydraulic clamps, resulting in higher clamping efficiency, shorter workpiece clamping time, and faster workpiece processing cycle speed.

[0027] Furthermore, the piston pusher is in the shape of a stepped shaft, with its smaller diameter end fitted inside the third piston hole and its larger diameter end fitted inside the first piston hole; a plurality of first through holes are arranged circumferentially around its central axis on the larger diameter end of the piston pusher, and the first through holes are used for clearance fit with the first column.

[0028] By configuring the piston pusher block as a stepped shaft, with its smaller diameter end fitted into the third piston hole and its larger diameter end fitted into the first piston hole, the piston pusher block can reduce vibration when subjected to instantaneous thrust through the guiding engagement of the smaller diameter end by the third piston hole and the guiding engagement of the larger diameter end by the first piston hole. This allows the piston pusher block to move stably towards the side closer to the connecting body, reducing the impact of the piston pusher block's vibration on the second piston, increasing the smoothness of the second piston's movement, and preventing the second piston from getting stuck in the second piston hole during its movement towards the side closer to the connecting body.

[0029] Furthermore, the first piston assembly also includes a compression spring fixing plate and a plurality of compression springs. The compression spring fixing plate is disc-shaped and is fixedly connected to the end of the connecting body near the support body by bolts, and covers the first piston hole. The compression spring fixing plate has a second through hole at its axial center that is clearance-fitted with the piston rod of the second piston. The compression spring fixing plate has a plurality of third through holes at intervals around the second through hole that are clearance-fitted with the first column. The compression springs are all disposed between the compression spring fixing plate and the piston push block. The end of the compression spring fixing plate facing the first piston hole has a plurality of frustums at intervals around the second through hole, and a compression spring is fitted on the outer circumferential surface of each frustum.

[0030] By setting the compression spring and the compression spring fixing plate, when the pull rod begins to move away from the support body, the compression spring can buffer the instantaneous thrust when the piston push block is subjected to instantaneous thrust. This allows the piston push block to move more stably towards the connecting body, reducing the possibility of the piston push block getting stuck. Consequently, the second piston is pushed more smoothly, further improving the stability of the second piston's movement and preventing the second piston from getting stuck in the second piston hole during its movement towards the connecting body.

[0031] Furthermore, the pull rod has a hollow structure, and its inner hole has an internal thread on the side near the first piston. The piston rod of the first piston has an external thread that mates with the internal thread at the end near the pull rod. An airtight channel is provided on the end face of the piston rod of the first piston near the pull rod. The airtight channel passes through the piston rod of the first piston, the connecting body, the support body and the positioning block in sequence and extends to the positioning surface of the positioning block.

[0032] When the positioning end face of the workpiece is tightened on the positioning surface of the positioning block, if there are dirt or impurities on the positioning end face of the workpiece, it cannot be guaranteed that the positioning end face of the workpiece and the positioning surface of the positioning block will fit tightly. However, by setting up the airtight channel through the above technical solution, the airtight channel is connected to the inner hole of the pull rod, so that gas can be discharged from the machine tool spindle to the airtight channel, realizing the airtightness detection of the positioning end face of the workpiece and the positioning surface of the positioning block. This can effectively identify whether there are dirt or impurities on the positioning end face of the workpiece, further ensuring the accurate positioning of the workpiece on the fixture, so as to avoid product processing quality problems.

[0033] Furthermore, the connector has an inner hole at one end near the support, and the inner hole of the connector and the end face of the support near the connector form the sealed space; the support is in the shape of a stepped shaft, and its larger diameter end is used to tightly fit and connect with the end face of the connector, and the expansion sleeve assembly is sleeved on the smaller diameter end of the support.

[0034] Furthermore, an annular protrusion is provided on the end face of the end where the support body is connected to the connector body. The outer peripheral surface of the annular protrusion matches the inner surface of the inner hole of the connector body. Multiple radial set screw holes are evenly distributed along the circumference on the inner surface of the inner hole of the connector body. Each radial set screw hole penetrates radially to the outer peripheral surface of the connector body.

[0035] By setting the radial set screw hole, the radial runout of the connector can be adjusted during the installation and connection process between the connector and the support, thus ensuring the overall radial runout accuracy of the fixture.

[0036] Furthermore, the intermediate connector is disc-shaped and coaxially arranged with the support body. On the side of the intermediate connector near the support body, a plurality of second columns are circumferentially spaced around its central axis. The end of each second column is inserted into the support body along the axial direction and passes out from the shoulder of the support body, and is fixedly connected to the end of the expansion sleeve assembly near the shoulder of the support body.

[0037] Furthermore, the expansion sleeve assembly includes an expansion sleeve and an expansion sleeve support, both of which are hollow stepped shaft structures; the inner hole of the expansion sleeve is interference-fitted with the outer circumferential surface of the expansion sleeve support; the larger diameter end of the expansion sleeve is attached to the shoulder of the expansion sleeve support and is fixedly connected to the shoulder of the expansion sleeve support by bolts; the larger diameter end of the expansion sleeve support is fixedly connected to the intermediate connecting member; the expansion sleeve support is sleeved on the end of the support away from the connecting member and is connected to the support by a guide key; a first annular groove is provided at the contact point between the support and the inner wall of the expansion sleeve support;

[0038] The expansion sleeve support body is provided with a second annular groove at the contact point with the inner wall of the expansion sleeve to form an oil cavity within the expansion sleeve assembly. The first oil circuit system includes a plurality of radial through holes formed at the bottom of the second annular groove and an oil circuit channel disposed within the support body. The oil circuit channel is used to connect the sealed space and the first annular groove, and the radial through holes are used to connect the first annular groove and the second annular groove.

[0039] Furthermore, at least one branch of the first oil circuit system is connected to the end face of the support body away from the connector body and is provided with a plug at the opening; both the first annular groove and the second annular groove are provided with corresponding oil seals. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the overall structure of the pull-back self-positioning hydraulic clamp in the embodiment. Figure 1 ;

[0041] Figure 2 This is a schematic diagram of the overall structure of the pull-back self-positioning hydraulic clamp in the embodiment. Figure 2 ;

[0042] Figure 3 This is a cross-sectional view of the connector structure in the embodiment;

[0043] Figure 4 This is a cross-sectional view of the first piston in the embodiment;

[0044] Figure 5 This is a cross-sectional view of the piston pusher block in the embodiment;

[0045] Figure 6 This is a cross-sectional view of the compression spring fixing plate in the embodiment;

[0046] Figure 7 This is a cross-sectional view of the intermediate connector in the embodiment;

[0047] Figure 8 This is a cross-sectional view of the support structure in the embodiment;

[0048] Figure 9 This is a schematic diagram of the assembly structure of the support, expansion sleeve assembly, and second piston assembly in the embodiment;

[0049] Figure 10 This is a cross-sectional view of the expansion sleeve assembly in the embodiment;

[0050] Among them, 1—connector, 2—support, 3—expansion sleeve assembly, 4—guide key, 5—first oil circuit system, 6—intermediate connector, 7—pull rod, 8—first piston assembly, 9—second piston assembly, 10—workpiece, 11—airtight channel, 12—positioning block;

[0051] 1.1—Radial set screw hole; 1.2—Bolt through hole;

[0052] 2.1—Annular protrusion; 2.2—First annular groove; 2.3—Third screw through hole; 2.4—Fifth through hole;

[0053] 3.1—Expansion sleeve support body; 3.2—Expansion sleeve; 3.3—Second annular groove; 3.4—First bolt; 3.5—Second bolt;

[0054] 5.1—Radial through hole; 5.2—Oil passage; 5.3—Steel ball; 5.4—Sealing screw; 5.5—Ball expansion plug;

[0055] 6.1—Second column; 6.2—Fourth through hole; 6.3—Second screw through hole;

[0056] 8.1—First piston, 8.2—First column, 8.3—Piston pusher, 8.4—First oil chamber, 8.5—Second oil chamber, 8.6—Second oil circuit system, 8.7—Compression spring fixing plate, 8.8—Compression spring;

[0057] 8.3.1—First through hole;

[0058] 8.7.1—Second through hole, 8.7.2—Third through hole, 8.7.3—Frustum, 8.7.4—First screw through hole;

[0059] 9.1—Second piston, 9.2—Third oil chamber, 9.3—Spring cover plate, 9.4—Support spring. Detailed Implementation

[0060] The technical solutions of the embodiments of the present invention will now be clearly and completely described with reference to the accompanying drawings:

[0061] Example:

[0062] like Figure 1 As shown, this embodiment provides a pull-back self-positioning hydraulic clamp, including a connecting body 1 and a support body 2 arranged coaxially; one end of the support body 2 near the connecting body 1 is tightly connected to the end face of the connecting body 1, and forms a closed space with the middle of the end face of the connecting body 1.

[0063] An expansion sleeve assembly 3 is fitted at the end of the support body 2 away from the connector 1. The expansion sleeve assembly 3 can slide back and forth along its axial direction on the support body 2. Both the support body 2 and the expansion sleeve assembly 3 are provided with a first oil circuit system 5. The first oil circuit system 5 connects the sealed space and the oil cavity in the expansion sleeve assembly 3.

[0064] A piston unit and an intermediate connector 6 are installed in the sealed space. A pull rod 7 is sleeved in the connecting body 1. One end of the pull rod 7 passes through the connecting body 1 from the end away from the support body 2 and connects the piston unit and the intermediate connector 6.

[0065] The intermediate connector 6 can reciprocate axially within the sealed space. The intermediate connector 6 is fixedly connected to the tie rod 7. One end of the intermediate connector 6 extends out of the sealed space and is fixedly connected to the expansion sleeve assembly 3. A positioning block 12 is sleeved on one end of the expansion sleeve assembly 3 near the connector 1. The positioning block 12 is fixedly connected to the support body 2 and is used to cooperate with the positioning end face of the workpiece 10.

[0066] The pull rod 7 is used to move away from the support body 2 to drive the piston unit to deliver hydraulic oil through the first oil circuit system 5 to the oil chamber in the expansion sleeve assembly 3, while driving the intermediate connector 6 and the expansion sleeve assembly 3 to move axially towards the side closer to the connector 1.

[0067] This causes the expansion sleeve assembly 3 to tighten the workpiece 10 while simultaneously pulling the positioning end face of the workpiece 10 onto the positioning surface of the positioning block 12.

[0068] Among them, the expansion sleeve assembly 3 can slide back and forth on the support body 2 along its axial direction, which can be achieved by various key connection methods, including but not limited to: spline connection, guide key connection, etc.

[0069] Preferably, in this embodiment, such as Figure 1 As shown, the expansion sleeve assembly 3 and the support body 2 are connected by a guide key 4;

[0070] By fitting the expansion sleeve assembly 3 onto the end of the support body 2 furthest from the connecting body 1, and connecting the expansion sleeve assembly 3 to the support body 2 via a guide key 4, the expansion sleeve assembly 3 can slide axially back and forth on the support body 2. Simultaneously, an intermediate connector 6 and a piston unit are installed in a sealed space, connected by a pull rod 7. When the pull rod 7 moves away from the support body 2, it drives the piston unit to deliver hydraulic oil through the first oil circuit system 5 to the oil chamber within the expansion sleeve assembly 3. This simultaneously moves the intermediate connector 6 and the expansion sleeve assembly 3 axially towards the connecting body 1, causing the expansion sleeve assembly 3 to tighten the workpiece 10 while simultaneously pulling the positioning end face of the workpiece 10 onto the positioning surface of the positioning block 12. This achieves the self-positioning function of the positioning end face of the workpiece 10, and because the positioning end face of the workpiece 10 is pulled onto the positioning surface of the positioning block 12, it ensures that the positioning end face of the workpiece 10 is aligned with the positioning surface of the positioning block 12. The tight fit between the positioning surfaces of the positioning block 12 ensures that the fit between the positioning end face of the workpiece 10 and the positioning surface of the positioning block 12 meets the machining accuracy requirements of the workpiece 10. This solves the technical problem in the prior art where, when the machine tool's airtightness detection function fails, the machine tool's airtightness detection accuracy decreases, or the machining accuracy requirements of the workpiece 10 are high, the accuracy of the machine tool's airtightness detection system cannot meet the corresponding requirements of the machining accuracy of the workpiece 10; it cannot guarantee that the fit between the positioning end face of the workpiece 10 and the positioning surface of the positioning block 12 meets the machining accuracy requirements of the workpiece 10; and the existing hydraulic fixture itself does not have an end face self-positioning function (i.e., it cannot automatically check whether the positioning end face of the workpiece 10 is tightly fitted with the positioning surface of the positioning block 12). When the airtightness test fails, it is necessary to manually repeatedly disassemble, inspect, clamp, and test the workpiece 10 until the airtightness test passes, resulting in low machining efficiency of the workpiece 10.

[0071] The tie rod 7, piston unit, and intermediate connector 6 can be configured in various ways, such as, but not limited to:

[0072] 1. The piston unit includes a piston disc and a piston; a pull rod passes through the middle of the piston disc and is fixedly connected to the piston disc; a piston is provided on the side of the piston disc near the connecting body; a first oil circuit system 5 is also provided in the connecting body 1; the piston is provided corresponding to the oil circuit hole of the first oil circuit system 5 on the connecting body 1; an intermediate connecting piece 6 is fixedly connected to the end of the pull rod 7 that enters the sealed space.

[0073] In summary, the pull rod 7 can be directly connected to the intermediate connector 6 and the pull-back piston. By moving the pull rod 7 away from the support body 2, the pull rod 7 directly drives the pull-back piston to deliver hydraulic oil through the first oil circuit system 5 to the internal oil chamber of the expansion sleeve assembly 3, and drives the intermediate connector 6 away from the support body 2, thereby causing the expansion sleeve assembly 3 to move closer to the connecting body 1. The configuration of the first oil circuit system 5 is determined by the location of the pull-back piston. If the pull-back piston is located on the support body 2, then the first oil circuit system 5 is provided in both the support body 2 and the expansion sleeve assembly 3. If the pull-back piston is located on the connecting body 1, then the first oil circuit system 5 is provided in the connecting body 1, the support body 2, and the expansion sleeve assembly 3, so as to connect the sealed space with the oil chamber inside the expansion sleeve assembly 3 (specifically, to connect the oil chamber of the pull-back piston and the oil chamber inside the expansion sleeve assembly 3).

[0074] Alternatively, preferably, in this embodiment, such as Figure 1 , Figure 2 and Figure 4 As shown, the piston unit includes a first piston assembly 8 and a second piston assembly 9. A pull rod 7 is fixedly connected to the input end of the first piston assembly 8. The first piston assembly 8 is used to drive the second piston assembly 9. The pull rod 7 is used to move to the side away from the support body 2 to drive the first piston assembly 8, and then drive the second piston assembly 9 to deliver hydraulic oil through the first oil circuit system 5 to the oil chamber in the expansion sleeve assembly 3.

[0075] Among them, such as Figure 1 , Figure 2 and Figure 4 As shown, a first piston hole is provided axially in the central region of one end of the connector 1 near the support 2;

[0076] The first piston assembly 8 includes a first piston 8.1 fitted inside a first piston bore. A first oil chamber 8.4 is formed between the first piston 8.1 and the bottom of the first piston bore. The piston rod of the first piston 8.1 passes through the bottom of the first piston bore and is fixedly connected to a pull rod 7. A third piston bore is formed at the center of the end of the piston body of the first piston 8.1 facing out of the first piston bore. A piston pusher 8.3 is fitted in the third piston bore. A second oil chamber 8.5 is formed between the piston pusher 8.3 and the bottom of the third piston bore. A second oil passage system 8.6 is provided in the first piston 8.1, and the second oil passage system 8.6 connects the first oil chamber 8.4 and the second oil chamber 8.5. The radial cross-sectional area of ​​the first oil chamber 8.4 is larger than the radial cross-sectional area of ​​the second oil chamber 8.5. The piston pusher 8.3 is used to drive the second piston assembly 9.

[0077] The piston body of the first piston 8.1 has a plurality of first pillars 8.2 arranged at intervals around the third piston hole at one end facing the first piston hole (in this embodiment, preferably, three first pillars 8.2 are evenly arranged around the third piston hole at one end facing the first piston hole). One end of each first pillar 8.2 extends out of the first piston hole along the axial direction and is fixedly connected to the intermediate connecting member 6.

[0078] Among them, such as Figure 1 , Figure 2 and Figure 4 As shown, a second piston hole is provided axially in the central region of one end of the support body 2 near the connector 1;

[0079] The second piston assembly 9 includes a second piston 9.1 sleeved in a second piston hole, a third oil chamber 9.2 formed between the second piston 9.1 and the bottom of the second piston hole, and the third oil chamber 9.2 is connected to the first oil circuit system 5; the piston rod of the second piston 9.1 passes through the intermediate connector 6 axially and abuts against the piston push block 8.3.

[0080] Through the above technical solution, as the pull rod 7 moves away from the support body 2 and drives the first piston 8.1 to move away from the support body 2, the volume of the first oil chamber 8.4 is compressed, causing the hydraulic oil in the first oil chamber 8.4 to be transported to the second oil chamber 8.5 through the second oil circuit system 8.6. The volume of the second oil chamber 8.5 increases, and since the radial cross-sectional area of ​​the first oil chamber 8.4 is larger than that of the second oil chamber 8.5, the hydraulic oil in the second oil chamber 8.5 will push the piston push block 8.3 to move closer to the support body 2, thereby pushing the second piston 9.1 and transporting the hydraulic oil in the third oil chamber 9.2 to the expansion sleeve assembly 3 through the first oil circuit system 5.

[0081] Under the premise that the radial cross-sectional area of ​​the first oil chamber 8.4 is greater than that of the radial cross-sectional area of ​​the second oil chamber 8.5, the ratio between the radial cross-sectional areas of the first oil chamber 8.4 and the second oil chamber 8.5 can be adjusted to adjust the ratio of the speed at which the pull rod 7 moves away from the support body 2 to the speed at which the piston push block 8.3 moves towards the support body 2. Compared to the technical solution of directly setting a pull-back piston in a closed space, fixing the piston rod of the pull-back piston to the pull rod 7, and fixing the intermediate connecting piece 6 to the piston rod of the pull-back piston or directly to the pull rod 7, the expansion speed of the expansion sleeve assembly 3 can be adjusted without adjusting the machine tool to adjust the moving speed of the pull rod 7. This ensures that when the pull rod 7 moves away from the support body 2, the expansion action of the expansion sleeve assembly 3 and the movement of the expansion sleeve assembly 3 towards the connecting body 1 achieve the best matching state.

[0082] The ratio between the radial cross-sectional area of ​​the first oil chamber 8.4 and the radial cross-sectional area of ​​the second oil chamber 8.5 can be adjusted by adjusting the diameter of the first piston hole, the diameter of the third piston hole, and the diameter of the piston rod of the first piston 8.1.

[0083] Preferably, in this embodiment, the radial cross-sectional area of ​​the first oil cavity 8.4 is greater than twice the radial cross-sectional area of ​​the second oil cavity 8.5.

[0084] By making the radial cross-sectional area of ​​the first oil chamber 8.4 greater than twice the radial cross-sectional area of ​​the second oil chamber 8.5, when the pull rod 7 moves away from the support body 2, the piston push block 8.3 moves closer to the support body 2 at a greater speed than the pull rod 7 moves away from the support body 2. Compared with the traditional pull-back hydraulic clamp, it can deliver hydraulic oil to the expansion sleeve assembly 3 more quickly, has a more efficient clamping efficiency, can shorten the clamping time of the workpiece 10, and speed up the processing cycle of the workpiece 10.

[0085] like Figure 5 As shown, in this embodiment, the piston pusher 8.3 is in the shape of a stepped shaft, with its smaller diameter end fitted into the third piston hole and its larger diameter end fitted into the first piston hole; a plurality of first through holes 8.3.1 are arranged circumferentially around its central axis on the larger diameter end of the piston pusher 8.3 (in this embodiment, preferably, three first through holes 8.3.1 are evenly arranged circumferentially around its central axis on the larger diameter end of the piston pusher 8.3), and the first through holes 8.3.1 are used for clearance fit with the first column 8.2.

[0086] By setting the piston pusher 8.3 as a stepped shaft, with its smaller diameter end fitted into the third piston hole and its larger diameter end fitted into the first piston hole, the piston pusher 8.3 can reduce vibration when subjected to instantaneous thrust through the guiding engagement of the smaller diameter end of the third piston hole and the guiding engagement of the larger diameter end of the first piston hole. This allows the piston pusher 8.3 to move stably toward the side closer to the connecting body 1, reducing the impact of the vibration of the piston pusher 8.3 on the second piston 9.1, increasing the smoothness of the movement of the second piston 9.1, and preventing the second piston 9.1 from getting stuck in the second piston hole during its movement toward the side closer to the connecting body 1.

[0087] like Figure 2 and Figure 6As shown, in this embodiment, the first piston assembly 8 further includes a compression spring fixing plate 8.7 and a plurality of compression springs 8.8 (in this embodiment, there are 3 compression springs 8.8). The compression spring fixing plate 8.7 is disc-shaped and is fixedly connected to one end of the connecting body 1 near the support body 2 by bolts, and covers the first piston hole. The compression spring fixing plate 8.7 has a second through hole 8.7.1 on its axis that is clearance-fitted with the piston rod of the second piston 9.1; the compression spring fixing plate 8.7 has a plurality of third through holes 8.7.2 spaced around the second through hole 8.7.1 that are clearance-fitted with the first column 8.2 (in this embodiment) In this embodiment, the compression spring fixing plate 8.7 has three third through holes 8.7.2 evenly distributed around the second through hole 8.7.1, which are clearance-fitted with the first column 8.2; the compression springs 8.8 are all arranged between the compression spring fixing plate 8.7 and the piston push block 8.3; the end of the compression spring fixing plate 8.7 facing the first piston hole is provided with a plurality of frustums 8.7.3 at intervals around the second through hole 8.7.1 (in this embodiment, the end of the compression spring fixing plate 8.7 facing the first piston hole has three frustums 8.7.3 evenly distributed around the second through hole 8.7.1), and a compression spring 8.8 is fitted on the outer circumferential surface of each frustum 8.7.3.

[0088] By setting up a compression spring 8.8 and a compression spring fixing plate 8.7, when the pull rod 7 begins to move away from the support body 2, the compression spring 8.8 can buffer the instantaneous thrust when the piston push block 8.3 is subjected to it. This allows the piston push block 8.3 to move more stably towards the connecting body 1, reducing the possibility of the piston push block 8.3 getting stuck. This, in turn, pushes the second piston 9.1 more smoothly and further improves the stability of the movement of the second piston 9.1, preventing the second piston 9.1 from getting stuck in the second piston hole during its movement towards the connecting body 1.

[0089] Among them, such as Figure 2 and Figure 6 As shown, in this embodiment, the compression spring fixing plate 8.7 is provided with a plurality of first screw through holes 8.7.4 at intervals around the second through hole 8.7.1 (in this embodiment, preferably, three first screw through holes 8.7.4 are evenly distributed around the second through hole 8.7.1). The first screw through holes 8.7.4 are used to screw in bolts so that the compression spring fixing plate 8.7 is bolted and fixedly connected to the end of the connecting body 1 near the support body 2.

[0090] Among them, such as Figure 2 and Figure 9As shown, the second piston assembly 9 also includes a spring cover plate 9.3 and a support spring 9.4. The spring cover plate 9.3 is disc-shaped and is fixedly connected to the end of the connector 2 near the support 1 by bolts, and covers the second piston hole. The spring cover plate 9.3 has a central hole along its axial direction at its axis that is clearance-fitted with the piston rod of the second piston 9.1. The support spring 9.4 is sleeved on the piston rod of the second piston 9.1 and is disposed between the spring cover plate 9.3 and the piston body of the second piston 9.1.

[0091] The end of the support spring 9.4 near the spring cover plate 9.3 can be fixedly connected to the spring cover plate 9.3, or it can be left unconnected;

[0092] The end of the support spring 9.4 near the piston body of the second piston 9.1 is not connected to the piston body of the second piston 9.1;

[0093] The support spring 9.4 is used to provide a counter-force to the piston body of the second piston 9.1 when adding or changing hydraulic oil to the third oil chamber 9.2 and the first oil circuit system 5, so that the refueling operator can judge whether the amount of hydraulic oil added has reached the preset amount by the pressure change during the hydraulic oil adding process.

[0094] like Figure 1 and Figure 2 and Figure 8 As shown, in this embodiment, the pull rod 7 has a hollow structure, and its inner hole has an internal thread on the side near the first piston 8.1. The piston rod of the first piston 8.1 has an external thread that matches the internal thread on the end near the pull rod 7. An airtight channel 11 is provided on the end face of the piston rod of the first piston 8.1 near the pull rod 7. The airtight channel 11 passes through the piston rod of the first piston 8.1, the connecting body 1, the support body 2 and the positioning block 12 in sequence and extends to the positioning surface of the positioning block 12.

[0095] When the positioning end face of workpiece 10 is tightened onto the positioning surface of positioning block 12, if there are dirt or impurities on the positioning end face of workpiece 10, it cannot be guaranteed that the positioning end face of workpiece 10 and the positioning surface of positioning block 12 will fit tightly. However, by setting up an airtight channel 11 through the above technical solution, the airtight channel 11 is connected to the inner hole of the pull rod 7, so that gas can be led out from the machine tool spindle to the airtight channel 11, realizing the airtightness detection of the positioning end face of workpiece 10 and the positioning surface of positioning block 12. This can effectively identify whether there are dirt or impurities on the positioning end face of workpiece 10, further ensuring the accurate positioning of workpiece 10 on the fixture, so as to avoid product processing quality problems.

[0096] like Figure 1 , Figure 2 and Figure 3As shown, in this embodiment, the connector 1 has an inner hole at one end near the support 2, and the inner hole of the connector 1 and the end face of the support 2 near the connector form a sealed space; the support 2 is in the shape of a stepped shaft, and its larger diameter end is used to tightly fit and connect with the end face of the connector 1, and the expansion sleeve assembly 3 is sleeved on the smaller diameter end of the support 2.

[0097] like Figure 1 , Figure 2 and Figure 3 As shown, in this embodiment, an annular protrusion 2.1 is provided on the end face of the end where the support body 2 is connected to the connector body 1. The outer peripheral surface of the annular protrusion 2.1 cooperates with the inner surface of the inner hole of the connector body 1. Multiple radial set screw holes 1.1 are evenly distributed along the circumference on the inner surface of the inner hole of the connector body 1. Each radial set screw hole 1.1 penetrates radially to the outer peripheral surface of the connector body 1.

[0098] By setting the radial set screw hole 1.1, the radial runout of the connector 1 can be adjusted through the radial set screw hole 1.1 during the installation and connection process between the connector 1 and the support 2, so as to ensure the overall radial runout accuracy of the fixture.

[0099] like Figure 1 , Figure 2 and Figure 7 As shown, in this embodiment, the intermediate connector 6 is disc-shaped and coaxially arranged with the support body 2. On the side of the intermediate connector 6 near the support body 2, a plurality of second columns 6.1 are arranged circumferentially around its central axis (in this embodiment, three second columns 6.1 are evenly arranged circumferentially around its central axis on the side of the intermediate connector 6 near the support body 2). The end of each second column 6.1 is inserted into the support body 2 axially and then passes out from the shoulder of the support body 2 and is fixedly connected to the end of the expansion sleeve assembly 3 near the shoulder of the support body 2.

[0100] Among them, such as Figure 2 , Figure 4 and Figure 7 As shown, in this embodiment, each of the first columns 8.2 has a bolt hole at the center of the end face extending out of the first piston hole along the axial direction. Correspondingly, the intermediate connector 6 has a plurality of second screw through holes 6.3 spaced around its central axis (in this embodiment, the intermediate connector 6 has three second screw through holes 6.3 evenly distributed around its central axis). The bolt passes through the second screw through holes 6.3 and is fixedly connected to the corresponding first column 8.2. The center of the intermediate connector 6 has a fourth through hole 6.2, which is used to make clearance fit with the piston rod of the second piston 9.1.

[0101] Among them, such as Figure 1 , Figure 2 , Figure 3 and Figure 8As shown, the shoulder of the support body 2 is provided with a plurality of third screw through holes 2.3 spaced apart around its central axis (in this embodiment, three third screw through holes 2.3 are evenly distributed around the central axis on the shoulder of the support body 2). Correspondingly, the end of the connecting body 1 near the support body 2 is provided with a plurality of bolt through holes 1.2 spaced apart around its central axis (in this embodiment, three bolt through holes 1.2 are evenly distributed around the central axis on the end of the connecting body 1 near the support body 2). The bolts pass through the third screw through holes 2.3 and the corresponding bolt through holes 1.2 to tightly connect the connecting body 1 and the support body 2. At the same time, the bolt through holes 1.2 are set as through holes to facilitate the use of long bolts to push the connecting body 1 out of the lathe spindle.

[0102] Among them, such as Figure 1 , Figure 2 and Figure 8 As shown, a plurality of fifth through holes 2.4 are arranged at intervals around the central axis on the shoulder of the support body 2 (in this embodiment, three fifth through holes 2.4 are evenly distributed around the central axis on the shoulder of the support body 2).

[0103] The fifth through hole 2.4 is used for clearance fit with the second column 6.1. The second column 6.1 passes through the corresponding fifth through hole 2.4 into the support body 2, and after passing through the shoulder of the support body 2, it is fixedly connected to the end of the expansion sleeve assembly 3 near the shoulder of the support body 2.

[0104] like Figure 1 , Figure 2 , Figure 9 and Figure 10 As shown, the expansion sleeve assembly 3 includes an expansion sleeve 3.2 and an expansion sleeve support 3.1. Both the expansion sleeve 3.2 and the expansion sleeve support 3.1 are hollow stepped shaft structures. The inner hole of the expansion sleeve 3.2 is interference-fitted with the outer circumferential surface of the expansion sleeve support 3.1. The larger diameter end of the expansion sleeve 3.2 is attached to the shoulder of the expansion sleeve support 3.1 and is fixedly connected to the shoulder of the expansion sleeve support 3.1 by bolts. The larger diameter end of the expansion sleeve support 3.1 is fixedly connected to the intermediate connecting piece 6. The expansion sleeve support 3.1 is sleeved on the end of the support body 2 away from the connecting piece and is connected to the support body 2 by a guide key 4. A first annular groove 2.2 is provided at the contact point between the support body 2 and the inner wall of the expansion sleeve support 3.1.

[0105] The expansion sleeve support 3.1 and the inner wall of the expansion sleeve 3.2 are provided with a second annular groove 3.3 to form an oil cavity in the expansion sleeve assembly 3. The first oil circuit system 5 includes a plurality of radial through holes 5.1 opened at the bottom of the second annular groove and an oil circuit channel 5.2 provided in the support 2. The oil circuit channel 5.2 is used to connect the sealed space and the first annular groove 2.2, and the radial through holes 5.1 are used to connect the first annular groove 2.2 and the second annular groove 3.3.

[0106] Among them, such as Figure 2 , Figure 9 and Figure 10 As shown, the expansion sleeve support 3.1 is fixedly connected to the second column 6.1 by the threaded hole on the end face of the second column 6.1 that protrudes from the shoulder of the support body 2 through the first bolt 3.4; the larger diameter end of the expansion sleeve 3.2 is attached to the shoulder of the expansion sleeve support 3.1 and is fixedly connected to the shoulder of the expansion sleeve support 3.1 by the second bolt 3.5.

[0107] Among them, such as Figure 1 , Figure 2 and Figure 9 As shown, at least one branch of the first oil circuit system 5 is connected to the end face of the support body 2 away from the connector 1 and is provided with a plug at the opening; the first annular groove 2.2 and the second annular groove 3.3 are both provided with oil seals;

[0108] like Figure 1 , Figure 2 and Figure 9 As shown, in this embodiment, preferably, the first oil circuit system 5 has two branches connected to the end face of the support body 2 away from the connector body 1 and a plug is provided at the opening; one branch facilitates the injection of hydraulic oil and is equipped with a steel ball 5.3 and a plugging screw 5.4 at the end, and the other branch facilitates the discharge of hydraulic oil and is equipped with a ball expansion plug 5.5 at the end.

[0109] The pull-back self-positioning hydraulic clamp provided by the present invention has at least the following technical effects or advantages:

[0110] 1. By fitting the expansion sleeve assembly 3 onto the end of the support body 2 away from the connecting body 1, and connecting the expansion sleeve assembly 3 to the support body 2 via the guide key 4, the expansion sleeve assembly 3 can slide back and forth along the axial direction on the support body 2. Simultaneously, an intermediate connector 6 and a piston unit are installed in a sealed space. A pull rod 7 connects the intermediate connector 6 and the piston unit. When the pull rod 7 moves away from the support body 2, it drives the piston unit to deliver hydraulic oil through the first oil circuit system 5 to the oil chamber within the expansion sleeve assembly 3. Simultaneously, it drives the intermediate connector 6 and the expansion sleeve assembly 3 to move axially towards the connecting body 1. This allows the expansion sleeve assembly 3 to tighten the workpiece 10 while simultaneously pulling the positioning end face of the workpiece 10 onto the positioning surface of the positioning block 12. This achieves the self-positioning function of the positioning end face of the workpiece 10. Furthermore, because the positioning end face of the workpiece 10 is pulled onto the positioning surface of the positioning block 12, the positioning end face of the workpiece 10 is guaranteed. The tight fit between the positioning surface of the workpiece 10 and the positioning surface of the positioning block 12 ensures that the fit between the positioning end face of the workpiece 10 and the positioning surface of the positioning block 12 meets the machining accuracy requirements of the workpiece 10. This solves the technical problem in the prior art where the machine tool airtightness detection system cannot meet the corresponding requirements of the machining accuracy of the workpiece 10 when the machine tool airtightness detection function fails, the machine tool airtightness detection accuracy decreases, or the machining accuracy requirements of the workpiece 10 are high; it cannot guarantee that the fit between the positioning end face of the workpiece 10 and the positioning surface of the positioning block 12 meets the machining accuracy requirements of the workpiece 10; and the existing hydraulic fixture itself does not have an end face self-positioning function (i.e., it cannot automatically fit the positioning end face of the workpiece 10 tightly with the positioning surface of the positioning block 12). When the airtightness detection fails, it is necessary to manually repeatedly disassemble, inspect, clamp, and perform airtightness detection on the workpiece 10 until the airtightness detection passes, resulting in low machining efficiency of the workpiece 10.

[0111] 2. Under the premise that the radial cross-sectional area of ​​the first oil chamber 8.4 is greater than that of the radial cross-sectional area of ​​the second oil chamber 8.5, the ratio between the radial cross-sectional area of ​​the first oil chamber 8.4 and the radial cross-sectional area of ​​the second oil chamber 8.5 can be adjusted to adjust the ratio of the speed at which the pull rod 7 moves away from the support body 2 to the speed at which the piston push block 8.3 moves towards the support body 2. Compared with the technical solution of directly setting the pull-back piston in the closed space, fixing the piston rod of the pull-back piston to the pull rod 7, and fixing the intermediate connecting piece 6 to the piston rod of the pull-back piston or directly fixing it to the pull rod 7, the expansion speed of the expansion sleeve assembly 3 can be adjusted without adjusting the machine tool to adjust the moving speed of the pull rod 7. This ensures that when the pull rod 7 moves away from the support body 2, the expansion action of the expansion sleeve assembly 3 and the movement of the expansion sleeve assembly 3 towards the connecting body 1 achieve the best matching state.

[0112] 3. By making the radial cross-sectional area of ​​the first oil chamber 8.4 greater than twice the radial cross-sectional area of ​​the second oil chamber 8.5, when the pull rod 7 moves away from the support body 2, the piston push block 8.3 moves closer to the support body 2 at a greater speed than the pull rod 7 moves away from the support body 2. Compared with the traditional pull-back hydraulic clamp, it can deliver hydraulic oil to the expansion sleeve assembly 3 more quickly, with higher clamping efficiency, which can shorten the clamping time of the workpiece 10 and speed up the processing cycle of the workpiece 10.

[0113] 4. By setting the piston pusher 8.3 as a stepped shaft, with its smaller diameter end fitted into the third piston hole and its larger diameter end fitted into the first piston hole, the piston pusher 8.3 can reduce vibration when subjected to instantaneous thrust through the guiding fit of the smaller diameter end of the third piston hole and the guiding fit of the larger diameter end of the first piston hole. This allows the piston pusher 8.3 to move stably towards the side closer to the connecting body 1, reducing the impact of the vibration of the piston pusher 8.3 on the second piston 9.1, increasing the smoothness of the movement of the second piston 9.1, and preventing the second piston 9.1 from getting stuck in the second piston hole during its movement towards the side closer to the connecting body 1.

[0114] 5. By setting a compression spring 8.8 and a compression spring fixing plate 8.7, when the pull rod 7 starts to move away from the support body 2, the compression spring 8.8 can buffer the instantaneous thrust when the piston push block 8.3 is subjected to instantaneous thrust, so that the piston push block 8.3 can move more stably towards the connecting body 1, reducing the possibility of the piston push block 8.3 getting stuck, and thus pushing the second piston 9.1 more smoothly, and further improving the stability of the movement of the second piston 9.1, preventing the second piston 9.1 from getting stuck in the second piston hole during the process of moving towards the connecting body 1.

[0115] 6. By setting up an airtight channel 11, which is connected to the inner hole of the pull rod 7, gas can be discharged from the machine tool spindle to the airtight channel 11, thereby realizing the airtightness detection of the positioning end face of the workpiece 10 and the positioning surface of the positioning block 12. This can effectively identify whether there are dirt or impurities on the positioning end face of the workpiece 10, further ensuring the accurate positioning of the workpiece 10 on the fixture, so as to avoid product processing quality problems.

[0116] 7. By setting the radial set screw hole 1.1, the radial runout of the connector 1 can be adjusted through the radial set screw hole 1.1 during the installation and connection process between the connector 1 and the support 2, so as to ensure the overall radial runout accuracy of the fixture.

[0117] The above are merely specific application examples of the present invention and do not constitute any limitation on the scope of protection of the present invention. All technical solutions formed by equivalent transformation or equivalent substitution fall within the scope of protection of the present invention.

Claims

1. A pull-back self-positioning hydraulic clamp, characterized in that: It includes a connector and a support body arranged coaxially; one end of the support body near the connector body is tightly connected to the end face of the connector body, and forms a sealed space with the middle of the end face of the connector body. An expansion sleeve assembly is fitted at one end of the support body away from the connecting body. The expansion sleeve assembly can slide back and forth along its axial direction on the support body. A first oil circuit system is provided in both the support body and the expansion sleeve assembly. The first oil circuit system connects the sealed space and the oil cavity in the expansion sleeve assembly. The sealed space is equipped with a piston unit and an intermediate connector. A pull rod is sleeved in the connector. One end of the pull rod passes through the connector from the end away from the support and connects the piston unit and the intermediate connector. The intermediate connector is capable of reciprocating along the axial direction within the sealed space. The intermediate connector is fixedly connected to the pull rod. One end of the intermediate connector extends out of the sealed space and is fixedly connected to the expansion sleeve assembly. A positioning block is sleeved on one end of the expansion sleeve assembly near the connector. The positioning block is fixedly connected to the support body and is used to mate with the positioning end face of the workpiece. The pull rod is used to move away from the support body to drive the piston unit to deliver hydraulic oil through the first oil circuit system to the oil chamber in the expansion sleeve assembly, and at the same time drive the intermediate connector and the expansion sleeve assembly to move along the axial direction towards the connector body. The piston unit includes a first piston assembly and a second piston assembly. The pull rod is fixedly connected to the input end of the first piston assembly. The first piston assembly is used to drive the second piston assembly. The pull rod is used to move away from the support body to drive the first piston assembly, and then drive the second piston assembly to deliver hydraulic oil through the first oil circuit system to the oil chamber in the expansion sleeve assembly. The central region of one end of the connector near the support body is provided with a first piston hole along the axial direction. The first piston assembly includes a first piston fitted inside a first piston bore. A first oil chamber is formed between the first piston and the bottom of the first piston bore. The piston rod of the first piston passes through the bottom of the first piston bore and is fixedly connected to the pull rod. A third piston bore is formed at the center of the end of the first piston body facing outward from the first piston bore. A piston pusher is fitted in the third piston bore. A second oil chamber is formed between the piston pusher and the bottom of the third piston bore. A second oil passage system is provided in the first piston, and the second oil passage system connects the first oil chamber and the second oil chamber. The radial cross-sectional area of ​​the first oil chamber is larger than the radial cross-sectional area of ​​the second oil chamber. The piston pusher is used to drive the second piston assembly. The piston body of the first piston has a plurality of first columns arranged circumferentially around the third piston hole at one end facing the first piston hole. One end of each first column extends out of the first piston hole along the axial direction and is fixedly connected to the intermediate connecting member.

2. The pull-back self-positioning hydraulic clamp according to claim 1, characterized in that: The support body has a second piston hole in the central region of one end near the connector body along the axial direction; The second piston assembly includes a second piston fitted inside the second piston bore, a third oil chamber formed between the second piston and the bottom of the second piston bore, the third oil chamber being connected to the first oil circuit system; the piston rod of the second piston passes through the intermediate connector along the axial direction and abuts against the piston push block.

3. The pull-back self-positioning hydraulic clamp according to claim 1, characterized in that: The piston pusher is in the shape of a stepped shaft, with its smaller diameter end fitted into the third piston hole and its larger diameter end fitted into the first piston hole; a plurality of first through holes are arranged circumferentially around its central axis on the larger diameter end of the piston pusher, and the first through holes are used to fit with the first column with clearance.

4. The pull-back self-positioning hydraulic clamp according to claim 1, characterized in that: The first piston assembly further includes a compression spring fixing plate and a plurality of compression springs. The compression spring fixing plate is disc-shaped and is fixedly connected to the end of the connecting body near the support body by bolts, and covers the first piston hole. The compression spring fixing plate has a second through hole at its axial center that is clearance-fitted with the piston rod of the second piston. The compression spring fixing plate has a plurality of third through holes at intervals around the second through hole that are clearance-fitted with the first column. The compression springs are all disposed between the compression spring fixing plate and the piston push block. The compression spring fixing plate has a plurality of frustums at intervals around the second through hole at the end facing the first piston hole, and a compression spring is fitted on the outer circumferential surface of each frustum.

5. The pull-back self-positioning hydraulic clamp according to claim 1, characterized in that: The pull rod has a hollow structure, and its inner hole has an internal thread on the side near the first piston. The piston rod of the first piston has an external thread that mates with the internal thread at the end near the pull rod. An airtight channel is provided on the end face of the piston rod of the first piston near the pull rod. The airtight channel passes through the piston rod of the first piston, the connecting body, the support body and the positioning block in sequence and extends to the positioning surface of the positioning block.

6. The pull-back self-positioning hydraulic clamp according to claim 1, characterized in that: The connector has an inner hole at one end near the support, and the inner hole of the connector and the end face of the support near the connector form the sealed space; the support is in the shape of a stepped shaft, and its larger diameter end is used to fit tightly with the end face of the connector, and the expansion sleeve assembly is sleeved on the smaller diameter end of the support.

7. The pull-back self-positioning hydraulic clamp according to claim 6, characterized in that: An annular protrusion is provided on the end face of the end where the support body is connected to the connector body. The outer peripheral surface of the annular protrusion matches the inner surface of the inner hole of the connector body. Multiple radial set screw holes are evenly distributed along the circumference on the inner surface of the inner hole of the connector body. Each radial set screw hole penetrates radially to the outer peripheral surface of the connector body.

8. The pull-back self-positioning hydraulic clamp according to claim 6, characterized in that: The intermediate connector is disc-shaped and coaxially arranged with the support body. On the side of the intermediate connector near the support body, a plurality of second columns are circumferentially spaced around its central axis. The end of each second column is inserted into the support body along the axial direction and passes out from the shoulder of the support body, and is fixedly connected to the end of the expansion sleeve assembly near the shoulder of the support body.

9. The pull-back self-positioning hydraulic clamp according to claim 1, characterized in that: The expansion sleeve assembly includes an expansion sleeve and an expansion sleeve support, both of which are hollow stepped shaft structures. The inner hole of the expansion sleeve is interference-fitted with the outer circumferential surface of the expansion sleeve support. The larger diameter end of the expansion sleeve is attached to the shoulder of the expansion sleeve support and is fixedly connected to the shoulder of the expansion sleeve support by bolts. The larger diameter end of the expansion sleeve support is fixedly connected to the intermediate connecting member. The expansion sleeve support is sleeved on the end of the support away from the connecting member and is connected to the support by a guide key. A first annular groove is provided at the contact point between the support and the inner wall of the expansion sleeve support. The expansion sleeve support body is provided with a second annular groove at the contact point with the inner wall of the expansion sleeve to form an oil cavity within the expansion sleeve assembly. The first oil circuit system includes a plurality of radial through holes formed at the bottom of the second annular groove and an oil circuit channel disposed within the support body. The oil circuit channel is used to connect the sealed space and the first annular groove, and the radial through holes are used to connect the first annular groove and the second annular groove.

10. The pull-back self-positioning hydraulic clamp according to claim 9, characterized in that: At least one branch of the first oil circuit system is connected to the end face of the support body away from the connector body and is provided with a plug at the opening; the first annular groove and the second annular groove are both provided with oil seals.

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