CN111376188A

CN111376188A - Expandable positioning fixture

Info

Publication number: CN111376188A
Application number: CN201811636443.4A
Authority: CN
Inventors: 李福华; 王志强; 李红豆; 余其林
Original assignee: Chongqing Hongjiang Machinery Co Ltd
Current assignee: Chongqing Hongjiang Machinery Co Ltd
Priority date: 2018-12-29
Filing date: 2018-12-29
Publication date: 2020-07-07

Abstract

An expandable positioning fixture comprises a mandrel, a plunger assembly and a sleeve; an expansion type containing cavity for containing liquid plastic is arranged in the mandrel, and the sleeve is assembled on the outer circle of the workpiece positioning section of the mandrel in an interference manner; the expansion cavity is divided into an expansion cavity, an extrusion cavity and an exhaust cavity, the expansion cavity is positioned in the center of the workpiece positioning section, the expansion cavity is provided with a central main channel and branch channels which are symmetrically radiated along the circumferential direction of the main channel, and the branch channels are communicated to a gap between the outer wall of the positioning section and the sleeve; the clamp positioning section extends backwards from the workpiece positioning section to form an airplane shape, the extrusion cavity and the exhaust cavity are respectively positioned in the two wings, the outlet is arranged at the tail end of each wing, and the extrusion cavity and the exhaust cavity are respectively communicated with the main channel of the expansion cavity; the plunger assembly is arranged in the extrusion cavity and extrudes the liquid plastic. The expandable positioning fixture can avoid the danger of pulling and scratching the inner hole of the part and simultaneously ensure the coaxiality requirement of the inner circle and the outer circle of the part.

Description

Expandable positioning fixture

Technical Field

The invention belongs to the technical field of machining positioning fixtures, and particularly relates to an excircle technician positioning fixture for a cylinder workpiece.

Background

The positioning and pressing of metal parts are the most applied in machining, different positioning fixtures are adopted for different structures and different materials, and for example, parts such as roller bushings, sliding bearings and the like of key parts of diesel engines have high requirement on coaxiality of inner circles and outer circles, and inner holes are made of soft materials. The taper mandrel is generally designed for processing, and the part can be fastened only by a certain external force when the taper mandrel is arranged on the part, so that the operation easily causes pulling injury and scratching to an inner hole, and particularly, the part with the very soft inner hole is particularly obvious. Also design into the location of cylinder mandrel, the positioning fixture who compresses tightly from the terminal surface is processed, has avoided causing strain, fish tail to the part hole, however, because of the hole must have certain clearance with the positioning mandrel just can install, just hardly guarantee the axiality of interior excircle to the part that the axiality required height.

Disclosure of Invention

In order to solve the problems, the invention designs a positioning clamp which can position and tension (compress) the excircle of rotary machining for parts (such as roller bushings, sliding bearings and other parts of key parts of diesel engines) with high requirement on coaxiality of inner and outer circles and soft inner hole materials, and solves the problems that the excircle of general rotary machining is positioned and machined by a taper mandrel, and the danger of pulling and scratching the inner hole exists; the cylindrical mandrel is used for positioning and is pressed from the end surface for processing, the problem that the requirement on coaxiality of an inner circle and an outer circle is difficult to ensure exists,

the technical scheme of the invention is as follows:

an expandable positioning fixture comprises a mandrel, a plunger assembly and a sleeve; the mandrel is internally provided with an expansion containing cavity for containing liquid plastics, the mandrel is divided into a workpiece positioning section and a clamp positioning section, and the sleeve is assembled on the excircle of the workpiece positioning section of the mandrel in an interference manner. The expansion cavity is divided into an expansion cavity, an extrusion cavity and an exhaust cavity, the expansion cavity is positioned in the center of the mandrel positioning section, the expansion cavity is provided with a central main channel and branch channels which symmetrically radiate along the circumferential direction of the main channel, and the branch channels are communicated to a gap between the outer wall of the workpiece positioning section and the sleeve. The clamp positioning section extends backwards from the workpiece positioning section to form an airplane shape, the extrusion cavity and the exhaust cavity are respectively positioned in the two wings, the outlet is arranged at the tail end of each wing, and the extrusion cavity and the exhaust cavity are respectively communicated with the main channel of the expansion cavity; the plunger assembly is arranged in the extrusion cavity and extrudes the liquid plastic, and the outlet of the exhaust cavity is sealed by a steel ball and an inner hexagon screw; the tail end of the airplane-shaped clamp positioning section plays roles in positioning and power transmission during machining.

Furthermore, the excircle of the workpiece positioning section of the mandrel is ground according to the corresponding inner hole of the sleeve, and the interference magnitude is not less than 0.05 mm.

Further, a protective sleeve is sleeved outside the sleeve.

Furthermore, the plunger assembly comprises a threaded sleeve, a compression screw and a plunger, the threaded sleeve is arranged at the outlet part of the extrusion cavity, the plunger and the compression screw are sequentially arranged in the threaded sleeve, and the plunger is driven to move by screwing in and screwing out the compression screw.

Furthermore, the main channel of the expansion cavity extends forwards to penetrate through the positioning section, a plug is adopted at the outlet part, and the plug is firmly welded to serve as a positioning hole to play a positioning role.

Furthermore, a counter bore is designed at the outlet part of the main channel, and a copper pad and a screw plug are arranged in the counter bore to play the roles of process hole and plugging.

Furthermore, the sleeve is a thin-walled part and is made of spring steel 65Mn through special heat treatment, the wall thickness range is 2.2-2.25mm, and the elastic effect of long-term use is guaranteed.

By adopting the clamp, in the clamping process, the protective sleeve is firstly taken off, the processed part is slightly sleeved into the outer circle of the sleeve for positioning, then an internal hexagonal wrench is inserted into the internal hexagonal of the compression screw, the compression screw is rotated, the plunger is pushed to move inwards, and pressure is transferred to the liquid plastic. According to the incompressible property of the liquid substance, when pressure is transmitted to the liquid plastic, the weakest part in the liquid plastic volume cavity can expand the outer circle of the thin wall of the sleeve, and after the part is tensioned (compressed), corresponding rotary processing can be carried out. When the part needs to be taken down after the processing is finished, the inner hexagonal wrench is inserted into the inner hexagonal of the compression screw, the compression screw is rotated in the opposite direction, the plunger is driven to move outwards, the pressure transmitted to the liquid plastic is released, the outer circle of the thin wall of the sleeve can elastically contract, a gap is formed between the part and the positioning mandrel, and the part can be taken down. The expandable positioning fixture avoids the danger of strain and scratch on the inner hole of the part, and simultaneously ensures the coaxiality requirement of the inner circle and the outer circle of the part.

The invention has unique positioning and tensioning (pressing) principles. And tightening the compression screw to push the plunger piston to move inwards and transfer pressure to the liquid plastic. The thin-wall excircle of the sleeve can be expanded, and corresponding rotary processing can be carried out after the part is positioned and expanded. The compression screw is screwed in the opposite direction to drive the plunger to move outwards, the pressure transmitted to the liquid plastic is released, the outer circle of the thin wall of the sleeve can elastically contract, and the parts can be taken down. The invention is mainly applied to the positioning and tensioning (pressing) of the holes of metal parts, for example, parts such as roller bushings, sliding bearings and the like of key parts of diesel engines, which have high requirement on the coaxiality of inner and outer circles and soft material of inner holes, can effectively avoid the inner holes of the parts from being scratched and scratched, and simultaneously ensure the coaxiality requirement of the inner and outer circles of the parts.

Drawings

FIG. 1: is a schematic structural view of an expandable positioning clamp

FIG. 2: is an enlarged view of section I in fig. 1;

FIG. 3: is an enlarged view of section II in FIG. 1;

FIG. 4: is an enlarged view of section III in FIG. 1.

In the figure: 1: a steel ball; 2: a socket head cap screw; 3: a mandrel; 4: a threaded sleeve; 5: a compression screw 1; 6: a plunger; 7: a protective sleeve; 8: a sleeve; 9: a copper pad; 10: a plug screw; 11: plugging; 12: expansion type cavity, 121: expanding the cavity; 1211: a main channel; 1212: a branch channel; 122: an extrusion chamber; 123: and an exhaust cavity.

Detailed Description

With reference to fig. 1, 2, 3 and 4, the present invention has the following embodiments:

the utility model provides an expandable positioning fixture has adopted unique design structure, includes 1 steel ball 1, 1 hexagon socket head cap screw 2, 1 mandrel 3, 1 swivel nut 4, 1 housing screw 5, 1 plunger 6, 1 protective sheath 7, 1 sleeve 8, 1 copper pad 9, 1 plug screw 10, 1 vexed plug 11.

The mandrel 3 is internally provided with an expansion type containing cavity 12 for containing liquid plastics, the mandrel is divided into a workpiece positioning section and a fixture positioning section, the workpiece positioning section is used for positioning a processed workpiece, the fixture positioning section extends backwards from the workpiece positioning section to be in an airplane shape, and the tail end of the airplane body of the airplane-shaped fixture positioning section plays roles in positioning and power transmission during processing.

The sleeve 8 is interference fitted over the outer circle of the workpiece locating section of the spindle 3.

The expansion cavity is divided into an expansion cavity 121, a squeezing cavity 122 and an exhaust cavity 123, the expansion cavity 121 is located at the center of the mandrel positioning section, the expansion cavity 121 is provided with a central main channel 1211 and branch channels 1212 which radiate symmetrically along the circumferential direction of the main channel, and the branch channels 1212 are communicated with a gap between the outer wall of the workpiece positioning section and the sleeve 8.

The clamp positioning section is provided with an extrusion cavity 122 and an exhaust cavity 12 which are respectively positioned in the two wings, the outlet is at the tail end of the wing, and the extrusion cavity and the exhaust cavity are respectively communicated with the main channel of the expansion cavity. The plunger assembly is arranged in the extrusion cavity 122 to extrude the liquid plastic, and the outlet of the exhaust cavity 123 is sealed by a steel ball 1 and a hexagon socket head cap screw 2.

And the excircle of the workpiece positioning section of the mandrel 3 is ground according to the corresponding inner hole of the sleeve 8, and the interference magnitude is not less than 0.05 mm. The sleeve 8 is a thin-wall part and is made of spring steel 65Mn through heat treatment, the wall thickness range is 2.2-2.25mm, and the elastic effect of long-term use is guaranteed. The sleeve 8 is sleeved with a protective sleeve 7.

The plunger assembly comprises a threaded sleeve 4, a compression screw 5 and a plunger 6, the threaded sleeve 4 is arranged at the outlet part of the extrusion cavity, the plunger 6 and the compression screw 5 are sequentially arranged in the threaded sleeve 4, and the plunger is driven to move by screwing in and out the compression screw 5.

The manufacturing and assembling steps of the positioning clamp are as follows:

the first step is to install the copper pad 9 into the counter bore step surface at the right end of the mandrel 3, screw the plug screw 10 and compress tightly, press in the bulkhead 11 and weld on the mandrel 3, and require no leakage under high pressure, see fig. 2.

And secondly, performing matched grinding on the corresponding excircle of the mandrel 3 according to the corresponding inner hole of the sleeve 8 to ensure that the interference magnitude is not less than 0.05mm, assembling the sleeve 8 on the mandrel 3 through cold fitting, and then finely grinding the excircle of the sleeve 8 to the size required by part positioning, referring to fig. 3.

The third step is to match and grind the excircle of the plunger 6 and the inner hole of the screw sleeve 4, and ensure that the matching clearance is 0.003-0.006 mm.

And fourthly, screwing the screw sleeve 4 into the mandrel 3, and ensuring that the sealing conical surface does not leak under high pressure after screwing. Liquid plastic is injected through the holes of the threaded sleeve 4, air in the volume cavity is discharged through the small holes on the mandrel 3, and when the air is completely discharged, the steel ball 1 is loaded, and the hexagon socket head cap screw 2 is screwed in and tightened. The plunger 6 is screwed into the compression screw 5, the whole is arranged in the hole of the thread sleeve 4, and the compression screw 5 is screwed so that the expansion amount of the outer diameter of the sleeve 8 is not less than 0.08mm, which is shown in figure 4.

Claims

1. An expandable positioning fixture comprises a mandrel (3), a plunger assembly and a sleeve (8); an expansion type containing cavity for containing liquid plastic is arranged in the mandrel (3), the mandrel is divided into a workpiece positioning section and a clamp positioning section, and the sleeve (8) is assembled on the excircle of the workpiece positioning section of the mandrel (3) in an interference manner; the expansion cavity is divided into an expansion cavity, an extrusion cavity and an exhaust cavity, the expansion cavity is positioned in the center of the mandrel positioning section, the expansion cavity is provided with a central main channel and branch channels which are symmetrically radiated along the circumferential direction of the main channel, and the branch channels are communicated to a gap between the outer wall of the workpiece positioning section and the sleeve (8); the clamp positioning section extends backwards from the workpiece positioning section to form an airplane shape, the extrusion cavity and the exhaust cavity are respectively positioned in the two wings, the outlet is arranged at the tail end of each wing, and the extrusion cavity and the exhaust cavity are respectively communicated with the main channel of the expansion cavity; the plunger assembly is arranged in the extrusion cavity to extrude the liquid plastic, and the outlet of the exhaust cavity is sealed by a steel ball (1) and an inner hexagon screw (2); the tail end of the airplane-shaped fixture positioning section plays roles in positioning and power transmission during machining.

2. The expandable positioning fixture of claim 1, wherein the outer circle of the workpiece positioning section of the mandrel (3) is ground according to the corresponding inner hole of the sleeve (8), and the interference is not less than 0.05 mm.

3. Expandable positioning clamp according to claim 1, characterised in that the sleeve (8) is sheathed with a protective sheath (7).

4. The expandable positioning fixture as claimed in claim 1, wherein the plunger assembly comprises a threaded sleeve (4), a compression screw (5) and a plunger (6), the threaded sleeve (4) is arranged at the outlet part of the extrusion cavity, the plunger (6) and the compression screw (5) are sequentially arranged in the threaded sleeve (4), and the plunger is driven to move by screwing in and screwing out the compression screw (5).

5. An expandable positioning fixture as claimed in claim 1, wherein the main channel of the expansion cavity extends forwards through the workpiece positioning section, and a plug (11) is used at the outlet part for positioning.

6. The expandable positioning fixture as claimed in claim 1, wherein a counter bore is designed at the outlet of the main channel, and a copper pad (9) and a screw plug (10) are arranged in the counter bore.

7. The expandable positioning clamp according to claim 1, wherein the sleeve (8) is a thin-walled part made of spring steel 65Mn by heat treatment, and has a wall thickness in the range of 2.2-2.25 mm.