CN110678413A

CN110678413A - Jack

Info

Publication number: CN110678413A
Application number: CN201880034750.7A
Authority: CN
Inventors: 堀元正; 山本泰正
Original assignee: Kanetec KK
Current assignee: Kanetec KK
Priority date: 2017-05-26
Filing date: 2018-03-30
Publication date: 2020-01-10
Anticipated expiration: 2038-03-30
Also published as: TW201900541A; WO2018216354A1; TWI746848B; CN110678413B

Abstract

The present invention addresses the problem of providing a jack that can make a contact portion contact a supporting object in a short time without rotating the contact portion by a normal telescopic operation regardless of the distance from the jack to the supporting object. As a solution, the jack (100) comprises: a base (10) having a slide shaft (12) and a slide shaft support (14); a housing (20) which is assembled to the sliding shaft support part (14) and provided with a housing internal thread (22) on the inner wall; a screw cylinder (30) which is screwed to the housing internal thread (22) by a screw cylinder external thread (32) formed on the outer wall, and which has a screw cylinder internal thread (36) and an operating portion (34), wherein the screw cylinder internal thread (36) is formed on the inner wall having the central axis coincident with the central axis of the outer wall and is a reverse thread to the screw cylinder external thread (32); and an abutting part (40) that is screwed to the threaded cylinder internal thread (36), wherein the sliding shaft (12) is inserted into the abutting part (40) in a non-rotating state, and wherein the abutting part (40) is movable along the sliding shaft (12).

Description

Jack

Technical Field

The present invention relates to a jack, and more particularly, to a jack with a screw mechanism for supporting a support object such as a workpiece or a table.

Background

When machining or the like is performed on a workpiece, the workpiece needs to be supported in an appropriate state. When supporting a workpiece, a plurality of telescopic jacks are arranged below the workpiece, and the workpiece is adjusted to be horizontal by adjusting the telescopic amount of the jacks.

As such a jack, for example, a jack having a structure as disclosed in patent document 1 is known. The jack disclosed in patent document 1 includes: a cylindrical body provided with an internal thread portion; a 1 st elevation threaded rod provided with an external thread portion to be screwed with the internal thread portion, an operation head integrally provided with the external thread portion, and an internal thread portion opened to an upper surface of the operation head; and a 2 nd elevation threaded rod which is provided with a male screw portion screwed with the female screw portion of the 1 st elevation threaded rod and is integrally provided with a support head, wherein the pitch of the male screw portion of the 2 nd elevation threaded rod screwed with the female screw portion provided in the 1 st elevation threaded rod is smaller than the pitch of the male screw portion of the 1 st elevation threaded rod screwed with the female screw portion of the cylindrical body.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016-16901984

Disclosure of Invention

Problems to be solved by the invention

The structure of the jack disclosed in patent document 1 has an advantage in that the correction adjustment of the workpiece supporting the object is easily performed. However, when the distance from the jack to the support surface of the workpiece is longer than the projectable length of the 1 st elevation screw rod, if the 2 nd elevation screw rod is not disposed in advance in a state in which the 1 st elevation screw rod projects, the support head portion rotates and comes into contact with the support surface of the workpiece, and therefore, there are problems that the operation becomes complicated, and that the time until the support head portion comes into contact with the workpiece support surface becomes long, which is obvious.

Means for solving the problems

Accordingly, the present invention has been made to solve the above-mentioned problems, and its object is as follows. That is, a structure of a jack is provided which can bring an abutting portion into abutment with a supporting surface of a supporting object in a short time without rotating by a normal telescopic operation regardless of a distance from the jack to the supporting surface of the supporting object.

The inventors of the present application have conducted extensive studies to achieve the above object, and as a result, have conceived the following configuration. That is, the present invention is a jack characterized by comprising: a base having a slide shaft and a slide shaft support portion for supporting the slide shaft in a state in which the slide shaft stands; a housing which is cylindrical, is assembled to the slide shaft support part, and has an internal thread on an inner wall; a threaded cylinder which is cylindrical, is screwed with the housing by using an external thread provided on an outer wall, is provided with an internal thread which is a reverse thread to the external thread of the outer wall on an inner wall whose central axis coincides with the central axis of the outer wall, and is provided with an operation part at an upper end part; and an abutting portion that is screwed to the female screw of the threaded cylinder, and through which the sliding shaft is inserted in a non-rotating state, the abutting portion being movable along the sliding shaft.

Thus, the housing is assembled to the base on which the slide shaft stands, and the contact portion through which the slide shaft passes can be raised relative to the housing without rotating by rotating the threaded cylinder relative to the housing. Further, the time until the contact portion comes into contact with the support surface of the support object can be shortened by adopting a configuration in which the operation of raising (extending) the threaded cylinder from the housing and the operation of raising (extending) the contact portion from the threaded cylinder are performed simultaneously.

Preferably, a stopper is attached to a lower end of at least one of the contact portion and the male screw of the threaded cylinder.

Thus, the threaded cylinder or the abutting portion does not fall off the housing.

Preferably, an abutting enlarged diameter portion is provided at an upper end portion of the abutting portion.

This makes it possible to reduce the contact pressure when the contact portion is in contact with the support surface of the object to be supported, prevent damage to the object to be supported, and support the object to be supported with a small amount of elastic deformation even if the object to be supported is highly elastic.

Further, it is preferable that a stopper for restricting rotation of the threaded cylinder with respect to the housing at an arbitrary position is provided in the housing.

This prevents the screw cylinder from rotating accidentally, and can maintain the support state of the support object in an appropriate state, thereby preventing damage to the support object, and the like.

Further, it is preferable that a magnet is disposed in the sliding shaft support portion.

Thus, the jack can be attracted to the magnetic body, and the degree of freedom of the place where the jack is installed can be improved.

Also, preferably, the sliding shaft is formed in a polygonal column.

Thus, machining for fitting the slide shaft and the slide shaft through hole in the slide shaft and the contact portion can be simplified.

Preferably, a plurality of portions in the circumferential direction of the outer peripheral surface of the slide shaft are formed with line contact portions that are in line contact with the abutment portions.

This reduces frictional resistance between the slide shaft and the contact portion, and allows the slide shaft to smoothly slide. Further, the contact portion and the slide shaft can be assembled in an appropriate state at all times.

Preferably, the contact portion further includes a contact fitting that is attachable to and detachable from the contact portion.

Accordingly, the support object can be supported by the contact fitting that matches the shape of the support object, and therefore the support object can be supported without damaging the support object.

ADVANTAGEOUS EFFECTS OF INVENTION

With the structure of the jack according to the present invention, regardless of the distance from the jack to the support surface of the support object, the abutting portion can be made to protrude in a non-rotational state and abut against the support surface of the support object in a short time by performing a simple telescopic operation of rotating only the threaded cylinder.

Drawings

Fig. 1 is a front view of a jack of embodiment 1.

Fig. 2 is a plan view of the jack of embodiment 1.

Fig. 3 is a side view of the jack of embodiment 1.

Fig. 4 is a cross-sectional view taken along line IV-IV in fig. 2.

Fig. 5 is an exploded assembly view of the jack according to embodiment 1.

Fig. 6 is a cross-sectional view showing a state in which the threaded cylinder and the abutting portion of the jack according to embodiment 1 protrude.

Fig. 7 is an exploded assembly view of the jack according to embodiment 2.

Fig. 8 is an explanatory cross-sectional view showing a state in which the slide shaft of the jack according to embodiment 2 is accommodated in the abutting portion.

Fig. 9 is a sectional view showing a state in which the threaded cylinder and the abutting portion of the jack according to embodiment 2 protrude.

Fig. 10 is a front view showing a modification of the fitting.

Fig. 11 is a plan view of the magnet holder attached to the jack according to embodiment 2.

Fig. 12 is a sectional view through XII-XII of the magnet base attached to the jack of embodiment 2.

Detailed Description

(embodiment 1)

Embodiments of a jack according to the present invention will be described below with reference to the drawings. As shown in fig. 1 to 6, a jack 100 of the present embodiment includes: a base 10 having a slide shaft 12; a cylindrical housing 20 assembled to the base 10; a cylindrical screw cylinder 30 screwed to the housing 20; and an abutment 40 threadedly coupled with the threaded cylinder 30.

As shown in fig. 1, 2, and 4 to 6, the base 10 includes a slide shaft 12 formed in a hexagonal prism shape, and a slide shaft support portion 14 for supporting the slide shaft 12 in a state where the slide shaft 12 stands upright. A lower portion of the slide shaft 12 is formed with a small diameter portion over a predetermined range, and an external thread 12A is engraved on an outer peripheral surface of the small diameter portion. The slide shaft support portion 14 has a female screw thread 14A formed at the center of the upper surface thereof and screwed into the male screw thread 12A of the slide shaft 12, and an assembly screw hole 14B formed in the outer peripheral surface thereof for assembling the housing 20. The slide shaft support portion 14 of the present embodiment is formed of a magnet.

As shown in fig. 4 to 6, the housing 20 is formed in a cylindrical shape having a thick portion whose thickness is larger than the thickness of the other portions in the predetermined height range on the upper side. The inner wall (inner circumferential surface) of the thick portion is engraved with a case internal thread 22. The center axis of the housing internal thread 22 of the present embodiment is on the same axis as the center axis of the slide shaft 12. A screw hole 24 penetrating the thick portion in the radial direction is formed in the thick portion of the housing 20, and a stopper 26 for restricting the rotation of the screw cylinder 30 with respect to the housing 20 at an arbitrary position can be screwed into the screw hole 24. The stopper 26 has a knob portion 26A and an abutting body 26B, and the abutting body 26B is screwed to the screw hole 24 and is capable of abutting against an outer peripheral surface at a screw-coupling portion of a screw cylinder external thread 32 of a screw cylinder 30 described later.

An assembly screw hole 28 is formed on the lower side of the housing 20 in an arrangement aligned with the assembly screw hole 14B arranged in the slide bearing portion 14. The assembly screw holes 14B and the assembly screw holes 28 are disposed at two locations on opposite sides of 180 ° in a plan view of the housing 20. The housing 20 and the base 10 are assembled together by screwing the assembly screws N into the assembly screw holes 28 and the assembly screw holes 14B, respectively.

As shown in fig. 4 to 6, the screw cylinder 30 is cylindrical, and has a screw cylinder external thread 32 provided on an outer wall (outer peripheral surface) and an operating portion 34 formed at an upper end portion of the screw cylinder external thread 32 and having a diameter larger than that of the screw cylinder external thread 32. The threaded cylinder 30 further has a threaded cylinder female thread 36, and the threaded cylinder female thread 36 is provided on an inner wall (inner circumferential surface) whose central axis coincides with the central axis of the outer wall. The threaded cylinder 30 is screwed to the housing 20 so as to be able to advance and retreat along the axial direction of the threaded cylinder 30 and the housing 20. The direction of the thread ridge of the screw cylinder external thread 32 and the direction of the thread ridge of the screw cylinder internal thread 36 are formed in opposite directions (opposite threads). The outer peripheral surface of the operation portion 34 is preferably subjected to anti-slip processing in advance. In the present embodiment, the outer peripheral surface of the operation portion 34 is knurled.

As shown in fig. 4 to 6, the contact portion 40 is formed in a cylindrical shape, and an internal space of the contact portion 40 is a sliding shaft insertion hole 42. A fitting portion 44 to be fitted to the slide shaft 12 is formed in a predetermined range in the height direction (extending direction) of the slide shaft insertion hole 42. As described above, the fitting portion 44 is formed only in a part of the range of the slide shaft insertion hole 42 in the height direction, and friction between the slide shaft 12 and the slide shaft insertion hole 42 can be reduced. Further, an abutment male screw 46 that is screwed into the threaded-barrel female screw 36 of the threaded barrel 30 is engraved on an outer wall (outer circumferential surface) of the abutment 40 on which the sliding shaft through-hole 42 is formed.

The abutment 40 is screwed to the threaded cylinder 30 in a state where the center axis of the abutment 40 coincides with the center axis of the threaded cylinder 30. The abutment male screw 46 and the cylindrical male screw 32 are formed as opposite screws, and the arrangement pitch of the thread of the abutment male screw 46 is the same as the arrangement pitch of the thread of the cylindrical male screw 32. By rotating the threaded cylinder 30 relative to the housing 20, the contact portion 40 formed in this manner can move along the slide shaft 12 in a non-rotational state.

In the contact portion 40 of the present embodiment, an abutment enlarged diameter portion 48 is provided at an upper end portion in the height direction of the contact portion male screw 46, and the abutment enlarged diameter portion 48 is formed to have a larger diameter than the contact portion male screw 46. By providing such an enlarged diameter portion for abutment 48, there are advantages in that: the contact pressure at the contact portion with the object to be supported can be reduced as much as possible, and the object to be supported can be supported with the amount of elastic deformation suppressed to the minimum. Further, a stopper 49 is attached to a lower end portion of the abutment male screw 46 to prevent the abutment 40 from coming off the threaded cylinder 30.

A method of operating the jack 100 of the present embodiment will be described. Here, a method of supporting a workpiece (neither shown) as a supporting object on a table of a magnetic body by the jack 100 during grinding will be described.

The jack 100 is used in a state of being attracted and fixed to a platform of a magnetic body by a sliding shaft support portion 14 formed of a magnet. When the user rotates the screw cylinder 30 with respect to the housing 20 fixed to the base 10, the screw cylinder 30 extends in a direction protruding (separating) from the upper surface of the housing 20. The abutment portion 40 is movable along the slide shaft 12 in a non-rotational state with respect to the slide shaft 12. The threaded cylinder external thread 32 formed on the inner wall of the threaded cylinder 30 and the abutment external thread 46 formed on the outer peripheral surface of the abutment 40 are formed as reverse threads. Thus, by rotating the threaded cylinder 30 relative to the housing 20, the threaded cylinder 30 can be made to protrude from the upper surface of the housing 20, and at the same time, the abutment portion 40 can be made to protrude (extend) from the threaded cylinder 30 in a non-rotated state along the slide shaft 12. That is, the threaded cylinder 30 and the abutment portion 40 can be simultaneously projected with respect to the housing 20 only by operating and rotating the threaded cylinder 30.

The user can rotate the operating portion 34 of the threaded cylinder 30 until the contact enlarged diameter portion 48 of the contact portion 40 comes into contact with the workpiece. After the contact enlarged diameter portion 48 comes into contact with the workpiece, the rotation operation of the operation portion 34 is stopped, and the operation of the first jack 100 is ended. Since the workpiece is supported by the plurality of jacks 100, the operation described above may be performed similarly for the other jacks 100. After the support of the workpiece is completed by all the jacks 100, the user finely adjusts the contact state between each jack 100 and the workpiece. Thereafter, if the user operates the stopper 26 to bring the abutting body 26B into abutment with the outer peripheral surface of the screw-coupling portion of the screw cylinder 30 to be screw-coupled with the housing 20 (the outer peripheral surface of the screw cylinder external thread 32) to restrict the rotation of the screw cylinder 30 with respect to the housing 20, the support of the workpiece by the jack 100 is completed. After the workpiece is supported by the jacks 100, the workpiece is ground.

When the jack 100 is to be removed after the grinding of the workpiece is completed, the threaded cylinder 30 and the contact portion 40 can be simultaneously inserted into the housing 20 simply by releasing the stopper 26 and rotating the threaded cylinder 30 in the above-described reverse direction.

In the present embodiment, as shown in fig. 6, when the contact portion 40 of the jack 100 is extended to a predetermined height, the anti-separation stopper 49 attached to the lower end portion of the contact portion male screw 46 comes into contact with the step 38 at the lower end portion of the thick portion of the internal space of the threaded cylinder 30. This restricts further extension of the abutment portion 40. When the extension of the abutment 40 with respect to the threaded cylinder 30 is restricted, the rotation of the threaded cylinder 30 is also restricted, so that the extension of the entire jack 100 can be restricted. In this way, the configuration of the contact portion 40 having the fitting portion 44 fitted to the slide shaft 12 has the following advantages: even in the jack 100 having the screw-coupled portions at two locations, the anti-separation stopper 49 may be disposed only on the abutting portion 40 side.

(embodiment 2)

The same structure as that of the jack 100 according to embodiment 1 in the jack 100 according to the present embodiment is illustrated with reference numerals used in embodiment 1, and a detailed description thereof will be omitted.

As shown in fig. 7 and 8, the slide shaft 12 of the present embodiment has a cross-sectional shape having an arcuate projection 12C in a part of the outer peripheral edge of the body 12B. The slide shaft 12 can be formed by cutting the outer peripheral surface of a cylinder with a cutting blade or the like. Here, a portion of the outer peripheral edge of the cylinder is cut with a cutting blade having a rectangular cutting cross section so as to overlap a portion in the width direction of the cutting cross section, thereby forming the slide shaft 12 having the arcuate projecting portion 12C. The arcuate projection 12C of the slide shaft 12 is formed such that the width W2 of the arc portion of the arcuate projection 12C is wider than the width W1 of the main body 12B. Here, the arcuate projections 12C are arranged at 3 positions at equal intervals along the outer periphery of the slide shaft 12.

The slide shaft insertion hole 42 of the contact portion 40 into which the slide shaft 12 is inserted has a shape in which an outer protrusion hole 42B corresponding to the position of the arc-shaped protrusion 12C of the slide shaft 12 is partially arranged on the outer peripheral edge of the circular center hole 42A. As shown in fig. 8, the arc-shaped protruding portion 12C of the slide shaft 12 is inserted into the outer protruding hole 42B of the slide shaft insertion hole 42, whereby the contact portion 40 can be set in a non-rotatable state with respect to the slide shaft 12. In the present embodiment, the linear contact portion T is formed where both end portions of the outer peripheral edge of the arcuate projecting portion 12C of the slide shaft 12 are in linear contact with the inner peripheral surface of the outer projecting hole 42B of the slide shaft insertion hole 42. This reduces the frictional force when the slide shaft 12 slides in the non-rotational state in the slide shaft insertion hole 42, and the sliding movement of the slide shaft 12 can be smoothly performed. Further, since 3 or more locations of the line contact portion T between the slide shaft 12 and the slide shaft insertion hole 42 are arranged along the circumferential direction, the slide shaft 12 can be assembled in a designed state when the slide shaft 12 is assembled to the contact portion 40 (the slide shaft insertion hole 42).

As shown in fig. 9, in the present embodiment, the slide shaft 12 and the slide shaft support portion 14 are integrally formed. The slide shaft support portion 14 is formed as a circular plate, and a bottom surface female screw 14C is formed from the bottom surface side of the slide shaft support portion 14 at the center position of the slide shaft 12. Drain holes 14D penetrating in the thickness direction of the slide shaft support portion 14 are disposed at a plurality of locations in the circumferential direction of the slide shaft support portion 14.

The slide shaft support portion 14 integrally formed with the slide shaft 12 is disposed at the step portion 29A formed inside the bottom portion of the housing 20. The slide shaft support portion 14 is attached to the lower portion of the housing 20 by bringing the slide shaft support portion 14 into contact with the tip end portion of the 3-piece screw N screwed in from the side surface of the housing 20 and fitting the C-shaped seal ring 50 into the groove portion 29B provided at the position of the housing 20 corresponding to the bottom surface position of the slide shaft support portion 14.

Further, when the slide shaft support portion 14 is not provided with the drainage hole 14D, a cover 60 (see fig. 7) for closing the opening portion of the slide shaft insertion hole 42 of the contact enlarged diameter portion 48 may be attached. By disposing a sealing member (not shown) in a contact portion of the cover 60 that contacts the slide shaft insertion hole 42, the slide shaft insertion hole 42 can be sealed in a sealed state.

As shown in fig. 9, a detachable contact fitting 70 may be attached to the slide shaft insertion hole 42 of the contact enlarged diameter portion 48. The insertion portion 72 of the contact fitting 70 may be appropriately changed to an externally threaded portion, a pin, or the like in a state where the inner peripheral surface of the slide shaft through hole 42 (the opening portion of the contact enlarged diameter portion 48) at the portion of the contact enlarged diameter portion 48 is coupled. Further, the abutment surface 74 of the abutment fitting 70 shown in fig. 9 is formed in a spherical shape, but the abutment fitting 70 formed as the abutment surface 74 as shown in fig. 10 may be employed, and the abutment surface 74 includes a V groove 74A and a concave groove 74B formed at the bottom of the V groove 74A. When the contact portion 40 is formed of a magnetic material, the magnet 76 can be appropriately disposed on the bottom surface of the contact fitting 70. The shape of the contact fitting 70 may be adapted to the shape of the contact portion of the object to be supported by the jack 100. A contact surface drainage portion (not shown) may be disposed on the contact surface 74.

As shown in fig. 11 and 12, the magnet portion 80 can be detachably attached to the slide shaft support portion 14 attached to the housing 20. The magnet portion 80 has a cylindrical shape having the same shape as the bottom surface of the slide bearing portion 14, and a magnet 82 is embedded in the bottom surface. The magnet portion 80 can be detachably attached to the slide shaft support portion 14 by inserting a screw (not shown) through the screw hole 84 and screwing the screw into the bottom surface female thread 14C of the slide shaft support portion 14.

Further, 4 drain grooves 86 are formed in the upper surface of the magnet portion 80 at equal intervals in the circumferential direction, and the drain grooves 86 extend radially outward of the magnet portion 80 about the screw hole 84. Accordingly, the liquid or the like entering from the opening portion of the slide shaft through hole 42 flows down through the gap between the slide shaft through hole 42 and the slide shaft 12 and the drain hole 14D, and is discharged from the drain groove 86 to the outside of the jack 100.

The jack 100 of the present invention has been described in detail based on the embodiments, but the technical scope of the present invention is not limited to the embodiments. For example, although the slide shaft 12 is formed in a hexagonal prism shape with respect to the base 10 of the above-described embodiment, the slide shaft 12 may be formed in another polygonal prism such as a quadrangular prism. Further, a shape in which a convex portion or a concave portion is provided in a part of the outer peripheral surface of the cylinder may be adopted. In short, the contact portion 40 may be moved along the slide shaft 12 in a non-rotational state with respect to the slide shaft 12 inserted through the slide shaft insertion hole 42.

In addition, with respect to the base 10 of embodiment 1, the form in which the slide shaft support portion 14 is formed of a magnet has been described, and a form in which a magnet is attached to the bottom surface of the slide shaft support portion 14 or a form in which a magnet is disposed in the slide shaft support portion 14 may be adopted. Further, if a magnet is disposed on the platform on which the jack 100 is provided, the sliding shaft support portion 14 may be formed of a magnetic material so that the magnet is not disposed.

Further, although the case 20 has been described as having the knob portion 26A and the abutting body 26B screwed to the screw hole 24 and abutting against the outer peripheral surface of the screw cylinder external thread 32 of the screw cylinder 30, the stopper 26 may be constituted by only the abutting body 26B (without the knob portion 26A) formed by a hexagon socket fastening screw (so-called fixing screw, japanese patent No. イモね). Moreover, the stopper 26 may be omitted.

Further, in the screw cylinder 30, as the operation portion 34, a flange shape having a larger diameter than the housing 20 is adopted, but the diameter of the operation portion 34 may be smaller than the housing 20. The operation portion 34 may be formed of one or more protrusions protruding from the outer peripheral surface of the upper end portion of the threaded cylindrical outer thread 32. In short, the specific form is not particularly limited as long as the screw cylinder 30 can be rotated.

In the above embodiment, the abutment portion 40 has the abutment enlarged diameter portion 48 formed to have a larger diameter than the abutment male screw 46 at the abutment portion with which the object to be supported abuts, but the abutment enlarged diameter portion 48 may be omitted. Even if the abutment enlarged diameter portion 48 is omitted, the abutment fitting 70 can be used by attaching the insertion portion 72 to the slide shaft insertion hole 42.

In the above embodiment, the form in which the retaining stopper 49 is attached to the contact portion male screw 46 of the contact portion 40 has been described, but the present invention is not limited to this form. For example, the anti-slip stopper may be attached to both the threaded-barrel external thread 32 and the abutment external thread 46, or may be attached only to the lower end of the threaded-barrel external thread 32 of the threaded barrel 30. In the case where the anti-separation stopper is to be attached to the cylindrical screw 32 and the abutment male screw 46, it is only necessary to attach the anti-separation stopper to at least one of the cylindrical screw 32 and the abutment male screw 46.

In addition to the above modifications, the modifications described in the embodiment and the like can be combined as appropriate.

Claims

1. A jack is characterized in that a jack body is provided,

this jack includes:

a base having a slide shaft and a slide shaft support portion for supporting the slide shaft in a state in which the slide shaft stands;

a housing which is cylindrical, is assembled to the slide shaft support part, and has an internal thread on an inner wall;

a threaded cylinder which is cylindrical, is screwed with the housing by using an external thread provided on an outer wall, is provided with an internal thread which is a reverse thread to the external thread of the outer wall on an inner wall whose central axis coincides with the central axis of the outer wall, and is provided with an operation part at an upper end part; and

and an abutting portion that is screwed to the female screw of the threaded cylinder, and through which the sliding shaft is inserted in a non-rotating state, and that is movable along the sliding shaft.

2. A jack as claimed in claim 1 in which,

an anti-drop stopper is attached to a lower end of at least one of the external thread and the abutment portion of the threaded cylinder.

3. A jack as claimed in claim 1 or claim 2,

an abutting expanded diameter portion is provided at an upper end portion of the abutting portion.

4. A lifting jack according to any one of claims 1 to 3 wherein,

a stopper for limiting rotation of the threaded cylinder relative to the housing to an arbitrary position is provided at the housing.

5. A lifting jack according to any one of claims 1 to 4 wherein,

a magnet is disposed on the sliding shaft support portion.

6. A lifting jack according to any one of claims 1 to 5 wherein,

the sliding shaft is formed in a polygonal column.

7. A lifting jack according to any one of claims 1 to 6 wherein,

line contact portions that are in line contact with the abutment portions are formed at a plurality of locations in the circumferential direction of the outer peripheral surface of the slide shaft.

8. A lifting jack according to any one of claims 1 to 7 wherein,

the jack further includes an abutting fitting that is attachable to and detachable from the abutting portion.