JPH0543464B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel screw drive mechanism which allows rapid engagement between the screw and the screw nut through relative movement between the screw and the nut. It is possible to connect and disengage, quickly passing through idle strokes,
Can be widely used as a manual bench vise where quick adjustment of relative distance or quick gripping is required, a bench vise for machine tools, or a sliding table for machine tools. It is something.

There are many known types of quick grip vises. US Pat. No. 2,102,602 (1937) discloses a mechanism in which the trajectory of the center of the screw is an arc when the screw disengages or engages the nut. The nut must therefore be slidably connected to the stationary body, resulting in insufficient strength. US Patent No.
No. 2430458 (1947) also states that the screw nut still remains on the screw after the screw is separated from the screw nut, and there the screw nut is held against the outer circumference of the screw by a spring and a pin. A mechanism is disclosed, and the mechanism imposes significant resistance on the tool. Furthermore, the patent application filed by the applicant with the European Patent Office (No. 88301613, see Figure 32) discloses a quick gripping mechanism in which the drive nut is provided outside the vise body and the mechanism is structurally complex. is disclosed.

It is an object of the present invention to overcome the above-mentioned deficiencies by using a one-way pawl and cam mechanism to effect vertical relative movement between the screw and the nut such that the screw engages and disengages the screw nut. It's about doing. This mechanism is simple in structure and low in cost.

The mechanism according to the invention comprises a movable sliding body,
It includes a stationary body, a screw, a screw nut seat, an eccentric cam, a one-way pawl device, a spring, a locating pin, etc., and the screw passes through the cam and the screw nut seat.

In one embodiment of the invention, both ends of the screw are respectively supported in two oblong holes in the end walls of the moving slide body, and the one-way pawl device is connected to the eccentric cam and the arm of the screw nut seat. placed between
In addition, a ratchet sleeve is used which is connected to the screw via a guide key. One or more one-way pawls are provided on the end surface of the ratchet sleeve, the pawls having vertical and slanted surfaces correspondingly engaging the vertical and slanted surfaces on the pawl groove of the eccentric cam. are doing. The sleeve is supported by a spring against the end face of the cam. Under the action of the cam, the screw moves vertically with respect to the screw nut seat.

In a second embodiment of the invention, the one-way pawl device employs a pawl pin placed within a radial hole on the cam and tensioned by a ring extension spring. The screw nut seat has two oblong holes which are threaded in their lower portions.

In a third embodiment of the invention, the nut seat is provided with a guide pillar on its bottom surface, which is vertically slidable along a guide hole on the base of the stationary body. The screw is secured in the radial direction,
Under the action of the cam, the nut seat is movable vertically with respect to the radially secured screw.

The invention will be explained below with reference to an exemplary machine vise with reference to the attached figures.

Embodiment FIGS. 1 to 14 show a first embodiment of a platform vise using a screw drive mechanism according to the present invention, which mechanism comprises a stationary body 21 having a hollow portion, and a stationary body 21 having a hollow portion. A movable body 22 placed in the hollow part of 21 and a pair of vice jaws.
jaw) 12, 14, handle 1, screw 2
0, an eccentric cam 17, a screw nut seat 19, a ratchet sleeve 9, a compression spring 8, a gasket 6, etc., and the movable body 22
is slidable along a guide track in the stationary body 21, and the handle 1 installed in the through hole at the left end of the screw 20 causes the screw to rotate to the left (N direction) or right (M direction). I can do it.

Both ends of the screw 20 are connected to the movable body 2
The two support holes 7, 23 are each in the shape of an oblong hole with two parallel side walls 101, and the width of the hole is as follows. It is substantially equal to the diameter of the screw so that the screw 20 can move up and down in the vertical direction. A gasket 6 is provided between the inner end surface 60 on the left-hand projection of the screw 20 and the outer end surface of the support hole 7 on the front vertical plate of the moving body 22. The right shoulder of the screw 20 is equipped with a cylindrical compression spring 44, and the end of the spring is supported against the inside of the rear vertical plate of the movable body 22 through a gasket 41. The end of the journal is
In order to prevent the neck journal from slipping and falling off, a gasket 42 and a stop collar (stop collar) are used.
collar) 43.

During assembly, it should be ensured that a gap δ exists between the end surface 60 on the left-hand projection of the screw 20 and the end surface 61 of the gasket 6. The width of δ is approximately 1/2 of the pitch of the screw 20
It is. This δ also allows the screw 20 to have a small amount of free axial movement, and then to adjust the appropriate A provision is made for engagement to be achieved.

A screw 20 provided with a keyway is connected to the ratchet sleeve 9 through the guide key 16, and the screw 20 also passes through an axial hole in the ratchet sleeve 9, and the screw 20 also passes through the outer thread 25. (See Figures 1 and 2).

The screw nut seat 19 is in the form of a saddle (see FIG. 3) and is fixed on the stationary body 21 by bolts 11. The two arms 40 on the seat 19 each have a concentric hole 38.
The cross-sectional shape of the hole 38 is defined by two arcs, an upper arc "a" and a lower arc "b" (see FIG. 4). The center of the upper arc “a” is O ₁
, and the central angle α of the circular arc “a” is 180° or less. The radius of the upper arc "a" is r ₁ and equal to the thread radius of the outer thread 25 on the screw 20. The surface on the upper arc “a” of the two holes is
Each has an inner thread 15 that can engage with an outer thread 25 of the screw 20. The circle center of the lower arc "b" is O ₂ , which is below the center O ₁ of the upper arc "a", and the two centers
There is an eccentric distance "e" between O ₁ and O ₂ .
"e" should be greater than the depth of the teeth of threads 15, 25, and the radius of the lower arc "b"
r ₂ means that when the screw 20 descends from position O ₁ to position O ₂ , the screw does not come into contact with any part of the inner wall above the hole in the seat 19 and can be freely displaced along the axial direction of the screw 20. should be larger than the thread radius of the outer thread on the screw 20 to ensure that.

The eccentric cam 17 is placed between one arm 40 and the ratchet sleeve 9. The curved surface of the cam has a downward stroke curved part (having the lowest point 32) and an upward stroke curved part (having the highest point 31).
(see Figure 6).
Moreover, the cam 17 also includes a positioning projection 52 and a positioning plane 51. With left rotation, the positioning protrusion 52 abuts the horizontal limiting plane 56 of the moving body 22, at which point the lowest point 32 on the cam curved surface is
The cam 17 and the screw 20 are exactly opposite the support surface 24 of the seat 19 so that they are in the most released position O ₂ (see FIG. 10). Similarly, by clockwise rotation (see Fig. 14), the positioning plane 51 is moved to the moving body 2.
At this point, the cam 1
The highest point 31 on the curved part of the upward stroke of 7
under the influence of the upward stroke curve of the cam 17 causing the axis of the screw 20 to be raised from position O ₂ to position O ₁ , contacts the cam support surface 24 and therefore its outer thread 25 seats. 19 (see FIG. 12). A one-way pawl groove 53 having a vertical surface 50 and an inclined surface 49 on the end surface 45 of the cam 17 (see FIGS. 6 and 13)
is provided.

The ratchet sleeve 9 is connected to the screw 20 via a guide key 16, and under the action of a cylindrical compression spring 8, the ratchet sleeve 9
One (or more) one-way pawl 58 formed by a vertical surface 47 and an inclined surface 48 (see FIGS. 5 and 9) is used to ensure that the cam 19 and the cam 19 are always compressed together. It has a flange 57 with.

Next, the operation sequence of the quick gripping stand vise according to the present invention will be described below. It is done in 5 stages, the second and third stages occur simultaneously, and the total operation time is about 1 second, the fourth and fifth stages also occur simultaneously, and the total operation time is about 0.5 seconds It is.

(1) Free adjustment stage of opening of bench vise.

Now, the lowest point 32 on the downward stroke curved surface of the cam 17 faces the cam support surface 24, and the cam 17
7 is in a released position with respect to the cam support surface 24 of the screw nut seat 19. The front and rear ends of the screw 20 are placed on the lower support surfaces 36 and 37 of the support holes 7 and 23 on the front and rear vertical plates of the moving body 22, respectively.
They are each supported (see Figure 7), and on the other hand,
The position of the support holes 7 and 23 ensures that the central axis of the screw 20 is at the center O ₂ of the lower arc "b" and at the same time the outer thread 25 on the screw 20
does not contact the inner surface of the seat 19 over the hole 38 at any part (see FIG. 8). Therefore, the moving body 2
2 can be manually pulled or pushed, and the movable body 22 is driven by a screw along the guide track in the stationary body 21 to quickly adjust the opening S of the jaw of the vise according to the size of the workpiece. 20 and can be slid quickly. Depending on the dimensions of the work piece 28, the
2, 14 to bring the moving body into contact with the workpiece 28.

(2) The step of engaging the outer thread of the screw with the inner thread of the nut seat.

When the handle 1 is turned to the right (in the direction indicated by arrow M in FIG. 2) to rotate the screw 20, the screw 20 also transmits the rightward rotation to the ratchet sleeve 9, while The pawl 58 of the sleeve 9 is within the pawl groove 53 of the cam 17,
Clockwise rotation of the ratchet sleeve 9 causes the inclined surface 48 of the pawl 58 to push against the inclined surface 49 of the pawl groove 53 (see the situation drawn with two-dot chain lines in FIG. 13), thus causing the compression spring By pressing the inclined surface 48 of the ratchet sleeve 9 under the action of an axial force from
On the cam support surface 24 of 9, the positioning plane 51 of the cam 17 has a lateral inner wall 55 for stopping the rotation of the cam.
(See Figure 14). At the same time, the highest point 31 on the upward stroke curve of the cam 17 has just reached the support surface 24 of the seat 19, and the screw 20 also
01 vertically to the highest position. That is,
The outer thread 25 of the screw 20 is connected to the hole 3 of the seat 19.
The central axis of the screw 20 travels an eccentric distance "e" until it engages the threads 15 in the screw 20 and the engagement ensures that the pair of inner and outer threads 15, 25 can rotate with respect to each other. beyond its initial position
vertically ascending from O ₂ −O ₂ to position O ₁ −O ₁ (12th
(see figure).

(3) The stage of gripping the work piece (see Figure 2).

Now, if the handle 1 continues to rotate in the right direction (M direction), the positioning plane 51 of the cam 17 will reach the limiting surface 55 of the side wall of the movable body 22, and the cam 17 will end its rotation. From (1st
4), the rotational movement of the ratchet sleeve 9 is applied to the inclined surfaces 48 and 49 belonging to the pawl 58 and the pawl groove 53 which are in contact with each other, and this is caused along the direction "H". Generates an axial component. When the axial component is greater than the axial compressive force of the spring 8, the ratchet sleeve 9
comes off from the pawl groove 53, and the end surface 45 of the cam 17
along direction "H" until it slides along direction "H". If the handle continues to rotate, the outer thread 25 of the screw 20 will be engaged with the inner thread 15 of the nut seat 19 and the thread will turn clockwise, and the seat 19 will be fixed to the stationary body 21. Therefore, the screw 20 advances along the axial direction "K" and rotates to the right at the same time. Therefore, the screw 20 connects the movable body 22 to the jaws 12, 1 via the end surface 60 on the left side protrusion and the gasket 6.
4 presses and moves until it grips the work piece.

(4) Stage for releasing the work piece.

After the workpiece has been processed and requires removal, the handle 1 is rotated to the left (N direction, see FIG. 1) to cause the screw 20 to rotate to the left. Since the outer threads 25 of the screw 20 initially engage the inner threads 15 of the seat 19, the screw 20 is displaced axially along the "H" direction and simultaneously rotates to the left to engage the gasket 42. Through the stop collar 43, the machine inserts the work piece 2.
8, the movable body 22 is pressed and moved along the direction "H".

(5) The step of separating the outer thread of the screw from the inner thread of the seat (see Figure 1).

When releasing the workpiece, i.e. when turning the handle 1 to the left, the ratchet sleeve 9 is driven by the screw 20, and the guide key 16 is also moved by a predetermined angle, and the pawl 58 is moved under the pressure of the compression spring 8. It is turned to the left until it falls into the pawl groove 53 (see Figure 9). The screw 20 continues its counterclockwise rotation to drive the ratchet sleeve 9, and the pawl 5
The cam 17 is rotated to the left through the two contacting vertical surfaces 47 and 50 on the pawl grooves 8 and 53 respectively, gradually bringing the cam into the release position. That is, the lowest point 32 on the downward stroke is moved until the positioning projection of the cam 17 contacts the horizontal limiting plane 56.
It is gradually rotated to its lowest position (see FIG. 10), whereupon the central axis of the screw 20 is vertically lowered from position O ₁ to position O ₂ by a height "e". The outer thread 25 of the screw 20
completely separates from the inner thread 15 of the seat 19.
At this time, the front and rear ends of the screw 20 descend onto the lower support surfaces 36 and 37 of the support holes 7 and 23 on the front and rear vertical plates of the movable body 22, respectively (see FIG. 7). As a result, the screw 20 can freely move forward or backward relative to the movable body 22, and the screw drive mechanism can be reactivated from the vise holder 1.
The apertures 2 and 14 allow rapid adjustment as described in step 1.

From FIG. 15 to FIG. 26, the second diagram according to the present invention is shown.
An embodiment is shown, and the embodiment shows a table vise for a machine tool, and includes a stationary body 63, a movable body 64, a screw 20, an eccentric cam 65, a screw nut seat 68, a one-way pawl pin 73, It includes a ring extension spring 76 and a positioning pin 74. In this embodiment, the one-way pawl device is attached to the pawl pin 7 instead of the ratchet sleeve 9 in the first embodiment.
3 is adopted. The moving body 64 is the stationary body 63
The screw 20 is slidable along the guide track within the screw nut seat 68 and the eccentric cam 65.
It passes through the hole inside. Screw nut seat 68
is in the form of a saddle with an upper top 88 (see FIG. 20) and is secured to the stationary body 63 by bolts 75. The hole in the screw nut seat 68 has two parallel side walls 87, an upper arcuate portion 86, and an outer thread 2 of the screw 20.
5 and a lower arcuate portion with internal threads 15 suitable for engagement.
The width of the oblong hole is substantially equal to the diameter of the screw 20. The eccentric cam 65 is placed within the screw nut seat 68, and the curved surface portion 92 of the eccentric cam 65 is cylindrical, and the upper cam support surface 94 of the nut seat 68
and the lower cam support surface 95,
The eccentric cam 65 has a radial hole 67 and a threaded hole 90 on the plane 89, and the eccentric cam 65
further includes a groove 77 for receiving a ring extension spring 76, which groove 77 surrounds the outer periphery of cam 65 and extends centrally through the end of radial bore 67 (see FIG. 18). The positioning pin 74 is fixed in a screw hole 90 of the cam 65 by a screw. Pawl pin 73 is placed within radial hole 67 of cam 65 and is radially slidable along hole 67. The pawl pin 73 further includes a hole 80 through which the ring extension spring 76 can pass. Ring extension spring 76 is placed around groove 77 in cam 65 and passes through hole 80 in pawl pin 73. The screw 20 has two claw grooves 8 formed by a vertical surface 83 and an inclined surface 82 along its axial direction.
1 (see FIGS. 23 and 26).

The front end plate of the movable body 64 is provided with two holes into which springs 71 are inserted.
There is a gap “δ” between the front end wall and the gasket 70.
, and allows a small amount of axial movement of the screw 20 so that proper engagement can be achieved. Gasket 93 is placed inside the front end wall of the movable body and prevents screw 20 from falling off.

When releasing the workpiece (see Figure 15),
When the screw 20 is rotated to the left (N direction), the pawl pin 73 falls into the pawl groove 81 of the screw 20 due to the action of the ring extension spring 76. The eccentric cam 65 is driven via the two contacting vertical surfaces 83 and 79 (see FIG. 23), so that the eccentric cam 65 rotates under the restriction of the two cam support surfaces 94 and 95 and the locating pin The screw 20 is raised vertically along the two parallel side walls 87 of the hole in the nut seat 68 until the head of the screw 74 contacts the restricting surface 84 of the nut seat 68 (see FIG. 22);
As the shaft of the screw 20 rises from its lowest position O ₂ -O ₂ to its highest position O ₁ -O ₁ , the thread 25 of the screw 20 separates from the thread 15 of the nut seat (see Fig. 21). , therefore the moving body 64
The vise opening "S" can be manually pushed and pulled for quick adjustment (see Figure 15).

When gripping a workpiece, align the inclined surface 82 of the claw groove 81 of the screw 20 with the inclined surface 78 of the claw pin 73.
The screw 20 is rotated to the right (direction M) so that the eccentric cam 65 rotates the ring extension spring 7 until the head of the locating pin 74 contacts the upper limiting surface 85 of the nut seat 68.
6 (see Figure 25).
At the same time, the rotation of the eccentric cam 65 causes the screw 20 to rotate along the two parallel walls 87 of the oblong hole of the nut seat 68.
is lowered to lower the shaft of the screw 20 from its highest position O ₁ -O ₁ to its lowest position O ₂ -O ₂ . Therefore, the thread 25 of the screw 20 meshes with the thread 15 of the nut seat 68 (see FIG. 24).
If the screw 20 continues to rotate, the inclined surface 78 of the claw pin 73 will move along the inclined surface 82 of the claw groove 81 of the screw 20 when the component force acting on the two inclined surfaces is larger than the tensile force of the ring spring 76. Then, the claw pin 73 slides until it escapes from the claw groove 81 (see FIG. 26), after which the screw 20 can continue to rotate. Since the outer thread 25 of the screw 20 engages the inner thread 15 of a nut seat 68 fixed on the stationary body 63, the screw 20
is advanced along the axial direction "K" while it rotates to the right and pushes moving body 64 through gasket 70 to grip the workpiece.

From FIG. 27 to FIG. 31, the third
An embodiment is shown in which the structure of the pawl pin, eccentric cam, and nut seat are basically the same as those of the second embodiment, but the nut seat 68
is provided on its bottom surface with a guidepillar 96 vertically slidable along a guide hole 97 on the base 100 of the stationary body 63. Moving body 64
Screw 20 supported by two holes in both end walls of
The nut seat 68 cannot move up and down vertically and only rotates. However, the nut seat 68 is
As a result, the screw threads 25 and 15 of the screw 20 and the nut seat 68 can move vertically so that they can engage and disengage from each other.

When gripping a workpiece, when the screw 20 is rotated in the right direction (direction M), the screw 20 drives the eccentric cam 65 via the pawl groove and the pawl pin 73, so that the eccentric cam 65 grips the two surfaces. 94 and 95, and since the screw 20 is radially fixed (see FIGS. 28 and 31), causes a vertical rise of the nut seat 68 over a distance "h". Therefore, the thread 1 of the nut seat 68
5 engages with the screw thread 25 of the screw 20 (meshing)
do. If the screw 20 continues to rotate until the claw pin 73 slides out of the claw groove of the screw 20,
The screw 20 then moves along the axial direction "K" during the continuation of the clockwise rotation and is moved through the gasket 70 to the moving body 64 to grip the workpiece.
push forward.

When releasing the work piece, if the screw 20 is rotated to the left (N direction), the screw 20 will be
The contacting vertical surfaces 83 and 79 on the pawl groove 81 and the pawl pin 73 respectively drive an eccentric cam 65, so that the cam 65 is driven in a direction perpendicular to the screw 20 which is radially fixed to the nut seat 68. The screw thread 25 of the screw 20 is therefore disengaged from the thread thread 15 of the nut seat 68, and the movable body is free to move in the axial direction (see Fig. 27). .

As described above in detail in each example, the present invention includes:
Since a screw nut seat with two arms is provided and the screw is passed through both members, an eccentric cam is placed between the arms of the screw nut seat and by rotating the eccentric cam, the screw nut can be rotated. A rising and falling force (bending moment) is applied between both arms of the screw nut seat, and this stress is only applied to both arms of the screw seat and does not extend to the bearings at both ends of the screw. Therefore, the bending deformation on the screw is minimized, and only the torsional force and axial force of the handle act on the screw, so the screw can exert a large gripping force under smooth action.
Rapid engagement between screw and screw nut,
The detachment was reliably achieved, and the present invention achieved the intended purpose with a simple structure and low cost.

The mechanism is capable of various variations which should be considered within the scope of the invention.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of a stand vice to which the drive mechanism according to the present invention is applied, and is a sectional view showing the stand vice in a released position. FIG. 2 is a cross-sectional view of the platform vise of FIG. 1 in a position where a workpiece is gripped.
FIG. 3 is a schematic diagram of the screw nut seat of FIG. 1. FIG. 4 is a side view of FIG. 3. Fifth
The illustration is a perspective view of the ratchet sleeve of FIG. 1. 6 is a perspective view of the eccentric cam of FIG. 1; FIG. FIG. 7 is a cross-sectional view taken from line A-A and line D-D in FIG. It shows the relative position of the screen journal. FIG. 8 is a sectional view taken along line B-B in FIG. 1, showing that the outer thread of the screw is separated from the inner thread of the axial hole in the screw nut seat when the base vise is in the released position. It shows the relative position after the FIG. 9 is an orthographic view with partial view E showing the pawls of the ratchet sleeve for engaging the pawl grooves on the cam when the base vise of FIG. 1 is in the released position; . FIG. 10 is a sectional view taken along line CC in FIG. 1, showing the relative position of the eccentric cam and the screw nut seat when the base vise is in the released position.
FIG. 11 is a sectional view taken along lines A'-A' and D'-D' in FIG. Figure 2 shows the relative position of the screw network journals within the support holes on the front and rear vertical plates. Figure 12 shows the lines in Figure 2.
B'-B' sectional view showing the outer threads of the screw engaged with the inner threads of the screw nut seat when the platform vise is in the gripping position. Figure 13 shows the second position when the base vise is in the gripping position.
The pawl of the ratchet sleeve is shown separated from the pawl groove of the cam shown in the figure. Figure 14 shows the lines in Figure 2.
It is a C'-C' sectional view showing the relative position of the eccentric cam and the screw nut seat when the table vise is in the gripping state. FIG. 15 is a diagram of a second embodiment of the present invention showing a machine tool stand vise in a released state. 16th
The figure is a diagram showing a gripping state of the stand vice shown in FIG. 15. FIG. 17 is a perspective view of the claw pin of FIG. 15. FIG. 18 is a perspective view of the eccentric cam of FIG. 15. FIG. 19 is a perspective view of the ring extension spring of FIG. 15; FIG. 20 is a perspective view of the screw nut seat of FIG. 15. Figure 21 shows
16 is a sectional view taken along line DD in FIG. 15. FIG. Figure 22 shows
16 is a sectional view taken along line EE in FIG. 15. FIG. Figure 23 shows
16 is a sectional view taken along line FF in FIG. 15. FIG. Figure 24 shows
FIG. 16 is a sectional view taken along line D'-D' in FIG. 16; Figure 25 shows
FIG. 16 is a sectional view taken along line E'-E' in FIG. 16; Figure 26 shows
FIG. 16 is a sectional view taken along line F'-F' in FIG. 16; Figure 27 shows
Figure 3 is a diagram of a third embodiment of the invention showing the platform vise in a released state; FIG. 28 is a diagram showing the stand vise of FIG. 27 in a gripped state. Figure 29 shows the second
FIG. 8 is a perspective view of the screw nut seat in FIG. 7; Third
0 is a sectional view taken along line PP in FIG. 27. Third
1 is a sectional view taken along line P'-P' in FIG. 28. Third
FIG. 2 shows a prior art screw drive mechanism. 1: Handle, 6, 41, 42, 70, 93:
Gasket, 7, 23: Support hole, 8, 44: Compression spring, 9: Ratchet sleeve, 11: Bolt, 12, 14: Vise jaw, 15: Internal thread, 16: Guide key, 17, 65: Eccentricity Cam, 1
9, 68: Screw nut seat, 20: Screw, 21, 63: Stationary body, 22, 64: Moving body, 24: Cam support surface, 25: Screw thread, 38: Hole, 40: Arm, 43: Stop collar , 47: Vertical surface of the nail, 48: Inclined surface of the nail, 4
9: Inclined surface of the claw groove, 50: Vertical surface of the claw groove, 51:
Positioning plane, 52: Positioning protrusion, 53: One-way claw groove, 56: Horizontal restriction plane, 58: One-way claw,
73: Claw pin, 74: Positioning pin, 77: Groove,
67: Radial hole, 78: Slanted surface of claw pin, 7
9: Vertical surface of the claw pin.

Claims (1)

[Claims] 1. A stationary body, a moving body, a screw, 2.
a screw nut seat with two arms; and an eccentric cam disposed between the two arms of the screw nut seat, the screw passing through a hole in the screw nut seat and the eccentric cam. and a mechanism by which the cam can slide on a cam support surface of the nut seat, the mechanism further including a one-way pawl device, and the screw rotates the eccentric cam by the one-way pawl device. driving the cam to cause vertical relative movement between the screw and the screw nut seat, thereby causing the threads of the screw to disengage and disengage the threads of the screw nut seat; A screw drive mechanism featuring: 2. The one-way pawl device adopts a ratchet sleeve, the sleeve is disposed between one arm of the screw nut seat and the end face of the eccentric cam, and is connected to the screw through a guide key, and On the end face of the ratchet sleeve, a one-way pawl correspondingly adapted to the one-way pawl groove on the end face of the eccentric cam is provided, the pawl being formed by a vertical surface and an inclined surface, and the spring is The screw drive mechanism according to claim 1, wherein the ratchet sleeve and the end face of the cam are pressed together in the axial direction. 3. When the eccentric cam is in contact with the one-way pawl groove formed by the vertical surface and the inclined surface and the horizontal limiting plane of the moving body, let the screw reach the lowest point of its downward movement "O ₂ ". a positioning protrusion that moves the lowest point on the downward stroke curved surface of the cam downward so as to separate the thread of the screw from the thread of the nut seat; the cam is further provided with a positioning plane; When in contact with the vertical limiting side surface of the movable body, the highest point on the upward stroke curved surface of the cam is raised to its highest position "O ₁ ", and the outer thread of the screw is connected to the inner thread of the nut seat. 3. A screw drive mechanism according to claim 1, wherein the screw drive mechanism rotates downwardly to contact a cam support surface on the screw nut seat for rotationally engaging the screw nut seat. 4. A screw nut seat is in the form of a saddle and fixed to the stationary body, the two arms of the seat having concentric axial holes having an upper arc and a lower arc, with the center of the upper arc The angle is 180° or less, the radius of the upper arc is equal to the radius of the outer thread of the screw, and the mating surface of the upper arc has an inner thread suitable for engaging the outer thread on the screw. and the center O ₂ of the lower arc is positioned below the center O ₁ of the upper arc, the radius of the lower arc is larger than the radius of the outer thread of the screw, and the center O ₁ of the two arcs is Screw drive mechanism according to any one of claims 1 to 3, wherein the distance between O ₂ is greater than the depth of the teeth of the thread. 5 Each of the two screw journals on the right and left ends of the screw is supported by two oblong holes on the front and rear end plates of the moving body, respectively, and the holes have two vertical parallel side walls; 5. A screw drive mechanism according to claim 1, wherein the width of the hole is substantially equal to the diameter of the screw, and the screw can move vertically up and down. 6. The one-way pawl device adopts a radial pawl pin positioned in the radial hole of the eccentric cam, the pawl is formed by a vertical surface and an inclined surface, and the ring extension spring is attached to the outer circumference of the eccentric cam. 2. The screw drive mechanism of claim 1, wherein the screw drive mechanism is disposed within a groove on the pawl pin and extends through a hole on the pawl pin. 7. The screw drive mechanism according to claim 1 or 6, wherein the screw is provided with a pawl groove formed by a vertical surface and an inclined surface along the axial direction of the screw. 8. The nut seat has an upper cam support surface, the hole in the nut seat has an oval shape with two vertical parallel walls, the width of the oval hole is substantially equal to the diameter of the screw, and the oval hole has an upper cam support surface. 8. A screw drive mechanism according to claim 1, wherein the lower arcuate portion of the screw has suitable threads for engaging the threads of the screw. 9. The curved portion of the eccentric cam is cylindrical, the cam has a radial hole for receiving a pawl pin and a groove for receiving a ring extension spring surrounding the periphery of the cam, and the locating pin It is fixed on an eccentric cam, and the eccentric cam is located at the lowest position.
When the screw is caused to rise from O ₂ to the highest position O ₁ , the thread of the screw disengages from the thread of the nut seat, and the cam causes the screw to descend from the highest position O ₁ to the lowest position O ₂ . Claims 1 and 6, wherein the screw is arranged so that the thread of the screw engages with the thread of the nut seat when the nut is raised.
The screw drive mechanism according to any one of Items 7 and 8. 10. The screw drive mechanism of claim 1, wherein the nut seat is provided with a guide pillar on its bottom surface suitable for sliding vertically along a guide hole on the base of the stationary body. 11 The screw is fixed in the radial direction,
10. An eccentric cam causes a vertical movement of the nut seat relative to the radially fixed screw to engage or disengage the threads of the nut seat with the threads of the screw. Screw drive mechanism as described in Section.