JP2000007291A - Screw jack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the breakage of a screw jack, if excessive operating force is applied thereto. SOLUTION: A screw jack is formed so as to transmit torque to a screw rod 6 via a small bevel gear 5 and a large bevel gear 4 to cause a ram 11 threaded to the screw rod 6 to be moved up and down, when operating force is applied to a handle joint 8, wherein a cutoff mechanism mounted with a ball 10 energized by a spring 9 is provided between the large bevel gear 4 and the screw rod 6 for setting the ball 10 into the screw rod 6 to thereby cause the large bevel gear 4 to idle when overtorque is applied to the large bevel gear 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a screw jack.

[0002]

2. Description of the Related Art Conventionally, a hand-operated screw jack having a structure as shown in FIG. 5 is known. In the figure, a jack body 23 composed of a bed 21 and a case 22 is shown.
A pair of bevel gears including a large bevel gear 24 and a small bevel gear 25 are provided. The large bevel gear 24 is provided with a screw rod 26 serving as a rotating shaft, and is rotatably supported by a thrust bearing 27 with its tooth surface facing upward. A small bevel gear 25 meshing with the large bevel gear 24 is rotatably supported by a support portion 22a provided on the side of the case 22, and a handle joint 28 is attached to a shaft end protruding from the support portion 22a. ing. The bevel gear 24 and the screw rod 2
The key 29 is used to fasten 6. The male screw portion of the screw rod 26 is provided with a ram 30 supported by the case 22 so as to be vertically movable.
The ram 30 is prevented from rotating by the engagement of the ram key 22b attached to the case 22 with the vertical groove 30a. The height of the washer 31a can be set by screwing the inner ram 31 inserted into the ram 30 in a screwed state. This screw jack is a handle joint 28
The ram 30 is raised and lowered by manually turning a jack handle (not shown) hooked on the ram 30. When the ram 30 rises to the maximum extension state, the ram key 22b comes into contact with the cut-out portion 30b at the lower end of the vertical groove 30a and acts as a stopper.

[0003]

In the above-described conventional screw jack, the force applied to the handle joint 28 is transmitted to the ram 30 via the bevel gears 25, 24 and the threaded rod 26 without any change. A relatively large jack handle is used. Therefore, the ram 30
Even when is in the maximum extension state, the operator can easily turn the jack handle to further jack up and apply excessive operating force (torque). In this case, the ram key 22b is broken, the teeth of the bevel gears 24 and 25 are missing,
2a may be destroyed. Also, the jack handle may be bent.

The present invention has been made in view of the above problems, and an object of the present invention is to prevent a screw jack from being damaged by preventing an excessive operating force from being applied to the screw jack.

[0005]

For this purpose, the following screw jack has been created. That is, a first aspect of the present invention is a screw jack formed such that a ram screwed to a screw rod is moved up and down by rotation of the screw rod. In the screw jack, an operating force applied to an input portion of the jack body is transmitted through the screw rod. It is characterized in that a power transmission path up to transmission to the ram is provided with a blocking mechanism for preventing transmission of excessive torque. The excessive torque here is a torque exceeding an allowable value.

In the above-described screw jack, when an excessive operating force is applied to the input portion of the jack body, the shut-off mechanism provided in the power transmission path operates, so that there is no possibility that excessive torque is transmitted. Therefore, damage of the screw jack is prevented. It is also suitable for use in which an excessive force exceeding an allowable value is not carelessly applied to the jack-up target.

According to a second aspect of the present invention, in the above screw jack, when the transmission torque applied in the direction to raise the ram exceeds an allowable value,
The transmission member interposed between the threaded rod and the driving member for rotating the threaded rod is displaced to the retracted position so that excessive torque is not transmitted.

In this screw jack, when an excessive torque is applied to raise the ram due to an excessive operating force, the transmission member is displaced to the retracted position and the transmission of torque to the threaded rod can be interrupted. On the other hand, since the shut-off mechanism does not act on the operating force acting in the direction of lowering the ram, if the ram becomes difficult to lower due to the application of some load to the screw rod, the operator responds accordingly. You can know, and you can respond quickly.

According to a third aspect of the present invention, in the above screw jack, the blocking mechanism is provided on the screw rod side, and the mounting member is mounted so that the transmitting member can protrude and retract, and the transmitting member projects from the mounting portion. A biasing member for biasing in a direction to be driven, and an engaging portion provided on the driving member side and capable of being disengaged from the transmission member. When transmitting torque from the joint portion to the screw rod via the transmission member in the direction of raising the ram, a contact portion for pressing the transmission member in a direction of pushing the transmission member into the mounting portion is formed. It is characterized by.

In this screw jack, when the pressing force applied to the transmitting member from the contact portion provided on the driving member side exceeds the urging force of the urging member, the transmitting member enters the mounting portion and the transmission torque is reduced. Will be shut off. That is, by appropriately setting the urging force of the urging member, it is possible to determine the upper limit of the transmittable torque of the power transmission path and regulate the jack-up force.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below. FIG. 1 is a longitudinal sectional view of the screw jack. As shown in the figure, a jack body 3 in which a bed 1 and a case 2 are integrated is provided with a pair of bevel gear devices including a large bevel gear 4 (also referred to as a driving member) and a small bevel gear 5. The bevel gear 4 is rotatably supported by a thrust bearing 7 provided on the bed 1 with its tooth surface facing upward, and a screw rod extending in a substantially vertical direction in a center hole 4 a of the bevel gear 4. 6 has a lower end 6a inserted therein.
A shut-off mechanism, which will be described in detail later, is interposed between the threaded rod 6 serving as a rotating shaft and the large bevel gear 4, and can transmit a torque of a predetermined magnitude. , The large bevel gear 4 idles.

On the other hand, a small bevel gear 5 meshing with the large bevel gear 4 is rotatably supported by a support 2a provided on the side of the case 2, and a shaft end 5a protruding from the support 2a.
A handle joint 8 (also referred to as an input unit) is screwed into the connector. The male screw portion 6b of the screw rod 6 is screwed into the female screw portion 11a of the ram 11 supported on the case 2 so as to be able to move up and down. The outer peripheral surface of the ram 11 extends in the axial direction. A vertical groove 11b is formed, and the ram 11 is prevented from rotating by engaging the ram key 2b attached to the case 2 with the vertical groove 11b. Therefore, the ram 11 moves up and down according to the rotation of the screw rod 6. The ram key 2b also functions as a stopper for abutting the cut-out portion 11c at the lower end of the vertical groove 11b when the ram 11 rises to the most extended state. Furthermore, inner ram 1
2 is supported in a state in which the male screw portion 12a is screwed into the upper female screw portion 11d of the ram 11. By screwing the inner ram 12, the height of the upper washer 13 attached to the top of the inner ram 12 is reduced. It can be set. In the case of this example, the male screw portion 6b and the male screw portion 12a are square screws.

Next, the shutoff mechanism will be described. FIG. 2 is a cross-sectional view illustrating a main part of the screw jack. As shown in FIGS. 1 and 2, an urging member (specifically, a mounting portion) provided at a lower end portion 6 a of the screw rod 6 (specifically, a mounting hole recessed in the peripheral surface of the lower end portion 6 a) is provided. Specifically, a spring 9 and a transmission member (specifically, a ball) 10 are mounted, and the transmission member 10 is attached by the urging member 9 to the mounting portion 6.
c is urged to protrude in the direction perpendicular to the axis. On the other hand, on the inner surface of the center hole 4a of the
An engagement portion (specifically, a hemispherical recess) 4b with which the transmission member 10 is engaged is provided at a position corresponding to the position of the transmission member 10. The torque between the threaded rod 6 and the bevel gear 4 via the transmission member 10 is provided. Communication takes place. When the engaging portion 4b presses the transmitting member 10, the transmitting member 10 is formed so that a component force directed toward the inside of the mounting portion 6c acts. By the urging force of 9, the engagement between the transmission member 10 and the bevel gear 4 is maintained, so that the bevel gear 4 and the screw rod 6 rotate integrally.

When an excessive torque based on an excessive operating force is applied between the screw rod 6 and the large bevel gear 4 when one of them is restrained, for example, the transmission member 1
0 is pushed into the mounting portion 6c.
, The relative displacement between the threaded rod 6 and the bevel gear 4 occurs at the same time as the transmission member 10 is displaced, and finally the transmission member 10 is pushed into the retracted position in the mounting portion 6c. As a result, the large bevel gear 4 is
Is idle, and no torque is transmitted.
The upper limit value (allowable torque value) of the torque when the transmission member 10 is displaced to the retreat position where torque transmission cannot be performed can be set by the spring constant of the urging member 9.
According to this blocking mechanism, transmission of excessive torque can be blocked in both forward and reverse directions.

Here, another example of the shut-off mechanism that can shut off transmission of excessive torque in one direction will be described. FIG. 3 is a sectional view showing a connection portion between the threaded rod 16 and the bevel gear 14. As shown in the figure, a lower end portion 16a of a screw rod 16 is inserted into a center hole 14a of a large bevel gear (also referred to as a driving member) 14, and a mounting portion (specifically, The urging member 9 and the transmission member 17 are mounted on the mounting hole 16c recessed in the peripheral surface of the lower end 16a, and the transmission member 17 is projected by the urging member 9 in the direction perpendicular to the axis. Has been energized. The mounting portion 1 is provided on the inner surface of the center hole 14a of the large bevel gear 14.
An engagement portion 14b is provided at a position corresponding to 6c so that the transmission member 17 is removably engaged. This transmission member 17
Is formed in a wedge shape, and a contact surface 17d extending substantially toward the axis of the screw rod 16 can contact the inner surface 16d of the mounting portion 16c and the contact surface 14d of the engaging portion 14b.
The inclined surface 17c that is inclined with respect to the contact surface 17d can contact the inclined surface (also referred to as a contact portion) 14c of the engagement portion 14b.

Therefore, in this shutoff mechanism according to another example, the large gear 14 in the direction of the arrow (counterclockwise) in FIG.
Is rotated, the torque is transmitted from the inclined surface 14c to the inclined surface 17c, and both the large bevel gear 14 and the screw rod 16 rotate integrally. However, when the transmitted torque exceeds the allowable value,
The component force generated by the pressing of the slope 14c in the direction of immersing the transmitting member 17 in the mounting portion 16c exceeds the urging force of the urging member 9, and the transmitting member 17 immerses in the mounting portion 16c and moves from the engaging portion 14b. Come off. As a result, the large bevel gear 14 becomes idle and no torque is transmitted to the threaded rod 16. Contrary to this, the clockwise gear 14
Is rotated, no component force is generated in a direction in which the transmission member 17 is immersed in the mounting portion 16c, so that the transmission torque is not interrupted.

When using the screw jack having the above configuration, the jack handle 19 hung on the handle joint 8 is turned by hand as shown in FIG. The torque applied to the handle joint 8 is transmitted to the small bevel gear 5, the large bevel gear 4, the transmission member 10, and the screw rod 6, and the screw rod 6 rotates to move the ram 11 up and down. The inner ram 12 and the upper washer 13 move up and down integrally with the ram 11. When the ram 11 is in the most extended state, that is, when the operator applies an excessive operating force to further rotate the jack handle 19 while the cut-up portion 11c at the lower end of the vertical groove 11b is in contact with the ram key 2b. Since the screw rod 6 cannot rotate, a torque exceeding a permissible value is generated in the power transmission path from the handle joint 8 to the screw rod 6. However, when the torque applied to the bevel gear 4 exceeds the allowable value, the shut-off mechanism shown in FIG. 2 operates, and the bevel gear 4 presses the transmission member 10 by the engaging part 4b to attach the mounting part 6c. Rotate after pushing in. As a result, since the large bevel gear 4 idles, no torque is transmitted, and no excessive torque is generated. Therefore, a failure caused by an erroneous operation such as the ram key 2b being damaged, the teeth of the bevel gears 4 and 5 being missing, the support portion 2a being broken, or the jack handle 19 being twisted is prevented.

In the screw jack provided with another blocking mechanism shown in FIG. 3, the bevel gear 14 is moved in the direction of raising the ram, that is, with respect to the threaded rod 6, by the arrow (counterclockwise) in FIG. When transmitting torque by rotating to
The same operation and effect as those of the above-described blocking mechanism can be obtained. On the contrary, when the bevel gear 14 rotates in the direction of lowering the ram, that is, clockwise, the blocking mechanism does not operate as described above, and the torque applied from the jack handle 19 is not blocked. Therefore, when the ram becomes difficult to descend due to a certain load applied to the screw rod 6, the operator can know the fact by responding, and quick response is possible.

Although the shut-off mechanism of the above-described embodiment is interposed between the threaded rod 6 and the large bevel gear 14, other parts, for example, between the small bevel gear 5 and the handle joint 8 are provided. You may interpose. The above-described screw jack is also suitable for use in which an excessive force exceeding an allowable value is not carelessly applied to a jack-up target. In addition, it is needless to say that the present invention can be implemented in various modified embodiments based on the knowledge of those skilled in the art.

[0020]

As described above in detail, according to the present invention, when an excessive operating force is applied to the input portion of the screw jack, the breaking mechanism prevents torque transmission by preventing the torque transmission. There is an effect that can be. Further, it is possible to prevent an excessive force from being carelessly applied to the jack-up target.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a screw jack according to an embodiment.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a cross-sectional view illustrating another example of the shutoff mechanism.

FIG. 4 is a perspective view of a screw jack.

FIG. 5 is a longitudinal sectional view illustrating a conventional screw jack.

[Explanation of symbols]

 Reference Signs List 1 bed 2 case 3 jack body 4 large bevel gear (drive member) 4b engaging part 5 small bevel gear 6 screw rod 6b male screw part 6c mounting part 8 handle joint (input part) 9 urging member 10 transmission member 11 ram 11a female screw Department

Claims (3)

[Claims] In a screw jack formed so that a ram screwed to a screw rod moves up and down by rotation of the screw rod, an operating force applied to an input portion of the jack body is transmitted to the ram via the screw rod. A screw jack equipped with a shut-off mechanism that prevents transmission of excessive torque in the power transmission path up to. 2. When the transmission torque applied in a direction to raise the ram exceeds an allowable value,
2. The screw jack according to claim 1, wherein a transmission member interposed between the screw rod and a driving member for rotating the screw rod is displaced to a retreat position so that excessive torque is not transmitted. . 3. The mounting mechanism, wherein the blocking mechanism is provided on the threaded rod side and on which the transmitting member is mounted so as to be able to protrude and retract; An engagement portion provided on the drive member side and formed to be detachable from the transmission member, and wherein the engagement portion has a screw rod from the engagement portion via a transmission member. 3. The screw jack according to claim 2, further comprising: a contact portion configured to press the transmission member in a direction of pushing the transmission member into the mounting portion when torque is transmitted in a direction in which the ram is raised.