Locking Means For Clamps

Abstract

A locking mechanism which can lock a clamp piece of a clamp both in the cping state and in the releasing state. Locking is realized by combination of cam members eccentric with regard to each other, one pair of which is provided on the clamp piece and the other pair of which is provided on an axis located near the clamp piece so that the latter pair of cam members is turned by a locking lever and restricts movement of the clamp piece by contacting the former. The clamp piece can be locked at any position without losing clamping ability when a plate to be clamped is inserted.

Description

This invention relates to a lock apparatus for locking a clamp piece of a clamp for clamping steel plates or similar plate members in the clamping state and in the releasing state.

In the conventional clamp in which the clamping strength is adapted to increase according to an increase in the weight of a plate member clamped and suspended by the clamp, rotary resilience in the clamping direction is imparted to the clamp piece by built-in springs so as to increase the clamping strength.

When an upward reaction is applied to a plate member suspended from the foregoing clamp, or when a plate member is perpendicularly suspended in the state in which the lower end thereof contacts the earth, the clamping strength is reduced to the pressure contact force imparted to the clamp piece by the spring only. As a result, the clamping strength thus weakened incurs an occasional risk of the plate member being detached from the clamp.

Moreover, since the clamp piece is adapted to constantly project inside of the clamp slit, said clamp piece interferes with the operation of clamping plate members, whereby the operational efficiency is decreased.

An object of this invention is to provide an apparatus which will control locking of the clamp in the clamping state and in the releasing state so as to increase the safety of the clamp by precluding the risk of occurrence of detachment of the suspended plate members therefrom. Said apparatus will further prevent the clamp piece from interfering with the clamping operation and will also allow the switchover of the lock means with simplicity.

These and other objects are accomplished by the parts, improvements, combinations and arrangements constituting this invention, a preferred embodiment of which is shown by way of example in the annexed drawings and herein described in detail. Of the drawings:

FIG. 1 is a perspective showing a preferred embodiment of this invention;

FIG. 2 is a vertical section showing the clamping state of the same;

FIG. 3 is a vertical section of the same showing the state in which the clamp is released;

FIG. 4 is a diagram showing the clamping state of the principal part of the lock apparatus of the same;

FIG. 5 is a diagram showing the state in which the clamp is released;

FIG. 6 is an elevation showing the detail of a clamp piece built in the same;

FIG. 7 is a sectional view of the clamp piece taken on the line VI--VI as indicated by arrows in FIG. 6;

FIG. 8 is an elevation showing the detail of a lock cam; and

FIG. 9 is a cross-sectional plan showing the particulars of the lock cam.

In the embodiment as shown in FIGS. 1 to 9, the numeral 11 designates a clamp body comprising side plates 12 and 13 secured in a state in which a required space is formed between the corresponding faces of said side plates 12 and 13.

A clamp slit 14 for inserting a plate member A thereinto is provided in each side plate 12, 13 of the body 11 upwardly from the lower edge thereof.

A pad 15 is secured to one side of the clamp slit 14 of the side plates 12 and 13. On the other side of the clamp slit 14 is a clamp piece 17 with its base end portion pivoted on an axis 16 provided in a slightly lower portion between the side plates 12 and 13, the forward end of the clamp piece 17 being oscillatable for contact with and detachment from the pad 15, and the clamp piece 17 and the pad 15 being adapted to clamp therebetween a plate member, such as a steel plate or the like.

As illustrated in detail in FIGS. 6 and 7, on both sides of the base end portion of the clamp piece 17, which has a penetration hole 18 externally fitting to an axis 16, are projectionally provided cam members 19 and 20 eccentric with regard to each other in the opposite directions from the axial center of the penetration hole 18. A zigzag face 21 is formed on the arcuate forward edge of the clamp piece 17 corresponding to the pad 15 thereby enabling clamping of the plate member A with reliability.

In the upper part between the side plates 12 and 13 is provided a bell crank 23 with its middle portion pivoted externally on an axis 22 mounted between said side plates 12 and 13, a rod 25 being pivoted at its upper end by a pin 24 on the right-hand end portion of the crank as shown in FIG. 2, the lower end of the rod 25 being pivoted by a pin 26 in the middle portion adjacent to the forward end of the clamp piece 17, the clamp piece 17 and the bell crank 23 being connected by a rod 25 so as to rotate in the opposite directions.

On the left-hand end portion of the bell crank 23 in FIG. 2 is an upright L-shaped rod 27 pivoted at its lower end by a pin 28; a suspension ring 29 projecting upwardly from the upper part of the body 11 is connected to the upper end of the L-shaped rod 27. The plate member A is clamped between the pad 15 and the clamp piece 17 by hoisting the suspension ring 29 by means of a hook on a crane or the like, whereby the forward end of the clamp piece 17 is brought adjacent the pad 15 through the action of the bell crank 23 and the rod 25.

The L-shaped rod 27, bell crank 23, link 25 and clamp piece 17 are adapted to have an increased clamping strength in proportion to an increase in the weight of the suspended plate member A.

Furthermore, a spring 30 is extended between the lower edge of the middle portion of the bell crank 23 and a suitable position in the left-hand middle portion of the body 11. A clockwise rotary force is imparted to the bell crank 23 in FIG. 2 by the tension of said spring 30, and a rotary force in the clamping direction is constantly imparted to the clamping piece 17 by said clockwise rotary force through the link 25.

A lock cam 32 is rotatably mounted by an axis 31 provided between the side plates 12 and 13 in a position adjacent the right-hand side of the base end portion of the clamp piece 17 as shown in FIG. 2.

As illustrated in detail in FIGS. 8 and 9, the lock cam 32 comprises cam members 35 and 36 continuously formed at both ends of a cylindrical member 34 and is provided with a penetration hole 33 externally fitted to the axis 31 so as to be eccentric with regard to the axial center of the penetration hole and the respective center of each other. A pin 37 is planted on the lateral face of the cam member 36.

One cam member 35 of the lock cam 32 is disposed so that its exterior periphery will correspond with that of one cam member 19 of the clamp piece 17; the other cam member 36 being disposed so that its exterior periphery will correspond with that of the other cam member 20 of the clamp piece 17.

A lock lever 38 is pivoted at its base end by a pin 39 on the right-hand end portion of the clamp body 11 as shown in FIG. 2, said lock lever 38 being fitted oscillatably. A spring 40 is extended between the free end of the said lever 38 and the cam member 36 of the lock cam 32.

By setting the lever 38 upwardly or downwardly, the tension of the spring 40 toward the lock cam 32 varies, whereby the corresponding cam members 19 and 35, or 20 and 36 are brought into contact with each other.

FIGS. 4 and 5 show the relation between the lock cam 32 when activated by the operation of the lever 38 and the cam members of the clamp piece 17. If the lever 38 is operated so as to set it upright, the spring 40 draws the lock cam 32 in the direction B as indicated by the arrow in FIG. 4, whereby a counterclockwise rotary force centering on the axis 31 is imparted to the lock cam 32 with the result that the cam members 19 and 35 on the front side are brought into abutment against each other, and the cam members 20 and 36 on the reverse side are detached from each other.

In FIG. 4, the contact point P between the cam members 19 and 35 is located above the line connecting the centers of the axes 16 and 31, with the result that the clamp piece 17 is rotatable only in the direction C indicated by the arrow, rotation in the opposite direction being precluded by the frictional force of the contact point, thereby sustaining the clamping of the clamp piece 17 in a locked state.

If the lever 38 is set downwardly, the spring 40 draws the lock cam 32 in the direction D as indicated by arrow in FIG. 5 thereby imparting a clockwise rotary force centering on the axis 31 to said cam 32, with the result that the cam members 19 and 35 on the front side are detached from each other and the cam members 20 and 36 on the rear side being brought into abutment against each other.

In FIG. 5, the contact point P' is located below the line connecting the centers of the axes 16 and 31 thereby enabling the clamp piece 17 to rotate in the direction E as indicated by arrow, the rotation in the opposite direction being precluded by the frictional force of the contact point P'. The result is that release of the clamp piece 17 is sustained in a locked state.

Now, the action of the foregoing embodiment will hereinunder be described in detail.

The lever 38 is set downwardly through the dead point of the spring 40 as shown in FIG. 3, whereby the clamp piece 17 is released from the locked state of clamping as shown in FIG. 5. Then, the suspension ring 29 is pressed downwardly against the spring 30 thereby rotating the clamp piece 17 in the direction E as indicated by arrow in FIG. 5 by means of the bell crank 23 and the link 25 so that said clamp piece 17 will be detached from the pad 15.

In FIG. 5, the tension of the spring 30 is precluded by the frictional force of the contact point P'. As a result, the opened state of the clamp piece 17 can be sustained at any required degree according to the thickness of the plate member A to be clamped.

Then, a part of the plate member A is inserted into the clamp slit 14, the lever 38 being set upright as shown in FIG. 2.

Because of the tension of the spring 40 resulting from the upright setting of the lever 38, the lock cam 32 is subjected to a rotary mutation from the state of FIG. 5 to that of FIG. 4, the cam member 35 being brought into abutment against the cam member 19 of the clamp piece 17.

Then, if the clamp body 11 is suspended from a crane or the like through the suspension ring, the bell crank 23 is rotated clockwise, the clamp piece 17 is rotated counterclockwise by the downward pressure of the rod 25 so as to be brought into pressure contact with the plate member A thereby enabling clamping of said plate member A between the clamp piece 17 and the pad 15 as shown in FIG. 2.

When the clamp piece 17 is moved in the direction C as indicated by arrow in FIG. 4, the cam member 19 is also subjected to rotary mutation. However, since a counterclockwise rotary force is imparted to the lock cam 32 by the spring 40, the contact point P between the cam members 19 and 35 remains unchanged, whereby the clamp piece 17 is perfectly locked without the risk of oscillation in the direction of permitting the plate member A to escape.

Therefore, even when an upward force is applied to the plate member A, or even in a non-suspension state in which the lower edge of the plate member A is in contact with the earth, the clamp is sustained with reliability unless the lever 38 is set downwardly.

To release the clamp from the locked state after the plate member A has been transported to a required location, the lever 38 is set downwardly. The cam members 19 and 35 are detached from each other, and the contact point P is released by the rotation of the lock cam 32 as shown in FIG. 4, thereby enabling the clamp piece 17 to oscillate in the opening direction; the clamp of the plate member A being released as a result.

Claims

What is claimed is:

1. A lock apparatus for a clamp, said clamp having a clamp body, a clamping piece rotatably pivoted at its base end on said clamp body, an abutment plate affixed to said clamp body opposite the clamping piece, and lifting means pivotally attached to said clamp body and to said clamping piece, whereby said clamping piece will rotate in the clamping direction toward the abutment plate when the clamp body is suspended by the lifting means and the item to be held will be clamped therebetween, said lock apparatus comprising

a pair of base cam members located on the base end of said clamp piece eccentric with regard to each other and the pivotal axis of the base end portion of the clamp piece,

a lock cam comprising a pair of lock cam members eccentric with regard to each other rotatably mounted for rotation between two positions on the clamp body at a position adjacent the base end of the clamp piece, one of said lock cam members engaging one of said base cam members when the lock cam is rotated in one direction, and the other of said lock cam members engaging the other of said cam members when the lock cam is rotated in the opposite direction, whereby movement of the clamping piece is restricted and said clamping piece is locked into position,

a lever mounted on the clamp body with its fixed base end pivoted adjacent the lock cam, and

a spring attached between the free end of the lever and the lock cam, whereby moving the lever upward will cause the lock cam to rotate in one direction and moving the lever downward will cause the lock cam to rotate in the opposite direction.