US3342521A

US3342521A - Torque grip lifting clamp

Info

Publication number: US3342521A
Application number: US474403A
Authority: US
Inventors: Raymond L Renfroe
Original assignee: J C Renfroe and Sons Inc
Current assignee: J C Renfroe and Sons Inc
Priority date: 1965-07-23
Filing date: 1965-07-23
Publication date: 1967-09-19
Anticipated expiration: 1984-09-19
Also published as: BE684354A; GB1145534A; DE1295151B; NL6610062A; FR1486901A

Description

Sept. 19, 1967 R. RENFROE 3,342,521

TORQUE GRIP LIF'TING CLAMP Filed July 23, 1965 2 Sheets-Sheet 1 INVENTOR RAYMOND L. RENFROE a ATTORNEYS p 19, 1967 R. L. RENFROE 3,342,521

TORQUE GRIP LIFTING CLAMP Fild July 23, 1965 2 Sheets-Sheet .2

. 4e 46 H05 m6 ATTORNEYS United States Patent 3,342,521 TORQUE GRIP LIFTING CLAMP Raymond L. Renfroe, Jacksonville, Fla., assignor to J. C. Renfroe & Sons, Inc., Jacksonville, Fla, a corporation of Florida Filed July 23, 1965, Ser. No. 474,403 17 Claims. (Cl. 29492) This invention relates to clamps and, more particularly, to clamps employing a torque gripping action for lifting articles such as plates, angles and other structural members.

Many different types of clamps have been developed for lifting heavy articles such as steel plates, angles and the like. In one common type of clamp, the article is engaged during lifting by fixed jaws through a torque gripping action. The heretofore available torque clamping devices have been beset by various disadvantages. For example, some such prior art clamps are not adapted to lift heavy articles. Others which are adapted to lift heavy articles are unduly complex and heavy, thereby making them expensive to manufacture and maintain and difficult to operate. Moreover, those prior art torque grip clamps are not completely suitable for moving an object from a horizontal position to a vertical position during lifting due to the fact that a reversal of the torque action occurs and a point is reached at which the torque is zero, thus raising the possibility that the clamp could slip off from the object being lifted.

To overcome the disadvantages of the prior art lifting clamp, it is an object of the present invention to provide an improved lifting clamp in which the jaws of the clamp may be locked into tight engagement with the article to be lifted prior to the lifting and in which a substantial torque gripping action is exerted on the article at all times during lifting.

Another object of the invention is to provide such a clamp which is provided wit-h means for automatically locking the shackle and lifting connection in a position where the torque is zero in order that the clamp may be readily removed from the article.

A further object of the invention is to provide an improved lifting clamp which is light in weight and simple in construction, thus making it easy to manufacture, maintain and operate.

A still further object of the invention is to provide such a lifting clamp employing a shackle and lifting connection pivotally connected to the body on an axis offset from the center thereof and not substantially higher than the axis of the jaws of the clamp so that a substantial torque gripping action is exerted on the article in any position to which the shackle member may pivot during lifting.

Still another object of the invention is to provide an improved lifting clamp employing a torque gripping action in which the jaws may be locked in tight engagement with the article prior to lifting.

One aspect of the invention is generally directed to a lifting clamp comprising a clamp body defining a vertical slot to receive an article to be lifted, a pair of opposed jaws connected to said body on opposite sides of said slot fixed against horizontal movement during lifting, a shackle member pivotally connected to said body on one side thereof at a pivot having an axis horizontally offset from said slot and not substantially higher than the axis of said jaws, said shackle member being normally free for pivotal movement in a vertical plane which includes the axis of said jaws,and a lifting connection attached to said shackle member so that a lifting force applied to said connection normally causes said jaws to exert a substantial torque gripping action on the article in various positions to which said shackle member may pivot during lifting.

The invention having been broadly described, certain preferred specific embodiments will now be discussed in detail with reference to the accompanying drawings in which:

FIGURE 1 is a side elevational view of a lifting clamp according to the invention attached to a steel plate, with the shackle being locked in its uppermost position;

FIGURE 2 is an end elevational view of the clamp of FIGURE 1;

FIGURE 3 is a sectional view, partially broken away, taken along line 3-3 of FIGURE 2;

FIGURE 4 is a sectional View taken along line 4-4 of FIGURE 1;

FIGURE 5 is a side elevational view of the clamp of FIGURE 1 showing the manner in which the shackle pivots about its pivotal connection to the clamp body during lifting;

FIGURE 6 is a side elevational view of a portion of the clamp of FIGURE 1 showing the lifting connection contacting the end of the locking lever means;

FIGURE 7 is a side elevational view of a modified form of a clamp, according to the present invention, showing the shackle member pivoted to the body at a point below the axis of the jaws; and

FIGURE 8 is an end view of the clamp of FIGURE 7.

Illustrated in the drawings is a clamp, generally referred to by the reference numeral 1.1, which may be constructed of any suitable material such as steel. The clamp 11 includes a clamp body 12 having a generally U-shaped configuration which defines a vertical slot 13-. In the normal position of the clamp prior to lifting, the clamp is in an upright position as shown in FIGURE 1 of the drawings. In this position the slot 13 extends from the bottom of the clamp upwardly into the body 12 and therefore may be defined as a vertical slot when the clamp is in its normal upright position shown in the drawings. Slot 13 is sutficiently wide to receive heavy articles such as steel plates or the flanges of beams such as I-beams, H-beams, channels, angles, and the like.

The clamp body 12 includes a front wall 15 and a rear wall 16 spaced apart to define a hollow space 17 in between, as best illustrated in FIGURE 2. The front and rear walls are connected at their bottom portions on I each side of slot 13 by a pair of

metal blocks

19 and 20.

The blocks 19 and 20- may be connected to the front and rear walls by any suitable means such as welding. In the position of the clamp as shown in FIGURES 1 and 4, block 19 is on the left side of slot 13 and block 20 is on the right side of slot 13.

Connected to the body 12 on opposite sides of the slot 13 are a pair of

opposed jaws

21 and 22. Jaw 21 is comprised of a circular insert 24 having a s-hap annular gripping ridge 25 projecting into slot 13 for gripping an article to be lifted. Insert 24 is swivel mounted in a countersunk hole in block 19 by any suitable means such as bolt 26 as best illustrated in FIGURE 4. Insert 24 is freely rotatable within the bore of metal block 19.

The opposed jaw 22 is comprised of an adjustable clamping screw 27 threadably received within a bore extending through block 20 of clamp body 12. Clamping screw 27 is provided on its inner end with a swivel mounted insert 28. Insert 28 is rotatably mounted in a countersunk hole in the inner end of clamping screw 27 by any suitable means such as screw 29. The inner end of insert 28.is provided with a sharp annular gripping ridge 30 which projects into slot 13 to grip an article to be lifted. Clamping screw 27 is provided on its outer end with any suitable handle means such as knurled knob 32 to permit the clamping screw to be manually adjusted to a plurality of fixed clamping positions. Although handle means 32 is shown in the drawings as a knurled knob, it will be understood that any other suitable form of handle means may be employed such as a hexagonal head or a projecting portion having an aperture therein to receive a pin or wrench.

The

swiveled inserts

24 and 28 of

opposed jaws

21 and 22 preferably are formed of a hard steel material so that they may effectively grip a steel plate or other article to be lifted. It is to be noted that

jaws

21 and 22 oppose each other on opposite sides of slot 13 along a horizontal axis.

Metal block 20 on the right side of slot 13 is provided with a pair of projecting

round bosses

33 and 34 on the outer sides thereof, as best shown in FIGURE 4. Boss 34 is provided with a threaded bore to receive a locking cap or set screw 35 which contacts a block 36 received in a countersunk hole communicating with the bore of metal block 20. Block 36 is fiat on the side which contacts set screw 35 and is threaded on the opposite side for engagement with the threads of clamping screw 27. The block 36 may be brought into tight engagement with clamping screw 27 to lock it in any desired fixed position by tightening set screw 35.

A shackle member 37 is pivotally attached to the projecting

bosses

33 and 34 of metal block 20 of the clamp body 12. Shackle member 37 is comprised of a pair of spaced, generally L-

shaped plates

38 and 39 connected at their extreme upper portions by a metal block member 41 as best shown in FIGURES 1 and 2.

Attached to shackle member 37 is a movable element 42 slidably and rotatably received within an aperture in block 41 of the shackle member. Element 42 is comprised of an elongated pin 43 having enlarged

heads

44 and 45 on its lower and upper ends, respectively, to retain it within the aperture in block 41 of shackle member 37. A lifting connection 46 having an aperture 47 extending therethrough projects upwardly from boss 45 to provide means for connecting the clamp to a cable or other lifting means.

It is to be noted that shackle member 37 is freely pivotable around the

bosses

33 and 34 of body 12 in the vertical plane which includes the axis of

opposed jaws

21 and 22, as best illustrated in FIGURE 5. Moreover, in the embodiment of the invention shown in FIGURES 1 through 6, the

bosses

33 and 34 forming the pivot for shackle member 37 provide an axis of rotation for the shackle offset from the center of slot 13. Preferably the pivotal axis of the shackle lies in the same or substantially the same horizontal plane as the axis of

jaws

21 and 22.

Shackle member 37 is limited in its pivotal movement at its uppermost portion by raised stop portions 48 provided at the top of front and

rear walls

15 and 16 of body 12, as best illustrated in FIGURE 3. It is to be noted that block 41 of shackle member 37 contacts the raised portions 48 when the shackle member is in its uppermost, generally vertical position with the lifting connection 46 directly above slot 13.

In the embodiment of the invention shown in FIG- URES 1 through 6, the body 12 of clamp 11 is provided with a locking lever means 51 freely pivotable about a pin 52 extending between and connected to the front and

rear walls

15 and 16 at a point adjacent the top of body member 12 on the side of the body above clamping screw 27. Lever means 51 is comprised of a wedge shaped inner portion 53 adapted to contact the lower head 44 of lifting connection 42 and a counterweighted outer portion 54 which normally causes the inner portion of the lever to pivot upwardly into contact with the movable element 42. Lever means 51 functions to automatically lock element 42 and, consequently, shackle member 37 in a position in which the lifting connection 46 is directly above slot 13 as best illustrated in FIGURES 1 and 3.

Movable element 42 is free for sliding vertical and rotative movement within the aperture of block 41 when the clamp is employed to lift an object. Lever means 51 locks the element 42 in place by virtue of the fact that the inner end 53 of the lever means engages pin 43 of lifting connection 42 immediately above head 44-.

In operation of the embodiment shown in FIGURES 1 through 6 of the clamp of the present invention, the shackle member 37 and its movable element 42 are normally locked in position directly above slot 13 by lever means 51 as shown in FIGURE 1. In this position, the clamp may be placed over an article to be lifted, such as plate 14, so that the plate extends into the slot 13. Clamping screw 27 may be manually adjusted into tight engagement with the plate 14 so that it is securely held between the

jaws

21 and 22. Movable shackle element 42 is then moved downwardly so its upper head 45 contacts block 41 and locking lever 51 is free to be manually pivoted in a counterclockwise direction as viewed in FIG- URE 1, out of contact with pin 43 and head 44 of the lifting connection. Upon subsequent application of a lifting force to lifting connection 46, the movable element 42 slides vertically upward through the aperture in block 41 until head 44 contacts the lower side of the block 41, and shackle member 37 begins to pivot around

bosses

33 and 34 as shown in FIGURE 5.

When the clamp 11 is in the position shown in FIG- URE 5, the body 12 is pivoted so that a substantial torque gripping action is exerted on the plate or other article being lifted by the

jaws

21 and 22. It is an important feature of the present invention that the torque gripping action is maintained on the plate 14 in any position to which the shackle member may pivot during lifting. This accrues by reason of the fact that shackle member 37 is pivotally connected to the body 12 at a point not substantially higher than the horizontal axis of the

jaws

21 and 22. By so positioning the pivot point, it is impossible for any reversal of the torque gripping action to occur during lifting, thus eliminating the possibility of the clamp slipping out from the jaws. Moreover, the torque gripping action is effectively maintained even though the clamp is in a horizontal position such as when it is employed to lift an object which is initially in a horizontal position.

When it is desired to release the clamp 11 from the article being lifted, the clamp and article are positioned on a supporting surface so that shackle member 37 may pivot to its normal position in contact with raised portion 41 directly above slot 13. As the lifting force is released, movable element 42 is free to move downwardly as shown in FIGURE 6 until head 44 contacts the end 53 of lever 51, cams the end 53 downwardly and slides past it. At this point, the lever end 53 slips over the top of the head 44. The screw 32 then may be manually adjusted out of engagement with the article being lifted and a small lifting force again applied to movable element 42 so that it is raised upwardly into locking engagement with lever 51 as shown in FIGURE 1. In this position, the lifting force is applied directly above the slot 13 along a line extending through the center of the slot so that no torque gripping action occurs between the

jaws

21 and 22. In this manner, a very effective means is provided for removing the clamp 11 from the article 14 at a point where the torque is zero. If desired the clamp may be utilized with the

jaws

21 and 22 set apart slightly further than the thickness of the article being lifted. This setting eliminates the necessity for loosening the jaws 22 before removing the clamp from the article.

In the embodiment of the invention shown in FIG- URES 7 and 8, there is provided a clamp 111 which is identical to the clamp 11 except as described hereinafter. The body 112 of clamp 111 is comprised of a solid integral piece rather than a pair of spaced walls. The body 112 on the side of the slot containing the clamping screw 127 extends further downwardly than the body on the opposite side of slot 113 so that shackle member 137 may be pivotally attached to the ends 133 and 134 of pivot pin 100 at a point below the horizontal axis of

jaws

121 and 122.

Shackle member 137 is comprised of a pair of spaced side plates integrally connected at their top by a block 141 in a manner similar to the embodiment shown in FIG- URES 1 through 6. Lifting connection 146, however, is fixedly attached to the top of block 41 of shackle member 37 rather than being adjustably connected thereto. In the embodiment of the clamp of FIGURES 7 and 8 no locking lever means are provided for locking the shackle in position directly above slot 13, thus leaving the shackle member free to pivot at all times. In all other significant respects, however, the clamp of the embodiment shown in FIGURES 7 and 8 operates in a manner similar to that described for the embodiment shown in FIGURES 1 through 6.

By locating the pivotal axis of shackle member 137 below the horizontal axis of the

jaws

121 and 122, a substantial torque gripping action is exerted on the article being lifted at all positions to which the shackle member may pivot during lifting, ranging from horizontal to vertical. For this reason, the clamp is precluded from slipping off at all times while the article is being lifted.

It will be understood that either of the embodiments shown may operate effectively with or without the means for locking the shackle member in position directly above the slot of the clamp and that the features shown in each of the embodiments may be incorporated into the other embodiment. For example, the clamp 11 may have the shackle pivot below the axis of

jaws

21 and 22. The clamp 111 may have the shackle pivot and the jaw axis in the same plane.

It is apparent that the lifting clamp of the present invention has several important advantages. A very significant advantage is that a substantial torque gripping action is exerted on the article being lifted at all times during lifting. This is due to the fact that the pivotal axis of the shackle member is located either substantially on or below the horizontal axis of the jaws of the clamp. Due to this particular construction, the only time at which the torque is zero is when the shackle member is positioned directly above the slot when the clamp is in position to be removed from the article being lifted. When locking means are employed on the clamp for automatically locking the shackle in position directly above the slot, a further advantage accrues by reason of the fact that the clamp may be readily removed from the article while the torque gripping action is zero.

Moreover, the particular construction of the clamp of the present invention permits the clamp to be relatively simple in construction and easy to maintain and operate. Further, due to the simplicity of construction of the clamp of the present invention, it is significantly lighter in weight than most heretofore known lifting clamps employed to handle heavy structural objects. It is also to be noted that the swivel action of the jaws as well as the lifting connection facilitates the lifting action in that it relieves any twisting action within the cable or other means connecting the clamp to the hoisting means.

While the invention has been described with particular reference to the embodiments mentioned, many other modifications may be made by persons skilled in the art without departing from the scope of the invention which is defined solely by the appended claims.

What is claimed is:

1. A lifting clamp comprising a clamp body defining a vertical slot having an open lower end to receive an article to be lifted,

a pair of opposed jaws connected to said body on opposite sides of said slot fixed against horizontal movement during lifting, said jaws having a horizontal axis, one of said jaws being fixed and the other of said jaws being movable along said axis,

a shackle member pivotally connected to said body on 6. one side thereof at a pivot having a horizontal axis horizontally offset from said slot on the same side of said slot as said movable jaw, said shackle member being normally free for pivotal movement in a vertical plane which includes the axis of said jaws,

and a lifting connection attached to said shackle member so that a lifting force applied to said connection normally causes said jaws to exert a. substantial torque gripping action on the article in various positions to which said shackle member may pivot during lifting,

said pivot axis being not substantially higher than the axis of said jaws so that the lifting clamp may be rotated to move said slot from a horizontal to a Vertical position while lifting an article without reversing said torque gripping action.

2. A lifting clamp as defined in claim 1 wherein said pivot axis and the axis of said jaws lie in substantially the same horizontal plane.

3. A lifting clamp as defined in claim 1 wherein said pivot axis is below the axis of said jaws.

4. A lifting clamp comprising a clamp body defining a vertical slot to receive an article to be lifted, a

a pair of opposed jaws connected to said body on opposite sides of said slot fixed against horizontal movement during lifting,

a shackle member pivotally connected to said body on one side thereof at a pivot having an axis horizontally offset from said slot, said shackle member being normally free for pivotal movement in a vertical plane which includes the axis of said jaws,

a lifting connection attached to said. shackle member so that a lifting force applied to said connection normally causes said jaws to exert a substantial torque gripping action on the article in various positions to which said shackle member may pivot during lifting, and

means for locking said shackle member against pivotal movement in a position with said lifting connection directly above said slot.

5. A lifting clamp as defined in claim 4 wherein said locking means comprises a lever pivotally connected to said body engageable with said shackle member when said lifting connection is pivoted to said position directly above said slot.

6. A lifting clamp as defined in claim 4 which includes stop means connected to said body for limiting pivotal movement of said shackle at its uppermost position with the lifting connection directly above said slot.

7. A lifting clamp as defined in claim 6 wherein said locking means is automatically engageable when the load on the shackle member is released and said shackle member is at said uppermost position.

8. A lifting clamp as defined in claim 5 wherein said shackle member has an aperture therein and includes an element extending vertically and slidably through said aperture, said lever being automatically engageable with said element at the lower end of the sliding movement of said element when the clamp is upright.

9. A lifting clamp as defined in claim 8 wherein said element includes a rod rotatable in said aperture.

10. A lifting clamp comprising a clamp body defining a vertical slot to receive an article to be lifted,

one of said jaws being horizontally adjustable to a plurality of fixed positions,

a shackle member pivotally connected to said body on one side thereof at a pivot having an axis horizontally offset from the center of said slot and not substanital- 1y higher than the axis of said jaws, said shackle member being normally free for pivotal movement 7 in a vertical plane which includes the axis of said aws,

a lifting connection attached to said shackle member so that a lifting force applied to said connection normally causes said jaws to exert a substantial torque gripping action on the article in various positions to which said shackle member may pivot during lifting,

and lever means engageable with said shackle member for locking said shackle member against pivotal movement when said lifting connection is directly above said slot.

11. A lifting clamp as defined in claim wherein one of said jaws is provided with an article engaging, swivel mounted insert.

12. A lifting clamp as defined in claim 10 wherein said pivot axis and the axis of said jaws lie in substantially the same plane.

13. A lifting clamping as defined in claim 10 wherein said adjustable jaw comprises a clamping screw threadably mounted in said body.

14. A lifting clamp comprising a clamp body defining a vertical slot to receive an article to be lifted,

a swivel mounted insert on the end of one of said jaws for engaging the article to be lifted,

a shackle member pivotally connected to said body on one side thereof at a pivot having an aXis horizontally offset from the center of said slot and not substantially higher than the axis of said jaws, said shackle member being normally free for pivotal movement in the vertical plane which includes the axis of said aws,

stop means connected to said body for. limiting pivotal movement of said shackle at its uppermost position when said lifting connection is directly above said slot, lifting connection attached to the upper portion of said element so that a lifting force applied to said lift ing connection normally causes said jaws to exert a substantial torque gripping action on the article in various positions to which said shackle member may pivot during lifting,

10 said shackle member has an aperture therein and including an element extending vertically and slidably through said aperture, said element being normally free for rotative movement in said aperture, and

lever means pivotally connected to said body engage- References Cited UNITED STATES PATENTS 2/1964 Olsen 292-104 X GERALD M. FORLENZA, Primary Examiner.

HUGO 0. SCHULZ, Examiner.

G. F. ABRAHAM, Assistant Examiner.

Claims

1. A LIFTING CLAMP COMPRISING A CLAMP BODY DEFINING A VERTICAL SLOT HAVING AN OPEN LOWER END TO RECEIVE AN ARTICLE TO BE LIFTED, A PAIR OF OPPOSED JAWS CONNECTED TO SAID BODY ON OPPOSITE SIDES OF SAID SLOT FIXED AGAINST HORIZONTAL MOVEMENT DURING LIFTING, SAID JAWS HAVING A HORIZONTAL AXIS, ONE OF SAID JAWS BEING FIXED AND THE OTHER OF SAID JAWS BEING MOVABLE ALONG SAID AXIS, A SHACKLE MEMBER PIVOTALLY CONNECTED TO SAID BODY ON ONE SIDE THEREOF AT A PIVOT HAVING A HORIZONTAL AXIS HORIZONTALLY OFFSET FROM SAID SLOT ON THE SAME SIDE OF AND SLOT AS SAID MOVABLE JAW, SAID SHACKLE MEMBER BEING NORMALLY FREE FOR PIVOTAL MOVEMENT IN A VERTICAL PLANE WHICH INCLUDES THE AXIS OF SAID JAWS, AND A LIFTING CONNECTION ATTACHED TO SAID SHACKLE MEMBER SO THAT A LIFTING FORCE APPLIED TO SAID CONNECTION NORMALLY CAUSES SAID JAWS TO EXERT A SUBSTANTIAL TORQUE GRIPPING ACTION ON THE ARTICLE IN VARIOUS POSITIONS TO WHICH SAID SHACKLE MEMBER MAY PIVOT DURING LIFTING, SAID PIVOT AXIS BEING NOT SUBSTANTIALLY HIGHER THAN THE AXIS OF SAID JAWS SO THAT THE LIFTING CLAMP MAY BE ROTATED TO MOVE SAID SLOT FROM A HORIZONTAL TO A VERTICAL POSITION WHILE LIFTING AN ARTICLE WITHOUT REVERSING SAID TORQUE GRIPPING ACTION.