US3297354A

US3297354A - Lifting clamp

Info

Publication number: US3297354A
Application number: US544662A
Authority: US
Inventors: Raymond L Renfroe
Original assignee: J C Renfroe and Sons Inc
Current assignee: J C Renfroe and Sons Inc
Priority date: 1966-04-11
Filing date: 1966-04-11
Publication date: 1967-01-10
Anticipated expiration: 1984-01-10

Description

Jan. 10, 1967 R. 1.. RENFROE LIFT ING CLAMP \NVENTOR RAYMOND L. RENFROE ,MSMMfiA 2 Sheets-Sheet 1 Original Filed July 8, 1964 ATTORNEYS Jan. 10, 1967 v L. RENFROE 3,297,354

LIFTING CLAMP Original Filed July 8, 1964 v 2 Sheets$heet 2 1 H05 H64 38 ll lNVENTOR RAYMOND L. RENFROE ATTORNEYS Patented Jan. 10, 1967 3,297,354 LIFTING CLAMP Raymond L. Renfroe, Jacksonville, Fla., assignor to J. C. Renfroe & Sons, Inc., Jacksonville, Fla., a corporation of Florida Continuation of application Ser. No. 381,193, July 8, 1964. This application Apr. 11, 1966, Ser. No. 544,662 13 Claims. (Cl. 294104) This application is a continuation of my copending application Serial No. 381,193, filed July 8, 1964, entitled Lifting Clamp now abandoned.

This invention relates to clamps for lifting articles such as steel plates and more particularly to such clamps having a locking device to retain the clamp jaws in closed position.

The present invention is an improvement of the invention disclosed in Joseph C. Renfroe United States Patent 2,654,630, issued October 6, 1953.

Such patent discloses a clamp comprising a clamp body having a slot to receive an article to be lifted. A pair of jaws are provided on opposite sides of the slot. One of the jaws is movable between open and close positions relative to the other jaw which is preferably, fixed. The movable jaw is operated by a shackle connected to the movable jaw by force multiplying linkage.

The clamp body includes a pair of spaced side plates. Mounted on the inside of one of the side plates and parallel thereto is a pivotal locking plate operated by a handle lever located outside of such side plate. A heavy tension spring connects the locking plate to the linkage which extends between the shackle and the movable jaw. By rotation of the locking lever handle to a closed position the spring exerts a heavy closing force on the movable jaw. At the same time, however, the spring tends to cant the pivot pin connecting the locking plate to the handle to a position inclined relative to its normal axis. This causes a binding action which makes the lever difiicult to operate.

Further, as can be seen in FIGURE 1 of Patent 2,654,- 630, the movable jaw and the link whichconnects it to the shackle is exposed outside of the clamp body where it can be damaged or jammed by the Weight of any object which happens to contact it.

An object of the present invention is to provide an improved lifting clamp of the general type disclosed in Renfroe Patent 2,654,630 having an easily-operated lock free from binding.

Another object of the invention is to provide such a clamp in which the improved lock may be easily assembled into and disassembled from the clamp body.

A further object of the invention is to provide such a clamp in which the linkage which operates the movable jaw is covered by the clamp body throughout its stroke.

Generally the invention relates to a lifting clamp which comprises a clamp body including a pair of spaced side plates, said body defining a slot through said side plates to receive an article to be lifted; a pair of opposed jaws mounted on opposite sides of said slot, one of said jaws being pivotally mounted for opening and closing movement relative to the other jaw; a shackle mounted for guided movement in said clamp body and adapted for connection to a lifting force; link means connecting said shackle to said movable jaw to close said movable jaw when a lifting force is applied to said shackle, said link means and said movable jaw forming an assembly; locking means comprising a pair of spaced locking plate members pivotally connected to said plates for rotation about an axis transverse to said side plates, a cross member eccentric with said axis connecting said plate members together at opposing positions adjacent said side plates, a spring connecting said cross member to said assembly, a manually operated handle pivotally connected outside of said clamp body for rotation about said axis, and means extending through one of said side plates to uon-rotatably connect said handle to one of said plate members so that rotation of said handle causes corresponding rotation of said plate members to move said locking means between a closed position where said spring exerts a jaw closing force on said assembly and an open position where said spring permits said movable jaw to remain open; and stop means to retain said locking means in closed position.

Preferably the means non-rotatably connecting the handle to the adjoining plate member is integral with such plate member. To facilitate assembly using the integral connecting means, there is provided an opening in the adjoining side plate surrounding and substantially larger than the connecting means. In accordance with a specific embodiment, a pair of coaxial pivots extend outwardly from and connect the plate members to said side plates, one of said pivots being formed by the non-rotatable connecting means and having one of its ends non-rotatably connected to the adjoining plate member. When the latter pivot is integral with the plate member, as it preferably is, the enlarged opening in the side plate surrounds'the pivotal axis and a removable spacer is mounted in such opening after assembly is complete.

The invention having been generally described, a preferred specific embodiment will now be set forth in detail with reference to the accompanying drawings in which:

FIGURE 1 is a front elevation of a clamp according to the present invention;

FIGURE 2 is a side elevation of the same clamp to an enlarged scale;

FIGURE 3 is a sectional view taken along the line 33 of FIGURE 2 showing the movable jaw in an open position, its operating linkage and the lock mechanism;

FIGURE 4 is a sectional view taken along the line 44 of FIGURE 3 showing particularly the lock mechanism and movable jaw;

FIGURE 5 is a sectional view taken along the line 55 of FIGURE 3;

FIGURE 6 is a sectional view similar to FIGURE 3 showing the clamp with its movable jaw in a closed position withthe lock retaining the jaw in such position; and

FIGURE 7 is an exploded view of the locking mecha- IllSm.

With reference to the drawings the invention includes a clamp body 11 which includes a pair of

side plates

12 and 13. Preferably the side plates are permanently connected together by a pair of

struts

14 and 15 which are welded to each of the plates. The plates are further connected by a thick web 16 which is also welded to the two plates.

The clamp body 11 defines a vertical slot 17 which ex tends through both of the

side plates

12 and 13 to receive an article to be lifted. The clamp is particularly adapted for the lifting of heavy steel plates used in construction. Mounted on opposite sides of the slot 17 are a pair of

jaws

18 and 19. The jaw 18 is fixed against axial movement and the jaw 19 is movable.

The jaw 18 is a conventional swivel jaw which is freely pivotable about its own axis around a connecting bolt 21 which is connected through an opening 22 in the web 16 and retains the jaw 18 against axial movement. The jaw 18 has a sharpened ridge 23 which grips the article being lifted.

The jaw 19 is pivoted about a removable pin 24 which extends through the

side plates

12 and 13. The pin 24 has an enlarged head 25 on one end and an opening at the other end to receive a cotter pin 26. The jaw 19 has an arcuate gripping face with a plurality of ridges or teeth 27 which bite into the article being lifted.

The movable jaw 19 is also connected by a pin 31 to one end of an elongated link means 32, the other end of which is connected by a pin 33 to the lower end of a shackle 34. The link means 32 comprises a pair of spaced

fiat link bars

35 and 36.

The shackle pin 33 extends through both of the

bars

35 and 36 and into a pair of opposed

vertical slots

37 and 38 in the interior surface of the

side plates

12 and 13.

The shackle 34 is movable vertically in the clamp body by the sliding action of the pin 33 in the

slots

37 and 38. The shackle at its upper end has a pair of lifting connections which define a large opening 41 and a small opening 42. The large opening 41 is adapted to receive a conventional lifting hook at the end of a hoisting cable. The small opening 42 is adapted to receive the connecting rod of a screw type clevis. Thus, the clamp can be employed with either type of lifting connection.

Desirably the small opening 42 is positioned above the axis of the large opening 41 and on the opposite side of the opening 41 from the movable jaw 19. Thus, when a lifting force is applied to the small opening 42 with the clamp mounted on a vertical plate, the shackle is rotated slightly to align the opening 42 with the

slots

37, 38 and the slot 17. When the clamp is mounted on a plate which is in a horizontal position with the movable jaw on top of the plate application of lifting force to the opening 42 causes the shackle to pivot and engage the strut 15 and apply a closing force to the jaw 19 in the manner fully described in Patent 2,654,630.

The large opening 41 also functions as a handle. Such opening is large enough to receive the fingers of a person carrying the clamp.

As shown in FIGURES 3 and 6 the shackle may be moved between an elevated position as shown in FIG- URE 6 and a depressed position as shown in FIGURE 3 in which the movable jaw 19 is closed and opened respectively. As also shown in these figures the lower corner 43 of each of the

side plates

12 and 13 covers the assembly composed of the movable jaw 19 and the link means 32 during the entire path of movement of such assembly except that the gripping portion of the movable jaw is exposed in the slot 17. This construction of the side plates protects the assembly of the movable jaw and link means against damage from being struck by objects during movement of the clamp. It also prevents the clarnp from being jammed by the weight of the object lying on the assembly and retaining the movable aw against movement.

Still further, since the pivot pin 31 is covered by both side plates over its entire path of movement, the pin 31 need not be fixed to any of the clamp structure. It is merely inserted through the link bars 35 and 36 and the movable jaw 19 and floats freely therein. The pin 31 is restrained against removal by the

side plates

12 and 13. In the clamp shown in Patent 2,654,630, it was necessary to provide a relatively permanent connection between the link bars and the pin connecting them to the movable jaw. Thus, when the movable jaw became worn or damaged, the entire assembly of the jaw and link means had to be replaced. In the present clamp the easy removal of the floating pin 31 enables replacement of the removable jaw alone. The link means 32 need not be replaced.

An important feature of the present invention is its improved locking device. Such device includes a pair of locking

plate members

51 and 52 connected together by a cross member 53 which is welded or otherwise per manently connected between the plate members. The plate member 51 has an elongated pivot 54 integrally connected thereto. The pivot 54 extends through an opening 55 in the side plate 12 which opening is substantiallylarger than .the pivot 54. Connected to the outer end of the pivot 54 outside of the side plate 12 is a lever handle 56 by means of a drive pin 57.

The space between the pivot 54 and the walls of the opening 55 is filled by a spacer sleeve 58 which preferably is integral with the handle 56. Alternatively, the spacer sleeve 58 may be a separate insert free of the handle 56.

The locking plate member 52 is connected to the side plate 13 by a pivot 60 which comprises a bolt having a smooth round head 61 with an axial opening to receive an Allen wrench. The smooth head 61 is received within an opening 62 in the plate member 52. The bolt 60 has a threaded stem 63 which extends through an opening 64 in the plate 13 and is connected to such side plate by a lock nut 65.

The cross member 53 has an opening 66 to receive one end of a heavy tension spring 57, the other end of which is connected to a pin 68 which is mounted between the link bars 35 and 36 of the link means 32.

The general operation of the locking device is similar to that of the locking device shown in Patent 2,654,630. In the latter device, however, there is only one locking plate member which corresponds to the member 51. The upper end of the tension spring is connected to a stud which protrudes from the locking plate. Since the locking plate has only one pivot extending through only one side plate of the clamp for connection to the handle, the spring tends to cant the pivot to a position inclined with respect to its normal axis. There is not such canting in the locking device of the present invention. tion of the second opposed plate member 52 connected by a second pivot to the opposed side plate 13 eliminates such canting. Thus there is no binding action between the spacer sleeve 58 and the opening 55. The handle is therefore easier to rotate. This case of operation enables a heavier spring 67 to be employed with no increase in the force required to turn the handle 56.

The use of the second plate member in the locking device, however, results in assembly problems, the solution to which is another important feature of the present invention. The handle 56 must be non-rotatably connected to the plate member 51 in order that rotation of the handle may cause corresponding rotation of such plate member. In this embodiment, the means connecting the handle 56 and the plate member 51 is the pivot 54. Because of the heavy forces involved, it is highly desirable to make the pivot 54 integral with the plate member 51. It is also important to keep the interior surfaces of the

plate members

51 and 52 free of protrusions at the pivots to leave the space between the plate members clear for the operation of the tension spring 67. Thus, the interior surfaces of the

plate members

51 and 52 are flush.

Assembly and disassembly is faciliated by the use of the large opening 55 and spacer sleeve 58 around the pivot 54. This arrangement permits the connected plate members with their protruding pivot 54 to be inserted between the

side plates

12 and 13 and the pivot to be inserted into the Opening 55. The handle 56 and spacer sleeve 58 are then mounted in their proper positions. The pivot 60 may then be inserted from the inside through the

openings

62 and 64.

When the handle lever 56 is rotated to a closed position as shown in phantom lines in FIGURE 1, the locking plate members assume a position as shown in FIGURE 6. The locking device is held in locked position by an over center mechanism. In the closed or locked position the tension spring 67 exerts a closing force on the assembly of the link means 32 and the movable jaw 19. In this position the axis of the spring 67 is inside of the pivot 54. Further rotation of the locking plate members is prevented by engagement with either the strut 15 or the link means 32 which function as stops.

When the handle is rotated in a clockwise direction as shown in FIGURE 1 until the axis of the spring 67 passes The addi-,

to the outside of the pivot 54, the spring then pulls the handle down toward the open position shown in full lines in FIGURE 1. In that position the spring exerts no closing force on movable jaw 19 which is permitted to remain fully open.

The locking plate member 51 is provided with a protruding pawl 71 which engages an upwardly facing surface 72 on the link bar 35 to lock the clamp in the open position. If desired in heavier clamps a pawl 71 may be mounted on each of the locking plate members to engage both of the link bars 35 and 36.

' The general operation of the clamp is the same as that fully described in Patent 2,654,630. Such operation will not be described in detail herein.

There has been illustrated and described what is considered to be a preferred embodiment of the invention. It will be understood, however, that various 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 which comprises a clamp body including a pair of spaced side plates, said body defining a slot through said side plates to receive an article to be lifted,

a pair of opposed jaws mounted on opposite sides of said slot, one of said jaws being pivotally mounted for opening and closing movement relative to the other jaw,

a shackle mounted for guided movement in said clamp body and adapted for connection to a lifting force,

link means connecting said shackle to said movable jaw to close said movable jaw when a lifting force is applied to said shackle, said link means and said movable jaw forming an assembly,

locking means comprising a pair of spaced locking plate members,

a pair of coaxial pivots extending outwardly from and connecting said plate members to said side plates, one of said pivots having one of its ends non-rotatably connected to one of said plate members,

a handle connected outside of said clamp body to the other end of said one pivot,

a cross member eccentric with said pivots connecting said plate members together, and

a spring connecting said cross member to said assembly,

said handle being manually rotatable about the axis of said pivots between a closed position Where said spring exerts a jaw closing force on said assembly and an open position where said spring permits said movable jaw to remain open, and

stop means to retain said locking means with said handle in closed position.

2. A lifting clamp according to claim 1 wherein said one pivot is integral with said one plate member, the other pivot is removably connected to the other plate member, said one plate member has an opening substantially larger than said one pivot to receive said one pivot, said clamp further comprising a removable spacer sleeve mounted in said opening around said one pivot.

3. A lifting clamp according to claim 2 wherein said spacer sleeve is integral with said handle.

4. A lifting clamp according to claim 2 wherein said other pivot comprises a bolt having a smooth round head upon which said other plate member is rotatable and a threaded stem connected to a nut outside of the other side plate.

5. A lifting clamp according to claim 4 wherein said spring is connected to said link means.

6. A lifting clamp according to claim 5 wherein said spring comprises an elongated tension spring having its longitudinal axis on opposite sides of said pivots when said handle is in open and closed positions respectively.

7. A lifting clamp according to claim 6 wherein at least one of said plate members has a protruding pawl engageable with said link means to hold said movable jaw open when said handle is in open position.

3. A lifting clamp according to claim 1 wherein said body side plates cover said assembly over its entire path of movement except for the movement of said movable jaw into said slot.

9. A lifting clamp according to claim 1 wherein said shackle has at its upper end a large opening to receive a lifting hook and a small opening to receive a connecting rod of a screw clevis, said small opening being located above the axis of said large opening and on the opposite side of said axis from said movable jaw.

10. A lifting clamp which comprises a clamp body including a pair of spaced side plates, said body defining a slot through said side plates to receive an article to be lifted;

locking means comprising a pair of spaced locking plate members pivotally connected to said side plates for rotation about an axis transverse to said side plates,

a cross member eccentric with axis connecting said plate members together at opposing positions adjacent said side plates,

a spring connecting said cross member to said assembly,

a manually operated handle pivotally connected outside of said clamp body for rotation about said axis, and

means extending through one of said side plates to nonrotatably connect said handle to one of said plate members so that rotation of said handle causes corresponding rotation of said plate members to move said locking means between a closed position where said spring exerts a jaw closing force on said assembly and an open position where said spring permits said movable jaw to remain open, and

stop means to retain said locking means in closed position.

11. A lifting clamp according to claim 10 wherein said means to non-rotatably connect said handle to said one plate member extends along said axis and serves as a pivot for said handle and said one plate member.

12. A lifting clamp according to claim 10 wherein said means to non-rotatably connect said handle to said one plate member is integral with said one plate member and said one plate member has an opening substantially larger than said last-named means to receive said lastnamed means.

13. A lifting clamp according to claim 12 wherein said means to non-rotatably connect said handle to said one plate member extends along said axis and serves as a pivot for said handle and said one plate member, there being a removable spacer mounted in said opening around said pivot.

References Cited by the Examiner UNITED STATES PATENTS 2,654,630 10/1953 Renfroe 294104 GERALD M. FORLENZA, Primary Examiner.

R. G. SHERIDAN, Assistant Examiner.

Claims

1. A LIFTING CLAMP WHICH COMPRISES A CLAMP BODY INCLUDING A PAIR OF SPACED SIDE PLATES, SAID BODY DEFINING A SLOT THROUGH SAID SIDE PLATES TO RECEIVE AN ARTICLE TO BE LIFTED, A PAIR OF OPPOSED JAWS MOUNTED ON OPPOSITE SIDES OF SAID SLOT, ONE OF SAID JAWS BEING PIVOTALLY MOUNTED FOR OPENING AND CLOSING MOVEMENT RELATIVE TO THE OTHER JAW, A SHACKLE MOUNTED FOR GUIDED MOVEMENT IN SAID CLAMP BODY AND ADAPTED FOR CONNECTION TO A LIFTING FORCE, LINK MEANS CONNECTING SAID SHACKLE TO SAID MOVABLE JAW TO CLOSE SAID MOVABLE JAW WHEN A LIFTING FORCE IS APPLIED TO SAID SHACKLE, SAID LINK MEANS AND SAID MOVABLE JAW FORMING AN ASSEMBLY, LOCKING MEANS COMPRISING A PAIR OF SPACED LOCKING PLATE MEMBERS, A PAIR OF COAXIAL PIVOTS EXTENDING OUTWARDLY FROM AND CONNECTING SAID PLATE MEMBERS TO SAID SIDE PLATES, ONE OF SAID PIVOTS HAVING ONE OF ITS ENDS NON-ROTATABLY CONNECTED TO ONE OF SAID PLATE MEMBERS, A HANDLE CONNECTED OUTSIDE OF SAID CLAMP BODY TO THE OTHER END OF SAID ONE PIVOT, A CROSS MEMBER ECCENTRIC WITH SAID PIVOTS CONNECTING SAID PLATE MEMBERS TOGETHER, AND A SPRING CONNECTING SAID CROSS MEMBER TO SAID ASSEMBLY, SAID HANDLE BEING MANUALLY ROTATABLE ABOUT THE AXIS OF SAID PIVOTS BETWEEN A CLOSED POSITION WHERE SAID SPRING EXERTS A JAW CLOSING FORCE ON SAID ASSEMBLY AND AN OPEN POSITION WHERE SAID SPRING PERMITS SAID MOVABLE JAW TO REMAIN OPEN, AND STOP MEANS TO RETAIN SAID LOCKING MEANS WITH SAID HANDLE IN CLOSED POSITION.