US2676838A

US2676838A - Horizontal and vertical pull plate-lifting clamp

Info

Publication number: US2676838A
Application number: US278864A
Authority: US
Inventors: Gardner Edward Merrill
Original assignee: MERRILL BROTHERS
Current assignee: MERRILL BROTHERS
Priority date: 1952-03-27
Filing date: 1952-03-27
Publication date: 1954-04-27
Anticipated expiration: 1971-04-27
Also published as: DE930113C; FR1075516A; BE518307A

Description

April 27, 1954 E. M. GARDNER 2,676,838

HORIZONTAL AND VERTICAL PULL PLATE-LIFTING CLAMP Filed March 2'7, 1952 2 FIG.5

INVENTDR .clamp. .o.fDu further. object of; the inventionjs to provide a liftin qllainpiwh gh isadap e de ecta sure Patented Apr. 27, 1954 UNITED STATES wens HORIZONTAL AND VERTICAL PULL PLATE-LIFTING CLAMP Edward Merrill Gardner, Brooklyn, N. Y., as-

signor to Merrill Brothers, New York, N. Y., a

corporation of New York Application March 27, 1952, Serial No. 278,864

9 Claims. (01. 294104) This invention relates to improvements in lifting clamps particularly adapted for gripping and lifting steel plates and other heavy articles presenting a relatively thin edge adapted to be received into the clamp.

The lifting clamp of the present invention is adapted to effect a sure grip on a steel plate, for example, when the lift or pull is vertical or horizontal or at any angle in between, and constitutes' an improvement on the applicants Patent No. 2,393,101 granted January 15, 1946.

With respect to the lifting clamp disclosed in said patent, it has been found that this clamp works perfectly, regardless of the direction of pull provided the short leg or jaw of the clamp is underneath the plate, but when the plate is lifted and then let down again, it is often lowered with the short leg or jaw of the clamp on top of the plate. Under these conditions, it has been found that in a number of cases, the clamp has released its grip on the plate and allowed the plate to fall, this being particularly true in handling plates of a thickness of about one fourth or less of the maximum capacity of the clamp.

7 In checking on the reasons for the release of the lifting clamp under the conditions referred to above, it was found that the gripping pressure on the camisrelaxed and in some instances re- .sulting in the inadvertent release of the clamp from the plate. V

In the use of the clamp disclosed in said patent, it has also been found that at times the operator would attach theclamp to a plate somewhat out of the normal rangeof the lifting crane and so that a side pull would be appliedt o the a clamp. causing a severe bending and tensile strain on one of the eyes of the lifting shackle.

In some instances the misuse of the clamp in this way has caused one side of the lifting shackle to stretch and rupture and the other side to bend and break, Whereas under normal conditions, the lifting shackle would have an ample safety factor.

Having in mindthe foregoing, the primary object of the present invention is to provide an improved lifting clamp which will be free 'of the weaknesses and ,defects encountered in tionwiththe; clamp referred to. above.

A further object of the. invention is to provide a lifting clamp for steel plates and the like, which .is; adapted to. maintain a sure grip on the plate,

regardlessjof its thickness, the position of the g 7 ith respect to the plate, and the direction ,conneca side direction pull or a pull in any other direc- According to theinvention the improved clamp, having a structure which avoids the difficulties referred to above, comprises a clamp body having spaced opposed depending portions between which the article to be lifted is held, a gripping pad on one of said depending portions facing the other depending portion, a cam member, having an arcuate article-gripping surface, pivoted in the other depending portion with its gripping surface facing toward the gripping pad, a leverage means for applying pressure to the cam member, including abell crank pivotally mounted in the body of the clamp with its inside angle facing generally toward the cam member, a connecting link in the cla-mpbody the ends of which are respectively-pivoted to the cammember and to one arm of the bell crank, and a liftin shackle connected to the other arm of the bell crank.

With this construction has been found that pressure will always be maintained on the cam member to grip the plate being handled without being released, since the pivot point of the arm of the bell crank to which the lifting shackle is connected can never come in line with the pivot of the bell crank and the direction of pull or lift applied to the clamp. In this construction,

the end of .the bell crank arm to which the liftting shackle is attache is always well within the body of the clamp, and, in accordance with a preferred construction, that arm of the bell crank extendsgenerally toward the center of the clamp,

is forked and spansa short shackle link to which it is pivoted, the short shackle-connecting link being in turn spanned by the lifting shackle and pivoted thereto, I he short shackle-connecting link provides an intermediate link connection belifting shackle;thisprojecting portion having at least two, important functions.

t provides an extended bearingsurface in the fork of the lifting shackle which increases the strength of the 7 connection between, the lifting shack-1e and the bell crank; and: provides amember having a point .or end which canbestruck with ahammer to break loose the. grip of the cam member on the plate when it is desiredto release. the clamp. I

The improved lifting clamp of the present invention provides a sure grip for steel plates and similar articles, regardless of the angle of pull applied to the clamp or of the clamps reversal, even in the handling of thin plates. The use of the bell crank in the leverage mechanism of the lifting clamp provides a means by which a gripping pressure is always applied when there is a pull on the shackle, since the arm of the bell crank to which the pull or turning moment is applied is located well within the body of the clamp and always inwardly with respect to the position of the pivot point of the bell crank.

Other objects, features and. advantages of the present invention are described more in detail hereinafter in connection with an illustrative embodiment of the improved lifting clamp shown in the accompanying drawings forming a part of this application.

In the drawings:

Fig. 1 is an elevational view of a lifting clamp embodying the features of the present invention, partly in section with one of the side plates of the clamp removed, the clamp being illustrated in connection with a vertical lift or pull on a vertically extending steel plate having a thickness of about 2 inches, for example;

Fig. 2 is a view similar to that of Fig. 1 showing a slightly modified body structure for the clamp and illustrating a vertical lift with the clamp, short leg up, gripping a horizontal steel plate having a thickness which may be somewhat less than one fourth inch;

Fig. 3 is an elevational view of the clamp of Figs. 1 and 2, looking from the left in Fig. 2;

Fig. 4 is a broken view similar to that of Fig. l, of a heavy duty lifting clamp constructed in accordance with the features of the present invention and adapted for handling plates of from two to twelve inches thick, and for lifting loads up to tons or more; and

Fig. 5 is a broken view looking from the right in Fig. 4 showing the structure of the lifting shackle.

Referring to Figs. 1, 2, and 3 of the drawings. the improved plate lifting clamp shown therein comprises a clamp body I0 having a short leg or jaw l2 and a long leg or jaw l4, spaced and facing each other to provide a slot 16 for receiving a plate It to be gripped and lifted by the clamp. The short jaw I2 is provided with a serrated gripping pad 26 extending slightly into the slot I6 and facing the longer leg or jaw l4.

The body ID of the clamp includes a pair of spaced

side plates

22 and 24, which are held in spaced relation by

spacing blocks

26, 28, and 3!]- and riveted together by means of rivets 32. The

spacing blocks

26 and 28 may have a thickness equal to the space between the plates or may have a thickness of only half the distance between the plates, the separate halves being integral respectively with the plates "22 and 24, so that they engage each other when the plates are riveted together. The spacer 30 preferably comprises a spacer ring which also serves as a stop for the gripping cam of the clamp, but it may have a larger area than that shown and may be of the same structure as the spacing portions 26 and :28, and also extend to the adjacent margin of the clamp.

The longer jaw 14 includes and houses a gripping cam 34, the lower portion of which is pivoted on a pivot pin 36 located in the lower portion of the jaw H1. The cam 34 includes an enlarged hub portion mounted between the

side plates

22 and 24, while the pin 36 is of the cotter pin type held in the body of the clamp by a cotter pin 38 (Fig. 3).

The leverage mechanism for actuating the serrated cam 34 into and away from gripping engagement with the plate l8 includes a bell crank 40 mounted between the

side plates

22 and 24 in the upper portion of the clamp body and pivoted therein on a pivot pin 42 held in place by a cotter pin 44. The bell crank 40 is arranged with its inside angle facing generally toward the cam 34 and its outer arm 46 is provided with an end portion having the same thickness as the cam 34. this arm being connected to the cam by a pair of connecting links 48, respectively arranged on opposite sides of the arm 46 and gripping cam 34 and being pivoted thereto by

pivot pins

49 and 54, respectively, the edges of which are each peened over into a counterbore to hold them against axial movement as shown in Fig. 3.

The other arm 52 of the bell crank 46 is forked, as indicated in Fig. 3 and is pivoted to the inner end of a connecting-lifting link 54 by means of a pin 56 held in place in the same way as pin 5!]. The lifting-connecting link 54 extends between the sides 5'! and 58 of a forked, twisted type lifting shackl 60 carrying a drop forged lifting ring 62 adapted to receive a hook 64 normally carried by a lifting crane or other lifting apparatus. The lower end of the lifting shackle 66 is pivoted to the lifting link 54 by means of a pin 66 located intermediate the ends of the link 54 and held in place axially in the same manner as

pins

49, 59 and 56. The projecting end 68 of the link 54 extends between the sides 51 and 58 ofthe forked shackle 66 and aids in keeping the lifting linkage in alignment and adds strength to the lifting shackle 64, which, in addition is a forged shackle in which the opposite sides are held together by an integral web 59. The ring 62 is preferably wider at the top than at the bottom, so that it is readily engaged by a heavy hook, such as the hook 64.

Most, if not all, parts of the clamp are of heavy forged steel and the leverage and lifting elements of thee lamp, except the ring 62, are arranged so that they readily fit Within the

side walls

22 and 24, as shown in Fig. 3. For example, the cam 34 has a relatively large hub which fits between the

plates

22 and 24, While the web of the cam is engaged on opposite sides between links 48, which also engage the opposite sides of the bell crank arm 46. The bell crank 40 includes a thick hub section integral with the forked ends of the arm 52 which fit between the

side plates

22 and 24, while the forked end of the lifting shackle 60 also fit between the

side plates

22 and 24, as they span the link 54.

Figs. 1 to 3 illustrate the structure of a clamp, particularly designed for handling up to siX ton loads or steel plates or other articles having a thickness up to 2 inches in thickness. Fig. 1 shows the clamp carrying a one inch steel plate with a vertical lift and it will be seen that the leverage applied by the pull exerts a counterclockwise torque on the bell crank 46 so that the arm applies pressure on the links 48 and cam 34 tending to rotate the cam 34 clockwise, or in a direction to increase its grip on the plate IS. The stop 30 is located at such a position that the cam 34 can never asssume a position where the ivot pin is in line with the

pivot pins

36 and 49. Therefore, the cam 34 will always be actuated toward a gripping position whenever pressure is applied on the connecting links 48.

The arrow on the bell crank 40 indicatesthe application of a counterclockwise torque in the lifting operation, and thearrows on the link 48 and the cam 34 indicate the direction of applied pressure, while the arrows on the link 54 and the ring 62 indicate the direction of pull in applying thecounterclockwise torque to the bell crank 40'. Assuming, for example, that the pull applied by the hook 64 is changed from the vertical position through a 90 angle to the left'in Fig. I, it will be seen that the same torque will be applied to the bell crank 40, and that there would be no possibility of the clamp being released from'the plate [8.

A counterclockwise torque is also applied to the bell crank 40 if it is assumed that the hook 64 and the lifting shackle 60 are swung to the right at'any angle down to the horizontal, because the pivot pin 56 would always be below a line between the pivot pins 44 and 58. Furthermore, as the lifting shackle 6c is pivoted on the pin 66 to a point approaching the horizontal, it will engage the upper end portion 12 of the spacer blocking 28 which, according to the structure in Fig. 1, extends up to about the height of the pivot pin 42 in the body of the clamp, or somewhat above the upper rivet 32'. If' the lifting shackle 60 is swung clockwise on the pivot pin 66, it will reach a point where it comes in contact with the spacer blocking edge i2 and will apply a leverage and a pull on the lifting link 54, so that a counterclockwise torque. on the bell crank 40 is insured.

The clamp shown in Fig. 2 has exactly the same structure as the. clamp shown in Fig. 1, except that the spacer blocking 28' does not include the projecting portion 12 shown in Fig. 1. In, Fig.2, the spacing 28' extends only slightly above the upper rivet 32 and considerably inwardly from the position of the pivot pin 42.

Fig. 2 illustrates the sure grip of'the lifting clamp'under one of the most adverse operating conditions, that is, a condition. in which the shorter jaw. I2 is on topv of a thin plate 14, about one fourth inch, and the pull on the lifting ring 62 is vertical. Even under this condition it will be seen that the extreme thinness of the plate 14, coupled withthe direction of pull on the clamp has not moved the pivot pin 56 into alignment with the pivot pins 42 and 66, and that, therefore, the pull on the clamp as seen in Fig. 2 is applying acounterclockwise torque to the bell crank 48, and consequently a gripping pressure on the cam 34. a

'If the pull in Fig. 2 is swung to the left, it will ,be apparent that the liftingtlinkage will pivot on pin 56 and increasethe torque applied to the bell crank 46. On the other hand, if the pull applied to the, lifting linkage in Fig. 2 is'swung to the right, there may be a slight movement of thel-ink 54 into engagement with the spacing blocking 28' but it will be insufficient to bring the pin 56 into alignment with the pivot pins42 and 66. Further swing of the pull towarclfthe right in Fig.2"will cause pivoting on the pin 66 and an increase in the counterclockv lise'torque applied to the bell crank 49.

Sometimes, after a thin plate has been lifted bya clamp, the operator decides that he wants to turn the plate over and let it down, which would bring the short jaw on top. Other clamps, as explained above, under such operating conditions, have actually been disengaged and the plate allowed to fall. Such mishaps are entirely avoided by the improved construction of the leverage mechanism of the clamp according to the present invention.

The modified form of clamp construction shown in Fig. 4 is particularly designed for heavy duty clamps adapted to take steel plates of from two to twelve inches thick and weighing up to tons. This clamp has essentially the same structure and includes the same leverage mechanism as the clamp shown in Figs. 1 to 3, but includes a modified lifting linkage. Where the elements in Fig. 4 are the same as in Fig. 1, they are referred to by the same numbers plus a prime.

In Fig. 4 the side plates of the clamp body It! each include an integral spacer block element 15 which extends somewhat above the level of the pivot pin 42",the body plates being held together at this point by a rivet 18. The lifting linkage connected to the forked arm 52 of the bell crank 46' includes a lifting-connecting link 86, one end of which is pivoted in the forked end 52' on the pivot pin 56', while the other end is pivoted on a pivot pin 82 in the forked end of a heavy lifting shackle 84 having an opening 86 for receiving the hook of a lifting crane. The lifting shackle as is a very heavy forged element in which the upper portion is provided with an opening wider at the top than at the bottom for receiving the hook of a lifting crane, whereas the lower end of the shackle 84 includes. the forked side section spanning the upper end of the link 80 and pivoted thereto by the pivot pin 82. I

If the lifting clamp shown in Fig. 4 is compared with the structure shown in Fig. 1, it will be apparent that, in a lifting operation, a counterclockwise torque (as seen in Fig. 4) will be applied to the bell crank 4t, regardless of the angle of pull on the lifting shackle 84. If this shackle is swung to the left on the pivot pin 82, it will be seen that a gripping torque-will always be applied by the bell crank 46". The same is true if the'lifting shackle 84- is swung to the right until the connecting link 80 engages the spacer blocking 16, or this blocking is engaged by the lifting shackle 84.

The use of the bell crank in the clamp provides a structure such that the gripping clamp is always urged toward gripping position, regardless From the foregoing, it will be seen that, regardless of the direction of pull on the lifting linkage of the clamp, there will always be a torque applied to the bell crank in a direction such that a gripping pressure will be applied to the cam 34, thereby preventing the release of any plate or object during a lifting operation or during a lowering operation.

of the direction of pull on the lifting linkage. Furthermore, the use of he bell crank in connection withthe. short connecting and lifting link 54 or St! provides acoinpact structure, in which a part of the lifting linkage extends into the body of the clamp and aids in its safe and efiective operation. Furthermore; the links 54 and 8t provide a means for connecting the lifting shackle to the arm of the bell crank so that a straight pull may bejapplied to the lifting shackle.

The bell crank of the lifting clamp shown in the drawings has an internal angle slightly greater than 90, but it may have an angle of 90, the bell crank being preferably arranged as shown so that the arm to which the pull is applied in a lifting operation, where a single lifting linkage is used, extends generally toward or over the receiving slot for theplate to be lifted.

'When the clamp grips a plate having about .7

maximum thickness'for the clamp as in Fig. 1,

the bell crank arm 52 is parallel to the connecting links 48, while in the other extreme, Fig. 2, the arm 52 inclines inwardly in the clamp body from the position of the pivot of the bell crank.

The projecting portion 68 of the link 54 has an important function in addition to those described above. Sometimes the cam member does not readily release from a plate after the plate has been brought to rest. In such case the projection 68 is struck with a hammer, which applies a sharp pull on the connecting links 48 to pull the cam member 34 away from the plate.

What is claimed as new is:

1. In a lifting clamp including a body having spaced opposed depending portions between which the article to be lifted is held, a gripping pad on one of said depending portions facing the other depending portion, and a cam member having an arcuate article-gripping surface pivoted in said other depending portion with its gripping surface facing toward the gripping pad, 8. bell crank pivotally mounted in said body above the cam member with its inside angle facing generally toward the cam member, a connecting link in said body for actuating the cam member toward and away from the gripping pad the ends of which are respectively pivoted by means of pivot pins to the cam member and to the arm of the bell crank extending generally toward the depending portion in which the cam member is pivoted, and a lifting shackle connected to the other arm of the bell crank lever for applying a torque to the bell crank and a gripping pressure of said link and cam member simultaneously with the application of a lifting pull on the clamp.

2. A lifting clamp as claimed in claim 1 in which the bell crank is pivoted in the body above the pivot point of the cam member.

3. A lifting clamp as claimed in claim 1 in which a slot is in the clamp body for receiving the article to be lifted, the arm of the bell crank to which the lifting shackle is connected extending generally toward said slot and downwardly from the pivot point of the bell crank.

4.. In a lifting clamp including a body having spaced opposed depending portions providing a downwardly extending slot when the clamp is in vertical lifting position said slot being adapted for receiving a plate or other article to be lifted, a gripping pad on one of said depending portions facing the other depending portion across said slot, and a cam member having an arcuate article-gripping surface and pivoted in said other depending portion opposite said slot with its gripping surface facing toward the gripping pad, a bell crank pivoted in the upper portion of said body with its inside angle facing generally toward said cam member, a connecting link in said body the ends of which are respectively pivoted to the cam member above the pivot point of the cam member and to the outside arm of the bell crank, and a lifting shackle connected to the other lifting arm of the bell crank lever for applying a pull thereto to effect a turning torque on the bell crank and apply a gripping pressure on the connecting link and cam member, the lifting arm of the bell crank being approximately parallel to the connecting link when the cam member is gripping an article of about maximum thickness for said slot, said lifting arm extending from the pivot point of the bell crank inwardly of said pivot point when the cam member is in gripping contact with an article of approximately minimum thickness with respect to the width of said slot.

5. A lifting clamp as claimed in claim 4. in which the said lifting arm of the bell crank is forked, and a connecting link is pivoted in the forked arm and in the lifting shackle.

6. A lifting clamp as claimed in claim 5, in which the lifting shackle includes a pair of parallel spaced legs forming a forked connection with the connecting link pivoted therein, the pivot point being at the ends of the legs and the link pivoted therebetween including a projecting portion beyond the pivot point engaging between said legs to increase the strength of the lifting linkage of the clamp.

'7. In a lifting clamp including a body having spaced opposed depending portions providing a slot in which the article to be lifted is held, a gripping pad on one or" said depending portions facing the other depending portion across said slot, and a cam member having an arcuate article-gripping surface pivoted in said other depending portion with its gripping surface facing toward and adapted to be moved across said slot toward the gripping pad, a bell crank pivotally mounted in said body with its inside angle facing generally toward the cam member, a connecting link in said body for actuating the cam member toward and away from the gripping pad'the ends of which are respectively pivoted by means of pivot pins to the cam member and to the outwardly-exteding arm of the bell crank, a lifting linkage connected to the inwardly-extending arm of the bell crank lever and including a lifting shackle, said inwardly-extending arm and said lifting shackle having forked ends, and a connecting lift link pivoted to said last-mentioned arm and to said lifting shackle respectively in the forked ends thereof.

3. A lifting clamp as claimed in claim '7 in which the clamp body includes a pair of spaced plates between which the cam member, the connecting link, the bell crank, the lift link and a portion of the lifting shackle are mounted and operate.

9. A lifting clamp as claimed in claim 7 in which said lift link is pivoted at a point intermediate its ends in the lifting shackle, one end portion of said lift link projecting beyond said point substantially intd the lifting shackle and serving to stiffen the lifting linkage with respect to any side pull on the clamp.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,011,660 Strathern Dec. 12, 1911 2,284,006 McLellan May 26, 1942 2,393,101 Gardner Jan. 15, 1946