US3076674A

US3076674A - Tongs

Info

Publication number: US3076674A
Application number: US44329A
Authority: US
Inventors: John R Anderson
Original assignee: Heppenstall Co
Current assignee: Heppenstall Co
Priority date: 1960-07-21
Filing date: 1960-07-21
Publication date: 1963-02-05
Anticipated expiration: 1980-02-05
Also published as: GB935232A; DE1207579B

Description

Feb. 5, 1963 ND Q 3,076,674

TONGS Filed July 21, 1960 '2' Sheets-Sheet 1 INVENTOR.

JOHN E A/vafwo/v Z mww Feb. 5, 1963 J. R. ANDERSON TONGS Filed July 21. 1960 T Sheets-Sheet z INVENTOR.

- A JOHN A? ANOEP'JON T Sheets-Sheet 3 J. R. ANDERSON 'IONGS rim Feb. 5, 1963 Filed July 21, 1960 IN VENTOR.

Feb. 5, 1963 J. R. ANDERSON TONGS Filed July 21. 1960 T Sheets-Sheet 4 Feb. 5, 1963 J. R. ANDERSON TONGS 'T Sheets-Sheet 5 Filed July 21, 1960 a awn INVENTOR. unwed/ 0523% 2% xam/950% Feb. 5, 1963 J. R. ANDERSON TONGS Filed July 21, 1960- F fil '7 Sheets-Sheet 6 Mun/7 w Feb. 5, 1963 J. R. ANDERSON 3,076,674

TONGS Filed July 21. 1960 T Sheets-Sheet 7 07 k 205 INVENTOR JON/V2 ANDERSON United States Patent 3,076,674 TONGS John R. Anderson, Pittsburgl1,,Pa., assignor to Heppenstall Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed July 21, 1960, Ser. No. 44,329 12 Claims. ,(Cl. 294-103) This invention relates to a relatively lower headroom tongs of the lever class in which there is a relatively fast and wide range of initial adjustment of work-engaging shoes and then full gripping pressureupon lifting of the lever means. More particularly, this invention relates to tongs of the single, or double, lever class in which there is one provision for relatively 'quickly moving the tongs shoes into initial engagement with the work to be handled and squeeze gripping thereafter for safe lifting upon raising of the lever or levers.

In the lifting or other handling of work, such as coils of metal, with tongs, it is desirable to have a tongs which will hang from a crane hook or other suspending device in relatively level position, whether the tongs is loaded or unloaded and whether or not the work-engaging shoes thereof are open or closed. Further, such a tongs should have a relatively wide adjustment between the shoes to handle the greatest possible number of sizes of loads likely to be encountered. At the same time, the travel of the respective shoes toward one another moving into initial engagement with work to be handled should be relatively fast, whether such travel is accomplished automatically by proximate vor remote control, or manually, as desired. And, it should be equally convenient to open the shoes as widely as desired and quickly so that the tongs can be set down promptly on the next work object, or on a stand while awaiting the next shop call for such purpose. At all times, the final gripping of the work must be certain and secure so as not to endanger personnel or equipment in the course of any lifting of that work by the tongs. These various objects are accomplished in a way not heretofore possible, by embodiments of the instant invention which, moreover, operate with a relatively lower headnoom requirement.

Other objects, features and advantages of this invention will be apparent from the following description and the accompanying drawings, which are illustrative only, in which:

FIGURE 1 is a side view of one embodiment of this invention in a tongs ofthe single lever class;

FIGURE 2 is a front view of the embodiment shown in FIGURE 1;

FIGURE 3 is a side view partly in section taken along line III-III of FIGURE 2; V 7

FIGURE 4 is a side view partly in section of the em:

bodiment shown in FIGURE 3 in which the shoes have been closed to initially engage the work and full gripping pressure applied to such work for lifting, shifting or other handling of it;

FIGURE 5 is a view taken along line V-V of FIG- URE 4;

FIGURE 6 is a view taken along line VI--VI of FIGURE 3;

FIGURE 7 is a view taken along line VII-VII of FIGURE 4;

FIGURE 8 is a view taken along line VIII--VIII of FIGURE 7;

FIGURE 9 is a side view partly in section of another embodiment of this invention;

FIGURE 10 is a view taken along line X-X of FIG- URE 9;

FIGURE 11 is aside view partly in section of the embodiment shown in FIGURE 9 in which the shoes have been closed to initially engage the work and full gripping pressure applied to such work for lifting, shifting or other handling of it;

FIGURE 12 is a view taken along line XII-XII of FIGURE 11;

FIGURE 13 is a view taken along line XIIIXIII of FIGURE 11;

FIGURE 14 is a side view of another embodiment of this invention in a tongs of the double lever class;

, FIGURE 15 is a side view partly in section of the embodiment shown in FIGURE 14 with the work subjected to initial gripping pressure of the shoes;

FIGURE 16 is a view of the embodiment shown in FIGURE 14 with work engaged and the tongs about to lift such work;

FIGURE 17 is a partial view taken along line XVII--XVII of FIGURE ,16; and

FIGURE 18 is a view taken along line XVIII-XVIII of FIGURE 16.

Referring to FIGURES l to 8, inclusive, of the draw ings, one embodiment 10 of this invention is provided with an inner shoe 11 and an outer shoe 12 between which work, which may be in the form of a coil 13 at a given time, is adapted to be initially and then fully gripped to enable tongs 10 to lift or shift -it as desired, Tongs 10 is of the so-called single lever class and has a rigid frame comprising a flat base plate 14 and laterally spaced upstanding walls 15 afiixed thereto, the base being adapted to rest'upon the top of a coil to be handled with one radial thickness of the coil in the space between

shoes

11 and 12. A bracket 16 is secured to the underside of plate 14 and provided with a succession of transverse registering openings 17 for pins 18 adapted to hold shoe 11 in selected longitudinal position in accordance with the position of its shank 19 extending rearwardly of the shoe, alternate positions being illustrated in FIG- URE l. Pins 18 may be held in place by snap rings or cotterpins. Shoe 11 is preferably provided with a convex face to abut the inside of a coil which the tongs is to handle. Such coils come in different heights due to different widths of strip in the respective coils, and also come in a wide variety of weights and thicknesses measured radially from the innermost wrap to the outermost. In the illustrated embodiments, the coils being handled are coiledunder tension which provides relatively tight wraps. In view of the range of work or coil sizes found in many plants, it is desirable to have a tongs available which will accommodate the greatest number of such sizes, thereby reducing equipment and handling costs.

An outer shoe bracket 20 is provided of generally L-shape in side elevation with transversely spaced side members 21 between the lower ends of which is affixed a shank 22 extending forwardly of outer shoe 12 so that it may be secured to bracket 20 by a bolt and nut assembly 23. The longitudinally extending walls 15am provided over the forward portion thereof with inwardly opposed and somewhat projecting bearing strips 24 affixed to the walls 15. The bearing strips are slidably engaged by guide recesses 25 in the outer sides of the respective members 21, which members are cross connected by bolt and spacer assemblies 26. Shoe 12 preferably has a concave face as shown in plan in FIGURE 5.

A nut 27 is provided with laterally extending mounting bosses 28 which fit into registering openings 29 in sides 21- so that as nut 27 is moved, it will correspondingly move bracket 20 and movable shoe 12, a forwardly extending opening 14a in plate 14-being provided to permit a relatively wide range of movement of such shoe. As shown, nut 27 is of the ball screw type and coopcrates with a ball screw threaded shaft 30. The threading of the shaft and nut may take other complementary forms, such as Acme, square or buttress threads, if desired. Threaded shaft 30 is provided with a smooth cylindrical slide portion 31 at the rear having a splineway 32 therein to cooperate with a shorter key 33, the laterally outwardly projecting portion of which key engages a key-way in a drive sprocket 34. Suitable means such as a thin spacing washer with an inwardly extending finger may be used to cover the ends of the key and hold it between the ends of the sprocket.

A split front collar 35 and a split rear collar 36 are fixed in position at the respective ends of the slide portion 31 and respectively engage

annular bearings

37 and 38 at different stages of an operation of the tongs 10. The

annular bearings

37 and 38 are positioned adjoining spool bearing liners 39' and 40 in a front bearing mount 41 and a rear bearing mount 42, respectively. Driven sprocket 34 is positioned between such bearing liners of the respective mounts, which mounts are secured to frame plate 14.

A reversible electric motor 43 with an integral reducer is fixed to a platform 44 supported by side angles 45 and studs 46 which can be adjusted to select the height of motor 43 and keep a sprocket chain 47 taut. The shaft of the motor 43 is fastened to a torque limiting friction coupling 48 which presses a driving sprocket 49 to drive sprocket 34 by means of chain 47 in either selected direction of rotation depending upon the stage of the operation of tongs 10. The motor 43 may be connected to a portable pushbutton station control connected thereto by suitable cables for operation by a person on the floor of the shop or plant where tongs is installed, and/ or by a control station in the cab of a crane, for example, having a hook 50 from which tongs 10 normally is suspended when it is being used to handle loads. A sheet metal guard 51 may be used to cover the chain reaches.

As sprocket 49 is rotated, it will correspondingly rotate the screw shaft 30. When that rotation is clockwise as viewed from the front of the tongs, the nut 27 will be moved to the left, as viewed in FIGURE 3, toward a clutch member 52 fixed to the front end of shaft 30. Conversely, when shaft 30 is rotated in a counterclockwise direction, the nut 27 will be moved to the right. Generally, bracket will be heavy enough to cause some axial sliding of shaft due to its rotation before there i any longitudinal movement of nut 27. Thus, a rotation of shaft 30 to move nut 27 to the left will normally first cause the shaft to slide to the right until collar abuts bearing 37 before such movement of the nut starts to take place; on the other hand, when the nut 27 is to be moved to the right toward the sprocket, the shaft will usually slide to the left until collar 36 abuts bearing 38 before the nut begins to move.

The front of clutch member 52 is provided in the illustrated embodiment with a clutch engaging surface in the form of teeth 53, or such engagement surface may be in the form of a frictional surface, or may have a castellated or other configuration, which will prevent rotation of shaft 30 when member 52 is longitudinally pressed by an opposing clutch member 54 in the form of a slidable thrust block. The block 54 in the illustrated embodiment is provided with a clutch engaging surface 55 having teeth to dovetail with teeth 53 when the clutch coupling is effected. Block 54 i provided with longitudinally extending lands 56 affixed thereto which slide in opposed grooves 57 along the inner sides of the sides 21. A forwardly extending link 58 on block 54 is pivoted between bifurcated forwardly extending lugs 60 integral with block 54, said lugs having registered holes therethrough for the pivot pin 59 which also extends through an opening at the rear end of link 58. A pivot pin 61 pivotally Lever brackets 65 extend upwardly and forwardly from the frame to which they are afiixed along the outside of the walls 15, spacing collars 66 welded to arms 62 and around fulcrum 63 being utilized to extend laterally between bearing flange 67 on bracket arms 65. Annular stops 68 secured to pivot shaft 63 maintain it in place for rotation of lever 62 thereabout. The laterally outer ends of shaft 63 extend beyond the positioning members 68 to act as a pivotal support for respective eyes 69 fixed to the lower ends of spring rods 70 in a connector counterbalance 71 to each side of the lever 62. Each such counterbalance includes, as more fully illustrated in FIGURES 3 and 4, a spring case 72- having a retainer end 73 with an opening therethrough for spring rod 70. The upper end of each case is fixed to a bent member 74 which has an opening therethrough for pivotal connection to a counterbalance pin 75 extending through the laterally spaced plates in a lifting clevis 76. Clevis 76 is pivotally connected at 77 to the upper outer end of a lever 62 and at 78 is provided with a necked spool sleeve 79 which is engageable by the crane hook 50. A spring 80 in each counterbalance 71 surrounds its respective spring rod 70 and is retained between retainer end 73 and a retainer 81 fixed at the upper end of the spring rod. Each spring exerts a bias urging the clevis plate 76 into the position shown in FIGURE 1 for assistance in keeping the base plate 14 and tongs 10 relatively horizontal.

A rearward extension 82 is provided on the arms of lever 62 to support an automatic alternating cam latching and unlatching mechanism 83 having an inverted T-headed latch bolt 84 to alternately cooperate with a latch keeper 86, having a slot 85, fixed to frame walls 15. The latch mechanism may be made in accordance with the disclosure of US. Patent No. 1,839,389 or 2,776,857 to alternately latch and unlatch as described therein or in my copending application S.N. 55,779 filed September 13, 1960 for Tongs.

In a typical operation, tongs 10 may be latched open with

shoes

11 and 12 open a selected distance apart. Lifting of the crane book 50 by the crane operator will remove the tongs 10 from a previously deposited coil and lever 62 will be in unextended position relative to the frame from which it cannot lift because the latch bolt head is engaging the underside of the keeper as illustrated in FIGURE 3. Moreover, spring 80 will be exerting its influence and shorten the distance between the

pivots

63 and 75 to keep pin 78 in the position illustrated in FIG-

URES

1 and 3 with the center of gravity of the empty tongs generally directly below pin 78 and the cables from which crane book 50 depends. By comparison, when tongs 10 is carrying a load, clevis 76 and counterbalance 72 will move into extended position as illustrated in FIG- URE 4 to shift pin 78 toward a position more directly above the combined center of gravity of the combined tongs and load. Thus, tongs 10 will hang relatively level in both loaded and unloaded condition.

Continuing the operation; if it is now desired to lift another coil 13, whether or not of the same size of the coil previously carried, tongs 10 is deposited thereon with shoe 11 entering the eye of the coil and the parts of the tongs generally in the position illustrated in FIGURES l and 3. Thereupon, motor 43 is energized from the pushbutton station in a reverse direction to close the shoes Generally, the rotation of screw shaft 30 resulting there from will first cause rear collar 36 to shift to the left as viewed in FIGURE 3 and abut its bearing 38, whereupon nut' 27 will move outer shoe 12 toward the coil until both shoes are in engagement with their respectively adjoining wraps with an initial gripping pressure determined by the setting of the torque limiting device 48 in frictional engagement with driving sprocket 49. The slippage of device 48 normally occurring when the predetermined initial gripping pressure due to the force of the motor is exerted is sufficient to maintain such initial gripping pressure and to avoid stalling the motor. During the travel together of the

shoes

11 and 12 into initial fgripping position, irrespectiveof the thickness of the work to-be lifted by the tongs, the

clutch members

52 and 54 remain out of" engagement and the lever 62 remains in its collapsed (unextended) position relative to the base of the tongs, even though the distance between nut 27 and pin 61 has been increased, without, however increasing the distance between'separated

clutch members

52 and 54. Consequently, when lever 62 is next lifted, its unlatching having been completed in the course of crane hook 50 commencing to rise after the initial gripping of the coil by the closed shoes, the safe lifting'gripping pressure that is applied will represent a relatively small upward movement of lever 62 and further movement together ofshoes Hand 12 compared with the possible normal travel of those shoes from open to initial gripping position. Moreover, irrespective of the size of the work to be handled, the distance which lever 62 rises-above the base plate 14 in reaching its extended position while applying the final.

ping position may represent a matter of several inches,

while the final gripping squeeze will be effective upon a further travel together of the shoes by movement through a matter of, say, one and one-quarter inches or less in many cases, upon lifting of lever 62.

When unlatched lever 62 rises, it will exert its final gripping pressure, or grip squeeze, in a manner illus trated in FIGURES 4 and 7, for secure liftingbecause, of the thrust of clutch block 54 against clutch member 52., Such pressing of clutch member 54 is provided by the movement of link 58 to the right as viewed in FIGURE 4 brought about by the counterclockwise swinging of offset 64 about fulcrum 63 whenlever 62 is extended. The

engagement between

clutch members

54 and 52 prevents any rotation of shaft 30 in the illustrated embodiment because of the positive interlocking between the respective sets of

teeth

53 and 54 preferred therein because of the generally frictionless relation between the threads of screw rod 30 and Saginaw nut 27. Such thrusting to the right as illustrated in FIGURE 4 to provide the final gripping pressure movement will normally slide shaft 30 acorresponding distance to the right so that the

collars

35 and 36 will both be out of engagement duringlifting with their

respective bearings

37 and 38. Consequently, the lifting pressure will be exerted through the clutch 5254, nut 27, the frame and shoes and not through the collar 35 and the bearing mounts. v

When coil 13 is deposited by lifting tongs 10, the 'I- head of latch bolt 84 will enter slot 85 and when the barrel 83d of the latch strikes the keeper 86, it will partially rotate the bolt due to its cam action toward the latched position illustrated in FIGURE 3, which is completed after the shoes are opened and crane hook ,50 next rises to remove the empty tongs. Upon'such deposit'of coil 13, motor 43 is again energized to rotate shaft 30 in a shoe opening direction moving collar 35 into abutment with hearing 37 and moving shoe ,12 to the left to separateit "from shoe 'l'l'torelease the grip upon the coil; Such rotation of screw shaft 30 can take place because in setting coil 13 down upon a firm support, the continued lowering of lever 62 disengages the clutch member 54 from member 52 and frees shaft 30 for rotation illustrated tongs 10. Then, whenthe empty latched tongs is carried away to its next job, the setting of the tongs down on the work and lowering hook 50 will cause the latch barrel 83a to strike the keeper 86 and the camming action will rotate the head of the latch bolt toward the dotted position shown in FIGURE 3 in alignment with the slot 85, which unlatching movement will be completed when crane hook next rises to grip squeeze and lift the new work following closure of the shoes thereon to initial gripping position in the manner described above.

In the manual embodiment illustrated in FIGURES 9 to 13, inclusive, parts thereof corresponding generally in construction and functioning to those set forth in the embodiment of FIGURES 1 to 8 have been provided with the same reference numerals respectively with the addition of a prime accent thereto and substantially all of the structure and operation of tongs 10 will be apparent upon reference to the description of such embodiment in FIGURES 1 to 8. In tongs 10', a driven gear member 34' is provided in the form of a worm wheel which is operated by a driving gear worm 100 keyed to a cross shaft 101 journaled in side walls 15. One end of shaft 101 projects through one side 15 for attachment of a hand wheel 102, which can be rotated in either direction to correspondingly rotate screw shaft 30. Shaft 30' as shown is provided with an Acme thread to cooperate with a corresponding female thread on the interior of nut 27. Clutch member 52' at the front of shaft 30 is provided with a conical roughened surface frictional face 53. The other clutch member in the form of thrust block 54' is provided with a conical recess 55 preferably also having a roughened frictional surface to cooperate with surface 53 when thetwo clutch members are pressed into clutching engagement by the lifting of lever 62' to hold shaft 30' against any rotation irrespective of whether anyone should try to turn hand wheel 102 at that time. In general, the manual embodiment 10' would be utilized in smaller quarters, or for a range of work which is smaller and/or lighter than work for which the previously described embodiment might be selected.

-A still further embodiment is illustrated in FIGURES 14 to 18, inclusive, of the drawings showing an embodiment of this invention in a'tongs of the double lever class which might be selected for very large and/ or very heavy coils or other work to be handled by the tongs.

In such still further embodiment, parts corresponding generally in construction and functioning to parts in the embodiment set forth in FIGURES 1 to 8 are provided with the same reference numerals, respectively, with the additionof a double prime acent. In the embodiment of FIGURES 14 to 18, a parallelogram linkage is provided comprising lever 62 and a generally opposed lever 200, the respective ends of such levers being pivotally engaged by

links

202 and 201, respectively. The links are pivotally connected at 203 to each other and to a bail 204 for a crane hook or other supporting device from which tongs 10" depends when in service. The fulcrum 63" of lever 62", however, is swingably connected to brackets 205 integral with the frame by straps 206. A crossbar 207 is also pivotally connected at one end to pivot 63 and at its other end to fulcrum pivot bolt 208 for lever 200. Bar 207 is provided with a rearward extension for latch keeper 86", such bar 207 comprising two parallel members, one on each side of motor 43" mounted on the tongs frame; the lever 200 and

links

201 and 202 likewise also being laterally spaced double members symmetrically positioned to each side of a longitudinal medial plane extending vertically through the axis of screw shafts30". Brackets 209 at the rear end of the tongs frame in alignment with the brackets 205 are provided with pivots 210 for the lower ends of the laterally spaced'arms of lever 200. Lever 62", which could also be made up in the form of laterally spaced memhers, is joined to the laterally spaced members in link 202 by the pivot pin 212 and lever 200 is connected to link 201 by a like pivot pin 211. Latch 83" is affixed to the right-hand end of lever 62", which is bifurcated for that purpose, substantially in the location illustrated in US. Patent No. 2,536,932 to cooperate with keeper 86" in the manner hereinbefore described. The levers further may be respectively cross connected by straps, in lieu of using bar 207 if desired, to provide positive vertical extension and contraction of both sides of the lever and link parallelogram action, in which event keeper 86" would be affixed in cooperating position to a support extending rearwardly from offset portion 213 of lever 200 to maintain keeper 86 substantially in the position shown.

The action of the mechanism for opening the shoes in tongs It)" and for closing the shoes to initial gripping position by means of motor 43", and of the latch 83", is as previously described. Such mechanism is shown in FlGURE in initial gripping position with rear collar 36 being provided in the form of a thrust bearing held in position on the rear end of shaft 30 by a nut 214. A similar thrust bearing comprises front collar 35 held in place by an annular stop 215. The raceways on the bearing mount side of the respective collars are rotatable so that no annular bearings have to be provided on the outward faces of the respective bearing mounts 41 and 42". The threading on shaft 30" and in nut 27" may be a conventional friction threading. The rear of nut 27 is provided with an annular flange 216 which is bolted fast to a cross yoke 217 extending between the rear ends of shoe bracket sides 21" to which said yoke is afiixed. The yoke 217 is provided with an opening through which shaft 36" extends. Clutch member 52" fixed to the shaft 39" is in the form of a conical frustum and preferably is made of a friction material to cooperate with the complementary recess surface 55" of thrust block 54". The forwardly extending laterally spaced lugs 60" of block 54" are directly connected to lever 62" by pivot pin 61" in view of the movability of fulcrum 63" due to strap 206. Thus, as bail 204 begins to rise, with the levers and links unlatched as illustrated in FIGURE 16, head pin 263 will increase its distance from base plate 14" extending the levers 62" and 200 and

links

201 and 202 to provide a final grip squeeze upon coil 13" for secure lifting thereof.

Terms used herein for orientation such as front, rear, side and movement directions are to be deemed used in a relative sense. Further, the illustrated embodiments may be utilized to pick up work of other shapes and sizes, or to pick up two coils in side-by-side relation with the respective shoes each engaging the innermost wrap in the eye of one of the respective coils. Still further, the automatic latch and keeper means illustrated may be replaced with other holding 9r latching means, whether automatic, semi-automatic, or manual, as desired, whenever there is to be provision in a tongs of this invention for keeping the lifting lever means in collapsed condition between lifting assignments.

Various modifications may be made in details of the illustrated embodiments and other embodiments provided without departing from the spirit of my invention or the scope of the appended claims.

I claim:

1.- A tongs comprising, in combination, a longitudinally extending frame, work gripping shoes in opposed relation operatively connected to said frame, at least one of said shoes being mounted on a slidable bracket operatively connected to said frame and movable in a straight line longitudinal direction toward and away from engagement with the other shoe to grip or release work, a substantially non-rotatable threaded nut operatively connected to said bracket to move it in accordance with movements of said nut in said direction, a threaded shaft extending through said nut and having a slidable portion rearwardly of said nut operatively connected to said frame, a clutch member operatively connected to said shaft forwardly of said nut, said shaft being movable to a limited extent rearwardly upon pressure being exerted against said clutch member to press it toward the rear, reversible means operatively connected to said frame for selectively rotating said shaft, a second clutch member operatively connected to said frame in opposed relation to said first-named clutch member and movable in said direction into and out of engagement with said first-named clutch member, and lever means to press said secondnamed clutch member into engagement with said firstnamed clutch member as said lever means lifts to move said shoes toward one another to grip said work with a sufficient squeezing pressure to enable it to be lifted.

2. A tongs as set forth in claim 1 in which said frame has a relatively horizontal base, said shoes extend below said base and there is a latch mechanism to latch and unlatch said lever means alternately and automatically.

3. A tongs as set forth in claim 1 in which said nut and shaft are provided with complementary relatively frictionless ball screw threads and said respective clutch members are provided with surface portions which provide a positive interlock with each other when said clutch members are in engagement. I

4. A tongs as set forth in claim 1 having a reversible electric motor mounted on said tongs and operatively connected to said shaft and a torque limiter interposed between said motor and shaft ineffective to turn said shaft when said clutch members are engaged irrespective of whether or not said motor is energized.

5. A tongs as set forth in claim 1 in which said lever means are either of the single or double lever class and there are latch means for said lever means to hold the latter in collapsed condition at predetermined times.

6. A tongs comprising, in operatively connected combination, a longitudinally extending frame, work gripping shoes in opposed relation operatively connected to said frame, slidable means mounting at least one of said shoes for movement in a straight line longitudinal direction toward and away from engagement with the other shoe to grip or release work, a substantially non-rotatable member operatively connected to said slidable shoe to move it in accordance with movement of said member either way in said direction, an engagement member positioned in opposed relation to said first-named member, opposed clutch means operatively and respectively connected to said members, said engagement member being movable along said straight line to cause engagement of said clutch means and fix the distance between said members, lever means operatively connected to said second-named member to move said clutch means into engagement as said lever means lifts to move said shoes relatively toward one another to grip said work with a sufiicient squeezing pressure to enable it to be lifted, and drive means for said first-named member movable along said straight line to a limited extent and adapted to be rendered inoperative upon said engagement of said clutch means.

7. A tongs as set forth in claim 6 in which said respective members are a nut and thrust block and said drive means includes a shaft provided with complementary threads and said clutch means are provided with surface portions respectively which at least frictionally interlock with each other when said clutch means are in engagement.

8. A tongs comprising, in operatively connected combination, a longitudinally extending frame, work gripping shoes in opposed relation, one of which is fixed to said frame, a bracket carrying the other shoe and movable longitudinally in said frame, a non-rotatable nut operatively connected to said bracket, a screw shaft extending through said nut and adapted to be rotated to move said nut and cause said other shoe to move relatively to said first-named shoe to initially grip work or to open a first clutch member fixed to the front of said shaft forwardly of said nut, said shaft being mounted on said frame and longitudinally movable a limited amount between respective end positions, reversible means for rotating said shaft in a selected direction, a second clutch member longitudinally movable along said bracket into and out of engagement with said first clutch member, and a lifting lever operatively connected to said second clutch member to urge it into engagement with said first clutch member tohold said shaft against rotation and move it intermediate said end positions to apply final gripping pressure to work engaged by said shoes when said lever is lifted from its substantially lowest position relative to said frame.

9. A tongs as set forth in claim 8 in which said lever is of the single class and there is a latch to latch or unlatch said lever in or from collapsed position.

10 A lever class tongs comprising, in operatively connected combination, a frame, at least one lifting lever connected to said frame, Work grips mounted on said frame in opposed relatively movable relation, a member operatively connected to said grips, rotatable means adapted to coast with said member to move said grips relatively to one another to cause them to open and to close and engage work with an initial gripping ressnre, drive means to rotate said rotatable means to move said member for said coaction, and means adapted to be moved by raising said lever relative to said frame to hold said rotatable means against rotation and shift it axially to cause said grips when in initial gripping pressure position to engage said work with a further gripping pressure, said drive means being inoperative to rotate said rotatable means when said lever is in said raised position relative to said frame.

11. A tongs as set forth in claim 10 comprising a latch mechanism adapted to latch and unlatch said lever when it is in lowered position relative to said frame.

12. A lever class tongs comprising, in operatively connected combination, work gripping members in opposed relation with said members movable relative to one another, a not connected to one of said members, a threaded shaft cooperating with said nut, lifting lever means, opposed engageable clutch parts respectively fixed to said shaft and said lever means, said shaft also being axially movable to a limited extent, reversible means for rotating said shaft to open said members or to close said members by movement relative to one another when said lever means are in lowered position, and means to operatively engage said clutch parts when said lever means are raised to prevent rotation of and move said shaft axially to cause work to be lifted by said members.

References ited in the file of this patent UNITED STATES PATENTS 2,803,489 Zito Aug. 20, 1957 2,830,842 Heppenstall et al Apr. 15, 1958 2,925,300 Kelley Feb. 16, 1960 2,945,609 Benes et a1. July 19, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 3,076 674 February 5, 1963 John R, Anderson It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4 line 19, after "of", strike out "a"; line 64 after "shoes", insert a period; column 5, line 70, after "rotation" insert by motor 43, completing a cycle of operatrons of the column 8,, line 70 after "open" insert a comma; column 9, line l8 for "and" read or -o Signed and sealed this 27th day of August 1963,

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer I Commissioner of Patents

Claims

10. A LEVER CLASS TONGS COMPRISING, IN OPERATIVELY CONNECTED COMBINATION, A FRAME, AT LEAST ONE LIFTING LEVER CONNECTED TO SAID FRAME, WORK GRIPS MOUNTED ON SAID FRAME IN OPPOSED RELATIVELY MOVABLE RELATION, A MEMBER OPERATIVELY CONNECTED TO SAID GRIPS, ROTATABLE MEANS ADAPTED TO COACT WITH SAID MEMBER TO MOVE SAID GRIPS RELATIVELY TO ONE ANOTHER TO CAUSE THEM TO OPEN AND TO CLOSE AND ENGAGE WORK WITH AN INITIAL GRIPPING PRESSURE, DRIVE MEANS TO ROTATE SAID ROTATABLE MEANS TO MOVE SAID MEMBER FOR SAID COACTION, AND MEANS ADAPTED TO BE MOVED BY RAISING SAID LEVER RELATIVE TO SAID FRAME TO HOLD SAID ROTATABLE MEANS AGAINST ROTATION AND SHIFT IT AXIALLY TO CAUSE SAID GRIPS WHEN IN INITIAL GRIPPING PRESSURE POSITION TO ENGAGE SAID WORK WITH A FURTHER GRIPPING PRESSURE, SAID DRIVE MEANS BEING INOPERATIVE TO ROTATE SAID ROTATABLE MEANS WHEN SAID LEVER IS IN SAID RAISED POSITION RELATIVE TO SAID FRAME.