US2385835A - Lever construction - Google Patents

Description

E. C. NEAL LEVER CONSTRUCTION Oct. 2, 1945.

4 Sheetshee; 1

. Filed Jan. 31, 1944 1720675 (fr/Z65 G JQZ Oct. 2 1 945. V E. c. NEAL 7 2,385,835

LEVER CONSTRUCTION 'Filed Jan. 31, 1944 4. Sheets-Sheet 2 Ogt. 2, 1945 I E. c. NEAL 7 2,385,835

LEVER CONSTRUCTION Filed Jan. 31; 1944 4 Sheets-Sheet" :s

'avzeszak/zd,

Oct. 2, 1945. E. c. NEAL LEVER CONSTRUCTION Filed Jan. 31 1944 4 Sheets-Sheet 4 Patented Oct. 2, 1945 LEVER. CONSTRUCTIQN Ernest 0. Neal, Chicago, 111 assignor oi one:

" 9 5M?! B l llii i 1" Application 31, 1944 SerialNoi 5:0;{00

This invention relates in general to a lever, and more particularly. to a compound lever providing tor the movement of a le'v'er'aboutr a fill;- crum'by the application of force to a portion of the lever through the medium of an auxiliary lever member and associated means havinfmoving contact witha surface ofthe lever member.

An object of this invention is to provide compact, safe, simple and emcient means providing for relative movement'ol a lever about a fulcrum by: the mechanical application of force to a portion of the lever through the medium of an aiix'iliary lever and cooperating means on the said partion of the lever and the auxiliary lever.

A further object of the invention isto provide a compound lever construction in'which relative movement of a lever about'a fulcrum is accomnlished by the mechanical application of force to a portion of the level through the medium of roller means having rolling contact with that portion of the lever, first in one direction and'then in an opposite direction, in a predetermined ratio and with a minimum of frictional loss;

Another object of the invention is to provide a lever construction including a plurality" of lever members arranged for relative pivotal movement wherein force is applied to one of the members through the medium of an auxiliary lever member' pivotally mounted on one of the'firs't mentioned members in adjustable angular 'spac'edr'ela' tion with the other of'said members andhav'in'g roller means arranged thereon "for r'bznng'en: gagement with an adjacent surface of the" said other member so that open the application'pf force to the said auxiliary lever memberin a predetermined direction the roller means will have rolling contact with the said surface, first in one direction and men in an opposite directionfto cause predetermined relative movement lit the i said first mentionedme'mbers.

'A further object of the invention is to provide a lever construction in which a holding'm'einber and a, lever' member are arranged for relative pivotal movement in parallel planes and including spring means interconnecting'the members and arranged to operate'normallv'to ii'rg'e' the lever member in a predetermined direction in relation to the holding member, an auxiliary member pivotally mounted ori tl'ie homing member in'ad justable angular s'paced'relation with the lever'member, and roller means arranged on the auxiliary levermeniberafor rolling-engagement with an adjacent siirface of'tli'lever' memberfthe arrangement beih'Q'such that upon the application of force in 'con'verging directions to corresponding portions of the holding member and the aizxiliaiy lever member, that force'will be translated by rolling contacfbett'veen the roller means and the lever member. first in one directiomand then in an opposite direction to the lever member to cause relative movement'of the lever member and the holding member.

Qther ob'jects oi. the inventioii'incliide the application of the stated principle of operation of the novellever construction to specific devices including a rod or cable"cutter, sheet metal shears; and a ratchetf "the provision of novel means for maintaining parts of such devices in spaced relation; the provision of novel safety means in such devices; and tbe'provision of novel cutting means, and means for mounting; demounting, and securing said cutting means 'in position on certain of such'devices. It willbe understood, of course; that the principle of'the invention is not limited in its application'to such devices but is applicable to mimerous otheridevices- Additional obiects,'advantages and capabi i es nherent in this invention will become readily apparent from the description thereof which QHOW This invention Iurther resides in the combination, construction and arraneement'ofparts illustrated in the accompanying drawings; and while there is shown therein preferred embodiments of the inventiomit is to be understood at the o e are susceptible of modification and change without departing'from the spirit or the invention.

The accompanying drawings illustrate a sevieiys therein are as follows: l is a a me i e q e .dsyice m d n e meme a iall in e tion w h t e a is n n t a erat n o ee-"Q 29 i: tign; v V

is e li9nal grnerv e i i v s e qce v al n t ine -3... o Fi fi; f-

t :1 a s tio al view a ong th li e 5 5-9 me 1, v.

is ity si e isw 9f he we lected embodiment of the invention, and the is t a o e ie? H shoyvnin"Flgflfbal ftiallv section lobkin'in the opposite' direction', vvith arrays indicating Y the action-of' the' spring v29.

. 51- which bears a of. the ears 32,-

direction of movement of the roller means immediately preceding;

Fig. 7 is a fragmentary side view of another form of device embodying the invention;

Fig. 8 is a detail view, partially in section, of a part of the device shown in Fig. '7;

Fig. 9 is a sectional view along the line 9@ r of 'Fig. '7;

in section v the invention;

. ra mema a-V Pa t lr nether: form of jzdeviceiejmbodying Fig. 11 is a detail view of parts of a device-r. 7 shown in Fig. 10, but in modified form; and

Fig. 12 is a fragmentary view of anothe'r for r'n of device to which the invention may be pplied. The particular form of devicehe'rei roses for the purpose of illustrating the invent 11 comprises an elongated lever member-"I having a handle or gripping portion l6 and a portionll,

of increased width, and a relatively shorter lever" member [8 having a portion [901? increased width and a curved neck Zllwith an elongated bearing surface 2|; :The members l5aand' l8 arearranged in. juxtaposition; as shown in Fig. 2;. andhave corresponding, adjacent flat surfaces 22- and 23. Themembers-l51and-l8 are interconnected by meansof a screw 24 received in corresponding openings'55 in the memberslfii and I8 and'form- 'ing a common p'ivot havingyan axis normal to the. surfaces ZZ -and 23 .at a point'disposed in spaced relation.- with theiri corresponding end portions. ".The'screw .2 4'sis-secured in. position by means of the nuts 25.:. Ascollar. or washerllfi The screw 31 is adiustablysecured in position by means of a nut 40, which bears upon an adjacent surface of one of theears 39, and has an axis disposed in spaced relation with respect to e the axis of the fulcrum connection screw 34. The

member 3| is provided with a handle or gripping portion 54 corresponding with the portion l6 of .the member l5. 7 Thaarrangement and configuratior of the desf rib i a t Ji 1 hat .ili mall .h .fi p of the roller 35 will contact and ride upon the rally willloein the position indicated in Figs. 2 and 5.01; the'drawings, and upon the application of force to the handle or gripping portion 2f 54 of the member iil, the member I5 being maintained. in position to cause that portion of the member'tl to move pivotally about the axis of the: screw 31 in. a direction towardthe handle .or-grippingrportion l6 of the member '15, the periphery of 'the, i roller :36 will have rolling: contact with the.- surface' 2 I-:of the 'member f8 first in one direction;;.as indicated by' the arrows :in Fig. -5, and then, in the opposite: direction; as indicated by the arrows; in Fig. -6,-to :causepivotal may also 'be provided 'on the screw 24 in'termediate the nuts 25 and the adjacent surfaces' of thelever member. The members :15 and 18 are freely *pivotable inparallel relation .about the axis Qf'thescrew'fl'. w 1

The members '15 and l8havecorresponding generally 'arcuate cut-away'portions 2 6 in".the

ssurfacesZZ and 23 and are provided with stops 2! arranged in opposite ends of those cut-away portions (in the p'osition shown in Fig. 5) and in'the forin'bf pins havingenlarged heads and receivedin openings 28, which are'provided inthe'memb'ers inangular spaced relation with-the axis of the screw 24. The 'cut'-away-'portions 25 are arrangedtore'ceive a spring or tension mem- 'ber 29. which is positioned inter-mediatethe stops '21: and acts normally to-urge the-neck portion 20 ofthe'member l 8 :in the direction" of the arrow in Fig.1. A' stop3fl' is provided on "the member 7 l5 to engage a co-operatingportion of thememher I 8 for limiting" its movement in response to An, auxiliary l ver member s i's 'pivotally movement of the member [8- about the axis ofithe screw 24' until the parts take the; position-shown in-Fig. 6. :It will be.=noted.that the-neck portion .20 of the member 18 extends on theside'of the .fulcrum pivotfl l remote fromithe, common pivot 24,that is to say; the surfac 2 l'. is spaced from the common pivot ;Z4*--a-; distance greater than-the spacement of the, common and 'fulcrum pivots Ziland 134.1 During the initialxportionsgof the power-stroke. the :roller 36 .will rollalong-the sursfacell in a direction outwardly, of the common pivot. until :thelever- 54 reaches a position in which the axes, of .the 'pivot pins, 34 and 31 V .arednalignment; During'the latter portions of mounted adjacent one'e nd thereof on the memspaced cars '32 "at one end thereof and having justably secured in :positionl by ;means of a nut upon an adjacent. surface of one The auxiliarylever mmber-thcarriesga :roller which is ;.rotatably mounted-on alscrewj'l- -treceived in coaxial;openingsE-38 in the spaced ears 1.39 provided on: the; -memberg:3lzvfor rotation'fil the plane of piv qmal movement/ofv the member-.118;

the power stroke, I after. the handle passes the aligned pivot-pin position, ;the, member, 36 .will roll on thesurface 2| in a-.r.everse direction inwardly toward-the common pivot--24: Theconstruction ande-arrangementof the leverage thus provides for maximum power multiplication dur: ing medial portions of the. power stroke andpro- .vides a most effective,powermultiplying=mecha-i nism', especially-well;adapt ed for use in cutters,

clippers; shears and the-like. Upon withdrawal of the -applied-force,;the spring 29, which is-compressed asshown in Fig. 6,; will act to return the parts tov the position shown in Fig. i 5:

The relative-dimensions; and arrangement of t parts ofthe lever construction thus described will; .of: course; depend onithe :particular purpose .for .whicndt is employed andthe. requisite deliv- .ery of power sand. will be varied according to well known, principles oftmechanics to meet particular needs, :Asshown; provision is madefor pivotal movement of. 1 the auxiliary levermember 31 through an. angle .of approximately degrees,

during whichrmovement-the -roller 36 contacts the surface v2i--toicause pivotal movement of the lever l8 through. an: angle :of approximately {'35 degreesw In'this' connection, the screw 31' serves as a- ;.stop whichengages the portion. .I Be of lthe member R5 to limit movement ofithe inember-3l -;;In Figs; 1. to fiinclusiye' the-invention'is ap- ,pliedtoa cuttingjdevice suitable for; cutting irods,

.cables' andithe like:

.means is provided on'th'e members l5 andl'8-:in

For; this purpose; cutting angular spaced relation withfthe axis: of the screw [-2 4'. 'Such'means ;may be) formed integrally bearing surface 2| of the lever member l8 during the operative movement of the lever 54 at the commencement of a power stroke, the parts genwith those members byv providing-cooperating cutting edges on suitable portions of the members. In'such an arrangementzthere is afdisadvantage of impaired usefulnessof the device due to thecutting edges becoming dulledor broken from'use, necessitating sharpemng, and ultimate- 1y rendering the device. useless. To obviate this diflicultygit is desirable'to provide removable cutting means in such a device. "As shown in c'eiving an article tobe cut. A plate: (having a cutting edge 43 is secured on the'member' l5, as by means of screws 44, and preferably inset in a recessed portion 4! of themember IS with its cutting edge adjacent'one edge ofthe cutaway portion 4|, as shown in Figs. 1 and'5. 'The'memher 8 is provided with a corresponding cutting edge. For this purpose a plate 46 having aacutting edge 41 is secured on the member ll, as by means of screws 44, and preferablyinsetzin arecessed portion 48' of that member with the cutting edge 41 arranged adjacent'the edge 49 of an extended portion 500i the member it. 'By manipulation of the screw--24,-=relative pivotal movement of-the members and I8 and-the corresponding cutting edges 43 and 41 may be adjusted to enable the desired cutting'action upon operation of the lever mechanism which has been described. i The corresponding end portions of themembers l5 and i8 adjacent the cutting means are preferably co-extensive and, as shown, have outer edges which are generally arcua-te in relation to the axis of the screw 24.'-="In order to maintain the adjacent surfaces 22 and 23 in generallypredetermined spaced relation, a guard 5| is provvided, as shown in Figs. 1, 2'3, 5 and 6. This guard-is similarly arcuate. in one direction and has depending side portions 52 extending adjacent opposite surfaces of the. members .l5. and I8, as shown inFig. 3. The guard is secured in position on the member 18- by means of'screws 53 and is relatively movable in'relation to -the member i5 between the 'positions showniii Figs.

'5 and 6. Theguard 5i acts not onlyto limitangular displacement of the members l5 and IS in the direction of the'axis- Ofthe screw 24 but to protect the'operator of. the device frominjury by flying fragments of articles scveredby the cuttingmeans. m 1

- In a modification of theinvention shown in Figs. 7, 8 and 9, shearing mcmbersioand 61 are interconnected by means of ascrew -i2,which is received in corresponding openings 63 in the members andadjustably'secured in position-by means of a nut 64 thereon; for relative pivotal movement aboutxthei axis of the screwand in parallel planes. The member. Ni hes-a portion '55 of increased width andra handle or gripping portion 66. The member 605 also is provided with an angular opening 61 for receiving :an. article to be cut and an adjacent shearing. edgeitdisposed *in angular spaced relation with the. axis of the opening 63 therein and the: screw 62; A guard 58, generally'similar in. arrangement to the guard 5!, is provided; on themember imbeingsecure'd theretoby screws. The member" BI, which is: relatively shorter than the member Dumasa corresponding shearing edge 1 fisiarranged co-operative .=shearing relation with the shearing edge and intangu'lar spaced relationlwith the axisof'thecpening 63 in the member 6| and-the screw 62; The member (it has. a. curved end portion 6! generally-op.- recite its shearing edge. and a rectilinear end; surface in arrangedin angular spaced relation with the said axis.

A. lever arm H, which has a handle or grippingportion 84 correspon in with the handle or gripping portion 66 of the member 68 is pivotally mounted; adjacent itsend remote from the-portion on the member 60 and for this purpose'is provided with spaced cars 12 at one end thereof and, having coaxial openings 13 therein for receiving screw 14 which is also received in a corresponding opening 1.5 in the member 60. The'serew :14 and the openings [3 and I5. have an axis disposed in angular spacedrelation with the axis of the screw 62 and the openings 63 and'is adjustably secured in position by means of a nut 16. i r

The arm H carries a roller 11 which is. rotatablymounted for rotation in the plane of pivotal movement of the member 6! on a screw 18: received in coaxial openings l! in the spaced cars provided on thearm. The screw N is adjustably secured in position .by means'of .-a nut which bears upon an adjacent surface of one of the-ears 80.. The common'axis of the. openings "l9 the screw i8 is disposed in angular spaced relation with-the axis of the screw -14 and the openings 13 and l5.

,.Spring means similar to that described in inclusive, is provided inv the device of Figs.- 7, 8

and 9 and arranged tooperateinrlike manner in the corresponding cut-away portions-82 in the -m8mbE1S'.50 and 6| in association'with the stops 83, whichccrrespond with the stops 21.

In other respects, the structure and arrangement of parts of the device generally -are similar to that shown in Figs. 1 to 6, inclusive.

As in the case of the device shown in Figs. 1 to 6, inclusive, the parts of the device shown in Figs. 7, 8 and 9 are so arranged and conformed that normally the periphery of the'roller fllxwill contact the adjacent surface I0 ofthe member '61 and the'parts will be in the position indicated in Fig. 7, and upon the application of force to the handle or gripping portion of the member H, the member .60 being maintained in position, to cause that portion of the member "H ;to move pivotally about the'axisof the screw 14 ina direction toward the handle or gripping portion 66 of the member 60, the periphery of the roller 11 will have rolling contact with the surface 10 0f the member 6 I, first in one directionand then in an oppositedirection, in the mannerdescribed in the caseofthe roller 36 and the surface 2 I, to cause pivotal movement of themember Slabout the axis of the screw 62 and resulting shearing movement of the shearing edge 69 in relationto theshearingedge 68. a Y i In Figs. 10 and 11, there is illustrated an. application. of the invention to a ratchet d evice. Such a device may'include a support on which a ratchet wheel 9| is rotatably mounted. *Agenerally upstanding lever-member 92 .is vmounted adjacent its lower end on the support 90 for relative pivotal movement in a vertical plane. The membersz carries a pawl 93 which is pivotally mounted adjacent one end thereof on; spin received in an opening 95 provided in the member 92, its opposite endbeingarranged. for en.- gagement with-the. ratchet wheel so as to cause rotation of; the. wheel upon pivotal movement. of

the mem er 92 in a v n. irectiqnposition shown therein.

" generally -curved. lever member 96- is mounted adjacent one end thereof on'the support -90 for relativepivotalinovementin a plane parallel to the plane of pivotal movement of the member 92 and is providedwithan opposite rectilinear end portion 91 disposed in angular spaced relationwith the pivotal axis of the member. "The member' SE is arranged so" that the curved surface 98fthe'reof will engage" the periphery'of a roller 99 mounted onthe member 92 adjacent it's'uppermost end for rotation about 'an axis disposed inparallel; angular spaced relation with'the pivotal axis of the pawl 93;

-' 'A'naux'iliary lever member I ismountedadjacent one end thereof on the support St for piv- -'otal movement about anaxis disposed in parallel,

angular spaced relation 'withthe pivotal axis of th'e'member 96. Themember-IUO carries'a I 'roller 'HH mounted for rotation about an*axis disposed in parallel angular spaced relation with 'the'pivotal axis of the member VI 00 and' arranged to have-rolling contact with the surface 'of "the end portion 91 of the member-96. f A'spring'or1tens'onmember I02 is anchored at its opposite endsjlltothe support 90 and the member 92 so asnormally to" urge-the free end pf the member 92 a predetermined'direction, as shown in' Fig; 10, t0 't he"left "viewing of the drawinga and thus to maintain the=parts in the Thei' 'arrangement and conformation" of the or parts is s'uch tha'tupon the application orf rce 'to the rneinber" I 0B in' a-given direction, to the left vie'wi'ng Fig.l0; the roller Ml will have rolling fcohtadt w ith the surfacefi'l first'to the left and then to the' lright, 'ca'using themember 96 to move pivotally i'n ananti-clockwisedirection and the said bearingqmember' on thecother sideofisaid -plane.-;.i 1

Z =2: A device of the character described compris ing a pair of members pivotally connected forrel- V .atively turning movement about a common pivot, a power levernhaving'an endvconnectedion one of said members forwrelative turning I movement thereon about a fulcrum-connection spaced from said. common pivot, the other of saidmembers having a cam comprising an elongated surface extending adjacent said fulcrum connection and on the-fside thereof remote from said common pivot; a; cam; driving roller on: said 3 power; lever "andwspa'ced from said fulcrum; connection in positionto bear upon said cam to relatively turn said memb'erszin' the performance of a power stroke; said zlcam "being movable by said driving roller, during a'power strokafrom a position "engaging said rollerwith itsaxis on one side-V of "the 'planeincluding the axis" of said fulcrum connectionand the axis of saidcommon pivotg'to a position'engagiiig said roller with itsiaxison theoothefiside of said plane-.2

A deviceof the'character described com- "prising a pair of members pivotally connected for relative turning movementabout a common pivot .and'having cooperating portions forming cutting V "jaws, "a power lever having an end'connectedon surface 98'to press'and' ride "upon the roller 99,

therebyproducing pivotalmovementof the member 92- about its axis against the actionof the;

spring I02 andresult'ant movement of the ratchet wheel 9| inaclockwise direction through the operation'of 'the pawlsax 11 Fig. 12 illustrates an additional kind-of device Ito which the invention niav be applied, namely,

snips 'I It in which opposed cutting members I I i "are brought together generallyin one plane to cut'a"wire or small 'rodym. Changes may be made in the form,"construc1- tion' and arrangement of the parts without' departing from 'th'e'spirit' of the invention; and the right is hereby reserved to make all such-"changes as-rainy fall within the scope of therfollowing claims A The invention is hereby claimed "as follows j *1;.fA deviceof the character described comprising'a pair of members pivotally connected for relatively turning movement about a'common pivot,

"a p'o'wer lever having anend connected on one of said imembe'rsfor relativefturning movement thereon about a fulcrumconnectionspaced from povvermultiplying means for relatively turning said members" in" theijpe'rformance of a power stroke, saidbearing surfa'ce being'movable'; dur ing a power stroke; from a position engaging said 'ingi'the' axis of said'fulcrum connectionand'the axis of said coinmon' pivot, to'a'position engaging bearing member onbne side of the plane includ-.

onepfsaid 'membe'rs for relatively turning move-r imentthereonfabout a fulcrum connection spaced from said common pivot, the other of said members having an elongated bearing surface extending" adjacent said fulcrum connection and oil-the side thereof: remote? from said common' pivot, and abearing member :on said power lever and spaced from said fulcrum connection-in position to bear upon said bearing surface whereby to' iprovide' pow'er multiplying means "for rela Z tively'turning said members in' the performance .-said-""common pivot, the other cr am members 7 upon said bearing; surface whereby to provide of a power" stroke; said bearing surface being movable; during a power stroke; from a position engaging-said ibearing member on one sideof the plane including the" axis 'of isaid fulcrum 'connection: and the axis of said common pivot, to a position engaging said bearing member-on; the other side of said plane; saidicutting jaws being many open position'iwhen said bearing member is spaced-from said plane on one side'thereof and completelyclosed when-the bearing member reaches "a position on the other side of Jsaid'plane.

4. A device of the cha'ractcr described compris- 7 'ing a pair of members pivotally connected for rell ative turning movement about a common: pivot and having cooperating portions formin cutting jaws; a power lever having an end'connected 'on one of saidmembers"for2relatively1turning move- 7 'mentthereon about a fulcrum connection spaced fromsaid common 'pivoh' the other oftsaid mem bers 'having an 'elongated I bearing surface extending adjacent 'said' fulcrum connection and 'on the side thereofremoteffrom said common pivot; and a bearing-member on saidpower lever l and spaced from 'said fulc'rum' connection inpos'ition to bearlupon'said bearing surface whereby provide: power multiplying means for relatively" turning said members in :the performance of a' power stroke, said bearing surface-being mov- 'able,"during a power stroke; from. a position;en-

gaging said bearingimember onao'ne side: of the plane including .theaxis -or said fulcrum con- "nection and 'the' axisof said common pivot, to 1 a position -engagingsaidbearing member on-the Io'ther "side 'of' 'said' plane, cutting jaws :being in '-f-'1i1ly: open positionlwhen said' bearing' member is space'df fromsaid'=planezon one vside thereon-said jaws being completels closed: when the bearing member reaches a position on the other side. of said plane and spaced. further. therefrom than when in jaw-open position; said bearing member passing through said plane im constant-engage.- ment with the bearing surface, during the jaw closing strok'eL- 5. A device of the character described comprising apair of members pivotally connected for relatively turning movement about a common pivot, a power lever having an end connected on one of said members for relative turning movement thereon about a fulcrum connection spaced from said common pivot, the other of said members having an elongated bearing surface extending adjacent said fulcrum connection and on the side thereof remote from said common pivot, and a bearing member comprising a roller on the power lever and spaced from said fulcrum connection in position to make rolling contact with said bearing surface, said bearing surface being movable by said roller during a power stroke, from a position engaged by said roller with its axis on one side of the plane including the axis of said fulcrum connection and the axis of said common pivot, to a position engaged by said roller with its axis on the other side of said plane, said roller being adapted to travel said bearing surface in a direction away from said common pivot when the axis of said roller is moving toward said plane on either side thereof, and viceversa.

6. A device of the character described comprising a pair of members pivotally connected for relatively turning movement about a common pivot, a power lever having an end connected on one of said members for relative turning movement thereon about a fulcrum connection spaced from said common pivot, the other of said members having an elongated bearing surface extending adjacent said fulcrum connection and on the side thereof remote from said common pivot, a bearing member on said power lever and spaced from said fulcrum connection in position to bear upon said bearing surface whereby to provide power multiplying means for relatively turning said members in the performance of a power stroke, said bearing surface being movable, during a power stroke, from a position engaging said bearing member on one side of the plane including the axis of said fulcrum connection and the axis of said common pivot, to a position engaging said bearing member on the other side of said plane, and spring means yieldingly urging said pair of members about said common pivot in a direction counter to the direction of said power stroke.

7. A device of the character described comprising a pair of plate-like elements supported in overlapping relationship and connected for rel-- atively turning movement about a common pivot, a power lever having an end connected on one of said elements for relative turning movement thereon about a fulcrum connection spaced from said common pivot, the other of said elements having an elongated bearing surface extending adjacent said fulcrum connection and on the side thereof remote from said common pivot, a hearing member on said power lever and spaced from said fulcrum connection in position to bear upon said bearing surface whereby to provide power multiplying means for relatively turning said e1ements in the performance of a power stroke, said elements being formed each with an arcuate slot curved about the axis of said common pivot as a center,-said fslots being in. registration to form. a cavity, anda coil; spring in said cavityand operatively connected with one of said elements at one end ofthecavitysand withth'e-iother ofsai'd elements at the other end of said cavity,. said spring serving-toyieldingly urge said elements inra direction counterto the direction oii' said'powerxstroke, said bearing surface being movable during a power stroke, from a position engaging said bearing member on one side of the plane including the axis of said fulcrum connection and the axis of said common pivot, to a position engaging said bearing member on the other side of said plane.

8. A device of the character described comprising a pair of lever members forming jaws and pivotally connected for relative turning movement about a common pivot to open and close said jaws, one of said members having an extension forming a handle, a power lever forming a handle and having an end pivotally connected on said one member for relative turning movement thereon about a power pivot spaced from said common pivot, the other of said lever members having a cam surface spaced from said common pivot a distance substantially greater than the spacement of said common and power pivots, a cam follower on said power lever and spaced from said power pivot in position to bear upon said cam surface to relatively turn said lever members to perform a jaw closing stroke against resistance, said lever members and power lever being movable, during the performance of a jaw closing stroke, from a position in which the cam surface engages said cam follower on one side of the plane including the axes of said power and common pivots, to a position in which said cam surface engages said cam follower on the other side of said plane.

9. A device of the character described comprising a pair of lever members forming jaws and pivotally connected for relative turning movement about a common pivot to open and close said jaws, a power lever having an end pivotally connected on one of said members for relative turning movement thereon about a power pivot spaced from said common pivot, the other of said lever members having a cam surface spaced from said common pivot a distance substantially greater than the spacement of said common and said power pivots, a roller on the power lever and spaced from said power pivot in position to make rolling contact with said cam surface, and to bear thereon whereby to relatively turn said lever members to perform a jaw closing stroke against resistance, said lever members and power lever being movable, during a jaw closing stroke, from a position in which the cam surface engages said roller with its axis on one side of the plane including the axis of said power and said common pivots, to a position in which said cam surface engages said roller with its axis on the other side of said plane, said roller rolling on said surface in a direction toward said common pivot as the axis of said roller is moved in a direction away from said plane, and vice-versa.

10. A device of the character described comprising a pair of members pivotally connected for relative turning movement about a common pivot, a power lever having an end connected to one of said members for relative turning movement thereon about a fulcrum connection spaced from said common pivot, the other of said members having an elongated bearing surface extending adjacent said fulcrum connection and on the side I thereof remote from said common pivot, a bear ing member on the power lever and spaced from *said. fulcrum connection in position to engage said bearing surface and; during the performance of a power stroke of said power lever, initially to ride along saidwbearing surface in a direction outwardly of the common pivot and

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