US2268728A

US2268728A - Shearing mechanism

Info

Publication number: US2268728A
Application number: US380943A
Authority: US
Inventors: Toop Frederick
Original assignee: Individual
Current assignee: Individual
Priority date: 1941-02-27
Filing date: 1941-02-27
Publication date: 1942-01-06
Anticipated expiration: 1959-01-06

Description

Jan. 6, 1942. -F. TooP 2,268,728

SHEARING MECHANISM Filed Feb. 27, 1941 5 Sheets-Sheet 1 Jan. 6, 1942. F. TooP 2,268,728

SHEARING MECHANISM Filed Feb. 27. 1941 5 Sheets-Sheet 2 73 v Fl 2 ,8!

4 66 24 'l" 3 a3 33 2'2 37 Fig l4 2 Zinncfitor F. Too P AR, 0Q 9.. "M I T F. TOOP Y Y 2,268,728

SHEARING MECHANISM Filed Feb. 27, 1941 5 Sheets-Sheet 5 Fl 3 Fl 4 Bnventor 'Clttorneg Ja .6,1942- F. TooP. 2, 8,12

SHEARING MECHANISM Filed Feb. 27, 1941 5 Sheets-Sheet 4 v F t? as 102- Jan. 6, 1942. F, +00, 2,268,728

SH EARENG MECHANISM 5 Sheets-She et 5 Filed Feb 27, 1941 Fig. [2

F. T'QQpSnvcntor attorney when either straight or Patented Jan. 6, 1942 UNITED STATES PATENT OFFICE SHEARING MECHANISM Frederick Toop, York, Pa.

Application February 27, 1941, Serial No. 380,943

14 Claims.

This invention relates to mechanically operated shears for cutting sheet material.

The invention is applicable to portable ma chines and also to stationary machines, and is concerned with various improvements in the construction of the shears, and in the driving mechanism by which rapid strokes of small amplitude are imparted to the cutting blades.

An object of the invention is to provide an improved shearing mechanism capable of cutting curved and straight lines with equal facility, of cutting sheet metal the thickness of which is relatively large for the size of the tool and also capable of attaining a relatively high output or rate'oi cut in feet per minute. i

Another object of the present invention is.to provide an improved heavy duty shearing mechanism of marked simplicity and great durability, I

In the accompanying drawings:

Fig. 1 is a perspective view looking at one side of a shearing tool embodying the present invention; I g

Fig. 2 is a perspective view-looking at the other a side of the tool;

Fig. 3 is a front elevation of the tool;

Fig. 4 is a bottom plan view;

Fig. 5 is a fragmentary plan of the lower cutting blade 01' the tool;

Fig. 6 is a vertical transverse section taken on the line 6-6 of Fi 1;

Fig. 7 is a vertical transverse section taken on the line 'l'! of Fig. 4;

Fig. 8 is a vertical transverse section taken on @Fig. 9;

Fig. 11 is a sectional view similar to Fig. 9

showing the cutting blades in closed position;

Fig. 12 is a sectional view similar to Fig. 10 of the operating mechanism in the position shown inFig. 11;

which the cutting blades are so constructed and arranged that full visibility of the work at the cutting point may be obtained irrespective of the position in which the tool is held.

connecting parts between the blades and the fram will ofier a minimum of obstruction to the free movement of the machine through the metal curved outlines are being cut. 2

Another object of the invention is to provide an improved shearingmechanism in which the supporting frame and the cutting blades are constructed so as to prevent bending of the work I sheet during the shearing operation.

Another object of the invention is to provide an improved shearing mechanism having two simultaneously movable cutting blades mounted rial.

With these and other objects in view the present invention comprises the novel features of construction and combination of elements which will be hereiafter described and claimed.

Fig. 13 is a perspective view of a piece of sheet metal having a slit cut therein;

-Fig. 14 is an enlarged sectional view of a piece or sheet steel Fig. 15 is an enlarged sectional view of a piece of sheet steel showing the manner in which ordinary shearing mechanism cuts a slit therein and Fig. 16 is an enlarged sectional view 01. a piece of sheet steel showing the manner in which the shearing mechanism 01 the present invention cuts a slit therein.

Referring to the drawings, the shearing mechanism may comprise a frame or shoe 2| which constitutes the base member of the tool, said frame being adapted to support the other parts of the tool and being adapted to be moved by anoperator ,over the work bench, table, or other support to guide the cutting elements of the tool through the work. r

Heretotore, in constructing mechanically operated shearing mechanisms or tools. in order to provide .a'tool which 'was portable and easily manipulated by an operator, the parts 01 such.

tools, and especially the parts constituting the supporting elements of the tools, were made of materials so light in weight that, when it was attempted to use the for cutting thick gaugeor heavy sheet steel, the tools would not stand up under such hard and severe usage. In other anisms, it has been necessary to design the tool in such a way that all working parts thereof function satisfactorily for their intended purpose.

It has been found that mechanically operated shearing mechanisms operate to best advantage and produce cleaner cuts when such shearing mechanisms embody two simultaneously movable cutting blades. It has also been found that the cutting blades should be so operated as to produce rapid strokes of small amplitude.

According to the present invention the base member 2| is formed of a substantial body of metal, as shown, and this member has a specific outline so as to cooperate with the other parts of the tool and thereby provide machine.

From the central portion of the base 2|, there projects forwardly on opposite sides of the base, a pair of

legs

22 and 23, the leg 23 being somewhat longer than the leg 22. The extremities of the

legs

22 and 23 are spaced apart a suitable distance from each other.

The upper surface of the base member 2|, and including the upper surface of both

legs

22 and 23, is formed a substantially flat or plane surface. From the tip of one leg around the back of the base 2| and to the tip of the other leg, the outer periphery of the base is substantially thick, as indicated at 24. The peripheral wall 24 may be arranged substantially at right angle to the plane of the top surface of the base 2|, as

shown in Fig. 9. The rear portion'of the

wall

22 and 23 and also thickens outwardly towards.

the outer peripheral wall 24, the construction being such that the bottom surface of the base is inclined outwardly and downwardly from the inner central portion thereof to the outer periphery thereof, as indicated at 25, Fig. 9.

The bottom surface 21 of the leg 23 is formed so as to provide a bearing surface for resting on 1 the work bench, table or other supporting surface on whichthe tool is used. v

The base 2|.is so shaped that when the portion 21 of the leg 23 is disposed on the work bench in the position illustrated in Figs. 1 and 3, and the tool held in the normal operating position shown, the leg 22 will be disposed at'a considerable distance above the level of the work bench. iiince the bottom of the leg 23 is comparatively row in width, the amount of friction prosurface will be reduced to a minimum.

a tough cutting by the engagement of the leg with the From the portion of the base 2| constituting the leg '22, there projects upwardly an arm 28 composed of three sections; namely, a substantially vertical section 29 which is integral with the leg 22, a horizontal section 30 which extends from the upper portion of the section 29 laterally across the front portion of the base towards the leg 23, and thirdly a section 3| which extends downwardly from the outer end of the section 30. The section 3|lis disposed a suitable distance above the base 2|, and the section 3| also terminates a suitable distance above the main portion of the'base.

Projecting rearwardly from the portion 29 of the arm 28, is another arm 32, adapted to be rigidly connected to the housing of the power operating mechanism of the tool.

The

legs

22 and 23 provide means to enable the lower cutter member 33 of the tool to be pivot ally mounted in the base 2|, and the arm 28 provides means to enable the upper cutter member 34 to be pivotally mounted on the base.

The lower cutter member 33 comprises an arcuate body disposed in the base, between the

members

22 and 23,

' At one'side, the front portion of the lower cutter member 33, adjacent to the leg 22, is

formed with a forwardly projecting portion 35 which is pivotally connected to the base 2| by means of a pivot pin 36 mounted in the leg 22, 4 4

as shown best in Fig. 7.

The other side of the lower cutter member 33 is formed with an arm 31 which is disposed substantially in parallel relationship to the leg 23. The arm 31 is formed with a trunnion 38 which is mounted in an opening 39 formed in the leg 23, as shown in Figs; 1 and 5.

I The pivots provided by the pin 36 and the trunnion 38 are disposedv at an angle to the horizontal work bench when the tool is disposed in the position shown in Fig. 3. However, such pivots are so arranged as to permit the lower cutter memberto swing freely within the base 2| in the manner to be hereinaftermore fully described.

by means of a screw 42. v

The inside' edge; of the blade 40 is inclined, as indicated at 43, Fig. 8, so as to provide a sharp cutting edge. A

The lower cutter member 33 is preferably so formed with a variable contour as to provide means for separating the parts of the sheet material-as it is. cut bythe machine and for guiding the sames'o that such cut material will be deformed a minimum amountduring the shearing operation. Therefore, the front edge of the Also, since the tool. is so constructed that. only the one leg 23 is adapted to support the tool on the work bench, the tool can be easily manip la'ted during operation thereof.

central portion of: the lower cutter member 33 is made very thin, as indicated at 44, Fig. 9.

The upper "surface of the lower cutter member 33 is substantially flat and is disposed in substantially. the same plane as the plane of the upper surface of the base 2| when the

cutter members

33 and 34 are in an intermediate position. On the other hand, the front edge of the lower cutter member 33 is thinnest at the zone 43 of the lower blade 43. From this thin zone.

2,2ca72s 44, the thickness of the lower cutter member 33 gradually increases rearwardly and laterally-to-- at the rear of the central portion of the lower cutter member 33, the outer peripheral wall 45 thereof has a thickness equal substantially to the thickness of the adjacent innerwall portion 25 of the base 2 I as shown in Fig. 9. j- Y In this way,- although there is a small gap between the

portions

25 and 45 of the base 2| and the lower cutter member 33, respectively, as

. shown in Figs. 9 and 11, due to the manner in of this vertical movement is so fast that the sheet material is prevented from lodging against the lower curved corner 48, of the front edge of the base 2|. r Y

Projectingrearwardly from the main body of the lower cutter member 33, is an, arm 41 which is operatively connected to the operating mechanism of the tool in'the manner to be hereinafter described.

\The upper cutter member 34 is pivotally mounted on a pin 48 carried by thesecfi'ons 29 and 3| of the arm 28, as shown in Figs. 1 and 2. The upper cutter member 34 comprises a head located in front of the pivot pin ;'48. and having 2 wards the, adjacent portions of the base 2|, and;

recess 49 after the blade has been properly set therein.

Projecting rearwardly from the uppercutter head 34 is an arm 51 which is operatively connected to the operating mechanism of the tool in the manner-to be hereinafter described.

Since the two

cutter blades

48 and 58 are adapted to operate rapidly, and since the movements of said blades are of small amplitude, the operating mechanism found most suitable for actuating the blades comprises reciprocated means operatively connected to the

arms

41 and 81 and constructed in the mannerto be hereinafter described and shown in Figs. 9, 10, 11

and 12.

An electric motor of any appropriate type or kind (not shown, with the exception of the front end portion of the motor shaft), is mounted within a casing having a main part II and an end portion 12 formed with an enlarged portion 13 to receive a housing 14 for the operating mechamsm.

The end of the casing II opposite to the end having the portion 12 may carry a handle (not shown) as is customary in the construction of manually operated power tools.

The housing I4 is removably secured to the portion 13 by screws I8 (Fig. 10) or by any other formed in the under portion thereof, a recess 49 for the upper blade 50.

- The head of the upper cutter member 34 is,

I as shown in Fig. 6, formed with a threaded opening 56 for the reception of a threaded sleeve 51. Disposed within the sleeve!" is the shank of a screw 58, the head of said screw being mounted in an opening 59 formed in the blade 58. The upper portion of-the sleeve 51 is formed with a hexagonal .head 58 which providesv means by which the sleeve may be engaged by a suitable tool, such as a wrench and disposed in the de sired position in the upper cutter member 34. A nut 6| is mounted on the upper. threaded extremity of the screw 58, said nut being adapted to be turned down tight against the head 88 so as' to lock the screw 58 rigid with-the sleeve. The recess 49 in which the blade 58 is mounted is formed with parallel side walls 62 and 63 (Figs.

1 and 4) and is open at each end. The slot thus provided for the blade '50 extends transversely across the front of the upper cutter member 34,

so that the-blade 58 canbe shifted laterally thereof. I

One end of the blade is formed with a beveled cutting edge 64 and this cuttingedge is adapted to be disposed in the desired relationship with respect to the cutting edge 43 of the lowerblade 48. The upper blade 58 canbe correctly positioned in the desired manner with respect to thelower blade 48 while the nut 8| is not securely tightened against the head of correctly positioned, the nut 8| is adapted to be made tight with the top of the sleeve 5'|.' A

set screw is mounted in the upper. cutter member 34 and-has atapered lower end portion 68 appropriate means, and the portion 12 may be removably secured to the portion II by any appropriate means (not shown) The housing 14 has a closure 80 removably se- I cured to the front end thereof by screws 8|.

The closure 88 is formed on its inner or rear side with parallel guides 82, between which are disposed two

reciprocative members

83 and 84.

The parallel guides 82 engage the side edges of the

members

83 and 84 and thereby prevent relative movement of these members except in a straight line, normally upward and downward or towards and from a support element or socket 88 formed in a boss 86 or extension of the housin The reciprocative member 83 is formed with an opening 81 ,which is made elongated transversely of the longitudinal center line of said member, as shown in Fig. 10.

An opening 88, similar in form to' the opening 81 is formed in the reciprocative member 84.

The member 84 is slidably mounted on the member 83, as shown in Fig. 9, and said member 84 is formed with asocket or element 83 adapted to receive a spherical end portion 98 of the arm 51, for operation of the uppercutter member 34 as hereinafter described. The arm 81 is adapted an opening 93 formed in the offset portion 94.

The portion 94 is formed with a socket or element 95 adapted toreceive a spherical end portion 98 ofv the arm 41 of the lower cutter member 33, the arm 41 extending through an open ing 98 formed in the closure 80.

' the sleeve 51. However, after the blade 58 is lateral sliding movementof the blade 50 in the I The member 83 is slidably mounted on a supporting member 99 preferably made integral with the portion 12 of the casing and extending from. the inner portion of said casing towards the closure 80, as shown in Fig. 9.

As shown in Fig. 10, the portion 94 of the member 83 provides a broad bearing surface adapted toengage the inner face of the closure 80 to thereby constitute a sliding guide for the member 83. In other words, the member 83 is slidably mounted between the closure 80 and the supporting member 99 and is thus held from lateral shifting movement therebetween. The member 94 also has another purpose, in that it functions as means for closing the exposed portion of the opening 88 in the closure 80.

Formed on the extremity of the motor shaft I is a gear IOI which has teeth in meshing relationship with the teeth of a gear I02.

The gear I02 is fixed to a shaft I03, mounted at one end in a bearing I04 mounted in the easing 13, as shown in Fig. 9.

The shaft I03 extends through the

openings

81 and 88 of the reciprocative members 83' and 84, respectively, and also through a bearing I05 formed in the closure 80.

A washer 91 is mounted on the shaft I03, and said washer is interposed between the reciprocative member 83 and the gear I02 so as to support the end of the member 83 opposite to the end supported by the member 99.

Formed on the shaft I03 is a'pair of eccentrically positioned elements I06 and I01 adapted to move in the

openings

81 and 88, respectively, of the

reciprocative members

83 and 84.

In order to prevent undue wear of the eccentrics I 06 and I01, said eccentrics are fitted with bushings I08 and I09, respectively, said bushings being preferably arranged concentric of said eccentrics, as shown in Figs. 9 and 10.

The eccentrics I06 and I01 are diametrically disposed with respect to the longitudinal center line of the shaft I03, the eccentric I06 extending laterally in one direction from the center of said shaft and the eccentric I01 extending laterally from the center of the shaft in the direction opposite to said eccentric I06. Both eccentrics and their respective bushings are circular in outline and the maximum diameter of the bushings is substantially equal to the minimum width of the

openings

81 and 88, as shown in Fig. 10.

The contours of the openings '81 and 88 and the arrangement of the eccentrics I06 and I01 are such that the

reciprocative members

23 and 24, which are disposed between the guides 22, move in a straight line across the axis of the shaft I03.

The outer end of the arm 32 is mounted in the socket 85, heretofore referred to, the end of the arm and the socket being so formed that the base 2| is made rigid with the housing of the operating mechanism.

In order to detachably connect the shearing tool to the power device, the portion IIO of the arm 32 is formed with a transverse slot or groove I I I adapted to receive the shank N2 of a springpressed locking-pin H3.

The locking-pin H3 is mounted in the boss 86 and arranged transversely of the device so as to extend across a portion of the socket 85, as shown in Fig. 10.

In order to permit the insertion of the end IIO into the socket 85 and the withdrawal of the 'arm 32 from said socket without the necessity of removing the locking-pin II3 from the device, said pin has a notch II4 formed in the portion of its shank II2 which normally extends'across the socket opening 85. The contour of the notch H4 is such that when the pin II 3-is turned to the position shown in Fig. 10, the full area of the socket opening 85 will be provided for the'insertion and the withdrawal of the arm portion H0. After the arm is mounted in the socket 85, as

shown in Fig. 9, the pin H3 is adapted to be rotated to the position in which the notch H4 is moved out of registration with the opening of the socket 85. In such position, the main shank portion 2 of the pin II 3 will be disposed in the groove III, thereby preventing movement f the arm 32 relative to the housing 14. In this way the tool will be rigidly connected to the power mechanism housing.

The pin I I3 is held in either of the two positions referred to above by a. coil spring II5 mounted in a recess H6 and encircling an end of the pin, said spring bearing at one end against a shoulder II1 and at the other end against a washer or disk II8 mounted on the extremity of said pin. The action of the spring II5 normally retains the operating head II8 of the pin H3 in engagement with a shoulder I20. The head I I9 is formed with a lug I2I adapted to engage the shoulder I20 when the pin H3 is in the position shown in Fig. 9.

The disposition of the eccentrics I06 and )1 with respect to the axis of rotation of the shaft I03 and the manner in which said eccentrics are arranged in the

reciprocative members

83 and 84, respectively, is suchthat said members will be moved simultaneously in opposite directions when the shaft I03 is rotated. The reciprocating movements of the

members

83 and 84 in opposite directions imparts a similar movement to the

arms

41 and 61, so that said arms will be alternately moved toward and away from each. other. In this way the cutting elements or blades 40 and will be operated to produce the desired shearing action.

By providing means, such as the element 85, for retaining the tool rigid with the motor casing, and by providing means, suchas the

reciprocative members

83 and 84, for simultaneously operating the

tool arms

41 and 61, the shock which occurs at the end of each reciprocative movement of the tool arms is neutralized, with the .result that the tool operates more smoothly than when a single reciprocative or cutting element is employed. I

It will be understood that in the case of a cutting tool having a single reciprocative member operated at considerable speed, first in one direction, and then in the opposite direction, the suddenness which the single reciprocative member changes its direction of movement, causes a pronounced shock in the mechanism. On the other hand, since both of the

reciprocative members

83 and 84 reverse their direction of move-.

ment simultaneously, the shock at one end balances the shock at theopposite end resulting from the change in direction of movement, so that little or no vibration or shock is produced in the operating mechanism and the mechanism operated thereby. Thus, the simultaneous double reciprocative action in opposite directions of the

members

83 and 84 produces a mechanical .movement simulating somewhat the smooth motion produced by a balanced wheel. For instance, after the

members

83 and 84 have attained their normal operating speed, the reciprocative movements of said members continue for a considerable length of time after the current supplied to the driving motor has been cut off. That is to say, the

arms

41 and 61 are actuated approximately three times longer by the present operating mechanism than is the case where a single reciprocative member is em;

ployed. Another feature of the present operating mechanism is that the double action of the I of the-cutters are relatively long.

which said arms are mounted in the

reciprocative members

83 and 84, respectively, is considerably greater than the distance from said pivots to the point at which the cutting edge of the blade 40 engages the cutting edge of the blade 50, the comparatively short reciprocating movements sides thereof, both cutters, as they pass through the skins I23 and I24, turn or bend the. skins towards the center of the sheet of metal, as indicated at I26. In this way there is no way for a ragged edge to be formed along the portion of sheet metal cut by the present tool, due to the manner in which the

cutters

40 and 50 are arranged and to the manner in which they operate.

As'shown in Fig. 13, the shearing mechanism of the present invention is so constructed that when a cut I28 is'made in a piece of sheet metal of the

members

83 and 84 which are transmitted by the

arms

41 and 61 to the blades 40 and 53, respectively, result in the blades being operated 'very rapidly with small amplitude. Thus the shearing action produced by the mechanism of the present invention comprises a multiplicity of very short cuts. a

It is well known that sheet metal as formed in the steel mill has a very. thin skin on each of its I29 the metal is not bent or otherwise distorted atthe point 130 of the cut. In other words, the.

action of the two cutter members 4|! and 50, as well as the construction of the base 2|, is such that the natural tendency of the sheet metal to flex or bend is not destroyed. Consequently the rapid cutting strokes of the

cutters

40 and 50 of slight amplitude, produces 'a clean cut in the sheet metal and the edges of the cut portions of the sheet metal will be smooth, as shown in Fig-13.

In cutting thin metal, that is to say, sheet metal not exceeding twenty-two gauge, there is very little resistance offered by the metal. On the other hand, when a shearing machine is used for cutting heavier metal, that is to say, sheet metal is being cut up. During the shearing operation,

after the shears have penetrated the skin on the surface of the sheet metal, the central portion of the sheet metal offers little resistance to the cutting action of the shears, with theresult that the cutting edges of the shears pass through the central portionof sheet metal more readily than the cutting edges pass through the upper and lower layers of skin of the sheet metal.

In the drawings, Fig. 14 shows an enlarged sectional view of a piece of ordinary sheet metal, such as sheet steel, which is designated generally by the reference numeral I22. The sheet of metal I22 has an upper skin surface I23, a bottom skin surface I24, and a central portion I25.

When shears having a shingle movable cutter are used for making a cut in the sheet metal I22, the action of the single cutter element in passing through the sheet metal produces ragged edges at thecut. These ragged edges are caused by the action of the cutter element as shown in Fig. 15, wherein it will be noted that, during downward movement of the cutter the tough upper skin I23 of the sheet metal is bent downwardly into the central portion of the sheet metal and the body of metal constituting the central portion isforced downwardly thereby forcing the cut edge portion of the lower skin I24 downwardly so as to produce the ragged edges above referred to.

It will be understood that the amount of cutting action produced by each stroke of the cutter having a thickness exceeding approximately twenty-two gauge, there is a greater resistance offered, and the resistance becomes reater as the thickness of the metal increases. Therefore, it has been found necessary to provide a portable power actuated shearing mechanism that will eliminate the resistance by opening up the metal in a progressive manner to permit the cutters to readily follow through with a minimum amount of manual force on the part of the operator. These results are obtained without in any way bending or distorting the metal during the cutting operation, The only way in which these results can be obtained is by the use of the double cutters that are operated simultaneously in the manner heretofore described. In other words, it is necessary to mount the lower cutter tained by the construction provided by the front or leading edge of the lower cutter member 33 from the point indicated at 44, Fig. 4, to the 'cutter member 33 moves downwardly as the blade of any shearing mechanismdetermines the h magnitude of the ragged. or rough cut edges formed on a" cut piece of sheet metal. The magnitude of the rough edges depends on the length of each stroke'. If thestrokes of the cutters are very short, then the ragged edges will not be as noticeable or pronounced as when the strokes By the present invention it has been the purpose to eliminate, as far, as possible, ragged edges along the out parts of sheet metal. Thus-as shown in Fig. 16, due to the manner in which the blades and Marc operated simultaneously, asthe cuttin'g edges of saidblades move simultaneously through the sheet of metal from both blade 40 moves upwardly during the cutting operationand in doing so forces the metal thereunder downwardly. At the same time the metal being cut is given a setting point at the front edges of the cutting blades. At the instant the metal is given the setting point at the front of the blades, the rear portion of the cutter member 33 holds the metal down, thereby eliminating any tendencyfor the metal which has been cut to rebound. By this action of the lower cutter member 33 the metal is opened sufliciently to permit the machine to follow through its work with a minimum amount of resistance. It will also be noted that this action is obtained without H causing any distortion of the metal as it is cut.

As shown in Fig. 3, during normal cutting operation the lower cuttermember33 is disposed in an elevated position above the plane of the work table or other support on which the leg 23 rests during the cutting operation. With the lower cutter member 33 thus disposed in an elevated position above the top of the work table,

free movement is permitted of all operating parts 01' the mechanism, as will be understood. In this way, the tool can be moved smoothly over the work table without the oscillating movements of the cutters being transmitted to the main base or shoe 2|.

Due to the manner in which the lower cutter member 33 is pivotally mounted in the

legs

22 and 23 by the

pivots

36 and 38, respectively, the lower cutter member 33 can be formed with the thin front edge 44 without affecting the strength or stabilityof said cutter member. Thus, it will be noted, that by the provision of the two

large pivots

36 and 38, which pivots are arranged at opposite sides at the front of the lower cutter member 33, the intermediate portion of said cutter member can be so shaped as to provide the thin leading or entrance edge 44, without reducing or otherwise impairing the strength of said cutter member. 'Should supporting means he used other than the type of supporting means provided by the

pivots

36 and 38, the whole body of the lower cutter member 33 would have to be'made much thicker and heavier so as to prevent said member from breaking during operation of the machine. The thin leading edge 44 permits the machine to move forwardly through the metal with little resistance.

Having thus described my invention, what I claim is:

1. A portable shears comprising a base member, a pair of movable cutting blades pivotally mounted in said base membensaid cutting blades being superposed with respect to each other and the pivots for said cutting blades being superposed with respect to each other, and means for imparting rapid movements to said cutting blades in opposite directions so that said blades will have shearing movements past the edges thereof of small amplitude.

2. A mechanically operated shearing mechanism comprising a base member adapted to be manually moved through the material being cut, a pair of movable cutter blades pivotally mounted in said base member, the pivot for the upper cutter blade being superposed in spaced relation with respect to the pivot of the lower cutter blade, and means for simultaneously operating said cutter blades so that said blades will have shearing movements of small amplitude.

3. In a motor operated shearing mechanism, a base member rigidly connected to the housing of the motor, a pair of cutter blades pivotally mounted in the base for shearing movement, each blade having its own pivot, an arm projecting from each blade, and means operated by said motor and operatively connected to said arms for simultaneously operating said blades so that the blades will have shearing movements "past the edges thereof of small amplitude.

4. In a' motor operated shearing mechanism,

tively within the openings of said reciprocative members, said eccentrics being located diametrically opposite each other with respect to the longitudinal center line of said eccentric shaft so that said members will be reciprocated simultaneously in opposite directions, and means for operatively connecting the extremity of said blade element arm to one of said reciprocative members and for operatively connecting the extremlO ity of the other said blade element arm to the other reciprocative member, so that said cutter blades will be operated by said reciprocative members.

5. In a motor operated shearing mechanism,

a base member rigidly connected to the housing of the motor, a pair of cutter blade elements pivotally mounted in the base, the pivot for the upper cutter blade being superposed in spaced relation with respect to the pivot of the lower cutter blade, an arm projecting from each blade element, a pair of members mounted in said motor housing for reciprocative strokes, each reciprocative member having an opening therein for receiving the end portion of each of said cutter blade element arm respectively, and means operrelation with respect to the pivot of the lower blade element, an arm projecting from each blade element, a pair of members mounted in said motor housing for reciprocative strokes, each reciprocative member having an opening therein,

40 a shaft operatively connected with the motor shaft and having two eccentrics thereon mounted respectively within the openings of said reciprocative members, said eccentrics being located diametrically opposite each other with respect to the longitudinal center line of said eccentric shaft so that said members will be reciprocated simultaneously in opposite directions, and means for operatively connecting the extremity of said blade. element arm to one of said reciprocative members and for operatively connecting the extremity of the other said blade element arm to the other reciprocative member, so that said cutter blades will be operated by said reciprocative members.

7. In a motor operated portable hand shear, a base member rigidly connectcd to the housing of the motor and having a pair of legs projecting forwardly therefrom and an arm of substantially inverted U-shape projecting upwardly therefrom,

a base member rigidly connected to the housing of the motor, a pair of cutter blade elements pivotally mounted in the base for shearing movement, an arm projecting from each blade element, a pair of members mounted in said motor housing for reciprocative strokes, each reciprocative member having anopeningtherein, a shaft operatively connectedwith the motor shaft and a lower cutter member pivotally mounted in the portion arranged in substantially parallel relationship to one of said legs, a blade mounted in said portion and having a cutting edge disposed on the side of said portion inwardly with respect to said leg, an upper cutter member pivotally mounted in said inverted U-shaped arm and having a blade carrying portion arranged above the forward end of said lower cutter member, a blade mounted in said upper blade carrying portion and having a cutting edge disposed at the side of said upper blade carrying portion to cooperate with the cutting edge of said lower blade to shear the material,

having two eccentrics thereon mounted respec-qs arms projectingrearwardly from both of said legs of said base and having a blade carrying cutter members, respectively, and means operated by said motor and operatively connected to the extremities of said cutter member arms for simultaneously operating said blades in opposite directions.

8. In a motor operated portable hand shear, a base member rigidly connected to the housing of the motor, 7 a lower cuttermember pivotally mounted in said base, an upper cutter member disposed in spaced relation above said lower cutter member and mounted in said base by a sepbase towards the rear edge thereof, the front edge portion of said base having a thickness at the central part thereof corresponding substantially to the thickness of the rear central portion of arate pivot, cutter bladescarried by both of said cutter members and arranged to shear the material, and means operated by said motor and operatively connected to both of said cutter members for simultaneously operating said blades in opposite directions to produce rapid cutting strokes of small amplitude. 9. In a motor operated portable hand shear, a base member rigidly connected to the housing of the motor and having an arcuate central portion and a pair of legs projecting forwardly therefrom, a lower cutter member pivotally mounted in said base member and arranged between the legs thereof, an upper cutter member pivotally mounted on said base and arranged in spaced relation above said lower, cutter member, and means operated by said motor and operatively connected to both of said cutter members for operating said cutter members to reciprocate the cutters simultaneously in opposite directions with respect to said base member..

10. In a motor operated shearing mechanism, a basemember rigidly connected to the housing of the motor, a pair of cutter blade elements pivotally mounted in the base, the pivot forthe upper blade'element being superposed in spaced relation with respect to the pivot of the lower bladeelement, an arm projecting from each blade element, a separate actuating member for each said cutter blade element, each actuating member having means for operatively connecting the arm of a cutter blade element thereto, and power transmitting means operatively connected to each of said actuating members and to the shaft of said motor so as to effect simultaneous reciprocative movements of said actuating members in opposite directions to thereby effect operation of said cutter blades by the operation ofsaid motor.-

11. In a power operated shearing mechanism,

a base member having a pair of legs projecting forwardly therefrom, a lower cutter member pivotally mounted in the legs of said base member and havingv a blade carrying portion arranged adjacent to one of said legs, said lower cutter member having its body extending from said the lower cutter member, so that when the device is in operation the parts of the material which are cut are separated only sufficiently to prevent deformation thereof a minimum amount and are guided unobstructedly towards the rear of the device, and means operatively connected to each of said cutter members for simultaneously moving the same in opposite directions of small amplitude.

12. In a power operated shearing mechanism, a base member having a pair of legs projecting forwardly therefrom, the central portion of said base extending rearwardly from said legs and having an arcuate front edge and an arcuate rear edge thicker'than said front edge, a lower cutter member pivotally mounted in the legs of said base and having a blade carrying portion arranged adjacent to one of'said legs, a blade mounted in said blade carrying portion in front of the pivots, said lower cutter member having a narrow front edge between said pivots and a 1 of the shearing mechanism, an upper blade carrying element pivotally mounted 'in said base above said lower cutter member and having a cutter blade mounted therein for cooperating with the lower cutter blade, and means for operating both cutters simultaneously in opposite 1 through the material being cut, a pair of movable directions.-

13. In a power operated shearing mechanism, a base member having a pair of legs projecting forwardly therefrom, alower cutter member pivotally mounted in the legs of said base member and having a blade carrying portion arranged adjacent to one of said legs, a cutter blade mounted in said blade carrying portion-in front of said pivots, an upper blade carrying element pivotally mounted in'said base by a pivot arranged in spaced relation above the pivots of said'lower cutter member, said upper blade carrying element having a cutter blade mounted therein in front of its pivot for cooperating with the lower cutter blade, said lower cutter member being arranged with respect to said base member so as to direct the cut metal which passes thereunder during the shearing operation downwardly beneath the bottom of the base member with-v out deforming the metal, and means operatively connected to both cutters for simultaneously operating the same in opposite. directions.

14. A. power operated shearing mechanism comprising a base member adapted to be moved 5 cutter blades pivotally mounted in the base tion projecting upwardly from said base member, Y

an upper blade carrying. element" pivotally mounted in said upwardly projecting portion of said base member and having a cutter blade mounted therein for cooperating with the lower cutter blade, the central portion of said base exmember,'said cutter blades being superposed with respect to each other and the pivots for said bladesbeing superposed with respect to each other sothat when the blades are moved about their pivots the'blades will have, a shearing movement' past the edges thereof; and means for sitending rearwardly from said legs and having a flat top surface and a bottom'surface of irregular contour of gradually increasing thickness rearwardly from the front edge of the respective pivots. j

multaneously operating said blades to cause the p blades to move inoppqsite directions about-their 'mnnna rcx roor.