US2053033A - Adjustable wrench - Google Patents

Description

Sept. 1, 1936. A P [BBOTT 053,033

ADJUSTABLE WRENCH Filed March 11, 1935 2 Sheets-Sheefl A 22. rw

m f I: 17/ I: W f m Sept. 1, 1936. v ,A. P. lBBOTi' .ADJUS TABLE WRENCH Filed March 11, 1955 2 Sheds-Sheet 2 i a k 90 7/ I 2 law 70/? Hem w? I? 155077 Patented Sept. 1, 1936 PATENT OFFICE ADJUSTABLE WRENCH Arthur Pearson Ibbott, Oxhey, Hertfordshire,

. England Application -March 11, 1935, Serial No. 10,556

2 Claims.

This invention is directed to an improvement in wrenches and is filed as a continuation in part of my application Serial No. 653,696, filed January 26, 1933. The improved wrench is of the adjustable type involving a fixed jaw and a movable jaw, the adjustment between the jaws to:grip an object being obtained through the manual operation of a cam forming part of the wrench structure.

In wrenches of this type it is of primary importance that the cam should shift the movable jaw through a maximum distance relative to the fixed jaw so that the wrench will have the widest possible range of jaw settings. It is further im- 15 portant that the angle between the direction of thrust of the movable jaw upon'the cam and a tangent to the cam surface at the point of cooperation between the movable jaw and said cam surface be such that the movable jaw is 20 held in its adjusted relation to the fixed jaw, and

that rotation of the cam by the movable jaw incident to the pressure on such jaw in the use of the wrench is prevented. If the angle referred to is at any point of cam adjustment be- 25 yond a-safe angle, hereinafter referred to as the critical angle, the cam will not hold the movable jaw in its adjusted position, and thus the efiectiveness of the wrench will be lost. If, however, the angle referred to be equal 'to, or less 30 than, the critical angle, the cam will not slip under the pressure of the sliding jaw thereon and the wrench will be effective for all positions within the limits of cam movement. It has been found that this critical angle is dependent upon 35 the size ofthe cam pivot, and that, in fact, it varies with the size of said'pivot, decreasing as the pivot is decreased. It will be clear that the smaller the critical angle the smaller will be the range of jaw settings of the wrench. It is true .40 that a cam of any desired throw can be obtained in'the case of any form of spiral cam by increasing the size of the latter, but, in considering a .cam appropriate in size to the wrench with which it is associated, there is a decided limit to the 45 size of cam which it is practical to use, and hence the necessary throw brought about by the cam, and thus the requirement of maximum cam-throw resulting from the form of cam employed must be determined with regard to the 50 ultimatesize of cam which is appropriate for the wrench with which it is to be associated.

The primary object of the present invention, therefore, is to. provide a cam appropriate to the wrench with which it is associated which shall 55 .givethe maximum possible throw for its size and yet in all positions of adjustment maintain a co-operating relation at somewhat less than the critical angle.

The invention in its preferred form of detail is illustrated by the accompanying drawings, of 5 which:

Figure 1 shows a wrench in elevation.

Figure 2 is a longitudinal section on the line 2-2 of Figure 1 drawn to an enlarged scale.

Figure 3 is a, longitudinal section of a wrench 10 drawn to the same enlarged scale showing a slightly modified arrangement of parts, but otherwise constructed in accordance with the preferred form.

Figure 4 is a diagram showing, in addition to a cam of the present invention, three cams of ordinary spiral type; and, Figure 5 is a diagram showing in the upper partthereof lift obtained plotted against length of cam surface in the case of each of the four cams of Figure 4, and in the lower part thereof degrees of rotation plotted against length of cam surface in each of the four cams shown in Figure 4.

The wrench as illustrated comprises a handle I having a fixed jaw 2 at one end thereof. A sliding jaw 3 is provided with an elongated sleeve section 4 which slidably embraces the handle and accurately guides the movement of the movable jaw toward and from the fixed jaw. Mounted on the handle through the medium of a pivot 5 is a cam 6, both pivot and cam being of particular construction and arrangement, as will hereinafter be more specifically referred to.

In the form shown in Figures 1 and 2 the cam directly engages the lower edge of the sleeve 4 so that as the cam 6 is turned in one direction the sleeve 4 and thereby the movable jaw is advanced towards the fixed jaw. A spring I, fixed at one end to a pin 8 seated in a longitudinal channel 9 in the handle I, is engaged at its other end with the movable jaw, as indicated at 10, so that the movable jaw is compelled to follow the cam in the inoperative movement of the latter that is to say, during opening movement of the wrench.

The construction shown in Figure 3 is similar in all respects, except that the spring 1 and the pin 8 are omitted, and that the cam 6 is formed at its inner face, that is the face next to the handle, with an edge flange H and the movable jaw is provided with a dependent projection l2 having a lip l3 to engage beneath the flange ll. Through the medium of this lip 13 in its co-operation with the flange I l the inoperative movement of the cam 6 will cause the sleeve 4 and thereby the movable jaw to move away from the fixed The essential features of the present invention reside primarily in the form of the cam and secondarily in the size of the pivot with respect to the cam. In order that the important details of the cam may be brought out, it is necessary to describe the details of conventional spiral cams and to point out particularly wherein the cam of the present invention differs from such spiral cams in order to avoid'exceeding the critical angle above referred to while at the same in time maintaining the maximum possible throw less than the critical angle and which for equal for the given size. 1

In Figure 4 there are represented in broken lines three cams of spiral type, and in full lines the cam of the present invention. I known, a spiral or snail cam gives equal rise for equal degrees of rotation, but gives unequal rise for equal lengths of cam periphery. Referring to Figure 4, it will be clear that for successive 90 sectors in any one spiral cam the throw is the same, but the length of cam periphery included is radically diiferent. Assuming, for example, that in the case of the spiral cam designated SI the length of cam periphery in the first sector 0-90 is of an inch, the length of cam periphery in the second sector 90-180 will be'l e inches, and the length of cam periphery. in the third sector l-270 will be 1% inches; expressing these measurements in 32nds of an inch, the respective lengths of cam periphery are 28, 42, and 52. For each of these peripheral lengths, however, the cam causes the same throw' of {-2 of an inch.

In Figure 5, lengths of cam periphery are plotted horizontally, and against these lengths there are plotted vertically in the upper half of Figure 5 corresponding cam throws, whilst, in the lower half of Figure 5, degrees of rotation are plotted vertically against the horizontally plotted lengths of cam periphery; the resulting graphs corresponding with the cams,- respectively, of Figure 4 being designated by the same references as are employed in that figure.

From a-consideration of Figures 4 and 5 of the drawings, it is apparent that in the spiral'cam Si the angle between the direction in which an element operated bears thereon and a tangent to the-cam surface at the point of engagement of said element therewith is at its. maximum, i; e. the cam surface is at its steepest, in the first sector 0-90. The steepness of the cam surface is at a maximum where the latter is nearest to the pivot ofthe cam and decreases from this point to the point where the surface is at its maximum distance from the cam pivot. The only part of the periphery of the cam SI which. is withinthe criticalangle is closely in the neighbourhood of its maximum distance from the pivot.

If, a spiral cam has the same minimum distance from its pivot asthe cam SI and is so designed as to be safe even at this region of its surface, then the cam designated S2 is obtained, but, as will be seen, the total throw of this cam'is .only about one half of the cam. SI. It will be clearthat the cam S2 is quite unnecessarilysafe, that is to say, its steepness is, to an'unnecessarily large extent, below the critical angle'throughout almost its entire length, i. e., except at its smallest distance from the pivot.

By increasing the distance of the cam surface from its pivot, a snail cam is produced which will give the same throw as the cam SI and still be safe throughout its length, the cam designated As is well S3 is obtained. This cam is unnecessarily safe,

quit impracticable.

As previously stated, it is of importance. to

maintain the angle of the cam somewhat less than the critical angle and at the same time secure the maximum throw or rise of the cam for the particular purpose for which the cam is intended, and it is, therefore, necessary that a cam be constructed which will at every point of its periphery maintain a more or less constant angle off steps of equal length on successive concentric circles of relatively slight constant increase in diameter. This is the cam of the invention and is illustrated by a full line at I in Figure liof'the drawings (the corresponding graph being a full line, designated by LinFigur'e 5. of the drawings). It will be seen that the cam I is of the same dimensional order and has substantially the same throw as the .u'nsafe'spiral cam SI. The cam I gives equal throws for equal lengths of cam periphery and is .of constant steepnessior safety throughout its length. 'Note that the graph I in Figure 5 is a straight line. Because, of this, the cam I gives twice the throw of. the small spiral cam S2 (which is unnecessarily safe throughout almost its entire length) :and is very considerably smaller than the large spiral cam S3 (which is unnecessarily safe throughout. substantially the whole of its length), the throw of the cam S3 being no greater than that of the cam I.

V In addition to the formation of the cam, an important detail of the present invention is the provision of the spring 1 shown in Figure Z'and constituting the preferred form of the invention in this respect. Itwill be understood that when the wrench is under operating pressure and close contact therefore maintained between the sleeve of the slidingjaw and the cam, such cam,-if the angle is correct as defined in the instant application, will not slip or rotate. In the ordinary mode of using; a wrench of this type, however, it is usual to turn it through about 60 for a hexagonal nut or for a square nut and then to remove the spanner and replace it on the succeedingfaces of the nut .toicomplete the tightening or loosening operation, as: the case may be.

This operation is, of course, repeated as often as is necessary in the. particular instance. Each time the wrench is released from the nut, 'as'for example for anew grip, the cam is free from pres sure and therefore free to rotate and, as a matter of fact, it does so rotate either owing to the oscillatory movements to which it issubjected in the operator's hands or to the unequal weights'of V thevarious portions. of the cam about its pivot.

In theuse of the spring, there is. inall positions of the sliding sleeve and movable jaw relative to the fixed jaw .a pressureiexerted by the spring between the sleeve and'cam'. This pressure 'is sufficient to maintain the-'sleevetightly pressed against the camand thus the cam is not free to rotate under its own unequally disposed weight but is held in the desiredposithe wrenchin' a new position for a further-turn ing movement does not necessitate any further adjustment of the cam. The spring pressure will cause the sliding sleeve to engage the cam with sufiicient holding effect to prevent the possibility of cam movement under its own weight.

Therefore, the wrench having once been adjusted to the nut may, in a conventional manner, be removed therefrom and reapplied thereto without further attention to the cam or its position, for the spring acts automatically to maintain the adjustment and permit reapplication to the wrench without necessity of further cam movement or adjustment. This is a particularly important detail in connection with wrenches of this type and in effect renders the wrench, when set, a rigid relatively fixed wrench relation between the fixed and movable jaws which will permit continued reuse of the wrench on the same nut or bolt without requiring any attention to the position or further control of the cam.

It has been previously stated that the relative diameter of the pivot, while a secondary factor, is nevertheless of importance in the particular arrangement defined. In the wrench disclosed, it is apparent that the resistance to friction is relied upon to prevent slip or backward rotation of the cam. This resistance is presented chiefly at the periphery of the cam but nevertheless is present in appreciable degree at the bearing of the cam on its pivot. The friction incident to the bearing of the cam on its pivot would naturally be greater on a relatively large bearing than on a relatively small bearing. The diameter of the pivot 5 is materially larger than that which would ordinarily be considered commercially appropriate to support a cam of the particular size employed, and it is found that, owing to the proportionately large friction at the bearing surface between the cam and the pivot, the critical angle is, in fact, increased. In other words, the larger the pivot, the steeper the cam may be without exceeding the critical angle, or, the larger the pivot, the larger is the throw which is obtainable with safety against slip during use of the wrench, and thus the use of a large pivot enables a larger range of jaw settings to be obtained.

The characteristically important features of the present invention, therefore, reside in the specific provision of a cam which in its operation provides the maximum rise or throw and which in its peripheral surface presents at no point an angle exceeding the critical angle and with such peripheral surface so formed that the angle of the cam is constant throughout; together with a pivot having a relatively increased bearing surface with respect to the cam in order to increase the frictional resistance at this point to cam slip.

What is claimed to be new is:

1. An operating means for an adjustable wrench of the type including a, handle carrying a fixed jaw, a movable jaw slidable with respect to the handle toward and from the fixed jaw, said operating means including a cam pivotally supported on the handle and cooperating with and operating the movable jaw toward the fixed jaw, the cam being of constant throw type with the jaw-engaging periphery of such curvature that the angle between the normal to said curvature at the point of contact of said movable jaw and cam, and the line of thrust of the movable jaw at said point will be less than the critical angle at which pressure on the movable jaw will cause a retrograde movement of the cam, the said line of thrust passing through the point of contact and the center of rotation of said cam, the operating surface of the cam approaching the critical angle with the minimum margin of safety against retrograde cam movement in order to insure the maximum possible throw of the cam and therefore maximum possible movement of the movable jaw in each increment of cam movement.

2. An operating means for an adjustable wrench of the type including a handle carrying a fixed jaw, a sleeve slidable on and guided by the handle, and a jaw on said sleeve, said operating means including a cam pivotally supported on the handle immediately below the sleeve, the handle and cam occupying such relative positions as to permit the handle below the cam to be grasped by the hand and the cam operated by the fingers of such hand, the cam having a constant throw peripheral surface cooperating with the edge of the sleeve, the said peripheral cam surface being so designed that the tangent at each point of said surface intersects a line at right angles to the axis of the sleeve at an angle which is slightly less than the critical angle at which the cam would be moved under pressure on the sleevecarried jaw in the operation of the wrench, the line of pressure of the movable jaw passing through the point of contact and the center of rotation of the cam, and means for maintaining the cam for pivotal movement and to increase the frictional resistance to the cam movement to thereby provide a further safety margin against retrograde cam movement under pressure on the sleeve-carried jaw in the use of the wrench.

ARI'HUR PEARSON IBBO'I'I.

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