US1962243A - Workholder - Google Patents

Description

June; 12, 1934.

M. w. HOWARD WORKHOLDER Filed NOV. 11. 1932 2 Sheets-Sheet 1 June 12, 1934. w. HOWARD 1,962,243

WORKHOLDER Filed NOV. 11, 1932 2 Sheets-Sheet 2 Patented June 12, 1934 UNITED STATES PATENT OFFICE WORKHOLDER Application November 11, 1932, Serial No. 642,253

4 Claims.

This invention relates to work holding jacks and is illustrated in. its machine aspect as embodied in a wood heel turning machine of the type disclosed. in United States Letters Patent No.

220,920 granted October 28, 1879, to Henderson and Paine.

The new step of the invention resides mainly in the method and means I have devised for enabling a work holding mechanism to clamp each unit of work with equal pressure regardless of such variations in dimensions as may occur in work blanks.

The special embodiment of the invention shown has been designed and applied to the purpose of clamping heel blanks preparatory to their presentation to the cutters of a wood heel turning machine. The essential invention is, however, applicable to machines used for other purposes, therefore the protection herein claimed is not limited to the specific use shown, especially in its broader aspects.

Machines of the Henderson and Paine type are provided with a jack for holding a heel blank and moving it past a rotary cutter. It is customary to clamp the heel blank by its toplift and heel seat surfaces with the previously formed breast surface resting against a gage. The jack includes a base plate on which the heel seat portion of the blank rests and a pivoted clamping member which may be moved into engagement with the toplift face of the blank. The clamping member is forced down on the blank by a hand operated screw suitably mounted in the jack frame, such jacks being known as screw jacks, or by a lever action, sometimes sup plemented by a screw, in which case they are known as clamp jacks.

Clamp jacks commonly use some sort of locking means such as a cam action or toggle joint to hold the pressure after it is applied.

Heel blanks vary considerably in their climensions due to the method of manufacture and to' meet this condition clamp jacks usually have incorporated in them some sort of cushioning device, usually a heavy spring in an attempt to cover this variation. Such cushioning devices fail to meet the requirements in that cushioned clamping is not positive and secure, and from the fact that the pressure varies according to the amount the spring is compressed thus tending to put too much pressure on the oversized blank and. too little on blanks that are undersized.

Screw jacks provide positive clamping and compensation for blank variation but require so much time and labor to operate that they have been largely abandoned in favor of clamp jacksv in spite of the faults of the latter as heretofore.

described. With the screw jacks some operators apply too much pressure on the blanks and others too little depending on the judgment or the strength of the operator.

It is essential that every blank is clamped with a uniform pressure sufficient to hold it firmly while being cut, but not suflicient to unnecessarily compress and distort the blank, as such distortion results in misshapen heels due to the springing back of the resilient wood into its original form after the heel has been shaped by the cutter and the excessive pressure has been released.

It is an object of the present invention to provide a jack which will clamp a blank with a sinle movement, with a minimum of effort, and which will provide automatic compensation for blank variation so that every blank is clamped with a uniform pressure of predetermined amount.

It is an important object of this invention to provide means by which the amount of compression given each blank can be determined and fixed by the factory manager and this amount, so determined, will be automatically applied to every blank regardless of its precise dimension, or of the skill, experience or strength of the operator.

Greater production is thus insured by reason of the fast and carefree operation of the jack, and better quality of workmanship results from the uniform and correct clamping of every blank.

These and other features of the invention will be apparent from the following description of an advantageous embodiment of the invention shown in the drawings in which 7 Fig. 1 is a side elevation of the jack and part of the turning machine.

Fig. 2 is an enlarged side elevation showing the jack in the open or work receiving position.

Fig. 3 is a fragmentary side View showing position taken bycompensating wedge in clamping standard, oversize and undersize blanks In the drawings only so much of the heel turning machine is shown as is necessary for the understanding of the present invention and reference may be made to Letters Patent No. 220,920 for further illustration and description of the parts and operation not fully disclosed herein.

The frame 10 of the turning machine has a cutter shaft 11 carrying a formed cutter head 12. Also mounted on frame 10 is shaft 13 which is parallel to shaft 11 and on which is mounted a swinging crane 14 carrying shaft 15. This shaft moves vertically under control of arm 16 riding on track 17 and carries on its upper end the jack holder 18. Pivotally mounted in the jack holder is the jack frame 19 controlled in its pivotal movements in holder 13 by track 20.

Mounted on jack frame 19 is plate 21 adapted to engage the heel seat face of a heel blank, an adjustable breast stop 22, and a pivoted toplift face clamping jaw 23 fitted with a plate 24 horizontally adjustable to properly engage heel blank 25.

straddle mounted on jack frame 19 are twin side members 26. These members are secured to the frame 19 by bolts 9 which pass through slots 19a in said frame and selectively through openings 26a in the side members, thereby providing the vertical adjustment required by heel blanks of diiferent heights. A pressure member or clamping lever 27 is pivotally mounted between the side members 26 at 28. Pivoted at 30 to the end of the lever 2'? is an adjustable abutment member 29 having a plurality of flat faces, each face being located at a different distance from the center of pivot 30 than any of the other faces for a purpose hereinafter explained.

Wedge 31, constituting a work variation compensating member, is slidably mounted between member 29 and member 23, these three members being held in gentle contact with each other by tension spring 32. Also pivotally mounted on side members 26 at 33 is an operating lever or member 34 which has a cam surface cooperating with a cam roll 35 mounted in clamping lever 2'7, and which has secured thereto, as by a bolt 45, a suitable operating handle 44. Wedge lever 36 connected by link 3'? to wedge 31 is pivotally connected to the operating member 34 at 38. Tension spring 39 acts to yieldingly pull wedge 31 in between members 23 and 29. Spring 39 is movably anchored to lever 40 pivotally mounted at 41 to operating member 34 and with its opposite end engaging roll 42 mounted in the pressure member or clamping lever 2'7.

An adjustable stop screw 43 is mounted in a boss integral with one of the side plates 26, and is located to limit the pivotal movement of pressure member or clamping lever 27 in one direction.

In operation, a blank 25 is placed on base plate 21 with its breast surface contacting breast stop 22, the jack being in the open or work receiving position shown in Fig. 2.

It will be noted that the pressure member or clamping lever 27 is resting against stop screw 43 and that cam roll 35 is thereby held out of contact with cam 34. Compensating wedge 31 is held out to the limit of its travel by portion 34a. of cam member 34 contacting wedge lever 36 holding it against jack frame 19.

On pressing handle 44 downward to clamp the blank two separate successive actions take place. First the compensating wedge 31 is drawn in by tension spring 39 acting through lever 36 and link 37 until clamping plate 24 is brought into light contact with heel blank 25 (it being understood that the relative strength of the springs 32 and 39 is such as to permit this action) after which spring 39 yields to allow the continuation of the clamping movement through the second action.

In the second action cam 34 contacts with cam roll 35 and moves pressure member or clamp! ing lever 27 about its pivot 28 to clamp heel blank 25 with a fixed amount of compression as determined by the setting of stop screw 43.

In clamping a heel blank, handle 44 is pressed downward until the lower forward part 3412 of cam member 34 contacts with jack frame 19, which provides a positive stop as shown in Fig. 1.

When in this position cam roll 35 always rests on the same part of cam 34, thus the angular movement of clamping lever 27 around its pivot 28 in the clamping direction always terminates at a definite fixed position with relation to the axes of rotation of cam member 34, roll 35, and lever 27. Therefore, the amount of clamping movement of lever 27 is determined by the retracted position from which the lever starts to move. This retracted or starting position is determined by the setting of adjusting screw 43. Accordingly, if adjusting screw 43 is turned down to a lower position the angular movement of the pressure member or clamping lever 27 will be greater and the amount of clamping compression on the heel blank will be greater, or, if the screw is turned up the movement and compression will be less.

If an extremely undersized blank as shown in dotted line at 252) (Fig. 3) is inserted in the jack, compensating wedge 31 will be drawn in to position shown at 31a. If the blank is extremely oversize as at 25c the wedge 31 will be drawn in only to position shown at 311).

Compensating wedge 31 will always bring clamping plate 24 into light contact with the heel blank before cam 34 contacts with cam roll 35 thus providing for an equal amount of compression on all blanks regardless of dimension variation.

The variation in dimension of the heel blank as shown at 25a and 25b in Fig. 3 is greater than is found in actual practice.

Lever 40 has three separate functions. First, it provides semi-locking means to assist in holding the jack in the closed position by the action of tension spring 39 holding a cam shaped portion 40a of lever 40 against roll 42 in such manner as to cause resistance against the lifting or opening movement of handle 44 and cam member 34 as shown in Fig. 1. Its second function is to assist in holding handle 44 and cam member 34 in the open or work receiving position by the action of tension spring 39 causing pressure to occur between another cam shaped portion 40b of lever 40 and roll 42 as shown in Fig. 2. Its third function is to reduce the amount of action of spring 39, an incidental effect of the two cam shapes above mentioned being to reduce the spring extension at the same time the movements of cam member 34 and wedge lever 36 act to increase said extension. This has the two fold advantage of giving long life to the spring and conserving the effort of the operator in extending the spring both in the opening and closing movements of handle 44.

Side members 26 are raised or lowered by means of the adjustment provided to the approximate position required to receive heel blanks of any given height such as blank 25 in Fig. 1, the

adjustable abutment member 29 being set on its intermediate face marked zero in the embodiment shown. If, after clamping several blanks to get the extremes of variation, it is found that compensating wedge 31 averages to operate too far in or too far out, member 29 is turned on its pivot to bring a higher face into contact with wedge 31 if the wedge is being drawn in too far, or a lower face if the wedge operates too far out. As shown, member 29 has two faces higher and two faces lower than the intermediate or zero face. One is higher, another 2/32" higher, a third lower and the fourth 2/32" lower than the zero face. The number and dimensions of these adjusting steps can be varied without departing from the scope of the invention. Member 29 rotates freely on its pivot 30 except as restrained by the pressure of wedge 31 actuated by tension spring 32 acting through jaw 23. This pressure is light, being only suiiicient to hold jaw 23, wedge 31 and member 29 in gentle contact with each other,. Consequently it is entirely feasible to revolve member 29 by hand until the desired face is in contact with wedge 31.

Having described the invention what I claim as new and desire to secure Letters Patent of the United States is:-

1. In a work holder, in combination, relatively fixed and movable clamping jaws, an operating member, a pressure member, a wedge interposed between said movable jaw and pressure member, a yielding connection between said operating member and wedge for moving the latter during the initial movement of the former to cause said movable jaw to engage the work, and means operable during a predetermined portion of the final movement of said operating member for positively moving said pressure member.

2. In a work holder, in combination, relatively fixed and movable clamping jaws, an operating member, a pressure member, a wedge interposed between said movable jaw and pressure member, an adjustable abutment member between said pressure member and wedge, a yielding connection between said operating member and wedge for moving the latter during the initial movement of the former to cause said movable jaw to engage the work, and means operable during a predetermined portion of the final movement of said operating member for positively moving said pressure member.

3. In a work holder, in combination, relatively fixed and movable clamping jaws, an operating member, a pressure member for forcing said movable jaw toward said fixed jaw, a wedge interposed between said movable jaw and pressure member, a yielding connection between said operating member and wedge whereby the initial movement of said operating member causes said wedge to move said movable jaw into engagement with work positioned on said fixed jaw, a cam operated by said operating member, and means cooperating with said cam for operating said pressure member, said cam being inoperative to move said pressure member during the initial movement of said operating member but acting to move the same during a predetermined portion of its subsequent movement.

4. In a work holder, in combination, relatively fixed and movable clamping jaws, an operating member having a definitely limited stroke, a pressure member for forcing said movable jaw toward said fixed jaw, an adjustable stop for determining the retracted position of said pressure member, a wedge interposed between said movable jaw and pressure member, a yielding connection between said operating member and wedge whereby the initial movement of said operating member causes said wedge to move said movable jaw into engagement with work positioned on said fixed jaw, a cam operated by said operating member, and means cooperating with said cam for operating said pressure member, said cooperating means being disengaged from said cam during the initial portion of the movement of said operating member but being engaged thereby at a point in said movement determined by said stop to move said operating member during the final portion of said movement.

MERTON W. HOWARD.

Mill

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