US1412806A - Strain reverter - Google Patents

Description

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DAVID C. KLAUSMEYER, 0F CINCINNATI, ORIG, ASSXGNGE T0 THE CINCJKNNATI BIGKFOBD TOOL COMPANY, 0l? O'LEY, CNCXNNT, 0R10, A COUTION @E j omo.

STN REVERS?.

rThis invention deals with machine-tools and it proposes an instrumentality dfor eliminating or reducing distortions or movements of frame-elements in consequenceof the variable resistance-eects of a tool in ln the development of machine-tools, two primary conditions are encountered; first, the inherent resiliency of the frame elements and, second, the back-lash inherent in the sliding joints employed for the purpose' o securing adjustment.

rlhe ultimate desideratum is, of course,

to secure an absolute lmmobility in the ad- 'ustments of the tool relative to the work and to. maintain this immobility throughout the tooling operation. rlhe back pressures resulting from the tooling operation operate to. flex the frame-elements in proportion to their resiliency, and it has been the universal practice to combat this tendency to yield by increasing the dimensions of the frame-elements, by peculiarly proportioning them, and by resorting to various reinforcements in their design. In the vearly days, no provision, beyond a more precise interittmg of the slideways, was made to correct t-he irregularities resulting from the back-lash (whichy was then regarded as unavoidable) but, subsequently,

special clamping devices were incorporated in the machine whereby the adjustable elements could be strongly clamped on their bearing ways after the adjust-ment in position of the element had been made.

During subsequent developments, the designing of machine-tools has been proceeded with on the general assumption that, from the' beginning to the end of the cutting operation, the work would oppose a substantially unvariable and continuous resistance to the tool; although it was recognized that this is not actually the case, but that, on the contrary, the pressure required to start the tool into the work will be materially different from that thereafter required to feed it during the normal cut-ting period. No means has heretofore been proposed, in

Specification of )Letters Patent.

Application led September 9, 1920. Serial ltd. @$09,143.

the. designing of machine-tools, for 0H'- settlng or compensating for this variation, and 1t has been considered as an unavoidable evil. In the case of'certain tools, notably drllls, it has for long been observed that a pressure, materially greater than, that required for normal cutting, must be put upon the drill tov cause it to initiallh penetrate the surface or sklnof the metal. likewise, it

was noted that, when the drill cut through the remote side' of the work, its advance -was not only unopposed but it actually manifested a decided tendency to ride the openlng, and.th1s rifling thereupon exercised a pronounced pull on the drill.

These effects are especially observable if the machme-tool be so designed, as in the f case of so-called radial drills, that the drilling-pressures tend to deflect a frame-element in a direction contrary to the deflection caused by its own gravity.v For example, a so-called radial-drill presents a column; vertically along which slides an overhanging arm that protrudes for a considerable distance transversely to the column. This arm is provided with a suitable mechanism for holding and rotating a drill which is arranged to project downwardly so as to pierce the work affixed to an underlying bed. 'f

However perfectly the arm may be fitted to the column, there must always be a certain amount of Aback-lash so long as the union admits of relative adjustment. rl`he weight ofthe arm takes up the back-lash between the arm and the column in the downward direction,A but obviously cannot take it up in theupward direct-ion. Consequently, any force urged upwardly against the overhanging arm and which in degree exceeds the weight of the arm assembly, will operate to lift the arm and swing it upwardly about its bearing on the column to the extent afforded by whatever amount of back-lash may exist. -This may happen when a large-sized drill is beingurged against the surface-skin of a casting by the mechanism for feeding the drill. The arm may be actually lifted, so to speak, against its own weight so that it swings upwardly in an arc, the center of which is located at its bearing on the column. lThis shifts the drill-point laterally, to a proportionate eX- tent, with the effect that the accuracy of the work is impaired. At the same time,

-this naturally introduces opportunities for vibration.

An attempt has been made, heretofore,to'

brought into their predetermined positions. of adjustment with the idea of" entirely eliminating every trace of result of much experience, it has been found, that, while thesel clamps greatly im rove the operation of the mechanism, nevert eless the correction is not absolute and that there still exists a great deal of chatter and vibration which is becoming more and more manifest as machine-tools are required to perform the increasingly heavy work of modern developments. It is debatable whether, in an absolute sense,even the most powerful clamps will actually eliminate all back-lash. or pre.- vent minute yields under the conditions obtained in actual practice.

But, irrespective of yields attributable to loose slideways, in consequence of the abovedescribed properties of a drill, alternateand variable strains are imposed upon the v arious frame-elements of the machine. First,

there exists an abnormall pressure straining.

and unduly deflecting the tool-support and the work-support apart. This occurs during the initial penetrating or starting period of the drill. Second, during the normal working-period the supports are urged apart to a less'pronounced degree by the normal drilling pressures.- Lastly, the supports are pulled together, i. e., deflecting in a contrary direction to a limited degree by the rifling effect above mentioned. Obviously, all of this interferes with the ultimate precision of the `machine-tool and it correspondingly stimulates the tendency of the tool to chatter and, to a certain extent, impairs the quality or accuracy of the work.

This invention undertakes to correct this difficulty in an entirely different way from anything heretofore conceived, instead` of depending entirely upon the use of clamps to prevent chatter, an auxiliary take-up conv trivance is' proposed; it being adapted in certain cases to serve, not so much for the purpose of taking-up back-lash, as to takeup` what may be regarded as the excess resiliency inthe frame-elements of the machine-tool. As' a result of special observations made in the course of developing this invention, it has been noted that no matter how heavily the parts may be constructed,

'within reasonable limits, or however completely they may be reinforced, or however thoroughly they may be clamped at their bearing surfaces, they still admit4 of a considerable amount of give owing to the normal excess elasticity or resiliency of the metal. In other words, the metal functions in a manner analogous toF a tapered spring back-lash. As a ifnaeoe and it will yield in an inverse (by reason of its shape) proportion to the pressure imposed upon it. v The conclusion was finally reached that, instead of attemptin to prevent deiiection solely by means o conventional reinforcing ribsI in the frame-elements, or by extrabraces, or bearing clamps, the deiiection produceable by the tool, should be anticipated, so to4 speak, through the agency of a special instrumentality capable of instituting an initial back-pressure of the same nature, and more or less of the same extent, as that which could be produced by I the Atool ;A thereby leaving, no substantial amount of residual deflection at the disposal of the tool. The ultimate effect of this device is', accordingly, to increase the stiffness of the machine, taken vas a whole, by flexing it to an extent be ond which the maximum thrusts of the too are incapable of eXercising any objectionable influence.

Other objects and advantages willbe in .part indicated in the following description hereof that they umay embody the same in.y

the various ways contemplated by this invention, drawings depicting a preferred typical construction have been annexed as a part of this disclosure, andI in such drawings like characters of reference denote corresponding parts throughout all the views, of

which:-

Fig. l is a frontelevation,'partly in section, of a radial drill embodying this invention. Fig. 2 is a fragmentary side elevation of a pneumatic system exemplifying one of the many ways of applying this invention. Fig.v 3 is a plan, partly in section, along line 3-3 of Fig. 2. Fig. 4 is a section through 4---fl` of Fig. 2 illustrating a type of valve which may be used if desired. Fig. 5 is a detail of an adjustable lever control for transmitting appropriate pressures lto the thrust rod.

resent elements ofva machine tool; the one carrying an appropriately mounted cutting tool, and the other being adapted to support the work. For purposes of adjustment, these elements are connected by a series of other elements providing various relative movements. This invention 1s applied more directly to one or the other of elements A and of representing this invention, here assumesA the form of a radial drill consisting of a base C providing a table or surface B suitable for i Referring to the drawings, A and B repatrasos supporting the work. A post D extends upwardly from the base C and pivotally suports a sleeve E; this sleeve, in turn, carryv mg the arm F which is vertically slidable thereon. 'Ihe elevation and depression of the arm is eected by a screw Gr driven by a suitable transmission I-I. The arm F is provided withslideways I on which rests the saddle or head A; thereby affording lateral ad'ustments of the cutter support J joured appropriately in the head A and suitably power driven. It is unnecessary to explain the detailsv of the foregoing arrangement inasmuch as, for theurposesl of this v ventiona case, they7 may be regarde as purelycon- Fig. 1 shows anumber of lates K resting on the table B with the cutting tool .L (here in the form of a drill) about to effect a tooling operation. .'Ihis drill, as it successively enters and' passes through the respective lates K, will be subjected togreat variations 1n duty. In fact, the drilling of a pile of plates of sheet-metal, is ordinarily a very troublesome operation. By means of this invention, the drilling may be e'ected easily and accurately, and this instance has been selected as best representing a typical embodiment of invention.

Mounted in head A is a thrust element M which admits of being moved against the y work support B or against any intervening portion of the work resting thereon.l By causing the thrust member M to press directly against the work K, a two-fold function is performed; the thrust not only being reverted as explained in the foregoing, -but the work being additionally clamped or secured against displacement and especially a ainst any tendency to clamp the drill.

arious arrangements may be resorted to within the sphere of this invention, for the purpose of exercising a "thrust between the member M and the elements A and B. In the example herein illustrated, the thrust lmember M is longitudinally movable in the bearing 1 and hasits upper end portion pro- 'vided with screw-threads 2. An internally threaded collar 3 circumscribes the threaded portion 2 and this collar is split and provided with a clamping bolt 4. By loosening the bolt'4, and rotating the rod M, it may be initially adjusted'into proximity with the work Kafter the drill L has been `brought approximately into position. The bolt 4, is

lthen tightened and the rod M may then be given an additional movement sufficient to produce the result described. While this additional movement -may be effected by screwing up the rod M before tightening the bolt 4, it is preferably effected by a resilient instrumentality such, for example, as a pneumatic system. 'Io this end, the collar 3 is provided with lateral openings 5 which receive pivot pins 6 carried by one end of a is mounted in head A. The other end of this lever 7 likewise provides pivot pins 9 which engage suitable recesses 10 in the lower head 11 of a plunger 12 actuated by a piston reciprocating within asuitable chamber 14 attached to the head A. A hand valve N is secured at some accessible point on the head A and admits ofbein manipulated to actuate the thrust rod through the linkage above described, 'Ihis valve may assume any conventional form; it being here shown as a 4-way valve.I By turning the handle (I` into the position lshown in full lines in Fig. -1, air under pressure will flow from a suitable source through the inlet ipe 15, thence throu h the channel 16 (seePFi 4) into the pipe 1 and then against the uner side of the piston 13. 'Ihis will raise the piston and deress the thrust rod M and revert theV strains. hen the inlet pipev 15 is connected with the pipe 17, the upper portion of the chamber 'wa s to various types of machine tools.

ithout further' analysis, the foregoing will so fully reveal the gist of this invention that others can, by applying current knowledge, readily adapt it for various utilizations without omitting certain features that, from the standpoint of the prior art, fairly constitute essential-characteristics of the generic or specific aspects of this invention, and therefore such adaptations should be and are intended to be comprehended within the meaning and range of equivalency of the following claims.

Having thus revealed this invention, I claim as new the following combinations of elements or equivalents thereof, and desire to secure the same by Letters Patent of the United States:

1. A machine-tool combining a bed adapted to support an article to-be machined; a

element/adjacent said bed; a tool-supporting member mounted on said frame-element; and means adjustably intervening between said member and thel work supported by said bed to urge the same apart so as to press said work onto its support and simultaneously counter-vail the strains in said member, said means being located closely adjacent said tool supportinrr member.

3. A machine-tool combining a bed; a frame-element adjacent said bed; a toolsupporting member mounted on said frameelement and extending over said bed; and means for exerting an upward adjustable strain om said member, said means being located closely adjacent said tool supporting member. fm

4r. A machine-tool combining a bed; a frame-element adjacent said bed; a toolsupporting member mounted on said frameelement and extending over said bed; and meansfor exerting an upward adjustable pressure against said member to reduce its gravitative deflection, said means being located closely adjacent said tool supporting member.

5. A^-machinetool combining a bed; a frame-element adjacent said bed; a tool-supporting member mounted-on said frame-element. and extending over said bed; and a thrust-rod intervening between said bed and arm and adjustable to flex said arm in opposition to the pull of gravity, said means being located closely adjacent said tool supporting member.

6. A machine-tool combining an upright frame-element; a tool-supporting member slidably mounted on it; means for retaining said member in a predetermined position on said frame-element; a work-support; auxiliary means; and a manually controlled instrumentality for so regulating the position of said auxiliary means with relation mutually to both said work-support and said tool-supporting member as to impose on` said member strains of the same nature asthose imposed on it by the tool when at work, said means being located closely adjacent said tool supporting member.

.7. A machine-tool combiningvan upright frame-element; a tool-supporting member slidably mounted on it; means for retaining 4 said member in a predetermined position on leo said frame element; Va work-support; an auxiliary support mounted on said member and adapted to be retracted during the preliminary adjustments in the position of said member, and adapted to be protruded towards the work-support to steady said member during tooling periods; and means for forcibly protruding said auxiliary support to create reverse strains in said frameelement.

8. A machine-tool combining an upright frame-element; a tool-supporting member led on said head and adapted towards the opposed support to strain saidv thrust said plunger forcibly against said Work.

9. A machine-tool combining an upright frame-element; a tool-supporting mem er slidably mounted on it; means for retaining said member in a predetermined position on sald frame-element; a work-support; and a forcibly urged compression means intervening between said member and the work-support adapted to bear directly against the work to exert pressure between said member and said work.

10. A machine-tool combining a tool-support; a work-support extending parallel therewith and spaced apart therefrom; a stationary frame-element located at the ends 'of said supports and extending transversely thereto, one of said supports being adjustable along'said frame-element; means embodying a compression element carried by one of said supports; and a device for adjustably determining the operative effect of said compression element whereby it will impose a limited repellent strain between said supports. f

11. A machine-tool combining a tool-support; a work-support extending parallel therewith and spaced apart therefrom; a stationary frame-element located at the ends of said supports and extending transversely thereto, one of said supports being adjustable along said frame-element; a head slidably mounted on one of said supports; and means embodying a compression element intervening between said head 'and the other support for straining said supports apart to a limited degree.

12. A machine-tool combining a tool-support; a work-support extending parallel therewith and spaced apart therefrom; a stationary frame-element located atv the ends of said supports and extending transversely thereto, one of said supports being adjustable along said frame-element; a head slidably mounted on one of said supports; and an auxiliary thrust member( slidabl mounto e urged supports apart to a limited degree.

13. A machine-tool combining a tool-support; a work-support extending parallel lll@ lll

therewith and spaced apart therefrom; a

stationary frame-element located at the ends of said supports and extending transversely thereto, one of said supports being adjustable along said frame-element; a head slidably mounted on one of said supports; a thrust plunger slidablv mounted in said head and adapted to be protruded therefrom; and

Leiaeoc means for restraining said plunger against retreat.

14. A machine-tool combining a bed adapted to support an article lto be machined; a tool-supporting member overlying said bed and normally urged by gravity towards the same; a frame-element located at a side of said bedl to carry said member; and resilient compression means acting counter to the pull of gravity to urge said member away from said bed against the restriction of said frame-element.

15. A machine-tool combining a bed; a frame-element adjacent said bed; la toolsupporting member mounted on said frameelement and extending over said bed; and resilient compression means intervening between said bed and member to urge the.

18. A machine-tool combining a bed; a.

frame-element adjacent said bed; a toolsupporting member mounted on said frameelement and extending over said bed; and an air-actuated thrust-rod intervening between said bed and arm and adjustable to flex said arm in opposition to the pull of gravity.

19. A machine-tool combining an upri ht frame-element; a tool-supportmg mem er slldably mounted on it; means for retaining said member in a predetermined position on said frame-element; a work-support; auxiliary means for initially imposing y,on said member strains of the same nature as those imposed on it by the tool when at work; and a pneumatic system for controlling said means. l

20. A machine-tool'combining an upright frame-element; a tool-supporting member slidably mounted on it; means for retaining said member in a predetermined position on said frame-element; a work-support; an auxiliary support slidably mounted on said member; and pneumatic means adapted to retract said support during the preliminary adjustments in the position of said member, and adapted to protrude it towards the work-support to steady said member during tooling periods.

21. A machine-tool combining an upright frame-element; a tool-supporting member slidably mounted on it; means for retaining said member in a predetermined position on said frame-element; a work-support, a plunger supportedby said member and vertically adjustable thereto; and a valve-controlled pneumatic system for actuating said pluner. g 22. A machine-tool combining an upright frame-element; a tool-supporting member slidably mounted on it; means for retaining said member in a predetermined position on said frame-element; a work-support; means intervening between said `member andv the Work-support adapted to bear directly against the work to exert pressure between said member and said work; an air-system for actuating said means; andv a handle carried by said member for controlling said\ 8,5

I witnesses.

DAVID o. KLAUSMEYER. Witnesses C. C. SLETE, ANNA M. HUssIAN. t

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