US2614369A - Sanding or rubbing attachment - Google Patents

Description

Oct. 21, 1952 Filed July 26, 1947 S. D. ROBINS SANDING OR RUBBING ATTACHMENT 3 Sheets-Sheet 1 INV ENTOR SAMUEL DAVIS ROBINS TTORNEY Oct. 21, 1952 s. D. ROBINS SANDING OR RUBBING. ATTACHMENT s Sheets-Sneet 2 Filed July 26, 1'94? Ill/1111717111 INVENTOR SAMUEL DAVIS ROBINS w JA-rToRNEYs Oct. 21, 1952 s. D. ROBINS 2,614,369

SANDING 0R RUBBING ATTACHMENT Filed July 26, 194'? 5 Sheets-Sheet 3 23 2 ARUWW l 7 I j I 24 4 27 26 I INVENTOR SAMUEL DAVIS ROBINS Patented Oct. 21, 1952 Samuel Davis Robins; Lawrence, N. assignor to Du -Fast, Inca New York, N; I}! acorporation inseam. my 26-, erial. resin 9 Glaims.

1. inv ntio rela es to. warn a d. a ull im r v ments n ub m a s for abilizing the m tion. or; s, vibrated bodies and especially providesan claims.- v

The. nventio con sts as novel nests-i e: ru t nsi arrang m nts, .ea aat mo ments e s n s o n and des l de, he accompany n (Ira, inss referred. to here: in and constitu n a pa tner Q i lus pr f r d mb diment o the invention, audio; ether wit the sscr nt n. ser o explain th r ple of h inven ion In th rubbing mashineart. as we as in th n nd sc en ng maehin art, it ha l n en common rac ice, o attu .,t1,1sse-Q e1 li e frame o he ni em an f. a ing e un erba ance s qen, a aotuati ig' the name subs a i y a it e ter- :s av t S 24 1 x e and t s. a ob e o th s i v n n to n a a immerse term ffl 'x e a mean i r' e en r ee l vi rate t p e odi s,

as are disclosed in U. s. Patents Nos. 2,032,382,

59 3940! 2,2 03%. a 0 3 9 and 23mm fer v erm ss e i thei n i n a r l syr iq m m of the live frame to, take place, but they fail to e sec i nin in -th en e ha u h flexible; I

ns ne anno Pres i e a circu a orbit r Qllt the live frame underconditions where out- 1 side, forces, may disturb the gyratory orbits or may end to place heavy rotational loads on'the live frame as a whole, That is, they do not have position stability; Such outside forces are commonly present in machines of all the classes mis ead h nei a d F1? 13?? deleterious fects. .4

Another object of this invention therefore is to, provide position stabilization for eccentrically Yrated bodies Without recourse to the ex- 1 pansiv'e mechanical stabilizing means which also are common in these arts. Position stabilization comesunder one of three common categories, to wit, geared. eccentrics, as exemplified by U. 3. Patent No, 2,395,537;' follower cranks (geared or not) as exemplified by U. S. Patent No. 2,247,- 993; and, pantographs, All of these accomplish not'. only the permissive function of the cheap flexible stabilizer but serve the added function of actually eliminating a general. rotation, either oscillatory or otherwise, of the live frame with respect to the dead frame. The first two types of stabilizers, namely, geared eccentrics and fol.-

plie throu h ailexib e liei Orbs, ail ents N s.- 32;3-82e 2.279930 n l s ch ses new, so a irans" 9 tabil z ng the moti n at the] i e rame, be it screen or rubb ng She is mpl yee, In most cases st bilizatiqn ,,,e' =tsg byi oms m o flexible t bilizing me s arse bsien the n e oiua ioa flexib ometime t e li e ame t the was massed p mitting lower cranks are objectionable on at least three grounds. They involve rotating parts whichnot only involve extra cost but additional wear and al d v ses to xc ude rt.- h v a s requ e greatprecision to ensure perfect timed relation to the master eccentric and this involves extra cost, Bantographhmeans of position stabilization is "to be preferred if-for no other-reason than because no precise. relation is called for in the ssemb ri pa ts of the, tos p n r n t appli ati n he a s-m t the machine.

is thereforeianother object of this invention to siti a a .n graph principle, of 'gy ratory bodies through the provision" of flexible elements only and without Occur, no ahaiaaaimoa for maintenance or metrically disposed flexible stabilizers; slich abilization, on the pantolubrication will be needed and the device will be practically immune to the presence of dirt, liquid, or abrasives.

A further object of this invention is to enable the utilization of so-called "hand or portable general purpose drilling machine as the power unit of an eccentrically vibrated portable or hand rubbing machine, through the provision of the improved motion stabilizing means of this invention. In this connection, it will be understood that portable rubbing machines, as taught by the prior art, are many and varied in type. In particular, the portable or hand type vibratory sanders are, in general, highly complex single purpose mechanisms producible only at a high cost of manufacture. They embody relatively high powered power units and the vibratory motion of the live frame or shoe is characterized by a relatively short stroke, e. g. inch or less, at a very high rubbing speed. On the other hand, general purpose, low cost, hand drilling machines such as the conventional /4 inch electric drilling machine commonly found in the home workshop are characterized by a relatively low power, for example, a 1.5-2.5 ampere rating and by a relatively low chuck speed in the range, for example, of 1000 to 2500 revolutions p r minute. This low chuck speed requires that if the drill is to be used to eccentrically vibrate a rubbing shoe, a long stroke of the rubbing shoe in the order of inch, for example, is required in order to obtain a practically useful rubbing s eed. Position stab lization of thrubbing shoe through the pee,

of known flexible stabilizing means s ch as the rubber skirts, rings and the like, common in the art, would not do for this for, if the rubber skirt,

for example, were flexible enoi-gh to permit the required large stroke and yet notbreak down, it would allow the live frame or shoe to rotate relative to the dead frame, or to deflect. Such rotation would inevitably result in overstressing of the flexible stabilizing means as deflection ofit due to vibration, plus thatdue to rotation, builds up. On the other hand, if a rubber skirt stabilizer were used and made strong enough so as not to go to pieces under the conditions of severe stress reversal, then the heat loss would be large and the power drain on the hand drill would be too high, thus making use of the rubbing shoe a practical impossibility On such drills. It is therefore another object of this invention to provide a new, useful and improved rubbing machine particularly adapted for use in surface sanding in the woodworking and allied arts, and to provide a new and useful rubbing attachment for low cost electric hand drills, to the end that the home workshop in particular may be provided, through the medium of such attachment, with both drilling machine and rubbing machine in one low cost, dual purpose tool.

In the accompanying drawings in which like numbers refer to like parts throughout the several views:

Figure 1 is a perspective view of a preferred embodiment of this invention as applied to a sander attachment for low cost electric hand drills, the View showing the hand drill (less chuck) and the rubbing attachment, including actuating eccentric, in exploded relationship, ready for assembly into a complete rubbing machine unit, the drill and detached chuck of the drill being shown in dash-dot outline;

Figure 2 is a view in vertical section along the medial longitudinal plane of the embodiment shown in Figure 1, the view showing the rubbing attachment and hand drill in assembled relat onship with the rubbing head in thereby displaced position, the hand drill (less chuck) being shown in dotted outline;

Figure 3 is a view in top plan of the embodiment shown in Figure 1 omitting the driving eccentric for the rubbing shoe in order to expose underlying parts, the rubbing head being shown in normal undisplaced position;

Figure 4' is a view in side elevation of the embodiment of Figure 1;

Figure 5 is a view in end elevation of the embodiment shown in Figure 1; and,

Figure 6 is a fragmentary view in section of a modified form of eccentric actuating means and its connection to the rubbing shoe of the embodiment of Figure 1.

In general, the motion of an eccentrically vibrated body may be positionally stabilized in accordance with this invention through the provision of a novel system of stabilizing link members flexibly connecting thelive frame to the dead frame and permitting a high degree of freedom of movement of the live frame in translation while preventing its rotation relative to the dead frame 1 In, accordance, with the preferred illustrative embodiment of this invention, an intermediate frame is 'jdisposed between the live frame and the dead frame and is flexibly connected to the respective frames by separate systems of stabilizing link members, disposed at right angles to each other.

The system of dead frame link members operates to prevent any rotation of the intermediate frame relative to the dead frame while permitting a to-and-fro substantially linear motion of translation of the intermediate frame substantially parallel to the dead frame, in one direction only. The system of live frame link members likewise operates to prevent any rotation of the live frame relative to the intermediate frame while permitting a to-and-fro substantially linear motion of translation of the live frame substantially parallel to the intermediate frame, in a direction at right angles only to the permited direction of movement of the intermediate frame. Thus, relative rotation of the live frame and the dead frame is wholly prevented by the torsional rigidity of the stabilizing system as a whole while the respective motions of the live frame and intermediate frame may be compounded to cause the live frame to move in a motion of curvilinear translation relative to the dead frame.

Means are provided for actuating the live frame through the application thereto of a radial force of preferably constant magnitude but of constantly changing direction to impart thereto a motion of translation which is preferably circular.

Advantageously, moreover, the dead frame may be constructed. and arranged for releasable locking engagement with the frame, motor housing or other fixed .portion of a portable electric drilling machine so as to provide a rubbing attachment combinable with the drilling machine to form the novel and improved rubbing machine of this invention. In such case, the usual chuck of the drill is removed and is replaced by the actuating means above-mentioned for engaging and eccentrically vibrating the live frame in statically and dynamically counter-balanced relationship. In such case also, the live frame is suitably fashioned td' serve as a rubbing shoe or head having provision for releasably securing thereto a layer of rubbing material such, for example, as a sheet of sand Paper or other abrashe material, by." means-lot certain. novel. quick release. fastening devices. of, invention.

It will be nnderstoodthatthe foregoinaweeneral description and: the; following detailed 'de scription as well are exemplary and explanatory of the invention but are not: restrictive thereof.

Referring nowmore particularly to the em bod-iment of this invention shown. in .Eigures; 1 to 5 of the accompanyingdrawings, a dead frame is disposed in spaced, parallel or substantially:

I 6; but ofconstantlychanging direction, substantiall-y :at its. center-of-gravity to. impart to, the live framev a motion of translation which :maybe re.- ciprocatory but is preferably an orbital motion oficircular translation. The actuating means asv here preferably embodied comprises a crank member i0 having a stub shaft Ii adapted to be-connected to a suitable prime mover, a crank pin l2 :at one side of the stub shaft, and a counterweight-portion 13 at the opposite: side.

The 'crankmember NJ as shown in Figure 2, is journalled to the live frame. I by means of suitable anti-friction journal means such as the ball-bearing unit I 4. in whose inner raceway the crank pin 12 is snugly but not tightly received. The tip portion of the crank pin is of a configuration which is preferably spherical as shown'to permit a degree .of self-aligning rocking action of the crank pin in the inner raceembodied are each constituted by :a short strip of flexible material such, for example, as power belting material capable, of under oing a practicallyinfinite number of flex stress reversals over a pulley of small diameter, e. g. f inch, without failure.

way .of :the bearing unit so that any minor angular displacement of .the live frame will not be'transmitted directly to the crank member. Moreover, the crank portion l2 and the journal unit l4are disposed and arranged with respect to the. live. frame so that the radial thrust force of the crank portion will be applied to the i live. frame substantially in the horizontal plane The intermediate. frame. 3 as here preferably embodied is of rectangular or substantially rectangular shape and comprises parallel side and end rails 6- and 1, respectively, preferably of metal, forming a rigid yet light weight open.

structure. I

Each of the end rails 1 serves as a terminal fitting fashioned to receive and firmly grip an end of one of the link members 4 whose other end is likewise received and firmly gripped by one of a pair of terminal fittings 8 each, likewise fashioned for the purpose and fixedly secured to the dead frame I at ends in parallel relation to each other and to said end rails 1 so that the link members 4 will normally parallel each other at the frame ends. Thus, by reason of the flexible nature of the link members 4 and their parallel arrangement, the intermediate frame 3 is capable of substantially linear to-and-fro movement parallel to the dead frame in one direction only, but is substantiallycompletely immobilized against rotation relative thereto.

Each of the side rails 6 also serves as a terminal fitting fashioned to receive and firmly grip an end of one of the link members 5 whose other end is likewise received .and firmly gripped by one of a pair of terminal fittings 9 each likewise suitably fashioned for the purpose and fixedly secured to the live frame 2 at its sides in parallel relation to each other and to said end rails I so that the link members 5 will normally parallel each other at right angles to the link members 4. Thus, by reason of the flexible nature of the link members 5 and their parallel arrangement, the live frame 2 is capable of substantially linear to-and-fro movement parallel to both the intermediate frame 3 and the dead frame I in one direction only which is at right angles to the permitted direction of movement of the interlive of the center-of-gravity of the live frame and preferablyso as to makev the center-of-gravity andcenter-of-actuation of the live frame closely coincident, within practical limitations of construction.

- The counterweight portion [3 of the crank member is likewise of 'a mass and arrangement affording optimum static and dynamic balance of the counterweight portion and live frame about the rotational axis of the stub shaft II.

} Moreover, in order to minimize dynamic un crank pin side of'the crank member so as to be frame 2 throughv the a plication thereto of a radial force of preferably constant magnitude balance caused by the creation of a couple tending to cause whipping of the stub shaft ll, the

counterweight portion is concentrated on the close to the live-frame substantially in the bearing plane.

It will be evident that the rotation of the crank member I 0 on the rotational axisof the stub shaft I'l coupled with the action of the stabilizing system will impart to the live frame 2 a motion of translation in a circular orbit, assuming the dead frame I to be held fixedly. The diameter of the orbit will obviously'be determined by the throw of the crank portion l2, and in the ap plication of this invention as a rubbing attachment for portable electric drilling machines, a throw of approximately one quarter of an inch has been determined to be advantageous in order to. obtain an efiicient rubbing speed.

For such application and in accordance with the preferred embodiment of this invention as illustrated in Figures 1 to 5 inclusive, the dead frame I is suitably constructed for releasable attachment to the barrel (motor housing) or other fixed portion of the drilling machine. Preferably, the dead frame, which may be referred to for convenience as the attaching head,

is provided with an aperture 16 designed to driving spindle of the drill.,: as indicated in Figure 2'.

- 'Means are provided for releasably firmly securing the attaching head I of the rubbing attachment to the drill. As here preferably embodied, a pair of fixed positioning lugs I9 carried by the attaching head I at one end of the aperture l6 are disposed to engage the barrelof the drill unit I1 at spaced points preferably in suitable apertures such as the series of cooling air ventilating apertures 2|] disposed cir' cumferentially of the drill motor housing. 'A movable clamping member 2| disposed in the aperture I6 at its opposite end is pivotally supported by and at one end of a clamping screw 22 which is in turn threadedly received in a lug 23 integral with the attaching head Other positioning lugs 24 integral with the movable clamping member 2| are disposed to engage the drill unit H at spaced points as in the ventilating apertures 20. The clamping member 2| is of a configuration complementary to the surface portion of the drill housing which it is adapted to engage, as is the attaching head I at the opposite end of the aperture l6. bers 25 preferably integral with the clamping member 2| extend outwardly therefrom in slid-' ing engagement with the attaching head and serve to maintain the clamping member in a generally upright position with respect to the at-' taching head. The pivotal connection of the clamping member to the clamping screw enables the former to accommodate itself to any slight irregularities in shape of the drill housing.

It will be apparent from the foregoing that the drill unit is adapted to be clamped in the aperture It between the attaching head I at one end of the aperture I6 and the screw actuated clampingmember 2| at the other end. The positioning iugs I9 and 24 serve precisely to locate the rubbing attachment vertically as viewed. in Figure 2 as a whole relative to the drill unit so that the crank pin I2 will be correctly positioned in the bearing unit I4 in the assembled relationship. It will be apparent also from a consideration of Figure 2, that in assembling the drill unit and rubbing attachment, a lateral displacement of the-live frame or rubbing head I in an amount equal to the throw of the crank'member I will be necessary. This displacement is shown in Figure 2 wherein the stabilizing link members 4 are shown in an extreme flexed position. Moreover,

although the terminal fitting 8 of the link mem-' bing attachment, as here preferably embodiedv comprises a relatively stiff flat member 28 forming a pressure plate of rectangular contour in plan, as seen in Figure 3, having upstanding marginal stiffening fianges 28 at its opposite sides and curved upwardly and inwardly turned end portions forming sockets 3B in which the ends of a sheet 3| of sand paper or other rubbing material are adapted to be removably secured. Reinforcement of the plate member 28 is efiected by a stiffening member 32 extending preferably from side-to-side of the pressure plate 28 and apertured to fit snugly over and around the bearing socket member I upon a circumferential Guide mem marginal base portion 33 providing abroad and ample support for the bearing socket IS on the pressure'plate 28. Fastening means 34 serve to hold the bearing socket in fixed position between the stiffening plate 32 and pressure plate 28 centrally of the latter. The stiffening plate 32 is offset at its opposite ends into engagement with the pressure plate 28 to which it is fixedly secured. It will be noted that the stiffening plate by reason of its spaced relation to the pressure plate 28 between its ends forms a light but strong box-like structure offering substantial resistance to flexing under load. Moreover, the stiffening member 32 provides a foundation or platform to which the terminal fittings 9 of the link members 5 are fixedly secured preferably by means of short spacing members 35 disposed between and secured to the stiffening plate 32 and the anchor members 9 at the respective opposite ends of the link members 5.

In accordance with this invention'also, means are provided at each end of the rubbing head for readily releasably securing the layer 3| of rubbing material to the rubbing head. The embodied securing means is designed to hold the rubbing material securely in substantially taut fashion between the ends of the shoe while enabling it to be replaced quickly for replacement by a simple yet fast-actingfastening device. tening means is disposed at'each end of the rubbing shoe, the fasteners being identical in construction, mounting and arrangement and as here preferably embodied each comprises an actuating' lever member 36 mounted between and upon brackets 31 fixedly secured to the stiffening plate 32, for pivotal movement on bearings 38 toward and away from the latter. Side flanges 89 of the lever member '36 provide pivot bearings 49 for the respective opposite ends of a spring-wire retaining member 4| which is preferablysubstantially coextensive in width with the pressure plate 28 and is adapted to be lodged substantially snugly in the pocket or recess 39 formed by each inturn'ed end portion of the pressure plate, as is bestshown in Figure 2. The position of the pivot bearings 40 in the side flanges 39 is one ensuring that in the locked position of the actuating lever member 36, as shown in Figure 2, the axis of the co-axial bearings 40 will lie between the pressure plate 28 and the inclined equilibrium reference plane connecting socket 30 with the axis of the bearings 40. It will be apparent that, as the right hand lever member, for example, in Figure 2 is rotated in a counter-clockwise direction, the distance between the axis of the bearing '40 and the base of the socket 30 will be shortened, thus placing the spring-wire retaining member ti under further compression until the rotational axis of bearing 48- lies in the equilibrium reference plane. Further rotation will result in the compressed spring-wire member, suddenly forcing the lever member through a substantially-greater angle into fully. released position, permitting the spring member to bedisengaged entirely from the locking recess for replacing therubbing material. automatic snap-action locking of the spring member in position as the bearing points move past the reference plane in a clockwise direction as viewed in Figure 2. A layer 42 of soft rubber or other suitable resilient material is preferably bonded to the under surface of the pressure plate so as to obtain a more uniform distribution of the rubbing pressure in operation.

In the operation of the embodiment of this in- One such fas-' The reverse operation will result in an I garage 'vention hewn pi fi ure t i nii i fi f si attachment for portable electric drills; :the rotation of the counterpoise crankmember '1 o by the drill motor throu'gl'i' the torque"- applied 'tafthe stub shaft H will result in the rubbinashoei being set'in a high speed motion'fof 'circular translation in the plane of the rubbing 'face. As previously noted, the'--"throw pf" the crank pin' I2 is desirably large, e. g. one uarter inch; in prde'rf to obtain a h'ignrubbing' speed in? the orbit "of movement; It will'be apparent, howeverjthat' the. highly flexible link members will 'oifer little re-' sistance to fiexure, thusfplacing substantially no objectionable load onxthe" power unit'jfrom this cause. At the same time, there can "benorelative rotation of the ru ling sho'e relative to; the power unit and thereis hence no overstressing of the stabilizing link members aswould occur were stress .due to deflection inrotation added'to that due to VibraA'Jon."Moreover, the "exertion of greater rubbing pressure onone'end ofthe rubbing shoe than on the other'cannot result 'i na stopping or diminishing of theextent'of sideways' motion of the end at which the pressure isincreased. Such "a change would impose undesir ably heavy loads on aflow 'powe'r' hand drill were the change permitted since a stopping of the sideways motion of the toe for example would double the Sideways motion of the heel, thus doubling the fiexuralstress. No such action is possible with the flexible pantograph stabilizing means of this invention; It will also'be apparent that by reason of the construction of thestabilizing means, the parts will require no oiling except for the bearing unit and the presence of abrasive materials will not result in wear of the stabilizing members, whose life is for all practical purpc'ses, infinite.

In Figure 6 there is depictediafl modified ram of eccentric connection betweerithe crankimerm ber Ill and rubbing shoe ,L 'llhe. construct on serves further to'reduce thevertical spac tion, l3 of the crank member and of the rubbing shoe i along the rotational axis. of? the stubsh'aft l I, thus further reducing the. couplc 'action-therefl between and-obtaining a closer approximation to complete dynamic equilibrium shown',:; the crank member ID' is recesseditof receive thebeari ,ing unit l4 which fits over a generally cylindrical pin 43 having'an annular mounting fiangeportion 44 fixedly secured with reference to the rubbing shoe between the stiffening plate 32 and the pressure plate 28. The crank action remains the same as in the embodiment of Figure 2, but the placing of the counterweight portion closer to the rubbing head reduces the magnitude of the couple tending to whip the shaft II and subject the bearings of the prime mover I! to side thrust.

The invention in its broader aspects is not limited to the specific mechanisms shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantage.

What is claimed is:

1. A rubbing device for attachment to hand drilling machines having a drill body, said device comprising an attaching head having an opening to receive said drill body and adapted to be releasably clamped to the drill body; a rubbing head; an intermediate rigid frame element between said attaching head and said rubbing head;

separate sets of flexible link members flexibly connecting said intermediate [frame element to said rubbing lheadand to said attaching head, respectively;thejlinkmembers of the respective sets ibeiiig. parallel to each other and the link members of 1 ones'et being at substantially right anglesgt'o the' link members of the other whereby translatory but notmtarymotion of said rubbing head relative to-said attaching headis permitted; and, .a crank membertobe conneeted to and rotated by the driving shaft of said drilling machine'forimparting motion to said rubbing head said .crank member beingljoiirnalledto said rubbin'ghead on an axiseccentric tothe a xis of said driving shaft when the drilling machine is in said opening. I

2. A rubbing device for attachment to hand drilling achinesxhaving drillbody, said device comprising'an attaching headhaving an opening toreceive said body and adapted to be releasably clamped tothe drill body; means on said attachinglhead movable into and out of a fixed position of engagement withsaid body for clamping said head to said bod-y; arubbi'ng'head articulated to said attaching head by separate link systems each comprised of parallelly extendingfiexible strips}. a crank member to be removably connectedto' sai'd' drilling machine for rotation thereby, said member havingjournalengagement with said'rubbinghead substantially at its center-ofgravity on an axis eccentric to the rotational axis of the crank-and having a counterweight portion for "statically and dynamically balancing said rubbing headrelative to said rotational axis;

31 The device comprisinga live frame; a dead frame; anintermediateframe; a system of par: allell-y' extending .fiexible stripsconnecting said intermediate. frame to said dead frame a separate system ofpa-rallelly extending flexible strips connecting said intermediateframe to said live frame, the. strips of each said system being adapted fto yield-"in directions: normal to the plane;

of said live frame'and' the strips-of one saidsystem being disposedat substantially right angles to thestri'ps of; the other; and, means toberois adapted to be inserted; movable clamping means carried by said head for fixedly securing said machine in said aperture to said head; a rubbing head articulated to said attaching head by separate link systems each comprised of parallelly extending flexible strips; and, means to be removably attached to and driven by said machine, for actuating said rubbing head.

5. A rubbing device for attachment to hand electric drilling machines having a body provided with a handle end and a driving shaft end, said device comprising an attaching head adapted to encompass the body of said drilling machine between its handle end and its driving shaft end;- clamping means for releasably securing said head to said body in a determined fixed position between said ends; a rubbing head having a journal bearing located centrally thereof; a crank member having a stub shaft adapted for operative engagement with and rotation by the driving shaft of said machine on an axis eccentric to the rotational axis of said journal bearing andfixed relative to said attaching head, said crank member having a crank pin journalled in said journal said frame to said rubbing head; whereby a gyratory motion may be imparted to said rubbing head by said drilling machine while rotation of said rubbing head relative to said attaching head is prevented.

6. A device for attachment to hand electric drilling machines having a body provided with a handle end, a driving shaft end and ventilating apertures intermediate said ends, said device comprising an attaching head adapted to encompass the body of said drilling machine in a determined fixed position between its handle end and its driving shaft end; means on said attaching head movable into and out of a fixed position of engagement with said ventilating apertures in said determined fixed position of said attaching head on said body, for clamping said head to said body; a movable head carried by said attaching head; and, means to be removably attached to and driven by said machine for actuating said movable head. i

7. In the combination of an electric motor and a rubbing device, the improvement comprising an attaching head connected to said motor; a rubbing head; an intermediate rigid frame element between said attaching head and said rubbing head; separate sets of flexible link members flexibly connecting said intermediate frame element to said rubbing head and to said attaching head, respectively, the link members of the respective sets being parallel to each other and the link members of one set being at substantially right angles to the link members of the other whereby translatory but not rotary motion of said rubbing head relative to said attaching head is permitted; and, a crank member to be connected to and rotated by the driving shaft of said electric motor for imparting motion to said rubbing head, said crank member being journalled to said rubbing head on an axis eccentric to the axis of said driving shaft.

8. A rubbing device in accordance with claim 4 wherein the movable clamping means for securing the drilling machine to said attaching head include means movable into and out of a fixed position of engagement with the ventilating apertures present on said drilling machines.

9. A rubbing device for attachment to hand drilling machines having a drill body, said device comprising an attaching head having an opening to receive said drill body and adapted to be releasably clamped to the drill body; a rubbing head; an intermediate rigid frame element between said attaching head and said rubbing head; separate sets of link members flexibly connecting said intermediate frame element to said rubbing head and to said attaching head, respectively,

" but not rotary motion of said rubbinghead relative to said attaching head is permitted; and, a crank member to be connected to and rotated by the driving shaft of said drilling machine for imparting motion to said rubbing head, said crank member being journalled to said rubbing head on an axis eccentric to the axis of said driving shaft when the drilling machine is in said opening.

SAMUEL DAVIS ROBINS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 681,254 Northway 1 Aug. 27, 1901 900,313 Schutz Oct. 6, 1908 1,469,926 Kirkegaard Oct. 9, 1923 1,482,294 Fraser Jan. 29, 1924 1,520,631 Dey et a1 Dec. 23, 1924 1,558,167 Herrick Oct. 20, 1925 1,785,065 Aborn Dec. 16, 1930 1,824,559 McCabe Sept. 22, 1931 1,868,507 Roos July 26, 1932 2,270,309 Kehle Jan. 20, 1942 2,276,534 Burleigh Mar. 17, 1942 2,301,853 Cannon Nov. 10, 1942' 2,335,614 Spievak Nov. 30, 1943 2,370,864 Krieger -.Mar. 6, 1945 2,500,850 Miller Mar. 14, 1950

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