US2498012A - Grinding machine - Google Patents

Description

H. E. SJSTRAND GRINDING MACHINE Feb. 2l, 1950 5 Sheets-Sheet 1 Filed March 18, 1946 9.1. I'I/ l.

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Feb. 2l,- 1950 H. E. sJOsTRAND v2,498,012

GRINDING MACHINE Filed March 18, 1946 5 Sheets-Sheet 2 82732975 as. iE:muuuuuununnumEmnLun 34 f 60 I 35 al1-nar Emau e'l 5J' sLP-ncf Feb. 2l, 1950 H. E. sJsTRAND 2,498,012

GRINDING MACHINE Filed March 1a, 194e 5 sheets-sheet 5 9/ ya' g 96ML! L 0f 40e 9 @h gg I'LVE "rial-j Hj alm a1 Emanu el 5 rand H. E. SJSTRAND GRINDING MACHINE Feb. 21, 1950 Filed March 18, 1946 Inv enla?,

d m r u HA mw m E ma l D m m 'j H Feb. 2li, 1950 H, E. sJsTRAND 2,498,012

GRINDING MACHINE Filed March l, 194e 5 sheets-sheet 5 Invenjonr,

Elmar ,EmamLEl 5 SJLI' and H fm UNITED STATES PATENT OFFICE GRINDING MACHINE I Hjalmar Emanuel. Sjstrand, Stockholnn, Sweden'.

Application March IS, 1946, Serial No. 655,129" In Sweden August 22, 1944 29. Glaims. l.

TheP present invention relates to. grinding mea-v chines. andl more particularly to such grinding machines for surface grinding of work-pieces of steelv or other hard material, in which a rapidly rotating grinding, or emery wheel is fed towards. or: away from the center of a rotating holder for the workfpiece, so that the feeding of the grinding Wheel with respect.J to the work-piece will take place along a spiral pat. in the grinding plane. In known grinding machines. of. said latter kind` the radial feed of.' the: grindingk wheel with respect to the. rotating holder for the work-piece is rendered possible by mounting the grinding wheel in. straight; carriagev guides in the frame structure, but suchy guides are subjected to contamination through emery grainsv orthe like, wherefore they are very rapidlyworn. out and. soon lose their capacity of; rectilinear precision guiding.

It is a primary object of the presentinvention to provide al grinding. machine of the type set forth, in which the inconveniences. fou-nd. in the known. machines are avoided. According to the inventionv this, obj ecthas. been attained by mounting the grinding wheel and. the. rotating Wornpiecefholder in supporting members, which are swingable with respect to eachother about anl axis which isl paralielwith. thev axis of rotation of the holder. Since the bearings, for the. swingable supporting member may be. effectively protected against grinding dust` or the like, a grinding, ma.- chine made according tothe invention will maintain, also after. a Very long use, its capacity of precision grinding in the grinding p1ane, which,is a fundamental condition for obtaining afirst class surface grinding work.

According to a preferred' embodiment of the invention thev swingable supporting member is made; in the form of an arm, which at. the end remote from the swinging axis carries the grind.- ing Wheel or the rotating holder for the workpiece. Preferably `the supporting arm is made displaceable in the direction of the swinging axis .along a slide member, which at its ends is swingably journalled in the. frame structure and which preferably includes plane sliding. surfaces.y By tightening the grip on the sliding surfaces of the slide member-, the. swingable supporting armz may befrigidly connected with the said member when the: machine. is being used as a surface grinding machine, so that every play is then avoided at thisi point, and by arranging the pointsv of jou-rnalling the slide member in the frame structure far apart sufcientL room may be obtainedv the A vertical direction tov render itx possi-ble. todimension the arm proper sufficiently rigid to avoid objectionable springiness in the arm. In the bearingsfor the guide member every objectionableplay may readily be.4 avoided by using, bearings of a suitable kind, for example ball bearings or dead .center bearings, and said bearings may, asalready 21?.;` indicated, readily be effectively' protected against.. grinding: dust or the like,` so that they will maintain. their precision. for alongtime.

When using the grinding machine according to the invention for surface grinding of Work-pieces the necessary lateral feed of thev sWinga-ble supporting member may be' effected by hand,l but it is preferable to effect the. lateralfeed automatically, for instancefin. dependence of theirotaf tion of the work-piece holder. According to the invention provisionsl may then bemade to. vary` the speed. of rotation of.. the work-piece holder and/or the angular speed of the swingabley supporting arm in such a manner that.. thev speed of feeding the.- grind-i-ng wheel with. respect to the. Work-piece along the spiral shaped feeding path becomes substantially constant independently of the momentary distance of the grinding wheel from the center ofthe holder.,l insuring a moreelfective utilization. of the machine` Primarily the grinding machine according to the invention is intended for performing surface grinding. of work-pieces.. of hardened steel or other hard materiali with the aidof a grinding wheel the plane of which forms. a. straight. or other angle with the Work-piece, butV it lmay also be arranged for surface. grinding by means of. a cupshaped grinding wheel. For said purpose the grinding wheel spindle is preferably journalled in a head which is turnable in. the. supporting member about anaxisfwhichisperpendicular to thevgrindling spindle.

Except for surface grinding of work-pieces. a grinding machine according. to thel invention may also be used for other purposesy such as for cylinder grinding, the work-piece being then placed centrally on the rotatable'hol'der. Iiit is. a. ques.- tion. of. cylindergrindng of. work-pieces having a circular cross-section' the "swingable supporting member is locked i'n the desired angular position, whereupon thevertical feed is effected by hand or by means ofan automatically operating vertical feed mechanismwith. whichthe machine may be equipped for this purpose. When cylinder grinding articles having a non-circular cross-seclindrical bodies. of rotation the supporting, member may in connection with. the vertical feed be swung, under control of a template` extending vertically from the. table and having a corresponding curvature. With the aid of a. cam device of the latter kind form. grinding may also. be effected on. one.- side only of la non-rotating` Worlepiece.v The rotatable holder ina grinding machine accordng to the invention is preferably made dividable in such a manner that only one part extends above the supporting member, so that after removal of said part the supporting member may be used directly as a holder for the work-piece. This is desirable particularly in surface grinding with the aid of a cupshaped grinding wheel and in form grinding.

The grinding wheel is preferably mounted directly on the shaft of a rapidly rotating electric motor which is carried by the corresponding supporting member. For driving the rotatable holder for the work-piece either a separate motor may be used, or the holder may be coupled to the grinding wheel motor through the intermediary of a reduction gear.

' Other objects and characteristic features of the invention will be clear from thefollowing detailed description of suitable embodiments with reference to the accompanying drawings.

In said drawings:

Figs. 1 to 3 show a grinding machine according to the invention in which the grinding wheel is supported by the swingable supporting member, Fig. l showing the machine in side view and partly in vertical section, Fig. 2 a top view of the machine and Fig. 3 a plan section on the line III-III in Fig. l. f Y

Fig. 4 shows on a larger scale a cross-section through the swingable supporting arm on the line IV-IV in Fig. 1.

Fig. 5 shows a hand-operated lateral feed screw.

Figs. 6 and 7 show on a larger scale a mechanism for automatically moving the supporting arm in a vertical direction, said mechanism being housed within the arm.

Fig. 8 shows diagrammatically a gear having a variable gear ratio included in the driving mechanism for the rotatable work-piece holder.

Figs. 9 and l0 show schematically the manner of using the machine for form grinding of workpieces.

y Figs. 11 and 12 show in side view and in top view a grinding machine according to the invention, in which the rotatable work-piece holder yis journalled in the swingable supporting member.

Fig. 13 shows a cross section through a grinding wheel ange having a bored hub for feeding lof screws 3. At the top and bottom the column is provided with projecting arms 4 and 5. By means of pivots received in corresponding bearing holes in the projecting arms 4 and 5 a second column 6 is mounted for rotation about an axis a-a which is perpendicular to the machined surface of the bottom plate. Said swingable column 6 has a substantially triangular crosslsectional shape and is provided at its two front corners with machined plane sliding surfaces which are parallel with the swinging axis a-a of the column. Slidably secured to the said swingable column is a substantially cylindrical hollow arm I provided with a rectangular foot 8 having a machined plane end surface, and with two machined bars 9 and IIJ secured thereto with screws II and I2, said bars forming together with the said end surface a guide which grips around the prismatic corners of the triangular column 6 and is adapted to be tightened thereagainst by drawing the screws Il and I2. To render possible a rapid tightening of the guide the screws are provided each with a wrench-like projection, and the said projections are coupled together by means of a link I4, so that both may be drawn simultaneously by means of a single handle I5. At its outer end the arm 'I is provided with a cylindrical bore I6 in which a pivot on a head II is received. The head may be locked in every desired angular position by means of a screw I8 which pulls together a longitudinal slit in the arm. The outer end of the head is shaped to form a plate I5 to which an electric motor 20 is secured by screws. On the end of the motor shaft a grinding wheel 2I is mounted by meansy of aiiange and nut. To enable adjustment of the,v

arm 1 in a vertical direction the turnable column 6 is provided with two projections 22 and 23, between which is journalled a screw 24 which extends transversely through the arm 1. The arm 'I is kept in the desired height position by a nut 25, see Fig. 4, which is threaded on to the screw 24, said nut being fitted between two bosses 26 and 21 on the inside of the arm through the intermediary of an axial ball bearing 28. For the turning of the nut 25 to effect vertical adjustment of the arm 'I serves a hand crank 29 on a transverse shaft 30, which is journalled in the arm and coupled with the nut 25 by means of a bevel gear 3|, 32.

In the front portion of the table surface of the base plate I there is provided a circular hole 35 into which a bearing housing 36 is tted. The outside of the bearing housing is provided with a flange 31 which bears on a machined surface on the underside of the base plate, where the flange is secured in position by means of a number of screws, not shown. On the inside the bearing housing has a cylindrical bore closed at its lower end by a bottom ring 38 secured to the housing by means of a number of screws, not shown. A conically bored sleeve 39 provided at the outside with an excentric cam surface 40 is journalled in the housing 3E by means of two ball bearings 4I, 42. A washer 43 serves to protect the ball bearings against d-ust or the like. The conical bore in the sleeve 39 is intended for receiving a correspondingly shaped conical member 44 on the underside of a circular disc or table 45 which serves to hold the work-piece during the grinding operation.

The rotatable sleeve 39 which carries the workpiece holder is preferably driven from the grinding motor 20. For said purpose the shaft of the latter is provided with a sprocket wheel 46 which by means of a chain 41 drives a chain wheel'48 on an intermediate shaft 49 journalled transversely and centrally in the head I'I. To the intermediate shaft 49 is coupled a flexible shaft 50 which extends vertically through the base plate and is provided at its lower end with a sprocket wheel 52, which by means of a chain 53 drives a chain wheel 54 mounted on the lower end of the rotatable holder sleeve 39.

Right opposite to the cam surface 40 on the rotatable holder sleeve 39 the bearing housing 32 is provided with a boss 55 in which is provided a radial bore 56 for a sliding pin 51 which carries at its outer end a rectangular head 58 having an extension 59 between which and a fixed pin 50 there is-tensioned a spring GI which strives to aragon-.ai

be brought into operative position with respect'y to a ratchet wheel 65 journalled in the base` plate,`

said ratchet wheel being thus moved stepwise by the-pin T in one direction orthe other depending upon which one of the two ratchets thatv occupies its operative position. The ratchet wheel G5 is` mounted on a bearing sleeve 66 threaded ontol a depending bearing pin 51, and it carriese at its` lower end a sprocket wheel 68. wheel drives by means of a roller chain 69 a chain wheel 'In mounted on the lower vend of an intermediate shaft 1 I, which iscarried vertically through the base plate. Atv itsy upper end said intermediate shaft is provided with a flange 12. whichrests on the upper surface of thev table, andA with a screw-threaded extension 'I3f provided with a hand operated nut M intended forv fixing a slotted Iarm 'I5 having a handle 15a in any desired angular position. The handle 15a can be used when it is desired to swing the grinding wheel by hand. By means of a link 'I6 the armf T51 isV pivotally connected with the lower projection 23` of the swingable column 6, whereby the turning movement of the arm is transmitted to the col-- umn, so that the latter will swing the grinding wheel 2'! towards the center of therotatable table 45 according as the rotation of the table progresses.

By shifting the pivot pin on the link 'I5 alongV the slot in the arm 'I5 a more rapid or slow feed-- ing of the grinding wheel towards the center of the rotatable work-piece holder may be obtained, and by selection of a suitable length for the link the feeding speed may be brought tov increase towards the center or to decreaseV towards the periphery. In such manner a compensation is` obtainable for the diiierence in the speed of the work-piece past the grinding wheel at different distances from the axis of rotation ofthe table. 'Ihe positive feeding of the grinding` wheel in dependence upon the rotation of the work-piece holder may be disconnected by loosening the' hand operated nut 14.

The extension 59 on the reciprocating: pin 51' referred to above reaches the center of a diaphragm pump 11, where it actuates the diaphragm. Said pump, which is shown diagram-V matically only in Fig. 3, is intended to pump soap water or other cooling liquid through tube orl hose lines, not shown, onto the grinding wheel.

When surface or plane grinding a larger workpiece with the aid of the machine described above, the work-piece is secured centrally on the rotatable holder or face plate 45'. By means of` the lateral' feed mechanism described the grinding wheel 2| is then fedv from the periphery of the work-piece towards the center of the holder at an increasing speed by swinging the supporting arm 1, the grinding wheel then consecutively grinding the work-piece along a spiral path which covers the entire surface of the work-piece. If instead the surfaces of a number of smaller workpieces shall be ground, the workpieces are preferably secured to the holder so as to form a ring about its center.

The accuracy with which the surface or plane grinding may be carried out by means ofthe machineu described is evidently dependent among Said sprocket other things thereon that therel is no objectiion`- aine-play; neither between the supportingarm. and the swingable column or between the latter and the frame structure. Any possible play between thev supporting arm and" the swingable column mayy bel eliminated;` entirely during the surface grinding operation byV previously tightening thev screwsf IIS andl I2l by means of," the handle I5. The bearingsy at' the endsof the swingable column preferably are made as dead center pins; having conical points, orl as ball bearings' arranged in the: v

arms Itand` 5 projecting from the frame column 2, whereby every playv may `be avoided also lin the bearings; In the latter case'it is often preferable to secure the pivots detach-ablyin the swingable.` column. The lower one` of said pivots may then, be. made' sufficiently long to project down through an opening inthe base plate I, whereby it is rendered possible to place the mechanism for swinging the column and thev supporting armv car'-y ried' thereby entirely below the machined tablesurface. The positioning inthe grinding machine shown of the bearings for the swinging col-umn farapart prevents the springiness' which is unavoid able at shorter bearing distances. The direction of rotation of the grinding wheelv and of the work-piece holder should preferably bel selected? so as` indicated by the arrows, i. e. the grinding' wheel should operate in a direction' opposite tofY the direction ofA rotation of the holder and'towards the column. Thel grinding dust will then be thrown over a surface of the work-piece, thathas not. yet been ground and away fromv the operator', so that it can be readily" collected by means of a funnel? or the like'. rIheA cooling liquid ows down". iin-to a channel 184 provided around! the' edge oi? the table, from which channel openings TS andiA pipes, not shown, conduct the liquid back toa container under the table;

'Ihe grinding machine according to Figs. vI to 3 may also be usedl for cylinder grinding of cylin-A drical work-pieces by means of the periphery ot an ordinary grinding wheel?. The work-piece` is then placed on the rotatable holder concentrically",` the grinding' motor is turned through! 90, tor example, the automatic lateral feed is disconnected by loosening the hand operated nut "I4, and an auxiliary device adapted for lockingth-e. swingable supporting armi-n the desired angular position is mounted instead on the machine. Suchl an auxiliary device, which may be used also during surface grinding operations for carrying out the lateral feedv by hand, is shown in Fig. 5.

According to` said. figure the auxiliary device consistsy of a screw spindle tily provided with a crank 8|", a bearing 82 and a nut. 83 for the feed.: From. the bearing 82' and from the nutl 83 project at right angles to the` screw spindle cylindrical pins 8K and 85 respectively. When the auxiliary device shown is used, the pin B4 projecting from the bearing is inserted in a bored and roamed hole 86' iin the table I, whereas the pin 85: on the nut is inserted int'of a. similar hole 8l at' the outerend-y of the lower projection 232 ofthe turnable column 6, whereupon the supporting arm. for the grinding wheel is set in the desired lateral position by turning the screw spindle byrneans of the handv cran-k 8 I.

The vertical' feed required during the cylinder y1t Figs. 6? and 7.

n said mechanism the nut 25 screwed onto the vertical feed screw 24 is provided not only with the bevelled gear wheel 32` intended for the hand feed but also with a, ratchet wheel 90. Adapted to cooperate with the latter are two ratchets 9| and 02 which are pivotally supported each at the end of a corresponding link .93 or 04, said links being carried in a slot in a bracket 95 secured to the wall of the supporting arm 1. Between pins 96 on the ratchets 9| and 92 is stretched a spring 91. For the purpose of setting any one of the ratchets in operative position, or both ratchets simultaneously in inoperative position, there is provided a cam disc 98 which is coaxial with the ratchet wheel and mounted on a sleeve 9S surrounding the screw spindle 24, said sleeve projecting through the wall of the supporting arm and carrying on its projecting end an operating handle |00. When the cam disc 98 takes up the position shown in Fig. 6, it

holds the 'upper ratchet 9| out-of engagement with the ratchet wheel 90, so that only the lower ratchet 92 is operatable for the purpose of driving the wheel in the direction of the arrow. By turning the cam disc 98 by means of the operating handle |00 the lower ratchet may instead be lifted out of engagement with the ratchet wheel, and the upper ratchet be permitted to take up instead an operative position for turning the nut in the opposite direction, and alternatively both ratchets may be lifted away from' their operative positions, the automatic vertical feed mechanism being then entirely disconnected. For the operation of the ratchets serves, in the embodiment shown, the transverse intermediate shaft 49 driven from the grinding motor, on which shaft there is mounted for that purpose an excentric disc |0| which actuates a rod |02 which is mounted for axial displacement in the supporting arm 1. By means of the mechanism described the automatic Vertical feed of the grinding wheel in dependence upon the rotation of the grinding motor is thus effected at a constant speed.

l Instead of driving the holder for thek workpiece at a constant speed as shown in Figs. l to 3, and compensating the tangential feeding speed, which in surface grinding varies with the distance of the grinding wheel from the axis of rotation, by altering the radial feeding speed,

it is possible, of course, alternatively to increase the speed of rotation of the work-piece according as the grinding wheel approaches the center of the holder while effecting the radial feed at a substantially constant rate. The desired increase of the speed of rotation of the holder may then be effected by incorporating, in the driving mechanism for the rotatable holder, a gearing having a variable gear ratio. Such a gearing may be designed in the manner illustrated by way of example in Fig. 8.

According to said figure, the holder sleeve 39 is driven by means of a gear wheel |03 mounted at the lower end of the sleeve from a smaller gear wheel |04 secured to a friction disc |05 which is driven from the iiexible shaft 50 by means of a small friction wheel |06. The latter is mounted on the end of an arm |01 which is swingable about a pin |08 depending from the base plate by means of a hub |09 on which the arm is pivoted to swing vin a plane through the pin. Cooperating with the arm |01 is an excentrically journalled cylinder provided with an operating arm and adapted, upon being turned by means of the operating arm, to lift the arm |01 and press 8. thesmall friction wheel |06 into engagement with the underside of the friction disc |05. Adapted to cooperate with the arm |01 is a cam disc ||2 mounted on an extension of the lower bearing pin of the swingable column 6, the arm being pressed against said cam disc by a spring H3, so that simultaneously with the feeding of the grinding Wheel towards the center of the workpiece holder in connection with the swinging-in of the supporting arm 7, the arm |01 and thus also the driving friction wheel |06 is swung towards the center of the friction disc |05. Through a suitable shaping of the cam ||2 it is evidently possible to secure that the tangential feeding speed of the rotatable table disc 45 or of the work-piece respectively with respect to the.

grinding wheel remains constant during the entire surface grinding operation.

To render possible a reversal of the direction of rotation of the work-piece holder, as may be desirable when using the machine for cylinder grinding, for example, the hub |00 of the arm |01 is provided with a projecting nger 4 with which an excentric disc H5 may be brought into engagement by turning the latter by means of the operating arm H5.

The grinding machine shown in Figs. l to 3 is also suitable for form grinding of a work-piece in a radial direction. When the machine is to be used for said purpose the automatic lateral feed mechanism is again disconnected by loosening the hand operated nut 14, whereupon a follower arm |20 similar to the one shown in Fig. 9, for instancegis bolted to the lower projection of the swingable column 6, possibly after disconnection of the link 1G. Centrally on the rotatable face plate or table 45 is secured a template |2| having the desired contour, with which template the end` of theffollower arm is brought into engagement by connecting a tensioned spring |22 between the arm and a point on the base plate. During rotation of the face plate 45, the spring |22 forces the arm |20 to follow the contour of the template I2 l, so that cam discs or other work-pieces secured to the face plate may be ground automatically in accordance with the shape of the template or pattern. In this connection the automatic vertical feed mechanism may also be used, as in ordinary cylinder grinding.

In case the machine is to be used for form grinding of Work-pieces in a vertical direction after a template it is suitable to mount on the swingable supporting member a follower arm |25, as shown in Fig. l0, and to mount on the upper surface of the grinding table, possibly after removing that portion 45 of the rotatable holder which projects above the table surface, an upright template |26 formed at one of its vertical sides with the profile |21 according to which the work-piece is to :be ground. A spring, not shown, holds the follower arm |25 in engagement with the template |26, so that in connection vwith the vertical feed there is transmitted to the swingable supporting member a lateral movement, which corresponds to the prole of the template. This kind of lateral guiding of the swingable supporting member may be used both in form grinding of bodies of rotation, the work-piece being then secured to the rotatable holder, as well as in form grinding on one side of the work-pieces which are secured directly to the table surface of the base plate.

The embodiment of the grinding machine according to the invention, which is shown in Figs. 1l and 1 2, differs from the one disclosed in Figs.

,tions is obtainable. Iseparate gearing having a variable gear ratio may 'wheel-the cooling .offers certain difficulties. 'f-simplel arrangement for eiectivelyisupplying cooling liquid'to thel portion of the work-piece ern- `braced bythe grinding wheel is shown -in Fig. 14. fAcco'rding to said gure there is mounted on the 1 to 3 substantially therein that the grinding wheel is journalled directly in the frame strucfture, i. e. in the stationary supporting member, whereas the rotatable holder for the work-piece is carried by that supporting member which is swingable with respect to the frame. The frame is `made in the form of a box |3ll having double Walls and two vertical sides open, the grinding motor with the grinding wheel |32 being xably mounted in the roof portion |3| of the frame box. Journalled between the roof portion |3|A and the bottom portion |33 of the frame box is the swingable column |34 along which the supporting arm |35 is vertically displaceable. At the outer end of the supporting arm |35 a face plate |36 intended to serve as a. holder for the work-piece is rotatably journalled about an axis which is parallel with the swinging axis of the supporting arm or column respectively. The rotatable holder |36 is here shown as driven from a separate electromotor |31. The mechanism for automatically swinging the supporting arm |35 has been left out from the drawing for the sake of simplicity as lhas also the mechanism for automatically effecting the vertical feed of the supporting arm. Said mechanisms may be of the same design as those previously described.

It should be clear that also in the machine shown in Figs. 11 and 12 thegrinding motor may be mounted ina turnable head, so that alternatively the grinding may be effected by means of a cup-shaped grinding wheel. It is also possible to remove the rotatable work-piece holder and use the plane upperv surface of the supporting arm for securing the work-piece.

In certain cases the motor |31 for driving the rotatable holder may advantageously be replaced by an oil turbine which may be varied with respect to its speed by automatic choking of the oil supply through a regulating valve connected with the movable supporting member, whereby an absolutely uniform transmission free from vibra- A friction gearing or other :tion so that the motor shaft forms right angles with the-rotating face plate 45, rit is of importance that all axial play is eliminated. This object may Abe secured by journalling the end of the motor shaft which is remote from the grinding wheel in vthe manner shown in Fig. 13. According to said figure the shaft is Aprovided with a double axial bearing, the intermediate race |40 of which is `secured to the shaft by means of a screw |4|. ABetween the outer race |42 and the bottom of the bearing housing |43 is inserted a tensioned helical .spring |44, which presses the inner race |45.against a washer |47 supported on the bearing shield |46. Sincethe radial bearing |48'of the motor permits of a free play in the axial direcltion, the motor shaft becomes elastically yielding from a definite normal' position in the direction 'away from the work-piece, whereby objectional axial play is eliminated.

When grinding with a cup-shapedgrinding A motor shaft by means of a hub |50 a fixing flange |5| for the grinding wheel |52 which is indicated in dot-and-dash lines. In the end of the hub nearest to the motor there is provided an annular channel |53, the innermost part of which is positioned farther away from the center than its open outermost portion. For the opposite or lower end of the hub one or more holes |54 are bored onto the innermost portion of the annular channel |53. If soap water or other cooling liquid is supplied to the annular channel through a pipe |55, the water will, on account of the centrifugal force, be pressed towards the bottom of the annular channel |53 and through the bores |54 further on to the inside of the cup-shaped grinding wheel |52, where it is ung by the centrifugal force towards the inner wall of the disc and further in under the working edge |56 of the grinding wheel. The cooling water is suitably supplied to the pipe |55 from the diaphragm pump TI.

The invention is not limited, of course, tothe embodiments shown on the drawings and described in detail above but modifications of different kind are conceivable within the scope of the invention. As 1a, holder for the work-piece there may thus be used, instead of the face plate shown in Figs. 1 to 3, a three-jawed chuck, for instance, a magnetic chuck, et cetera, the conical fixing member adapted to be inserted in the rotatable sleeve positioned entirely below the plane upper surface of the table then facilitating the exchange of holders. As already indicated the machine may, of course, also be used when the holder is removed. For surface grinding a cup-shaped grinding wheel is then preferably used, the grinding wheel being moved back and forth with respect to the work-piece by swinging the supporting arm.

In cases when it is desired to use as a holder for the work-piece a magnetic chuck fed with direct current, it is suitable to take up an axial bore in the conical securing pin, one pole of the current source being then connected to a centrally positioned isolated sliding contact at the lower end of the pin, whereas the other pole may be connected to the metal body of the chuck. If it is desired instead to have both poles insulated, an insulated slip ring may be arranged around the sliding contact, a brush holder of Turbex or the like being mounted below the pin to permit two carbon brushes to press in an axial direction against the central contact and the slip ring.

In all the embodiments described the grinding wheel may, of course, be replaced by a cutting tool, for instance amilling cutter having hard metal knives. Furthermore, some of the detail constructions describedA may be used Ain other combinations and in other kinds ofworking machines than those described by way ofy example. This is true particularly with respect to the manner of journalling the swingable and'vertically displaceable supporting members and with respect to the arrangement of an angular gear cooperating'with the vertical feed screw for adjustment of the vertical-position of the grinding Wheel. Even other modifications are conceivable within the scope of the invention.

What is claimed is:

1. A machine for grinding plane surfaces, comprising in combination a frame, a rigid arm mounted oz'rsaid'frame so as to be swingable about a stationary axis, a rst spindle rotatably mounted witlr'its =.axis in fixedpositionin said frame, a second'spindle rotatablymounted at the free. end i of ysaid jj swingably mounted rigid arm encadre il with its axis in fixed position with respect to said arm, a grinding wheel mounted' on one of said spindles, a holder for` the work-piecel mounted on the other one of said spindles, the axis of rotationA of the spindle carrying the work-piece holder being parallel with the swinging axis of the rigid arm, an electric motor to cause the spindle carrying the grinding wheel to rotate at a high speed, means including a reduction gea-r 'adapted to cause the spindle carrying the workpiece holder to rotatel at a low speed, means' for adjusting the position ofY saidk rigid arm in the direction of its; swinging axis therebyV enabling the distancey between the grinding wheel and the work-piecel holder to be. adjusted and means for holding the rigid arm in fixed axial position after adjustment.

2. A grinding machine as claimed in claim 1, in which the plane of rotation ofV thegrindingwheel forms a right angle with the plane of rotation of .k

the work-piece holder;

3. A grinding machinev asclaimed in claim 1, in which theV plane ofI rotation of the grinding wheelI is parallel with the pla-ne of rotation of the work-piece holder;

4. A grindingl machine as claimed in claim 1,

in' which. theA angle between the plane ofY rotation 'of' theI grin-ding wheel and the pla-ne ci rotation of' the work-piece holderI is adjustable.

5.. A. grindingu machine'r as claimed in claim 1, in. which the4 Work-piece holder is adapted to be driven from the'grinding wheel: motor through the intermediary of4 a reduction gear comprising a flexible shaft.

6i A grinding machine as' claimed in claim 1,

:in which the work-piece' holder is dividable` and 'comprises a sleeve having a tapered bore, which tis journalled in the frame of the machine, the

upper part-of the work-piece holder being adapted gto*v he detachably secured in ther tapered bore of said sleeve by means of a correspondingly tapered pin.

7'. A grinding machine as claimed in claim 1,

in which the reduction gearing is adapted to change its gear ratio automatically in depend'i f ance of the distance of the grinding' wheel from the center of the work-piece holder.

8*. A grinding machine asv claimed in claim 1,

lin which theI reductiony gearing consists of a friction disc with which a` driving wheel` cooperf ates' at a variable distance from the center of the disc, the said driving wheel being journalled at the free end of an arm which is` swingable about an axis that is parallel withthe axis of rotation of theY friction disc under the inuence ofA a cam position through the shifting of.` a camV device cooperating therewith.

10. A grinding machine. as claimed in, claim 1, in which the reduction gearing consists of a friction disc with which ay driving wheel cooperates ata variable distance-from the'center of the-disc,

' the, said driving Wheel' being ionrnalled at the free. end ci" anarmwhich is swingable about an f axis that' is parallel with the axis of rotation of the friction disc under the influence of a cam :which is turnedsimulta'neously with: the swingablel supporting mem'her'and' Whereinntl'ie swing-- able arm for the grindingwheelis. adaptedE iro-he operated through a handfoperated cam or' the like, by' means of' which thel arm maybellocked in any desired position with respect to the center of the friction disc at the opposite side thereof-1 11. A grinding machine as claimed in cla-im '1', comprising also` a mechanism for automaticalhl displacing the swingable' rigid arm', in the direction of the" axis of rotation of the work-piece holder for theA purpose of facilitating theV use of the machine asa cylinder` grinding machine.

l2. A- gri'nding machine as claimed'v in claim. 1', in which the adjustment' of" one of the support:- ing members in. theY direction off' rotation of the liol'der is effected by means of a screw' anda nut, one of the saidE screw members being'adaptedto be rotated lo'y` ther motorfor driving the grinding spindlel and` the rotatable worin-piece holder through'the intermediary ora movement transl mitting mechanism.

13- A grinding machine as claimed' in claim- L2, in which oneI of' the screw members carries a ratchet'. wheel stepping mechanism, which. is driven from the electric motor through thefintermed-iary of' a cam.

14. A grinding machine as: claimed in. claim. I, characterized in that the adjustment of" one of the supporting members i'n. the direction, of rotation of; the holder'is eiected'- by meansof ascrew andA a nut' operated by a. ratchetwheel stepping mechanism and whereinv the stepping mechanism comprises two ratchetsl operating in diii'erentr di rectiions, means being*provided'l fork makingoneof said ratchets operable or: both inoperable;

15'. A grinding machine as'claimediin claim: 14, in whichv the ratchets are adapted to cooperate aswell with a cam disc which isfcoaxi'al with the ratchet wheel and is adapted to be turnedl from without, said camdisc servingby its5 rotation to lift one or' both ratchets ontov engagementfwith the ratchet wheel.

16`. A grinding machine" as ciiaimedvi'n claim* 1. in whichy the adj 'ustment of one of the supporting members in the direction of rotation ofthehoid'er is effected by' means ci' a screw and? anutoperated by a ratchet Wheel stepping mechanism. and wherein a driving cam for the stepping mecha.- nism is positioned on'- a transverse shaft" journailed! in the swingable supporting' member' and is adapted to cooperate with a rod coaxial with the supporting arm and displaceable in its-1ongitudinal direction, said rod being adapted to actuate, at the end remote', fromi the. cam, the ratchets through tlfrei-V intermediary of? two links, which attheir'f'ree ends pivotallysupporttheitwo ratchets between which; a. spring tensionedf..

l?. A grinding machine` :reclaimed in claim 1, in whichA the swingable supporting member is provided with a follower member' adapted: for cooperation withl a. curved disc1 or. templateI arranged on. the rotatable work-piece holder;V so that the machine; i f beiusedi for for-nr grindin of worin-piecesv in a, radial.` direction.

18'. An grindingmachine. as.l claimed in. claim: 1, in which the swingacle.r supporting member. is provided with a followerf for cooperation in connection withV the vertical feed with a. template extending from the otherl supporting member.

19: A grinding: machine as claimed; in claim 1, in. which the; grinding wheelistmounted; directly on. theV shaft: of. anelectromotorssad motor' being provided at' the endy remote from the grinding wheel. with a double axial; bearing which is pressed by a. spring. intoy engagement with1-the outer side of the bearing shield for the purpose of avoiding objectionable axial play.

20. A grinding machine as claimed in claim l, in which the grinding wheel spindle is provided with a flange for mounting a cup-shaped grinding wheel, said flange being provided on the side nearest to the motor with an annular channel for receiving soap water or the like, the innermost portion of said channel being positioned farther away from the axis than its outermost open portion and being arranged to communicate with the opposite lower side of the grinding wheel through a number of axially extending channels.

21. The grinding machine of claim 1 wherein the grinding wheel spindle is driven by an electric motor and the work-piece spindle is driven by the said motor through the intermediary of a reduction gear comprising a iiexible shaft, said electric motor being mounted -in a head which is rotatable about an axis perpendicular to the grinding wheel spindle, said flexible shaft being connected to a transverse intermediate shaft included in the reduction gearing and journaled in the head.

22. A grinding machine, suitable for surface grinding, having one supporting member for a grinding wheel and another supporting member for a work-piece, in which one of the supporting members is swingable with respect to the other about an axis perpendicular to the grinding plane, the swingable supporting member being displaceable in the direction of the said swinging axis along a guide having sliding surfaces, which guide is swingably journalled in the other supporting member and means 4for securing the swingable supporting member in iixed axial position against said sliding surfaces.

23. A machine for grinding plane surfaces, comprising in combination a frame, a rigid arm mounted on said frame so as to be swingable about a stationary axis, a rst spindle rotatably mounted with its axis in fixed position in said frame, a second spindle rotatably mounted at the free end of said swingably mounted rigid arm with its axis in xed position with respect to said arm, ra grinding wheel mounted on one I said spindles, a holder for the work-piece mounted on the other one of said spindles, the axis of rotation of the spindle carrying the work-piece holder being parallel with the swinging axis of the rigid arm, means to cause the spindle carrying the grinding wheel to rotate at a high speed, means to cause the spindle carrying the workpiece holder to rotate at a low speed, means for adjusting the position of said rigid arm in the direction of its swinging axis thereby enabling the distance between the grinding wheel and the work-piece holder to be adjusted, means for holding the rigid arm in iixed axial position after adjustment, and means for automatically swinging said rigid arm to cause a feeding movement of the grinding wheel in the grinding plane towards or away from the center of rotation of the work-piece holder.

24. A grinding machine as claimed in claim 23, in which the mechanism for automatically swinging the swingable supporting member is adapted to operate in dependence upon the rotation of the work-piece holder.

25. A grinding machine as claimed in claim 23, in which the mechanism for automatically swinging the swingable supporting member is designed so as to cause the swinging movement to take place at an angular velocity which increases during the approach of the grinding wheel to the center of the work-piece holder.

26. A grinding machine as claimed in claim 23, in which the mechanism for automatically swinging the swingable supporting member comprises a ratchet wheel coupled to the swingable supporting member and adapted to be moved stepwise in one direction or the other under control of a cam which rotates together with the work-piece holder.

27. A grinding machine as claimed in claim 23, in which the mechanism for automatically swinging the swingable supporting member comprises a ratchet wheel coupled to the swingable supporting member and adapted to be moved stepwise in one direction or the other under control of a cam which rotates together with the work-piece holder and wherein said ratchet wheel is adapted to drive an intermediate shaft which is parallel with the swinging axis of the supporting member and is coupled through a radially extending arm and a link with a point on. the supporting member positioned at some distance from the swinging axis, the pivotal connection between the link and the radially extending arm being displaceable along the arm for the purpose of changing the character of the transmission of movement.

28. A grinding machine as claimed in claim 23, provided with a detachable hand-operated screw mechanism for swinging the swingable supporting member.

29. A machine for grinding plane surfaces, comprising in combination a frame, a guide member swingably journaled at its ends in said frame, a rigid arm slidably supported on said guide member, means for adjusting the position of said arm on said guide member in the direction of the swinging axis of the latter, means for locking the arm in its adjusted position on said guide member, a rst spindle journaled in said frame, a second spindle j ournaled at the free end of said arm, a grinding wheel mounted on one of said spindles, a holder for the work-piece mounted on the other one of said spindles, the axis of rotation of the spindle carrying the work-piece holder being parallel with the swinging axis of the rigid arm, means to cause the spindle carrying the grinding wheel to rotate at a high speed, means to cause the spindle carrying the workpiece holder to rotate at a low speed, and means for slowly swinging said rigid arm to cause a radial feeding movement of the grinding wheel in the grinding plane towards or away from the center of rotation of said work-piece holder.

HJALMAR EMANUEL SJSTRAND.

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

UNITED STATES PATENTS Number Name Date 709,020 Lahodny Sept. 16, 1902 1,698,909 Currier Jan. 15, 1929 2,137,140 Lewis l Nov. 15, 1938 2,284,056 Indge May 26, 1942 2,359,969 Carson Oct. 10, 1944

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