US2419940A - Grinding machine - Google Patents

Description

May 6 1947' H. E. BALSIGER ErAL 2,419,940

GRIHDING MACHINE Filed March 3, 1944 5 Sheets-Shoot l .1. ula? a..

Summer {lazoLn 841.31652 'Jou/v .aLLER Gttorncg May 6 1947. yH. E. BALSIGER Erm. 2,419,940

GRINDING MACHINE Filed March I5, 1944 5 Sheets-Sheet 2 Bnventor #4201.0 544.51692 Jou/v 4 .BoLLER JM): MAK

Gttomeg May 61 1947 H. E. BALslGr-:R ETAL 214191940 GRINDING MACHINE Fned laren s. 1944 s sheets-sheet 3 May 5, 1947- H. E. BALslGc-:R Erm. 2,419,940

GRINDING' MACHINE Filed March v3, 1944 5 Sheets-Sheet 4 May 6 1947 H. E. BALslGl-:R ETAL 2,419,940

GRINDING MACHINE Filed March 3, 1944 5 Sheets-Sheet 5 Snoentor #from I anus/cre Jo/wv A. Bac l. 5 2

attorney Patented May 6, 1947 GRINDING MACHINE Harold E. Balsiger, Waynesboro, Pa., and John A. Boiler, Thurmont, Md., assignors to Landis Tool Company, Waynesboro, Pa.

Application March 3, 1944, Serial No. 524,948

21 Claims.

This invention relates to a grinding machine, particularly of the centerless type.

It is an object of this invention to provide a machine of the centerless type having new and improved features of design.

A further object is to provide a novel means for mounting a control wheel support for angular adjustment in a vertical plane.

A further object is to provide a simple means for effecting said angular adjustment.

A further object is to provide a control wheel support which may also be angularly adjusted in a horizontal plane and traversed or adjusted in any angular position.

A further object is to provide a dressing tool for the control wheel permanently mounted on the work rest which is in turn mounted on th'e bed.

A further object is to provide novel means for varying the speed of the control wheel.

A further object is to provide an improved driving means for said control wheel.

A further object is to provide a simplified control means for all operating conditions.

In the drawings:

Figure 1 is a front elevation.

, Figure 2 is a plan view partly broken away to show the grinding wheel feed mechanism.

Figure 3 is an enlarged front elevation of the control wheel support partly in section to show adjusting mechanisms.

Figure 4 is'a left end elevation of the control wheel mounting partly in section to show means for tilting andtraversing same.

Figure 5 is a partial plan view showing the positionof the parts during the dressing of the con trol wheel.

Figure 6 is a front elevation of the same.

Figure 'I is a wiring diagram.

Fgure 8 is a piping diagram.

Figure 9 is a section on line 9--9 of Figure 10.

Figure 10` is a partial front elevation of the valve knob and latch for the control wheel traverse movement.

Numeral l indicates the bed of a machine, li a grinding wheel base slidably mounted thereon for movement toward and from a work piece i2. A grinding wheel i is rotatably mounted on said base i I. Said grinding wheel may be moved toward and from working position by means of a screw 20, rotatably mounted in said wheel support and engaging a nut 2| secured to said bed. Said screw may be rotated by means of hand wheel 25 acting thru a differential transmission not shown, a shaft 28 having a worm gear 21 thereon meshing with the teeth of a worm wheel 28 on said screw. Shaft 28 may be rotated either by means of hand wheel 25 or by a. handle 29 in ring 3i which may be clamped to hand wheel 25 by means of a clamping bolt 30. The range of movement of handle 29 may be limited by any suitable combination of stop devices. The grindwheel i5 is driven by a motor (not shown) on the wheel base.

Control wheel.-A control wheel 35 is rotatably mounted on a wheel base 36 and driven thru a V belt drive by a variable voltage motor 3l mounted on said base 36.

Said V belt drive includes a jackshaft 33 driven by motor 31 thru V belts 32. A lubricating pump is driven from said jackshaft. V belts 34 connect said jacksh'aft and the spindle 38 on which control wheel 35 is mounted. Under some conditions an adjustable chain belt drive may be used between said jackshaft and said spindle as shown in Figure 3. However such a drive must be kept free from backlash. So long as a part of the drive is resilient and the drive as a whole is free from lost motion the desired results may be attained.

This structure represents a decided improvement over previous control wheel drives. Such drives consisted of a geared speed change from which the control wheel was driven directly or thru a belt. The favorable characteristics of the belt portion of the drive were decidedly outweighed by the unfavorable characteristics of the geared speed change mechanism.

For example said control wheel rotates at a predetermined speed. As soon as a work piece is introduced into the grinding throat it is picked up by the grinding wheel which tends to rotate the work at the sainer surface speed as the grinding wheel. The control wheel prevents the rotation of said work at such a speed but in so doing its own speed is increased so that the control wheel is really being partially driven by the grinding wheel thru the medium of the work. Where there is a geared speed change in the control wheel drive, this tendency of the control wheel to be driven by the rotating work piece is suddenlyl checked when the backlash in said speed chage is taken up. This results in damage to the surface being ground and is directly proportional to the amount of stock being removed. The ability of the grinding wheel to remove stock is thus limited by the characteristics ofthe control Wheel drive. When a drive consisting only of resilient V belts or one in which a combination of V belt and backlash-free-chain belt is used, the belt partially cushions the shock of the change in the control wheel drive from driving to being driven and transmits to the motor all such changes in speed. Motor 31 is designed for this type of operation and assists in said cushioning action. When said wheel is thus driven the iiow of current is reversed and resistance to the reverse now acts as a dampening brake on the motor. This is generally known as regenerative braking. By using such a drive the amount of stock which may be removed without effecting the ground surface is greatly increased.

Said motor 35 is energized by a variable voltage generator |44 mounted in the bed of the machine and adjusted by means of a rheostat, also in the bed, the handle of which is identified by numeral 49. This type of drive makes possible the slow motor speed required by a control wheel using only the limited reduction available with a belt transmission instead of a geared reduction unit. With only a belt drive between motor and wheel spindle the over running tendency of the Wheel is immediately transmitted to the motor and the action cushioned yby the effect of the regenerative braking circuit on the motor. Wheel 35 on base 36 may be adjusted angularly in a horizontal plane for grinding tapered surfaces or in a vertical plane for effecting an axial feeding movement of a Work piece for thru feed grinding operation. Said control wheel may be adjusted toward and away from the grinding wheel for work pieces of various diameters. Said control wheel may also be moved axially either manually or by power. The means for effecting the above adjustments consists of a member 45 pivotally and slidably mounted at 46 on bed I9 for angular adjustment thereon. The pivot member 46 is set in preloaded ball bearings 41 in order to provide a rigid mounting. Angular adjustment of member 45 is effected by means of screw 49 one end of which is rotatably mounted in the bed I9, the other end of which is threaded and inserted in a nut 49 in member 45. Integral with member 45 is a cylinder 59 in which is slidably mounted a piston I having a piston rod 52 one end of which is threaded. Said threaded end has a hollow hexagonal portion 64' into which a wrench may be inserted for rotating said piston rod. Said threaded end 53' fits a nut 53 which is secured to a slide member 55. A lock nut 54 serves to lock slide 55 in adjusted position relative to piston 5 I.

Membel- 45 has formed thereon two upwardly facing bearing surfaces, 56 and 51, one V and one flat respectively. Member 55 has correspond ing V and fiat surfaces 69 and 6| respectively for engaging surfaces 56 and 51 on member 45.

Member 55 has a pair of upwardly facing guide surfaces extending transversely tn those on the underside thereof. One of these guides 65 has a curved surface instead of the conventional V. The other guide 66 has a nat surface. A member 61 having a curved surface 69 for mating with guide 65 is secured to the underside of control wheel base 36 by means of screws 69.

The ilat guide 66 has slidably mounted thereon a rectangular block 15 in which is inserted a hardened button 16. A vertical adjusting screw 11 threaded in a nut 19 in base 36 rests on said button. The upper end of said screw extends thru the top of base 36 and has a hollow hexagonal portion 19 into which a wrench may be inserted for turning same. A sleeve 99 on said screw is graduated in terms of angles to which the control wheel may be tilted. A clamp for said screw consists of a setscrew.9| having a beveled-point 92. One end or a pin 93 engages the surface of screw shaft 11, the other end has a beveled point 94 in contact with point 92. By mounting motor 31 on control wheel base 36 and driving wheel 35 thru resilient V belts the entire drive may be tilted vas a unit with said base.

Feed mechanism-control wheel-The means for adjusting the control wheel toward and from the grinding wheel consists of a feed screw 99 one end of which is threaded in a nut 9|. Said nut is mounted on a bracket 92 which in turn is mounted on slide 55. The other end of said screw is supported in base 36 on spaced ball bearings 93 and 94. Between said bearings a worm wheel 95 is mounted on said screw shaft. A worm gear 96 on shaft 91 engages said worm wheel. A handwheel 98 on shaft 91 serves as a means for turning said shaft gears and screw for adjusting base 36 and control wheel 35 toward and from the grinding wheel I5.

Work rest.-The work supporting device consists of a base member II9 mounted directly on bed i9. Said base is slotted to receive a work supporting bar III. Said bar has a work engaging surface inclined in the direction of the control wheel. Work pieces are held in position just before and after the grinding operation in the case of thru feed grinding by means of guides I I2 pivotally mounted on the base ||9 and urged toward the work by resilient means not shown.

-Dressing device for grinding wheel-The dressing device for the grinding wheel I5 consists of a bracket |99 attached to base II. A tool supporting member I9| is slidably mounted on said bracket for a reciprocating movement relative thereto. A diamond tool |92 is mounted on support member |93 which is adjustable vertically and horizontally relative to wheel I 5 by means of a knob |99 on a feed screw not shown. The reciprocating movement is effected by a piston |94 in cylinder |95 and connected to member |9| by piston rOd |06.

Dressing device for control wheel.-The means for dressing the control wheel consists of a diamond holder in the form of a block |29 mounted on the rear of one of the guides |I2. Said block has a diamond tool |2| removably mounted therein in position to engage the surface of control wheel 35.

Hydraulic features-The hydraulic system consists of two hydraulic motors 59 and |95. Motor 59 provides the traverse movement oi' control wheel slide 55. Motor |95 receives fluid under pressure simultaneously with the supply to motor 59.

Fluid under pressure is supplied by a pump |39 driven by motor |3|. Flow of fluid in said system is heldA uniform by pressure operated relief valve |32 in conjunction with throttle valve |33 as described in copending application Serial No. 390,432. filed April 25, 1941.

Said fluid under pressure passes from valve |33 thru line |35 and reversing valves |49 and I4I. Valve |49 directs fluid to one side or the other of cylinder 59 thru lines |51 and |59. The rate of flow thru said valve is controlled by a throttle valve |91 which is built into valve |49.

In the Same manner fluid under pressure is directed by valve I4I thru line |46 or line |41 to cylinder |95, the rate of flow being controlled by throttle valve |99. Valve |49 is normally locked in inoperative position by means of a latch |95 pivotally mounted on the knob of said valve and held in slot |69 by spring |61. The reason for sentially of a seriesgenerator |44 having series fields |50 and |5| and-a rheostat |52 fo'.` varying the output ofsaid generator. Said'generator is connected to a series type motor 31 having a series field |55 and a resistor |58 which may be set for a predetermined motor speed, in this case a speed suitable for dressing the control wheel and which is substantially higher than the range of speeds used for grinding which are determined by the rheostat |52.

The regenerative braking of motor 31 is accomplished in the following manner. An electric valve |53 is provided inthe motor generator circuit between generator |44 and generator series field |5|. This valve permits current to flow only from left to right in the excitation circuit, that is, from generator |44 to motor 31. As soon as grinding begins the work is caused to rotate by the action of the grinding wheel I5 and in turn tends to drive the control wheel 35 and its motor 31 at a slightly faster rate than normal. In previous control wheel drives this tendency would be checked before aiiecting said motor 31, usually by a geared reduction unit. However, back lash in Such a unit would cause an abrupt check in this increased speed which would have an undesirable affect on the work being ground. In this invention, only a belt drive connects motor 31 with control wheel 35 and the increase in speed is transmitted directly to the motor. Said motor thus driven becomes a generator. The load on the original generator being reduced, the flow of current thru fields |5| and |55 is also reduced and the normal tendency of the motor is to increase speed. However, rectifier 220 provides the necessary additional excitation for the field windings |5| and |55 to enable said motor to maintain the selected speed and to resist any tendency to increase said speed. The current now generated by the motor will flow from motor 31 thru rectifier 220 back to generator |44 but said current cannot flow back thru field windings |5| and |55 to decrease the excitation. Preventing a decrease in motor excitation is essential to aid in the braking operation for motor 35. Regenerative braking is thus applied to the control wheel drive and functions during the entire grinding operation to provide a smooth running control wheel. This effect is made possible because the variable voltage drive is capable of carrying substantially full load at speeds low enough that even with the limited speed reduction ratio of belt drive the necessary control wheel Speeds may be obtained.

Alternating current is suppliedto motors |3|. |40, |42 and |43 from lines I, 2 and 3 thru suit able relays. Said relays are energized by current at a lower voltage than that used on the motors. Said current is supplied from lines and 3 thru a transformer |60 to lines |6|and |62. A master start switch |33 and a, master stop switch |64 are inserted in line |6|. Line |82 is a return line.

A selector switch |10 may be set to determine which motors should be in operation for each of the conditions of setting up, grinding, and dressing. The grinding wheel motor is controlled by a relay |15 actuated by a coil |16. One contact |11 of said relay is connected to a normally open contact |18 in relay |19.A Said relay controls oil pump motor |3| and is actuated by coil |80. A normally closed contact |8| in relay |19 includes the rheostat |52 in the variable voltage generator. Said rheostat is set for driving control wheel 35 at a. predetermined speed for grinding. .Contact |18 in relay |19 and contact |11 in relay |15 when closed complete a circuit which includes resistor |56 in the field circuit of control wheel motor 31. The purpose of this circuit is to drive said control wheel at a relatively high speed for dressing.

A third relay |85 having a coil |86 controls the generator driving motor |42 and coolant pump motor |43 which are connected in parallel. Lines |81 and |88 supply the primary oi transformer 2|0. The transformer secondary 2| supplies rectifier 220 in the variable voltage drive circuit for control wheel 35.

` Operation In order to start the machine, the operator presses master start button |53. This energizes coil |90 of relay |9| to close said relay and direct current to selector switch |10. Said relay also establishes a holding circuit for coil |90. With contact |1| of' said selector switch closed, coil |80 would be energized thru line 200 to close relay ber 45.

|19 and start the oil pump motor |3|.

The first operation is to set up the machine.

For this operation the only motor which might be needed would be the oil pump motor` |3|. By

4closing contact |1| of selector switch |10, current is directed thru line 200 to energize coil of relay |19 which closes the circuit to oil pump motor 3|. The control wheel 35 may then be adjusted toward the grinding wheel I5 by turning rhand wheel 88 until said wheel is in position for a Work piece of the desired size. This isv determined by adjusting wheel 35 until the work piece has moved up the inclined surface of bar s0 that the center of the work is in the desired position relative to the center of the wheel.

This position may be above or below the centers of wheels l5 and 35 depending on the kind of work to be ground. Work supporting bar may be raised or lowered when necessary by any suitable adjusting means. The desired angle of skew may be obtained at this time by turning screw 11 until said angle is indicated on graduated sleeve 80. If it is desired to grind a tapered work piece, wheel 35 may be so ad-v justed by turning screw 48 until the desired taper is indicated on a graduated plate 4| on mem- Grinding wheel i5 is then shifted forward by hand wheel 25 until it engages a gauge or master work piece at which point ring 3| is clamped to hand wheel 25 by means of clamping bolt 30 and the feed may be effected by moving handle 23 which is mounted in said ring. The extent of movement of said handle in both directions is limited by positive stops.

It is desirable that the wheels |5 and 35 be properly dressed before beginning a grinding operation. For this operation,y the selector switch |10 is turned to the dress position. In this position contacts |12 and |13 are both closed. Contact 1| actuates relays |15 and |35 to operate wheel motor |40, and generator drive motor |42 and coolant pump motor |43. Contact |13 actuates relay |19 to start oil pump motor III. Operation of relay |19 opens the contact |0| to thus open the circuit thru rheostat |52 thus removing said rheostat from the circuit of generator field Said rheostat controls the grinding speed of control wheel 35. At the same time, contact |18 is closed inserting resistor |56 in motor field circuit |55. Said resistor |55 is adjusted to cause said motor to run at a relatively high speed suitable for dressing.

Assuming that the wheel 35 has already been tilted to the desired angle of skew, a gauge or finished work piece, while resting on bar is rubbed against the stationary wheel 35 leaving a mark thereon. Said wheel is then withdrawn as described above` to a position in line with diamond |2I. Said diamond is raised or lowered to the mark on the wheel and reversing valve |48 isshifted to direct fluid to the head end of cylinder 50. The wheel is thus caused to traverse past the diamond |2| with said diamond following the path of travel of the work thereon. Valve |48 is reversed and iiuid directed to the rod end of cylinder 50 to return wheel 35 to its original position.

If wheel 35 has been thrown out of alignment with grinding wheel |5 by the skewing adjustment, this condition may be corrected by loosening lock nut 54 and turning shaft 52 in nut 53 by inserting a wrench in the hollow hexagonal head 54. By this means base 35 may be shifted to place wheel 35 in alignment with grinding wheel I5.

Diamond |02 is always in alignment with the surface of grinding wheel i5. This alignment is maintained of course by periodical adjustment of knob |08. Traverse of the diamond |02 across wheel i5 is initiated by shifting valve |4| to direct fluid under pressure to the head end of cylinder |05. Said diamond then makes a pass across the wheel l5 and is returned to starting position by shifting valve |4| in the opposite direction.

With the dressing and set up operations completed the operator is ready to begin a grinding operation. The selector switch is turned to the position marked grind. In order to clarify the functions of the selector switch they may be listed as follows:

Set up-Oil pump motor only.

Dress-Oil pump, wheel and coolant motor and control Wheel.

Grind-Wheel and coolant motors only and control wheel.

Thus in the grinding position contactor |14 is closed to direct current thru line |95 to actuate relay |15 for the grinding wheel motor |40 and thru line |91 to actuate relay |85 for coolant pump motor |43 and generator motor |42 to control wheel motor 31.

For thru feed work the grinding wheel is shifted forward to provide a grinding throat of the desired size, assuming of course that the control wheel has been tilted to the desired angle and the work supporting bar adjusted to the desired height. A work piece i2 may be inserted manually in the grinding throat or may be fed thereto by any suitable loading device. Said work is caused to move axially by 8 the control wheel 35 while being ground by the grinding wheel |5.

For plunge cut grinding the work is placed in the grinding throat either manually or by some sort of loading device. The grinding wheel Il is moved forward by means of lever 20 or by some suitable power means. The forward movement of said grinding wheel continues to a predetermined position determined by the limit of movement of handle 25 at which point the work should be ground to size. The grinding wheel Il is then backed oil' and the work |2 removed from the grinding throat.

We claim:

1. A center-less grinding machine comprising e grinding wheel and a control wheel, a support for said control wheel, a pair of guide surfaces on said support for movement thereof toward and from said grinding wheel, means for effecting said movement, one of said guide surfaces being curved about an axis parallel with said direction of movement and means for tilting said control wheel support on said curved surface away from a vertical position. r

2. A grinding machine having a bed, a wheel support thereon movable toward and from s work piece, said support having two guide members, one having a flat surface, the other having a surface curved transversely of the direction of movement of said support, said nrst member consisting of a separate slide and an adjustable connection between said slide and said support.

3. A grinding machine having a bed, a grinding wheel and a control wheel having opposed peripheral faces, one of said wheels being movable toward the other for a grinding feed, a work rest for supporting a work piece in operative relation to said peripheral faces, a dressing tool mounted on said work rest and means for eifecting a traversing movement of said control wheel past said tool.

4. A grinding machine having a bed, s grinding wheel and a control wheel having opposed peripheral faces, one of said wheels being movable toward the other for a grinding feed, a work reet for supporting a work piece in operative relation to said peripheral faces, a dressing tool mounted on said work rest, means for effecting a relative traversing movement between said control wheel and said tool and means to prevent said traversing movement when said wheel is in forward or grinding position.

5. A grinding machine having a bed, a grinding wheel and a control wheel having opposed peripheral faces, one of said wheels being movable toward the other for a grinding feed, work guides for directing a work piece into operative relation to said peripheral faces, a dressing tool mounted on one of said guides and means for effecting s traversing movement of said control wheel past said dressing tool.

6. A grinding machine having a bed, a grinding wheel and a control wheel having opposed peripheral faces, one of said wheels being movable toward the other for a grinding feed, a work rest for supporting a work piece in operative relation to said peripheral faces, a dressing tool mounted in a fixed position on said machine in the same plane as the axis of the work, means for tilting said control wheel so that it causes the work to move axially across the face of the grinding wheel, and means for effecting a traversing movement of said control wheel past said dressing tool whereby to dress said wheel along the/path of travel of the work. f

'7. A grinding machine having opposed grinding and control wheels, ysupports for said wheels, means for mounting one of said supports for movement toward and from the other, means for effecting angular adjustment of one of said supports in both a vertical and horizontal plane, said support being slidably mo-unted for a traversing movement, a dressing tool and ymeans for effecting said movement past said dressing tool in any position of angular adjustment.

8. A grinding machine comprising a bed, a swivel table mounted thereon, for angular adjustment relative thereto, a carriage slidably mounted on said table for a traversing movement thereon a wheel base slidably mounted on said carriage for movement transversely relative thereto, spaced guide surfaces on said wheel base, mating f guide surfaces on said carriage, one of said guides being cylindrical in shape and means for tilting said base on said cylindrical guides.A

9. A grinding machine having opposed grinding and control wheels, supports for said wheels,

. means actuated by fluid under pressure for effecting a traversing movement of one of said wheels and means for adjusting said wheel in an axial direction relative to saidother wheel.

10. A grinding machine comprising a bed, a grinding wheel support,4 a grinding wheel rotatably mounted thereon, a second wheel support, a control wheel rotatably mounted thereon and peripherally opposed to said grinding wheel, said control wheel base having two guide surfaces for movement toward and from the grinding wheel, one of which is curved about/an axis extending transversely of the control wheel axis for movement toward and from the grinding wheel, means for tilting said support on said curved guide surface and means for effecting relative axial movement between said wheels to bring them into proper alignment after tilting.

l1. A grinding machine having a bed, a grinding wheel and a control wheel having opposed peripheral faces, one of said wheels being movable toward the other for a grinding feed, a work rest for supporting a. work piece in operative relation to said peripheral faces, a dressing tool,

lmeans for effecting a relativer traversingmover ment between said tool .and onez'oi ysaid wheels, means for driving said wheel at a speed suitable for grinding and also at a speed suitable for dressing, and a common control means for said wheel speed and said traversing means.

l2. A grinding machine having a bed, a grinding wheel and a control wheel having opposed peripheral faces, one of said wheels being movable toward the other for a grinding feed, a work rest for supporting a work piece in operative relation to said peripheral faces, a dressing tool, means for effecting a relative traversing movement between said tool and an abrasive wheel including a hydraulic motor, a pump for supplying uid under pressure to said motor, means for driving said wheel at speeds suitable for grinding and also at a speed suitable for dressing and a common control means for said wheel speed and said fluid under pressure.

13. A grinding machine comprising a bed, a grinding wheel and a control wheel rotatably mounted thereon, a work rest between said wheels.

means for effecting axial, transverse and angular adjustment of one of said wheels relative to the other, hydraulic means for effecting one ofy ing the speed of one of said motors for dressing 10 or grinding and means for selectively controlling said motors for each of the conditions of set up, dress and grind.

14. A grinding machine comprising a bed, a

swivel table mounted thereon, for angular adjustrnent relative thereto, a carriage slidably mounted on said table for a traversing movement thereon a wheel base slidably mounted on saidr carriage for movement transversely relative thereto, spaced guide surfaces on said wheel base, mating guide surfaces on said carriage, one of said guides being cylindrical in shape and means for tilting said base on said cylindrical guides, means for driving said wheel including a motor, driving belts connecting said motor and said wheel, said motor being mounted on said wheel base and tiltable therewith.

15. A grinding machine comprising a bed. a Wheel base slidably mounted on said bed, an abrasive wheel rotatably mounted on said'base, said wheel base having spaced supporting surfaces, one disposed substantially beneath said wheel and being curved transversely of the direction of movement of said base, the other. at'the opposite side of said base and comprising a slidable member separate from said base and means for raising and lowering one end of said base relative to said second support member,

16. A grinding machine comprising a supporting member, a wheel base, an abrasive wheel rotatably mounted on said base, means disposed substantially beneath the abrasive wheel for supporting said wheel base on said supporting member so that the wheel base may be tilted in a plane substantially parallel with the axis of the abrasive wheel, and supporting devices located at'one side of said supporting means for supporting said wheel base on said support member, said supporting devices including an adjustable means whereby said wheel base may be positively tilted to different set angular positions.

17. vA grinding machine comprising a supporting member, a' wheel base, an abrasive wheel rotatably mounted on said base, means disposed substantially beneath the abrasive wheel for supporting said wheel base on said supporting memxber so that the wheel base may be tilted in a abrasive wheel, and supporting devices located at one side of said supporting means for supporting said wheel base on said support member, said devices including a curved portion on said base and a flat member independent of said base and spaced from said curved portion.

18. A grinding machine having abed, a grinding wheel and a control wheel having opposed peripheral faces, one of said wheels being movable toward the other for a grinding feed, a work rest for supporting a work piece in operative relation to ksaid peripheral faces, a dressing tool, hydraulic means for effecting a relative traversing movement between said tool and one of said wheels including a motor driven pump, means including a motor for driving said wheel at a speed suitable for grinding and also at a speed suitable for dressing, and common control means for said motors for changing said wheel speed when said traversing movement is initiated.

19. A centerless grinding machine comprising a bed, wheel supports mounted on said bed, a grinding wheel rotatably mounted on one oi.' said supports, a control wheel mounted on the other of said supports, means for driving said control wheel including a variable voltage drive mechanism consisting of a motor and generator in a loop circuit, said control wheel and motor being Y `,subject to an overhauling load, said loop circuit including a generator series field winding which in response to said overhauling load would normally reduce the motor field strength and cause increased motor speed, and a separate source of current for supplementing the output of the generator for energizing said fields whereby to cause said motor to maintain a uniform control wheel speed and to resist an increase in said speed.

20. A centerless grinding machine comprising a bed, wheel supports mounted on said bed, a grinding wheel rotatably mounted on one of said supports, a control wheel mounted on the other of said supports, means for driving said control wheel including a variable voltage drive mechanism consisting of a motor and generator in a loop circuit, said control wheel and motor being subject to an overhauling load, said loop circuit including a generator series field winding which in response tc said overhauling load would normally reduce the motor eld strength and cause increased motor speed, said overhauling load causing said motor to function as a generator, a device for preventing passage thru said nelds of a current in the direction of that generated by said motor and thus to counteract the effect of said overhauling load on said control wheel.

21. A grinding machine having opposed grinding and control wheels, supports for said wheels, means for mounting one of said supports for movement toward and from the other, means for effecting angular adjustment of one of said sup- 12 ports in a horizontal plane, said support being slidably mounted for a traversing movement, s dressing tool and means for effecting said traversing movement past said dressing tool in any position of angular adjustment while maintaining a fixed angular relation between the wheel axis and the direction of traverse.

HAROLD E. BAIBIGER.. JOHN A BOLLER.

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

UNITED STATES PATENTS Number Name Date 2,184,011 Flanders Dec. i9. 1939 1,882,814 Haas Oct. 18, 1932 1,887,154 Guild et al. Nov. 8. 1982 1,483,748 Sanford Feb. 12, 1924 1,733,087 Heim Oct. 22, 1929 1,733,090 Holmes Oct. 22, 1929 1,733,092 Einstein Oct. 22, 1929 1,842,375 Einstein Jan. 28, 1932 1,892,453 Fuller Dec. 27, 1932 1,938,757 Einstein et al. Dec. 12, 1933 1,978,279 Ogilvie Oct. 23, 1934 2,210,137 Bergstrom Aug. 6, 1940 FOREIGN PA'I'ENTB Number Country Date 526,998 German June 12, 1931 549,128 German Apr. 23, 1982 851,895 German Oct. 21, 1937

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