US1909953A - Grinding machine - Google Patents

Description

May 23, 1933. I Q R. A. HEALD 1,909,953

GRINDING MACHINE Filed April 29, 1932 gmntoe I ucsma flEHEald Patented May 23, 1933 UNITED STATES.

PATENT OFFICE 3101mm) A. new), or woncnsrnn. MASSACHUSETTS, AssIeNoa r m awn MACHINE COMPANY, or woacEsrnn,.uAssAcnUsErrs, A conroaA'rIoN or Ime- BACHUSETTS GRINDING MACHINE Application filed April 29, 1982. Serial No. 608,201.

' The present invention relates to grinding machines and particularly to armechamsm for procuring a dressing operation on thedressing mechanism is entirely satisfactory on the usual grade of grinding wheels, as the dressing tool is appreciably harder than the wheel and is not destroyed by the rotation of said wheel past said tool. However, in the harder type of wheels as, for example, a grinding wheel consisting of diamond particles, tungsten carbide, or other very hard materials bonded together, the usual dressing tool is inefi'ecti've since the wheel formed of i these hard materials is as hard as, orharder than, the dressing tool and thelatter 1s cut and destroyed without procuring any appreciable dressing action on the wheel.

The only satisfactory method for the dressing of grinding wheels formed of these hard materials is to subject them to the action of a rotating dressing wheel of a similar hard material, and, by relative movement of the the dressing action on the slower moving surfaces of the dressing wheel and the grinding wheel being dressed, the latter is reduced to the desired. size and a suitable smooth cutting surface is established. In this dressing operation, the faster moving wheel procures wheel and accordingly, in the use of a rotating dressing wheel for dressing a rotating grinding wheel of equally hard material, the

dressing wheel must be moving at a relatively faster surface speed than the wheel being cut or dressed. It is accordingly one of the objects of the present inventiorrtaprovide for dressing a grinding wheel with a rotating dressing tool by driving the grinding wheel at a sloyv rate of speed-relative to the dressing wheel as said grinding wheel is brought into engagement with the dressing wheel.

While the grinding wheel is operating upon a workpiece to be ground, the surface speed ofthe wheel must be relatively high in order to procure a proper cutting action and to leave a smooth finished surface on the workpiece, and, if an attempt were made to dress said grinding wheel while-it is moving at the high rate of surface speed for a cutting operation, it would be necessary to drive the dressing wheel at an excessive rate of speed in order that the surface speed of the dressing wheel should be substantially greater than the surface speed of the grinding wheel. It is accordingly a further object of the present invention to provide for diminish ing the normal cutting rate of speed of a grmding' wheel when the latter is moved into o ipraltive relation to a rotating dressing w ee Other and further objects and advantages- Fig. 1.

' ike reference characters refer tolike parts in the different figures.v

Referring to Fig. 1, the grinding machine illustrated rovides a reciprocatory table or carriage 1 y movement of which, on longitudinal slide-ways, not shown, on the base of the machine, a grinding traverse betwee the grinding wheel and workpiece ispr cured. The Igrinding wheel spindle 2 is suit.

ably journa ed in-a. wheelhead 3 which is mounted on a cross-slides: carried by the table 1, said cross-slide providing for a transverse feeding movement between the ing wheel and the workpiece.- A wor ead 5 is carried on a bridge 6 which spans the slide-ways provided for the movements of the table 1.

In the construction shown, the grinding mounted against rotat1on on the forward end of a shaft 8, journaled in the base of the machine. Said shaft carries a pinion, not shown, which engages with a rack mountl ed on the under side of the table 1, to procure longitudinal movement of said table in response to rotation of said pilot wheel.

The crossfeed movement of the grinding wheel is procured by rotation of a threaded crossfeed shaft 11, which is, journaled in hearings in the table 1, and engages with a threaded nut, not shown, on the under side of the cross-slide 4. The forward end of the crossfeed shaft has secured thereto a ratchet wheel 12 which is actuated by a pawl 13, the latter carried on one end of a lever 14 pivotally mounted on the table 1. Rocking movement of the lever 14 procures a step-by-step rotation of the crossfeed shaft in response to movement of the. grinding wheel over thesurface of the workpiece and ing journaled on anti-friction bearin accordingly movement of the grinding wheelhead 3 transversely of the machine. A cam 15 is adjustably mounted on a horizontal bracket 16 extending from the bridge 6, and a roller 17 on the end of the lever 14 engages with and is depressed by said. cam 15, thereby elevating the pawl 13 to turn the ratchet wheel, said cam being positionedto engage said roller in response to the maprocatlons of the grinding wheel over the surface of the workpiece. A hand wheel ,18 is also mounted on the end of the crossfeed shaft 11 for procuring movement of the crossslide manually, when desired.

The grinding wheel 20 on the end of the spindle 2 is driven by an electric motor 21 I mounted on the cross-slide 4, said motor havin a pulley 22 connected by a belt 23 to a pu ley,24,-Fig. 2, journaled on anti-friction bearings 25 on a shaft 26 supported by a lug 26a on the cross-slide 4. Said pulley provides-a conical clutch face 27 which cooperates with a similarly-shaped conical clutch face 28 on a pulley 30, the latter beon the shaft 26 and being slidable longitudi- -nally of said shaft for se aration of said clutch faces 27 and 28. spring 32 surrounding the shaft 26 normally urges the pulley 30 to the right toward the pulley 24 to bring said clutch faces into engagement to procure rotation of the pulleys 24 and 30 as a unit. The pulley 30 is connected by a belt 33 to a pulley 34 on tht end of the grinding wheel spindle 2, and the pulleys are of proper size so thatthe grinding wheel 20 is normally rotated directly from the motor 21 through the pulleys 24 and 30 'at the high rate of speed desirable for a cuttin action.

The ing wheel is dressed by moving saidv wheel over the surface of a rotating latter being pivotally mounted on a bracket 37 secured to the base of the machine. The

dressing wheel 35 is properly positioned relative to the grinding wheel by a stop 38 on the dressing wheel 35 carried by an arm 36, the

bracket 37 which engages the arm 36 when the latter is in the operative position shown in full lines in Fig. 3, at whlch time the dressing wheel 35 is in position to engage the.

carries a roller 40 which engages a cam 41 secured to the table 2, said cam raising the arm 36 into the inoperative position shown in dotted lines in Fig. 3 as the grinding wheel 2 is moved from the dressing position of Fig. 1 into operative relation to the workpiece by movement of the table 1. The dress.-

ing wheel is maintained in inoperative position by engagement between cooperating surfaces 42 and 43 on the arm 36 and the bracket 37 respectively. Rotation of the dressing,

wheel 35 is procured by an electric motor 44 carried by the upper 'end of the arm 36, said dressing wheel35 being secured to the end of the drive shaft 45 of said motor 44.

As above stated, the grinding. wheel 20, which is normally rotated at. a rapid rateof speed by the motor 21, is slowed down substantially as said grinding wheel 20 approaches the dressing wheel 35 in order that f the surface speed of the grinding wheel shall i be less than the surface speed of the dressing wheel, the latter being driven at a constant speed by the motor 44. Referring now to Fig.2, the cross-slide 4 provides integral ex-' tensions 46 and 47 which provide ' alined bores 48 and 50 through which a shaft 51 extends, the latter being parallel-to the slide-ways on which the table 1 is mounted. Said shaft 51 carries a small conical faced pulley 52 which is positioned to engage with'a corresponding conical surface 53 on the pulley-'30, and a larger conical faced pulley 54 which is arranged to engage with a conical surface 55 on the pulley 24, both said conical faced pulleys 52 and 54 being secured against rotation and also against axial sliding movement on the shaft 51. The extension 47 carries a stud 56 on which an arm 57 is pivotally mounted, said arm providing opposed flat surfaces 58 and 60, the former being in aline-' ment with and engaging therighthand end of'the shaft 51. The end of the arm 57 provides a handle 61 by which said arm is manually operated, and in order to reduce the speed of rotation of the grinding wheel 20, the

handle 61 is moved toward the left, thereby shifting the shaft 51 carrying the conical faced pulleys 52 and 54 to the left. As the shaft 51 to the left first brings the pulley 52 into engagement with the surface '53 on the pulley 30 and in response to further movement of said'shaft 51 the pulley 54 is brought into engagement with the conical surface 55. Said further movement of the shaft 51, which brings the pulley 54 against the surface 55, procures separation of the pulley 30 from the pulley24, said pulley 30'moving to the left axiall on the shaft 26 against the spring 32 to with raw the clutch face 27 from the clutch face 28 so that rotation of the grinding wheel 20 is then procured indirectly through rotation' of the shaft 51 as a countershaft. The pulley-24'drives the pulley 54 to turn the shaft 51, thereby rotating the pulley 52 and accordingly rocuring rotation of the pulley 30 1 and thus t e grinding wheel 20. v The relative sizes of the pulleys are such that this change in the drive of the grinding wheel materially reduces the surface speed of the grinding wheel until it is substantially slower than the surface speed of the dressing wheel.

The reduction in speed of the grinding 30 @wheel may be procured automatically as the grinding wheel is brought into operative relation to the dressing wheel. Referring again to Fig.2, the base of the machine has a bracket 62 extendingupwardly therefrom, said bracket carrying adjacent its upper end a member 63 having a bore 64 therethrough in alinement with the shaft 51. Saidbore receives a cylindrical member 65 having a projecting end 66 which engages the flat surface 40 60 on thearm 57 'A-spring 67 within the bore 64 is positioned between the right hand end of the cylindrical member 65 and a cap 68 for the end of said bore, thereby normally urging the member 65 toward the left.

As the grinding wheel is now moved toward the right by rotation of the pilot wheel 7 to bring said grinding wheel into dressin position, the projecting end 66 of the cylin rical member65 engages the flat surface 60 of the arm 57, thereby rocking said arm to the left and procuring axial shifting movement of the shaft 51 to reduce the rate of rotation of the grinding wheel in the manner above ointed out. As the spring 67 is substantially eavier than the spring 32, the pulleys 24 and 30 are spaced apart before the spring 67 is compressed, during the right hand movement of the table 1, said separation taking lace before the grinding wheel is in oppose relation to the dressing wheel. During the dressing operation, the grinding wheel 20 is manually reciprocated over the surface of the dressing 7 wheel, which. reci rocation procures compression of the s ring 67, said spring, while 65 said wheels. are in engagement, maintaining are in driving engagement, movement of the the shaft 51. in the relative position shown,

with the pulleys 24 and 30 dlsengaged.

From the foregoing, it will be apparent that-the rate of rotation of the grinding wheel is materially reduced as it is moved into operative relation to the dressing tool in response I to movement of the carriage carrying sald grinding wheel, v1n order to procure a dress- 1 ing operation on said grinding wheel. It 7'5.

will be further noted that the reduced speed of the grinding wheel remains constant dur- 1 ing reclprocation of the grinding wheel over .the surface of the dressing tool, and, as the I grinding wheel is moved away from the dressing tool, the normal speed of said. grinding wheel is automatically restored. The normal high rate of speed of the grinding wheel,

during the grinding operation on a workpiece, not shown, carried by a workholding member journaled in the workhead 5, is thus reduced as the table is moved to withdraw said wheel from the workpiece and to bring said grinding wheel into engagement with i the dressing wheel.

I claim, p 1. In a' grinding machine, a rotary rinding member and aworkholding mem er, a

carriage on which one of said members ismounted, means for driving said grinding member at a rapid rate of speed during a cutting operation on a workpiece 1n' the workholding member, and means for varying the rate of rotation of said grinding member in response to movement of said carriage.

2. In a grinding machine, a rotary rinding member, means to procure a trans atorymovement of the grinding member, and means responsive to the translatory move.- ment-for varying the rate of rotation of said grinding member.

3. In a device of thecharacter described, a grinding wheel and a dressing tool, means to move said grinding wheel into contact with said dressing tool to procure a dressing operation on said wheel, and means, automatically operative-t0 reduce the speed of rotation of said grinding wheel as thelatter isbrought into c'ontact with the dressing tool.

4. Ina device of the character described, a grinding wheel and a dressing tool, means to move said grinding wheel intocontact with said dressing toolto procure a dressingoperation on said wheel, means for driving said 7 grinding wheel at a-predetermined rate of said wheel, means .for driving said dressing tool' at a predetermined rate of speed, means for rotating the grinding wheel. at a predetermined rate of speed, and means automati:

cally operative to varythe relative speeds tive position relative to said dressin of rotation of the grinding wheel and the dressing tool as the latter is brought into contact with the grinding wheel.

6. In a grinding machine, a grinding wheel and a dressing Wheel, a carriage on which one of said wheels is mounted to procure a relative movement of said wheels, means for driving said grinding wheel at a predetermined rate of speed, and means for substantially varying the speed of rotation of said wheel as t e latter is moved into operative position relative to the dressing tool.

7. In a grinding machine, a grinding wheel member and a workholding member, a carriage on which one of said members is mounted, means to procure a rapid rate of rotation of said grinding wheel when the latter is in operative relation to a workpiece in said workholding member, a dressing tool spaced from said workholding member, means to withdraw said grinding wheel from the workpiece to move said grinding wheel into operaitoo and means responsive to said with rawal movement to materially reduce the speed of rotation of said grinding wheel.

8. In a grinding machine, a grinding wheel member and a workholding member,

a carriage on which one of said memthe speed of rotation of said grinding wheel,

said means maintaining the reduced speed during the reciprocation of the grinding wheel over the surface of the dressing tool.

9. In a grinding machine, a rotar grinding wheel, a rotary dressing whee means for driving said dressing wheel at a predetermined rate of speed, means for procuring .a translatory movement of said grinding wheel to move the latter into operative engagement with the dressing wheel and to protranslatory movement of said grinding wheel to move the latter into operative engagement with the dressing wheel and to procure a reciprocatory .movement of said grinding Wheel over the surface of said dressing wheel, and means responsive to said translatory movement materially to vary the speed of rotation of the grinding wheel relative to the rotation of the dressing wheel, whereby the surface speed of the grindin wheel is substantially slower than the sur ace speed of the dressing wheel, said speed varying means maintaining the rotation of said grinding wheel constant during the reciprocation of said wheel over the surface of the dressing wheel.

11. In a device of the character described, a rotary spindle having a pulley thereon, a drivin motor having a pulley thereon, a pair 0 cooperating pulleys having cooperating clutch faces normally in operative engagement, one of said pulleys being axially movable relative to the other'to withdraw said clutch faces from operative engagement,

belts connecting saidpair of pulleys respectively to said motor pulley and said spindle pulley, and means for spacing said pair of pulleys apart to withdraw said clutch faces from operative engagement and for establishing a positive drive between said pair of pulleys, whereby the latter are rotated relatively to one another, thereby to vary the speed of rotation of said spindle.

12. In a grinding machine, a rotarygrinding member, a dressing member, means to procure a translatory movement of one of said members for a relative movement of the grinding member into operative relation to the dressing member, and means responsive to the translatory movement for varying the rate of rotation of said grinding member.

13. In a device of the character described,

a grinding wheel and a dressing tool, means to procure a relative movement between said wheel and tool for contact of said wheel with said tool to procure adressing operation on said wheel, and means automatically operative to reduce the speed of rotation of said grinding wheel as the latter is brought into contact with the dressing tool.

" RICHARD A. HEALD.

substantially slower than the surface speed of the dressing wheel.

10. In a grinding machine, a rotary grinding wheel, a rotary dressing wheel, means for driving said dressing wheel at a predetermined rate of speed, means for procuring a

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