US2119296A - Grinding machine - Google Patents

Description

May 31, 1938. w. D. SCHMIDT 2,119,295

GRINDING MACHINE Filed Jan. 15, 1937 4 Sheets-Sheet 1 I I l May 31, 1938. w. D. SCHMIDT GRINDING MACHINE Filed Jan. 13, 1937 4 Sheets-Sheet 2 WEZZaq/ra 6km I May 31, 1938. .w. D". SZHMlDT '7 2,119,295

GRINDING MACHINES Filed Jan. 13, 1957 4 Sheets-Sheet 3 May 31, 1.938. w. D. SCHMIDT GRINDING MACHINE Filed Jan. 13, 1957 4 Sheets-Sheet 4 Patented May 31,. 1938 lJNlTE oaiuomc MACHHNE William E). Schmidt, Worcester, Mass" assignor to The Hcald hine (Jompany, Worcester, Mass, a corporation of Massachusetts Application January 13,1937, Serial No. 120,4M

liil Claims.

The present invention relates to grinding machines and particularlyto a machine in which the relative crossfeed movement between the wheel and workpiece may occur at a rapid rate until the grinding wheel engages the workpiece.

In grinding machines operating upon cylindrical or tapered surfaces, the grinding wheel is normally given a crossfeed movementrelative to the workpiece to bring the wheel and workpiece into grinding contacts, and thereafter to procure successively deeper and deeper cuts in the work'- piece until the latter reaches the desired finished size.

In internal grinding machines, it is essential that the workpiece and the grinding wheel at the beginning of the grinding operation be positioned transversely of the machine relative to each other, so that the grinding wheel may enter the bore of the workpiece when either the wheel or the workpiece is given an axial movement. The

wheel is subsequently moved transversely to bring the grinding wheel and workpiece into grinding contact, and for reducing theinoperative time of each grinding operation, this crossfeed movement must'take place as rapidly as possible. One of the principal objects of the present invention is to provide for a rapid cross-v feed movement with a provision for reducing the rate of crossieed movement immediately upon engagement between the wheel and workpiece independently of the unfinished size of the workpiece.

In a copending application filed by Schmidt and Blood, Serial No. 68,291, filed March 11, 1936,

" is disclosed a structure by which the rate of crossfeed movement is reduced upon engagement between the wheel and the workpiece, and this structure incorporates a grinding wheel which is a conductor of electricity and forms part of a. circuit which is closed upon engagement between the wheel and the workpiece. This arrangement is entirely satisfactory in operation, but there are occasions when such an arrangement is not desirable, either by reason of the type of workpiece, the latter not being a conductor, or where the coolant forms such an insulation that a suitable electrical contact between the wheel and workpiece cannot be eflected. A further object of the present invention is to provide for the reduction in the rate of crossieed movement without the necessity for having a wheel or a workpiece which is an electrical conductor.

lihe present invention accordingly incorporates an alternative mechanism for accomplishing the same result as in the dchmidt and Blood application above referred to. In the present invention, the rate of crossfeed movement, or other change in the grinding operation, is procured in response to a slight lateral movement of the workhead on its supporting structure resulting from engagement between the wheel and workpiece. Only a very small amount of lateral movement is necessary, and the arrangement is such that the change in the operation occurs immediately upon engagement of the workpiece by the grinding wheel.

Other and further objects and advantages of the invention will more fully appear from the following detailed description, taken in connection with the accompanying drawings, in which- Fig. 1 is a frontelevation of a machine embodying the invention.

Fig. 2 is a plan view of the machine of Fig. i.

Fig. 3 is a vertical section substantially along the line 3-t of Fig. 2.

Fig. 4 is a vertical section substantially along the line 4-4 of Fig. 3, with parts broken away to show the crossfeed mechanism more clearly.

Fig. 5 is an end elevation partly in section of a part of the crossfeed mechanism.

Fig. 6 is a fluid pressure diagram.

Fig. 7 is a wiring diagram.

Like reference characters refer to like parts in the different figures.

Referring first to Fig. 1, the machine has the usual reciprocatory table i provided in an internal grinding machine; either the grinding wheel or the workpiece to be ground is carried on said table, the reciprocations of the latter operating in either case to produce a relative translatory movement between the wheel and the workpiece. In the construction shown, the table supports and carries a work head 2 and the wheelhead 3, Figs. 2 and 5, is mounted on a bridge t which spans the guideways t, Fig. 3, provided by the base 6 of the machine for the movements of the table i. The grinding wheel i is carried on a spindle t journalled in the-wheelhead t, and is suitably rotated at a high rate of speed by any well known mechanism, which, in the present instance, consists of a motor, not shown, in the base of the machine, connected by a belt, also not shown, to a pulley t on the spindle.

The workpiece 11, Figs. 1 and 2, is mounted in a suitable work-supporting structure which may be in the form oi a chuck it carried one. spindle ii journalled in the workhead. The chuck is preferably driven at a relatively slow rate of speed from a motor it connected to the spindle M by a belt it. The clutch mechanism M, of

any well known construction, provides for stopping the rotation of the chuck without interference with the operation of the motor l2. The clutch mechanism is under the control of a handle l5 easily accessible to the operator of the machine.

The reciprocations of the table i to cause the desired relative traverse between the rotating grinding wheel and the work-supporting structure are imparted in any well known manner, as by the use of fluid pressure controlling and reversing mechanism, one type of which is described in the Blood and Burns Patent No. 2,011,705, dated August '20, 1935. It is suificient to note for the purpose of the present application that reversal of the table is procured at each end of the normal working stroke by spaced reversing dogs i6 and I1, which are carried by blocks 88 and i9 adjustably mounted on the front of the table i and adapted alternately to engage and move a reversing lever 26. The reversing lever is connected by suitable mechanism to a reversing valve 2|, Fig. 6. The reversing lever 20 during the grinding operation, when the grinding wheel is within the bore of the workpiece, is so located as to be engaged alternately by the reversing dogs.

Referring now to Fig. 6, the pump 22, driven by a motor 23, directs fluid under pressure from a tank 24 through a pipe 25 to a casing 26 in which the reversing valve 2| is positioned. The casing 26 has an inlet port 21 to which the pipe 25 is connected, and also has spaced outlet ports 28 and 29 connected by pipes 30 and 3|, respectively, to the left and right hand ends of a cylinder 32 mounted in the base of the machine. A piston 33, slidable in the cylinder. has a piston rod 34 connected to a depending lug 35 on the table I. The reversing valve alternately directs fluid under pressure from the inlet port 21 to the outlet ports 28 and 29 and, at the same time, connects the opposite outlet port to an exhaust port 36 suitably connected to the tank.

The crossfeed movement between the workpiece and the grinding wheel is obtained by transverse movement of the wheelhead 3 on the bridge 4. Movementof the cross-slide 31, Fig. 3, on which the wheelhead is mounted, is effected by rotation of the crossfeed screw 38, which is held against endwise movement by antifriction bearings 39 engageable with the rearward end thereof. The crossfeed screw engages an internally threaded portion 40 of the crossslide for effecting the transverse movement thereof. On the forward end of the crossfeed screw 33 is mounted a gear 4i which meshes with a pinion 42 secured against turning movement on a shaft 43 journalled in a housing 44 for the cross-feed mechanism. Also secured to the shaft 43 in spaced relation to the gear 42 is a ratchet wheel 45 engageable by spaced oppositely direct ed pawls 46 and 41, Fig. 4, carried by an annular member 48 secured against turning movement on a sleeve 49 journalled on the shaft 43. The sleeve 49 has an integral pinion 50 engageable bya rack 5| horizontally slidable in the casing 44, said rack being held in engagement with the pinion by a bearing 52. The rack 51 is shifted by a fluid pressure mechanism, hereinafter described in detail, and procures through the pawl and ratchet arrangement a rotation of the shaft 43, and accordingly a rotation of the crossfeed screw. Manual rotation of the crossfeed screw is by a hand wheel 43' on the end of the shaft 43.

The pawl and ratchet arrangement is fully described in the Guild Patent No. 1,971,138, dated August 21, 1934. It is sufficient to note for the purpose of the present application that this double pawl arrangement permits, during the return of the crossfeed slide to original position in readiness for a subsequent grinding operation, a compensation for the reduction in size of the grinding wheel as a result of wear and the dressing operation performed thereon during the preceding grinding operation. With reference again to Figs. 3 and 4, it will be noted that both of the pawls are normally held in operative engagement with the ratchet by a spring 53, so that a rotation of the annular member 48 provides a corresponding rotation of the ratchet 45. The pawl 41 is operative during the crossfeed movement. and the pawl 46 is operative during the retraction of the crossfeed movement, the latter involving a counterclockwise rotation of the member 48. The pawl 46 is rendered inoperative during a part of the movement of the annular member 48 in the counterclockwise direction, so that the cross-slide is retracted a slightly shorter distance than it is moved during the crossfeed movement.

To effect this compensatory movement, the

shaft 43 has journalled thereon an arm 54 having a gear segment 55 on the outer end thereof. The gear segment engages with a pinion 56 on a shaft 51 journalled in the front wall of the housing 44. The outer end of the shaft 51 has a knurled knob 58 by which said shaft is turned for shifting the position of the arm 54. Integral with the arm 54 is a cam 59 in a position for engagement with a pin 60 on the pawl 46 just before the termination of the crossfeed movement. tion of the crossfeed movement, the pawl 46 is inoperative and a rotation of the annular member 48 procures no corresponding movement of the ratchet wheel until the pawl 46 is released by the cam 59. During the remainder of the counterclockwise movement of the member 48, the retraction of the crossfeed movement takes place.

Referring now to Figs. 4 and 6, the rack 5| is carried on the end of a piston rod 6|, extending from a piston 62 slidable in a horizontally positioned cylinder 63 mounted on the front of the bridge. Fluid under pressure is directed alternately to opposite ends of the cylinder 63, for procuring a crossfeed movement and the retraction thereof. As shown in Fig. 6, fluid under pressure from the pipe 25 passes through a pipe 64 to the inlet port 65 of a reversing valve casing 66 for a reversing valve 61 for the crossfeed mechanism. An outlet port 68 in the casing is connected by a pipe 69 to the left hand end of the cylinder 63, and a port 10 is connected by a pipe H and suitable valve mechanisms, hereinafter described, to the right hand end of the cylinder. An exhaust port 12 for the reversing valve casing providesfor exhaust of fluid from the end of the cylinder, and this port is suitably connected to the tank 24.

The admission of fluid to the right hand end of the cylinder 63 from the valve 61 is controlled by a horizontally slidable valve 13 positioned in a casing 14 forming part of a housing 15, Fig. 5, mounted in front of the wheelhead. The pipe II is connected to a port 16 in the casing 14 and fluid connection is normally provided between this port and an outlet port TI. by a reduced portion 18 of the valve. The port 11 is connected by a conduit 19 to the right hand end of the Thus during the first part of the retraccylinder 63. Fluid under pressure thus enters the cylinder 63 for a crossfeed movement at a maximum rate.

When the grinding wheel engages the workpiece the valve 13 is automatically shifted, by mechanism hereinafter described, for cutting oil the flow of fluid through this valve. The crossfeed movement is then under the control of a valve an, Figs. 4 and 6, positioned in a casing 8| in a block 82 mounted on the front of the bridge above the cylinder 63. The pipe II is connected by a branch conduit 83 to a channel 84 in the block 82, this channel intersecting spaced bores in the block in which a rough feed valve 85 and a fine feed valve 86 are respectively positioned. The casing M has a port 51 communicating with the valve 85 and a port til communicating with the valve 86.

Thevalve all is normally in the position shown, with a reduced portion 89 of said valve provlding fluid connection between the port and a. channel Bil in the casing M and block t2, this channel communicating with a channel at to the right hand end of the cylinder 53. Thus when fluid flowing through the valve I3 is cut off, the crossfeecl movement continues at a reduced rate as determined by the setting of the rough feed valve 85.

During the grinding operation, and subsequent to the shifting of the valve it, the valve til is automatically shifted by mechanism hereinafter described, thereby cutting off the port ti, and establishing fluid connection from the port ill, around a reduced portion M of the valve to a channel 93 intersecting the channel lid. The rate of crossfeed movement is thus further reduced and continues at an extremely slow rate as determined by the line feed valve 86.

With reference to Fig. 4, the valve all is normally held in the position shown by a coil spring 95 at the right hand end of the valve. Movement of the valve to the left beyond the position shown is limited by a plunger 95 engageable with the left hand end of the valve and positioned in a projecting lug 96 on the cylinder 63. A cap 91 on the lug limits movement of the plunger to the left. During the grinding operationa cam 98 on the member d8 engages a roller 99 on the plunger 95, thereby shifting the valve W to the right as above pointed out.

The structure above described is similar to structure already described and claimed in prior patents and pending applications and is not, of itself, the present invention.

The latter involves, in connection with the above or similar grinding machine elements, the attainment of the objects and novel features above set forth. In accordance with the present invention, the movement of the wheelhead relative to its sup porting structure; resulting from engagement be tween the wheel and a workpiece procures a change in the grinding operation, which, in the present embodiment of the invention, is a reduction in the rate of crossfeed movement.

Referring to Fig. 5, the wheelhead t is mounted for a sl ght oscillation relative to the supporting structure, and, is accordingly supported on a slide Itll, which is secured in turn to the cross-slide ti, by one or more flat springs Hill. The latter are secured to a lug Ill? on the slide and form a cantilever support for the wheelhead to which the upwardly extending ends of the springs are secured. A projecting lug Hill on the wheelhead is normally slightly spaced from the slide Hit and is moved into engagement therewith by contact between the wheel and the workpiece.

When the wheelhead is rocked counterclock- 'wise, a solenoid "it is energized, as later derocking movement by energization of the solenoid I. The armature I08 of the solenoid, which is connected to the arm I05, is also integral with the valve It for movement of the latter when the solenoid is energized.

The wheelhead 3 has aprojecting rod I09 having its free end located between two coils lid and III on a bracket II? secured to the slide IM, by which the energization of the solenoid I04! is procured. A hood I It extends over the wheelhead 3 and associated mechanism and has a heating coil lI l therein for maintaining a constant temperature therein, so that the actuating mechanism will function uniformly. A thermometer H5 may be positioned in the hood lid, if desired.

' With reference-to Fig. '7, a source of alternating current is represented by the parallel leads lid and ill to which the heating coil IM is connected by leads Md and lid. In the lead lid is positioned a thermostatically controlled switch lid for maintaining a constant temperature under the hood.

The primary winding Ill of a transformer is connected to the leads lit and Ill, and one terminal of the secondary winding I22 is connected to the opposed coils llii and III by a lead lid. The opposite terminal of the secondary winding I22 is connected by a lead I241 to one terminal of each of a pair of opposed coils I25 and lit oppositely wound on a magnetic core Ill. The opposite terminals'of these coils I25 and IE6 are connected to the terminals of the coils H0 and III by leads I28 and I29. The

' two coils lid and Ill form two arms of a Wheatlid and Ill, no voltage will be induced in a secondary winding lid on the core I21.

The winding ltll is connected by leads. Ill and IM to opposite terminals of a suitable bridge rectifier Ids of familiar construction. The other terminals of this recifier are connected by leads tilt and tilt to the coil lit of a suitable microamnieter it'll. The indicating needle lid of this micro-atnmeter is in a position to engage the conducting fluid its in a cup ltd. A source of direct current is represented by the parallel leads l ill and M2, one of which is connected to the needle EM and the other connected to the solenoid ltd. The opposite terminal of the solenoid is connected by a lead M3 to the cup ltd. When the Wheatstone bridge becomes unbalanced by rocking of the wheelhead. thereby shifting the position of the rodidd relative to the coils Md and Ill, the micro-ammeter will be energized, thereby roclring the needle I38 for closing the circuit through the solenoid are.

In the operation of the machine, a workpiece having been positioned in the worlrhead and the latter having been set in rotation, the wheel and work are brought into operative relation by shifting the reversing valve ill from the position shown, this valve movement being effected by a lever Mi l on the front of the machine, the lever being suitably connected to the reversing rate, moving the wheel laterally from the position shown in Fig. 3, into engagement with the workpiece bores. When engagement between the workpiece and grinding wheel takes place, the wheelhead is rocked counterclockwise, Fig. 5,

thereby procuring energizatlon of the solenoid IM for locking the wheelhead against further rocking movement and for shifting the valve 13 to reduce the rate of crossfeed movement. The solenoid continues to be energized during the remainder of the grinding operation.

When the workpiece is ground to the desired size the grinding operation is terminated by any suitable mechanism, which may be the controlling mechanism of the Blood and Burns Patent No. 2,011,075, above cited. In any event, the grinding operation is brought to a close by an extended movement of the table I to the left into the rest position shown. During the extended movement, a cam I45, Fig. 1, on the table, engages the projecting arm 6 of a switch .1 positioned in the lead I32 to break the circuit through the solenoid I04 in readiness for a subsequent grinding operation. 'When the solenoid is de-energized the wheelhead returns 'to the position shown, thereby restoring the position of the rod I09 to again balance the Wheatstone bridge.

During the extended movement of the table the valve 61 is also shifted into the position shown for a retraction of thecrossfeed movement. When the solenoid I04 is de-energized, the valve 13 is restored to original position allowing exhaust of fluid through this valve from the cylinder 63.

From the foregoing it will be apparent that the present invention provides a mechanism by which a change in the grinding operation is effected upon engagement between the grinding wheel and the workpiece by the arrangement shown, the change involving a reduction in the rate of crossfeed movement procured by a movement of the wheelhead relative to'the machine. By this arrangement the wheel may be moved laterally of the workpiece at a maximum rate until it comes in contact with the workpiece.

I claimf 1. In a grinding machine, a wheel supporting member having a wheel thereon, a work-supporting member having a workpiece mounted therein, means for procuring a relative movement between said members, means responsive to engagement between the wheel and the workpiece for procuring a movement of one of said members relative to the supporting structure therefor, and means responsive to said last movement for locking the movablemember against further movement relative to the supporting structure, said last means including a cam.

2. In a grinding machine, a wheel supporting member having a wheel thereon, a work-supporting member having a workpiece mounted therein, means for procuring a relative movement between said members, means responsive to engagement between the wheel and the workpiece i'or procuring a movement of one of said mem bers relative to the supporting structure therefor, and means responsive to said last movement for locking the movable member against further movement relative to the supporting structure, said last means including a cam and a solenoid for actuating said cam.

3. In a grinding machine, a wheel supporting member having a wheel thereon, a work-supporting member having a workpiece mounted therein, means for procuring a relative movement between said members, means responsive to engagement between the wheel and the workpiece for procuring a movement of one of said members relative to the supporting structure therefor, and means responsive to said last movement for locking the movable member against further movement relative to the supporting structure, said last means including a cam and a solenoid 'for actuating said cam, said solenoid being energized in response to said last movement.

4. In a grinding machine, a wheel supporting member having a wheel thereon, a work-supporting member having a workpiece mounted therein, means for procuring a relative movement between said members, means responsive to engagement between the wheel and the workpiece for procuring a movement of one of said members relative to the supporting structure therefor, means responsive to said last movement for procuring a change in the rate of relative movement between the members, and cam means simultaneously operative for locking the movable member against further movement relative to the supporting structure.

5. In a grinding machine, a wheel supporting member having a wheel thereon, a work-supporting member having a workpiece mounted therein, means for procuring a relative movement between said members, means responsive to engagement between the wheel and the workpiece for procuring a movement of one of said members relative to the supporting structure therefor, means responsive to said last movement for procuring a change in the rate of rela-. tive movement between the members, cam means simultaneously operative for locking the movable member against further movement relative to the supporting structure, and a solenoid for shifting said cam, said solenoid being actuated in response to said last movement.

6. In a grinding machine, a wheel supporting member having a wheel thereon, a work-supporting member having a workpiece mounted therein, hydraulically actuated means for procuring a relative movement between said members, means responsive to engagement between the wheel and the workpiece for procuring a movement of one of said members relative to the supporting structure therefor, valve means for controlling the hydraulically actuated means, cam means for locking the movable member against movement relative to the supporting structure, and a solenoid for actuating the cam and valve, said solenoid being energized in response to the movement of the movable member relative to the supporting structure.

'7. In a grinding machine, a wheel head having a wheel spindle journalled thereon for supporting a grinding wheel, a workhead having a workpiece mounted therein, means for procuring a relative movement between said heads, means responsive to engagement between the wheel and the workpiece for procuring a shifting movement of one of said heads relative to the supporting structure therefor, means for procuring a change in the rate of relative movement between the for unbelencine the circuit to energize the solemold in response to seicl shifting movement.

8. In o grinding machine, a wheel hesol havingn Wheel spindle :lournollecl thereon for supporting at grinding wheel, a worhheed heving a Worn- ;piece mounted therein, end menus for procuring n relstive movement between seitl heotls to bring the wheel and workpiece into entzngement, moons for supporting one of the needs for shitting movement relstive to its supporting structure in response to engagement between the Wheel rind Worirpiece, on armature carried by the shiite'ole heed for shifting movement, it coil corned by the supporting structure reletive to which the armeture is movable, ecircuit including ssicl cell, c. solenoid ncloptecl to he enereinetitiv n chnnne in the circuit resulting from movement of the craneture relntive to the coil, and means controlled by sold. solenoid for procuring; e change in the reintive movement between the beetle,

9. In a grinding machine, it wheel henti having a wheel spindle journolleci thereon tor supporting a, grinding wheel, at worltheeti hovinn e worrpiece mounted therein, hyoroiilicnllr ectuotetl means for procuring a relstive movement be tween said heaols to brine; the Wheel and Workpiece into engagement, means for supporting one of the heads for shifting movement relotive its supporting structure in response to enenee= merit between the wheel and workpiece, on terms ture carried by the shiitohle sees for shifting movement, s. coil corriecl by the supporting structure reletive tovvhichthe srmnture is movable,

e circuit incliniint said coil, a. solenoid oriented to he energized by a choose in the circuit resulting i'rom'movement of the ormoture relative to the coil, and a, valve controlled. by said solenoid ior procuring n cheese in the relstive movement between the hectic.

it. in ennning sunshine, to wheel supporting member having as Wheel thereon, n work-supportinn niemher lint/ins n workpiece monnteo'i therein,

hvtlrenlicnliy nctnetetl moons ior nrocnrlnn n relntivemovement between said members to hiring the wheel and workpiece into engagement, means noici scented to he energised by it change in the circuit resulting from movement oi the ormetnre relsitive to the coil, e valve controlled by seiti solenoid for procuring it change in the relative movement tween the memloers, snol com moons niso unrier the control of ssicl solenoid tor loching the shiiteble member escinst further move ent relative to the supporting structure.

"til D. IT.

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