US2445146A - Internal grinding machine - Google Patents

Description

July 13, 1948. A. MATHYS 2,445,146

' INTERNAL GRINDING MACHINE I Filed Jan. 15, 1945 5 Sheets-Sheet 1 July 13, 1948. M. A. MATHYS INTERNAL GRINDING MACHINE 5 Sheets-Sheet 2 Filed Jan. 15, 1945 jr'zverzfor A/Zaf/J6 y 13, 4 M. A. MATHYs 2,445,146"

INTERNAL GRINDING MACHINE .w q) 7 fiverzor R 4 -MaocA.MaZ/5 s Patented July 13, 1948 INTERNAL GRINDING MACHINE Max A. Mathys, Detroit, Mich., assignor to Ex- Cell-O Corporation, Detroit, Mich., a corporation of Michigan Application January 15, 1943, Serial No. 472,444

2 Claims. 1

The present invention relates to improvements in machine tools, and has particular reference to automatic internal grinding machines of the type disclosed in the patents to Blood et al. Nos. 2,011,705 and 2,027,627, issued, respectively, on August 20, 1935, and January 14, 1936.

In internal grinding machines of the aforesaid type, the work spindle is advanced relatively from a rest position in a rapid approach movement axially of the grinding wheel into grinding position, then is reciprocated to effect grinding of an internal surface in the workpiece, and, when the workpiece has been ground to the desired depth, is returned to the rest position. During the grinding operation, a relative progressive cross-feed is imparted to thegrinding' wheel. Axial separation of the workpiece and the grinding wheel may be efiected at an intermediate point in the grinding operation to permit wheel dressing.

Entry of the grinding wheel into the workpiece at the start of the cycle and also after dressing, and withdrawal thereof from the workpiece for dressing and again at the end of the grinding operation, presents a problem when the workpiece has an internal lip or other obstruction which the grinding wheel must pass to reaclf the range of grinding reciprocation. The primary object of the present invention is to provide an automatic internal grinding machine in which the grinding wheel is automatically retracted transaxially from the normal line. of reciprocation for each entry of the wheel into the work, and each withdrawal thereof from the work so as to avoid interference with any obstruction on the workpiece in its normal path of movement.

A more specific object is to provide a new and improved grinding machine of the foregoing character in which the reciprocatory movements, the cross-feed movements, and the retract movements between the workpiece and the grinding wheel are synchronized throughout the machine operation.

Other objects and advantages will become apparent as the description proceeds.

In the accompanying drawings,

Figure 1 is a front elevational view of a grinding machine embodying the features of my invention.

Fig. 2 is a plan view showing the relationship of the work and tool spindles.

Fig. 3 is a diagrammatic representation of the hydraulic transmission system incorporated in the machine.

Fig. 4 is a diagrammatic representation of the electrical drive and control system incorporated in the machine.

The internal grinding machine, disclosed for purposes of illustration, comprises a main base l on which a table 2 is mounted for reciprocation from a rest position at the left into a grinding position at the right. The table may support or the work to be either the grinding wheel ground. In the present instance, a work spindle 3 is mounted on the tablel, and has. a suitable chuck 4 for supporting a workpiece A. The chuck 4 is adapted to be released by a mechanism (not' fully shown) having an operatin handle 5 for the purpose of loading the rough workpiece and removing the finished workpiece.

Different kinds of workpieces having internal ribs or projections located outwardly of the surface to be ground may be machined. In the present instance, the workpiece A is shown as the outside race of a ball bearing consisting of a cylindrical sleeve 6 having a conical raceway 'I at the inner end. Due tothe conical or tapered form of the raceway 1, the spindle 3 is adjusted at an angle to the line of reciprocation as shown' in Fig. 2, and as a result the outer end of the sleeve 6 is located in the normal path of grinding reciprocation. To gain entry of the grinding wheel into position to grind the raceway 1,'it is necessary for the wheel to clear the outer end of the sleeve 6.

Mounted on the right end of the base I is a tool head 8 arranged for shifting movement transversely of the table 2. A spindle 9, extendline of reciprocation of the tool head 8, anding longitudinally of the the table 2, is journaled in carries a grinding wheel H] on its outer left end. An electric drive motor II is mounted on the table 2, and is connected through belts l2 to drive the work spindle 3. shown, may be provided for driving the grinding spindle 9.

Also mounted on the table therewith and located somewhat in advance of the work chuck 4 is a dressing device l3 having a dressing tool It adapted to be projected into the path of the grinding wheel I0 to dress the periphery of the latter at a predetermined point in the machine cycle. The dressing device l3 comprises a hydraulic cylinder l5 and a piston l6 reciprocably disposed therein. When the pressure in the cylinder is is relieved through a line H, the piston IB is retracted to withdraw the dressing tool It into an inoperative position.-

When fluid under pressure is supplied through the line ll to the cylinder IS, the piston l6 Any suitable means, not

2 for movement entry of the grinding wheel I0 into the workpiece A in position to grind the conical raceway 'l, the tool head 8 is shifted rearwardly to locate the grinding wheel in normal grinding position, and the work table 2 is reciprocated back and forth in the grinding range at a reduced speed for rough grinding. At the end of the roughing cut, the grinding wheel I0 is again retracted laterally out of engagement with the workpiece A to avoid interference with the cylindrical sleeve 6, and the work table 2 is given an amplified or extended movement to the left to withdraw the wheel from the work past the dressing tool I4. Following the dressing operation, the work table 2 is again advanced into grinding position, and the grinding wheel I0 is returned into cutting engagement with the work. Thereafter, the work table 2 is reciprocated at a still further reduced speed for finish grinding. A cross-feed is imparted to the grinding wheel l0 during both rough and finish grinding. When the workpiece A has been ground to the desired depth, the grinding wheel I ll is again retracted out of the path of the cylindrical sleeve 6, and the work table 2 is returned to the rest position.

The work table 2 is translated by an automatically controlled hydraulic transmission. In the present instance, the transmission is the same as that disclosed in the patent to Blood et 9.1., No. 2,011,705, to which reference may be had for a more detailed understanding of the specific con-' struction. Briefly described, the hydraulic transmission includes a cylinder 18 mounted in the base of the machine, and a piston l 9 reciprocable in the cylinder and having a piston rod 20 connected to the table 2. Referring to Fig. 3, fluid under pressure is adapted to be supplied by a pump 2| connected through a system of valves to the inlet port 22 of a main reversing valve 23. The valve 23 has two outlet ports connected, respectively, through lines 24 and 25 to opposite ends of the cylinder l8. With the reversing valve 23 in the position shown, fluid under pressure is admitted to the right-hand end of the cylinder It for urging the table 2 to the left into the rest position, and the fluid in the left-hand end of the cylinder I8 is discharged through the line 24 and the direction valve 23 to an exhaust line 25. It will be understood that when the main valve 23 is shifted into the opposite or reverse position, fluid under pressure will be admitted to the lefthand. end of the cylinder ill for urging the table 2 to the right into the grinding position. and fluid exhausting from the right-hand end of the cylinder will pass through the line 25 and valve 23 to the line 26.

The line 24 is connected to the left end of the cylinder [3 through a channel 21 adapted to be blocked when the piston I9 nears the left-hand position, and also through an inlet check valve 28 opening to the extreme end of the cylinder. As aresult, fluid under pressure is free to pass to the left end of the cylinder [8 at all times upon appropriate adjustment of the valve 23,

4 but upon movement of the piston l9 into its lefthand position, the channel 2'! will be blocked to cushion the movement of the table 2 as it is brought to rest.

The hydraulic transmission system includes a series of valve structures for automatically controlling the rate at which fluid under pressure is supplied from the pump 2| tothe hydraulic actuator during different portions of the machine cycle. The inlet port 22 of the main valve 23 is connected through a line 29 to a manually adjustable orifice valve 30 having a relatively large orifice 3| for receiving fluid during the rapid approach, and a relatively restricted orifice 32 for controlling the rate of reciprocation during rough grinding. The selection of the orifices 3i and 32 is under the control of a rate control valve 33 having an adjustable spool plunger 36. Upon adjustment of the plunger 34 into the right-hand position shown in Fig. 3, the pressure line 35 of the pump 2| is connected directly to a line 36 opening to the relatively unrestricted orifice 8!. Upon movement of the plunger 34 one step to the left, the inlet to the line 36 is blocked so that the relatively unrestricted orifice 3! is rendered inoperative.

The valve 33 is also connected through a line 3'! to a dresser control valve 38 having an adjustable spool plunger 39. When the plunger 39 is in the left-hand position of adjustment as shown in Fig. 3, the valve 38 connects the line 31' from the valve 33 to a line 40 connected with the relatively restricted orifice 32 in the orifice valve 30, and also connects the cylinder I5 of the wheel dressing device l3 to exhaust. The connection from the cylinder [5 is through the line H, the valve 33, a line 4| and the valve 38 to a drain line 42. In the right-hand position of adjustment of the plunger 39, the valve 38 serves to block the direct connection between the lines 31 and 40, and to establish a connection through an adjustable orifice 43, the orifice serving to control the rate of movement of the work table 2 during the dressing operation. In this position, the valve 38 also serves to connect the line 4| to the pressure inlet line 3! so that fluid under pressure is supplied to the cylinder 15 to render the dressing device 13 operative.

It will be understood that the valves 23, 33 and 38 are operated automatically in timed sequence in the course of the machine cycle.' The valve 23 has a hand lever 44 for starting the cycle, and is automatically oscillated through dogs (not shown) on the table 2 to reciprocate the table when in grinding position.

In the initial approach movement of the table 2, the valve plunger 34 occupies the right-hand position and the valve plunger 39 occupies the left-hand position as shown in Fig. 3 so that fluid under pressure from the pump 2| is directed through the lines 35 and 36, the large orifice 3| and the line 29 to the main control valve 23, and then through the line 24 to the left end of the cylinder l8 so as to efiect movement of the table 2 to the right at a rapid rate. As the table reaches the grinding position, the valve plunger 34 is shifted one step to the left into an intermediate position, thereby blocking the connection to the I line 36, and the valve plunger 39 is unchanged.

' stop and rapid the {rough grinding operation, the valve plunger 36 is adjusted into its right-hand position to project the dresser plunger [1, and the leftward movement of the table 2 is extended to effect separation of the workpiece A from the grinding wheel In in a dressing stroke at a rate determined by the setting of the dressing control orifice 43. Upon reentry of the grinding wheel l6 into the workpiece A, the valve plunger 34 is adjusted into its left-hand position, and the plunger 39 is returned into its left-hand position. As a result, fluid is directed from the pump 2| through the line 35, the valve 33, the line 31, the valve 38, the line 46 and the orifice 32 in the valve 36 to the pipe 29, but the plunger 34 serves to restrict the fiow area between the lines 35 and 31 so that the rate of travel of the table 2 is reduced for finish grinding.

Movement of the work table 2 to the left beyond the grinding range determined by the reversing dogs for the main valve 23, first, in the dressing stroke and, later, in the return stroke to rest position, is effected by a shiftable control bar (not shown) operable by ahydraulic actuator 45 under the control of two solenoid valves 46 and 41. The actuator 45 comprises a cylinder 48 having fluid supply lines 49 and 50 opening to opposite ends. A piston is neciprocable in the cylinder 48, and is formed in one end with a recess 52. A second piston 53 also reciprocable in the cylinder 48 and adapted to enter the recess 52, and has a rod 54 extending from one end of the cylinder for operating the aforesaid control bar.

The solenoid valves 46 and 41 are of the spring centered type, and are shiftable respectively against the action of the spring means by solenoids SVI and SV2. Each of the valves has a connection with the pressure line 35 of the pump 2|, and with exhaust lines 55. The valve 46 also has a connection with the line 56 to the large end of the cylinder 48 and the valve 41 has a connection with the line cylinder 48.

When both solenoids SVI and SV2 are energized, as shown in Fig. 3, fluid under pressure from the line 35 is directed through the valves 46 and "to both lines 49 and 50 to opposite ends of the cylinder 48 so that the rod 54 is fully projected. This is the condition which prevails during the approach movement of the work table 2. When both are deenergized as they are during rough and finish grinding, the valves 46 and 41 connect opposite ends of the cylinder 48 through the lines 49 and 50 to the exhaust lines 55 so that the rod 54 is in its innermost retracted position. When only the solenoid SVI is energized, the valve 46 serves to connect the cylinder line 50 to the pressure line 35, and the valve 41 serves to connect the cylinder -line 49 to the exhaust line 55 so that the piston 53 is actuated to project the rod 54 one step outwardly to institute extended movement of the work table 2 in the dressing stroke. At the end of the grinding operation, both solenoids SV 1 and SV2 are again energized to fully project the rod 54 so as to institute the return movement of the work table 2 into the rest position.

A cross feed movement is imparted to the tool head 8 during the grinding reciprocation of the table 2 un=til the workpiece A is ground to final depth. This cross-feed is imparted automatically to the tool head 8 by a. cross-feed mechanism fully disclosed in the aforesaid patent toBlood at al. No. 2,027,627 to which reference may be had for 49 to the rod, end of the 'a more detailed understanding. Briefly described, the cross feed mechanism is operable through a. gear rack 56 by a hydraulic actuator 51 a. cylinder 58 and. a p'ston 59. The rod end of the cylinder 58 is'open to a line 60 adapted for connection by the valve 33 to the pressure line 35" during the stop and rapid approach movements of the work table 2', and to an exhaust llne 6|- during .the grinding operation. The other end of the cylinder 58 is open to a line 62 adapted to be connected to an exhaust line 63 by a valve 64 when the line so is connected to pressure, and to be blocked from said exhaust line by said valve when the line 60 is connected to exhaust.

The line 60 is also connected by a selection valve 65 to receive fluid through either or both of two adjustable restricted orifices 66 and 61 from a line 68 leading from the valve 38. During rough grinding, the valve 65 is positioned to connect both orifices 66. and 61 between the lines 62 and 66 so that a relatively large volume of fluid is supplied to the actuator 51 to impart a comparatively rapid cross-feed to the grinding wheel l0. During fin-'- lsh grinding, the valve 65 is adjusted to cut out the orifice 66 so as to reduce the rate of cross-feed. During dressing, the flow is throttled by the ori-' fice 43. Resetting of the cross-feed mechanism may be accomplished by a hand valve 69 for connecting the line 62 to the line 68.

Lateral retraction of the-grinding wheel [6 to avoid interference with the workpiece A upon each axial entry, reentry and withdrawal, is obtained by shifting the tool head 8 without disturbing the cross-feed adjustment. The means for this purpose includes a lever (not shown) operable by a hydraulic actuator 10 having a cylinder 1| and a piston 12 therein. The piston 12 has av rod 13' extending from one end of the cylinder 1| for connection to the retract mechanism. The large end of the cylinder 1! is open to the line 56 for connection to pressure by the valve 46 when the solenoidSVl is energized to effect wheel retraction, and for connection to exhaust when the solenoid is deenergized for rough and finish grinding. The other end of the cylinder 11 is connected to an exhaust line 14. A switch LS1 for controlling the work spindle motor II is operable by a hydraulic actuator 15 connected across the lines 35 and 66. Hence, the switch is closed during the grinding and dressing operations, and is open during the rapid approach movement of the work table.

Electrical control circuits and operation Electric current for an electric motor 16 for driving the hydraulic pump 2|, a coolant pump motor 11, and the work spindle motor H, is sup-,- plied from main lines L1, L2 and L3 upon closing a main switch 18., The lines L1 and L3 areconnectedthrough a transformer 19 to control circuits having supplylines L4 and L5.

The hydraulic pump motor 16 and the coolant pump motor 11 are adapted to be connected to the lines L1, L2 and L3 by normally open con, tacts H1 adapted to be'engaged upon excitation of relay coil H by closing a manual starting switch 80. When the starting switch is closed, the circuit for the coil H is completed from the line L4 through th coil H, the starting switch '80, a normally closed manual stop switch BI, and two normally closed parallel limit switches LS5 and LS6 to the line L5. The limit switch LS5 is arranged to open only when the grinding wheel 10 is worn down. The limit switch LS6 is opened when the work table 2 is all the way out in its rest,

position. .Energization of the coil H serves to close holding contacts H2 across the starting switch 80.

Adapted for connection across the lines L4 and Ls are a pluralityof relay coils W, CRI CR3, CR2 and TR'I. The circuit, for the relay coil W is adapted to be established upon closing of the limit switch LS1, the circuit being from the line L4 through the coil W, the limit switch-LS7, the holding contacts Hz, the stop switch 81, and the limit switches LS5 and LS6. It will beevident that ii the relay coil H is not excited, the circuit for the relay coil W cannot be completed. Upon excitation of the relay coil W, contacts Wiare closed to connect the work spindle motor H to the lines L1, L2 and L3. Also adapted to be connected across the lines L4 and L5 are thetwo solenoids SW and SVZ for actuating the valves 46 and 41 respectively.

The relay coil CR! controls three normally open contacts C-Rll, CRl2 and.CRl-3. The relay coil CR3 controls normally closed contacts CBS-.1 and CR3-3, and normally open contacts ORB-2., CR3--l and CHE-r5. The relay coil CR2 controls normally closed contacts CR2-| and normally open contacts CR22. The relay coil TRl isadapted upon energization to close a timingswitch 'IRl-Al When the table is at the rest position, the relay coil CR3 will be energized, the circuit having been completed in the previous cycle upon closing the timing relay switch TRI-I and the limit switch L'Sl, which is closed when the table 2 is all the way forward. The relay CR3 consequently has closed contacts CR3-2 to maintain the circuit through the contacts LS3--A of the limit switch LS3. Contacts CR3-I are open to disable the circuit for the relay coil CRI, andcontacts CR3-3 are open to disable the holding circuit for the relay coil CR2. Contacts CR3-4 and CRii-li are closed so that the solenoids SVI and SV2 are energized.

To initiate the machine cycle, the starting valve 23 is shifted manually into the starting position, and thereupon the table '2 starts on its rapid traverse forward movement to the right. Since during the approach both solenoids SV! and SV2 are energized, the grinding wheel in is located in laterally retracted position to permit entry into the workpiece A without interference with the forward end of the cylindrical sleeveis. At the end of the approach movement of the table 2, with the grinding wheel Ill located within the workpiece A in position to grind the conical raceway l, the limit switch LS3 is actuated momentarily to open the contacts LS3A and to close the contacts LSZi-B, thereby breaking the circuit for the relay coil CR3, and as a result opening the contacts CHE- l and CR3-5 to break the circuits for the solenoids SVI andSV2. Upon deenergization of the solenoids, the grinding wheel I0 is shifted laterally into cutting engagement with the workpiece A. At the same time, the valve plunger 34 is shifted into its rough grinding position, thereby connecting the large end of the cylinder to drain to close the limit switch LS'l, and the rod end of the cylinderii't to drain to institute the cross-feed. Closing the limit switch LS7 completes the cir cuit for the'relay coi-l W to close contacts W1 in the :circuit for the work spindle motor H.

The table 2 is now reciprocated in the grinding range at a reduced speed determined by the orifice 32, and the grinding spindle 9 is given a cross-feed to grind the raceway l in a roughing operation. At the end of roughgrinding, the

limit switch LS2 is closed, and then at the end of the forward reciprocation of the table 2, the limit switch LS1 also is closed, thereby establishing a circuit for the relay coil CRI, from the line L; through the coil CRI, the contact CR2,-I and CR34 and the limit switches LS2 and LSI to the line L5. Excitation of the relay coil CRI closes contact CRI-l vto establish a holding circuit across the limit switches LSl and LS2; also closes contacts CRl-2 in the circuit for the relay coil CR2 to prepare the circuit for subsequent completion; and closes contacts CRl-3 to establish the circuit for the solenoid SVI. Consequently, the grinding spindle 9 is retracted to separate the grinding wheel ill from the conical raceway lor the workpiece A, and the piston 5| is actuated to project the, rod 54 partially outwardly so as to cause the table 2 to move through an extended dressing stroke. At the same time, the valve 38 is shifted to direct fluid to the cylinder l5 so that the dressing tool M will take a cut across the periphery of the wheel It). After reentry of the wheel in into the workpiece A in the return dressing stroke, the limit switch LS3 is actuated momentarily to close the contacts LS3B, thereby establishing a circuit for the relay coil CR 2, Energization of the relay coil CR2 serves to close contact CR2-2 to establish a holding circuit across the contacts ORA-2 and LS3-B, the contacts CR33 at this time beingin closed position, The relay coil CR2 also opens contacts CR2-l to interrupt the circuit for the relay coil CRl, and upon deenergization of the latter, the contacts CRl-l, CRl-2 and URI-3 are opened to deenergize the solenoid SV! and again move the grinding wheel Ill laterally into engagement withthe workpiece A.

' Thereafter, the grinding cycle continues in a finish operation until the desired size is reached, at which time the limit switch LS4 is closed by the cross-feed of the tool head 8 to complete the circuit for the timing relay TRI. After a predetermined delay, during which thecross-feed is stopped by a positive abutment, the rela coil T-R'l closes the contacts TRII. As soon as the table 2 then reaches the end of its forward travel in the final grinding stroke, the limit switch LSI is closed, thereby again completing a circuit for the relay coil CR3. Energization of the relay coil CR3 serves to open the contacts CR3I and CR33 to interrupt the circuits for the relay coils CR! and CR2, and serve to close holdin contacts CR3-2, and contacts CR3-4 and CR'35, again energizing the solenoids SVI and SV2. As a result, the grinding wheel I'll .is retracted from the finished surface of the workpiece A, and the piston 53 is actuated to fully project the rod 54 so as to institute return movement of the'table 2 into rest position remote from the grinding wheel.

' I claim as my invention:

v1; A grinding machine comprising, in combination, a base, atraverse slide mounted for reciprocation on said base, a cross-feed slide mounted on said base for transverse movement, a rotary work spindle mounted on one of said slides for supporting a workpiece having an internal surface to be ground, a rotary spindle supporting a grinding wheel and mounted on said other slide, means for automatically advancing said traverse slide in an approach movement from a position external of said workpiece to an operative grinding position, and then reciprocating said traverse slide with said grinding wheel in engagement with said surface, and means including a hy-- draulic actuator controlled by an electricallyoperated valve for maintaining said grinding wheel laterally retracted out of line with said surface during said approach movement, and electric control means for said valve including a limit switch actuated by said traverse slide to efiect movement of said grinding wheel laterally into cutting engagement with said surface after'entry of said wheel into said workpiece.

2. A grinding machine comprising, in combination, a base, a traverse slide mounted for reciprocation on said base, a cross-feed slide mounted on said base for transverse movement, a rotary work spindle mounted on one of said slides for supporting a workpiece having an internal surface to be ground, an electric motor for driving said spindle, a rotary spindle for supporting a grinding wheel and mounted on said other slide, means for automatically advancing said traverse slide in an approach movement from a remote position to an operative position, and then reciprocating said traverse slide in a grinding range, means including a hydraulic actuator for maintaining said grinding wheel laterally retracted out 10 of line with said surface during said approach movement and for shifting said grinding wheel into normal position after entry into said workpiece, and electric control means including a limit switch operable hydraulically to complete the drive circuits for said motor upon entry of said wheel into said workpiece.

MAX A MATHYS.

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

UNITED STATES PATENTS Number Name Date 1,816,082 Heald et a1. July 28, 1931 1,826,178 Kempton et a1 Oct. 6, 1931 1,997,978 Raule Apr. 16, 1935 2,011,705 Blood et a] Aug. 20, 1935 2,027,627 Blood et al Jan, 14, 1936 2,029,511 Steiner et a1. Feb. 4, 1936 2,127,856 Blood Aug. 23, 1938 2,156,970 Burns May 2, 1939

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