US3302336A - Workpiece support for grinding machine - Google Patents

Description

:Feb. 7, 1967 I c. J. BOWMAN 3,302,336

WORKPIECE SUPPORT FOR GRINDING MACHINE I Filed April 29. 1964 V 6 Sheets-Sheet l I O3 v LI- (\1 U) U g INVENTOR.

CHARLES JBOWMA BY ATTORNEYS Feb. 7, 1967- c. J. BOWMAN 3,302,336

WORKPIECE SUPPORT FOR GRINDING MACHINE Filed April 29, 1964 e sheets-sheet 2 w--wv. .-v-v--vf @dr v m V// /V 7 n mm om Feb. 7, 1967 c. J. BOWMAN 3,302,336

WORKPIECE SUPPORT FOR GRINDING MACHINE Filed A ril 29, 1964 6 SheetsSheet 5 WORKPIECE SUPPORT FOR GRINDING MACHINE Filed April 29. 1964 6 Sheets-Sheet 4 s4 s5 Y 88 92 95 3 A SOL T i T SOL E9 3 4 Feb. 7, 1967 c. J. BOWMAN 3,302,336

WORKPIECE SUPPORT FOR GRINDING MACHINE Filed April 29. 1964 6 Sheets-Sheet, 5

I Feb. 7, 1967 c. J. BOWMAN 3,302,336

WORKPIEGE SUPPORT FOR GRINDING MACHINE Filed April 29. 1964 6 Sheets-Sheet 6 L1 SW2 L2 1LSI 2|.s1 m \P 4CR3 3 w c 1 H R 1 2cm Q 3CR3 w I 4cm SOL3 L3CR2 so| 4 '4CR2 4/ 3LS1 1CR2 y Q i U @CR2 l 5cm I I v 501.1 L5CR2 r J I I 1P1 2P1 SOL 5 SOL s 2P2 3P1 United States Patent 3,302,336 WORKPIECE SUPPORT FOR GRINDING MACHINE Charles J. Bowman, Cincinnati, Ohio, assignor to the Cincinnati Milling Machine Co., Cincinnati, Ohio, a corporation of Ohio Filed Apr. 29, 1964, Ser. No. 363,444 Claims. (CI. 5150) The present invention relates to a grinding machine and more particularly to structure for supporting a workpiece therein.

In grinding operations, the finish produced on a workpiece will depend to a significant extent on the support given the workpiece during grinding. In the preferred form of the present invention, which is particularly suitable for long workpieces, a support is situated opposite the grinding wheel and moves with the grinding wheel along the workpiece during grinding. The support does not make metal-to-metal contact with the workpiece but, instead, exerts a fluid pressure force thereon. The fluid pressure force is generated by the application of fluid through a valve to the support, and the magnitude of the pressure, and hence the magnitude of the supporting force opposing the force of the grinding wheel on the workpiece, is controlled by the valve. The valve is operated in response to the load on the grinding wheel motor to raise the fluid pressure force whenever the force exerted by the grinding wheel on the workpiece decreases. This urges the workpiece toward the grinding wheel to raise the force of the grinding wheel on the workpiece. Thus, the grinding force is maintained substantially constant, and irregularities in the finish of the workpiece, due to a fluctuating grinding force, is avoided.

It is therefore one object of the present invention to provide an improved workpiece support for a grinding machine. It is another object of the present invention to provide a grinding machine workpiece support which moves with the grinding wheel as the grinding wheel moves along the workpiece for grinding. It is yet another object of the present invention to provide mechanism which travels along the workpiece for the application of a fluid pressure force to the workpiece. It is still another object of the present invention to provide a support operable to supply a variable fluid pressure force to the workpiece. It is a further object of the present invention to provide a fluid supporting force to the Workpiece varying in response to the grinding force on the workpiece. It is an additional object of the present invention to provide a support to maintain a constant grinding force on the workpiece. Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be' made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

In the drawings:

FIG. 1 is a plan view of a grinding machine incorporating the present invention;

FIG. 2 is a view taken on the line 22 of FIG. 1;

FIG. 3 is a view taken on the line 33 of FIG. 2;

FIG. 4 is a view taken on the line 44 of FIG. 1;

FIG. 5 is a view taken on the line 55 of FIG. 4;

FIG. 6 is a hydraulic diagram showing hydraulic elements of the machine;

FIG. 7 is a schematic diagram showing elements for control of the fluid support force; and

chine elements.

3,302,336 Patented Feb. 7, 1967 There is shown in FIG. 1 a grinding machine having a base 10 on which is mounted a headstock 11 and a footstock 12. One end of an elongated cylindrical workpiece 13 is clamped in headstock chuck 14, which is rotated by motor 15, and the other end of the workpiece 13 is supported by the footstock 12. A carriage 16 is mounted on Ways 17 on the base for movement along the workpiece and parallel thereto. This longitudinal movement of carriage 16 is effected by a feed screw 18 which is journaled in the base and rotated by a feed motor 19 (see FIG. 2) mounted in the base and operatively connected through gears 20, 21 and 22 to the feed screw (see FIG. 6).

The carriage 16 has ways 25, as shown best in FIG. 3, which slidably receive a wheelhead 26 for movement towards and away from the workpiece 13. The wheelhead carries a grinding wheel 27 which is rotated by a grinding wheel motor 28. Cross feed movement of wheelhead 26 on carriage 16 is effected by means of threaded feed shaft 29 which is threadedly received in a nut 30 tightly secured in the wheelhead so that rotation of the shaft in one direction or the other moves the wheelhead towards or away from the workpiece. The feed shaft 29 is journaled in housing 31 of a pick feed mechanism, indicated generally at 32, as shown best in FIGS. 4 and 5. The pick feed mechanism 32 includes a reciprocating pick feed motor 33 comprising cylinder 34 and piston 35 received in the cylinder. The piston is connetced by rod 36 to rack 37 which is engaged with gear 38. Gear 38 is loosely received on shaft 29 adjacent a ratchet wheel 39 which is pinned to shaft 29 at 40. Gear 38, which has one edge cut away to receive a block 41 secured thereto, is rocked in one direction and then the other by recipro cation of piston 35. A stud 42 secured in block 41 Pivotally receives a pawl 43 which engages the ratchet teeth 44 of ratchet wheel 39. Movement of piston 35 in one direction rotates shaft 29 in a predetermined direction through pawl 43 and ratchet wheel 39. Movement of piston 35 in the other direction effects no rotation of shaft 29 since the pawl slides over the ratchet teeth. A crank pin 45 on the end of crank arm 46 can be swung by rotation of knob 47 upwardly to engage the end of pawl 43 and render the pawl ineffective to rotate the ratchet wheel, and hence the shaft 29, in either direction of movement of piston 35. When the pin 45 is up to disengage the shaft 29 from pick feed motor 33, the shaft 29 can be rotated in either direction by handwheel 48.

A support 51 is received in the carriage 16 and extends therefrom under the workpiece. At its outer end, support 51 extends upwardly and supports a shoe 52 adjacent the workpiece and on the opposite side thereof to the grinding wheel. The shoe, as shown best in FIG. 7, has horizontal edges 53, vertical edges 54, and two vertical intermediate ribs 55, 56. The intermediate ribs divide the shoe into three surfaces, or pockets, 58, 59, 60. Three fluid pressure lines 61, 62, 63 are connected respectively to vertical passages 64, 65, 66. Passage 64 communicates with orifices, or openings, 67 in pocket 58; passage 65 communicates with orifices 67 in pocket 59; and passage 66 communicates with orifices 67 in pocket 60-. A screw 68 connected to support 51.and threadedly received in carriage 16 permits lateral, or cross, adjustment of support 51. Rotation of handwheel 69 (connected to screw 68) in one direction or the other moves shoe 52 towards or from the axis A of the workpiece.

The instantaneous force exerted on the workpiece by the shoe (acting to the right as viewed in FIG. 2) will depend on the instantaneous pressure in the shoe pockets. The shoe pocket pressure, in turn, will depend on the rate of fluid supplied to the pockets and the amount of resistance to discharge of fluid from the pockets. The fluid discharges from the pockets between the edges and the workpiece and, consequently, the amount of resistance to discharge of fluid from the pockets is affected by the span of the gap G between the edges of the shoe and the workpiece. The greater the span of the gap G, the lower the resistance to discharge of fluid from the pockets, and the lower the pressure in the shoe pockets.

Conversely, for any given size of gap G, the force acting to push the workpiece into the grinding wheel 27 depends on the rate of flow of hydraulic fluid to the shoe 52. In the machine shown, the flow of fluid to the shoe is controlled in response to the grinding force as represented by the load on the grinding motor. More specifically, the flow of fluid to the shoe is increased (to increase the force acting to push the workpiece toward the wheel) when the load on the motor decreases. Thus the fluid force tends to increase when the grinding force tends to decrease, thereby pushing the work into the wheel to maintain the grinding force steady.

There is shown in FIG. 6 a pump 75 which takes fluid from sump 76 and delivers it under pressure to a pressure line 77. A relief valve 78, connected between pressure line 77 and sump 76, determines the maximum pressure in the pressure line. A solenoid operated reversing valve 79 has a pressure port 80 connected to pressure line 77 and a pair of discharge, or exhaust ports, 81, 82 connected to a return line 83. When solenoid SOL1 is energized, the valve member 84 is shifted to the right against the bias of spring 85. This connects motor line 86 to pressure line 77 and motor line 87 to return line 83. With these pressure conditions in motor lines 86 and 87, which are connected to opposite ends of pick feed motor 33, the piston 35 thereof is at the right in cylinder 34. When solenoid SOL1 is deenergized, the valve member 84 is shifted to the left by spring 85, the pressure conditions in motor lines 86, 87 are reversed, and the piston 35 is shifted to the opposite end of cylinder 34.

Another solenoid operated reversing valve 88 has a pressure port 89 connected to pressure line 77 and a pair of discharge ports 90, 91 connected to the return line 83. When solenoid SOL3 is energized (and solenoid SOL4 deenergized) the valve member 92 is shifted to the right, connecting motor line 93 to pressure line 77 and motor line 94 to return line 83. With these pressure conditions in motor lines 93, 94, rotary hydraulic motor 19 to which they are connected will drive the carriage 16 to the left as viewed in FIG. 1. When solenoid SOL4 is energized (and solenoid SOL3 deenergized), the valve member 92 is shifted to the left, the pressure conditions in motor lines 93, 94 are reversed, and the carriage 16 is driven to the right. With neither solenoid SOL3 nor SOL4 energized, the springs 95 hold valve member 92 centered, isolating the motor lines from the pressure and return lines so the carriage remains at rest.

There is shown in FIG. 7 a hydraulic system for supplying fluid under pressure to the shoe 52. A pump 100 takes hydraulic fluid from sump 101 and delivers it under pressure to pressure line 102 which is connectd to a line 103 leading to the shoe lines 61, 62, and 63. Some fluid from pressure line 102 is returned to the sump through fixed resistance 104 (defined by a choke coil or restricted passage) and line 99, and some is returned to the sump through pressure reducing valve 105, the variable resistance 106 (defined by a valve operable in response to the grinding wheel motor load), and line 99. The valve 106 has a movable valve member 107 (biased to the left as viewed in FIG. 7 as by a spring 108) which is shifted to the right against the bias of the spring by a torque motor (represented by coil 109). The extent of movement of valve member 107 to the right depends on the magnitude of the current flowing through coil 109, the greater the current, the further to the right valve member 107 is shifted.

The load on motor 28, which will depend on the force A source 119 of alternating current is connected across a potentiometer 120 and the fixed, but adjustable, voltage tapped by movable arm 121 is impressed through transformer 122 across the alternating current terminals 123, 124 of a rectifier circuit 125. The direct current voltage developed across terminals 126, 127 is therefore fixed (when arm 121 is stationary) but adjustable (when arm 121 is adjusted). The terminals 117, 126 are connected together by line 128, which is connected to terminal 118 through load resistance 129 and to terminal 127 through load resistance 130. Terminal 118 is connected to one end of coil 109 and terminal 127 is connected to the other end of coil 109 so that the magnitude and direction of the current flowing through the coil is an indication of the magnitude of the voltage at terminal 118 which measures the motor load (and hence the grinding force) with respect to a reference voltage at terminal 127. The magnitude of current flow through coil 109 is greatest when the motor load is lightest and decreases as the motor load increases.

Potentiometer 120, which is defined by a semi-circular resistor, is connected to the wall of housing 31 adjacent to, but insulated from, a semi-circular conductor 135, as shown in FIG. 4. Arm 121 is defined by a brush mounted on a conducting ring 136. The conducting ring 136 is snugly received on ratchet wheel 39 for rotation therewith and for selective angular adjustment relative thereto. The ring 136 is in continuous electrical contact with conductor through brush 137. As shown in FIG. 7, source 119 is connected across resistor 120 and the primary winding 122a of transformer 122 is connected between one end of resistor 120 and conductor 135 which is in continuous electrical communication with brush 121.

For operation of the grinding machine, a workpiece 13 is inserted between headstock 11 and footstock 12, and support 51 is adjusted, by handwheel 69, to establish a gap G of predetermined span. The wheelhead 26 is moved toward the work by handwheel 48 until grinding wheel 27 is in abrading contact with the work and, after the wheelhead has been adjusted, ring 136 is adjusted on ratchet wheel 39 (thereby adjusting brush 121 with respect to resistor 120) to establish a predetermined reference voltage at terminal 127. As shown in FIG. 7,'the shoe 52 has four proximity probes spaced along the upper edge of the shoe. Each proximity probe controls two switch contacts, closing the contacts when the probe is adjacent the metal workpiece. Each probe is aligned with one side of a shoe pocket, and the two probes on opposite sides of each pocket jointly control a blocking valve in the hydraulic line leading to the pocket. Thus, as shown in FIGS. 7 and 8, probe switch contacts 1P1 (operated by probe IP) and probe switch contacts 2P1 (operated by probe 2P) are connected in series across lines L1 and L2 with solenoid SOL5 of blocking valve BVl in line 63; probe switch contacts 2P2 (operated by probe 2P) and probe switch 3P1 (operated by probe 3P) are connected in series across lines L1 and L2 with solenoid SOL6 of blocking valve BV2; and probe switch contacts 3P2 (operated by probe 3P) and probe switch contacts 4P1 (operated by probe 4P) are connected in series across lines L1 and L2 with solenoid SOL7 of blocking valve BV3. When a workpiece is in registration with both edges of a pocket (58, 59, or 60) both probes aligned with the edges of that pocket are energized and both switches operated by each of the probes are closed so that the solenoid of the blocking valve in the line leading to that pocket is energized, holding the plunger of the valve to the left as viewed in FIG. 7, and connecting the shoe line (61, 62, or 63) to line 103. In this manner, fluid flows from pump 100 to a pocket only when the workpiece is in front of the pocket.

To start the grinding operation, switch SW1 is momentarily closed after switch SW2 has been closed, energizing relay 3CR. Relay 3CR is sealed in through normally open contacts 3CR1 and normally closed contacts 4CR3. With relay 3CR energized, solenoid SOL3 is energized through normally open contacts 3CR2 to start motor 19 and move carriage 16 (with the grinding wheel 27 and support shoe 52) to the left as viewed in FIG. 1.

It will be noted that since valve 106 defines a passage between line 103 and sump line 99, the pressure in line 103 (and hence in shoe lines 61, 62, 63 connected thereto) will be affected by the position of valve member 107. If, during grinding, there is any tendency for the workpiece to bow away from the grinding wheel, the grinding force (and the current in line 110) will decrease, lowering the voltage at terminal 118 with respect to the reference voltage at terminal 127. This will increase the current through coil 109 and move valve member 107 to the right, closing the passage through the valve 106 from line 103 to sump 101. Thus, the pressure inline 103 increases,-

increasing the fluid pressure force in the pockets. This increased pressure force acts on the workpiece, urging the workpiece into the grinding wheel 27. This increases the load on the motor to raise the voltage at terminal 118, making it more nearly equal the value of the reference voltage at terminal 127, thus dropping the current through coil 109. In this manner, the valve 106 controls the force on the workpiece to maintain a constant grinding force.

When the carriage 16 reaches the left end of base (as viewed in FIG. 1) limit switch 2LS is operated, closing normally open contacts 2LS1 and energizing relay 2CR. This energizes relay 4CR through normally open contacts 2CR1 and, at the same time, relay 3CR is dropped as contacts 4CR3 open. With relay 3CR deenergized, relay 4CR is sealed in through normally closed contacts 3CR3 and normally open contacts 4CR1. Thus, normally open contacts 4CR2 close and normally open contacts 3CR2 open, energizing solenoid SOL4 and deenergizing solenoid SOL3. This shifts valve member 92 to the left, reversing motor 19 to move carriage 16 to the right.

At the same time motor 19 is reversing direction, the pick feed mechanism 32 is operated. When either relay 1CR or relay 2CR is energized, normally open contacts 1CR2 or 2CR2 are closed, energizing relay SCR, since, at this time, normally closed contacts 3LS1 are closed. Relay 5CR is sealed in, until operation of limit switch 3LS opens contacts 3LS1, by normally open contacts 5CR1. When relay 5CR is energized, normally open contacts 5CR2 close, energizing solenoid SOL1. This shifts valve plunger 84 to the right, connecting the left end (as viewed in FIG. 6) of cylinder 34 to pressure line 77 and connecting the right end of cylinder 34 to return line 83. This shifts piston 35 to the right and rotates (through gear 38, pawl 43, and ratchet wheel 39) shaft 29 an incremental amount to advance grinding wheel 27 an incremental amount. After piston 35 is almost at the right end of cylinder 34, limit switch 3LS is operated, opening contacts 3LS1 to deenergize relay SCR. This deenergizes solenoid SOLl, and valve plunger 84 is shifted to the left to reverse the pressure conditions in cylinder 34. Thus, piston 35 retracts, limit switch 3LS is released, and the mechanism is ready for the next pick-feed operation.

It will be noted that each incremental advance of the grinding wheel, followed by movement of the grinding wheel along the work, results in diminution of the diameter of the workpiece with a corresponding increase in the span of gap G. Thus, unless some compensating adjustment were made for this periodic increase of gap size, the fluid pressure force exerted at the shoe (which is affected by gap size in that the larger the gap, the smaller the fluid pressure that develops in the pocket) would, although still varying as the grinding force varies, diminish with each pass of the grinding wheel. This is avoided in the mechanism disclosed herein by the automatic rotation of ring 136 (since ring 136 is mounted on wheel 39 for rotation therewith), on each pick feed, to angularly adjust brush 121 and thereby increase the reference voltage at terminal 127. This tends to increase the current flow through coil 109 (for any given grinding force and motor load), thereby holding valve member 107 further to the right to decrease the fluid discharged through valve 106 to sump. Thus, more fluid is supplied to shoe 52 and the fluid pressure in the shoe pockets is maintained despite the larger flow from the pockets through the larger gap G.

When the carriage 16 reaches the right end of base 10, limit switch lLS is operated, energizing relay 1CR. This energizes relay 3CR through normally open contacts 1CR1 and, with relay 3CR energized, relay 4CR is dropped out because normally closed contacts 3CR3 open. With relay 3CR energized, and relay 4CR deenergized, solenoid SOL3 is energized and solenoid SOL4 deenergized to again reverse motor 19. At the same time the pick feed mechanism is again operated.

I claim:

1. In a grinding machine, the combination comprising:

(a) means to rotate an elongated workpiece,

(b) a carriage movable along the workpiece and having a rotatable grinding wheel for abrading contact with the workpiece,

(c) a support on the opposite side of the workpiece from the grinding wheel and movable along the work piece with the carriage, said support having a sup port surface facing the workpiece,

(d) and means to supply fluid under pressure between said support surface and the workpiece.

2. In a grinding machine, the combination comprising:

(a) means to rotate an elongated workpiece,

(b) a carriage movable along the workpiece and having a rotatable grinding wheel for abrading contact therewith,

(c) a support on the opposite side of the workpiece from the grinding wheel and connected to the carriage for movement therewith, said support having a surface facing the workpiece and having a fluid passage therethrough terminating at an opening in said surface,

(d) and means to supply fluid under pressure to said fluid passage to create a fluid pressure force on the workpiece opposing the force created by said abrading contact.

3. In a grinding machine, the combination comprising:

(a) means to rotate an elongated workpiece for grind- (b) a carriage movable along the workpiece and having a rotatable grinding wheel for abrading contact therewith,

(c) a support on the opposite side of the workpiece from the grinding wheel and movable along the workpiece with the carriage, said support having a support surface facing the workpiece,

(d) means continuously to supply fluid under pressure :between said support surface and the workpiece to establish a fluid pressure force therebetween during grinding,

(e) and means to vary the rate at which fluid is supplied between said support surface and said workpiece to vary the fluid pressure force therebetween.

4. In a grinding machine, the combination comprising:

(a) means to rotate an elongated workpiece for grind- (b) a carriage movable along the workpiece and having a rotatable grinding wheel for abrading contact therewith,

(c) a support on the opposite side of the workpiece from the grinding wheel and movable along the workpiece with the carriage, said support having a sup- Iport surface facing the workpiece and closely spaced thereto, 7

(d) means continuously to supply fluid under pressure through said support for discharge between said support surface and the workpiece to establish a fluid pressure ,for-ce therebetween during grinding,

(e) and means responsive to the force exerted by said abrading contact to vary the rate at which fluid is supplied between said support surface and said workpiece to vary thefluid pressure force therebetween.

5. In a grinding machine, the combination comprising:

(a). means to rotate an elongated workpiece for grind- (b) a carriage movable along the workpiece and having a grinding wheel for abrading contact therewith,

(c) 'an electric motor to rotate the grinding wheel,

(d) a support on the opposite side of the workpiece from the grinding wheel and movable along the workpiece with the carriage, said support having a support surface facing the workpiece,

(e) means continuously to supply fluid under pressure through said support for discharge between said support surface and the workpiece to establish a fluid pressure force therebetween during grinding,

(f) a hydraulic valve to control the flow of fluid to the support,

(g) and means responsive to the load on the motor to operate the valve.

References Cited by the Examiner UNITED STATES PATENTS 427,091 5/1890 Landis 51238 X 671,448 4/ 1901 Morton 51-238 1,864,584 6/1932 Cowdery 515O X 1,875,486 9/1932 Peaslee 51-238 1,885,233 11/1932 Cole 51238 20 LESTER M. SWINGLE, Primary Examiner.

Claims (1)

1. 3. IN A GRINDING MACHINE, THE COMBINATION COMPRISING: (A) MEANS TO ROTATE AN ELONGATED WORKPIECE FOR GRINDING, (B) A CARRIAGE MOVABLE ALONG THE WORKPIECE AND HAVING A ROTATABLE GRINDING WHEEL FOR ABRADING CONTACT THEREWITH, (C) A SUPPORT ON THE OPPOSITE SIDE OF THE WORKPIECE FROM THE GRINDING WHEEL AND MOVABLE ALONG THE WORKPIECE WITH THE CARRIAGE, SAID SUPPORT HAVING A SUPPORT SURFACE FACING THE WORKPIECE, (D) MEANS CONTINUOUSLY TO SUPPLY FLUID UNDER PRESSURE BETWEEN SAID SUPPORT SURFACE AND THE WORKPIECE TO ESTABLISH A FLUID PRESSURE FORCE THEREBETWEEN DURING GRINDING, (E) AND MEANS TO VARY THE RATE AT WHICH FLUID IS SUPPLIED BETWEEN SAID SUPPORT SURFACE AND SAID WORKPIECE TO VARY THE FLUID PRESSURE FORCE THEREBETWEEN.

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