US2537389A - Grinding machine - Google Patents

Description

Jan. 9, 1951 ALT ETAL 2,537,389

GRINDING MACHINE Filed Oct. 7, 1947 3 Sheets-Sheet l INVENTORS AL WW1. A; 2' BY JA cal Dtqklk 7mm kawayfis I Arromvzgs A. F. AL-T ETAL GRINDING MACHINE Jan. 9, 1951 Filed Oct. 7', 1947 2 2 M v I m y e N D a mu; m I mww n w A A Nm\ 5 Patented Jan. 9, 1951 ATENT cmcr demonic MACHINE Alvin F. Alt and Jacob Decker, Cincinnati; Ohio,

assignors; to The (lincinnati Miiling Machine Cincinnati, Ohio, a corporation of Ohio Annotation ot obe'r 7, 1947, Serial N6. 778,314

This invention rel atspto grinding machines anym re partietuah to improvements in in feeding mechanisms therefor.

4 One of the objects of this invention is to provide an improved precision grinding machine which will grind wo'rk t6 very limited tolerances respects both diameter and roundness.

Another ob-iect of this invention is to provide a machine which will have a contmuons feeding ni'otioh until the desired size of work has been reached and still maintain a high degree of precision with respect to size and roundness of work.

A further bbject of this invention is to provide an improved automatic size control grinding machine.

Other objects and advantages of the present invention should be readiyvapp'ar'ent by reference to the following specification, considered in conjunction with the accompanying drawings formingva 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 denarting from or exceeding the spirit of the invention. &

In the drawings in which like reference numerals indicate like or similar parts:

Figure 1 is a front view of a machine embodying the principles of this invention. v

Figure 2 is a diagram of the hydraulic control circuit of the machine.

Figure 3 is a view showingan enlarged View of onevof the valve control mechanisms;

Figure 4 is a detail view of an adjustable trip control plate.

Figure 5 is an elevational view partly in diagrammatic form showing the size control mechanism and connections thereto;

, In the grinding or work diameters to a precision dimension by the infeeding method; it is cus-l tomary to stop the infeeding motion of the grinding wheel at some predetermined point and aliow a dwell before the grinding wheel retracts tor the, purpose of a11owing the work to make a i e w rotations tofacilitate rounding up of the work as well as obtaining a predetermined dimension as to size. Withoutsuch tarry allowance, itis very diflicult to obtain work that is round within desirable tolerances. Many factors cause this result, some of the more important of which are due to the fact that the Work has a tendency to spring slightly under the pressure of the wheel and another is that the wheel may not be cutting freely; It should also be obvious, however, that by allowing time for a tarry that it takes, longer to grind a given work piece.

9 Claims. (01. '51 165) By means of this invention a feeding cycle for the grinding machineis provided which produces a rapid traverse motion of the grinding wheel until engagement with the work is established, followed by a normal infeeding. rate during which most of the stock removal iseffected after which a very slow feed rate predetermined in accord: ance with the tolerance allowancefor roundness is created until an automatic sizing mechanism, which is in engagement with thework, closesa circuit atthe moment the'work reaches a pre% determined size, energization of this circuit causing immediate retraction of the grinding Wheel. 7 a 1 v r This invention includes the discovery that by making this slow feed rate a function of the tollferan'ce allowed for roundnessof the work that very accurate results. may be obtained. In view f hi t e ha ism o hi in nt ns :sp contrive'dthat fihe lag etwe n the. fi f bn of the circditand the actual retraction of the grinding wheel is a frac tion of a second and is er f e thhnih amount pf ee ef c e .3 3 n h si i fih infeed 136 .536 and not g'reaterthan thetolerance allowedon theworlt for roundness it is insuredthat the overrunaiter the closing'oi the sizing control switch will be less thanthe infeed per second, and therefore less than the tolerance allowed for rcnndness. j p v ferring to the drawings, Figure 1 shows a m chine embodying the principles of this inventiona'nd this machine comprises, in generalia bed it upon which is slidably mounted a work supporting table H having'a headstock i2 and a tailsto'cl: lsio'r supporting awo'rk piece for ro tation in the customary manner. As shown in Figure 2, a grinding when :4 is rotates-1y mounted ii'pon a tress slide l5 which is suitably some on thebed Hifor relative movement toward and from a work piece indicated diagram tically by the reference numeral 56. I A suitable cross feed screw ii is in threaded engage} with a nut portion IE or the slide i5 and cperenveiy connected to the hand wheel 59 shown on the front of the bedlfl. The hand wheel l8 may' be utilized for roughly determining the position of the grinding wh eel with respect to the work and may be utilized for effecting coin"- p'ensaticns in the positional? the wheel.

In the automatic infeeding cycle the cross feed screw 5? is provided with a piston 29 which slidablymounted in a cylinder 2| formed integral with the bed It whereby the screw 21 is recipcoated axially to eiiect advance and retrac tio'n (5f 171E giifidifig wheel. The piston 29 is and a second piston 22 slidably mounted in a cylinder 23 is connected by a piston rod 24 to the wheel slide 45 for effecting retraction of the grinding wheel.

The cylinder 2| is connected by line 25 to port 25 of a by-pass valve 2?, the plunger 28 of this valve having an annular groove 29 which is normally in position to connect port 26 to port 39. The last-named port is connected by channel at to port 32 of a servo-control valve 33. Also, the cylinder 23 is connected to the servo-valve by a channel 34 which leads to port 35 of the by-pass valve, the plunger of which hasa second annular groove 35 which is in position to connect port 35 to port 3? and channel 38 which leads to port 39 of the servo-valve. The servo-valve has a pressure port 48 which is connected to the delivery line 4| of a pump 42 which has an intake 43 through which fluid is withdrawn from 'a reservoir 44. The servo-valve also has a pair of exhaust ports 45 and 46 which are connected to the return line 41 which leads to the reservoir 44.

The servo-valve has a slidable bushing 48 mounted therein which is normally urged toward the left as viewed in Figure 2 by a spring 49. This movement is limited by a cam 59. A pivoted bell crank is interposed between the end of the bushing 48 and the cam, one arm of the bell crank being provided with a roller 52 which rides on the cam surface. The servo-valve also has a plunger 53 which is slidable within the bushing and normally urged toward the left by a spring 54. The valve plunger has a socket connection at 55 with the end of a feed back lever 56 and the clockwise movement of this lever is limited by a set screw 51 engaging a fixed abutment 55. The position of the valve plunger 53, as determined by the set screw 51 relative to the position of the bushing 48 as determined by the cam 50 when in sure on the piston 22 to hold the grinding wheel in a retracted position. At this time the line 3| which leads to cylinder 2! will be connected to reservoir through the interconnection of ports 32 and 46 by the annular groove 60 in the valve plunger 53.

The cam 59 is interconnected for rotation by the infeed control lever 6! which, as shown in Figure 3, is pivotally connected at 52 for oscillatory movement in the plane of the drawing, and

also for rotary movement about the axis 63. The lever is connected by a link 54 to a slidable valve plunger 65 which is provided with a flange 55 against which a spring 6'! acts to hold the valve plunger in the position shown. It will be noted that this valve plunger has an annular groove 68 which, in the position shown, interconnects ports 69 and 10. The port 59 is connected by the branch line H to the main reservoir line 41. The port 19 is connected by a channel 12 to a port 13 located in the end of a short circuiting valve I4 shown in Figure 2. The pump supply line M has a branch connection to a third port 16 whereby when the control lever 61 is manually pulled to the left as viewed in Figure 3 the pressure port 76 is connected by the annular groove 68 of valve plunger 55 to port '10, thereby admitting pressure to the lower end of the short circuiting valve and causing the plunger 16 of the valve to shift upward against the resistance of a spring 11.

The purpose of the short circuiting valve 14 is to short circuit or interconnect both ends of an infeed control cylinder 18 which has a piston 19 that is connected to a rack piston rod 80. This rack intermeshes with a pinion 8| which is formed integral with the bushing 82 shown in Figure 3. When the operator starts the cycle of operation he pulls the lever 6| toward him to operate the short circuiting valve so as to short circuit or interconnect opposite ends of the cylinder l8 and then he rotates the lever 61 in a clockwise direction as viewed in Figure 2 from the starting position indicated by the dash and dot line 83 and in so doing he moves the rack piston rod 99 downward and this becomes possible because of the short circuiting of both ends of the cylinder 18. Upon movement of the lever 61 from the position 83 to the position indicated by the dash and dot line 84 the piston 1'9 has moved down sufilciently to uncover a port 85.

The cylinder 18 also has a port 86 which is connected by channel 81 to port 88 of the shortcircuiting valve and when this valve is moved upward, this port is connected by groove 89 in the valve plunger 16' with port 90, and this port is connected by channel 9| to port of cylinder 18.

When the control lever 5! moves from the position 83 to the position 84, it also rotates the cam 59, whereby the angular surface 92 on the cam will cause counterclockwise rotation of the bell crank 51 and shift the servo-valve bushing 48 toward the right a suflicient distance that the pressure port 40 becomes connected to port 32 whereby pressure fluid will flow to cylinder 21, causing rapid advance of the piston 20 and thus rapid inieed of the grinding wheel. This rate of movement will continue until a collar 93 operatively connected for movement with the screw I'I engages the end of the lever 55, causing counterclockwise rotation thereof and movement of the servo-valve plunger 53 toward the right to thereby follow up the movement of the bushing 48, tending to close the pressure port 40.

There is no exact limit upon how far the lever 59 is rotated manually by the operator to effect the rapid movement, and the length of this movement is determined by the operator observing that the grinding wheel has become engaged with the work and has started grinding. At this point the operator releases the lever 6| which is then returned to its normal position by the spring 61 shown in Figure 3, and through valve plunger 68 releases the pressure on the short-circuiting valve because the port 10 is then connected to the exhaust port 59.

When the valve plunger 16' of the short circuiting valve returns to its normal position it connects port with port 94 and port 88 with port 95. The port 94 is supplied with pressure from the pump line'll through interconnection of ports 95 and 91 by the annular groove 98 in the reversing valve plunger 99 of a reversing valve I00. The port 91 is connected by channel I G! to port 94. It will now be seen that pressure fiuid will flow through line 9! to the upper end of cylinder [8 and thereby continue the downward movement of the piston 19, but the movement will now be under power and not manual control. The rate of this movement is controlled in the following manner.

The return fluid flowing through line 81 and interconnected ports 88 and 95 will continue thr gh l e i I02 and interconnected ports I03 flllidi passing through line. i196; goes. to: a fast feed.

rate control valve: I208: and: the" fluid: ll

valve. I165; The line 16,. however; is act... connected to. a port. I:I:Ilof: a on off. valve l. and. this. port is connecteclatonor; Zibv he nular groove H3 in the valve plunger: HA, plunger is normally maintained the pos ti n shown by a. spring I I.5-.. The slow feed valve I109 isset. for a very slow feed. rate; the entrees or which will be explained later; and. therefor sine it. has. a. higher resistance to flow than. the who i018: most of the. fluid: will; pa s throne. the valve I08: durin the normal inieedins movementoi the grinding wheel. 7

. Duringthe downward feedings movement of the piston to; the cam 56; is: continuously rotated continually moving theservoevalve bushin to ward the right, which increment is cont uousls! followed up. by the feed back connection to the servo-valve plunger 53. Thus, the grindingwheel is. moved in under the direotcontrol the servovalvewhich, in turn, is remotely controlled by the, rate of movement 01- the piston is, this rate of; movement being determined by the setting of the rate control valves H38 and W9. At some prede, termin-ed point before the work has reached its final size, such as at the position indicated by the line H6 for the control lever M in Figure 2, the rate of infeeoling movement of the grindingwheel, is automatically changed toa veryslow feed rate. This is accomplished by means of a trip meme be-r II'I which is attached by bolts I It to the periphery IIQ of the rotatable member 82-. This trip member is adapted to engage a finger I255 secured to a lever I2I which is pivoted at i2 2 to a fixed part of the machine. The lever I2-I has a connection at- I23 to the plunger I2 3 of a pilot valve I25. This pilot valve has a pressure port I26 Whichis supplied by the pump 42 and when the plunger I24 is moved upward through trip operation the pressure port I26 is connected by the annular roove iZ'I in the valve plunger to port I28 whereby fluid pressure will flow through line I29 to the lower end of the cut-off valve III, thereby shifting the plunger MA upward as viewed in Figure 2. This will disconnect port IE6 from port H2 and thereby block further flow to the rate valve I88 whereby all th now must no pass through line it? to the slow rate. valve I 29- This will materially reduce the rate of m v men of the infeed control piston 19., and, throu h the various connections to the servo-valve, thereby all).

connected has a reciprocabie plunger I ls slidably mounted therein and the lower end of this plung er engages the periphery of: the Work. The up per end of this arm operates an indicator I35 and also operates a switch con ained Within the i'graduallvas the work reduces in diameter -until he piv ted support its. wh ch is; at ached at .0

wheel ho sin wh reby. it: may

to cause; secretion th zsolencid 1- 1 the Q1 lea of t s. so no' op ates hrough a lev Il a tov depress the p un er 2 ofv the iziaisev a ve 21-. resul s; n &- f t v lv being W uectedtomort Mt whi h is c no ted o the e erv volt l ne so that the .fi d. cy inder an exhaust o reservoir. P rt and its, l ne 3 tram c lind r 2 s c nected. to pressure ort :2 the; annulareroove. 36; in valve lu ger it whereby the pump pressure from Line; M di rec ly ente yl nd r 3 to cause immediate traotion of the dine wee] and indep ndent oi the rest; or he circuit.- e r nd-i s, w s. hus mo ed o t i nga em nt. with the ve b wit-h ot Wartime ferthe rest of he c cuit to. be

reset; for startin The. bv-nass alve as a ewnd pr ssure p r Maul-m en conn ct-eel by e i ting o the plun er 2.8. to por M by he annular gr ove 5 so. that flui ur ss re will; now flow through line: I46 to port I or located the lower end of, the reversin valve. w e eby the rev r i g valve eer 9.9 .lmediately Sh i es oward- 'ljhis will. result n pr ssu 96 be ng; is: connected iromnort B nd c nected to po t Ill-3 whereby the fluid. p s ure W now flow. through line Iilli and the short the; val e to line 81 and thereby tothe lower end of the in; feed cylinder 18 to cause upward movement, or Piston l3. Port 9:1 of' the reversing valve to. which the. upper end of cylinder in is. connec d. W ll be connected to the exhaust port Mg whereby 11 id may discharge from the upper end: at the, iniced control cylinder.

Thus, as the grinding wheel is being retracted, the manual control lever BI is being rotated power back to its. starting position, and. this move ment will continue until a trip, pin Mil carried b the rod 89 rotates the lever 121 and shifts the pilot valve downward to its original position. It will be noted that the piston l9 is provided with an interdrilled passage i511 which will register with a port IE1 at about the time the port 85 closes so that the fluid in the. upper end of the cylinder may still be exhausted to reservoir through the line 552.

When the pilot valve plunger returns to its original position port I28 will become reconnected to. an exhaust. port I55. which will release, .2.13. pressure in the lower end of the cuteofi valve H I so that the plunger Illi thereof will be restored to its original position.

Referring to Figure 3., attention is invited to the fact that the rotatable member 82 which is rotated by the handle 69 about the fixed stud-82 has an arc-uate groove we formed therein and that he fixed member 232' has an in-terdrilled pressure port 555 and an interdrilled exhaust port 56. Intermediate these ports is a third port I??? whi h is conn cted bv l ne 558 to a re s r switch 59, at the beeinning or" the cycle when ammat e positions s is eroove I54 moved sure 3 to the n;

sure port I55 with'port I51 and thereby close the pressure switch I59; It will be noted that the pressure switch I59 is connected in series in the control circuit I38 for the solenoid I31 Thus, this switch is closed during the entire infeed cycle but when the lever returns to its startin position the port I51 is connected to the exhaust port I56 which results in the pressure switch I59 opening the circuit I38, thereby releasing the solenoid I31 whereby the valve plunger 28 of the by-pass valve returns to the position shown due to the fact that the back pressure in line d1 entering the port MI will pass through the interdrilled passage IEO to the lower chamber I6I of the valve housing and push the plunger back to its normal position. This will result in the line I46 from the lower end of the reversing valve being connected to the return line IISI whereby the spring I62 will shift the reversing valve plunger to its return position.

The operator may now swing the sizing gage out of the way and remove the finished work piece, insert a new work piece between the centers of the machine and then return the sizing device into engagement with the work, but at this time since the work is an unfinished piece, the plunger I34 will be held upward in such position as to hold the switch of the sizing device open so that the circuit to the solenoid I37 will not be energized when the pressure switch I59 is closed at the beginning of the next cycle.

The machine thus has a cycle of operation comprising a rapid traverse stroke of the grinding wheel from its work clearing position into grinding engagement with the work, a feed stroke during which most of the stock is removed from the work, and a short feed stroke at a very slow rate, the last rate being a function of the tolerance allowed on the work for roundness. The sizing device is in continuous engagement with the Work during this continuous infeeding motion at the difierent rates, and when the exact size is reached immediate separation between the grinding wheel and the work is effected.

It will be noted that there is no provision for an intentional dwell, and that reversal in the direction of movement of the grinding wheel is made as instantaneously as possible Without waiting for resetting of the various control elements in the control circuit. The use of a dwell is normally for the purpose of rounding'up the work but is time-consuming. The object here is to grind within the same minimum tolerances for roundness of the order of .0001" or .0002" without the use of a dwell. By careful experimentation, we have discovered that by making the slow infeed rate per second of time equal to the tolerance allowed for roundness of the work which, in turn, is equal to the rate of stock removal per second which is a function of the feed rate and the rate of rotation of the work, that the desired tolerance may be obtained and with greater surety. In View of this, the slow feed rate valve has been provided and made efiective at the proper time at the end of the infeeding stroke to produce the desired feed rate per second which is equal to or less than the tolerance allowed for roundness of the work.

What is claimed is:

1. In a grinding machine having a grinding wheel and a work support, the combination of power operable means for feeding the grinding wheel toward the work support to progressively effect a reduction in the size of work carried by the work support, said power operable means'inthe grinding wheel, a hydraulic control circuit including a reversing valve for controlling the direction of movement of said piston means, a source of pressure, and an additional valve for directly connecting said source of pressure to said piston and cylinder means to effect retraction of said grinding wheel independent of said reversing valve.

2. In a grinding machine having a grinding wheel and a work support, the combination of power operable means for shifting the grinding wheel toward the work support to progressively effect reduction in the size of work carried thereby including a servo-motor control mechanism, a. hydraulic motor for driving said mechanism, a reversing valve for said motor, a source of pressure for supplying fluid to said motor, and an additional valve for directly connecting said source of pressure to said power operable shifting means to effect immediate retraction of the grinding wheel independent of said mechanism.

3. In a grinding machine having a grinding wheel, a grinding wheel support and a work support, the combination with fluid operable means for shifting the grinding wheel support toward the work support to progressively eiiect reduction in the size of work carried by the work support including a hydraulic control circuit having a source of pressure connected thereto, and valve means for controlling the rate of operation of said power operable means, of an electrical work sizing gage mounted on said grinding wheel support, and valve means connected for operation by said gage for directly connecting said source of pressure to said fluid operable means independent of said first-named valve means for effecting retraction of the grinding wheel support.

4. A grinding machine having a work support and a grinding wheel support mounted for relative movement to advance and retract one with respect to the other, means actuated by fluid pressure to efiect said advancing relative movement, 2. source of fluid pressure, and a control mechanism for governing the flow of fluid pres sure from said source to said means whereby the rate of flow becomes the sole determinant of the rate of said relative movement, said mechanism including manually operable means for adjusting said flow to a fast rate to effect said relative movement at a rapid traverse rate, a power operable mechanism for reducing said flow to effect said relative movement at a normal grinding rate, a subsequently operable device to further restrict the flow to yield a slow rate per second which is less than the tolerance on the work for roundness, and a sizing device responsive to continuous reduction of the work and effective in response to a predetermined work size during said slow rate to effect immediate separation of said supports.

5. A grinding machine having a work support and a grinding wheel support mounted for relative approach and retractive movements one with respect to the other, means actuated by fluid pressure to effect the advancing relative movement, a source of fluid pressure, valve means intervening the source of fluid pressure and said actuable means for controlling the rate of flow from said source to said actuable means, cam means for actuating said valve means to vary said rate of fluid flow, manual means operable on said cam means to cause a rapid traverse flow, power operable means eflective on said cam means to restrict the flow and thereby produce a normal grinding rate, means actuable bysaid power operable means and operatively effective on said cam means to further restrict the flow to efiect a predetermined slow rate of relative movement per second that is less than the tolerance allowed on the work for roundness, a sizing mechanism responsive to the size of the work, and means operable thereby to effect immediate separation of said supports during said slow rate of movement.

6. A grinding machine having a work support and a grinding wheel support mounted for relative movement one with respect to the other, fluid operable means for efiecting said relative movement, a source of fluid pressure therefor, and

control mechanism for governing the flow of pressure fluid from said source to said means including manually operable means for adjusting said flow to obtain a rapid traverse rate of relative movement, means for restricting the rate of flow to said means to produce a normal grinding rate of relative movement, means subsequently operable by the moving support for automatically effecting a further restriction in the rate of flow to produce a rate of relative movement which is less than the tolerance allowed for roundness of the work, and means dependent on the size of the work and effective during said slow rate of movement to eiTect immediate separation of said supports whereby any overrun will be less than the tolerance allowed on the work for roundness.

7. A grinding machine having a work support and a grinding wheel support mounted for relative movement one with respect to the other, piston and cylinder means for effecting a relative advancing movement of one of said supports toward the other, a source of fluid pressure, valve means for controlling the rate of flow of fluid pressure to said cylinder means and the flow of fluid from said cylinder means, a control mechanism for actuating said valve means for governing the rate of fluid flow therethrough including manually operable means for adjusting said valve means to obtain a rapid traverse rate of relative movement, means operative upon said valve means for restricting the rate of flow therethrough to produce a normal grinding rate of relative movement, means subsequently operable for eifecting a further restriction in the rate of flow to produce a rate of relative movement which is less than the tolerance allowed for roundness of the work, and means dependent on the size of the work and effective during said slow rate of movement and operative upon said piston and cylinder means to eflect immediate separation of said supports.

8. In a grinding machine having a grinding wheel and a work support, the combination of power operable means for feeding the grinding wheel toward the work support to progressively effect retraction in the size of work carried by the work support, said power operable means including piston and cylinder means for shifting the grinding wheel, a hydraulic control circuit including valve means for controlling the rate of said shifting movement, a source of pressure, an electrical sizing gage for continuously measuring the work during the grinding operation, said gage having a switch adapted to be closed upon the work attaining a predetermined size, an electrical circuit in series with said switch and an electrically operable valve in said circuit for actuation by the closing of said switch for directly connecting said source of pressure to said piston and cylinder means to effect retraction of said grinding independent of said valve means.

9. In a grinding machine having a grinding wheel and a work support, the combination of power operable means for feeding the grinding wheel toward the work support to progressively efiect a reduction in the size of work carried by the work support, said power operable means including piston and cylinder means for shifting the grinding wheel, a hydraulic control circuit including valve means for controlling the rate of movement of said piston means, trip controlled means effective on said valve means for reducing the rate of movement to a slow rate, a source of pressure, an electrical sizing gage operatively engaged with the work being ground and having a switch adapted to be closed during said slow rate of movement and an electrically operable valve electrically connected to said switch for operation thereby to directly connect said source of pressure to said piston and cylinder means independent of said valve means to effect immediate retraction of the grinding wheel upon the work attaining the gage determined size.

ALVIN F. ALT. JACOB DECKER.

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

UNITED STATES PATENTS Number Name Date 2,000,553 Alden May 7, 1935 2,115,678 Belden Apr. 26, 1938 2,267,391 Astrowski Dec. 23, 1941 22,448,874 Flygare Sept. 7, 1948 2,448,921 Silven Sept. 7, 1948 2,464,142 Marshall Mar. 8, 1949

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