US2092721A - Automatic grinding machine - Google Patents

Description

' ARTER u 2,092,721

' AUTOMATIC GRINDING MACHINE Filed March 13, 1956 4 Sheets-Sheet 2 ATTORNEY.

3 Sept; 7,}1'937.

H. ARTER 2,092,721 AUTOMATICGRINDING MACHINE Filed March 13, 1956 4 Sheets-Sheet 3 INVENTOR w Q ATTORNEY I Patented Sept. 7, 1937 U TED sTATESgPATENTQ F Harry Arter, Worcester, Mass; assignor to Arter Grinding Machine Company, Worcester, Mass, a corporation of Massachusetts Application March 13,- 1936, Serial Nemesis 10 Claims. (01. 51 -95) This invention relates to automatic grinding read in connection with theaccompanying drawmachines and other machine tools. It will be ings, and the novel features will be particularly herein. disclosed as embodied in a grinding mapointed out in the appended claims. chineof the general type shown and described in In the drawings, i i

United states Letters Patent No. 1,736,967. Figure 1 is a verticabsectional view, somewhat 5 Inmachines of this general character, autodiagrammatic in character, of an, automatic, matic mechanism is provided for producing relagrinding machine organized in accordance with tive approaching and receding movements of the this invention;

work and grinding. wheel, or other tool, during Fig. 2is a development of i a typical cam used each cycle of operations of the machine. Usually in the construction. shown in Fig. 1; g 10 this operation is accomplished by means of a Fig. 3 is a diagrammatic view of said cam; power driven cam and suitable connections Fig. 4 is a diagrammaticview of. an hydraulic through which said cam is enabled-to move the system showing the provision for self-replenish tool toward and from the work, it ordinarily being ment of the liquid column; utilized for power more convenient to move the tool than the work. transmitting purposes which forms an important 15 In a typical construction the operating mechafeature of this invention; nism is so organized and arranged as to produce a Fig. 5is a view similar to Fig. 4 illustrating a rapid approach of the tool to the working zone, another hydraulicsystem embodying features of then a relatively slow approach in the working the invention; i l

zonewhich brings the tool in contact with the Fig. 6 is a diagrammatic view illustrating still 20 work and feeds it at a predetermined rate, next another modification; a dwell during which the tool finishes its opera- Figs. '1 audit are plan and. development views tion and sizes the work to the desired dimen respectively, of a cam used in the system shown sions, and finally a quick receding movement of inFig. 6;

the tool. In prior machines it has been custom- Figs. 9 and 10 are-corresponding views of 25 ary to transmit mechanically the motion 1mg anothercam; and r t parted by some power driven element, such as a Fig. 11 is a view similar to Fig. 1 showing a cam, to the tool head, and the matter of arranganother modification; l H a ing and positioning the various elements oithe Referring first to Fig. Lthe machine there 3 transmitting mechanism relatively to the other showncomprises a frame! onwhich is mounted parts of the machine frequently is extremely a bed piece 2 connected with the frame by a pivot troublesome and inconvenient and imposes unde- 2' about which the bed may be angularly adsirable limitations upon the design. Furtherjusted relatively to the frame. A wheel head 3 more, such a transmitting mechanism does not is mounted'inguidewaysprovided in the bed 2 permitof any large degree of flexibility; either for sliding movement toward and from the work 35 as to the location of the parts, or to the desirable supporting mechanism, indicated diagrammatimodification of the movements transmitted to cally at 6. Adjustment of the wheel head and them or by them. In addition, these mechanisms the parts carried thereby relatively to .the work are expensive t'o'manuiacture, and the degree of may be made through operation 'of the hand 40 accuracy with which they will operate is affected wheel 'I. The grinding wheel 5 is secured rigidly 40 greatly by the nature of the design and consetoashaft 4 which is mounted on a quill 46, the quently, by those limitations which the design quill being supported for limited rotative movehas been compelled to meet." ment about its own center 0, while the shaft 4 The present invention deals especially with is eccentrically disposed with reference to said these considerations. It aims to devise apower center. The arrangement is such that rotation 45 transmitting mechanism for use in such relationof the quill in a counterclockwise direction will ships as those above described, which will have move the shaft I and the wheel 5 away from the the desirable features of convenient adaptability work while a rotative movementof the quill in to different designs, simplicity in? construction, the opposite direction will have a reverse effect.

flexibility, accuracy in operation, and economy in It-will be observed that the mounting of the 50 constructionlcosts. The invention involves both wheel, the wheel head and the bed are such that a new method and also a novel machine organizacompensation for wear of the'giinding wheel may tion. easily be made through adjustment of the hand The nature of the invention will be readily wheel 1.. Suitable adjustments for the taper of understoodfrom the following description when the work can also readily be produced, while the 55 relative approaching and receding movements of the work and wheel produced through the movement of the quill 46 are independent of, and unaffected by, the adjustments just described.

All of these parts may be constructed, arranged and operated in the manner disclosed in the patent above referred to, and reference may be made thereto for a more complete disclosure of the construction and operation of the various units of the machine, and more especially of a typical mechanism for operating the quill similar to that illustrated at 46.

In the machine disclosed in the patent above referred to, the operation of the quill is produced solely by mechanical means. With a view to avoiding the limitations which the use of such a mechanism necessarily involves, the present invention proposes to replace the mechanism for transmitting the movement of the power operated cam to the quill with a column of fluid so arranged that the motion of the cam will be faithfully and accurately transmitted to the quill.

It is recognized that in any fluid pressure system leakage is unavoidable, and that the effect of leakage occurring in successive cycles of operation of a machine of the type here shown, would seriously impair the accuracy of such operations. Accordingly, another important object of this invention is to compensate for such leakage at intervals so frequent that any cumulative effect will be avoided and the system will be maintained continuously in such condition that it will function faithfully and accurately.

Referring again to Fig. 1, the cam shaftwhich controls the time relation of the functions of the machine is illustrated at 24". It carries a cam 25, the operating'surface of which is divided into four sections, as illustrated more clearly in Figs. 2 and 3, which control the movements of the wheel toward and from the work and divide said movements into substantially the four periods above referred to. The slopes C--D of the cam produce the quick movement of the wheel away from the work; the lobe D-A holds the wheel stationary but away from the work; theslope AB permits the rapid approach of the wheel toward the work, and the section B-C permits a controlled approach of the wheel. in the working zone, this section being functionally divided, as hereinafter described, into approach and dwell periods. The foregoing constitutes a complete cycle 'of thecam.

As shown in Fig. 1, the cam 25 operates a bell crank lever 26 which is connected through a link to the piston rod 2I of a piston 28 working in a cylinder 35 which is attached to the machine at any convenient point. Starting at'the point C on the cam, it first moves the lever in such a direction as to tend to compress the liquid in the cylinder, and this motion is transmitted through the liquid columnin the pipe 23, which connects the cylinder 35 with another cylinder 36 mounted within the wheel head. The movement of the piston 23 thus is transmitted to and produces a corresponding movement of the piston 30 in the latter cylinder. Projecting from the piston 30 isa piston rod 31 bearing against an arm 32, so that the upward movement of the piston produces a counter-clockwise rotation of the quill l6 and therefore moves the wheel away from the work. When the roll 26' on the upper end of the lever 26 rides up the slope C-D of the cam and on to the lobe 'D- -A, the arm 32 will be raised until it strikes the adjustable stop 34. The parts remain in this Position until the cam 25 has revolved far enough to allow the roll to start down the slope AB. At this time the spring 33 acts through the arm 32 to rotate the quill in a clockwise direction, the rate of this rotation, however, being controlled continuously by the contour of the cam. This control is effective by virtue of the fact that a solid, substantially noncompressible column of liquid continuously connects the pistons 23 and 30. During this clockwise rotation of the quill, the grinding wheel 5 is moved toward the work, this motion being rapid during the interval AB and more gradual as the roll follows the slope 3-0. At some point in this slope the wheel comes in contact with the work, the grinding operation is begun,

, and it is completed during the dwell which occurs after the projection 38 on the quill has come into contact with the stop 31 on the wheel head. The cycle then has been completed, and the parts are ready for a repetition of this cycle.

A very important feature of this invention resides in the adjustment whereby any desired portion of the slope BC of the cam can be used to control the approaching and wheel feeding movement. That is, this movement can be terminated at any point in the slope 3-0, and the remainder of said slope can. be utilized for the dwell period. Thus the slope B-C can be functionally divided, as above indicated. This result is effected by the adjustment of the stop 3|. The manner in which it is produced will be best understood by first describing the hydraulic system ggnnected with the power transmitting column Referring more especially to Fig. 4, it will be seen that the hydraulic system there illustrated includes a pump l3 which may be driven as H- lustrated in Fig. 1, and which draws oil from the tank I and forces it through a pipe IS in which a relatively low pressure is maintained by the automatic relief valve l3 through which a stream of oil is always flowing. This pressure must be sufncient to move the pistons 23 and 30, but unable to overcome the resistance of the spring 33. Oil from the pipe it can pass through the check valve 2| into the transmitting column in the pipe 23 when the pressure in this column islower. than that in the pipe i3.

It should also be observed that, assuming the stop 34 to be so adjusted that it just permits the complete transmission of the entire movement produced by the lobe C-D, any downward adjustment of the stop will result in preventing the full transmission of the movement of the piston 28 to the piston 30. In other words, the piston 30 will force the arm 32 against the stop 34 at some point in the slope C-D of the cam. The excessive pressure created in the hydraulic column by the continued movement of the piston 28 after the piston 30 has been stopped,

will be relieved by the escape of oil through the automatic relief valve 22, this valve being set to hold a pressure considerably higher than the valve l3, but to relieve the pressure before any parts would be unduly stressed. Under such conditions, and upon the return movement of the quill produced by the spring 33, the rotation of the. quill. will be interrupted by the stops 31 and 33 while the roll 26' is on some part of the slope 3-0, the exact point on this slope being determined by the adjustment of the stop 34. A further rotation of the cam after this point has been reached would, if other conditions permitted, reduce the hydraulic pressure in the pipe 29 to zero, and during the restvofthis rotation, until the roll starts upthe slopeC-D, the pistons 28* and 30 "would beleft in a free or floating condition,tliere being no tendency tomove them in' either direction.

Thus any desired portion of the slope B-C of l the cam can be utilized in controlling the approach of the wheel to the work and. its feedingmovement at apredetermined speed after'the grinding operation has been initiated.

The interval of abnormallylow pressurejust described is utilized to introduce new fluid into the system to replace'any loss-that has occurred during the cycle due to the escape of liquid "through the pressure relief valve '22because of excessive pressures created. As above stated, oil under low pressure is maintained continuously fiowing through the pipe l6; Consequently, as soon as thehydrostatic pressure in the'pipe 29 falls below thatin the-pipe l6, oil will flow autoif this loss is allowed to accumulate it will introduce serious errors insubsequent cycles, and eventually will make the transmitting mechanism inoperative. However, the arrangement above dscribed for replenishing the loss of liquid which escapes through the pressure relief valve, alsooperates automatically to replace any liquid lost by leakage. In other words, the power transmitting portion of the system is automatically filled with chat the end of each cycle and before the next cycle is commenced, so that there can beno accumulation of lost motion dueto leakage from any cause. i

Such an hydraulic system as that shown may also be used in connection with the hydraulic operation of other elements of the system, and it iscontemplated that the invention may be applied to machines equippedwith a hydraulic systemfisedto, Pe other ions. Suchan embodiment of the invention is illustrated diagrammatically in Fig. 5. Here the supply tank I4, pump |3,and pipe it are arranged as above described'butthe pipe i6 is connected to a valve 40, located in avalve casing 4|, and the valve is operated by a cam 39, mounted on the cam shaft 24,whichalso carries the cam 25 previously referred to. The valve mechanism 40-4I and its operating'cam constitute a control mechanism for operating a piston 44 which may be made to move any load, indicated diagrammatically at 4 5. Thepressure relief valve I1 maintains the pressure in the supply pipe 16 necessary for operating the piston 44.

In this arrangement the oil exhausted from the cylinder inwhich the piston 44 works andfrom the valve cylinder 4i is returned through pipes Illa and I811, and'a branch pipe I80 runs from the pipe 180, to the check valve2l, thus conducting. oil to the pipe 29 which connects the cylinders 35 and 36 of the construction shown in'Figs. land 4., Apressure relief valvey22 als'ois connected into this system to function as in the arrangernent previously described. In order to maintain in this system a pressure 'Eufficientto move the " pistons 28 and 30, as previously described, while still limiting this pressure to the requirements of the spring. 33, a pressure relief valve I9 is connected to the discharge end of the pipe la and is itself connected through the pipe 20 with the tank 14. ,7 This valve is so adjusted that it maintains the desired pressure on the;

system I841, I81), I80 and 29, such pressure being predeterminedv and varied to'suit the requirements.;of individual cases by adjustment of the valve l9. Thus this hydraulic system can be made toserve several purposes. The systemillustrated diagrammatically in Fig. 5 is shown also in Fig. 1,

only those parts of the system necessary to an. understanding of the operation of Fig. 1 being illustrated, however, in the latter figure.

Instead of using the power stroke of thepiston 28 to move the wheel 5 outwardly as in the constructions above. described, and utilizing a spring 1 to produce the inward moyement of the wheel, these operations may be reversed. In some sit uations such a reversal is desirable in order to avoid alterations of the feeding movement which might be necessary if the arm 32 of the quill 46,

remained against the stop 34 for an excessively long time. It is also contemplated that if a large.

retraction of the wheel is desired, or when other special conditions make it advantageous, the piston 28 may be replaced bya plurality of pistons, one of which will operate to produce the slow motion of the wheel, and another toefiectIits quick retracting movement. Such a construction] is illustrated in Fig. 6. Here the spring 33 rotates the quill 46in a direction tolmove the grind ing wheel away from the work, this movement be-, ing limited by the stop 34, while the piston produces the opposite rotation of the quill. Also,

the quick retracting, movement of the wheel,

while the cam 48, Figs. 6, 9, and 10, controls the slow motion of the wheel Inthis arrangement the pistonwhich produces the outward movement may conveniently be of large diameter, thus permitting-a camof smallrise to produce a relatively large retracting movement of the wheel, :while that which controls the slow. motion can .be of smaller diameter so that long slow motion surfaces of the cam maybe utilized, and thus the efiect of slight inaccuracies in the surface of the cam will be minimized.

In order to cushion the wise would be caused by the sudden stopping of .the piston 44, Fig. 6, at each end of its stroke, the two'pipes 42 and .43, which conduct liquid shock which other to and from the cylinder in which this piston works, may beconnected closelyadiacenttothe cylinder by pipes GI .and 62, respectively, and :ipressure relief valves may be connected in to these two pipes so that the flow, permitted through one pipe will be opposite to that. through the :other. pressures slightly higher than the operating pressures inthe pipes 42 and 43. The valve 40 customarily is timed to. close either port which These valves should be set. toopen at momentarily serves as. theexhaust, an instant before the piston reaches the end of its stroke.

and the high pressure. set up by the momentum of the piston andthe parts moving with it thus is exerted on the oil trapped in the pipe which,

immediately prior to this instant, has been conducting the exhaust oil. With the arrangement shown, the high pressure so created can be relieved through one-or the other of the pipes 5| and 62 by the opening of its pressure relief valve, but the valve can be adjusted so that it will-give the desired cushioning action to the piston and bring it to a stop before it reaches the endof its stroke.

It will be observed that the motions of the cam 25 which are transmitted to the quill 45 can be modified by making suitable changes in the ratio of the arms'of the lever 25, or in the ratio of the areas of the pistons 28 and 30.

In addition, the lever 25 may be made adjustable to increase or decrease the basic motion of the cam 25 which is utilized in operating the parts driven therefrom. Such an arrangement is illustrated in Fig. 11 in which the. general machine organization shown is essentially like that illustrated-in Fig. 1, but the cam shaft 24 and cam 25 have been moved into a diiierent location. Also the cylinder 35, in which, the piston 28 works, is located horizontally. Instead of the lever 25, a compound lever mechanism is utilized to transmit motion from the cam 25 to the piston. This mechanism comprises a lever 52 having a roll 53 mounted in its free end and running on the surface of the cam 25. Another lever 54, extending in agenerally parallel relationship' to the lever 52, bears against the end of the piston rod. The movement of the lever 52 is transmitted to the lever 54 by means of a roll 55, mounted in a block or holder 56, which slides in a dove-tail guideway formedin the lever 52. Bolts 51, extending through a long slot in the lever 52, are threaded into the block 56 and serve to hold it in any position of adjustment.

It will be clear from an inspection of Fig. 11 that adjustment of the block 56 downwardly to ward the cam will increase the movementvimparted to the piston-28 by a given throw of the cam, while adjustment of the block 55 upwardly will decrease said movement. Thus the basic motion of the cam 25 can be increased or decreased through appropriate adjustments of this compound lever mechanism.

Initial adjustment of the entire wheel head may be made manually toward and from the work by means of the hand wheel I. Since this adjustment involves a movement of translation of the cylinder 36 relatively to the frame I, some provisionfor it must be made in the pipe or hydraulic transmitting column 29. This may consist in introducing a flexible section 60, Fig. 11, in the pipe 29. Or, swivel jointed rigid sections of pipe may be included in these connections between the cylinders 35 and 36 to accomplish the same object. In either event the sections should not be of variable volume.

The invention thus provides a fluid actuated transmitting mechanism for use in automatic grinding machines and other machine tools which is relatively simple in construction, can be manufactured economically, is readily adaptable to a great variety of designs, while avoiding the complications andlimitations which necessarily are involved in producing the same operations mechanically, and which, in addition, is flexible in operation and extremely accurate.

While in the machine above described the reciprocating movement of the wheel 5 toward and from the work occurs in the arc of 'a circle around the center of the quill, it is obvious that the invention is equally applicable to the production of a straight line reciprocating movement of the wheel, or of any suitable movement of the wheel head to carry the wheel toward and from the work. Likewise, this mechanism is useful in producing an axial reciprocating movement of the. wheel as for example, in grinding to a shoulder.

While I have herein shown and described typical embodiments of my invention, it will be understood that the invention may be embodied in a great variety of forms without departing from the spirit or scope thereof. For example, while I have shown pistons working in cylinders to produce the hydraulic transmission of the movements desired, it is obvious that these 7 devices could be replaced by bellows, diaphragms,

vanes, or the like, where desirable, the latter elements being equivalents of the former.

Having thus described my invention, what I desire to claim as new is:

1. In a grinding machine, the combination of a grinding wheel, means supporting said wheel for reciprocating movement toward and from the work, a power driven cam, a piston operated by said cam, a second piston, cylinders for said pistons, means confining a. column of liquid connecting said cylinders and operative to hydraulically transmit motion from one of said pistons to the other, means connecting said second piston with said wheel to cause the latter piston to move the wheel relatively to the work, liquid supplying means connected with said column and including a pump and a liquid supply line leading from said pump to said column, a check valve in said line permitting liquid to flow into the column, and means for automatically maintaining pressure in said supply line sufllcient for operating purposes.

2. In a grinding machine, the combination of a grinding wheel, means supporting said wheel for reciprocating movement toward and from the work, a power driven cam, a piston operated by said cam, a second piston, cylinders for said pistons, means confining a column of liquid connecting said cylinders and operative to' hydraulically transmit motion from one of said pistons to the other, means connecting said second piston with said wheel to cause the latter piston. to move the wheel in one direction relatively to the work, a spring connected with said wheel to move it in the opposite direction when permitted to do so by said second piston and its connections with said cam, liquid supplying means connected with said column and including a pump and a liquid supply line leading from said pump to said column, a check valve in said line permitting liquid to flow into the column, and means for automatically maintaining pressure in said supply line sufiicient for operating purposes and of such a value that said spring can return said second piston against said pressure but only as said cam permits such return. I v

3. In a grinding machine, the combination of a grinding wheel, means supporting said wheel for reciprocating movement toward and from the work, a power driven cam, a piston operated by said cam, a second piston, cylinders for said pistons, means confining a column of liquid con necting said cylinders and operative to hydraulically transmit motion from one of said pistons to the other, means connecting said second piston with said wheel to cause the latter piston to move the wheel in one direction relatively to the work, a spring connected with said wheel to move it in i said second pistonand its connections withsaid cam, liquid supplying means connected with said column and including a pump and a liquid supply 1 machine. l l '1. In a grinding-machine, the combination with a grinding wheel, a shaft supporting said wheel, a rotary quill in which said shaft is mounted eccentrically, an arm rigid with said quill and extending laterally therefrom, a power driven cam,

HARRY 5 ,lineleading from said pump to said column, a piston operated by said cam, a second piston, 5 means for limiting the pressure maintained'in cylinders for said pistons, means confining a said supplyline to a substantially predetermined column of liquid connecting said cylinders and 1 value, at check valvein said line permitting liquid operative'totransmit the motion of said first pisa to flow into the column, and a pressure relief ton to said second piston, means connecting said 10, valve connectedwith said column and limitingthe secondpiston with said arm to cause the movepressure created therein. H I ment of the latter piston to rock said quill in one 4. Ina grinding machine, the combination of a& direction, a stop for limiting the movement so machine frame, abed mountedon said frame, a transmitted to said arm, a spring connected with Pi o co nection between said bed and said i said arm to move it in the opposite direction, and. 1 frame whereby the bed may beadjusted angularly a second stop for limiting the movement of the 15 about said connection relatively to the frame, a .arm produced by said spring, one of said stops grinding wheel mounted on said bed for reoiprocabeing adjustable. tion toward and from the work, a power d ve y 8. A grinding machine according to'preceding i earn, a piston operated by said cam, a second claim 7, including a liquid supplying means compistomoylindrs fo Said Pistons, means co nec prising a pump and a supply lineleading fronr 20 ring d secondipiston h saidiiwheel to Cause 1 saidpump to said column, a check; valve in said i t latter Piston 9 e e Wheel, and means supply line permitting the free flow of fluid thereconfining a column of liquid extending u from into said column, a pressure relief valve f said pivotalconnection and connecting said cylconnected th Said column, and means cooperi tfor yd y transmitting motion ating with said pump to maintain a minimum 25 from sa d fi t Piston Said Second D Q operating pressure in said column and for limiting 5- lnalg i i the Combination t said pressure to a value below that applied to a grinding Wheel, @Tshaft Supporting, S Wheel, the system by the action of said spring on said a rotary quill in which said shaft is mounted second pistor l ,y eccentrically; an arm rigid with said quill and 9 A grinding machine according to preceding 30 extendin laterally th ef a power driven .claim 3, including asecondhydraulicallyactuated cam, a piston pe ated by-said cam, a second unit to which liquid is supplied by said pump, P Cylinders S Pistons, means @011- power driven means positively connected with fi n a column of l qui connecting Said Y said shaft for controlling the operation of said inders a ope F ra the m of second unit, and means for maintaining the nor- 35 Sa d fi D fi I O d se Piston, d means mal operating liquid pressure forsaid second unit conne tinesaid second p s with a -a to at a different value from that in said hydraulic cause the movement of the latter piston to rock transmitting column n 1 a n Qt l 10. In a grinding machine, the combination of 6. In a r n m e wmb na h" a grinding wheel, means supporting said wheel for 40 a grinding Wheel, a Shaft pp ng 8 9 ee a reciprocating movement toward and from the rotary quill inwhich said shaft is mounted eccenwork, two power driven cams independent p151 trically, an arm rigid with said quill and extendt perated by said respective Cams third a y thc ifro I f driven 5 D piston, cylinders for said pistons, means confining $0 iopelated b S F Q E Piston} W1 a column of liquid connecting the cylinders for 5 ders for said pis n m co fi e um the first two pistons with that for said third of quid. connecting said cy fl Operative pistonto hydraulically transmit motion from the i to trans the motion Iifirst P t W said firsttwo pistons to the third piston, means con- Sec P mea j n t e a Sew dl necting saidthirdpiston with said wheel to move 5 ton with said arm to cause the movement-of; the the wheel relatively to the work, and means for latter piston to rock saidquill, and means for automatically maintaining the same basic volume automatically maintaining the same'basic volume- 101 liquid in said hydraulic transmission column of liquid in said hydraulic transmission column fduring the movement of said wheel by saidthird during the movement of saidwheel bysaid'second piston in successive'cycles of operation of the piston in successive cycles of operation of the machine. 55

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