US2078695A - Automatic lathe and fluid circuit - Google Patents

Description

April 1937- E. J. SVENSON 2,078,695

AUTOMATIC LATHE AND FLUID CIRCUIT Original Filed March 27, 1930 10 Sheets-Sheet 1 Ernest J5venson 2 7% (Q550 mw APril 1937- E. J. SYENSON 2,078,695

AUTOMATIC LATHE AND FLUID CIRCUIT l0 Sheets-Sheet 2 Original Fued'uarcn 27, 1950 .Ezuevvfior Ernest J 5112715071 April 27, 1937. J v so 2,078,695

AUTOMATIC LATHE AND FLUID CIRCUIT Original Filed March 27, 1930 10 Sheets-Sheet 25 April 7, 1937. E. J. svENsoN 2,078,695

AUTOMATIC LATHE AND FLUID CIRCUIT Original Filed March 27, 1930 10 Sheets-Sheet 4 E li/67225 l'rneszfil5veno7z,

April 27, 1937. E; V N 2,078,695

' AUTOMATIC LATHE AND FLUID CIRCUIT Original Filcgizlflarch 2'7, 1930 10 Sheets-Sheet 5 April 27, 1937. a J. SVENSON 2,078,695

numonuvrxc 1.1mm AND mm: cmcul'r Original Filed March 27, 1930 10 Sheets-Sheet 6 [WU/e525 15116725072 @%wg@ M9 995.

April 27, 1937. E. J. SVENSON AUTOIATIC LATHE AND FLUID CIRCUIT Original Filed March 27, 1930 10 Sheets-Sheet 'T Ernest J 5112725072; @w m e.

wfiw 8w $6M Kw? I \mqh MWM QQQN W QQN w Q i Q o o www mm M M NN NW Q9 QQM NM 0 Wm N w MN NM H ./1CC r :(CCCC CCCCCQCB a w/// //////////////A///// //////7/////// NM 5 QR April 27, 1937. E. J. SVENSON AUTOMATIC LATHE AND FLUID CIRCUIT hamr:

A K h iii dww fl:

Original Filed March 27, 1930 10 Sheets-Sheet 8 A 27, 1937. F. J. SVENSON AUTOIATIC LATHE AND FLUID CIRCUIT 10 Sheets-Sheet 10 Ell/6w" finestJSvmwon mwwu Hm w (U WM Patented Apr. 27, 1937 UNITED STATES PATENT OFFICE Application March 27, 1930, Serial No. 439,306

Renewed February 8, 1937 219 Claims.

My invention relates generally to automatically actuated material working apparatus, and particularly to apparatus such as automatic lathes equipped with a fluid or hydraulic system of control.

My present invention relates in a general way to apparatus or machines of the type shown in my co-pending application, Serial No. 391,130, filed September 9, 1929. My present invention. however, contemplates the provision of improved structural features, by means of which cutting operations and the like may be performed upon a work piece in a more expeditious manner. To bring to pass these desirable results, I propose to provide a lathe or metal cutting machine. in which the constituent number of parts is reduced greatly, the structural arrangement is unusually rigid, and the combination of machine elements is exceedingly simple. This simple yet durable 2o structural arrangement will enable my device to be operated with a minimum amount of skill and effort on the part of an attendant, and it is also my purpose to so arrange the cooperating machine elements so as to render the control thereof foolproof.

One of the important objects of my present invention is to provide, in combination with movable machine elements, such as tool carriages and the like, a system of fluid control which is not only exceedingly simple in arrangement and economical to manufacture, but which is also exceedingly efllcient and positive in controlling the movement of these machine elements. To this end I propose to provide what I shall hereinafter refer to as a closed, valveless, fluid circuit. in combination with the machine elements, such as tool carriages and the like. which are to be shifted. This novel and practical valveless fluid circuit is not only adapted for use, in connection with the control of machine tools. but has a very broad application in various fields wherein it is desirable to hydraulically effect the shifting of Another object of my invention is to provide hydraulic means, in combination with a machine spindle, whereby a governed amount of movement of tool carriages and the like may be obtained per revolution of said spindle. In other words, I propose to correlate the movement of the spindle with the movement of the tool carriages, and in order to presenta practical, workable arrangement, I contemplate directly coupling with the spindle a plunger pump ofa new and practical design which is free from fluid leakage or slippos (CI. bit-4t) Still another object of my present invention is to provide, in combination with elements to be moved, such as machine tool carriages and the like, a fluid system of control having a closed high pressure circuit and an associated low pressure circuit, said high pressure circuit being employed for feeding purposes, and the low pressure circuit for rapid traverse movements.

More specifically, my invention contemplates the provision of the abovementioned associated high and low pressure fluid circuits which are so arranged that each of said circuits is operable independently of the other.

A further object is to eliminate the necessity of employing complicated fluid control valves and the like which have not only been very expensive, but which have also had a decided tendency by reason of fluid leakage. etc., to materially reduce the propelling effectiveness of the fluid pumping mechanism forming apart of the circuit which normally includes such control valves. To remedy this condition I propose to provide a new and improved single control for governing the movement of a plurality of machine tool carriages and the like. which may be conveniently manipulated without disturbing or affecting in any way the propelling effectiveness of the pump included within the feeding circuit.

A still further object of my invention is to provide. in combination with machines as above set forth. a continuously operable low pressure fluid propelling mechanism, such as a gear pump, and a high pressure fluid propelling mechanism, such as a plunger pump, which is directly coupled with the machine spindle, the propelling effectiveness of one of said pumps being totally independent of the propelling effectiveness of the other.

Another object is to overcome the disadvantaxes and difnculties resulting from the use of clutch and other transmission arrangements which have been employed in connection with machine tools and the like.

These and numerous other objects and advantages will be more apparent from the following detailed description when considered in connection with the accompanying drawings, wherein- Figure 1 is a plan view of an automatic lathe which is constructed and arranged in accordance with the teachings of my present invention:

Figure 2 is a front elevational view of the device shown in Figure l;

Figure 3 is a vertical sectional view taken longitudinally of the machine substantially along the line H of Figure 5;

Figure 4 is an end elevational view as viewed from the left of Figure 2, a portion of the upper structure thereof being broken away to more clearly disclose the position of the upper fluid reservoir;

Figure 5 is a vertical transverse sectional view taken substantially along the line 55 of Figure 2;

Figure 6 is an enlarged fragmentary sectional view taken transversely of the guide bar along the line 6-6 of Figure 2;

Figure 7 is a view of the device shown in Figure 6, said view being taken substantially along the line 11 of Figure 6;

Figure 8 is an enlarged plan sectional view of the main drive shaft and its associated driving elements;

Figure 9 is a detail sectional view of the clutch control mechanism, said view being taken substantially along the line 5-9 of Figure 8;

Figure 10 is a horizontal sectional view of the clutch control cylinder and piston, said view being taken substantially along the line ill-I0 of Figure 9;

Figure 11 is an enlarged plan view of the dog supporting slide, the mechanical mechanism controlled by the rear tool carriage for causing the actuation of said slide, the main control or reversing valve, and the valve for controlling the longitudinal movement of the front carriage, said valves being shown in section in order to disclose more clearly the structural characteristics thereof;

Figure 12 is a vertical sectional view taken transversely of the rear tool carriage substantially along the line l2l2 of Figure 1;

Figure 13 is a fragmentary vertical sectional view of the slide and associated parts, said view being taken along the line l3l3 of Figure 11;

Figure 14 is a plan view of the slide, said slide being shown in its advanced position as distinguished from the neutral position shown in Figure 11;

Figure 15 is a fragmentary transverse vertical sectional view taken substantially along the line i5l5 of Figure 11;

Figure 16 is a. similar transverse sectional view taken along the line |6-l6 of Figure 11;

Figure 17 is also a transverse sectional view taken along the line l|--|| of Figure 11;

Figure 18 is a central longitudinal sectional view of the reversing valve taken substantially along the line |8IB of Figure 11;

Figure 19 is a transverse sectional view of the right end of the reversing valve taken along the line i9l9 of Figure 11;

Figure 20 is a sectional view similar to Figure 19, disclosing the relative positions occupied by the valve ports when said valve has been rotated so as to effect the discharge of fluid from one extremity of the valve chamber for reversing pur- P Figure 21 is a central sectional view of one of the high pressure plunger pumps disclosing the manner in which fluid is received and discharged y a d D p;

Figure 22 is a transverse vertical sectional view of said pump taken substantially along the line 2222 of Figure 21;

Figure 23 is a diagrammatic representation of the fluid circuit for controlling the movement of the tool carriages, the control or reversing valve being shown in its neutral position;

Figure 24 discloses the reversing or control valve when said valve has been shifted to its forward or starting position;

Figure 25 discloses said valve in its reverse position; and

Figure 26 is a fragmentary vertical sectional view of the continuously operable gear pump.

Referring now to the drawings more in detail wherein like numerals have been employed to designate similar parts throughout the various figures, it will be observed that for the purpose of illustrating one practical application of my invention I have shown the same as applied to an automatic lathe. This lathe comprises a suitable base 30 which serves to support a machine frame 32, Figures 1 to 5 inclusive. In order to set forth more clearly the structural arrangement of my improved material working machine or lathe, I shall describe successively various general units which together constitute the machine in its entirety.

Head stock The head stock is designated-generally by the numeral 34, Figures 1 to 5 inclusive, and a casing portion 32:; of the head stock forms an integral upwardly extending section of the main frame 32, as clearly shown in Figures 2 and 3. Mounted within the head stock housing 32a is a spindle 36, Figure 3, the reduced or outward extremity of the spindle being mounted within a suitable anti-friction bearing 38, and the inner work supporting extremity of the spindle being mounted within a tapered bearing ill. The spindle is provided with a tapered opening 42 and is also flanged to present a face plate 44. For a more detailed description of the specific arrangement of the spindle bearings, reference is made to my above mentioned co-pending application, Serial No. 391,130. Rotation is imparted to the spindle 36 by means of a main drive gear 46, which is keyed to the spindle and is driven through the agency of a pinion 18. Figure 8, and a pair of change gears 50 and 52. The gear 52 is connected directly to a man drive shaft 64, and the mechanism for controlling the operation of this drive shaft will be described later. Mounted upon the spindle 36 and rotatable with the gear 46 is a roller chain sprocket 56 which is connected by means of a suitable chain 58 to gears of a pair of fluid propelling mechanisms or pumps 82, to be described later.

Tail stock The tail stock is indicated generally by the numeral 64, Figures 1 to 3 inclusive, and includes an upright frame section 66 which is slidably mounted upon ways provided within the main frame 32. The upper portion of the frame 66 presents a casing 88, and slidably mounted within the casing 66 is a sleeve Ill. Longitudinal movement of the sleeve 10 within the casing Gil is controlled by means of a hand wheel I! which is mounted upon a screw 14 extending within a screw block 16, Figure 3. The opposite extremity of the sleeve "I supports a center piece ll which is rotatably mounted within the sleeve by means of suitable anti-friction bearings an and 82. The specific structural arrangement oi this center piece 18 and mountings therefor form a part of the invention disclosed in my above mentioned co-pending application. A suitable lever 84 is employed to secure the sleeve 10 in its various positions of longitudinal adjustment within the casing 68.

Front carriage The front carriage of the machine is designated generally by the numeral 86, Fisures 2 and 5. This carriage structure includes a tiltable base or frame 88 which is clamped upon a horizontally disposed cylindrical member or bar IIII by means of screws 92. The cylindrical bar 90 is mounted in suitable bearings 94 and 96, Figure 3, disposed on opposite sides of the front carriage frame 88. The bar 90 is capable of longitudinal and rotatlve movement within said bearings. The frame 88 extends upwardly and forwardly of the bar IIII, as clearly shown in Figure 5, the outer or forward portion of the frame being supported by a depending screw 98, the lower extremity of which carries a roller Hill. This roller rests upon a guide bar I02 which is pivotally mounted at one end by means of a pin I04, Figure 2, the opposite extremity of said bar resting upon the upper end of a piston rod IIIB which forms a part of a fluid actuated mechanism I08. Slidably mounted in guides provided along the upper portion of the frame 88 is a slide III) which provides a mounting for a tool holder III. This tool holder II! carries a suitable metal cutting tool II4, Figure 5, which is secured in position by means of clamping screws H6. The slide III] is adjustable toward and awayfrom the axis of a supported work piece II8 by means of a screw I20. The upward movement of the guide bar I02 about its pivot I04 serves to swing the front carriage 86 about the axis of the bar 80, and thereby carry the tool II4 into proper cutting relation with respect to the work piece. For a more detailed description of the structural arrangement of the front carriage frame 88 and its associated parts, reference is made to my above mentioned co-pending application.

The upward movement of the piston rod I08 is occasioned in response to the admission of a suitable fluid, such as oil, through a pipe line I22. Figures 2 and 23, which communicates with the chamber of a cylinder I24 mounted on the front side of the machine frame 32. This fluid acts upwardly against a piston I26 at the lower end of the piston rod I06, and fluid from the opposite side of the piston I25 is discharged through a pipe line I28. The upward movement of the bar IE2 is interrupted by a stop I 30, Figures 2, 6, and 7. The underside of this stop I" is formed with an inclined surface, which is adapted to be engaged by a complementary inclined surface at the free extremity of the bar I02. The inclination of these surfaces is such as to cause the bar III! to be urged toward the front surface of the machine frame 32, and thereby prevent said bar from experiencing vibrations during the operation of the machine. The stop I" is vertically adjustable by means of a screw I32 which is supported by a bracket I34. Thus, the degreee of upward movement of the bar III! may be determined by adjusting the position of the stop I38 by means of the screw I42. The pipelines I22 and III are connected to a constantly driven fluid propelling mechanism I36, Figures 4 and 23, through the medium of a control valve Ill, said fluid propelling mechanism and control valve to be described later in more detail.

Pipelines I29 and III are also connected at opposite extremities of the cylinder I24, and these pipe lines establish communication between the cylinder I24 and a fluid actuated mechanism I 83, Figures 3 and 23, which is employed to impart longitudinal movement to the cylinder bar 04.

This mechanism I includes a cylinder I in which a piston I3! is reciprocabie, and this piston I31 is connected to one extremity of the cylindrical bar 90 in any suitable manner, such as by means of a piston rod I39. A pipe line I is connected to one extremity of the cylinder I35, and a pipe line I43 is connected to the opposite end of said cylinder. The mechanism I33 is operated in timed relation with respect to the operation of the mechanism I IIB, as will later more fully appear.

It is to be noted that the work piece and spindle rotate in the direction indicated by the arrow in Figures 4 and 5.

Rear carriage The rear carriage of my apparatus is denoted generally by the numeral I40, Figures 1 and 5. This carriage includes a slide I42 mounted on guides I44, Figure 12, of a guide frame I48. This guide frame I48 is supported by the main machine frame 32, as clearly shown in Figures 5 and 12. Mounted upon the slide I42 is a tool holder I48 which is adapted to carry a cutting tool I50, said tool being secured in position by means of suitable clamping screws I52. Movement of the rear tool holder and slide toward and away from the work piece I I8 is occasioned in response to the movement experienced by a piston I54, which forms a part of the fluid actuated means which I have designated generally by the numeral I56, Figures 5 and 23. This mechanism I56 includes a cylinder I58, and the piston I54 which is reciprocabie within said cylinder is connected to a piston rod I60. The outer extremity of this piston rod is adjustably connected to a bracket arm I62 depending from and secured to the outer extremity of the slide I42. Pipe lines I64 and I shown diagrammatically in Figure 23connect the opposite extremities of the cylinder I58 with the high pressure pumping mechanism 62, while pipe lines I68 and I'lfl connect the opposite extremities of said cylinder with the main control valve I88, which is connected with the low pressure pumping mechanism I36. Movement of the piston I54 inwardly causes the tool IBII to be carried into operative association with the work piece for the purpose of making a facing cut across the work as distinguished from the peripheral cutting action of the tool H4. The fluid actuated mechanisms I08, I83, and I56 are operated in timed relation in a manner to be described later.

Fluid supply for feeding purposes The mechanism which I have previously designated by the numeral 62. includes a pair of plunger pumps I12 and Illa, Figures 1, 2, 4, and 21 to 23 inclusive. These plunger pumps are conveniently mounted upon the upper portion of the head stock frame 82a immediately above the spindle 36. Each of these pumps I12 and Illa includes a stationary cylinder block or housing I14, Figures 21 and 22, in which a plurality of radial pistons or plungers I" are reciprocably mounted. Movement is imparted to these pistonsby a ring I'll which is supported by an antifriction hearing I carried by a rotary driving member III. This rotary driving member I82 is coupled by means of a tongue and groove connection I84 with a tapered or frusto-conical rotary valve I46 which is mounted within a complementary tapered bearing I88. The upper end of each of the chambers, in which the pistons I" are reciprocabie, is connected by means of 7 a passageway I with companion ports I92 provided in the tapered bearing member I88, Figure 21. This rotary valve I86 is provided with peripheral ports I94 and ISla which are adapted to register successively with the radially positioned passageways I90. The peripheral port I91 communicates with an annular port I96 provided in the bearing member I", while the peripheral port I9la communicates by means of a longitudinal passageway I98 with a chamber 200, which is enclosed by means of a casing 202. A suitable anti-friction thrust bearing 20. is provided to take up end thrust experienced by the rotary valve, and an abutment screw 206 serves to adjustably position the valve within its bearing or seat. The chamber 290 communicates with the pipe line I64, and the annular port or chamber I98 communicates with the pipe line I66.

When the driving ring I18 is positioned coaxially with respect to the rotary valve I86, no movement will be imparted to the pistons I16, but when said ring I18 is eccentrically positioned with respect to the axis of the rotary valve, and the driving member IE2 is revolved, said pistons will be reciprocated during each complete revolution of said driving member. Pivoted fingers 298 are interposed between the adjustable driving ring I18 and the pistons I16 so as to eliminate side thrust during the movement of said pistons. R0- tation is imparted to the driving member I82, or what might properly be called a coupling driving member, through the agency of a journal or a sleeve 2"]. This sleeve 2"! is supported by antifriction bearings 2I2 and 2 within an annular casing 2I6, said sleeve being keyed to a roller chain sprocket or gear 2I8. The driving or coupler member I82 is driven by the sleeve 2M and is laterally shiftable within said sleeve through the agency of a longitudinal shiftable member 229. This member 220 is provided with an extension 222 which is angularly disposed with respect to the axis of rotation of the journal or sleeve 2"), and by longitudinally shifting the member 229 as by means of the micrometer adjusting ring 224, the driving member and its supported driving ring I18 may be sensitively adjusted.

While I have in a separate application, Serial No. 430,867, flied February 24, 1930, now matured into Patent No. 1,989,111, described and claimed specifically the plunger pump or fluid propelling means shown in Figures 21 and 22, I have also described in some detail the structural arrangement of this pump in the present application in order that the high pressure closed fluid circuit, about to be described, may be understood more readily. This will be appreciated more easily when it is understood that the plunger pump just described is of such a nature as to positively preclude fluid slippage or leakage. Heretofore, in using conventional types of fluid plunger pumps, the leakage or slippage of fluid through the rotary valve fittings, as well as other of the pump fittings, has been so great as to positively prevent the use of such devices in a closed or valveless fluid circuit. The gear 2IB is directly connected with the gear 56 on the spindle 36 by means of the roller chain 58 previously referred to. A single roller chain may be employed for propelling both of the plunger pumps I12 and l12a, as clearly shown in Figures 4 and 23.

Rear carriage feeding circuit From the foregoing it will be apparent that when rotation is imparted to the work supporting spindle 36, the plunger pump I12 will simultaneously be activated. This will result in the displacement of fluid at high pressure by the pistons 16 through the ports in the rotary valve and into the pipe line I68, and this fluid at high pressure will be directed against the rear carriage piston I54. Fluid from the portion of the chamber in front of the piston I54 will be discharged through the pipe line I84 to the intake side of the pump I12, or, in other words, into the chamber 200, Figure 21. This fluid will be directed through the longitudinal passageway I98 in the rotary valve and thence into association with those pistons which are experiencing their inward stroke. That is to say, fluid from the advancing end of the rear carriage piston is employed to charge the pump I12, and fluid under high pressure from the discharge side of the pump is being employed to advance the rear carriage piston. To relieve against the development of excessive pressures within the closed circuit, I provide a suitable pressure relief mechanism 226, as clearly shown in Figure 23.

The fact that I use a fluid propelling mechanism or pump which is free from the usual fluid slippage or by-passing, enables me to employ what may be termed literally a closed or valveless fluid circuit. By employing a closed fluid circuit, in combination with a non-leakable fluid pump which is directly co ected with a rotary portion of the machine, suc as the work supporting spindle, I am able to obtain a governed amount of movement of a shiftable machine element, such as a tool supporting carriage for each revolution of the spindle. In other words, the movement of the tool carriage is correlated with the rotary movement of the work supporting spindle. This presents a'very practical and extremely simple arrangement which has a very broad application in the machine tool industry, as well as in other flelds.

Front carriage feeding circuit The pump l12a is identical in construction and operating characteristics to the pump I12 already described, and is directly connected to the spindle 36 by means of the roller chain 58. A pipe line 228 is connected with the high pressure or discharge side of the pump I12a, Figure 23, and connects with the pipe III which, in turn, is connected to one end of the cylinder I35 of the fluid operated mechanism I33. The intake side of the pump HR: is connected with the opposite extremity of the cylinder I35 through the agency of the pipe I43, a cut-oil valve 239, and a pipe line 232. When the valve 230 occupies the position shown in Figure 23 communication between the pipe lines I43 and 232 is broken, but when said valve is shifted in a manner later to be described, to a forward position, as indicated by the dot and dash lines in Figure 23, communication is established between the mechanism I 33 and the intake side of the pump I12a. Thus it will be apparent that when the valve 230 occupies its open position and rotation is ex perienced by the spindle 3B, the piston I31 and consequently the front tool carriage 86 will be moved to the left, Figures 3 and 23. A conventional pressure relief mechanism 234 is connected between the pipe lines 228 and 232 to relieve against the building up of excessive pressures in the system. It will be seen that the feeding circuit, which includes the mechanism I33 and the pump I12a, is a closed circuit, and that the longitudinal movement of the front carriage is tax correlated with the rotative movement of the spindle. That is to say, for each revolution of the spindle, the front tool carriage will be shifted to the left a predetermined distance, Figures 3 and 23.

Low pressure fluid supply From the description given thus far it will be understood that forward movement of the rear tool carriage I48 will take place when the spindle 36 is rotated. I shall now proceed to describe the parts comprising a fluid circuit which includes the continuously driven low pressure mechanism or pump I36. This pump I36 is mounted at one end to the rear of the machine, as clearly shown in Figure 4. This pump is driven by a roller chain 235 connected with a sprocket 236 which is mounted upon the main drive shaft 54, Figure 8, and which is connected to a continuously rotatable clutch member 238. This clutch member is directly connected through ehe agency of the roller chain 248 to any suitable driving means, such as an electric motor 242, Figure 4.

This pump I36 may be a gear pump, and I prefer to employ the type of gear pump disclosed in my co-pending application, Serial No. 430,868, filed February 24, 1930, now matured into Patent No. 1,912,737. The intake side of the gear pump I36 is connected with a fluid or oil reservoir 244, Figures 4 and 23, by means of a suitable pipe line 246. By having this reservoir 244 positioned above the pump I36, 011 is continuously supplied to the pump under slight pressure, and thus air is prevented from entering the fluid circuit. In order to prevent the introduction of foreign matter within the oil of the reservoir 244, I provide a strainer or screen 248, as shown in Figure 4. The pump I36 is mounted upon a bracket 258 and may be shifted on said bracket in order to make adjustments with respect to the roller chain 235. Variation in displacement of the gear pump I36 may be obtained by merely adjusting the position of a lever 252. This lever serves to operate a central valve 253, Figure 26, within the lower gear 255 of the gear pump. This gear 255 is pro vided with a plurality of radial passages 251 which are adapted to communicate with a valve port 259 to prevent oil from becoming heated. The valve port 258 may also be adjusted so as to vary the fluid displacement, and this arrangement has a very practical application in connection with automatic lathes and machines of like nature. For a more detailed description of this gear pump I36, reference is made again to my above mentioned co-pending application.

Low pressure control for rear carriage The discharge side of the gear pump I36 is connected to a pipe 254 which, in turn, has a common connection with branch lines 256 and 258, as clearly shown in Figure 23. These branch lines are connected to the control or reversing valve I38. This valve I38, Figures to inclusive and Figures 23 to inclusive includes a central casing or housing 288, which is supported on the forward side of the machine frame 32. The housing 288 is capped at one end by a casing section 268a, and at its opposite end by a casing section 2682). A cylindrical valve member 282 is longitudinally shiftable within the casing 268 and is provided with a series of valve ports 264, 266, and 268. The valve member 262 may be manually shifted by means of a single control lever 218, Figures L 2, and 11, one extremity of said valve having a pivotal connection with the inner extremity of the control lever or handle 218. In Figures 11, 18, and 23 the valve member 262 occupies what will be referred to hereinafter as its neutral position. In this position the branch line 256, Figure 23, communicates with the annular port 268, and this annular port, as shown in Figure I11, in that instant communicates with a chamber section 212 in the casing section 268?). This chamber section 212 is connected by a return pipe line 214, Fig. 23, an adjustable restricted oriflce 216, and a pipe line 218 with the reservoir 244. Thus fluid is circulated through the pump I38, the valve I38, and the restricted oriflce 216. Fluid from the branch line 258 passes into the annular valve port 264 and from this port is conducted through a longitudinal passageway 288 in the casing 2680. to a chamber section 282 which is oppositely disposed from the chamber section 212. A passageway 284 connects the port 264 with the chamber 212, as clearly shown in Figure 11. In this manner the fluid pressure is balanced at each er'rtremity of the valve member.

By imparting a movement to the control handle or lever 218 to the right, Figure 11, the valve member 262 will be moved to the left so as to occupy the position shown in Figure 24. This position will be referred to hereinafter as the forward position. Fluid is now directed from the branch line 258 through the annular valve port 264 and thence through the pipe line I18 which connects with one extremity of the rear carriage cylinder I58. In this connection it is to be noted that the pipe line I68 is connected also with the valve I38. Consider, for example, that the machine spindle 36 is at rest and the valve member 262 is shifted to the forward position shown in Figure 24. Forward movement in response to the pressure of the fluid directed into the cylinder I58 from the pipe line I18 will cause the rear carriage piston I54 to experience a rapid forward movement. This movement will be referred to hereinafter as the rapid traverse movement which is required to bring the rear carriage tool I 58 into operative association with the work piece. Attention is directed to a fluid actuated mechanism 286, Figures 1, 9, 10 and 23, which is operatively connected with a clutch mechanism 288, Figures 8 and 9, later to be described. This fluid operated mechanism 286 includes a cylinder 288 and a piston 282 reclprocably mounted therein. This piston 292 is connected as by means of a piston rod 294 with means for operating the above mentioned clutch mechanism 288. One extremity of the cylinder 288 is connected to the pipe line I18 by means of a line 288, and the opposite extremity of said cylinder is connected to the pipe line I68 by a pipe line 288. Upon shifting the valve member 262 to its forward position as above set forth, the piston 282 of the mechanism 286 is shifted to the left, Figures 10 and 23, so as to actuate the clutch mechanism 288 and thereby cause the main drive shaft 54 to be rotated. Rotation of this drive shaft obviously causes rotation of the work supporting spindle 36. In response to the actuation of a mechanically shifted slide mechanism 388, Figures 11 and 14, later to be described, the valve 262 is returned to its neutral position shown in Figure 23, at a predetermined interval. This predetermined interval is determined by the distance the tool I58 must be moved in order to bring said tool into operative association with the work. In other words, the tool is subjected to a rapid traverse movement by the low pressure fluid so as to bring said tool quickly into operative relation with the work piece. With the valve 262 shifted to its neutral position, the low pressure fluid circuit including the pipe lines I68 and I16 is rendered functional ly inoperative, and the high pressure fluid circuit which includes the plunger pump I12 and the pipe lines I64 and I66 is rendered functionally operative. That is, fluid under high pressure is directed against the rear carriage piston I64 .to effect the feeding of the tool I56 across the face of the work piece. Thus it will be apparent that the low and high pressure fluid circuits are operable independently of each other.

When the feeding stroke of the rear carriage piston I64 has been completed, the valve 262 may be shifted manually or automatically to its reverse position shown in Figure 25. When the valve is shifted to this position, fluid from the gear pump I36 is directed through the branch line 256 into the annular valve port 268 and thence through the pipe line I68 in the direction indicated by the dotted arrows, Figure 23. Reversing the direction of flow of the fluid in the pipe line I68 causes the piston 292 within the clutch control mechanism 266 to be shifted to the right, Figure 23, thereby disconnecting the driving motor from the main drive shaft 56, and consequently arresting the rotation of the work supporting spindle 36. The rear carriage piston I64 is rapidly urged in a reverse direction, and fluid from the pipe line III! is returned to the valve port 266, Figure 25. Fluid from this port 266 is directed through a longitudinal passageway 302 which communicates with the valve chamber 212. Thus the fluid is returned from the chamber section 212 through the pipe line 2", the restricted orifice 216 to the reservoir 2. It should be understood that the adjustable restricted orifice 216 supplants the usual spring operated relief valve, and has been found more practical and emciently operable than any fluid relief devices which have been in common'use heretofore. The size of the orifice 216 is adjusted by means of a suitable valve member 211 which is mounted within a casing 219. The size of the orifice 216 may be adjusted to maintain a predetermined desired low pressure in the circuit for preventing any air from entering the circuit, and I have found that undue heating of the fluid which has been experienced heretofore in using spring valves and the like is eliminated when my simple adjustable orifice arrangement is employed.

When the rear carriage piston I54 reaches the limit of its rearward stroke, the valve 262 may be manually or automatically shifted to its neutral position, and the cycle of operation Just described may be repeated. It is to be noted that the spindle 36 is at rest during the rearward movement of the tool I 66, thereby permitting an operator to remove the completed work piece and insert another work piece. The time element in operating machines of the type described is an important factor and, as stated above, my invention contemplates reducing to a minimum the time required to set up a work piece in the machine and to complete the cutting operations on said work piece.

Low pressure control for front carriage Thus far I have described the manner in which a low pressure fluid circuit is employed to impart rapid traverse movement to the rear carriage cutting tool, and I shall endeavor now to describe the manner in which the low pressure fluid is employed to control the front carriage tool Ill. As set forth above, the pipe line I28 is connected at one extremity to one end of the cylinder I24, Figures 2 and 23. The opposite extremity of this pipe line I 26 is connected to the valve I36. Similarly the pipe line I22 serves to communicate the other end of the cylinder I24 with the valve I38, and it will be seen that these pipe lines I22 and I26 are diametrically positioned with respect to the pipe lines I66 and I'll already described.

When the valve member 262 occupies the neutral position shown in Figure 23, the circuit including the pipe lines I22 and I28 is functionally inoperative, but when the valve 262 is moved to its forward position, as shown in Figure 24, low pressure fluid is directed through the pipe line I22 and thus against the lower end of the piston I26. This causes the rapid upward movement of the tiltable guide bar I62 and consequently a rapid swinging oi the tool III toward the work piece. As stated above, the upward movement of the. Piston I26 is limited by the engagement of the free end of the guide bar with the adjustable stop I36. At a predetermined interval which is determined by the shifting of, a slide mechanism 366. later to be described, the valve 230, Figures 11 and 23, is shifted to the dot and dash position shown in Figure 23, and as described above, the valve member 262 is shifted to its neutral position. Under these conditions a high pressure fluid from the pipe line 228 passes through the pipe line Ill and thence into the cylinder I35 of the fluid actuated mechanism I33. This causes the front carriage cutting tool to be moved across the peripheral surface of the work piece to the left, Figures 3 and 23, at a feeding rate. When the tool II reaches the limit of its peripheral cutting stroke, the valve member 262 is shifted manually or automatically to the reverse position, as above described. This causes the spindle 36 to stop rotating, and thus renders the fluid in the front carriage feeding circuit functionally inoperative as a propelling medium. The flow of low pressure fluid in the pipe lines I26, I3I, I43, I, I29, and I22, Figure 23, is reversed, thereby causing a rapid reversal of the piston I31 which actuates the front tool carriage. The front tool carriage is swung downwardly, thereby maintaining the tool I I4 out of engagement with the work piece during the reverse movement thereof. When the front carriage reaches its starting position, the valve 230, Figures 1]. and 23, is shifted to its closed position, and the valve member 262 is moved to its neutral position.

It should be understood clearly that my invention is by no means limited to the specific arrangement and timing of the tool carriages shown in the accompanying drawings. In the foregoing description I have stated that the front carriage is swung upwardly to bring the tool II4 into proper position with respect to the work piece for making a peripheral cut longitudinally of said work piece. However, this front carriage tool may be employed for actually making a cut during its movement transversely of the work piece, as well as during its movement longitudinally thereof. In other words, a feeding movement may be imparted to the front carriage about its support without departing from the broad scope of my invention. In fact, in certain instances it may be desirable to employ only the swinging or oscillating movement of the front carriage, and the longitudinal movement, if any, of the carriage may be employed for additional purposes not specifically shown in the drawings,

A device constructed in accordance with the teachings of my invention may be employed for making a great variety of cuts in a work piece, and hence it should be understood clearly that the specific arrangement and timing of the cutting tools as described above is representative of only one of a wide range of constructions which might be employed.

Automatic fluidcontrol mechanism Means for automatically controlling the move ment of the valve member 262 and the valve 230 includes the above mentioned slide mechanism 300.1 lgures 11 to 14 inclusive. This slide mechanism comprises a horizontal slide 304 which carries a plurality of dogs 303, 303, 3), M2, and 3i3. The movement of the slide 304 is controlled by the rear carriage slide I42. The bottom of this slide I42 supports a rack bar 3l4 which drives a ear 3l6, and this gear 3|6 actuates a shaft 3I8 which carries a bevel gear 320. This bevel gear 320 meshes with a companion bevel gear 322 carried by a shaft 324. The outer end of this shaft 324 carries a pinion or gear 328. This gear or pinion 326 is secured irictionally upon the shaft 324 by means of a suitable collar 328, Figure 15, and associated clamping nut 330. The frictional mounting of the gear 326 upon the shaft 324 is such that said gear will rotate with the shaft for driving a rack bar 332 which is carried on the underside of the slide 304. If the slide 304 meets with resistance beyond a predetermined amount, the gear 326 will not rotate with the shaft 324, thereby preventing any parts of the slide from being subjected to undue strains and stresses. In Figure 11 I have shown the position occupied by the slide 334 when the machine is at rest and the control valve member 262 occupies the neutral position shown in Figure 23. Consider now that the valve member 282 is moved to its forward position shown in Figure 2.4 by shifting the control handle 210 to the right, Figure 11. This control handle carries an arm 334 which makes a slotted connection with a slidable shaft 336. This shaft 336 is mounted within a sleeve or casing 338, which is formed integral with the casing section 260b, and the outer end of this shaft 336 detachably supports a depending lug 340. As the rear tool carriage I42 experiences its forward movement, the slide 304 is moved to the right, Figure 11, and the dog 3"! is eventually carried into engagement with the depending lug 340, thereby causing the shaft 336 to be shifted rearwardly. This causes the valve member 262 to be moved to its neutral position. At a predetermined interval, which is in accordance with the nature of the work piece, the dog 306 is carried into engagement with 9. depending lug 342 detachably supported at the outer extremity of the valve member 330. This causes said valve to be moved to its open position so as to effect the iongitudinal feeding movement of the front tool carriage. As the slide 304 continues to move to the right, the dog 3l2 eventually engages a bell crank 344, and this engagement takes place when the tool carriages have reached the limit of their advancing strokes. The bell crank 344 is connected to one end of a rack bar 346 which traverses the upper portion of the valve mechanism I38, as clearly shown in Figures 18 to 20 inclusive. This rack bar 348 meshes with teeth formed on the peripheral surface of a rotary balancing membcr 348, and the shifting of the bell crank as above described causes the member 348 to be shifted from the position shown in Figures 13 and 19 to the position shown in Figure 20. When this balancing member is shifted to the position shown in Figure 20, pressure of the fluid within the chamber section 282 of the valve I33 is relieved, said fluid passing from the chamber section through a port 350 and thence into a return pipe 352 which connects with the oil reservoir 244. Relieving the pressure in this chamber 282 causes the valve member 262 to be unbalanced, and thus automatically shifted to the reverse position shown in Figure 25. A spring 354 at one extremity of the rack bar 346 causes said bar to be automatically shifted outwardly when the dog 3i2 is moved away from the bell crank 344, thereby automatically reestablislzing the closed position of the valve 343.

At this point it should be understood that automatic means, other than the unbalancing arrangement just described, may be employed for imparting a reversing movement to the valve member 262 without departing from the spirit and scope of my present invention. The mechanism whereby the fluid pressure on said valve member is unbalanced is particularly applicable in instances where a very quick reversal of the valve member is required. However, in other instances it may be advisable to employ a simple mechanical control, which will directly engage the valve member 232 to effect the reversal thereof. Such an arrangement is not shown in the drawings, but my present invention contemplates means other than the specific valve unbalancing arrangement for effecting the automatic shifting of the valve member 262 within its casing or housing 260.

When it is desirable to manually control the shifting of the valve 262, it is only necessary to shift the lugs 340 and 342 out of the path followed by the dogs on the slide 304. This is readily accomplished by merely pulling outwardly on the pins which support these lugs and then imparting a slight rotary movement thereto, so as to shift said lugs out of the path of movement of the dogs on the slide. Obviously this may be accomplished without disturbing the position of the dogs on the slide. Thus, in instances where the operator wishes to have complete manual control of the machine, it is only necessary to quickly shift the normally depending lugs 340 and 342 in the manner described.

Shifting the valve member 262 to its reverse position causes the rear tool carriage to be moved rearwardly and the front tool carriage to be moved toward its starting position. When these tool carriages reach the limit of their movement, a dog 3i 3 on the slide 304 engages the depending lug 340, and thereby automatically moves the valve member 262 to its neutral position, and the dog 303 closes the valve 330, Figure 11.

Clutch and driving mechanism The clutch mechanism 288, Figure 8, is similar to that disclosed and described in connection with my above mentioned co-pending application and may be of any practical design. The mechanism disclosed includes a clutch memher 356 which is axially movable in response to the movement ofactuating arms 353. The movement of the member 356 into engagement with a rotary friction disk 360, in response to outward movement imparted to the arms 358. causes power to be applied to the drive shaft 54 from the prime mover or motor 242. This outward movement of these arms 353 is occasioned in response to the shifting to the left of the piston rod 294.

This movement of the piston rod 264 causes a horizontally disposed arm 362 connected there- I with to rotate a vertical shaft 364 which, in turn, causes arms 366 supporting a yoke 368 to move a member 316, Figure 8, into engagement with the arms 356. When the piston rod 294 is moved to the right, Figure 10, the clutch elements are disengaged and the prime mover 242 is disconnected from the drive shaft 64. The outer end of the drive shaft 54, Figure 8, carries a. pulley 312 which may be connected to a cooling pump (not shown). The specific structural characteristics of the clutch mechanism is a part of my present invention, only as it enters into the general combination, and therefore it should be understood that said invention is not limited in any sense to a particular type of clutch mechanism.

This clutch mechanism 288 and associated driving elements including the main drive shaft 54, the change gears 56 and 52, as well as the pinion 48, is supported by a bracket 314 and a bracket 316. These brackets are detachably mounted upon the rear side of the head stock casing 321:, as clearly shown in Figure 8. By supporting these parts which comprise the transmissionin the brackets 314 and 316, I am able to subass semble the parts before securing the entire unit to the head stock. This arrangement consider- Till ably reduces the amount of machining work on the head stock and bed, and also enables said head stock to be secured conveniently and rigidly in position upon the machine base. This is of utmost importance in connection with the design of machines which are to be subjected to heavy duty operating conditions.

Statement of operation Consider that the dogs on the slide mechanism 366 have been properly positioned on the slide 364, that is, in accordance with the desired timing of the movements of the rear and front cutting tools. Consider also that the electric motor or prime mover 242 is operating and thus driving the gear pump I36. A work piece is secured in position between the head stock spindle and the tail stock center piece. After the work has been set up properly, the operator moves the control handle 216 to the right, thereby shifting the control valve 262 to its forward position as shown in Figure 24. This causes low pressure fluid from the gear pump to effect a rapid traverse movement of the rear carriage tcol toward the work piece and also causes the front carriage to be swung about its axis so as to bring the tool supported thereby into proper position for making a peripheral cut upon the,

work piece. The clutch control mechanism 286 is also activated by the low pressurefluid so as to operatively connect the main' drive shaft 54 and consequently the spindle 36 with the prime mover. This causes the actuation of the high pressure variable displacement plunger pumps I12 and NM. The dog supporting slide 364 is moved in response to the forward movement of the rear carriage slide, and at a predetermined interval the control valve member 262 is shifted to its neutral position through the action of the dog 3I6, and the valve 236 is shifted to its open position through the action of the dog 366. The plunger pumps I12 and H20 are now included within a closed valveless fluid circuit, the displacement of fluid from the pump I12 causing a forward feeding movement of the rear carriage tool across the face of'the work piece,

and the fluid displaced by the pump I124: causing the front carriage tool to be fed longitudinally of the work piece. Upon the completion of the feeding stroke of these cutting tools, the valve member 262 is automatically shifted to its reverse position in response to the engagement of the dog 3I2 with the bell crank 344. The engagement of the dog with the bell crank 344 causes the valve member 346 to be rotated sufllciently to eflect the release of the fluid from within the chamber section 262, thereby unbalancing the fluid pressures at the opposite extremities of the valve member 262. The shifting of the valve member 262 to the reverse position causes a reversal in the direction of flow of fluid in the low pressure circuits, with the result that the clutch control mechanism 266 is operated to disconnect the spindle 36 from the prime mover. The reversal of flow in these circuits also causes a rapid reverse movement of the front and rear tools, and when these tools reach their starting position the dog 3|! engages the depending lug 346, thereby shifting the valve member 262 to its neutral position. The work piece does not rotate as the cutting tools are reversed, and hence the operator may use this period to good advantage in removing the work piece and inserting another. After a subsequent work piece has been set up in the machine a repetition of the cycle just described is obtained by merely shifting the control handle 216 to the right.

As a precaution against the possibility of leakage in the cylinders of the fluid actuated mechanism I66, I33, and I66, which might result from wear or improper adjustment, I employ bleed passages 386 and 362, Figure 18, in the valve casing 266. Experimental work has shown that these restricted openings 366 and 382 will serve to replenish any fluid which is lost as a result of the above mentioned improper adjustment. This experimental work disclosed that it is not necessary to employ these restricted openings when the fluid actuated mechanisms are in proper adjustment, but I have found that a 3'! inch hole will not injure or cause any difference in action in the closed valveles; circuit during the feeding stroke if the load of the piston is of a puisative nature. The area of one of the cylinders in the average construction is approximately ten square inches, and therefore it will be understood that it is impossible to place any load on the piston which would force the fluid through a 1 inch hole so as to cause a pulsated action. As stated above. these holes 386 and 362 are merely employed in instances where compensation must be made for the adjustment of the cylinders. These holes merely serve as compensating means to prevent the building up of too great a pressure on the advancing side of the piston.

Summary by A system oi control enables the use of a single, simple, three-position valve which is connected only to a low pressure circuit. In other words, leakage or fluid slippage which has been experienced heretofore in using conventional control valves in high pressure fluid circuits, is completely obviated by my improved arrangement. In my device, the high pressure circuit is operable independently of the low pressure circuit, and no valves of any kind are required in said high pressure circuit. Through the agency of this closed valveless circuit combined with my improved variable displacement plunger pump directly driven from the work supporting spindle, I able to obtain a predetermined feeding movement of an actuator piston per revolution of the work supporting spindle. The tapered valve arrangement combined with the stationary block for supporting the radial pistons, presents a pumping structure which is particularly adaptable for use in closed circuits. This results from the fact that the tapered valve positively prevents leakage toward its smaller end, and any slow leakage of fluid at its larger end is redirected to the intake side of the pump. This is to be distinguished clearly from pumping devices which have been employed heretofore, wherein a high degree of fluid slippage has been experienced along the surfaces of the rotary valves, thereby causing the overheating of the fluid and a material decrease in the propelling efficiency of the pump. In other words, my invention provides, in combination with an actuator piston, a pumping mechanism having valveless ducts extending between said pump and the actuator piston, and the fluid medium confined within said parts being substantially non-compressible, imparts a positive and constant propelling force against the actuator piston. Thus, the high pressure circuit may be termed aprimary circuit, and the low pressure circuit may be termed a secondary circuit, said primary circuit being used for feeding purposes, and the secondary circuit for the purpose of rapid traverse. It should be understood that means other than that disclosed in the drawings, may be employed for imparting rapid traverse move ments to the tools without departing from the spirit and scope of my present invention. In

other words, my present invention contemplates other mechanical arrangements which would serve to impart such movements at predetermined intervals to the tool carriages.

It will be apparent from the foregoing description that my invention contemplates the provision of a hydraulic actuator system for controlling the movement of machine parts and the like in such a manner that uniform movement of the machine part is positively effected in direct accordance with volumetric displacement of fluid to the intake portion of the actuator cylinder irrespective of variations in fluid pressure or load to which the actuator piston may be subjected during its feeding stroke.

To explain this advantage from a more practical viewpoint, I call attention to the fact that the present invention is particularly adaptable for use with metal cutting machines, such as lathes, milling machines, and the like, wherein the tool or work is frequently subjected to varied degrees of resistance during the cutting operation. For example, in a milling machine equipped with the present hydraulic system of control, the table of the milling machine carries the work and is moved horizontally by the hydraulic actuator past a rotary cutter. If the cutter is rotating in such a direction that the teeth of the cutter exert a force which is in a direction opposite to the direction of movement of the table, then the pressure of the fluid on the trailing side of the piston is greater than the pressure of the fluid on the opposite side. On the other hand, if the cutter is rotating in a direction so that the cutting teeth exert a force in the same direction as the table, then the pressure of the fluid on the advancing side of the actuator piston will be greater. It will be apparent that, unless the hydraulic circuit is arranged in a particular manner to meet these conditions, the table will experience a non-uniform or pulsating action, due to the variations in fluid pressure on the opposite sides of the piston.

In the present invention the plunger pump is connected to the opposite sides of the actuator cylinder in such a manner that a uniform movement of the tool or carriage propelled by the actuator piston is positively effected in direct accordance with the volumetric displacement of fluid to the intake portion of the cylinder irrespective of the resistance encountered by the tool or carriage in its travel. That is to ay, even though a milling machine carriage or lathe tool meets with varying degrees of resistance during its travel (resulting from soft spots in the metal, or non-circular form of the part to be turned in the lathe), the volumetric displacement to the intake side of the cylinder continues at a uniform rate, and therefore the piston must likewise travel uniformly in accordance with such displacement.

The plunger pump ls connected with the advancing side of the piston in such a manner that fluid confined in front of the advancing side of the piston must be returned at the same rate as the fluid displaced to the intake side of the actuator piston by the plunger pump. By this arrangement the fluid bodies controlled by the action of the plunger pump operate similarly to a lead screw in a lathe wherein no slippage takes place.

Another example in which a variation in fluid pressure occurs on opposite sides of the actuator piston is in a machine, such as a drill press having a vertically disposed drill holder, which must be vertically reciprocated. By employing a vertically reciprocable actuator piston within a cylinder in conventional machines, some auxili ary means must be provided to prevent gravity from acting upon the piston so as to urge it downwardly. In the present invention no auxiliary means need be provided to prevent gravity or other forces from shifting the actuator piston, because when the fluid body is positioned beneath a vertically disposed piston, it is locked in position, and, although it is subjected to greater pressure than the fluid on the opposite side of the piston; no variation nor non-uniformity of piston movement will occur. That is to say, the uniform movement of the piston which drives the machine part is positively effected in direct accordance with the volumetric displacement of the fluid (not pressure) to the intake portion of the cylinder.

The phenomenon just described should also be considered in connection with the variations in fluid pressure on the opposite sides of the actuator piston which result when the tool carriage is suddenly changed from rapid traverse to feed. It will be recalled that during the rapid traverse of the machine part or carriage, fluid from the large displacement gear pump passes through the main control valve into one end of the actuator cylinder, and fluid from the opposite end of said cylinder passes through said valve and is returned to the reservoir through a restricted oriflce which sets up the required degree of back pressure. The instant that the main control valve is shifted from its rapid traverse to its neutral or feeding position, the opposite sides of the feeding circuit are completely sealed from the rapid traverse fluid, and the momentum of the tool carriage will cause a sudden building up of pressure at the advancing side of the actuator piston and a sudden lowering of fluid pressure on the opposite side. This sudden building up of pressure might properly be referred to as a preloading action". That is to say, the fluid sealed within the, forward side of the actuator cylinder experiences a sudden increase in pressure at the instant that the small displacement or feed pump becomes functionally operative. This preloading action serves to positively prevent any stuttering or pulsating efl'ects when the tool begins its cutting operation. Heretoi'ore considerable difllculty has been experienced with conventional hydraulic systems of control when the fluid pressure on the opposite sides of the actuator piston varies. In fact, it has been common practice to employ relief valves to pernut the fluid to by-pass when sudden increases in fluid pressure are experienced, and obviously under such conditions no preloading of the fluid can take place, and hence a non-uniform or stuttering action takes place when the shiftable machine part changes from one speed to another. Therefore, it will be apparent that this sudden increase in pressure or preloading action conditions the fluid on the intake side of the small displacement or feed pump in readiness to charge said pump the instant that the main control valve clips off the low pressure fluid and renders the closed feeding circuit functionally operable. At this point it should also be understood that various types of prime movers, such as multi-speed motors. may be employed to impart rotation to the machine spindle.

Attention is called to the fact that by employing the secondary low pressure circuit, in combination with the primary or high pressure circuit, I am able to constantly change the fluid in said high pressure circuit. This will .be clear when it is understood that each time the secondary circuit functions, fluid from said circuit is taken into one end of the actuator piston cylinder and discharged from the opposite end. This prevents the fluid in the closed primary circuit from deteriorating.

By having the transmission elements carried by brackets which are detachably mounted upon the head stock frame, a very practical transmission unit is presented. This may be readily assembled before mounting upon the machine, and while in operation said unit does not impart any undue strain on the head stock frame. The changeable gears provide a convenient arrangement for varying the spindle speed, and it will be under stood that other forms of speed varying devices may be employed which come within the scope of my present invention. The gear pump is convenientl-y connected to the transmission and is readily accessible for purposes of replacement and the like. By employing a variable displacement gear pump, as shown, the fluid displacement in the low pressure circuit may be varied without varying the speed of the prime mover. By having the oil reservoir placed at a higher level than the gear pump, oil is constantly supplied under slight pressure to said pump, and air is completely eliminated from the circuit. It is to be noted that the prime mover or motor is housed in a ventilated chamber and may be adjusted for taking up wear in the roller chain. The automatic control of the clutch by means of the mechanism included within the low pressure circuit, provides a very simple and positively acting device. It is to be noted also that this control is operated independently of the high pressure fluid circuit. It should be understood that the invention is not limited to the specific arrangement of the disclosed clutch construction, but contemplates the provision of a clutch control which will timingly control the rotary movement of the work supporting spindle.

It will be understood from the foregoing description that the discharge side of the rapid traverse or gear pump I is never connected with the intake side of the feed pump during the operative functioning of the feed pump. That is to say, when the actuator I56 moves forwardly in response to the action of the pump I", fluid discharged from said actuator is subjected to back pressure setup within the restricted oriflce 21!, and this back pressure exerts itself upon the fluid within the conduit I which connects with the intake side of the plunger pump III. In this manner air is positively precluded from entering the intake side of the feed circuit during the rapid forward advancement of the actuator piston Ill. when the actuator piston IN is moved in a reverse direction, the plunger pump I72 stops, and hence, while the duct or conduit I communicates with the fluid discharged by the gear pump I", no movement of fluid in the duct I or I takes place, and thus air is positively precluded from entering the feed circuit. During the reverse movement of the actuator piston I the fluid discharged thereby is subjected to back pressure set up by the restricted orifice 2", and this pressure exerts itself upon the fluid in the duct I, thereby preventing any movement of the fluid in said duct. In the above-described manner, any air which may be taken in through the action of the gear pump I" is positively prevented from entering the feed circuit. This is of the utmost importance in preventing the actuator, and consequently the tool driven thereby, from experiencing a pulsating movement. By having this construction. the

feed pumps may beplaced above the level of the reservoir without the possibility of any fluid flowing out of the feed circuit, and without the possibility of air being introduced within said circuit.

From the foregoing it will be apparent that I- provide two independent circuits. namely, a high pressure circuit which is connected to the plunger pump, and a low pressure circuit which is connected to the gear pump. The low pressure circuit is initially placed in operative position by shifting the main valve, and at this interval the high pressure circuit is in an inoperative state. The actuation of the low pressure circuit causes the high pressure circuit to be rendered functionally operative. and the low pressure circuit is then rendered functionally inoperative. thereby allowing the high pressure circuit to impart feeding movement to a tool carriage independently of any other circuit. At a predetermined interval, and in response to the move-

Images