US2271615A

US2271615A - Hydraulic power unit

Info

Publication number: US2271615A
Application number: US163210A
Authority: US
Inventors: Russell E Bauer
Original assignee: Ex-Cell-O Corp
Current assignee: Ex-Cell-O Corp
Priority date: 1937-09-10
Filing date: 1937-09-10
Publication date: 1942-02-03
Anticipated expiration: 1959-02-03

Description

Feb; 3, 1942. U R 2,271,615

HYDRAULIC POWER UNIT Filed Sept. 10, 1937 6 Sheets-Sheet l iNVENTOIL @usse E, 604192 P z 9 M m M,

Feb. 3, 1942. R. E. BAUER HYDRAULIC POWER UNIT Filed Sept. 10, 1957 6 Sheets-Sheet 2 NVENTOE/ L/66e// (5. 50419)" Feb. 3, 1942. R. E. BAUER 2,271,615

7 HYDRAULIC POWER UNIT Filed Sept. 10, 1937. 6 Shecs-Shet 3 .m passe, if ,ga'u e2 @TA'ITO ways Feb. 3, 1942.

R. E. BAUER 2,271,615

HYDRAULIC POWER UNIT Filed Sept. 10, 1957 6 Sheets-Sheet 4 Feb. 3, 1942. I R, E, AU R 2,271,615

HYDRAULIC POWER UNIT Filed Sept. 10, 1937 v e Sheets-Sheet 5 Feb, 3, 1942. R. E. BAUER HYDRAULIC POWER UNIT F' iled Sept. 10, 1937 6 Sheets-Sheet 6 IN VE/V TOB 5 662%! jrme/v ys.

Z asse/l u v a g mv a machine base 2.

Patented li'eb. 3,1942

POWER- UNIT Russell E. Bauer, Detroit, Mich., assign'or to Ex- Cell- Corporation, Detroit, Mich., a corporation of Michigan Application September 10, 1937, Serial No. 163,210

11 Claims.

The present invention relates to improvements in hydraulic power units adapted for use in machine tools.

One of the objects of the invention is to provide a novel hydraulic power unit which is compact, self-contained and hydraulically controlled and operated.

The unit may comprise a rotary recfprocable spindle as the movable machine element. Another object is to provide a new and improved power unit having novel hydraulic operating means in which the motive fluid is locked by valve means to prevent any movement or creeping of the spindle or machine element during idle periods.

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

In the accompanying drawings,

Figure 1 is a perspective view on a reduced scale of a machine, with the hydraulic power unit embodying the features of the invention.

Fig. 2 is a side elevational view of the hydraulic power unit with the front cover removed.

Fig. 3 is a plan view of the hydraulic power unit without the drive motor;

Fig. 4 is an end elevational view of the hydraulic power unit.

Fi 5 is a fragmentary longitudinal sectional view of the hydraulic power unit on an enlarged scale taken substantially along line 55 of Fig. 3.

Fig. 6 is a diagrammatic representation of the hydraulic transmission for the unit. Fig. 7 is a view similar to Fig. 6 but showing the transmission in condition for rapid approach.

Fig. 8 is a view similar to Fig. 6 but showing the transmission in condition for slow feed.

Referring more particularly'to the drawings, the hydraulic control unit embodying the features of my invention comprises a'self-contained housing I adapted to be adjustably mounted "on The unit is of the quill or ram type, comprising a suitable tool spindle 3 journaled in and movable axially with a nonrotatable reciprocable quill 4. A hydraulic operating mechanism is fully contained within the unit for imparting to the spindle 3 a cycle comprising a rapid approach, two different feeds selectively available without, feed interruption or as jump feeds, a selectively available dwell at the end of the forward stroke, a rapid return, and an automatic stop.

The quill 4 extends slidably through a large cylinder 5 formed integral with the casing I, and closed at opposite ends by suitable pilot caps 6 and I. A piston 8 is secured to the quill 4 for reciprocation in the cylinder 5. The quill 4, which constitutes the piston rod for the piston 8, extends from the cylinder 5 through two closely lapped hardened steel bushings 9 and I0 which are secured in the pilot caps 6 and I, and which provide a hydraulic seal. An annular wiper plate II, secured to the pilot cap 6,'encircles the outer 'end of the quill 4 and prevents foreign matter from getting into the cylinder 5. A guide arm I2 is keyed to the rear end of the quill 4, and projects into a slot I3 formed in the base wall oi. the casing I parallel to the quill to prevent rotation in the course of reciprocation.

Also formed in the casing I is a small cylinder I4 parallel to the cylinder 5 and closed at the ends by pilot caps I5 and IS. A small piston" I1 is reciprocable in the cylinder I4, and has a piston rod I8 extending slidably through sealing bushingsIS and 20 in the caps I5 and I6. A wiper plate 2i is secured to the cap I5, and encircles the outer end of the rod I8. The outer ends of the quill 4 and piston rod I8 are rigidly connected for joint movement by a suitable face plate 22. The motors or actuators, comprising the cylinder 5 and piston 8 and the cylinder I4 and piston I1, constitute a hydraulic transmission for reciprocating the spindle 3.

The forward end of the spindle 3 extends through the face plate 22, and is journaled thereir'i'in a suitable double row antifriction hearing The outer raceway of this bearing is confined in a recess 24 in the plate 22 by means of an annular clamp plate 25. The inner raceway is confined against a shoulder 26 on the spindle 3 by means of a lock nut 21.

The spindle 3 preferably is tubular in form, and the outer end is ground to close limits on the inside diameter and formed with" a longitudinal internal key slot 28. If the unit is to be used for single tool operation, a suitable sleeve with a taper bore (not shown) is inserted into the spindle 3. If the unit is to be used for multiple tool operation, a suitable multiple tool or a single antifriction bearing 30 confined by a plate 3| in a bearing housing 32. This housing has an axial sleeve 33 fitted to the iner end of the quill 4, and secured thereto and to the guide arm I2 by means of a dowel pin 34.

To provide a suitable rotary drive connection, a spline bushing 35 is keyed within the rear end of the spindle by a pin 35 and is locked in position by a nut 31. A. drive shaft 38 extends into the inner end of the spindle i and is axially splined to the bushing 35.

The shaft 38 is suitably journaled in'a gear housing 39 bolted to the rear end of the casing I and closed by a cover 48. Also journaled in the housing 39 in parallel relation to-the shaft 38 are an idler shaft ll and a power inlet shaft 42. The shaft 38 is driven from the shaft 42 through reduction gearing consisting of a gear 43 on the shaft 42, idler gears 44 and 45 on the shaft H and a gear 46 on the shaft 38. The gears are removably splined to the shafts. Preferably, all

of the shafts are splined to the same dimension,

and all of the gears have the same splined hole and the same face width. As a result, the necessary drive speed range is obtained with a relatively small number of gears, using each g'ear interchangeably in different positions.

The power inlet shaft 42 projects through the cover 48 for connection to a suitable source of power. In the present instance, a pulley 41 is keyed to the shaft 42, and connected through a belt 48 to an electric motor 49 on a bracket 58.

One edge of the bracket 58 is pivoted by a pin 5| to a cover 52 closing the top of the casing I, and

the other edge is adjustable by means of a screw 53 for properly tensioning the belt 48. Preferably, the belt 48 is enclosed by a removable guard 54.

The hydraulic operating mechanism comprises a suitable pump 55 taking motive fluid from the interior of the casing I, the bottom of which constitutes a sump, and discharging to a pressure line 56. The pump 55 is mounted within the casing I on an adapter plate 51 secured to the housing 39, and'is keyed directly to the inlet shaft 42 which is driven constantly at the most convenient pump speed. The sump may be supplied with fluid through an opening 58 in one side wall of the casing I, and normally closed by a plug 59. A screen filter 68 is mounted in the opening 58. Also mounted inthe side wall of the casing I, below the filler plug 59, is a sight gage 6|.

Th'e motive fluid in the line 56 is substantially maintained at a predetermined pressure by an adjustable relief valve 62 discharging to the sump, and is adapted to be supplied to the cylinders 5 and I4 through a control valve 63. In its present, form, this valve comprises a valve bore 64 having a central pressure port 65 connected to the line 56,

rapid traverse ports

66 and 61 at opposite sides of the port 65 and connected respectively through

lines

68 and 69 to opposite ends of the small cylinder l4, and feed ports 18 and H located outwardly of the

ports

66 and 61 and connected respectively through lines 12 and 13 to opposite ends of the large cylinder 5. A valve plunger 14 of the spool type is reciprocable in the bore 64, and is formed with an axial bore open at opposite ends to exhaust chambers and 11 connected to a drain line 18 leading to the sump.

The valve 63 is operable hydraulically under the control of two pilot valves 19 and 88 and a dwell mechanism 8I. Formed on opposite ends of the valve plunger 14 are two pistons 82 and 83 which are of relatively small and large diameters, and which extend slidably into two cylinders 84 and 85 der 85 opens to a line 86 adapted to be connected by the dwell mechanism 8i either to a pressure line 81 leading from the valve 63 in the transverse plane of the port 65, or to a drain line 88 opening to the drain chamber 16.

The dwell mechanism 8i comprises a bore 89 connected at opposite ends to the pressure line 81 and a line 98, and having suitable intermediate port connections with the

lines

86 and 88. A valve piston 9| is slidable in the bore 89, and is urged in one direction by a spring 92 to close the line 88 and connect the

lines

88 and 81. Movement of the piston 9! against the action of the spring 92 serves to interrupt the connection between the

lines

86 and 81 and to connect the

lines

86 and 88.

The line 98 has an unrestricted branch line 93 and a parallel restricted branch line 94, under the control of the pilot valve 19. The restriction in theline 94 is provided by an adjustable orifice 95. The pilot valve 19 may be of any desired conat opposite ends of the valve bore 64. The cylinstruction, and is herein shown as of the rotary type, having a bore 96 with port connections at peripherally spaced points with the

lines

56, 38. 93 and 94, and having a plug 9? formed with a flow passage terminating with suitably,dimensioned and located

ports

98 and 99 at opposite sides of a land area I88. The plug 91 has an axial operating shaft I 8I extending to one side of the casing I and provided with a hand lever I82. In the intermediate position of the plug 91, the

lines

88 and 93 are closed, and the lines 56 and 94 are connected. In the left-hand position, the ports 98' and 99 are open to the

lines

88 and 93 and the line 56 is disconnected. In the right-hand position, the lines 88 and 94 are closed, and the

lines

56 and 93 are connected.

To provide means for moving the valve plunger 14 against the pressure in the cylinder 84 into feed position, a feed collar I83, having a larger pressure area than the piston 82, is slidable on the piston 83 within a cylinder I84 and for engagement, with a shoulder I on the plunger 14. The outer end of the cylinder I84 is open to a line I86 adapted for connection by the pilot valve 88 either to the drain line 88 or the pressure line 56.

Provision is also made for forcing the valve plunger 14 into neutral position against the pressure in the cylinder 85. The means for this purpose comprises a stop collar I81, with a larger pressure area than the piston 83, slidable on the piston 82 within a cylinder I88 and for engagement with a shoulder I89 on the right endportion of the plunger 14. The outer end of the cylinder I88 is open to a line II8 adapted for connection by the pilot valve 88 either to the pressure line 56 or the drain line 88.

The pilot valve 88 may be of any desired character, and in the present instance is shown as of the rotary type, having a bore III with suitable peripherally spaced port connections with the

lines

56, 88, I86 and II8, and a valve plug 2 with a recess H3 and connected spaced recesses H4 and H5. The arrangement i such that in stop position, the lines 88 and I86-are connected by the recess H4 and the lines 56 and II8 are connected by the recess I I3, and in feed position, the lines 88 and II8 are connected by th recesses H4 and H5 and the lines 56 and I86 are connected by the recess H3. The valve plug H2 has an axial operating shaft II6 extending to one side of the casing I.

In the feed position, the control valve 63 limits the discharge of fluid from the exhaust ends of the motive cylinders and I4 to a feed drain line II! which is closed by the valve 80 in stop position, and which is adapted to be connected through a fiow passage H8 in the plug II2 selectively to one or the other of two parallel restricted lines H9 and I20 connected respectively through adjustable orifices I2I and I22 to the drain line 18. The selective feed adjustment does not effect the various connections between the

lines

56, 88, I06 and H0. The orifices I2I and I 22 may be of any suitable character, and are accessible for adjustment from one side of the casing I. It will be understood that these orifices are adjusted to provide unequal restrictions where different feeds are required.

To obtain a constant rate of feed for either orifice selection, a governor valve I23 is interposed in the drain line 18. This valve comprises a bore I24 connected at opposite ends respectively to the line Ill and a line I25 from the orifices I2I and I22, and having a port connection intermediate its ends with the line 18. A plunger I26 is slidable in the bore I24, and provides a graduated fiow restriction between the lines I25 and 18. A Spring I21 tends to urge the plunger I26 against the pressure in the line H1 in a direction to decrease the flow resistance. Hence, the outlet pressure of the selected orific I2I or I22 is varied in accordance with the inlet pressure to maintain a constant'orifice pressure drop and therethrough a tool feed of constant rate regardless of variations in the work load.

The pilot valves 19 and 80 are automatically controlled in accordance with the movement of the spindle 3 to define a predetermined cycle. In the present instance, the valve shafts IOI and H6 are provided at the outer ends with a plurality of triggers engageable in predetermined sequence by a selected series of dogs. dogs may be varied as to selection and spacing to obtain the desired cycle.

An illustrative cycle comprises rapid approach, fast feed, rapid jump traverse, slow feed, dwell,

reverse, rapid return and stop. To obtain this.

cycle, there is fixed on the outer end of the valve shaft IOI a reverse trigger I28, and on the shaft II6, a first feed trigger I29, a second feed trigger I30, and a stop trigger I3I. Integral with-the trigger I30 is a jump feed trigger I32. In addition, positioning arms I33 and I34 are fixed on the shafts WI and H6, and extend with their ends in overlapping relationship so that movement of the valve 80 into stop position will effect movement of the valve 19 into intermediate or neutral position. The various triggers I28 to I32 These are adapted for engagement respectively by a plurality of dogs I35 to I39 which are removably and adjustably mounted on two parallel dog shafts or rods I 40 and I 4| rigidly connected at their forward ends to the face plate 22 for movement therewith. The other ends of the rods I40 1 and MI extend slidably through a guide bracket I42 on one side of the casing I. In the present instance, the dogs I36, I31 and I38 are carried by the rod I 40 and other dogs are mounted on the rod I M. The dog I39 is pivotally mounted in a bracket I43 on the rod MI, and i normally held in exact operative position by a spring I44 so as to be operative upon movement to the left and ineffective in the reverse direction. It will be understood that the coacting triggers and dogs are mounted on the respective supports for proper alignment longitudinally of the path of movement.

The

various valves

63, 19 and 80, the dwell mechanism 8I with the orifice valve 95 and the orifice feed valves I2I and I22 with the governor I23 are built into a compact hydraulic control panel I45 which is suitably mounted as a unit in one side of the casing I. A side cover I46 secured to the casing I may be removed to obtain access to the panel I45. The valve shafts I0 I and H6 project through the casing I, and may be operated from either end. Thus, the lever I02 may be shifted to the stub end of the shaft IOI. Similarly, a hand feed knob I41. may be secured to either end of the shaft I I6. The triggers, dogs and dog bars are located in a recess I48 formed in the side of the casing I opposite the panel I45, and normally closed by a side cover I49. Feed shafts I50 and I5I extend from the orifice feed valves I2I and I22 into the recess I48 for adjustment, and are therein provided with suitable graduated dials I 52.

As described, the valve 19 is operable manually by means of the lever I02 on the unit. If desired, a remote control may also be provided. In the present instance, this control consists of a cylinder I53 removably mounted in the forward end wall of the casing I. A piston I54 is reciprocable in the cylinder I53, and has a piston rod I55 formed with a gear rack I56 meshing with a gear I51 on the shaft I M Suitable fluid supply and exhaust lines I58 and I59 open from opposite ends of the cylinder I53 to the exterior of the casing I for connection with conduits leading to a hand or solenoid actuated valve I60 for single or multiple unit control. The valve I60 also has connections with the pressure line 81 and the exhaust line 88. In neutral position, the lines are blocked; in the right-hand valve position, pressure is supplied to the line I58 to effect rapid approach; in the left-hand valve position, pressure is supplied to the line I59 to effect rapid return.

With the parts as shown in Fig. 6, fiuid under pressure is supplied to the cylinders 84, 85 and I08, and hence the control valve 63 is held in neutral position. Since the line I I1 also is blocked by the valve 80, the fluid is locked in all ends of the motor cylinders 5 and I4 so that no axial spindle movement can take place.

To institute rapid advance (Fig. 7), the hand lever I02 is moved into its left-hand position. This connects the line 93 to the drain line 88, and thereupon the pressure fluid in the line 81 depresses the plunger 9| to connect the cylinder 85 through the line 86 to the drain line 88. Since there is no pressure in the cylinder I04, the pressure in the cylinder 84 will force the main valve plunger 14 fully to the left. As a result, pressure fluid is supplied from the line 56 only through the line 69 to the rear end of the small cylinder I4, and the front ends of both cylinders 5 and I4 are connectedthrough the lines 68 and the bore 15 and chamber 11 to the exhaust line 18. The line 13 is open to the chamber 11, and directs a part of the exhaust fluid into the rear end of the large cylinder 5 to keep the latter filled. The spindle 3 is advanced rapidly since the available fluid is supplied only to the small cylinder. By this means a rapid approach can be practicably obtained by the use of a small pump.

At a predetermined point in the advance or forward movement, the dog I36 will engage the trigger 29 to rock the valve one step in a counterclockwise direction. The same adjustment may be made at any time by means of the hand knob I41. As a result, the cylinder I08 is connected through the line I I8, valve recesses I I5 and Ill and the line 88 to the exhaust chamber I6, and pressure fluid is supplied from the line 58 through the valve recess H3 and the line I86 to the cylinder I84. Also, the feed exhaust line III is connected to the line H8 and orifice I2I. The collar I03 now forces the valve plunger ll against the pressure in the cylinder 84 into feed position. In this position, both lines 68 and 13 are connected to the pressure line 56, and both lines 68 and I2 are cut oil from the chamber I6 and connected to the restricted line I H to effect a feed with a heavy cutting thrust. Th governor I23 maintains a constant feed rate regardless of load variations.

Subsequently, the dog I39 will engage the trigger I32 to return the valve 80 into rapid advance position. If a jump feed is not desired, the dog I38 is removed. a

At a still later point in the advance movement, the slow feed dog I31 will engage the trigger I38 to move the valve 88 counterclockwise through the first feed position into asecond feed position, thereby connecting the line ,I I! to the line I28 and orifice I22 (Fig. 8), while obtaining the other feed adjustments as previously described.

Shortly before the end of the rapid advance, the reverse dog I35 will engage the trigger I28 to rock the valve I9 clockwise into initial neutral position, and then the quill 4 will move against a positive stop and stall; Adjustment of the valve 18 brings the arms I33 and I34 toward each other, but does not affect the valve 88 which is inefiective to control the return spindle movement. The valve I9 connects the lines 56 and 94, thereby supplying pressure fluid through the dwell orifice 95 and the line 98 to the bottom of the plunger 8|. After a dwell period, determined by the restriction in the valve 95, the plunger 9| reaches its top position to connect the

lines

86 and 81, thereby supplying pressure fluid to the cylinder 85. Thereupon, the valve plunger I4 is moved fully into the right-hand position to connect the line 68 to the pressure line 56, and the lines 69, I2 and I3 to exhaust, for rapid return. A

If a dwell is not desired, the valve 95 is adjusted to remove the flow restriction, and in this event reversal will occur immediately after engagement of the trigger I28 by the dog I35. In

any event, immediate reversal can be obtained when desired by manually adjusting the valve a large cylinder for feed traverse, a small pump operating at moderate pressures may be employed. The hydraulic control valves being built into one complete panel also require very little space. As a result, the construction of the unit may be made compact. Duringeidle periods, all

of the ends of the cylinders are blocked by valves so that the spindle cannot move or creep.

I claim as my invention:

1. A self-contained hydraulic power unit comprising, in combination, a casing adapted to be mounted upon a machine frame, a spindle mounted in said casing for rotation and axial reciprocation, a small piston and cylinder motor and a large piston and cylinder motor mounted in said casing for reciprocating said spindl,-and a hydraulic control mechanism in said casing, said mechanism including a main control valve having a pressure inlet and having a restricted drain outlet and an unrestricted drain outlet and having a rapid approach position in which one end of said small motor is connected to said inlet and the other ends of said motors are connected to said unrestricted drain outlet, a rapid return position in which the reverse end of said small motor is connected to said inlet and the other ends of said motors are connected to said unre- I9 through neutral into its extreme right-hand position to connect the pressure line 56 to the unrestricted line 93 instead of the line 94.

At the end of the rapid return, the dog I38 stricted drain outlet, an advance feed position in which the pressure ends of said motors are connected to said inlet and the exhaust ends of said motors are disconnected from said unre-.

stricted drain outlet and connected to said restricted drain outlet, and a stop position in which said motors are disconnected from said inlet and said unrestricted drain outlet, a pilot valve for efiective movement of said control valve selectively into feed} position during the approach movement or into'stop position during the return movement, and when said main valve is in stop position closing said restricted drain outlet, and a second pilot valve for effecting movement of said control valve selectively into approach position for rapid traverse or feed depending on the position of said first mentioned pilot valve, or into reverse position when said first mentioned pilot valve is out of stop position, and dogs movable with said spindle for controlling said pilot valves.

2. A self-contained hydraulic power unit comprising, in combination, a casing adapted to be mounted upon a machine frame, a spindle mounted in said casing for rotation and axial in said casing for reciprocating said spindle, and

. a hydraulic control mechanism in said casin will engage the trigger I3I to return the valve 80 to initial position and the latter throughthe arms I33 and I34 will insure location of the valve i9 in central position, to stop the operation.

More particularly, the cylinder I84 will'b'e -exhausted and the cylinder I08 will be connected to the pressure line so that the collar I81 will shift the control valve 63 to the left into neutral position.

It will be evident that I have provided a novel hydraulic power unit which is self-contained. The unit may be employed in difierent machine tools and may be mounted in any suitable position. Each unit may be controlled separately or a group of units may be mounted on a singlemachine base and operated through a single remote control. By employing a small cylinder for rapid traverse and both a small cylinder and .said mechanism including a restricted drain outlet, a main control valve having a pressure inlet and an unrestricted drain outlet and having a rapid approach position in which one'end-oi said small motor is'connected to said inlet and the other ends of's'aid motors are connected tovsaid unrestricted drain outlet, :1 rapid return position in which the reverse end of said smallmotor is connected to said inlet and the other ends of said motors are connected to said unrestricted drain outlet, an advance feed position in which the pressure ends of said motors are connected to said inlet and the exhaust ends of said motors are disconnected from said unrestricted drain outlet and connected to said restricted drain outlet, and a stop position in which said motors are disconnected from said inlet and said unrestricted drain outlet; a pilot valve for eflecting movement of said control valve selectively into trol valve selectively-into approach position for rapid traverse or feed depending on the position of said first mentioned pilot valve, or intoreverse position when said first mentioned pilo valve is out of stop position.

3. In a self-contained hydraulic power unit adapted to be housed in a casing mounted upon a machine frame with a spindle mounted in said casing for rotation and axial reciprocation, the combination of a hydraulic transmission for reciprocating said spindle, a source of pressure fluid, an unrestricted drain, a restricted drain including a throttle orifice, a control valve reversibly adjustable to connect said source selectively to opposite ends of said transmission and adjustable during spindle movement in one direction to connect the exhaust from said transmission selectively to said restricted drain or to both of said drains and movable into stop position to disconnect said transmission from said source and said unrestricted drain, and a plurality of pilot valves operable conjointly to control said control valve, one of said pilot valves being operable to block said restricted drain when said control valve is in stop position.

4. A self-contained hydraulic power unit comprising, in combination, a casing adapted to be mounted upon a machine frame, a spindle mounted in said casing for rotation and axial reciprocation, a hydraulic transmission embodying a plurality of cylinders having pistons reciprocable therein and interconnected tomove in unison for reciprocating said spindle, a source of pressure fluid, a drain, and means including a control valve for connecting a selected number less than all of said cylinders 'to said source and drain and for also simultaneously directing at least a portion of the pressure fluid from the forward face of a non-selected one of the pistons substantially directly to the rear face thereof and independently of said drain. v

5. In combination, a hydraulic transmission for reciprocating a machine tool-element, a source of pressure fluid, an unrestricted drain and a plurality of restricted drains, means for individually adjusting the restriction of said restricted drains, and means including a main control valve for connecting said transmission reversibly to said source and said unrestricted drain to impart rapid advance and return movements to the machine tool element, said last mentioned means alternatively being operable to disconnect said transmission from said unrestricted drain and to connect said transmission to said source and to one of said restricted drains for a slow feed movement of the machine tool element in a for ward direction, and including a pilot valve for selecting the one of the plurality of the restricted drains to which said transmission is connected to thereby control the rate of feed in accordance with the adjustment of the restriction in the selected restricted drain.

6. In combination, a hydraulic transmission embodying a plurality of cylinders having pistons reciprocable therein and interconnected to move in unison for reciprocating a machine tool element, a source of pressure fluid, an unrestricted drain and a plurality of restricted drains, means for individually adjusting the restriction of said restricted drains, means including a main control valve for connecting a selected number less than all of said cylinders reversibly to said source and said unrestricted drain to impart rapid advance and return movements to the machine tool element and for also alternatively connecting all oi said cylinders reversibly to said source and one-of said restricted drains for a slow feed movement of the machine tool element in one direction, said last mentioned means including a single pilot valve selectively adjustable for determining in the movement in said one direction the number of cylinders to which fluid is supplied through said main valve from said source and also the one of said restricted drains to which the selected cylinders are connected.

7. The combination with a hydraulic transmission for reciprocating amachine tool element at a plurality of selected speeds, and means including a rotary pilot valve for controlling the speed setting of said transmission, of a pair of spaced elongated members rigid with said machine tool element and paralleling its path of movement, an oscillatable actuator for said pilot valve projecting between said members with its axis oi oscillation transverse thereto, and dogs'adjustably mounted on said members for engagement with said actuator in the reciprocation of said machine tool element, the ones of said dogs on opposite ones of said members actuating to oscillate said actuator in respectively opposite directions during the course of longitudinal movement of said members in one direction.

8. The combination, with a hydraulic transmission for reciprocating a machine tool element selectively at a feed rate, at a rapid advance rate or at a rapid return rate, means including a first rotary pilot valve for reversing the direction of movement of the transmission, means including a second rotary pilot valve for changing the speed of the transmission and for stopping the same, of a pair of spaced elongated bars rigid with said machine tool element and paralleling its path of movement, oscillatable actuators for said pilot valves projecting between said bars with their axes of oscillation transverse thereto, and dogs adjustable longitudinally of said bars for engaging and moving said actuators in the course of reciprocation of said machine tool element to control cyclically the operation of said transmission, said dogs including at least two arranged to operate the actuator of said second pilot valve and disposed on respective ones of said pair of bars, whereby to shift said second valve in opposite senses during movement of said machine tool element in one direction.

9. The combinationwith a variable speed drive mechanism for a reciprocable machine tool element, of a pair of elongated spaced-members fixed to the element and movable longitudinally with it, means including an oscillatable device projecting between said members and transverse to them for controlling the operation of said drive in response to oscillation of said device, and abutments adjustably mounted on respective ones of said members at points spaced along said members from each other for contacting said device and oscillating it in respectively opposite directions during movement of the element in one direction.

10. In a self-contained hydraulic power unit adapted to be housed in a casing supported upon a machine frame with a spindle mounted in said casing for rotation and axial reciprocation, the

selectively to opposite ends of said transmission and adjustable during spindle movement in said one direction of movement to connect the exhaust from said transmission to said unrestricted drain for rapid traverse or to disconnect said exhaust from said unrestricted drain for feed movement and movable into stop position to disconnect said transmission from both said source and said unrestricted drain, and a plurality of pilot valves operable conjointly to control said control valve, one of said pilot valves being operable to block said unrestricted drain when said control valve is in stop position.

11. The combination with a variable speed drive mechanism for a reciprocable machine tool element, of a support for said element having a recess in one side, a pair of elongated spaced members fixed to said element and movable within said recess longitudinally with said element, means including an oscillatory device projecting bet-ween said members and transverse thereof for controlling the operation of said drive mechanism by reverse oscillation of said device. said device being mounted on a shaft journaled in said support and projecting to opposite sides thereof to permit actuation from either end; and abutments adjustably mounted on respective ones of said members at spaced points along said members from each other for contacting said device and oscillating it respectively in opposite directions during movement of said element in one direction.

RUSSELL E. BAUER.