US2416339A - Hydraulic power unit - Google Patents

Description

' Feb. 25, 1947. M, MATHYs 2,416,339

HYDRAULIC POWER UNIT I Filed Feb. 17, 1941 6 Sheets-Sheet 1 7720A: A. mat/23$ Feb. 25, 1947, M. A. MATHYS 2,416,339

HYDRAULIC rowan Unn- Filed Feb. 17, 1941 6 Sheets-Sheet 6 59 i max A. 7724172516 M'T ws Patented Feb. 25. 1947 2,416,339 Q UNITED STATES PATENT OFFICE HYDRAULIC POWER UNIT Max A. Mathys, Detroit, Mich, asslgnor to Ex- Cell-O Corporation, Detroit, Mich., a corporation of Michigan Application February 17, 1941, Serial No. 379,211

22 Claims. 1

The present invention relates enerally to imrovements in hydraulic power units, and has particular reference to such unit having a spindie mounted for rotation and'axial translation, and having self-contained means for driving the spindle and for translating the spindle automatically through a predetermined program of movements, such for example, as a cycle comprising a rapid approach, a forward feed, and a rapid return. v

One of the objects of the invention is to provide a novel hydraulic power unit which is simple, compact and sturdy in construction and which is extremely powerful, rapid, eflicient and silent in operation. a

Another object is to provide a new and improved power unit embodying a hydraulic actuating system capable of utilizing extremely high pressures without resulting in excessive heat.

A further object is to provide a novel hydraulic power unit which is adapted to maintain a uniform adjustedrate of feed regardless of variations in resistance.

A more specific object is to provide a new and improved power unit embodying a variable delivery pump, and an orifice control for effectinga uniform rate of feed uninfluenced by changes in the pump delivery pressure.

Still another object is to provide a power unit embodying a novel hydraulic system for translating the spindle, which system utilizes relatively high working pressures so as to minimize irregularities and inaccuracies in the feed movement automatically caused by the presence of entrained air or vapor in the motive fluid, and

consequently to obtain a uniform rate of feed regardless of varying resistance to the movement of the actuator. 4

A further object is to provide a new and imroved hydraulic power unit in which the component elements, such as the pump, the valves.

and the actuator are so correlated that leakage is automatically compensated for and not reflected in the feed movement of the actuator under varying load conditions.

Another object is to provide a power unit having novel means for controlling the operation of a power unit embodying the features of my invention. a

. Fig. 2 is a fragmentary front side elevational view of the power unit, partially sectioned along line 22 of Fig. 1. v

Fig. 3 is a longitudinal vertical sectional view of the power unit taken substantially along-line 3-3 of Fig. 1.

Fig. 4 is a fragmentary transverse vertical sectional view taken substantially along line 4-4 of Fig. 3, and illustrating the control valve.

Fig. 5 is a fragmentary sectional view taken substantially along line 55 of Fig. 4.

Fig. 9 is a plan-development of the periphery of the control valve.

Fig. 10 is a diagrammatic representation of the hydraulic control circuit of the power unit.

Fig. 10a is a fragmentary view of a modified form of pump control line adapted for use in the circuit.

Figs. 11a to 11c are aset of fragmentary transverse sectional v'ews illustrating the adjustment of different axia y spaced portions of the control valvewhen the latter is in stop position.

Figs. 12a to 12c are corresponding views of the control valve in rapid approach position.

Figs. 13a to '13s are corresponding views of the control valve in forward feed position.

Figs. 14a to lie 'are corresponding views of the control valve in reverse or rapid return position. Figs. 15 and 16 are views of the pump valve taken respectively in the directions of the arrows the spindle actuator automatically, and having a single manual control operable within the limits of the automatic range without likelihood of injury to the structure.

Further objects and advantages will 'become.

apparent as the description proceeds.

In the accompanying drawings, Figure 1 is a forward end elevational view of l5l5 and l6-l6 of Fig. 3.

Fig. 17 is a fragmentary sectional view of the control valve taken along line ll-ll of Fig. 4.

Referring more particularly to the drawings,

the power unit constituting the exemplary embodiment of the invention comprises a hollow housing I adapted to be mounted in fixed position on a suitable support (not shown). The housing 1 preferably is generally rectangular in shape, longitudinally and transversely. A mounting base or plate 2 is integral with the bottom of the housing I, and is formed with a central longitudinallocating groove 3.

The housing'l has an internal space, the lower portion of which constitutes an enclosed liquid reservoir 4, and is formed in the forward end over the reservoir with an internal solid body structure 5. A cover plate 6 is removably secured t the forward end of the housing. I, and serves to lose one end of the interior. Bimilarly, the other end of the housing I is closed by a removable gear case 1 having a cover plate 8.

A longitudinal spindle 9 is mounted for rotation and axial reciprocation inthe housing I, and projects from the forward end thereof for attachment of a suitable tool or workpiece. To support the spindle 9, a tubular quill It! extends through, and is mounted for reciprocation in, a cylinder ll formed in the body structure 5. Two

flanged heads or bushings I 2- and I3 are rigidly secured to opposite ends of the body structure 6 to close the cylinder II, and serve as guides for opposite end portions of the quill III. The quill I is formed intermediate its ends with a piston l4 slidably disposed in the cylinder H, and the opposite endportions of the quill therefore c'onstitute piston rods. In the present instance, the

piston I4 is of the differential type, with the rear area approximately equal to twice the forward area.

The forward end of the quill l0 extends from the cylinder head 1 l2 through an alined opening or bore in the cover plate 6. A sleeve I6 is fitted in the bore 15, and is formed at its inner end with an external peripheral flange l1 seated in a counterbore I 8, and at its outer end with an internal peripheral flange l9 in wiping engagement with the quill III to prevent the entry of chips and other foreign matter. The cylinder head I2 is seated in a counterbore in the ini, ner end of the sleeve l6. Consequently, the cover plate 6 serves to maintain the cylinder head I2 and the sleeve l6 both tightly in position. An oil seal 2| is confined within the sleeve l6 in wiping engagement with the quill l0. Any fluid reaching the sleeve I6 is returned through a passage 22 to the reservoir 4 within the housing I. A tubular bearing housing 23 has an internal flange 24 at one end secured coaxially to the quill Ill. The spindle 9 extends in peripherally spaced 3 relation through the quill lll' thereby defining an intervening clearance space 25, and projects through the flange 24. The forward end of the spindle 9 is'formed with an-enlarged nose 26 which projects from the bearing housing 23, and

which is suitably supported therein by a radial and end thrust anti-friction bearing 21. More particularly, the inner raceway of the bearing 21 i -is confined on the spindle nose 26 against an inj wardly facing annular shoulder 29 by an annu-' lar nut 29, and the outer raceway isconfined in 1 a counterbore 30 in the housing 23 by an annular nut 3|. The bearing 21 is closed from the exterior by a washer 32 and oil seal 33 secured in Consequently. the spinis connected for axial movement therewith.

Formed in, and opening to, the outer end of the spindle nose 26 is an axial bore 34 adapted to receive a removable socket member 35. In the present instance, the member 35 is formed with 1 a, conventional taper socket '36 adapted to receive the shank of a tool (not shown). member 35 may be adjusted axially within the spindle nose 26 by means of a nut 31 to compensate for tool wear, a spline key 38 serving to con- The socket Such head would have an operative drive connec- 1 tion with the spindle 9 through the bore 34.

The rear or inner end of the spindle 9 is longitudinally splined for independent axial movement relative to a rotary drive sleeve 43 journaled in the gear case I. More particularly, this 15 sleeve 43 is mounted in spaced anti-friction ball bearings 44 supported respectively in the gear case I proper and the cover 8. The inner end of the quill 10 in its rearward-position telescopes freely with the contiguous end of the spline sleeve 43, 20 and is open to the interior of the housing I. It may be mentioned at this time that any liquid tending to leak past the piston M in the cylinder H, from one side to the other, will be intercepted by a peripheral drain groove 45 open- 25 ing through radial passages 46 in the piston to the clearance space 25, and from there will drain through the inner end portion ofthe quill ID to the reservoir 4. The path of drainage to the reservoir 4 is represented schematically in Fig. 10

so by the catch pan 4 and the line 4 The rotary drive for the spindle9 comprises a gear 41 removably keyed to the spline sleeve 43 between the bearings 44. Meshing with the gear 41 is a gear 48 removably keyed'to a drive shaft 95 4'9 journaled in spaced anti-friction bearings 50 mounted respectively in the gear case vI proper and the cover 8. The shaft 49 extends through the gear case to the exterior of the housing I, and a pulley 5| adapted to be connected to a suitable source of power (not shown) is fixed on the outer end. The gears 41 and are located within a recess 52 in the outer face of the case I proper, and may be changed, upon removal of the cover 8, to obtain different selected speed ratios in the spindle drive from the power input shaft 49.

A hydraulic system (Fig. 10) is incorporated in the power unit for translatingthe spindle 9 ax-' ially through a predetermined program of movements. While different cycles may be employed,

an illustrative cycle comprises rapid I approach from the stop position, forward feed. automatic reverse, and rapid return to the stop position.

' Optionally, a dwell may be provided at the end of the forward feedland before reverse. In the present system, the rate of feed and the period of dwell are subject to accurate adjustment and control.

The hydraulic system, in its preferred form," 60 comprises generally a variable delivery pump 53 driven at a constantspeed by the shaft 49, The pump 53 has an inlet line 54 taking fiuid from the reservoir or sump 4, andv a discharge line 55 for supplying fluid under pressure. A control valve 56 is operable to connect the pressure line 55 selectively to two supply lines- 51 and 58 leading to opposite ends of the cylinder II, and also The pump (Figs. 3 and a) shown in the drawings, is of the type having parallel annularlyarranged piston and cylinder units, and is mounted on the inside of the gear case 1 within the housing I. In its preferred form, the pump 58 comprises a stationary valve member 88 and a rotarycylinder body 8|, having flat annular end the cylinder body 5|. Formed in the bore 88 are internal splines 58 which interflt slidably with longitudinal splines I8 on the inner end of the shaft 4-8 to establish the drive connection for the pump 53, and which are relatively short so as to permit a limited amount of peripheral float of the cylinder body 8| and thereby insure accurate seating of the valve faces 52 and 53,

Formed in the cylinder body 5| in parallel uniformly spaced relation about the bore 58 are a the other end is closed to define a pressure champlurality of pump cylinders H having cylinder ports 12 opening from the inner ends to the valve face 83. Suitable pump pistons or plungers 18 are respectively reciprocable in the cylinders II. The plungers 13 are urged outwardly by coiled compression springs 14. These springs engage the inner ends of the cylinders II, and extend into bores I5 in the inner ends of the plungers 18 so that the latter may be comparatively short in length.

A swash plate I8 having a flat bearing face I1 is in operative association with the outer ends of the plungers l3, and when inclined is adapted to cause reciprocation of the plungers in uniformly timed sequence upon rotation of the.

cylinder body 5|. Bearing shoes 18 are connected by means of suitable inserts I8, for universal pivotal adjustment, to the outer ends of the plungersl3, and have flat faces in sliding engagement with the bearing face 11 of the swash plate 18., The swash plate 15 is mounted in the housing I on a pivot pin 88 atone end for angular adjustment about an axis extending transversely of the axis of rotation of the cylinder body 8i. point adjacent the axis of each plunger 18- as the latter reaches top dead center position at the end of the pressure stroke. As a result, the

' plate I6 is adjusted into a plane perpendicular to the shaft 48, no reciprocation will be imparted to the plungers 18- and the pump displacement will be zero. In the reciprocation of the plungers 13, those on the suction stroke take in fluid from the line 54, and those on the pressure stroke discharge fluid to the line 55. For further details of the pump valve porting, reference may be had to a copending application, Serial No. 348,904,.iiled July 31, 1940', by Ira J. Snader and Max A. Mathys (now Patent'No. 2,299,235, issued October 20, 1942) a a 15 to level off the latter.

Preferably, the pin 88 is located at a- 50 a c v The swash plate 18 is angularly adjustable about the pin 88 to vary the displacement of the pump. Within the broad aspects of the present invention, such adjustment may be effected 5 by any suitable means. In the present instance,

10 control pressure. and to increase the delivery upon a decrease in the pressure. The particular means for this purpose comprises a balancing plunger 8| and a control plunger 82 acting on the free end of the swash plate I8 in a direction The balancing plunger 8! establishes a condition of balance against the v hydraulic reaction-in the cylinder II, and inthe s plate into its maximum stroke position.

The pressure balancing plunger 8! (Fig. 8) isv reciprocable in a bore 88 formed in the body structure 5 of the housing and extending transversely ofthe pin 80. One end of the bore 88 opens toward the free end of swash plate 15, and

-ber 84 and is connected through a branch line 85 to the pressure line 55 of the pump 53. A shoe 88 is connected by means of an insert 8'! for 6 universal pivotal adjustment to the outer end of the plunger 8|, and bears s'lidably against a fiat face 88 on the rear of the swash plate 16. The diameter of the plunger 8| and the moment arm of force exerted thereby on the swash plate 15 are such that this force willsubstantially counterbalance the hydraulic reaction in the pump cylinders II. Since the delivery pressure ofthe pump 53 is always connected through the lines 55 and 85 to the pressure chamber 84 at the inner end of the plunger 8|, the swash plate 15 structure 5 of the housing I and opening transversely of the pin 88 to the rearface 88 of the swash plate I8. A shoe 80 is connected by means of a suitable insert 8| (Fig. 3) for universal pivotal adjustment to the outer end of the plunger 82, and slidably engages the face 88. A positive stop is provided to limit the position of maximum inclination of the swash plate 15 which determines the maximum pump delivery. In the present instance, this stop consists of a plug 5 82 positioned in the inner end of the bore 88 for engagement by the plunger 82. Opening from the innerendof the bore 88, between the plunger 82 and the plug 82, is a pump control line 83. This linemay be connected to any suitable source of control pressure, and in the present instance is adapted to be connected by the control valve 58 to the exhaust side of the cylinder ll so as to utilize the back pressure under orifice control .70 versely through the body structure 5 of the housing l, and a valve plug 85 mounted for rotary adjustment therein. It will be understood that the various lines or passages 55, 51, 58, 58 and 88 have appropriate port openings to the periphcry of the valve bore 84. The valve 58 may be In the present mg to the bore I I3.

constructed to provide any desired program of d v axial movementsof the spindle 9, and in the present instance is of the four-position type, defining a cycle comprising rapid approach, forwar feed, reverse, rapid return' and stop. I

' r In its preferred construction, the valve plug 96 is formed in one transverse plane b-b (Figs. 4.

y 8 I posite sides of the grooves I26 and open to the peripheral grooves I94 and I95. The grooves I21 preventleakage from the pressure ports I99 and I9I and the groove II9 to the groove I26, so that variations in the pump pressure will not be refiected in the rate offeed as controlled by the orifice I25. It will be understood that theeffective flow area of the orifice I is controlled by the position of the tapered notch I23, and is progressively reduced upon rotary adjustment or the plug II4 to move in a direction of decreasing lateral area across the orifice.

Assuming that the spindle 9 is in retracted stop position, the control valve 58 'willoccupy the position shown in Figs. 11b, 11c and 11d. In this position of the valve, the line 51 to the forward ripherally spaced radial ports I99, I9I and I92 opening to the pressure bore 99, and hence constituting pressure ports. The outer end of the 'port I92 is peripherally elongated as indicated at I93.

The cylinder lines 51 and 58 open at diametrically opposite points to the bore 94 in the plane of the ports I99, I9I and I92. Also formed in the plug 95 are two axially spaced peripheral exhaust groove I94 and I95 which are interconnected by two peripherally spaced longitudinal grooves I9, termediate t epressure ports I9I and I92, 'and 3 102 and I99. The exhaust line 59 opens to the bore 94 in the plane of the groove I95. Two additional longitudinal exhaust grooves I98 and I99 are formed in the plug 95 respectively between the notches 98' and 91, and open to the peripheral roove I94.

v The pump control line 93- opens to the periphery of the valve bore 94 in a transverse plane d-d (Figs. 4, 9, 11d, 12d, 13d and 14d). Formed in the periphery of the plug 95 is a longitudinally inclined pressure groove II9 which extends from the pressure port I9I to the plane d-d, and two short'longitudinal exhaust grooves III and H2 which extend from the peripheral exhaust groove I95 through the plane d-d, and which are approximately in alignment with the ports I9I and I99.

Formed in one end of the valve plug 95 is an axial orifice valve bore I I3. An orifice valve plug nd I 91 located respectively inend of the cylinder II is blocked, the line 58 from the other end of the cylinder is connected through I9I-I95 to the exhaust line 59, and the pump control line 93 is connected through II9--I9I- 99999'| to the pressure line 55 of the pump 53. The pressure in the line 93 causes the swash plate 16 to level ofi into no-delivery position so that the pump serves only to maintain a constant low pressure in the line 55 equal to the pressure in the line 93. a

Upon adjustment of the valve 56 in a counterclockwise direction (Figs. 12b, 12c, and 12d) into H4 is secured by means of a flat key II5 for rotary adjustment in the bore H3, and has an actuating shaft I I6 formed with 'an adjusting dial III disposed against the outer end of the control valve plug 95.' If desired, a spring washer I I8 may be interposed between the plug 95 and the dial II'I-to take up lost motion and to provide a frictional retaining means. is slotted to receive a suitable hand tool for rotatably adjusting the plug H4, and is appropriately graduated to indicate theselected feed adjustment.

' Theorifice valve plug I I4 is formed with an axial bore I I9 which opens through a radial port I 29 to a peripheral groove I 2| in turn connected The dial I IT through a radial port I22 in the plug 95 to the peripheral exhaust groove I95. Also formed in the plug H4 is a tapered peripheral notch I23 which is connected at its large end through a radial port I24 to the bore H9; and which is rotatably adjustable across an orifice I25 open- I25 opens to a longitudin'algroove I28 formed in planes 0-0 and dd. Suitable small drain V- grooves I21 are formed in the plug 95 along op- The outer end of the orificerapid approach position, both cylinder lines 51 and 58 are connected through I99-I92-99-98 to the pressure line 55, and the pump control line 93 is connected through Il2-I95 to the exhaust line 59. Consequently, the swash plate I6 is adjusted by the springs 14 into maximum delivery position as determined bythe stop 92.

Because of the difierential area of the piston I4, fluid displaced from the front end of the c linder II is directed to the large end of the c linder. The rapid approach, therefore, occurs at a maximum rate of speed.

Upon subsequent adjustment of the valve 56 in a clockwise direction into forward feed position (Figs. 13b, 13c and 13d),'the line 58 is connected through I93--I9299-989'| to the pressure line 55,.the line 5'! is connected through I26-the orifice I25I23-I2 4-II9 I29I2I I22-I95 to the exhaust line 59, and the pump control line 93 likewise is connected to the groove I26 at the inlet side of the orifice. Consequently,

the orifice I23 meters the fluid discharging from the forward end of the cylinder II, and the back pressure thus created is utilized to reduce and control the discharge of the pump 53 to the desired uniform feed rate.

At the end of the forward feed, the control valve 56 is. reversed (Figs. 14b, 14c and 14d) to effect a rapid return of the spindle 9 into initial stop position. In this condition of adjustment of the valve 56, the line 51 to the forward end of the cylinder I I is connected through I9I-99. 98-91 to the. pressure line 55, the line 58 from the rear end of the cylinder is connected through I Ill-I95 directly to the exhaust line 59, and the pump control line 98 is connected through III- I95 to the exhaust line 59'. Consequently, the

clusion of both plunger 8| and 82. in thediagrammatic disclosure, the pump 53 has been shown in the position of zero displacement. In 9 the actual construction, the plungers 8I and 82 are disposed side by side at the same distance I from the pivotal axis of the swash plate I6 and for maximum displacement the swash plate aerasse would occupy a position of maximum inclination. 7

Since the rear area of the piston I I is twice as large as the forward area, and since in rapid approach the opposite ends of the cylinder are interconnected, the rapid return and the rapid approach will have the same rate of movement.

The orifice control in the exhaust side of, the hydraulic system sets up a back pressure which is utilized to control the displacement of the variable delivery pump during feed operation. This stantially at zero displacement, but does supply fluid to maintain the system under low pressure. During feed condition, the control pressure and the spring pressure are in sensitive balance. The foregoing arrangement serves ideally to dampen any pressure pulsation tending to occur. Thus,

the opening pressure imparted to the swash plate 16 by the springs 14 is comparatively light, and

a momentary closing pressureimpulse is com-. paratively high. Consequently, one side of the harmonic pulsation curve is slowed down, although the action is so rapid that it is not discernible to the eye, thereby resulting in eflective dampening.

The pump delivery pressure will vary over a wide range, depending on the work resistance, and onoccasion may be extremely high. However, the pressure for regulating the pump .53 during feed operation, being independent of the pump delivery pressure, is relatively constant,

' and may be comparatively low and much less than'the maximum pump-pressure. The low control pressure is advantageous since less heat will be generated in the passage of fluid through the orifice than if a high pressure were employed.

Also, pulsations are more eflectively eliminated with the use of a low control pressure. While a comparatively low control pressure is desirable, it should be sufliciently high to avoid substantial changes in the compressibility of the fluid. I have found that in the present installation, a sensitive control is obtained when the back pressure created by the orifice is maintained above 110 pounds per square inch. The most suitable orifice pressure and hence the pump control pressure can be determined from the compressibility curve of the motive fluid for each installation. In a typical curve, the compressibility initially increases rapidly with an increase in pressure, and then levels oil. and increases only slightly as the pressure continues to increase over a substantial range. If the pressure is selected In this range where the compressibility of the fluid is fairly uniform, the control of the pump will have a low elasticity. regardless of loadv variations, changes in fiuid viscosity, the presence of entrained vapors and pressure vibrations in the system.

- The valve plug 35 is confined in the bore 94 against endwise movement and for rotary adjustment. To this end, a collar I28 is removably keyed on one end of the valve plug 95 for rotation therewith, and is rotatable within-a counterbore I29 in one end of the valve bore 34. A hand knob I30 isflxedtotheextremeendotthevailveplug 95 at the front of the housing I and serves to confine the collar I23 in position, and as a means for adjusting the valve 58 manually. A collar I3I is keyed to the other end of the valve plug 95 and is rotatably confined in a counterbore I32. The collar I3I is held in position by an abutting collar I33 fixed on the extreme and of the plug 95. It will be seen that the valve plug 35 and the collars I28 and I3I are confined in bled relation within the bore 34 by the hand knob I33 and the collar I33. The extreme ends of the valve plug 95 are of the same diameter so that the hand knob I30 and the collar I33 may be interchanged if it should be desired to adjust the valve manually from the other side of the housing I.

To provide means for adjusting the valve 55 in timed relation to the axial movements of the spindle 9, a dog bar I34 is connected at its forward end by a pin I35 to theiiange or faceplate 40 of the housing 23. The pin I35 is rigi y threaded into the dog bar I34 and has an accurate sliding fit with a radial bore I35 in the face plate 40. The bar I34 extends slidably through a hole I31 in the front cover 5 and an alined hole I38 formed in the side of the housing I, and is therein supported to provide a slight clearance I33 between the bar and the face plate 43. The loose connection between the dog bar I34 and the face plate 40 serves to maintain the quill II securely against angular displacement without requiring close accuracy in alinement.

Formedin the bar I34 is a longitudinal groove I 40 for adjustably supporting a plurality of valve control dogs. In the present instance, three dogs are shown, namely, a stop dog I, a feed dog I42, and a reversing dog I43. To support the dogs, the longitudinal groove I43 is formed with three accurate faces I44; I45 and I45. Suitable clamping screws I41 are threaded through each dog into engagement with the bar I34 opposite the face I46. The clamping pressure is mainly absorbed by the face I46 and comparatively small pressures are absorbed by the faces I44 and I45. Consequently, the main pressure is absorbed longitudinally of the screws I41 so that even with a large clamping pressure, no substantial bending force is imparted to the dog bar. Although more than half of the dog bar is cut away, the bar affords a rigid support for the dogs and retains a good sliding fit in the bores I31 and I33.

The dogs "1,": and m are arranged m selective engagement with dog abutments I45, I49 and I50 on the collar I23. These abutments are spaced axially of the collar I 23 to avoid interference, and are movable successively into position for engagement by the respectivedogs.

Coacting with the dog control is a spring reversing mechanism. In its preferred form, this mechanism comprises the collar I3I which is slidably disposed respectively in bores I55 and I55,-

opening tangentially to opposite sides of the valve bore 94, and are adapted for engagement with the ward movements.

. v 1 11 to hold the abutment I48 against the stop dog -I4I (Fig. 11a) in stop position.

' To start the cycle, the valve 56 is rotated in a.

counter-clockwise direction, for example by means of the hand knob I30, thereby forcing the plungers I 53 and I54 (Fig. 12a), and moving the abutment I49 into the path of the feed dog I42 (Fig. 12e). Inthis position, the plungers I53 and I54 engage the periphery of the reverse collar I3I, and hence are ineffective. The ;valve 56 is now in position to effect the'rapid approach movement of the spindle 9.

At the end of the forward approach movement,

the feed dog I42, which travels with the quill I0, engages the abutment I49 to rotate the-valve 56 clockwise througha predetermined angle into the 4 forward feed position. As a result, the abutment I50 is moved into the path of the reverse dog I43 (Fig- 13e), but, the plungers I53 and I54 still remain in engagement with the periphery of the collar I3I (Fig. 13a). The spindle 9 now moves as a feed rate determined by the setting of the" adjustable groove I23.

At the end of the feed movement, the reverse dog I43 engages the abutment I59 to rotate the effect the rapid return movement of the spindle 9 into the initial stop position.

-At the end of the rapid-return, the stop dog I4I engages the abutment to rotate the valve 56 counter-clockwise against the spring action of the plungers I53 and I54 into the stop position (Figs. 11a and 11c).

Instead of reversing the valve 56 immediately at the end of the forwardfeed, a dwell may be interposed before reversal. Such dwell is obtained by means, of a valve reversing mechanism having a. time delay. To render such dwell mechanisms functionally operative, the reverse dog I43 is removed, and the quill I9 is caused to engage a positive stop at the end. of the for In the present instance, the forward end of the cylinder I I, upon engagement with the piston I4, serves as the stop.

The dwell mechanism (Figs. 4, 5, 7 and comprises a tubular or hollow floating plunger I56 reciprocable in a, bore I60 formed in the body structure 50f the housing I and transversely intersecting the main valve bore 94. A gear I6I rigid with the valve plug 95 meshes with a longitudinal gear rack I62 formed in the side of the plunger I59. The range of the reciprocation of f the plunger I59 is suitably limited by a stop plug 1 I63 removably, inserted in-one end of the bore I60, and an actuating piston I64 slidable in a cylinder bore I65 opening to the other end of the bore I60. The actuating piston I64 has a head I66 defining its retracted position, and is movable inwardly against the contiguous end of the plunger I 59 to shift the latter, together with the plungers I53 and I54, into one end position in engagement 1 i with the stop plug I63, and thereby to locate.

the'control valve 56 in reverse position; Move- I ment of the plunger I59 into the other end position against thepiston I64 when the latter is 35 to the orifice.

The closed end of the cylinder bore I65 is connected through a line I61 to a dwell and relief valve I68 (Figs. '1 and 10). This valve comprises a sleeve I69 fixed in a bore I10 in the gear case 5 1, and having an axial bore "I open at one end to a drain line I12 leading to the reservoir 4. Threaded into the other end of the bore I10 is a closed tubular cap I13 connected to a branch,

of the drain line I12. A valve plunger I 14 is 10 reciprocable in the bore "I; and has a stopflange I normally urged into engagement with the inner end of the sleeve I69 by a coil compression spring I16 confinedwithin the cap I 13.

Two spaced'annular grooves I11 and I18 are 15 formed in the outer periphery of the sleeve I69,

and open respectively through radial ports I19 and I80 to the bore I1I. nected respectively to the pressure line 55 and the line I 61. Formed in the periphery of the valve plunger I14 aretwo axially spaced grooves I8I and I82 movable selectively into registration with the ports I80. Suitable openings I83 are formed in the-flange I15 connecting the groove I I82 to the interior of the cap I13.

The valve plunger I14 is formed in one end portion with an axial bore I84. The outer end of this bore is closed by a screw plug I85, and the inner end is connected through a passage I86 open to the port I19. An orifice plug I81, with a restricted axial orifice I88 in one end wall, is

removably threaded into the inner end of the bore I84 and is spaced from the plug I85 so that the middle portion of the bore defines a confined space open to the interior of the plug and hence The intermediate portion of the bore I84, at the downstream side of the orifice I88 is connected through a 'passagel89 in the I plunger I14 to the groove IBI.

' The inner end of the bore I'II opening to the 0 line I12 is reduced in diameter to define a relief valve passage I90, and the corresponding end of the valve plunger I 14 is reduced in size to constitute a relief valve memberJSI. slidable in the passage. Hence, the plunger I19 is formed with a pressure face I92 open to the ports I 19. Suitable tapered grooves I93 are formed in the periphery of the valve member I 9! for movement into and out of communication with the ports I19. I

In operation, the valve member I14 normally occupies the position, shown in Fig. 7, in which the roove I8I is closed, and the tapered grooves I93 are out of communication with the port W9. At this time, no fluid passes through the valve I68, and the cylinder I is relieved through I 61-I18-I80I82I88-I13 ,I12 to the reservoir 4. Upon feed movement of the quill I0 into the forward end position against the positive stop, the spindle 9 will of course come to a stop, and upon the cessation of motion, thepi'essure in the pump control line 93 will drop, thereby causing an increase in the pump displacement. Since the delivery fluid has no place to go, the pump pressure will rise. The rising pressure, acting on 1 the pressure face I92, will ultimately shift the valve plunger I14 to move the groove I82 out of communication with the ports I80, and the groove I8I' into communication therewith. Thereupon, a flow connection is established to the cylinder I65 from the pump 53 through 55-I11-I19 I86-I88-I84-I89I8I-I80--I18 and I61. The transmitted pressure acts on the piston I64 to move the latter at a graduated rate depending on the flow rate through the orifice I88. It

J5 will be understood that the elevated pressure,

These grooves are con- 6 l3. which acts on the plunger 8| serves to. reduce the pump displacement, and hence the orifice 199 sets up a pressure difierential influencing the .volume output of the pump and the supply of ward-end of thecutting feed movement. As soon as the valve56 is near the stop position, the

spring-actuated plungers I53 and I54 will' act I to complete rotation thereof quickly into reverse position.

The pressure rise during the dwell period is limited to a predetermined maximum. Should the pump pressure rise to this maximum, which is determined by the pressure of the spring I16,

it will move the valve plunger I14 sufliciently to open the tapered grooves I93 to the ports I19, and thereby cause excess fluid to be relieved through the relief valve passage I90 to the drain line I12. In this condition, the valve I68 will act both as a dwell return and a relief valve. Thus, for the longer dwell periods, the relief of excess fluid serves to maintain the pump delivery pressure substantially constant, and the orifice I88 passes fluid entirely under pressure control to meter the supply to the cylinder I65-at a rate determined by the orifice flow characteristics. 1

Optional means is provided for actuating the control valve 56 by remote control. When the remote control is not utilized, the hollow plunger I59 is open at both ends so as to be pressure balanced for free manual operation of the valve 56 bymeans of the hand knob I30. When the,

remote control is desired, the plunger I59 is closed by threading a plug I94 (Fig. 5) into one end. Two fluid lines I95 and I96 open to opposite ends of the bore I60, and are adapted to be connected by a remote control pilot valve I91 to exhaust or selectively to pressure.

The valve I91 comprises a valve housing I98 mounted on a suitable support, such as a plate I99 attached to some part of the machine frame (not shown) on which the power unit is used.

Formed in the housing I98 is a valve bore 200 having longitudinally spaced port connection with the pump branch pressure line 85, the exhaust line 59 and the remote control lines I95 and I96.

14 plunger 20I. In the'neutral position, the valve plunger 20 I connects both lines I95 and I96 to the exhaust line 59 and blocks the'pressure line 85 sothat the remote control plunger I59 is pressure balanced to permit free adjustment of the valve 56 by the dogs Ill, I42 and l43 or by operating of the hand knob I30.

Upon energization of the solenoid 203, for ex ample at any time desired or in case of emergency during the forward translation of .the quill I0, the plunger will be shifted to connect the remote reverse line I96 to pressure and the line I95 to exhaust. 56 will be shifted into reverse position. Thereupon, the spring 205 again returns the valve member 20! to neutral. movement of the quill I0, the stop dog I moves the valve 56 into stop position and maintains it there until the next cycle is initiated by again energizing the solenoid 202.

It will be noted that the hydraulic power unit is subject to manual control, either by means of the hand knob I or the remote control at any point within the limit of the automatic range without likelihood of injury to the structure. The unit is compact and sturdy, and can be operated at a relatively high fluid pressure without creating objectionable heating since no excess fluid required to be discharged through a relief valve is normally delivered by the pump.- Any leakage in the hydraulic system is automatically com.- pensated for sincethe orifice control will reflect such leakage and adjust the pump displacement accordingly. By using a suitable pump control pressure in the low-compressibility range of the fluid and by compensating for any leakage, a uniform rate of feed movement is obtained regardless of load variations.

It is to be understood that while the invention has been shown as incorppralledvin a hydraulic power unit of the quill type, various features thereof are also applicable to hydraulic power units of the sliding head type.

-In instances where a comparatively high control pressure is desired, it may be advantageous v to provide a modified pump control line 93a hav- A valve plunger 20I of the spool type is slidably adjustable in the bore 200. v

The valve plunger 20I may be adjustable by any suitable means, and in the present instance two solenoids 202 and 203 controlled by electric push buttons (not shown) are mounted'on the support I99 and have cores or armatures 204 connected respectively to opposite ends of the plunger.

Upon energization of the solenoid 202, the plunger 20I will be shifted in a direction (Fig.

10) to connect the remote start line I95 to pres- I sure and the line I96 to exhaust. Thereupon, the pressure fluid acting on the remote control plunger I59 will shift the control valve 56 from the stop position into the rapid approach or starting position. As soon as this adjustment is effected, I

the push button is released to deenergize the solenoid. A coiled compression spring 205, inter-' posed between the valve plunger 20I and a bracket 206 on the support, then returns the plungerto intermediate neutral position. Expansion of the spring 205 is limited by abutment with the housing I98 to prevent over travel past neutral of the ing interposed therein a check valve 201 permitting free flow to the control plunger 02, and a parallel flow restriction 209 for dampening the flow of fluid from the plunger. Such optional construction is indicated'in Fig, 10a, the. modified line 93a being used in lieu-of the line 93 in- Fig. 10.

The pump 53 per se is covered in my copending divisional application, Serial No. 710,153, filed November 15, 1946.

I claim as my invention:

1. A hydraulic power unit comprising, in comblnation, a hydraulic motor, a variable delivery pump having an adjustable member for controlling the pump displacement, spring means in said pump acting on said member in a direction to increase the displacement of said pump, means for driving said pump, an exhaust line, hydraulic means for counterbalancing said member against the pump reaction, hydraulic means acting on said member in a direction to decrease the displacement of said pump, and a control valve,

adapted in one positionjto connect said pump and exhaust line to opposite sidesof said motor and being adjustable into a stopposition to block the forward side of said motor, toconnect the other side of said motor to said exhaust line, and to connect-the outlet of said pump to the last As a result the control valve At the end of the return mentioned hydraulic means whereby to adjust Y said pump into position of zero displacement;

2. Ahydraulic power unit comprising, in combination, a piston and cylinder motor, a variable delivery pump, means for driving said pump, said pump having an actuating member adjustable to vary the displacement from zero to maximum,,

means for counterbalancing said member against the pressure reaction in said pump, valve means for connecting said pump reversibly to opposite ends of said motor, and for varying the resistance to flow oithe fluid discharging from said cylinder for rapid traverse and feed operation.

andhydraulic means responsive to the pressure of the discharge end of said motor for automatically adjusting the displacement of said pump to obtain maximum displacement during rapid traverse, and substantially constant reduced displacement during feed operation.

3. A hydraulic power unit comprising, in combination, a cylinder, a piston slidably disposed in said cylinder, a variable delivery pump have ing a pressure discharge line, means for driving said pump, an exhaust line, adjustable valve 1 means for connecting said discharge line and said exhaust line selectively to opposite ends of said cylinder to translate said piston at rapid traverse and feed rates, orifice means connected to receive fluid discharging from said cylinder during feed operation, and means responsive to the pressure at the inlet side of said orifice means for controlling the displacement of said pump to maintain a substantially constant rate of fluid flow through said orifice under varying load conditions during feed operation.

4. A hydraulic power unit comprising, in combination, a cylinder, a piston slidably disposed in said cylinder, a variable delivery pump having a pressure discharge line, means for driving.

said pump, an exhaust line, adjustable valve means for connecting said discharge line and said exhaust line selectively to opposite ends of said cylinder to translate said piston at ripid traverse and feed rates, orifice means selectively available under the control of said valve means for setting controlling the pump displacement,spring means in said pump acting on said member in a direc tion to increase the displacement of said pump;

means for driving said pump, an exhaust line,hydraulic means for counterbalancing said member against the pump reaction, hydraulic means acting on said member-in a direction to decrease the displacement of said pump and responsive to the pressure in said exhaust line exerted in opposition to said spring means, and a control valve adapted in one position to connect said pump and spring means in said pump acting on said member up a back pressure in said exhaust line during feed operation, and means responsive to the pressure at the discharge side of said cylinder for controlling the displacement of said pump.

5. A hydraulic power unit comprising, in combination, a cylinder, a piston reciprocable in said cylinder, a translatable element connected with said piston, a drive shaft, a variable delivery pump driven by said shaft and having an adjustable element for controlling the pump displacement, supply lines opening to opposite ends of said cylinder, an exhaust line having a restricted adjustable oriflce control passage and a parallel less restricted passage, pressure responsive means operable to shift said adjustable element respectively in response to an increase or decrease-in pressure in said exhaust 'line to decrease or increase saidpump displacement, a rotary control valve for connecting said supply lines selectively to said pump and to said passages and said pressure responsive means selectively to said passages whereby to translate said first-mentioned element selectively at a rapid approach, 'forward feed or rapid return, and means controlled by the translation of said first-mentioned element for auto matically adjusting said valve.

6. A hydraulic power unit comprising, in combination' with a translatable element, a hydraulic motor for translating said element, a variable delivery pump having an adjustable member for in a direction to increase the displacement of said pump, means for driving said pump, an exhaust line, hydraulic means for counterbalancing said member against the pump reaction, hydraulic means acting on said member in a direction to decrease the displacement of said pump and responsive to the pressure in said exhaust line exerted in opposition to said spring means", and a control valve adapted in one position to connect said pump in parallel to opposite sides of said motor and to connect second mentioned hydraulic means to said exhaust line to effect adjustment of said member into position for maximum pump displacement, and being adjustable into another position to connect one end of said motor to said pump and the other end of said motor to said exhaust line, and to interpose a flow restriction in said exhaust line to adjust said member into position for reduced pump displacement.

8. A hydraulic transmission for a reversibly movable machine tool element comprising, in combination, a-hydraulic motorior translating said element, supply lines opening to opposite sides of said motor, a variable delivery pump having a pressure discharge line and an adjustable control membermovable to vary the pump displacement through a range from zero to maximum, spring means acting on said member in a direction to increase said pump displacement,

means responsive to the discharge pressure of said pump for substantially counterbalancing said member against the pumping reaction, an exhaust line, acontrol valve adjustable into position to connect said supply lines respectively to said discharge and exhaust lines to eilect movement of said element in one direction, stop means for positively limiting the movement of said element said member with said .stop means to adjust said valve out of said position.

9. A hydraulic transmission renal reversibly movable machine tool element comprising, in

combination, a hydraulic motor for translating said element, supply lines opening to opposite mum, spring means acting on said member in a direction to increase said pump displacement, means responsive to the discharge pressure of said pump for substantially counter balancin said member against the pumping reaction, an exhaust line, a control valve adjustable into position to connect said supply linesrespectively to said discharge and exhaust lines to eflect movement of said element in one direction, stop means for positively limiting the movement of said element in said one direction, a restricted flow orifice functionally interposed to receive fluid discharging from said motor through said exhaust line when said element is moving in said one direction, means including a hydraulic actuator acting on said member in opposition to said spring means and responsive through-a control line to adjust said member to decrease the pump displacement upon an increase in the pressure at the inlet side of said orifice and to increase said displacement upon a decrease in the pressure at. the inlet side of said orifice, said valve being adjustable into a second position to reverse the connections of said supply lines to said discharge and exhaust lines and thereby to 'efiect movement of said element in the reverse direction, and means including a hydraulic actuato'r automatically operable in response to a predetermined pressure rise in said discharge line upon engagement of said element with said stop means to adjust said valve into said second position after a predetermined dwell period of said element.

10. A hydraulic tra'nsmission for a reversibly movable machine tool element comprising, in combination, a hydraulic motor for translating said element, supply lines opening to opposite sides of said motor, a variable delivery pump hava ing a pressure discharge line and an adjustable control member movable to vary the pumpdisplacement through a range from zero to maximum, spring means acting on said member in a direction to increase said pump displacement, means responsive to the discharge pressure of said pump for'substantially counter balancing said member against the pumping reaction, an exhaust line, a control valve adjustable into position to connect said supply lines respectively to said discharge and exhaust lines to effect movement of said element in one direction, stop means said supply lines reversiblyto said delivery and exhaust lines, a hydraulic valve motor having a reciproca ry plimcer extending transversely of said valveand geared thereto, automatic means for adjusting said valve in'timed relation to the movement of said element, a remote control pilot valve normally in intermediateneutral position to connect opposite ends of said valve motor to said exhaust line, and being-adjustable oppositely out of said neutral position to connect said delivery and exhaust lines reversibly to opposite ends of said valve motor, and manually controlled means for selectively adjusting said pilot valve at any time within the range of control oi said automaticmeans. V

12. A hydraulic transmission for a reversibly movable machine tool element comprising, in combination, a hydraulic motor for translating said element, supply lines opening to opposite sides of said motor, a pump having a delivery line, an exhaust line, a rotary control valve adjustable into opposite limit positions to connect said supply lines reversibly to said delivery and exhaust lines, a hollow plunger reciprocable transversely of said valve and operatively geared to said valve, means for automatically adjusting said valve in timed relation tothe movement of said element, and a hydraulic actuator for shifting said plunger. a

13. A hydraulic transmission for a reversibly movable machine tool element comprising, in

, combination, a hydraulic motor for translating haust lines, a hydraulic valve motor having a for positively limiting the movement of said element in said one direction, means including a hydraulic actuator acting on said member in opposition to said spring means and operable in response to "the pressure in said exhaust line to efiect an increase in pump displacement upon a decrease in the exhaust pressure and a decrease in pump displacement upon an increase in the exhaust pressure, said valve being further adjustable tovary the back pressure in said exhaust line whereby to effect adjustment of said pump control member.

ll. A hydraulic transmission for a reversibly movable machine tool element comprising, in combination, a hydraulic motor for translating said element, supply lines opening to opposite sides of said motor, a pump having a delivery line, an exhaust line, a rotary control valve adjustable into opposite limit positions to connect said element, supply lines opening to opposite sides of said motor, a pump having a delivery line, an exhaust line, a rotary control valve adjustable into opposite limit positions to connect said supply lines reversibly to said delivery and exreciprocatory hollow plunger extending transversely of said valve and geared thereto, automatic means for adjusting said valve in timed relation to the movement of said element, a ,re-' mote control pilot valve normally in intermediate neutral position to connect opposite ends of said valve motor to said exhaust line, and being adjustable oppositely out of said neutral position to'connect said delivery and exhaust lines reversibly to opposite ends of said valve motor, manually controlled means for selectively adjusting said pilot valve at any time within the range of control of said automatic means, and hydraulic dwell means for shifting said plunger when said pilot valve is in neutral position.

'14. A hydraulic transmission for a reversibly movable. machine tool element comprising, in

combination, a hydraulic motor for translating a direction to increase said pump displacement,

means responsive to the discharge pressure of said pump for substantially counter balancing said member against the pumping reaction, an exhaust line, a control valve adjustable into position to connect said supply lines respectively to said discharge and exhaust lines to efiect movement of said element in one direction, stop means for positively limiting the movement of said element in said one direction, hydraulic meansineluding a plunger acting on said member in opposition to said spring means in a direction to decrease the pump displacement'and having a pressure control line adapted for connection to said 20 increase the displacement "of said pump, means for driving said pump, hydraulic means for counterbalancing said member against the hydraulic bination with a translatable element, a hydraulic *motor for reversibly translating said element, a delivery pump having a pressure discharge line,-

,a direction valve for connecting said line reversibly to opposite sides of said motor, means itor positively limiting the movement of said element in one direction, a hydraulic actuator for reversing said valve tov efiect movement of said element in the'other direction and having a ipressure control line, and a dwell and, relief valve operable bya predetermined rise in pressure in said discharge line upon engagement of said element with said means to relieve said discharge line for diversion of excess fluid andto connect a said discharge line through an oriflce to said control line whereby to effect a delayed reversal ;of said direction valve by said actuator.

16. A hydraulic power unit, comprising, in combination with a translatable element, a hydraulic motor for reversibly translating said element, a

delivery pump having a pressure discharge line, a direction valve for connecting said line re- I :versibly to opposite sides of said motor, means for positively limiting th movement of said element in one direction, a hydraulic actuator for reversing said valve to effect movement of said element in the other direction, and having a pressure control line, a dwell valve normally conditioned to connect said control line to exhaust and being operable by a predetermined rise in pressure in said discharge line upon engagement of said element with said means to connect said discharge line through a flow rectriction to said control line, and means normally closed during the translation of said element and operative to relieve excess fluid from said discharg line to limit said pressure rise to a substantially constant maximum, whereby to eflect a delayed reversal of said direction valve by said actuator.

17. A hydraulic power unit, comprising, in comreaction of said pump, hydraulic means acting on said member in a direction to decrease the displacement of said pump, and control valve means selectively adjustable to direct fluid from said pump to said motor to effect operation of said motor, or to connect said pump to said last-mentioned hydraulic means wherebyito adjust said pump into position of substantially zero displace-- ment.

19. A hydraulic power unit comprising, in combination, a reversible hydraulic motor, a variable delivery pump, means for driving said'pump, said pump having an actuating member adjustable to vary the displacement from zero to maximum, means for counterbalancing said member against the hydraulic pressure reaction in said pump, an exhaust line including a passage with a flow restriction and a less restricted passage about said restriction, and valve means for connecting said pump reversibly to opposite ends of said motor bination with a translatable element, a hydraulic motor for reversibly translating said element, a delivery pump having a pressure discharge line, a, direction valve for connecting said line resersibly to opposite sides of said motor, means ior positively limiting the movement of said element in one direction, a hydraulic actuator for reversing said valve to eifect movement of said element in the other direction, and having a pressure control line, a dwell valve normally conditioned to connect, said control line to exhaust and being operableby a predetermined rise in pressure in said discharge line upon engagement of said element with said means to connect said discharge line through a flow restriction tosaid control line, means normally closed during the translation of said element and operative to relieve excess fluid from said discharge line to limit said pressure rise to a substantially constant maximum, whereby to effect a delayed reversal of said direction valve by said actuator,- and a pilot valve operable independently of said actuator to eflect reversal oisaid direction valve;

and for directing fluid discharging from said motor to said exhaust line selectively through said first named passage or through said less restricted passage about said restriction respectively for feed and rapid traverse "operation, and pressure 1 responsive means selectively connectible by said valve means to said exhaust line ahead of said restriction for automatically adjusting said memher to adjust the displacement of said pump tov obtain respectively maximum displacement dur'- ing rapid traverse, and substantially constant, reduced displacement during feed operation.

, 20. A hydraulic transmission for a reversibly movable machine tool element comprising, in

combination, ahydraulic motor for translating said element, supply lines opening to opposite sides of said motor, a pump having a delivery line, an exhaust line,'a rotary control valve adjustable into opposite limit positions to connect said supply lines reversibly to said delivery and exhaust lines, a plunger reciprocable transversely of said valve and operatively geared to said valve, means for automatically adjusting said valve in timed relation to the movement of said element, a hydraulicv actuator having a control line and a piston movable in response to the supply of pressure fluid through said control line out of idle position into end engagement with said plunger to move said plunger from the adjacent end position into an intermediate position, load and fire mechanism operable upon movement of said plunger into said intermediate position to continue movement thereof into the opposite end position, and means automatically operable upon a predetermined rise in pressure, in said delivery line to supply fluid under pressure at agraduated rate to said control line.

21. A hydraulic transmission for a reversibly movable machine tool element comprising, in combination, a hydraulic motor for translating said element, supply-linesopening to opposite sides of said motor, a pump having a delivery line, an exhaust line, a rotary control valve adjustable into opposite limit positions to connect said supply lines reversibly to said delivery-and i 18. A hydraulic power unit comprising, in com- 3 ling the pump displacement, spring means in said pump acting on said member in a direction to.

exhaust lines,'a plunger reciprocable transversely of said valve-and operatively geared to said valve, means for automatically adjusting said valve in timed relation to the movement or said element, a

hydraulic actuatorhaving a control line and a piston movable in response to the supply oi. pressure fluid through said control line out of idle 21 position into end engagement with said plunger to shift'the latter, and means automatically operable upon a predetermined rise in pressure in said delivery line to supply fluid under pressure at a graduated rate to said control line,

22. A hydraulic power unit comprising, in com- 7 exhaust line, and control valve means having different selective conditions of adjustment, in one of which said pump is connected to opposite sides of said motor and said second hydraulic means is connected to said exhaust line, in another of which said pump is connected to one side 01' reduced pressure area of said motor and the other side of said motor and said second hydraulic means are connected to said exhaust line, in another of which said pump is connected to said other side of said motor and said oneside of said motor and said second hydraulic means are connected to said exhaust line in advance of said fiow restriction, and in another of which said one side of said motor is blocked and said other side of said motor is connected to said exhaust line and said pump-is connected to said second hydraulic means. MAX A. MAT-HYS.

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

UNITED STATES PATENTS Number Name Date 1,521,884 Higgins Jan. 6, 1925 2,129,828 Dunn Sept. 13, 1938 1,974,137 I Ferris Sept. 18, 1934 2,005,018 West et a1 June 18, 1935 2,160,217 Kingsbury May 30, 1939 1,996,466 Ernst Apr. 2, 1935 2,001,059 Ferris May 14, 1935 2,238,061 Kendrick Apr. 15, 1941 2,130,393 Johnson Sept. 20, 1938 1,838,028 Ernst et al. Dec. 22, 1931 1,893,076, Flygare Jan. 3, 1933 1,943,061 Douglas Jan. 9, 1934- 1,952,690 Strom Mar. 27, 1934 1,969,063 Ernst etal. Aug. 7, 1934 1,978,346 Ernst et al. -11 Oct. 23, 1934 2,000,553 Alden May 7, 1935 2,071,677 Wood Feb. 23, 1937 2,269,697 Silven Jan. 13, 1942 2,030,888 Morgan Feb. 18, 1936 2,063,414 Tweddell Dec, 8, 1936 2,110,393 Edwards Mar. 8, 1938 2,056,896

Douglas Oct. 6, 1938

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