US2139173A - Control circuit for broaching machines - Google Patents

Description

Dec. 6, 1938. M; ROMAINE ET A; 2?.,`.l.'.9,l73

CONTROL CIRCUIT FORA BROACHING MACHINES Original Filed March l, 1953 3 Sheets-Sheet l Dec. 6, 1938. M RQMAlNE ET AL 2,139,173

CONTROL CIRCUIT FOR BROACHING MACHINES original Filed March 1, '1953 3 sheets-sheet 2 7 ljj 5 im JM, "f5 ya. i061 /Zf ATTORNEY.

De. 6, 1938. M, ROMAINE ET A1. 2,139,173

CONTROL CIRCUIT FOR BROACHING MACHINES Original Filed March l, 1953 3 Sheets-Sheet 3 /I v ATTORNEY.

Patented Dec. 6, 1938 UNITED STATES PATENT OFFICE CONTROL CIRCUIT .FOR BROACHING MACHINES Millard Romaine, Cincinnati, and Erwin Gr'.

Roehm, Norwood, Ohio, assignors to The Cincinnati Milling Machine Company, Cincinnati, Ohio, a corporation of Ohio 14 Claims.

This invention relates to improvements in broaching machines and is a division of our application therefor illed March 1, 1933, Serial Number 659,226 and issued as Patent No. 2,063,756 on December 8, 1936.

One of the principal objects of the present invention is the provision in connection with a breaching machine of the reciprocating type of an, improved hydraulic actuating mechanism for controlling the tooling and non-tooling move- 4ments of the broach.

A further object of the present invention is the provision in conjunction with a machine tool of the character described of an improved 4hydraulic actuating circuit for effecting satisfactory tooling and facilitating rapid retraction of the broach or tool member.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification considered in conjunction with the accompanying drawings, forming a part thereof, and it is to be understood that any modications may be made in the exact structural details there shown and described, within the scope of the appended claims, Without departing from or exceeding the spirit 'of the invention.

In the drawings:

Figure 1 is a diagrammatic View of the complete hydraulic circuit and controls therefor.

Figure 2 is a sectional View illustrating the distributor and reversing valve for controlling the movement of the hydraulic motor device.

Figure 3 is a sectional View taken on the line 3 3 of Figure 2.

Figure 4 is a sectional view through the balancing valve.

f Figure 5 is a sectional view taken on the line 5 5 of,` Figure 4.

Figure 6 is a fragmentary sectional view illustrating the valve controlling mechanism.

Figure 7 is a sectional view as on the line 'l-'I of Figure 6.

Figure 8 is a further sectional view as on the line 8-8 of Figure 6.

Figure 9 is a diagrammatic View similar to Figure '1 of the hydraulic circuit and control therefor showing the system conditioned for rapid traverse of the motor to the left, and

Figure 10 is a similar vieW showing the system conditioned forfeeding movement of the motor in a right hand direction.

In view of the fact that the general structural details of the broaching machine shown for purposes of illustration as actuable by our present improved hydraulic, circuit and described and claimed in detail in our co-pending application above referred to, said general elements have been omitted herefrom with the exception that to facilitate general understanding of the invention there has been illustrated diagrammatically the cylinder A for the piston B having a piston rod C engageable with the reciprocable broach carrier or the like D said cylinder or hydraulic motor device potentially controllable by our improved mechanism as hereinafter described.

The hydraulic` system for effecting and controlling the movement of the piston B'and consequently of the table D connected thereto, is diagrammatically illustrated in Figure 1 and as there shown comprises a sump or tank I for containing the uid, preferably oil, utilized in the system. In View of the large quantities of oil necessary to effect the operation of the parts, there is shown a pair of pumps 2 and 3 respectively having a suction line 4 and 5 for drawing the iiuiyd from the tank and discharging said fluid under pressure into conduits or lines Econnected with each pump.

A pressure control or relief valve 1 is provided for determining the pressure in the line 6 with which line is also connected a suitable gauge 8. The line 6 and its branch line 9 terminate in a valve, indicated generally bythe numeral I0 and constituting a directional control or reversing valve. The valve II) connects the line 6 or its branch line 9 with either of three conduits, Il, l2 and I3, the latter extending directly to the tank or sump I for short circuiting the system and the other two terminating respectively at the right and left hand ends of the cylinder A.

The valve IIJ is shown in Figure 1 as in position to short circuit the system and return the fluid in the lines 6 and 9 to the sump or tank I. As also shown in this ligure, between the there is provided a second valve for permitting, when in the proper position, the rapid escape of the fluid from one side of the piston and indicated generally by the numeral I4. This valve Ill is connected by a line or conduit I5 with the line or conduit I2 extending from the left hand end of the table cylinder. The other side of the Valve i4 is connected by the line or conduit I6 with the conduit I3 terminating in the sump or tank I. The valves Ill and I4 are shown structurally in Figure 2 as enclosed within a single casing I1 having a pair of bores formed therein and disposed one above the other. Within the longer bore is the reversing valve which comprisesl a 40 reversing valve I0 and the piston and cylinder t v valve bushing I8 having formed therethrough sets of radial ports I9, 20, 2|, 22, 23, 24, 25 and 26, each set being connected by a circumferential groove 21 formed on the exterior of the bushing. Extending through the bushing bore is a spool type valve 28 having cannelures 29, 3|] and 3| for connecting certain of the sets of radial ports in different combinations. The chamber containing the bushing |8 is closed at opposite ends by heads 32 and 33 which are substantially identical in construction and in each of which is mounted a guide 34 for a headed sleeve 35 and piston plungers 36 and 36a. rlhe guides 32 and 33 are further provided with chambered plugs 31 through which the head of the sleeve 35 shifts and connected with the outer ends of the plugs are conduits 38 and 38a of a control hydraulic system to be later described and which effects the shifting of thevalve 28.

The releasable blocking valve I4, for relieving the back pressure facilitating rapid exhaust of the hydraulic medium, is mounted in the shorter of the bores in the casing I1 and comprises a bushing 39 similar to the bushing |8 which has formed therethrough sets of radial ports 40, 4|, 42, and 43. In the bore through the bushing is a spool type valve 44 having a cannelure 45 adapted in one position to connect the sets of ports 4| and 42 and in the other position to interrupt the connection thereof. The ends of the chamber containing the bushing 39 are closed in the same manner as the ends of the chamber containing the bushing I8 and said closures each have mounted therein the piston plungers 46 and 41 of different-areas, whereby with equal pressures on the ends thereof, the valve will be shifted by the larger piston plunger 41 for a, purpose that will be later made clear. 'I'he said chamber closures also include the plugs 48 and 49 with which are respectively connected one terminus of conduits 50 and 5I which are a part of the control hydraulic circuit.

The hydraulic control circuit above referred to comprises a pump 52 having a suction line 53 for drawing the hydraulic uid or medium from the tank I and discharging sam'e into the line or conduit 54. The line 54 terminates at a pilot valve indicated in its entirety'in Figure 1 by the numeral 55. The valve 55 is adapted in one position to connect the hydraulic medium with a pair of lines or conduits 56 and 51 which respectively terminate in lines or conduits 58 and 59. The conduit 58 in turn connects with conduits 38a and 5| respectively actuating the piston plungers at the left hand ends of the valves, as seen in Figure 2, While the conduit 59 connects the conduits 38 and 50 extending from the right hand ends of said valves. The valve 55 is also adapted, in different positions thereof, to connect the line 54 independently with either line 56 or 51 and to connect the other with branch conduits or lines`60 and 6I which terminate in a common discharge line 62 that has its terminus in the sump or tank I whereby the reversing or directional control valve and the blocking-power actuated relief valve are shifted to different operative positions.

The pilot valve 55 and mechanism for controlling and operating it is shown structurally in Figures 6, 7 and 8, particularly in Figure 7. As there shown, the valve comprises a casing 63 mounted Within a recess 64 formed in a bracket 65. The valve casing 63 has formed thereinl a bore in which is pressed thevalve bushing 66 having formed therethrough a plurality of sets of radial ports 61, 68, 69, 10 and 1| with which the ends of conduits 68, 51, 54, 56 and 6I respectively connect. Extending through the bushing 66 isa spool type valve 12 having formed thereon cannelures 13, 14 and 15 Which in the several positions of the valve connect the conduits or complete the different circuits above enumerated. The valve 12 has formed integral therewith a stem in which is formed a notch 16 receiving the ball end 11 of a load and fire dog 18. The dog 18 is provided with two shallow notches 19 and 88 intermediate which is a notch 8|. The several notches are connected by contoured or cam shaped wells which co-operate with the nose' 82 of a latch 83 pivoted at 84 Within the recess 84 of the bracket 65. A spring 85 has its one end anchored to the bracket 65 and its other end connected with the latch 83 for yieldingly urging the latch about its pivot to cause engagement between the nose 82 thereof and the load and re dog 18.

The operation of the load and re dog is such that with the valve in the position as shown in Figure '7, the latch 83 engages the shallow notch 19 for holding the valve in its extreme left hand position and a slight movement of the valve to the right will disengage the notch 19 and latch, causing said latch to ride over the peak or apex of the joined walls of the notches 19 and 8| whereupon the valve Will be actuated to its neutral position until the latch is in the deep notch 8| thereof. When the valve is in its extreme right hand position, the latch is engaged with the shallow notch whereupon a slight movement of the dog o1 valve in the opposite direction results in the reverse movement of the parts until the latch again comes to rest in the large or deep notch 8|.

The dog 18 is secured to a shaft 86 which spans the recess 64 and projects beyond the limits of the bracket 65 and is journaled at one end in said bracket and on the other end in a plate 81 secured to the face of the bracket 65. To the rear end of the shaft 86, which extends beyond the journal thereof in the bracket 65, is secured an elongated arm 88 having journaled in each end thereof a roller 89 and 90. The rollers 89 and 90 are adapted to be respectively engaged by cam faces 9| and 92 formed on reversing dogs 93 and 94 adjustable through slots 95 and 96 formed in or secured to the side of the table D.

The operation of these parts is as follows: With the dog 18 in the position shown in Figure 7 and the arm 88 in the position shown in Figure 8, the table D is moving to the right as seen in these figures. 'I'he table carries with it the dog 93 the cam face 9| of which will eventually engage the roller 89 and tend to depress same thereby oscillating the arm 88, shaft 86 and dog 18 in a counterclockwlse direction, unseating the latch 83 from the shallow notch 19 whereupon the camming action or the firing of the latch 83 and d-og 18 by the spring 85 is had, as above described yfor returning the pilot valve to its normal or neutral position. The dog 81 and consequently the valve 12 is initially shifted by manual means,

for which purpose the shaft 86 journaled in thev anism, the lever 91 has three positions, indicated in Figure 1 as rapid return, stop and feed.

CTI

` table.

The parts are shown with the lever 91 in its neutral or stop position at which time, as above described, the pressure from the pump 52 through the line 54 is connectedv by the cannelure 14 of the pilot valve 12 with the conduits or lines 56 and 51. The same pressure will therefore be in the lines 58 and 59 and consequently in'the conduits 5|, 50, 38a and 38. These conduitsdirect the pressure against piston plungers 41, 46, 36a, and 36. Since the piston plungers 36 and 36a are of the same'cross section it will result in the centralization of the reversing valve u28, as shown in Figure 1, while since the piston plunger 41 is of a greater cross section than the piston 46, it will result in the valve 44 being shifted to its extreme right hand position. At this time then the pressure in line 6 from the pumps 2 and 3 will be short circuited through the branch line 9, cannelure 3| of the valve 28 with the return conduit I3 which terminates in the sump or tank I, resulting therefore in no movement of the At the time of shifting of the piston plungers 36, 36a, and 41 the hydraulic medium ahead of these plungers was respectively exhausted through ports I9, 26 and 43 Which respectively connect with branch exhaust lines 98, 99 and |00 each of, which is connected with a conduit or port and in turn emptying into a conduit or port |02 connected with a conduit |03 terminating in the sump or tank I. l

If the lever 91 is now shifted to the right or to the feed position, as shown in Figure 1, the pilot valve would be shifted to the left and thereby connect through the cannelure 14 the lines 54 and 56 and would connect through the cannelure 13 the lines-51 and 60. At this time the conduit 58 and conduits 38a and 5| would be under pressure While the conduit 59 and conduits 38 and 50 would be connected to the exhaust. Since the rapid traverse valve 44 would already be to its right hand limitiof movement no further movement would be imparted thereto, but b y relieving the pressure on the piston plunger 36 the reversing valve 28 would be shifted to its extreme right hand position. This then would uncover the port 23 and cover the port 25 so that the pressure in the line 6 would be coupled or connected through the cannelure 30 with the conduit I2 and act on the left hand face of the piston, thereby moving the table to the right. At this time the exhaust ahead of the piston would be connected through the conduit II to the port 2| and through the cannelure 20 with the port 20 and a conduit |04 connected therewith. The conduit |04 passes through a back pressure balancing valve indicated in its entirety by the numeral |05, which will be explainedin detail later. The table will continue to move in a direction toward the right at va feeding rate of speed until one of the table dogs 92 or 93 engages with its roller on the arm 88 and thereby shifts the Valve to its neutral or stop position, whereupon the table will be brought to a standstill.

The lever 91 is now shifted to the left or to the rapid traverse position for thereby connecting the control pressure line 54 with the line 51 and connecting the line 6| with the line 56. This then reverses'the pressures in conduits 58 and 59 and consequently in the control conduits to the piston plungers. In other words piston plungers 46 and 36 are now under pressure for shifting the rapid traverse Valve 44 to its left hand position and shifting the reversing valve 28 to its left hand position. At this time the charge pipe |30 with the sump or tank I.

Jfull capacity of the pumps 2 and 3 is being discharged into the small end of the cylinder that is, the end through which the large piston rod is disposed. Since the capacity on both sides of the piston is thereby greatly changed, the piston and parts carried thereby will tend to move at a rapid rate. And to insure that the oil or other hydraulic medium can escape fast enough from the large end of the cylinder, use is made not only of the conduit I2 through the conduit I3, but also through the branch conduit I 5 which is at this time connected with the conduit I6 and conduit I3. From this it will be seen that the piston and parts operated thereby are travelling at a rapid rate toward their initial position. IThis movement continues until the other dog 03 or 94 on the table engages the other of the rollers on the arm 88 and again returns the valve to its neutral or stop position.

The back pressure valve |05 is employed for' insuring a continuous even movement of the table and consequently the cutters and to eliminate any possible surging or running ahead thereof. This valve is shown structurally in Figures 4 and 5 and comprises a casing |06 having formed therein a chamber containing the valve bushing this end of the bushing bore is a'plug II8 having threaded therein the screw ||9 forming one l abutment for a spring |20 that abuts on? its other end with the piston plunger I I1. Mounted 1n the bore of the bushing |01 on the other side Of the valve |I4 is a shiftable abutment |2| contacted on one side `by a spring |22, whose characteristic and effective length may be varied by means of a screw |23 with the threads of which the spring I22 meshes. The screw |23 is threaded through a plug which closes this end of the bushing bore.

Referring now to the diagrammatic illustration in Figure 1, it will be noted that the normal discharge line from the reversing valve I0 has extending from it three conduits |25, |26 and |21. Conduit |25 is connected with'the bushing port I I3 and therefore places the pressure on the outer end of the piston plunger II1 equal to the pressure in the line I0. The conduit I26-connects with the port III and has a resistance therein which is relatively low and consists of a coil or pipe I28 having a comparatively small bore therethrough. The conduit, I21 connects with the port IIlII and also has a hydraulic resistance therein which is comparatively high as respects the hydraulic resistance I28 and also comprises a coil I 29 having a bore thereinsmaller than that in the coil |28'. The port IIII is connected by a dis- The ports |08 and II2 are connected by branch conduits |3| and |32 with the discharge conduit |03 and constitute drains for draining the hydraulic medium that may leak past the piston plunger II1 and spring abutment |2I.

The operation of this 'valve is as follows: When the table-is moving in a feeding direction the discharge of uid from the piston and cylinder-is, as above described, into the conduit I 04 from which it passes through conduits |25, |26

and |21. Inasmuch as the chamber at the left hand end of valve |05, containing spring |20 into which the end of piston ||1 projects, and the chamber between the right hand end of valve |44 and the shiftable abutment I2I are closed chambers, under any condition of constant pressure in the general line |04, the pressure effects in these chambers will be equal. Under these conditions, the right hand end of valve I|4 having a greater area than the area of the piston plunger I I1, the pressure will tend tomove valve I I4 to the left, as viewed in Figures 1 and 4. This would normally shut off the discharge port I I to line |30, preventing escape of the back pressure fluid through line |26, resistance |28. Therefore, to supplement the pressure action against piston I I1, use is made of the adjustable compression spring |20, also reacting on plunger II1, with the result that the combined effect of pressure and spring action on plunger ||1 is sufficient in amount to counterbalance the pressure effect through line |21 on the right hand end of valve II4, causing a normal centralized positioning of the valve, as particularly brought out in Figure l, such that the exhaust fluid will have an unrestrained return to reservoir through lines |26-|30. However, in the event there is a sudden surge in piston movement, tending to displace a larger amount of fluid than the normal flow for which the parts are adjusted, resistance |28 will effect an increase of pressure in line |04 which will immediately react through line |25 increasing the pressure effect against piston 1, moving valve |I4 to the right and thus increasing theA resistance to discharge through port III, maintaining the volumetric ilow a constant. The pressure increase thus created will also be effective in line 21, tending to force an additional amount of the hydraulic fluid through line |21, resistance |29 into the space between the shiftable abutment |2| and the right hand end of valve |I4. The fact that abutment |2| is positioned by the adjustable characteristic spring |22 permits this to act as an accumulator when the initial pressure reaction against I I1 moves valve |I4 to the right and permits instantaneous throttling movement, in spite of the fact that an increased pressure is being established through the resistance |29.

Conversely, when the pressure drops in line |04, the accumulator abutment |2I reacting on the substantially trapped quantity of oil will have an immediate effect to move valve I|4 to the left prior to the reverse drainage of a portion of the trapped fluid through. coil |29.

It will thus be seen that an improved pressure controlled rate determining valve structure has been provided which will insure discharge of the exhaust medium at a constant rate irrespective of existing back pressure conditions or attempted volumetric discharge fluctuations.

.From the foregoing description considered in conjunction with the accompanying drawings, the structure, operation and advantages of our improved hydraulic control system as particularly applicable to broaching machines or other machine tools, should be clearly understood and it will be noted that we have provided an improved system particularly adapted for preventing surging of a movable tool during the cutting operation and for facilitating the rapid return thereof for a new cutting stroke.

What is claimed is:

1. An hydraulic circuit for control of the piston and cylinder mechanism of a machine tool including an hydraulic medium for operating the piston and cylinder, a reversing valve in said circuit for selectively directly the pressure medium to opposite ends of the cylinder, an hydraulic control circuit including a pilot valve for controlling the position of the reversing valve, a manually operable direction indication lever coupled with the pilot valve for operating same and simultaneously indicating the direction of movement of the table, aback pressure control valve in the circuit for controlling the back pressure from the piston and cylinder to insure uniform rate of movement of the table during feeding, a valve in the circuit for controlling the discharge of the medium from the other end of the cylinder and connections between the pilot and said valve for actuating the latter as the pilot is shifted to effect reversal of table operation whereby rapid movement of the table when moving in the opposite direction is facilitated.

2. An hydraulic circuit for control of the piston and cylinder mechanism of, a machine tool including an hydraulic medium for operating the piston and cylinder, a reversing valve in said circuit for selectively directing the pressure medium to opposite ends of the cylinder, an hydraulic control circuit including a pilot valve for controlling the position of the reversing valve, a manually operable direction indication lever coupled with the pilot valve for operating same and simultaneously indicating the direction of movement of the table, a back pressure control valve in the circuit for controlling the back pressure from the piston and cylinder to insure uniform rate of movement of the table in one direction, a valve in the circuit for controlling the discharge of the medium from the other end of the cylinder to permit a rapid movement of the table when moving in the opposite direction, and means connecting the said valve with the pilot valve whereby the position of the valve is determined by the adjustment of the pilot valve.

3. An hydraulic motor control system of the character described including a source of hydraulic pressure medium including a transmitting conduit, a pair of motor conduits, a reversing valve intermediate the several conduits for selectively coupling the pressure transmitting conduit with one or the other of the motor conduits, said reversing valve having an intermediate stop position, means for selectively positioning the reversing valve in either of said three posi-l tions, a blocking valve permanently associated with one of the motor conduits, a reservoir connection associated with the blocking valve whereby the motor conduit is connected to reservoir when said valve is moved to unblocking position, and connections between the reversing valve and blocking valve effective to maintain the blocking valve in closed position as respects two positionings of the reversing valve and to shift the valve to unblocking position affording an outlet to reservoir when the reversing valve is moved to its third effecting position.

4. An hydraulic circuit for actuation of a piston and cylinder mechanism including a reversing valve for alternately connecting the circuit with opposite ends of the piston and cylinder mechanism, a pressure by-pass valve in the circuit for relieving the back pressure in one end of the cylinder to permit a rapid movement in one direction, hydraulically actuated pistons for reversely shifting said reversing and pressure bypass valves, the pistons on the pressure by-pass valve being of unequal area whereby the said valve is by application of pressure toboth pistons thereof actuated in one direction, and a separate hydraulic control circuit including a control valve having portions for directing the pressure simultaneously to one or the other of the pistons of the reversing and pressure by-pass valves whereby the said valves are simultaneously shifted in accordance therewith, said control valve having portions for simultaneously connecting the pressure to, both of the pistons of the valves for moving said valves into a position hydraulically to lock the piston and cylinder in a given position.

5. A control mechanism for a reversible hydraulic motor, including a source of hydraulic actuating medium, a pair of conduits oppositely `coupled with the motor for input or withdrawal of actuating medium therefrom, a three-position reversing valve intervening said source and the conduits for selective couplingof either of said conduits with the motor for actuation thereof, a two-position reservoir connection control valve associated with one of said motor conduits, balanced piston members oppositely associated with the reversing valve for actuation thereof, whereby pressure against either of the pistons will effect maximum movement of the valve in one direction or the other, while equal pressuresl will effect centralization of the valve, and unbalanced piston members oppositely associated with the reservoir valve whereby equal pressures will cause a positive closing movement thereof, and a cornmon pilot circuit for the pistons of both valves whereby pressure may be selectively correspondingly directed against the pistons at either or both termini of both of said valves, substantially as and for the purpose described.

6. In an hydraulic mechanism of the character described, the combination with a reversely hydraulic motor including a pair of conduits oppositely connected to the motor and alternatively employable for introduction in or exhaust of actuating hydraulic medium therefrom, of a normally closed reservoir connection for one of said conduits, a reservoir connection control valve therefor, a rate determining valve selectively coupleable with the other of said conduits, a control valve member for simultaneously coupling the hydraulic actuating medium with one of said conduits and coupling the other of said conduits with the rate determining valve, and means for simultaneously shifting the control valvejmember and the reservoir connection control valve.

7. Ilhe combination with a reversible hydraulic motor, of means for controlling the rate and direction of actuation thereof "including a source of hydraulic medium under pressure, conduits oppositely coupled to the motor for conduction of medium to one side or the other thereof for effecting its reverse actuation, a first valve means shiftable into a position to couple the-medium with one or the other of said conduits and into a third position to disconnect the medium from both of said conduits, a back pressure control valve, said rst mentioned valve having a portion eective in one position to couple one of the motor conduits to said back pressure control valve when the other of the motor conduits is coupled yto pressure whereby said back pressure control sitionings of said rst and third valves, said means including a rst set of piston devices operatively related to the first mentioned valve effective to shift the same to an extreme position in one directionor the other when subject to hydraulic pressure, a second set of' limited movement pistons associated with said rst valve and effective when simultaneously subjected to pressure to shift said first valve to an intermediate position, opposed actuating .pistons of unequal areas associated with the' third valve whereby when the piston of greater area is subject to pressure either alone or in conjunction with the .exertion 4of corresponding pressure against the other piston, said third valve will be shifted thereby in a given direction and will be hydraulically shiftable in the opposite direction only in the absence of pressure against the piston of greater area, a rst hydraulic control circuit coupled in parallel with one pair of pistons of the first valve and one of the pistons of the third valve, a second hydraulic control circuit coupled in parallel with the other pistons of the first valve and third valve, and means for selectively directing pressure individually to either or both of said control circuits for effecting variable positonings of said first and third valves, substantially as and for the purpose described.

8. The combination with a reversible hydraulic motor, of means for controlling the rate and direction of actuation thereof including a source of hydraulic medium under pressure, conduits oppositely coupled to the motor for conduction of medium to one side or the other thereof for effecting its reverse actuation, a first valve means shiftable into a position to couple the medium with one or the other of said conduits and into a third position to disconnect the medium from both of said conduits, a back pressure control valve, said first mentioned valve having a portion eifective in one position to couple one of the motor conduits to said back pressure control valve when the other of the motor conduits is coupled to pressure whereby said back pressure control valve will determine the back pressure resistance to actuation of the motor, an auxiliary reservoir connection for the opposite motor conduit, valve means normally blocking the flow through said auxiliary reservoir connection, and hydraulically actuable means for determining the effective positionings of said rst and third valves, said means including a rst set of piston devices operatively related to the first mentioned valve effective to shift the same to an extreme position in one direction or the other when subject to hydraulic pressure, a second set of limited movement pistons associated with said first valve and effective when simultaneously subjected to pressure to shift said first valve to an intermediate position, opposed actuating pistons of unequal areas associated with the third valve whereby when the piston of greater area is subject to pressure either alone or in conjunction with the exertion of corresponding pressure against the other piston, said third valve will be shifted thereby in a given direction and will be hydraulically shiftable in the opposite direction only in the absence of pressure against the piston of .greater area, a rst 'hydraulic control circuit coupled in parallel with one pair of pistons of the first valve and one of the pistons of the third valve, a second hydraulic control circuit 4coupled in parallel with the other pistons of the first valve and third valve, means for selectively dlrecting pressure individually to either or both 0f 75 said control circuits for effecting variable positionings of said first and third valves, trip operable means for determining the effective action of the control circuit coupling means, and trip devices shiftable by the motor for actuation of said trip operable means.

9. In a-mechanism of the character described, the combination with a reversible hydraulic motor and a source of actuating pressure therefor, a pair of conduits coupled with opposite ends of the motor, an intervening control mechanism including a first Valve mechanism having inlets from the source of pressure and outlets to both of said conduits, said valve mechanism including a shiftable part movable to a first position to couple one of said conduits to pressure, to a second position disconnecting pressure from vboth of said conduits, and a third position coupling the pressure to the other of said conduits, said valve being further provided with an exhaust flow conduit, means on the movable member effective in one position thereof for coupling one of said motor conduits to the exhaust conduit, an auxiliary exhaust connection for the other motor conduit including a valve for prevention of flow through saidexhaust conduit, and an hydraulic couple between said valve and the movable member of the'iirst mentioned valve whereby said valves are simultaneously actuable, said valves having portings inversely effective as respects establishment of exhaust connections therethrough for the respective motor conduits.

10. In a hydraulic transmission of the character described, a back pressure line control valve including a pressure actuable throttling device for varying the effective discharge passage through the valve, a direct pressure connection subject to varying conditions in the back pressure line coupled with the valve for reaction in a direction to increase the restriction thereof, an

accumulator associated with the valve for yieldingly resisting said closing action, and means for effecting variable pressures in said accumulator.

1l. In a hydraulic transmission of the character described, a back pressure line control valve including a pressure actuable throttling device for varying the effective discharge passage through the valve, a direct pressure connection subject to varying conditions in the back pressure line coupled with the valve for reaction in al direction to increase the restriction thereof, an accumulator associated with the valve for yieldingly resisting said closing action, means for effecting variable pressures in said accumulator, said means including a hydraulic couple between the back pressure line and the accumulator, and means in the couple for effecting a .time delay in the pressure variations of the accumulator as respects pressure variations in the direct pressure connection.

12. In a hydraulic transmission of the character described, the combination with the motor of a back pressure conduit extending therefrom, means for controlling both constant and surge effects of discharge in the back pressure line comprising a valve body having inlet and discharge ports, a valve therein shiftable variably to restrict the discharge from the back pressure line by way of said ports, a plunger, resilient means for urging the plungerinto engagement with the valve for effecting a restrictive movement thereof, means impoundintg` a back pressure fluid adjacent the plunger whereby the latter has an'hydraulic piston effect supplementing the yielding means in urging the valve into a restricting position, said valve having a piston portion effective in opposition to the plunger and of greater area than said plunger, means providing a chamber enclosing the piston, and means coupling the back pressure to said chamber for reactance on the piston, said means including a resistance creating pressure drop during flow of liquid into the chamber, whereby a temporary differential in the effective pressures on the plunger and piston is created, substantially as and for the purpose described.

13. In a hydraulic transmission of the character described, the combination with the motor of a back pressure conduit extending therefrom, means for controlling both constant and surge effects of discharge in the back pressure line comprising a valve body having inlet and discharge ports, a valve therein shiftable variably to restrict the discharge from the back pressure line by way of said ports, a plunger, resilient means for urging the plunger into engagement with the valve for effecting a restricting movement thereof, means impounding a back pressure fluid adjacent the plunger whereby the latter has an hydraulic piston effect supplementing the yielding means in urging. the valve into a restricting position, said valve having a piston portion effective in opposition to the plunger` and of greater area ythan said plunger, means providing a chamber enclosing the piston, means coupling the back pressure to said chamber for reactance on the piston, said means including a resistance creating pressure drop during flow of liquid into the chamber, whereby a temporary differential in the effective pressures on the plunger and piston is created, said chamber forming means including a shiftable element for varying the effective size of the chamber, and yieldable means urging said member in a direction to reduce the effective area of the chamber substantially as and for the purpose described.

14. In a hydraulic transmission of the character described, the combination with the motor of a back pressure conduit extending therefrom, means for controlling both constant and surge effects of discharge in the back pressure line comprising a valve body having inlet and discharge ports, a valve therein shiftable variably to restrict the discharge from the back pressure line by way of said ports, a plunger, resilient means for urging the plunger into engagement with the valve for effecting a restricting movement thereof, means impounding a back pressure fluid adjacent the plunger whereby the latter has an hydraulic piston effect supplementing the yielding means in urging the valve into a4 restricting position, said valve having a piston portion effective in opposition to the plunger and of greater area than said plunger, means providing a chamber enclosing the piston, means coupling the back pressure to said chamber for reactance on the piston, said means including a resistance creating pressure drop during flow of liquid'into the chamber, whereby a temporary differential in the effective pressures on the plunger and piston is created, said chamber forming means including a shiftable element or varying the effective size of the chamber, yiidable means urging said member in a direc ion to reduce the effective area of the chamber, and means for individually adjusting the yielding pressure devices oppositely effective as respects said passage restricting valve.

LUILARD ROMAINE.

ERWIN G. ROEHM.

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