US2267177A - Power transmission - Google Patents

Description

' Patented Dec. 23, 1941 POWER TRANSMISSION L. Raymond 'lwyman, Detroit, Mich, mm: to

Vickers Incorporated. Detroit, Mich, a comration of Michigan Application October 7, 1937, Serial No. 167,780

, 10 Claims.

This invention relates to power transmissions and more particularly to those of the type comprising one or more fluid pressure energy translating devices, one of which may function as a pump and another as a fluid motor. The invention is particularly concerned with a power transmission of this character which is particularly adapted to drive an alternately reciprocable load device, for example the table of a grinding machine.

It is an object of the present invention to provide a power transmission system wherein is incorporated a control panel connected between a pump and motor for controlling the operation of the motor in a manner to provide alternate reciprocating motion of the motor in continuously repeating cycles with independently adjustable dwells at the end of each reciprocation and with adjustable speed of motion. I

In the art of machine tools it is. frequently desirable to operate a reciprocating member with a continuous to and fro motion. It is also necessary that the length of stroke, the speed of motion, and the time of dwell at the end of each stroke be adjustable through reasonably wide limits in order to provide for flexibility in adapting the machine to various operations on work pieces of different characters. In a tool such as a grinding machine, it is importantthat when once adjusted for a certain length of stroke that subsequent changes in speed of operation do not alter the stroke of the feed table since it is frequently desirable to grind at one feed rate for rough grinding and at a different feed rate for finish grinding. Were the stroke changed when the feed rate is changed, it is obvious that the surface covered by the grinding wheel during finish grinding would not be coextensive with that covered by the wheel during rough grinding. It is also essential that, after the dwell at the end of each stroke, the table be accelerated smoothly and also that a smooth deceleration .be accomplished prior to the dwell.

It is accordingly an object of the present invention to provide a power transmission system incorporating a control mechanism whereby the.

above results are provided.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred form of the present invention is clearly shown.

Referring now to the drawing wherein is illustrated diagrammatically a power transmission system incorporating a, preferred form of the 30 binations for various purposes.

present invention, l indicates a tank containing a suitable power transmission fluid such as l0 l6 and is adapted to discharge oil to the tank 10 through a by-pass conduit 20 both whenever a predetermined safe pressure is exceeded in the conduit l8 and whenever the chamber 22 thereof is vented by connecting conduit 24 to the tank.

The valve 18 may be of any suitable construction and the one shown is of the type illustrated in the patent to Harry F. Vickers 2,043,453.v ,Conduit l6 and a return conduit 26 are connected to a control panel or. block 28 at ports 30 and 32,

respectively.

The control panel 28 is illustrated as havin three sections 34, 36, and 38 which, for convenience in illustration, are shown in a single plane although it will be understood that in actual construction the parts may be more compactly arranged. Preferably, but not necessarily,

the sections 84, 36; and 38 may be constructed as' separate assemblies constituting standard units which may be joined together in different com- The section 34 includes pilot and servo-operated reverse and blocking valves for starting,-stopplng, and reversing the table. The section 38 contains manual and table-operated valves for starting and stopping cyclic operation of the table while the section 38 contains feed controlling valves for regulating the speed of operation of the table.

A pair of ports 40. and 42 connect by pipes 44 and 46 to the left and right-hand ends respectively of a table operating fluid motor 48. The

latter comprises a cylinder 50 containing a piston 52 having its rod 54 connected to the grinder table 56. The table 58 carries a flipper dog 58 S and fixed dogs 80 and 62. The dogs may be iongitudinally adjustable along the table as is well known in the art. The dogs 58 and 60 cooperate with trip arms 83 and 64 which constitute the operating means for a valve spool 66 located in a bore 68 in the block 34. Flipper dog 58 is adapted to operate the trip arm 63 clockwise when the table moves to the right and may be ,swung out toward the observer to pass the trip arm 63 at A certain times. The fixed dog is adapted to actuate trip arm 84 counterclockwise when the table moves to the left. The dog 58 and arm 63 may be located in a different plane from that of the dog 80 and arm 84. Fixed dog 82 is adaptedto depress a plunger 10 when the table moves to the right after flipper dog 58 has passed the trip arm 83.

The valve spool 88 is provided on its right-hand end with two grooves 12 and 14 which, together with ports 15, 18, 18, 80 and 82 in the bore 88, constitute a pilot reverse valve for transposing connections between a pressure conduit 84 and a tank conduit 88 on the one hand and a pair of conduits 88 and 80 on the other hand. The spool 88 at its left-hand end is provided with a groove 92 which, together with ports 84, 98, and 88 formed in the bore 88, constitute a three-way blocking valve for selectively blocking either a conduit I or a conduit I02 while connecting the other to the tank I0 through a conduit I04. Conduits I08 and I08 connect the opposite ends of bore 88 with the tank for preventing trapping of oil as the spool 88 is operated in eitherdirection. Spool 88 is preferably provided with tapered portions H0 and I I2 adjacent the groove 92 for the purpose of providing gradual closure of the ports 94 and 88.

Mounted in-a bore H4 in the block 34 is a servo-operated valve spool II8 which controls reversal of fluid flow between the pump I8 and the motor 48. The valve spool H8 is adapted to be shifted to the right andleft by fluid pressure exerted on its opposite ends. This fluid pressure is controlled by the pilot valve at the right-hand end of valve spool 88 and also by certain ports on the spool II8 itself. Conduits 88 and 90 connect with the left and right-hand ends of the bore II4 through check valves H8 and I20 respectively. In parallel with the check valves are a pair of adjustable needle valves I22 and I24 which connect with the bore I I4 at ports I28 and I28 respectively. The conduits 88 and 90 also communicate directly with ports I30 and I32 formed in the bore H4. The spool H8 is provided with a pair of grooves I34 and I38 which are open to the ends of the spool through internal passages I38 and I 40.

The spool H8 is provided to the left of its mid-portion with a groove I42 having tapered end portions which is adapted to selectively connect a port I44 either with a port I48 or a port I48. The latter two ports connect with the conduits I00 and I 02 respectively. To the right of its mid-portion, the spool H8 is provided with two grooves I50 and I52 which, together with ports I54, I58, I58, I80, and I82, constitute a four-way reversing valve for selectively reversing connections between the ports 40 and 42 on the one hand, and port 30 and a passage I84 leading into the block 38 on the other hand.

The passage I84 communicates with a hydrostatic flow controlling valve generally designated as I88 which, together with a manually adjustable restrictor I88, maintains a constant but adjustable rate of flow from passage I84 to port I44 through a passage I10. The valve I88 comprises a chamber I12 in communication with passage I84 and a chamber I14 in communication through a passage I18 with the restrictor I88. A valve member I18 is adapted to control flow from chamber I12 to I14. control of a piston I80, the lower side of which is subjected to the pressure in chamber I14 through a conduit I82 while the upper side is subjected to tank pressure through a conduit I84. A light spring I88 urges the valve I18 down wardly.

The valve I18 is under the' Within the block 38 there is provided a manually operable rotary pilot valve I88 which, in the position shown, connects a port I90 with a port I92. When moved clockwise the valve is adapted to block the port I90 and when moved counterclockwise is adapted to connect port I90 with a port I94. Port I90 is connected to conduit 24. Port I84 connects to the tank through a conduit I98 which also connects by a branch I98 with the tank conduits I08 and 88 in the block'34; The port I92 connects by a conduit 200 with a valve 202 formed on the stem 10. The valve 202 is adapted when the stem 10 is depressed to connect conduit 200 with the tank line I98 through a conduit 204.

,Theposition of the parts illustrated in the drawing represents the conditions just after the table has completed a stroke to the left and the connections have been reversed to start a stroke to the right. The fluid flow and the applied pressure in the various circuits is as indicated by the arrows on the drawing, solid line arrows indicating flow or applied pressure in circuits where the flow or applied pressure is always in the same direction while the dotted arrows indicate flow or applied pressure in circuits where such flow or applied pressure is either reversed in direction or shifted to a branch conduit during the opposite movement of the table.

In operation the pump I2 is started causing fluid to be withdrawn through suction conduit I4 and delivered to delivery pipe I8. With the relief valve I8 closed as shown, pressure builds up in the conduit I8 and is transmitted to the motor 48. In the position of the parts illustrated in the drawing the table 88 is traveling to the right, the valve spool 88 having been shifted and I54, conduit I84, chamber I12, valve I18,

chamber I14, conduit I18, restrictor I88, conduit I10, ports I44 and I48, conduit I02, ports 98 and 98, conduit I04, 'port 32 and pipe 28 to the tank During this movement of the table the hydrostatic valve I88 acts to maintain a fixed pressure in the chamber I14 so that the rate of flow through the restrictor I 88 is maintained substantially constant. Since the pressure in pipe I10 is tank pressure which; is ordinarily atmospheric and since the pressure in the conduit I18 is constant, the quantity of fluid which can pass the restrictor I 88 in a given interval must also be constant. Should the pressure in chamber I12 tend to rise due to relieving of the load on the table 58, this pressure is transmitted through conduit I82 to the lower side of piston I tending to raise the same against the spring I88 and thus tending to close the valve I18. Likewise, should the pressure tend to fall, opposite action is produced tending to open the valve I18. The valve I18 thus comes to a stabilized condition wherein there is a small pressure drop therethrough which is 'varied automatically to compensate for differences in load at the table 58.

As the table 58 continues to move to the right,

the flipper dog 58 contacts trip arm 83 shifting hand end of cylinder 58 to the tank and causing the table 56 to stop with a predetermined deceleration. At the same time the pilot valve at the right end of 'spool 66 reverses connections so that conduit 84 is connected to conduit 88 while conduit 86 is connected to conduit 98. Pressure fluid is thus caused to flow from the port 38 through conduit 84, ports 18 and 88, conduit 88, and check valve II8 to the left end of the bore II4. Fluid expelled from the right end of the bore II4 passes through port I28, needle valve I24, conduit 98, ports 18 and'15, conduits 86, I98 and I96 to the tank. The spool II6 accordingly moves to the right at a speed determined by the setting of the needle valve I24.

In practice it has been found most satisfactory to arrange the port spacings on the valve 68 as shown in the drawing. These are so arranged that as the tapered portion I I2 just completes its closing of the port 98 in its leftward movement, the recess 14 is just cracked open to the port 18. The most satisfactory opening at this point is of the order of a few thousandths of an inch when the right-hand edge of the tapered portion H2 is in line-to-line relation with the lefthand edge of the port 98. With this arrangement the table continues to move to the right carrying the spool 66 to the left after the latter has been shifted to the aforementioned position. This continued travel arises from several causes, one of them being the momentum of the table and associated parts and another being the slight compressibility of the oil and expansion of conduits which takes place when the return line 48 from the cylinder 48 is blocked, thus causing pressure to build up therein. Still a third factor contributing to the continued movement of the table after the port 98 isclosed is the unavoidable leakage around the periphery of the spool 66 from the port 98 axially toward the port 96. This leakage, of course, decreases rapidly as the spool continues its leftward movement. In addition, as the recess 14 approaches the edge of the port 18, the leakage from port 18 to port 88 increases rapidly, thus starting movement of the valve spool II6 before recess 14 actually opens to the port 18. These factors together are best compensated for and a smooth stop with the spool 86 completely shifted to its left-hand position is best insured by the arrangement of ports illustrated.

The spacing of the ports in the bore I I4 and the grooves I42, I58 and I52 on the spool II8 are .such thatthe first movement of the spool 6 to the right does not alter any of the connections. As soon as spool H6 is moved to the right sumciently for groove I36 to open to port I32, fluid from the right-hand end of bore I I4 is permitted to exhaust rapidly through conduit. I48, groove I36, port I32, conduit 98, and the same other connections as before to the tank I8. Spool II6 accordingly moves rapidly to the right to the end of its stroke. is caused to move to the left. Pressure fluid from port 38 passes through ports I58 and I56, port 42 and pipe 46 to the right hand end of cylinder 58. Fluid exhausted from cylinder 58 returns through pipe 44, port 48, ports I68 and I62, passage I64, valve I66, conduit I16, restrictor I68, conduit I18, ports I44 and I46, conduit I88, ports 94 and 96, conduit I84, port 32, and pipe 26 to the tank. During the interval while spool I I6 is moving slowly under control of the needle valve I24, the table remains stationary causing a dwell in its cycle of operation.

Under these conditions the table 56 It will be noted-that while the return-.of fluid to port 32 was blocked. at port 98 that there was no flow through the restrictor I88. Accordingly pressure tends to build up in chamber I14 thus completely closing valve I18. As the spool II6 completes itsrapid movement and flowis again resumed through the restrictor I68, acceleration will be dependent upon the speed of opening of the valve 118. Thus with a slight restriction in the passage I82, a small but appreciable interval may elapse before valve I18 moves downwardly to its normal position of stability. It is thus insured that the table starts in motion grad ually as distinguished from what has beenthe case with previous hydrostatic flow controlling;

valves which act to maintain a constant pressure drop across therestrictor, and which, when the flow is blocked through the restrictor, to move to fully open position.

As the table continues its left-ward movement, flxed dog 68 contacts trip arm 64, shifting spool '66 to the right and again blocking the flow of fluid returning from the motor 48. Blocking in this case occurs as the tapered portion II8 blocks port 94. The pilot connections to the ends of bore II4 are also reversed at this time and spool H6 is caused to travel slowly at first to the left and then to rapidly continue to the end of its stroke as previously described. The length of dwell at this end of the stroke is thus determined by the adjustment of the needle valve I22. After the spool I I6 has completed its stroke, connections are made as shown in the drawing and as described heretofore for causing the'table to move to the right again. This cycle of operation, including a left-ward feed, a dwell, a right-ward feed, and a dwell, is continued as long as may be desired.

When it is desired to stop the continuous cyclic motion of the table, the flipper dog 58 may be manually lifted up to pass the trip arm 63 as the table moves to the right and thereafter when dog 62 depresses plunger 18, relief valve I8 will be vented through conduit 24, ports I98 and I92, conduit 288, valve 282, conduits 284, I98 and I96, to the tank. The table will thereupon. remain stationary due to the opening of relief valve I8 and the by-passing of fluid from the delivery conduit I8 through by-pass 28.

When it is again desired to start the table, the tripper arms 63 and 64 may be turned clockwise by a suitable handle, not illustrated, and thereafter when pilot valve I88 is manually turned clockwise to block of! port I98, the relief valve I8 will again close, causing pressure to build up in the delivery conduit I6 and starting movement of the table to the left. When fixed dog 68 again contacts tripper arm 64, the table is caused to dwell and reverse and the cyclic operation continues as previously described.

If at any time during normal cyclic operation it is desired to stop the table instantly, the pilot valve I88 may be operated counterclockwise to connect ports I98 and I94 and thus vent relief valve I8 without waiting'for table 58 to move completely to the right into stopping position.

The panel block 36 has been shown and described as a convenient starting and stopping control device particularly adapted for grinder table operation although it will be understood that the same could be omitted together with dog 62 and other simpler means provided for controlling venting of the relief valve I8. It will also be apparent that the panel block 38 may be used with other forms of main control block either of the alternately reversing type or 01' the intermittent unidirectional flow type. a

It may also be noted that the main power circuit between the pump I2 and the motor 40 is particularly advantageous for obtaining positive control 01' the reversal action at the end of each motor stroke. It will be seen that the valve portions I50 and I02 act as a conventional'tour-way reverse valve for selectively transposing the motor conduits with respect to the supply conduit 30 and the return conduit I64. The return path after passing through the flow regulating means I" and I60 is divided at the valve portion I42 to flow alternately either through conduit I or I02. 'The return flow is again directed to a single path at the valve portion 92 where it returns to tank through the connections I04, 32 and 26. Thus the valve portions I42 and 92 act as three-way valves connected in series with one another, the former being actuated concurrently with the reverse valve ISO-I52 and the latter concurrently with the pilot valve 12-14. This arrangement insures a positive stopping of the motor at the end of each stroke by the blocking of the return path at port 94 or port 98.

Movement of the motor can then only be resumed after the reverse valve has shifted carrying with it the valve portion I 42 to thereby again open the return path.

While the form of embodiment oi the invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. In a hydraulic power transmission system the combination of a pump, a fluid motor operable in opposite directions, fluid supply and return connections between the pump and motor, a valve operated by the motor for blocking one of said connections after a predetermined movement of the motor, a pilot valve shiftable in opposite directions after a predetermined movement of the motor, a control valve in said connections for reversing the flow of fluid to the motor and controlled by the pilot valve, and means for reestablishing flow through said connections in the opposite direction when the control valve is 2. In a hydraulic power transmission system the combination of a pump, a fluid motor operable in opposite directions, fluid supply and return connections between the pump and motor, a three-way valve operated by the motor for blocking one of said connections after a predetermined movement of the motor, a pilot valve shiftable in opposite directions by the motor, a control valve in said connections for reversing the flow of fluid to the motor and controlled by the pilot valve, and means in a three-way series circuit with said three-way valve for reestablishing flow through said connections in the opposite direction when the control valve is shifted.

3. In a hydraulic power transmission system the combination of a pump, a fluid motor operable in opposite directions, fluid supply and return connections between the pump and motor, a three-way valve operated by the motor for blocking one of said connections after a predetermined movement of the motor, a pilot valve shiftable in opposite directions by the motor, a control valve in said connections for reversing the flow of fluid to the motor and controlled by the pilot valve, and means in a three-way series cir- -cuit with said three-way valve for reestablishing flow through said connections in the opposite direction when the control valve is shifted. said three-way valve being mechanically connected with the pilot valve.

4. In a hydraulic power transmission system the combination of a pump, a reversible fluid motor operable by fluid supplied by the pump, and a control system for causing the motor to operate in alternately reversing strokes, said control system including a valve for reversing the flow of fluid to the motor, a pilot valve actuated by the motor at the end of a stroke for initiating operation of said reversing valve, means for delaying operation of said reversing valve to eiIect flow reversal until a predetermined interval after operation of the pilot valve, and a third valve also operated by the motor at the end of a stroke for stopping operation of the motor until the refluid flow to the motor.

5. In a hydraulic power transmission system the combination of a pump, a reversible fluid motor operable by fluid supplied by the pump, and a control system for causing the motor to operate in alternately reversing cycles, said control system including means for reversing the flow of fluid to the motor, a pilot valve actuated by the motor at the end of a cycle for initiating operation of said means, manually operable means for at times preventing normal actuation of the pilot valve to prevent reversal of flow to the motor and thereby continue motor operation in one direction, means operated by the motor for stopping the motor after a predetermined travel thereof in said one direction, means for manually shifting the pilot valve, and a manually operable start-stop control member and means operated thereby upon movement to one position to start the motor from its stopped condition and, upon movement to another position, to stop the motor independently of the momentary position 01 the motor.

6. In a hydraulic power transmission system a pump and a fluid motor operable by fluid supplied thereto by the pump, and control means for stopping and smoothly accelerating the motor including an adjustable restrictor for controlling the speed of the motor, a valve-on the outlet side of the restrictor for blocking flow of fluid to stop the motor, and an automatic valve on the inlet side of the restrictor for maintaining a fixed pressure ahead of the restrictor during flow therethrough, said valve having opposed piston areas exposed to the pressure ahead of the restrictor and to a fixed low pressure whereby the valve will close when flow through the restrictor is stopped and in opening on restoration of flow through the restrictor will serve to control the acceleration of the motor.

7. In a hydraulic power transmission system a pump and a fluid motor operable by fluid supplied thereto by the pump, and control means.

- said restrictor for additionally blocking the path of fluid through said restrictor, and means retarding the opening of said pressure responsive valve.

8. In a hydraulic power transmission system a pump and a fluid motor operable by fluid supplied thereto by the pump, and control means.

for stopping and smoothly accelerating the motor including a blocking valve for stopping the motor, and a flow controlling valve in series with the blocking valve for regulating the speed of travel of the motor, said flow controlling valve being responsive to pressure changes to close when the blocking valve is closed whereby on starting of the motor the opening movement of the flow controlling valve will serve to control the acceleration of the motor.

9. In a hydraulic power transmission system the combination of a pump, a fluid motor operable in opposite directions, fluid supply and retum connections between the pump and motor, a

three-way valve operated by the motor for blocking one of said connections after a predetermined movement of the motor, a pilot valve shiftable in opposite directions by the motor, a control valve in said connections for reversing the flow of fluid to the motor'and controlled by the pilot valve, and means including a three-way valve mechanically connected with the control valve and connected in a three-way series circuit with the first three-way valve for reestablishing flow through said connections in the opposite direction when the control valve is shifted.

10. In a hydraulic-power transmission system the combination of a pump, a fluid motor operable in opposite directions, fluid supply and return connections between the pump and motor, a valve operated by the motor for blocking the return connection after a predetermined movement of the motor, a pilot valve shiftable in opposite directions after a predetermined movement of the motor, a control valve in said connections for reversing the flow of fluid to the motor and controlled by the pilot valve, and means for reestablishing flow through said connections in the opposite direction when the control valve is shifted.

L. RAYMOND TWYMAN.

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