US2283516A - Hydraulic transmission - Google Patents

Description

R. TYLER HYDRAULIC TRANSMISS ION May 19, 1942.

Filed May 24, 1940 INVENTOR.

HAN-SUM TYLER BY I W Patented May 19, 1942 2,283,516 nrpnaouc TRANSMISSION Ransom Tyler, Greenfield, Win, assignor to The Oilgear Company, Milwaukee, Wis., a corporation of Wisconsin Application May 24, 1940, Serial No. 336,909

6 Claims.

This invention relates to hydraulic transmissions of the type employed to transmit power intermittently. The transmission to which the invention relates in particular includes a hydraulic motor, an accumulator for supplying liquid to the motor at a rapid rate to cause the motor to operate at high speed and a pump for charging the accumulator.

An object of the invention is to provide a transmission of this character with means for bypassing both the pump and the motor when the accumulator is nearly discharged. I

Another object is to provide a transmission having a reciprocating motor and means for bypassing the motor when it has completed its stroke.

Another object is to provide a transmission with an accumulator having incorporated therein valve means for bypassing the motor when the accumulator is nearly discharged.

Another object is to provide a transmission with an accumulator having incorporated therein valve means for permitting liquid to escape therefrom when the accumulator is fully charged and for bypassing the motor when the accumulator is nearly discharged.

Other objects and advantages will appear from the following description of the transmission shown schematically in the accompanying drawing in which the views are as follows:

Fig. 1 is a diagram of the hydraulic circuit of a transmission in which the invention is embodied, the parts being shown in the positions occupied when the motor is idle and the accumulatonfully charged.

Fig. 2 is a view showing the accumulator fully discharged.

Fig. 3 is a view showing the control valve in a position differentfrom that shown in Fig. 1.

For the purpose of illustration, the invention has been shown embodies in a transmission having a reciprocating motor of the spring return type but it is to be understood that the invention may be as readily embodied in a transmission having a difierent type of motor, such as a rotary motor which is to operate intermittently or a reciprocating motor which is operated in both directions by liquid.

As shown, the transmission includes a hydraulic motor I consisting of a stationary cylinder 2, a piston 3 fitted in cylinder 2 and provided with a rod 4 which extends through one -end only of cylinder 2, and a spring 5 for retracting piston 3.

Liquid for operating motor I is supplied thereto by a constant delivery pump 6 and an accumulator I under the control of a valve 6 having two heads or pistons 9 and I0 formed thereon and closely fitted in the bore of a stationary valve casing ll, valve 6 being constantly urged downward in respect to the drawing by a spring l2 arranged between piston l0 and the end of casing Pump 6 draws liquid from a reservoir l5 and discharges it into a supply channel, I6 which has a check valve I'I arranged therein to protect pump 6 from high pressures resulting from the sudden stalling or motor I.

Supply channel I6 is connected to control valve casing II at a point between pistons 9 and I0, the upper end of motor cylinder 2 is connected by a channel l8 to valve casing II at a point above piston l0, and both ends of valve casing II are connected to a drain channel I9 which discharges into reservoir l5.

Accumulator I includes a stationary cylinder 20 having a bore 2| formed therein, a plunger 22 fitted in bore 2| and a spring 23 which constantly urges plunger 22 upward and is arranged in a stationary spring chamber 24.

Cylinder 20 is connected at its upper end to supply channel l6 and has two annular grooves or ports 25 and 26 formed in the wall of bore 2|. Port 25 has a branch of drain channel I9 connected thereto, port 26 is connected by a channel 21 to channel l8 intermediate the ends thereof, and communication between ports 25 and 26 is controlled by plunger 22 which has a reduced portion 28 formed in the lower part thereof so that ports 25 and 26 communicate with each other when plunger 22 is in its upper position as shown in Fig. 2.

Operation If the parts are in the positions shown in Fig. 1 and pump 6 is started, pump 6 will draw liquid from reservoir l5 and dischargeit into channel l6. Since communication between channels IS and I8 is blocked by valve 8, pump pressure will rise until it reaches a predetermined maximum as determined by the resistance of accumulator spring 23 and then the liquid discharged by ",spring 23 will move plunger 22 upward at a very high speed and cause it to expel liquid from bore 2| into channel I6. This liquid, together with the liquid discharged by pump 6 during upward movement of plunger 22, will flow at a very rapid rate through channel I6, valve casing II and channel I8 to the upper end of motor prepare accumulator l-for the next cycle of operation.

The speed of piston 3 and the force exerted by it during or at the end of its working stroke will depend largely upon pump pressure and the masses to be moved, it being found in actual practice that a small piston operated from an accumulator system is capable of making a complete reciprocation through a distance of nine inches in less than one tenth of a second. The overall speed of motor I will depend upon the speed at which valve 8 can be operated eiliciently and the volumetric capacity of pump 6, one hundred or more strokes per minute being ordinarily required.

Means for operating valve 8 have not been shown for the reason that such means form no part of the present invention. Ordinarily however, valve 8 is operated through suitable linkage by a cam which moves it to the position shown in Fig. 3 and then releases it to permit spring I2 to return it to the position shown in Fig. 1.

If motor I is to perform it work at a point intermediate the ends of theworking stroke of piston 3, such as performing a punching or cutting operation, motor I and accumulator I are ordinarily so proportioned that the volume of liquid expelled from bore. 2| by piston 22 during its upward movement is just sufficient to cause piston 3 to make a stroke of the desired length so that, when piston 3 reaches the end of its working stroke, plunger 22 will have been raised high enough for the reduced portion 28 thereof to connect port 26 to port 25 (Fig. 2) and thereby reduce pump pressure substantially to zero. Spring 5 will then raise piston 3 and cause it to eject liquid from the upper end of motor cylinder 2, through channels I8 and 21, ports 25 and 26 and drain channel I9 into reservoir I5, and the liquid discharged by pump 6 at this time will flow through channel I6, valve casing II, channels I6 and 21 and ports 25 and 26 into drain channel I9. If valve 8 is released so that spring I2 can return it to the position shown in Fig. 1 before or during the return stroke of piston 3, all or a part of the liquid ejected from cylinder 2 by piston 3 will flow through channel I8 and valve casing II into drain channel I9.

If motor I is to perform its work at the end of the working stroke of piston 3, such as performing a riveting operation, the work piece is so arranged as to cause piston 3 to stall before Y plunger 22 rises high enough to open port 26 to v V port 25.. When piston 3 stalls, the liquid discharged by pump 6 willventer bore 2| and move plunger 22 downward to prepare accumulator 'I for,-the next cycle of operation regardless of whether or not valve 8 has been returned to the position shown in Fig. 1. Then when valve 8 .retumed to the position shown in Fig. 1, spring 5 will raise piston 3 as previously explained.

The high speed transmission disclosed herein by said pump with liquid for operating said motor, said accumulator being provided with means effective during operation of said pump and responsive to said accumulator being nearly charged for connecting said channel means to drain.

2. In a hydraulic transmission, the combination of a motor, a pump for supplying liquid to said motor, channel means including a valve for connecting said motor either to said pump or to drain, an accumulator connected to said channel means between said valve and said pump and provided with means for bypassing said pump in response to said accumulator becoming fully charged, and means operable with said accumulator for directing the discharge from said pump and said accumulator to drain in response to said accumulator becoming nearly discharged.

3. In a hydraulic transmission, the combination of a motor, a pump for supplying liquid to said motor, channel means including a valve for connecting said motor either to said pump or to drain, an accumulator cylinder having the pressure end thereof connected to said channel means between said pump and said valve and having a port formed therein intermediate the ends thereof and connected to drain and a second port spaced from said first port and connected to said channel means, spring means arranged at the other end of said accumulator cylinder, and a plunger fitted in said accumulator cylinder in engagement with said spring means so that liquid delivered to said accumulator cylinder by said pump will move said plunger against the resistance of said spring means until the end of said plunger uncovers said first port and permits said pump to discharge therethrough to drain, said plunger having a reduced portion so positioned that movement of said plunger a predetermined distance toward said pressure end will cause said portion to connect said ports to each other;

4. In a hydraulic transmission, the combination of a stationary cylinder, a piston fitted in said cylinder and constantly urged toward its retracted position, a pump for supplying liquid to said cylinder, channel means including a valve for connecting said cylinder either to said pump or to drain, and an accumulator connected at its pressure end to said channel means between said valve and said pump and adapted to be charged by said pump with liquid for operating said piston, said accumulator being provided with means efiective during operation of said pump and reretracted position, a pump for supplying liquid to said cylinder, channel means including a valve for connecting said cylinder either to saidpump or to drain, an accumulator connected to said channel means between said valve and said pump and provided with means for bypassing said pump in response to said accumulator becoming fully charged, and means operable with said accumulator for directing the discharge from said pump and said accumulator to drain in response to said accumulator becoming nearly discharged.

6. In a hydraulic transmission, the combination of a stationary cylinder, a piston fitted in said cylinder and constantly urged toward its retracted position, a pump for supplying liquid to said cylinder, channel means including a valve for connecting said cylinder either to said pump or to drain, an accumulator cylinder having the pressure end thereof connected to said channel means between said pump and said valve and having a port formed therein intermediate the ends thereof and connected to drain and a second port spaced from said first port and connected to said channel means, spring means arranged at the other end of said accumulator cylinder, and a plunger fitted in said accumulator cylinder in engagement with said spring means so that liquid delivered to said accumulator cylinder by said pump will move said plun er against the resistance of said spring means until the end oi. said plunger uncovers said first port and permits said pump to discharge therethrough to drain, said plunger having a reduced portion so positioned that movement of said plunger a predetermined distance toward said pressure end will cause said portion to connect said ports to each other.

RANSOM TYLER.

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