US2732165A - Fluid pressure operated systems - Google Patents

Description

Jan. 24, 1956 F. M. COLLINGWOOD 2,732,165

FLUID PRESSURE OPERATED SYSTEMS Filed Jan. 9, 1952 MA \A FLUID PRESSURE OPERATED SYSTEMS Frank M. Collingwood, Padgate, Wanington, England,

assignor to Electro-Hydraulics Limited, Warrington, England, a company of Great Britam Application January 9, 1952, Serial No;- 265,667

6 Claims. (Cl. 251- 25) This invention relates to fluid operated systems, and concerns more particularly remote control 'meansfor actuatinga valve which controls the supply-of 'fluid, forexample, from storage tank to use in apparatusremote from the tank. In such fluid pressure operated systems, it is known to control the supply of fluid by means of a servomotor which actuates the control valve or'valves, and this invention concerns this known type of system.

In 'known arrangements of this type, the-fluid on the exhaust side of the servo-motor is normally returned to tank, but where the servo-motor is situatedremotely or at a considerable distance from the tank, such an arrangement introduces unnecessary complications; furthermore,

it is undesirable, in order to' overcome these complications, to exhaust the fluid to atmosphere, b'eca'use, amongst other reasons, the fluid is wasted.

The object of this invention is to provide a fluid pressure operated system of the type'described, but in which the complications and disadvantages referredto above are obviated.

According to the present invention, in a'fluid pressure operated system of thetype described,'there is provided a discharge cylinder, into Which-fluidfromthe exhaust side of the servo-motor is exhausted onthe return stroke of the servo-motor piston, the said discharge cylinder being so arranged as to dispose of the' exhaust fluidby supplying the said exhaust fluid to the-systemon the discharge side of the control valve or valves.

One form of construction of a fluidpressure'operated system according to this invention is-illustrated diagrammatically in section in the accompanying drawing in which there is provided a fluid storage tank 1 from which the fluid may be supplied by any suitable means, for example, by pump, (not shown), the tank 1 communicating with the main supply pipe 2, in which is arranged a main control valve 3, the pipe leading to, for example, a container or other apparatus (not shown), to which the fluid is to be supplied. The control valve 3 is coupled through a lever 4 to the piston rod 5 of a servo-motor piston 6, to the cylinder 7 of which servo-motor the main supply line is branched as at 8 before the main valve, so as to supply fluid to the left-hand side of the piston 6, through a passage 9 in a wall of the cylinder 7. Communication between the branch 8 and a passage 10 leading to the other side of the piston 6 is controlled by a pilot valve 11. The pilot valve 11 includes a valve stem 12 having a valve head on each end, each valve head 13, 14 being adapted to cooperate with a valve seat, the pilot valve 11 being biased by a spring 15 so as to close communication between the main supply line branch 8 and the right hand side of the piston 6, a by-pass 16 being provided between the two valve seats of the pilot valve, which preferably is of the solenoid type. The valve head 13 of the pilot valve 11 controls passage past the valve to a discharge cylinder 17 in which is arranged to slide a piston 18 carried by a plunger 19, the piston being biased by a spring 20 towards the right hand end of the discharge cylinder 17. Such end pressure can now pass through the main supply line 2 through its branch line 8, past the head 14 of the pilot 2,732,165 Patented Jan. 24, 1956 ice of the discharge cylinder is pr'ovided witha discharge aperture'21 communicating with a discharge pipe 22, which leadsin-to the main supply line 2 beyond the outlet end of' the main valve 3, the said discharge pipe 22 including a pressure relief valve 23 and anon-return valve 24.

This system works as follows:

Whenthe main supply valve3 is closed (as shown in the figure) so that-there is 'no delivery of fluid, the pilot valve-11 is biased by its spring 15, so that communication between'the main supply line 2 and the right hand side of the piston 6 is closed. When it is desired to allow fluid to-pass from the main supply pipe-2 past the-main valve 3, the said valve 3 is operated-so as to allow passage of fluid past the valve. To enable' this to be done, the pilot valve -11 is operated electrically so that communication can'be established between themain supply-line 2 and the right hand side of the piston 6. By so operating the pilot valve, communication between said valve 11 and the discharge cylinder '17 is closed by the valve head 13. Fluid under valve to theright hand side of the servo-motor cylinder arid, at the same time, through the passage 9 to the left hand side of the servo-motor, and, due to the difierence in pressure areas acting on the piston 6, the piston is moved with respect to its cylinder (i. e. to the left as shown) and through its lever connection 4 with the piston rod 5 actuate's the main valve 3 to open the main supply line.

Whenit is desired to close the main valve 3, the pilot valve 11 is 'operated so thatcornmunication between the main supply line 2 and the right hand side of the piston is cut ofli, whilst communication past the valve head 13 to the discharge cylinder 17 is-open. Fluid under pressure, therefore, continues to be supplied to the left hand side -of the servo-motor piston through passage 9, which piston is thereby -'caused'to retract into the cylinder, and, there- 'fore, through its lever connection closes the main valve.

Fluid in'the servo-motor cylinder at the right side of the piston passes through the passage 10 past the head 13 of the pilot valve into the discharge cylinder 17, acting on the piston 18 to move it to the left against the actionof its biasing spring 20. When the main valve 3-has closed, the pressure in the main supply pipe 2 behind the main valve 3, i. e. to the left of the valve shown, soon-drops to a value which enables the spring 20 in the discharge cylinder to counteract any fluid pressure acting through the pipe 22 on the piston 18 to move back in the cylinder, thereby expeliing fluid therein through its discharge aperture 21 into the discharge line 22, and thence past the non-return valve 24 into the main supply line to the left of the main valve.

It will be appreciated that the non-return valve 24 in the discharge line 22 assures that the fluid from the main supply line 2 cannot enter the discharge cylinder 17, when the main valve 3 is open, whilst the pressure relief valve 23 assures that no damage can arise if there is any undue rise in pressure in the discharge line 22, due to any unforeseen cause.

Finally, it will be understood that, due to the provision of the discharge cylinder and its associated parts, there is no waste of fluid since when the main valve is closed, any fluid in the servo-motor cylinder is discharged into the discharge cylinder, and therefrom expelled into the discharge line, thence to the main supply line, so that a fluid pressure servo-system of the so-called closed type is provided, i. e. a type in which any loss of fluid is reduced to a minimum.

A construction according to this invention is particularly useful when there is no, or little, pressure drop across the main valve 3.

I claim:

1. A fluid operated system including a pipe line having a main valve therein for controlling the flow of fluid through said pipe from one side of said valve, and remote control means for opening and closing said valve, said remote control means comprising a fluid pressure operated motor separate from said valve and comprising a cylinder having a piston slidable therein, a piston rod connected to one side of said piston and projecting through one end of said cylinder and connected to said valve, said piston rod reducing the effective area of a side of said piston to which it is connected, a fluid line providing constant communi cation between said end of said cylinder and said pipe line at said side of said valve, a second cylinder, a piston therein having means biasing it for movement toward one end thereof, a fluid line connecting said end of said second cylinder to said pipe line at the other side of said valve, 2. check valve in said last-named fluid line opening toward said pipe line, and a valve device for selectively connecting the other end of said motor cylinder to said end of said second cylinder and to said last-named fluid line at said one side of said main valve.

2. A fluid operated system as claimed in claim 1 in which said valve device comprises two connected valve elements having seats respectively and alternately engageable by said valve elements, one valve element controlling communication between. said other end of said motor cylinder and said pipe line at said one side of said main valve and the other valve element controlling communication between said end of said second cylinder and said other end of said motor cylinder.

3. A fluid operated system as claimed in claim 1 wherein said valve device comprises a pair of valve chambers in fixed communication with each other, one valve chamber having a seat and a valve element engageable therewith to control communication between such chamber and said end of said second cylinder, the other valve chamber being in fixed communication with said other end of said motor cylinder and having a seat, and a valve element engageable therewith for controlling communication between said other valve chamber and said pipe line at said one side of said valve, said valve elements being connected to each other and respectively and alternately engageable with said valve seats.

4. A fluid operated system comprising a main valve movable between open and closed positions, an inlet line leading to said valve, an outlet line leading from said valve, a motor separate from said main valve and comprising a cylinder having a piston therein and a piston rod extending therefrom and mechanically connected to said main valve, means responsive to fluid pressure for biasing said piston for movement toward one end of said cylinder to move said main valve to one of its positions, a second cylinder, a piston therein having means biasing it for movement toward one end thereof, a fluid line connecting said end of said second cylinder to said outlet line, a check valve in said fluid line closing away from said outlet line, and means for alternately selectively connecting said end of said motor cylinder to said inlet line, to move said valve to its other position, and to said end of said second cylinder.

5. A fluid operated system as claimed in claim 4 wherein said last-named means comprises a shuttle valve having valve elements connected to each other and alternately engageable with seats to connect said one end of said motor cylinder with said end of said second cylinder and with said inlet line.

6. A fluid operated system comprising a main valve movable between open and closed positions, an inlet line leading to said valve, an outlet line leading from said valve, a motor separate from said main valve and comprising a cylinder having a piston therein and a piston rod extending therefrom and mechanically connected to said main valve, means responsive to fluid pressure for biasing said piston for movement toward one end of said cylinder to move said main valve to one of its positions, means for admitting fluid from said inlet line to said end of said motor cylinder to move said piston against its biasing means to move said main valve to its other position, a second cylinder, a piston therein having means biasing it for movement toward one end thereof, an exhaust line connecting said end of said motor cylinder to said one end of said second cylinder, a manually controllable valve in said exhaust line, a fluid line connecting said one end of said second cylinder to said outlet line, and a check valve in said fluid line opening toward said outlet line.

References Cited in the file of this patent UNITED STATES PATENTS 443,789 Ongley Dec. 30, 1890 668,202 Nethery Feb. 19, 1901 746,337 Junggren Dec. 8, 1903 1,051,768 Rumold Jan. 28, 1913 1,584,407 Thomas May 11, 1926 1,938,958 Goldman Dec. 12, 1933 2,148,268 Kerr Feb. 21, 1939 2,290,479 Mercier July 21, 1942 t. w 'I'"

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