US 2778378 A
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Jan. 22, 1957 F. G. PRESNELL CKING VALVE Filed July 28, 1952 COMBINATION SEQUENCE AND L0 M 7 o M a a 7 I J W 0 7 a 3m u 6 w w M 6 67 w m 0 9 M 0 w z W 7 w [M E.\'TOR. FRANK G. PRESNELL ATTORNEY ii "sited States COMBINATION SEQUENCE AND LOCKING VALVE Frank G. Presnell, Los Angeles, Calif., assignor to Bendix Aviation Corporation, North Hollywood, Calif a corporation of Delaware Application July 28, 1952, Serial No. 301,353
5 Claims. (Cl. 137-469) This invention relates to hydraulic systems for automatically operating two motor cylinders in sequence, and more particularly to the construction of the sequence valve that causes the automatic sequential operation.
An object of the invention is to provide a sequence valve structure that functions both as a pressure responsive sequence valve and a check valve to prevent reverse leak- .age flow during the period when holding pressure is applied.
Still another object of the invention is to provide against leakage in a sequence valve of the type that opens only in response to a predetermined pressure but remains open so long as the pressure is above the predetermined value, wherein said valve is adapted to be used in a system incorporating either single or double action motor cylinders.
Other more specific objects and features of the invention will appear from the description to follow.
It is known to connect two motor cylinders in parallel to a single control valve and to provide a pressure-responsive valve in the circuit leading to one motor so that this motor does not function until the pressure in the line rises to a predetermined value greater than that required to operate the first cylinder. This causes the first cylinder to operate and move through its stroke before the second cylinder begins to move. However when the first cylinder has completed its stroke the pressure immediately rises to a pressure sufficient to open the pressure-controlled valve and permit flow to the second cylinder to operate it. Pressure controlled sequence valves of the type referred to remain open as long as the pressure in the line is maintained above the opening pressure. Theoretically, closure of the control valve holds pressure in the cylinder lines to prevent reverse movement thereof in response to the loads applied thereto. However, many commonly used control valves are not tight and permit slight leakage. As long as the pressure remains above the opening value the sequence valve will remain open and will not prevent such leakage. Leakage through imperfectly sealing control valves can be prevented by insertion of locking valves between the control valve and the cylinder. A locking valve contains check valves which are adapted to seat perfectly and prevent reverse flow except when control pressure is applied to the other end of the cylinder whereupon a small motor piston in the locking valve lifts the check valve to permit the return flow.
The present invention provides a single sequence valve so constructed that it prevents any leakage return flow, thereby eliminating the necessity of providing a separate locking valve in the system. This is done by incorporating 2 a check valve in the sequence valve itself by means of a simple construction that does not materially increase the cost of the sequence valve;
In the drawing:
Fig. 1 is a schematic diagram of a hydraulic system incorporatingone form of sequence and locking valve in accordance with the invention for single action motor cylinders; and
Fig. 2 is a schematic diagram showing an alternative form of sequence and locking valve in accordance with the invention for double action motor cylinders.
Referring to Fig.1, the system therein disclosed comprises a reservoir 10 supplying fluid to a pump 11 which delivers it to a'four way control valve 12. The valve 12 is connected to the reservoir 10 by a return line 13 and also has connected thereto two motor lines 14 and 15 respectively. The motor line 14 is connected directly to a motor cylinder 16 and indirectly through a sequence valve 17 in accordance with the invention and a line 18 to a second motor cylinder 19.
The cylinder 16 has a'piston 16a therein adapted to be connected by a piston rod 16b to a load to be lifted. The motor cylinder 19 likewise has a piston 19a adapted to be connected by a piston rod 1% to a load to be lifted. It is to be understood that a load is constantly applied to each of the piston rods 16b and 1% so that the pistons are moved downwardly by the load whenever fluid pressure is released from the cylinders. The upper ends of the cylinders 16 and 19 may be vented to atmosphere as shown. V
The selector or control valve 12 has a neutral position in which the pressure line from the pump 11 is connected directly to the return line 13, an up position in which the output of the pump is connected to the line 14 and the return line 13 is connected to the line 15, and a down position in which the output of the pump is connected to the line 15 and the line 14- is connected to the return line 13.
The sequence and locking valve 17 comprises a body 22 having a pair of control ports 23 and 24 connected to the lines 14 and 15 respectively, and a motor port 25 connected to the motor line 18. The port 23 connects with a passage 27, one end of which terminates at a valve seat 30 and the other end of which communicates with a chamber 31 containing a piston 32. The other end of the chamber 31 connects to the control port 24.
The body 22 also defines a chamber 34 which is connected to the port 25. This chamber 34 contains a piston element of the same diameter as the seat 30 and consisting of a head 35 and a bellows 36, the head 35 being secured in sealing relation to one end of the bellows 36, the other end of which is connected in sealing relation to the end wall of the chamber 34. The interior of the bellows so can be evacuated although this may not be necessary in all cases. The purpose of the bellows 36 is to isolate the left end of the head 35 from the chamber 34 so that pressure existing in the chamber will urge the head always in a leftward direction.
There is normally seated against the seat 3t) a check valve consisting of a poppet 3'7 having a stem 37:: which is guided for longitudinal movement in the head 35 and is urged toward the seat 34) by a light helical compression spring 38 which is compressed between the poppet 37 and a flange 35a on the head 35. A much heavier helical compression spring as is compressed between the flange 35a and the left end of the chamber 34. The spring 49, acting through the piston element head 35 and the stem 37a of the poppet 37 normally holds the latter firmly against its seat to prevent any flow through the valve between the ports 23 and 25 respectively. However, the spring-4i) is so proportioned as to be overcome y a undetermined. pressure n. e nastase. Z7 acting.
against the poppet 37 so that when the pressure rises above the predetermined value the valve 37 is forced p to pe i flow om the port 23 nt e hamb as. and. thence out hr ug e p 25 o he m o If there is little resistance to movement of; the motor 19, the pressure will not reach a high value in the chamber 34 until the motor hascornpleted its movement, but thereafter the pressure will rise in the chamber 34 to the value existing in the passage 27. This pressure acts against the face of the piston element head 35 to move the latter to the left against the force of the spring 40, but the light spring 38 will still urge the poppet 37 toward the seat 30 to prevent any reverse flow from the motor back to the control valve 12;.
In actual operation, the load applied to the piston of the motor 16 might be such as to require three hundred pounds to elevate the piston 16a, If it is desired that the motor In complete its movement before the motor 1 begins to move, the spring 40, in the sequence valve 17, be so proportioned as to hold the poppet 37 seated until a substantially higher pressure, say 409 pounds, is developed in the passage 27. This permits a liberal margin. The result is that when the control valve 12 is moved into up position the motor 16 is actuated through its full stroke before the pressure rises in the line he and the passage 27 of the valve 17 suhiciently to unseat the poppet 37 against the high force developed thereagainst by the spring 40. 'However, when the motor 16 has completed its movement, the spring 46 is cornpressed to permit the poppet 37 to open and let the line fluid flow through the valve and the line 18 to the second motor 19 which. is thereupon moved through its stroke. When the motor 19 has completed its stroke there is no further fluid flow to either motor and the output of the pump 11 is released back to the reservoir through the usual relief valve 50.
If it is desired to hold both motor pistons in elevated position the operator will then restore the control valve 12 to neutral position, in which the motor lines 14 and 15 are blocked and the pump output is connected to the return line 13. It may be assumed, however, that the control valve 12 is of a type that does not perfectly seal off the motor lines 14 and 15, with the result that therev is some slight leakage from the line 14 back through the valve 12 and the return line 13 to the reservoir.
However, the valve 17 prevents any return leakage from the cylinder 19 into the port and out through the port 23, because the poppet 37 acts as a check valve to prevent such flow even though the pressure in the chamber 34 is sutficient to maintain the spring 4a compressed so that the piston element head 35 does not con tact the left end of the valve stem 37a.
When it is desired to permit return of the motor piston 1% by the force of the load applied thereto, the control valve 112 is moved into down position which applies the output of the pump 11 through the line 15 to the port 24 where it is delivered to the right end of the chamber 31. At the same time, the line 14 is connected through the control valve 12 to the return line 13, so that the pump output pressure is applied to the piston 32 to move it from right to left. This causes a projecting stern 32a on the piston 32 to contact the poppet 37 and open it to permit return flow from the line 18 through the valve to the line 14 and back to the control valve 12. The area of the piston 32 is made sufficiently large relative to the area of the valve seat to enable the piston 32 to overcome any pressure force that may be existing in the chamber 34 and tending to hold the valve 37 in seated position.
Fig. 2 shows the application of the invention to a sequence and locking valve for use with two double acting motor cylinders which are intended to be moved positively in both directions by pressure fluid. This system,
h? 5 33? f. 1 5- 9 P ?l a reservoir 19 a pump ill, a control when, a return line 13 and a pair of motor lines 14 and 15 respectively. The two lines and 15 are directly connected to opposite ends of one motor cylinder 6%, and are also connected to the opposite ends of the second motor cylinder 61 through a valve 62 in accordance with" the invention.
The valve 62- comprise a housing 63 having a pair of control ports 64 and 65 respectively, and a pair of motor ports 66 and a7. respectively, which are connected to opposite ends of the motor cylinder '61.
The control ports 64 and 65: are connected directly to opposite ends, of a chamber 69 containing a piston '70. The motor ports 66 and 67 are connected directly to a pair of chambers '72 and'73vrespectively, which chambers are respectively connected to the left and right ends of the chamber 69 by valve seats '74 and respectively.
A ball check valve 76 is normally held against the seat 7% by a piston element 78 which is positioned in the cnamber 72 and extends through a cylindrical passage communicating the left end of the chamber 72 with the atmosphere. The piston element is preferably provided with some form of sealing ring 82 to prevent any leakage therepast. The. piston element '78 has a face 254 on its right end adapted to seal with an orifice 86 which divides the chamber 72' into a main compartment containing the piston element 78 and a smaller compartment 8 3 in which the ball check valve 76 is located. A light compression spring 9!} is interposed between the piston element 78 and the ball 76 to constantly urge the latter against the seat '74, this spring 99 being largely positioned in a recess 92 provided therefor in the piston element 78.
The right end of the valve 62 is identical with the left end, containing a ball check valve 77, a piston element 79, and a check valve spring 91,
Each of the piston elements 78 and 79 is strongly urged inwardly into seating relation with the orifices 86 and 87 respectively by powerful helical compression springs 94 and 95 respectively.
Let it be assumed that the motor 65) is to be operated prior to operation of the motor 61, and that the maximum pressure required to move the motor- 60 is 300 pounds and that the springs 94 and 95 are proportioned to permit unseating of the piston elements 73 and 79 at a pressure of 400 pounds per square inch. Manipulation of the control valve 12 into up position applies the output of the pump 11 to the line 14 and directly to the lower end of cylinder 60, causing the piston therein to rise. At this time the pressure in the line 14 is applied to the left end of the chamber 69, moving the piston 70 therein to the right and causing it to unseat the check valve 77 and the piston element 79 so that the upper end of the motor 61 is connected to the return line 15. However the motor 61 does not operate atthistime because no pressure fluid is applied to its lower end;
After the motor 64) has completed its stroke, the pressure rises in the line 14 and. in the left end of thecylinder 69 to 400 p. s. i., which, acting against the right end of piston element 78 is suff cient to overcome the spring 94. The check valve 76 therefore opens andthe piston element 78 is moved away from the orifice 36 sufiicient to permit the flow of fluid through theport 66 to the lower end of the motor 61, causing the latter to move through its stroke. When the motor 61 has completed its stroke the pressure rises to a high value in the chamber 72, which pressure acting against the piston element 78, holds it away from the orifice. 84. When the control valve 12 is subsequently restored to neutral position the high pressure is maintained in the chamber 72 and in the lower end of the .motor 61 despite any leakage through the control valve 12, because the ball check valve '76 is strongly seated in response to the pressure and prevents any leakage from the port 66 to the port 64.
camera When the motors are to be reversed the control valve 12 is moved into its opposite end position, that is, the down position, under which condition the pressure fluid is applied to the line 15 and the line 14 is connected to return. The operation in this direction is exactly the same as that described except that now it is the ball check valve 76 and the piston element 78 that are maintained unseated by the piston 70, and the piston element 79 is moved into open position in response to the pressure in the line 15 only after motor 60 has completed its stroke.
It will be observed that the systems of Figs. 1 and 2 respectively utilize two different methods of making the piston element 35 responsive to the pressure in the chamber 34 without introducing a pressure drop between the ports 23 and 25 in Fig. 1 and the ports 64 and 66 in Fig. 2. In Fig. 1 this is done by means of the bellows 36 which keeps pressure ofi the left face of the piston head 35. In Fig. 2 pressure is kept off the left face of the piston element 78 by exposing the left end or face thereof to atmospheric pressure. It is usually desirable to utilize as fully as possible the available pressure to operate the second motor 19 or 61 as the case may be. If-the spring 40 or the spring 94 is overcome by a pressure of 400 pounds and 500 pounds is required to move the motor 19 or 61, then only 500 pounds pressure needs to be delivered by the pump 11 in each case, because there will be no pressure drop in the valve 17 or the valve 62. Whenever the pressure in the chamber 34 in Fig. 1 or the chamber 72 in Fig. 2 exceeds the value necessary to overcome the spring 40 or the spring 94, then the only resistance to flow from the pump through the valve to the motor cylinder is the negligible pressure drop across the check valve produced by the light spring 38 in Fig. 1 or the light spring 90 in Fig. 2. Obviously the bellows 36 of Fig. 1 could be substituted for the cylinder 80 in Fig. 2 and vice versa.
It is usually desirable to make the effective pressure area of the piston element 35 the same as the area of the seat 30 in Fig. 1 and make the area of the portion of the piston element exposed to atmosphere in Fig. 2 of the same area as the orifice 86 so that the pressure required to hold the springs 40 and 94 compressed is the same as the pressure required to initially compress them.
It will be apparent that the valve construction described prevents leakage only from the second cylinder 19 in Fig. l and 61 in Fig. 2. It does not prevent leakage from the first cylinder back through the control valve. If it is desirable to prevent such leakage it can be done by means of a conventional locking valve.
Although for the purpose of explaining the invention, a particular embodiment thereof has been shown and described, obvious modifications will occur to a person skilled in the art, and I do not desire to be limited to the exact details shown and described.
1. A valve of the type described for connection between a control valve and a motor comprising: a body having a motor port and a pair of control ports and defining a chamber connected to said motor port; a check valve connecting said chamber to one control port operative to open in response to flow from said one control port to said chamber; a piston element cooperating with said check valve and movable into and out of a position in which it resists free opening of said check valve, yieldable means interposed between said piston element and check valve urging said check valve toward a position to prevent flow from said chamber to said one control port, force means exerting a predetermined force on said piston element urging it into said position for resisting opening of said check valve, said piston element including two opposed faces one of which constitutes a surface exposed to the pressure in said chamber and so directed and proof said check valve, the other face being associated with means isolating said other face from existing pressure in said chamber; and means in said valve body, responsive to a selected pressure in said other port, said last mentioned means being engageable with the check valve and operative to overcome the force of the yieldable means interposed between the check valve and the piston to permit flow between the chamber and the first mentioned control port.
2. Apparatus according to claim 1 in which said check valve comprises a valve seat of substantially the same area as said piston element face and aligned with said piston element and a poppet interposed between said seat and said piston element and normally seated by said piston element.
3. A valve of the type described for connection between a control valve and a motor comprising: a body having a motor port and a pair of control ports and defining a chamber connected to said motor port; a check valve connecting said chamber to one control port directed to open in response to flow from said one control port to said chamber; a piston element cooperating with said check valve and movable into and out of a position in which it resists free opening of said check valve, force means exerting a predetermined force on said piston element urging it into said position for resisting opening of said check valve, said piston element having a surface exposed to the pressure in said chamber and so directed and proportioned that predetermined pressure thereon acts to overcome said force means and move said piston element out of said position to permit normal check valve action of said check valve; said piston element including opposed faces one of which constitutes said exposed sur face, and means isolating the other face from pressure in said chamber; means responsive to pressure in the other control port for mechanically opening said check valve; said chamber comprising two compartments joined by an orifice aligned with and of the same area assaid one piston element face, one compartment being connected to said motor port and containing said piston element and the other compartment containing and being connected to said one control port by said check valve, said piston element being in sealing engagement with said orifice in said position and clear of said orifice when out of said position, and said second compartment and check valve being so longitudinally dimensioned that when mechanically opened said check valve mechanically displaces said piston element from said orifice.
4. Apparatus according to claim 3 including light spring means for maintaining said check valve seated in the absence of other forces thereon.
5. Apparatus according to claim 3 in which said check valve comprises a valve seat of substantially the same area as said piston element face aligned with said piston element and a spring urged ball check member interposed between said seat and said piston element and normally seated by said piston element.
References Cited in the file of this patent UNITED STATES PATENTS 1,644,265 Noble Oct. 4, 1927 1,697,404 Raymond Ian. 1, 1929 1,773,268 Jenkins Aug. 19, 1930 2,138,125 Schultz Nov. 29, 1938 2,162,898 Rotter June 20, 1939 2,287,936 Hose June 30, 1942 2,292,294 Rotter Aug. 4, 1942 2,591,528 Filstrup Apr. 1, 1952