US2704087A - Hydraulic valve unit - Google Patents

Description

March 15, 1955 R. s. LINDSAY I 2,704,087

HYDRAULIC VALVE AUNIT Filed Aug. s', 1 949 3 sheets-sheet 1 10M J I f March l5, 1955 R, s, |N|'35AY 2,704,087

HYDRAULIC VALVE UNIT Filed Aug. 5, 1949 3 sheets-sheet 2 (Ittornegs March 15, 1955 Y R. s. LINDSAY 2,704,087

HYDRAULIC VALVE UNIT Filed Aug. 5, 1949 3 Sheets-Sheet 5 Gttornegs United States Patent O 2,704,087 HYDRAULIC VALVE UNIT Rolland S. Lindsay, Detroit, Mich., assignor to Haller Machine and Manufacturing Company, Detroit, Mich., a corporation of Michigan Application August 3, 1949, Serial N o. 108,327 6 Claims. (Cl. 137-119) This invention relates to hydraulic machinery and, in particular, to hydraulic control valves.

One object of this invention is to provide a hydraulic control valve unit which automatically defers the feeding of pressure fluid to a main hydraulic device, such as a main hydraulic cylinder until another hydraulic device, such as an auxiliary hydraulic cylinder, has been sulficiently supplied therewith to accomplish an operation which it is desired to accomplish prior to the start of operation of the main device.

Another object is to provide a hydraulic control valve unit of the foregoing character which defers this feeding of pressure fluid to the main cylinder until a predetermined pressure has been built up in the auxiliary cylinder.

Another object is to provide a hydraulic control valve unit or package valve which in a single assembly provides the functions of preliminarily supplying pressure fluid to an auxiliary cylinder while a portion of the pressure fluid is permitted to flow through a constricted orifice into another portion of the valve, which restricted ow eventually becomes suflicient to shift another portion of the valve unit and thereafter to divert the llow of pressure iluid to the main cylinder while the auxiliary cylinder continues to remain under pressure until the main cylinder has performed its work.

Another object is to provide a hydraulic control valve unit or package valve of the foregoing character which is especially well adapted to supplying pressure uid initially to a work gripping cylinder until the work, such as a metal sheet or strip, has been gripped with a predetermined pressure to hold it fast Without slipping, whereupon the valve shifts automatically to thereafter supply pressure lluid to a main hydraulic cylinder which then feeds the work to a work processing machine, such as a punch press.

In the drawings:

Figure 1 is a central vertical longitudinal section through a valve unit according to one form of the invention, with its parts in its forward stroke position for the start of feeding pressure fluid to an auxiliary cylinder prior to feeding it to a main cylinder;

Figure 2 is a horizontal section taken along the line 2 2 in Figure 1;

Figure 3 is a horizontal section taken along the line 3-3 in Figure l;

Figure 4 is a vertical cross-section taken along the broken line 4 4 in Figure 1;

Figure 5 is a vertical cross-section taken along the broken line 5 5 in Figure 1;

Figure 6 is a vertical longitudinal section similar to Figure 1 but showing the valve with its parts in its return stroke position; and

Figure 7 is a diagrammatic side elevation, partly in vertical section, showing the valve unit of the invention applied to the feeding of sheet metal to a punch press.

In general, the valve unit or package valve of this invention consists of a valve block or casing having a central bore with a piston or spool valve therein, the spaced heads of which may be shifted to selectively control the distribution of pressure fluid to one of a pair of service ports while permitting the discharge of fluid from the other service port through the valve to a reservoir or other point of disposal. Prior to the admission of pressure fluid to the service port, which is temporarily blocked by a pressure-responsive springpressed plunger, pressure fluid is admitted freely to an auxiliary service port leading to an auxiliary hydraulic device, such as a work-gripping cylinder, which it is desired to actuate before a main hydraulic device, such as a work feeding cylinder, is permitted to operate. At the same time, pressure-fluid is also admitted freely "ice through a constricted orifice leading to the operating chamber of the service port blocking piston, building up pressure therein until this is suflcient to shift this valve piston and open up the main service port to the free ilow of pressure fluid to the main cylinder. With the work thus securely held by the auxiliary gripping cylinder, the main cylinder or feeding cylinder then accomplishes this function of feeding the work to the machine which it serves, such as a punch press.

When the machine has accomplished its operation upon the work, the valve spool or main valve plunger is shifted, either automatically by the motion of a portion of the machine, such as the punch press platen, or manually. When this occurs, the heads of the valve spool or plunger have now been shifted into positions where pressure iluid is now supplied to the service port which was formerly in exhaust, and the service port formerly supplied with pressure fluid is now in exhaust. Before free exhaust is permitted, however, the service port blocking piston must again be shifted by the building up of pressure therein as before, but through a different passageway on the opposite side of the blocking piston, shifting the blocking piston and permitting free exhaust of the fluid from the service port now in exhaust. The work-gripping cylinder or auxiliary cylinder is meanwhile permitted to discharge its uid freely into the exhaust line, thereby releasing its grip upon the work, after which the shifting of the service port blocking plunger permits the feeding cylinder or main cylinder' to reverse its stroke and retract the work gripping device preparatory to a new feeding stroke of the main cylinder, completing the cycle.

Referring to the drawings in detail, Figures 1 to 4 inclusive show the valve unit, generally designated 10, according to one form of the invention, as consisting generally of a casing 11 having a cylindrical main bore 12 closed at its opposite ends by end members or caps 13 and 14 and containing a ported valve sleeve 15 in which a main valve spool or piston valve member 16 is reciprocable. Also included in the valve unit 10, as described more in detail below, is a service port blocking valve 17 and a pressure fluid inlet relief valve 18 having an end member or cap 19. The casing 11 is roughly in the form of a block having on its under side an inlet passage or port 20 into which is threaded a pressure fluid inlet pipe 21. The inlet passage or port 20 opens into the central portion of the main valve bore 12 and has a relief valve bore 22 opening into it. The relief valve bore 22 has a port 23 with a conical seat surrounding its junction with the inlet passage 20 (Figure l) and at its outer end is closed by the cap 19 previously mentioned. Reciprocably mounted in the bore 22 is a cupshaped hollow relief valve plunger 24 having its forward end beveled to engage the valve seat 23 and having a reduced diameter portion 25 adjacent its forward end and containing cross ports or drainage ports 26 opening into its interior bore or socket 27. Seated in the bore 27 is one end of a compression coil spring 28, the forward end of which is seated in a corresponding socket 29 within the cap 19 (Figures l and 3) and which is engaged by an abutment disc 30 which in turn is engaged by an adjustment screw 31 threaded into the threaded bore 32 and having a lock nut 33 for locking it in posi tion. The adjusting screw 32 furnishes a means of regulating the pressure exerted by the spring 28 uponthe,

relief valve plunger 24 and consequently regulates the pressure at which the relief valve will admit pressure fluid from the inlet passage 20 into the relief valve bore 22. The cap 19 is secured tothe casing 11 by screws 34 (Figure 3).

Opening out of the relief valve bore 22 is a reliefinto the main bore 12 between the outlet passage 40 4and the pressure uid inlet passage 20 is an auxiliary service port 41 (Figures 2 and 4) into which is threaded an auxiliary service pipe 42.

The valve sleeve 15 is in the form of a hollow cylinder which is fixed in position within the main valve bore 12 and has three annular grooves in the periphery thereof, namely a middle groove 43 and end grooves 44 and 45 (Figures l and 2). The middle groove 43 is aligned with the pressure fluid inlet passage 20 and has four ports 46 (Figure 4) whereas similar ports 47 and 48 respectively open from the end grooves 44 and 45 into the valve bore 49 within the valve sleeve 15 within which the valve spool or piston valve member 16 reciprocates. Due to the irregular section line 4-4 of Figure l along which Figure 4 is taken, the upper port in the valve sleeve 15 is the port 48 in the annular groove 45, whereas the lower port is the port 46 in the annular groove 43.

Opening out of the valve bore 12 in alignment with the end grooves 44 and 45 in the valve sleeve 15 are main service ports or passageways 50 and 51 respectively and having main service pipes 52 and 53 threaded therein (Figure 1). The pipes 52 and 53 lead to the opposite ends of the main hydraulic cylinder or other main hydraulic device to be controlled, whereas the auxiliary service pipe 42 (Figures 2 and 4) leads to the auxiliary hydraulic cylinder or device to be controlled, as described below in connection with Figure 7. The service port blocking valve 17 reciprocates to and fro transversely across the service port or passageway 51, opening it or closing it, under the conditions described below.

Reciprocably mounted within the valve sleeve bore 49 are the spaced heads 54 and 55 of the valve spool or piston valve member 16, the heads 54 and 55 being spaced apart from one another bv a distance equal to the separation of the ports 47 and 48 (Figures l and 2). The heads 54 and 55 are separated from one another by the valve stem 56 of reduced diameter which forms, in effect, an annular chamber 57 surrounding the stem 56 between the heads 54 and 55 within the valve sleeve bore 49. Beyond and to the left of the head 55, the valve member 16 is provided with a valve stem extension 58 which is surrounded by a compression spring 59, one end of which engages the outer surface of the head 55 and the other end of which is seated against an abutment disc 60 located in the end of a socket 61 within the end cap 14, the socket 61 consisting of a bore terminating in a counterbore 62 (Figures 1 and 2). The compression spring 59 tends to urge the valve member 16 to the right into the position shown in Figure 6. and the abutment disc 60 also serves as a stop for the end 63 of the valve stem extension 58 when the valve member 16 is in its Figure l position. The end cap 14 is secured bv the screws 64 to the left-hand end of the casing 11. closing that end of the valve bore 12.

To the right of the right-hand valve head 54, the valve stem 56 terminates in a valve rod 65 of reduced diameter which passes through a bore 66 in the end cap 13, which contains an oil ring 67 to prevent leakage along the rod 65. The end can 13 is secured by the screws 68 to the righthand end of the valve casing 11 (Figure 2). The service port blocking valve 17, which opens or closes the service port or passa ge 51. consists of a hollow plunger 69 reciprocable in a bore 70 which crosses the service port or passage 51 transversely (Figure 4). The plunger 69 is of a length slightlv greater than the diameter of the service port or passage 51 so as to completely close it ofil in the position shown in Figure 4. rhe passage 70 is long enough and hence thel casing 11 thick enough to permit the piston plunger 69 to withdraw substantially completelv into the left-hand end thereof so as to completely open the service port or passage 51, which is shown closed in its Figure 4 position.

The closed end of the piston or plunger 69 is provided with a stop proiection 71, the end 72 of which contacts the inner surface. of a closure plate 73 which is secured by the screws 74 (Figure 4) to the valve casing 11 to close the right-hand end of the transverse bore 70. A constricted lower bv-pass port or passageway 75 of restricted diameter leads from the lower end of the service port or passageway 51 beneath the plunger 69 to the operating chamber 76 of the plunger 69 forming the right-hand end of the transverse bore 70. The passageway 75 is of a sufficiently small diameter to appreciably retard the ow of pressure uid therethrough and hence to delay the opening of the blocking valve 17. Extending between the upper portion of the service port or passage 51 above the plunger 69 and the operating chamber 76 is an L-shaped constricted upper by-pass port or passage 77 having a valve seat 78 closed by a ball check valve 79 which is urged into its closed position by a compression spring 80, the rearward end of which is seated against a plug 81 threaded into the counterbore 82 which joins the by-pass port or passageway 77.

The blocking valve plunger 69 is provided with a socket 83 which receives the forward end of a compression spring 84 (Figure 4), the rearward end of which engages an abutment disc 85 mounted in the left-hand end of the transverse bore 70. The abutment disc 85 is engaged by an adjusting screw 86 threaded through a threaded bore 87 extending through a closure plate 88 which is secured by the screws 89 to the casing 11 at the left-hand end of the valve bore 70 in a position complementary to the closure plate 73. A lock nut 90 holds the screw 86 in its adjusted position, the screw 86 being used to adjust the closing pressure exerted upon the valve plunger 69 and hence to regulate the opening pressure of the service port blocking valve 17.

Figure 7 shows a typical application of the valve unit 10 to delay the supplying of pressure uid to a main hydraulic device or cylinder until an auxiliary hydraulic device or cylinder has been actuated. In particular, the installation shown by way of example in Figure 7 consists of a punch press, generally designated 91 having a platen or ram 92 reciprocable vertically in guides 93 and having a punch 94 secured to its lower end. The punch 94 cooperates with a die 95 bolted to the bed 96 of the punch press 91. Bolted to one of the guides 93 is a bracket 94a to the lower end of which the valve unit 10 is bolted. Bolted to the platen 92 is a cam 97 having a curved cam surface 98 upon which rides a cam roller 99. The cam roller 99 is mounted upon an axle 100 carried by a yoke 101 mounted on the outer end of the valve rod 65. The exhaust pipe 38 leads to an oil reservoir (not shown) whereas the pressure fluid inlet pipe 21 leads to the valve unit 10 from a hydraulic pump (also not shown). A Hexible hose 102 leads from the auxiliary service pipe 42 to an auxiliary hydraulic device or work clamping device 103. The latter is of the type described and claimed in the Haller application, Serial No. 44,622, led August 17, 1948, for Pressure Fluid Clamp, which is a division of Haller Patent 2,467,740, issued April 19, 1949, for Step-by-Step Feeding Device, and its details are beyond the scope of the present invention.

For the purposes of the present disclosure, the clamping device 103 consists of a casing or cylinder block 104 mounted bridge-like above and spanning the stock S and having its ends extending downward to rest upon a movable support or cross-head 105 and separated from it by an elongated opening 106 through which the stock S passes. The stock S may be in the form of coil stock, that is, sheet steel or other metal or sheet material in the form of a coil o1' elongated strip, and this is guided over a stationary support 107 to a position between the punch 94 and a die 95. Normally, the stationary support 107 is provided with a hydraulic clamping device similar to the clamping device 103 and operating alternately therewith from an auxiliary service port similar to the port 41 but aligned with the valve sleeve groove 44 rather than the groove 45 (Figure 2). The fixed clamping device releases the sheet or stock S while the movable clamping device 103 grips it and vice versa. The clamping device 103 has a coupling 108 connected to the hose 102 and opening into an inclined passage 109 which leads to a plurality of operating chambers 110 for cylinder bores 111 containing spaced parallel inclined plungers 112 engaging a transverse clamping roller 113 mounted in a cavity 114 of wedge-shaped cross-section. Conseuuently, when the hose 102 and auxiliary service pipe 42 supply pressure uid to the operating chambers 110, the plungers 112 are pushed downward in an inclined path to wedge the roller 113 into the space between the wedge-shaped cavity 114 and the upper surface of the stock S so as to clamp it firmly against the cross-head 105.

The cross-head 105 reciprocates in spaced guides 115 which are bolted as at 116 to the punch press bed 96. The guides are longitudinally grooved to guide the cross-head 105 in its reciprocation. Secured as at 117 to the cross-head 105 is a piston rod 118 forming a part of a main hydraulic motor 119 and connected to a stock feeding piston 120 reciprocable in the bore 121 of a main hydraulic cylinder 122. The latter is closed at its opposite ends by heads 123 and 124 and is provided at its opposite ends with ports 125 and 126 connected respectively to the service pipes 52 and 53 leading to the service ports or passages 50 and 51 respectively. Mounted on the cylinder 122 is a transverse support 127 having a guide groove 128 therein for the reception of the axle support 129 of axles 130 carrying grooved guide rollers or pulleys 131. The latter engage the opposite edges of the stock S and hold it in alignment with the opening 106 between the clamping device 103 and the cross-head 105.

Operation In the operation of the invention, such as in the punch press work feeding installation shown in Figure 7, pressure fluid enters the uid inlet port or passage 20 through the inlet pipe 21 from the pump (not shown). When the platen 92 is in its raised position at the beginning of its downward or working stroke, the cam roller 100 is riding on the raised portion of the cam surface 98 of the cam 97, consequently, the valve rod 65 and valve spool or valve member 16 are pushed inwardly into the position shown in Figures 1 to 5 inclusive. Consequently, pressure iluid passes through the inlet port or passage 20 (Figure 1) into the middle groove 43 of the valve sleeve 15 and thence through the ports 46, annular chamber 57, ports 48, and left end annular groove 45 of the valve sleeve 15 into the service port or passageway 51. This, for the time being, is blocked by the blocking valve 17 (Figure 4), the piston 69 of which is yieldingly held squarely across the service port or passage 51 by the thrust of the coil spring 84, temporarily preventing ow of pressure uid to the stock feeding piston 120. Pressure uid, however, immediately flows through the constricted lower by-pass passage 75 into the operating chamber 76 of the blocking valve 17 at a retarded rate of speed, gradually building up pressure within the operating chamber 76. In the meantime, however, pressure uid has been flowing freely out of the left end annular groove 45 in the valve sleeve 15 through the auxiliary service port 41 (Figures 2 and 4) into the auxiliary service pipe 42 and thence through the hose 102 (Figure 7) to the movable clamping device 103, shifting the plungers 112 downward in an inclined path and wedging the clamping roller 113 tightly against the stock S and consequently clamping the work against the cross-head 105.

In the meantime, suicient pressure uid has flowed through the constricted lower by-pass port 75 (Figure 4) into the operating chamber 76 of the blocking valve 17 to overcome the thrust of the coil spring 84. As a consequence, the pressure iluid in the operating chamber 76 shifts the blocking valve plunger 69 to the left, opening the connection between the lower and upper portions of the service port or passage 51, thereafter permitting pressure uid to enter and flow through the service pipe 53. The pressure fluid thus enters the rearward or right hand end of the cylinder bore 121 through the port 126 (Figure 7) and acts against the piston 120, causing it, the piston rod 118 and the cross-head 105 to move to the left, advancing the sheet S which has just been clamped thereto by the action of the pressure fluid reaching the clamping device 103 through the hose 102. It will be understood that the stationary clamping device (not shown) similar to the movable clamping device 103 and mounted above the stationary support 107 is unclamped at this time while the clamping device 103 is clamped, so that the stock S is free to be moved to the left beneath the punch 94 and over the die 95.

The platen 92 now moves downward to punch the workpiece out of the stock S, and at the same time the cam 97 moves downward, causing the roller 100 to ride to the low portion of the cam surface 98, permitting the valve rod 65 and valve spool or valve member 16 to move outward (to the left in Figure 7 or to the right in Figures 1 and 2) under the inuence of the compression spring 59, shifting the valve spool 16 into the position shown in Figure 6. When this occurs, the auxiliary service port 41 and auxiliary service pipe 42 are immediately connected through the annular groove 45 and sleeve ports 48 to the left-hand end of the valve bore 12 (Figure 6). Consequently, lluid is immediately released from the operating chambers 110 of the movable clamping devices 103 to ow through the hose 102, auxiliary service pipe 42, ports 41 and 48, left-hand end of the cylinder bore 12 into the outlet port or passage 40 and thence into the 6 exhaust` passage 36 and exhaust pipe 38. This releases the clamping plungers 112 and the clamping roller 113, consequently releasing the clamping grip of the latter upon the stock S.

Meanwhile, the same shifting of the valve member 16 with its heads 54 and 55 into the position of Figure 6 permits pressure iluid to flow from the inlet pipe 21 and port 20 through the middle annular groove 43 and ports 46, the annular chamber 57, the right-hand end ports 47, the right-hand end groove 44, and the service port or passage 50 into the service pipe 52 leading to the port 125 at the forward end of the cylinder 122. The pressure acts against the piston to return the cross head 105 to its retracted position shown in Figure 7, but before it can do so, the iluid is temporarily prevented from leaving the rearward or right-hand end of the cylinder bore 121 by the blocking valve 17 which has closed immediately under the inuence of the coil spring 84 when the valve was shifted to the position of Figure 6. This occurred by reason of the connection of the operating.

of the service port 51, the ports 48, and the left-hand end of the main valve bore 12.

While the movable clamping device 103 has been releasing its grip, the similar stationary clamping device (not shown) mounted above the stationary support 107 has been gripping the stock S, it having been connected to an auxiliary service port similar to the port 41 (Figure 2), but located near the other end of the cylinder bore in communication with the right-hand end groove 44. The delay which permits this to take place occurs by reason of the fact that the iluid being forced out of the right-hand end of the cylinder bore 121 through the port 126 and pipe 53, although blocked by the blocking valve 17 temporarily, passes through the constricted upper bypass port or passage 77, forcing the check valve 79 to open by overcoming the thrust of the coil spring 80. This permits pressure to build up gradually again in the operating chamber 76 until there has been a sufficient accumulation of pressure to again shift the blocking valve piston 69 to the left (Figure 4), reopening the service port or passage 51. The uid may then pass freely out of the rearward end of the cylinder 122 to the exhaust pipe 38 by way of the service pipe 53, the port or passage 51, the annular groove 45, the ports 48 (Figure 6), the left-hand end of the valve bore 12, the outlet port 40 and the exhaust passageway 36 (Figure 3). The piston 120, piston rod 118 and Across head 105, together with the movable clamping device 103 then move to the right to their retracted positions shown in Figure 7, completing the cycle.

If at any time the pressure within the inlet port 20 rises to a point where it overcomes the thrust of the relief valve spring 28, such as when the piston 120 reaches the end of its stroke, the relief valve piston 24 is pushed to the right (Figures l and 3), opening the port 23 between the inlet port or passage 20 and the forward end of the bore 22. The pressure lluid thus is tree to pass directly from the inlet port or passage 20 through the port 23 into the port or passage 35 (Figures 3 and 5), and thence through the exhaust passage 36 into the exhaust pipe 38 and thence back to the reservoir.

What I claim is:

l. A hydraulic control valve unit comprising a casing having a valve bore and a pressure lluid inlet port and exhaust port, a pair of main service ports and an auxiliary service port communicating with said valve bore; a main valve member in said valve bore selectively movable into a plurality of positions connecting said inlet port with one of said main service ports while connecting said exhaust port with the other main service port; a blocking valve in one of said main service ports selectively movable to open and close the same, a yieldable element normally yieldingly urging said blocking valve into its service port closing position, said auxiliary service port being disposed in free communication with the space between said fluid inlet port and the main service port equipped with said blocking valve when said inlet port and said valve-equipped main service port are in communication with one another, said blocking valve having a valve operating chamber, an operating piston therein movable in the opposite direction to the direction of thrust of said yieldable element to overcome said thrust and shift said blocking valve into its open position in response to the attainment of a predetermined fluid pressure in said valve operating chamber, and a constricted uid passageway connecting said valve operating chamber to said inlet port to impede the flow of pressure fluid therethrough and delay opening of said blocking valve until after pressure fluid has owed from said inlet port through said auxiliary service port.

2. A hydraulic control valve unit comprising a casing having a valve bore and a pressure uid inlet port and exhaust port, a pair of main service ports and an auxiliary service port communicating with said valve bore; a main valve member in said valve bore selectively movable into a plurality of positions connecting said exhaust port with the other main service port; a blocking valve in one of said main service ports selectively movable to open and close the same, a yieldable element normally yieldingly urging said blocking valve into its service port closing position, said auxiliary service port being disposed in free communication with the space between said iluid inlet port and the main service port equipped with said blocking valve when said inlet port and said valve-equipped main service port are in communication with one another, said blocking valve having a valve operating chamber and a valve-operating piston therein movable in the opposite direction to the direction of thrust of said yieldable element to overcome said thrust and shift said blocking valve into its open position in response to the attainment of a predetermined uid pressure in said valve operating chamber, and a pair of constricted fluid passageways connecting said operating chamber to said valve-equipped main service port on opposite sides of said blocking valve to impede the ow of pressure luid therethrough and delay opening of said blocking valve until after pressure uid has ilowed from said inlet port through said auxiliary service port.

3. A hydraulic valve unit comprising a casing having a main valve bore, a pressure-fluid inlet port, an exhaust port, a pairof main service ports and an auxiliary service port communicating with said valve bore; a main piston valve reciprocably mounted in said valve bore and having heads selectively movable into a plurality of positions connecting said inlet port with one of said main service ports while connecting said exhaust port with the other main service port; a blocking valve disposed across one of said main service ports and selectively movable to open and close the same, a yieldable element normally yieldingly urging said blocking valve into its service port closing position, said auxiliary service port being disposed in free communication with the space between said uid inlet port and the main service port equipped with said blocking valve when said inlet port and said valveequipped main service port are in communication with one another, a blocking valve operating chamber in said casing, a blocking valve operating piston reciprocably mounted in said operating chamber and connected to said blocking valve, said operating chamber having a passageway opening into said valve-equipped service port inwardly of said blocking valve, said operating piston being movable in the opposite direction to the direction of thrust of said yieldable element to overcome said thrust and shift said blocking valve into its open position in response to the attainment of a predetermined uid pressure in said valve operating chamber whereby to defer opening of said blocking valve until after pressure fluid has owed from said inlet port through said auxiliary service port.

4. A hydraulic valve unit comprising a casing having a main valve bore, a pressure-fluid inlet port, an exhaust port, a pair of main service ports and an auxiliary service port communicating with said valve bore; a main piston valve reciprocably mounted in said valve bore and having heads selectively movable into a plurality of positions connecting said inlet port with one of said main service ports while connecting said exhaust port with the other main service port; a blocking valve bore disposed across one of said main service ports, a blocking valve member shiftably mounted in said blocking valve bore and 4selectively movable to open and close the same, a yieldable element normally yieldingly urging said blocking valve into its service port closing position, said auxiliary service port being disposed in free communication with the space between said uid inlet port and the main service port equipped with said blocking valve when said inlet port and said valve-equipped main service port are in communication with one another, a blocking valve operating chamber in said casing, a` blocking valve operating piston reciprocably mounted in said operating chamber and connected to said blocking valve, said operating chamber having a passageway opening into said valveequipped service port inwardly of said blocking valve, said operating piston being movable in the opposite direction to the direction of thrust of said yieldable element to overcome said thrust and shift said blocking valve into its open position in response to the attainment of a predetermined uid pressure in said valve operating chamber to defer opening of said blocking valve until after pressure fluid has ilowed from said inlet port through said auxiliary service port.

5. A hydraulic valve unit comprising a casing havingy a main valve bore, a pressure-Huid inlet port, an exhaust port, a pair of main service ports and an auxiliary service port communicating with said valve bore, a main piston valve reciprocably mounted in said valve bore and having heads selectively movable into a plurality of positions connecting said inlet port with one of said main service ports while connecting said exhaust port with the other main service port; a blocking valve bore disposed across one of said main service ports, and a blocking valve member reciprocably mounted in said blocking valve bore and selectively movable to open and close the same, a yieldable element normally yieldingly urging said blocking valve into its service port closing position, said auxiliary service port being disposed in free communication with the space between said fluid inlet port and the main service port equipped with said blocking valve when said inlet port and said valve-equipped main service port are in communication with one another, said blocking valve having a valve operating chamber, a valve operating piston therein movable in the opposite direction to the direction of thrust of said yieldable element to overcome said thrust and shift said blocking valve into its open position in response to the attainment of a predetermined tluid pressure in said valve operating chamber, and a constricted fluid passageway connecting said valve-operating chamber to said inlet port to delay opening of said blocking valve.

6. A hydraulicfvalve unit comprising a casing having a main valve bore, a pressure-iluid inlet port, an exhaust port, a pair of main service ports and an auxiliary service port communicating with said valve bore, a main piston valve reciprocably mounted in said valve bore and having heads selectively movable into a plurality of positions connecting said inlet port with one of said main service ports while connecting said exhaust port with the other main service port; a blocking valve bore disposed across one of said main service ports, a blocking valve member reciprocably mounted in said blocking valve bore and selectively movable to open and close the same, a yieldable element normally yieldingly urging said blocking valve into its service port closing position, said auxiliary service port being disposed in free communication with the space between said fluid inlet port and the main service port equipped with said blocking valve when said inlet port and said valve-equipped main service port are in communication with one another, said blocking valve having a valve operating chamber, a valve operating piston therein movable in the opposite direction to the direction of thrust of said yieldable element to overcome said thrust and shift said blocking valve into its open position in response to the attainment of a predetermined fluid pressure in said valve operating chamber, and a pair of constricted uid passageways connecting said valveoperating chamber to said valve-equipped main service port on opposite sides of said, blocking valve to delay opening of said blocking valve.

References Cited in the le of this patent UNITED STATES PATENTS 1,823,426 Ferris Sept. 15, 1931 2,096,073 Spencer Oct. 19, 1937. 2,130,618 Gnavi Sept. 20, 1938 2,161,642 Stroup June 6, 1939 2,200,824 Herman May 14, 1940 2,301,028 Esch Nov. 3, 1942 2,499,235 Tyson Feb. 28, 1950

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