US3013577A - Pressure responsive valve for hydraulic systems - Google Patents

Description

Dec. 19, 1961 H. HILDRE 3,013,577

PRESSURE RESPONSIVE VALVE FOR HYDRAULIC SYSTEMS Filed March 51, 1958 2 Sheets-Sheet 1 FIG. 1.

INVENTOR: HA NS H L DRE.

H. HILDRE Dec. 19, 1961 PRESSURE RESPONSIVE VALVE FOR HYDRAULIC SYSTEMS 2 Sheets-Sheet 2 Filed March 51, 1958 INVENTOR: HA N S H L DRE.

United States This invention relates to a pressure responsive valve for hydraulic systems.

In such systems comprising at least two hydraulic motor circuits connected in aiding mechanical relation to the same shaft, it is sometimes desired to maintain one hydraulic motor circuit in an idling position disconnected from the main supply of pressure fluid, while the remaining motor circuit receives all the pressure fluid, until a given pressure differential is exceeded in the system. In idling, the idling motor circuit is driven as a pump by the working motor circuit, and the inlet of the idling circuit must be connected to the discharge side of the system in order to reduce the circulation resistance in the idling motor circuit as much as possible.

It is an object of the present invention to improve the pressure responsive control valves for effecting such disconnection and short circuiting of a hydraulic motor circuit when the pressure diiferential between the supply side and the discharge side of the hydraulic system is below a given value, and to effect connection of the inlet of the motor circuit to the pressure side and simultaneously disconnection of the short circuit as soon as the pressure exceeds said given value, by providing a valve of the kind set forth in a rugged, simple and highly eflicient construction.

A further object of the present invention is to obtain a pressure responsive valve of the kind aforesaid, in which the valve member is readily shifted from'one position to another without assuming intermediate positions at pressure lying in the neighbourhood of the desired changeover pressure for the device.

I Another object of the present invention is to obtain a valve of the kind aforesaid, wherein the valve member is shifted smoothly over from one position to another although the forces acting on the valve member necessarily must be considerable, if the desired mode of operation is to be obtained. According tothe present invention and from one aspect thereof, a pressure responsive valve for hydraulic systems comprises a hollow casing, a partition within said casing dividing the interior into an upper chamber and a lower chamber, an outlet for fluid from the upper chamber, a first inlet for pressure fluid into theupper chamber, a second inlet for discharge fluid into the lower chamber, an opening arranged in said partition for communication between the upper chamber and the lower chamber, a cylinder in the wall of the lower chamber in axial alignment with said first inlet and closed in one end, the cross sectional area of said first inlet exceeding the cross sectional area of said cylinder by a defined amount, a valve member having on its upper end a first face for closing said inlet, a second face intermediate its ends for closing said opening and a third face arranged on a piston flange integral with said valve member and received within said cylinder so as to face towards the closed end thereof and to form a fluid pressure receiving face opposing said first face, a bore extending axially through said valve member for said first face to said third face, a compression spring received within said cylinder for urging said valve member to a position wherein said first face closes said first inlet and said. secondface is spaced from said opening, and means for regulating the spring force ofsaid compression spring.

atet ce In order that the invention may be more clearly under- Patented Dec. 19, 196 1 FIGURE 3 is a diagrammatic sectional view of the I valve member as taken on the line IIIIII of FIGURE 2, FIGURE 4 is a diagrammatic sectional view of the valve member as taken on the line IVIV of'FIGURE 2, FIGURE 5 is a sectional view of a part of a flange of the valve member as taken on the line V-V of FIG- URE 4.

Referring particularly to FIGURE 1, the hydraulic system in which the pressure responsive valve according to the present invention is embodied will first be described. This system comprises a main supply line 1 continuously supplying hydraulic pressure fluid, preferably oil, in a single direction from a non-reversible pump 2 to a manually adjustable control valve 3. By manually adjusting said control valve 3 to different positions the fluid may either be led back to the pump 2 through a main return line 4, or may be supplied to a motor circuit 10 connected by a feed conduit 13 to the control valve 3. The discharge from the motor circuit 10 is by means of a discharge conduit 16 conducted back to the pump 2, through the main return line 4.

A branch conduit is branched off from the feed conduit 13 and leads to a pressure responsive valve generally designated with the reference numeral 81. This valve controls the feed of hydraulic fluid to a motor circuit 82 by being connected to the inlet 83 of said motor circuit.

In the hydraulic system shown in FIGURE 1, the outlet of the motor circuit 8 2 is connected by means of a conduit 84 to the main discharge, as represented by a branch 85, from the discharge conduit 16 to the valve. This, however, should be regardedas only an example, as the outlet may be conducted to the control valve 3 or directly connected to the main return line 4.

The valve 31 will now be described in greater detail, referring first to FIGURES 1 and 2. The device has a main casing 101 the interior of which is divided into an upper chamber 102 and a lower chamber 103, by means of a partition 104. The casing 101 is provided with flanges 105 by means of which the control device 81 may be flanged to the housing of a motor forming the motor circuit 82 controlled by the corresponding branch 85 is in constant communication with the lower chamber 103. p

The branch conduit 80 is led axially into the upper end wall of an upper inlet 106 which opens at its lower end into the upper chamber 102. The upper end wall is formed by an annular cover plate 107 to which the pipe forming the branch conduit 80 may be welded or otherwise secured.

A cylindrical opening or bore 108 is arranged in the partition 104 in direct axial alignment with the upper inlet 106, said opening 108 having greater diameter than said inlet 106.

A lower cylinder 109 is arranged in the bottom of the lower chamber 103 in direct axial alignment with the inlet 106 and the opening 108. The lower cylinder 109 is terminated downwardly by a spring casing 110 at its lower end.

A valve member 111 co-operates with the upper inlet 106, the opening 168 and the lower cylinder 109 by having an upper piston flange 112 secured to the upper end of a valve stem 113 and co-operating with the upper inlet 106, an intermediate piston flange 114 co-operating with the cylinder opening 198, and a lower piston flange 115 secured to the lower end of the valve stem 113 and cooperating with the lower cylinder 109. All three piston flanges are snugly fitted within their respective cylinders and openings.

When comparing FIGURE 1 and FIGURE 2 it will be seen that the valve member 111 may assume an upper position with the upper piston flange 112 positioned in the upper end of the inlet 106, while the intermediate flange 114- is positioned remote from the opening 1418 in the partition 104 and allows free and unthrottled communication between the upper chamber and the lower chamber. The piston flange 115 is then positioned in the upper end of the lower cylinder 109 (FIGURE 1).

It will be seen that the valve member 111 also may assume a lower position wherein the upper piston flange 112 is positioned remote from the upper inlet 1136 and allows free and unthrottled communication between the branch 80 and the upper chamber, while the intermediate flange is received within the opening 1118 and prevents communication between the two chambers through this opening 198. The piston flange 115 is pressed in this position down near the end of the lower cylinder 109.

The distance from the upper end of the upper piston flange 112 to the lower end of the intermediate piston flange 114 is greater than the distance from the lower end of the inlet 106 to the opening 108, so that the intermedi ate piston flange 114 closes the opening 192% before the upper piston flange 112 allows any communication between the branch conduit 83 and the upper chamber.

Normally the valve member 111 is urged to its uppermost position of FIGURE 1 by a compression spring 119 arranged within the spring casing 110.

The valve member 111 is provided with an open ended central bore 140 extending from the upper face of the upper piston flange 112 and down to the lower face of the valve member. Through said bore the lower face of the lower valve flange 115 will be subjected to the pressure of the pressure fluid over its entire lower face.

In the present embodiment, the upper valve flange comprises two concentric parts, an upper cylindrical part 141 and a lower cylindrical part 142 having somewhat greater diameter than the upper part 141. As will further appear from the drawings, specifically from FIGURE 3, the lower part 142 is provided with four symmetrically arranged grooves or recesses 143 on its peripheral face for throttled supply of fluid to the shoulder between the cylindrical parts 141 and 142.

correspondingly, the inlet 1416 is arranged to comprise two cylindrical bore parts, that is a lower cylindrical bore part 144 receiving the lower cylindrical flange part 142, and an upper smaller cylindrical bore part 145 receiving the upper cylindrical flange part 141. Both cylindrical bores 144, 145 are machined to a close fit with their associated flange parts 142, 141, respectively. The shoulder between the bores forms a seating for the lower cylindrical part 142.

The intermediate valve flange 114 is on its lower face provided with four recesses 147, the intention of which will be explained later.

The lower face of the lower valve flange 115 is provided with a head 14% having a frusto'conical shape, corresponding substantiaily to a frusto-conical part 14? of the spring housing. The head ends in a protrusion 15-11 which receives the upper end of the compression spring 119, and which also defines the outlet of the axial bore 140.

The spring 119 is at its lower end received by a spring supporting piece 151 carried by a control screw 152. The screw 152 is received within a threaded bore 153 in the lower end of the spring housing, the outer end of the screw being covered by a threaded cap 154.

It remains to be noted that the cross sectional area of the upper cylindrical bore 145 is by a well regulated amount greater than the cross sectional area of the lower cylinder 109.

The mode of operation of the present valve will now be explained. As is well known in the art, a face receiving the pressure from hydraulic pressure fluid will be subjected to a force equalling to the pressure multiplied by the cross sectional area. If pressure fluid also acts against a second face opposing the first one, the resulting force will be equal to the difference between the cross sectional areas in question, multiplied by the pressure. Consequently, the valve member of the present invention will be subjected to a downwards directed force equal to the difference between the upper face of the flange part 141 and the effective cross sectional area of the cylinder 109, multiplied by the pressure of the driving hydraulic fluid. As the force of the compression spring 119 acts upwards against such force, the valve member 111 will remain in its uppermost position of FIGURE 1, until the pressure within the system exceeds the value at which the downward force created as explained above exceeds the upwards force from the compression spring. Then, the valve member will start to move downwards.

By means of the control screw 152 the upward force from the spring 119 may be regulated as desired to correspond to a desired change-over pressure.

However, it appears that the valve member 111 may move downwards over the axial distance of the cylinder head 141, when the pressure exceeds the change-over pressure, before anything happens. This ensures that temporary pressure shocks will not remove the valve member from its seat in the inlet 106 and bring about change-over, due to the increase in area which is described later.

When the lower flange part 142 of the piston flange 112 moves downwards, away from the shoulder between the cylindrical bores 144, 145, a suction will be created beneath said shoulder. If the fit between the cylinder part 141 and the cylinder bore 145 is sufliciently tight (as it should be, for obvious reasons) no pressure fluid will leak through to such space. However, the grooves 143 will enable a small amount of discharge fluid from the chamber 102 to leak into the space beneath the shoulder, preventing a vacuum within said space, which would otherwise prevent downwards movement of the valve member.

When the upper edge of the cylindrical head 141 passes the shoulder between the bores 144, 145, during the downward movement of the valve member, pressure fluid will come to action against an area corresponding to the cross sectional area of the cylindrical bore 144. There will be some leakage of oil through the grooves 143, but such leakage will be limited due to the restriction of said grooves, and the pressure within the system will not be affected thereby. Thereby, the valve member will be moved further downwards, as the difference in areas now will be considerably increased. Such further movement will bring the intermediate piston flange 114 to be received within its associated opening 108.

The form of the recesses 147 of the lower side of the flange 114 will enable the flange to be guided into position before the opening 108 is closed.

It has been mentioned in the preceding that the inter.- mediate flange 114 will be received in and close the opening 108 before the upper flange 112 opens the upper inlet 1%. Because the associated motor circuit 82 is driven as a pump by the first motor circuit, suction is created in the upper chamber 102. It might have been dangerous, therefore, if said chamber in this position would have been entirely closed. However, the grooves 143 will in such intermediate position allow sufficient hydraulic fluid through from the conduit to prevent any substantial braking efiect on the motor circuit 82. Further, such intermediate position will only last for a very short moment, as the downward force on the valve member for changing same to its lower position is considerable.

Finally, the upper flange 112 will be removed from the associated inlet 1%, whereby pressure fluid will flow into the upper chamber 102, acting against the upper face of the intermediate flange 114'. As said flange has a greater cross sectional area than the area of the flange 112, the valve member will be urged further down to its lowermost position.

From now on, i.e. when the valve member has been shifted to the position of FIGURE 2, pressure fluid flows through the wide-opened upper inlet 16-5, into the upper chamber 162 and into the inlet 33 of the motor circuit 32, wherefrom it is discharged through the outlet 84 to the lower chamber 193. Herefrorn, the discharge fluid is removed through the conduit 85. In other words, the motor circuit has been connected and will remain connected, as long as the valve member remains in the position of FiGURE 2.

In the position of FIGURE 2, pressure fluid acts against the upper face of the piston flange 114 in opposition to the pressure fluid acting against the lower face of the piston flange 115 plus the upward force from the spring 119. In order to ensure that the motor circuit 32 is not disconnected before the conditions of overload are removed, the cross sectional area of the flange 1 14 considerably exceeds the cross sectional area of the flange 11$. As'soon as the pressure is decreased below the pressure at which renewed disconnection is desired, the upward force from the spring 119 will force the valve member upwards, whereby same will be returned to the position of FIGURE 1.

it must be remembered that the forces acting on the valve member in order to obtain smooth change-over from one position to another, necessarily must be considerable. Thus, for obtaining a flow without undue friction losses, it may be desirable to have cross sectional dimensions of the inlet 1th: amounting to, say about 40 cm. whereas the change-over pressure may amount to from 15 kg./cm. and upwards, most often from 20 kg/crn. and upwards. For obtaining a smooth changeover, the differences in areas should be great.

However, the use of great area differences will also have the efiect that the valve member when changing over from one position to another will be moved abruptly downwards, and may strike sharply against the bottom of the lower cylinder 109. The head 148, however, forms a dampening means for absorbing the shocks in the last part of the downward movement. It appears readily from FIGURE 2 that the head 148 when moving downwards will be received within a narrowed portion of the cylinder 109 and the portion 149 of the spring housing 110. The mass of hydraulic fluid within the trapped space above the corresponding shoulder will have to pass a restricted flow path between the wall portion 149 and the head 148, and will form a shock absorber during its pass. Therefore, it is possible to obtain change-over of the valve member by a considerable force, without any danger that the valve member will be subjected to undue stresses in the last part of its downward movement.

During return, a similar trapping effect is observed at the shoulder between the bore parts 144 and 145, where the trapped fluid will escape through the grooves 143.

Finally, it should be noted that the dimensions of the 6 axial bore 140 is important for the correct working of the valve. It is readily apparent that the bore 140 will dampen any pressure shocks occurring in the system,

whereby such shocks will not be transferred to the lower face of the valve member. Therefore, if the system is subjected to sudden changes in the pressure whereby the change-over pressure is repeatedly exceeded, the dampening effect of the axial bore will enable change-over to proceed, even if the mean value of the pressure of the system does not exceed the change-over pressuref This is highly desirable, as such shock waves will tend to subject the system to undue stresses, and should be avoided by decreasing the driving pressure.

The dampening efi'ect aforesaid may be made more significant by restricting the axial passage 14% correspondingly.

What I claim is:

l. A pressure responsive valve, comprising a hollow casing having a bore arranged in the interior thereof, a valve member axially displaceable in said bore, the casing also having ports arranged at spaced axial positions along said bore, an inlet at one end of said bore for supplying pressure fluid in an axial direction to said bore, spring means for urging said valve member towards said inlet, said inlet comprising first and second cylindrical portions, said second cylindrical portion having larger diameter than the first cylindrical portion, an inlet shoulder face interconnecting said cylindrical portions, said valve memher having a head facing towards said inlet, said head comprising first and second cylindrical parts and a valve member shoulder face between the same, said first part having a diameter insuring a tight fit within said first cylindrical portion and said second part having a diameter insuring a tight fit within said second cylindrical portion, said valve member having a first end position in which the valve member shoulder face is urged towards said inlet shoulder face, a first intermediate position in which the first and second cylindrical parts are still received with a tight fit within said first and second cylindrical portions, respectively, whereas the valve member shoulder face is spaced from the inlet shoulder face, a second intermediate position in which the second cylindrical part is received within the second cylindrical portion whereas the first cylindrical part is spaced from the first cylindrical portion, and a second end position in which the first and second cylindrical parts are spaced from the inlet to allow a flow of pressure fluid into the associated end of said bore, and means for supplying fluid to the interface at said shoulder faces to prevent a vacuum being created in the closed space thereat when the valve member moves from said first end position through said first intermediate position to the second intermediate position.

2. A pressure responsive valve according to claim 1, wherein the fluid supplied to said interface is supplied through throttling grooves provided on the valve member.

3. A pressure responsive valve according to claim 1, wherein the fluid to said interface is supplied by throttling passages constituted by small axial grooves at the second cylindrical face.

References Cited in the file of this patent UNITED STATES IATENTS 2,323,021 Ernst June 29, 1943 2,374,588 Doran Apr. 24, 1945 2,563,192 Scruggs Aug. 7, 1951 2,674,260 Thrush Apr. 6, 1954 2,816,565 Dalhaug Dec. 17, 1957

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