United States Patent [191 Jackson 1 June 26, 1973 HYDRAULIC FUSE Harry Yale Jackson, Cherry Hill, NJ.
 Assignee: Eaton Corporation, Cleveland, Ohio  Filed: July 29, 1971  Appl. No.: 167,311
3,464,439 9/1969 Budzich .II. 137/504 Primary Examiner-Henry T. Klinksiek Assistant Examiner-Robert J. Miller Attorney-Teagno & Toddy  ABSTRACT A hydraulic fuse includes a body defining a cylindrical bore therethrough. A tubular piston including a radially extending opening therein is located in the cylindrical bore of the body and is resiliently biased to a normally open position. The tubular piston member is of low mass and is movable against the force of a resilient biasing means in response to fluid flow quantities above a predetermined maximum. During movement of the tubular piston against the force of the resilient biasing means the internal wall of the cylindrical bore partially closes the radial opening in the tubular piston member thereby increasing the pressure drop across the piston member and further urging the piston member to move to a no-flow or closed position. The tubular piston member may be provided with a pilot flow opening therethrough so that a predetermined quantity of flow may exist across the piston member when the radial opening therein has been completely closed.
5 Claims, 1 Drawing Figure --IIllllIl.-
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. INVENTOR. HARRY YALE JACKSON ATTORNEY g// LL Q/ HYDRAULIC FUSE BACKGROUND OF INVENTION 1. Field of Invention This invention relates to a hydraulic flow control valve. More particularly this invention relates to a highly accurate and responsive flow control valve.
2. Discussion of the Prior Art Hydraulic fuses of the type designed for the purpose of preventing or restricting fluid flow through a line upon the occurrence of an excessive flow rate are known in the art. Illustrative of devices of this type are the following U.S. Pats;
Waterman No. 2,821,209 Jan. 28, 1958; Martin No.
2,926,690 Mar. 1, 1960; Foster No. 3,060,959 Oct. 30, I962; Tillman No. 3,476,141 Nov. 4, 1969. Each of the above patents disclose operable hydraulic flow control devices of the type intended to restrict or prevent fluid flow through a line upon the occurrence of an excessive fluid flow rate therethrough. Of the above U.S. Pats., No. 2,821,209, 2,926,690 and 3,476,141 operate in an essentially similar manner. A movable piston element is normally biased to a position axially spaced from a valve seat. The piston has an area exposed to upstream flow and the spring force acting on the piston is sufficient to maintain the piston spaced from the valve seat during normal flow conditions.
In the event of excessive flow across the device, which is indicative of an excessive pressure drop thereacross, the pressure force acting upon the upstream area of the piston will cause the piston to move against the resilient biasing force and cause the piston to seat axially on the valve seat.
Foster, U.S. Pat. No. 3,060,959, operates in a generally similar manner except that the resilient means biasing the piston towards a normally open position is eliminated by differential areas on the piston member and the upstream pressure is stored in an annular chamber 14 in FIG. 1 to cause the piston 9 to move against an axial valve seat 21 upon the occurrence of an excessive pressure drop across the valve.
Each of the above patents discloses a movable piston member having a relatively high mass and which close by movement of the piston member against an essentially axially directed valve seat. With the exception of Martin, U.S. Pat. No. 2,926,690, each of the above prior art devices require relatively complex machining on either the movable piston or the valve seat or both in order to obtain the proper operating characteristics.
SUMMARY OF THE INVENTION The invention of the present application is a much more simple and efficient flow control device than those disclosed in the prior art. The hydraulic fuse of the present application comprises a body having a cylindrical bore therethrough, a hollow cylindrical piston member located within the bore adapted to cooperate therewith to control the flow of fluid across the valve. The hollow cylindrical piston includes a closed end located toward the upstream side of the valve and a plurality of radial openings through the side walls thereof transverse to the sliding axis of the piston. The piston is normally resiliently biased to a full flow position whereat fluid flow through the transverse openings and the piston is unrestricted by the walls of the cylindrical bore. During periods of excessive fluid flow, the pressure drop across the valve is such that the pressure acting upon the area of the closed end of the tubular piston causes the piston to move against the biasing force of the resilient means thereby partially closing the transverse openings therein. As the tubular piston moves against the force of the resilient biasing means, the wall of the cylindrical bore and the valve body partially closes the transverse openings through the cylindrical piston. This closing causes a further pressure drop and continued movement of the piston until the transverse openings are completely closed and fluid flow therethrough prevented.
A regulated flow opening may be provided through the closed end of the piston member to permit a regulated quantity of fluid flow even though the transverse openings are completely closed. This feature is desirable where the nature of the hydraulic system in which the fuse is to be installed requires a leakage flow through the fuse even though the hydraulic system has failed. One example of such a system would be in the area of load raising hydraulic systems where leakage is desirable in order to slowly lower the load to the floor rather than have it remain suspended while workmen repair the failure.
BRIEF DESCRIPTION OFTHE DRAWING The drawing discloses a longitudinal section through a hydraulic fuse embodying the features of the present invention.
DESCRIPTION OF A PREFERRED EMBODIMENT In the drawing there is shown a longitudinal section through a hydraulic fuse 10 which is adapted to be connected in a hydraulic line having a normal directional fluid flow from left to right in the drawing and as indicated by the direction of the arrows. The hydraulic fuse 10 comprises a body 12 having a first inlet bore 14 therein. Adjacent the inlet bore 14 is a flow control bore 16 of somewhat reduced diameter. Toward the outlet end of the body 12 is a third cylindrical bore 18 having a diameter larger than the diameter of the flow control bore 16. The bores 14, 16 and 18 define a fluid flow path through the body 12. Located within the body 12 is a piston member 20. The piston member 20 includes a cylindrical thin walled tube portion 22 hav-' ing a plurality of transverse openings 24 therein. The total effective flow area of these openings 24 is approximately equal to the flow area of the bore of the tube 22. The cylindrical tube portion 22 is closed at one end 26 except for a regulated fluid flow passage 28 therethrough and is of a diameter to provide a slip fit with the control bore 16 when disposed therein. Located at another portion on the thin walled tube portion 22 is a radially extending flange 30 which is located within the bore 18 of the body 12 and is normally biased by a coil spring 32 into engagement with a shoulder 34 defined by the body 12 between the bores 16 and 18. The shoulder 34 limits the movement of the piston member 20 toward the left in the drawing. The spring 32 is supported on an annular washer 36 also located within the bore 18 of the body 12. The washer 36 is in turn supported within the bore 18 of the body 12 by an annular snap ring 38 which cooperates with a groove 40 in the 4 body 12 of the hydraulic fuse 10. The spring 32 is given a predetermined preload so that the piston member 20 is normally biased against the shoulder 34 of the body 12 to permit a predetermined flow of fluid across the valve from left to right in the drawing without restriction. Thus there is substantially no pressure drop across the fuse during normal flow rates.
However, if a flow rate across the valve becomes excessive, as for instance when a hydraulic line ruptures downstream, there will exist downstream of the transverse openings 24, a pressure drop of such magnitude that the difference in pressure upstream of the openings 24 and that downstream of the openings 24 is sufficiently great when multiplied by the differential areas of the closed end 26 of the piston member 20 that the piston member 20 will be moved toward the right in the drawing against the force of the spring 32. As the piston member begins to move toward the right, the cylindrical bore 16 of the body member 12 will cover a portion of the transverse openings 24 thereby creating an even larger pressure drop between the upstream and downstream fluid in the valve thereby creating an even greater tendency of the piston member 20 to move to the right and restrict fluid flow therethrough. The piston member 20 will continue to move under the effects of excessive flow until the transverse openings 24 are completely within the bore 16 of the body 12 and fluid flow therethrough prevented.
In the embodiment shown in the drawing, the closed end 26 is provided with a restrictive or secondary flow orifice 28 therethrough. This will permit the flow of a predetermined quantity of fluid across the valve even though the transverse openings 24 are completely covered by the bore 16 of the body 12. Upon alleviation of the excessive flow, the pressure force on the closed end 26 of the piston member 20 will fall below the returning force of the spring 32 and the piston member 20 will return to its fully opened position.
The use of a thin wall tubular piston member and radially extending flow control orifices therein greatly simplifies the valving structure required to regulate flow across the valve. in fact, no valve seat is required. Flow regulation is accomplished in a very simple and direct manner using the internal bore 16 of the body 12 to regulate flow through the openings 24 in the piston member 20 as the piston member moves to the right in response to excessive fluid flow. Further, the use of a tubular piston permits accurate control over the inertia of the piston and permits rapid and precise control of fluid flow by use of a relatively low mass piston member.
Further, the use of a tubular piston member having radial openings therein permits a greatly simplified regulation of flow of the type desired in the hydraulic fuse because movement of the piston member 20 toward the right in the drawing in response to an excessive flow may be used to immediately close portions of the openings 24 so that the pressure drop across the piston member increases even further thereby tending to move the piston member 20 against the force of a spring 32 to a fully closed position more rapidly and positively than could be expected in the prior art devices without complex machining operations having been performed on the piston members of the prior art devices.
The use of a thin walled cylindrical piston member furtherfacilitates the provision of a flow path through the piston which is most nearly compatible with the other flow areas in the hydraulic system thereby reducing or minimizing the pressure drop in the hydraulic system due to the hydraulic fuse l and thus increasing the efficiency of operation of the hydraulic system over hydraulic systems using prior art hydraulic fuses. The flow areas across the pistons of the prior art devices are inherently limited by the structure used. It is possible by the use of the concept of the present invention of providing a cylindrical thin walled tube as the piston member to obtain a flow area across the piston greater than that possible in operable axial piston type hydraulic fuses such as those known in the prior art. This is extremely important because a hydraulic fuse must provide minimum restriction to flow during normal operation in order to preserve efficiency of the hydraulic system. On the other hand, the fuse must provide some restriction to excessive flow in order to create the pressure drop necessary to actuate the fuse.
A further advantage of a relatively thin walled tubular piston member is that any change in momentum of the hydraulic fluid occurring across the piston due to a restriction in flow occurs transversely to the axis of piston movement and therefore has no effect on operation of the hydraulic fuse.
I now claim:
1. A hydraulic fuse comprising:
a body member having a circular bore defining a fluid flow path therethrough,
a thin-walled tubular cylindrical piston member loosely received within said bore for sliding movement relative thereto between a first position and a second position, i
said tubular piston member being open at the downstream end thereof and closed at the upstream end and having an opening in a radial wall portion thereof adjacent said closed end,
said radial wall portion extending beyond said bore to provide a flow path through the fuse which is radial to said tubular piston at said opening in a radial wall adjacent the upstream end thereof and axial to said piston at the downstream end thereof,
said radial wall portion cooperating with said bore to reduce the area of the flow path through the fuse when the piston moves from said first position toward said second position, and
means providing a predetermined biasing force between the body and the piston urging the piston toward said first position whereby a fluid flow rate beyond a preselected level in the direction from said first position toward said second position will move the piston to said second position thereby closing off said flow path.
2. The hydraulic fuse of claim 1 wherein said body member has a counterbore axially disposed at one end of said bore, and said radial wall portion extends into said counterbore;
3. The hydraulic fuse of claim 1 wherein said body member has a counterbore axially disposed at each end of said bore, said tubular piston member has a flange at one end thereof and said biasing means comprises a spring engaging said flange, one of said counterbores cooperating with said radial wall portion of said tubular member to define a portion of the flow path through the fuse, while the other of said counterbores provides a housing for said spring and said flange and means for said spring to act against to bias said flange and said piston to said first position.
4. The fuse of claim 1 wherein said tubular piston member has a secondary flow opening in the closed end thereof providing a leakage flow path through the fuse when said piston is in said second position.
5. The fuse of claim 1 wherein the area of the opening in the radial surface is substantially equai to the area defined by the internal wall of the tubular piston.
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