NORMALLY CLOSED FLUID SWITCHING LOGIC ELEMENT

Abstract: A normally closed fluid switching logic elements has a plurality of radial ports (36) to a first chamber (34). A poppet (22), connected to a piston (14) within the element, moves between an open position off its poppet seat (24) and a closed position. In the open position another port is provided to the first chamber permitting fluid flow. The poppet (22) is biased to the closed position by a spring (26), but also by fluid pressure at either or both ports. The poppet (22) may be displaced only by a pressure in a second chamber (30) behind the piston (14). In one configuration this opening pressure is provided from an external source. In other configurations, the opening pressure is derived from the first chamber, from the pressure outside the poppet (22) and from either of these.

Description: -1- Description NORMALLY CLOSED FLUID SWITCHING LOGIC ELEMENT Technical Field This invention relates generally to a fluid valve and more particularly to a switching logic element having a normally closed characteristic. Switching logic elements utilize an unbalanced poppet which is spring loaded on a seat; however, without additional fluid pressure to bias the poppet against the seat, flow can occur between the input and output ports. These valves are called "normally open" because of the need for fluid pressure to close them. The complementary logic element - normally closed - has not previously been available. Such a normally closed logic element would require a positive or pilot pressure input to be opened and to remain open. The need for a pilot pressure is an operating requirement for fail safe applications, i.e. if the source of fluid pressure is cut off either inadvertently or because of system shut down, the valve should close to prevent loss of load supporting pressure by flow through the logic element. Background Art Prior art, U.S. Patent No. 2,799,466, discloses a valve held in its closed position by spring and hydraulic pressure until an electrically operated valve opens relieving the hydraulic pressure. Prior art, U.S. Patent No. 3,076,630, discloses a valve held in its closed position by spring and hydraulic pressure until a solenoid is actuated to relieve the hydraulic pressure. Prior art, U.S. Patent No. 3,083,727, discloses a valve held in its closed position by spring and hydraulic pressure until an abrupt pressure increase at the valve inlet causes it to open because the pressure holding it closed does not rise as quickly. Prior art, U.S. Patent No. 3,858,841, discloses a valve held in the closed position by inlet pressure ducted above the valve until a solenoid is energized to relieve this closing pressure. Prior art, U.S. Patent No. 3,903,919, discloses a valve which has a normally closed configuration. The valve is held closed by spring and hydraulic pressure until a solenoid and is energized to relieve the hydraulic pressure. Prior art, U.S. Patent No. 4,283,040, discloses a valve which will remain open while a solenoid is energized. When the solenoid is de-energized, hydraulic pressure increases behind the valve causing it to close. Prior art, U.S. Patent No. 4,305,566, discloses a normally open valve which has a two-stage operation. A solenoid causes the first stage to close which results in a hydraulic pressure rise which, together with spring force, closes the valve. Prior art, .U.S. Patent No. 4,463,929, discloses a valve held closed by spring and hydraulic pressure. In one mode of operation, an abrupt increase in inlet pressure will cause the valve to open because of the lag for the closing hydraulic pressure to rise. Disclosure of Invention A fluid logic element has a main fluid flow path between a central port having a poppet and seat closure, and a plurality of radial ports. The poppet is biased against the seat, not only by a spring, but also by fluid pressure applied at either or both ports. The poppet can be removed off its seat only by the application of fluid pressure in a chamber behind a piston connected to the poppet. This opening fluid pressure or pilot signal may be applied from a third port through the logic element body to the chamber from an independent third source, or derived through an orifice from the pressure at the radial ports or the central port by configuration modifications. When the opening pressure is derived from pressure at the radial ports or central port, it can be overridden by venting the chamber behind the piston through the third port which will cause the valve to close. A manual override configuration is also presented. Brief Description of Drawings Figure 1 is a cross-section of a normally closed fluid switching logic element in accordance with the invention; Figure 2 is a detail of an end view of the logic element of Figure 1; Figure 3 is an alternate embodiment in cross-section having the pilot pressure derived from the pressure applied at the central port; Figure 4 is an alternative embodiment in cross-section having the pilot pressure derived from the pressure applied at the radial ports; and Figure 5 is an alternate * embodiment in cross-section having a manual over-ride feature and a structure i which pilot pressure is derived from either radial ports or the central port. Best Mode for Carrying Out the Invention Referring to Figure 1, a normally closed fluid switching logic element will now be described. Although the specific configuration shown in Figure 1 and other configurations d scribed herein were designed and built for operation with hydraulic liquid, it should be recognized that other liquid or gas switching logic elements are also contemplated. Body 10 has a longitudinally extending bore 12.in which piston 14 is slidably supported. Body 10 has secured to it, by wire loop 16, extension 18. Wire loop 16 is used as the fastening device only by way of example, other fastening arrangements may also be used. Piston 14 has secured to it, e.g. by screw threads, extension 20 which includes poppet 22. In the position shown in Figure 1, poppet 22 is held against seat 24 ofj extension 18 by spring 26. One end of spring 26 bears against shoulder 28 of extension 18, while the other end of spring 26 bears against one side of piston 14. Piston 14, and poppet 22, are consequently biased to force poppet 22 against seat 24 (to the left in Figure 1). In the configuration illustrated in Figure 1, body 10 and one side of piston 14 to form a variable volume chamber 30 with port 32 providing the only fluid passage to chamber 30. On the other side of piston 14 is variable volume chamber 34 which has a plurality of radially extending ports 36 through extension 18. Ports 36 are primary fluid ports. Poppet 22, when moved away from seat 24 (to the right in Figure 1), provides a cental port which is also a primary port communicating with chamber 34. Thus fluid will flow from radial ports 36 to the central port when poppet 22 is unseated, or will flow in the reverse direction depending on which pressure is higher. As is customary with fluid handling elements, O-ring 37, positioned between shoulders 38 and 40 provides a seal , between variable volume chambers 30 and 34. It will be observed that fluid pressure applied to the outer side of popped 22 will tend to force it against seat 24 rather than tend to open it. Also, fluid pressure within variable volume chamber 34 will also tend to force poppet 22 against seat 24 because of the greater area of piston 14 exposed to this pressure when compared with the area of poppet 22 exposed to this pressure. Thus logic element closing forces will be exerted by both these pressures and spring pressure. It will be appreciated by those skilled in the art that these forces can be modified by changing differential areas and springs. Also, it will be recognized that friction forces which must be overcome may be significant due to the close fits and seals used to prevent leakage, although some currently available seal elements may reduce friction to a negligible force. The logic element of Figure 1 can only be opened by -5- applying fluid pressure in variable volume chamber 30 through port 32 of an amount sizable enough to overcome the closing forces discussed above. Moreover, if this opening pressure drops, poppet 22 will reseat, thereby preventing fluid from moving between ports 36 and the central poppet port. The normally closed fluid switching logic element of Figure 1 and the alternate configurations still to be described, have exterior body configurations which facilitate their mounting within a manifold to thereby become components in a fluid circuit. The operating modes and principles are equally applicable to other uses which may require different exterior body configurations. Since these exterior body feature are not part of the present invention and are similar or identical to those skilled in the art, no detailed discussion of these will be presented. O-rings 42, which may be supplemented by additional seals such as sacrificial seals, are located at positions where sealing is required with shoulders adjacent to them to restrict axial movement. Threads 44 have been provided for mounting as mentioned above. Referring to Figure 2, the outer circumference of poppet 22 (which can be seen in Figure 1 to extend axially for a short distance) is guided and supported when it moves outwardly off its seat on lands 23 which are interspaced with axially extending grooves 25. This arrangement provides free flow of fluid through the central port while still maintaining poppet 22 in correct alignment. Referring now to Figure 3, an alternate embodiment of the normally closed fluid switching logic element of Figure 1 will be described. Body 10 and its extension 18 remain t he same as in Figure 1. Passage 46, however, is provided in this embodiment between cavity 48 (which extends from variable volume chamber 30) and the central opening in poppet 22. Orifice 50 is located in passage 46 to produce a pressure drop so that the pressure in chamber 30 will be somewhat less than the pressure outside poppet 22. With -6- passage 32 closed and the pressure outside poppet 22 rising, a pressure will be reached which will cause piston 14 to move and poppet 22 to open. Thus the pressure outside poppet 22 provides the pilot signal or pressure to open the poppet port. When passage 32 is opened the fluid in chamber is vented and poppet 22 will close. Figure 4, is an alternate embodiment of the normally closed fluid switching logic element of Figure 1 with the pilot signal in this case derived from the pressure in variable chamber 34. The only change from the Figure 1 embodiment is the addition of passage 52 containing orifice 53 which extends between cavity 48 and variable volume chamber 34. The figure 4 embodiment provides a logic element which remains closed until the pressure in variable volume chamber 34 rises high enough so that the resulting pressure in variable volume chamber 30 causes poppet 22 ' to open. This pressure will rise only if passage 32 is closed, and poppet 22 will reclose if passage 32 is opened to relieve the pressure in chamber 30. Figure 5 discloses additional features which can be used with the basic normally closed fluid switching logic element of Figure 1 to provide other capabilities. Element body 60 has secured to it extension 62 using wire loop 64 (the use of a wire loop is only exemplary of one way in which they may be secured). Body 60 has a longitudinally extending bore 66 in which piston 68 is slidably supported. Also contained in bore 66 is manual adjusting base 67 which can be screwed in by loostening lock nut 69 and turning threaded end 71 to move from the position shown in Figure 4 to a position in which it will force piston 68 to the right (as shown in Figure 4). As with the previous embodiments, piston 68 is connected to poppet 70, so that moving piston 68 to the right.will unseat poppet 70 and open the element for flow between radial ports 72 and the central port about the periphery of poppet 70. (An intermediate element 73 is illustrated which is secured between piston 68 an poppet 70, in this example by threads. Element 73 is fabricated as a I -7- separate item for facilitating manufacturing, but the element functions as if piston 68 and poppet 70 were the same piece.) This manual adjusting feature over-rides the normal need for a fluid pressure signal in chamber 74 before fluid will flow through the element; however, the manual over-ride may also be used to create only a slight flow, with a pressure signal to chamber 74 causing full opening of the central port by displacement of poppet 70. The Figure 5 embodiment also incorporates two tortuous passages to chamber 74. One passage 76 extends centrally from the bore through poppet 70 to chamber 78 which contains ball 80. Chamber 78 is connected by passage 82 to chamber 74. Another passage 84 extends from variable chamber 86 to chamber 78. Ball 80 will assume a position to block either passage 76 or passage 84 in favor of the passage having the higher fluid pressure. As a consequence, a pilot signal to open poppet 70 may be derived from fluid pressure at poppet 70 or at ports 72. All of the embodiments of the invention provide a normally closed fluid switching logic element which will interrupt fluid flow between two ports unless a pilot pressure signal of sufficient magnitude is provided to open the fluid passage. Although normally closed fluid switching logic elements in accordance with the invention have been illustrated and described, it will be evident that changes and modifications can be made without departing from the spirit of the invention and the scope of the appended claims.

Claims: Claims A normally closed fluid switching logic element comprising: a body having a bore therein and a poppet seat at one end of said bore; piston means slidably supported in said bore separating said bore into; a first variable volume chamber on one side of said piston; a second variable volume chamber on the other side of said piston; a poppet connected to said piston through said poppet seat and having a closed position in which it is against said seat and having an open position in which it is displaced from said seat; biasing means tending to force said poppet to its closed position; the open position of said poppet forming a first fluid port connected to said first variable volume chamber; a second fluid port connected to said first variable volume chamber; and a third fluid port connected to said second variable volume chamber. A normally closed fluid switching logic element in accordance with claim 1, wherein: said biasing means is a spring. A normally closed fluid switching logic element in accordance with claim 1, further including: a passage from said second variable volume chamber through said poppet; and said passage includes an orifice. A normally closed fluid switching logic element in accordance with claim 1, further including: a passage from said first variable volume chamber to - - said second variable volume chamber; and said passage includes an orifice. 5. A normally closed fluid switching logic element in accordance with claim 1, further including a passage from said second variable volume chamber through said poppet; a passage from said second variable volume chamber to said first variable volume chamber; and means closing one of said passages in response to opening of the other. 6. A normally closed fluid switching logic element in accordance with claim 5, wherein: said passages connect with a common chamber; and said means closing one of said passages in response to opening of the other is a ball in said common chamber. 7. A normally closed fluid switching logic element in accordance with claim 5, further including: adjustable means mounted in said body for moving said poppet a desired distance off said poppet seat. « 8. A normally closed fluid switching logic element in accordance with claim 6, wherein: said piston means includes a piston member, an intermediate member and an extension on which said poppet is located. 9. A normally closed fluid switching logic element comprising: a body having a passage therein extending axially from one end ; a poppet seat at said one end of said passage; piston means slidably supported in said passage separating said passage into first and second chambers; a first port into said first chamber provided by said passage through said poppet seat; a second port extending radially into said first chamber; a poppet connected to said piston through said poppet seat and having a closed position in which it is -10- against said poppet seat and an open position in which it is displaced from said seat; piston and poppet areas exposed in said first chamber with said poppet in its closed position being such that fluid pressure applied within said first chamber tends to keep said poppet in its closed position; biasing means tending to force said poppet to its closed position; and a third port connected to said second chamber whereby fluid pressure may be applied to a piston area to displace said poppet from its seat. 10. A normally closed fluid switching logic element in accordance with claim 9, further including: a passage from said second chamber through said poppet; and; said passage includes an orifice . 11. A norma l ly c los ed fluid switching logic e lement in accordance with claim 9 , further including : a passage from said first chamber to said second chamber; and said passage includes an orifice. 12. A normally closed fluid switching logic element in accordance with claim 9, further including: a passage from said second chamber through said poppet; a passage from said second chamber to said first chamber; and means closing one of said passages in response to opening of the other. 13. A normally closed fluid switching logic element comprising: a body having a bore therein extending from one end; a body extension secured to said body near said one end; said body extension having a poppet seat formed therein and a plurality of lands and grooves extending outwardly from said seat; piston means slidably supported in said bore forming a first chamber on one side of said piston means and a second chamber on the other side of said piston means; a piston extension secured to said piston means and having a poppet on the end thereof slidably mounted on said lands; said poppet having a closed position in which it is against said poppet seat and an open position in which it is displaced from said seat; a first port into said first chamber provided through said poppet seat when said poppet is in its open position; a plurality of second ports extending radially into said first chamber; biasing means tending to force said poppet to its closed position; and a third port connected to said second chamber whereby fluid pressure may be applied to piston area to displace said poppet from its seat. 14. A normally closed fluid switching logic element in accordance with claim 13 further including: threads on the exterior of said body to secure it in a receptacle. 15. A normally closed fluid switching logic element in accordance with claim 13 further including: a passage from said second chamber through said poppet; and said passage including an orifice . - 16. A norma l ly c lo s ed f luid sw it ching logi c e l ement in accordance with claim 13 further including : a passage from said first chamber to said second chamber; and said passage including an orifice. 17. A normally closed fluid switching logic element in accordance with claim 13 further including: a passage from said second chamber through said poppet: a passage from said second chamber to said first chamber; and I -12- eans closing one of said passages in response to opening of the other. 18. A normally closed fluid switching logic element in accordance with claim 17, wherein: said passages connect with a common chamber; and said means closing one of said passages in response to opening of the other is a ball in said common chamber.

Inventors: CLARK RICHARD J, CLARK, RICHARD, J.
Applicants: CLARK RICHARD J, SUN HYDRAULICS CORP, CLARK, RICHARD, J., SUN HYDRAULICS CORPORATION
Application year: 1986
Main classification: F16K31
IPC codes: F16K31