PRESSURE RELIEF VALVE

Abstract: A pressure relief valve for air or other gases is provided in a first chamber (2a, 2b) which is positioned intermediate a second chamber (12) having a higher air or gas excessive pressure, and a third chamber (22) having a lower excessive pressure than the air pressure in the second chamber (12). Through the first chamber (2a, 2b) extends a connection rod (1) which is displaceable in its lengthwise extension and which is provided with a first sealing means (3) which is arranged, when affected by the pressure inside the first chamber (2a, 2b) and against the action of a spring (6), to move the connection rod (1) in one of the directions of displacement of the latter. On the connection rod (1) is also mounted a second sealing means (9) which is arranged upon displacement of the connection rod (1) in said direction, to close a passage (7) formed in the first chamber (2a, 2b).

Description: Pressure Relief Valve The subject invention concerns a pressure relief valve for air or other gases, which valve is arranged inside a first chamber which is positioned intermediate a second chamber having an excessive air or gas pressure, and a third chamber having an excessive pressure which is lower than the excessive pressure inside the second chamber. Within various technological fields highly pressurized air or gas contained in a pressure tank must be transferred to a chamber from which the air or gas is discharged periodically via a discharge valve to initiate operations of various kinds. The insertion of a simple transition valve between the pressure tank and said chamber could be disadvantageous inasmuch as it forces the discharge valve inside the chamber to operate at highly varying pressures inside the chamber. The work to be effected by the pressure surges resulting from the opening of the discharge valve could to a large extent be impaired by such pressure variations. The subject invention provides a pressure relief valve wherein the deficiencies outlined above have been eliminated. The characteristic features of this pressure relief valve appear from the appended claims. The invention will be described in closer detail in the following with reference to the accompanying drawing, which is a vertical longitudinal sectional view through the pressure relief valve as well as through a second valve cooperating with the pressure relief valve and designed for a particular application. The basic component of the pressure relief valve is a connection rod 1 which is arranged for lengthwise displacement to and through a first chamber which is divided into two intercommunicating spaces 2a and 2b. Integrally secured to the connection rod inside the space 2b is a flanged seal 3 which upon an excessive pressure inside the chamber 2a, 2b tends to move to the right relative to the drawing figure together with the connection rod 1. The connection rod 1 passes through a washer 4 dividing the chamber into the two spaces 2a and 2b but which does not prevent the propagation of excessive pressure from one space to the other. A compression spring 6 is inserted between said washer 4 which serves as an abutment surface and a body 5 which is integrally secured on the connection rod 1, said compression spring biasing the connection rod 1 towards the left relative to the drawing figure. A narrower section la on the connection rod 1 projects through a passage 7 of slightly larger diameter dimension than said narrower section and into an ante-chamber 8 positioned externally of the first chamber 2a, 2b. A second seal 9 is positioned in this area, said seal serving to close the passage upon displacements of the connection rod to the right relative to the drawing figure. An inlet pipe 10 is positioned at the mouth of said ante-chamber 8, said inlet pipe 10 betrrg formed with a number of narrow channels. The significance of this inlet pipe 10 will be explained in further detail in the following. Preferably, the pipe 10 is a piece of cane. In order to explain the mode of operation and function of the pressure relief valve in accordance with the invention the latter is illustrated in the drawing figure when applied in an air gun to which reference is made herein only as far as some functionally essential components are concerned. The gun has a cartridge 11 containing compressed air. The cartridge is sealingly screw- hreaded into the gun body with the pressure relief valve inserted in the cartridge, and it also comprises a second chamber 12 in which air is compressed to a hig pressure, e.g. 1500 N. When the threaded cartridge 11 is screwed in position the free end of the connection rod 1 projects into abutment against one end of a lever 13. This lever 13 is articulated for pivotal movement about a pivot shaft 14 and a tension spring 15 is attached to the lever end opposite to the connection rod. A catch arm 17 which is pivotably mounted on an articulation shaft 16 is positioned- below the lever 13 with the catch arm end proximate to the lever 13 resting on a roller 18. The latter is actuated by the gun trigger mechanism which is of conventional construction and therefore has been omitted from the drawings in order not to unnecessarily clutter the latter. The catch arm 17 cooperates with a hammer 19 which is mounted for rotational movement about a shaft from a biased position (loading position) to a firing position which is the one illustrated in the drawing figure. Upon firing, the hammer 19 hits a firing valve 21 which opens a passage from a third pressure chamber 22 in communication with the first pressure chamber 2a, 2b via an outlet 23 into the pipe 24 of the gun barrel. A spring 25 which is inserted in the chamber 22 rapidly closes the firing valve 21. Any bullet present inside the pipe 24 therefore will be shot rapidly out of the pipe by the brief pressure surge which was generated during the moment that the firing valve 21 was in open condition. As mentioned in the aforegoing, the initial pressure inside the chamber 12 is assumed to be about 1500 N. Preferably, the pressure inside the chamber 22 is about 70 N. When a shot is fired, the pressure inside the chamber 22 drops. Consequently, also the pressure inside chamber 2a, 2b goes down. The compression spring 6 is dimensioned in such a manner that in this position it is able to act upon the flanged seal 3 and thus will displace the connection rod 1 somewhat towards the left relative to the drawing figure. This causes the seal 9 to open the passage 7 and air which is pressurised to a high excessive pressure inside the chamber 12 is forced through the inlet pipe 10 and the ante-chamber 8 and into the chamber 2a, 2b and upwards into the chamber 22. The inlet pipe 10 which is made from cane and, as mentioned before, is in the form of a number of minute channels rather than one big tubular passage, makes the air flow into the chamber 2a, 2b at a comparatively slow pace despite the considerable pressure differential. Consequently, no strong pressure surge is generated. In addition, the fine-bore channel configuration of the inlet pipe 10 has a cleaning effect on the air and ' -prevents any dust or dirt particles from being entrained in the air and impair the sealing efficiency of the valves. The narrow passage 7 also assists in preventing too rapid intake of air into the chamber 2a, 2b. When the pressure rises inside the chamber 2a, 2b the air forces the flanged seal 3 and consequently the connection rod 1 to the right relative to the drawing figure against the action of the compression spring 6 until the seal 9 again closes the passage 7. The connection rod 1 also presses against the lever 13, pivoting the latter clockwise relative to the drawing figure against the action of tension spring 15. Thanks to the operation of the pressure relief valve in accordance with the invention as described above the pressure inside the chamber 22 will be maintained at the same level prior to each firing in the course of a series of firings, with the result that the firing valve 21 will operate in an exactly identical manner upon each firing and consequently each bullet will behave in exactly the same manner. This assists in the obtainment of precise target results. When the pressure inside the chamber 12 sinks to a considerably lower level after the firing of a large number of shots, the pressure rel ef valve can .no longer build up the desired high pressure inside the chamber 22. Instead, the compression spring 6 is allowed to force the connection rod 1 somewhat further to the left relative to the figure. Consequently, the tension spring 15 is allowed to pivot the lever 13 to a position in which the lower end thereof will be positioned directly above the inner end of the catch arm 17. In this position, the catch arm 17 cannot pivot into position behind the lever 13 and consequently firing can no longer take place. How far down one wishes to allow the pressure to sink inside the chamber 12 before the device is locked against further firing is determined by the strength of the spring 6 of the pressure relief valve. By giving the spring sufficient strength, it is thus ensured that the device is secured against firing when the pressure inside the chamber 12 still is comparatively high, in order to maintain even air gun performance in the, course of a series of firings. The pressure relief valve in accordance with the invention could of course be applied in other technological fields within the scope of the appended claims, and it could also be designed differently from the embodiment illustrated in the drawing figure and described herein.

Claims: CLAIMS 1. A pressure relief valve for air or other gases, which valve is arranged inside a first chamber (2a, 2b) which is positioned intermediate a second chamber having an excessive air or gas pressure and a third chamber (22) having an excessive pressure which is lower than the excessive pressure inside the second chamber (12), c h a r- a c t e r i z e d t h e r e i n that a lengthwise displaceable connection rod (1) extends through the first chamber (2a, 2b) and supports thereon a first seal (3) which is affected by the pressure inside the first chamber (2a, 2b) and tends to displace the connection rod (1) in one of its directions of displacement, a spring means (6) which is inserted between an abutment face (4) and a body (5) which is integrally secured to the connection rod (1), said spring (6) biasing the connection rod (1) in the opposite direction, and a second seal (9 which is mounted on the connection rod (1) and which is arranged, upon displacement of the connection rod (1) in the first direction, to clos a passage (7) formed in said first chamber (2a, 2b). 2. A pressure relief valve as claimed in claim ^ c h a r a c¬ t e r i z e d t h e r e i n that the dimensions of the passage (7) in the first chamber (2a, 2b) only slightly exceeds the width of the connection rod (1) in this area. 3. A pressure relief valve as claimed in claim 1, wherein the second seal (9) is positioned in an ante-chamber (8) associated with the first chamber (2a, 2b), c h a r a c t e r i z e d t h e r e i n that in the inlet of said ante-chamber (8) from the second chamber (12 is arranged an inlet pipe (10) formed with a plurality of minute channels.

Inventors: OLOFSSON SIGFRID MARENIUS, OLOFSSON, SIGFRID, MARENIUS
Applicants: PERSIMA INVENT AB
Application year: 1990
Main classification: F16K15
IPC codes: F41B11