Fluid handling – Destructible or deformable element controlled – Destructible element
Reexamination Certificate
1997-10-16
2001-11-13
Rivell, John (Department: 3407)
Fluid handling
Destructible or deformable element controlled
Destructible element
C137S625260, C244S1220AF
Reexamination Certificate
active
06314982
ABSTRACT:
This invention relates to a link apparatus capable of accommodating relative extension and/or retraction, and defining a fluid passage.
In existing examples of such apparatus, extension or retraction of the apparatus may displace fluid into or out of the apparatus with a possible increase or decrease in fluid pressure. This can cause difficulties as the variation in pressure and/or fluid displacement may have undesirable effects elsewhere in the system. For example, if the link is in a fluid logic circuit, the variation in fluid pressure due to extension or retraction may be misinterpreted as a pressure signalling pulse. Whilst there are many different applications for such apparatus, a particular application of interest to the applicants is the telescopic “trombone” unit which extends between an ejector seat and the airframe in a military aircraft. This unit is required to transmit a signal in the form of a pressure pulse or a shock wave from the seat to a canopy jettison unit during an emergency ejection procedure. In normal operation the unit must accommodate limited extension and retraction movement due to relative movement, e.g. due to differential thermal expansion etc, but this must not produce anything that might be seen as a pressure pulse, otherwise there could be disastrous consequences.
Accordingly, this invention provides a fluid link apparatus capable of extension and/or retraction, and comprising a body element and a piston means housed at least partially within said body element and slidably moveable along an extension/retraction axis, the body element and the piston element each having a fluid inlet/outlet port, and the apparatus including fluid passage means connecting said inlet/outlet ports, said passage means being configured so that the net displacement of fluid between said inlet port and said outlet port upon extension or retraction within pre-set limits is nil or relatively low.
Preferably, said body element includes two seal regions which seal against the piston element at longitudinally spaced locations and allow sliding movement of said piston element, and define between them a confined volume.
The piston element preferably includes a generally longitudinal bore extending from its distal end and terminated by at least one generally transverse bore opening into a region of said body element between said two seal regions.
The piston means conveniently includes a collar element arranged to cooperate with said seal regions to limit routine extension and/or retraction movement of the piston means, and the collar element may be releasably attached to said piston means by a frangible connection to allow removal thereof and to allow separation of said piston element and said body element.
The piston means is advantageously movable into a position in which the portion of the passage leading from the piston inlet/outlet port is blocked, but the portion of the passage leading from the body inlet/outlet port is vented to the exterior of the body element.
The piston means and said body element may each include attachment means for attachment to a respective structural component, for example an ejector seat and the airframe in an aircraft, respectively.
In one embodiment, said inlet/outlet ports extend generally perpendicularly, whilst in another said inlet/outlet ports are generally in-line.
Whilst the invention has been described above it extends to any inventive combination of the features set out above, or in the following description or claims.
REFERENCES:
patent: 789971 (1905-05-01), Harrington
patent: 3466062 (1969-09-01), Deplante
patent: 3473557 (1969-10-01), Loe
patent: 3608584 (1971-09-01), Vaughn
patent: 4613101 (1986-09-01), Herndon
patent: 5261454 (1993-11-01), Pavlica et al.
patent: 5370522 (1994-12-01), Lindner
BAE Systems plc
Pillsbury & Winthrop LLP
Rivell John
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