Seal for a joint or juncture – Seal between relatively movable parts – Piston ring or piston ring expander or seat therefor
Reexamination Certificate
1999-07-27
2001-07-03
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Piston ring or piston ring expander or seat therefor
C277S437000, C277S460000, C277S502000, C277S578000
Reexamination Certificate
active
06254103
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a seal, and in particular to a seal capable of withstanding high pressures and suitable for use in the fuel supply system for a compression ignition internal combustion engine.
BACKGROUND OF THE INVENTION
In the fuel system for a compression ignition internal combustion engine, very high fuel pressures are commonly encountered. For example, in a fuel system of the common rail type, the fuel pressure within the common rail may be around 2000 bar. Clearly, in order to achieve such a pressure, and in order to optimise efficiency it is important to restrict leakage from the various parts of the fuel system, for example the fuel pump and the fuel injectors, to a very low level. In particular, at such high pressures, the fuel pressure within bores formed in the components used in the fuel system may dilate and as a result, the clearance between the walls of the bores and any members slidable within the bores may increase giving rise to increased leakage.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a seal suitable for use in a variety of fuel system applications whereby leakage of fuel can be restricted to an acceptable level even when the fuel system is to be operated at high fuel pressures.
According to the present invention there is provided a seal comprising a support member having an outer periphery of substantially circular form, and a resilient seal member mounted upon the support member, the seal member, when occupying a relaxed condition, having an outer periphery of generally circular form and a diameter greater than that of the support member, the seal member and support member being eccentric to one another when the seal member occupies the relaxed condition, the seal member being compressible towards a compressed condition in which the seal member and the support member are of substantially equal diameter and are substantially coaxial.
The seal member may include a region of split ring like form.
The seal may further include a cover member, the seal member being located between the support member and the cover member.
According to another aspect of the invention there is provided a high pressure fuel pump comprising a pumping plunger reciprocable within a bore under the influence of a cam arrangement, and a seal of the type defined hereinbefore carried by the pumping plunger, the seal member of the seal engaging the wall of the bore, the seal being arranged to substantially prevent fuel from flowing between the pumping plunger and the wall of the bore when the pumping plunger moves in a first direction.
According to a further aspect of the invention there is provided a fuel injector comprising a valve needle slidable within a bore, a surface associated with the needle being subject to the fluid pressure within a control chamber defined, in part, by a piston slidable within a bore, and a seal of the type defined hereinbefore associated with the piston to restrict the escape of fluid from the control chamber between the piston and the bore within which the piston is slidable.
According to another aspect of the invention there is provided a fuel injector comprising a valve needle slidable within a bore, the needle carrying a seal of the type defined hereinbefore located so as to restrict leakage between the needle and the wall of the bore.
Where the injector is of the outwardly opening type, an additional seal of the type defined hereinbefore may be provided.
In each of the applications described hereinbefore, the use of the seal is advantageous in that leakage of fuel or another fluid at high pressure can be restricted to an acceptable level. The resilience of the seal member is sufficient to ensure that leakage is restricted to an acceptable level even if dilation of the bore within which the seal is located occurs, in use. It will further be appreciated that by using such a separate seal, components slidable within bores, in use, do not need to be machined to the same level of accuracy as in prior, arrangements in which the fit of the components within the bores governs the level of leakage.
According to another aspect of the invention there is provided a method of manufacturing a seal comprising the steps of securing a seal member having a substantially circular periphery to a support member having a substantially circular periphery such that the seal and support members are substantially coaxial, and deforming the seal member to increase its diameter such that the seal member is eccentric to the support member after deformation.
A step of grinding the seal may be performed prior to the step of deforming the seal member.
The seal member may be provided with an arcuate slot, the step of deforming the seal member including the step of fracturing the seal member radially outwardly of the slot. This may be achieved by applying fluid under pressure to the slot.
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Knight Anthony
Lucas Industries
Michael & Best & Friedrich LLP
Pickard Alison K.
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