Pumps – Expansible chamber type – Biasing means effects induction stroke of abutment driven,...
Reexamination Certificate
1999-07-02
2001-04-17
Freay, Charles G. (Department: 3746)
Pumps
Expansible chamber type
Biasing means effects induction stroke of abutment driven,...
C123S495000, C092S153000
Reexamination Certificate
active
06217299
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to an integrated pump and tappet unit for a fuel feeding system of an internal combustion engine.
Large diesel engines refer here to such engines that are applicable for instance for main propulsion engines or auxiliary engines for ships or for power plants for production of heat and/or electricity.
In order to accomplish fuel injection under high pressure into a cylinder of an engine a high pressure pump is needed as well as phasing of the operation of the pump according to the operating cycle of the cylinder, which can be accomplished by means of a tappet member controlled by a cam shaft or the like member of the engine. In so-called common pressure or common rail systems and their applications this kind of phasing is not necessary, but nevertheless the operation of the pump may be controlled by means of corresponding members. In accordance with known techniques the pump and the tappet are arranged to be entirely separate units. In this case a separate lubrication is arranged for the pump, whereby fuel, especially heavy oil utilized in modern engines, cannot enter the tappet unit, in which it could be mixed with the lubrication oil. The pump and tappet then each need, however, a body of their own, which increases the manufacturing costs and requires more space.
It is further known to connect the pump and the tappet to each other, which makes the construction simpler and decreases the manufacturing costs. However, in known solutions in which the pump and tappet are connected together, mixing of the fuel with the lubrication oil is possible, as a consequence of which the quality of the lubrication oil decreases and affects the whole circulation of lubricant. This may result in the pump and the tappet becoming stuck and may even result in damage of various kinds to the bearings, including the crank shaft bearings.
SUMMARY OF THE INVENTION
An aim of the invention is to provide an improved pump and tappet unit, with which the advantages of integration can be achieved but from which the drawbacks of the known solutions can be eliminated. A further aim is to create a solution which is applicable to high pressure feeding of fuel and which may easily be connected as part of a fuel feeding system in which a pressure accumulator unit common to at least two cylinders of an engine is utilized and in which the fuel is first pumped under low pressure from a fuel tank into the system.
In accordance with the invention the pump and tappet body comprises a one-piece casting and the tappet member and the piston member are connected to each other by means of a tappet arm which passes sealingly through a flange member fixed to the body so that entry of fuel from the fuel chamber to the side of the tappet member is prevented. When the members required for both the pumping and tappet functions are arranged inside of such a one-piece pump and tappet body, a simple and cost effective solution can be accomplished.
A one-piece casting, as opposed to an assembly of multiple pieces, is essentially homogeneous. Use of a one-piece casting for the pump and tappet body is advantageous because the one-piece casting is simple and inexpensive to construct and manufacture, and avoids certain disadvantages associated with manufacturing the body from multiple pieces, such as the presence of joints through which fuel can leak and the cost of assembly.
The flange member is with advantage provided with a duct for leading lubrication oil into a lubricator groove abutting the tappet arm. By further providing the flange member with a sealing ring, which is located between the lubricator groove and the fuel chamber, mixing of fuel and lubrication oil, with harmful results for the operation of the unit, can effectively be prevented. The body may further include a chamber located between the flange member and the piston member for collecting possible fuel leaked from the fuel chamber. When the collecting chamber is provided with a drain duct the space above the flange member remains de-pressurized, which is advantageous for the sealing arrangement in the flange member and hereby assists in fulfilling the aims of the invention.
The fuel chamber is with advantage connected through a non-return valve to a low pressure fuel line included in the fuel feeding system for leading fuel from a fuel tank into the fuel chamber. In addition the low pressure fuel line is provided with a control valve upstream of the non-return valve. In this way, the arrangement according to the invention can with advantage form a part of a fuel feeding system, in which the feeding of fuel from a fuel tank into the cylinders of an engine occurs through both a low pressure part and a high pressure part of the feeding system.
The body with advantage includes a pipe element or structure, through which the low pressure fuel line is led, and has ducts for connecting the pipe element with the fuel chamber. In addition the pipe elements of the bodies of successive pump and tappet units are connected to each other for providing a common low pressure fuel line. By leading the fuel further through a constant pressure valve of the like back into the fuel tank, the uniform low pressure fuel feeding line can be arranged to form a closed loop.
REFERENCES:
patent: 3902404 (1975-09-01), Breit
patent: 3951046 (1976-04-01), Lochmann et al.
patent: 4465049 (1984-08-01), Eckert et al.
patent: 5419298 (1995-05-01), Nolte et al.
patent: 5567134 (1996-10-01), Inoue
patent: 608638 (1960-11-01), None
patent: 80328 (1990-01-01), None
patent: 38637 (1931-06-01), None
patent: 2 129 883 (1984-05-01), None
Freay Charles G.
Smith-Hill John
Smith-Hill and Bedell
Tyler Cheryl J.
Wartsila NSD OY AB
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