Metal working – Burnishing
Reexamination Certificate
1999-03-08
2002-06-18
Hughes, S. Thomas (Department: 3726)
Metal working
Burnishing
C123S188800, C073S047000, C029S705000, C029S888420, C029S888440
Reexamination Certificate
active
06405419
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to internal combustion engine preconditioning and testing systems, and more particularly, to an arrangement that exercises and burnishes intake and exhaust valves in their respectively associated seats in a cylinder head to improve the quality of the seal therebetween and that identifies valves that do not provide an adequate seal.
2. Description of the Related Art
There is a need in the engine assembly industry for a system that permits leak testing in an engine head assembly with sufficient resolution to determine whether a problem exists, or is expected to exist, in the mating valve surfaces. The performance of a leak test in a production environment applied to engine intake and exhaust valves is difficult. A primary reason why valves and seats do not form adequate seals is that contaminants and small surface imperfections exist between the mating surfaces. Usually, minor imperfections are quickly burnished out during normal engine operation and result in no long term quality issues. However, the early assembly imperfection and contaminations permit excessive leakage through the valve assembly. Engine manufacturers cannot in practice fail all of the assemblies that have this leakage condition during the manufacturing process as such would require failure of many leaking valve assemblies that would correct themselves during normal engine operation.
The prior art has sought to achieve a solution to this problem by constructing equipment that uses a conventional engine cam and/or hydraulics to exercise a valve assembly prior to a leak test. This action burnishes-in the valves to an extent that permits a more accurate leak test to be performed. It is a problem with known equipment, however, that the extent of burnishing is directly proportional to the load experienced by the mating valve surfaces and the amount of “hits” (or cycles) that the valve assembly is permitted to experience during the burnishing operation. In a known hydraulic system, the “hits” in the mating valve seats are not of optimum amplitude as a result of the amount of mass and fluid that has to be returned by an engine valve spring before it contacts the seat. It is also a disadvantageous characteristic of known arrangements that the amplitude of the “hits” is minimized since an engine cam that is used to drive the valves is optimized to minimize the valve loading.
There is a need, therefore, for an arrangement that quickly exercises the engine valves to achieve an amount of burnishing adequate to permit a valid and accurate leak test to be performed thereafter. The amplitude of the “hits,” however, should not be so large as to damage the valves or the seats in the cylinder head.
It is, therefore, an object of this invention to provide an arrangement that exercises and burnishes engine intake and exhaust valves so that adequate leak testing can be conducted immediately thereafter.
It is another object of this invention to provide an arrangement that improves the quality of the seals effected between engine valves and their respective seats.
It is also an object of this invention to provide an engine valve exercising arrangement that can operate over a broad range of operating speeds.
It is a further object of this invention to provide an arrangement that quickly exercises the intake and exhaust valves of an internal combustion engine with the application of valve loading that is greater than that which is achieved by a conventional valve train.
SUMMARY OF THE INVENTION
The foregoing and other objects are achieved by this invention which provides, in a first apparatus aspect thereof, an arrangement for seating a valve in valve seat in a first side of a cylinder head of an internal combustion engine. The valve is of the type having a valve sealing portion for communicating with the valve seat and a valve stem that is accessible on a second side of a cylinder head. In accordance with the invention, a source of reciprocating motion effects reciprocation along a predetermined linear path of reciprocation. A first jig defines a predetermined location of the cylinder head in relation to the source of reciprocating motion. A coupling arrangement couples the source of reciprocating motion to the valve in the cylinder head. Additionally, a second jig is provided for communicating with the first side of the cylinder head and defining a test chamber that surrounds the valve seat and the valve sealing portion.
In one embodiment of this aspect of the invention there is provided a ram for applying a force to the second jig and urging same into sealed relation with the first side of the cylinder head. In some embodiments, the ram also urges the cylinder head against the first jig whereby it is maintained in fixed relation with respect to the source of reciprocating motion.
A valve rotating arrangement, which may be incorporated in the cylinder head, causes the valve to rotate with respect to the valve seat as the valve is displaced reciprocatingly along its respective displacement path. Such rotation enhances the valve seating in the valve seat of the cylinder head.
The test chamber is provided with a fluid input to permit delivery thereto of a fluid whereby a pressure retention test is performed in the test chamber. In one embodiment, the fluid input is in the form of a air inlet. There is additionally provided a pressure sensor that produces a signal responsive to the pressure in the test chamber.
One or more sealing elements are provided for sealing apertures in the cylinder, as would be the case with a fuel injector of a Diesel engine.
In an embodiment of the invention, the source of reciprocating motion includes a source of rotatory motion for rotating about an axis of rotation. An eccentric cam is coupled to the source of rotatory motion and arranged to rotate therewith. A linear drive arrangement has a first end thereof arranged to communicate with the valve stem of the valve, the linear drive arrangement and the valve being displaceable along parallel respective displacement paths. Additionally, a cam follower is coupled to the eccentric cam and to the linear drive arrangement. In this manner, the linear drive arrangement is urged into reciprocating linear motion in response to the rotation of the eccentric cam.
In a highly advantageous embodiment of the invention, the eccentric cam is formed of a closed, substantially annular protuberance extending substantially axially parallel to the axis of rotation. The substantially annular protuberance has radially inward and radially outward facing surfaces. In this embodiment, the cam follower is formed of first and second cam follower rollers that are arranged substantially parallel to one another and to communicate with respective ones of the radially inward and radially outward facing surfaces of the substantially annular protuberance.
In a further embodiment of the invention, the linear drive arrangement is formed of a reciprocating element that is coupled to the first and second cam follower rulers. The reciprocating element has a first predetermined cross-sectional configuration. A stationary guide way is provided with a predetermined cross-sectional configuration that corresponds to that of the first predetermined cross-sectional configuration of the reciprocating element, and thereby accommodates same therewithin. In a highly advantageous embodiment, a Teflon® sheet insert is interposed between the reciprocating element and the stationary guide way for reducing friction therebetween. It has been discovered that this arrangement provides a highly advantageous low-friction reciprocating system that does not require any additional lubricants. In fact, most known lubricants increase the friction between the Teflon® sheet insert and the reciprocating element. The application of excessive force to the valve stem by the reciprocating element is precluded by a resilient overload element that provides a resilient accommodation of a force that would exceed a predetermined magnitude. The res
Juranitch James C.
Olschefski Robert D.
Hong John C.
Hughes S. Thomas
Rohm & Monsanto, PLC
Veri-Tek Inc.
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