Expansible chamber devices – Piston – With ported chamber in piston part for circulating heat...
Reexamination Certificate
1999-06-17
2001-08-28
Look, Edward K. (Department: 3745)
Expansible chamber devices
Piston
With ported chamber in piston part for circulating heat...
C092S231000, C029S888042
Reexamination Certificate
active
06279455
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to an engine and more particularly to a method and apparatus for making a piston used in the engine.
BACKGROUND ART
The development of engines over the past few years have included increasing the horse power without increasing the displacement of the engine. To obtain the increased horsepower, it has been necessary to increase the combustion pressures within the combustion chamber which are transferred through the piston into the connecting rod and crankshaft.
Such increase in pressures have required the improvement of the integrity of the piston to withstand the increased stresses thereon. In the past and in many cases today, such pistons are made of aluminum or cast iron. Or, in some applications have used an articulated piston having a steel head and an aluminum skirt. Such an example is shown in U.S. Pat. No. 5,040,454 issued on Aug. 20, 1991 to Benny Ballheimer and Stephen G. Shoup.
As the pressures of engine designs increase, further requirements for the improvement of the integrity of the piston to withstand the increasing stresses thereon has become more apparent. As the pressures increase and consequently the stresses increase attempts have been made to resist, for example, bending stresses. One such example, is shown in U.S. Pat. No. 3,877,351 issued Apr. 15, 1975 to Eugen Barfiss. A ring zone of an upper part being made of steel and being supported by a lower part consisting of an aluminum alloy. The upper part and the lower part are joined by a bolted connection in a removable method of attachment. Additionally, U.S. Pat. No. 4,346,646 issued Aug. 31, 1982 to Jürgen Ellermann discloses a crown of steel being connected with a piston body of aluminum. An annular skirt supports the piston body. The crown and the piston body are joined by a bolted connection in a removable method of attachment.
Other piston assemblies are joined in a fixed manner such as by welding. For example, U.S. Pat. No. 5,359,922 issued Nov. 1, 1994 to Jose M. Martins Leites et al. discloses a method of manufacturing an articulated piston head wherein two portions are joined by friction welding. U.S. Pat. No. 5,245,752 issued Sep. 21, 1993 to Andre Lippai et al. discloses a two-piece piston having two portions friction welded together, U.S. Pat. No. 4,286,505 issued Sep. 1, 1981 to John K. Amdall discloses a two piece piston being joined by a brazing process, and U.S. Pat. No. 3,974,381 issued Aug. 10, 1976 to Manfred Rohrle et al. discloses a method of welding a workpiece including an electron beam welding.
However, in many applications, the complexity of the piston design increases the cost of manufacturing. For example, with some welded designs flash occurs which can separate and contaminate the lubricating and cooling liquid. Additionally, some welds cause a stress riser in an undesired location resulting in a failed piston. And, with some bolted joints, additional strength is required at the bolted joint requiring additional parts and assembly time.
The present invention is directed to overcoming one or more of the problems as set forth above.
DISCLOSURE OF THE INVENTION
In one aspect of the invention a two piece unitary piston is comprised of a head member being made of a material having a preestablished material strength, has a bottom surface and an inner support portion defining a support surface. A skirt member is made of a material having a preestablished material strength being substantially the same as the preestablished material strength of said head member. The head member has an upper outer support surface being aligned with the bottom surface forming an interface. And, an inner support portion defines an upper inner support surface forming an interface. Each of the interfaces is in contacting and supporting relationship with the support surface and the bottom surface of the head member respectively. The interface formed by the upper inner support surface being aligned with the support surface is joined by a welding process. The interface formed by said upper outer support surface being aligned with said bottom surface is joined by the welding process. And a piston cooling gallery is formed by the upper inner support surface and the support surface interface and the upper outer support surface being aligned with the bottom surface interface.
In another aspect of the invention a method of making a two piece unitary piston is comprised the following steps. Forming a head member of a material having a preestablished strength, the forming defining a bottom surface and a support surface being spaced from said bottom surface. Forming a skirt member of a material having a preestablished strength being substantially the same as the preestablished material of the head member, the forming defining an upper outer support surface and an upper inner support surface being spaced from said upper outer support surface. Positioning the bottom surface of the head member in contacting and supporting relationship with the upper outer support surface of the skirt member. Positioning the support surface of the head member in contacting and supporting relationship with the upper inner support surface of the skirt member. Welding the interface of the bottom surface and the upper outer support surface. Welding the interface of the support surface and the upper inner support surface. Combining fixedly the head member and the skirt member forming a piston cooling gallery.
REFERENCES:
patent: 4011797 (1977-03-01), Cornet
patent: 4581983 (1986-04-01), Moebus
patent: 4727795 (1988-03-01), Murray et al.
patent: 5359922 (1994-11-01), Martins Leites et al.
patent: 5645028 (1997-07-01), Matsuoka et al.
patent: 5778846 (1998-07-01), Mielke
patent: 6032619 (2000-03-01), Zhu et al.
patent: 2730120-A (1979-01-01), None
Cain Larry G.
Caterpillar Inc.
Lazo Thomas E.
Look Edward K.
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