Expansible chamber devices – With lubricating means – Piston has lubricant retaining or conducting means
Patent
1982-04-05
1985-05-28
Cohen, Irwin C.
Expansible chamber devices
With lubricating means
Piston has lubricant retaining or conducting means
91488, 92248, F16J 108
Patent
active
045193002
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates generally to a filled piston for use in fluid pumps and motors and more particularly to a filled piston having a centrally disposed tube therein.
BACKGROUND ART
Conventionally the pistons employed in axial piston pumps and motors are hollow and contain a lightweight filler material to reduce the high inertia forces acting on the piston during operation of the pumps and motors. A passage normally extends through the filler material and through the base portion of the piston to transmit hydraulic fluid through the piston to lubricate the bearing surfaces of the components associated with the piston. Examples of such filled pistons are described in U.S. Pat. No. 3,984,904 which issued to Charles H. Schlecht on Oct. 12, 1976, U.S. Pat. No. 3,707,113 which issued to Hein et al on Dec. 26, 1972 and U.S. Pat. No. 3,633,467 which issued to Watanabe et al on Jan. 11, 1972.
One of the problems encountered with such filled pistons is the formation of cracks or cavities in the passage in the filler material during the manufacturing process. It has been found that the high pressure hydraulic fluid passing through the passage tends to erode the crack or cavity. Such eroded material is then carried into the bearing surfaces associated with the piston thereby damaging the bearing surfaces. In some cases, the eroded material blocks the passage in the base portion of the piston and thereby blocks the flow of lubricating fluid to the bearing surfaces which again causes damage to the bearing surfaces.
Because of the above problem, it is necessary to visually inspect the passage in every piston with a cystoscope type instrument to insure that there are no cracks or cavities in the passage. Such 100% inspection adds to the manufacturing time and thus increases the total cost of manufacturing the piston. Moreover because of the stringent requirements that the fluid passage not have any visible cracks therein, approximately 40% of the filled pistons are scrapped.
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 present invention a piston having a base portion, a hollow skirt portion, and a core of lightweight filler material situated within the skirt portion includes a tube extending axially through the core of filler material and having an inner end portion connected to the base portion, and means for interlocking the tube and the core of filler material.
The problem of assuring that no cracks or cavities exist in the passage in the filler material is solved by utilizing a tube extending axially through the core of filler material. Since the passage for transmitting the lubricating fluid through the piston to the bearing surfaces is formed by the tube itself, it is not necessary to visually inspect the passage.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view of one embodiment of the present invention.
FIG. 2 is a cross sectional view of a second embodiment of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Referring now to FIG. 1, a piston is generally indicated by the reference numeral 10 and includes a base portion 11, a skirt portion 12, and a core 13 of lightweight filler material situated within a cavity 14 of the skirt portion 12. The core 13 of filler material is interlocked with the skirt portion 12 by a plurality of projections, one of which is shown at 16, extending inwardly into the cavity 14 sufficiently to engage and mechanically interlock the core. An orificed passage 17 and an axially aligned bore 18 are provided in the base portion 11.
A tube 19 extends axially through the core 13 of filler material and has an inner end portion 21 pressed into the bore 18 for connecting the tube 19 to the base portion 11. Preferrably the inner end portion 21 is knurled with a portion of the knurled inner end portion providing a means 22 for interlocking the tube 19 and the core 13 of filler material. A passage 23 in the tube communicates with the ori
REFERENCES:
patent: 3319575 (1967-05-01), Havens
patent: 3574293 (1971-04-01), Vriend
patent: 3633467 (1972-01-01), Watanabe
patent: 3707113 (1972-12-01), Hein et al.
patent: 3984904 (1976-10-01), Schlecht
patent: 4216704 (1980-08-01), Heyl
Adomis, Jr. Peter P.
Martin Millard J.
Caterpillar Tractor Co.
Cohen Irwin C.
Grant John W.
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