Expansible chamber devices – Piston – Plural separable parts
Reexamination Certificate
1999-03-30
2001-08-21
Lopez, F. Daniel (Department: 3745)
Expansible chamber devices
Piston
Plural separable parts
C092S058000, C092S072000
Reexamination Certificate
active
06276261
ABSTRACT:
The invention relates to a piston assembly of a hydraulic radial piston-type machine comprising a cylindrical piston body to which is from the side lying opposite to the piston head connected a guide portion in which there is arranged and form-locked a rolling member.
FR-A-2 368 619 for example already discloses the above mentioned piston assembly. Here a rolling member is incorporated into the piston in the guide portion thereof. In order to reduce wear and tear of the piston and the cylinder with said solution the piston itself has to be made with relatively great length resulting in a relatively great distance between the axis of the rolling member and the piston crown causing, when operating, relatively high lateral loads to the wall of the piston and the cylinder, respectively. The consequence thereof is that the entire dimension of the hydraulic motor is rather big.
GB-A-2 064 700 also discloses the above mentioned piston assembly but has similar drawbacks in particular relating to wear and tear.
It is the principal object of the invention to create a piston assembly that will suppress the drawbacks of known solutions.
According to the invention the aim as set above is solved in that a rolling element is arranged in the piston head. This essentially means that the portion of a contact surface of the rolling element which lies close to the piston head is always arrange as close to the piston head as possible. According to a preferred embodiment of the invention said portion is always arranged in the piston head with a circular cross-section. More precisely, said portion lies in the area between the piston head and a step extending radially inward and dividing piston head from a guide portion.
The above-mentioned arrangement of the rolling element according to the invention is attained by a two-part piston design comprising a cylindrical body and a shell-like cover. The latter is mounted onto a cylindrical portion of the piston body and form-locked and force-locked therewith. With such an embodiment of the piston assembly that portion of the contact surface of the rolling element which lies close to the piston crown is arranged between the piston crown and an end piston surface abutting the step.
According to the invention it is also provided that the piston has a one-part design. In that case the cylindrical body and the shell-like cover are joined into a single solid unit. However, also with such an embodiment that portion of the contact surface of the rolling element which lies close to the piston head is arranged between the piston crown and the step which separates the piston head from the guide portion.
The piston assembly according to the invention may also comprise a bearing bush.
REFERENCES:
patent: 2295199 (1942-09-01), Carvelli
patent: 2860614 (1958-11-01), Burnand
patent: 3046950 (1962-07-01), Smith
patent: 4144798 (1979-03-01), Cyphelly
patent: 4719843 (1988-01-01), Nöel
patent: 5081906 (1992-01-01), Lemaire et al.
patent: 2 368 619 (1978-05-01), None
patent: 2 064 700 (1981-06-01), None
Jacobson Price Holman & Stern PLLC
Lopez F. Daniel
LandOfFree
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