Expansible chamber devices – With releasable stop or latch means to prevent movement of... – Means includes element interfitting between working member...
Reexamination Certificate
1998-08-13
2001-02-13
Look, Edward K. (Department: 3745)
Expansible chamber devices
With releasable stop or latch means to prevent movement of...
Means includes element interfitting between working member...
C092S028000
Reexamination Certificate
active
06186047
ABSTRACT:
The present invention relates to a device for locking the sliding of the rod of a linear actuator such as, for example, a fluid actuator.
A unidirectional locking device known from the document DE-A-2 219 824 comprises:
an outer body fast with or adapted to be fastened to an end of a casing of the actuator in an arrangement such as to surround the rod,
means defining, in the body, at least one pair of radially-facing wedging surfaces associated with the body and with the rod, respectively,
rolling members which are disposed between the wedging surfaces of the or each pair of surfaces and which can be wedged between the surfaces as a result of their rolling in one direction and as a result of a constriction of the coupling between the wedging surfaces and the rolling members, the control piston being arranged so as to engage each rolling member in order to urge it in the release direction as a result of a thrust exerted on the piston in the opposite direction to the force exerted by the resilient repulsion means, and
resilient repulsion means reacting between the body and the rod through each rolling member and tending to urge the latter in the wedging direction.
In this known device, the rolling members are constituted by balls which are loosely arranged between a conical inner surface of an annular element fixed to the body of a linear fluid actuator, and a cylindrical outer surface of the rod of the actuator. The balls are not positively guided along the rod when the wedging and unwedging movements take place.
The friction between the balls and the wedging surfaces may be inadequate for ensuring effective wedging and locking, owing to the presence of oil or grease in the tapered annular space.
The object of the invention is to provide a locking device of the type defined above, which does not have the aforementioned disadvantages, and in which the rolling members are guided along the rod of the linear actuator.
According to the present invention, this object is achieved by means of a locking device of the type defined above, wherein the body or an element fixed to the body has a series of longitudinal, peripheral grooves, and in that each rolling member is guided in a respective groove as it rolls along said wedging surfaces.
A locking device according to the invention is suitable for use not only for actuators having rods of circular cross-section but also, advantageously, for actuators having rods of other, for example, prismatic cross-sections.
The wedging and release of the rolling members does not rely upon their rolling friction on the wedging surfaces; on the one hand, wedging is achieved and is always ensured by the resilient thrust of the repulsion means; on the other hand, release is achieved by means of the positive thrust of the control piston.
The invention also relates to a unit for the bidirectional locking of the sliding of the rod of a linear actuator, wherein it comprises a pair of unidirectional locking devices as claimed acting in axially opposite directions.
The invention further includes a linear actuator comprising a unidirectional locking device or a bidirectional locking unit, as claimed.
Throughout the present description and in the claims, the term “piston” indicates not only an actual piston on which a fluid pressure acts, but also an operating member such as the movable core of an electromagnet; the terms “axial”, “radial”, “chordal”, their derivatives and similar terms indicate directions with reference to the axis of the actuator rod.
REFERENCES:
patent: 2139185 (1938-12-01), Engel
patent: 3050943 (1962-08-01), Thorel et al.
patent: 3107582 (1963-10-01), Royster
patent: 3217609 (1965-11-01), Royster
patent: 3251278 (1966-05-01), Royster
patent: 4791856 (1988-12-01), Heim et al.
patent: 2 219 824 (1973-10-01), None
patent: 33 19 402 (1984-11-01), None
patent: 0 103 555 (1984-03-01), None
patent: 2 185 532 (1987-07-01), None
patent: 48261 (1918-05-01), None
International Search Report for PCT/EP97/00632.
Look Edward K.
Merchant and Gould P.C.
Ready S.R.L.
Rodriquez Hermes
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