Motors: expansible chamber type – Three or more cylinders arranged in parallel radial or... – Radially disposed cylinders
Reexamination Certificate
2000-07-27
2002-02-19
Thorpe, Timothy S. (Department: 3746)
Motors: expansible chamber type
Three or more cylinders arranged in parallel radial or...
Radially disposed cylinders
48
Reexamination Certificate
active
06347572
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydraulic motor comprising:
a cylinder block which comprises at least a first group of cylinders disposed radially relative to an axis of rotation, each cylinder being connected to a cylinder duct and co-operating with a piston suitable for sliding in said cylinder;
a reaction member mounted to rotate relative to the cylinder block about the axis of rotation;
an internal fluid distributor constrained to rotate with the reaction member about the axis of rotation and provided with distribution ducts suitable for being connected to the cylinder ducts so as to put said ducts in communication with fluid inlet and fluid outlet ducts of the motor; and
selection means suitable, in a first configuration, for making it possible to connect the cylinder ducts of the cylinders of the first group to the distribution ducts and, in a “piston-declutching” second configuration, for putting said cylinder ducts in communication with a fluid discharge enclosure, the pistons co-operating with the cylinders of the first group being suitable, in said declutching configuration, for being retracted into said cylinders towards the axis of rotation.
BACKGROUND OF THE INVENTION
A motor of that type is known from Document FR 2 710 111. When the motor operates at maximum cubic capacity, all of the cylinders are fed periodically with fluid under pressure. As is known, it is possible to interrupt feeding all of the cylinders periodically with fluid so that the motor delivers no torque. As is also known, it is possible to interrupt feeding some of the cylinders with fluid, the other cylinders continuing to be fed periodically with fluid, so that the motor operates at partial cubic capacity.
Thus, the invention is applicable both to a motor in which all of the cylinders belong to the first group and are thus suitable for all being made inactive, and also to a motor further comprising a second group of cylinders, which cylinders continue to be active when the cylinders of the first group are made inactive.
As indicated in FR 2 710 111, it is known that the pistons that are mounted to slide in the cylinders of the first group can be “declutched”, an operation which consists in causing said pistons to cease to bear against the reaction member or “cam”, thereby eliminating friction and premature wear. For that purpose, a “declutching” device makes it possible to maintain the pistons in question in the retracted configuration in which they are retracted inside their respective cylinders.
As also indicated in FR 2 710 111, the declutching operation and the “re-clutching” operation, which consists in putting the pistons back into abutment against the cam, are difficult and, unless certain precautions are taken, they can give rise to the pistons striking the cam violently.
To avoid such violent shocks, FR 2 710 111 recommends using selection means which comprise an individual selector for each of the cylinders of the first group, with the individual selector being controlled in such a manner that, to declutch or to clutch the piston slidably mounted in the cylinder with which it is associated, it can be activated during the relative rotation of the cylinder block and of the cam only while the axis of the cylinder is passing through a position in which it is adjacent to the crest of an undulation on the cam.
That system is quite satisfactory, but it is relatively costly because it requires the presence of as many individual selectors as there are cylinders in the first group. It also needs suitable control means for activating each of the individual selectors at precise times.
Document FR 2 677 409 discloses a hydraulic circuit making it possible to declutch the pistons of a hydraulic motor. That circuit includes a shuttle valve interposed on the ducts that connect the orifice of the pump to the inlet and outlet main orifices of the motor. That system is external, and it is mounted on the motor, which increases the overall size of the motor. In addition, the declutching is applied without exception to all of the pistons of the motor. Finally, the problems of shocks on declutching and on re-clutching are not avoided.
OBJECTS AND SUMMARY OF THE INVENTION
An object of the present invention is to provide a system that is simple and disposed inside the motor and that makes it possible to declutch the pistons slidably mounted in the cylinders of the first group, while substantially avoiding the phenomena of shocks between the pistons and the cam during declutching and re-clutching of the pistons in question, even at speeds of rotation that are relatively high, e.g. about 100 revolutions per minute (r.p.m.) and higher.
This object is achieved by the selection means comprising a single declutching selector constrained to rotate with the cylinder block about the axis of rotation and provided with a communication duct for each cylinder of the first group of cylinders, the selector being suitable for taking up a first position, corresponding to said first configuration, in which the communication ducts make it possible to connect the cylinder ducts of the cylinders of the first group to the distribution ducts, a second position corresponding to said declutching configuration, and an intermediate transitional position between said first and second positions, and in which the cylinder ducts of the cylinders of the first group are connected together via an isolated enclosure.
When the selector is in the first position, the cylinder ducts of the cylinders of the first group are normally connected to the distribution ducts and are thus alternately connected to the fluid inlet and to the fluid outlet, so that the pistons slidably mounted in said cylinders are active. When the declutching selector is in the second position, the cylinder ducts of the cylinders of the first group are all connected to the fluid discharge enclosure so that the pistons slidably mounted in said cylinders are inactive and can be retracted into said cylinders, i.e. they are declutched. Preferably, the fluid discharge enclosure is merely a portion of the inside space of the motor, which portion is connected to a leakage return duct.
When the selector is in the transitional position, the cylinder ducts of the cylinders of the first group are all connected together via an isolated enclosure. The term “isolated enclosure” is used to designate a portion of the inside space of the casing of the motor, which portion is isolated from the various “functional” ducts of the motor, i.e. the ducts that are connected to ducts external to the motor, such as an inlet duct or an outlet duct, or else an auxiliary duct connected to the booster circuit of the motor to perform an auxiliary function of the motor (braking control, etc.). In other words, the isolated enclosure is connected neither to the inlet nor to the outlet, nor to any auxiliary pressure external to the motor.
In this transitional position, the pistons of the cylinders of the first group can be displaced in their respective cylinders as a function of their positions on the cam. In other words, they are not locked in given positions inside their cylinders, but rather they can follow the undulations of the cam, the volumes of fluid displaced by the retraction or “inward” motion of certain pistons compensating for the volumes of fluid displaced by the outward motion of the other pistons, the motor being constant-velocity.
It is only after the selector has gone through its transitional position that the cylinders of the first group are connected to the fluid discharge enclosure. Thus, the invention makes it possible to avoid putting the fluid discharge enclosure in direct contact with the inlet or the outlet of the motor, which would prevent said motor from operating properly. However, during the displacement of the selector, the cylinder ducts of the cylinders of the first group are not isolated from one another, which avoids locking the pistons slidably mounted in the cylinders.
Advantageously, the declutching selector is formed by a slide mounted to slide in
Martin Louis
Rouillard Jean-Marie
Souply Jean-Pierre
Gray Michael K.
Ladas & Parry
Poclain Hydraulics Industrie
Thorpe Timothy S.
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