Power plants – Pressure fluid source and motor – Having a mechanical clutch or brake device in the power train
Reexamination Certificate
1999-12-30
2001-09-25
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Having a mechanical clutch or brake device in the power train
C091S498000
Reexamination Certificate
active
06293100
ABSTRACT:
The present invention relates to a hydraulic motor comprising:
a casing;
a reaction member integral with or secured to the casing and having an internal periphery that defines a reaction profile; and
a cylinder block which is mounted so that the cylinder block and the reaction member rotate relative to each other about an axis of rotation, the cylinder block comprising a plurality of piston-and-cylinder sets disposed radialy relative to the axis of rotation and suitable for being fed with fluid under pressure;
an internal fluid distributor constrained to rotate with the casing about the axis of rotation, and provided with distribution ducts that can put the cylinders in communication with fluid feed and exhaust ducts; and
a braking system comprising first and second braking means constrained to rotate respectively with the casing and with the cylinder block about the axis of rotation, a brake piston suitable for taking up both a brake-releasing position and a braking position in which it urges the first and second braking means into braking engagement so as to prevent the cylinder block and the casing from rotating relative to each other, and means for displacing the brake piston between said braking and brake-releasing positions.
The invention applies more particularly to motors in which the brake acts as a parking brake or as a safety brake, i.e. in which the brake acts without dissipating energy and below a predetermined speed, which varies depending on the embodiment, and which is about 100 revolutions per minute (r.p.m.) on average.
In known motors of the above-mentioned type, the first braking means are generally constituted by a first series of brake pads in the form of rings which are secured to a portion of the casing referred to as the “brake casing”, via axial fluting. The brake casing is fixed to the other portions of the casing by screws or any other suitable securing means. The second braking means are constituted by a second series of brake pads in the form of rings interposed between the pads of the first series, and constrained to rotate with a brake shaft by means of axial fluting. The brake shaft is itself constrained to rotate with the cylinder block by means of fluting. The brake piston is disposed in the brake casing, at one end thereof. It is generally urged in the braking direction by a spring washer, and it is hydraulically displaced in the brake-releasing direction by means of a fluid under pressure contained in a brake release chamber.
Such known systems are generally satisfactory but they suffer from several drawbacks.
Firstly, they are made up of quite a large number of parts that are difficult to assemble together. In addition, during braking or during brake release, the piston can “slip” relative to the brake disk that is closest to it. Furthermore, brake disks are subjected to considerable stress from the braking torque. They must be extremely strong in the region of the fluting, in which region the stresses are extremely high because of the smallness of the contact areas between the fluting on the disks and the fluting on the part (the brake casing or the brake shaft) to which they are secured.
An object of the invention is to improve known systems so as to provide safe and effective braking with a small number of parts, or, at least, with parts whose dimensioning and method of assembly are such that they make it possible to limit the manufacturing cost of the “brake” portion of the motor.
This object is achieved by the fact that the brake piston is constrained to rotate with the casing about the axis of rotation and it has a substantially radial active braking face, a first brake member belonging to the first braking means being integral with or secured to said active face.
As described below, constraining the brake piston to rotate with the casing may be achieved by keying it by means of coupling profiles provided with fluting, or, preferably, with undulations which are free from sharp edges or angles. The undulations form a curve whose tangent can be determined at all points. The brake piston is a part of relatively large dimensions (in particular of large thickness), so that achieving the keying poses no particular difficulty.
The brake piston or the coupling profiles can easily be organized to withstand high braking torque. The first brake member is integral with or secured to the active face of the piston, which means that it is either directly constituted by said active face, or it is machined in said active face, or else it is formed by a separate part (a series of teeth of a positive clutch, or a first brake pad) which is fixed to said active face by any known means.
In which case, it is easy to choose the fixing means, e.g. welding, so that they withstand the braking torque. In addition, it is easy to ensure that the contact areas between the first brake member and the braking piston are relatively large (these areas are formed on radial faces), so that the stresses to which the coupling between the first brake member and the piston is subjected on braking are proportionally less high than the stresses to which the coupling between the first disk and the part (casing or brake shaft) with which it is constrained to rotate is subjected in conventional systems.
Advantageously, the first and second braking means respectively comprise a first series of positive clutch teeth and a second series of positive clutch teeth, the first series of teeth being integral with or secured to the active face of the brake piston.
In which case, motor manufacture and motor assembly are made even simpler. The first series of teeth may be machined directly on the active face of the brake piston, or else they may be provided on an annular ring, itself fixed to the brake piston. Similarly, the second series of teeth may be machined directly on a radial face of the cylinder block or on some other part that is prevented from rotating relative to the cylinder block, or else they may be formed on an annular ring fixed to the cylinder block or to some other part. In addition, the forces involved on braking, which forces affect the first braking means (first series of teeth) are transmitted in full to the casing by means of the brake piston being constrained to rotate with said casing.
Preferably, the motor includes a coupling collar which forms a portion of the casing and which has an internal axial face with which an external axial face of the brake piston co-operates to key said piston so that it is constrained to rotate with the casing, said internal and external axial faces having coupling profiles suitable for this purpose.
The coupling collar is advantageously directly adjacent to the reaction member and it may even be constituted by an axial extension of the reaction member, which extension is integral with said reaction member.
In which case, the coupling profile of the internal axial face of the coupling collar is chosen to be analogous to the reaction profile. Thus, since the reaction member is correctly dimensioned to transmit the drive torque, it is guaranteed that the members via which the braking torque passes are also correctly dimensioned. In addition, the machining of the coupling profile formed on the internal axial face of the coupling collar is simplified because it makes use of at least some of the lobes of the cam.
The coupling collar may also be constituted by an annular part which is interposed between the reaction member and the “distribution cover” portion of the casing, which portion surrounds the distributor. In which case, it is very simple to fix the coupling collar to the other portions of the casing. In addition, the brake piston is then situated in an annular space provided around the distributor under the collar, so that the overall axial size of the motor is reduced. Even in this case, it is advantageous to machine the internal periphery of the coupling collar in a manner such that it is provided with undulations whose trough portions correspond to at least some of the trough portions of the reaction member. This simplifies first
Allart Bernard
Bigo Louis
Noel Alain
Perot Marc
Ladas & Parry
Lazo Thomas E.
Look Edward K.
Poclain Hydraulics Industrie
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