Hydrostatic transmission controls

Claim 2

Hydrostatic transmission comprising an hydraulic generator or pump driven by a drive motor such as an electric motor or a heat engine and at least two receptors or hydraulic motors adapted to be fed in parallel by the generator and interconnected mechanically to propulsion devices and with at least one of which is associated a system adapted to vary such receptor''s output or delivery per shaft revolution to a null value, characterized by the fact that the transmission also comprises means to cause a fluid to act at will, under increasing or decreasing pressure, simultaneously upon a pressure-responsive device adapted to control the aforesaid system for adjusting the receptor output and upon an interruption device also responsive to such pressure and adapted to isolate from the generator the first receptor with which that system is associated, the aforesaid pressure-sensitive control device and the interruption device being pressureactuated differentially so that, as the fluid pressure increases, the pressure-sensitive control device at first reduces the first receptor''s output progressively down to a null value, then the interruption device isolates that receptor, whereupon the other receptor is fed either by only part of the output of the first generator so long as the first receptor is fed in parallel or by the entire output thereof when the first receptor is isolated.

Claim 3

Hydrostatic transmission, according to claim 1, wherein the receptors drive respective traction wheels carried on the opposite ends of the same axle of an automotive vehicle, characterized by the fact that the two receptors are mechanically interconnected, respectively, two auxiliary pumps of identical output connected in series in a closed fluid circuit, wherein on the one hand devices are provided to bleed off an excess of fluid from either of the branches of the closed circuit upon occurrence of excessive pressure therein, and on the other hand there are provided for the respectIve receptors corrective devices responsive to pressure and adapted to control, respectively, the aforementioned adjusting systems, the overall effect being such that when one of the pumps rotates more rapidly than the other the resulting excessive fluid pressure in one of the branches acts upon the corrective device for the more rapidly rotating receptor to reduce its output.

Claim 4

Hydrostatic transmission according to claim 1, characterized by the fact that the aforesaid control device is made up of a piston slidably fitting in a cylinder to provide fluid displacement spaces and adapted to be fluid displaced counter to the bias of a retraction device in a direction corresponding to reduction in output of the first generator to a limiting position in which that output is null when the fluid pressure acting upon that piston reaches a given value, and the aforesaid interruption device is made up of a distributor controlled by an hydraulic jack and adapted to be displaced counter to the bias of an elastic device from a position in which the two receptors are fed in parallel to a position in which the first receptor is isolated when the pressure of fluid that feeds the jack reaches a selected threshold higher than the aforementioned given value.

Claim 5

Hydrostatic transmission according to claim 3, characterized by the fact that the jack and the fluid displacement spaces in the cylinders are connected by another distributor either to an auxiliary source of fluid under pressure or to a reservoir by way of a choke.

Claim 6

Hydrostatic transmission according to claim 4, characterized by the fact that the aforementioned distributor is formed so that, when it occupies a position in which it isolates the first receptor, the latter is fed by the auxiliary source.

Claim 7

Hydrostatic transmission according to claim 2, characterized by the fact that the aforementioned bleed devices are made up of chokes connecting the respective branches of the closed circuit to a reservoir.

Claim 8

Hydrostatic transmission according to claim 2, characterized by the fact that the corrective devices are identical with control devices for the respective receptors.

Claim 9

In a hydrostatic transmission suitable for connecting a drive motor to traction wheels of a motor vehicle, wherein an hydraulic generator or pump feeds in parallel at least a pair of receptors or hydraulic motors, at least one of which has associated therewith pressure-responsive means for adjusting its output, the improvement comprising an auxiliary source of fluid under pressure; an interruption device interposed between the generator and a first one of the receptors and having two operative positions, means biasing the interruption device to a first position in which there is circuit continuity between the generator and the first receptor as well as between the generator and the second receptor, pressure-responsive means for shifting the interruption device to a second position in which the circuit continuity between the generator and the first receptor is broken; and a speed-control distributor having a low-speed position and a high-speed position and being movable at will from one position to the other, the distributor in the low-speed position connecting the auxiliary source to a reservoir at negligible pressure, and in the high-speed position connecting the auxiliary source to the pressure-responsive means for adjusting the first receptor''s output and to the means for shifting the interruption device to its second position so that the first receptor is isolated from the generator by such shifting of the distributor after its output has been adjusted to a null value, whereupon the second receptor is driven faster by reason of receiving that part of the generator output that went to the parallel-fed first receptor in the first position of the distributor and the interruption device.

Claim 10

In a hydrostatic transmission suitable for connecting a drive motor to traction wheels of a motor vehicle, wherein an hydraulic generator or pump feeds in parallel at least a pair of receptors or hydraulic motors, at least one of which has associated therewith pressure-responsive means for adjusting its output, the improvement comprising an auxiliary source of fluid under pressure; an interruption device interposed between the generator and a first one of the receptors and having two operative positions, means biasing the interruption device to a first position in which there is circuit continuity between the generator and the first receptor as well as between the generator and the second receptor, pressure-responsive means for shifting the interruption device to a second position in which the circuit continuity between the generator and the first receptor is broken; and a speed-control distributor having a low-speed position and a high-speed position and being movable at will from one position to the other, the distributor in the low-speed position connecting the auxiliary source to a reservoir at negligible pressure, and in the high-speed position connecting the auxiliary source to the pressure-responsive means for adjusting the first receptor''s output and to the means for shifting the interruption device to its second position so that the first receptor is isolated from the generator by such shifting of the distributor after its output has been adjusted to a null value, whereupon the second receptor is driven faster by reason of receiving that part of the generator output that went to the parallel-fed first receptor in the first position of the distributor and the interruption device.

Claim 11

Hydrostatic transmission according to claim 8, including flow regulating means in the circuit from the auxiliary source to the distributor and choke meanS between the distributor and the reservoir, said means being effective to smooth out changes in flow and pressure of fluid to and from the pressure-responsive means, whereupon transitions between speed ranges are gradual, both when the distributor is moved to the high-speed position, thereby actuating the pressure-responsive means, and when the distributor is moved to the low-speed position, thereby releasing the pressure therefrom.

Claim 12

Hydrostatic transmission according to claim 9, including a third receptor located on the same side of the distributor as the first receptor and driven in parallel therewith, the third receptor also having associated with it pressure-responsive means for adjusting its output, and including also a fourth receptor located on the same side of the distributor as the second receptor and driven in parallel therewith.

Claim 13

Hydrostatic transmission according to claim 10, including a pair of pumps interconnected mechanically to the first and third receptors, respectively, and in a closed fluid circuit to one another, and an antislip distributor having a first position in which the respective branches of the closed circuit are connected to one another so as to equalize the pressures therein, and having a second position in which the branches are connected, respectively, to the pressure-responsive means for the first and third receptors in such a direction as to equalize the pressures in the respective branches by actuation of at least one of the pressure-responsive adjusting means, so as to adjust the outputs of the respective receptors to equalize their speeds, despite differences in the resistance to rotation thereof such as may be attributable to unequal traction of respective wheels driven thereby.