Motors: expansible chamber type – Three or more cylinders arranged in parallel radial or... – Cylinders parallel to rotation axis
Patent
1996-07-24
1998-05-19
Freay, Charles G.
Motors: expansible chamber type
Three or more cylinders arranged in parallel radial or...
Cylinders parallel to rotation axis
417269, 92 57, 92 71, F01B 106
Patent
active
057524289
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a hydraulic axial piston motor having a cylinder drum which is connected, so that it is non-movable axially, to a shaft and so that they rotate together, and which has at least one cylinder, for each cylinder a piston arranged in the cylinder, which piston bears at its end projecting from the cylinder drum against a swash plate via the intermediary of a slider shoe, a pressure-applying arrangement for holding at least one slider shoe against the swash plate and a control plate with control "kidneys".
The cylinder drum of an axial piston motor is one of the essential parts involved in producing the torque on the shaft. U.S. Pat. No. 4,771,676 therefore discloses two possibilities for fixing the cylinder drum on the shaft: firstly, a splined connection and, secondly, construction of the cylinder drum and shaft in one piece. The splined connection does allow an axial movement of the cylinder drum and shaft relative to one another, but in the case of an axial displacement it is obviously impossible to ensure freedom of movement also between the cylinder drum and the shaft in the circumferential direction to the necessary extent; as a result, rattling can occur here.
Conversely, in the normal production of motors, it is impossible to install without axial play a shaft that has been made in a relatively large production run. This play can be kept very small, but in the case of an axially non-movable connection between the cylinder drum and the shaft, internal leakage of the motor may occur on axial movement of the shaft, namely, either in the region of the control plate, when the cylinder drum lifts away from the control plate, or in the region of the swash plate, when the slider shoes lift away from the swash plate. An axial displacement of the shaft can occur, for example, when the motor is coupled by way of a helical gearing to a work machine to be driven. Another problematical case involves the operation of the motor in an installation in which the shaft is vertical. Such configurations can result in the motor failing to start because the pressure build-up required for this does not reach as far as the cylinder; on the contrary, the hydraulic fluid flows prematurely through drainage channels.
SUMMARY OF THE INVENTION
The invention is therefore based on the problem of providing a motor which can be operated reliably even with a shaft predisposed to axial play.
In the case of a motor of the kind mentioned in the introduction, this problem is solved in that the pressure-applying device is mounted so as to be axially movable relative to the cylinder drum, that between the control plate and the cylinder drum there is arranged a pressure plate that is axially movable relative to the cylinder drum, this pressure plate having for each cylinder a through-opening which is connected in a fluid-tight manner to the cylinder, and that between the pressure-applying device and the pressure plate there is provided an expanding device which acts on the pressure-applying device and the pressure plate with oppositely directed forces.
By that means, irrespective of the axial position of the shaft, which is at the same time the deciding factor for the axial position of the cylinder drum, one can ensure that both in the region of the control plate and in the region of the swash plate the engagement of the relevant elements with respect to one another is reliably sealed. These elements are, in the region of the swash plate, the slider shoes, which are kept permanently in engagement with the swash plate by the pressure-applying device, so that they are not able to tilt. If they were to tilt, on the one hand undesirable losses due to leakage would occur, and on the other hand the control behaviour of the motor would be severely disrupted. Since the pressure-applying device is axially movable with respect to the shaft, but on the other hand is loaded by the expanding device permanently in the direction towards the swash plate with a force, this contact pressure is then independe
REFERENCES:
patent: 1860278 (1932-05-01), Eckels
patent: 2992619 (1961-07-01), Nilges
patent: 3187644 (1965-06-01), Ricketts
patent: 5247794 (1993-09-01), Benson et al.
Danfoss A/S
Freay Charles G.
Tyler Cheryl J.
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