Patent Application
20110186758
Not applicable
Not applicable
I. Field of the Invention
The present invention relates generally to hydraulic motors and, more particularly, to controlling the operation of disc valve hydraulic motors using an integral non-contact encoder system to generate control signals.
II. Related Art
Many devices have used external signals to control the operation of hydraulic motors, however, there yet remains a need to obtain more precise operation control of such motors by using feedback information gained by an integral non-contact encoder system using a rotating magnet which has heretofore not been incorporated in such motors. Such a system could be used to control motor operation using a programmable logic controller (PLC), or the like, to control rpm's or precisely position the motor shaft for tool alignment purposes, or the like.
By means of the present invention, there is provided a disc valve hydraulic motor assembly that includes a rotary valve that rotates in accordance with the motor output shaft and in which a two-pole bolt magnet (N/S 180° apart) is mounted in alignment with the center of the rotating valve to rotate with the rotating valve. The corresponding end housing of the disc valve hydraulic motor that is spaced from and disposed beyond the rotating valve is provided with a central opening or port aligned with the magnet. A non-contact sensor encoder is mounted in the opening in the housing to receive signals from the rotating magnet. The encoder also has an internal magnet that magnetically couples to the magnet in the motor so that the encoder rotates in the same manner as the magnet bolt. This provides the motor with an integral feedback system. A stainless steel plug device is provided in the opening in the end housing such that it is interposed between the internal parts of the motor exposed to high pressure hydraulic fluid and the non-contact sensor encoder to isolate the encoder from the hydraulic fluid pressure that it would have to endure if it was exposed to the inside of the motor. It has been found that using stainless steel for such a plug avoids interference with the operation of the magnet and sensor encoder.
A method of modifying a hydraulic motor having a rotating disc valve is also contemplated in accordance with the provision of the magnet and non-contact sensor encoder. It should be noted that the output from the sensor encoder is an analog, quadrature or SSI signal which becomes an input to a controller. In this manner, the encoder provides feedback information which, in turn, can be used by a control device to control a hydraulic valve that operates the hydraulic motor, or the like, according to a control program. Thus, the feedback system provides a unique way of knowing the position of the output shaft or the speed of the output shaft which can be used for precisely aligning the motor shaft with an object to operate a tool or closely controlling the rpm's of the motor. Thus, the system can be associated with a programmable logic controller (PLC) or any of many other types of systems that will occur to those skilled in the art.
In the drawings:
A detailed description of an embodiment of the present invention follows which is presented as an example of a typical embodiment to allow an understanding of the inventive concepts involved. It will be understood, however, that the embodiment presented is intended merely as an example and is not meant to limit the scope of the invention in any manner.
In
The hydraulic motor fragment of
In operation, of course, the magnet bolt 50 in extension 52 rotates with the rotating hydraulic motor valve 46 such that, when the motor is operated, the magnet bolt 50 assumes a permanent alignment with the motor shaft such as the shaft shown at 16 in
Thus, one such use of the signal received from sensor 38 is to control the precise alignment of the motor shaft 16 so that a tool such as a chuck (not shown) attached to the shaft can be precisely aligned to operate a remote device. In addition, motor rpm and other qualities can be precisely controlled. It will be appreciated that the signal from the sensor 38 can be used in conjunction with a programmable logic controller (PLC) which may be programmed to produce an analog, digital or SSI output.
It should be noted that a motor of the class suitable for modification in accordance with the present invention may be an Eaton 6000 Series, for example, manufactured by Eaton Corporation having an office at Eden Prairie, Minn. A non-contact encoder of the class suitable for use in the present invention may be obtained, for example, from Joral Corporation of New Berlin, Wis., as a 16 mm or 16 mm non-contact sensor encoder, which is operable with a variety of magnets, including bolt magnets, in a well known manner.
This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the example as required. However, it is to be understood that the invention can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself.
