Abstract:
A corrosion resistant hydraulic motor includes a housing, an output shaft extending through an opening in the housing, a sealing member contacting the output shaft and a water proof coating disposed on an exterior surface of the housing and on the sealing member. The sealing member is configured to cooperate with the output shaft to preclude corrosive material from passing through the opening into an internal compartment of the motor.

Description:
BACKGROUND 
       [0001]    Hydraulic motors are prone to rust and/or corrosion when used in corrosive enviroments such as salt and sand spreaders, marine applications, swimming pools, ect. To combat against rust and corrosion, hydraulic motor manufactures paint, epoxy coat, powder coat or electroless nickel coat hydraulic motors. 
         [0002]    Current coatings and treatments are not totally effective against prohibiting rust and corrosion. For example, paint and epoxy type coatings chip and then flake off. Moreover, transition points, e.g. points between different components and/or different materials of the hydraulic motor, allow infiltration under the paint type coatings, which results in the coating flaking off. Electroless nickel is expensive and will still allow rusting on porous cast surfaces. 
         [0003]    To avoid the problems associated with known coatings, those skilled in the art have attempted to isolate the hydraulic motor from the corrosive enviroment. For example, where hydraulic motors have been used to move water in swimming pools, the motor has been placed in a sealed chamber where the output shaft of the motor extends from the sealed chamber. Hydraulic oil or another lubricant is then placed in the sealed chamber to further protect the motor. This assemlby, however, is prone to leak. 
       SUMMARY OF THE INVENTION 
       [0004]    A method for providing a corrosion resisting barrier to a hydraulic motor includes the following steps: applying a corrosion resistant coating to an outer surface of a housing of the hydraulic motor such that substantially the entire outer surface is covered with the coating; and sealing an opening through which an output shaft of the hydraulic motor extends in a manner that allows the output shaft to rotate while inhibiting infiltration of corrosive material through the opening into the hydraulic motor. 
         [0005]    A corrosion resistant hydraulic motor includes a housing, an output shaft extending through an opening in the housing, a sealing member contacting the output shaft and a water proof coating disposed on an exterior surface of the housing and on the sealing member. The sealing member is configured to cooperate with the output shaft to preclude corrosive material from passing through the opening into an internal compartment of the motor. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a sectional view of a hydraulic motor incorporating a corrosion resistant system. 
       
    
    
     DETAILED DESCRIPTION 
       [0007]    An example of a hydraulic motor  10  that is resistant to rust and corrosion will be described in detail below. The components of the motor  10  are more fully described in pending U.S. patent application Ser. No. 11/382,171, entitled Gerotor Motor and Brake Assembly, which is incorporated by reference herein in its entirety. The corrosion resistant coating and/or system that is described below can be used with other types of hydraulic motors and devices, and is not limited to be used with only the motor  10  that is described below. 
         [0008]    With reference to  FIG. 1 , the hydraulic device  10 , which can also operate as a pump in a manner that is known in the art, includes a housing assembly that includes a front housing section  12  and a rear housing section  14 . The housing sections attach to one another via bolts (not shown) received in bolt holes (not shown) formed in the housing sections. 
         [0009]    A gerotor assembly  16  connects to the rear housing section  14 . In the depicted embodiment, the rotor assembly  16  is similar to a known gerotor assembly that includes a stator and a rotor, accordingly further description is not provided. 
         [0010]    A wobble stick  18 , also referred to as a drive link or a wobble shaft, connects to the rotor of the gerotor assembly  16  in a known manner. The wobble stick  18  connects to an output shaft  22 , also in a known manner. Since the motor  10  is designed to be used in a corrosive environment, the outer surface of the output shaft  22  can be electroless nickel coated. 
         [0011]    A wear plate  24  is sandwiched between the rear housing section  14  and the rotor assembly  26 , The wear plate  24  includes a plurality of openings (not visible) radially spaced from a rotational axis of the output shaft  22 . The openings in the wear plate  24  communicate with the cells (either expanding or contracting) formed in the rotor assembly in a manner that is known in the art 
         [0012]    An end plate  26  attaches to the gerotor assembly  16  on an opposite side of the gerotor assembly as the wear plate  24 . In the depicted embodiment, the end plate  26  closes the housing assembly for the moveable components of the hydraulic motor. 
         [0013]    When operating as a motor, rotation of the output shaft  22  is caused by delivering pressurized fluid to the expanding cells of the gerotor assembly  16 . The hydraulic motor  10  can also operate as a pump when the output shaft  22  is driven by an external power device, for example a gasoline or diesel engine. 
         [0014]    The hydraulic motor  10  also includes a brake assembly  28  that acts to restrict rotation of the output shaft  22 . The brake assembly  28  is more fully described in U.S. patent application Ser. No. 11/382,171. 
         [0015]    In the hydraulic motor  10  depicted in  FIG. 1 , two ports, only one port  32  is shown in  FIG. 1 , allow for the ingress and egress of hydraulic fluid. A fitting  34  (two fittings are provided, one for each port) connects in the first port  32  to allow for the connection of a fluid hose to the motor  10 . In the depicted embodiment, the fitting  34  is a known corrosion resistant fitting such as stainless steel, zinc dichromate or a yellow dichromate fitting. The fluid hoses are connected to a pressure source, in the case where the hydraulic motor is used to deliver power to the output shaft  22 , or to a hydraulic device that is to receive pressurized fluid, in the case where the hydraulic motor is used as a pump. 
         [0016]    A thrust bearing assembly  40 , which in the depicted embodiment includes two washers having a thrust bearing sandwiched between them, surrounds the output shaft  22 . A seal retainer  42  that retains a seal  44  fits around the output shaft outside of the thrust bearing assembly  40 . A seal support  46  and dust cover fits around the output shaft  22  to protect the seal  44  and other internal components. The seal  44  cooperates with the front housing section  12 , the seal retainer  42  and the output shaft  22  to define a boundary for the hydraulic fluid moving through the motor. 
         [0017]    A flange  50  attaches to the front of the front housing section  12  via conventional fasteners (or similar mechanical attachment). The flange  50  is similar to a flange that is used with a speed sensor assembly that is more fully described in U.S. patent application Ser. No. 10/474,110, entitled Speed sensor flange assemblies, which is incorporated by reference herein. 
         [0018]    In the depicted embodiment, the flange is made of plastic, for example an acetal; however, the flange can be made from another material that does not easily corrode in an aqueous environment. The flange  50  includes a central through-bore  52  that is dimensioned to snugly receive the output shaft  22 , More particular to the depicted embodiment, the flange  50  includes a shoulder  54  that contacts the peripheral surface of the output shaft  22 . The flange also includes a central counter bore  56  that receives a seal  58  and a rear counter bore  62  that is greater in diameter than the central counterbore. 
         [0019]    The shoulder  54  and the seal  58  protect the internal components of the hydraulic motor  10 , in addition to the seal  44 , dust cover  46  and seal retainer  44  that are disposed in the front housing section  12 . If desired, the counter bores  56  and  62  can be filled with a lubricant, e.g. oil, to further protect the internal components of the hydraulic motor. In such an instance, the flange  50  may include an additional opening through which the lubricant can be introduced. 
         [0020]    The hydraulic motor  10  includes a corrosion resistant coating  70  that in combination with the flange  50  and seals  44  and  58  protects the motor so that it can be used in a corrosive environment. The flange  50  can act as a sealing member to inhibit the infiltration of corrosive material into the internal compartments of the hydraulic motor. The corrosion resistant coating  70  can be a polyurethane material, an aliphatic polyurea elastomer, or a similar waterproof material, that is sprayed onto the housing sections  12 ,  14 ,  16 ,  24  and  26  of the motor  10  after the motor has been assembled. If desired, the motor  10  can be dipped into a tank containing the corrosion resistant material. In either case, the output shaft  22  and a portion of each fitting  34  are masked so that the coating does not adhere to these components. 
         [0021]    The corrosion resistant coating adheres to the housing sections to form a protective barrier so that air and moisture cannot penetrate to the metal housing sections. The corrosion resistant coating  70  can be applied between about ⅛″ to about ½″ inches thick, preferably about ¼″ inches thick. The corrosion resistant coating  70  can provide a continuous coating between adjoining components of the motor  10  (see, for example, where the front housing section  12  contacts the rear housing section  14 ). 
         [0022]    The corrosion resistant system incorporates the plastic (or other non-corrosive material) flange  50  in conjunction with the corrosion resistant coating  70 . The flange can also be plastic coated or coated with a non-corrosive material. The corrosion resistant coating  70  coats a part of the flange  50  in addition to the remainder of the external surface of the metal components  12 ,  14 ,  16 ,  24  and  26  of the motor  10 . By coating a portion of the flange  50 , no metal portion of the motor  10  (except for the fittings  34  which will be described in more detail below) is exposed. The plastic flange  50  provides a large surface area for the corrosion resistant coating  70  to adhere to. Use of the plastic flange  50  also allows for the shoulder  54 , the seal  58  and any fluid that is trapped by the flange to further protect the motor  50 . Alternatively, the front surface of the front section  12  (the surface that abuts the flange  50  in  FIG. 1 ) can be coated up to the opening that the output shaft  22  extends through and the seal support  46  and the seal  44  that are disposed in the front section  12  can be used to protect the internal components of the motor  10 . 
         [0023]    The fittings  34  are installed prior to coating the motor. Outer portions, (with respect to the rear housing section  14 ) are masked prior to coating. Accordingly, when the coating  70  is applied, the fittings  34  are partially coated. The joint or transition point between the motor port  32  and the standard available corrosion resistant fittings  34  are totally coated eliminating (or greatly reducing) the likelihood of corrosion at the transition point between the motor and the corrosion resistant fitting. A connection between the fitting  34  and a fluid supply hose (not shown) is still possible after the motor has been coated. 
         [0024]    A corrosion resistant hydraulic motor has been described. Modifications and alterations will occur to those upon reading and understanding the preceding detailed description. The invention is not limited to only the embodiments disclosed above. Instead, the invention is broadly defined by the appended claims and the equivalents thereof.