Patents by Inventor Duncan McRae

Duncan McRae has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20030216208
    Abstract: A hydrostatic transaxle axle assembly for a vehicle such as a grass mowing lawn or garden tractor comprising a housing for an internally disposed hydrostatic transmission having a variable-displacement hydraulic pump fluidly connected to a fixed-displacement hydraulic motor, the hydraulic motor being connected by differential gearing to axle shafts supported in the housing. The housing is formed by three housing members, two of which are preferably separable on a parting plane coincident with the longitudinal axes of the axle shafts. One of the housing members being provided with an opening to allow a portion of one of the other housing members to extend through, and where the extending housing member contains within its interior a number of internal fluid passages for fluidly connecting the hydraulic pump to the hydraulic motor.
    Type: Application
    Filed: June 18, 2003
    Publication date: November 20, 2003
    Applicant: HYDRO-THOMA LIMITED
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Publication number: 20030199354
    Abstract: An axle assembly for use in lawn tractors, pedestrian walk-behind mowers and snow blowers in the form of a housing having an internally disposed hydrostatic transmission and speed reducing gearing. An input shaft supported in the housing for driving a variable-displacement hydraulic pump of the hydrostatic transmission, the pump fluidly coupled to a fixed-displacement hydraulic motor of the hydrostatic transmission, and where the motor is drivingly connected through the speed reducing gearing to an output axle shaft or shafts. A mechanical differential disposed within said housing for applications requiring differential speeds of said axle output shafts. The housing being formed by three housing members and joined together along a substantially planar and horizontally peripheral seam formed therebetween such that two of said housing members are to one side of said seam and join with the third housing element.
    Type: Application
    Filed: June 6, 2003
    Publication date: October 23, 2003
    Applicant: HYDRO-THOMA LIMITED
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Publication number: 20030192402
    Abstract: A hydrostatic transmission and gear transmission located in the same or separate housings structures, and mechanically drivingly connected together by a power transmission shaft. That housing structure surrounding the hydrostatic transmission defining a first internal volume containing the hydrostatic transmission components and providing a receptacle for the hydrostatic fluid. That housing structure surrounding the gear transmission defining a gear compartment sump. As one example, the housing structure surrounding the hydrostatic transmission may further define a second internal volume to operate as an overflow receiver for fluid transferred from the first internal volume. A duct operating in accordance with the siphon principle connects the internal volumes and where a pressure restriction valves ensures an above ambient pressure level in the volumes when the hydrostatic and gear transmission is operating. Alternatively, the gear compartment sump may act as the second internal volume.
    Type: Application
    Filed: May 29, 2003
    Publication date: October 16, 2003
    Applicant: HYDRO-THOMA LIMITED
    Inventors: George Duncan McRae Arnold, Christian Helmut Thoma
  • Patent number: 6626065
    Abstract: A hydrostatic transmission and gear transmission located in the same or separate housings structures, and mechanically drivingly connected together by a power transmission shaft. That housing structure surrounding the hydrostatic transmission defining a first internal volume containing the hydrostatic transmission components and providing a receptacle for the hydrostatic fluid. That housing structure surrounding the gear transmission defining a gear compartment sump. As one example, the housing structure surrounding the hydrostatic transmission may further define a second internal volume to operate as an overflow receiver for fluid transferred from the first internal volume. A duct operating in accordance with the siphon principle connects the internal volumes and where a pressure restriction valves ensures an above ambient pressure level in the volumes when the hydrostatic and gear transmission is operating. Alternatively, the gear compartment sump may act as the second internal volume.
    Type: Grant
    Filed: May 15, 2001
    Date of Patent: September 30, 2003
    Assignee: Hydro-Thoma Limited
    Inventors: George Duncan McRae Arnold, Christian Helmut Thoma
  • Patent number: 6607462
    Abstract: An axle assembly for use in lawn tractors, pedestrian walk-behind mowers and snow blowers in the form of a housing having an internally disposed hydrostatic transmission and speed reducing gearing. An input shaft supported in the housing for driving a variable-displacement hydraulic pump of the hydrostatic transmission, the pump fluidly coupled to a fixed-displacement hydraulic motor of the hydrostatic transmission, and where the motor is drivingly connected through the speed reducing gearing to an output axle shaft or shafts. A mechanical differential disposed within said housing for applications requiring differential speeds of said axle output shafts. The housing being formed by three housing members and joined together along a substantially planar and horizontally peripheral seam formed therebetween such that two of said housing members are to one side of said seam and join with the third housing element.
    Type: Grant
    Filed: February 11, 2002
    Date of Patent: August 19, 2003
    Assignee: Hydro-Thoma Limited
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Patent number: 6564550
    Abstract: A hydrostatic transaxle axle assembly for a vehicle has the housing is formed by three housing members, two of which are preferably separable on a parting plane coincident with the longitudinal axes of the axle shafts. One of the housing members being provided with an opening to allow a portion of one of the other housing members to extend through, and where the extending housing member contains within its interior a number of internal fluid passages for fluidly connecting the hydraulic pump to the hydraulic motor.
    Type: Grant
    Filed: April 30, 2002
    Date of Patent: May 20, 2003
    Assignee: Hydro-Thoma Limited
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Publication number: 20020189251
    Abstract: A hydrostatic transaxle axle assembly for a vehicle such as a grass mowing lawn or garden tractor comprising a housing for an internally disposed hydrostatic transmission having a variable-displacement hydraulic pump fluidly connected to a fixed-displacement hydraulic motor, the hydraulic motor being connected by differential gearing to axle shafts supported in the housing. The housing is formed by three housing members, two of which are preferably separable on a parting plane coincident with the longitudinal axes of the axle shafts. One of the housing members being provided with an opening to allow a portion of one of the other housing members to extend through, and where the extending housing member contains within its interior a number of internal fluid passages for fluidly connecting the hydraulic pump to the hydraulic motor.
    Type: Application
    Filed: July 25, 2002
    Publication date: December 19, 2002
    Applicant: HYDRO-THOMA LIMITED
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Publication number: 20020173398
    Abstract: A hydrostatic transmission connected by means of a power transmission shaft to a speed reducing transmission, the housing structure surrounding said transmissions defining a first and second internal volumes. The first internal volume providing a receptacle for the hydrostatic fluid and for containing the hydrostatic transmission components. The second internal volume, which may or may not contain the gear train components, operates as an overflow receiver for fluid transferred from the first internal volume. A duct disposed in the housing provides the only flow path between the volumes and any fluid volume change in the first internal volume due to temperature variation is translated in a change in depth in the overflow receiver. Preferably, the duct operates in accordance to the siphon principle and catering for fluid volume change internally is a significant improvement over current practice where reliance is placed on external paraphernalia to achieve this end.
    Type: Application
    Filed: May 15, 2001
    Publication date: November 21, 2002
    Applicant: Hydro-Thoma Limited
    Inventors: George Duncan McRae Arnold, Christaian Helmut Thoma
  • Publication number: 20020124560
    Abstract: A hydrostatic transaxle axle assembly for a vehicle such as a grass mowing lawn or garden tractor comprising a housing for an internally disposed hydrostatic transmission having a variable-displacement hydraulic pump fluidly connected to a fixed-displacement hydraulic motor, the hydraulic motor being connected by differential gearing to axle shafts supported in the housing. The housing is formed by three housing members, two of which are preferably separable on a parting plane coincident with the longitudinal axes of the axle shafts. One of the housing members being provided with an opening to allow a portion of one of the other housing members to extend through, and where the extending housing member contains within its interior a number of internal fluid passages for fluidly connecting the hydraulic pump to the hydraulic motor.
    Type: Application
    Filed: April 30, 2002
    Publication date: September 12, 2002
    Applicant: HYDRO-THOMA LIMITED
    Inventors: Christian Helmut Thoma, Geroge Duncan McRae Arnold
  • Publication number: 20020116923
    Abstract: A hydrostatic transaxle axle assembly for a vehicle such as a grass mowing lawn or garden tractor comprising a housing for an internally disposed hydrostatic transmission having a variable-displacement hydraulic pump fluidly connected to a fixed-displacement hydraulic motor, the hydraulic motor being connected by differential gearing to axle shafts supported in the housing. The housing is formed by three housing members, two of which are preferably separable on a parting plane coincident with the longitudinal axes of the axle shafts. One of the housing members being provided with an opening to allow a portion of one of the other housing members to extend through, and where the extending housing member contains within its interior a number of internal fluid passages for fluidly connecting the hydraulic pump to the hydraulic motor.
    Type: Application
    Filed: April 30, 2002
    Publication date: August 29, 2002
    Applicant: HYDRO-THOMA LIMITED
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Publication number: 20020115519
    Abstract: An axle assembly for use in lawn tractors, pedestrian walk-behind mowers and snow blowers in the form of a housing having an internally disposed hydrostatic transmission and speed reducing gearing. An input shaft supported in the housing for driving a variable-displacement hydraulic pump of the hydrostatic transmission, the pump fluidly coupled to a fixed-displacement hydraulic motor of the hydrostatic transmission, and where the motor is drivingly connected through the speed reducing gearing to an output axle shaft or shafts. A mechanical differential disposed within said housing for applications requiring differential speeds of said axle output shafts. The housing being formed by three housing members and joined together along a substantially planar and horizontally peripheral seam formed therebetween such that two of said housing members are to one side of said seam and join with the third housing element.
    Type: Application
    Filed: February 11, 2002
    Publication date: August 22, 2002
    Applicant: HYDRO-THOMA LIMITED
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Patent number: 6427442
    Abstract: A hydrostatic transaxle axle assembly for a vehicle such as a grass mowing lawn or garden tractor comprising a housing for an internally disposed hydrostatic transmission having a variable-displacement hydraulic pump fluidly connected to a fixed-displacement hydraulic motor, the hydraulic motor being connected by differential gearing to axle shafts supported in the housing. The housing is formed by three housing members, two of which are preferably separable on a parting plane coincident with the longitudinal axes of the axle shafts. One of the housing members being provided with an opening to allow a portion of one of the other housing members to extend through, and where the extending housing member contains within its interior a number of internal fluid passages for fluidly connecting the hydraulic pump to the hydraulic motor.
    Type: Grant
    Filed: March 23, 2001
    Date of Patent: August 6, 2002
    Assignee: Hydro-Thoma Limited
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Patent number: 6346059
    Abstract: An axle assembly for use in lawn tractors, pedestrian walk-behind mowers and snow blowers in the form of a housing having an internally disposed hydrostatic transmission and speed reducing gearing. An input shaft supported in the housing for driving a variable-displacement hydraulic pump of the hydrostatic transmission, the pump fluidly coupled to a fixed-displacement hydraulic motor of the hydrostatic transmission, and where the motor is drivingly connected through the speed reducing gearing to an output axle shaft or shafts. A mechanical differential disposed within said housing for applications requiring differential speeds of said axle output shafts. The housing being formed by three housing members and joined together along a substantially planar and horizontally peripheral seam formed there between such that two of said housing members are to one side of said seam and join with the third housing element.
    Type: Grant
    Filed: April 17, 2000
    Date of Patent: February 12, 2002
    Assignee: Hydro-Thoma Limited
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Patent number: 6343471
    Abstract: An axle assembly for use in lawn tractors, pedestrian walk-behind mowers and snow blowers in the form of a housing having an internally disposed hydrostatic transmission and speed reducing gearing. An input shaft supported in the housing for driving a variable-displacement hydraulic pump of the hydrostatic transmission, and where the motor is drivingly connected through the speed reducing gearing to an output axle shaft or shafts. A mechanical differential disposed within said housing for applications requiring differential speeds of said axle output shafts. The housing being formed by three housing elements in which two are disposed adjacent one another on one side of a parting plane and the third one disposed on the opposite side of the parting plane. Of the two internal chambers formed by the three housing elements, one chamber contains the hydrostatic transmission and the other chamber contains the speed reducing gearing.
    Type: Grant
    Filed: April 3, 2000
    Date of Patent: February 5, 2002
    Assignee: Hydro-Thoma Limited
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Publication number: 20010010154
    Abstract: A hydrostatic transaxle axle assembly for a vehicle such as a grass mowing lawn or garden tractor comprising a housing for an internally disposed hydrostatic transmission having a variable-displacement hydraulic pump fluidly connected to a fixed-displacement hydraulic motor, the hydraulic motor being connected by differential gearing to axle shafts supported in the housing. The housing is formed by three housing members, two of which are preferably separable on a parting plane coincident with the longitudinal axes of the axle shafts. One of the housing members being provided with an opening to allow a portion of one of the other housing members to extend through, and where the extending housing member contains within its interior a number of internal fluid passages for fluidly connecting the hydraulic pump to the hydraulic motor.
    Type: Application
    Filed: March 23, 2001
    Publication date: August 2, 2001
    Applicant: Unipat AG
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Patent number: 6237332
    Abstract: A hydrostatic transaxle axle assembly for a vehicle such as a grass mowing lawn or garden tractor comprising a housing for an internally disposed hydrostatic transmission having a variable-displacement hydraulic pump fluidly connected to a fixed-displacement hydraulic motor, the hydraulic motor being connected by differential gearing to axle shafts supported in the housing. The housing is formed by three housing members, two of which are preferably separable on a parting plane coincident with the longitudinal axes of the axle shafts. One of the housing members being provided with an opening to allow a portion of one of the other housing members to extend through, and where the extending housing member contains within its interior a number of internal fluid passages for fluidly connecting the hydraulic pump to the hydraulic motor.
    Type: Grant
    Filed: October 4, 1999
    Date of Patent: May 29, 2001
    Assignee: Unipat AG
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Patent number: 6231466
    Abstract: A hydrostatic transaxle axle assembly for a vehicle such as a grass mowing lawn or garden tractor comprising a lly disposed hydrostatic transmission having a variable-displacement hydraulic pump fluidly connected to a fixed-displacement hydraulic motor, the hhousing for an internaydraulic motor being connected by differential gearing to axle shafts supported in the housing. The housing is formed by at least three housing members, two of which are separable on a first parting-plane arranged to be perpendicular with respect to the longitudinal axes of the axle shafts. One or two of the housing members being provided with an opening to allow a portion of another housing members, called the radiator member portion to extend through, and where the extending portion contains within its internal structure a number of fluid power transmitting passages arranged for the purpose of fluidly connecting the hydraulic pump with the hydraulic motor.
    Type: Grant
    Filed: November 16, 1999
    Date of Patent: May 15, 2001
    Assignee: Unipat AG
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Patent number: 6178746
    Abstract: An improved hydrostatic transmission useful as a speed changing device having a single output shaft or a pair of outwardly extending shafts for use, for example, in small vehicles such as lawn and garden tractors. The hydrostatic transmission output may be mechanically coupled to the wheel driving axle by a gear or chain drive, or alternatively may have such means included in the same housing package containing the hydrostatic transmission. When a differential action is needed between the drive wheels of the vehicle, the differential may then also be included in the same housing package. In whichever of such configurations, the hydrostatic transmission comprises a radial piston pump fluidly coupled to a single or twin larger displacement axial piston motor of the swash-plate type by means of a fluid coupling valve supported by the housing.
    Type: Grant
    Filed: February 23, 1999
    Date of Patent: January 30, 2001
    Assignee: Unipat AG
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Patent number: 6076428
    Abstract: An axle assembly for use in lawn tractors, pedestrian walk-behind mowers and snow blowers in the form of a housing having an internally disposed hydrostatic transmission and speed reducing gearing. An input shaft supported in the housing for driving a variable-displacement hydraulic pump of the hydrostatic transmission, the pump fluidly coupled to a fixed-displacement hydraulic motor of the hydrostatic transmission, and where the motor is drivingly connected through the speed reducing gearing to an output axle shaft or shafts. A mechanical differential disposed within said housing for applications requiring differential speeds of said axle output shafts. The housing being formed by three housing members and joined together along a substantially planar and horizontally peripheral seam formed there between such that two of said housing members are to one side of said seam and join with the third housing element.
    Type: Grant
    Filed: October 6, 1998
    Date of Patent: June 20, 2000
    Assignee: Unipat AG
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold
  • Patent number: 6058704
    Abstract: A hydrostatic transmission having a housing for an internally disposed variable-displacement hydraulic pump and fixed-displacement hydraulic motor, a framework for supporting the hydraulic pump and motor components within said housing in a manner whereby the loads generated by the pressure medium flowing between pump and motor are absorbed into the framework. The framework to support a pintle-valve which as the fluid coupling means between pump and motor.
    Type: Grant
    Filed: March 20, 1998
    Date of Patent: May 9, 2000
    Assignee: Unipat AG
    Inventors: Christian Helmut Thoma, George Duncan McRae Arnold