PDM transmission with articulated torque transfer
A ball-CV style transmission suitable for use in a Positive Displacement Motor (PDM). A shaft provides shaft wings received into housing receptacles on a housing. A Unitary Torque Transfer Element (UTTE) is interposed between each shaft wing and housing within each housing receptacle, with a spherical surface on the UTTE received into a recess preferably on the housing. The UTTEs float within their corresponding housing receptacles so as to maintain torque transfer contact between all thrust surfaces during articulated rotation of the shaft with respect to the housing. The UTTEs preferably float generally radially towards the shaft centerline as angular deflection increases during articulated rotation.
1. An articulated transmission disposed to transmit torque via misaligned rotation, the transmission comprising:
a shaft having a shaft centerline about which the shaft is disposed to rotate, the shaft providing a plurality of shaft wings on one end thereof, the shaft wings extending generally radially from the shaft centerline;
each shaft wing providing a shaft bearing surface;
a generally cylindrical housing having a housing centerline about which the housing is disposed to rotate, the housing having a plurality of housing receptacles formed therein, each housing receptacle for receiving a corresponding shaft wing; and
a plurality of unitary torque transfer elements (UTTEs), each UTTE providing a UTTE spherical surface and a planar UTTE bearing surface on opposite sides of the UTTE;
wherein each housing receptacle provides a housing bearing surface wherein a housing recess is formed in each housing bearing surface;
wherein a shaft wing and a UTTE are received into each housing receptacle such that within each housing receptacle, the UTTE spherical surface is received into the housing recess and the UTTE bearing surface opposes the shaft bearing surface;
wherein, responsive to misaligned rotation of the shaft centerline with respect to the housing centerline and regardless of angular deflection of the shaft centerline with respect to the housing centerline experienced within each housing receptacle during an articulated revolution of the shaft: (1) the UTTE bearing surfaces are free to slidably displace against corresponding shaft bearing surfaces; (2) the housing recesses restrain the UTTEs from movement in at least a radial direction with respect to the housing centerline; and (3) the UTTEs are free to tilt within the housing recesses.
2. The transmission of claim 1 , in which the UTTEs float at least generally radially with respect to the shaft centerline when the UTTE bearing surfaces slidably displace against corresponding shaft bearing surfaces.
3. The transmission of claim 1 , in which:
each shaft wing further provides a shaft backlash surface such that each shaft bearing surface opposes a shaft backlash surface on a neighboring shaft wing;
each housing receptacle further provides a housing backlash surface to oppose a corresponding shaft backlash surface; and
wherein the transmission further includes a backlash energizer assembly interposed between at least one opposing shaft backlash surface and housing backlash surface.
4. The transmission of claim 3 , in which the backlash energizer assembly includes a puck separating a set screw and a backlash energizer Belleville washer.
5. The transmission of claim 3 , in which the backlash energizer assembly includes a puck.
6. The transmission of claim 5 , in which the puck includes a laminate of metal and elastomer layers.
7. The transmission of claim 1 , in which at least one housing receptacle further includes a housing release channel, and in which housing release channels extend housing recesses such that UTTE spherical surfaces may float within housing release channels responsive to said misaligned rotation of the shaft centerline with respect to the housing centerline.