A drive transmission device, which is included in an image forming apparatus, includes a drive transmission device including first and second rotary bodies, first and second grooves, a link device linking the first and second rotary bodies, a stopper, a guide groove, and a communication portion. The link device includes first and second inserting bodies and a link body linking the first and second inserting bodies. The stopper stops the first projection from being detached from the first groove. The guide groove guides the first projection into the first hollow body. The communication portion causes the guide groove and the first groove to communicate with each other. The first hollow body relieves the second projection closer to the first rotary body than the stopper in the axial direction of the first rotary body and in the direction of rotation of the first rotary body in assembly.

A downhole motor drive shaft assembly includes a drive shaft having a longitudinal rotational axis, a plurality of drive key sockets, an end housing having a longitudinal rotational axis, a plurality of circumferentially spaced axial keyways, and a concave spherical thrust bearing surface, and a drive key operatively connecting each drive key socket with a respective axial keyway for transferring torque from the drive shaft to the end housing. The drive key includes a substantially planar drive face slidably engaging the axial keyway, and a radiused, cylindrical back portion rotatably engaging the drive key socket, the substantially planar drive face and radiused, cylindrical back portion forming a nominal half-circle.

A downhole motor drive shaft assembly includes a drive shaft having a longitudinal rotational axis, a plurality of drive key sockets, an end housing having a longitudinal rotational axis, a plurality of circumferentially spaced axial keyways, and a concave spherical thrust bearing surface, and a drive key operatively connecting each drive key socket with a respective axial keyway for transferring torque from the drive shaft to the end housing. The drive key includes a substantially planar drive face slidably engaging the axial keyway, and a radiused, cylindrical back portion rotatably engaging the drive key socket, the substantially planar drive face and radiused, cylindrical back portion forming a nominal half-circle.

A linkage system for transmitting torque includes a central element, an input arm and an output arm. The central element has four sides and a top and bottom. The input arm and an output arm each have a head portion for connecting with the central element and a body portion. The head portion of each of the input and output arms defines a bearing surface having a first radius. The input and output arms engage the central element such that the bearing surfaces of the heads are offset by 90 degrees.

A linkage system for transmitting torque includes a central element, an input arm and an output arm. The central element has four sides and a top and bottom. The input arm and an output arm each have a head portion for connecting with the central element and a body portion. The head portion of each of the input and output arms defines a bearing surface having a first radius. The input and output arms engage the central element such that the bearing surfaces of the heads are offset by 90 degrees.

A drive transmission device, which is included in an image forming apparatus, includes a drive transmission device including first and second rotary bodies, first and second grooves, a link device linking the first and second rotary bodies, a stopper, a guide groove, and a communication portion. The link device includes first and second inserting bodies and a link body linking the first and second inserting bodies. The stopper stops the first projection from being detached from the first groove. The guide groove guides the first projection into the first hollow body. The communication portion causes the guide groove and the first groove to communicate with each other. The first hollow body relieves the second projection closer to the first rotary body than the stopper in the axial direction of the first rotary body and in the direction of rotation of the first rotary body in assembly.

A hub built-in type drive axle includes one hub housing assuming a role of an external race of a constant velocity joint and a role of a wheel hub simultaneously, wherein the outboard constant velocity joint center is positioned within the full length of the hub housing, and a structure in which a bear housing and a boot assembly ring, including a boot, do not rotate whether the driveshaft 1 rotates is maintained so that performance may be improved, durability may be enhanced, and noise may be minimized.

A hub built-in type drive axle includes one hub housing assuming a role of an external race of a constant velocity joint and a role of a wheel hub simultaneously, wherein the outboard constant velocity joint center is positioned within the full length of the hub housing, and a structure in which a bear housing and a boot assembly ring, including a boot, do not rotate whether the driveshaft 1 rotates is maintained so that performance may be improved, durability may be enhanced, and noise may be minimized.

A compensating coupling comprises two outer coupling parts, namely an input-side coupling part and an output-side coupling part, both of which are to be connected to rotatable elements, more particularly shafts, and a center coupling part, which can be moved to a limited extent relative to the outer coupling parts. The center coupling part is composed of: a tube piece in the form of a damping element; and two tube end pieces, which are fastened to the tube piece and which are each designed to be fitted onto one of the outer coupling parts in a centered manner by ball head centering.