Patent Description:
Double cardan joints are adapted to transfer rotation between two non-parallel shafts. As can be seen in <FIG>, which illustrates a conventional double cardan joint <NUM>, the conventional double cardan joint <NUM> includes two universal joints connected between an input shaft <NUM> and an output shaft <NUM>. The conventional double cardan joint <NUM> includes an input yoke <NUM> connected to a center yoke <NUM> (often referred to as an H yoke) via an input cross-member <NUM> (forming a first universal joint) and an output yoke <NUM> connected to the center yoke <NUM> via an output cross-member <NUM> (forming a second universal joint).

The conventional double cardan joint <NUM> is a complex joint that includes an aligning ball-joint <NUM>, such as a spherical needle bearing, that centers and aligns the double cardan joint <NUM>. However, the aligning ball-joint <NUM> is relatively expensive and requires grease to function. As the grease can get contaminated, the conventional double cardan joint <NUM> is typically covered by a sleeve (not illustrated) to seal the double cardan joint <NUM> to prevent contaminants, such as water and dust, from reaching the aligning ball-joint <NUM>. Such sleeves add further costs to a conventional double cardan joint <NUM>.

Furthermore, in the event of contamination of the grease, the conventional double cardan joint <NUM> has to be disassembled to replace the contaminated grease.

The above-described background relating to double cardan joints is merely intended to provide a contextual overview of some current issues and is not intended to be exhaustive. Other contextual information may become apparent to those of ordinary skill in the art upon review of the following description of exemplary embodiments. <CIT> describes a double cardan elastically centered with a conventional double cardan formed by an input shaft, two annular cardan crosses, a double fork and an output shaft, and a centering device and <CIT> describes a constant velocity universal joint comprising an aligning disc <NUM> provided with a socket part <NUM> having a cylindrical hole for rotatably supporting the spherical projections 7a, 7a of the pins <NUM> of pinyokes 1A, 1B, and moreover a compression coil spring <NUM> to elastically support the spherical projections la, la is provided inside the cylindrical hole.

The present invention generally provides a double cardan joint with a resilient member positioned between and coupling the universal joints of the double cardan joint as set out in the appended set of claims. The resilient member is adapted to support the input and output shafts and is adapted to center and align the double cardan joint.

By positioning the resilient member between the universal joints to center and align the double cardan joint, the conventional aligning ball-joint is not necessary. As such, the total cost of the double cardan joint is significantly reduced due to the removal of the expensive aligning ball-joint. Furthermore, the resilient member does not require the same sealing considerations as the aligning ball-joint since the resilient member does not require grease. As such, the sleeve required for sealing the conventional double cardan joint is not necessary, leading to further savings.

The present invention provides a double cardan joint assembly, including: an input yoke; an input cross-member coupled to the input yoke; an output yoke; an output cross-member coupled to the output yoke; a center yoke coupled to the input cross-member forming an input universal joint with the input yoke and the input cross-member and coupled to the output cross-member forming an output universal joint with the output yoke and the output cross-member; and a resilient member positioned between the input universal joint and the output universal joint, the resilient member adapted to center and align the double cardan joint assembly. The resilient member spans between an input arc guard of the input yoke and an output arc guard of the output yoke. Alternatively, in an example not being part of the present invention, the resilient member spans between the input cross-member and the output cross-member. In such case, the resilient member spans between the input cross-member and the output cross-member through the input arc guard of the input yoke and the output arc guard of the output yoke. In one embodiment, the resilient member includes one or more of a linear spring, a coil spring, and a wave spring. In another embodiment, the resilient member includes an elastic component. Optionally, the resilient member includes a combination of elastic and rigid components.

In another illustrative embodiment, the present invention provides a shaft assembly, including: an input shaft; an output shaft; and a double cardan joint coupling the input shaft to the output shaft. The double cardan joint includes an input yoke; an input cross-member coupled to the input yoke; an output yoke; an output cross-member coupled to the output yoke; a center yoke coupled to the input cross-member forming an input universal joint with the input yoke and the input cross-member and coupled to the output cross-member forming an output universal joint with the output yoke and the output cross-member; and a resilient member positioned between the input universal joint and the output universal joint, the resilient member adapted to center and align the double cardan joint assembly. The resilient member spans between an input arc guard of the input yoke and an output arc guard of the output yoke. Alternatively, in an example not being part of the present invention, the resilient member spans between the input cross-member and the output cross-member. In such case, the resilient member spans between the input cross-member and the output cross-member through the input arc guard of the input yoke and the output arc guard of the output yoke. In one embodiment, the resilient member includes one or more of a linear spring, a coil spring, and a wave spring. In another embodiment, the resilient member includes an elastic component. Optionally, the resilient member includes a combination of elastic and rigid components.

The present invention also provides a method for manufacturing a double cardan joint assembly, the method including: providing an input yoke; providing an input cross-member coupled to the input yoke; providing an output yoke; providing an output cross-member coupled to the output yoke; coupling a center yoke to the input cross-member forming an input universal joint with the input yoke and the input cross-member; coupling the center yoke to the output cross-member forming an output universal joint with the output yoke and the output cross-member; and positioning a resilient member between the input universal joint and the output universal joint, the resilient member adapted to center and align the double cardan joint assembly. The resilient member spans between an input arc guard of the input yoke and an output arc guard of the output yoke. Alternatively, in an example not being part of the present invention, the resilient member spans between the input cross-member and the output cross-member. In such case, the resilient member spans between the input cross-member and the output cross-member through the input arc guard of the input yoke and the output arc guard of the output yoke. In one embodiment, the resilient member includes one or more of a linear spring, a coil spring, and a wave spring. In another embodiment, the resilient member includes an elastic component. Optionally, the resilient member includes a combination of elastic and rigid components.

The present invention is illustrated and described herein with reference to the various drawings, in which like reference numbers are used to denote like system components/method steps, as appropriate, and in which:.

Again, the present invention relates to a double cardan joint with a resilient member positioned between the universal joints of the double cardan joint, which is adapted to center and align the double cardan joint. The resilient member replaces the need for an aligning ball-joint used in conventional double cardan joints.

By positioning the resilient member between the universal joints to center and align the double cardan joint, the complexity of the double cardon joint is reduced and the cost of the double cardan joint is significantly reduced. First, the conventional, expensive aligning ball-joint is not required. Second, without requiring grease, the resilient member does not require the same sealing considerations as the aligning ball-joint. As such, the sleeve required for sealing the conventional double cardan joint is also not required, resulting in further savings.

<FIG> is a schematic illustration of one embodiment of the double cardan joint <NUM> of the present invention. Referring to <FIG>, the double cardan joint <NUM> includes an input yoke <NUM>, an input cross-member <NUM>, a center yoke <NUM>, an output yoke <NUM>, an output cross-member <NUM>, and a resilient member <NUM> disposed between the input yoke <NUM> and the output yoke <NUM>.

The input yoke <NUM> is adapted to be disposed at an end of an input shaft <NUM>. The input yoke <NUM> can be coupled to or unitarily formed with the input shaft <NUM>. The input yoke <NUM> is adapted to couple with the center yoke <NUM> via the input cross-member <NUM>, forming an input universal joint. The input yoke <NUM> couples to the input cross-member <NUM> at <NUM> degrees relative to the coupling between the center yoke <NUM> and the input cross-member <NUM>. The input cross-member <NUM> includes orthogonal arms <NUM> adapted to couple with the input yoke <NUM> and the center yoke <NUM>. Caps <NUM> are positioned over the arms <NUM> to secure the arms <NUM> to the respective yoke and retaining devices <NUM>, such as retention clips, are positioned to secure the caps <NUM> in position relative to the respective yoke. The input cross-member <NUM> thereby provides relative movement between the input shaft <NUM> and the center yoke <NUM> along two orthogonal axes. The input shaft <NUM> and input yoke <NUM> may also have a degree of rotational freedom. Fewer degrees of motion freedom may also be utilized.

The output yoke <NUM> is adapted to be disposed at an end of an output shaft <NUM>. The output yoke <NUM> can be coupled to or unitarily formed with the output shaft <NUM>. The output yoke <NUM> is adapted to couple with the center yoke <NUM> via the output cross-member <NUM>, forming an output universal joint. The output yoke <NUM> couples to the output cross-member <NUM> at <NUM> degrees relative to the coupling between the center yoke <NUM> and the output cross-member <NUM>. The output cross-member <NUM> includes orthogonal arms <NUM> adapted to couple with the output yoke <NUM> and the center yoke <NUM>. Caps <NUM> are positioned over the arms <NUM> to secure the arms <NUM> to the respective yoke and retaining devices <NUM>, such as retention clips, are positioned to secure the caps <NUM> in position relative to the respective yoke. The output cross-member <NUM> thereby optionally provides relative movement between the output shaft <NUM> and the center yoke <NUM> along two orthogonal axes. The output shaft <NUM> and output yoke <NUM> may also have a degree of rotational freedom. Fewer degrees of motion freedom may also be utilized.

The resilient member <NUM> is adapted to support the input shaft <NUM> and the output shaft <NUM>. The resilient member <NUM> is also adapted to center and align the double cardan joint <NUM>. By centering and aligning the double cardan joint <NUM>, the angles of the input universal joint and the output universal joint are the same, such that any variation of angular velocity that occurs in the input universal joint is essentially canceled out by the variation in angular velocity that occurs in the output universal joint.

The resilient member <NUM> includes one or more resilient components, such as a linear spring, a coil spring, a wave spring, an elastic component, and/or the like. In the embodiment illustrated in <FIG>, the resilient member <NUM> includes a coil spring spanning between an input arc guard <NUM> of the input yoke <NUM> and an output arc guard <NUM> of the output yoke <NUM>. These arc guards <NUM> and <NUM> are designed to protect the associated cross-members <NUM> and <NUM> as well as provide structural stability to the associated universal joints. In embodiments, each of the input arc guard <NUM> and the output arc guard <NUM> includes a spring seat that is adapted to receive an end of the resilient member <NUM>.

<FIG> is a schematic illustration of an embodiment of the double cardan joint <NUM> not being part of the present invention. In the embodiment illustrated in <FIG>, the resilient member <NUM> includes a coil spring spanning between the input cross-member <NUM> and the output cross-member <NUM> directly, passing through the arc guard <NUM> or <NUM> associated with each universal joint. Each arc guard <NUM> and <NUM> is slotted for such purpose. In embodiments, each of the input cross-member <NUM> and the output cross-member <NUM> includes a spring seat that is adapted to receive an end of the resilient member <NUM>.

<FIG> is a schematic illustration of a further embodiment of the double cardan joint <NUM> of the present invention. In the embodiment illustrated in <FIG>, the resilient member <NUM> includes an elastic component, such as a flexible rubber component, spanning between the input arc guard <NUM> of the input yoke <NUM> and the output arc guard <NUM> of the output yoke <NUM>.

While the embodiments in <FIG> illustrate a single component for the resilient member <NUM>, in some embodiments, the resilient member <NUM> includes multiple resilient components. In further embodiments, the resilient member <NUM> includes a combination of resilient and rigid components.

Claim 1:
A double cardan joint assembly (<NUM>), comprising:
an input yoke (<NUM>);
an input cross-member (<NUM>) coupled to the input yoke (<NUM>);
an output yoke (<NUM>);
an output cross-member (<NUM>) coupled to the output yoke (<NUM>); and
a center yoke (<NUM>) coupled to the input cross-member (<NUM>) forming an input universal joint with the input yoke (<NUM>) and the input cross-member (<NUM>) and coupled to the output cross-member (<NUM>) forming an output universal joint with the output yoke (<NUM>) and the output cross-member (<NUM>); characterized by
a resilient member (<NUM>) positioned between the input universal joint and the output universal joint, the resilient member (<NUM>) adapted to center and align the double cardan joint assembly (<NUM>), wherein the resilient member (<NUM>) spans between an input arc guard (<NUM>) of the input yoke (<NUM>) and an output arc guard (<NUM>) of the output yoke (<NUM>).