Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling facilitates relative axial motion between coupled... – Coupler includes antifriction rolling body engageable with...
Reexamination Certificate
1999-11-30
2001-04-17
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling facilitates relative axial motion between coupled...
Coupler includes antifriction rolling body engageable with...
C464S906000, C464S146000
Reexamination Certificate
active
06217456
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a telescopic shaft, for connecting two joints. In particular, a telescopic shaft comprising an outer part and an inner part which are provided with running grooves of which two are arranged opposite one another and which receive balls for the purpose of axially adjusting the two parts relative to one another and for transmitting torque between the two parts.
U.S. Pat. No. 5,624,318 describes a driveshaft connecting two constant velocity joints into which there is integrated a telescopic shaft or a telescopic shaft portion which compensates for any changes in length occurring when the joint angles are changed. The telescopic shaft comprises an outer part in the form of a sleeve and an inner part in the form of a shaft portion. The inner part adjustably enters a bore of the outer part in the direction of the common longitudinal axis of both parts. In the bore of the outer part there are provided circumferentially distributed outer running grooves which extend parallel to the longitudinal axis. In the outer face of the inner part there are provided inner running grooves which are arranged opposite the outer running grooves. The outer running grooves and inner running grooves are distributed around the longitudinal axis at identical pitches. Each pair of inner running grooves and outer running grooves accommodates a plurality of balls which serve to transmit torque and which together, form an anti-friction bearing for adjusting the outer part and inner part relative to one another in the direction of the longitudinal axis.
For designing a telescopic shaft or telescopic shaft portion, the inner part constitutes the part which determines the pitch of the inner running grooves and the size and number of the balls, taking into account the torque values to be transmitted and the peak loads occurring in a predetermined application, for example in the driveshaft of a motor vehicle. The pitch for the outer running grooves in the bore of the outer part is thus also determined. However, as the outer running grooves are arranged on a larger diameter than the inner running grooves, there occur webs between each two outer running grooves in which, due to the greater circumferential distance of the outer running grooves, there are accumulated larger material masses than between inner running grooves of the inner part which closely adjoin one another in the circumferential direction. For the outer part this means that the disadvantageous distribution results in distortion during hardening. This distortion necessitates subsequent machining. Rough tolerances cannot be admitted because any rotational play or any resistance against displacement changing along the path of adjustment is not acceptable as it adversely affects functioning. Subsequent machining increases costs.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a telescopic shaft which is designed in such a way that distortion cannot occur during hardening, or that any distortion that does occur is minimized to such an extent that the required functional clearances are ensured without the need for subsequent machining . The telescopic shaft can also be produced cost-effectively .
In accordance with the invention, this and other objects and advantages are achieved by providing a telescopic shaft having an outer part which comprises a longitudinal axis, a bore centered on the longitudinal axis, an even number of outer running grooves which are uniformly distributed around the longitudinal axis and which are arranged in the wall of the bore so as to extend parallel to the longitudinal axis. The outer part is provided with a circular-cylindrical outer face in the length portion comprising the outer running grooves. The telescopic shaft further includes an inner part which enters the bore of the outer part, whose longitudinal axis, in the assembled condition, coincides with that of the outer part. The outer face of the inner part comprises inner running grooves which are uniformly distributed around the longitudinal axis and extend parallel thereto. The number of inner running grooves corresponds to half, or a third of, the number of outer running grooves, with each of the inner running grooves being arranged opposite each second or third circumferentially distributed outer running groove, thus forming pairs. The telescopic shaft also includes balls, a plurality of which are rollingly arranged in each pair of opposed outer running grooves and inner running grooves.
An advantage of the present invention is that, due to the negligible differences in wall thickness, i.e. due to a more even distribution of masses and the symmetrical design, practically no distortion occurs during hardening. As a result, there is no need for subsequent machining. In addition, the outer part is more lightweight, so that the masses to be accelerated and decelerated are smaller.
Note that the outer part is provided with outer running grooves whose number can be divided by 3 and/or 2 and results in an integral figure of inner running grooves.
According to a preferred embodiment, a cage, which is sleeve-like, is arranged between the outer face of the inner part and the wall of the bore of the outer part. The cage comprises radial through-holes in which the balls are received and from which they project inwardly and outwardly for the purpose of engaging the pair-forming outer running grooves and inner running grooves.
Particularly advantageous conditions are obtained if the outer part with the outer running grooves is produced by round form-kneading, or rotary swaging starting from a tube and using an inner tool which comprises the inner contour of the outer part. Producing the outer part by a non-chip forming method leads to good surfaces and makes it possible to observe close tolerances and achieve a high degree of repeat accuracy. In addition, there is achieved an advantageous structure and reduction in production costs.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and appended claims, and upon reference to the accompanying drawings.
REFERENCES:
patent: 3203202 (1965-08-01), Brownyer
patent: 3808839 (1974-05-01), Teramachi
patent: 4103514 (1978-08-01), Grosse-Entrup
patent: 4254639 (1981-03-01), Teramachi
patent: 4764154 (1988-08-01), Teramachi
patent: 5611733 (1997-03-01), Jacob et al.
patent: 5624318 (1997-04-01), Jacob
patent: 44 19 341 C1 (1994-06-01), None
patent: 44 19 373 C2 (1994-06-01), None
patent: 197 39 934 A1 (1997-09-01), None
patent: 1 292 557 (1971-07-01), None
patent: 2 311 117 (1997-10-01), None
Browne Lynne H.
GKN Lobro GmbH
Thompson Kenn
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