Rotary shafts – gudgeons – housings – and flexible couplings for ro – Overload release coupling – Torque transmitted via resiliently biased positive drive...
Reexamination Certificate
1998-10-05
2001-03-06
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Overload release coupling
Torque transmitted via resiliently biased positive drive...
Reexamination Certificate
active
06196924
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is based upon and claims priority to German Patent Application 197 44 154.8 filed Oct. 7, 1997, which is herein expressly incorporated by reference.
BACKGROUND OF THE INVENTION
The invention relates to a torque limiting coupling for a driveline for driving agricultural implements. A coupling hub has first recesses which start from the cylindrical outer face and are distributed around the longitudinal axis. The first recesses extend parallel to the longitudinal axis. Furthermore, the coupling hub has second recesses which extend at a right angle relative to the first recesses. The second recesses are open towards the outer face and towards the first recesses. The torque limiting coupling has a coupling sleeve which, with a bore, is coaxially arranged around the coupling hub. Grooves are distributed in the coupling sleeve bore in accordance with the first recesses. The grooves extend parallel to the longitudinal axis and have a supporting face. Driving members, in the form of oblong slides, are adjustable in the first recess relative to the longitudinal axis. On the driving member outsides, on the head faces facing the bore of the coupling sleeve, the driving members each have a torque transmitting face supported on a supporting face of a groove of the coupling sleeve in the torque transmitting position. In the torque transmitting position, the driving members enter the groove. On their radial insides, the driving members have at least one first switching face. In addition, at least one spring-loaded switching cam is associated with each driving member. The switching cam is adjustably positioned in the associated second recess. The switching cam includes at least one second switching face. The switching cam is in contact with the driving member at its end face which faces the first recess and the first switching face. Two covers bridge the radial distance between the coupling hub and the coupling sleeve. The two covers are axially secured to the coupling sleeve. The two covers guide the first portion of the coupling hub, which portion includes the first recesses.
A torque limiting coupling is described in DE 41 37 829 A1. Here, the radially inner ends of the driving members include two switching faces. One face provides support in the transmitting position. In the other position, the face provides support in the disconnected position. Accordingly, the switching cams are provided with two second switching faces. The purpose of the further switching faces is to reduce the forces required to load the driving members towards their torque transmitting position to prevent the driving members from wearing or being damaged when entering the grooves. A further purpose is to reduce the switching speed. The switching speed is the speed at which the driving members start to enter the grooves in the coupling sleeve to be able to be transferred into the torque transmitting position. In DE 41 37 829 A1, a seal is shown, however it only serves to prevent dust from entering during field applications. Otherwise, the components are merely greased.
DE 30 01 566 A1 describes an overload coupling with radially displacable driving members. The driving members, via a torque transmitting face, are held in contact with a corresponding face of a groove-shaped recess in the sleeve-like outer part. The driving members are held by a switching cam acting on the inner ends of the switching faces in order to be able to transmit torque. The switching cam is spring-loaded. The switching faces, at the inner ends of the driving members and the corresponding supporting faces at the switching cams, are designed for the overload position in which the driving members are disengaged from the groove. Thus, the driving members can snap back into the engaged position. The faces which support the driving members in the torque transmitting position and the faces for the friction bearing of the hub, are supplied with lubricating oil. The faces are connected to the lubrication system of an internal combustion engine via a lubricating oil supply channel.
U.S. Pat. No. 4,919,244 describes integrating a disconnection mechanism or an overload coupling into a gearbox running in an oil bath. The overload coupling has radially displacable driving members. The driving members, in their radially outwardly displaced position, are held under the influence of a switching cam acting on their radially inner ends. The switching cam is spring-loaded. In the disconnected position, the mutually contacting faces of the switching cam and of the driving members are designed so that only a slight free force acts outwardly onto the driving members. Further, the faces mutually supporting one another are supplied with lubricant. One of the gears has radially extending bores in its tooth gaps. The bores guide the oil received from the housing to the cooperating faces of the driving members and switching cams.
SUMMARY OF THE INVENTION
It is an object of the invention to reduce the switching speed, especially in the case of couplings with a high transmission performance. Further, the invention ensures that during freewheeling, up to the point when such a speed is reached, the driving members are prevented from entering the grooves in order to reduce wear.
In accordance with the invention, seals are provided to seal the coupling hub, coupling sleeve and covers. Thus, the seals make the unit oil-proof. Oil fills the unit at least partially in the free space between the coupling hub, coupling sleeve and covers. The oil filling degree in the free space and the viscosity of the oil is selectable to achieve the desired re-engagement behavior. The oil filling degree reaches at least twenty (20%) percent of the free space and the viscosity amounts to at least 80 cSt (mm
2
/s).
Thus, during rotation, oil moves outwardly towards the bore wall of the bore of the coupling sleeve. If, in a case of overloading, the driving members move radially inwardly, so that they fully enter the first recesses of the coupling hub, the grooves in the bore of the coupling sleeve are filled with oil. In the case of a relative rotation between the coupling hub and the coupling sleeve, the driving members can no longer enter the grooves. In practical terms, the driving members slide on the oil in the region of the grooves and remain in their inwardly displaced position. Only when a low speed is reached is the amount of time taken by the driving members to pass over the grooves sufficient to allow the driving members to enter the grooves. In the process, oil is displaced out of the grooves. During the displacement process, the oil has to pass the gaps between the components. This results in a dampened re-engagement speed. When the re-engagement speed is reached, the final position of orientation of the coupling hub and coupling sleeve relative to one another, allowing the driving members to enter the grooves, is reached within a few rotations, so that there is no wear-causing ratchet effect. Overall, it is possible to achieve a long service life. The re-engagement behavior can be changed specifically by the filling degree and by the viscosity of the oil used. It is proposed to fill approximately twenty (20%) percent of the free spaces with oil. However, in a preferred embodiment, the filling degree ranges between fifty (50%) percent and ninety-five (95%) percent. The viscosity of the oil used preferably ranges between 80 cSt (mm
2
/s) and 460 cSt (mm
2
/s).
Although the teaching according to the invention can be applied to couplings whose driving members comprise only one switching face at the mutually supporting regions of the driving members and switching cams, preference is given to an assembly where two switching faces at each of the driving members and associated switching cams are provided. Two faces are provided to support the driving members by the spring-loaded switching cams. The other faces are provided to provide support in the disconnected position with a reduced force.
To guide the oil in a specific way, the first re
Adamek Wolfgang
Kampf Klaus
Browne Lynne H.
Dunwoody Aaron
GKN Walterscheid GmbH
Harness & Dickey & Pierce P.L.C.
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