Blade for liquid friction couplings
This is a continuation-in-part application of Ser. No. 905,887 filed on Sept. 10, 1986, now abandoned. 
     This invention relates to a blade for liquid friction couplings, which blade comprises a disc having effective end faces which are formed with a plurality of essentially radially extending interruptions. 
     Blades of that kind are already known from German Patent Specification No. 2,135,791. In that known blade the interruptions in the effective or end faces consist of radial slots, which do not serve only to facilitate the filling of the housing of the coupling with a viscous liquid but have mainly the function to increase the torque limit of the coupling. But the radial slots which interrupt the end faces greatly decrease the stiffness of the blades and the tongues which remain between the slots can easily be deformed. such deformations may result in a contact with the blades of the other set, which may rotate at a different speed, so that the wear of the blade will be increased and the stability of the entire multiblade unit will be reduced. 
     From German Patent No. 1,192,887 it is known to provide blades consisting of unslotted, solid-surfaced discs which have axially protruding corrugations. But in comparison with blades having slots defined by sharp edges, the obviously gentle transition from one corrugation to the next will reduce the torque limit. Besides, the undeformed serrated annular portion which is provided in the blade and serves to non-rotatably connect the blade to the associated coupling section is relatively thin so that the strength of the toothed joint connecting the blade to the driving or driven coupling section is adversely affected. Finally, the amplitude of the corrugations in the axial direction of the coupling are relatively large so that the axial dimension of a coupling comprising a given number of blades will appreciably be increased. 
     For this reason it is an object of the invention to eliminate said disadvantages and to provide a blade which is of the kind described first hereinbefore and which permits the torque limit to be increased in spite of a loss of strength and without an increase of the blade spacing. 
     This object is accomplished in accordance with the invention in that the interruptions are formed by grooves and the grooves provided on the two end faces are staggered from each other. 
     Contrary to the radial slots of the known blade, the grooves result only in a negligible decrease of the stiffness and strength of the blade. For this reason the grooves may be provided in a relatively large number so that the torque limit can be considerably increased over that of a coupling having smooth-surfaced blades. Because the grooves obviously have sharp longitudinal edges, the transmission of torque will be improved also in comparison with corrugated blades. Because there is no risk that free tongues defined by slots may be deflected out of the plane of the blade, the distances from the adjacent blades of the other set may be decreased so that the torque limit will inherently be increased. Besides, a larger number of blades can be accommodate in a coupling having a given total length so that the torque limit can be increased further. 
    
    
     An illustrative embodiment of the invention is shown in the drawings, in which 
     FIG. 1 is an elevation showing a blade for a liquid friction coupling, 
     FIG. 2 is an enlarged sectional view taken along the line A--A&#39;, and 
     FIG. 3 is a cross-sectional view of a liquid friction coupling having blades in accordance with the present invention. 
    
    
     Referring to FIGS. 1 and 2, a so-called inner blade 1, which is non-rotatably connected to the shaft section of the liquid friction coupling, is provided with a serrated portion 2 for making said connection and is provided at its periphery with apertures 3, which facilitate the filling of the housing of the coupling. The blade 1 is formed on its two effective end faces with a plurality of radially extending interruptions, which consists of grooves 4, 4&#39;. The grooves 4 of one end face are staggered from the grooves 4&#39; on the other end face. The blade 1 is a substantially flat disc. 
     A liquid friction coupling 10 in accordance with the present invention is illustrated in FIG. 3. The liquid friction coupling 10 has multiple inner blades 1 non-rotatably connected to a shaft of the liquid friction coupling by means of longitudinal ribs 12. Multiple outer blades 5 similar to inner blades 1 are connected to the liquid friction coupling housing by means of longitudinal ribs 14. A viscous fluid fills the housing. Inner blades 1 and outer blades 5 both are provided with grooves 4, 4&#39; on their respective faces, the grooves 4 of one face being staggered from the grooves for 4&#39; on the other face. Corresponding faces of inner blades 1 and outer blades 5 are in confronting relationship with each other with the viscous fluid between the confronting faces. 
     While the invention has been described by reference to specific examples, this was for purposes of illustration only and should not be construed to limit the spirit or scope of the invention.