FLEXIBLE DRIVE COUPLING

Abstract: Flexible drive coupling having a driving hub and a driven hub (10, 11) which are attached each to one leaf spring element (12, 13). The two leaf spring elements are interconnected at diametrically opposite locations spaced radially from the hubs. An engagement spot for the leaf spring element is provided at a distance from at least one of said locations.

Description: FLEXIBLE DRIVE COUPLING The invention relates to a flexible drive coupling having a driving hub and a driven hub which are attached each to one leaf spring element, said leaf spring elements being interconnected at a radial distance from the hubs at diametrically opposite locations. Flexible drive couplings of this type can replace universal joints when the relative angular displacement of the hubs is not too large, and provide the advantage as compared with universal * joints that the output rotational speed will be independent of the angular displacement and thus will equal the input rotational speed. Moreover, the flexible drive coupling does not have elements mounted for sliding movement in relation to each other, which makes the coupling free from maintenance and cheap to manufacture. If a large angular displacement is required, several flexible drive couplings can be interconnected in series. Flexible drive couplings are known in several different embodiments. One problem encountered at all these couplings is that the leaf spring elements are subject to fatigue when the coupling is operating and therefore have a fairly short life particularly at large angular displacement. The purpose of the invention is to improve the coupling in this respect, and for this purpose the coupling of the kind referred to above has obtained according to the invention the characteristics appearing from claim 1. In order to explain the invention in more detail an embodiment thereof will be described below, reference being made to the accompanying drawing in which FIG. 1 is an end view of the flexible drive coupling of the invention, FIG. 2 is a side view, partly an axial sectional view, of the coupling in FIG. 1, FIG. 3 is an enlarged detailed sectional view along line III-III in FIG. 1, and FIG. 4 is a fragmentary detailed sectional view similar to FIG. 3 of a modified embodiment. In the drawing there are shown two hubs 10 and 11 one of which should be driving and accordingly can be mounted to a driving shaft, and the other one should be driven and thus can be mounted to a driven shaft. The hubs are connected each to one leaf spring element 12 and 13, respectively, which forms a square but also can form a rhomb, a web 14 and 15, respectively, being provided in the square or rhomb, extending between two opposite corners of the square or rhomb and having the associated hub attached thereto. At the other two opposite corners the two leaf spring elements are interconnected by means of rivets 16, but the interconnection can also be provided by means of bolt or screw connections or by welding or brazing. The leaf spring elements are formed such that the hub ends are mutually spaced, and allow angular displacement of the coupling more or less from the condition shown in which the hubs are located substantially coaxially with each other. When the coupling is operating in an angularly displaced condition, the leaf spring elements will be subject to continuous bending alternatingly in one direction and the other at the locations where the hubs are attached and where the leaf spring elements are interconnected. In order to reduce the stress of the leaf springs associated with such bending the attachment is arranged in the manner shown with regard to the connection between the hubs and the leaf spring .elements. At each side of the leaf spring element 12 and 1.3, ' , respectively, two support leaf springs (or support plates) 17 and 18 are provided which engage opposite sides of the leaf spring element and may be of equal length or, as shown herein, may have different lengths. The two support leaf springs should be stiffer than the leaf spring element to form an engagement spot for the leaf spring element at the outer free end of the support leaf spring. At this end, the support leaf spring preferably is rounded at the side facing the leaf spring element, and such rounding can be provided by bending outwards the free end of the support leaf spring as shown in FIG. 3. In the preferred embodiment, the support leaf springs, as in the embodiment shown, have different lengths in order that the support leaf springs shall be engaged at different spots when the leaf spring element is bent alternatingly at one side and the other. By this arrangement there will not be obtained at the engagement spots alternating stress at a single spot of the leaf spring element but a pulsating stress at two mutually spaced spots, which means that the life of the leaf spring element will be substantially increased. The embodiment can be further improved by forming at least one and preferably the longer support leaf spring 17 in the manner shown in FIG. 4. At the side facing the leaf spring element 12, material has been removed from the support leaf spring 17 by milling at 19 at the outer free end of said spring such that the support leaf spring forms two engagement spots radially spaced, one at the inner end of the milled portion which the leaf spring element first engages at angular displacement and another engagement spot at the free end of the support leaf spring. The depth of said milled portion need not be more than a fraction of 1 mm, and the length should be so great that the milled portion extends below the outer free end of the support leaf spring. In an embodiment having a length difference of 3 mm between the support leaf springs 17 and 18, a milled portion having a length of 5 mm and a depth of 0.1 mm has been found to provide considerable extension of the life of the leaf spring element 12. The life is of the order 70 to 100 times larger than that of an embodiment having support leaf springs of equal length and without the milled portion.

Claims: CLAIMS 1. Flexible drive coupling having a driving hub and a driven hub (10, 11) which are attached each to one leaf spring element (12, 13), said leaf spring elements being interconnected at a radial distance from the hubs at diametrically opposite locations, c h a r a c t e r i z e d in that an engagement spot for the leaf spring element is provided at a distance from at least one of the attachments. 2. Drive coupling as claimed in claim 1, c h a r a c t e r i z e d in that an engagement spot is provided at each side of the leaf spring element (12, 13). 3. Drive coupling as claimed in claim 1 or 2 , c h a r a c t e r i z e d in that the engagement spot is formed by a support, leaf spring (17, 18) engaging the leaf spring element (12, 13). 4. Drive coupling according to claims 2 and 3, c h a r a c t e r i z e d in that the support leaf springs (17, 18) have different lengths. 5. Drive coupling as claimed in claim 3 or 4, c h a r a c t e r i z e d in that the support leaf spring or each support leaf spring (17, 18) is rounded at the free end thereof at the side facing the leaf spring element (12, 13). 6. Drive coupling as claimed in claim 5, c h a r a c t e r i z e d in that the rounding is provided by the end of the support leaf spring being bent outwards. 7. Drive coupling according to any of claims 1 to 6, c h a r a c t e r i z e d in that at least one of the support leaf springs (17, 18) has two engagement spots radially spaced. 8. Drive coupling as claimed iri claim 7, c h a r a c t e r i z e d in that the two engagement spots radially spaced are provided by material being removed by milling (at 19) at the free end of the support leaf spring at the side thereof facing the leaf spring element (12). 9. Drive coupling as claimed in any of claims 1 to 8, c h a r a c t e r i z e d in that the engagement spots are provided at the attachment between each hub (10, 11) and the associated leaf spring element (12, 13). 10. Drive coupling as claimed in any of claims 1 to 9, c h a r a c t e r i z e d in that each leaf spring element (12, 13) forms a rhomb or square having a web (14, 15) between two opposite corners, each hub (10, 11) being attached to the web of the associated leaf spring element and the leaf spring elements being interconnected at the other two opposite corners.

Inventors: GERBERT GOERAN, LANDAEUS KJELL, GERBERT, GOERAN, LANDAEUS, KJELL
Applicants: GERBERT GOERAN, LANDAEUS KJELL, GERBERT, GOERAN, LANDAEUS, KJELL
Application year: 1986
Main classification: F16D3
IPC codes: F16D3