MECHANICAL COUPLING FOR ELASTIC AXIAL AND RADIAL CONSTRAINT WITH TORSIONAL FREEDOM, ESPECIALLY FOR ELASTIC PIVOTS AND SUSPENSIONS AND THE LIKE

Abstract: Mechanical coupling for elastic axial and radial constraint with torsional freedom, especially for elastic pivots and supsensions and the like, comprising, according to the invention, a composite tubular member made of metal and elastomer (11) that exhibits high axial and radial rigidity and the ability to absorb vibrations induced by the mechanical system in which it is fitted and to compensate for manufacturing tolerances in that system, and a tubular insert (15), made of nonwear plastic material with a low coefficient of friction which is coaxial and integral, in the form of a fixed inner sleeve, with said composite tubular member (11) and engages with a rotating metallic component (16) fitted coaxially with respect to said tubular insert to provide the torsional freedom.

Description: MECHANICAL COUPLING FOR ELASTIC AXIAL AND RADIAL CONSTRAINT WITH TORSIONAL FREEDOM, ESPECIALLY FOR ELASTIC PIVOTS AND SUSPENSIONS AND THE LIKE The present invention relates to a mechanical coupling for elastic axial and radial constraint with torsional freedom, especially for elastic pivots and suspensions and the like. The mechanical coupling according to the present invention finds application in, for example, the following sectors (the list that follows is an indication and not exhaustive) : - the automotive sector, for • elastic pivots for the connection of the suspension levers of front and/or rear axles; • elastic pivots for connecting the anti-roll bar to the frame; • elastic pivots for leaf-spring/frame connection; • elastic pivot for the connection of the reaction rod of the power train; farming and earth-moving machinery, for • cabin support; • joint for excavator arm; - rail and tram sector, for • power cardan joints; • steering box links. Mechanical couplings are known, consisting generally of coaxial metal bushes between which a rubber sleeve is compressed (in effect making a rubber bush) . These are used for absorbing torsional, axial and radial deformations. The main shortcoming of these known couplings is the need to find a "physical" compromise between deformations in the axial and radial directions, and torsional deformations. In particular, radial rigidity and torsional rigidity (at least within the range of limited angular amplitude of about +30 degrees max.) are found to be directly proportional to each other and dependent on the amount of rubber inserted between the metal sleeves. Moreover, axial rigidity is always low and it is impossible to absorb axial and/or torsional overloads. Taking the above shortcomings as its starting point, the present invention aims to provide a remedy thereto. It is therefore the principal object of the present invention to provide a mechanical coupling, and in particular an elastic pivot or suspension, that is capable of reacting as an elastic constraint in the axial and radial directions, while yet at the same time presenting no torsional constraint at torque values close to zero (that is, "torsional freedom") or at any rate negligible in comparison with the forces present. With this object in view, the present invention provides a mechanical coupling for elastic axial and radial constraint with torsional freedom, especially for elastic pivots and suspensions and the like, whose essential characteristic is the subject of the main claim, which should be regarded as incorporated here in its entirety. Further advantageous characteristics are described in the dependent claims. The mechanical coupling according to the invention presents many advantages, which may be summarized in its ability to provide: great radial rigidity, - great axial rigidity, very low torsional rigidity, absorption of axial and/or radial overloads without permanent deformation, while making the coupling itself independent of physical limits resulting from its construction and/or from the use of conven¬ tional constructional materials or processes. The present invention will become clearer in the following detailed description, with reference to the attached drawings, which are provided purely by way of non-restrictive example, in which: Figures 1 and 2 are views in axial section of two different examples of embodiments of the mechanical coupling for elastic axial and radial constraint with torsional freedom, in particular for elastic pivots and suspensions and the like, according to the present invention; Fig. 3 is a partial view showing a detail in plan view of a component of the device shown in Fig. 2. With reference to Fig. 1, the numeral 10 indicates the whole of the mechanical coupling for elastic axial and radial constraint with torsional freedom, in one example of an embodiment of the invention. Said device 10 essentially comprises a composite tubular member 11 made up of two coaxial metal sleeves by way of an inner bush 12 and an outer bush 13, between which there is bonded a layer of elastomeric material 14, especially natural rubber, which in effect makes a rubber bush. Into the interior of said composite tubular member 11 there is driven, coaxially and with appropriate interference by way of a fixed sleeve, a first tubular insert 15 made of nonwear plastic material with a very low coefficient of friction and high mechanical strength, which is flanged at one axial end 15.1, bringing it back against the layer of elastomeric material 14. Another tubular insert 16, of a metallic material, is fitted so as to rotate coaxially inside said first tubular insert 15. The numeral 17 denotes outer rings attached like flanges to the axial ends of said other tubular insert 16, while 18 denotes an inner ring set between an outer ring 17 and the non- flanged axial end of said first tubular insert 15, made of the same plastic material, to hold the coupling 10 together. By means of the above construction, the mechanical coupling 10 performs the following specific functions: very rigid reaction to axial and radial stresses owing to the compression with limited deflection of the elastomer 14 bonded between the two metal sleeves 12, 13 and further pre-compressed by a drawing action on the outer sleeve 13; virtually no reaction to torsional torque, thanks to the relative rotation between the inner insert 16, made of metallic material, and the integral unit formed by the insert 15, made of plastic material with a low coefficient of friction, and by the composite tubular member 11, i.e. by the metal sleeves 12, 13 with the bonded elastomeric layer 14. Said mechanical coupling 10 is constructed by bonding sa-id layer of elastomeric material 14 between said two metal sleeves 12, 13 by a process of hot co-moulding, subjecting said elastomeric layer 14 to further pre-co pression by a drawing action on the outer sleeve 13, driving in coaxially said first insert 15, made of low-friction plastic material, with interference to form a sleeve which is fixed with respect to the inner metal sleeve 12, and fitting said other insert 16, made of metallic material, so that it can rotate coaxially inside said first insert 15. A layer of chemical grease, e.g. silicone grease, is advantageously introduced between said first insert 15 and said other insert 16 to improve the performance of the coupling and prevent noise from developing between the components. With reference now to Figures 2 and 3 of the drawings, the number 20 denotes the mechanical coupling for elastic axial and radial constraint with torsional freedom, in another example of an embodiment of the invention. Said coupling 20 essentially comprises a composite tubular member 21 made up of two coaxial metal sleeves by way of an inner bush 22 and an outer bush 23, between which there is bonded a layer of elastomeric material 24, especially natural rubber, which in effect makes a rubber bush. Into the interior of said composite tubular member 21 there is driven, coaxially and with appropriate interference by way of a fixed sleeve, a tubular insert 25, made of plastic material with a low coefficient of friction and high mechanical strength, and flanged at one axial end 25.1, bringing it back against the layer of elastomeric material 24. A first pin 26, comprising an eye end 26.1 and an axially hollow cylindrical body 26.2, made of a metallic material, is driven cold, to give an interference fit, into another pin 27 comprising an eye end 27.1 and a cylindrical body 27.2, also made of a metallic material. The resulting assembly is then fitted so as to be able to rotate coaxially inside the tubular insert 25. 28 is a plastic ring inserted between a flange part 26.3 of said first pin 26 and said tubular member 21 with the fixed sleeve 25, while 27.3 is a flange part of said other pin 27 placed against the flange 25.1 of said fixed sleeve 25. By means of this construction, the mechanical coupling 20' offers the same functions and the same advantages as shown with reference to the coupling 10. As will be clear from the foregoing, the coupling according to the present invention essentially comprises: • a composite tubular member co-moulded in metal and elastomer (11; 21) that exhibits high axial and radial rigidity while also having the ability to absorb vibrations induced by the mechanical system in which it is fitted and to compensate for manuf cturing tolerances in that system, and • a tubular insert made of nonwear plastic material with a low coefficient of friction (15; 25) which is coaxial and integral, in the form of a fixed inner sleeve, with said composite tubular member (11; 21) and engages with a metallic component (16; 26) fitted coaxially and rotatably inside it to provide the torsional freedom. In practice, of course, many variants may be made of what has been described and illustrated purely by way of non- restrictive examples, without thereby departing from the scope.of the invention and hence from the scope of this industrial property document. For example, instead of a layer of natural rubber, a layer of other elastomeric material, such as nitrile rubber, VAMAC etc. can be bonded between the metal sleeves.

Claims: CLAIMS 1. Mechanical coupling for elastic axial and radial constraint with torsional freedom, especially for elastic pivots and suspensions and the like, the coupling being characterized in that it comprises a composite tubular member made of metal and elastomer (11; 21) that exhibits high axial and radial rigidity and the ability to absorb vibrations induced by the mechanical system in which it is fitted and to compensate for manufacturing tolerances in that system, and a tubular insert (15, 25) made of nonwear plastic material with a low coefficient of friction which is coaxial and integral, in the form of a fixed inner sleeve, with said composite tubular member (11; 21) and engages with a rotating metallic component (16; 26) fitted coaxially with respect to said tubular insert to provide the torsional freedom. 2. Mechanical coupling according to Claim 1, characterized in that it comprises a composite tubular member (11; 21) made up of two coaxial metal sleeves, e.g. by way of an inner bush (12; 22) and an outer bush (13; 23), between which there is bonded a layer of elastomeric material (14; 24), e.g. natural rubber, which in effect makes a rubber bush, and also a tubular insert (15, 25) made of plastic material with a low coefficient of friction and high mechanical strength, driven into the interior of said composite tubular member, coaxially and with appropriate inter¬ ference by way of a fixed sleeve, in such a way as to provide an integral assembly that reacts as an elastic constraint in the axial and radial directions, and furthermore comprises a rotating component (16; 26) made of a metallic material and fitted coaxially inside said tubular insert (15, 25) in such a way as at the same time to present no torsional constraint at torque values close to zero (that is, "torsional freedom") or at any rate negligible in comparison with the forces present, by relative rotation between said rotating component (16, 26) and said integral assembly (11, 15; 21, 25) . 3. Mechanical coupling according to Claim 1 or 2, charac- terized in that a layer of grease, e.g. chemical grease, is introduced between the opposing surfaces of said tubular insert (15; 25) and of said rotating component (16; 26) to improve the performance of the coupling and prevent noise from developing between these components. 4. Mechanical coupling according to one or more of the previous claims, characterized in that it is constructed by bonding a layer of elastomeric material (14; 24) between two tubular metal sleeves (12, 13; 22, 23) by a process of hot co- moulding, subjecting said elastomeric layer (14; 24) to further pre-compression by a drawing action on the outer sleeve (13; 23), driving in coaxially a tubular insert (15; 25), made of low- friction, high-mechanical strength plastic material, with inter¬ ference to form a sleeve which is fixed with respect to the inner metal sleeve (12; 22), and fitting a component (16; 26), made of metallic material, so that it can rotate coaxially inside said insert (15; 25) .

Inventors: CASELLA GIUSEPPE, CASELLA, GIUSEPPE
Applicants: CASELLA GIUSEPPE, F I B E T S P A, CASELLA, GIUSEPPE, F.I.B.E.T. S.P.A.
Application year: 1996
Main classification: F16F1
IPC codes: B60G7, F16F1