A DEVICE FOR ATTACHMENT OF A MACHINE MEMBER TO A SHAFT

Abstract: A device for attachment of a machine member (2) to a shaft (3), whereby the machine member has an opening (4) for said shaft. The opening (4) has on one hand surface portions (5) of a shape corresponding to the shape of the shaft (3), cylindrical or tapering, and on the other hand surface portions (6) having a shape corresponding to the shape of the clamping surfaces of a clamping sleeve, for allowing optional attachment of the machine member (2) directly on the shaft (3) or by means of the clamping sleeve.

Description: The present invention relates to an arrangement for securing an inner ring of a bearing to a shaft either directly on the shaft or via a clamping sleeve, wherein said inner ring is provided with a bore for receiving said shaft therein, said bore having a first surface of a shape, such as cylindrical or tapering, corresponding to the shape of the shaft and a second surface corresponding to the shape of a clamping sleeve. When mounting a bearing on a shaft, it is possible either to mount the inner ring of the bearing directly on the shaft by means of a press fit, a shrinkage fit or a glue joint or by means of a clamping sleeve having tapering grooves or threads, whereby the clamping force around the shaft is caused mainly by axial displacement of the inner ring relative to the clamping sleeve. Depending on which type of attachment is chosen, e.g. in connection with a ball bearing, different types of inner race rings must be available for the bearing. For mounting directly upon the shaft, which might be cylindrical or tapering, inner race rings having a cylindrical bore or a tapering bore resp. shall be used. At mounting with sleeve are used inner race rings having tapering portions corresponding to those of the clamping sleeve. Furthermore, the dimension of the bearing must be increased. Manufacture and stock-keeping of several different standard types of the same element, i.e. in this case bearing inner race rings, of course implies a big cost. The purpose of the present invention is to provide a more flexible system for securing an inner ring of a bearing to a shaft, which substantially reduces the required number of standard types of the same element and therefore implies a cost-saving both regarding manufacture and stock keeping. This has been achieved by an arrangement according to claim 1. An arrangement of the type defined in the preamble of claim 1 is shown in US-A-2397703. This publication shows a ball bearing having an inner ring extending axially in one direction beyond the raceway of the inner ring. In conventional manner the inner ring is provided with a tapering surface intended to cooperate with a corresponding tapering surface on a clamping sleeve. The clamping sleeve has a cylindrical extension upon which the axial clamping force is applied. Theoretically, it might be possible to secure the inner ring to the shaft without clamping sleeve by using the cylindrical inner surface on the extension of the inner ring. However, this would mean that the inner ring was secured to the shaft outwardly of the raceway of the inner ring, thereby resulting in an uncontrollable radial pretensioning of the bearing. DE-A-2120534 shows an arrangement for securing a machine element to a shaft by means of two clamping rings located at opposite sides of the machine element and having oppositely directed conical clamping surfaces. EP-A-251016 discloses a mounting device similar to that shown in Fig. 3 in the present application. However, this prior art design does not allow securing of the inner ring directly on the shaft without using an intermediate sleeve. The invention hereinafter will be further described with reference to some embodiments shown in the accompanying drawings. Fig. 1-3 are axial sections through different embodiments of the invention. In the figures an inner ring 2 of a ball bearing 1 is attached to a shaft 3. The inner ring 2 has a bore 4 provided firstly with cylindrical portions 5 and secondly with tapering portions 6. The bearing shown in Fig. 1 is attached directly upon the cylindrical shaft 3 by means of a shrinkage fit, a press fit or a glue joint, thus that the cylindrical portions 5 of the bore 4 cooperate with the shaft 3. For tapering shafts 3 the portions 5 of course shall have a taper corresponding to that of the shaft 3. In the embodiment shown in Fig. 2 the inner ring 2 of the bearing 1 is mounted on the shaft 3 via a clamping sleeve 7 having tapering grooves 8 and threads 9. The tapering grooves 8 cooperate with tapering portions 6 of the inner ring 2, whereas a nut 10 is tightened around the threads 9 of the sleeve 7. The inner ring 2 furthermore has cylindrical bore portions 5, which in this case however are inactive. Grooves 8 as well as threads 9 form a small angle to the axis of the sleeve, preferably a smaller angle than the friction angle in each contact, i.e. for an angle α shall tan α < µ where µ is the friction coefficient in each contact. The friction coefficient in a contact steel to steel is about 0.15, whereby the angles are preferably smaller than about 10°. The friction surfaces thereby are irreversible. The inner ring 2 shown in Fig. 3 has cylindrical portions 5 and tapering thread flanks 11 cooperating with corresponding thread flanks 12 in the clamping sleeve 7, which thread flanks for a small angle to the axis of the sleeve 7. The inner ring 2 is provided with a key grip 16 and tightening of the joint is effected by the inner ring being turned in relation to the sleeve 7. When turned, the two opposed tapering surfaces 13, 14 in the inner ring 2 and in the sleeve 7, respectively, press against each other, whereby a counterstay is established thus that the turning results in the thread flanks 11, 12 being pressed radially against each other and the sleeve 7 is deformed to seizing position around the shaft 3. The sleeve 7 is slotted 15 at the end situated in front of the key grip 16 in order to lock the inner ring 2 against the sleeve 7 by turning, when so required. According to the invention second surface portions on the inner ring adapted for cooperation with corresponding surfaces both on the clamping sleeve and on the shaft are located within the axial extent of the raceway of the inner ring 2. This means that the bearing 1 can be secured to the shaft 3 while simultaneously ensuring that a desired pretensioning of the bearing is maintained both if the bearing is secured directly to the shaft or via an intermediate clamping sleeve. The advantages gained by combining in one inner ring a cylindric and tapering bore are, beside lower manufacturing and store-keeping costs, that it at shaft mounting, i.e. mounting directly upon the shaft, is possible to use a shaft of bigger diameter for the same bearing. The inner ring furthermore will get a lower susceptibility to creeping, due to a higher concentration of the surface pressure in the pressing joint. At mounting with sleeve it is in a corresponding manner not necessary to increase the size of the bearing as compared to mounting directly on the shaft. The size of the cylindrical surfaces 5 is adapted to appropriate surface pressures against the shaft 3 and which corresponds to the material in question, e.g. steel or plastic material. The positioning of the cylindrical or tapering surfaces 5 and 6, respectively, can be adapted to the resultant load in the bearing type. Such a possible positioning is symmetrical to the radial centre line, see Fig. 1.

Claims: 1. An arrangement for securing an inner ring (2) of a bearing to a shaft (3) either directly on the shaft (3) or via a clamping sleeve (7), wherein said inner ring (2) is provided with a bore (4) for receiving said shaft (3) therein, said bore having a first surface (5) of a shape, such as cylindrical or tapering, corresponding to the shape of the shaft (3) and a second surface (6, 11, 13) corresponding to the shape of a clamping sleeve (7) characterized in that said first surface (5) comprises a plurality of first surface portions, and said second surface (6, 11, 13) comprises a plurality of second surface portions, whereby said first surface portions are arranged at opposed ends of the inner ring (2) and separated by said second surface portions, both first surface portions and second surface portions being located within the axial extent of the raceway of the inner ring (2) and whereby further the second surface portions have a tapering shape with their respective smallest diameter corresponding to the diameter of the most adjacent first surface portion. 2. An arrangement according to claim 1, wherein the second surface portions are tapering portions (6, 13) and/or thread flanks (11), which form a small angle relative to the longitudinal direction of the clamping sleeve (7), preferably smaller than the friction angle in the respective contact surfaces. 3. An arrangement according to claim 1 or 2, wherein first surface portions (5) are arranged at the opposed distal ends of the inner ring (2). 4. An arrangement according to claim 3, wherein the first surface comprises four axially spaced first surface portions (5) separated by three second surface portions (6). 5. An arrangement according to claim 3 or 4, wherein the first surface portions (5) are cylindrical and the second surface portions (6) have their conicalities in the same direction. 6. An arrangement according to claim 1 or 2, wherein the first surface portions (5) are cylindrical and the second surface portions (11, 13) comprise portions having their conicalities in opposite directions. 7. An arrangement according to claim 6, wherein the second surface portions comprise a tapering portion (13) having its conicality in a first direction and a threaded portion with a thread flank having its conicality in a second direction opposed to said first direction. 8. An arrangement according to claim 7, wherein first surface portions (5) are arranged at the opposed distal ends of the inner ring (2). 9. An arrangement according to claim 8, wherein the first surface comprises four axially spaced first surface portions (5), and wherein the tapering portion (13) is located between two adjacent first surface portions at one end of the inner ring (2).

Inventors: ADOLFSSON, RUNE
Applicants: SKF NOVA AB
Application year: 1988
Main classification: F16D1
IPC codes: F16C35, F16D1