MXPA99010522A - Self-aligning bearing structure - Google Patents

Abstract

A thermoplastic bearing liner (30) having compliant and compensating structure to adjust for a misalignment of a shaft (74) insertably received therein, the bearing liner comprises a hollow, substantially cylindrical shaped member (32) having two ends and an intermediate portion. An external rib (40, 42) extends circumferentially and projects radially from at least one of the two ends. A finger member (48, 50) is mounted adjacent a distal end of the external rib and extends circumferentially from the external rib.

Description

"SELF-ALIGNMENT BEARING STRUCTURE" BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to bearings for linear, reciprocating and rotary arrows, and more specifically to a thermoplastic bearing liner having a flexible and compensating structure. 2. DESCRIPTION OF THE RELATED TECHNIQUE A movable arrow supported by a bearing requires a low friction surface where the arrow comes into contact with the bearing. The low friction surface can be achieved, for example, by the application of a lubricating substance, such as oil or grease, by using a bearing liner constructed of low friction material, or by combining a lubricant, oil or grease, with the use of a low friction bearing shell Bearing liners constructed of wear resistant low friction materials such as nylon, acetal, polycarbonate or polytetrafluoroethylene are known in the art. For example, U.S. Patent No. 2,675,283 issued to Thomson ('623) discloses a sleeve bearing comprising a layer of low friction material bonded to the inside of a metal support sleeve which is wound into a cylindrical shape with its end closely adjacent to each other. Conventional bearing liners for linear, rotary and / or reciprocating arrows are typically one-piece molded low friction plastic constructions that are configured as hollow cylinders. The bearing liners typically have a spacing or gap extending from one end of the cylinder to the other. This spacing or space allows, inter alia, that the bearing shell be compressed to a smaller diameter so that it can be inserted axially into a bore of the housing. In applications where the movement of the arrow exerts axial forces on the bearing shell, especially with reciprocating arrows, the bearing shell must have a means to stop it within the bore of the housing in order to prevent it from ejecting. . Eyelashes have been employed for this purpose, in certain applications, a bearing liner will have one or more flanges extending radially from the end or ends of the bearing. The flange or flanges may extend to the bore of the bearing without overlapping the edge of the bore to provide means for retaining the bearing liner or the flange may be received in a recess on the inner surface of the bore of the bearing where it engages when the bearing liner is inserted into the hole. Typical prior art bearing liner configurations are disclosed, for example, in U.S. Patent Number 4,913,562 issued to Rosen. Despite this, problems sometimes arise in applications such as hydraulic and linear linear actuators when the movement of the arrow is not in perfect alignment with the bearing axis. The pivoting movement in a linear or reciprocal arrow, or the precession of a rotary arrow, will place great stress on the corner of the bearing shell where the flange is placed. In this way, the amount of the linear liner material in contact with the arrow is greatly reduced, frequently leading to increased friction, increased wear and decreased duration expectation. The flanges of the lining frequently break under the forces exerted by the movement of the non-axial arrow. Clearly, then there is a need for an improved bearing liner that would extend the useful life of the liners manufactured from preferred low friction materials, which are used today. An improved bearing liner will also increase the reliability of the machinery in which the liner is incorporated.

COMPENDIUM OF THE INVENTION Accordingly, an object of the present invention is to provide a bearing liner having end flanges configured to withstand greater degrees of misalignment of the shaft without failure. A further object of the present invention is to provide a bearing liner of last use employed formed of low friction materials which are known in the art. It is still a further object of the present invention to provide a bearing shell that is configured to transfer a load, due to a misalignment in the arrow, which is normally concentrated in the corners of the lining, up to a central portion of the lining. In this way, in fact, the bearing liner disclosed has a flexible and compensating structure that is self-aligning, to compensate for misalignments in the arrow and to maximize the surface contact area between the arrow and the liner. inete These and other objects, features and advantages of the present invention will become apparent from the following detailed description of the illustrative embodiments, which should be read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference is made to the following description of the exemplary embodiments thereof, and to the accompanying drawings, wherein: Figure 1 is a cross-sectional side view of a bearing liner in accordance with the prior art; Figure 2 is a perspective view of a bearing liner in accordance with the present invention; Figure 3 is a cross-sectional side view of a bearing shell with an arrow inserted therein; and Figure 4 is a cross-sectional side view of a bearing shell with a misaligned arrow therein.

DETAILED DESCRIPTION OF A PREFERRED MODALITY Referring now to the drawings in detail, initially to Figure 1, there is shown a cross-sectional side view of a bearing liner 20 of the prior art type having radially extending flanges 22 and 24, one flange at each one of the two ends of the bearing shell 20. The flanges 22 and 24 overlap the edges of the housing bore to retain the liner 20 in the housing 26. Figure 1 illustrates the manner in which non-axial arrow movement can damage the flanges 22 and 24 placed on the ends of the liner. 20 of the prior art bearing, as will be described below. Even though the deflection of the arrow 28 from the axial alignment in the bearing shell 20 has been exaggerated to some degree in Figure 1 for purposes of illustration, it will be readily apparent that whether the arrow 28 exhibits a linear, reciprocal movement or rotary, any non-axial movement will place great stress on the bearing shell 20 at a point at which the arrow 28 comes into contact with the corners formed by the flanges 22 and 24, and the cylindrical portion of the bearing 20. Since the prior art bearing liner 20 does not provide a means for realigning itself to compensate for misalignment in the arrow 28, the resultant stress being concentrated at the corners, as described above. In many cases, the application of a considerable amount of effort at the corners where the eyelashes and the cylindrically formed members intersect will cause the eyelashes to break. Referring now to Figure 2, there is shown a perspective view of a bearing liner 30 in accordance with the present invention. The bearing liner 30 is shown having a hollow cylindrical central portion 32 to insertablely receive an arrow in the bore 34. The bearing liner 30 further includes two end portions, each end portion having a flange 36 and 38 mounted thereon. . The flanges 36 and 38 each comprise circumferentially extending outer ribs 40 and 42 projecting radially from the end portions of the central portion 32. The outer ribs 40 and 42 each comprise a proximal end 44 mounted adjacent or at the end of the central portion 32 and a distal end 46. The finger members 48 and 50 extend circumferentially from the ends 46 distant from the external ribs 40 and 42 projecting toward the central portion 32. Figure 3 illustrates a cross-sectional side view of a bearing liner 50, in accordance with the present invention. The bearing liner 50 has a hollow member configured essentially cylindrical having two ends 54 and 56, and an intermediate portion 57. The outer ribs 58 and 60 extend circumferentially and project outwards from the ends 54 and 56, respectively. The outer ribs 58 and 60 include proximal ends 62 and 64 mounted adjacent the ends 54 and 56, and distal ends 66 and 68. The finger members 70 and 72 extend circumferentially from the distal ends 66 and 68 and project toward the intermediate portion 57. The obtuse angles alpha and beta are formed between the finger members 70 and 72, and external ribs 58 and 60, respectively. The bearing liner 50 is preferably constructed as a monolithic unit and formed of a low friction polym matl, such as e.g. nylon, acetal, polycarbonate and polytetrafluoroethylene. The matl selected preferably provides flexibility in the bearing liner 50. It is also proposed that the external ribs 58 and 60, and the finger members 70 and 72 are constructed independently of the essentially cylindrical shaped member 52 and then joined by a fixation technique, such as ultrasonic welding. In addition, the bearing shell 50 can be molded into two interlacing pieces (e.g., in a male / female configuration). Alternative manufacturing techniques are proposed to reduce the complexity and cost of the manufacturing process, and to reduce the time required to install the bearing liner in the field. Under optimum operating conditions, the arrow 74 will be in perfect axial alignment with the bearing liner 50, such that the arrow 74 contacts the internal surface area 76 uniformly across the surface area. The load transmitted by the arrow 74 will therefore be transmitted uniformly through the internal surface area 76. The load is then transmitted through the external ribs 58 and 60 to the finger members 70 and 72. Since the distal ends 80 and 82 of the finger members 70 and 72 are typically retained within a bore of a section of the machinery or a set of support bearings, a bending momentum develops through the fingers members 70 and 72, and the external ribs 58 and 60. The bending momentum will cause the magnitude of the alpha and beta angles to decrease. Advantageously, the bending momentum will cause the intermediate portion 57 of the bearing shell 50 to flex inward towards the arrow 74, thereby forcing more uniform contact along the internal surface area 76 in the intermediate portion 57 in instead of concentrating the force in the corners. In this way, highly stressed end contact points are eliminated as a function of the applied load. Figure 4 illustrates a bearing liner 50 of the present invention assembled from a bore of a section of the bearing or support machinery or assembly 78, as is known in the art. For purposes of illustration, the arrow 74 is shown in exaggerated axial misalignment in the bearing liner 50. As seen in the prior art bearing liners (refer to FIG. 1), axial misalignment will result in concentrated stress at the corners formed by the flanges 22 and 24, and the cylindrical portion of the bearing liner 20 . This concentrated effort frequently leads to a rapid failure of the bearing shell.

In accordance with the present invention, as illustrated in Figure 4, the additional load applied to the bearing shell 50 due to axial misalignment is transferred from the arrow to the inner surface area 76 through the outer ribs 58 and 60 towards the members. of finger 70 and 72. As shown, the ends 80 and 82 remote from the finger members 70 and 72 are typically restricted within a bore of a section of the machinery or a bearing or support assembly 78. Therefore, as shown by the dashed lines, the finger members 70 and 72 are forced inward thereby lowering the alpha and beta angles and advantageously create a bending momentum around the outer ribs 58 and 50. In In contrast to the bearing liner of the prior art, as shown in Figure 1, the stress due to misalignment in the bearing liner of the present invention is not concentrated in the corners formed by the external ribs 58 and 60, and the member 52 configured essentially cylindrically. The bending momentum created by the new configuration of the finger members 70 and 72, vis-a-vis the outer ribs 58 and 60 causes a flexure of the bearing shell 50 whereby the intermediate portion 57 flexes towards the arrow 74 and section 54 and 56 are pushed away from arrow 74 in the misalignment direction. Therefore, the object of this invention is achieved, i.e., a bearing liner is provided which is configured to transfer a load, due to a misalignment in the arrow, which is typically concentrated at the corners of the liner, towards a portion. center of the bearing shell. In this way, the uniform load distribution will be extended to the useful life of the bearing liner. Although the illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it should be understood that the invention is not limited to those precise embodiments, and that various other changes and modifications may be made therein. without deviating from the scope or spirit of the invention. All these changes and modifications are intended to be included within the scope of the invention, as defined by the appended claims.

Claims (9)

R E I V I N D I C A C I O N S

1. A bearing shell, comprising: a hollow member, of essentially cylindrical configuration having two ends and an intermediate portion; an external rib extending circumferentially and projecting radially from at least one of the two ends, the outer rib having a proximal end and a distal end; and a finger member mounted adjacent the distal end of the outer rib, the finger member extends circumferentially and projects outwardly from the outer rib.

2. A bearing liner according to claim 1, wherein the bearing liner is flexible and resilient.

3. A bearing liner according to claim 1, wherein the bearing liner is constructed as a monolithic unit.

4. A bearing liner according to claim 1, wherein the bearing is formed of low friction material. - 1 '

5. A bearing liner according to claim 4, wherein the low friction material is a polymeric material. A bearing liner according to claim 5, wherein the polymeric material is selected from the group consisting of nylon, acetal, polycarbonate and polytetrafluoroethylene. A bearing liner according to claim 1, wherein an angle formed between the outer rib and the finger member is within the range of 90 ° to 180 °. A bearing liner according to claim 1, wherein the finger member projects from the distal end of the outer rib to the intermediate portion of the essentially cylindrical configuration member. 9. A bearing shell, comprising: a hollow member, essentially cylindrical shaped having two ends and an intermediate portion; and means for aligning the bearing liner to correct misalignment in an arrow received inseparably within the hollow member, of essentially cylindrical configuration.