LOCKING DEVICE FOR THREADED FASTENER

Abstract: A fastener assembly comprising a nut (20) and a locking washer (24). The washer (24) is mounted on a skirt car­ ried by the nut (20) so that the washer (24) cannot be separated from the nut. The nut (20) and the washer (24) having facing cam surfaces formed in such a manner that as the nut is tightened on a workpiece (14), the nut (20) engages the washer (24) to rotate same. Vibra­ tions tending to loosen the washer (24) cause the cam surfaces to wedge the washer between the nut (20) and the workpiece (14) to thereby tighten the assembly. Both the nut (20) and the washer (24) have a hexagonal configuration so that they can be engaged together by a wrench for loosening same.

Description: This application is a continuation-in-part of application Serial No. 060,901, filed June 12, 1987 for a LOCKING DEVICE FOR THREADED FASTENER. Background of the Invention This invention is related to a fastener assembly having a locking washer connected to a hexagonal nut in such a manner that the nut can be rotated either in one direction to tighten both the nut and the washer on a workpiece, or with the washer in the opposite direction to loosen both the nut and the washer from the workpiece. The washer rides on a skirt carried by the nut so that the washer cannot be reversed when being assembled on the workpiece. Locking washers, either individually or in a pair, are commonly mounted on the under surface of a bolt head or with a nut where the workpiece is subjected to vibration. Some vibrations tend to cause the bolt or the stud, on which conventional washers are mounted, to elongate thereby loosening the nut. Locking washers, however, tend to remain tight because they have a pair of confronting cam surfaces that rotate one with respect to the other, to accommodate any elongation or contracting of the bolt. One such locking arrangement is illustrated in United States Patent No. 4,134,438 which issued January 16, 1979 to Bengt O. Frieberg and Arthur B. Herpolsheimer. Locking washers are commonly used in industry, however, a couple of problems have arisen. When used in an industrial application with relatively unskilled help, the washers are sometimes assembled in a reverse position so that the cam surfaces do not face one another. When so mounted they lose their primary function to respond to changes in bolt length. Another problem is that when locking washers having a circular edge are locked in position, the bolt cannot be loosened. Any attempt to unscrew the nut or bolt that is on the same side of the workpiece as the washers, simply makes the assembly tighter. The opposite end of the bolt or the stud is usually on the back side of the workpiece. If accessible, the user can loosen the assembly. However, if the opposite end of the stud or bolt is inaccessible, the user has to crack either the nut or the bolt head to remove it from the workpiece. The prior art suggests that to prevent a nut from being separated from conventional, non-locking applications, a flared end section can be formed on the nut to retain the washer. Such an arrangement is illustrated in United States Patent No. 2,257,479 which issued September 30, 1941 to Carl G. Olson, and United States Patent No. 4,362,449 which issued December 7, 1982 to Emil J. Hlinsky. However, this arrangement provides a permanent fastener assembly. Locking washers having the same peripheral shape as a cooperating nut, that is a six-sided configuration, are illustrated in United States Patent No. 3,417,802 which issued December 24, 1968 to Carl O. Oldenkott. However, there is no suggestion of this typ of fastener in which the washer is inseparable from the nut before being assembled on the workpiece. Another lock washer arrangement is illustrated in United States Patent No. 3, 263,727 which issued August 2, 1966 to Arthur B. Herpolsheimer. This fastener also suggests only a separable nut and washer. GB-A-907 826 shows and describes a fastener assembly according to the preamble of claim 1 with the fastener body and the lock washer defining two separate parts which may be combined and assembled in different ways, only one way being the correct one. By unskilled persons the washers may be assembled in a reverse position so that the cam surfaces do not face one another. Another problem arises in that the washers may be separated from the fastener nut and get lost; in this case the nut too cannot be used. Moreover, the two separate parts are difficult to handle during the assembling procedure. The broad purpose of the present invention is to provide an improved fastener assembly in which a locking nut is connected to a locking washer by means of a skirt that extends from the nut opening. The washer is mounted on the skirt so as to be rotatable with respect to the washer as well as axially movable to a position in which cooperating cam elements on opposing faces between the washer and the nut are separated. The cam elements are arranged so that when the nut is being fastened, the cam elements engage one another so that the nut rotates the washer. Both the washer and a portion of the nut have hexagonal configurations so that the washer can be rotated by a wrench in the unfastening direction to remove both the washer and the nut from the workpiece. This arrangement obviates the problem of removing the nut from a stud after it has been fastened on a workpiece in a position in which the opposite end of the stud is inaccessible to the user. The nut does not have to be cracked to remove the fastener assembly from the workpiece. The washer has a wide circular base to enlarge the surface area between the washer and the workpiece. Preferably, teeth are mounted on the face of the washer engaging the workpiece to improve the seizure between the washer and the workpiece. Still further objects and advantages of the invention will become readily apparent to those skilled in the art to which the invention pertains upon reference to the following detailed description. Description of the Drawings The description refers to the accompanying drawings in which like reference characters refer to like parts throughout the several views and in which: FIGURE 1 is a view illustrating a fastener assembly embodying the invention being tightened on a workpiece; FIGURE 2 is a view similar to Figure 1, but showing a wrench mounted on both the nut and the washer to loosen the assembly from the workpiece; FIGURE 3 is a sectional view showing the nut and washer assembly; FIGURE 4 is a view of the top of the nut; FIGURE 5 is a view of the bottom of the nut as seen along line 5-5 of Figure 3; FIGURE 6 is a view of the top of the washer; FIGURE 7 is a view of the bottom of the washer; FIGURE 8 is an enlarged view of one of the teeth mounted on the washer; and FIGURE 9 is a fragmentary view of the opposing cam elements. Description of the Preferred Embodiment Referring to the drawings, Figures 1-2 illustrate a fastener means, generally indicated at 10, mounted on a threaded stud 12 which is secured to a workpiece 14. A wrench 16 is used for tightening the fastener means on the stud in the clockwise direction, as illustrated in Figure 1, to apply a load on the workpiece. The wrench is rotated in the opposite direction, as illustrated in Figure 2, for loosening the fastener means and releasing the load on the workpiece. Referring to Figures 1-3, the fastener means comprises a nut 20 having an integral skirt 22, and a locking washer 24. Referring to Figures 3, 4 and 5, the nut has a six-sided conventional hexagonal external configuration 28 engaged with wrench 16 having a conventional nut-receiving opening. The nut has an internal opening 30 having threaded means 32 formed in a generally cylindrical configuration about an axis of rotation 34. The nut has a body 36 with an under surface 38 having cam-engaging means, as illustrated in Figures 5 and 9. The cam- engaging means comprises six cam elements 40A-40F arranged end-to-end, each including an inclined front face 40 and a rearwardly inclined cam surface 42. Each inclined face 40 is located at a corner of the hexagonal nut configuration. The width of each cam element extends from the central opening to the hexagonal corner. The top surface of the fastener body is beveled at 44 to provide a nose for receiving robotic fastening means. Skirt 22 has a cylindrical configuration and a flared, annular, outer end 46. Figures 3 and 6-9 illustrate washer 24. Washer 24 has a cam face 50 facing nut surface 38. Face 50 has six cam-engaging elements 52A-F. Each cam-engaging element has an inclined face 54 and a front face 56. Each front face 56 engages a corresponding front face 40 of the nut, as viewed in Figure 9. The inclined cam faces of the washer are adapted to slideably engage the inclined cam faces of the nut when the nut and washer are in contact. When the washer is engaged with the nut, the nut turns the washer when rotated in the clockwise direction, as viewed in Figure 1. The washer will turn the nut when the washer is rotated in the opposite direction. The upper external portion of the washer has a hexagonal configuration 60, with the same diameter as the hexagonal configuration 28 of the nut. However, the diameter of hexagonal configuration 60 can be larger or smaller than the nut so long as the washer can be engaged by a wrench to loosen the washer from the workpiece. Preferably, the hexagonal configuration of the washer is the same as the nut so that a single wrench 16 can engage both the washer and the nut when their hexagonal corners are aligned, one with the other. The washer has a central opening 62 which is slideably mounted on the cylindrical skirt. Each cam element on the washer extends from opening 62 to a corner of the hexagonal configuration. The opposite face 70 of the washer is substantially parallel to cam face 50 and forms the lower surface of an annular lip 72 which enlarges the seizing area between the washer and the workpiece. Face 70 has eight seizing teeth 74A-G, equally spaced around the lower face of the washer. Each of the seizing teeth has a surface 76 that is perpendicular to the face of the washer, and an inclined surface 78 disposed at an angle of about 30 degrees with respect to face 70, as best illustrated in Figure 8. Referring to Figures 3-6, opening 62 is enlarged at 78 to form a larger opening. Opening 62 has a diameter which slideably accommodates the diameter of the skirt but is less than the diameter of flared outer end 46. The diameter of opening 78 is slightly greater than flared end 46 so that it abuts an annular shoulder 80 when the washer is at the limit of its travel on the skirt. Thus, the washer is moveable toward the nut to an engaged position in which the cam elements on the washer engage the cam elements on the nut. In this position, the nut and the washer may be rotated either in an opposite direction, or together in the same direction, as illustrated in Figures 1 and 2. The washer is moveable to a separated position in which the cooperating cam elements clear one another so that the washer can be rotated about the skirt. The fastener assembly is mounted on stud 12 as illustrated in Figure 1. Wrench 16 is employed to engage the nut to rotate it in the clockwise direction so that it applies a load through the washer on the workpiece as the cam elements on the nut engage the cam elements on the washer. The nut then cannot be rotated in the reverse direction. Vibrations which elongate the stud or tend to loosen the nut will merely cause the cam surfaces of the cooperating cam elements to move such that the washer becomes tighter. The reason is because the cam rise angle on the cam elements is greater than the lead angle on the threads of the nut. Any tendency of the nut to become loosened causes the washer to become wedged between the nut and the workpiece. The fastener assembly can then be loosened either by applying the wrench on the hexagonal configuration of the washer to rotate it in the loosening direction which in turn rotates the nut. The nut and the washer must be aligned so that the wrench 16 can engage both the nut and the washer to rotate them in the loosening direction. The wide base of the nut provides a substantial surface for engaging the workpiece and makes it more suitable for efficiently and tightly locking the nut in place then can be achieved by comparable nuts with a conventional hexagonal diameter.

Claims: A fastener assembly for releasably applying a load to the surface of a workpiece, comprising a threaded fastener body and a locking washer, the threaded fastener body (36) having an internal opening (30) formed about an axis, and threaded means (32) formed in a generally cylindrical configuration in said opening (30) about said axis; said fastener body (36) having first structure (28) engageable by a tool (16) for rotating the fastener body about said axis in either a first direction for tightening same against a workpiece (14) or in the opposite direction for loosening same from the workpiece (14); the fastener body (36) having a cam face (38) with a cam element (40A-40F); a locking washer (24) having a central opening (62), the washer (24) having a cam face (50) with a cam element (52A-52F), the washer (24) having structure engageable by a tool (16) for rotating the washer (24) about said axis with said body (36) for loosening same from the workpiece (14); characterized in that the fastener body (36) has a skirt (22) extending axially therefrom; the opening (62) of the washer being mounted on the skirt (22) so as to be rotatable about said axis, the washer (24) being axially movable along said skirt (22) to a first axial position and a distance sufficient for the cam element on the washer (24) to pass the cam element on the body (36) as the washer (24) is being rotated on the skirt (22) about said axis; the cam element (52A-52F) on the locking washer (24) being axially movable on the skirt (22) to a second axial position engageable with the cam element (40A-40F) on the fastener body (36) for cooperating with same to lock the washer (24) against rotation with respect to the fastener body (36), and the skirt (22) and the locking washer (24) having inter-engaging means (46) preventing separation of the locking washer (24) from the skirt (22). A fastener assembly as defined in claim 1, characterized in that the tool-engaging structure on both the fastener (36) and the washer (24) are engageable by the same tool for loosening same. A fastener assembly as defined in claim 1 or 2, characterized in that the tool-engaging structure on the body (36) is a six-sided structure. A fastener assembly as defined in any one of claims 1 to 3, characterized in that the tool-engaging structure on the locking washer (24) is a six-sided structure. A fastener assembly as defined in any one of claims 1 to 4, characterized in that the washer (24) has a thickness greater than the axial length of the skirt (22). A fastener assembly as defined in any one of claims 1 to 5, characterized in that the fastener-engaging structure on the washer (24), and the fastener body (36) are adapted to be simultaneously engaged by a wrench. A fastener assembly as defined in any one of claims 1 to 6, characterized in that a first portion of the washer (24) has a hexagonal tool-engaging section of a first diameter, and a second portion of the washer (24) has a circular configuration of a greater diameter, the second portion being engageable with the workpiece (14). A fastener assembly as defined in anyone of claims 1 to 7, characterized in that the fastener body (36) and the washer (24) have cooperating axially directed cam faces (38, 50) opposing one another and, respectively, having wedge-shaped cam means with front faces interengaging when the fastener body (36) is rotated in the tightening direction and inclined ramp faces with a rise angle greater than the lead angle of the thread means (30) of the fastener body (36). A fastener assembly as defined in any one of claims 1 to 8, characterized in that the washer(24) has a first body portion and an internally formed second body portion, the first body portion being formed to define a drive head having the cam face (50) and a plurality of wrench-engageable vertical side surfaces (60), and the second body portion being defined by an enlarged radially extending flange member (72) having a substantial flat frictional engaging surface (70) adapted to engage the surface of a workpiece (14) to which is secured said threaded fastener. A fastener assembly as defined in claim 9, characterized in that the frictional engaging surface (70) is an annular face generally parallel to and opposite the cam face (50) of the washer (24) and having an outer, generally circular, circumferential border with a diameter at least as great as that of the tool-engaging structure on the locking washer (24), and an inner diameter at least as great as the diameter of the fastener body opening (30), the skirt (22) and the washer (24) having interengaging means (46, 80) to prevent separation of the washer (24) from the skirt (22).

Inventors: MCKINLAY, ALISTAIR N.
Applicants: HONG KONG DISC LOCK COMPANY, LTD.
Application year: 1989
Main classification: F16B39
IPC codes: F16B39