LAMINATED NUT WITH ONE WAY INSTALLATION

Abstract: A laminated nut (10) comprising a plurality of conical spring disc washers (14a-d) and a cage (16) for receiving and holding the disc washers (14a-d) in a stacked, aligned relationship to define a central opening (22) threaded to be matably received upon an associated threaded bolt (12), including protrusion means (28) extending radially, outwardly from the cage (16) to inhibit gripping of the nut (10) by a wrenching tool (30) at one axial end whereby the nut (10) will only be threaded onto the bolt (12) by the wrenching tool (30) beginning with the opposite end of said nut (10).

Description: The present invention relates to free spinning laminated nuts utilizing laminations of hex shaped hardened coned-disc springs, having a central opening tapped to match threads on an associated bolt. Such nuts have stacked aligned multiple discs retained by a steel outer hex shaped cage. The wrenching dimensions are preferably selected to conform to standard SAE-Metric sizes. Examples of such laminated nut structures are shown and discussed in U.S.-A-­ 4,383,787, issued to Reynolds on May 17, 1983. The noted laminated nuts are free running on the bolt until seated. A locking force between the nut and bolt results from the application of additional torque and rotation after initial seating. The additional torque compresses and partially flattens the conical spring discs whereby a mechanical interference occurs between the thread flanks of the nut and bolt; it is believed that this is at least partially due to the change in hole size of the nut as the conical discs flatten. The resultant thread interference and retained spring load between thread flanks resists unloading that might otherwise occur as a result of tensile or vibrational loads. Thus, the independently loaded conical spring threaded segments when flattened create a thread interference that tends to lock the nut against rotation or loosening when subject to such loads. Since the above noted locking action occurs when the laminated nut is applied in one direction, the nut must be correctly oriented onto the associated bolt to assure proper installation. Thus it would be desirable to provide means to inhibit a reverse or incorrect orientation of the nut onto the bolt so as to ensure proper installation, whether such installation is done manually or with automatic feed and installation equipment. It is an object of the present invention to provide an improved laminated nut structure having means on the cage to inhibit a reverse or incorrect orientation and hence improper installation of the nut onto an associated bolt. In the present invention, radial protrusions, which are non-load-bearing, are formed at one end of the cage such as to provide a means for preventing other than the appropriate end of the nut from being gripped by a wrench and thus to inhibit improper orientation and installation on the associated bolt. While protrusions beyond the normal periphery of the nut adjacent one axial end thereof are disclosed in US-A-4 269 248, and US-A-3 511 118, in both cases they are in connection with solid nuts with a function entirely different from the function of the protrusions of the present application which are specifically associated with nuts comprising laminated washers which must only be inserted on a threaded bolt with one orientation. Thus, in US-A-4 269 248, the protrusions act as a support for a peripheral sprung load bearing flange and in US-A-3 511 118, the protrusions are provided to simplify carrying of the nut by a wrench to a location of limited access. Other objects, features and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, in which: Figure 1 is a pictorial view of a laminated nut embodying features of the present invention, including a plurality of coned-disc springs held by a cage, with some parts shown broken away and with the socket wrench of an installation tool for the nut partially shown; Figure 2 is a top elevational view of the laminated nut of Figure 1; Figure 3 is a side elevational view of the laminated nut of Figure 1, with some parts shown broken away, for installation on an associated bolt, only partially shown, with the tool partially shown and in driving relationship on the laminated nut; Fig. 4 is a view similar to Fig. 3 depicting the laminated nut improperly oriented relative to the associated bolt and installation tool; and Fig. 5 is a view taken in the direction of the lines 5-5 in Fig. 4 illustrating the interference provided by protrusions on the nut inhibiting the nut from being received within the wrench socket. Looking now to the drawings, a laminated nut 10, embodying features of the present invention, is shown prior to installation on an associated bolt 12 (only partially shown). The nut 10 is constructed of a series of hex shaped hardened coned, disc springs 14a-d which are held in an assembled, stacked relationship via a cage 16. The laminated nut 10 has a top side 18 and a bottom side 20. As noted in order to secure the desired locking feature between nut and bolt, the nut 10 should be mounted on the bolt 12 with the bottom side 20 being the leading end of the nut 10 as it is threaded onto the bolt 12 and hence with the top side 18 being the trailing end of the nut 10. As shown in the drawings, the laminations or springs 14a-d define a central bore 22 which is threaded to be matably, threadably received upon the bolt 12. Thus when properly installed, the laminations or disc springs 14a-d are intially dished centrally outwardly from the bolt 12 or axially outwardly from the bottom side 20 towards the top side 18. The cage 16 can be formed of sheet metal and includes an annular bottom ring or cup portion 23 and a plurality of axially extending fingers 24. In one form of the invention the cage was constructed of spring steel having a Rockwell hardness of between around Rc 39 and Rc 45. In the form of the invention shown, six fingers 24 are circumferentially arranged in a hexagonal pattern around the periphery of the ring portion 22 with each engaging a corresponding flat of the hexagonally shaped outer surface of the laminations or disc springs 14a-d. The outer end portions 26 of the fingers 24 are folded radially inwardly to grip the uppermost disc spring 14a. Also the bottom surface of the ring portion 22 can be dished axially inwardly to generally conform to the dished contour of the lowermost disc spring 14d. In order to inhibit improper orientation of the laminated nut 10 onto the bolt 12 the cage 16 is provided with a plurality of radially outwardly extending protrusions 28. The protrusions 28 are located at the base or lower extremity of the cage 16 i.e. at the lower extremity of the cage fingers 24 or cup portion 23. The protrusions 28 are preferably at the extreme lower end of the cage 16 in order to provide as little effective wrenching area as possible at the bottom side 20 of the nut 10 in order to inhibit an operator from installing the laminated nut 10 in a reverse or improper direction on the bolt 12. While one protrusion 28 is provided at the base of each of the cage fingers 24 a plurality of protrusions less than six could be effectively used. The protrusions 28 as shown are generally arcuately shaped and of a limited circumferential extent to facilitate formation during the blanking in the construction of the cage 16. It is believed that by limiting the circumferential extent of the protrusions 28 any adverse effect on the strength of the cage 16 will be minimized. This limited circumferential length of each of the protrusions 28 is preferably less than around one half of the circumferential length of the associated one of the sides of the nut 10. The laminated nut 10 is adapted to be installed by a conventional socket wrench 30 (see Figs. 1 and 3) which is adapted to receive and engage the corners of the nut 10. As can be seen from Figures 4 and 5, the protrusions 28 inhibit such engagement from the bottom side 20 of the nut 10. It should be noted that the fingers 24 extend width wise along the flats of the washers or disc springs 14a-d such that they end near one of the hexagonal corners defined by the stack of disc springs 14a-d; the protrusions 28 are located substantially at one end of the base of the fingers 24 near one of these corners; this location near the corners resists overriding by the socket wrench 30 especially where the wrench 30 is of a type having a generally circular opening having twelve engaging points and which is adapted to grip the nut 10 generally solely at its corners. Thus it can be seen from the drawings (Figs. 4 and 5) that with the latter type wrench the protrusions 28 prevent engagement and driving of the nut 10 from the wrong end. Also, with the protrusions 28 located at one axial extremity of the nut 10, the wrenching surfaces of the wrench 30 can be fully engaged along the axial length of the corners of the nut 10 to provide full bearing surfaces when the nut 10 is properly engaged for installation in the correct direction. The protrusions also provide for obvious visual orientation and limit driving engagement during installation with hand service tools such as box, open ends or adjustable wrenches.

Claims: 1. A laminated nut (10) having a plurality of circumferentially, externally disposed corners adapted to be gripped by mating surfaces on a wrenching tool (30) for installation onto an associated threaded bolt, said nut (10) comprising a plurality of conical spring disc washers (14), said disc washers (14) being orientated to provide load retention when threaded onto the associated bolt (12) with one axial end (20) being the leading end to engage the bolt, a cage (16) receiving and holding said disc washers in a stacked, aligned relationship to define a central opening (22) threaded to be matably received upon the associated threaded bolt (12), said cage including a ring portion (23) and a plurality of axially extending fingers (24) cooperating with said ring portion to hold said disc washers (14) in said stacked, aligned relationship, characterized by protrusion means (28) extending radially, outwardly from a location proximate to said one axial end (20) of said cage (16) said protrusion means (28) extending from said cage to an extent to be outside the inner contour of a standardised wrenching tool (30) adapted to be associated with said nut when such wrenching tool is engaged with said nut, said protrusion means (28) comprising the sole means for preventing the wrenching tool being fitted over said one axial end to grip the nut and being substantially non-load-­ bearing after installation of the nut onto an associated threaded bolt (12). 2. The laminated nut of claim 1, with said protrusion means comprising a plurality of protrusions (28) extending radially outwardly from said cage (16) at locations proximate to different ones of said fingers. 3. The laminated nut of claim 2, with said protrusions (28) being of a limited width which is less than around one half of the width of said different ones of said fingers (24). 4. The laminated nut of claim 2 or 3, with said disc washers (14) having flat surfaces which with said cage (16) define the flat sides of said nut (10), said different ones of said fingers (24) extending circumferentially along associated ones of said flat surfaces on said disc washers for an extent substantially coextensively with said flat surfaces of said disc washers with said protrusions (28) located proximate to the associated ones of said corners. 5. The laminated nut of claim 2, 3 or 4, with said protrusions (28) extending radially outwardly from said cage (16) at locations proximate to the externally disposed corners of said nut. 6. The laminated nut of any preceding claim, having a plurality of flat sides in a hexagonal shape. 7. The laminated nut of any one of claims 2 to 5, with said protrusions being generally arcuately shaped. 8. A laminated nut according to any preceding claim in combination with a threaded bolt member upon which it is received to provide a threaded fastener assembly.

Inventors: REYNOLDS, RICHARD LEE
Applicants: PAC-FASTENERS
Application year: 1987
Main classification: F16B39
IPC codes: F16B23, F16B37, F16B39, F16B41