PLASTIC ENCAPSULATED NUT AND WASHER ASSEMBLY

Abstract: A plastic encapsulated nut and washer assembly includes a plastic retainer (60) for holding a nut (12) and washer (20) in axially aligned abutting relation ready for aasembly with an external threaded member (40). A portion of the plastic retainer provides an annular seal around the washer when the nut is tightened on a threaded member and an extension bore (66) is formed in the plastic material for providing a lock-nut function when the threaded member is extended into the extension bore from the threaded bore (14) of the nut (12).

Description: The present invention relates to a nut and washer assembly as specified in the preamble of claim 1. Such a nut and washer assembly as disclosed in US-A-3 800 396 includes for example an ordinary hex nut, an ordinary disk-shaped washer and a lock washer enclosed with a shrunk sleeve of plastic material, such as cellulose, polyethylene, polypropylene, polyvinylidene chloride, polyethylene theraphthalate or the like thus to hold the enclosed parts together in alignment for alleviated combined use. When the respective assembly is applied to a threaded male element, it is first threaded on manually as far as possible or desired. Then the plastic sleeve has to be broken to allow tightening of the nut by use of a wrench. GB-A-830 722 discloses another threadable assembly including a nut and a retainer permanently bonded to and surrounding the nut, this retainer being made of silicone rubber. In this case the nut is a specially designed nut including a hexagonal flange and adjacent grooves to hold the rubber retainer on the nut, a relatively thin-walled portion of this retainer encapsulating the hexagonal flange. At one end thereof the retainer forms an annular lip axially protruding over the end of the nut and deformable outwardly when the nut is applied to thus form as seal around the nut whereas the other end of the retainer may be closed by a cap portion including a cylindrical side wall portion aligned with the threaded bore of the nut to form a chamber for receiving a toggle switch. The inner diameter of the cylindrical side wall portion is shown to be considerably smaller than the minimum diameter of the thread. Starting from this basis the invention as claimed aims at improving a nut and washer assembly including a plastic retainer as specified in the preamble of claim 1 to obtain additional advantages such as particularly a reliable permanent seal of the nut and washer same as the end of the threaded element upon which the assembly is applied. In the nut and washer assembly of the present invention a single molded plastic retainer performs a variety of functions such as: 1. It retains a nut and washer in correct juxtaposition for easy mounting in a proper relationship on the respective threaded male element. 2. It retains the washer loosely enough to permit definitive coaxial alignment of the washer with regard to the nut. 3. It provides itself wrench engageable surfaces. 4. It completely encapsulates and protects the nut and washer same as the exposed end of the threaded element threaded into and, as the case may be, through the nut. 5. It allows the use of ordinary polygonal nuts and disk-shaped washers. Additionally, according to claim 6, it can easily be formed to lockingly engage the threads of a threaded element protruding over the nut. In the following a corresponding preferred embodiment is described in detail in connection with the annexed drawings, in which FIG. 1 is a side elevational view of a new and improved nut and washer assembly constructed in accordance with the features of the present invention; FIG. 2 is a cross-sectional view taken substantially along lines 2-2 of FIG. 1 and illustrating the nut and washer assembly in use with a seal established around the periphery of the washer against an external member; FIG. 3 is across-sectional view similar to FIG. 2 showing the nut and washer assembly alone; and FIG. 4 is a top plan view of the nut and washer assembly. Referring now more particularly to the drawings, therein is illustrated a new and improved nut and washer assembly constructed in accordance with the features of the present invention and referred to generally by the reference numeral 10. The nut and washer assembly 10 includes a common, ordinary metal hex or square nut 12 having a central threaded bore 14 extending between opposite end faces 16 and 18 and an ordinary annular washer 20. The washer is maintained in position adjacent the outer end face 16 of the hex nut and is aligned with a central bore 22 of the washer in coaxial alignment with the threaded bore 14 of the hex nut 12 as shown in FIGS. 2 and 4. The washer 20 includes flat or planar inner and outer end faces 24 and 26, and the inner end face of the washer is positioned adjacent to and abuts against the outer end face 16 of the hex nut 12. The opposite outer end face 26 of the washer is exposed externally for bearing contact against an adjacent surface 28 of an external part such as a sheet member 30 against which the nut and washer assembly 10 is mounted. Typically, a second external part 32 is secured adjacent the first part 30 and both parts are provided with aligned apertures 34 and 36, which apertures, are positioned in coaxial alignment with the central aperture 22 of the captivated washer 20 and the threaded bore 14 of the hex nut 12 along a common axis 38. A threaded shank 40 of a cap screw 42 or other threaded element is easily extended through the aligned apertures or bores 36, 34 of the external parts and the washer bore 22 to engage the female threads of the threaded bore 14 of the encapsulated hex nut 12. The illustrated cap screw 42 includes an enlarged hex-shaped head 44 having planar wrench flats 46 adapted to receive a wrench used for tightening the threaded shank 40 into the internal female threads in the bore of the hex nut 12. A washer 48 may be provided on an unthreaded portion of the shank 40 adjacent the hexagonal head 44 thereof to bear against the external part 32 as illustrated in FIGS. 1 and 4 so that when the cap screw 42 is tightened, the external parts 30 and 32 are compressed between the captivated washer 20 and the external washer 48 adjacent the head 44 of the cap screw fastener 42. Referring to FIG. 3, the nut and washer assembly 10 includes a retainer 50 formed of molded plastic material and especially designed and adapted to encapsulate and enclose the metal nut 12 and portions of the washer 20 in abutting, adjacent relation thereto as shown in FIGS. 1, 2 and 3. The retainer is effective to maintain the threaded bore 14 of the hex nut 12 in coaxial alignment with the washer bore 22 along the axis 38 in readiness to receive a threaded shank 40 of a cap screw 42, bolt or other external threaded fastener element. The retainer 50 is formed of relatively rigid, somewhat resilient plastic material molded in place around the hex nut 12 to encapsulate the same and includes a lower cylindrical portion 52 having a circular open end 54 partially closed by an inwardly extending annular lip 56 for loosely retaining the washer 20 within a cylindrical internal recess 58 as shown. The cylindrical portion 52 is integrally joined to an intermediate body portion 60 having a hexagonally-shaped transverse cross section with six (6) wrench flats 62 spaced outwardly parallel of respective wrench flats 64 on the sides of the hex nut 12 between the opposite end faces 16 and 18. An annular flat surface 53 at the junction between the lower end segment 52 and the intermediate body portion 60 provides a wrench stop shoulder on the retainer 50. The intermediate retainer portion 60 is formed with an axially aligned extension bore 66 extending upwardly of the end face 18 of the embedded hex nut 12 coaxially along the central axis 38. The bore 66 projects upwardly into a cup-shaped closed cap portion 70 of the plastic retainer 50. The bore 66 has an internal diameter that is greater than the minimum thread diameter of the threaded bore 14 of the hex nut 12, but less than the maximum or major diameter of the threaded bore as shown in FIGS. 2, 3 and 4. Accordingly, when the threaded shank portion 40 of a cap screw 42 or other threaded element is overdriven and extended into the bore 66 beyond the inner end face 18 of the hex nut 12, the threads interfere with and cut into the plastic material of the inner wall surface of the bore 66. The displaced plastic material engages the threads and provides a lock-nut function. Because the material of the retainer 50 is molded in place around the hex nut 12 and is somewhat resilient, the initial threading of a threaded segment 40 of the cap screw 42 into the locking or extension bore 66 results in thread cutting action and at the same time serves to accommodate the over-travel of the threaded shank 40 as illustrated in FIG. 2. The cap portion 70 of the plastic retainer 50 is provided with a crowned outer end wall 68 and a cylindrical side wall having vertical slots 72 formed therein and spaced equilaterally around the central axis 38. The slots 72 extend downwardly into the intermediate portion 60 and terminate at rounded lower ends 74 spaced below a transition level 76 or plateau formed between the upper cap portion 70 at the upper end of the plastic retainer 50 and the intermediate portion 60. The equilaterally disposed slots 72 are designed to accommodate wrench elements of a specialized wrench or the like which can be mounted on the cap portion 70 for tightening or loosening the nut and washer assembly 10 as desired. Referring now to FIG. 2, a cap screw 42 or other threaded element having a threaded shank 40 is first extended through the apertures 34 and 36 of the external members or parts 30 and 32 which are to be secured together and the threaded shank is passed through the central opening 22 in the captivated washer 20 to engage the female threads of the bore 14 of the encapsulated hex nut 12. The washer 20 is freely rotatable with respect to the embedded hex nut 12 until tightening is completed because the recess 58 of the plastic retainer 50 is slightly larger than the captivated washer 20. The flats 62 of the intermediate retainer portion 60 of the retainer 50 are provided to accommodate a conventional socket, open end or box end wrench, etc. so that the needed torque can be applied to the nut and washer assembly 10 while the hex head of the cap screw 42 is similarly held or turned by a wrench or other implement. As the inner end of the threaded shank 40 initially engages the threaded bore segment 14 of the embedded hex nut 12, the washer 20 is still free to rotate relative to the hex nut because the recess 58 is slightly greater in thickness than the thickness of the washer 20 (as illustrated in exaggerated form in FIG. 3). Eventually, the free end portion of the threaded shank 40 penetrates upwardly into the bore 66 provided in the upper portion of the intermediate retainer portion 60 and begins to cut threads into the plastic wall of the bore as continued threading proceeds. As the threaded shank 40 is tightened in the hex nut 12 of the nut and washer assembly 10, the washer 48 is pressed against the underside of the external part 32 to squeeze the parts 30 and 32 tightly together against the exposed outer surface or end face 26 of the captivated washer 20. The lip 56 of the retainer 50 has a shallow inwardly and upwardly extending frustoconically-shaped lower surface 78 (FIG. 3) and the lip is gradually forced or extruded radially outwardly from between the surfaces 26 and 28 as the shank is threaded further into the hex nut 12 until approximately the condition as shown in FIG. 2 is obtained wherein substantially all of the area of the abutting facing surfaces 26 and 28 of the washer 20 and the external member 30, respectively, are pressed tightly together in direct contact. The lower end face 24 of the hex nut 12 is pressed tightly against the upper surface 24 of the washer 20 to effect a tight seal and firmly secure the nut and washer assembly 10 in place and establish an enclosure and seal around the washer 20 against the upper surface 28 of the external part 30. The nut and washer assembly 10 is easy to use and provides a lock-nut feature and a tight peripheral, annular seal 78A (FIG. 2) around the outer perimeter or edge of the captivated washer 20. Moreover, the engaged threaded segments of the external cap screw 42 and the encapsulated hex nut 12 are well protected from the external environment and are tightly sealed and enclosed to inhibit corrosion and deterioration. From the foregoing, it will be seen that the nut and washer assembly 10, including the hex nut 12, the captivated washer 20 and the retainer body 50 provides an economical, convenient and ready solution for pre-aligning and maintaining the female threaded bore 14 of the hex nut 12 in coaxial alignment with the bore 22 of the captivated washer 20 in readiness for assembly with an external threaded element, such as the a shank 40 of a cap screw 42 or other threaded element. The bore 66 provides a lock-nut function and an annular seal 78A is established around the perimeter of the captivated washer 20 when the assembly 10 is fully tightened. The nut and washer assembly 10 is formed by molding in place the hex nut 12 within the plastic retainer 50. The bore 66 is formed along with the recess 58 on opposite sides of the nut during the original molding operation and after the molding process is complete, the washer 20 is inserted into the recess by deflection of the sealing lip 56 and movement of the washer inwardly through the opening 54. Once the washer is fully inserted in the recess 58, the lip 56 returns to a normal condition and the washer is loosely retained and is freely rotatable relative to the hex nut 12, which nut is secured against and rotated by the plastic retainer 50. The intermediate body portion 60 of the nut and washer assembly 10 permits the use of an ordinary wrench for tightening or loosening and a specialized type of pin wrench may be utilized for tightening or loosening the nut and washer assembly 10 by extending pin elements into the elongated slots 72 formed in the upper end cap portion 70 and intermediate body portion 60 of the retainer 50. While the invention has been described with reference to details of the illustrated embodiment, it should be understood that such details are not intended to limit the scope of the present invention as defined in the appended claims.

Claims: A nut and washer assembly (10) comprising a nut (12), a washer (20) and a plastic retainer (50) molded around said nut and washer for holding them in aligned and abutting relation and including an annular lip (56) extending inwardly beyond said washer (20) from the outer periphery thereof, characterized in that said plastic retainer (50) is permanently molded around said nut (12) from a rigid yet somewhat resilient plastic material and further includes an external surface (62) engageable with a tool for turning said nut and washer assembly (10) on a threaded element (40) and a cap portion (70) closing the end of said retainer (50) remote from said lip (56), said lip (56) loosely retaining said washer (20) in said retainer (50) to an extent to permit free rotation of said washer (20) relative to said nut (12) before tightening the same against an external part (30) adjacent said lip (56). The nut and washer assembly (10) of claim 1, characterized in that said lip (56) is wedge shaped in cross-section and deflectable radially outwardly by tightening the assembly (10) against an adjacent part (30) to thus form a seal around said washer (20) whereas allowing immediate contact of said washer and said adjacent part (30). The nut and washer assembly (10) of claim 1 or 2, characterized in that said nut (12) is an ordinary nut having planar sides (64) forming a polygonal cross-section transversely of its threaded bore, and said tool engageable surface (62) of said retainer (50) is formed by planar sides spaced outwardly of and in parallel to said planar sides (64) of said nut (12). The nut and washer assembly (10) of anyone of the preceding claims, characterized in that said retainer (50) includes a cylindrical portion (52) around said washer (20) aligned with an adjoining portion (60) which includes said tool engageable surface (62), said cylindrical portion (52) being large enough in diameter to form a wrench stop shoulder (53). The nut and washer assembly (10) of anyone of the preceding claims, characterized in that said retainer (50), at its end remote from said lip (56), includes a bore (66) aligned with the threaded bore (14) of said nut (12) for lockingly engaging threads of a threaded element (40) threaded into said nut and washer assembly (10) beyond said nut (12). The nut and washer assembly (10) of claim 5, characterized in that the diameter of said thread engaging bore (66) is between the minimum and maximum thread diameters of said threaded element (40). The nut and washer assembly (10) of claim 5 or 6, characterized in that said thread engaging bore (66) is provided at least partially in a cylindrical side wall portion of said cap portion (70).

Inventors: MACLEAN, BARRY L.
Applicants: MACLEAN-FOGG COMPANY
Application year: 1989
Main classification: F16B37
IPC codes: F16B33, F16B39, F16B43, F16B37, F16B3