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SCREW RETAINING AND ALIGNING COVER . PLATE
FIELD OF THE INVENTION 5
The invention relates to a cover plate for completing the enclosure of an outlet box, the plate having a mounting screw retaining and aligning assembly integrally formed in an aperture in the plate. The cover plate can be used as a wall plate to complete the enclosure of an 10 outlet box located in a wall. The outlet box may be used to house and mount various types of electrical wiring or connective devices, such as switches, receptacles, motor outlets, telephone and television connective devices and the like. If there is no device in the box, the '5 wall plate is designed as a blank having only apertures for receiving the mounting screws. In all other cases, the plate has openings to suit the purpose of the device.
BACKGROUND OF THE INVENTION 20
As anyone who has removed and tried to replace a cover plate for an electrical wall switch or outlet knows, the screws used are very small and tend to fall out of the aperture in the plate. This can occur during removal or installation of the plate. Sometimes the 25 screw merely falls to the floor where it can be retrieved easily, although this does waste time. In other situations, sometimes the screw falls into an inaccessible area and thus another screw must be obtained, which wastes even more time. This problem is of course also encoun- 30 tered by the commercial construction electrician who, for example, is installing literally thousands of these cover plates in a new large office building. Complicating this problem is the widespread use of plastic cover plates of various different colors, such as ivory, brown, 35 black and red, which have prepainted mounting screws to match the color of the plate. Thus, the installer cannot substitute just any extra screw if a color matched screw is lost and must waste additional time obtaining a substitute screw of the correct color. 40
Another problem associated with installing such cover plates is the difficulty of aligning the relatively small screw with the internally threaded bore provided on the switch or outlet assembly and inserting the screw into the front of the bore to make the necessary 45 threaded connection. It is difficult to align the screw and find the threaded bore because the screw tends to pivot in the aperture in the cover plate. Of course, when there is a misalignment, the screw tends to fall out of the cover plate, especially since the screw and therefore the 50 notch in the head is so small and easily slips from a screw driver used therewith.
SUMMARY OF THE INVENTION
Accordingly, a primary object of the present inven- 55 tion is to provide a screw retaining and aligning cover plate for completing the enclosure of an outlet box so that the screw does not fall from the plate and the screw is easily inserted into an internally threaded bore coupled to the box. 60
Another object of the present invention is to provide such a screw retaining and aligning cover plate that is inexpensive and easy to manufacture and is reusable.
Another object of the present invention is to provide such a cover plate that includes a retaining and aligning 65 assembly integrally formed with the plate.
Another object of the present invention is to provide such a cover plate that can retain and align a screw
upon merely pushing the screw into an aperture in the plate.
Another object of the present invention is to provide a cover plate with a screw retaining and aligning assembly that does not deleteriously effect the aesthetics of a conventional cover plate, is unobstructive, blends into the contour of the plate, and is covered by the head of the mounting screw.
The foregoing objects are basically attained by providing a plate for completing the enclosure of an outlet box, the plate being secured adjacent the box by means of a threaded member receivable in a threaded bore coupled to the box, the combination comprising a generally planar body portion; means defining an aperture in the body portion for receiving the threaded member therethrough; and means on the body portion and extending into said aperture for engaging a threaded portion of the threaded member when the member is fully inserted into said aperture to align the longitudinal axis of the threaded member substantially perpendicular to the body portion for ease of insertion of the threaded member into the threaded bore coupled to the box.
Advantageously, the means for engaging the threaded member or screw comprises a pair of opposed, spaced flexible webs integrally formed with the body portion and extending into the aperture. Each of the webs is in the form of a chordal segment of a circle and these webs have straight, parallel distal edges receiving the threaded member therebetween. In addition to these large or major webs, the means for engaging includes a pair of opposed, spaced minor webs integrally formed with the body portion and the major webs and extending into the aperture. These minor webs are in the form of ring segments. Also forming the means for engaging is an inwardly and downwardly tapered frustoconical bore, i.e., a countersink, formed in the body portion coaxially with the aperture to coact with the major webs in aligning the screw or threaded member which has an inwardly and downwardly tapered frustoconical surface on the bottom of the head thereof.
Advantageously, the ratio of the largest major web radial width to the diameter of the bore or aperture from which the major webs extend is between about 1:3.70 to about 1:4.88. In addition, advantageously the ratio of the major web thickness to the largest major web radial width is between about 1:2.86 to about 1:5.00. The plate, and therefore the integral webs, are formed from polymeric material which is thermoplastic or or any other material having resilient and flexible rather than brittle properties.
Other objects, advantages and salient features of the present invention will become apparent from the following detailed description which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention.
Referring now to the drawings which form a part of this original disclosure:
FIG. 1A is a top plan view, not to scale, of a prior art upper jaw for a cable clamp having an annular flange located inside a bore for receiving a screw;
FIG. IB is a sectional view taken along lines IB—IB in FIG. 1A;
FIG. 2A is a top plan view, not to scale, of another prior art upper jaw for a cable clamp with a pair of opposed fins located in a bore receiving a screw therein;
FIG. 2B is a sectional view taken along lines 2B—2B in FIG. 2A;
FIG. 3 is a fragmentary, front elevational view of a cover plate in accordance with the present invention substantially to scale and showing the two opposed 5 major webs, two opposed minor webs and the frustoconical bore, all integrally formed in the cover plate;
FIG. 4 is a bottom plan view in section taken along lines 4—4 in FIG. 3;
FIG. 5 is a side elevational view in section taken 10 along lines 5—5 in FIG. 3;
FIG. 6 is a front elevational view of a duplex receptacle cover plate in accordance with the present invention;
FIG. 7 is a rear elevational view of the cover plate 15 shown in FIG. 6;
FIG. 8 is a fragmentary side elevational view in section taken along lines 8—8 in FIG. 6 showing a screw about to be inserted into the cover plate;
FIG. 9 is a side elevational view in vertical section of 20 a cover plate in accordance with the present invention having a screw inserted therein and aligned with the internal threaded bore in a duplex receptacle located in ■ an outlet box with the screw about to be inserted into the bore; 25
FIG. 10 is a top plan sectional view taken along lines 10—10 in FIG. 9 showing a screw retained and aligned in a cover plate and about to be inserted into an internally threaded bore, this figure being to scale where one inch equals 0.1 inch; 30
FIG. 11 is a front elevational view of a cover plate in accordance with the present invention having two screw receiving apertures therein;
FIG. 12 is a rear elevational view of the cover plate shown in FIG. 11 with two ribs extending outwardly 35 from each of the screw receiving apertures;
FIG. 13 is a side elevational view in section taken along lines 13—13 in FIG. 11;
FIG. 14 is a top plan sectional view taken along lines
14— 14 in FIG. 12 and enlarged; and 40 FIG. 15 is a top plan sectional view taken along lines
15— 15 in FIG. 12 and enlarged, this enlargement being less than the enlargement of FIG. 14.
In the patent literature, applicant is unaware of any prior device that addresses the problem as set forth above and solves it in the manner set forth herein. However, there are a number of U.S. patents that are relevant to the claimed invention including U.S. Pat. Nos. 50 1,927,780 to Anderson; 2,399,958 to Tinnerman; 3,155,808 to Wiley; 3,173,265 to Bixby; 3,432,793 to Muska et al; 3,969,011 to Yamada; 4,009,797 to Lee; and Re. 29,752 to Jaconette, Jr.
In addition to this patent literature, applicant is aware 55 of two prior art devices, the first being shown in FIGS. 1A and IB and the other being shown in FIGS. 2A and 2B.
Referring to FIGS. 1A and IB, a removable part or upper jaw 12 of a cable clamp is illustrated, these draw- 60 ings not being to scale. A full description of this jaw 12 in general is found in U.S. Pat. No. 3,571,781 issued to Gartland et al. Although not shown in the patent, devices have been made and sold which include, as seen in FIGS. 1A and IB, an annular flange 14 located in an 65 aperture and having a slightly larger cylindrical bore 15 above the flange and a frustoconical bore 16 below the flange, the smaller diameter of the frustonconical bore
As seen in Table 1, the ratio of the flange 14 radial width to the diameter of the bore 15 from which the flange extends is from about 1:11.23 to 1:16.39. Thus, the flange is extremely small relative to the bore size, substantially smaller than is shown in the non-scale drawing of FIGS. 1A and IB.
In addition, from Table 1 it is seen that the ratio of the flange 14 thickness to the flange radial width is about 1:0.82 to 1:1.45 so that the thickness is substantially the same as the width of the flange.
The material used to construct jaw 12 is thermoplastic such as nylon sold by DuPont under the trademark Zytel.
The purpose of the flange 14 used in jaw 12 is merely to maintain the screw 17 in the aperture in the upper jaw so that it does not easily fall out when the jaw is inverted. This occurs since the major diameter of the threads of screw 17 is greater than the inner diameter of the undeformed annular flange 14. As seen in FIG. IB, a smooth part of the screw shank is received by the annular flange 14 after the threaded part is pushed through the flange, unlike the present invention where the webs grip a threaded part of a screw. The jaw 12 and annular flange 14 provide no alignment capability, especially because of the play between the outer diameter of the smooth shank and the inner diameter of the annular flange 14. Due to the relatively small size of the flange's width, it can be sheared by the threads of the screw being pushed therethrough. The upper jaw 12 also tends to be backed off by the screw on unscrewing.
Referring now to FIGS. 2A and 2B, another prior art upper jaw 20 for a cable clamp is shown, not to scale, which includes in an aperture two opposed fins 21 and 22 with two cylindrical bores 23 and 24 formed on opposite sides of the fins, bore 24 having a slightly larger diameter than bore 23. A general description of jaw 20 is provided in U.S. Pat. No. 3,784,961 to Gartland, Jr. which, however, does not disclose the fins shown in FIGS. 2A and 2B.
As seen in these figures, a screw 25 is received in bores 23 and 24 as well as between fins 21 and 22. In operation the smooth shank is received between fins 21
As seen from Table 2, the ratio of the largest fin radial width to the diameter of bores 23 and 24 from which the fins extend is about 1:26.32-1:23.26 relative to bore 23 and about 1:16.39-1:15.15 relative to bore 24. Thus, the fins are extremely small relative to the bores receiving them.
In addition, the ratio of the fin thickness to the largest fin radial width is about 1:0.94-1:0.65 for bore 23 and about 1:1.5 to 1:1.1 for bore 24. Thus, each of the fins is about as thick as it is wide in its largest radial width.
The flexibility of these fins is not especially critical in these devices because these screws are initially installed at the factory with the aid of machine-powered screwdrivers. In addition, the use of a No. 8/18 screw, rather than a No. 6/32 as in the present invention, means that 45 a lesser number of threads per inch are present and thus the threads are coarser. This allows greater latitude in displacing the screw transversely so that the threads can be "walked" through the less flexible fins, either inwardly or outwardly of the aperture.
The material used to construct jaw 20 is also thermo plastic such as nylon sold by DuPont under the trademark Zytel.
Referring now to FIGS. 3-10, the present invention is illustrated in a duplex receptacle cover plate 30 having, as seen in FIG. 6, upper and lower openings 31 and 32 for two female connectors and a central aperture 34. 60 As seen from the rear in FIG. 7, the cover plate 30 is comprised of a generally planar, main body portion 35 with a peripheral flange on the inner surface of the body portion 35. The plate is resilient and flexible and is made from thermoplastic nylon such as that material sold by 65 DuPont under the trademark Zytel FE-3221.
As best seen in FIGS. 3, 4 and 5, the central aperture 34 comprises a frustoconical bore 38, a cylindrical bore
39, two opposed major webs 40 and 41, two opposed minor webs 42 and 43 and a cylindrical bore 44. All of these form a retaining and aligning assembly for a threaded member or screw 46, as seen in FIG. 8, to be inserted in the aperture 34 and carried by the plate 30.
The frustoconical bore countersink 38 is downwardly and inwardly tapered, includes an angle of about 82° and extends into the body portion 35 from the outer substantially planar surface 48.
The cylindrical bore 39 is coaxial with cylindrical bore 38 and extends inwardly from the innermost and smallest diameter end of the frustoconical bore 38.
As seen in FIG. 3, the part of aperture 34 into which the major and minor webs 40-43 extend, is substantially circular being defined by cylindrical bores 39 and 44. These webs are initially molded with and are therefore integral or unitized with the main body portion 35 of the plate.
The distal edges 50 and 51 of the major webs 40 and 41 are straight and parallel and form chords of a circle defined by the bores 39 and 44. In plan view each major web is a chordal segment. The major webs have the same size and shape and their outer surfaces are substantially planar and coplanar and their inner surfaces are also substantially planar and coplanar as seen in FIGS. 3, 4 and 5.
The two opposed minor webs 42 and 43 are also integrally formed with the body portion 35 and are also integrally formed with each of the major webs 40 and 41 during the molding of the plate. In plan view each of the minor webs is a ring segment, the distal edges thereof being a portion of a cylinder. The outer surfaces of the minor webs are substantially planar and coplanar and the lower surfaces are also substantially planar and coplanar. In addition, all of the outer surfaces of all four webs are substantially coplanar and all of the inner surfaces of all four webs are substantially coplanar.
The cylindrical bore 44 is formed from a cylindrical boss 53 integrally formed with the body portion 35 and extending inwardly therefrom, the cylindrical bore 44 extending inwardly from the base of each of the major and minor webs. Bores 39 and 44 have substantially the same inner diameter.
While the various parts shown in FIGS. 3-5, and 10, are to scale, Table 3 is set forth below including the important dimensions and ratios of the webs relative to the plate 30.
WEBS OF FIGS. 3-15
As seen from Table 3, the ratio of the major web radial width to the diameter of the bore 39 from which
the webs extend is between about 1:3.70 to about 1:4.88. Thus, the major webs are flexible.
In addition, the ratio of the major web thickness to the major web radial width is between about 1:2.86 to about 1:5.00, which contributes to the flexibility of the 5 major webs.
As seen in FIGS. 8, 9 and 10, the screw 46 is a conventional No. 6/32 screw, illustrated in FIG. 10 to scale. The designation "No. 6" indicates that, based on the American Standard Coarse And Find Threads defi- 10 nition, the basic major diameter, or the outer diameter, of the threads at the crest is 0.134 inch and the basic minor diameter, or the diameter of the roots of the threads, is 0.099 inch. The designation '732" indicates that there are 32 threads per inch on the screw exter- 15 nally threaded body or shank SS as seen to scale in FIG. 10.
In addition to the shank 55, the screw 46 includes a head 56 having a round top surface 57 penetrated by a notch 58 and a frustoconical bottom or underlying sur- 20 face 59 tapered inwardly and downwardly and including about 45°.
Insertion Of The Screw Into The Plate
As seen m FIG. 8, the screw 46 is longitudinally aligned with aperture 34 in the plate 30. To insert the screw 46 into a retaining and aligning position in the plate 30, the screw is pushed through the aperture so that the screw threads flex and push the major webs 40 ^ and 41 inwardly to the plate, away from the head 56 of the screw and radially outward of the shank 55 as best seen in FIG. 10. The webs are also slightly inelastically deformed. Thus, as insertion takes place, the threads on shank 55 index past the major webs and these webs 35 engage and retain the screw therebetween, thus captivating the screw to the plate and preventing the screw from falling out of the plate. This insertion is complete when the frustoconical surface 59 on the bottom of the head 56 engages and seats on the frustoconical bore 38 40 in the aperture 34, as shown in FIG. 10.
In this configuration, the major webs 40 and 41 tightly grip and engage the opposing threads of the screw and retain, or captivate, the screw in the aperture. Moreover, this engagement of the major webs 45 with the screw in combination with the seating of the frustoconical surface 59 of the screw head against the frustoconical bore 38 centers the head relative to the bore 38, thereby aligning the longitudinal axis of the screw shank 55 substantially perpendicular to the outer 50 surface 48 of plate 30. This alignment is maintained by the substantially equal and opposite forces applied inwardly against the threads by the two webs.
In this configuration, the screw 46 is easily inserted into a threaded bore formed in an electrically insulated 55 portion of an electrical receptacle or switch, such as a duplex receptacle 61 shown in FIGS. 9 and 10.
As is evident, the number of threads per inch in the No. 6/32 screw used with the present invention is much greater than the number of threads per inch in the No. 60 8/18 screw used with the prior art device of FIGS. 2A and 2B. With these finer threads of the No. 6/32 screw, pushing the screw axially of an aperture containing webs therein would tend to significantly shear these webs, if they were not very flexible. However, by mak- 65 ing the webs rather flexible, as are major webs 40 and 41, they will flex significantly to permit passage of the threads without undue shearing.
Coupling The Plate To The Outlet Box
As seen in FIG. 9, a conventional duplex receptacle 61 having two sets of female contacts in portions 62 and 63 is secured via screws 64 and 64' within a metallic or plastic outlet box 65 which is rigidly and conventionally secured in an opening 66 in a wall 67.
Centrally formed in the receptacle 61 between the female contact portions 62 and 63 is an integrally threaded female connection or bore 68 for receiving the threaded shank 55 of the plate screw 46. If desired, this bore 68 can have a countersink 69 at its entrance and may be lined with a metal sleeve which is internally threaded to receive the wall plate screw.
After the screw 46 is secured in plate 30, as seen in FIGS. 9 and 10, the plate is maneuvered adjacent wall 67 and the shank 55 of the screw is inserted into internally threaded bore 68, at which time the screw is rotated clockwise relative to the plate and is threadedly coupled to the bore and the receptacle in a covering position. As this clockwise rotation takes place, the threads index relative to the webs, these webs flexing and sliding relative to the rotating threads. There is little tendency for the screw to back the plate outwardly.
Because the screw 46 is retained in the plate and aligned substantially perpendicular to the plate, the accurate insertion of the screw into the bore 60 is readily facilitiated and the screw does not tend to fall out of the plate.
Once the screw 46 is fully threaded into bore 68, the cover plate 30 completes the enclosure of outlet box 65 and is secured against wall 67 with flange 36 contacting the wall.
Cover Plate Of FIGS. 11-15
As seen in FIGS. 11-15, a slightly modified cover plate 70 is shown which has a plurality of apertures 34' formed therein, like aperture 34 described above, except for two differences. These include a shorter cylindrical boss 53 and two integral inwardly facing ribs 72 and 73 extending radially outward from the cylindrical boss 53 and transverse of the plate 70.
These ribs 72 and 73 extend inward from the main body portion 75 of plate 70, stopping short of the plane containing the edge of the peripheral flange 76 surrounding the main body portion 75.
This type of cover plate 70 can be used to close off an empty outlet box in a wall or, if a central rectangular aperture 79 shown in phantom in FIG. 11 were used, then the plate 70 could be used to cover a switch located in an outlet box. In an electrical switch, the metallic strap which is available to mount the plate is relatively thin, on the order of 0.060 inch. With this thickness only two threads can be formed in a bore in the strap for receiving the plate mounting screw and thus no countersink is available for guiding the mounting screw tip. Therefore, positioning and captivating the screw in the plate is very important.
Of course, any number of receptacles or switches can be covered by the plate illustrated herein with the aperture and webs in accordance with the present invention being provided in the necessary locations. Rather than merely using the plate illustrated herein for electrical receptacles or switches, it could be utilized with any type of electrical device having a cover plate coupled to a box receiving the device therein by means of a threaded member. One example would be a cover for a