US3438534A - Faceplate - Google Patents

Description

April 15, 1969 P. J. z w s 3,438,534 7 FACEPLATE Filed Jan. 8, 1968 Sheet of s FIG. 2 BYj a \32 O FIG. 4 1 I .3 Inventor L 4 PAUL J. ZERWES ATTYS.

April 15, 1969 P. J. ZERWES I 3,438,534

FACEPLATE Filed Jan. 8, 1968 Sheet 2 of 3 FIG. 7

Inventor PAUL J. ZERWES FIG. 6 BYfaZ m ,{W

ATT Y5.

April 15, 1969 P. J. ZERWES FACEPLATE Sheet Filed Jan. 8, 1968 FIG. 11

PAUL J. ZERWES ATTYS.

United States Patent O "7 U.S. Cl. 220-243 23 Claims ABSTRACT OF THE DISCLOSURE A faceplate of suitably molded plastic material for use as a cover for an electrical outlet box, said plate including a knockout portion selectively to provide a predimensioned access opening to an electrical appliance, and comprising a body having outer and inner faces and back to back oppositely opening, endless congruent grooves formed in said outer and inner faces, the outer diameter of said endless oppositely opening grooves defining the predimensioned opening, the knockout portion being provided with relief means in the form of reduced thickness portions, preferably radially arranged along intersecting lines to cause the knockout portion progressively to be segmented during severance of the knockout portion from the body by application of impact force thereupon; the outer diameters of the endless grooves having rounded edges whereby to prevent fractures, once started within the knockout portion, from progressing to the remanent body of the plate.

This invention relates generally to faceplates having predimensioned knockout portions for providing access openings at the time of use and more particularly, is concerned with the provision of a plastic molded face plate construction including at least one knockout portion and means for ensuring chip-free selective severance of said portion to form chip free bordered access openings with reduced likelihood of fracture of the remanent plate portion during such severance.

Faceplates of the character with which this invention is concerned are utilized as covers for electrical outlet or junction boxes mounting one or more electrical appliances such as toggle switches, electrical outlet receptacles, telephone jacks and the like. Such face plates are provided with predimensioned openings of standardized dimension to accommodate the varied devices or provide access thereto. The overall size of the face plate likewise is standardized. Since more than a single appliance may be housed in one outlet box, several openings of varied configuration and dimension may be required in a single faceplate. Present trends in the construction of of new housing and indusrtial buildings, are to provide many opportunities for location of electrical appliance means by providing a plurality of electrical outlet or junction boxes linked to the electrical system but far exceeding the estimated initial need therefor. Such boxes may be provided with a mounted electrical appliance to which access is not desired until some time subsequent to the completion of construction. Occasionally the boxes may be roughed in, no electrical connections or appliance means being housed therein. :In these instances, as well as the former others, a blank or imperforate face plate is utilized until access to the connection or appliance or box is sought. Obviously, when access is sought, say for the installation of a light switch or mounting of an electrical outlet receptacle, a telephone jack and the like, a new wall plate having the proper dimensioned opening formed therein is required. It would be desirable if the blank plate could be converted to the new use rather than replaced. However, formation of neat and precise dimensioned and configured openings in the 3,438,534 Patented Apr. 15, 1969 ice blank plates, particularly of the plastic molded variety, and on the site of the installation, is difficult in view of the ready and generally uncontrollable frangibility of the plates. The problem further is acute where a multigang installation is considered and access to only one of the mounted appliances is desired. Here an especially fabricated face plate is needed having certain located openings but blank in other areas. Still another face plate will be needed for access to a second or other of the mounted receptacles. Even in single gang installations, different purpose appliances often require different dimensioned access openings, again requiring different faceplates. In view of the above, the inventory of faceplates which must be carried by the dealer and the tradesman is burdensome.

Accordingly, a need has arisen for a versatile, multipurpose faceplate, this need in turn giving rise to many attempts by the prior art at solution. Faceplates have been provided with predimensioned weakened or semiscored knockout portions so that an otherwise imperforate blank wall plate may be utilized to cover the outlet or junction box to which access is not desired at the time of installation. The knockout portion is severed from the remanent portion of the plate by a blow from a sharp instrument directed to said portion to establish the desired access opening. Where single gang plates having different dimensioned openings otherwise would be required, wall plates which have concentric, progressively weakened portions of differing dimension have been provided, with the thickness of each concentric portion varying so that either one or the others selectively can be severed from the plate.

Notwithstanding the advantage provided by many of the above mentioned structures, difficulties have been encountered in their use which reduce their effectiveness and advantage. In the course of severing the knockou portion or portions from available faceplates, severance rarely has been clean. Often, chips are formed on the remanent portion of the plate surrounding the opening formed by such severance. This results in a deleterious effect upon the appearance of the finished installation. In other instances, the force applied to the knockout portion may not be centered properly thereupon whereby only a portion of the knockout area is cleared, the other remaining either intact or, at least, attached to the plate body. On many occasions, even application of light force, say from a hand punch or hammer may cause fracture of the remanent plate portion, requiring a new, replacement plate. Further, presently there still remains an unfilled need, particularly in multigang type installations, for a face plate with greater versatility and antifracture capability than heretofore available and this invention is directed to fulfilling that long felt need.

Accordingly, a principal object of this invention is to provide a face plate of the character described which includes a predimensioned knockout portion capable of being severed cleanly therefrom.

Another object of this invention is to provide a face plate of the character described which includes a predimensioned knockout portion having means for preventing fracture of the plate during severance independent of the location thereon to which force is applied.

Another object of this invention is to provide a face plate of the character described which includes a predimensioned knockout portion having means to ensure fragmentation and complete removal thereof from the plate body on the application of force thereupon.

Another object of this invention is to provide a faceplate of the character described which includes at least one predimensioned knockout portion having means to prevent chipping of the remanent material of the plate bordering the resulting opening on severance of said portion from the plate body.

A further object of this invention is to provide a faceplate of the character described readily adaptable for formation as a plastic molded product and provided with knockout means, wherein said knockout means includes relief means on one face thereof comprising at least a pair of reduced thickness portions arranged along lines which intersect within the knockout means to ensure that any blow or force applied within the area of the knockout means will cause complete severance thereof from the plate and the formation of a clean, chip-free bordered opening of given dimension and/or configuration.

A still further object of this invention is to provide a faceplate of the character described wherein knockout means are provided by formation of a predimensioned knockout portion connected to the remanent body of the faceplate by a reduced thickness web located between the outer and inner faces of said plate, said web being provided by a pair of congruent back to back endless grooves, each formed in a respective outer and inner face of the plate opening respectively thereto and the outermost wall of one groove having a rounded edge whereby to prevent continuation of a fracture, once started within the knockout portion, from progressing to the remanent portion of the plate to cause fractures to appear therein.

A further object of the invention is to provide a single or multigang faceplate structure having a plurality of weakened portions each of the same or of differing dimension and/or configuration concentrically or serially arranged, said portions having means whereby selective severance of one or the other of said plurality results in a cleanly framed opening or openings yet without the fracture of the remanent plate body enabling increased versatility in usage and, particularly in multigang structures, resulting in greater acceptability for electrical purposes because of the unified or monolithic structure thereof in contrast to presently available face plates of the segmented type which can be broken away to build up multigang plate arrangements.

Other objects and advantages of the herein invention will become obvious to those skilled in this art as several preferred embodiments thereof are described hereinafter in detail with reference to the accompanying drawings.

In the drawing:

FIG. 1 is a top plan view of a single gang face plate formed in accordance with the invention.

FIG. 2 is a rear view of the face plate shown in FIG. 1.

FIG. 3 is a reduced vertical sectional view taken along lines 3-3 of FIG. 1 and in the direction indicated.

FIG. 4 is an elongated fragmentary sectional view taken along lines 44 of FIG. 1 and in the direction indicated.

FIG. 5 is a top plan view of a single gang face plate according to the invention modified to provide one of a selected diameter access opening.

FIG. 6 is a rear view of the face plate of FIG. 5.

FIG. 7 is an enlarged fragmentary sectional view taken along lines 77 of FIG. 6 and in the direction indicated.

FIG. 8 is a rear view of a face plate according to the invention modified for use over a duplex receptacle wiring device.

FIG. 9 is a sectional view taken along lines 9-9 of FIG. 8 and in the direction indicated.

FIG. 10 is an enlarged fragmentary rear view of a face plate according to the invention modified for use over interchangeable wiring devices.

FIG. 11 is a fragmentary rear view of a multigang face plate according to the invention modified for use over a toggle switch device.

FIG. 12 is a sectional view taken along lines 12-12 of FIG. 11 and in the direction indicated.

FIG. 13 is an enlarged fragmentary sectional view taken along lines 13-13 of FIG. 11.

Referring now to the drawings, a faceplate constructed in accordance with the invention is designated generally by reference character 10 and comprises a generally flat body 12 of rectangular configuration having sides 14 and ends 16 which slope rearwardly to define a rear rim 18. Faceplate 10 preferably is formed of a thermosetting phenolic type plastic molding material by molding or casting procedures but the invention is not limited to such a product. The plate 10 is provided with both longitudinal and transverse ribs 20 and 22, respectively, on the rear face 28 thereof both for strengthening purposes and to provide thickened portions to support openings 24. Openings 24 receive the fastening means ordinarily employed to secure the faceplate in covering relationship to the electrical outlet box (not shown) or to secure a particular bracket or the like thereto, say for the support of a telephone jack (not shown). Each opening 24 is countersunk from the outer face 30 of the plate to a depth necessary to receive the fastening means in a flush fit with said face 30. Portions 32 of increased thickness relative to the ribs 20 and 22 may be provided additionally to support the formation of the openings and any fastening means passed therethrough.

The faceplate 10 has a knockout portion 34 in the body 12 thereof, which portion 34 is severed therefrom to form an opening of standardized, required diameter for mounting of a telephone jack therein. The portion 34 is connected frangibly to body 12 by a reduced thickness connecting web 36 recessed from both the inner and outer faces 28 and 30 of said body 12. The portion 34 is of circular perim-etric configuration, having its center located equidistant from the perimetric edges 38 of the plate 10. A circular endless groove 40 is formed in the body 12 opening to the outer face 30 thereof and a matching circular endless groove 42 is provided in the inner face 28 in back-to-back congruent relation to said groove 40 and opening to said face 28.

The faceplate 10, according to the invention, is provided with means to ensure that severance of portion 34, as by application of a hammer blow thereupon, results in a clean break creating an opening of maximum diameter, the portion 34 being detached from the body 12 leaving no chippings on the remanent bordering edge of said opening. Further, the invention is directed to the provision of means whereby the severance can be effected without transfer of the shock to the remanent portion of body 12 whereby to prevent formation of partial or full fracture or fractures therein. The means contemplated by the invention to prevent fracture of the remanent portion of the plate comprise the definition of the knockout portion by endless groove means formed in both inner and outer faces and by the provision of additional relief groove means within the body of the so-defined knockout portion, preferably upon the inner or rear face thereof. The means contemplated by the invention to provide assurance of a clean break of the knockout portion from the plate body without chipping of the remanent portion surrounding the opening comprises the expedient of providing a rounded edge at the outermost wall of each knockout defining groove so that fracture stresses from the force applied to the knockout portion do not extend therepast into the plate body but are distributed along the weakened connecting web whereby they seem to concentrate along the connecting web aiding in the preferential severance of the knockout portion 34 from the body.

Accordingly, the portion 34 is of substantially the same thickness as the body 12 and has a generally imperforate outer face 30a coplanar with the outer face 30 of body 12. A pair of relief grooves 44 and 46 is provided in the inner face 28a of portion 34, said grooves being symmetrically arranged relative to the center of the portion 34 and intersecting through said center. The grooves 44 and 46 are generally rectangular in cross section and, preferably, are substantially wider than the defining groove means, grooves 40 and 42 which together define the web 36. The grooves 44 and 46 extend across the portion 34 so that ends are spaced from communication with endless groove 42 leaving a strengthening bridge 52 therebetween. Extension of the grooves 44 and 46 into the groove 42 is possible without substantial loss in effectiveness. The depth of the grooves 44 and 46 is selected to exceed the depth of grooves 40 and 42 by an amount substantially coplanar with the fioor 50 of groove 40. The thickness of the grooved areas of portion 34 is at least twice the thickness of the web 36. Although in the illustrated embodiments the widths of the grooves 44 and 46 relative to the widths of the grooves 40 and 42 are of the order of 2:1, this specific relationship is not critical so long as grooves 44 and 46, the relief grooves, are substantially wider than the circular endless grooves 40 and 42, the knockout portion defining grooves. The outer diameter corner 53 at each of the circular grooves 40 and 42 is rounded, preferably having a radius of curvature from 0.010 to 0.020. This serves to prevent the continuation of a fracture, once started within a given diameter of portion 34 from progressing to the body 12, either to result in fracture thereof or chipping of the said edge.

The grooves 44 and 46 thus divide the knockout portion 34 into segments whereby upon application of impact force to a location anywhere within the area of the portion 34, the shock of the blow is transmitted along the said grooves radially from the point of impact and through the center of portion 34 regardless of the location of said point of impact within the area of portion 34. The lines of fracture will occur at the weakened, thinner portions before transmission thereof to the main body of the plate and are then transmitted to the web and distributed around the web, the energy thereof being dissipated in causing separation of the portion 34, first to fragmentation from and then free of, the body 12. The fragmentation of portion 34 into segments along the intersecting lines of the relief grooves 44 and 46 and the subsequent impact of the blow carrying these fragmented portions in its direction causes the fragments or segments to bend at the web 36 providing additional leverage to force the separation thereof from body 12 at the web. The rounded corners 53 are believed to divert any shock or fractures to the web additionally to aid in effecting clean separation of portion 34 from the body 12. Because of the rounded corners, the web is fractured Without chipping of the outer peripheral edge defining the endless circular groove, which edge now defines the mouth of the resulting opening at both inner and outer faces of the plate 10. Portions of the thin web 36 which may remain as flash or burr easily can be removed by passing a screw driver or punch thereagainst, thereby leaving a cleanly defined finished opening of proper dimension since the outer diameter of the circular endless grooves 40 and 42 is selected to be equal to the desired opening diameter.

It has been found in practice that best results are obtained when the resulting segmented areas do not have a width or length dimension greater than the minimum width of any portion of the remaining remanent portion. Further, as stated above, it has been found that best results occur where the minimum thickness of the knockout portions 34 is at least twice the thickness of the web 36 and the depth of the grooves 44 and 46 is greater than the depth of the circular endless grooves 40 and 42. Portions 52 between the ends of the grooves 44 and 46 and the circular web are intended to prevent inadvertent severance of the knockout portion 34 and aid in fracture-free handling, packing and shipping of the wall plates 10.

In FIGS. 5-7 there is illustrated a faceplate according to the invention modified to provide, selectively, openings of different diameters, said plate being designated generally by reference number and is similar in many features of construction to plate 10. Plate 10, too, is intended to mount over a single gang telephone box (not shown) but is used where different size access openings may be required, depending upon the installation concerned. Plate 10' is provided with a knockout portion 34 frangibly connected to body 12 by means of a web 36 defined by a pair of congruent back to back concentric circular endless grooves 46' and 42 formed on the inner and outer faces 28 and 30 of plate 10' and opening to said opposites faces.

Plate 10 differs from plate 10 in that knockout portion 34' is formed as three concentrically arranged knockout portions 54, 56 and 58 arranged to be severed in selectively progressive order to provide the desired diameter opening. The outer portion 54 is connected frangibly to the body 12 of plate 10' by web 36 defined between outermost circular endless grooves 40 and 42'; the intermediate portion 56 is connected at its outer diameter to portion 54 by web 66 and at its inner diameter, to the inner portion 58 by web 62 selected of a thickness less than the thickness of webs 36 and 60.

A pair of circular congruent back to back endless grooves 64, 66 are formed in the outer and inner faces 30a and 28a, respectively, of the knockout portions to define said intermediate portion 56 and are similar in depth and configuration to those outer circular endless grooves 40' and 42. The outer portion 54 and the intermediate portion 56 have the same thickness as the wall plate 10, while the inner portion 58 has a thickness dimension substantially less than that of the body 12. Inner portion 58 is defined by an inner circular endless groove 68 arranged concentrically relative to grooves 64 and 66 and o ening to the outer face 30a, and by a central recess 70 opening to the inner face 28a of body 12. The diameter of recess 70 is substantially equal to the diameter of the area defined by the innermost circular groove 68; said recess '7 0 having a floor 72 and a rounded outer edge wall 74 having a radius of curvature between 0.010 to 0020- the same as corners 53. Likewise, the outer diametric edge wall of each circular groove 40, 42, 64, 66 and 68 is rounded to substantially the same radius of curvature, and, as well, a common degree of depth. The floors 50, 76 and 78 of grooves 40, 64 and 68, respectively, are coplanar while the floor S0" of groove 42 is coplanar with floor 80 of groove 66.

Should an opening equal to the outer diameter of groove 68, be desired, a blow is brought against the inner portion 58 and severance thereof from portions 54, 56 and the remanent body 12 will occur without fracture of any of the remanent portions or chipping of the edge portions surrounding the resultant opening.

Now attention is directed to the reduced thickness areas formed at recesses 82 opening to the inner face 28a of portion 54 and arranged symmetrically spaced apart along the portion 54. These recesses 82 are of substantially rectangular configuration having relatively fiat floors 86 and are arranged, in this instance, apart along a pair of lines 88, 90 taken through the center of portion 58. As illustrated, these recesses are arranged at the three, six, nine and twelve oclock positions on a clock face reference. The fioor 86 of each recess 82 extends across the width of portion 54 just short of grooves 40 and 64, leaving bridging portions 83 and 84. Bridging portion 84 is of greater width than bridging portion 83 so as to provide additional support when severance of portion 56 is desired. This aids in the prevention of fracture of portion 54 during severance of portions 56 and/ or 58.

The knockout portion 58, of course, being of lesser thickness than portions 54 and 56, and being connected to by the web 62 of lesser thickness than the others, webs 36 and 60, a blow directed to a location anywhere upon its surface, will fracture the web 62 and cause severance of said portion 58 from the remanent portions. Thus an Opening having a diameter equal to the outer diameter of the innermost groove 68 will be formed. Openings of diameters equal to the outer diameters of respective grooves 40' and 64 can be formed by applying the force to the respective knockout portions 54 and/or 56.

Attention now is directed to the embodiments of the invention illustrated in FIGS. 8-10, inclusive. In FIG. 8 there is illustrated a faceplate designated generally by reference character 100 which is modified to function as a single gang duplex receptacle plate.

Plate 100 is provided with a pair of like knockout portions 102 formed therein and spaced apart by a narrow section 104 of the plate. Portions 102 differ from portion 34 of plate 10 by the provision of supplemental relief recesses or grooves, generally designated by reference character 106. Such expedient is required due to the different configuration opening required for use of the plate with a duplex electrical receptacle. Said last mentioned opening is of ovular or oblong like configuration, larger than the circular opening required in plate 10 and, hence, necessitates the removal of a greater amount of material than removed in the form of knockout portion 34. Additional difiiculties arise in avoiding fracture of the remanent portions of plate 100 since the standardized opening 108 provided for receiving fastening means (not shown) is formed in the narrow section 104 weakening that section and rendering it more subject to fracture than the remainder of the plate (aside from the knockout portions 102).

The knockout portions 102 are defined by the formation of congruent back to back endless groove pairs, namely endless grooves 110 and 112 in opposite faces of the plate 100, said grooves being of the same depth and configuration and defining a connecting Web 114. The grooves 110 and 112, instead of being circular, are of the configuration to define the oblong type outline opening required by the duplex receptacle. A rounded corner 116 is provided at the outermost edge wall of the grooves 110 and 112 of radius of curvature between 0.010" to 0.020", the same as say, corner 53 in plate 10.

The rear face 118 of knockout 102 is provided with a pair of relief grooves 120 and 122 similar to grooves 44 and 46 of plate 10. These grooves 120 and 122 intersect in the center of the portion 102 and extend radially to a location just short of intersecting groove 12, leaving a strengthening bridging portion 124. Additional relief in the form of secondary grooves and/ or recesses is required since the segments which would result upon attempted fracture of the unsupplemented knockout portion 102 from plate 100 would otherwise be too large and would transmit fractures to the remanent plate 100. Accordingly, a circular endless groove 126 of like depth and configuration is formed in the rear face 118 of knockout portion 102 having its center common with the point of intersection of the grooves 120 and 122. Shorter grooves 128 extend radially outward from groove 126 to terminate just short of the groove 112, leaving a portion 124 therebetween. The grooves 128 are arranged along the circumference of the groove 126 at a spacing of about 80 apart. The operation involved in establishing the openings required is identical to those described with respect to use of plate 10 and need not be repeated again.

In FIG. 10, a slightly modified version of plate 100 is illustrated. This plate 100' is intended for use with an interchangeable wiring device, namely either a TV jack, a pilot light housing, a switch or a simple ordinary or round receptacle (all not shown). The opening configuration desired to be formed by removal of the knockout portion 102' provided in plate 100' is smaller than that required in use of plate 100.

Looking solely at the knockout portion 102', same is defined by a pair of like, congruent back to back grooves 110' (not visible) and 112 formed in opposite faces of the plate 100'. On the inner face 118' of portion 102', there is provided a pair of relief recesses 120 and 122' taken along intersecting lines but not actually intersecting. A circular endless groove 126' is provided in the inner face 118 of portion 102', the center thereof being common with the center of said intersecting lines and the recesses 120' and 122 enter said groove 126' along its circumference; said recesses being spaced apart along said circumference by an angle of about 86. Bridging portions 124' are defined between the groove 112' and the outermost end of recesses 120' and 122' for strengthening purposes. Common with plates 10, 10 and 100, the outermost diameters of grooves and 112 are provided with a rounded corner 116.

Looking now to FIGS. 11-13, a multigang wall plate 200 is illustrated, this plate being utilized as a switch plate and carries a plurality of knockout portions 202 arranged serially along the width of the plate 200. These knockout portions 202 can be removed to form openings of the rectangular configuration required for receipt therethrough of the operating handle of a toggle switch (not shown). In plate 200, the knockout portions 202 are defined by provision of a pair of congruent back to back endless grooves 210 and 212 in opposite faces of the plate. The rear face 218 of the knockout portion 202 is provided with a pair of intersecting relief grooves 220 and 222 of the same width, depth and cross section as the relief grooves previously described in respect of the other embodiments of the invention. The grooves 220 and 222 extend just short of intersecting the defining groove 212 so that strengthening bridging portions 224 are defined.

As can be seen from the sectional view of FIG. 13, the basic cross-sectional configuration of the endless grooves 210 and 212 and the rounded corner 216 is common to all embodiments of the invention heretofore described. In use of plate 200, any one or more of the knockout portions 202 may be removed without causing fracture of the remanent portion of the plate and without chipping of the edges of said portion bordering the thus formed opening either on the inner or outer faces 228, 230 of the plate.

Accordingly, there has been described a series of faceplates having one or more knockout portions provided therein by means of one or more pair of congruent back to back endless groove means formed in the outer and inner faces of the plate to define such knockout portion, relief means on the inner face of the knockout portion in the form of symmetrically arranged grooves and/or recesses extending generally just short of intercepting the adjacent endless groove means and the outermost diameter of each endless groove having a rounded corner; said knockout structure capable of being severed from the plate selectively, progressively by application of an impact force, as by a punch or other instrument, thereupon Without fracture of the remanent portion of the plate or chipping of the portions of the plate bordering the opening thereby formed.

I :claim:

1. A faceplate for an electrical outlet box installation mounting a wiring device therein, said faceplate comprising a body portion having inner and outer faces and at least one knockout portion therein capable of being severed therefrom to form an access opening of predefined size and configuration for receipt of a portion of the wiring device, said knockout portion having an inner face, congruent endless groove means formed in both the inner and outer faces of the plate body in back-to-back relation thereby to define said knockout portion, relief means in the form of reduced thickness portions formed in the inner face of said knockout portion and said endless groove means having the outermost edge thereof rounded, whereby application of an impact force upon the knockout portion causes separation thereof from said plate body without fracture of the remanant plate body.

2. A faceplate as claimed in claim 1 in which said relief means comprise at least a pair of recesses symmetrically arranged within the area of the knockout portion and spaced from the inner edge thereof.

3. A faceplate as claimed in claim 1 in which said relief means comprise at least two intersecting grooves, each groove being of a width and depth substantially greater than the width and depth of the endless groove means.

4. A faceplate as claimed in claim 1 in which said endless groove means define a perirnetric configuration other than circular.

5. A faceplate as claimed in claim 1 in which said endless groove means comprise grooves of equal depth.

6. A faceplate as claimed in claim 1 in which said endless groove means comprise a pair of endless, opposite grooves defining a frangible connecting web.

7. A faceplate as claimed in claim 6 in which said endless grooves have a depth substantially twice the thickness of the web defined thereby.

8. A faceplate as claimed in claim 1 in which'said endless groove means comprises at least a pair of spaced circular opposite grooves and the edge portion of the plate body adjacent the outer peripheral edge of each of said grooves having a rounded corner and said rounded corner having a radius of curvature between 0.010" and 0.020".

9. A faceplate as claimed in claim '8 in which said knockout portion has a central recess formed in the innermost face thereof, said recess having a depth greater than the depth of the endless groove means and a diameter equal to the diameter of said innermost face.

10. A faceplate as claimed in claim 1 in which said endless groove means comprises a pair of opposite endless grooves formed in opposite inner and outer faces of said plate body, the outer diameter of said grooves being equal to the dimensional extent of the access opening desired.

11. A faceplate as claimed in claim 10 in which said relief means comprise a pair of elongate grooves formed in the inner face of said knockout portion and along lines intersecting within said knockout portion.

12. A faceplate as claimed in claim 11 in which said pair of grooves have a depth and width greater than the depth and width of the endless groove means and intersect through the center of said knockout portion.

13. A faceplate as claimed in claim 12 in which said pair of grooves are twice as wide as said endless groove means.

14. A faceplate as claimed in claim 12 in which said thickness of said knockout portion coincident with said relief means is between 40 and 60 percent of the thickness of the plate body.

15. A faceplate as claimed in claim 1 in which said knockout portion is ovular in perimetric configuration and said relief means comprise at least a pair of intersecting grooves of width greater than the width of said endless groove means, said intersecting grooves having the ends thereof spaced from said endless groove means and secondary groove means disposed on the inner face of said knockout portion and symmetrically arranged relative to the center thereof.

16. A faceplate as claimed in claim 15 in which said secondary groove means comprise an endless, substantially circular groove having its center common with the intersection of said intersecting grooves.

17. A faceplate as claimed in claim 15 in which said secondary groove means comprise an endless, substantially circular groove concentrically arranged relative to said endless groove means and having radial extensions symmetrically formed outwardly therefrom along the outer circumferential edge of said endless substantially circular groove and extending to a location short of intersection with said endless groove means.

18. A faceplate as claimed in claim 1 in which said endless groove means comprise at least two pair of oppositely opening grooves formed in each of said inner and outer faces of said plate body, said pairs arranged concentrically one relative to the others and said relief means comprises recesses formed in the inner face within the outermost one of the knockout portions but spaced from the endless groove means defining same.

19. A faceplate as claimed in claim 18 in which said recesses are elongate and the longer dimension is equispaced radially relative to the center of said knockout portions and symmetrically about said center.

20. A faceplate as claimed in claim 1 in which said endless groove means are concentrically arranged to define connecting webs between knockout portions and the remanent plate body, said connecting webs being of progressively reduced relative thickness from the innermost web to the outermost web.

21. A faceplate as claimed in claim 20 in which the thickness of the knockout portions are substantially twice the thickness of the outermost connecting web adjacent thereto.

22. A faceplate as claimed in claim 20 in which the relief means comprises grooves of depth and width greater than the depth and width of the endless groove means.

23. A faceplate having a plurality of knockout portions spaced serially arranged along the plate and capable of selective severance from the plate, each of said knockout portions being defined by a pair of back-to-back congruent endless grooves of common depth formed in the inner and outer faces of said plate and each of said endless grooves having the outer diameter Wall defining same provided with a rounded corner portion and relief means within said knockout portions on the inner faces thereof, said relief means comprising reduced thickness sections extending radially relative to the center of said knockout portions but non-communicating with the endless grooves, severance of any one or more of said knockout portions resulting in a fracture-free, chip-free remanent plate portion.

References Cited UNITED STATES PATENTS 576,810 2/ 1897 De Rycke 220-27 X 1,295,168 2/1919 Hooker 220-27 1,933,117 10/1933 Markle 220-27 X 2,586,858 2/1952 Parsons.

2,787,398 4/ 1957 Smith 220-242 JOSEPH R. LECLAIR, Primary Examiner. JAMES R. GARRETT, Assistant Examiner.

US. Cl. X.R.

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