US3874765A

US3874765A - Connector cover

Info

Publication number: US3874765A
Application number: US407086A
Authority: US
Inventors: Earl A Gilmore; Kenneth E Merklen
Original assignee: Gulf and Western Industries Inc
Current assignee: EAGLE SIGNAL CONTROLS CORP A CORP OF DE; Gulf and Western Industries Inc
Priority date: 1973-10-17
Filing date: 1973-10-17
Publication date: 1975-04-01
Anticipated expiration: 1992-04-01

Abstract

A protective and strain relief cover of sheet material construction is provided for a printed circuit board connector block having a multiplicity of conductor wires extending therefrom. The cover is U-shaped in cross section and includes a pair of legs and a bridging portion adapted to recieve the conductor wires therebetween. The legs of the cover are retained against lateral spreading by interengaging tab assemblies at opposite ends of the cover and which tabs also serve to interconnect the cover with the connector block. The legs of the cover are apertured to receive a tying strap by which the conductor wires are clasped in place with respect to the cover.

Description

United States Patent 1 1 11 1 3,874,765

Gilmore et al. 1 1 Apr. 1, 1975 1 1 CONNECTOR COVER 3.732.526 5/1973 Punako 339/103 R x 3,794,960 2/1974 Sugar 4 1. 339/107 [75] Inventors: Earl A. Gilmore, S1lv1s. 111.; Kenneth 3 803 530 4 1974 L 339/10; R x

E. Merklen, Cos Cob. Conn. I apml u T OR APPLICA N 173] Ass1gnee: Gulf & Western Industries, Inc., FOREIGN PATEN S no S New York NY 1.074.108 H1960 Germany 339/164 R Filed: out 171 1973 Primary Iimminer-Roy D. Frazier 2 l] App| 407 Assistant Exmniner-Lawrence J. Staab Attorney, Agem, 0r FirmMeyer, Tilberry & Body [52] U.S. 339/103 M, 24/16 PB.113/116 P 151 Int. Cl l-lOlr 13/58 [57] ABSTRACT [58] Field of Search 24/16 PB; 29/183, 190: A protective and strain relief cover of sheet material 113/116 PV, 119; 339/103-107, 136-140, 36 construction is provided for a printed circuit board connector block having a multiplicity of conductor [56] References Cited wires extending therefrom. The cover is U-shaped in UNITED STATES PATENTS cross section and includes a pair of legs and a bridging 1 Us I mg Lunman 9H0, R X portion adapted to recieve the conductor wires there 15311151 11/1929 WM-.j;.';;"""';jjjijjjj;.i.i-... 211/190 tttwttthe tht tttttttttt tttttttt 211111.531 6/1935 Galuntc 29/190 x lateral spre'ttdmg by lmerengagmg tab assembhes 1199319 4 194 Edwards c t 339 X opposite ends of the cover and which tabs also serve 2.318.230 5/1943 Jones 339/136 M to interconnect the cover with the connector block. 2.474.908 7/1949 Morin 29/1911 X The legs of the cover are apertured to receive a tying 3. 5 3 10/1 Ctlrbflugh BI 339/103 M X strap by which the conductor wires are clasped in 3.152119 10/1964 Murray et 21]. 339/105 UX place i h respect to h cover 3.277.426 10/1966 KlostcrmunnH... 339/136 M X 3.676.837 7/1972 Newman 339/103 R 20 Claims, 9 Drawing Figures CONNECTOR COVER The present invention relates to the art of electrical couplings and, more particularly, to a cover for a multiple conductor connector block.

In the printed circuit board industry, connector blocks of insulating material are well known coupling components which provide for disengageably connecting a plurality of electrical conductor wires to printed conductors on a circuit board. In this respect, the printed conductors terminate at an edge of the board and the connector block has an opening adapted to receive the edge of the board. Further, the connector block carries a plurality of contacts which are mounted therein for engagement with the printed conductors when the connector block and circuit board are assembled. A corresponding number of wires are electrically interconnected with the contacts and extend from the block.

The electrical conductors extending from the connector block are flexible and are bendable individually and as a unit relative to the connector block. Accordingly, during assembly or disassembly of the connector block with the circuit board, as well as during use of the assembly, the conductors are subject to bending and flexing relative to the connector block which often leads to separation of one or more of the conductors from its contact within the block, or damage to the electrical connection therebetween. It will be appreciated, therefore, that it becomes highly desirable to protect the conductor wires against flexing relative to and- /or separation from a connector block during and following assembly of the block with a circuit board and during disassembly thereof from the circuit board.

In accordance with the present invention, the desired protection of the conductor wires extending from a connector block of the foregoing character is achieved by a cover structure readily interconnectable with the conductor block. The cover is generally U-shaped in cross section and when assembled with a connector block the conductor wires are disposed in the space between the legs and bridging portion of the U and are clasped in place with respect to the cover by a tying strap component separate from or attached at one end to the cover. In addition to the protective function, the cover is economical to produce and operatively associate with a connector block and conductor wires, whereby production and installation costs are minimized. More particularly, the cover preferably is produced from thin sheet metal or plastic by first stamping or otherwise cutting a blank from the material and then relatively bending and interengaging portions of the blank to provide the U-shaped cover structure. The cover is then ready for assembly with respect to a connector block and the conductor wires extending therefrom. The legs of the U are provided with opposed openings for the tying strap which, if separate from the cover, is inserted through the openings to underlie the conductor wires. The free ends of the strap are then interengaged such as by twisting to clasp the conductor wires against the bridging portion of the U. In a modification of the strap feature, one end of the strap is fastened to the cover adjacent one of the strap openings in the legs of the U. The free end of the strap is then inserted through the two openings to underlie the conductor wires, and the free end of the strap and the second opening are structurally interengageable to clasp the conductor wires in place.

It is an outstanding object of the present invention to provide a protective cover for a multiple conductor connector block which is of simple construction and is readily assembled and disassembled with respect to a connector block.

Another object is the provision of a cover of the foregoing character which is economically and econimically produced and is comprised of a minimum number of parts.

Still another object is the provision of a cover of the foregoing character which is formed from a blank of sheet material and which is retained in its formed shape for interconnection with a connector block by interengaging components integral with the blank.

A further object is the provision of a cover of the foregoing character in which the conductor wires of a connector block are releaseably clasped to the cover by a flexible tying strap carried by or separate from the cover.

Still another object is the provision of a cover of the foregoing character in which the tying strap is carried by the cover and is cooperable therewith to clasp the conductor wires in place.

The foregoing objects, and others, will in part be obvious and in part pointed out more fully hereinafter in conjunction with the written description of preferred embodiments of the invention appearing in the accompanying drawings in which:

FIG. I is a perspective view of a blank from which a cover made in accordance with the present invention is formed;

FIG. 2 is a perspective view of a cover erected from the blank of FIG. 1 and shown in assembled relationship with respect to a connector block;

FIG. 3 is a side elevational view of the cover illustrated in FIG. 2;

FIG. 4 is an end view, partially in section, of the cover and connector block assembly illustrated in FIG. 3, the section being along line 4-4 in FIG. 3;

FIG. 5 is a perspective view of another embodiment of a cover made in accordance with the present invention, showing the cover in assembled relationship with a connector block;

FIG. 6 is an end elevation view, partially in section, of the cover and connector block assembly illustrated in FIG. 5, the section being along line 6-6 in FIG. 5;

FIG. 7 is an end elevation view of the cover illustrated in FIG. 5 showing the cover prior to assembly with a connector block;

FIG. 8 is a side elevation view of a portion of the cover illustrated in FIG. 7, the view being along line 8-8 in FIG. 7; and,

FIG. 9 is a side elevation view of a portion of the cover illustrated in FIG. 7, the view being along line 99 in FIG. 7.

Referring now in greater detail to the drawings wherein showings are for the purpose of illustrating preferred embodiments of the present invention only and not for the purpose of limiting the invention, a connector block cover made in accordance with the present invention is advantageously formed from a onepiece blank of sheet material such as blank 10 illustrated in FIG 1. Any suitable material, such as plastic, light gauge sheet metal or resin impregnated fiberboard can be employed. In the embodiment illustrated in FIG. 1, the blank is produced from a sheet of light gauge aluminum and is cut to provide opposed side edges 12 and I4 exending generally parallel to an imaginary axis A midway therebetween, and opposed

end edges

16 and 18 extending generally parallel to one another and perpendicular to axis A.

Imaginary lines

20 and 22 extend parallel to axis A and on opposite sides thereof and divide the blank into

side portions

24 and 26 and intermediate portion 28 for the purpose set forth more fully hereinafter.

One end of blank has a pair of

tabs

30 and 32 disposed on opposite sides of axis A and extending longitudinally from end edge 16 approximately the same distance.

Tabs

34 and 36 extend laterally inwardly from tab 32 towards tab 30 and are integral with one another and with tab 32 along

fold lines

38 and 40. The opposite end of the blank is provided with similar tabs located at diagonally opposite corner areas of the blank from the corresponding tabs extending from edge 16. In this respect, tab 42 similar to tab 30 extends longitudinally from end edge 18 of the blank and from the corner of the blank diagonally opposite that from which tab 30 extends. Similarly, a tab 44 similar to tab 32 extends longitudinally from end edge 18, and

tabs

46 and 48 extend laterally from tab 44 towards tab 42 and are integral with one another and with tab 44 along

fold lines

50 and 52.

Tab portions

34 and 46 are provided with

openings

54 and 56, respectively, for the purpose set forth hereinafter. Further, the blank is provided with a pair of

openings

58 and 60 adjacent end edge 16 and on opposite sides of axis A for the purpose set forth hereinafter.

The cover structure illustrated in FIGS. 2, 3 and 4 of the drawing is adapted to be formed by erecting blank 10. In this respect, the blank is bent or curved relative to axis A to provide a U-shaped wall structure in which

portions

24 and 26 of the blank define the legs of the U and intermediate portion 28 defines the bridging portion of the

U. Tabs

34 and 36 are then bent relative to tab 32 so that tab 34 extends inwardly of the U and is generally perpendicular to tab 32 and tab 36 is generally parallel to

tabs

32 and 30 and is disposed in facial overlying engagement with the outer surface of tab 30. Similarly,

tabs

46 and 48 are bent relative to tab 44 so that tab 46 extends inwardly of the U and is generally perpendicular to tab 44 and tab 46 is generally parallel to

tabs

44 and 42 and facially overlies the latter tab. The tab structures at opposite ends of the cover

interengage leg portions

24 and 26 to restrain lateral separation thereof and, as pointed out hereinafter, further serve to support the cover relative to a connector block and to facilitate the interconnection therebetween. It will be appreciated, of course, that the described sequence of folding the various portions of the blank can be varied to achieve the erected structure.

When the cover is erected in the foregoing manner, it is adapted to be assembled with respect to a connector block having conductor wires to be protected thereby. It will be appreciated that the connector block may be defined by a variety of structural configurations. the structure illustrated being illustrative of one such structure with which the cover of the present invention can be employed. More particularly, with reference to FIGS. 2, 3 and 4 of the drawing, a connector block 62 is illustrated as being generally rectangular in cross-sectional contour having an outer or top surface 64,

opposite sides

66 and 68 and mounting lugs 70 ex tending from opposite ends thereof, only one of which lugs is visible in the drawings. A plurality of conductor wires 72 extend upwardly from top surface 64 and have inner ends disposed within the block and electrically interconnected in a well known manner with contact terminals not illustrated. Further, in a manner well known, the bottom of the block is slotted to receive the edge of a printed circuit board B having printed conductors C on at least one surface thereof for engaging the contacts within the connector block.

When assembled with the connector block shown,

legs

24 and 26 of the cover overlie

sides

66 and 68 of the connector block, respectively, and bridging portion 28 is spaced above outer surface 64 of the connector block. Conductors 72 extend upwardly from outer surface 64 of the connector block into the space thus defined and thence outwardly from one of the open ends of the cover.

Tabs

34 and 46 at opposite ends of the cover overlie mounting lugs of the connector block to position the cover vertically with respect thereto, and

apertures

54 and 56 in

tabs

34 and 46 are adapted in the embodiment disclosed to receive the shanks of threaded fasteners 74 by which the cover is releasably interengaged with the connector block. In the embodiment illustrated, fasteners 74 are freely rotatable relative to mounting lugs 70, and suitable retaining elements 76 interengage the shanks of the fasteners to retain the cover in place with respect to the connector block while permitting rotation of the fasteners 74. It will be appreciated, however, that mounting lugs 70 of the block can be provided with openings threaded for engagement with fasteners 74 to achieve the desired interconnection, or that nuts or the like can be threaded onto fasteners 74 to achieve the desired interconnection. While the cover is preferably interconnected with the connector block through

tabs

34 and 46, it will be appreciated that the interconnection between the connector block and cover can be otherwise achieved. In this respect, for example, fasteners such as screws or threaded studs could extend through the leg portions of the cover and into threaded engagement with the connector block.

In addition to covering and protecting the conductors during engagement and disengagement of the connector block with the printed circuit board, the cover of the present invention advantageously enables the conductor wires to be readily clasped to the cover to provide strain relief for the conductors. In this respect,

openings

58 and 60 in

legs

24 and 26 of the U-shaped wall are adapted to receive a flexible tying strap 75 which extends beneath conductors 72 and the free ends of which are then interconnected to draw the conductors into tightly clasped relationship against bridging portion 28 of the cover. Tying strap 75 can be of any suitable material for this purpose, such as, for example, paper or plastic coated wire, or a suitable string or cord material, Paper or plastic coated wire is preferred in that the ends thereof can be readily twisted together and tightened to draw the conductor wires tightly against the cover.

Preferably,

openings

58 and 60 extend downwardly along

legs

24 and 26 to provide for the tying of various sizes of bundles of conductors in the foregoing manner. While a single elongated opening is provided in each of the legs for this purpose, it will be appreciated that the legs could each be provided with a plurality of vertically spaced openings to achieve the same purpose. Further, it will be appreciated that such openings, whether single or multiple, could be provided at either or both ends of the U-shaped wall or at other locations between the opposite ends thereof depending on the arrangement of the conductor wires leading from the connector block.

A modification of the cover described hereinabove is illustrated in FIGS. 5-9 of the drawing. The modified cover is produced from a blank of plastic sheet material, such as polyethylene, corresponding structurally to the blank illustrated in FIG. 1 with the exception of the

openings

58 and 60 provided in the latter blank, and the blank when erected forms a cover structurally similar to the cover illustrated in FIGS. 2-4. Moveover, the modified cover is disclosed in assembled relationship with a connector block corresponding in structure to that illustrated in FIGS. 2-4. Accordingly, like numerals appear in FIGS. 5-9 to indicate components of the cover corresponding to the components illustrated in the embodiment of FIGS. 1-4.

Referring now to FIGS. 5-9,

legs

24 and 26 and bridging portion 28 of the U-shaped wall define a space in which conductors 72 of connector block 62 are disposed when the cover is in assembled relationship with respect to the connector block. Further, when the cover is erected and assembled on the connector block,

tabs

34 and 46 overlie mounting lugs 70 at the corresponding end of the connector block, and

tabs

36 and 48 facially engage the outer surfaces of

tabs

30 and 42, respectively, to restrain lateral separation of

legs

24 and 26.

In the present embodiment, leg 26 of the cover is provided with a tying strap 80 having an end 82 suitably interconnected at 83 with leg 26. Preferably, strap 80 is of plastic material, such as polyethylene, and end 82 of the strap can be attached to leg 26 such as by heat welding, or through the use of a separate fastener such as a metal or plastic rivet. Leg 26 is provided with an opening 84 beneath end 82 of the strap, and leg 24 of the U-shaped wall is provided with an elongated opening 86 opposite opening 84 and strap 80.

In the embodiment illustrated, the longitudinally opposite side edges of opening 86 are provided with saw tooth-like serrations 88 and the longitudinaly opposite side edges of strap 80 are provided with similar serrations 90. When the cover has been erected for assembly with a connector block, strap 80 depends along the outer surface of leg 26 of the cover in the manner illustrated in FIGS. 7 and 9 of the drawing. When the cover is assembled with respect to the connector block and the conductor wires extending therefrom, the free end of strap 80 is inserted through opening 84 in leg 26 and thence through opening 86 in leg 24 in a manner whereby conductors 72 are disposed in the space between bridging portion 28 and strap 80. The free end of the strap is then pulled outwardly and upwardly of leg 24 so that the conductors are tightly clasped against bridging portion 28. The longitudinal widths of strap 80 and opening 86 are such that serrated edges 90 of the strap cooperatively interengage with serrated edges 88 of the opening to lock tying strap 80 in place against unintended release of the clasped conductors. In the embodiment disclosed, such locking action is enhanced by providing the

serrations

88 and 90 with generally parallel longitudinally extending top edges 88a and 90a, respectively.

While it is preferred that the opposite side edges of opening 86 and strap 80 are serrated, it will be appreciated that other interengaging structures between the strap and opening, including modifications of the serration structures illustrated, can be employed to achieve the same purpose. Further, while serration of both edges of the strap and both edges of the opening provides a more positive interengagement of the strap and opening, interengagement can be achieved by serrations or other suitable interengaging edge structures along one or the other of the corresponding edges of the opening and strap. Futher, it will be appreciated that the interengagement can be accomplished by serrating the opposite edges of the strap alone for engagement with straight side edges of the opening. Many other arrangements for achieving a structural interengagement between the strap and opening will be apparent from or suggested by the foregoing description and can be employed to achieve the desired clasping of the conductors.

While considerable emphasis has been placed herein on the fact that the tab arrangements at the opposite ends of the U-shaped wall of the cover are disposed adjacent the bottom or free edges of the legs of the U and extend longitudinally outwardly of the corresponding end edge of the cover wall, it will be appreciated that the tab arrangements can be provided at other locations along the free edges of the legs of the U, and/or at other locations between the bridging portion and free edges of the legs of the U. Still further, it will be appreciated that the like tab components of the tab assemblies at opposite ends of the blank can be disposed on the same side of the blank axis as opposed to being disposed in diagonally opposite comers of the blank as illustrated herein. Many modifications with regard to the location and structure of the components providing the tab assemblies can be made without departing from the purpose thereof.

Still further, while the material of the blank of the cover embodiment of FIGS. 2-4 is described as being sheet aluminum and the material of the blank of the embodiment of FIGS. 5-9 is described as being polyethylene, it will be appreciated that the metal can be other than aluminum, the plastic other than polyethylene and that metal, plastic or other suitable sheet meaterial can be employed for both cover embodiments. Where metal is used for the cover of the embodiment of FIGS. 5-9, the tying strap would be of plastic or other suitable flexible material. With regard to the tying straps of the cover embodiments described, the twisted end type strap for the embodiment of FIGS. 2-4 can be replaced by other strap structures. For example, the strap can be a plastic strip having an aperture at one end and cooperably serrated side edges extending therefrom so that the second end of the strip can be inserted through the opening to form a loop. The size of the loop depends on the extent to which the second end is pulled through the opening, and the serrations and opening interengage to prevent unintended reverse movement of the second end through the opening. With regard to the strap for the embodiment of FIGS. 5-9, the attached strap can be replaced by a strap separable from the cover wall. For example, end 82 of the strap can be provided with a head structure which would engage leg 26 of the cover body around opening 84 and limit movement of the strap through the opening when the serrated end of the strap is inserted through

openings

84 and 86 to underlie the conductors.

Since many embodiments of the present invention can be made and since many changes can be made in the embodiments herein illustrated and described, it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the present invention and not as a limitation.

Having thus described our invention, we claim:

1. A cover for a multiple conductor electrical connector block, comprising generally U-shaped wall means of sheet material including a pair of generally parallel legs and bridging means interconnecting said legs in spaced relationship, said legs having ends spaced from said bridging means, and tab means on each of said legs interengaging said legs to limit spreading of said ends in the direction perpendicular to said legs, said tab means including a first tab on one of said legs and a second tab on the other of said legs, said first tab having an outer surface parallel to said one leg, a third tab extending from said second tab toward said one leg, and a fourth tab extending from said third tab and overlying said outer surface of said first tab to restrain separation of said legs in said direction.

2. The cover according to claim 1, wherein said wall means includes opposed strap receiving openings, and strap means cooperable with said openings and wall means to clasp the conductors of a connector block in the space between said wall means and strap means.

3. The cover according to claim 2, wherein said wall means has opposite ends, said opposed openings being located in said wall means adjacent one of said opposite ends.

4. The cover according to claim 2, wherein said strap means has opposite ends extending through said openings, means restraining one of said opposite ends of said strap means against passage through the corresponding opening in the direction toward the other opening, and means between said one end and the other of said opposite ends of said strap means for releaseably interengaging said strap means and said other opening.

5. The cover according to claim 4, wherein said means for interengaging said strip means and said other opening includes serrations on said strap means interengageable with at least one of the edges defining said other opening.

6. The cover according to claim 4, wherein said other opening has opposed serrated edges and said strap means has opposed serrated edges interengageable therewith.

7. The cover according to claim 4, wherein said wall means has opposite ends, said tab means including tabs on each of said legs at each of said opposite ends of said wall means.

8. A cover for a multiple conductor electrical connector block, comprising generally U-shaped wall means of sheet material including a pair of generally parallel legs and bridging means interconnecting said legs in spaced relationship, said legs having ends spaced from said bridging means, tab means on each of said legs interengaging said legs to limit spreading of said ends in the direction perpendicular to said legs, said wall means having opposite ends, said tab means including tabs on each of said legs at each of said opposite ends of said wall means, said tabs including a first tab on one of said legs and a second tab on the other of said legs, said first tab having an outer surface parallel to said one leg, a third tab extending from said second tab toward said one leg, and a fourth tab extending from said third tab and overlying said outer surface of said first tab to restrain separation of said legs in said direction.

9. The cover according to claim 8, wherein said legs of said wall means have opposite end edges and said tabs are disposed longitudinally outwardly from the corresponding end edges of said legs.

10. The cover according to claim 9, wherein said legs, bridging means and tabs are integral with one another.

II. The cover according to claim 10, wherein said third tab is apertured for interconnecting the cover with a connector block.

12. A cover for a multiple conductor electrical connector block, comprising generally U-shaped wall means of sheet material including a pair of generally parallel legs and bridging means interconnecting said legs in spaced relationship, said legs having ends spaced from said bridging means, tab means on each of said legs interengaging said legs to limit spreading of said ends in the direction perpendicular to said legs, said wall means including opposed strap openings, strap means cooperable with said openings and wall means to clasp the conductors of a connector block in the space between said wall means and strap means, said strap means having opposite ends extending through said openings, means restraining one of said opposite ends of said strip means against passage through the corresponding opening in the direction toward the other opening, means between said one end and the other of said opposite ends of said strip means for releasably interengaging said strip means and said other opening, said wall means having opposite ends, said tab means including tabs on each of said legs at each of said opposite ends of said wall means, said tabs including a first tab on one of said legs and a second tab on the other of said legs, said first tab having an outer surface parallel to said one leg, a third tab extending from said second tab toward said one leg, and a fourth tab extending from said third tab and overlying said outer surface of said first tab to restrain separation of said legs in said direction.

13. The cover according to claim 12, wherein said legs of said wall means have opposite end edges and said tabs are disposed longitudinally outwardly from the corresponding end edges of said legs.

14. The cover according to claim 13, wherein said wall means is plastic and said strap means is a plastic strip, and means fastening said one end of said strap means to said wall means to provide said restraining means.

15. A sheet material blank for forming a U-shaped cover for an electrical connector block, said blank having an axis, an exposed pair of side edges extending in the direction of said axis and opposed pair of end edges extending laterally with respect to said axis, first and second tabs extending from each of said end edges in the direction of said axis and on opposite sides thereof, and tab means extending toward said axis only from said second tabs at each of said end edges, said first tabs being located at one of the diagonally opposite corner areas of the blank, and said second tabs being located at the other of the diagonally opposite corner areas.

16. The blank according to claim 15, and openings through said blank between said end edges and on opposite sides of said axis.

17. The blank according to claim 15, wherein said sheet material is metal.

18. A sheet material blank for forming a U-shaped cover for an electrical connector block, said blank having an axis, an exposed pair of side edges extending in the direction of said axis and an opposed pair of end edges extending laterally with respect to said axis, first and second tabs extending from each of said end edges in the direction of said axis and on opposite sides thereof, tab means extending toward axis from one of said first and second tabs at each of said end edges, and openings through said blank between said end edges sheet material is plastic.

Claims

11. The cover according to claim 10, wherein said third tab is apertured for interconnecting the cover with a connector block.

17. The blank according to claim 15, wherein said sheet material is metal.

18. A sheet material blank for forming a U-shaped cover for an electrical connector block, said blank having an axis, an exposed pair of side edges extending in the direction of said axis and an opposed pair of end edges extending laterally with respect to said axis, first and second tabs extending from each of said end edges in the direction of said axis and on opposite sides thereof, tab means extending toward axis from one of said first and second tabs at each of said end edges, and openings through said blank between said end edges and on opposite sides of said axis, at least a portion of the edges of one of said openings through said blank being serrated.

19. The blank according to claim 18, wherein said first tabs are located at one of the diagonally opposite corner areas of the blank, said second tabs are located at the other of the diagonally opposite corner areas, and said tab means extend from said second tabs.

20. The blank according to claim 19, wherein said sheet material is plastic.