US3532840A

US3532840A - Electrical switch having interlocking cover and casing members

Info

Publication number: US3532840A
Application number: US674186A
Authority: US
Inventors: Werner Robert Bauer
Original assignee: Robertshaw Controls Co
Current assignee: Fleet National Bank
Priority date: 1965-02-08
Filing date: 1967-10-10
Publication date: 1970-10-06
Anticipated expiration: 1987-10-06

Description

' Oct. 6, 1910 w. R. BAUER 3,532,840

ELECTRICAL SWITCH HAVING INTERLOCKING COVER AND CASING MEMBERS Filed Oct. 10, 1967 5 Sheets-Sheet 1 FIG-4 FIG-5 I ,/1

291 v, w m %g 2109A INVENTOR WERNER ROBERT BAUER HIS ATTORNEYS Oct. 6, 1970 I 1 w. BAUER 3,532,840

ELECTRICAL SWITCH HAVING INTERL OCKING COVER AND CASING MEMBERS Filed Oct. 10. 19s? 3 Sheets-Sheet 2 56 FIG-ll E 4; Io 6, 2 I23 2 I2 38 I f 58 I E 5 351/ |2| I 5 l k K EB, 64 66 84 6O 7O 75 88 FIG-8" h I I I 10 7 I03 IOS 22 "M 23 BY 2 m woe ' HIS ATTORNEYS h I23 45 FIG-I012; 45 2912 INVENTOR' WERNER ROBERT BAUER United States Patent OfiCe 3,532,840 Patented Oct. 6, 1970 US. Cl. 20067 19 Claims ABSTRACT OF THE DISCLOSURE This application discloses a switch, casing, and cover therefor. This switch construction may be made very small. The outer surfaces of the casing walls and cover may form a substantially rectangular outer surfaced construction of very minute size with only the actuator plunger and terminal connectors extending therefrom. The casing has four side walls, with one of said side walls being relatively thick compared to the three other side walls. This thick side wall receives an electrical conductor rod and conductor bars which have conductor receiving extensions through which the electrical conductors or wires may be secured. The conductor rod is substantially straight inside the casing and the conductor bars have stationary contact elbows inside the casing which are alternatively contacted by movable contacts of a switch blade. The switch blade tongues are pivoted in opposite notches in opposite sides of the straight conductor rod. The thick wall also has fastener openings for fastening the switch casing and cover to any desired support. The cover also has cover fastener openings aligned with the fastener openings in the thick wall. If desired, the cover may be provided with a hook construction that may be inserted into a hook receiving opening in the thick wall.

This application is a continuation-in-part of applicants copending applications, Ser. No. 431,107, filed February 8, 1965, now abandoned, and Ser. No. 642,614, filed March 8, 1967, now Pat. No. 3,449,534.

This invention relates to a switch, casing, and cover therefor.

One of the features of this invention includes a cover with a hook construciton which may be inserted in a wall of the switch casing in a manner to fasten the cover securely to the casing in an ei-ficient and simple manner.

Another feature of this invention includes a very small switch, casing, and cover therefor, which may have very small dimensions, and which may be made with substantially rectangular outer surfaces, if desired.

Another feature of this invention includes a substantially straight common terminal rod and two electrically conductor bars, each bar having an integral contact elbow to be contacted by the movable contacts of a switch construction, which may include a switch blade with pivot tongues pivoted on opposite sides of the straight conductor rod.

Another feature of this invention includes a casing having a thick supporting or holding wall which is relatively and substantially thicker than the three other side walls and the bottom wall to which thick wall a cover may be secured in an efficient manner.

Another feature of this invention includes said hook construction with a bent portion that may be straightened slightly while the hook construction is being inserted in the hook receiving opening to secure the hook in a hook ledge in the hook receiving opening. The hook receiving opening may extend completely through the casing wall so that a hook straightening bar and/or a hook releasing tool may be inserted in the opposite uncovered end of the hook receiving opening.

Other features of this invention are apparent from this description, the appended claimed subject matter, and/or the accompanying drawings in which:

FIGS. 1 and 2 are respectively top plan and side elevation views of the outer walls of the switch shown in FIGS. 3-12, and made according to this invention, the views being drawn to actual scale in the application drawings.

FIG. 3 is a perspective view on a somewhat larger scale taken from the rear of FIG. 2.

FIG. 4 is a greatly enlarged cross-section taken along the line 44 of FIG. 1.

FIG. 5 is a cross-section taken along the line 5-5 of FIG. 4.

FIG. 6 is a view somewhat similar to FIG. 5, but with parts in elevation and with the hook construction straightened by the insertion of a bar.

FIG. 7 is a view somewhat similar to FIG. 5 but taken along the line 77 of FIG. 4.

FIG. 8 is a transverse cross-section taken along the line 8-8 of FIGS. 4 and 7.

FIG. 9 is an inside perspective view of the cover for the casing.

FIG. 10 is a top plan view taken from the line 1010 of FIG. 9.

FIG. 11 is a plan view of the switch blade of FIGS. 4 and 7 before the movable contacts have been secured thereto.

FIG. 12 is a perspective view of the conductor rod and switch blade of FIGS. 4 and 7.

FIGS. 13 and 14 are views somewhat similar to FIGS. 1 and 2, but showing another embodiment of the invention.

FIG. 15 is an enlarged cross-section taken along the line 1515 of FIG. 13.

FIG. 16 is a view taken along the line 16-16 of FIG. 15.

FIG. 17 is a plan view of the switch blades of FIGS. 15 and 16 before the movable contacts have been secured thereto.

FIG. 18 is a view similar to FIG. 17, but showing a diiferent construction of tension members.

FIG. 19 is a side view of the blade of FIG. 17, with the movable contacts attached thereto.

FIG. 20 is a perspective view of the switch blade and supporting rod of FIGS. 15 and 16.

FIG. 21 is a cross-section along the line 2-121 of FIG. 15 in reduced scale.

Certain words indicating direction, relative position, and the like, are used in the specification and claimed subject matter for the sake of brevity and clearness of description. However, it is to be understood that such words are used only in connection with the illustrations in the drawings, and that the parts of the actual embodiments,when in use, may have entirely different directions, relative positions, and the like. Examples of such words are vertical, horizontal, upper, lower, etc.

FIGS. 1-12 show an extremely small snap switch which has a surprisingly high current capacity. FIGS. 1 and 2 are top and side views of the outsile of the switch casing drawn to scale on the original patent application drawings. The actual dimension for FIG. 1 is .385 inch for the length. The width is approximately as proportionally shown. For FIG. 2 the dimensions are .265 x .385 inch.

Such switch may have an insulative casing 10 having an integral or homogeneously formed plastic insulative wall or 'wall construction including two opposite first or long sides or

side walls

12 and 14, two opposite end or second or

short side walls

16 and 18, and a bottom wall 20. These walls may be integrally or homogeneously joined together to form a switch cavity 26 which may be closed by a flat cover 22.

The word homogeneous is used herein in the specification and claimed subject matter as defined in Websters International Dictionary, G. & C. Merriam Company, Springfield, Mass, as follows: of uniform structure or composition throughout, and to be such as produced by the molding methods that can be used to produce the casing and cover of this invention.

The casing may be a rectangular sided casing in which the

side walls

12, 14, 16 and 18 and bottom wall 20 may have rectangular outer surfaces which may be joined or molded together integrally or homogeneously to produce the switch cavity 26 with an opening along the uncovered edges 19 of the

side walls

12, 14, 16 and 18. The cover 22 may have an outer rectangular surface 29. The cover 22 covers the uncovered edges 19 of

said side walls

12, 14, 16 and 18 and forms a completely rectangular covered switch construction. The casing 10 may be molded or formed of suitable phenolic material. The cover 22 may be molded or formed of any suitable material. For example, if desired, the cover may be made of any suitable transparent moldable material, such as Lexan, which is a transparent polycarbonate. This permits viewing of the switch condition at any time through such cover.

The

walls

12, 14, 16, 18 may have uncovered edges 19 which may be covered and uncovered by means of the cover 22. The cover 22 may be secured to the

walls

12, 14, 16 and 18 by the hook construction 23 to be further described.

Before the cover 22 is placed over the switch cavity 26, a switch construction 28 is placed in the cavity 26 in such a manner that the switch parts can be properly secured in the cavity 26 by the covering action of the cover 22.

The switch construction 28 may include a rigid, straight, flat metal electrically conductive rod 30 with opposite relatively wide

flat sides

32 and 34 and opposite relatively

narrow edges

36 and 38.

The rod 30 may be embedded in preformed notches 40 and 42 in the

opposite side walls

12 and 14 and extends out of the side wall 14, which wall 14 is substantially relatively thick relatively to the

other side walls

12, 16 and 18, and bottom wall 20. Suitable fastener casing mounting holes 44 may extend through the wall 14 for mounting the switch on a support panel and the like. The cover 22 may have cover holes 45 which align with the casing holes 44. A suitable electrical conductor receiving opening or fork construction or end 46 is provided at the end of rod 30 for attaching an electrical conductor, if desired. The rod 30 has opposite tongue and receiving notches 37 and 39.

A first electrical conductor bar 48 extends out of and is embedded in the side wall 14 and has a first inward stationary contact elbow 50 extending into the switch cavity 26. Another or second electrical conductor bar 52 extends out of and is embedded in and extends out of the side wall 14 and has a second contact elbow 54 spaced from the first elbow 50. These

bars

48 and 52 may have ends 46 similar to rod end 46. The bars may also have edges similar to the edges of rod 30. These

bars

48 and 52 and the rod 30 may each be similarly embedded in preformed separate notches 53 in wall 14, as shown, and have shoulders 49 to lock them in place. These

bars

48 and 52 and rod 30 have their edge constructions arrested by the arresting surfaces 55 of the notches 53. The other edge constructions of the

bars

48 and 52 and rod 30 may be provided with barbs 57 which engage the raised

portions

103, 104 and 105 of the cover 22 later to be described.

A snap action sheet metal blade 56 has outer flat ribbon shaped

tension members

58 and 60 and opposite end 4

cross member

62 and 64 joined integrally with the

tension member

58 and 60.

The

tension members

58 and 60 extend past and outside the rod edges 36 and 38.

The blade 56 has a first, or inward, relatively flexible, snap tongue 66 with one tongue end 68 integrally connected to the first blade end cross member 64 and with its other tongue end 70 engaging the rod notch 37.

The blade 56 also has a second, or inward relatively stiff pivot tongue 72 with one tongue end 74 integrally connected to the other or second blade end cross member 62. The other pivot tongue end 75 engages the other rod notch 39.

The blade 66 also has convex surfaced movable contact members 78 and 80 on the blade end cross member 64 which alternately engage the

stationary contact elbows

50 and 54.

The flexible snap tongue 66 has opposite longitudinally

arcuate edges

82 and 84. The stiff pivot tongue 72 has opposite longitudinally

parallel edges

86 and 88. These

tongues

66 and 72 have many characteristics and advantages.

For example, the blade 56 of the switch may be an entirely flat ridgeless snap action sheet metal flexible blade entirely free of relatively sharp right angle stilfening bends or ridges, and having the outer ribbon shaped

tension members

58 and 60 joined integrally with blade

end cross members

62 and 64. Such blade may have the inward relatively flexible longitudinally arcuate edged snap tongue 66, and the relatively stiff longitudinally parallel edged pivot tongue 72. The cooperation of these two tongues during the snap action of the blade is such that much less force is required to actuate the blade past the snapping zone than is required with a substantially parallel sided flexible tongue.

Said blade 56 may have substantially parallel sided relatively stiff unperforated compression tongue 72 integrally joined to the cross member 6-2 and extending and terminating in a stright transverse inner end 75 which rocks or pivots in a straight notch 39 in the straight pivot rod 30 of the switch.

The relatively flexible compression tongue 66 extends inwardly and terminates in a straight transverse inner end 70 which rocks on the straight notch 37 on the other side of such pivot rod 30.

Said flexible compression tongue 66 is so shaped that it produces a much more evenly distributed stress throughout the length of such flexible tongue. For this purpose, the flexible tongue 66 is provided with arcuate

longitudinal edges

82 and 84. These arcuate edges may be symmetrical with respect to each other, and may also be convex or concave with respect to each other.

The stress distribution throughout such flexible arcuate sided flexible tongue 66 is such that there is a much less flexing force needed to snap the switch blade past the snap point than is required with a substantially parallel sided compression flexible member.

A plunger 90 engages the blade end cross member 62 and extends out of the side wall 12. The plunger has an enlargement or bead 92 to provide suitable enlarged contact with the cross member 62 and the side wall 12, and to limit upward movement of the plunger 90. The plunger 90 may be of any desired cross section, such as square, round, or the like.

A compression leaf spring 94 may be V shaped with one edge engaging the cross member 62 and the other end engaging a notch 96 in the wall 14. The spring 94 returns the blade to its upper position in FIG. 4 after the blade has been pushed down by the plunger 90 and then released.

The blade 56 snaps down when the plunger is pushed down to move the

blade tension members

58 and 60 past the snap point of notch 37.

The notches 37 and 39 are not as wide as the rod side 32 and have end shoulders 98 for preventing undue sidewise displacement of the blade 56.

The

holes

44 and 45 may be used to receive mounting screws. The holes 45 may be countersunk at one end to receive countersunk screw heads.

It is to be noted that the fastener holes 44 and 45 may receive screws that hold the cover 22 against one end of the wall 14 and hold the cover 22 against the adjacent ends of

walls

112, 116 and 118. This is an advantageous construction.

The cover may have a rectangular flat outer surface 29. The main part of its inner surface 100 may be rectangular and fiat. The raised

portions

101, 102, 103, 104, 105 engage various parts of the casing and prevent the cover 22 from being displaced. This also prevents the hook construction 23 from being accidentally unhooked. These raised portions also add rigidity to the cover 22. The raised

portions

103, 104 and 105 are engaged by the barbs 57 of the

bars

48 and 52 and rod 30, as shown in FIGS. 5 and 7.

The hook construction 23 has a hook 106 which engages the hook ledge 107 at the end of the slanting side 108 of the hook receiving opening 109.

The hook construction or finger 23 normally is not long enough to hook over the ledge 107 when the cover 22 is being applied to cover the casing. The hook finger 23 is slightly bent or has a bend so that a bar or tool 111 may be inserted in the opening 109 to cause the bend to be straightened sufiiciently to allow the hook 106 to be hooked over the ledge 107 while the cover is being applied, as shown in FIG. 6. Thereafter the bar or tool 111 may be removed, and the hook 106 will then engage the ledge 107, as shown in FIG. 5.

The opening 109 is between the casing openings 44.

The hook receiving opening 109 extends completely through the side wall in which it is located, such as in thicker side wall 14. This provides an uncovered external opening 109A through which the bar 111 and/or a releasing tool may be inserted. Such releasing tool may release the hook 106 from the ledge 107 when it is desired to release and remove the cover 22 from the casing 20.

The

side walls

12, 14, 16 and 18 have respective substantially rectangular

outer surfaces

113, 115, 117 and 119. The bottom wall has substantially rectangular outer surface 121. The cover 22 has the large substantially rectangular outer surface 29 and the smaller substantially rectangular edge outer surfaces 123. These substantially

rectangular surfaces

29, 113, 115, 117, 119, 121 and 123 form an outer substantially rectangular surfaced casing and cover construction. This construction may be made very small in size, as shown in actual scale in FIGS. 1 and 2. Such construction may be easily and effectively mounted on any desired support structure by fasteners, such as screws and the like, which may be inserted through the casing and cover openings 44- and 45, with the heads of the screws engaging the outer surface 29 of the cover 22. The screw heads alternatively may be countersunk in the cover 22, in a manner similar to that later described.

FIGS. 13-20 show an extremely small snap switch which has a surprisingly high current capacity. FIGS. 13 and 14 are top and side views of the outside of the switch casing drawn to scale. The actual dimensions for FIG. 13 are .190 x .385 inch and for FIG. 14 are .260 x .385 inch. The weight is .57 gram.

Such switch may have an insulative casing 110 having an insulative wall or wall construction including two opposite sides or

side walls

112 and 114, two

opposite end walls

116 and 118, and a bottom wall 120. These walls may be integrally joined together to form a switch cavity 126 which may be closed by a fiat cover 122.

The

walls

112, 114, 116, 118 may be covered and uncovered by means of the cover 122. The cover 122 6 may be secured to the

walls

112, 114, 116 and 118 by any suitable means, such as by adhesive means, fasteners, and the like.

Before the cover 122 is placed over the cavity 126, a switch construction 128 is placed in the cavity 126 in such a manner that the switch parts are properly secured in the cavity 126 by the covering action of the cover 122.

The switch construction 128 may include a rigid straight, fiat metal electrically conductive rod 130 with opposite relatively wide

flat sides

132 and 134 and opposite relatively

narrow edges

136 and 138.

The rod 130 may be embedded in

preformed notches

140 and 142 in the

opposite side walls

112 and 114 and extends out of the side wall 114, which wall 114 is relatively thick relatively to the

walls

112, 116 and 118. Suitable screw mounting holes 144 may extend through the wall 114 for mounting the switch on a support panel and the like. A suitable electrical conductor receiving opening 146 is provided for attaching an electrical conductor, if desired. The rod 130 has opposite tongue

end receiving notches

137 and 139.

An electrical conductor bar 148 extends out of and is embedded in the side wall 114 and has an inward stationary contact first elbow 150 extending into the switch cavity 126. Another electrical conductor bar 152 extends out of and is embedded in and extends out of the side wall 114 and has a second elbow 154 spaced from the first elbow 150. These

bars

148 and 152 may be embedded in preformed notches in wall 114, as shown in FIG. 21, and have shoulders 149 to lock them in place.

A snap action sheet metal blade 156, somewhat similar to blade 56, has outer flat ribbon shaped

tension members

158 and 160 and opposite

end cross members

162 and 164 joined integrally with the

tension members

158 and 160.

The

tension members

158 and 160 extend past and outside the rod edges 136 and 138.

The blade 156 has an inward, relatively flexible, snap tongue 166 with its tongue end 168 integrally connected to the blade end cross member 164 and with its other tongue end 170 engaging the rod notch 137.

The blade 156 also has an inward relatively stiff pivot tongue 172 with one pivot tongue end 174 integrally connected to the other blade end cross'member 162. The other pivot tongue end engages the other rod notch 139.

The blade 156 also has convex surfaced movable

con tact members

178 and 180 on the blade end cross member 164 which alternately engage the stationary contact e1- bows 150 and 154.

The flexible snap tongue 166 has opposite longitudinally arcuate edges 182 and 184. The stiff pivot tongue 172 has opposite longitudinally parallel edges 186 and 188. These

tongues

166 and 172 have all of the characteristics and advantages heretofore described.

A plunger 190 engages the blade end cross member 162 and extends out of the side wall 112. The plunger has an enlargement or head 192 to provide suitable enlarged contact with the cross member 162 and the side wall 112. The plunger 190 may be of any desired cross section, such as square, round, or the like.

A compression leaf spring 194 may be V-shaped with one end engaging the cross member 162 and the other end engaging a notch 196 in the wall 114. The spring 194 returns the blade to its upper position in FIG. 15 after the blade has been pushed down by the plunger 190 and then released.

The blade 156 snaps down when the plunger is pushed down in a manner similar to the blade '56 heretofore described.

The

notches

137 and 139 are not as wide as the rod 132 and have end shoulders 198 for preventing undue sidewise displacement of the blade 156.

The blade 156A of FIG. 18 is substantially similar to the blade 156 of FIG. 17. The blades 156A and 156 may be used in the same switch construction of FIGS. 13-16, 20

7 and 21. The main difference between the blades 156 and 156A is that the tension ribbon members 158A and 160A remain of uniform thickness for a greater length than the

ribbon members

158 and 160. Otherwise the two blades 156 and 156A are substantially the same.

The holes 144 may be used to receive mounting screws,

as previously described. Such holes may be threaded, as

shown, or unthreaded, if desired. The holes may be countersunk at 145 at one end to receive countersunk screw heads.

Alternatively, the holes 144 may receive screws that fasten the cover 122 to one end of the wall 114 and hold the cover 122 against the adjacent ends of

walls

112, 116 and 118.

Also, the switch may be simultaneously covered and mounted on a panel and the like by screws or bolts passing through holes 114 and being screwed or bolt d on the panel as desired. This simultaneously secures the cover 122 to the

walls

112, 114, 116 and 118, and the casing 110 to the panel and the like.

While the form of the invention now preferred has been disclosed, as required by statute, other forms may be used, all coming within the scope of the claimed subject matter.

A new, useful and unobvious switch, casing, and cover therefor have thus been provided by this invention.

What is claimed is:

1. Incombination:

a switch casing having two opposite first side walls, two opposite second side walls and a bottom wall joined together to form a switch cavity with an opening along uncovered edges of said side walls;

a rigid .flat metal electrically conductive rod embedded in one of said first side walls with opposite relatively wide flat sides and opposite relatively narrow edges, said rod having a straight portion extending into said cavity and a portion extending out of said one of said first side walls, said rod having opposite tongue and receiving notches in said flat sides;

a first electrical conductor bar embedded in and extending out of said one of said first side walls and having a first stationary contact elbow in said switch cavity;

a second electrical conductor bar embedded in and xtending out of said one of said first side walls and having a second contact elbow in said switch cavity;

a snap action sheet metal blade having opposite outer tension members and opposite end cross members joined integrally with said tension members, said tension members extending past and outside said rod edges, said blade having a first tongue integrally connected to a first one of said blade end cross members with a first tongue end engaging a first one of said rod notches, said blade having a second tongue integrally connected to the second one of said blade end cross members with a second tongue and engaging the second one of said rod notches, said blade having movable contact means on said first one of said blade end cross members alternately engaging said stationary contact elbows;

a plunger passing through one of said side walls and actuating said second one of said blade end cross members;

and a casing cover engaging and closing upon said uncovered edges of said side walls, one of said side walls having a hook receiving opening with a hook locking ledge, said cover having a hook construction extending therefrom into said hook receiving opening with a hook engaging and locking with said locking ledge to lock said cover to said casing; said hook construction having a bend therein intermediate said cover and said hook that normally causes said hook to be short of said ledge when said cover member is fully engaged against said uncovered edges of said side walls whereby said bend was temporarily straightenend by auxiliary means to permit said hook to further extend from said cover and reach beyond said ledge for the subsequent engagement and locking therewith after said auxiliary means was removed from its straightening action on said bend.

2. A combination according to claim 1 in which said one of said first side walls is a thicker side wall that is substantially thicker than the other side walls.

3. A combination according to claim 1 in which said thicker side wall has casing fastener holes extending through said thicker side wall and said cover has cover fastener holes aligned with said casing fastener holes for receiving fasteners to attach said casing and cover to a support structure.

4. A combination according to claim 1 in which said hook receiving opening has a slanting side which is engaged by said hook construction and flexes said hook construction while said hook construction is being inserted in said hook receiving opening.

5. A combination according to claim 1 in which said hook receiving opening extends completely through said one of said side walls to provide an uncovered external opening through which said auxiliary means is insertable.

6. A combination according to claim 5 in which said auxiliary means comprises a tool that is temporarily insertable in said uncovered external opening to aid in straightening said bend to engage said hook ledge while said hook construction is being inserted in said hook receiving opening.

7. A combination according to claim 4 in which said one of said walls is a substantially thicker side wall that is substantially thicker than the other side walls.

8. A combination according to claim 7 in which said casing fastener holes extend through said thicker side wall and said cover has cover holes aligned with said casing fastener holes for receiving fasteners to attach said combination to a support structure.

9. A combination according to claim 8 in which said hook receiving opening is located between said casing fastener holes.

10. A combination according to claim 1 in which a compression spring is located in said switch. cavity and urges said second one of said cross members toward said plunger.

11. A combination according to claim 1 in which said side walls, bottom wall and cover have outer substantially rectangular surfaces, and said substantially rectangular surfaces form an outer substantially rectangular surfaced casing and cover construction.

12. In combination:

a switch casing having side walls and a bottom wall joined together to form a switch cavity with an opening along uncovered edges of said side walls;

a switch construction in said switch cavity with a switch actuating plunger extending out through one of said walls;

one of said side walls having a hook receiving opening with a hook locking ledge;

and a casing cover engaging and closing upon said uncovered edges of said side walls and having a hook construction extending into said hook receiving opening with a hook engaging and locking with said locking ledge to lock said cover to said casing, said hook construction having a bend therein intermediate said cover and said hook that normally causes said hook to be short of said ledge when said cover member is fully engaged against said uncovered edges of said side walls whereby said bend was temporarily straightened by auxiliary means to permit said hook to further extend from said cover and reach beyond said ledge for the subsequent engagement and locking therewith after said auxiliary means was removed from its straightening action on said bend.

13. A combination according to claim 12 in which said hook receiving opening has a slanting side which is 75 engaged by said hook construction and flexes said hook construction while said hook construction is being inserted into said hook receiving opening.

14. A combination according to claim 12 in which said hook receiving opening extends completely through said one of said side walls to provide an uncovered external opening through which a tool is insertable.

15. A combination according to claim 14 in which said auxiliary means comprises a tool that is temporarily insertable through said uncovered external opening to aid in straightening said bend to engage said hook ledge while said hook construction is being inserted in said hook receiving opening.

16. A combination according to claim 12 in which one of said side walls is a substantially thicker side wall that is substantially thicker than the other side walls and has said hook receiving opening.

17. A combination according to claim 16 in which said thicker side wall has casing fastener holes extending through said thicker side wall and said cover has cover fastener holes aligned with said casing fastener holes for receiving fasteners to attach said casing and cover to a support structure.

18. A combination according to claim 17 in which said References Cited UNITED STATES PATENTS 3,255,333 6/1966 Schuchard 200-159 3,335,900 7/ 1967 Mackiewicz.

3,337,702 8/1967 Brevick et a1.

3,412,225 11/1968 Rogers et al.

3,449,534 6/ 1969 Bauer.

ROBERT K. SCHAEFER, Primary Examiner D. SMITH, JR., Assistant Examiner US. Cl. X.R.