US3646244A

US3646244A - Adjustable floor receptacle mount

Info

Publication number: US3646244A
Application number: US65778A
Authority: US
Inventors: Stephen W Cole
Original assignee: C W COLE AND CO Inc
Current assignee: C W COLE AND CO Inc
Priority date: 1970-08-21
Filing date: 1970-08-21
Publication date: 1972-02-29
Anticipated expiration: 1989-02-28

Abstract

An adjustable floor receptacle mount is provided that includes a housing movable within a stationary casing fitted into a circular opening in a concrete floor. The housing and the casing are each formed of a pair of interlocking extruded channel structures whose walls are shaped to facilitate the installation and operation of the floor receptacle mount. In order to simplify the withdrawing of the housing from a recessed position within the casing, a cap provided on a cover plate for the housing and operating in conjunction with a latching mechanism pops up when the housing is unlatched. The cap thus provides a convenient handle by which the housing can be quickly pulled out of the casing in the floor when it is desired to use the electrical service provided by the receptacles on the sides of the housing.

Description

ited States tent Cole Feb. 29, 1972 [54] ADJUSTABLE FLOOR RECEPTACLE MOUNT Primary Examiner-William T. Dixson, Jr.

Assistant Examiner-James R. Garrett [72] Inventor: Stephen W. Cole, Altadena, Calif. Anomey |ohn M tl [:3] :slsignee: W.2(lIolle9:0Co., Inc., El Monte, Calif. 7 1 ABSTRACT 2 d: 1 l e ug An adjustable floor receptacle mount is provided that includes PP 78 a housing movable within a stationary casing fitted into a circular opening in a concrete floor. The housing and the casing are each formed of a pair of interlocking extruded channel [52] U.S. Cl Nd/57, stmctures whose walls are shaped to facilimm the installation [51] Int Cl 6 and operation of the floor receptacle mount. In order to sim- [58] Fie'ld 4 3 5 3 plify the withdrawing of the housing from a recessed position i within the casing, a cap provided on a cover plate for the housing and operating in conjunction with a latching mechanism pops up when the housing is unlatched. The cap thus provides [56] References Cited a convenient handle by which the housing can be quickly UNITED STATES PATENTS pulled out of the casing in the floor when it is desired to use the electrical service provided by the receptacles on the sides 2,811,574 10/1957 Guerrero ....174/57 fth housing 2,811,575 10/1957 Guerrero ....174/57 3,433,886 3/1969 Myers ..174/57 10 Claims, 9 Drawing Figures Patented Feb. 29, 1972 3,646,244

3 Sheets-Sheet 2 I N VE/V Toe STEPA/E/V W C045 yalwydfa Patented Feb. 29, 1972 3 Sheets-Sheet 5 INVEN roe. STEP/, E/VII I C045 ADJUSTABLE FLOOR RECEPTACLE MOUNT This invention relates to adjustable floor receptacle mounts and more particularly to a novel structure for such a mount.

It is highly desirable to provide a movable housing in a floor receptacle mount that can be either lowered within a stationary casing providedin the floor and latched in a hidden position therein flush with the surrounding floor area or that can be easily lifted out of the casing and held in a withdrawn position above the level of the floor in which position the electrical receptacles on the sides of the housing are readily available for providing service to electrical equipment.

It can be readily appreciated that when it is desirable to provide such an adjustable floor receptacle mount that extends through an opening provided in a concrete floor, it simplifies and reduces the expense of the labor of installation thereof if the recess or opening to be bored in the concrete floor is of a circular configuration. This, however, requires that the casing for the mount to be placed in this circular opening be of a circular configuration. It is also appreciated that in order to latch the housing when it is in its hidden position within the casing or to unlatch the housing so that it can be lifted therefrom when it is desired to use the services provided by the receptacles, it is of advantage to apply a rotative force in some manner to the housing. However, this rotative force is of no effect unless the surface of the casing in which the housing vertically slides is shaped so as to resist such rotation.

Accordingly, in order to provide shapes for the casing and housing of an adjustable floor receptacle mount which will accommodate these and other requirements without having to machine or specially fabricate the parts, the present invention provides for forming the casing and housing of extruded open channel structures that can be readily manufactured in a continuous manner. The extruded open channel structures are so shaped that two separate lengths of the identically shaped structures can be interlocked or mated together by sliding the side edge portions thereof lengthwise within each other to form a hollow closed cross-sectional unit. Thus, the casing is formed of two lengths of interlocked identically shaped channel structures such that although the cross section of its wall configuration is generally circular, its interior wall configuration is formed with flat surfaces on diametrically opposed portions thereof. The housing is likewise formed of two lengths of interlocked identically shaped open channel structures such that although the cross section thereof is generally square, the corner walls thereof are rounded to conform with a close sliding fit within the circular wall of the casing. Thus, the rounded corners of the housing are permitted to slide vertically along the circular interior wall of the casing while the flat sides of the housing abutting the flat surfaces on diametrically opposed portions of the interior wall of the casing restrain the housing from rotation therein. It should be noted that by forming the casing and housing of extruded structures other useful shapes can be readily provided which will facilitate the installation and operation of such adjustable floor receptacle mounts.

When a floor receptacle mount is residing with its housing in its hidden position within the casing in the floor, a cover plate on the upper end of the housing is positioned flush with the level of the floor and latched tightly against a trim ring attached to the stationary casing such as to seal the mount. Because the cover plate is flush with the floor with no protruding parts, there is no way of grasping hold of the cover plate after being unlatched in order to lift the housing out of the floor without using a special tool to pry or otherwise lift up the cover plate. Thus, it is highly desirable to provide a built-in device on the mount for being able to simply lift the housing after it is unlatched such that it can be withdrawn from the casing when service connections are to be made to the receptacle thereon, and then lowered back into the casing when the service connections are no longer required.

The adjustable floor receptacle mount of the present invention provides a cap on a bolt extending through the center of the cover plate for the housing which operates in conjunction with its latching mechanism such that the cap pops up above the level of the cover plate when the housing is unlatched. The cap thus provides a convenient handle by which the housing can be quickly pulled out of the casing in the floor.

Accordingly, the broad object of the present invention is to provide improvements in the construction of adjustable floor receptacle mounts.

Another object of the present invention is to provide an improved structure for such a mount by manufacturing both the stationary casing and the movable housing therefor out of extruded channel structures.

Another object of this invention is to provide a novel popup device operating in conjunction with a latching mechanism for facilitating the lifting of the housing of the floor mount when it is in its hidden position in the casing flush with the level of the floor.

The manner in which the above objects are accomplished in accordance with the invention, as well as other objects, advantages and features thereof, will become apparent from the following description and the accompanying drawings wherein:

FIG. 1 is a top plan view of the floor receptacle mount of the present invention shown with the movable housing in its hidden position flush with the level of the floor;

FIG. 2 is a vertical sectional view of the floor receptacle mount showing the casing with the movable housing in its hidden position therein flush with the level of the floor;

FIG. 3 is a perspective view of the floor receptacle mount shown with the movable housing in its withdrawn position above the level of the floor;

FIG. 4 is a vertical sectional view of the floor receptacle mount showing the casing with the movable housing in its withdrawn position therein so as to extend above the level of the floor;

FIG. 5 is a perspective view showing the details of the trim ring as viewed from below the floor level;

FIG. 6 is a plan and partially horizontal sectional view of the mount taken generally at different levels along line 6-6 of FIG. 2;

FIG. 7 is a perspective view showing the details of the cover plate assembly for the housing;

FIG. 8 is a horizontal sectional view of the mount taken along line 88 of FIG. 2 and showing the latching mechanism in its latched and unlatched positions; and

FIG. 9 is a horizontal sectional view of the mount taken along line 99 of FIG. 2 and showing the spring supported stop for holding the housing in its withdrawn position.

Like referenced numerals correspond to like elements throughout the figures of the drawings.

Referring to the drawings, the adjustable floor receptacle mount of the present invention includes an inner housing denoted by reference character 10 and an outer casing denoted by reference character 16. The housing 10 is movable within casing 16 which is stationarily held in a circular opening 35 provided in a concrete floor. In FIGS. 1 and 2 the movable housing 10 is illustrated in its recessed or hidden position within casing 16 in which it is flush with the level of the floor. In FIGS. 3 and 4 the movable housing 10 is illustrated in its withdrawn or in-use position in which the upper half thereof is pulled out of the casing 16 and extends above the level of the floor.

Housing 10, which is generally square in cross section, is formed of two identically shaped lengths of

aluminum extrusions

11 and 12 the sides of which are interlocked at 13 and 14 by sliding the projections on the side end portions thereof within each other to form a hollow closed cross-sectional unit, as shown in FIGS. 6, 8 and 9. More specifically, as shown at 13 in FIG. 6, a side projection 11d of extrusion 11 is slid lengthwise into the opening of a side end projection 12d of extrusion 12. The corners, such as 11f, of the housing 10 are rounded such that the housing is slidably mounted within the generally circular stationary casing 16 which is likewise formed of two identically shaped lengths of

aluminum extrusions

17 and 18 the side edges of which are interlocked at 20 and 21, similarly to the extrusions of housing 10, as shown in FIGS. 6, 8 and 9. The

identical extrusions

17 and 18 forming casing 16 provide respective flat surfaces 170 and 18a on diametrically opposite sides of the internal wall thereof which together with respective shoulders 18b and 17b provide for mating with the respective opposing flat sidewalls 12a and 11a of the

identical extrusions

12 and 11 forming movable housing 10.

The housing is provided with a top circular cover plate 22 which has a bridge member 24 secured to the underside thereof by welding, for example, as shown in FIG. 7. The ends of bridge member 24 extend downwardly and inwardly to form

brackets

26a and 26b. The cover plate 22 is securely attached to the upper end of housing 10 by mounting

screws

28a and 28b extending through the flat back and front walls 110 and 120, respectively, of housing 10 and the downwardly extended portions of

brackets

26a, 26b of bridge member 24. The inwardly extending portions of

brackets

26a and 26b have a horizontal barrier 32 attached thereto by mounting

screws

32a and 32b. The horizontal barrier 32 serves to shield receptacles 19 mounted within the housing 10 from dirt, water or other foreign matter. The periphery of cover plate 22 projecting beyond the sides of the inner housing 10 is provided on the underside thereof with a peripheral gasket 25 (FIG. 2). A bottom circular cover plate 30 provided with a sealing gasket 31 is secured onto the bottom end of housing 10 by mounting screws 33.

The flat back and front walls 11c and 120, respectively, of housing 10 are provided with rectangular openings 38 (FIG. 2) to accommodate the electrical receptacles 19 on a pair of panels which are attached to these walls by mounting screws 15a. It should be understood that a variety of replaceable panels 15 formed to accommodate a variety of electrical receptacles 19 can be provided for attachment to the front and back walls of housing 10 in the aforementioned manner. As indicated in FIG. 9, a vertical barrier 68 may be inserted in grooves 12b and 11b formed on the respective flat sidewalls 12a and 11a of housing 10 when it is desirable to have the mount provided with electrical devices or receptacles 19 of high and low potential requirements.

The stationary casing 16 is formed with four radially extending

ribs

17c, 17d, 18c and 18d equally spaced about the outer circular wall thereof for facilitating the positioning of casing 16 into the circular opening 35 provided in the concrete floor. As shown in FIGS. 2 and 6, a trim ring 37, preferably formed of a stamping, is positioned over the opening 35 in the floor with its outer periphery forming a circular rim 23 extending over the edge thereof and with its inner periphery stepped downwardly to form an inner flange 27. Flange 27 is formed with side portions positioned over the interlocking end portions and 21 of the outer casing 16 so as to be held thereon by mounting screws 20a and 21a. A sealing gasket 38a is positioned under circular rim 23.

It should thus be understood that casing 16 is positioned in opening 35 provided in the concrete floor and supported therein by the trim ring 37 which has its inner flange 27 attached to the upper end of outer casing 16 and its outer rim 23 extending about the circular edge of opening 35. Outer rim 23 sits above the surface of the concrete floor such that its upper surface matches the level of the tile 34, for example. The lower portion of casing 16 extending below the lower surface of the concrete floor is provided with a sleeve 40 that can be vertically positioned along the lower end portion of casing 16 such that its upper flange 41 contacts the lower surface of the concrete floor. Screws 42 passing through sleeve 40 engage threaded openings in the interlocking wall portions of the casing 16 (FIG. 9) to hold the sleeve 40 in this position.

As shown in FIG. 2, it is contemplated that the space surrounding the portion of the floor receptacle mount located below the concrete floor is enclosed by a metal box 46 which is attached to the undersurface of the floor by screws 48. The inside surface of box 46 is lined with an asbestos insulation, for example, so as to serve as a heat barrier for the floor mount. A

connector 61 attached to a central opening in the bottom cover 30 provides for holding flexible cable 63 such that its ends can extend upwardly within housing 10 and be connected (not shown) to the electrical receptacles 19 held on the side panels 15 of housing 10. The other end of cable 63 is attached by connector 66 on the wall of box 46 to an outlet box 64.

It should now be clear that the movable housing 10 with the cover plate 22 attached on the upper end thereof can slide vertically within the stationary casing 16 to either its hidden position flush with the level of the floor as illustrated by FIGS. 1 and 2 or to its withdrawn position above the level of the floor as illustrated by FIGS. 3 and 4. In a manner to be described in the ensuing description, when the housing 10 is latched in its hidden position the outer periphery of cover plate 22 is sealed by gasket 25 compressingly engaged against flange 27 of trim ring 37 and when the housing 10 is held in its withdrawn position the outer portion of bottom cover 30 is sealed by gasket 31 which abuts up against the lower end of casing 16.

The housing 10 is held in its withdrawn position by a pair of spring supported stops 45a and 45b which are positioned intermediately within the housing 10 on opposite walls 12a and 11a thereof with the lower ends of the spring supports 43a and 43b held by screws 44a and 44b. The stops 45a and 45b extend through respective openings 39a and 39b provided on the opposite sidewalls 12a and 11a of the housing 10 into the recesses provided between the circular wall of the casing 16 and the sidewalls of the housing 10, as shown in FIG. 9. Stops 45a and 45b are provided with slanted surfaces such that as the housing 10 is raised past the inner flange 27, the stops 45a and 45b are deflected inwardly. Then, upon the housing 10 reaching its withdrawn position the stops 45a and 45b snap back out through openings 39a and 39b so as to rest against the upper surface of inner flange 27.

Mounted on the cover plate 22 and within the upper portion of inner housing 10 is a mechanism which is used for latching housing 10 to the casing 16 when it is in its recessed position within the casing 16. This mechanism also operates to facilitate the lifting of the housing 10 out of its recessed position. To this end, cover plate 22 is formed with a circular well 29 in the center thereof which seats cap having a slot 53. Cap 50 forms the head of a bolt 51 whose threaded body passes through a central clearance opening 52 provided in the center of cover plate 22. A spring 54 positioned between the underside of cap 50 and the upper surface of the well 29 on cover plate 22 tends to urge the bolt 51 in an upward position (FIG. 4). A horizontally disposed latch member 55 provided with latching

end portions

57a and 57b is provided with a threaded opening 58 in the center thereof for receiving the threaded body of bolt 51. A nut 59 is provided on the lower end of the body of bolt 51. A spring 60, positioned between the nut 59 and the lower surface of latch member 55, takes up any slack in the threads so as to urge the latch member 55 into an upward position such that it tends to move with the rotation of bolt 51 until it meets a resistance. As shown in FIGS. 2, 6 and 8, when the cap 50 is forced down against the spring 54, the latch member 55 is lowered such that its

end portions

57a and 57b can be rotated in a clockwise direction into horizontally disposed slots 62a and 62b respectively provided on the opposite sidewalls 12a and 11a of inner housing 10. Upon being rotated about 45, the

end portions

57a and 57b, respectively, bear against the surfaces 17f and 18f of the interlocking end portions 21 and 20 of the casing 16. Further tightening of the cap 50 in a clockwise direction then causes threaded bolt 51 to draw up on the latch member 55 such that the

end portions

57a and 57b thereof bear upwardly against the depending

inner shoulders

65a and 65b provided on diametrically opposing sides of inner flange 27 of the trim ring 37. This compresses the gasket 25 provided on the periphery of the cover plate 22 so as to seal the floor receptacle housing 10 in its recessed position within the casing 16.

When the floor receptacle housing 10 is to be withdrawn from the casing 16 to its in-use position above the concrete floor, the cap 50 is rotated in a counterclockwise direction by turning a coin or a similarly shaped object positioned in the slot 53. The initial turning of the cap 50 provides for loosening the latch member 55. As shown in FIGS. 4 and 7, upon further rotation in this direction, the latch member-55 rotates with the bolt 51 because of the force of spring 60 until the

respective end portions

57a and 57b of the latch member 55 clear the horizontally disposed slots 62a and 62b in the opposite sidewalls 12a and 11a of housing 10, and moves to the position shown in H6. 8, in which the

end portions

57a and 57b respectively contact the flat front and back walls 12c and llc of the housing. The nut 59 on the lower end of the bolt 51 prevents the bolt from inadvertently being rotated out of latch member 55. Latch member 55 is now free to move upwardly by the force of spring 54 such that the bolt 51 and cap 50 pop up, as shown in FIG. 4, so as to provide a convenient handle for lifting the housing out of the casing 16.

As described previously, the housing 10 is lifted until gasket 31 on bottom cover plate 30 bears against the bottom end of casing 16 at which time the spring-supported stops 45a and 45b snap out into flange 27 to support the housing 10 in its withdrawn position. When it is desired to again position the housing into its recessed position in the floor, the stops 45a and 45b can be pressed inwardly and the housing 10 is then lowered down into the casing 16 while being held by cap 50. The cap 50 is then pressed down against spring 54 which lowers the latch member 55 such that rotating the cap 50 in a clockwise direction by inserting a coin in its slot 53 will rotate the latch member 55 approximately 45 until arrested by the

end portions

570 and 57b thereof respectively contacting the inner locking portions 20 and 21 of the casing 16 (FIGS. 6 and 8). When in this position the

end portions

57a and 57b of the latch member are below the depending

shoulders

65a, 65b on inner flange 27 of the trim ring 37. Thus, continued tightening of cap 50 in a clockwise direction causes the end portions of the latch member 55 to bear upwardly against the

inner shoulder

65a and 65b of the trim ring 37. This causes the periphery of the cover 22 to bear down on the gasket 25 so as to seal the mount while in its recessed position.

Although the description herein has been concerned with a particularly illustrative embodiment, it is to be understood that the invention is subject to various modifications in both the construction ad arrangement thereof without departing from the spirit of the invention. The invention, therefore, should be considered as including all possible modifications and variations coming within the scope of the invention as defined in the appended claims.

What is claimed is:

1. An adjustable floor receptacle mount comprising a casing adapted to be stationarily positioned in a circular opening in the floor of a building, a trim ring having an inner flange with depending shoulders and being attached to the upper end of said casing, a housing mated for sliding movement within said casing, said housing being provided with receptacles on the vertical sidewalls thereof, a circular cover plate attached to the upper end ofsaid housing, a bolt having a cap on the upper end thereof and a threaded body extending downwardly through an opening in the center of said cover plate, a spring beneath the cap of said bolt for urging said bolt in an upward direction, and a latching means threadably engaged to the body of said bolt, whereby when said bolt is depressed down against the action of said spring and is rotated in one direction the latching means bears upwardly against the shoulders on the flange of said trim ring so as to latch said housing within said casing in a recessed position in which said cover plate is flush with the floor, and whereby when said bolt is rotated in the other direction the latching means is freed of said trim ring shoulders and the bolt'is lifted up by the action of said spring such that the cap on the upper end thereof can be used as a 1 handle to raise the housing out of the casing to a withdrawn position in which the receptacles on the said sidewalls thereof are exposed for use above the floor.

2. The invention in accordance with claim 1 wherein said housing and said casing are each formed of a pair of identically shaped lengths of extrusions which are interlocked at the side edges thereof.

3. The invention in accordance with claim 2 wherein the housing formed by said interlocked identically shaped lengths of extrusions has a generally square cross section with rounded corners, and the casing formed by said interlocked identically shaped lengths of extrusions has a generally circular cross section with flat portions on diametrically opposite inside surfaces thereof, and wherein said housing is mated to slide within said casing with the rounded corners thereof engaging the circular inside wall of said casing and with the flat sides thereof engaging the flat portions on the inside wall of said casing.

4. The invention in accordance with claim 1 wherein said circular cover plate is provided with a peripheral gasket on the underside thereof which bears against the flange of said trim ring when said housing is latched to said casing by said latching means.

5. The invention in accordance with claim 4 wherein said latching means comprises a transverse latching member with a threaded opening in the center thereof for receiving the threaded body of said bolt, and wherein said housing is provided with transverse slots on opposite sidewalls thereof into which the ends of said transverse latching member can be rotated so as to engage the lower end of the flange shoulders of said trim ring for latching said housing to said casing.

6. The invention in accordance with claim 3 wherein the outer circular wall of said casing is provided with a plurality of spaced longitudinally extending ribs to facilitate the installation of said casing in the circular opening of the floor.

7. The invention in accordance with claim 1 wherein the housing is provided with a pair of spring-supported stops extending through openings in the opposite sidewalls thereof, and wherein said stops project out of said housing onto the upper surface of the flange of said trim ring to hold said housing when in its withdrawn position above the floor.

8. The invention in accordance with claim 5 including an additional spring on the body of said bolt urging said latching member in an upward direction, whereby when said bolt is depressed down against the action of said spring and is initially rotated in one direction the latching member is rotated with the bolt to a position below the flange shoulders of said trim ring, and whereby further rotation of said bolt draws the circular cover plate down on the flange of said trim ring such that the peripheral gasket compressingly seals the cover plate.

9. In an adjustable floor receptacle mount, the combination comprising a casing stationarily positioned in an opening in a floor, a housing provided with electrical receptacles on the vertical sidewalls thereof, a cover plate secured to the upper end of said housing, said housing being shaped to have a sliding movement within said casing to a recessed position in which said cover plate is flush with the level of the floor and a withdrawn position in which the receptacles thereon are exposed for use above the floor, latching means for latching said housing in its recessed position within said casing, and a cap located on the center of said cover plate, said cap being supported so as to be urged into an upward position above the cover plate when said housing is not latched to said casing by said latching means whereby said cap can be used to withdraw said housing from said casing.

10. In an adjustable floor receptacle mount, the combination comprising a casing formed of a pair of identically shaped lengths of extrusions which are interlocked along the side edges thereof, said casing having a generally circular cross section with flat portions on diametrically opposite inside surfaces thereof, a trim ring attached to the upper end of said casing, said casing being adapted to be stationarily positioned in a circular opening in the floor of a building with the trim ring projecting over the rim of said opening, a housing formed of a pair of identically shaped lengths of extrusions which are interlocked along the side edges thereof, said housing having a generally square cross section with rounded corners, a circular cover plate attached to the upper end of said housing, said between a recessed position in which said cover plate is flush with the level of the floor and a withdrawn position in which the receptacle devices thereon are exposed for use above the floor.

Claims

1. An adjustable floor receptacle mount comprising a casing adapted to be stationarily positioned in a circular opening in the floor of a building, a trim ring having an inner flange with depending shoulders and being attached to the upper end of said casing, a housing mated for sliding movement within said casing, said housing being provided with receptacles on the vertical sidewalls thereof, a circular cover plate attached to the upper end of said housing, a bolt having a cap on the upper end thereof and a threaded body extending downwardly through an opening in the center of said cover plate, a spring beneath the cap of said bolt for urging said bolt in an upward direction, and a latching means threadably engaged to the body of said bolt, whereby when said bolt is depressed down against the action of said spring and is rotated in one direction the latching means bears upwardly against the shoulders on the flange of said trim ring so as to latch said housing within said casing in a recessed position in which said cover plate is flush with the floor, and whereby when said bolt is rotated in the other direction the latching means is freed of said trim ring shoulders and the bolt is lifted up by the action of said spring such that the cap on the upper end thereof can be used as a handle to raise the housing out of the casing to a withdrawn position in which the receptacles on the said sidewalls thereof are exposed for use above the floor.

10. In an adjustable floor receptacle mount, the combination comprising a casing formed of a pair of identically shaped lengths of extrusions which are interlocked along the side edges thereof, said casing having a generally circular cross section with flat portions on diametrically opposite inside surfaces thereof, a trim ring attached to the upper end of said casing, said casing being adapted to be stationarily positioned in a circular opening in the floor of a building with the trim ring projecting over the rim of said opening, a housing formed of a pair of identically shaped lengths of extrusions which are interlocked along the side edges thereof, said housing having a generally square cross section with rounded corners, a circular cover plate attached to the upper end of said housing, said housing being mated to slide within said casing with the rounded corners thereof engaging the circular inside surfaces of said casing and with opposite sides thereof engaging the flat portions on the diametrically opposite inside surfaces of said casing, and receptacle devices mounted on the vertical walls of said housing, said housing being slidable within Said casing between a recessed position in which said cover plate is flush with the level of the floor and a withdrawn position in which the receptacle devices thereon are exposed for use above the floor.