This invention relates to spirit levels and is directed particularly to a simple and inexpensive spirit level for permanent attachment to the top of a rectangular picture frame to assist in the straight hanging thereof.
Various spirit level devices for positioning structures and apparatus relative to a horizontal plane have heretofore been devised. Such spirit level devices as are known, however, are deficient in various respects, principally because of their complexity, size and cost. It is, accordingly, the principal object of this invention to provide a simple, inconspicuous and inexpensive spirit level device that may be left attached to the top of a rectangular picture frame to facilitate precise vertical hanging.
A more particular object of the invention is to provide a spirit level device which, upon its attachment to a picture frame, will be small enough not to disturb the aesthetic value of the framed picture.
Yet another object of the invention is to provide a spirit level device of the above nature and so constructed in strips of connected units as to be sufficiently flexible enough to permit high density packaging in roll form .
Other objects, features and advantages of the invention will be apparent from the following description when read with reference to the accompanying drawings. In the drawings, wherein like reference numerals denote corresponding parts throughout the several views:
FIG. 1 is a top view of the picture frame leveling device embodying the invention;
FIG. 2 is a longitudinal cross-section taken along the line 2--2 of FIG. 1 in the direction of the arrows;
FIG. 3 is a partially disassembled view, in perspective, of the leveling device;
FIG. 4 is a transverse cross-sectioned view, in perspective, of the leveling device, illustrating constructional details; and
FIG. 5 shows a roll containing a plurality of the leveling devices.
Referring now in detail to the drawings, reference numeral 1 designates, generally, a spirit level device embodying the invention which comprises, generally, a flexible base tape 3 and a transparent blister tape 4, said base tape being longitudinally affixed against one side of said transparent blister tape so as to enclose the blister shaped longitudinal cavities formed therein to define closed chambers. The chambers are almost filled with a liquid 5 of suitable viscosity, the remaining space creating a bubble 2, preferably of air, but which may be of other fluid not soluble in said liquid. Transverse markings 6--6 on the transparent blister tape 4 provide a ready reference for determing position with respect to the horizontal plane.
The base tape 3 is provided on the outside with a pressure-sensitive adhesive coating 8 for affixing along the top of a framed picture. The coating 8 is covered with a protective paper tape 9 that is peeled off when the device is ready to be affixed to the frame.
Whereas FIG. 1 shows transparent blister tape 4 being of somewhat smaller width than the base tape 3, this is not critical to the invention and selection of the relative width will depend upon the requirements of the manufacturing process whereby good sealing of the blister cavity is achieved. As further illustrated in FIG. 1 transverse perforations 7 are provided at regular intervals along the tape assembly to permit the easy separation of individual level units for use.
Referring now to FIG. 2, which shows a cross-section of the invention, it may be observed that when the device is placed upon the surface for which levelness is to be determined, the bubble 2, due to its inherent nature, will always appear at the uppermost portion of the curved blister and will fall either to the left or to the right of markings 6--6, thereby indicating the higher side of the picture frame. The frame will be leveled when the bubble 2 comes to rest centrally between the markings 6--6.
As illustrated in FIG. 3 the above described composite tape level can conveniently be manufactured by placing the transparent blister tape 4 upsidedown in a suitable jig or supporting structure maintaining it in horizontal position, then filling the blister cavities with the required amount of liquid 5, and finally applying the base plate 3 from above in a progressive fashion from one end to the other so that complete sealing is effected between the tapes. It will be understood that just enough liquid 5 will be deposited in each of the cavities of the transparent blister tape 4 to leave a suitably sized air bubble remaining in the chambers defined between the interassembled tapes. The face-to-face securment of transparent tape 4 to the base tape 3 will preferably be effected by heat sealing, it being understood that said tapes will be of such materials as to be compatible with the process.
Before separation along the transverse perforations 7, of individual ones of the level units for use, the tape assembly can be supplied as a continuous roll as illustrated in FIG. 5. In this connection it will be understood that the transparent blister tape 4 and the base tape 3 will be of flexible enough materials to permit such packaging in rolls.
While I have illustrated and described herein only one form in which my invention can conveniently be embodied in practice, it is to be understood that this embodiment is presented by way of example only and not in a limiting sense. The invention, in brief, comprises all the embodiments and modifications coming within the scope and spirit of the followig claims.