Card – picture – or sign exhibiting – Signs – Stretched or tensioned
Patent
1997-05-19
2000-12-26
Green, Brian K.
Card, picture, or sign exhibiting
Signs
Stretched or tensioned
40741, 381021, G09F 1700
Patent
active
061639958
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention is directed to expandable artists' frames and preloading springs therefor.
BACKGROUND OF THE INVENTION
An expandable artists' frame of the kind is disclosed in IT-A-1,031,812 and in the corresponding U.S. Pat. No. 4,050,498.
In this frame the ends of the frame sides are cut at 45.degree. and slidably housed into hollow angular supports, whereby a V-shaped strip-like spring is also housed in the bisecting line of each hollow angular support between the abutting bevelled ends of two adjacent frame sides and tends to bias apart the side ends from each other.
At the ends of said frame sides are also provided longitudinal slots which allow said hollow angular supports to be slidably inserted along said slotted side ends.
Besides a hollow box-like construction, the known angular or L-shaped supports have a number of structural and functional expedients. These include a bisector-like diagonal wall defining inside the hollow support, between the abutting side ends, an air space capable to house a preloading V-shaped spring, and outside the hollow support, a corner filling wall portion capable of supporting the canvas in the corner area, when the bevelled side ends are at a distance from each other, that encompasses all the possible different expansion positions of the artists' frame.
The frames according to the teaching of U.S. Pat. No. 4,050,498 provide a functionally acceptable preloading action onto the canvas fixed to the artists' frame or stretcher. However, the preloading action allows only a limited expansion stroke of the frame sides.
Furthermore, from a manufacturing and handling point of view, the frames present limits and shortcomings.
First of all the artists' frames require four plastics hollow angular supports. The structural and functional expedients of the disclosed hollow angular supports increase the synthetic material costs and require complicated and costly moulds.
Notwithstanding these expedients, the stiffness obtained with the hollow angular supports is limited by an opening at the internal corner of the hollow angular support. This opening is necessary for inserting the respective V-shaped preloading spring.
Furthermore, in order to permit insertion of the spring, the preloading springs require a preliminary closure of the spring legs, practically with an abutment of the legs one against the other, and consequently a strong closing force which can only be applied by means of special tools, so that the V-shaped springs are not suitable for manual introduction by the user.
It is further to be noted, that the preloading force exerted by these known sprigs decreases, that it is determined by the spring dimensions, and that it is not adjustable by the user.
It is further to be pointed out, that the components of these artists' frames, except the canvas and the staples or nails, that is the frame sides, the hollow angular supports and the springs are dimensionally mutually adapted for forming the frame in question, and do not allow the use of single components per se, that is as distinct parts for making, for example, expandable frames of other kinds or sizes. In other words, the single components of the artists' frame disclosed in U.S. Pat. No. 4,050,498 can not be used with expandable frames in general, for example with expandable frames having wedges, which as is known require the machining of appropriate seats or slots for housing the wedges into the frame sides at the respective internal corner.
The arrangement of these known wedges for statically preloading the canvas and the respective seats or slots for housing the wedges can be seen, from example, in U.S. Pat. No. 3,882,616. However, the artists' frame disclosed in this patent is not provided with springs for dynamically preloading the canvas.
The present invention further relates to improved hollow angular supports for expandable frames in accordance with the present invention.
A further expandable frame is disclosed in DE-C-581,549. In this artists' frame, in the respective bevelled oppo
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patent: 80135 (1868-07-01), Carroll
patent: 159012 (1875-01-01), Wright et al.
patent: 339276 (1886-04-01), Dodge
patent: 996915 (1911-07-01), Engelmohr
patent: 4050498 (1977-09-01), Lucchetti
patent: 4301853 (1981-11-01), Vidal
Lucchetti Walter
Zanella Carlo
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