Static structures (e.g. – buildings) – Lazy tong extension unit
Patent
1984-05-18
1986-04-08
Murtagh, John E.
Static structures (e.g., buildings)
Lazy tong extension unit
52646, 40610, A47F 513, E04B 274
Patent
active
045803757
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a collapsible lightweight exhibit panel of the kind composed of mainly square units of pivotally connected rods.
DESCRIPTION OF THE PRIOR ART
On the basis of general principles for the configuration of collapsible lightweight structures, as exemplified in U.S. Pat. No. 3,968,808, prior art exhibit panels have been made which are formed from units each having a box-like frame with front and rear vertical unit surfaces extending in mainly parallel flat relationship, and with horizontal and vertical side faces, each of which is defined by two side rods pivotally connected with each other in a scissor-like manner. The ends of the side rods are each pivotally connected at its opposite ends with corner joints located in the respective central joint connected with the four corner joints in the rear unit face by substantially diagonally extending rods. Link rods are pivotally connected to the four front corner joints of the unit front face and to intermediate pivotal joints on the corresponding diagonal rods. Corner joints and side rods are common with corresponding adjacent units so that corner joints on a common side between adjacent units are connected to pairs of diagonal rods and link rods of the adjacent units.
This type of prior art collapsible exhibit panel is made self-supporting by selecting a ratio of the length of the link rods relative to the length of the diagonal rod sections between the corner joints and the pivotal joints to the link rods which is different from the ratio of the length of side rod sections from front corner joints to scissor joints relative to the length of side rod sections from rear corner joints to the scissor joints. The self-supporting effect is caused by the fact that the diagonal rods between a central joint located inside the unit and four corner joints due to the action of link connections to the four remaining corner joints are exposed during erection or unfolding of the panel to an increasing bending action until a switch-over position is achieved, in which this bending action is at a maximum.
After passage of the unstable switch-over position the system occupies by itself a stable erected condition in which the diagonal rods extend substantially in a common plane in an equal load balance with the scissor-like rod systems in the unit side faces. Since as a result thereof a considerable stress arises in the diagonal rods during unfolding and folding by the passage of the unstable switch-over position, the operation of the panel requires quite a considerable exercise of force, and by the use of thin-walled light metal tubes for the rod connections of the panel there is a considerable risk of deformation. The central joint and the diagonal rods in the erected condition extend substantially in the above mentioned common plane. As a result of the fact that the panel is designed also with a central joint for the link rods which extend past their pivotal connections with the diagonal rods, this asymmetric structure of the unit entails that for each unit the latter central joint will be located outside the unit frame, so that one surface of the erected panel is not usable for the arrangement of posters.
Moreover, since the known panel mentioned above is only kept in the erected condition by the self-supporting effect described, there will be a rather narrow limit to the load which may be applied to the panel without risk of collapse.
In a similar manner, another exhibit panel known from U.S. Pat. No. A-4,276,726 is designed to be generally unsymmetrical with a single central joint located rather close to the unit surface constituting the front side of the panel intended for the arrangement of posters. In this case, the asymmetric structure makes the unit less suited for the construction of high exhibit panels because the front and rear surfaces of the panel will be unequally loaded, particularly when posters are arranged on the front surface, whereby permanent obliquities may arise.
The prior art panels have been designed in either c
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patent: Re31641 (1984-08-01), Derus
patent: 415667 (1889-11-01), Edwards
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patent: 3978634 (1976-09-01), Mack
patent: 4241746 (1980-12-01), Rothe
patent: 4437275 (1984-03-01), Zeigler
Nodskov Preben
Thelander Finn
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