Static structures (e.g. – buildings) – Mechanism operated relatively movable shaft assembly – Tilts relative to base
Patent
1990-02-23
1991-11-05
Chilcot, Jr., Richard E.
Static structures (e.g., buildings)
Mechanism operated relatively movable shaft assembly
Tilts relative to base
52632, 52732, 182 2, E04H 1234
Patent
active
050622455
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a telescopic beam.
Known forms of telescopic beams find applications in numerous fields ranging far beyond the eponymous optical magnifier. They may for example be used as radio aerials, parts of collapsible furniture, components of cranes, and in hydraulic or pneumatic devices. In general telescopic beams can be used whenever it is desired to constrain movement to a linear (although not necessarily straight) path. A similar function is served by slides used for example in furniture drawers, particularly filing cabinet drawers.
Known telescopic beams are composed of a series of members stowed within one another and as such will hereafter be referred to as being of reducing section. A common disadvantage of a reducing section beam is that successive members in the series are accommodated broadly within the periphery of the immediately preceding section, and therefore for members of similar wall thickness and type of material the bending stiffness of the sections is the lower according to their position in the series. A further disadvantage with some designs is the relatively great variation in bending stiffness according to the direction of bending, for example drawer slides are stiff in the vertical direction, but are commonly flexible in the direction horizontally sideways to their direction of travel. Yet a further major disadvantage of existing telescopic beams and slides is the fact that, due to the need for special tooling for each component of different cross-section, the production of a new telescope or slide is an expensive undertaking.
Broadly the present invention provides a telescopic beam having a cross-section of essentially spiral or modified spiral form such that a beam is made up of a nested array of members of substantially identical cross-section (in profile and dimension) and substantially constant cross-section along their axis; the members being rotationally offset to one another about an axis of the beam parallel to their own axis and engaging one another such that relative movement between two adjacent beams is constrained to be in the direction of their axis. Thus a series of members can be assembled to produce a telescopic device, the maximum number of members in any device being defined by the magnitude of the rotational offset incorporated in the particular section used. It will be apparent that the invention however allows considerable versatility in the choice of any value of rotational offset allowing for any number of sections from a minimum of two to a maximum restricted only by the practical limits of the production process and material chosen.
In a basic form the invention consists of a beam cross-section in the shape of an arc of an Archimedean spiral, that is a spiral whose change in distance from the center is constant with change in angular location. Typically a second identical section will fit inside or outside the first, provided it is first rotated about the center of the spiral by an amount which depends on the thickness, and geometry, of the material being used. In practice the pure form of the spiral will have to be modified for example to allow for different material thickness in different parts of the spiral, to produce flat sections in the spiral, to provide running clearance between sections, to accommodate production tolerances, to provide working voids between sections for example to accommodate travel stops, springs bushes and the like, or to provide a means to prevent relative rotational movement of adjacent sections in the plane of the cross-section.
In a variation of the invention, a telescopic device may be assembled from members whose cross-sections are not identical, but whose form follows the principles already established in the invention. Similarly, member cross-sections may differ due to features on their radially internal or external faces. Alternatively, the cross-section of the members may be varied along the length of the beams.
The angular extent of the spiral around a central axis of the beam will normally be appr
REFERENCES:
patent: 701042 (1902-05-01), Holmes
patent: 2165426 (1939-07-01), Tuttle et al.
patent: 3292956 (1966-12-01), Schiansky
Chilcot Jr. Richard E.
Watson Linda J.
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