Spiral staircases

Claim 2

A modular step unit for a vertebrate spiral staircase, comprising: a tubular newel boss; a tread member attached to and radially extending from said newel boss; said newel boss having end faces lying generally in a plane at right angles to the axis of said boss and parallel with the plane of the face of said tread, said boss having means for securing said boss to immediately adjacent bosses, including, a cross member provided at each end of said boss in a plane at right angles to the axis of said boss, said cross member at least partially closing its adjacent end and extending laterally in said plane on both sides of the axis of said boss sufficiently to accommodate means for bolting said boss to axially aligned adjacent bosses, and wherein said boss defines means, including at least one aperture in a wall thereof, for providing access for a tool when joining adjacent bosses.

Claim 3

A step unit as claimed in claim 1, in which said boss is provided at each end with a cross member, in a plane at right angles to the axis of said boss, which at least partially closes such end and extends laterally in said plane on both sides of the axis of said boss sufficiently to accommodate means for bolting said boss to an axially aligned boss of any adjacent unit.

Claim 4

A step unit as claimed in claim 2, in which one of said cross members protruding axially beyond one end of said boss, and said boss at its other end extending axially beyond the other said cross member, thereby constituting spigot and socket means for connection of adjacent step units.

Claim 5

A step unit as claimed in claim 2, in which both ends of said boss extend axially beyond said respective cross members.

Claim 6

A spiral staircase comprising an assembly of step units according to claim 2, in each of which said step units both ends of said boss extend axially beyond said respective cross members, and in which a free but close fitting sleeve is interposed between adjacent step units and acts to facilitate alignment of said bosses while assembling said staircase.

Claim 7

A spiral staircase having a plurality of substantially similar steps, comprising: a plurality of vertically axially aligned tubular bosses, each boss having a member fixed across the inside diameter of said boss adjacent each end thereof, said members having at least one clearance hole defined therein; a bolt element passing through clearance holes of a first said member of a first boss and of the next adjacent member of the next adjacent boss in said plurality of axially aligned bosses; and means, including said bolt member, for axially tightening said first member to said next adjacent member wherein said first boss and said next adjacent boss are tensed between said first member and said next adjacent member; said bosses having complementary ends formed to firmly interengage with each other under compression of said axial tightening means.

Claim 8

A spiral staircase having a plurality of substantially similar steps, comprising: a plurality of vertically axially aligned tubular bosses, each boss having a member fixed across the inside diameter of said boss adjacent each end thereof, said members having at least one clearance hole defined therein; a bolt element passing through clearance holes of a first said member of a first boss and of the next adjacent member of the next adjacent boss in said plurality of axially aligned bosses; and means, including said bolt member, for axially tightening said first member to said next adjacent member wherein said first boss and said next adjacent boss are tensed between said first member and said next adjacent member; said bosses having complementary ends formed to firmly interengage with each other under compression of said axial tightening means.

Claim 9

A staircase as claimed in claim 6, in which the effective axial length of said boss is that of the required rise between adjacent treads.

Claim 10

A staircase as claimed in claim 6, in which the effective axial length of said boss is less than the required rise between treads.

Claim 11

A staircase as claimed in claim 6, in which said boss has spigot means at one end and complementary socket means at the other end, said spigot means on one end of any one such boss being adapted to fit into said socket means of an adjacent boss when such bosses are assembled together.

Claim 12

A spiral staircase comprising an assembly of step units according to claim 6, said step units being secured together with said bosses in axial alignment, and in which separating spacers are disposed between opposing end faces of adjacent bosses, and the vertical height of the rise between adjacent treads of said staircase is equal to the effective axial length of one such boss added to the thickness of one of said spacers.

Claim 13

A spiral staircase comprising an assembly of step units according to claim 6, in each of which said step units one of said cross members protrudes axially beyond one end of said boss, and said boss at its other end extends axially beyond the other said cross member, thereby constituting spigot and socket means for connection of adjacent step units.

Claim 14

A spiral staircase comprising an assembly of step units as claimed in claim 6, in which said bosses are filled with concrete after assembly.

Claim 15

A spiral staircase comprising an assembly of step units as claimed in claim 6, in which said bosses are filled with concrete after assembly, and in which rod-like reinforcing elements extending at least between adjacent step units are located within said bosses.

Claim 16

A spiral staircase comprising an assembly of step units according to claim 6, said staircase connects adjacent storeys of a building and is attached to the building at least once for each storey.

Claim 17

A vertebrate spiral staircase having superimposed prefabricated modular cantilevered step units one upon another, each step unit comprising a tubular boss, a radially extending tread attached to said boss, each end face of said boss lying generally in a plane at right angles to the axis of the boss and parallel with the plane of the face of the tread, wherein said boss is provided at its upper and lower end respectively with a cross member; said staircase further comprising a newel formed by a plurality of said bosses assembled in adjacent step units in columnar relationship by a screw threaded connection in which a bolt passes through coaxial holes within cross members of at least two adjacent bosses, is carried by and protrudes from one cross member of one such boss and connects with socket means operatively associated with the cross member of the immediately adjacent boss, whereby the tightening of the screw threaded connection supplements axial compression, due to the weight of the assembly between adjacent units without disturbing the radial positioning of the step units; and further wherein each said boss is provided with means, including at least one aperture in a wall, to provide access for a tool when tightening the screw threaded connection, the arrangement being such that a weight loading applied to any intermediate step unit is supported both by the shear stress between the interfaces of the boss of the step unit and the bosses of the immediately adjacent steps above and below that intermediate step, and by tension in each bolt or spindle connecting that boss to the immediately adjacent bosses.

Claim 18

A vertebrate spiral staircase having superimposed prefabricated modular cantilevered step units one upon another, each step unit comprising a tubular boss, a radially extending tread attached to said boss, each end face of said boss lying generally in a plane at right angles to the axis of the boss and parallel with the plane of the face of the tread, wherein said boss is provided at its upper and lower end respectively with a cross member; said staircase further comprising a newel formed by a plurality of said bosses assembled in adjacent step units in columnar relationship by a screw threaded connection in which a bolt passes through coaxial holes within cross members of at least two adjacent bosses, is carried by and protrudes from one cross member of one such boss and connects with socket means operatively associated with the cross member of the immediately adjacent boss, whereby the tightening of the screw threaded connection supplements axial compression, due to the weight of the assembly between adjacent units without disturbing the radial positioning of the step units; and further wherein each said boss is provided with means, including at least one aperture in a wall, to provide access for a tool when tightening the screw threaded connection, the arrangement being such that a weight loading applied to any intermediate step unit is supported both by the shear stress between the interfaces of the boss of the step unit and the bosses of the immediately adjacent steps above and below that intermediate step, and by tension in each bolt or spindle connecting that boss to the immediately adjacent bosses.