An apparatus for tensioning a helical spring mounted generally concentrically on an elongate round shaft having a shaft diameter, said spring having a first end fixed to a building support and a second end anchored to a spring cone lockably mounted on the shaft, said apparatus comprising:
- (a) a ratchet wheel assembly comprising:
- a.1 a trunnion having a substantially semi-cylindrical inner surface with a diameter slightly greater than the shaft diameter, and having a concentrically semi-cylindrical outer surface defining an open side;
- and
- a.2 a pair of primary ratchet wheels, each having a centroidal opening, plus a radial slot contiguous with the centroidal opening and having two slot edges, said radial slot extending radially from the centroidal opening to the wheel's perimeter so as to intersect with and define a gap in said perimeter;
- wherein:
- a.3 the centroidal opening of each primary ratchet wheel is large enough to allow the shaft to be disposed therewithin, and concentrically with the primary ratchet wheel;
- a.4 the width of each radial slot is at least slightly greater than the shaft diameter;
- a.5 the perimeter of each primary ratchet wheel defines a continuous plurality of uniformly-spaced cogs between the edges of the primary ratchet wheel's perimeter gap;
- and
- a.6 the primary ratchet wheels are spaced apart and coaxially mounted to the trunnion with their radial slots aligned with the open side of the trunnion, such that the ratchet wheel assembly can be positioned substantially coaxially over the shaft;
- (b) a pair of bridging elements, each bridging element being associated with a corresponding one of the primary ratchet wheels;
- each bridging element having an arcuate-edged section defining a plurality of cogs configured and spaced to match the cogs of the corresponding primary ratchet wheel;
- wherein each bridging element is selectively operable between:
- b.1 an open position, in which the arcuate-edged section is substantially clear of the perimeter gap and radial slot of the corresponding primary ratchet wheel so as to permit positioning of the ratchet wheel assembly coaxially over the shaft;
- and
- b.2 an engaged position, in which the arcuate-edged section bridges the perimeter gap of the bridging element's corresponding primary ratchet wheel such that the cogs of the bridging element and the corresponding primary ratchet wheel combine to form a continuous and uniformly-spaced series of cogs;
- (c) locking means, for releasably locking the bridging elements in the engaged position;
- (d) spring cone engagement means, for releasably engaging the spring cone such that the spring cone will rotate with the ratchet wheel assembly;
- and
- (e) a pair of levers, each lever having a hub section rotatably mountable around the outer surface of the trunnion in association with one of the primary ratchet wheels, each lever having a pawl member with an inner end and an outer end, said inner end defining a cog-engaging surface and a non-engaging surface, each pawl member being mounted to its corresponding lever such that the pawl member may be retractably extended such that the cog-engaging surface may engage the cogs of one of the primary ratchet wheels and its corresponding bridging element;
- wherein said apparatus may be substantially coaxially mounted over the shaft when the bridging elements are in the open position, whereupon:
- (f) the bridging elements may be moved to, and releasably locked in, the engaged position, thereby to prevent disengagement of the apparatus from the spring shaft;
- (g) the spring cone engagement means may be releasably engaged with the spring cone;
- (h) the pawl members may be positioned to engage the cogs of the primary ratchet wheels in a desired orientation;
- and
- (i) with the spring cone free to rotate about the spring shaft, the levers may be cooperatively manipulated to rotate the spring cone in a desired direction around the shaft, thereby tensioning or alternatively relaxing the tension in the torsion spring, until a desired degree of tensioning has been achieved, whereupon the spring cone may be locked in position relative to the shaft, the bridging elements may be moved to the open position, and the apparatus may be disengaged from the shaft.