Release mechanism for locking hinge for multi-positioned ladder

  • US 4,697,305 A
  • Filed: 11/21/1986
  • Issued: 10/06/1987
  • Est. Priority Date: 02/14/1985
  • Status: Expired due to Term
First Claim
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1. An improved hinge and release mechanism for collapsible ladders, said hinge being of the type wherein first and second members each have a head portion and a ladder stringer-engaging portion, the first and second members being pivotally engaged for rotation about a pivotal axis extending generally perpendicularly through a circular pivot aperture in said head portions and having respective first locking apertures which are at radially spaced positions from the pivotal axis and can be selectively aligned or misaligned by mutual rotation of said first and second members about the pivotal axis, and at least one locking pin which is selectively inserted through the locking apertures, when aligned, to adjust the hinge from an unlocked to a locked position, thereby preventing mutual rotation of the first and second members, the improved hinge further comprising:

  • (a) a tubular hub member having an inner diameter slightly smaller than a diameter of the pivot aperture in the head portions of the first and second members and adapted for being journalled therein, said tubular hub member one end being a locking end, and the other opposite being an unlocking end, and a longitudinal axis corresponding to the pivotal axis, and further having an opening therethrough which forms a guide aperture about the longitudinal axis;

    (b) a guide shaft disposed in the hub member for both (i) axially slidable translation between extended and retracted positions with respect to the locking end of the hub member and along the longitudinal axis through the guide aperture, and (ii) rotation within the guide aperture about the longitudinal axis;

    (c) a handle member disposed completely outside the hub member and being secured to the guide shaft adjacent the unlocking end of the hub member and extending outwardly from the longitudinal axis approximately to the radially spaced position of the first locking apertures, said locking pin being secured to the handle member and being oriented in mating relationship with respect to the first locking apertures when in common alignment;

    (d) bias means for applying an axial biasing force to the guide shaft to urge the guide shaft toward the retracted position wherein the aligned locking pin and locking apertures are in a locked and mated configuration;

    (e) a hinge release mechanism comprising;

    (1) a release plate having a contact side and an opposing operating side with a plate diameter exceeding the inner diameter of the tubular hub member, said contact side being adapted for depression toward the hub member;

    (2) a first annular flange having an axial length projecting toward the hub member from the operating side of the plate and having a tubular cross-sectional configuration which is characterized by an inner tubular diameter which is slightly larger than the outer diameter of the hub member;

    (3) a second annular flange having an axial length substantially equal to the axial length of the first annular flange projecting toward the hub member from the operating side of the plate and having a tubular cross-sectional configuration which is characterized by an outside tubular diameter which is slightly smaller than the inside diameter of the hub member, such that in combination with the first annular flange, said second annular flange forms an annular channel such that said hub member can telescopically mate within the annular channel when the guide shaft is in the partially extended position, whereby the hub is held within said annular channel and lateral movement of the hub is prevented;

    (4) means for coupling the guide shaft in fixed rotational attachment to the release plate at a central portion thereof and within an area enclosed by the annular flanges;

    (f) means for housing said bias means in direct physical contact between the hinge release mechanism and the locking end of the tubular hub member, and(g) retaining means for holding the first and second members in a juxtaposed position at a fixed location along the longitudinal axis and mounted on the periphery of the hub member wherein the means for coupling the guide shaft and release plate in fixed rotational attachment comprises a second shaft, said second shaft and said second annular flange including means for attachment, said means for attachment comprising a radial bore in the second annular flange and the second shaft, respectively, having common alignment and being sized to fit a locking pin which comprises part of the coupling means and which is inserted into the bore to lock the shaft and release plate in fixed axial rotation;

    said second flange encloses a locking recess adapted to receive the second shaft and including a bore aligned with the bore of the first flange and extending diametrically through both sides of second flange to enable insertion of said locking pin through the first flange and into the two respective bore openings of the second flange and the bore of the second shaft.

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