AU2002317532C1 - Retractable Ladder - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT invention Title: "RETRACTABLE LADDER" The following statement is a full description of this invention, including the best method of performing it known to us: 2 TITLE: RETRACTABLE LADDER BACKGROUND OF THE INVENTION 1. Field of the Invention THIS INVENTION relates to a retractable ladder.

The invention is particularly suitable for, but not limited to, a retractable ladder for vehicles such as concrete mixers.

2. Prior Art Concrete mixers are usually provided with fixed ladders to enable the driver/operator to climb the mixer to check/monitor the charging of the mixer bowl with the ingredients; the degree of consistency of the concrete mix; the moisture level of the concrete mix; and the discharge of the concrete mix from the bowl.

Most, if not all, existing ladders, do not comply with the Australian Standards for ladders. Furthermore, as the ladders are fixed and must not impede the movement of the concrete mixers on the road or on building sites, the lower ends of the ladders are usually spaced a considerable distance above the ground, requiring the driver/ operator to step up a considerable height to reach the lower rung.

SUMMARY OF THE PRESENT INVENTION It is an object of the present invention to provide a retractable ladder which provides relatively easy access for a driver/ operator to a position enabling him/her to view the interior of a concrete mixing bowl.

3 It is a preferred object of the present invention to provide such a retractable ladder which can be easily extended when in use and easily retracted for transport.

It is a further preferred object of the present invention to provide such a ladder which can be safely locked in the transport position.

It is a still further preferred object of the present invention to provide a ladder which is relatively inexpensive to manufacture and which can be installed as original equipment manufacture (OEM) or supplied as a retro-fitting to existing concrete mixers.

Other preferred objects of the present invention will become apparent from the following description.

In a broad aspect, the present invention resides in a retractable ladder assembly for a vehicle including: a ladder, movable between a lowered (or extended) position and a raised (or retracted) position, having a pair of stiles interconnected by a plurality of vertically spaced rungs; and a support frame mountable on a vehicle, the support frame having an upper support member to receive the ladder in slidable movement in substantially vertical direction, a lower support member to receive the ladder for slidable movement in a substantially vertical direction and/or lateral movement in a substantially horizontal direction, first support means on the support frame to support an 4 upper end of the ladder when the ladder is in its lowered (or extended) position, and a second support means on the support frame to releasably secure the ladder in its raised (or retracted) position.

Preferably, the second support means is also operable to locate the ladder relative to the lower support frame when the ladder is in its lowered (or extended) position.

Preferably, a cross-bar interconnects the upper ends of the stiles of the ladder.

Preferably, the upper support member includes a substantially rectangular frame having an aperture through which the ladder extends.

Preferably, one or more blocks, preferably of resilient material, are provided in the aperture to releasably engage the crossbar to provide the first support means.

Preferably, the lower support member has a second support frame, in the form of a rectangular frame, yoke or cradle, with an aperture having a width several times greater than the depth of the ladder stiles to allow the ladder to move from a first position spaced from the vehicle when in its lowered (or extended) position, and a second position, closer to the vehicle, when the ladder is in the raised (or retracted) position.

Preferably, the second support means includes a pair of loops (or fingers) interconnected by a shaft rotatably mounted on the lower support frame and operable to engage hook means on at least one of the stiles of the ladder to secure the ladder in the raised (or retracted) position.

Preferably, the second support means also includes hook means on the lower support frame to releasably engage one or more of the rungs on the ladder when the ladder is in the raised (or retracted) position.

Preferably, the loops or fingers of the second support means are rotatable to engage the stiles of the ladder when the ladder is in the first position to prevent lateral movement of the ladder towards the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully understood, a preferred embodiment will now be described with reference to the accompanying drawings, in which: FIG. 1 is a schematic rear view of a concrete mixer, fitted with the ladder of the present invention, when the ladder is in the raised (or retracted) position; FIG. 2 is a similar view, when the ladder is in the lowered (or extended) position; FIG. 3 is a schematic side view corresponding to FIG. 2; FIG. 4 is a perspective view showing an intermediate portion of the ladder and the lower support frame, when the ladder is 6 in the lowered (or extended) position; FIG. 5 is a similar view, when the ladder is in the raised (or retracted) position; and FIG. 6 is a perspective view showing the upper end of the ladder and the upper support frame, when the ladder is in the raised (or retracted) position (with parts being omitted for clarity).

DETAILED DESCRIPTION OF THE DRAWINGS A mixer 10 has a frame 11 mounted on a vehicle chassis (not shown), the mixer frame 11 rotatably supporting a mixer bowl 12 with a rearwardly directed mouth 13. The bowl 13 has a ring 14 supported by trunnion rollers (not shown) on an A-frame An operator's platform 16, with a safety rail 17, is provided on one side of the A-frame 15 to enable an operator to inspect the interior of the mixer bowl 12.

As shown in more detail in FIGS. 4 to 6, a retractable ladder assembly 20 has a ladder 21 with a pair of substantially vertical stiles 22, 23 of C-section aluminium) interconnected by a plurality of vertically-spaced rungs 24 of substantially D-section aluminium). As shown in FIG. 6, a cross-bar 25 interconnects the upper ends of the stiles 22, 23.

The operator's platform 16 provides the upper support frame 30 (see FIG. which has an aperture 31 adapted to receive the stiles 22, 23 of the ladder 1 for substantially vertical sliding movement.

Polyurethane (or other resilient material) bushes 32, 33 are provided at the ends of the aperture 31, and have recesses adapted to receive the respective ends of the cross-bar 25 (so that the cross-bar 25 is substantially flush with the operator's platform 16 when the ladder is in its lowered (or extended) position).

The lower support frame 40 (see FIGS. 4 and 5) has a substantially U-shaped support cradle or yoke 41 mounted on the Aframe 15 by a support arm 42. A hook member 43 is provided on the underside of a cross-bar 44 of the cradle 41, the hook member 43 being adapted to engage one of the rungs 24 of the ladder 21 when the ladder is in its raised (or retracted) position.

A pair of loop members 45 are provided on a shaft 46, journalled in a pair of bushes 47 on the cross-bar 44. As shown in FIG. 4, the loop members 45 are adapted to engage the stiles 22, 23 of the ladder 41 when the ladder 21 is in its lowered position. As the ladder is moved upwardly towards the raised position, the loop members 45 swing upwardly and inwardly to enable the stiles 22, 23 of the ladder 21 to swing laterally inwardly towards the cross-bar 44.

One of the loop members 45 engages a hook member 25 on the ladder stile 22 to limit the maximum upward movement of the ladder 21.

When the ladder 21 is fully raised, it is lowered a small distance to allow a rung 24 to be releasably engaged in hook member 43 on the 8 cross-bar 44. The relationship between the hook member 43 and rung 24, and the loop member 45 and hook member 25, ensures that the ladder 21 will be retained against the cradle 41 while the vehicle is in transport.

To enable the ladder to be lowered to the extended position, the ladder 21 is raised until the rung 24 is released from the hook member 43, and the lower end of the ladder 21 is swung outwardly and pulled downwardly, the loop members 45 swinging downwardly and outwardly to hold the lower end of the ladder in a position away from the cross-bar 44 of the cradle 41 (and thereby away from the vehicle).

It will be readily apparent to the skilled addressee that the hook member 43 may be replaced by two or more hook members on the cross-bar 44 of the support cradle 41; and that each of the loop members 45 may engage respective hook members 25 on the stiles 22, 23.

While the retractable ladder assembly has been described with reference to the installation on a concrete mixer, it can be used on other vehicles, including liquid or gas tankers; bulk material transport vehicles (including gravel trucks, grain railway wagons); earth moving machines (including graders and scrapers); and other vehicles which require ladders for access, eg., to engine compartments, operator's cabins or the like.

9 Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention.

Claims (9)

1. A retractable ladder assembly for a vehicle including: a ladder, movable between a lowered (or extended) position and a raised (or retracted) position, having a pair of stiles s interconnected by a plurality of vertically spaced rungs; and a support frame mountable on a vehicle, the support frame having an upper support member to receive the ladder in slidable movement in substantially vertical direction, a lower support member to receive the ladder for slidable movement in a substantially vertical direction and/or lateral movement in a substantially horizontal direction, first support means on the support frame to support an upper end of the ladder when the ladder is in its lowered (or extended) position, and a second support means on the support frame to releasably secure the ladder in its raised (or retracted) position.

2. A ladder assembly as claimed in Claim 1 wherein: the second support means is also operable to locate the ladder relative to the lower support frame when the ladder is in its lowered (or extended) position.

3. A ladder assembly as claimed in Claim 1 or Claim 2 wherein: a cross-bar interconnects the upper ends of the stiles of the ladder; the upper support member includes a substantially 11 rectangular frame having an aperture through which the ladder extends; and one or more blocks, of resilient material, are provided in the aperture to releasably engage the cross-bar to provide the first S support means.

4. A ladder assembly as claimed in any one of Claims 1 to 3 wherein: the lower support member has a second support frame, in the form of a rectangular frame, yoke or cradle, with an aperture having a width several times greater than the depth of the ladder stiles to -allow the ladder to move from a first position spaced from the vehicle when in its lowered (or extended) position, and a second position, closer to the vehicle, when the ladder is in the raised (or retracted) position.

5. A ladder assembly as claimed in Claim 4 wherein: the second support means includes a pair of loops or fingers, interconnected by a shaft rotatably mounted on the lower support frame, and operable to engage hook means on at least one of the stiles of the ladder to secure the ladder in the raised (or retracted) position.

6. A ladder assembly as claimed in Claim 5 wherein: the second support means also includes hook means on the lower support frame to releasably engage one or more of the rungs 12 on the ladder when the ladder is in the raised (or retracted) position.

7. A ladder assembly as claimed in Claim 5 or Claim 6 wherein: the loops or fingers of the second support means are rotatable to engage the stiles of the ladder when the ladder is in the first position to prevent lateral movement of the ladder towards the vehicle.

8. A retractable ladder assembly for a vehicle substantially as hereinbefore described with reference to the accompanying drawings.

9. A concrete mixer incorporating the retractable ladder substantially as hereinbefore described with reference to the accompanying drawings. DATED this eleventh day of December 2002. MIXERS AUSTRALIA PTY LTD By its Patent Attorneys FISHER ADAMS KELLY