Fire escape – ladder – or scaffold – Ladder – Supporting surface compensating means
Reexamination Certificate
1998-03-12
2001-05-29
Chin-Shue, Alvin (Department: 3634)
Fire escape, ladder, or scaffold
Ladder
Supporting surface compensating means
C182S201000, C182S204000
Reexamination Certificate
active
06237718
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to means for levelling ladders and the like including trestles and other work platforms. More particularly, the invention relates to means for quickly and easily extending one or more of the legs of such a ladder or the like and locking or securing the same in position to compensate for any unevenness in the terrain on which the ladder etc is used, so that a stable and safe use of the ladder or like is achieved.
BACKGROUND OF THE INVENTION
Although the following description refers generally to ladders, no limitation is intended thereby. Any related device including, but not necessarily limited to, step ladders, extension ladders, trestles, work platforms, scaffolding, sawhorses, workbenches and other work tables etc having leg members (including picnic tables and the like), wherein such device is normally required to be set on level ground to provide a level step, platform or other level work area in order to be safely used, is also contemplated. The invention may also be employed in other circumstances where extendable legs or their equivalent are required, whether or not a levelling of the device itself is paramount or even achieved. For example, it is well known to use so-called strutting devices (ie a single leg member) which can be extended and locked in such extended position to provide temporary support, for example to jack up beams or sheets of cladding during construction. Such devices would also benefit from use of the invention therein.
Of necessity, ladders are used on a variety of surfaces and in many instances the ground or surface on which they are used is uneven, sloped or stepped. Conventional ladders having fixed length legs are rendered unsafe by even the slightest unevenness, particularly where longer lengths of ladder are involved, as the weight loading in relation to the centre of gravity is paramount. In other words the higher one goes on a non level ladder, the greater the danger there is of overbalancing. In the past it has been necessary to chock up one or more legs of a ladder to overcome any unevenness in the terrain. However, this also renders the use of the ladder relatively unsafe as the chock itself may move, or the ladder can otherwise slip off it, with disastrous consequences.
In order to overcome the inherent lack of safety and other difficulties in using blocks and chocks etc, attempts have been made to produce so-called ladder levelling devices. Conventional ladder levellers are usually add-on devices which can be expensive and cumbersome. In any event, to safely level a ladder using previously known devices, it is generally necessary that the person intending to use the ladder do so in a standing position, whilst operating the relevant mechanism, and at the same time sighting a gauge or level and maintaining the overall stability of the ladder. In many instances this can be a complex task, given the degree of adjustment required for known ladder levelling devices.
It would therefore be extremely advantageous to provide a simple means of levelling a ladder, which is relatively easy to use and which is itself extremely safe to use.
OBJECT OF THE INVENTION
The present invention has therefore been conceived out of the need to provide a relatively inexpensive but safe, easily operable means or mechanism, whereby each of the legs of a ladder or similar device can be independently extended to accommodate any unevenness in the terrain on which the ladder is to be employed. At the very least, the invention provides an alternative to presently known methods of levelling ladders and the like.
Although the present invention allows an integrated approach to the problem, in so far as the levelling device may be integral (ie built-in) to the ladder or other device, the invention may also be utilised as an add-on feature for an otherwise conventional ladder or device having legs, where by suitable modification the invention may also be employed.
DISCLOSURE OF THE INVENTION
According to the present invention there is provided a leg extension means providing independent extension for a single leg, suitable for use in levelling a ladder or other device requiring a level step, work platform or the like, or otherwise suitable for use in providing variable extension to the leg, comprising a first leg member and a second single extending leg member substantially parallel with and in slideable relation therewith, a belt, strap, cable or the like co-operating therebetween and a clamping arrangement operable on the belt, strap, cable or the like to produce an extendable leg which can be secured or made fast over a range of extended lengths and wherein the clamping arrangement may be activated to extend the extending leg member and to secure the said belt, strap, cable or the like in order to fix the length of the extendable leg, or released as required to allow adjustment by way of either extension or contraction of the extending leg member to accommodate variations in the terrain on which the ladder or other device is used.
Preferably, the leg extension means is telescopic in arrangement, the first leg member comprising either a hollow tube or having other suitable cross section (for example a C-shaped cross section) to otherwise contain the second extending leg member, so that in the unextended state, the second extending member is substantially contained within the first member, whilst in the fully extended state, one end portion of the second member remains within the first member and is supported thereby to a sufficient degree that the leg remains substantially rigid in use.
Alternatively, with advantage, the extending leg member may be located about the first leg member, which arrangement is particularly suited when the leg extension means is an add-on to an existing ladder or the like.
As a further alternative, the second extending leg member may be located adjacent and alongside the first leg member and slideable within hook or loop like elements, fixedly attached and substantially perpendicular to the first leg member, the said hook or loop elements providing sufficient containment of the second extending member as described above.
It is generally preferred that the clamping mechanism be located on the first leg member rather than the extending leg member. More preferably the belt, strap or cable passes about a pulley or guide arrangement located on the same member as the clamping mechanism, to facilitate easier operation of the clamping device by locating it in a more suitable location than would be possible without utilising such pulley or guide. In other words, in one version of the simplest form of the invention, the belt, strap or cable is fixedly attached by one end at or near to the top portion of the extending member, the belt simply passing down the extending leg member. between it and the first leg member which lies adjacent to it over sufficient of its length to maintain its stability, to a clamping means located on the first leg member, which of necessity would therefore be located towards the free end of that first leg member. However, operation of the clamping device would normally be more difficult if thus located, as it would be relatively near the ground in a typical use situation. On the other hand in certain situations where in fact the “leg” extends upward, eg in the aforementioned strutting device, in which an extending member is caused to be extended upwards from first “leg” member in the form of a base support unit, the location of the clamping device adjacent the free end thereof may in fact be more practicable. Nevertheless, for the bulk of applications, in which the extending member is extended downwards to lengthen a more conventional leg, such arrangement would not be so convenient.
Therefore, instead, in a preferred form of the invention, the belt, strap or cable is fixedly attached by one end at or near to the top portion of the extending member as described above, the belt passing down and around a single pulley or fixed guide, for example in the form of a bar, located on the fir
Chin-Shue Alvin
Schindler Edwin D.
Thompson Hugh B.
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