Fire escape – ladder – or scaffold – Safety device for ground-supported ladder – Terminal foot or shoe
Reexamination Certificate
2001-10-03
2003-12-02
Lev, Bruce A. (Department: 3634)
Fire escape, ladder, or scaffold
Safety device for ground-supported ladder
Terminal foot or shoe
C182S201000, C182S204000, C248S188800
Reexamination Certificate
active
06655497
ABSTRACT:
The present invention is a stabiliser for ladders.
When a ladder is installed for use in an inclined position against a wall, instability of the lower end of the ladder may arise from various sources. For example, if the ladder is inclined to the ground at too shallow an angle, or if the ground surface is unduly irregular or of limited friction, such as when the surface is wet, there may be a serious risk of the foot of the ladder slipping away from the wall, with potentially catastrophic consequences. In UK Patent Specification No. 2216168 I have described a ladder stabiliser which I devised to deal with the foregoing problem and in practice, that stabiliser has proved very effective in a wide range of conditions for preventing the slippage of the ladder foot away from a wall.
However, there is the further problem of lateral slippage, most usually of the upper end of a ladder, which can arise when the surface upon which the foot of the ladder is placed is inclined in a direction which is generally parallel to the surface of the wall, that is sideways relative to the plane of the ladder. In an attempt to overcome this problem, various devices have been proposed, for attachment to the individual ladder feet with the aim of extending one or both of the ladder stiles. By way of example, UK Patent Specification No 1578143 describes and illustrates one form of device for attachment to the lower end of a ladder stile in order to extend the stile; if appropriate, a device of this type may be attached to each ladder stile.
Unfortunately, the leg attachments of UK Specification No 1578143 provide no protection against slippage of a ladder foot outwardly away from a wall, except to the extent that the attachments may include rubber or related components to somewhat enhanced grip.
It is therefore an object of the present invention to provide a form of ladder stabiliser by means of which the danger of slippage of the ladder feet outwardly away from wall, and also the danger of sideways slippage of the ladder feet generally parallel to a wall, may both be countered.
The ladder stabiliser according to the present invention comprises a rigid, generally flat base having a linear channel extending along a first, upper surface thereof, which channel is defined by a pair of generally parallel, upwardly-extending channel side members having upper edges directed towards each other, and at least one ladder attachment by means of which a ladder stile may be extended downwardly.
In use of the ladder stabiliser, one or preferably two of the ladder attachments are attached to one or both of the ladder stiles and then the attachments are introduced into the channel. Most preferably, the lateral dimension of each ladder attachment is such that it is greater than the distance apart of the upper edges of the channel side members, such that the ladder attachments may only be introduced into the channel from one end thereof—and will remain therein when the ladder is lifted.
Thus, by means of the ladder stabiliser as herein defined, a ladder may be modified both to counter the effects of ground slope in the direction of the width of the ladder and also to enhance the resistance of the foot of the ladder to slippage away from a wall. With the latter consideration in particular in mind, it is strongly preferred that the lower surface of the ladder stabiliser be of enhanced frictional value, for example in the form of a rubber or like surface and/or with surface irregularities, as described below.
The channel, defined by its generally parallel, upwardly-extending side members, may be of various possible cross-sectional shapes, subject only to the requirement that the upper edges of the side members are directed towards each other. Thus, by way of example, the channel side members may be generally parallel to each other, with their upper edges turned inwardly from the side members, for example at right angles thereto. As one alternative, the side members may simply be shaped so as to define a channel of which the widest lateral dimension is at a lower level than the open top of the channel, for example, by their being inwardly inclined in an upward direction.
The channel preferably extends throughout the length of the base but may extend for less than that length if desired.
In one preferred form of the stabiliser according to the present invention, the channel is mounted upon a separate base. Conveniently, that base may in turn have a uniform cross-sectional shape and may be formed by extrusion. In a particularly preferred form, the base is formed of two aligned parts, which may be moved apart from each other in order to provide an extended base for the stabiliser.
The base, whether is be formed integral with the channel or separately, is preferably square, or more preferably rectangular, in plan. In the latter case, the longer dimension of the rectangular base is preferably aligned parallel to the channel.
The underside of the stabiliser, as mentioned above, is preferably of enhanced frictional value. As indicated, this result may be achieved by means of the structure of the undersurface of the stabiliser, for example by irregularities or projections in or from the surface, and/or by forming that surface of a frictional material. In a particularly preferred form of the stabiliser according to the invention, the undersurface is formed of a vulcanised rubber and is moulded in position, preferably with an irregular surface, upon the underside of the base of the stabiliser.
Any risk of slippage of the ladder in a direction which is generally parallel to the plane of the wall or the like against which the ladder is inclined is reduced by means of the ladder attachment or attachments by which each ladder stile may be extended downwardly. One possible form of such stile extender is described in the above-mentioned United Kingdom Patent Specification No. 178143, which was published in November 1980. However, while the device described in that specification would appear to be of potential use for extending the length of the ladder stile, it does exhibit two disadvantages in practice. First of all, the stile is extended by locating an extension member in a selected one of a number of spaced-apart transverse slots. However, in order to impart integrity to the unit in which the extension member is housed, those slots must be spaced apart by sufficient distances to enable the unit to support the whole weight of the ladder and its user. Thus the adjustment of the length of the stile is essentially a step-wise adjustment. Secondly, the necessary design of the device inevitably makes the product relatively expensive to produce and may as a result discourage a potential user from purchasing what could otherwise be an advantageous aid to ladder safety when incorporated in a stabiliser according to the present invention.
With these latter disadvantages of such a prior product in mind, I have developed and have described in the specification of United Kingdom Patent Application No 9920698.9 an improved form of levelling support by means of which a ladder stile may be extended, which support comprises an elongated hollow first member for attachment to a ladder stile, an elongated second member slidable linearly within said first member, adjustment means comprising two interengaging non-planar surfaces each associated with one of said first and second members and locking means to secure said surfaces in their mutually interengaged positions. By means of this levelling support, the relative linear movement of the two members may be rendered continuous or nearly so, thereby enabling the support to be matched more closely to the desired extended stile length than was hitherto possible. Secondly, it becomes possible to design and construct the levelling support more readily and potentially more cheaply than has hitherto been the case.
Thus this latter form of levelling support or ladder extender may very advantageously be used as a feature of the ladder stabiliser according to the present invention. However, the stabiliser may be used
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