Fire escape – ladder – or scaffold – Self-sustaining – Ladder
Reexamination Certificate
2000-07-31
2002-07-16
Stodola, Daniel P. (Department: 3634)
Fire escape, ladder, or scaffold
Self-sustaining
Ladder
C182S107000, C248S238000
Reexamination Certificate
active
06419047
ABSTRACT:
This invention relates to ladders and in particular to portable ladders.
Portable ladders usually comprise two side members, and interposed between the side members are located a plurality of conveniently spaced rungs. The number of rungs depends upon the length of the side members. Extending ladders comprise a number, generally two or three, of smaller ladders slidably disposed within the main ladder and capable of being secured to an upper rung of the main ladder. All these ladders are intended to rest at their lower end on the ground and at their upper end against a hard object, such as brickwork, scaffolding, tree, and the like. In this specification, the term “ground” includes any solid surface on which ladder is generally used, such as, for example, compacted soil, lawn, concrete, paving, wood. The object of a ladder is to enable a workman to attain a greater working height. Such use is conventional and extends to the professional workman and the amateur user around the house.
Many accidents are unfortunately associated with the use of ladders. Such accidents are not only those of missing rungs whilst climbing or coming down a ladder, but also those caused by the bottom of a ladder slipping on the ground. In such an event, the top of the ladder will move down the object against which it is resting, so causing the ladder to become unsteady and the user to fall. This can occur even though the ladder is initially being used within the recommended angle range of between 25° and 75° to the horizontal.
In order to assist in overcoming the problem of ladder slippage on the ground, caps are usually placed on both the upper and lower ends of the side members. Where the side members are tubular, caps are place on each of the four ends of the side members. Such caps have a smooth external surface and fit snugly over each end; the caps are generally made from hard rubber or plastic material by moulding. Where the side members have a rectangular or T- or I-cross section, the caps are similar but may have external ribs, having orientation at right angles to the line of the side member. Wooden portable ladders generally have no such caps.
However, the area of contact of the end caps with the ground, even if ribbed, is very small, and hence slippage can still and does occur. To overcome the problem, a second person, in addition to the person up the ladder, is usually employed to stand on the lowest rung of the ladder (but such a practice increases labour costs), or pegs are driven into the ground against the bottom end of the side member (but such practice can unacceptably damage the ground). Ladder stoppers are also known comprising an aluminium T-piece bonded to a vulcanised rubber base, part of which can be slipped under the ladder caps.
There is therefore a need for a device that can be used on ladders to enable a workman to work up a ladder in the knowledge that any tendency to slip is considerably reduced.
According to the present invention, there is provided a portable ladder having improved resistance to slippage which comprises side members and rungs and at least one securing member which is pivotally and latchably attached to the lower end of at least one side member, the securing member having friction member on its lower surface for co-operating with the ground on which the ladder is to be mounted, the pivot being arranged so that the securing member is not proud of the lower end of the side member when the securing member is not in use.
Therefore in operation, the ladder is placed against, for example, a wall, and rests on the ground. The securing member is placed on the ground by pivoting it from the side member, and is locked into position on the ground using the latching member. The friction member on the lower surface of the securing member is thus firmly on the ground to resist slippage of the ladder.
The securing member may be made from any suitable material provided that it is strong; conveniently it can be made from any material used in the manufacture of ladders, such as, for example, aluminium or aluminium alloy, steel. The securing member may be tubular or have a rectangular or T- or I-cross-section, but preferably has a flat lower surface. The securing member is pivotally attached at or towards the lower end of at least one, preferably both, side member. This is to enable the securing member to rest against the ladder during non-use, and to allow the securing member to be adjusted to rest on the ground when the ladder is being set up for use. The pivot can, for example, be a hinge or a bolt or rivet through both the securing member and the side member. The pivot can be provided with biassing member, suitably a spring, which bias the securing member towards the ladder. The pivot can provide that the securing member rests on the ground outward or inward of the ladder, that is the angle between the ground and the ladder can be obtuse or acute, preferably acute. Preferably the securing member is pivotally attached to both side members and comprises a plate extending essentially completely between the side members. The pivot is arranged so that when the securing member is not in use it is not proud of the lower end of the side member.
The friction member on the securing member can be any material that substantially increases the friction between the securing member and the ground. Suitable material includes, for example, rubber, including vulcanised rubber, and similar material such as semi-rigid thermoplastic, and such material may include ridges and dimples on its lower surface as an aid to friction. The friction member might include small metal studs or spikes for aiding grip onto the ground. In a modification of the friction member, there may be provided additional mechanism for raising and lowering such studs or spikes as required. The friction member may be replaceable, and the securing members may be interchangeable so that a variety of friction member may be used as appropriate for variation in the ground type that the ladder may be required to rest. The securing member with the friction member attached can be used in conjunction with conventional end caps. The friction member therefore spreads friction contact over a wide area so increasing stability of the ladder and security for the user.
The securing member is latchably attached to the lower end of at least one side member. The latch is intended to ensure that the securing member stays locked in position when it has been placed on the ground. The latching member may comprise an arm, of adjustable length, which swings out from the side member and fits into a co-operating receptor on the securing member. Thus, after the securing member has been pivoted onto the ground, the length of arm of the latching member may be adjusted to ensure that the securing member remains firmly on the ground. More conveniently, the latching member may be a ratchet mechanism on or associated with the pivot whereby the action of rotating the securing member on the pivot acts against a ratchet, which can then be released after the ladder has been used. Thus, after the securing member has been pivoted onto the ground against the ratchet, the securing member is firmly located on the ground immediately after the ladder has been placed against, for example, a wall. After use, the ratchet can be released and the securing member can be pivoted back against the ladder. The latching member may also be a simple friction device on the pivot. Preferably, the latching member comprises stays which swing out from the side member and co-operate with notches in the securing member.
In a further aspect of the present invention, a kit of parts is provided for use in improving resistance to slippage of a portable ladder which comprises at least one securing member, pivot member and latching member for attachment to the lower end of at least one side member of the ladder, the securing member having friction member on its lower surface for co-operating with the ground on which the ladder is to be mounted and the pivot being arranged so that the secur
Hay Martin A.
Stodola Daniel P.
Thompson Hugh B.
LandOfFree
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