Fire escape – ladder – or scaffold – Safety device for ground-supported ladder
Reexamination Certificate
2000-02-07
2002-07-02
Stodola, Daniel P. (Department: 3634)
Fire escape, ladder, or scaffold
Safety device for ground-supported ladder
C182S214000
Reexamination Certificate
active
06412599
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a protective, load dispersing device that prevents the slippage of a ladder as well as preventing damage to the surface against which the ladder rests. An in alternate embodiment, the protective bumpers can be used to protect one or more sides of a three dimensional object.
2. Description of the Prior Art
There are two common problems arising from the use of ladders in work on buildings, particularly on or near their roofs, which are minimized by the novel device according to this invention.
First, the thrust component of the combined weight of the ladder, the user, and any equipment the user may be carrying is commonly born by two small areas of contact between the side members of the ladder and the structure receiving the ladder. The tendency of that thrust component on the gutter is to dent it, and in the worst case to deform the edge of the gutter to the point where it collapses. As the gutter flexes, the areas of contact between the and the ladder decrease until the gutter edge supports only the corners of the undersides of the ladder. It is then that the maximum deformation of the gutter profile and the greatest damage to its paint occur. Additional damage is caused as the ladder slides against the gutter while the user is moving on the rungs.
Second, ladders have the tendency to slip sideways when there are small movements by their feet, typically caused by the feet being placed in error by the user on soft ground or on un stable propping material. Since the width of a ladder is small compared with its height, when the weight of a user of the ladder is near its top, the rate of sideways slippage accelerates the farther the line of the feet diverges from the horizontal. The prior art has addressed this problem by affixing, in some way, the upper part of the ladder to the building, roof or gutter. This solution is unsatisfactory, however, since fixing the top can require the ladder's feet to be in a location which may not be stable, and the user is then dependent for his security on the upper fixing means.
The device according to the present invention overcomes defects in the prior art by allowing the upper part of the ladder freedom of positioning both along a support surface, thereby permitting the feet of the ladder to be located on the necessary firm and level support.
All these tendencies to damage are eliminated by use of the device according to this invention, which places a flexible, non-slip, non-abrasive, non-electrically-conductive bearing surface between the ladder's side members and the gutter or other feature of the structure against which the ladder rests.
Several other patents have been granted for inventions intended to prevent ladders from slipping along their upper support surfaces, but none so far has offered a solution to the foregoing problems of damage to the upper support surface and slipping. For example, U.S. Pat. No. 3,948,353, issued to Lane, teaches an non-free-standing ladder with flanged and lined cut-out portions along the side members of its upper section, said cut-out portions being intended to hook over the upper support, with the lining providing an anti-skid surface. It can be readily seen that manufacturing the ladder claimed in Lane with its flanged cut-out portions would be more expensive than for the standard metal or Fiberglas ladder commonly available, and to which this invention is adapted, of which the side members are extruded or molded with the same cross section along their entire lengths. Furthermore, since the ladder in Lane is intended to be hooked over a fixed upper support, such as a gutter, the ladder user has a restricted opportunity of adjusting the foot of the ladder to find a stable lower support, which is a safety measure of even greater importance than any such measures taken at the upper end of the ladder, since, without a stable lower support, the ladder should not be used. Also, when the ladder is being used, that is, when weight is applied to it, any flexing of the ladder, which always occurs, and any effort of the lower end of the ladder to find a stable footing, will tend to drag down the upper support over which the ladder is hooked. This might seriously damage, for example, a lightweight aluminum gutter used as the upper support.
U.S. Pat. No. 5,121,813, issued to Funston, teaches a rigid leg member to provide stable support for the lower end of a ladder, combined with a hooking support for hooking to, for example, a gutter. A separate lower support as in Funston is not part of the present invention, which relies on the user establishing a stable footing for his ladder, and assists the user in doing this by allowing the upper support of the ladder to be adjusted up or down the length of this invention, without hooks or fixing means at the upper support. The tendency to drag the gutter down by hooked elements is the same in Funston as in Lane, in addition to which, the metal hook elements in Funston would tend to scratch the painted surface of the upper support.
U.S. Pat. No. 4,924,971, issued to Rice; U.S. Pat. No. 4,601,365, issued to Davis; and U.S. Pat. No. 4,580,661, issued to Thomson, Jr., all teach inventions that require installation on or in the upper support, which in the cases of Davis and Thomson, Jr. appear to be restricted to gutters. To an extent the initial installation negates the purpose of their devices, since the ladder must be used initially to install the securing methods. This contrasts with the benefits of the present invention, where the safety device is installed on the ladder before use and requires no fixing to the upper or lower ladder support surface. The present invention also enables a non-free-standing ladder to be lengthened or shortened, and moved along the support surface, without adjustment of the device. In the case of Rice, the invention must be reinstalled at the upper support for each new location in order for the ladder to be moved; in the cases of Davis and Thompson, Jr., the inventions must be moved when the ladder is moved, or additional devices installed at the new locations.
U.S. Pat. No. 5,293,958, issued to Swiderski et al., and U.S. Pat. No. 4,754,842, issued to Southern both teach devices for propping the tops of ladders away from walls. This feature enables a ladder user to work up to the level of the top of a wall or possibly slightly above, but does not permit the user safely to step off the ladder on to the roof of a structure. By contrast, the present invention enables the user to safely step from the ladder to the roof since the ladder rests against lower edge of the roof, while reducing the possibility of the ladder's slipping sideways.
U.S. Pat. No. 4,974,699, issued to Boring, U.S. Pat. No. 4,726,446, issued to Perbix, and U.S. Pat. No. 4,469,194, issued to McBride, all teach attachments to the upper end of a ladder, intended to rest against a vertical wall. They are therefore not adapted to the purpose of allowing the user to step from the ladder on to the roof of the walled structure. The devices taught by Boring, Perbix and McBride would be difficult to align with a roof edge from a position at the bottom of the ladder, because of their short length. Because of their configurations, Boring having a circular cross section, and McBride having a narrow rectangular section, these devices would be prone to slipping off the edge of the roof. Perbix, would prevent the ladder side members of an extension ladder from sliding within one another when the ladder is shortened.
SUMMARY OF THE INVENTION
The present invention is directed to a load-dispersing device non-free-standing ladders, or other devices that require reduction of horizontal slippage. The device further reduces damage of delicate surfaces. The single strip load-dispersing bumper, can be used in combination with a ladder having side rails with a load bearing surface. The bumper consists of a pair of flexible, resilient, load-dispersing members, each of which has a contact area and
Harris, Jr. Wilfred L.
Thompson John G.
Parker Sheldon H.
Snead Kimberly O.
Stodola Daniel P.
Thompson Hugh B.
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