LADDER SAFETY DEVICE

Abstract: A ladder safety device including a carrier structure (11) capable of attachment to a ladder so as to carry the feet of the ladder. Structure (11) incorporates fixedly mounted first interconnect device (14), ground-engaging feet devices (15A, 15B) and the linkage arrangement (17, 18) connected to the ground-engaging devices (15A, 15B) and including a second interconnection (18) and which is capable of releasably interconnecting with the first interconnect device (14) to enable verticality of a ladder when the ground-engaging devices (15A, 15B) engage an inclined surface. Rigidity between the ground-engaging devices (15A, 15B) and the carrier structure (11) is provided by interconnection of the first and second interconnect device (14, 18).

Description: LADDER SAFETY DEVICE This invention relates to a ladder safety device. According to the present invention a ladder safety device comprises a carrier structure capable of attachment to a ladder so as to carry the feet of the ladder, said structure incorporating fixedly mounted first interconnect means, ground-engaging means mounted to enable variable inclination of said ground-engaging means with respect of said structure, and linkage means connected to the ground-engaging means and including second interconnect means for releasably interconnecting with said first interconnect means whereby, in use, to permit by selective interengagement of the first and second interconnect means verticality of a ladder when the ground-engaging means are supported by an inclined surface, with rigidity between the ground-engaging means and the carrier structure provided by interconnection of the first and second interconnect means. The first and second interconnect means may each take the form of a toothed rack or one may take the form of a rack whilst the other may take the form of a member having at least one tooth which is interengageable with the rack. Alternatively, one may take the form of a member defining a series of sockets whilst the other is in the form of a member having at least one spigot. A still further alternative is for one to take the form of a member defining a series of spigots whilst the other is in the form of a member having at least one socket. In an alternative form the first and second interconnect means comprise friction surfaces in which case a hand-operable clamp is provided on the structure for clamping these surfaces together to render the inter¬ connection rigid. Preferably the linkage means is resiliently biassed against said interconnection being effected in the absence - 2 - of ladder weight being applied to said carrier structure. Preferably the linkage means includes a stop member which, in the absence of ladder weight, supports the second interconnect member. Preferably said first interconnect means and said second interconnect means each extend generally horizontally when the device is in use, the first interconnect means being substantially at right angles to the length of the ladder. Preferably said ground-engaging means comprises a pair of feet members each pivotally mounted on the lower portion of the carrier structure. Alternatively the ground-engaging means may comprise a pair of feet members each slidably mounted on the carrier structure. Preferably the carrier structure is of box-like configuration dimensioned to receive the ladder feet in a sliding fit. Preferably the carrier structure incorporates clamp means for clamping to the ladder. The clamp means may clamp to the ladder feet or to a ladder rung or tread. Embodiments of the present invention will now be described by way of example with reference to the accompanying drawing, in which: Fig. 1 is a front view of a device according to the present invention; Fig. 2 is a rear pictorial view, of the Fig. 1 device; and Figs . 3, 4 and 5 schematically illustrate alternative versions of device according to the present invention; As is shown in the drawings a ladder safety device 10 comprises a box-like carrier structure 11 having a front panel 11A, side panels 11B and a truncated rear panel 11C, the side panels being braced by a bar 12 which forms a platform for supporting the feet of a - 3 - ladder (not shown) in the regions where by bar 12 meets with the side panels 11B, the depth and spacing of the panels 11B of the structure 11 being dimensioned to receive the ladder feet in a sliding fit. As is shown in Fig. 1 the structure 11 has an upper portion to which is affixed a toothed rack 14 the teeth of which extend horizontally and are downwardly presented. The lower portion of the structure 11 supports ground-engaging means in the form of a pair of feet members 15A, 15B, each pivotally mounted at 16A, 16B, to enable variable inclination of the ground-engaging means with respect to the upper portion of the structure 11. Toothed linkage means 17 releasably interconnect the ground-engaging means with the fixed rack 14, means 17 including a toothed link member 18 with horizontally extending teeth which are upwardly presented and which, in use, engage with the teeth of the fixed rack 14. Member 18 is connected by pivotally mounted links 19A, 19B, to the respective feet members 15A, 15B, each of the links 19A, 19B, being resiliently biassed by respective springs 20A, 20B, to hold the link member 18 against a stop member 21 secured to the lower portion of the structure 11 so that there is an absence of engagement between link member 18 and rack 14 in the absence of ladder weight being applied to the structure 11. The feet members 15A, 15B, may incorporate enlarged ground-engaging portions in order to reduce the applied pressure when the device is in use. When the safety device 10 is in use and weight is applied via the ladder to the structure 11 feet members 15A, 15B, in mechanical reaction with the ground or other supporting structure pivot and cause member 18 to move away from stop member 21 into engagement with the fixed rack 14, the tooth-to-tooth interengagement providing rigidity to the device 10. When the ground-engaging - 4 - means formed by feet members 15A, 15B, are supported by an inclined surface vertically of the ladder is achieved by lateral movement of member 18 with respect to the fixed- rack 14 prior to enmeshing of the teeth, this being achieved automatically by hand manipulation of the ladder axis and intermittent release of the ladder weight from the structure 11 which, in turn, permits intermittent release of the enmeshing teeth and lateral movement of member 18 under the influence of one of the foot members 15A, 15B against the ground. It will be appreciated that the presence of springs 20A, 20B, is optional and in the event that a resilient biassing means is provided this need not be in the form of springs as illustrated. Furthermore although the pitch of the teeth on link member 18 requires to match that of the teeth on rack 14 to permit enmeshing the shape of the teeth on member 18 need not be exactly the same on components 14 and 18. For example, the teeth on rack 14 may be provided with offset apices to reduce the possibility of apex to apex jamming which although existing with a small probability level is desirably minimised in the interests of safety. In another modification the tooth racks are replaced with members defining pin and socket interconnections and the protruding ends of the pins may be coned or domed to facilitate entry into the sockets. The feet members may incorporate individual extension pieces providing extension in either or both of the vertical and horizontal directions, these extension pieces being connected to the feet members by clamps. The stop member 21 may be replaced with a pair of spaced roller elements which, together function as a sotp member for the moving member 18. Springs 20A, 20B may act indirectly on the linkage means 17, for example, by biassing roller elements against the upper surface of the member 18. - 5 - In the version of the device 10' illustrated in Fig. 3 the structure 11 with its front panel 11A' is provided with slidably mounted feet members 15A' , 15B', by virtue of mountings 16A 1 , 16B 1 , formed by lateral extension of fixed member 14' at the top of the structure and by a member 23 at the bottom of the structure. Links 19A' , 19B' , interconnect feet members 15A' , 15B' , with movable member 18' which is supported by rollers 21' . The mating surfaces of members 18' , 14' in this instance are friction surfaces and rigidity of interconnection is assured by a hand operated clamp 22 which is mounted on the structure 11. Operation of device 10' is essentially the same as that of device 10. In the Fig. 4 form of the device feet members 15A, 15B are mounted by pin and slot connections 27A, 27B on the structure 11 and are interconnected by bar member 18 by pin joints 28A, 28B, member 18 being capable of sliding laterally with respect to a guide member 29 fixedly secured to the structure 11. Interengagement between toothed members 14 and 18 occurs when the device is in use by virtue of the pin- and slot connection 27A, 27B the slots of which are formed in the carrier 11 and extend vertically, which is orthogonally with respect to member 18. In the Fig. 5 form of the device the feet members 15A, 15B are united and mounted on the carrier 11 by a single pin and slot connection 30, the pin being carried by the carrier 11. The members 15A, 15B are also pivotally connected to bar member 18 which is capable of sliding laterally with respect to stud members 14A, 14B secured to the carrier. Toothed members 14C, 14D interengage with toothed parts of member 18 to provide security. The safety device which has been described also finds use with a ladder in the form of a stepladder in which case it can be used either on the front feet formed by a tread-carrying styles or on the rear feet.

Claims: - 6 - CLAIMS 1. A ladder safety device comprises a carrier structure " (11) capable of attachment to a ladder so as to carry the feet of the ladder, said structure (11) incorporating fixedly mounted first interconnect means (14) , ground- engaging means (15A, 15B) mounted to enable variable inclination of said ground-engaging means (15A, 15B) with respect of said structure (11) , and linkage means (17, 18) connected to the ground-engaging means (15A, 15B) and including second interconnect means (18) for releasably interconnecting with said first interconnect means (14) whereby, in use, to permit by selective interengage ent of the first and second interconnect means (14, 18) verticality of a ladder when the ground-engaging means (15A, 15B) are supported by an inclined surface, with rigidity between the ground-engaging means (15A, 15B) and the carrier structure (11) provided by interconnection of the first and second interconnect means (14, 18) . 2. A ladder safety device as claimed in claim 1, wherein the first and second interconnect means (14, 18) each take the form of a toothed rack. 3. A ladder safety device as claimed in claim 1, wherein one of said means (14, 18) takes the form of a rack whilst the other takes the form of a member having at least one tooth which is interengageable with the rack. 4. A ladder safety device as claimed in claim 1, wherein the first and second interconnect means (14, 18) comprise friction surfaces. 5. A ladder safety device as claimed in any preceding claim, wherein the linkage means (17, 18) is resiliently biassed against said interconnection being effected in the absence of ladder weight being applied to said carrier structure 11. - 7 - 6. A ladder safety device as claimed in any preceding claim, wherein said first and second interconnect means (14, 18) each extend generally horizontally when the device is in use, the interconnect means (14, 18) each being substantially at right , angles to the length of the ladder. 7. A ladder safety device as claimed in any preceding claim, wherein said ground-engaging means (15A, 15B) comprises a pair of feet members each pivotally mounted on the lower portion of the carrier structure (11) . 8. A ladder safety device as claimed in any one of claims 1 to 6 , wherein the ground-engaging means (15A, 15B) comprises a pair of feet members each slidably mounted on the carrier structure (11) . 9. A ladder safety device as claimed in any preceding claim, wherein the carrier structure (11) is of box-like configuration dimensioned to receive the ladder feet in a sliding fit. 10. A ladder safety device as claimed in any preceding claim, wherein the carrier structure (11) incorporates clamp means (22) for clamping to the ladder.

Inventors: FERGUSON WILLIAM HOUSTON, FERGUSON, WILLIAM, HOUSTON
Applicants: FERGUSON WILLIAM HOUSTON, FERGUSON, WILLIAM, HOUSTON
Application year: 1988
Main classification: E06C7
IPC codes: E06C7