GB2543593A

GB2543593A - A portable extendable ladder incorporating a fall arrest system that limits the impact forces on the user and the ladder

Info

Publication number: GB2543593A
Application number: GB1606774.6A
Authority: GB
Inventors: Gordon Atkinson Arthur
Original assignee: Individual
Current assignee: Individual
Priority date: 2015-10-19
Filing date: 2016-04-18
Publication date: 2017-04-26
Also published as: GB201518506D0

Abstract

A fall arrest system for a ladder 1 that is substantially within the confines of the ladder has an energy absorbing device 5 situated above the user that may be pneumatic or mechanical in operation. A rope 2 extends from the energy absorbing device down the length of one side of the ladder and has a rope grab device 3 to which the users harness is attached. The harness is attached by way of a semi-rigid lanyard, which is preferably constructed of a stiff textile webbing 6 with a stiffening component 7. A further lanyard 8 connects the users harness to the opposite side of the ladder to the rope grab device in order to prevent a falling user from approaching too near that edge of the ladder. The energy absorbing device is preferably a cylinder containing a plurality of elastomeric cushions (12, fig 6) interspersed by spacers (13, fig 6).

Description

) A portable extendable ladder incorporating a fall arrest system that limits the impact forces on the user and the ladder.

There are many situations, both in domestic and trade circumstances, where access to areas that are at a considerable height above the ground is required and the means to access these areas in the majority of cases is by ladder. Should the user fall from the ladder because of an accidental slip whilst performing a task or as a result of a medical condition the resulting injuries are invariably serious. In order to overcome this problem this invention relates to a portable ladder that can be used in various situations and contains substantially within its confines a system that prevents injury to the user should an accidental fall from the ladder occur. This invention proposes a ladder which may consist of a single section or a plurality of sections, each section being a separate entity and containing it's own fall arrest system. The stiles of the ladder are essentially of a rectangular 'C' section extrusion as produced by a major ladder manufacturer.The stile at one side of the ladder contains a rope mounted within the stile, extending from top to bottom of the ladder, and secured to the ladder at it's lower end. Surrounding the rope and mounted on a plate that is slideably contained within the stile and has a range of movement over the full length of the stile is a rope grab device that operates at the commencement of a potential fall. The end of the rope that is opposite to the secured end is connected to an energy absorbing device mounted within the ladder stile.

An essential feature of this invention is embodied in the lanyard that connects the safety harness worn by the user to the operating lever of the rope grab device. The design of this lanyard and the way it is used reduces the free fall distance before the rope grab begins to operate.

The advantages of the proposed invention are:

The user is able to ascend and descend the ladder without obstruction, both of the rungs or the area within the ladder stiles, which in itself could be the cause of a potential fall.

The methods used in the invention to reduce the impact loads on the ladder stiles and on the user in the event of a fail produce a product that is safer and more comfortable to the user.

When using an extendable ladder the user is always connected to a fall arrest system even when passing from one section to another.

The extendable versions of the invention can be collapsed into a self contained portable item of equipment without other loose items having to be considered.

The invention will now be described solely by way of example with reference to the accompanying drawings in which:

Figure 1 shows the arrangement of the principal items.

Figure 2 shows a section looking down along the ladder stiles.

Figure 3 shows the lanyard connecting the user's safety harness to the fail arrest device.

Figure 4 shows the arrangement when the energy absorbing device is mounted on the stile opposite to that in which the rope grab is situated.

Figure 5 shows the sideways movement restraining lanyard.

Figure 6 shows the preferred arrangement of an energy absorbing device.

Item 1 is a sample of a commercially available ladder which may be a single section used to access areas situated relatively near ground level or it could be a sample of a commercially available extendable ladder consisting of a plurality of sections fitting together and height adjustable in the normal manner. The stiles of the ladder are essentially of a rectangular 'C' section extrusion having a strengthening lip at each of the two outer extremities as shown in Figure 2. The rungs of the ladder that also connect the stiles together may be of hollow triangular section.

Item 2 is a rope which may be of the Kemmantle type as used by rock climbers or it could be of another lightweight material and which is secured to the inside of the ladder stile on one side only near the bottom. The rope could be either on the left side stile or on the right side stile. In one embodiment of the invention the upper end of the rope forms a loop and is attached to the lower end of an energy absorbing device - item 5 mounted at the top of the ladder. In another embodiment, the uppermost rung of the ladder has a small pulley - Item 9 at each end of the rung and the rope passes through the uppermost rung, travelling over the pulleys, and down to the energy absorbing device mounted inversely at the top of the ladder on the opposite stile to the rope grab, as shown in Figure 4.

Item 3 is rope grab device to which the user is attached by means of a lanyard connecting his safety harness to the operating lever - item 4. The rope grab device can pass along the rope without hindrance until downwards pressure is applied to item 4 when a cam action in the device locks onto the rope and prevents further downwards movement.The rope grab is mounted on a slideable plate which can move along the inside of the ladder stile whilst being retained in the stile by the lips at the extremities of the stile section. It is important that the rope grab is able to move easily and one way that this may be achieved is to use ball bearings as travelling wheels on the mounting plate. Other methods may be to use low friction plastic materials.

Item 5 is the energy absorbing device to which the rope is connected.

If the rope were to be mounted directly to the ladder stile without an energy absorbing device interposed between then, depending on the weight of the falling person and the length of the free fall before the rope grab took effect, the resulting impact load on the stile may exceed the design load limit of the ladder. By inserting item 5 to bring the falling person gradually to a halt within a suitable distance the impact load on the stile may be reduced to an acceptable level. Item 5 may be pneumatic in operation or it could be mechanical, such as an extending tension spring or other device. A preferred arrangement is shown in Figure 6 where item 10 is a hollow cylinder having a closed end with a means to suspend the cylinder from the ladder stile. Slideably mounted within the cylinder is a rod - item 11 containing a plurality of compressible elastomeric cushions- items 12, interspersed with spacers - items 13 which may be of a plastics material or of metal. Both items 12 and 13 are able to move along the rod - item 11 but are retained by an end stop - item 14 fixed to one end of the rod - iteml 1 and are prevented from exiting the cylinder - item 10 by a closed end having a hole locating the rod - item 11 centrally within the cylinder - item 10. The end of the rope containing the rope grab is secured to the end of the rod - item 11 by means of a shackle. When a load is applied to the rope the elastomeric cushions - items 12 compress and bring the rod and rope to a gradual halt.

Item 6 is a sample of one of the lanyards connecting the user's safety harness to the rope grab. When using an extendable ladder the user must transfer from one section to another. In this invention, as the user ascends or descends to reach the next section of the ladder, he keeps the lanyard he is then using in position until he has also connected the lanyard of the next section to the rope grab device. He can then disconnect the previous lanyard and continue his movement having been connected to a fall arrest system during the transfer.

As previously mentioned, the impact load on a ladder stile during a fall is dependent on the length of the free fall distance from when the fall commences to the point when the rope grab operates and applies load to the rope and consequently to the ladder stile. It is therefore advantageous if the free fall distance can be kept to a minimum. In existing applications using a rope grab device in other products, the rope grab is pulled up the rope by the lanyard trailing behind the safety harness to a certain degree. In the event of a fall in this situation, the harness on the user has to fall below the rope grab position before any braking effect can take place. In the proposed invention, the lanyard connecting the safety harness to the rope grab propels the rope grab up the rope above the user and is therefore always in a position to take immediate effect.

Figure 3 shows a semi-rigid lanyard arrangement in which the lanyard material - Item 6 is composed of a stiff textile webbing terminated at both ends in a locking carabiner. Along one or both edges of the webbing a stiffening component - Item 7 is laid which is flexible but has a predisposition to retain a straight form. An extension of this continues along part of the carabiners at each end and prevents them from deviating from being parallel to the webbing body. Items 6 and 7 may be encapsulated together in heat shrink tubing.

Each of the two lanyards may be kept attached to Item 4 of the rope grab when not in use and the free end may be clipped to the rope.

In order to prevent the user's movement from approaching too near the edge of the ladder during a fall, a flexible restraining lanyard - Item 8 connects the ring of the safety harness to a ring travelling along the stile opposite to the rope grab as shown in Figure 5.

Claims

1. An integrated fall arrest system for a portable ladder, substantially contained within the confines of the ladder, in which the arresting device is always positioned above the user thereby limiting the free fall distance and consequently the impact force on the user and the ladder and comprising, a rope and rope grab device, an item connecting the user's safety harness to the arresting device consisting of a semi-rigid lanyard, a sideways movement restraining lanyard.

2. A fall arrest system according to claim 1 in which the rope containing the rope grab is secured to the ladder with an energy absorbing device interspersed between the two, the energy absorbing device consisting of a plurality of elastomeric cushions interspersed by spacers.