APPARATUS FOR CARRYING A LOAD UP AND DOWN STAIRS

This invention relates to load carrier comprising a support having at least one wheel at one end, a handle at an opposite end and an adjustable traction device designed to hinge relative to the support from a stowed position to a deployed position where it serves to assist in moving the carrier up and down stairs.

The invention was particularly devised for application in the design of a suitcase (which term is used in this specification to refer to any travelling bag). However the principle of the invention could be used in other mechanisms such as trolleys or stair lifts where there is a requirement to carry heavy goods, materials or people of limited mobility up or down a flight of steps or stairs.

Numerous previous attempts have been made for moving loads up and down stairs. Some previous proposals have employed a technique in which a traction device is used to bridge two or more stair edges so as to avoid a bumping effect as the load is pulled or driven up the stairs. Patent specification US 2996133 describes one such mechanism, which employs a pair of endless traction belts driven by a motor. The traction device needs to be supported at the correct angle for which purpose locking pins 53 are inserted into holes 55 as shown in Figs 3 and 5 of the abovementioned patent specification. A similar principle, proposed for use on a shopping trolley, is described in patent specification US 4130291. This mechanism employs struts 24 and 25 of unequal length, to support a traction device at the desired angle. Each of the struts 25 is

telescopic and is provided with set-screws 53 to lock it at the desired position of adjustment.

A disadvantage of both of these known proposals is that the adjustment mechanism (the pin-and hole arrangement in the first example and the set-screw arrangement of the second) will take a significant time to operate. This may be unacceptable in certain situations. For example, a traveller approaching a flight of steps with a suitcase is likely to decide that it is easier to carry the suitcase up the steps than to operate such mechanisms.

This invention provides a load carrier of the type described above characterised by a supporting stay for holding the traction device in its deployed position, the stay being designed to hinge relative to both the traction device and to the support and to slide relative to at least one of them as the support is hinged from its stowed to its deployed position.

By employing this technique it becomes possible to deploy the traction device quickly and conveniently as the user approaches a flight of steps; and equally quickly to return it to its stowed position after use.

The traction mechanism can take the form of an endless belt supported on suitable rollers as in the prior patent specifications referred to. Alternatively it could have runners or some other friction-reduction element. One preferred construction employs

pivoted flaps having a high friction surface on one side and a low friction surface on the opposite side. The flaps are attached along one long side to the base of a suitcase so that they will trail behind the movement. During forward movement the low-friction side faces down, whilst any attempt to move in the opposite direction causes the high- friction surface to face downwardly thereby resisting unwanted reverse downward slippage.

In an optional variant of the invention it is envisaged that an energy store could be incorporated into the design. This would store energy released when the load moves downwardly; and release the energy during upward movement. A suitable energy store could be provided by helical tension springs and these could be housed in compartments in or next to a suitcase base. A suitable mechanism would be needed for tensioning the springs during downward movement. In one design each spring is connected to a wire or similar flexible member. Rotation of the wheels and/or the movement of the traction device during downward movement causes this wire to wind around a drum thereby causing the spring to stretch. A release mechanism allows controlled release of the stored energy to drive the load effortlessly up stairs when required.

The storing of energy during downward movement for later use during upward movement is considered to be both novel and inventive. Thus, in accordance with another aspect of this invention there is provided a load carrier comprising a support having at least one wheel at one end and a handle at an opposite end; characterised by

an energy store, means for charging the store with energy derived from downward movement of the carrier and means for using the stored energy for assisting upward movement.

The invention can either be employed as a built in feature of a complete suitcase or can be employed in a trolley specifically adapted to receive a suitcase. Also, the invention is applicable in fields other than suitcases. For example it could be used for general- purpose trolleys, shopping trolleys, wheelchairs for invalids, and push-chairs for infants.

One way in which the invention may be performed will now be by way of example with reference to the accompanying drawings in which: -

Fig 1 is a perspective view of a suitcase constructed in accordance with the invention, illustrated with its traction device shown in a stowed position;

Fig 2 shows the suitcase of Fig 1 but with the traction device illustrated in a deployed position;

Fig 3 shows the same suitcase being moved up a flight of stairs; and

Fig 4 shows a schematic detail view of an alternative traction device for use on a suitcase like that of Figs 1 to 3.

Referring first to Fig 1, the illustrated suitcase has a load-support in the form of a rectilinear container 1. A lid IA, forming a top surface of the container, can be opened to access the interior. At one end of a base IB are wheels 2 allowing the container to be pulled easily over smooth surfaces using a rigid handle 3 at the opposite end of the base IB.

A traction device 4, in the form of a smooth-surfaced skid plate, is hinged at 5 about an axis parallel to that of the wheels 2 so that it can be pivoted from a stowed position, as shown in Fig 1, to a deployed position, as shown in Fig 2.

Referring to Fig 2, a stay 6 is hinged to a free edge of the skid plate 4 and to a slide plate 7, and serves to hold the skid plate 4 firmly in its deployed position by virtue of a triangular configuration defined by components 1, 4 and 6. The slide plate 7 is mounted on rails 8 fixed to the base of the container 1 and terminates in a secondary handle 7A. By pushing and pulling this handle 7A, the user is able to quickly adjust the skid plate between its stowed and deployed positions. Detent arrangements are preferably included to maintain it in the desired one of these positions.

Fig 3 shows the skid plate 4 in use as the suitcase is being pulled up a flight of stairs. The skid plate is sufficiently long to bridge at least two stair edges and its smooth bottom surface allows even a heavy load to glide relatively effortlessly either up or down the stairs without a significant bumping effect.

It will be appreciated that the illustrated construction is just one of many possible examples of how the invention may be implemented. The relative dimensions of the suitcase 1, skid plate 4 and stay 6 may be varied; and traction devices more complex than the simple skid plate 4 may be employed. For example, rails may be fitted to the lower surface of the skid plate to reduce friction. Another possibility would be to employ an endless belt similar to those described in the prior patent specifications referred to earlier. A particular advantage of the latter arrangement is that movement of the belt can be regulated so as to control downward movement; and in a variation of this technique, potential energy released during this downward movement can be stored, e.g. in as spring for subsequent use during the next upward movement.

Fig 4 shows a skid 4A on which are mounted a number of flaps 13 of flexible material. When the load is pulled up a sloping surface, or a flight of stairs, each flap swivels about its fixed edge so that its free edge trails behind the direction of movement. One side of each flap (the side visible in the drawing) is coated with a low- friction synthetic plastics material. The opposite side presents a high- friction surface to resist downward movement. In an alternative design, not shown, the flaps could be relatively rigid but hinged for swivelling movement though a limited range so that they lie flat for upward movement, when the case is being pulled forward, but hinge away from the base of the case to resist downward movement under the effect of gravity.