The Client is a wheelchair user who also has some limited mobility on her feet. She is unable to bend down. She has a recent baby which currently sleeps in a crib by her bed. As the child grows he will need a cot. However, the Client would not be able to bend over a cot to lift and / or change her baby, even with a drop side cot.
Therefore, she asked if a cot could be modified so that she could get the arms of her wheelchair under it (approx. 900mm from the floor). In order to be useable the cot side would need to open fully, and for safety the cot would need to lower to near floor height (approx. 300mm from the floor) when the child is sleeping or playing in it.
Structure and mechanics:
The Client purchased and supplied a wooden drop side cot. It was decided to fit this with a ‘lifting tower’ at each end, each powered by a 600mm stroke 12V actuator, to give a cot base height range of 300mm to 900mm.
The lifting towers each use two 700mm ball bearing cabinet slides, mounted at 90 degrees to each other to give stiffness in both sideways and fore-and-aft directions. The slides are mounted on an ‘L’ section tower made from 60x30mm hardwood, which is in turn mounted on a 60x40mm section hardwood base rail at each end of the cot. The moving parts of the lifting towers are screwed directly to the original cot ends. The moving part of each tower is formed from a 40x40mm hardwood batten to which the cabinet slides are screwed. The actuator at each end lifts this batten via a machined acetal bracket.
To increase sideways stiffness, the lower parts of the lifting towers are joined together under the cot floor with a further 60x40mm section hardwood rail, with stiffening braces at each end. This rail also carries the remote control receiver, cables and fuses.
Non-slip, non-marking rubber feet are fitted under the base rails.
When all assembled, the structure was found to be remarkably stiff and stable in both lowered and raised positions.
Cot side door:
The original cot drop side was cut into 4 sections, and hinged to form 2 separate folding doors. These were mounted in a frame comprising 20x20mm hardwood rails at the sides and 25x25mm aluminium channels top and bottom. This assembly is self-contained and is bolted between the cot end panels. The ‘inner’ ends of the central folding door panels have acetal bobbins fitted which are free to slide in the aluminium channels. The doors are held closed by top and bottom adjustable pull latches (Figure 2)) at the middle hinges, which when pulled tight hold the doors firmly shut.
The aluminium top rail and the hinges were covered in soft foam for safety
Lift and lower control is by a Quachip remote RF relay, rated 7 amp at 12VDC. This has two key fob units, which were programmed for ‘toggle’ operation (ie press once to start, again to stop, in both directions). Power is provided by a 120W 12V packaged power supply, which is mains powered.
5 amp fuses are fitted into the supply line to each actuator. The total current drawn by both actuators when lifting a test weight of 55Kg was approximately 4.5 amp.
The lifting cot fills two functions. Firstly, it allows our Client to get her wheelchair arms under the cot base so she can change and attend to her baby, and secondly the cot can be lowered to the floor so it can also serve as a playpen in the limited space in the Client’s house.
The concertina doors allow full width access to the cot in either raised or lowered position.