Beds – Invalid bed or surgical support – Vertically movable support for whole body of user
Patent
1995-10-17
1998-09-08
Meyers, Steven N.
Beds
Invalid bed or surgical support
Vertically movable support for whole body of user
5600, 91 4A, 60469, 60477, A47B 700, F16D 3102, F15B 2104
Patent
active
058026380
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an apparatus and method for supporting a load at an adjustable height and in particular but not exclusively to adjustable chair-beds for use in supporting patients during medical treatment and to a method of raising and lowering the patient with minimal effort. The invention also relates to a gas spring for use in such apparatus.
It is known to provide adjustable chair-beds in which a patient is supported on a rest portion which can be adjusted in height relative to a base. This is particularly useful where the chair-bed is to be used in one mode for transportation or rest for the patient and in another mode for supporting the patient during medical treatment. Typically such chair-beds have a rest portion which is jointed to provide a lea rest, footrest and back rest which can be adjusted relative to a fixed seat to allow the patient to adopt a suitable attitude in the above modes.
Height adjustment in such chair-beds is typically effected by means of a hydraulic ram acting between the base and the rest portion. In co-pending application GB-9225791.4 the applicant discloses an alternative arrangement in which a hydraulic ram acts on a pivotal linkage connecting the base to the rest portion, the arrangement being such that a height adjustment is achievable which exceeds the available travel of the hydraulic ram.
During upward adjustment of such chair-beds, a foot-pump is generally employed to actuate the ram and work done in raising the rest portion and the load carried by the rest portion is dissipated during subsequent downward adjustment when the hydraulic ram is simply allowed to relax to its non-extended configuration. Repeated height adjustment therefore requires considerable energy to be expended by the operator particularly where exceptionally heavy patients are supported.
According to the present invention there is disclosed apparatus for use in supporting a load at an adjustable height comprising a rest portion for supporting a load in use, a base connected to the rest portion by a linkage facilitating adjustment of the height of the rest portion relative to the base and locking means selectively operable in a locking state to lock the position of the rest portion relative to the base and in an unlocked state to facilitate height adjustment, wherein the apparatus further comprises spring means operable at least when the locking means is in an unlocked state to apply a spring force directly or indirectly between the base and the rest portion and adjustment means operable independently of height adjustment to adjust the spring force such that an upward component of the spring force acting on the rest portion has a value which is thereby adjustable to exceed the weight of the rest portion by an amount substantially corresponding to the weight of the load.
An advantage of such apparatus is that during downward height adjustment the load and the rest portion travel in opposition to the upward component of spring force through a distance equal to the adjustment in height so that the work done in compressing the spring means is available as stored energy which is recoverable during subsequent upward height adjustment. The stored energy is essentially the product of the upward component of spring force and the distance travelled, subject to any losses inherent in the spring means.
Preferably the spring means comprises a gas spring.
The use of a gas spring has the advantage of providing a compact structure of low mass and high efficiency.
Preferably the gas spring comprises a cylinder defining a chamber receiving a quantity of gas, a first piston movable within the cylinder in response to pressure of the gas, and the adjustment means is operable independently of the position of the first piston to vary the volume of the gas within the chamber.
Since the force exerted by a gas is proportional to the gas pressure and since the gas pressure is dependent upon the available volume within the chamber, the adjustment means provides a means of adjusting the force applied by the gas spring
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patent: 5245718 (1993-09-01), Krauska
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patent: 5303437 (1994-04-01), Hung
Kalogroulis Alexander Joseph
Parker George Christopher
Sanders Mark A.
Keymed (Medical & Industrial Equipment) Ltd.
Meyers Steven N.
Pham Tuyet-Phuong
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