Introduction

Background:

COPD is a disease in which the lungs have difficulty keeping their shape and the patient to inhale and exhale. COPD is irreversible, and as a result many patients are permanently wheelchair-bound and must also carry oxygen tanks. Weight gain is common with COPD sufferers and being underweight or overweight can adversely affect the patient’s health [1-2]. The device to be designed is intended to help wheelchair-bound COPD patients assess their relative health through their weight, as physical exercise is absolutely essential to keep COPD patients healthy. Another goal is to further increase the convenience encountered by wheelchair-bound users of weighing one’s self at home.    

            The device to be designed is intended to help wheelchair-bound COPD patients assess their relative health through their weight, as physical exercise is absolutely essential to keep COPD patients healthy. Wheelchair scales have been designed and brought to market: A search on the U.S. Patent and Trademarks Office website resulted in numerous examples of devices intended to adapt a standard weighing platform or scale to wheelchair use [6]. The purpose of most scale adapting methods is to check the forward motion of the wheelchair by its wheels; many contain supports for contact with the wheelchair chassis itself to keep the platform surface from contacting either the back set or front set of wheels. Rishel (U.S. Pat. No. 5,448,022) describes a tip-on wheelchair scale adaptor consisting of a support on which the front of the wheelchair chassis is tipped and a support holding the back of the wheelchair so that both wheels are off the platform.

Disadvantages of platforms adapting scales to wheelchair-bound individuals include significant wobble [6], which may cause discomfort to older persons. Also, this arrangement, as do many of the patented wheelchair scale platforms, requires “only one assistant” for each weighing operation. An improvement on the design is found in U.S. Pat. No. 6,268,572, where Wilson outlines a design for a platform with an access ramp to be placed on a standard weighing device, so that the individual can access the scale independently. However, the weight may need to be read by an assistant, as it is visible through a slot cut out in the platform (placed over the scale) and can be under the wheelchair chassis [6].  

Based on the prior art of patented wheelchair scale adaptors patented, as well as the prior art status of any weighing device using a strain gage or similar measuring method, it can be concluded that the device cannot be patented based on its ability to weigh a wheelchair-bound individual. Many products exist on the market for the weighing of individuals in wheelchairs; most of these designs are lacking compatibility with standard computer systems and an interface that is easily accessible to individuals with hearing or vision impairments. The ability of the product to be patented is limited; however, it can offer options that cannot be found in the market yet.

There is a large variety of products on the market of wheelchair scales incorporating various features. Wheelchair scales can be mechanical (typically balance-beam scales) or electronic (transducer-based), and have features added such as wheels and folding parts for easy storage and setup and smart-card functionality and/or memory for storing previous weights and weight of the wheelchair for taring. The wheelchair scale model by Seca model 664 [4] is a state of the art wheelchair scale that is lightweight, portable, and has the option of being able to store the weights of wheelchairs belonging to multiple users on smart cards. The weighing platform is large enough to accommodate any wheelchair user and can be entered using low-grade ramps from either the front or back. Shallow protective railings on either side of the weighing platform opposite the access ramps on either side are alternatively used as handles and the entire scale folds into a compact unit for side storage. The unit costs $1875 dollars plus $65 for shipping/handling [4].

Detecto, a division of Cardinal Scale Manufacturing, offers several models, mechanical and digital [3], with large rubberized-mat weighing platforms (minimum 26” by 30”) and a capacity and resolution standard in the industry (500lb and 0.2 lb, or 1000lb and 0.5 lb res. respectively). The FHD133II/FD144II Geriatric/Bariatric digital wheelchair scale incorporates a keypad with the display unit for typing in the wheelchair weight for taring. An ABLEDATA database search for wheelchair scales turned up 12 devices, even including a “do it yourself” entry on how to build a plywood platform to adapt a bathroom scale to a wheelchair [5]. A typical wheelchair scale solution costs within the range of $1400 to $3200 and most scales have load limits around 500 lb and 800 lb with resolutions of 0.2 lb. Most wheelchair scales are accessed by ramps leading to the platform, usually with safety barriers on either side of both ramp and platform.