Chicagoland & Northwest Indiana's Handicap Accessibility Equipment Dealer

Acorn Stairlift Technical information

Modern stair lifts can be found with a wide variety of features such as adjustable seat height, battery isolation switches, call stations, ‘flip-up’ rail, key switch, folding step, speed governor, seatbelt, soft start and soft stop.

Rails


Straight rails for use on domestic staircases are usually made from extruded aluminium or steel and come in various
cross-sectional shapes. These rails may, typically, weigh over 30 kg, depending on the length. In most applications they are attached to the steps with metal brackets (sometimes called “cleats”).  If a rail crosses a doorway at the bottom of the stairs or causes an obstruction a hinge can be fitted so the end of the rail can be folded back out of the way when not in use.  Curved rails are made from materials such as steel or aluminium and come in various cross-sectional shapes according to the designer. Individual designs vary a lot and probably the key criterion is to make the curves with the smallest radius possible so they will wrap tightly around objects such as newel posts.  The sections of curved rails usually packaged well to prevent damage in transit and are unwrapped and assembled on site.
Rails for wheelchair platform stairlifts may be secured to walls in addition to the step fixings.

Carriages


The carriage is the component which moves along the rail and normally runs on small diameter rollers. In most designs the carriage is pulled by a cable or chain, or driven along the inclined rail by a rack and pinion system or other drive arrangement.  Most domestic carriages have a seat with arms and a footrest. Some special models have a stand-on platform also known as a “perch” seat. For users with shorter legs a short seat can be fitted, to make the lift more comfortable to sit on. Stairlift manufacturer such as Minivator Ltd have a number of different seat types depending on your individual needs.  The conventional layout for a typical domestic stairlift is to have the seat at right angles to the rail so the user travels “sidesaddle”. At the top of the staircase the seat can be swivelled, commonly through around 45 degrees or 90 de grees.  Then locked in place to allow the user to alight from it onto a landing. Stairlifts are available with either a manual swivel or a powered swivel, depending on the users ability.  Most swivel seats have a safety switch so the stairlift won’t move unless the seat is locked into its travel position. Special models with seats facing the bottom of the staircase have been produced for users with spinal or other conditions which prevent use of the conventional seat layout. More room is need on the landing with these special seats.

Power Source

Early stairlifts mostly had alternating current (AC) drive motors which ran at full mains voltage (around 100 volts in North America, 230 volts in Europe). An “energy cable” ran alongside or through the rail to carry the power from the supply point to the carriage.  More recently, domestic stairlifts have been powered from rechargeable batteries and use direct current (DC). One of the selling points is that a DC stairlift will continue to function during a power outage, provided the batteries are sufficiently charged. Most stairlifts have a ‘chargepoint’ where the unit will ‘park’ to charge its batteries. Some straight stairlifts have the ability to continuously charge no matter where they are left along the track.  With most DC models the batteries are accommodated within the carriage and travel with it.  Some models, however, were designed with three phase motors and the batteries (three in total) were housed in a cabinet mounted near the top or bottom of the rail. An inverter system was used to convert the DC energy to three phase AC.  The power rating of drive motors for domestic straight rail stairlifts may be around 250 watts. The power requirement will
be greater for heavy loads, very steep inclines, and wheelchair platform stairlifts.

Controls

Stairlifts are largely operated using a control on the arm of the lift. This is either a switch or a toggle type lever. This larger toggle switch enables users even with limited mobility or painful condition to use stairlifts easily and safely.
Electronic controls are used extensively. Many stairlifts have radio frequency or infrared remote controllers. It is
known that radiation from devices such as fluorescent lights can interfere with infrared stairlift controls. Also, heat and incandescent lights can, in some circumstances, have an adverse effect.  Control circuit design varies greatly among the different manufacturers and models. Curved rail stairlifts have more complex controls than those with straight rails.  The seat of a curved rail stairlift may have to be tilted so it remains horizontal whilst going around curves and negotiates different angles of incline. This requires an additional motor and link system.  Also, the carriage is slowed down on bends but travels faster on straight runs. This means a more complex control system.  Modern controls have small microprocessors which “learn” the characteristics of the journeys and keep the data in memory. They also record the number of journey and direction. This assists service engineers on maintenance calls.  Some development was started at the onset of the 21st Century Stairlifts into self-diagnostic controls. The idea was that
stairlifts would predict when components were starting to deteriorate and automatically pass the information to the service provider so a visit could be arranged.

It will shut down at the slightest touch on the safety sensors

 

Safety


To satisfy safety codes stairlifts usually have cut-out switches connected to “safety edges” and other protective devices so the drive power is disconnected if something goes wrong. Modern lifts have a high degree of comfort, but safety is always paramount. “Safety edges” are a common feature to the power pack and footplate. “Safety edges” ensure that if there is any obstruction on the stairs the stairlift will automatically stop and only travel away from the obstruction.  Stairlifts are used by people of all ages and child car seats can usually be fixed to a standard stairlift seat using the seat belt provided with the stairlift system.  Codes of practice and technical specifications apply to stairlift manufacture.
In North America these codes may be relevant:


• ASME A17.1 – 1990, Safety Code for Elevators and Escalators
• ASME A18.1 – 2005 Safety Standard for Platform Lifts and Stairway Chairlifts

Produced by American Society of Mechanical Engineers
An important specification used by stairlift manufacturers in Europe was British Standard BS 5776: 1996 Specification For Powered Stairlifts, produced by The British Standards Institution.

Note: codes of practice and technical specifications are updated occasionally. These references may be out of date by the time they are read and are shown as examples.

Travel speed


Stairlifts normally have “soft” starts so the user is not jerked as the carriage starts to move. Typical travel speed for
domestic straight rail stairlift carriages range between 0.07 metres per second (13.78 feet per minute, 0.16 miles per hour) and 0.15 metres per second (30 feet per minute, 0.34 miles per hour). The speed of curved rail stairlift carriages may vary on the journey if the controls cause them to slow on inclines and bends.

References
• Disability History Museum Catalog Card
• Elevator World, Volume One, No 1 January 1953
• The Stairlift Institute Charity.
• The Chambers Dictionary, Chambers, 2003
• Hansard, UK Parliament House of Commons Daily Debates record. References to stairlifts: 16 Mar 1990 :
Column 395; 7 May 2002 : Column 3WH; Westminster Hall, Sylvia Heal in the Chair; 14 Jun 2004 : Column 744W
From Wikipedia, the free encyclopedia

Leave a Reply