26-02-2013, 03:21 PM
LINEAR ACTUATOR SYSTEM FOR HOSPITAL BED IN HEALTHCARE INDUSTRY
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Abstract— linear actuator system for hospital bed is provided incorporating a segmented, adjustable patient support structure having a plurality of flexible air impervious air bags releasable secured thereto. An air supply is provided for maintaining controllable inflation of selected groups of the air bags with air pressure therein being selectively and automatically adjustable for patient comfort and for emergency patient care. Each of the air bags has a single air inlet in communication with the air supply and multiple air vent holes along the upper side portions thereof or ventilation, patient heating or cooling and removal of moisture. Convex upper surface portions of the air bags facilitate support of the patient without wrapping of air bag material about the patient. The fluidized hospital bed system is powered electrically with both AC and DC current, enabling battery override in the event of failure of the AC power supply. The power supply system also permits the hospital bed to be disconnected from the AC power supply and transported to other areas of the hospital facility while continuous operation is maintained by the self-contained DC supply. Patient support and positioning apparatus enables the bed structure to support patients of virtually any size and weight. A movable footboard and collapsible bed-rail assembly are provided which promote patient comfort and easy access such as for emergency patient care treatment.
INTRODUCTION
As an engineering student, Linear motion is much in demand in all sectors of industry and the linear actuator is one of the responses. Linear actuator is a device that develops force and motion, from an available energy source, in a linear manner, as opposed to rotationally like an electric motor. The linear actuator is generally less cumbersome than a cogged belt, simpler than a rack and pinion and more economical than a ball screw. Linear actuator is available in a wide variety of models with different sizes, torques and rotation angles. Linear Actuators is particularly useful for straightforward x-y, or x-y-z, positioning systems.
A linear actuator is an actuator that creates motion in a straight line, as contrasted with circular motion of a conventional electric motor. Linear actuators are used in machine tools and industrial machinery, in computer peripherals such as disk drives and printers, in valves and dampers, and in many other places where linear motion is required. Hydraulic or pneumatic cylinders inherently produce linear motion; many other mechanisms are used to provide a linear motion from a rotating motor.
Linear actuator system for hospital bed parts is a kind of electric drive device. It turns the rotary movement of the motor to the linear reciprocating movement of the actuator. It can be applied to various simple or complex processes as executive machinery, in order to realize the remote control, centralized control or automatic control. Linear actuator system for hospital bed parts is a universal auxiliary device driver. The advantage of linear actuator system for hospital bed parts is reliable performance, quick action, smooth operation, low noise, convenient installation, low price, etc.
METHODOLOGY
here are various methods of achieving linear motion. Several examples are mechanical actuators, hydraulic actuators, piezoelectric actuators, electro-mechanical actuators and linear motors. In the majority of linear actuator designs, the basic principle of operation is that of an inclined plane. The threads of a lead screw act as a continuous ramp that allows a small rotational force to be used over a long distance to accomplish movement of a large load over a short distance. Figure below show a conceptual design of a basic linear actuator.
stepper motor - linear actuator system
The system converts rotary motion (in the form of an electric motor) to linear motion. When an electrical source is applied to the motor, the threaded shaft is driven and the nut rides up and down in the corresponding direction. This action provides an extension and retraction capability for tasks requiring a linear displacement. Note that in this example the nut and red tube do not rotate, merely "ride" the threads on the spinning shaft up and down.
Important performance specifications to consider when searching for linear actuators include stroke, maximum rated load or force and maximum rated speed. Stroke is the distance between fully extended and fully retracted rod positions. The maximum rated load or force is not the maximum static load. The maximum rated speed is the maximum actuator linear speed; typically rated at low or no load.