Patent Publication Number: US-2007113344-A1

Title: Movable bed with an independent wheel suspension system

Description:
TECHNICAL FIELD OF THE INVENTION  
      The present invention relates generally to movable beds and, more particularly, to a system and method for providing an independent wheel suspension system for a movable bed.  
     BACKGROUND OF THE INVENTION  
      In order to provide mobility most movable beds (e.g., hospital beds) are mounted on wheels or casters. Hospital bed wheels are usually provided with a locking mechanism so that the wheels are not able to rotate when the locking mechanism is engaged. When it is desired to move the hospital bed the locking mechanism on the wheels is disengaged and the wheel are able to rotate freely.  
       FIG. 1  illustrates a prior art hospital bed  100  showing the typical size and placement of the hospital bed wheels  110 . Prior art hospital bed wheels  110  are connected directly to the hospital bed frame  120 . Therefore, when a hospital bed wheel  110  rolls over an obstacle (e.g., a cable mounted on the floor or a threshold in a doorway) the wheel rises up over the front of the obstacle, passes over the top of the obstacle, and falls down behind the obstacle to impact the floor. Each of the hospital bed wheels  110  that pass over the obstacle transmits the impact directly to the bed frame  120 .  
      If a patient is in the hospital bed when the hospital bed  100  is being moved and the wheels  110  of the hospital bed  100  pass over an obstacle on the floor, the patient will feel the impact when the wheels  110  of the hospital bed  100  hit the floor after passing over the obstacle. The impact is felt because the wheels  110  of the hospital bed  100  are directly connected to the bed frame  120 . The forces that are experienced by the wheels  110  are directly transmitted to the bed frame  120  and to the patient.  
      For these reasons, it would be very advantageous to have a movable bed that would not allow the forces that are experienced by the wheels to be transmitted to the bed frame and to the patient. There is a need in the art for a hospital bed that is capable of protecting a patient in the bed from receiving impacts that occur due to a hospital bed moving over obstacles on a floor.  
     SUMMARY OF THE INVENTION  
      To address the above-discussed deficiencies of the prior art, it is a primary object of the present invention to provide a movable bed (such as a hospital bed) that is capable of protecting a person in the bed from receiving impacts that occur due to the movable bed moving over obstacles on a floor.  
      The movable bed of the present invention comprises a bed frame and an independent wheel suspension system. The independent wheel suspension system comprises a plurality of wheel assemblies. A wheel assembly is attached to each of the four corners of the bed frame of the movable bed. Each wheel assembly comprises a bed wheel and a shock absorber. The shock absorber comprises a first end attached to the bed frame and a second end attached to a bed wheel. The shock absorber comprises a damping mechanism (e.g., a spring or a hydraulic liquid) that resists the vertical motion of the bed wheel when the bed wheel passes over an obstacle on the floor.  
      In one advantageous embodiment the shock absorber may comprise a robust shock absorber of a type that is often employed on an off-road bicycle.  
      The independent wheel suspension system of the present invention also comprises a pivotal wheel assembly that may be pivoted downwardly and locked into a down position with respect to the bed frame to provide the additional support for the bed frame. When the additional support is not required the pivotal wheel assembly may be unlocked and then pivoted upwardly and locked into an up position with respect to the bed frame. The pivotal wheel assembly does not touch the floor when it is pivoted upwardly and locked into its up position.  
      It is an object of the present invention to provide a movable bed that is capable of protecting a person in the bed from receiving impacts that occur due to the movable bed moving over obstacles on a floor.  
      It is another object of the present invention to provide a hospital bed that is capable of protecting a patient in the bed from receiving impacts that occur due to the hospital bed moving over obstacles on a floor.  
      It is also an object of the present invention to provide a movable bed that comprises a bed frame and an independent wheel suspension system.  
      It is another object of the invention to provide an improved wheel assembly for a movable bed.  
      The foregoing has outlined rather broadly the features and technical advantages of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features and advantages of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they may readily use the conception and the specific embodiment disclosed as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention in its broadest form.  
      Before undertaking the DETAILED DESCRIPTION OF THE INVENTION below, it may be advantageous to set forth definitions of certain words and phrases used throughout this patent document: the terms “include” and “comprise”, as well as derivatives thereof, mean inclusion without limitation; the term “or,” is inclusive, meaning and/or; “each” means every one of at least a subset of the identified items; the phrases “associated with” and “associated therewith,” as well as derivatives thereof, may mean to include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicable with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, or the like. Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior uses, as well as future uses, of such defined words and phrases.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      For a more complete understanding of the present invention and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like parts, in which:  
       FIG. 1  illustrates a perspective view of a prior art hospital bed;  
       FIG. 2  illustrates side view of a hospital bed constructed in accordance with the principles of the present invention;  
       FIG. 3  illustrates a wheel assembly of the present invention;  
       FIG. 4  illustrates a shock absorber of the present invention;  
       FIG. 5  illustrates another advantageous embodiment of the hospital bed of the present invention;  
       FIG. 6  illustrates a method for manufacturing a hospital bed of the present invention; and  
       FIG. 7  illustrates a wheelchair constructed in accordance with the principles of the present invention.  
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIGS. 2 through 7 , discussed below, and the various embodiments used to describe the principles of the present invention in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the invention. Those skilled in the art will understand that the principles of the present invention may be implemented for any type of suitably arranged hospital bed.  
       FIG. 2  is a diagram  200  illustrating a side view of a hospital bed  210  that comprises a hospital bed frame  220  of the present invention. A wheel assembly  230  is attached to each of the four corners of bed frame  220 . (Only two corners are shown in the side view of  FIG. 2 ). A wheel assembly  230  comprises a hospital bed wheel  240  and a shock absorber  250 . That is, each of the four wheels  240  in the wheel assemblies  230  that support bed frame  220  is attached to a shock absorber  250 . When a wheel  240  passes over an obstacle (not shown in  FIG. 2 ) the wheel  240  rises over the obstacle and falls down onto the floor after passing over the obstacle. Shock absorber  250  cushions the impact because each wheel  240  is directly connected to its own associated shock absorber  250 . Each shock absorber  250  in a wheel assembly  230  is directly connected to the bed frame  220 . The forces that are experienced by the wheels  240  are directly transmitted to the shock absorber  250 .  
      Because of the cushioning effect of each shock absorber  250  a patient (not shown) in the bed  210  that is supported by bed frame  220  will not feel the impact when the wheels  240  of the hospital bed  210  hit the floor after passing over an obstacle. Shock absorber  250  may comprise one of a number of different types of shock absorber.  
      Each wheel  240  is connected to its own associated shock absorber  250 . This feature provides independent wheel suspension for the hospital bed  210 . Therefore a small obstacle that is encountered by only one wheel  240  will not affect the other wheels. The impact that is experienced by a single wheel that encounters a small obstacle will be cushioned by the shock absorber  250  that is associated with that single wheel. The other wheels will pass by the obstacle without hitting the obstacle.  
       FIG. 3  is a diagram  300  illustrating a side view of a wheel assembly  230  of the present invention. Wheel assembly  230  comprises wheel  240  and shock absorber  250 . An axle  310  of wheel  240  is connected via yoke  330  to an inner sliding tube  320  of shock absorber  250  at a first lower end of shock absorber  250 . Bed frame  220  is connected to an outer tube  340  of shock absorber  250  at a second upper end of shock absorber  250 .  
       FIG. 4  is a diagram illustrating a cross sectional side view  400  of shock absorber  250 . Wheel  240  (not shown in  FIG. 4 ) is directly connected to the inner sliding tube  320  of the shock absorber  250  via axle  310  and yoke  330 . Inner sliding tube  320  of shock absorber  250  is located within outer tube  340 . Inner sliding tube  320  slides within outer tube  340 . A damping mechanism  410  within shock absorber  250  mechanically resists the upward sliding motion of inner sliding tube  320  with respect to outer tube  340 . The damping mechanism  410  of shock absorber  250  may comprise a spring, a hydraulic liquid, or other similar apparatus for providing resistance to mechanical motion. In  FIG. 4  the damping mechanism  410  is shown as a spring  410 .  
      In one advantageous embodiment of the invention, the shock absorber  250  comprises a robust shock absorber of the type that is employed on off-road bicycles known as “mountain bikes.” A robust shock absorber of this type is disclosed in U.S. Pat. No. 4,971,344.  
       FIG. 5  is a diagram  500  illustrating another advantageous embodiment of the hospital bed  510  of the present invention. In this embodiment the hospital bed  510  comprises a hospital bed frame  520  to which five wheel assemblies  530  have been attached. (Only three wheel assemblies  530  are shown in the side view of  FIG. 5 ). Each of the five wheel assemblies  530  comprises a wheel  540  and a shock absorber  550 . The location of the fifth wheel assembly  530  may be selected to be at a central location under hospital bed  510 . The presence of the fifth wheel assembly  530  provides additional support for a heavy load (e.g., an extremely obese patient).  
      In another advantageous embodiment of the invention, the fifth wheel assembly  530  may be pivotally attached to the bottom of the bed frame  520  by a pivot  560 . The fifth wheel assembly  530  may be pivoted downwardly and locked into a first position in which the wheel  540  of the fifth wheel assembly  530  is in contact with the floor. The fifth wheel assembly  530  may also be pivoted upwardly and locked into a second position in which the wheel  540  of the fifth wheel assembly  530  is not in contact with the floor. In this manner, the fifth wheel assembly  530  may be used only when it is necessary to support a heavy load in the hospital bed  510 .  
       FIG. 6  is a flow chart  600  showing the steps of an advantageous embodiment of a method for manufacturing a hospital bed in accordance with the principles of the present invention. In the first step of the method, a plurality of wheel assemblies is constructed in which each wheel assembly comprises a hospital bed wheel and a shock absorber (step  610 ). In the second step of the method, a first wheel assembly is attached to a first corner of the hospital bed frame of a hospital bed (step  620 ).  
      In the third step of the method, a second, a third and a fourth wheel assembly is attached to each of the remaining three corners of the bed frame of the hospital bed (step  630 ). In the fourth step of the method, a fifth pivotal wheel assembly is attached to the hospital bed frame of the hospital bed at a central location under the hospital bed frame (step  640 ).  
      In the fifth step of the method, the fifth pivotal wheel assembly is pivoted downwardly and locked into position when it is desired to provide additional support for the hospital bed frame of the hospital bed (step  650 ).  
      Although the movable bed of the present invention has been described with reference to an embodiment that comprises a hospital bed, it is understood that the movable bed of the invention is not limited to a hospital bed. The hospital bed is only one example of a movable bed. The movable bed of the present invention may comprise an operating table, a gurney, a massage table, or any type of movable bed.  
      The independent wheel suspension system of the present invention may be attached to a bed frame of a bed when the bed is initially constructed. Alternatively, the independent wheel suspension system of the present invention may be used to retrofit a bed frame of a preexisting bed (either movable or non-movable). The old bed supports (wheels or legs) are removed from the bed frame and replaced with the independent wheel suspension system of the present invention. In this manner the benefits of the invention may be added to beds that already exist.  
      The independent wheel suspension system of the present invention may also be attached to a frame of a structure for moving persons who are not able to walk. For example, the independent wheel suspension system of the present invention may be attached to a wheelchair or similar type of structure. As previously described, the independent wheel suspension system of the present invention provides shock absorbers for that cushion impacts as the wheels pass over obstacles on the floor.  FIG. 7  illustrates a wheelchair  700  that is equipped with the independent wheel suspension system of the present invention.  
      Although the present invention has been described with several embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims.