Patent Publication Number: US-2006010643-A1

Title: Caster with powered brake

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims benefit of U.S. Provisional Patent Application Ser. No. 60/588,054 to Hornbach et al., entitled CASTER WITH POWERED BRAKE (Attorney Docket No. 8266-1196) filed Jul. 15, 2004, the entirety of which is herein incorporated by reference. 
    
    
     BACKGROUND AND SUMMARY OF THE INVENTION  
      This invention relates to casters attached to a base frame for rolling a frame from location to location and a braking mechanism for controlling the casters.  
      Hospital beds are typically designed to be moved from location to location in a hospital or other health care facility. Therefore, beds have wheels or casters which permit the hospital bed to be rolled and steered between locations. During movement it is desirable to have free rolling wheels but upon reaching the desired location, brakes are usually applied to the wheels to maintain the bed at the desired location.  
      It is well known to provide hospital beds with brake/steer casters which include mechanisms for blocking the rotation of the casters, i.e. braking mechanisms. Some beds with four caster wheels include pedals located on opposite sides of the bed which control the braking. Examples of such beds are shown in U.S. Pat. No. 5,377,372 and PCT Publication No. WO 00/51830 both of which are incorporated herein by reference.  
      According to one embodiment of the present invention, A caster apparatus is provided comprising an axle, at least one wheel coupled to the axle, a housing coupled to the axle, a cylinder providing an axis of rotation for the axle, wheel, and housing, the cylinder defining a first footprint relative to a floor, and a brake. The brake is at least partially received within the cylinder and the brake defines a second footprint relative to the floor, the second footprint being fully within the first footprint.  
      Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of illustrated embodiments exemplifying the best mode of carrying out the invention as presently perceived. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
      The detailed description of the drawings particularly refers to the accompanying figures in which:  
       FIG. 1  is a perspective view of a caster apparatus including a brake; and  
       FIG. 2  is an exploded view of the caster apparatus of  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
      Referring to the drawings,  FIGS. 1 and 2  illustrate a caster apparatus  10  of the present invention. The caster apparatus  10  includes a hydraulic actuator  1 , a housing  6  that partially receives actuator  1  therein, a roller bearing  7  and axle bearing  5  that allow housing  6  to rotate relative to actuator  1 , a cover  3 , a pair of wheels  4 , an axle  8  that rotatably couples wheels  4  to housing  6  and cover  3 , and end caps  9  that couple wheels  4  to axle  8 .  
      In the pictured embodiment, actuator  1  is a hydraulic actuator including a mount plate  12 , a cylinder  14  coupled to mount plate  12 , a piston  16  slidably received in cylinder  14 , a spring (not pictured) located within cylinder  14 , and a stop  2  made of rubber or other suitable soft material attached to an exposed end of piston  16 . Although actuator  1  is described herein as a hydraulic actuator, other actuators may be used including pneumatic actuators, electrical actuators, and any other suitable actuators.  
      Mount plate  12  is generally flat and rectangular with a plurality of apertures therein. Illustratively, five apertures are shown, one near each corner and a centrally located hydraulic aperture  18 . The apertures near the corners of mount plate  12  are positioned and sized for attaching mount plate  12  to a larger structure such as a patient support. Hydraulic aperture  18  is generally centrally located to align with cylinder  14 . Hydraulic aperture  18  is configured to attach to a hydraulic line (not pictured) and to conduct hydraulic fluid between the hydraulic line and cylinder  14 .  
      Cylinder  14  is sized to be received within housing  6  and bearings  5 ,  7  and includes a bore therein (not pictured) to receive piston  16  and the spring therein. Hydraulic actuator  1 , and more specifically cylinder  14 , acts as a rotation axle for caster apparatus  10 . Piston  16  is slidably received in cylinder  14  such that hydraulic fluid supplied to cylinder  14  urges piston  16  out of cylinder  14 . Cylinder  14  and piston  16  are attached to a patient support via plate  12  so as to place cylinder  14  and piston  16  in a generally perpendicular orientation relative to and in close proximity to a floor. As such, extension of piston  16  out of cylinder  14  causes rubber stop  2  on the end of piston  16  to abut the floor causing a frictional relationship therebetween, thus braking the caster apparatus. The spring (not pictured) biases piston  16  to retract into cylinder  14 . Therefore, while pressure generated by the introduction of hydraulic fluid to cylinder  14  can overcome the force of the spring, in the absence of such hydraulic force, the spring retracts piston  16  into cylinder  14 . Thus, pistion  16  of actuator  1  is biased to a non-braking position.  
      Bearings  5 ,  7  are generally ring-like, are received within a cylinder bore  24  of housing  6 , and include cylinder bores  20 ,  22  respectively to receive cylinder  14  therein. Bearings  5 ,  7  allow housing  6  to rotate relative to cylinder  14 . Bearing  7  provides an upper bearing surface  34  that contacts plate  12  and cylinder bore surface  36  to abut and slidably engage cylinder  14 . Bearing  5  provides a cylinder bore surface  38  to abut and slidably engage cylinder  14 .  
      Housing  6  is a generally cylindrical body including cylinder bore  24  and axle bore  26 . Cylinder bore  24  is illustratively a multi-diameter bore. A main section of cylinder bore  24  is sized to be just larger than cylinder  14 . End sections of cylinder bore  24  are of larger diameters sized to receive bearings  5 ,  7  therein. Axle bore  26  is preferably of a constant diameter. Furthermore, axle bore  26  is perpendicular to and does not intersect cylinder bore  24 . Axle  8  is rotatably received in axle bore  26 . Wheels  4  couple, fixedly or rotatably, to axle  8 .  
      Cover  3  approximates a half-shell with axle bores  30  and a cylinder bore  32  defined therein. Cover  3  couples to axle  8  such that cover  3  shields the upper sides of wheels  4  and housing  6  while allowing the respective lower ends of wheels  4  and housing  6  to extend therebelow. Cylinder bore  32  is sized and shaped to allow cylinder  14  and bearing  7  to extend therethrough.  
      Housing  6 , bearings  5 ,  7 , cover  3 , axle  8 , and wheels  4  combine to form a wheel assembly that freely rotates relative to actuator  1 . Alternatively, bearing  5  fixedly attaches to cylinder  14  and is designed to slidingly bear against housing  6 . In such an embodiment, bearing  5  prevents housing  6  from sliding off cylinder  14  in that bearing  5  is larger than the main section of cylinder bore  24 .  
      The size and placement of wheels  4 , axle  8 , housing  6 , and hydraulic actuator  1  are configured such that when piston  16  is withdrawn into cylinder  14 , rubber stop  2  is not in contact with the floor. Furthermore, extension of piston  16  through hydraulic activation causes rubber stop  2  to frictionally engage the floor to cause braking. In another embodiment, hydraulic activation of actuator  1  causes extension of piston  16  which raises wheels  4  out of contact with the floor to likewise cause braking.  
      As previously discussed, bearings  5 ,  7  allow housing, and thus wheels  4  attached thereto, to rotate relative to hydraulic actuator  1  to provide a rotating caster. Thus, the location and orientation of hydraulic actuator  1  provides a rotating caster with a hydraulically activated brake located within the footprint of a rotation axle of the caster.  
      In use, caster apparatus  10  is selectively hydraulically activated. Hydraulic fluid is supplied to caster apparatus  10  to activate hydraulic actuator  1 . Activation of hydraulic activator  1  extends piston  16  out of cylinder  14  such that rubber stop  2  abuts the floor. The abutment of rubber stop  2  with the floor causes a frictional engagement to brake the caster apparatus  10  and any patient support or other device attached thereto. Removal of hydraulic fluid from caster apparatus  10  is effected either through the application of negative pressure to cylinder  14  or by reduction in pressure applied to cylinder  14  to allow the spring to push fluid out of cylinder  14  with piston  16 . Removal of hydraulic fluid from cylinder  14  allows rubber stop  2  to disengage from the floor. Disengagement allows caster apparatus  10  to roll and rotate to transport the patient support or other device.  
      Many caster apparatus  10  may be linked together so as to be activated and deactivated simultaneously. Alternatively, each caster apparatus  10  is independently activated to selectively assist in steering the patient support or for some other purpose.  
      It should be appreciated that the present invention has applications in the area of bariatric care. Often, bariatric patients are difficult to move from one patient support to another. Accordingly, it is desirable to be able to perform surgeries on a long term care patient support or an otherwise mobile patient support such that movement between a plurality of patient supports is not necessary. However, during surgical procedures it is also desirable for the patient support to be stationary. Thus, the present invention allows a usually mobile patient support to achieve stability suitable for surgical procedures.  
      In another embodiment, caster apparatus  10  of the present invention is be linked with a powered drive system such as those described in U.S. Pat. No. 6,749,034 titled MOTORIZED TRACTION DEVICE FOR A PATIENT SUPPORT and U.S. patent application Ser. No. 10/336,576 titled BRAKING APPARATUS FOR A PATIENT SUPPORT the disclosures of which are both incorporated by reference herein. In one such embodiment, engagement of push handles that activate a drive system would also de-energize caster apparatus  10  to release any braking being performed thereby.  
      Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the present invention.