Abstract:
A brake mechanism, for use in connection with a portable cart having at least one wheel, includes an elongated rod rotatably coupled to the cart, a turning means coupled to the rod for rotating the rod about a centerline from a first position to a second position, at least one cam extending radially outward the said rod, a brake shoe means coupled to the cart, spring means disposed between the cart and the brake shoe means, the spring means being disposed so as to force the brake shoe means against the wheel of the cart, and wherein the at least one cam is disposed so as to compress the spring and force the brake shoe means away from the wheel when the rod is rotated from the first position to the second position.

Description:
This application is a continuation-in-part of provisional application 60/132,899 filed May 6, 1999 and a continuation application from International Application S.N. PCT/US00/12237 filed May 6, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of braking mechanisms, and more specifically to a braking mechanism that can be used on or in connection with a wheeled cart or other device. 
     2. Description of the Related Art 
     One braking mechanism which is known in the prior art is described in U.S. Pat. No. 3,710,895. The device in the &#39;895 patent describes a brake an retention system which can be used with food or beverage service cart of the type commonly found in commercial airliners. That patent taught the use of “feet” or other elements which could, when a handle was released, deploy and engage the floor surface. A pair of oppositely extended elements resist motion in both directions. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the limitations of the prior art by providing a braking mechanism which engages directly the wheels of the cart without requiring engagement with a carpet or other smooth surface floor. With the present invention, the braking mechanism consists of pairs of oppositely directed shoes that are spring loaded to engage a section of the wheel circumference. When engaged, any motion of the wheel is opposed by both a frictional and wedging contact with a brake shoe. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. A is a perspective view of a wheeled cart of the type which might employ the cart-brake mechanism of the present invention. 
     FIG. 1 is perspective view of a pair of wheeled casters connected by an axle which employs the cart-brake mechanism of the present invention. 
     FIG. 2 is a front view of the caster and brake rod assembly used in the present invention. 
     FIG. 3 is a bottom view of the caster and brake rod assembly used in the present invention. 
     FIG. 4 is a detailed perspective view of brake rod assembly used in the present invention. 
     FIG. 5 is a perspective view of one of the casters. 
     FIG. 6 is a front view of one of the casters. 
     FIG. 7 is a side view of one of the casters. 
     FIG. 8 is a cross sectional view of the caster taken along the line A—A in FIG. 6, showing the brake shoes in the locked position. 
     FIG. 9 is a cross sectional view of the caster taken along the line A—A in FIG. 6, showing the brake shoes in the unlocked position. 
     FIG. 10 is an exploded perspective view of the brake shoe assembly. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A cart-brake mechanism for use with a wheeled cart or other device will be described. In the following description, for the purposes of explanation, specific components, operations and construction details are set forth in order to provide a more thorough understanding of the present invention. It will be apparent to those skilled in the art, however, that the present invention may be practiced without these specific details. In other instances, well known elements or other structures have not been described in detail so as not to obscure the present invention unnecessarily. 
     Referring first to Figure A, a wheeled cart which might employ the braking mechanism of the present invention is illustrated. The cart shown illustrates a cart with a spring loaded device that is free-wheeling so long as an operating mechanism such as a handle or grip is engaged. When the handle or grip is released, a cam mechanism rotates to permit spring-based brake shoes to engage the cart wheels and prevent motion in either the forward or reverse direction. It will be apparent to those skilled in the art, however, that the braking mechanism is not restricted to this type of cart, and can be used with any type of wheeled cart. 
     A cart  10 , as shown in Figure A, includes wheels  20 , a fixed handle  22 , and movable handle  24 . The location of the fixed handle  22  and movable handle  24  will be a matter of design choice, and will vary based on the type of cart used. The specific location of the handles is not a critical feature of the present invention. It has been found, however, that the arrangement of the handles  22 ,  24  in Figure A results in an efficient operation of the cart  10  while it is being moved from place to place. 
     Referring next to FIG. 1 the major components of the brake mechanism  28  are shown. In the preferred embodiment, the brake mechanism  28  is used with a pair of casters  30 . These casters  30  are mounted on the bottom of the cart (not shown in FIG. 1) so as to be positioned on opposite sides of the cart and aligned to roll in a parallel path. Although the preferred embodiment uses a pair of casters  30 , it will be apparent to those skilled in the art that a single caster may usefully employ the mechanism of the present invention and can hold a cart against movement. 
     A brake rod  32  coupled between the casters  30 . The brake rod  32  is mounted so as to be free to rotate about its longitudinal axis. Attached to the brake rod  32  is a pull arm cam  34 . The pull arm cam  34  is rigidly fixed to the brake rod  32 . Although FIG. 1 illustrates a specific position for the pull arm cam  34 , it will be apparent to those skilled in the art that the pull arm cam  34  can be placed at any position along the length of the brake rod with equal effectiveness. 
     Attached to the pull arm cam  34  is one end of a cable  40 . The opposite end of the cable  40  is attached to the moveable handle  22  (shown in Figure A). The cable  40  is positioned within the cart  10  so as to be normally taut. When the movable handle  24  is depressed, the cable  40  pulls on the pull arm cam  34 . This causes the brake rod  32  to rotate about its own axis. Further details concerning the operation of the brake mechanism are given below in connection with FIGS. 8 and 9. 
     Referring next to FIG. 2, a front view of the casters  30  and brake rod  32  is shown. FIG. 3 is a bottom view of the same assembly. FIGS. 2 and 3 more clearly illustrate the relationship between the casters  30  and the brake rod  32 . 
     A detailed view of the pull arm cam  34  and brake rod  32  is shown in FIG.  4 . As can be seen, the pull arm cam  34  is a thin member which is generally in the shape of a circle. The outer periphery of the pull arm cam  34  is curved. The curved edge has a narrow slot  37  formed into its edge. This slot is best shown in FIGS. 2 and 3. Also formed into the pull arm cam  34  is an aperture  36 . The aperture  36  allows the cable  40  (not shown in FIG. 4) to anchor to the pull arm cam  34 . The curved edge  35  of the pull arm cam  34  is provided so that rotation of the brake rod  32  smoothly takes up the cable  40 . The pull arm cam  34  has attached to it a sleeve  38 , and a threaded nut is placed within the sleeve  38  to rigidly attach the pull arm cam  34  to the brake rod  32 . 
     Referring again to FIG. 4, the brake rod  32  includes a pair of bearings  42  which assist in the rotation of the brake rod  32 . Located at each end of the brake rod  32  are pins  44 , which mount the separation cams, described below with reference to FIGS. 8 and 9. 
     Referring next to FIGS. 5,  6  and  7  further details of the casters  30  which are used in connection with the present invention are shown. FIG. 5 is a perspective view of a caster  30 . FIGS. 6 and 7 are front and side views of the caster  30 , respectively. The caster  30  includes a wheel  50 . The wheel  50  is supported by two support arms  52 . Attached to the top of the support arms  52  is a mounting plate  54 . The mounting plate  54  attaches the caster  30  to the cart  10 . Also included in the caster  30  are a pair of brake shoes  60 . The structure and operation of the brake shoes are described below in connection with FIGS. 8 and 9. 
     FIGS. 8 and 9 are cross sectional views of the caster  30  taken along the line A—A in FIG.  6 . For the purposes of simplicity, the representation of the support arms has been removed from this Figure. FIG. 8 shows the marking mechanism in its normal locked position. The brake shoes  60  are forced inwards by a spring  62 . The brake shoes  60  contact the wheel  50  and the frictional force exerted prevents the wheels from turning. Each brake shoe  60  prevents the wheel  50  from turning in a particular direction. When the wheel  50  rotates in the clockwise direction, the brake shoe  60  on the right acts to stop the motion of the wheel  50 . When the wheel  50  rotates in the counterclockwise direction, the brake shoe  60  on the left engages the wheel  50 . 
     Referring again to FIG. 8, it can be seen that the brake shoes  60  are directed in their travel by guide pins  64 . A guide pin bracket is attached to the mounting plate  54  of the cater  30 . This bracket is used to support both the guide pins  64  and the brake shoe  60 . Attached to the brake shoe  60  is a slide  65 . The slide  65  is fixed to the brake shoe  60 . It bears against the mounting plate  54  as the brake shoe  60  travels in and out. An exploded perspective view of the brake shoe, the guide pin and the slide are shown in FIG.  10 . 
     FIG. 8 also illustrates an end view of the mounting rod  32 . Attached to the mounting rod is a separation cam  70 . The separation cam  7  attaches to the mounting pins  44  which were described above with respect to FIG.  4 . It is to be understood that the mounting rod  32  and separation cam  70  are not a part of the caster  30 . The separation cams  70  are used to unlock the brake shoes  60  from their normally locked position. 
     The operation of the mounting cam  70  is best illustrated in FIG.  9 . FIG. 9 is a cross sectional view of the caster  30  taken along the line A—A in FIG.  6 . Unlike FIG. 8, FIG. 9 shows the brake mechanism in the unlocked position. In this Figure, the separation cam  70  has been rotated through approximately ninety degrees. The edges of the cam  70  contact the brake shoes  60 . This forces the brake shoes  60  apart and away from the wheels  50 , thereby allowing the wheels  50  to rotate freely. 
     The operation of the brake mechanism of the present invention is, as indicated above, quite simple. In a normal resting situation, the brake shoes  60  are forced into the wheel&#39;s  50 , causing the wheels  50  to be locked in place, and thereby preventing movement of the cart. When it is desired to move the cart, the moveable handle  40  is depressed. This causes the cable  40  which is attached to the handle to pull against the pull arm cam  34 . The pull arm cam  34  in turn rotates the brake rod  32 . The separation cam  70  is fixed to the brake rod  32 . The separation cam  70  also turns, thereby forcing the brake shoes  60  apart, and away from the wheels. The cart  10  is then free to move. When the movable handle  40  is released, the springs  62  force the brake shoes  60  against the wheels  50 . This locks the wheels  50  in place, and prevents movement of the cart  10 .