2. Description of the Related Art One braking mechanism which is known in the prior art is described in United States Patent No. 3,710, 895. The device in the'895 patent describes a brake an retention system which can be used with a 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 Figure A is a perspective view of a wheeled cart of the type which might employ the cart-brake mechanism of the present invention.

Figure 1 is perspective view of a pair of wheeled casters connected by an axle which employs the cart-brake mechanism of the present invention.

Figure 2 is a front view of the caster and brake rod assembly used in the present invention.

Figure 3 is a bottom view of the caster and brake rod assembly used in the present invention.

Figure 4 is a detailed perspective view of brake rod assembly used in the present invention.

Figure 5 is a perspective view of one of the casters.

Figure 6 is a front view of one of the casters.

Figure 7 is a side view of one of the casters.

Figure 8 is a cross sectional view of the caster taken along the line A-A in Figure 6, showing the brake shoes in the locked position.

Figure 9 is a cross sectional view of the caster taken along the line A-A in Figure 6, showing the brake shoes in the unlocked position.

Figure 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 Figure 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. These casters 30 are mounted on the bottom of the cart (not shown in Figure 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 32coupled 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 34. The pull arm 34 is rigidly fixed to the brake rod 32.

Although Figure 1 illustrates a specific position for the pull arm 34, it will be apparent to those skilled in the art that the pull arm 34 can be placed at any position along the length of the brake rod with equal effectiveness.

Attached to the pull arm 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 moveable handle 22 is depressed, the cable 40 pulls on the pull arm 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 Figures 8 and 9.

Referring next to Figure 2, a front view of the casters 30 and brake rod 32 is shown. Figure 3 is a bottom view of the

same assembly. Figures 2 and 3 more clearly illustrate the relationship between the casters 30 and the brake rod 32.

A detailed view of the pull arm 34 and brake rod 32 is shown in Figure 4. As can be seen, the pull arm 34 is a thin member which is generally in the shape of a circle. The outer periphery of the pull arm 34 is curved. The curved edge has a narrow slot 37 formed into its edge. This slot is best shown in Figures 2 and 3. Also formed into the pull arm 34 is an aperture 36. The aperture 36 allows the cable 40 (not shown in Figure 4) to anchor to the pull arm 34. The curved edge 35 of the pull arm 34 is provided so that rotation of the brake rod 32 smoothly takes up the cable 40. The pull arm 34 has attached to it a sleeve 38, and a threaded nut is placed within the sleeve 38 to rigidly attach the pull arm 34 to the brake rod 32.

Referring again to Figure 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 Figures 8 and 9.

Referring next to Figures 5,6 and 7 further details of the casters 30 which are used in connection with the present invention are shown. Figure 5 is a perspective view of a caster 30. Figures 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 Figures 8 and 9.

Figure 8 is a cross sectional view of the caster 20 taken along the line A-A in Figure 6. For the purposes of simplicity, the representation of the support arms have been removed from this Figure. Figure 8 shows the braking mechanism in its normal locked position. The brake shoes 60 are forced inwards by the 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 rotates in the clockwise direction, the brake shoe on the right acts to stop the motion of the wheel. When the wheel rotates in the counterclockwise direction, the brake shoe on the left engages the wheel.

Referring again to Figure 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 caster.

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 is fixed to the brake shoe 60. It bears against the mounting plate 54 as the brake shoe travels in and out. An exploded perspective view of the brake shoe, the guide pin and the slide are shown in Figure 10.

Figure 8 also illustrates an end view of the mounting rod 32. Attached to the mounting rod is a separation cam 70. The separation cam attaches to the mounting pins 44 which were described above with respect to Figure 4. It is to be understood that the mounting rod 32 and separation cam 70 are not a part of the caster 20. The separation cams are used to unlock the brake shoes 60 from their normally locked position.

The operation of the mounting cam 70 is best illustrated in Figure 9. Figure 9 is a cross sectional view of the caster 20

taken along the line A-A in Figure 6. Unlike Figure 8, Figure 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 apart and away from the wheels, thereby allowing the wheels 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 wheels 50, causing the wheels to be locked in place, and thereby preventing movement of the cart. When it is desired to move the cart, the moveable handle 22 is depressed. This causes the cable 40 which is attached to the handle to pull against the pull arm 34. The pull arm in turn rotates the brake rod 32.

The separation cam 70 is fixed to the brake rod. The separation cam 70 also turns, thereby forcing the brake shoes apart, and away from the wheels. The cart is then free to move. When the moveable handle is released, then springs force the brake shoes against the wheels. This locks the wheels in place, and prevents movement of the cart.