Shielded castor with spring

A castor, which can efficiently absorb shock and the ball wheel of which can be alternatively received in or protruding beyond a cup-like shield thereof for positioning or moving. The caster comprises a sleeve which is secured to a hoop on the frame of a baby-walker for receiving a spring and a central shaft which comprises a ball wheel on the bottom. The sleeve comprises a Z-shaped track on its wall surface for the sliding and positioning therein of a lateral guide which is inserted therethrough and secured to the central shaft. A cup-like shield is secured to the bottom end of the sleeve to protect the ball wheel.

BACKGROUND OF THE INVENTION 
The present invention is related to castors and more particularly to a 
castor for baby-walker and other movable objects. 
Regular baby-walkers are generally fastened with fixed rollers or castors 
for moving. The rigid structure of the rollers or castors can not provide 
any shock absorbing effect. Therefore, a baby may be easily hurt while 
learning to walk by means of a baby-walker. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a castor for baby-walker 
and other movably objects which includes a suspension system to absorb 
shock so that the ball wheel thereof can be smoothly and stably move along 
the surface of the ground. 
Another object of the present invention is to provide a castor which 
includes a spring specially designed to permit the ball wheel thereof to 
be automatically received inside a cup-like shield so that the movable 
objects can stand firmly on the ground when a baby sits down, and to 
permit the ball wheel thereof to be automatically protruding beyond for 
rolling so that the movable objects can be moved along the ground when a 
baby stands up. 
Still another object of the present invention is to provide such a castor 
for baby-walker, in which the ball wheel can be fixedly received in a 
cup-like shield permitting the positioning of a baby-walker on the ground, 
or fixedly set to protrude beyond a cup-like shield permitting the moving 
of a baby-walker on the ground.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIGS. 1 and 2, a castor in accordance with the present 
invention is generally comprised of a a vertical sleeve 1, a circular 
steel hoop 2, a cup-like shield 3, a central shaft 4, a spring 5, an 
universal knuckle 6 and a ball wheel 7. The sleeve 1 comprised a 
substantially Z-shaped track 11 which includes an upper, leftward branch 
track 110 and a lower, rightward branch track 111, an internal flange 10 
in the bottom for supporting the central shaft 4, and an external flange 
12 on the top for securing to a bottom plate 20 of the circular hoop 2 by 
means of four screws 13, 14, 15 and 16. The circular hoop 2 is fixedly 
secured to the frame 8 of a baby-walker by mean of a lock screw 21. The 
cup-like shield 3 is secured to the bottom end of the sleeve 1 by means of 
screw joint permitting the central shaft 4 to move vertically 
therethrough. A rubber cushion 31 is mounted on the circular bottom edge 
of the cup-like shield 3 to strengthen its friction against the ground. 
The spring 5 and the central shaft 4 are set in the boring bore of the 
sleeve 1 permitting the top end of the spring 5 to stop against the bottom 
surface of the bottom plate 20 of the circular steel hoop 2 and the bottom 
end of the spring 5 to stop against the collar 41 of the central shaft 4. 
The central shaft 4 comprises a bolt hole in its upper end beneath its 
collar 41 for the fastening therein of a lateral guide 42 which is 
inserted through the Z-shaped track 11 of the sleeve with its one end 
exposed out of the sleeve 1 to control the moving range of the central 
shaft 4 within the Z-shaped track 11. The central shaft 4 partly extends 
out of the sleeve 1 inside the cup-like shield 3 for the connection 
thereto of the universal knuckle 6 and the ball wheel 7. 
The operation of the present invention is outlined hereinafter. When a baby 
is sitting in a baby-walker according to the present invention, the 
downward pressure of the body weight of the baby forces the ball wheel 7 
of the castor to retreat in the cup-like shield 3 permitting the rubber 
cushion 31 of the cup-like shield 3 to contact the ground. Under this 
condition, the lateral guide 42 is moved to the upper limit position in 
the Z-shaped track 11 and the spring 5 is squeezed to compress on the 
central shaft 4 (see FIGS. 1 and 2). As soon as the baby stands up, the 
central shaft 4 of the castor of the baby-walker is immediately forced by 
the spring 5 to extend downward permitting the ball wheel 7 to protrude 
beyond the cup-like shield 3 (see FIGS. 3 and 4). Under this condition, 
the lateral guide 42 is moved to the lower limit position in the Z-shaped 
track. By means of the effect of the spring 5, the ball wheel 7 is 
permitted to float within the range of the Z-shaped track 11. Therefore, 
the ball wheel 7 can be smoothly moving along the surface of the ground 
while the baby is walking in the baby-walker, and the spring 5 serves as a 
suspension system to reduce the vibration of the baby-walker. When the 
baby is sitting down, the friction effect of the rubber cushion 31 
stabilizes the positioning of the baby-walker on the ground. 
The lateral guide 42 may be move upward to set in the upper circular hole 
112 of the upper branch track 110 so that the ball wheel 7 can be 
constantly and completely received inside the cup-like shield 3, or the 
lateral guide 42 may be moved downward to set in the lower circular hole 
113 of the lower branch track 111 to let the ball wheel 7 constantly 
protrude beyond the cup-like shield 3 so that the baby-walker can be 
freely moved to steer. The arrangement of the upper circular hole 112 and 
the lower circular hole 113 is for the positioning of the lateral guide 42 
in the upper branch track 110 or lower branch track 111 to protect the 
lateral guide 42 from breaking away. 
As indicated above, the present invention is to provide such a design of 
castor which is practical for use in a baby-walker to ensure maximum 
safety. The present invention can also be used as a castor for chairs, 
blocks, ladders or some other moving objects. 
As foregoing statement, the present invention may be variously embodied. 
Recognizing various modification been apparent, the scope herein shall be 
deemed as defined in the claims set forth hereinafter.