1) Field of the Invention
The invention is related to a caster structure, which utilizes a clip element to transversally move two brake elements and to function as a brake with respect to the wheel and the vertical shaft.
2) Description of the Prior Art
As known, for convenient movement, the legs on the bottom of an office chair are casters and are made of plastic material. The general caster is to vertically insert a pin in the wheel base of the caster. By fixing the upper shafts to the bottom ends of the chair legs, the wheel bases are allowed to rotate with respect to the shafts and the chair legs. Thus, the rotation of a wheel body is advantageous to chair movement and the chair functions with brake and rotation constraint. Most of such casters equip a brake device on one side of the wheel body. By pushing the brake device downward, the brake device inside a control wheel base functions as a brake with respect to the inner wheel inside a wheel body and the wheel stops rotation.
The prior caster utilizes a function of pushing brake device downward to stop the brake body inside a wheel base with respect to the wheel. The state of caster braking achieves the objective of fixing chair position with no movement, however, the wheel base can be rotated with respect to the shaft and the movement direction can not be controlled. When the contact condition of the wheel and the ground is not good and minor movement is allowed, the device with the casters can be easily moved and makes the casters further move to certain direction. Also, occasionally, the rotation direction for the casters can not be controlled and the extruded wheel base becomes the obstacle on the ground.
Under the above considerations, the prior caster can not simultaneously function braking and rotation direction fixture. Also, further improvement is needed for the design. On the basis of thorough research and detailed planing with constantly improvement, the inventor finally developed the invention.
The primary objective of the invention is to provide a caster structure functioning brake and rotation constraint. It is to utilize a single clip element transversally moving two brake elements and to simultaneously function positioning with respect to the wheel and the vertical shaft. The wheel is braked and the wheel base can not be rotated. The characteristics of the main structure are described as follows:
The wheel base is in a semi-circular shape, of which the horizontal bottom interior forms a horizontal container groove. One end of the container groove extends upward to form a groove, which joins a vertical shaft opening for the penetration of a shaft. With respect to the groove on the container groove, the vertical shaft opening extends upward to form an opening. Thus, the shaft with respect to the opening forms a convex ring with a positioning groove. One end of the opening is connected with a clip element. The connecting portion of the clip element equips a long-end and a short-end with respect to the connecting portion center. Inside the container groove is a transversal slide base. One end of the slide base constantly hits the connecting portion of the clip element by the push of a spring element. The lower contact portion forms a bevel angle, which is advantageous to the rotation of the connecting portion of the clip element. On the other end, a fixture pin passes through a slot of the wheel base, thus, the pin extrudes outward to reach the ditch of the wheel. On the end, a clip block is inserted. The block hits the end of the slide base by the push of a spring and transversally moves together with the slide base to the positioning groove of a convex ring on the shaft of the opening. When the clip element is pushed for dual-brake, the connecting portion rotates and pushes the slide base against a spring from the long-end and makes a fixture pin in the ditch of the wheel. By the push of a spring, the clip block moves together with the slide base to the positioning groove of a convex ring on the shaft and no rotation is allowed for the wheel base.