Abstract: A castor includes a castor body, an operation unit, a locking unit, and two rollers. The operation unit includes a pressing plate and a rotation member. The locking unit includes a locking module, a stop ring, a locating member, and an upper positioning plate. The locking module has a locking member and a braking member. When the driving portion of the rotation member presses the first ramp of the pressing plate, the locating member is locked in the locking hole of the upper positioning plate. When the driving portion presses the second ramp of the pressing plate, the first engaging portion of the locking member engages the first locking portion of the stop ring, while the second engaging portion of the braking member engages the second locking portion of each of the rollers.

Abstract: A castor includes a castor body, a waterproof gasket, a bearing, a top cover, a shaft, a bushing, a washer, and a snap ring. The castor body has a receiving recess to receive the waterproof gasket and the bearing. The top cover is mounted on the castor body to cover the waterproof gasket and the bearing. The waterproof gasket is located between the castor body and the bearing and has a sealing flange. Thus, the sealing flange of the waterproof gasket is disposed between the top cover and the castor body to isolate the bearing completely, so that even when the castor touches water unintentionally, the water cannot contact the bearing, thereby preventing the bearing from being rusted or worn out so as to enhance the lifetime of the bearing of the castor.

Abstract: A protective device for a castor includes a mounting ring, and a driving piece secured on the mounting ring. The mounting ring has an outer periphery formed with a breakable portion which is located beside the driving piece. The driving piece has a first end extending from the mounting ring and a second end formed with a pull tab. When the mounting ring is released by tearing the breakable portion, the mounting ring is directly driven by the driving piece to remove from each of the two rollers of the castor. Thus, the user only needs to apply a single action to pull the pull tab of the driving piece so as to remove the protective device from the castor completely so that the protective device can be removed from the castor easily and quickly.

Abstract: A lifting device for a chair includes an upright support post, a tapered locking sleeve adjustably mounted on the support post, a tapered pressing sleeve mounted on the locking sleeve, a stepping ring having a mounting tube which is mounted on the pressing sleeve, and a dustproof cover abutting a top of the mounting tube of the stepping ring and secured on a top of the pressing sleeve. Thus, the pressing sleeve surrounds the locking sleeve to distribute the pressing force evenly, and the locking sleeve surrounds the support post to distribute the pressing force evenly so as to prevent the pressing sleeve and the locking sleeve from being worn out or broken due to a stress concentration and to enhance the lifetime of the lifting device.

Abstract: A castor includes a castor body, a first bushing mounted on a top of the castor body, a bearing mounted in the first bushing, a top cover mounted on the top of the castor body to cover the first bushing and the bearing, a second bushing mounted on a bottom of the castor body, and an upright shaft in turn extending through the top cover, the bearing, the castor body and the second bushing. Thus, the distance between the top cover and the second bushing is increased so that the bearing and the castor body can bear a heavier load. In addition, the distance between the top cover and the second bushing is increased so that the upright shaft and the second bushing can bear a greater rotational force.

Abstract: A protective device for a castor includes a mounting ring, and a driving piece secured on the mounting ring. The mounting ring has an outer periphery formed with a breakable portion which is located beside the driving piece. The driving piece has a first end extending from the mounting ring and a second end formed with a pull tab. When the mounting ring is released by tearing the breakable portion, the mounting ring is directly driven by the driving piece to remove from each of the two rollers of the castor. Thus, the user only needs to apply a single action to pull the pull tab of the driving piece so as to remove the protective device from the castor completely so that the protective device can be removed from the castor easily and quickly.

Abstract: A lifting device for the backrest of a chair includes a fixed member, a movable member movably mounted on the fixed member and having an elongate slideway and a plurality of locking grooves, a locking bolt extending into the slideway of the movable member and detachably locked in one of the locking grooves of the movable member, a slide secured on the locking bolt to move the locking bolt, and an elastic member biased between the slide and the fixed member to push the locking bolt toward one of the locking grooves. Thus, the movable member is moved relative to the fixed member to adjust the height of the backrest so that the height of the backrest can be adjusted according to a user's requirement, and the backrest can support the user's back efficiently.

Abstract: An armrest assembly for a chair includes an armrest support, a mounting sleeve movably mounted on the armrest support, an armrest mounted on the mounting sleeve to move in concert with the mounting sleeve, and a lifting device mounted between the armrest support and the mounting sleeve and operable between a first position where the lifting device is locked to lock the mounting sleeve onto the armrest support and a second position where the lifting device is unlocked to unlock the mounting sleeve from the armrest support so that the mounting sleeve is movable relative to the armrest support freely. Thus, the mounting sleeve is movable relative to the armrest support so as to adjust the height of the armrest so that the height of the armrest is adjusted freely to support a user's arm comfortably.

Abstract: An armrest assembly for a chair includes an armrest support, a mounting sleeve mounted on the armrest support, an armrest mounted on the mounting sleeve, and a lifting device mounted between the armrest support and the mounting sleeve to lock or unlock the mounting sleeve onto or from the armrest support. Thus, the mounting sleeve is movable relative to the armrest support so as to adjust the height of the armrest so that the height of the armrest can be adjusted freely to support a user's arm comfortably. In addition, a user only needs to pull the armrest upward to adjust the height of the armrest so that the user can adjust the height of the armrest easily and quickly in an energy-saving manner.

Abstract: An armrest assembly includes a mounting bracket, a limit member mounted on the mounting bracket, and an armrest support mounted on the limit member. The bottom of the mounting bracket is provided with a slideway which has a first side provided with an upright limit face and a second side provided with an oblique limit face. The limit member has a first side provided with an upright mating face abutting the upright limit face and a second side provided with an oblique mating face abutting the oblique limit face. Thus, the upright mating face and the oblique mating face are limited by the upright limit face and the oblique limit face respectively, so that the limit member is moved in the slideway smoothly and stably without producing any vibration to facilitate movement of the armrest support relative to the mounting bracket.

Abstract: An armrest assembly for a chair includes an armrest support, a mounting sleeve mounted on the armrest support, an armrest mounted on the mounting sleeve, and a lifting device mounted between the armrest support and the mounting sleeve to lock or unlock the mounting sleeve onto or from the armrest support. Thus, the mounting sleeve is movable relative to the armrest support so as to adjust the height of the armrest so that the height of the armrest can be adjusted freely to support a user's arm comfortably. In addition, a user only needs to pull the armrest upward to adjust the height of the armrest so that the user can adjust the height of the armrest easily and quickly in an energy-saving manner.

Abstract: A castor assembly includes an upright support shaft, a leg mounted on the support shaft and a pressing sleeve mounted between the upper end of the support shaft and the leg. The upper end of the support shaft has a retaining groove. The pressing sleeve has an inner wall provided with an inner flange retained in the retaining groove of the support shaft and an outer wall provided with an outer flange. The leg has an end portion provided with a receiving space pressing the outer flange of the pressing sleeve. Thus, the support shaft is combined with the leg by the pressing sleeve to prevent from defining a gap between the support shaft and the leg so that the support shaft will not hit the leg so as to prevent from producing noise or vibration.

Abstract: A lifting device for a chair includes an upright support post, a tapered locking sleeve adjustably mounted on the support post, a tapered pressing sleeve mounted on the locking sleeve, a stepping ring having a mounting tube which is mounted on the pressing sleeve, and a dustproof cover abutting a top of the mounting tube of the stepping ring and secured on a top of the pressing sleeve. Thus, the pressing sleeve surrounds the locking sleeve to distribute the pressing force evenly, and the locking sleeve surrounds the support post to distribute the pressing force evenly so as to prevent the pressing sleeve and the locking sleeve from being worn out or broken due to a stress concentration and to enhance the lifetime of the lifting device.

Abstract: An armrest assembly for a chair includes an armrest support, a mounting sleeve movably mounted on the armrest support, an armrest mounted on the mounting sleeve to move in concert with the mounting sleeve, and a lifting device mounted between the armrest support and the mounting sleeve and operable between a first position where the lifting device is locked to lock the mounting sleeve onto the armrest support and a second position where the lifting device is unlocked to unlock the mounting sleeve from the armrest support so that the mounting sleeve is movable relative to the armrest support freely. Thus, the mounting sleeve is movable relative to the armrest support so as to adjust the height of the armrest so that the height of the armrest is adjusted freely to support a user's arm comfortably.

Abstract: A castor assembly includes a castor body, a threaded rod rotatably mounted on the castor body, a lower adjusting cover surrounding the threaded rod to cover the threaded rod and secured on the threaded rod to rotate the threaded rod relative to the castor body, an upper adjusting cover surrounding the threaded rod to cover the threaded rod and retractably mounted on the lower adjusting cover, and an elastic member mounted on the threaded rod and biased between the threaded rod and the upper adjusting cover to push the upper adjusting cover outwardly relative to the lower adjusting cover. Thus, the threaded rod is covered by the lower adjusting cover and the upper adjusting cover to enhance the aesthetic quality of the castor assembly.

Abstract: A castor includes a dustproof cover, a support shaft detachably mounted on the dustproof cover and two rollers mounted on the support shaft respectively and received in the dustproof cover respectively. The dustproof cover has an inner portion provided with a support post. The support post has a lower end provided with an arcuate locking recess detachably locked onto the support shaft. Thus, each of the rollers is encompassed by the dustproof cover completely so that the dustproof cover can isolate the rollers to prevent hairs, dirt or dusts from entering the rollers easily. In addition, the support shaft can be detached from the dustproof cover so that the support shaft and the rollers can be removed from the dustproof cover to facilitate the user clearing dirt, dusts or hairs accumulated in the dustproof cover and the rollers.

Abstract: An armrest assembly includes a mounting bracket, a limit member mounted on the mounting bracket, and an armrest support mounted on the limit member. The bottom of the mounting bracket is provided with a slideway which has a first side provided with an upright limit face and a second side provided with an oblique limit face. The limit member has a first side provided with an upright mating face abutting the upright limit face and a second side provided with an oblique mating face abutting the oblique limit face. Thus, the upright mating face and the oblique mating face are limited by the upright limit face and the oblique limit face respectively, so that the limit member is moved in the slideway smoothly and stably without producing any vibration to facilitate movement of the armrest support relative to the mounting bracket.