Linear Actuator

Abstract

A linear actuator, in particular telescopic legs for height-adjustable tables, and comprising an outer profile ( 18 ), a spindle ( 7 ) mounted at an upper end of the outer profile, a transmission ( 8 ) connecting the spindle ( 7 ) with a reversible electric motor, a spindle nut ( 11 ) secured against rotation on the spindle ( 7 ), an intermediate profile ( 10 ) mounted with its one end on the spindle nut ( 11 ), a guide at a lower end of the outer profile ( 18 ) for the intermediate profile ( 10 ), a cord element ( 12, 20; 26 ) secured at the lower end of the outer profile ( 18 ) and connected via a guide with an inner profile ( 14 ), such that this together with the intermediate profile ( 10 ) is telescopically pushed out of and into the outer profile ( 18 ) by the rotation of the spindle. When the inner profile ( 14 ) is secured against rotation on the intermediate profile ( 10 ), and the rotational securing of the spindle nut ( 11 ) is constituted by longitudinal guides in the outer profile ( 18 ), then an actuator is achieved which per se is secured against rotation, i.e. when applied in telescopic legs, there is no need to have a rotational protection via the leg. In general, the structure is slender and may thereby be used in thin telescopic table legs.

1 . A linear actuator comprising an outer profile ( 18 ), a spindle ( 7 ) mounted at an upper end of the outer profile, a transmission ( 8 ) connecting the spindle ( 7 ) with a reversible electric motor, a spindle nut ( 11 ) secured against rotation on the spindle ( 7 ), an intermediate profile ( 10 ) mounted with its one end on the spindle nut ( 11 ), a guide at a lower end of the outer profile ( 18 ) for the intermediate profile ( 10 ), a cord element ( 12 ,  20 ;  26 ) secured at the lower end of the outer profile ( 18 ) and connected via a guide with an inner profile ( 14 ) so that this together with the intermediate profile is telescopically pushed out of and into the outer profile ( 18 ) by the rotation of the spindle, wherein the inner profile ( 14 ) is secured against rotation on the intermediate profile ( 10 ), and the rotational securing of the spindle nut ( 11 ) is constituted by longitudinal guides in the outer profile ( 18 ), so that the spindle nut with the intermediate profile ( 14 ) moves on the spindle ( 7 ) by the rotation thereof. 
     
     
         2 . A linear actuator according to  claim 1 , wherein the cord element is a chain ( 12 ). 
     
     
         3 . A linear actuator according to  claim 1 , wherein a curve-shaped piece ( 13 ) is secured to the lower end of the intermediate profile ( 10 ) as a guide for the chain. 
     
     
         4 . A linear actuator according to  claim 1 , wherein the inner profile ( 14 ) and the intermediate profile ( 10 ) are configured with mutual means for guiding the inner profile ( 14 ) on the intermediate profile ( 10 ). 
     
     
         5 . A linear actuator according to  claim 1 , wherein a rod is secured to the end of the intermediate profile ( 10 ) where the chain is secured, said rod being guided on the pipe. 
     
     
         6 . A linear actuator according to  claim 1 , wherein the intermediate profile ( 10 ) and the outer profile ( 18 ) are pipes of circular cross-section. 
     
     
         7 . A linear actuator according to  claim 1 , wherein longitudinal ribs ( 35 ) are provided internally in the outer profile ( 18 ), said ribs being fitted in grooves ( 22 ) in the spindle nut ( 11 ) for securing it against rotation. 
     
     
         8 . A linear actuator according to  claim 1 , wherein at the lower end of the outer profile ( 18 ) there is an end plug ( 23 ) having a through and guide hole for the intermediate profile ( 10 ), and there is also a through opening for the inner profile ( 14 ). 
     
     
         9 . A linear actuator according to  claim 1 , wherein the inner profile ( 14 ) is guided on the side of the intermediate profile ( 10 ) with a longitudinal T-shaped guide fin ( 23 ) thereon, and which is received in a corresponding groove ( 24 ) in the inner profile ( 14 ), and which simultaneously secures it against rotation. 
     
     
         10 . A linear actuator according to  claim 1 , wherein a cylindrical plug ( 25 ) is secured on the lower end of the intermediate pipe ( 10 ), said cylindrical plug having a through and guide hole for the inner profile ( 14 ) which has a substantially quadrangular cross-section. 
     
     
         11 . A linear actuator according to  claim 1 , wherein the inner profile ( 14 ) is moved by a wire having two runs ( 26   a ,  26   b ) extending opposite each other on the intermediate profile ( 10 ). 
     
     
         12 . A linear actuator according to  claim 11 , wherein at the top the wire runs around a pair of deflection wheels ( 27 ) mounted in the spindle nut ( 11 ), and at the bottom the wire runs around another pair of deflection wheels ( 28 ) mounted in the plug ( 25 ) on the end of the inner profile ( 14 ). 
     
     
         13 . A linear actuator according to  claim 11 , wherein the wire is additionally moved around upper and lower guide faces ( 29   a ,  29   b ) in an end plug ( 29 ) secured at the upper end of the inner profile ( 14 ). 
     
     
         14 . A linear actuator according to  claim 1 , wherein the end plug ( 23 ) on the outer profile ( 18 ) is configured as a wire tensioner. 
     
     
         15 . A linear actuator according to  claim 14 , wherein the end plug consists of two parts ( 23   a ,  23   b ), one part ( 23   a ) of which is provided with legs ( 30 ) provided with barbs, and the other part ( 23   b ) of which is provided with slots ( 31 ) for receiving the legs of the first part ( 23   a ), and the side walls of the slots ( 31 ) are likewise provided with barbs for cooperation with the barbs of the legs ( 30 ). 
     
     
         16 . A linear actuator according to  claim 15 , wherein the side walls of the slots ( 31 ) are configured to protrude freely upwards and resiliently toward each other for firm engagement with the legs of the part ( 23   a ). 
     
     
         17 . A linear actuator according to  claim 1 , wherein an outermost section ( 1 ) in a telescopic leg is secured to the motor housing, while an intermediate section ( 2 ) is secured to the spindle nut ( 11 ) by screws through diametrically disposed longitudinal slots ( 34 ) in the outer profile ( 18 ), while an innermost section ( 3 ) is secured to the plug ( 25 ) at the end of the intermediate profile ( 10 ). 
     
     
         18 . A linear actuator according to  claim 1 , wherein a bracket ( 21 ) for securing a telescopic leg is secured to the free end of the inner profile ( 14 ), and a skid coupling is integrated in the bracket between the part which is to be secured to the inner profile ( 14 ) and the part which is to be secured to the telescopic leg. 
     
     
         19 . A linear actuator according to  claim 18 , wherein the skid coupling comprises a first part ( 21   a ) and a second part ( 21   b ) configured with bosses and a wave-shaped wall, respectively, said bosses engaging and being capable of yielding resiliently to each other. 
     
     
         20 . A linear actuator according to  claim 19 , wherein the first part is a circular disc, where the bosses ( 36 ) are provided on the outer side, and this part ( 21   a ) is received in a circular well ( 38 ) at the end of the second part ( 21   a ), where the wave shape is provided in the side wall of the well ( 38 ). 
     
     
         21 . A linear actuator according to  claim 20 , wherein the bosses ( 36 ) are provided on a resilient portion of the circular disc. 
     
     
         22 . A linear actuator according to  claim 21 , wherein the first part ( 21   a ) is centered in the second part with a hole ( 41 ) around a hub ( 42 ) in the second part ( 21   b ).