GB826314A - Artificial legs - Google Patents

Abstract

826,314. Dashpots. MAUCH, H. A. Nov. 5, 1957 [Nov. 5, 1956], No. 34520/57. Class 108(3) [Also in Group VI] A dashpot connected between the shank and thigh of an artificial leg includes a fluid containing housing and means for displacing the fluid in the housing through channels in the housing wall, the channels being so arranged that there is graduated resistance to flow of fluid caused by the displacing means. The hollow shank 2 is connected directly to the thigh 1 by a bolt 4 and through a dashpot 7 to a pivot pin 8 in the thigh 1 parallel to, and ahead of or behind the bolt 4. The dashpot 7 includes a cylinder 10 partially filled with liquid and pivotally connected to a bracket 9 in the shank 2. A housing 16 filled with the same liquid is contained within and spaced from the cylinder 10. A piston rod 38 is connected to the pivot pin 8 and carries pistons 40, 39 movable within the housing 16 and the cylinder 10 respectively. A bushing 26 within the housing 16 has holes 47, 48 towards each end, channels 49, 50 in the bushing wall connecting the holes 47, 48 with chambers 33, 25 at opposite ends of the bushing 26 respectively. Seals 37, 24 separate the chambers 33, 25 from the housing interior, the seals 37, 24 being deformable to allow fluid to flow in one direction only from the chambers 33, 25 into the housing. The housing 16 is closed by a cover 30 having an aperture for the passage of the piston rod 38 and threaded into the housing 16 above the bushing 26. The upper part of the bushing 26 is also threaded in the housing 16. The chambers 33, 25 are formed between the bushing 26 and the cover 30 and the bottom of the housing 16 respectively, the size of each chamber being adjustable by screwing the cover and/or the bushing into the housing by varying amounts. As the knee is flexed the piston rod 38 and pistons 39, 40 move downwardly relative to the cylinder 10 and the housing 16. Liquid in the cylinder 10 passes through apertures 45 in the cylinder piston 39. The housing piston 40 pushes liquid below it through holes 47 in the lower part of the bushing whence it flows upwardly through channels 49 into the chamber 33 and past the upper seal 37 into the housing above the piston 40. The holes are so arranged that the piston 40 passes them progressively in its downward travel so that the number of holes 47 open to the liquid decreases and thus the movement of the piston is increasingly damped as the knee approaches full flexion. Similarly, as the piston 40 is raised, its movement is increasingly damped as the knee approaches full extension, the holes 48 in the upper part of the housing being progressively passed by the piston 40. A relief vent 19 is provided between the housing 16 and the cylinder 10.