Patent GB-214268-A (GB)
Title: Improvements in astatic apparatus for use as cushioning means, suspension means, power accumulation and the like
IPC: F16F9/02
Filed: 1924-04-11
Abstract: 214,268. Martin, E. April 13, 1923, [Convention date]. Void [Published under Sect. 91 of the Act]. Pneumatic springs.-In an astatic apparatus for use as cushioning or suspension means or for power accumulation &c., and comprising a piston and cylinder or an extensible and collapsable device of the bellows type, atmosphere pressure acts as the principal resistance so that the resistance is practically constant at all points of the stroke. As shown in Fig. 1, the apparatus comprises a cylinder 1 in which moves a piston 2 with a rod 3 passing through the cylinder cover 4 and provided with leather or other packing 5 to ensure tightness. The space between the piston and the bottom of the cylinder is permanently exhausted of air thrugh an orifice 6 which is then closed. The cover 4 has an orifice 8 to allow atmosphere, pressure to act freely on the top of the piston and provide a constant resistance to withdrawal of the piston-rod. In a modification, the cylinder contains two oppositely arranged pistons with rods passing through end covers, the space between the covers being evacuated. The apparatus may be arranged to resist compression instead of extension by suitable selection of the evacuated space. Two or more piston and cylinder units of the same or unequal dimensions may be combined. Thus the rod of a larger piston 11 may have an arm passing through a slot in the rod of a smaller piston which comes into action only when the rod of the larger piston has been withdrawn through a certain distance; or as shown in Fig. 7, the end of a piston-rod of a cylinder 1 engages a slot 16 in a lever 15 pivoted at 17 to a frame which carries the cylinder 1 and has guides 19 on which slides a smaller cylinder 1<1>. The pistonrod 3<1> of the cylinder 1<1> is forked to surround the lever 15 and is provided with a roller 18. When the piston-rod 3<1> is on the line c-d, the smaller piston has no action, and the farther the cylinder 1<1> is moved to the left, the greater becomes the action of the main piston in increasing the resistance to raising the end 7 of the main piston-rod. A helical spring may be arranged to surround the rod 3, Fig. 1, the piston 2 and the cover 4 to add a progressive resistance to the constant-resistance of the piston. The evacuated chamber may be constituted by a container made of a flexible impervious material 9, Fig. 2, such as leather, india-rubber, or metal foil, connected to two plates 10, rigid rings 11 being arranged within the container to cause regular collapsing when the container returns to its original length after being extended. The surface of the plates 10 determines the resistance to elongation of the container. The apparatus may be employed alone, with similar apparatus, or with apparatus of other type, and for various purposes such as the suspension of vehicles, as a power accumulator for automatic mechanism clockwork games &c., the effort necessary for the withdrawal of the piston-rod 3, Fig. 1, serving to balance a body suspended from the end of the cylinder 1, thus constituting a system in neutral equilibrium.