Shock absorber having nonadjustable metering

A nonadjustable shock absorber for soft contact deceleration of a shock load including, a low pressure zone (44), a hydraulic cylinder (10) having a high pressure zone chamber (12), a piston (20) in said cylinder (10) for movement under a shock load through a predetermined total stroke length from an initial position to a final position therein, and fluid pathway metering control means for controlling high pressure fluid escaping from the high pressure zone chamber (12), into the low pressure zone (44), ahead of the piston (20), as the piston (20) moves from the initial position in response to a shock load, said fluid pathway metering control means serving to control the high pressure fluid escape rate as a function of piston displacement from the initial position, wherein the improvement comprises:

• (a) said fluid pathway metering control means comprises four fluid metering pathways, of which the first three fluid metering pathways are approximately linear spaced apart, each having a predetermined area, and which operate to successively restrict the amount of high pressure fluid escaping from the high pressure zone chamber (12), and the area of each of the four spaced apart fluid metering pathways being closed off at a first, a second, a third and a fourth transition point as the piston moves from the initial position through its predetermined total stroke to its final position to create a number one, two, three, four and five control zones and to provide a triangular shaped force profile during the compression of the shock absorber;
• (b) said number one control zone, extending from the initial position of said piston to said first transition point, and having a length of from 23 percent to 26 percent of the total length of the piston stroke;
• (c) said number two control zone, extending from the first transition point to the second transition point, and having a length of from 23 to 26 percent of the total length of the piston stroke;
• (d) said number three control one, extending from the second transition point to the third transition point, and having a length of from 24 to 26 percent of the total length of the piston stroke;
• (e) said number four control zone, extending from the third transition point to the fourth transition point, and having a length of from 13 to 18 percent of the total length of the piston stroke;
• (f) said number five control zone, extending from the fourth transition point to the total stroke position of the piston, and having a length of from 2 to 10 percent of the total length of the piston stroke;
• (g) the shock load ranges in a predetermined design ratio from a minimum weight to a maximum weight;
• (h) the ratio, of the combined metering areas of the first and second metering pathways, to the combined metering areas of the third and fourth metering pathways matches the design ratio of the minimum weight to the maximum weight to provide self compensating dampening;
• (i) said control means successively restricting the amount of high pressure fluid escaping from the high pressure zone chamber further comprises;
• (1) a metering and check valve plate (36) carried by the piston (20) and having a cylindrical fluid pathway (42);
• (2) and a metering pin (40,40a,40b,40c) having one end fixedly mounted in said high pressure zone chamber (12) and having the other end received in said metering and check valve plate cylindrical fluid pathway (42);
• (3) said metering pin (40,40a,40b,40c) having a progressively increasing cross section area from said other end thereof towards the fixed end thereof, whereby, when the piston (20) is moved from said initial position through its stroke, said pin (40,40a,40b,40c) is axially moved through said cylindrical fluid pathway (42) so that more of the high pressure cylindrical pathway area (42) is obstructed by said pin (40,40a, 40b,40c) as the piston (20) moves through its stroke to restrict the flow of high pressure fluid therethrough.