CA1155146A - Self-adjusting shock absorber having staged metering - Google Patents

Abstract

Title: SELF-ADJUSTING SHOCK ABSORBER HAVING STAGED METERING

ABSTRACT OF THE DISCLOSURE
In a fluid displacement-type shock absorber, a piston res-ponding to an impacting load moves within a cylinder, forcing hydraulic fluid therein out of one or more orifices into a reser-voir. The resistive force of the piston depends upon its velocity, and the area of the orifice or orifices which control the rate at which the fluid can be displaced. The total available orifice area for discharging fluid from the cylinder is progressively reduced as the piston is displaced from its initial position upon impact. The fixed orifice structure defines successive control regions, each of which is designed to provide a predetermined resistance profile and related deceleration control for a respec-tive load system or mass system. The lightest mass system, traveling at its maximum velocity within the design range, reaches its limiting deceleration rate in the first control region. The heaviest mass system traveling at its lowest velocity within the design range, reaches its limiting deceleration rate in the last control region. All loads in the design range are decelerated over the full stroke of the piston in being brought to rest.

Description

~SS146 Title: SELF-ADJUSTING SHOCK ABSORBER HAVING STAGED METERING

BACKGROUND OF T~ lNVENTION

The invention relates generally to the field of shock absorbers or energy absorption or energy dissipation devices, and particularly to fluid displacement-type shock absorbers.
Shock absorbers are normally designed to decelarate a load, i.e., a moving mass, to rest without damage. Most loads have a deceleration limit expressed in G's as a multiple of the effect of gravity. Approaching or exceeding the G limit by stopping too abruptly, risks substantial damage to the load itself. De-celeration which is too abrupt can burst hydraulic shoc~ absorbers.
Moreover, since the shock absorber transmits force to the struc-ture on which it is mounted, the mechanical strength of the struc-ture must also be ta~en into account, particularly if a load may have a positive velocity at the end of the stroke of the shock absorber, and structural or mechanical stops are used to position such load systems, wherein, the remaining energy of these systems are absorbed elastically by the restraining structure.
There are many industrial appLications, for example~ rail-roads or foundries, where very heavy loads are encountered re-quiring very large stopping forces. In a foundry, for example, where large metal castings are made, the sand molds into which the molten metal is poured, referred to as the "cope" and "drag', are conveyed to and from their respective stations on a "head carriage". These carriages, weighing on the order of 50,000 pounds, are generally accelerated to velocities of 5 feet per second by pneumatic cylinders which apply forces on the order of M
15,000 pounds. Typical hydraulic fluid displacement-type shock absorbers used for this type of application have bore sizes rang-ing from 3 to 4 inches, and piston strokes or displacements of 6 to 8 inches. It is conventional in this type of shock absorber to provide some means of diminishing the orifice area used to control the rate of fluid flow out of the cylinder, under the action of the piston, into a reservoir of some kind. This can be accomplished with a plurality of axially spaced holes through the cylinder wall. As these holes are passed up by the piston head, they are covered and no longer are available as exit ports for the fluid. The size and spacing of the orifice holes used deter-mines the deceleration characteristics that can be provided by such devices. An example in the railway industry is referred to in U. S. Patent No. 3,301,410 to Seay.
one of the problems in industrial applications such as foundries is accommodating the wide variety of load systems en-countered, whether due to variations of mass and/or velocity alone or in combination with constant or varying propelling forces. In very simple terms, a relatively stiff shock absorber i8 needed for a heavy mass-high intensity load system~ and a relatively soft shock absorber is needed ~or a light mass-low intensity load system. Conventional shock absorbers are designed to handle con-stant mass-constant intensity load systems.
The conventional way to accommodate a variety of constant mass-constant intensity load systems is to use what has been called an "adjustable" shock absorber having some means of mechan-ically adjusting or presetting the relative size of the orifices in a multi-port hydraulic shock absorber, as shown, for exampla, in U. S. Patent 4,071,122 to Schupner. While it is generally understood that the most efficient way to arrest a constant mass-constant intensity load system is to provide a constant level of resistance over the entire stroke of the shock absorber, and there-by, constant deceleration, the design efficiency of conventional adjustable shock absorbers is seriously hampered by the inability to reach an optimum preadjustment for the shock absorber. Such preadjustment not only requires advance knowledge of the exact mass, and intensity of the load system which will be encountered, and the ability to pre-establish the optimum adjustment setting required without use of expensive electronic instrumentation but also that the intensity of the load system remain constant through-out the deceleration excursion. once adjusted for a specific constant mass-constant intensity load system, the conventional shock absorber can only handle small deviations from the exact mass, and intensity of this load system. For example, it cannot efficiently stop a load system whose mass may be lower or higher than that accounted for by the adjustment setting utilized, or whose intensity tends to vary over the stroke due to increasing propelling force. Moreover, conventional adjustable shock ab-sorbers are only provided with one mode of adjustability, that is, the size of their oriPices can be ad~usted but their locations cannot be. The conventional adjustable shock absorber can there-for do no more than adjust for constant mass~constant intensity load systems, for example, by rotating a sleeve to eclipse the orifices in a fixed spaced hole system as shown, for example, in U. S. Patent No. 4,071,122. This type of sleeve structure also introduces a temperature-dependent error factor due to leakage, ~15~
as some of the h~draulic fluid leaving the orifices flows between the outside of the pressure tube, containing the orifices, and the inside of the adjustment sleeve, containing the adjustment apertures, thereby bypassing the controlling apertures.

SUMMARY OF THE INVENTIO~

The general objective of the invention is to greatly in-crease the operating range of a fluid displacement-type shock absorber by designing a specific orifice structure that can accommodate a large number of different load systems or mass systems, wherein the intensities of these load sys-tems or mass systems may remain constant or vary over a wide range, whereby, the need for any adjustments of the controlling orifices is eliminated, and furthermore, to provide predetermined decelera-tion control for each mass system or load system considered with-in the design range of the device, and to accomplish such deceler-ation control most efficiently by utilizing the full stroke or full displacement of the device for arresting each individual mass system or load system considered.
These and other related o~jects of the invention are achieved in a shock absorber with a fixed orifice structure inherently pro-viding adaptive control of two or more mass system3, of constant, or varying intensities. The orificed structure contains a pro-gression of control regions, each distinctively different in ori-fice area size, wherein the area size of each control region diminishes progressively as a continuum, from the origin of the progression (zero stroke position of piston displacement) to stroke termination; wherein, each control region is responsive to a corresponding mass system and its respective intensity; wherein, ' il5S~46 the equivalent mass of the mass system is used as a measure of the intensity of the mass system; wherein, the progression re-ferred to is based upon the ordering of all mass systems or equiva-lent mass systems considered within the selected design range of the device, and the deceleration rates imposed upon these mass systems or equivalent mass systems is by design choice; wherein, the rate at which the area size of each control region diminishes with respect to displacement can be defined by the deceleration rate imposed upon each respective mass system by design choice;
wherein, each control region is preferably designed to provide a constant rate of deceleration for its respective mass system;
wherein, control regions designed for externally motivated or externally propelled mass systems are preferably designed for speed controlled mass systems to accommodate the highest intensity levels of such mass systems during their deceleration modes; and wherein, this invention device may also be referred to as a de-celeration control device.
In that each control region of the device according to the invention is designed to provide a specific deceleration rate for its corresponding mass system, the ordering of these control regions must comply with the ordering of the mass systems, the ordering used by this invention being from the smallest mass system of lowest intensity to the largest mas~ system of highest intensity. In this design, for example, the first control region that the piston traverses from its initiaL position, will provide a constant rate of deceleration for the smallest mass system of lowest intensity, whereas, the last control region will provide a constant rate of deceleration for the largest mass system of ~ ' l~S5~46 highest intensity. If the available exit orifice area is plotted against piston displacement for the entire stroke, the result is a graph which depicts a continuous series of connected segments of different exponential curves, starting at the beginning of the stroke with the total area or all orifices used, and decaying to zero at the end of the stroke.
If a series of axially spaced holes is used, the result is a step function approximation of an exponential segment curve.
If a specifically contoured tapered metering pin orifice structure or equivalent is employed, a smooth orifice curve can be obtained.
In one embodiment, the diameter of the holes in a given control region is held constant and the exponential decay is provided solely by axial spacing of the holes, wherein, the sizes of the holes may or may not vary from region to region.
In accordance with the invention, an incoming mass system in a sense "seeks out" its corresponding control region. If the mass system is an intermediate mass system of intermediate intensity, it will tend to reach its maximum allowed deceleration in its res-pective intermediate control region.
~ he unique aspects of the invention include the ability o a single device, without the need of adjustment mechanisms, to provide predetermined deceleration control, and total arrestment for two or more different mass systems, wherein, these mass systems may be constant intensity mass systems or mass systems of varying intensity, and to achieve such deceleration control most efficient-ly by utilizing the full displacement stroke of the device for the arrestment of each of the mass systems; wherein, the total dis-placement stroke of the device is a function of (a) the total .~ ~

~lS5146 number of different mass systems being controlled~ (b) the velo-cities of each of these mass systems at the zero stroke position of piston displacement, and (c) the deceleration rates imposed upon these mass systems by design choice.
DESCRIPTION OF THE DR~WINGS
Fig. 1 is an elevational view of a shock absorber according to the invention having a portion of the outer sleeve broken away to reveal the inner cylinder with a pattern of holes to be dimensioned and spaced as described hereinafter according to the invention.
Fig. 2 is a view similar to that of Fig. 1~ except that the inner cylinder is in section, illustrating an alternate embodiment employing a tapered pin dimensioned and contoured as described hereinafter according to the invention.
Fig. 3 is a composite containing Graphs I, II, III and IV de-picting buffing force FB(x)~ velocity V(x)~ and orifice area A(x) versus displacement, respectively, and related Equations 1 through 5 Fig. 4 is a composite containing Graphs V, VI and VII of orifice area, deceleration and velocity versus displacement, res-pectively, according to the invention.
Fig. 5 is a calibrated Graph VIII of orifice area versus dis-placement for a pair of control regions corresponding to Example 1 in the following deseription~ aecording to the invention.
Fig. 6 is a Graph rX of orifice area versus displacement for four different load systems, showing control regions corresponding to Example 2 in the following deseription, according to the inven-tion.
DESCRIPTION OF SPECIFIC EMBODIMENTS
The following disclosure is offered for public dissemination in return for the grant of a patent. Although it is detailed to insure adequacy and aid understanding~ this is not intended to prejudice that purpose of the patent which is to cover each new inventive concept therein no matter how others may later disguise it by variations in form or additions or further improvements.
The shock absorber of Fig. 1 co~prises a cylinder assembly 10 having an outer cylindrical body or casing 11 and a coaxial inner cylinder 12. A piston assembly 13 has a piston 14 sealingly slidable within the inner cylinder 12. A piston rod 15 is coaxi-ally secured to the piston 14 and extends out through a coaxial opening in the cylinder assembly 10 terminating in a shock re-ceiving pressure member 17. The other ends of the cylinders 11 and 12 are closed. A coil compression spring 18 coaxially sur-rounding the distal portion of the piston rod 15 bears against the outer face of the cylinder assembly 10 and the annular shoulder provided by the pressure member 17 thus urging the piston rod 15 out of the cylinder assembly 10 and causing the piston 14 to assume an initial position J as indicated in Fig. 1. The annular volume between cylinders 11 and 12 forms a reservoir 19 for hydrau-lic fluid. A resilient cellular pad 20, such as nitrogen mole-cules encapsulated in rubber, is located in reservoir 19. The inner cylinder 12 is also filled with hydraulic 1uid and is in fluid communication with the re~ervoir 19 via axially and circum-ferentially spaced holes 21 and 21d formed through the wall of the inner cylinder 12 in the stroke portion of the cylinder, i.e., between the initial and final positions, J and K, of the face of the piston 14.
The cylinder 12 has one or more flow openings 22 which per-mit filling the inner cylinder 12 with hydraulic fluid behind the 1155~46 piston 14 during the compression stroke of the piston 14. A chec]~
valve (not shown) is typically arranged in the piston 14 to seal the piston 14 during the compression stroke. On the return stroke, the check valve opens allowing hydraulic fluid to flow from the portion of the cylinder 12 behind the piston 14 to the portion of the cylinder 12 ahead of the piston via the piston 14. Openings 22a (shown in phantom) in the inner cylinder 12 at the end around the piston rod 15 place the portion of the inner cylinder 12 be-hind the piston 14 in continuous fluid communication with the reservoir 19. Thus, in effect, the portion of the inner cylinder 12 behind the piston forms a part of the hydraulic fluid reservoir 19.
~ part from the orifice structure, the structure of the shock absorber shown in Fig. 1 may be conventional. Further details of the conventional structure, to the extent applicable or desirable, can be found in the prior literature, for example, U. S. Patents Nos. 3,301,410 and 4,071,122.
In use, the cylinder assembly 10 is typically mounted to a fixed structure. If desired, however, the piston rod assembly 13 may be secured to a fixed structure and the opposite face o~ the cylinder assembly 10 can be left ~ree to receive the shock force.
When an object or mass system strikes the pressure member 17, its momentum is transmitted to piston assembly 13, which in turn transmits this momentum to the fluid contained in cylinder 12. As a result o~ this momentum exchange, piston assembly 13, and the adjacent body o~ fluid it impinges upon are accelerated.
The resultant velocity of the object or mass system, the piston assembly, and the adjacent body of fluid depends upon the rate at _ llSS~6 which the body of fluid can be displaced from orifices 21 and 21a by the impending momentum of the object or mass system. As the piston 14 moves away from its initial position in the cylinder 12, fluid is forced out of the holes 2la and 21 into the reservoir 19. At the beginning of the compression or working stroke of the piston 14, the amount of resistive force provided by holes 21 and 21a is determined by the total area of these holes or orifices.
For example, if there are n holes, each o~ diameter d, the total area through which fluid can escape from the inner cylinder lZ
would be n~d2/4. As the piston 14 forces oil out through the holes, it would eventually come to the point where it passes by and closes off the hole which is closest to the face of the approaching piston 14. Once this first hole had been passed, relative to an n-hole system, the area available for discharging fluid would be (n~ rd2/4, one hole having been eliminated from the remaining orifice pattern or orifice structure. As the piston continues its working stroke, the holes are successivel~ passed and closed by the piston, thereby progressively diminishing the number of holes discharging oil from the cylinder 12 into the reservoir 19. As a result of the decreasing area available, rela-tive to the impending momentum of the object or mass system, the rate at which fluid can escape the c~linder is decreased, the objective being to decelerate the moving ob~ect or mass system to a rest position at a controlled rate before the piston 14 reached the end of its stroke at K.
Axially spacing the holes 21 provides a way of making the orifice area decline stepwise as a function of piston displacement.
The circumferential displacement of the holes has no effect on the .~

operation of the orifices. It is their axial displacement and diameter which determines the decay rate of the orifice area.
Arbitrarily, five circumferential displacements, each 15 apart, are designated as A, B, C, D and E, as indicated in Fig. 1. There are other known orifice structures for accomplishing this purpose, some of which do it smoothly or continuously instead of stepwise.
one of these is shown schematically in Fig. 2. As in the embodi-ment of Fig. 1, the shock absorber of Fig. 2 comprises a cylinder assembly 10', including a similar outer cylinder 11 and a modified coaxial inner cylinder 12', the annular volume between them again forming a similar oil reservoir 19. Instead of holes 21, the cylinder assembly 10' has a coaxial metering pin 23 tapered down toward its distal end. The larger end of the metering pin 23 is secured coaxially to the closed end of the cylinder 12' in close proximity to the end position K of the full stroke. The pointed end of pin 23 is received in apertured coaxial cylindrical bore 24 dimensioned to receive the entire working length of the metering pin 23. As the piston assembly 13' moves through its worlcing stroke, the bore 24 is in communication with the reservoir 19 via holes 25 and 26 through the piston assembly 13 and the cylinder 12', respectively. As the piston assembly 13' moves away from its initial pO9 ition, the metering pin cross-section intercepted by the opening in the piston 14' increases continuously. The pin 23 can be contoured according to any given mathematical relation-ship to displacement of the piston 14'. Examples of hydraulic shock absorbers using metering pins to determine the orifice area as a function of displacement are shown in U. S. Patents Nos.
3,729,101 to Brambilla et al, 3,774,895 to Willich et al, 3,568,856 ,.,~, 1155~46 to Knippel~ 3,693,768 to Erdmann and 3,3~8,703 to Powell et al.
Except where otherwise indicated, in the following descrip-tion and in the claims, ~he term orifice structure or orifice means is meant to encompass axially displaced holes and tapered metering pins. In addition, the term is intended to encompass slots, grooves, projections and any other types of structural features in a hydraulic shock absorber which has the effect of progressively decreasing the rate at which fluid can escape from the cylinder as a function of piston displacement. Any structure or combination of structures which has this capacity can be em-ployed to implement the invention described herein.
Fig. 3 shows four graphs which illustrate the underlying principles of orifice area metering versus piston displacement in fluid-displacement shock absorbers. Assume that an object to be decelerated, having mass M, and propelling force Fp, strikes the piston assembly of a hydraulic shock absorber with an initial velocity V(o) = vO. The object has a design deceleration limit a(x) ~: L which is no~ to be exceeded while the object is deceLer-ated from VO to zero over a given distance or stroke XT.
The best way to keep peak deceleration low is to design the system so that the deceleration is as constank as possible. From Graphs I, II and Eq. t2), it is apparent that in order to maintain a(x) constant, the ratio FB(x)/M (x) must remain constant. Graph III and Eq. (4) illustrate pictorially and mathematically the velocity versus displacement profile V(x) for constant decelera-tion. Graph IV and Eq. (6) illustrate pictorially and mathematic-ally the orifice area versus displacement profile A(x) required to decelerate the equivalent mass system Me(x), depicted in Graph .~.

l~S51~6 I, at a constant rate. Note that Eq. (6) is derived from Eq. (5) for Me(o) = Me(x) = Me(xT) = constant, and that V(x) and A(x) de-cay at the same exponential rate relative to displacement when this is true. Manufacturers of conventional fixed orifice, and adjustable orifice shock absorbers design their orifice structures to accommodate such mass systems, and/or equivalent mass systems.
That is, mass systems wherein Fp(x) and thereby Me(x) remain con-stant throughout the intended deceleration stroke xT.
For a spaced hole orifice structure defining a single con-trol region wherein all orifice holes are of the same size, and d = Diameter of orifice hole N = Total number of orifice holes n = n orifice hole n = 1, 2, 3 ........ N
A(n) = Remaining orifice area as a function of the nth hole location, then A(n) = (N-n)~rd /~ Eq. (7) From Eq. (S), Eq. (6) and Eq. (7), the spacing of orifice holes can be expressed as follows:
X = XT ~1- (1- N) Me(O)} 2 Eq. (8)

2~
X = X ~ - (1- N) J ~ Eq. (9) where the location of the axis of each orifice hole is determined by subtracting hal~ its diameter d~ in Equations (8) and (9).
When metering by conventional methods, that is~ using a single control region~ and assu~ing that the equivalent mass as a function of displacement x remains constant, that is, Me(x) =
Me(O) = Me(XT) = constant, where X = O defines the beginning of the control region, and X = XT defines the end of the control region or its total extent, it is apparent from Equation (8) that the spacing of such orifice holes becomes solely a function of the number and size of holes as given in Equation (9).
It is this principle that the manufacturers of conventional adjustable shock absorbers use to design their orifice structures, namely, by maintaining a fixed spaced hole system and simultane-ously varying the area size of all orifice holes by equal amounts to maintain the n/~ ratio given in Equation (~) constant. This allows such manufacturers to adjust for different mass systems with one mode of adjustability, and to provide a constant rate of deceleration for such mass systems when their equivalent mass remains constant throughout the deceleration excursion.
This is also the reason why conventional adjustable shock absorbers cannot be adjusted to provide a constant rate of de-celeration for mass systems wherein the propelling force varies with displacement, such as depicted in Graph II, and why such systems are inefficient.
To simplify the explanation of the principles of the present invention, I shall refer to the intensity of mass systems as a measure of the equivalent mass of these systems, wherein this measure is given in Equation (1) of Fig. 3.
The present invention utilizes the principle of cascading control regions as a continuum within the extent of a common stroke control entity. Each control region is specifically de-signed to provide a constant rate of deceleration for its respec-tive or corresponding mass system in a specific sequential order.
The order referred to is from the lowest intens ity to the highest ,_., " ~
1~55146 intensity for such mass systems or from the lightest mass to the heaviest mass for non-propelled mass systems.
This method allows for the control of mass systems of con-stant intensity as well as mass systems of increasing or varying intensity within a given range of design.
Within the range of design, such mass systems eventually reach their respective control regions as they progress into the co~mon stroke control entity to their common location of total arrestment, that is, stroke termination.
Fig. 4 (Graphs V-VII) illustrates the basic principle of the present invention. Graph V shows orifice area in a fluid displacement-type shock absorber as a function of piston displace-ment from an initial position oE the piston at x=O corresponding to the point of impact of an object to be decelerated. The initial segment of the area curve 27 is a parabola of the same form as in Graph IV. Taken together with the dashed extension 27a of curve 27, it represents the decay rate of the orifice area Ao over a stroke of length Sl. Instead of allowing the original cur~e 27 to decay to zero at Sl through the extended portion of the curve 27a, the progress of parabola 27 is halted at point S' Truncation point S'l defines the beginning of a new parabola of amplitude A'o. The decaying ori~ice area beginning at point S'l follows the trajectory 28. At point S'l the curve of the orifice area A is continuous but changes direction abruptly to a lower rate of decay. The area decays alon~ curve 28 and if allowed to proceed as in the Graph IV, it would traverse the dashed extended curve 28a and decay to zero at point S2, that is, the stroke length from the start of parabola 28 at point S'l. Instead of allowing the parabola 28 to complete its trajectory, the progress along curve 28 is arrested at truncation point S'2 where a new parabola with initial amplitude A~o is begun. If this is the last of the cascading parabolas, the orifice area is allowed to decay to zero over the full trajectory of the curve 29. The orifice area finally declines to zero at point S3 measured from the start of curve segment 29 at S'2.
The connected parabolic line segments 27, 28 and 29 in Graph V define control regions 1, 2 and 3. By determinin~ the initial orifice area Ao and the truncation points S', ~ach control region can be designed for constant deceleration of a different mass system. Region 1 with curve segment 27 is designed for con-stant deceleration of the lowest intensity mass system. Regions 2 and 3 are designed for constant deceleration of an intermediate intensity and the highest intensity mass systems, respectively.
In Graphs VI and VII of deceleration and velocity versus displacement, respectively, three loads to be decelerated, referred to as loads 1, 2 and 3, have di~ferent mass and the same impact velocity VO. Each object also has the same design limit L for maximum deceleration, and no propelling force. Examining the curves in Graphs VI and VII together~ one will notice that the order of the load intensities i8 reversed ~rom top to bottom. In control region 1, the load with common velocity VO and the l~est mass undergoes constant deceleration as indicated by curve 31 in Graph VI and the corresponding curve 35 in Graph VII. Curve 35 is a true parabola along with its extension 35a to the virtual stroke Sl. Following the corresponding deceleration curve 31 in Graph VI, object 1, (lowest intensity load) undergoes constant .' ~lS5~46 deceleration throughout region 1 and decreasing deceleration in regions 2 and 3. Similarly, for -the intermediate intensity load, object 2, the deceleration curve 32 and velocity curve 36 indi-cate that the load undergoes constant maximum deceleration L in control region 2, and outside control region 2, deceleration is less than L. I~hus in Graph VII, curve 36 between the truncation points S' (i.e., control region 2) is a true parabola. Likewise, for the highest intensity load, the deceleration curve 33 in Graph VI and velocity curve 37 in Graph VII indicate that the maximum design constant deceleration limit L is realized only in the last control region, throughout which, that is, from point S'2 to S3, the ve]ocity curve is parabolic.
With respect to the low mass system for which region 1 is designed, the curve 27 does not continue along its projected path 27a; at x=S'l the rate of orifice closure "slows down" or "backs off" at the start of curve segment 28, not unlike reducing the pressure on a brake pedal. ThUS the deceleration rate falls as shown in Graph VI.
The graphs in Fig. 4 are exaggerated for the sake of clarity.
The total energy expended by the shock absorber in bringing the object to rest is directly proportional to it~ mass and mu~t ultimately dissipate all of its kinetic energy (1/2 mv2) which it had at impact. ~his is reflected in Graph VI since the product of area under each of the curves and the respective mass is repre-sentative of the total kinetic energy (l/2mv2) of each respective mass system, that is m ~ a(x)dx = 2 mV (Eq. (10) ~ ...

11551~6 where the intensity of mass system m = me(x) constant, and a(x) represents the deceleration rate of this mass system as a function of displacement, and ST = Sl' + S2' + S3 or the total stroke illustrated in Graph V.
It is also important to note that subsequent control regions are designed with reference to the intensity of the load system at the beginning of the control region. Thus, for the intermediate mass load, the second control region is designed to give constant deceleration to an object of intermediate intensity now traveling at velocity VO' having already been decelerated through control region 1. Similarly, the third control region is designed to provide constant deceleration for a load with the highest mass or highest intensity of the three, now traveling at a velocity VO'', having been decelerated through the two preceding control regions.
The initial total orifice area Ao is chosen solely with res-pect to the load system having the lightest mass and/or intensity.
The first truncation point S'l terminating the first control region and starting the second region is determined as that displacement of the piston at which the first intermediate mass (load system of intermediate intensity) reaches its maximum allowable deceler-ation L as shown in Graph VI. If the rate of orifice c los ure continued to Eollow the projected curve 27a in Graph V, the inter-medi.ate mass curve 32 would exceed the deceleration limit as shown by projecting the curve 32a in Graph VI. Instead~ a new parabolic decay of the orifice area is begun at point S'l to control the deceleration of the intermediate mass. Similarly, the last trun-cation point S'2 is determined as that displacement of the piston at which the object with the highest mass (load system of highest ~ ..^

.

~lSS~6 intensity) first reaches its maximum deceleration Limit L. If the orifice area were to continue to decay at the rate exhibited by curve 28a in Graph V, the high mass load would exceed its de-celeration limit as indicated by the projected curve 33a.
The system described above in connection with Fig. 4 can be extended to any number of control regions as desired. In certain industrial applications, load systems of constant and varying intensities can be classified into predictable discrete categories.
For example, the object to be decelerated on a particular process line may be 12,000 pounds or 30,000 pounds and it may be travel-ing at either 2 feet per second or 8 feet per second, and be motivated by a propelling force of 6,000 lbs. or 8,000 lbs., wherein the propelling force motivating the object may vary from 0 lbs. to either of the maximum values given or remain constant at either of the two values given. The sixteen distinct combin-ations of weight tmass), velocity, and propelling force can be specifically accommodated in the orifice pattern according to the invention. It can also be shown that the deceleration rate im-posed upon any intermediate load system, that is, any load fiystem not defined but whose intensity lies between the minimum and maximum values designed for, by a device o~ this invention, sh~ll not ex-ceed the maxirnum limitg of design~ when the imp~ct velocity of this intermediate load system falls within the design range.
A shock absorber can also be designed, according to the in~
vention, having only two control regions. Since this is the least complex system, a specific shock absorber with two control regions will be described in detail.

~ .~.

1~551~6 Example l In this example, the shock absorber orifice structure according to the invention is designed to handle two load systems, each having distinctively different intensities or equivalent masses. To simplify matters, the weight of the impacting objects, Nos. 1 and 2, will be arbitrarily chosen as 10,000 and 20,000 pounds, respectively. The masses of these objects, Ml = 310.56 lb.-sec. /ft and M2 = 621.12 lb.-sec. /ft, are obtained by dividing their respective weights by 32.2 ft/sec.2. Let vl and V2 be the changing velocities of objects 1 and 2 during the stroke.
At the point of impact, x=0, both objects are defined to have the same impact velocity vl=v2=Vo=4 ft/sec. To further simplify matters, consider the deceleration limit L to be 24 ft/sec.2, the same by design for both objects and assume that they have no propelling force.
Since there are no propelling forces involved, the intensi-ties of these two load systems can be defined by their respective rest masses lsee Eq. (1) in Fig. 3]. The controlling orifice structure required to accommodate these two load systems will therefore require two consecutive control region~ 1 and 2~ With reference to Graph VIII of tiig~ 5, Sl is th~ total virtual stroke length of region 1~ and Sl' is the actual stroke of region 1~
i.e.~ the truncation point for first orifice area decay curve.
S2 is the actual stroke length of the last region, region 2.
The virtual stroke length Sl associated with region 1 can be obtained from the formula, Sl=Vo2/(2L). Eq. (11), where Sl=1/3 ft. or 4 inches as shown in Fig. 5. Although region 1 is designed for constant deceleration of object 1, the truncation ~. .

1~55146 point S'l~ defining the extent of or length of region 1, is de-termined by finding the point at which object 2, separately im-pacting the shock absorber, would reach the deceleration limit L according to the following formula:

1- /2m2SlL~ 2 ( 1 21 S'l = Sl Ll -( ~2 1 ~ Eq. (12) Substituting the numerical values, S'l is 1/4 ft. or 3 inches as shown in Fig. 5.
Next, the stroke S2 of the second and last region must be determined. However, this cannot be done in the same manner that the virtual stroke Sl associated with region 1 was determined since there is an unknown velocity to consider now~ ThusJ at x=S'l~ the velocity of the second object after it has been de-celerated through the first control region is determined accord-ing to the following formula:

S ~ l ~ ml/ (2m2 ) ( J Eq. (13) Substituting the numerical values~ v2' at x=S'l (the b~ginning of the second control region) is 2.828 ~t/sec. Since the de-celeration limit is the same for the 6econd body, the stroke in the second control region is: S2=(v2')2/~2L~. Eq. (14), where S2= 1/6 ft. or 2 inches, i.e., 3.0 to 5.0 inches as shown in Fig.

5. The entire stroke length of course is s'l + S2 = ST or 5 inches.
Next, one must determine the values of Ao, the t~tal orifice area available at the beginning of the stroke and Ao', the total -2i-1~55~'46 ori~ice area remaining at point x=S'1 The formula for the orifice area as a function o displacement in the first control region is (1 - ,9 ) Eq. (15) At x=0, Al=Ao, and kl is a constant based on the mass density of fluid, the area of the piston and the orifice coefficient of dis-charge. For a 2 inch bore shock absorber with hydraulic fluid :~ ~
of mass density 1.677 lb.-sec. /ft.4 (slugs per cubic ft.), kl = 1.777 x 10 5 lb.-ft.2-sec.2. Substituting the numericaL

values, Ao= 1.953 x 10 4 ft 2 or 0.02812 in.2 as indicated in Fig 5 ~. , The formula for the orifice area in the second region is:

: ` / k2 ~ / ~ X - S ' 1 ~ /
A2 = V2 m L 1 - Eq. (16) where, v2' is the velocity of the second object at the start of thc second control region and k2=kl. At x=S'1~
A2=A~o =9.764 x 10 5 ft 2 or 0.01406 inches2, as indicated in Fig. 5.
Now that the orifice area profile versus displacement is known for Examplc 1, i~ must be implemented. ~his can be done directly with the metering pin embodiment of Fig. 2. To accom-plish this, the orifice opening 24 in the piston 14' is sized in conjunction with coaxial metering pin 23 to provide a cylindrical orifice opening 24a whlch is equal to Ao at position J. From position J, metering pin 23 must be tapered continuously to stroke termination position K to provide the reduction of orifice .

- : -, . .

, , , , . .~ -, - ~
.

1155~46 area required in accordance with the curve of ~ig. 5. For example, at x = S'l~ the cylindrical orifice area remaining when the cross-sectional area of the pin at this location is subtracted fr~m the cross-sectional area of orifice opening 24 in the face of piston 14' should be equal to A~o~
Because of the increased structural re~uirements of the metering pin embodiment, it is p~eferred, however, to use a suc-cession of holes through the cylinder wall as shown in Fig. 1 to approximate the continuous orifice area curve. To use discrete holes, the exact total number of holes and the precise diameter of each or the average diameter must be established. For example, in the system of Fig. 5, it is evident that half of the total orifice area is allocated to each control region. Thus, holes of the same diameter could be used and half of those holes allocated to one region and half to the other. If many regions are involved, the total orifice area at the beginning of each region will de-termine the proportion of the number of holes which are allocated to any given region. Given the orifice area for any region, the number of holes and their diameter for that region can be manipu-lated as desired. However, it is convenient to use the same diameter holes throughout any given region, although the diameter of the holes can vary from region to region.
The formula for the axial displacement, D, of each successive hole of diameter d in a given control region can be derived from Equation (9) as follows:
Let XT be represented by the total virtual stroke of each control region, Sl~ S2....... etc. Let x be represented by D, the distance from the beginning of each control region to the nth hole of that ,, 1~5~i14~;

control region. Let N be represented by Ao, the total orifice area required at the beginning of each control region or the re-maining orifice area required at the beginning of each control region relative to a spaced hole orifice structure, wherein, Ao--Ao, A'o~ A''o ... etc., relative to each respective control region. Let n be represented by n~d /4, the area size of n holes of diameter d, where ~l~dl/4, n2~r d22/4, .... etc., is representative of a specific control region.

Then from Eq. (9) 2 Dl = Sl 1 (1 1~ 1 ) --~ 21 Eq. tl7) where subscript notations 1 represent references to control region 1 in Equation 17.
Arbitrarily using three holes of diameter 0.07721 inch with a virtual stroke of 4 inches for the first region, the displace-ment from x=0 for the first three holes can be determined from the expression for D as 1.1836, 2.1836 and 2.9614, respectively.
The total orifice area for the second control region (i.e., Ao~) is 0.014046 inch. If a drill size of 0.06686 inch for the diameter of four holes is arbitrarily chosen for region No. 2, their dispLacements from the point x=S '1 (the start of the second control region) are as follows: 0.8416, 1.4666, 1.8416, and l.g666, respectively. This brings the axial separation between the last two holes in control re~ion No. 2 to within 0.05814 inch.
If this or any of the other axial separations are too close, the holes may be offset circumferentially.

EX~MPLE 2 In this example the shock absorber orifice structure accord-ing to the invention wiLl be designed to handle four distinctive-ly different load systems. To explain more clearly the signifi-cance placed on the intensity of these load systems, each rest mass selected will be motivated by one of the prope~ling forces common to the other. To further simplify the subscript notations used in identifying these mass systems by the respective inten-sities, we will use the same impact velocity for all four load systems, and impose the same limiting deceleration rate restric-tions upon them.
The following subscripted equations will be used to define and/or obtain the parameters of design required, that is, in-tensities, orifice area sizes, truncation locations, deceleration rates and velocities. Numerical values will not be obtained, but rather the equations will be written in general to relate to any number of different load systems that could have been selected to identify a given design range.
In the Glossary of Terms provided, and throughout the follow-ing equations, a notation is introduc~d which is meant to convey the process most clearly. For example~ within the range of the first control region~ oc x(i)C x(i,i')~ x(l,l'), i, and i' are used as locations of design reference, namely~ the beginning or origin of each control region, and the termination or truncation location of each control region, respectively.
When x(i) is represented as x(l), x(l) is not necessarily x(i) evaluated at one point i = L~ as in usual notation, bu-t rather, x(i) is used to represent the displacement taken from an "

i location of design reference. For example, for any displace-ment in region x(l,l')~ x(i)C lX(l,l') + X(2,2')], x(i) may be represented as x(2), wherein, with reference to the i = 1 loca-tion, x(2) would be equal to the extent x(l,l') and with refer-ence to the i = 2 location, x(2) may be equal to zero or the extent x(2,2') or obtain any value in between, where the extents of the control regions X(l,l') and X(2,2') may be represented as X(l) and X(2) for brevity, respectively.
Since the equivalent mass or intensity of a load system may vary from one location to another, Equation l given formerly will be exparded as follows:

fF [Xli)~ ~
~ q[X(i)l ~a lXti)] + MmqlX(i)]J Eq. tl8) The parameters of design in Equation 18 are expressed as functions of displacement X(i), and subscripts m-n-q are used as identifiers of mass, force, and velocity, respectively.
Since the deceleration rate amnq(i), imposed upon an Mmnq(i) or ~ q(i) load system at the particular location i, is a function of the resistive force FB(i) encountered by the load system at this Location, and mnq( ) E~. ~l9) where the constant k(i) is some function of the mass density of the fluid, the orifice discharge coefficient, and the piston area of the shock absorber device, then at onset of impact or at the origin of the first control region i = l, the equivalent mass or ..r --26 ~

-~ .

55~46 intensity of any load system at this location can be obtained by the following equations:

mnq(i) = q F (i) Eq. (20 ~ FB(i) J
or as nt ) mn~ Eq. ~21) k (i)V mnq(i) where the resistive force FB(i) is proportional to the velocity squared of the fluid being forced or metered through the control-ing orifices, and thereby proportional to the velocity squared of the mass system or load system providing the momentum.
Now if we introduce a relative order number "c~, wherein this order number is used in conjunction with an i location of design reference to identify the order of intensity of a particu-lar Mmq(i) or Mmnq(i) load sys-tem, where the intensity of an Mmq(i+C) or Mmnq(i+c)load system is greater than the intensity of an Mmq(i) or Mmnq(i) load system at the i location of refer-ence; wherein the order number "c" may take on integer values from c=l to c=N-l~ where N repre~ent~ the total number of load systems considered within a given design range, wherein, the intensity of an Mmq(i+l) or M nq(i+l) load system is greater than the intensity of an M q(i) or M nq(i) load system, and the inten-sity of an Mmq(i+2) or M n~(i+2) load system is greater than the intensity of an Mmq(i+l) or Mmnq(i+1) load system, then the equa-tions for deceleration, and velocity of these load systems are ~, ~t -27-defined as ~ollows:

mnq {~mq~i+c)-M IX(i)~ ~ B[X(i,i+c)][ 2 ~mna ma(i~c)~Mmnq[X(i)l] [H[X(i)~ ) Eq. (22) HIX(i)] = Ll S(i)] Eq. (~3) B[X(i i+c)] = Mmnq~ ] Eq. (24) M (i+c) B'lX(i,i+c) = M ~X(i)]-Mm~(i+c) ~. (25) Eq. (26) where notations (i,i+c) are relative placement identi~iers used to position a particular Mmq(i+C) or Mmnq~i+c) load system at an i location o~ design reference and X(i,i+c) represents the relative displacement of a particular Mmq(i+C) or Mmnq(i+C) load system from an i location of design reference, and the parameters given in Equation 22 are defined as follows:

FnlX(i~c)] A force o~ n-magnitude acting on an Mmnq(i+c) load system, expressed as a function of displacement of this load system Mmq(i+c) The intensity of an Mmq(i+c) load system Mmnq[X~i)] The intensity of an Mmnq(i) load system expressed as a function of displacement X (i) 115~i~4~;

S(i) The virtual stroke of an i location control region Vmnq(i,i+c) The velocity of a particular Mm~i+c) or Mmna(i+c) load system at an i location of desian reference amnq[X(i, i+c)l The deceleration rate of a particular Mmq~i+c) or Mmn~(i+c) load system at an i location of design reference, - expressed as a function of its relative displacement from this location Accordingly, 2F [Xti~c)lS(i) ~ BlX(i,i~c)' Vmnq~X(i i+c)~ ~ [V2mnq(i~i+C) + Mmq(i+c)-~mnqlx(i)~ Etx(i)~

2FnlX( +c)lS(it 1/2 _ _ mq(l+C)~MmnqlX(i)~ H 1 X ( i ) ] . Eq . ( 2 7 ) , .. ..
where truncation locations S', referred to in Example 1, represent the shortest X[i,i+C] displacements. These displacements define the locations at which the Mmq(i+C) or Mmnq(i+C) load systems first reach their limiting deceleration rates Lmnq(i~C). This relative displacement is measured from thc origin i of an Mmq(i) or Mmnq(i) control region, and X[i,i-~c] as defined as follows:

B'~X(i,i+c)]
. F [X(i~c)]
, M [X(i]-M (i+c) ~ Lm"q(i+C) Xli,i+cl=S(i) 1- mnq mq Mmnq~X(i)]FnlX(i+C)~ Mmnq~x(i)lv~mnq(i~i+c) Mma(i+c)Mmnq~X(i)~-M mq~i+c) 2Mmq(i+c)S(i) Eq. (28) --29_ From ~quation 2, FB(i) can be written as FB(i) = Mmnq(i) amnq( Eq. (29) Then from Equation (19) and Equation (2~) _ _ 1/2 mnq k(i) mnq F,q. (30) and expressing Amnq~i) as a function of displacement, Equation (30) can be written as ~ 1/2 AmnqlX(i)] = Mmnq[X~i)lamnqlx(i)~ VmnqlX(i)] Eq. (31) Then for constant deceleration, when amnq~i) = amnq[X(i~] = constant, and k(i) = klX(i)] = constant, from F.quation (4) we get Vmnq[X(i)] = Vmnq(i) [1 S(i)] Eq. (32) Then from Equation (30) and Equation (31), AmnqlX(i)] can be defined as A q~X(i)] ~ Amnq(i) [1 ST~] ~ Eg. (33) and when Mmn~(i) = Mmnq[X(i)l = constan~ throughout a given control region, Equation 33 can be de~ined as an expansion of Equation 6, where _ _ 1/2 mnq[X(i)] = Amnq~i) _ _ Eq. (34) .

To avoid numeric computations~ in Example 2, the Fn(i), FB(i) and Mmq(i) parameters will be given the following proportional magnitudes at the i = 1 location of design reference:

M21(1) = 2Mll( ) F2 (1) = 2Fl(l) FB(l) = 2F2(1) Furthermore, in this example, the Fn(i) forces motivating the mass systems will remain constant with respect to displacement, and each control region will be designed to maintain the deceler-ation rate of its respective load system constant throughout its extent, wherein, amnq~i) = amnqtX(i)~ = LmnqlX(i)~ and s(~ E~. (35) Since Vmnq(l) and Amnq(l) is common for the four load systems considered in this example, FB(l) will also be common~ and the intensities of the Mmnq(l) load systems can be established and defined at this i=l location o design reference~ with rcspect to the proportional magnitudes of the Mmq(l) and Fn(l) mass systems and motivating forces given, respectively.
From the Fn(l), FB(l) and Mmq~l) values given, and E~uation (20) we can define the Mmnq(l) load systems and order them, that is, from the lowest intensity first to the highest intensity last, as follows:

.
, ~

( 111~ ) ~) 11 ( ~}

j 121~ ~ ~al21(1) Mmn~ Fl(l) _ MATRIX 1 211( ~ ~a211tl) 21( )~

221(1) =~) M21~1)}

where, Mlll(l) C Ml21tl)~ M211( ) 221 Note that for the Mlll(l) load system given in Matrix 1, the load system of lowest intensity, alll(l) is given as Llll(l).
This was done to indicate that control region 1, the extent of which will be defined as X(l~l') or X(l) will be designed to maintain the deceleration rate of this load system constant at its limiting value Llll(l)~ where Llll(l) Llll[X( )]
fore, since Fl(l) = Fl[X(l)] = constant, and ~11(1) = Mll(2) =
constant~ that is Mmq(i) = Mmq(il)~ from Equation 18 we find that Mlll(l) = Mlll[X(l)] = constant, and that, at the i' = 1' location (truncation point of control region 1), 111(1 ) M111(2) 1~
, Mmnq(i) - Mmnq~i~) and from Equation ~35) S(l) = V ~ ) E~. (36) ~15S146 From Matrix 1, relative to the "c" order number ( M121(1) M121 (1+1) where c = 1 Mmnq(l+c) ~ M211~1) = M2~ +2) where c = 2 MATRIX 2 ~ 221(1) - M221(1+3) where c = 3 Then from Equation 28, we find that X[~ l]=X[1~2]cX[1,3]<X[1,4]
wherein the M121(1+1) load system reaches its limiting decelera-tion rate L121(2) before load systems M2llll+2) and M221(1+3).
The X[1,2] displacement must therefore be used as the extent of control region 1 to insure that the Ml2l[x(l)] load system does not exceed the limiting deceleration rate Imposed upon it by design choice.
Accordingly, X[1,2] = X~l,l'] = X(l) Since the extent of control region 1 defines the origin or beginning of control region 2, that is, the i=2 location of de-sign reference, we can establish the intensities of all subsequent load systems at this location of design reference by use o.~ Equa-tions 18, 22 and 27 and order them from tho lowest intensity to the highest intensity as follows ! M121(2) = ~ + M11~2)}

M l2) ~ M ~2~ = { 1(2) + M (2 ~ ~ATRIX 3 221(2) ~a (2) ~ M21(2)~

~155146 Although the limiting deceleration rates Ll11(2) and L121(2) are common for both load system 1 and load system 2, respectively, that is, Llll(2) = L121(2), and rest mass system Mll(l) remains constant, that is Mll(l) = Mll(2) MLl( ). , 2 1( ) M111(2) Mlll(l), the intensity of load system 2, at the i = 2 location of design reference, must be greater than the intensity of load system 1 at this location, that is, M121(2)~ Mlll( ) If control region 2 is designed to maintain the deceleration rate of the M121(2) load system constant at the limiting value L121(2), through the X(2) extent of this control region, wherein M121[X(2)] also remains constant throughout this extent, that is M121(2 ) M121(3) = M121(2), then from Matrix 3, relative to the "c" order number system adopted ~ M211(2) = M211(2+1) where c = 1 Mmnq(2+c) MATRIX 4 ~ M221(2) = M221(2+2) where c = 2 Then from Matrix 3 and Matrix 4, for Mmnq(2) = Ml2l(2) =
M121[X(2)], Mmq(i+C) = M21(i+c) = M21(2+2) = M21(2) and Fn[X(i+c)] = F2[X(i+c)] ~ F2[X~2+2)] = F2(2), and ~rom Equation 28~ after finding V mnq~i~i+c) = V 22L(i,i+c) = V 221(2,2+2) and from Equation 27, wherein V221(2,2+2) is obtained as V221[X(1,1+3)]
evaluated at X(i) = X(l), that is, V22l(x(1,1+3)] - V211(2,2+2) =
V221(2) at X(l) = X(l), we find that X[2,2+2] = X[2,4]~ X[2,3]

wherein the M221(2+2) load system reaches its limiting deceleration ~155146 rate L221(3) before load system M2ll(2+l). Therefore, the in-tensity of the M21l(2+1) load system at this location, M211(3), becomes superfluous. This being justified in that any expansion of the existing orifice area from this location, having a decay rate predicat~d upon a load system of higher intensity, will contain the momentum of load system 3 below its limiting change level. The X[2,4] displacement must therefore be used as the extent of control region 2 to insure that load system M221[X(2)]
does not exceed its lImiting deceleration rate ~ 21(3). Accord-ingly, X~2,4] = X12,2'~ = X(2) V 121(2) and 2L1211X(2)1 Eq. ~37) The V121~2) velocity of load system 2 can be ohtained by ~auation 27, where V121(2) = V1211X~l,l+l)] evaluated at X~l) = X(l), wherein Vmnq(i~i+C) = V121(1,1~1) = V121(1), Fn[X(i+c)~= F~lX(l+l)] = F2(1), Mma(i+c) = Ml~ l) = Mll(l) X~i)l = MllllX~l)l = Mlll(l) Since the extent of control region 2 defines the origin or beginning of control re~ion 3, that is, the i-~3 location of design reference, and there are no subse~uent load systems of higher intensity then the M221(3) load system at this location, 221(3) L221~3)' F2(3) = F2(2)~ and M21(3) - M2 (2), control region 3 is designed for load system 4, that is, load s~stem 4 is now defined as Mmnq(3), where mna(3) ~ M221(3) =~ L (3) ~ M21(3)} .~ATRIX S

Therefore, the last control region, control region 3, is designed to maintain the deceleration rate of the M221(3) load system constant at the limiting value L221(3), throughout the X(3) extent of this control region, wherein, X(3) = S(3). There-fore, M (~') = M221(4) = M221(3) = M22llXt3)]

V 221(3) and S(3) = -2L221(3) E~. ~38) r The V221(3) velocity of load system 4 ~M221(3) , can be obtained by Equation 27, where V221(3) V2211X( , )]
at X(2) = X(2~, wherein Vmnq(i~i+c) = V221(2, ) 221 Fn[X(i+c)] = F2[X(2 ~2)1 = F2(2), Mmq(i~C) = M21(2+2) = M21(2), MmnqlX(i)] M1211X(2)] = M121(2)-Now that we have established and defined these load systems, and established that the intensities of the load systems will re-main constant througlout their respective control regions, rela-tive to the parameters of design selected in this example, we can identify these load systems in relation to their respective control regions and order of intensities as follows:

(M~ Xtl,l')] = ~ M lX(l)] ~

mnq~X(i~ M1211X(2,2')1 = ~ ~ MlllX(2)]3 MATRIX 6 I ~21X(3~
M221tXt3~3') ] - L221tX(3) ] 21tX(3) 1 11551~6 where X(i) = X(i,i'), and ST = X~l~l') + X(2,~ (3,3~) Ea. (39) or ST - X(l) + X(2) ~ ~(3) Eq. (40) where Xt3) = S(3).

For Example 2, since Mmnq(i) Mmnq[ mnq wherein Mmnq[X(i)] remains constant throu~hout the X(i) extent of its respective cnntrol region, Eauation 33 can be evaluated as follows:
For i = l,and O'X(i)~X(l,l') = X(l):
__ 111 E111(1)L111(1 ~ Vlll(l~ [1 ~ S(ll Eq (41) X(l) Alll~X(1)3 . . ..
~ where in Equation 41, X(l) = O
1 where in Equation 41, X(l) = 1 X(l) where in Equation 41, X(l) = X(l) For i = 2, and X(l)~X~i)~tX(l,l')+X(2,2')]=tX(l~X(2)1:

~Ml 21 ( 2 ) L ~3 Vl 21 ( 2 ) [X(i)-X(l)] = X(2) Al?ltx(2)l where in Equation 42, X(2) = O
1 where in Equation 42, X(2) = 1 X(2) where in Equation 42, X(2) = X(2 ......

For i=3, and ~X(l)+X(2)~X(i)~X(l,l')+X(?,2')~X(3,3') =
!X(l)+X(2)~x~3) ~

~221(3)L221(33221(3) ~ ~ ~7~-J Eq. (43) tX(.i)-X(l)-X(2)1=X(3)A2211X(3)]

O where in E~uation 43, X(3) = O
1 where in Equation 43, X(3) = 1 X(3) where in Equation 43, X(3) = X(3) Now that all the pertinent data has been obtained, the orifice area pattern can be representea graphically as illustrated in Fig. 6.
Then if Equation 17 is expanded to represent the axial displacement "D" as a function of two variables, location i, and displacement X(i), relative to the equations given, the location of orifice holes in a spaced hole ~evice of this invention can be determined indepen~.~ntly for each control region as follows:

~ D[i,X(i)] = ~ 4~lx ( i) 3 ~ 2 ) E~ 4) where A[X(i)] represents the total remaining orifice area expressed as a function of displacement X(i) from a given i location of de-sign reference, n(i) represents the nth orifice hole of the given i location control region, wherein, n(i) = 1, 2, 3,....N(i), where N(i) represents the total number of orifice holes used in the given i location control region, where S(i) represents the total virtual stroke of the given i location control region, and l~SS14~;
d(i) represents the size of orifice holes used in the given i location control region, wherein all N(i) orifice holes within the given control region are of the same d(i) size.

For exa~le, with reference to Fig. 5 of Example 1, for i=l, X(i)=X(l)=0, A[X(i)l=A[X(l)]-A[0]= .02812 in. , N(i) = N(l) = 3, d(i) = d(l) = .07721 in., and S(i) = S(l) = 4.0 in., with respect to control region 1, Eauation 44 becomes D[l,X(l)] = S~ d4([)]n(1)~ q (45) and for n(l) D[l,X(l~]~,in.

1 1.1836 2 2.1~36

3 2.9614 Based on the foregoing disclosure, and the aspect of prac-ticality and manufacturing economics, it has been established that a device of this invention, having a total displacement stroke of 6.0 inclles~ can be manufactured to control as few a.s two distinctively different load systems and as many as 64 dis-tinctively d:iffe.rent load flystems~ Further, a device of this invention having a greater displacement can be economically manufactured to control a greater number of distinctively differ-ent load systems.
The shock absorber system described herein accomplishes deceleration control over a wide range of distinctively differ-ent load systems, wherein each load system is defined by its rest mass, velocity, limiting deceleration rate, and propelling force, .

l~SS~46 wherein when in effect, such propeLliny forces may vary or remain constant. Without any adjustment mechanism, this type of shock absorber provides individual deceleration control, and total arrestment for all load systems considered within the scope of its design range, wherein these load systems may be constant in-tensity load systems or load systems of varying intensity, and accomplishes this most efficiently by utilizing the full displace-ment stroke of the device for the arrestment of each load system Thus~ the self-adjusting shock absorber described hereln provides proportional stopping forces: low stopping forces for low momen-tum load systems and higher stopping forces for higher momentum load systems. The self-adjusting shock absorber can also accommo-date intermediate load systems, that is, load systems not specific-ally accounted for but whose intensity lies between minimum and maximum design values when the impact velocities of such inter-mediate load systems fall within the design range.
Because the system does not require adjustment mechanisms for varying the orifice area, the shock absorber's performance stability relative to temperature is increased because there is no inherent leakage. ~he installation time is reduced 9 ince there is no need ~or trial runs and adjustments, so long as the loads to be decelerated are known to be within the wide design range. Since the shock absorber has already been designed to handle a wide range of load intensities, the guesswork is taken out of load system deceleration control.

-Rest Mass Body at rest or having no motion Mass System or Load Body in motion with or without external System force applied Equivalent Mass A measure of force relative to motion, or a measure of mass relative to motion, or a measure of force and mass relative to motion Intensity A measure of the equivalent mass of a load system reLative to its existing state, wherein the measure may vary with respect to time and place Equivalent Mass System An equivalent mass, as deflned above, with or Load System or without external forces applied Potential The ability to do work Potential Energy A state of energy that has the abiLity to do work Potential State A specific state of energy measured with respect to location, displacement and time Total Energy State A specific state of one or more forms of energy, such as potential energy, and kinetic energy, measured with respect to location, displacement and time Kinetic Energy The energy of a body in motion Limiting Deceleration The deceleration rate imposed upon an Rate M~ or an ~ mass system or equivalent m~a~s system,n~y design choice, which may not be exceeded Rest mass of m-magnitude measured in the FT-LB~EC ~ystem Mm Mass system or equivalent mass system of q magnitude-m, having a finite velocity of magnitude-q, wherein, the magnitude of the mass or the eguivalent mass of this system is measured in the FT-LB-SEC ~ystem Mmn Ma9s system or equivalent mass system com-q posed of a rest mass of m-magnitude, having an applied force of n-magnitude; wherein, the rest mass and applied force have a common velocity of q-magnitude; wherein, .. ~ .

- ..

. . .

llSS~46 ~nnq (Cont.) the magnitude of the mass or the equiva-lent mass of the combined system is measured in the FT-LB-SEC system (i) Rest mass of m-magnitude, wherein the magnitude of the rest mass is measured at the specific location (i) in the FT-LB-SEC system Mm[X(i)] Rest mass of m-magnitude expressed as a function of displacement X(i), wherein, the magnitude of the rest mass, measured at the specific location (i)~ remains constant with respect to displacement X(i), wherein the magnitude of the rest mass is measured in the FT~LBffEC system M (i) Mass system or equivalent mass system, mq where.in the magnitude of the mass of this system is measured at the specific loca-tion (i) in the FT-LB-SEC system Mm ~X(i)] Mass system or equivalent mass system, q expressed as a function of displacement X(i), wherein, the magnitude of mass or equivalent mass of this system, measured at the specific location (i), may vary or remain constant with respect to displace-ment X(i), wherein the magnitude of the mass or the equivalent mass o~ this system is measured in the FT-LB-SEC system mnq Mass system or equivalent mass system, wherein the magnitude of the mass of this system is measured at the specific loca-tion (i) in the FT-LB-SEC system Mmn [X(i)] Mass system or equivalent mass system q expressed as a ~unction o~ displacement X(i)~ wherein~ the magnitude of mass or the equivalent mass of this system, measured at the specific location (i), may vary or remain constant with respect to displacement X(i), wherein, the magnitude of the mass or the equivalent mass of this system is measured in the FT-LBffEC system Vq A velocity of q-magnitude measured in the FT-SEC system V (i) A velocity of q-magnitude, wherein the q magnitude of velocity is measured at the specific location (i) in the FT-SEC system ~l~S~46 Vq~X(i)~ A velocity of q-magnitude expressed as a function of displacement X(i), wherein, the magnitude of velocity, measured at the specific location (i), may vary or remain constant with respect to displace-ment X(i), wherein, the magnitude of velocity is measured in the FT-SEC system Vmnq~X(i)] The velocity of an Mmq or an Mmnq mass system or equivalent mass system ex-pressed as a function of dispLacement X(i), wherein, the magnitude of velocity of the Mmq or Mmn mass system or equiva-lent mass system,qmeasured at the specific location (i)~ may vary or remain constant with respect to displacement X(i), where-in, the magnitude o~ velocity is measured in the FT-SEC system amn (i) The deceleration rate oE an M~q or an q Mmnq mass system or equivalent mass system, wherein the magnitude of the de-celeration rate of the Mmq or Mmnq mass system or equivalent mass system lS
measured at the specific location (i) in the FT-SEC sys tem amnq[X(i)] The deceleration rate of an Mmq or an Mmnq mass system or equivalent mass system expressed as a function of displacement X(i), wherein, the magnitude of the de-celeration rate of the Mmq or Mmnq mass system or equivalent mass system, measured at the specific location (i), may vary or remain constant with respect to displace-ment X(i), wherein, the magnitude of the deceleration rate is measured in the FT-SEC
system mnq( ) The limiting deceleration rate imposed upon an Ml~g or an Mmnq mass system or equivalent mass system, wherein the maynitude of the limiting deceleration rate imposed is measured at the specific location (i) in the FT-SEC sys~em Lmnq[X(i)] The limiting deceleration rate imposed upon an Mmq or an Mmnq mass system or equivalent mass system, expressed as a function of displacement X(i), wherein, the magnitude of the limiting deceleration rate imposed upon the Mmq or Mmnq mass system or equivalent mass system, measured at -the specific location (i), may vary or remain constant with respect to displace-ment X(i), wherein, the magnitude of the limiting deceleration rate is measured _ r~ in the FT~EC system ~43 ~

~55~46 Fn A force of magnitude-n, measured in the LBS-force system Fn(i) A force of n-magnitude, wherein the magni-tude of force is measured at the specific location (i) in the LBS-force system Fn[X(i)~ A force of n-magnitude, expressed as a function of displacement X(i), wherein, the magnitude of force, measured at the specific location (i), may vary or re-main constant with respect to displace-ment X(i), wherein, the magnitude of force is measured in tne LBS-force system (i) = i A location of design reference established by a particular Mmq or Mmnq mass system or equivalent mass system; wherein, this Mmq or Mmnq mass system or equivalent mass system has reached its limiting de-celeration rate at this location; wherein, upon reaching its limiting deceleration rate, this mass system or equivalent mass system can be defined at this location as an Mmq(i) or Mmnq(i) design mass system or equivalent design mass system; wherein, the specific location or design reference can be used to identify this design mass system or evivalent design mass system;
wherein, this specific location of design reference can also be considered a loca-tion of common reference for all mass systems or equivalent mass systems con-sidered X(i) A displacement from an i location of design reference X(i) The extent of an X(i) displacement, measured from an i location of design reference (i) ~ a il ~ location of d~sign reference establish-ed by a particular Mma(i~c) or Mmn(i~c) mass system or equivaIent mass sys~em, wherein, this mass system or equivalent mass system has reached its limiting deceleration rate at this location within the shortest X(i) displacement; wherein, the X(i) extent X(i,i') of this displace-ment defines the respective (i,i') con-trol region; wherein, this ~q(i+c) or Mmnq(i+C) mass system or equlvalent mass system can be redefined at this (i)' location as an Mmq(i) or Mmnq(i) design mass system or equivalent design mass system ~lS5~6 (i,i') Locations of design reference used to identify the control region established for an Mmq(i) or Mmnqti) design mass system or equivalent design mass system Xli,i') The design extent of an X(i) displace-ment, bounded by two locations of de-sign reference, whi.ch is used to de~ine the extent of an (i,i') control region, wherein, a specific X(i,i') extent can be used -to identify a specific Mmq(i) or M~nnq(i) design mass system or equlvalent deslgn mass system with reference to an ordering matrix; wherein, the ordering matrix is used to define all design mass systems or equivalent design mass systems in the ordering sequence established for them c ~ relative order number used in conjunc-tion with an (i) location of design reference to identify a particular mass system or equivalent mass system with respect to its ordered location from an Mmq(i) or Mmnq(i) design mass system or equivalent design mass system~ wherein, the design mass system or equivalent design mass system has been defined by an ordering matrix; wherein, the ordering matrix is established to define the rela-tive order of all mass systems or equiva-lent mass systems at a common location of design reference (i); wherein, ths ordering matrix is also established to define the relative order of all design mass systems or equivalent design mass systems with respect to all (i) locations of design reference, and wherein, this relative order number "c" may take on integer values rom c=l to c=N-l (i+c) A random combination number u~ed to identi~y a particular Mmq(l+c) or Mmnq(i~C) mass system or equivalent mass system with respect to its ordered loca-tion from an Mmq(i) or Mmnq(i) design mass system or equivalent design mass system , wherein, the desiyn mass system o.r equivalent design mass system has been defined by an ordering matrix, wherein, the Mmq(i+C) or Mmnq(i+C) mass system or equivalent mass system is larger than an Mmq(i) or M~nnq(i) design mass system or equivalent design mass system, and larger than or equal to an ~nq(i+l) or Mmnq(i+l) mass system or equivalent mass system 1~55~6 Mmq(l+c) A particular mass system or equivalent mass system identifiable with respect to its ordered location from an Mmq( ) or Mmnq(i) design mass system or equiva-lent design mass system~ wherein, the design mass system or equivalent design mass system has been defined by an order-ing matrix Mmnq(i+C) Same as for Mmq(i+C) Mmq(i+l) A particular mass system or equivalent mass system identifiable with respect to its ordered location from an Mmq(i) or Mmn~(i) design mass system or equivalent deslgn mass system, wherein, the design mass system or equivalent design mass system has been defined by an ordering matrix; wherein, the Mmq(i+l) or Mmnq(i+l) mass system or equivalent mass system is the closest larger mass system or equiva-lent mass system to an Mmqti) or Mmnq(i) design mass system or egulvalent deslgn mass system, and wherein, an Mm~(i+2) or Mmnq(i+2) mass system or equivaIent mass system is the next closest larger mass system or equivalent mass system .... etc.
X(i+c) A reference displacement, used in general to represent the displacement of an Mmq(i+c) or Mmnq(i+c) mass system or equivalent mass system (i,i+c) A relative location placement identifier, used to position a particular Mmq(i+C) or Mmnq(i+C) mass system or equivalent mass system at an (i) location of design reference V nq(i,i+c) The velocity of a particular Mm~i+c) or Mmnq(i+C) mass system or equiva ent ma~s system at an (i) location o~ design reference X(i,i+c) The relative di.splacement of a particular Ml~q(i+c) or Mmnq(i+c) mass system or equivalent mass system from an (i) loca-tion of design reference vmnq[x(i~i+C)] The velocity of a particular Mm~(i+c) or Mmnq(i+c) mass system or eguiva ent mass system at an (i) location of design reference, expressed as a function of its relative displacement from this (i) location of design reference S(i) The X(i) displacement progression re-quired to generate a complete i location control region, that is, the total virtual stroke of the control region H[X(i)] A dimensionless displacement ratio used to define parametric variations

Claims (16)

1. A shock absorber for decelerating impacting loads, said shock absorber being of the type comprising a closed hydraulic cylinder, a piston in said cylinder having a predetermined stroke from an initial position to a final position therein, and fluid passageway means for discharging fluid from the portion of the cylinder ahead of the piston as the piston moves away from its initial position in response to an impacting load, said passage-way means having means for controlling the fluid discharge rate as a function of piston displacement from said initial position, wherein the improvement comprises:
said controlling means without adjustment providing a progressively diminishing fluid discharge rate as a function of said piston displacement as said piston traverses a predefined portion of its stroke, defining a control region, to approximate a predetermined de-celeration profile for one nominal design mass system, and providing a progressively diminishing fluid dis-charge rate as a function of said piston displacement as said piston traverses another predefined portion of its stroke, defining another control regions to approxi-mate a predetermined deceleration profile for another nominal design mass system characterized at its point of impact, and thereafter in the case of an applied propelling force, as different from said one mass system in that its mass, velocity and propelling force defining an equivalent mass system is substantially different from that of said one mass system at its point of impact.

2. The shock absorber as set forth in claim 1, wherein said predefined portions of said stroke correspond to the initial portion and the final portion of said stroke, respectively, the mass system with respect to which the controlling means provides a predetermined deceleration profile in the initial portion of said stroke having a minimum intensity among a plurality of mass systems in a design range to which said shock absorber is sub-jected and the mass system with respect to which said controlling means provides a predetermined deceleration profile in the final portion of said stroke having a maximum intensity among said plurality of mass systems.

3. The shock absorber as set forth in claim 1 or 2, where-in said predetermined deceleration profile is a constant level of deceleration.

4. The shock absorber of claim 1, wherein said predefined portions of said stroke are consecutive adjacent portions of said stroke such that the respective control regions are consecutively continuous.

5. The shock absorber of claim 4, wherein the end of the first one of said consecutive control regions is determined as the point at which a predetermined level is obtained for the first time in the deceleration of an object for which the next control region is designed to provide said predetermined deceleration profile,

6. The shock absorber of claim 1, wherein the relationship between the fluid discharge rate and piston displacement through-out each of said control regions is determined in accordance with the velocity at the beginning of the respective control region of an object which at its point of impact, and thereafter in the case of an applied propelling force, had the respective equiva-lent mass for which said control region provides a predetermined deceleration profile.

7. The shock absorber as set forth in claim 1, wherein said controlling means includes orifice means for progressively diminishing the orifice area for fluid discharge with respect to each control region, the approximate decay rate of the orifice area as a function of piston displacement being different at the end of said one control region from that at the beginning of an-other control region.

8. The shock absorber as set forth in claim 7, wherein said orifice means provides an exponentially decaying orifice area with piston displacement in a given control region.

9. The shock absorber as set forth in claim 7, wherein said orifice means includes a plurality of axially spaced dis-charge ports through said cylinder.

10. The shock absorber as set forth in claim 9, wherein said discharge ports corresponding to a given control region are axially spaced over the corresponding portion of the stroke.

11. The shock absorber as set forth in claim 10, wherein for a given control region, said fluid discharge ports each pro-vide the same rate of discharge, the decay rate of the orifice area being provided by a progressively closer axial spacing of said discharge ports in a direction toward said final position of said piston.

12. The shock absorber as set forth in claim 11, wherein the discharge rate of the individual discharge ports in one of said control regions differs from the fluid discharge rate of the individual discharge ports in another control region.

13. The shock absorber as set forth in claim 7, wherein said orifice means includes metering means, having means for approximately parabolically decreasing the total orifice area for fluid discharge from the cylinder with respect to piston displacement in a given control region.

14. The shock absorber as set forth in claim 13, wherein said control regions are consecutive and correspond to first and second adjacent portions of said stroke, said orifice means terminating the preceding approximately parabolic relationship between the rate of orifice area decay and piston displacement at a truncation point between said first and second control regions, such that a new parabolic relationship with a slower initial rate of orifice area decay with respect to piston dis-placement than the immediately preceding rate is begun in the second control region.

15. The shock absorber as set forth in claim 7 wherein said orifice means includes a fluid discharge orifice and a metering pin of progressively diminishing cross-section having an end of smaller cross-section which is received in said orifice, and means for advancing said pin axially through said orifice with increasing piston displacement from said initial position such that more and more of said orifice is obstructed by said pin, whereby the orifice area for fluid discharge from the cylin-der is progressively diminished over the stroke of the piston.

16. A shock absorber for decelerating objects impinging thereagainst, said shock absorber being of the type comprising a hydraulic cylinder, a piston in said cylinder and having a pre-determined stroke therein from a first position adjacent one end of the cylinder to a second position adjacent the other end of the cylinder, a piston rod extending externally of said cylinder from said piston, means resiliently biasing said piston to said first position, a hydraulic reservoir and fluid passageway means from the cylinder to the reservoir through which the hydraulic fluid in the cylinder flows to the reservoir when the piston moves toward the second position in response to a shock force to be absorbed being applied to the piston, said passageway means having orifice means therein for controlling the rate of flow of hydraulic fluid to the reservoir and thereby establishing the resistance of the shock absorber to shock forces, said orifice means providing different rates of flow for different parts of the stroke of the piston as it moves from said first position to said second position, said shock absorber being subjected to shock forces consisting of a plurality of different equivalent mass systems including a maximum mass system and a minimum mass system, said shock absorber being characterized by:
said orifice means establishing a rate of flow to the reser-voir, for an initial part of said stroke as said piston moves away from said first position, such that there is a constant de-celeration of the object associated with the minimum mass system during said initial part of the stroke, and establishing a rate of flow to the reservoir, for a final part of said stroke as said piston moves to the second position, such that there is a constant deceleration of the object associated with the maximum mass system during said final part of the stroke.