Aeration preventing shock absorber

A shock absorber comprising a cylinder, cylinder head having a relief check valve therein including an annular valve spool, relief valve ball, spring support, valve spring and valve cap, piston, piston head, outer case, foot valve body, dust cover, piston bellows and pivot bushing assemblies.

BACKGROUND OF THE INVENTION 
This invention relates to a shock absorber for railcars. More specifically, 
the invention relates to a shock absorber for use on a trailer on flat car 
(TOFC) service railcar utilizing a single axle truck. 
In the development of more fuel efficient railcars for trailer on flat car 
(TOFC) service some types of fuel efficient TOFC railcars which are 
comprised of articulated units having non-cushioned trailer hitches 
installed thereon control the forces transmitted to the trailer load 
through the use of end-of-car cushioning devices on the TOFC railcar and 
the use of shock absorbers between the trucks and frame of the TOFC 
railcar. These types of articulated TOFC railcars offer significant 
advantages over the conventional eighty-nine foot (89') flat railcar in 
loading of the trailers on the TOFC railcar and fuel savings during 
operation of the train. 
While some prior art shock absorbers may be utilized for such new 
articulated TOFC railcars, it is desirable to have a shock absorber 
designed specifically for use in such railcars. Typical prior art shock 
absorbers are described or referred to in U.S. Pat. Nos. 3,556,264, 
3,682,103, and 4,106,412. 
SUMMARY OF THE INVENTION 
The shock absorber of the present invention is designed for use in the fuel 
efficient, articulated TOFC railcars and is a reliable, easy to 
manufacture unit having an improved means for oil control to prevent 
aeration of the oil or air entrainment in the oil during use thereby 
yielding improved performance. The shock absorber of the present invention 
comprises a cylinder, cylinder head, piston, piston head, outer case, foot 
valve body, dust cover, piston bellows, and pivot bushing assemblies.

DESCRIPTION OF THE INVENTION 
Referring to FIG. 1, the shock absorber 10 of the present invention 
comprises cylinder 12, cylinder head 14, piston 16, piston head 18, outer 
case 20, foot valve body 22, dust cover 24, piston bellows 26 and pivot 
bushing assemblies 28. 
The cylinder 12 comprises a cylindrical annular member 30 having a 
chamfered annular surface 32 on the interior of one end thereof, annular 
recess 34 on the interior of the other end thereof, upper annular recess 
36 on the exterior of one end thereof and lower annular recess 38 on the 
exterior of the other end thereof. 
The cylinder head 14 comprises a cylindrical annular member 40 having a 
bore 42 therethrough having, in turn, first annular seal recess 44, second 
annular seal recess 46, and annular oil recess 48 therein, counter bore 49 
which sealingly engages upper annular recess 36 of the cylinder 12, 
annular bellows lip 50 on the exterior of one end thereof, annular bellows 
recess 52 on the exterior thereof, threaded exterior portion 54 which 
engages a portion of the outer case 20, annular seal recess 56 on the 
exterior thereof, oil transfer bore 58 connecting annular oil recess 48 
with the exterior end surface 60, relief valve bore 62 having, in turn, 
threaded portion 64, intermediate portion 66, conical surface 68 and 
reduced diameter portion 70, oil transfer bore 72 connecting relief valve 
bore 62 to oil return tube bore 74, oil return tube 76 and fixed orifice 
bore 77 which extends from annular end surface 79 of the cylinder head 14 
to oil return tube bore 74. The oil return tube 76 comprises a spiral 
wound tubular member 78 which has an overall inner diameter slightly 
larger than the exterior diameter of cylinder 12, an overall outer 
diameter slightly smaller than the interior diameter of the outer case 20 
and an overall length sufficient for the outlet 80 of the tubular member 
78 to be located near the top of the foot valve body 22 and extend 
substantially below the free surface of the oil in the shock absorber 10 
contained between the cylinder 12 and outer case 20 when the shock 
absorber 10 is in operation. The inlet 82 of the tubular member 78 is 
secured to oil return tube bore 74 of the cylinder head 14. 
The piston 16 comprises an elongated cylindrical member 84 having a reduced 
diameter portion 86 on one end thereof, threaded portion 88 on one end 
thereof, bellows recess 90 in the exterior surface on the other end 
thereof and dust cover end 92 secured to the other end thereof. 
The piston head 18 comprises a cylindrical annular member 94 having 
threaded bore 96 therethrough, a plurality of holes 98 surrounding 
threaded bore 96 and extending through piston head 18, annular seal recess 
100 in the exterior thereof and ring valve plate 102 which covers the 
plurality of holes 98 in piston head 18 and has a bore 104 therethrough 
having, in turn, a diameter sufficient to allow the ring valve plate 102 
to move freely upon the reduced diameter portion 86 of the piston 16 when 
the plate 102 is installed thereon. The ring valve plate 102 moving on the 
piston 16 in response to oil contained within cylinder 12 flowing through 
the plurality of holes 98 in piston head 18 into the cavity 202 formed 
between cylinder 12 and piston 16. If desired, a spring 103 (shown in 
dotted lines) may be included on the reduced diameter portion 86 of the 
piston 16 to bias the ring valve plate 102 into engagement with the piston 
head 18. 
The outer case 20 comprises a cylindrical elongated annular member 106 
having a threaded bore 108 on one end thereof, first bore 110, second bore 
112, and outer case cover 114 secured to the other end thereof. 
The foot valve body 22 comprises a cylindrical member 116 having first bore 
118 receiving annular recess 38 of cylinder 12 therein, second bore 120 of 
smaller diameter than bore 118, end 122 having, in turn, a plurality of 
holes 124 therein, cylindrical exterior surface 126, annular chamfered 
surface 128, end surface 130 which abuts the interior of outer case cover 
114 and foot valve plate 132 which overlies the plurality of holes 124 and 
is slidably retained in second bore 120 by abutting the end surface 134 of 
cylinder 12. If desired, a spring 136 (shown in dotted lines) may be 
installed between end surface 134 of cylinder 12 and foot valve plate 132 
to bias the plate 132 against end surface 133 of foot valve body 22. 
The dust cover 24 comprises a cylindrical elongated annular member 138 
having one end secured to dust cover end 92 while the other end surrounds 
the upper portion of the outer case 20. 
The piston bellows 26 comprises an elastomeric, resilient bellows 140 
having one end 142 retained within annular bellows recess 90 in the 
exterior surface of piston 16 while the other end 144 is retained within 
annular bellows recess 52 in the exterior of cylinder head 14. 
The pivot bushing assemblies 28 each comprise cylindrical pivot housing 146 
which is secured either to dust cover end 92 or outer case cover 114, 
elastomeric bushing 148 and pivot bushing 150 contained within elastomeric 
bushing 148. 
The first annular seal recess 44 in the cylinder head 14 contains suitable 
elastomeric piston wiper seal 152 therein while second annular seal recess 
46 in cylinder head 14 contains suitable elastomeric piston seal 154 
therein, annular seal recess 56 contains suitable elastomeric seal 156 
therein and annular seal recess 100 in piston head 18 contains suitable 
metallic piston seal ring 158 therein. 
Referring to FIG. 2, the relief check valve assembly 160 located within the 
cylinder head 14 is shown. The relief check valve assembly 160 comprises 
valve spool 162, relief valve ball 164, spring support 166, valve spring 
168, valve cap 170, set screw 172, and elastomeric seal 173. 
The valve spool 162 comprises an elongated, cylindrical, annular member 174 
having a first bore 176 therein, second bore 178, annular recess 180 in 
the exterior thereof and plurality of holes 182 therethrough which allow 
communication between first bore 176 and annular recess 180. 
The relief valve ball 164 comprises a spherical ball which is received 
within valve spool 162 in first bore 176 and covers second bore 178. 
The spring support 166 comprises a cylindrical shaft 181 having a 
cylindrical head 183 on one end thereof which has, in turn, recess 184 
therein to receive relief valve ball 164 therein. 
The valve spring 168 comprises a spirally wound valve spring slidably 
retained within first bore 176 of valve spool 162 having an overall inner 
diameter sufficiently large to slidably receive cylindrical shaft 181 of 
spring support 166 therein such that one end of the valve spring abuts the 
cylindrical head 183 of spring support 166. 
The valve cap 170 comprises a cylindrical member which is slidably received 
within bore 62 of cylinder head 14 and has chamfered surface 186 on one 
end thereof. 
The set screw 172 comprises a cylindrical member having a threaded exterior 
surface 188 thereon which engages threaded portion 64 of relief valve bore 
62 of cylinder head 14 and recess 190 in one end thereof to engage a 
suitable tool to allow the installation of the set screw 172 in the 
cylinder head 14. 
Referring to FIG. 3, the cylinder head 14 is shown from the bottom. The 
fixed orifice bore 77 is offset from the reduced diameter portion 70 of 
relief valve bore 62. The fixed orifice bore 77 extends angularly across 
the cylinder head 14 and intersects oil transfer bore 72 to allow fluid 
flow from annular cavity 202 to annular cavity 204. 
Referring again to FIG. 1, during operation of the shock absorber 10 when 
the piston 16 having piston head 18 thereon is forced downwardly in the 
cylinder 12 toward the foot valve body 22, the foot valve plate 132 is 
forced by the oil within cavity 200 to cover the plurality of holes 124 in 
the foot valve body 22 thereby preventing the oil within the cavity 200 
from flowing therethrough. When the oil within cavity 200 is prevented 
from flowing through the foot valve body 22, the oil flows into annular 
cavity 202 formed between cylinder 12 and piston 16 through the fixed 
orifice holes 98 in the piston head 18 thereby lifting ring valve plate 
102 from the piston head 18. If a spring 103 is utilized to retain the 
ring valve plate 102 in position preventing oil flow through the plurality 
of holes 98 in the piston head 18, the spring 103 need only apply enough 
force to the ring valve plate 102 to retain the plate 102 in position when 
the shock absorber 10 is in a non-vertical position. 
Since annular cavity 202 has a smaller volume than that of cavity 200, when 
the piston 16 having piston head 18 thereon is forced downwardly in the 
cylinder 12 toward the foot valve body 22 excess oil within annular cavity 
202 flows through fixed orifice bore 77 until the pressure within annular 
cavity 202 increases sufficiently to cause relief ball 164 to be unseated 
from bore 178 of the valve spool 162 thereby allowing oil to also flow 
through oil transfer bore 72 into oil return tube 76 and into annular 
cavity 204 between cylinder 12 and outer case 20. 
When the piston 16 is moved upwardly within cylinder 12 towards cylinder 
head 14, the ring valve plate 102 is forced by the oil within annular 
cavity 202 to cover the plurality of holes 98 in the piston head 18 
thereby preventing the oil within the annular cavity 202 from flowing 
therethrough. At this point, the oil within annular cavity 202 flows 
through fixed orifice bore 77 until the pressure within annular cavity 202 
increases sufficiently to cause relief ball 164 to be unseated from bore 
178 of the valve spool 162 thereby allowing oil to also flow through oil 
transfer bore 72 into oil return tube 76 and into annular cavity 204 
between cylinder 12 and outer case 20. While the piston 16 is moving 
towards cylinder head 14, due to the pressure differential between cavity 
200 and annular cavity 204, the oil in annular cavity 204 is caused to 
flow through holes 124 in foot valve body 22 lifting the foot valve plate 
132 from the foot valve body 22. If a spring 136 is utilized to retain the 
foot valve plate 132 in position blocking flow through holes 124 in the 
foot valve body 22, the spring 136 generally only need apply enough force 
to the foot valve plate 132 to retain the plate 132 in position blocking 
holes 124 in the foot valve body when the shock absorber 10 is in a 
nonvertical position. 
During operation of the shock absorber 10 the performance of the shock 
absorber 10 is not substantially degraded due to the aeration of the oil. 
By utilizing an oil return tube 76 to return the oil from cavity 202 
through relief check valve 160 to cavity 204 formed between cylinder 12 
and outer case 20 with the outlet 80 of the oil return tube 76 being 
located substantially below the free surface level of the oil in the 
cavity 204 aeration of the oil in the shock absorber 10 due to air being 
entrained in the oil as the oil exits fixed orifice bore 77 and/or relief 
check valve 160 through oil transfer bore 72 is substantially eliminated 
thereby optimizing the performance of the shock absorber. Also, the spiral 
oil return tube 76 acts as a series of baffle members in the cavity 204 to 
prevent aeration of the oil due to movement of the oil within the cavity 
204 during operation of the shock absorber 10. In this manner, the oil 
return tube 76 performs a dual function of the return of the oil from 
cavity 202 to 204 without aeration or the control of oil flow within 
cavity 204 without aeration thereby eliminating the separate usage of oil 
return tubes and baffles. 
By utilizing the surface 134 of the cylinder 12 to retain the foot valve 
plate 132 in position in the foot valve body 22 the manufacture of the 
shock absorber has been simplified since an additional member secured to 
either the cylinder 12 or foot valve body 22 to retain the foot valve 132 
is not required. 
The piston bellows 26 is utilized to keep the piston 16 free of dust, dirt 
and abrasive material when in service thereby extending the life of the 
shock absorber 10. 
By sizing cavity 202 to contain any ratio of the volume of cavity 200 the 
compression to extension hydraulic dampening ratio can be adjusted as 
required and the shock absorber 10 has a sufficient volume of oil present 
in the cylinder 12 at all times to ensure the desired performance of the 
shock absorber 10 without overheating or other degradation of the oil.