Force absorbing device and force transmission device

A force absorbing device and a force transmission device are provided including at least one member having a tubular configuration. A second member extends into one end of the tubular member and engages it in an interference fit to form a permanent joint. The tubular member and the second member have complementary bends at the permanent joint. The force absorbing device may include one or two such permanent joints. In the force transmission device, two such permanent joints are provided. The joints are made by cutting a tubular member to a desired length, press fitting a portion of a second member into one end of the tubular member to form a reinforced zone, and bending the second member and the tubular member at the reinforced zone to form the complementary bends and the permanent joint.

BACKGROUND OF THE INVENTION 
The present invention relates generally to novel joints and devices 
employing members having a tubular configuration and more particularly to 
novel automotive suspension and support devices, such as anti-sway bars, 
torsion bars, and the like. 
In automotive suspension and support systems, such components as anti-sway 
bars and torsion bars have been made from solid cylindrical metal stock. 
Typically, such stock would vary in diameter from 7/8 inch to 11/4 inch 
depending on the weight of the automobile and the particular ride 
characteristics desired. One problem with this prior construction is that 
components are typically quite heavy. For example, an anti-sway bar, 
sometimes referred to as a stabilizer bar, having a one inch diameter and 
a forty-two inch bushing to bushing length would weigh more than nine 
pounds. Typically, such anti-sway bars include one or more bends, as 
illustrated in U.S. Pat. No. 3,315,952. Although it is known that tubular 
material weights less than solid material, and although techniques for 
bending tubular material are also well-known, as illustrated in U.S. Pat. 
No. 1,903,436, to data no technique has been utilized successfully for 
making such anti-sway bars or torsion bars out of tubular material. The 
reason for this is that it is a characteristic of tubular material that 
once it is bent it is drastically weakened in the transition area. Thus, 
if the tubing is utilized in an application such as an anti-sway bar where 
a large amount of stress will be placed upon it, the tubing will tend to 
buckle and fail catastrophically in the transition area. 
SUMMARY OF THE INVENTION 
Accordingly, a force absorbing device and a force transmission device have 
been provided including at least one member having a tubular 
configuration. A second member extends into one end of the tubular member 
and engages it in an interference fit to form a permanent joint. The 
tubular member and the second member have complementary bends at the 
permanent joint. The force absorbing device may include one or two such 
permanent joints. In the force transmission device, two such permanent 
joints are provided. The joints are made by cutting a tubular member to a 
desired length, press fitting a portion of a second member into one end of 
the tubular member to form a reinforced zone, and bending the second 
member and the tubular member at the reinforced zone to form the 
complementary bends and the permanent joint. 
OBJECTS OF THE PRESENT INVENTION 
An object of the present invention is the provision of force absorbing and 
force transmitting devices which are lighter in weight than those 
heretofore available. 
A further object of the present invention is the provision of light weight 
force absorbing and force transmitting devices having performance 
characteristics which are nearly identical to those of heavier devices. 
Another object of the present invention is the provision of a novel joint 
construction enabling the use of tubular material in applications 
requiring bends under stress. 
A further object of the present invention is the provision of a method of 
making force absorbing and force transmitting device from tubular 
material. 
A still further object of the present invention is the provision of a 
method of joining tubular material to another member. 
Another object of the present invention is the provision of a method of 
making force absorbing and force transmitting devices which is both simple 
and inexpensive. 
Other objects, advantages, and novel features of the present invention will 
become apparent from the following detailed description of the invention 
when considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a preferred embodiment of a force absorbing device of 
the present invention. FIG. 1 shows a torsion bar generally shown at 10 
including a first member 12 having a tubular configuration. The tubular 
member 12 includes end portions 14 and 16 and main body portion 18 between 
ends 14 and 16. The end portion 14 includes an attachment means, 
illustrated as a hexagonal fitting 20. The torsion bar 10 further includes 
a second tubular member 22 having end portions 24 and 26. The end portion 
24 of tubular member 22 engages the end portion 16 of tubular member 12 in 
an interference fit, so that a permanent joint 28 exists between tubular 
members 12 and 22. Although tubular member 12 is shown as extending into 
the interior of tubular member 22, it is to be understood that it is 
within the scope of the invention to reverse the positions of these 
members so that tubular member 22 would extend into the interior of 
tubular member 12. The tubular members 12 and 22 include complementary 
bends at the permanent joint 28. 
The torsion bar 10 is affixed to the frame of an automobile in a 
conventional manner by means of bushing 30 on the frame of the automobile. 
The torsion bar 10 is preferably held by the bushing 30 in the doubled, 
and therefore reinforced, zone of the bar. Likewise, the hexagonal fitting 
20 is adapted to mate with a corresponding fitting on the automobile 
frame. The end 26 of the tubular member 22 also includes an attachment 
means (not shown) which permits end 26 to be affixed to the automobile 
suspension system. For example, the end 26 of tube 22 may be flattened and 
drilled to include a mounting hole. The tubular members 12 and 22 could be 
made from a variety of materials but are preferably made from manganese 
steel alloys. 
FIG. 1A illustrates a second embodiment of a force absorbing device of the 
present invention. A torsion bar 40 includes a tubular member 42 having 
end portions 44 and 46. A second member, preferably in the form of a solid 
steel bar 48, includes end portions 50 and 52. End portion 50 of steel bar 
48 extends into end portion 46 of tubular member 42 and engages end 
portion 46 in an interference fit. Thus, a permanent joint 54 exists 
between bar 48 and tubular member 42. The bar 48 and the tubular member 42 
include complementary bends at the permanent joint 54. End portion 52 of 
bar 48 includes an attachment means which is illustrated as an eyelet 56. 
The eyelet 56 is adapted to be fastened to an automobile suspension 
system. 
The torsion bar 40 further includes an attachment means on the end 44 of 
tubular member 42 for anchoring the torsion bar to the frame of an 
automobile. In this embodiment the attachment means includes a solid steel 
bar 58 having ends 60 and 62. End 60 of bar 58 extends into end 44 of 
tubular member 42 and engages end 44 in an interference fit. Thus, a 
permanent joint 64 exists between bar 58 and tubular member 52. The bar 58 
and tubular member 42 further include complementary bends at permanent 
joint 64. The end 62 of bar 58 is preferably flattened and includes an 
eyelet 66 for attaching bar 58 to the frame of an automobile. The torsion 
bar 40 is further anchored to the automobile frame by means of bushing 30, 
as discussed in connection with the torsion bar shown in FIG. 1. Although 
tubular member 42 is illustrated as having constant inside and outside 
diameters, it is within the scope of the present invention to either 
increase or decrease the diameter of tubular member 42 to alter the 
performance characteristics of the torsion bar 40. Thus, the main body 
portion 68 of the tube 42 may have one set of inside and outside diameters 
and the ends 44 and 46 may have a second set of inside and outside 
diameters. 
To illustrate the increased weight effectiveness, i.e. performance per unit 
weight of the torsion bars embodying the principles of the present 
invention, consider the following example. A torsionbar built in 
accordance with the principles of the prior art employed solid metal 
stockvarying in outside diameter from 1.05 inches to 1.285 inches and 
weighed 15.2 pounds. On the other hand, a torsion bar such as that 
illustrated in FIG. 1 had a first tube with an inside diameter of 1.2 
inches and an outside diameter of 1.4 inches and a second tube having an 
inside diameter of 1.4 inches and an outside diameter of 1.6 inches. This 
torsion bar exhibited nearly identical performance characteristics to that 
of the prior art torsion bar but weighed only 7.9 pounds, a savings of 7.3 
pounds or nearly 50 percent. 
FIG. 2 illustrates a force transmission device of the present invention and 
FIG. 2A is an end view of the device shown in FIG. 2. The force 
transmission device is illustrated as an anti-sway bar 70 including a 
tubular member 72 having end portions 74 and 76. A member 78, preferably 
in the form of a solid steel bar, includes ends 80 and 82. End 80 of solid 
member 78 extends into end 74 of tubular member 72 and engages tubular 
member 72 in an interference fit. Thus, a permanent joint 84 exists 
between tubular member 72 and solid member 78. Solid member 78 and tubular 
member 72 include complementary bends at joint 84. The member 78 includes 
attachment means 86 at end 82. The attachment means 86 is preferably a 
flattened portion on the end 82 including a mounting hole adapted to be 
affixed to an automobile suspension system. The anti-sway bar assembly 70 
is secured to an automobile frame by means of a pair of bushings 88 on the 
automobile frame. 
A second solid member 90 identical to the member 78 is joined to end 76 of 
tubular member 72 in the same manner as that discussed above. As is most 
clearly seen in FIG. 2A the end portions 74 and 76 of tubular member 72 
preferably have a reduced outside and inside diameter with respect to the 
main body portion 92. This reduction in inside diameter is designed to 
keep the size of solid member 78 and 90 to a minimum while retaining the 
desired performance characteristics of the anti-sway bar. It should be 
understood that it is within the scope of the present invention for the 
members 78 and 90 to be tubular instead of solid. In this case the joints 
84 and 94 would be similar to structure to the joint 28, shown in FIG. 1. 
Thus it is apparent that in accordance with the principles of the present 
invention, a new anti-sway bar has been provided which retains the 
performance characteristics of prior anti-sway bars but at the same time 
greatly reduces the weight of the bar. For example, an anti-sway bar 
constructed in accordance with the principles of the prior art and made 
from a solid bar having a one inch diameter and a forty-two inch bushing 
to bushing length would weigh about 9.34 pounds. However, an anti-sway bar 
constructed in accordance with the principles shown in FIGS. 2 and 2A and 
having an outside tube diameter of 1.2 inches and an inside tube diameter 
of 1 inch would slightly outperform prior anti-sway bars but would weigh 
only 4.1 pounds. This amounts to a weight reduction of 5.24 pounds or more 
than 56 percent. 
Referring now to the schematic illustrations of FIGS. 3A through 3E, a 
method of making a preferred joint in accordance with the principles of 
the present invention will be described in detail. A tube 100 is first cut 
to proper length as shown in FIG. 3A by a cutting tool 102. Any suitable 
cutting means will suffice such as shearing or turning means. Should the 
end of the tube require a reduction in inside diameter, it is run through 
an extruder 104, as shown in FIG. 3B. The jaws of the extruder 104 are set 
at an angle .alpha. preferably between 8 degrees and 12 degrees. It may 
further be desirable to flare the ends of the tube 100 before press 
fitting a member into the end of the tube. This is illustrated in FIG. 3C 
by forcing a tapered die 108 into the end of the tube 100. A solid member 
110 is cut to a desired length and an attachment means 112 is formed on 
one end thereof in accordance with known methods. The solid member 110 is 
then press fitted into the reduced end portion of tube 100, preferably by 
suitable hydraulic means, as shown in FIG. 3D. This press fitting 
operation creates a reinforced zone 114 in the doubled area occupied by 
both the tube 100 and the solid member 110. The members 110 and 100 are 
then bent at the reinforced zone 114, as shown in FIG. 3E. This is 
preferably accomplished by means of a known rocking die assembly 116. When 
press fitting the member 110 into the member 100, it is important to 
maintain a snug interference fit to create significant hoop tensile 
stresses in the tube 100. Of course, it is apparent how this method can be 
utilized to form the force absorbing and force transmitting devices of the 
present invention, as illustrated in FIGS. 1 and 2. For example, the force 
absorbing device of FIG. 1 would require only a single such joint, whereas 
the force absorbing device shown in FIG. 1A would require two such joints. 
The force transmission device shown in FIG. 2 would also require two such 
joints. It should further be apparent that tubular members only may be 
utilized to form the joints of the present invention, as illustrated in 
FIG. 1. In this case especially, the reduction step illustrated in FIG. 3B 
may be eliminated. 
A method of forming a second embodiment of the present invention is 
illustrated schematically in FIGS. 4A through 4D. Here a tubular member 
120 may be cut to any desired length as illustrated in FIG. 3A. The 
internal diameter of the tube 120 is then increased in diameter by means 
of extruder jaws 122. Once again, an 8 degree to 12 degree taper on the 
extruder jaws 122 is preferred. A slug of metal 124 is extruded to a 
desired outside diameter by an extruder 126, as illustrated in FIG. 4B. 
The slug 124 is reduced to an outside diameter sufficient to achieve an 
interference fit with the inside diameter of the unreduced portion of tube 
120. As shown in FIG. 4C the slug 124 is then inserted into the widened 
end of tube 120 until it engages the interior of the body portion of the 
tube 120. At this point, the slug 124 is press fitted, preferably by 
suitable hydraulic means into the body portion of the tube 120 to form a 
reinforced zone 128. The widened portion of tube 120 is then reduced to a 
desired internal diameter by means of extruder 126, as shown in FIG. 4D. 
The tube 120 and the slug 124 are then bent at the reinforced zone 128, as 
shown in FIG. 4E. This is accomplished by means of a known rocking die 
130. This alternate method of bending tubular members can be utilized 
quite effectively in making the force absorbing and force transmitting 
devices of the present invention. Thus, the torsion bars and anti-sway 
bars made by this method would contain a continuous tubular member 
reinforced at the bends by press fitted slugs of material. 
Thus, in accordance with the principles of the present invention, novel 
force absorbing and force transmitting devices are provided which are 
considerably lighter in weight than those heretofore available. 
Furthermore, this reduction in weight is accomplished at no sacrifice in 
the performance characteristics of these force absorbing and force 
transmitting devices. This greater weight effectiveness is accomplished 
since the present invention utilizes joint and bend constructions which 
permit the use of tubular material where heretofore solid material was 
required. Additionally, the methods employed by the present invention 
utilize relatively simple and inexpensive manufacturing techniques. This 
is contrasted with the manufacturing techniques required for making solid 
torsion and anti-sway bars which required expensive heat treating of stock 
steel. 
While there have been described what are at present considered to be the 
preferred embodiments of the present invention, it will be obvious to 
those skilled in the art that various changes and modifications may be 
made therein, without departing from the invention, and it is, therefore, 
aimed in the appended claims to cover all such changes and modifications 
as fall within the true spirit and scope of the invention.