Force recording seat belt assembly

A safety belt assembly of the present invention measures the amount of force exerted on the assembly and also the point in time when a force was exerted on the assembly. The assembly includes a first and second member associated with one another, mechanism associated with the first and second members for resiliently restraining relative movement and movably retaining said members with respect to one another; a mechanism responsive to relative movement of the first and second members for enabling a measurement of force and indicating a point in time when a force was exerted on the assembly; and a mechanism for securing the assembly to a safety belt and/or a buckle or anchor.

TECHNICAL FIELD 
The present invention generally relates to the field of seat belt 
assemblies and, more specifically, to seat belt assemblies having devices 
for measuring the force exerted on the belt during collisions and for 
indicating when the collision took place. 
BACKGROUND AND SUMMARY OF THE INVENTION 
Several industries, including motor vehicle, transportation and insurance, 
desire to have a device in the safety belt system of a motor vehicle which 
will indicate whether or not the safety belt was worn during an impact 
collision. Also, if the device was worn, when the collision occurred. In 
the past, the loading could only be determined when the belt was abraded, 
chafed or if the metal supports were bent or broken. However, many vehicle 
collisions are not severe enough as to bend or break the metal supports 
since they are made of very durable material. Thus, by a visual 
examination of a built-in safety belt assembly, it is not always possible 
to determine if the safety belt assembly was subject to a collision or if 
excessive forces had been exerted on the assembly. 
In order to overcome the inability to determine whether or not a safety 
belt was worn during a collision, it is one of the primary objects of the 
present invention to provide a safety belt assembly which determines the 
amount of force exerted on the safety belt assembly. 
An additional objective of the present invention is to provide the point in 
time when the excessive force was exerted on the safety belt assembly. 
To achieve the foregoing objectives, the safety belt assembly according to 
the present invention includes a first and second plate associated with 
one another; a flat elongated biasing member associated with the plates 
for resiliently restraining relative movement and movably retaining the 
plates with respect to one another; a mechanism response to relative 
movement of the plates for enabling a determination of an amount of force 
exerted on the assembly; and a mechanism for securing the assembly with a 
conventional safety belt and buckle. 
Also disclosed is a mechanism substantially similar to the above described 
assembly having a mechanism responsive to movement of the plates for 
indicating a point in time when a force was exerted on the assembly. 
Further, an assembly including both a mechanism for enabling a 
determination of an amount of force exerted on the assembly combined with 
a mechanism for indicating a point in time when a force was exerted on the 
assembly is disclosed. 
From the following description and claims, taken in conjunction with the 
accompanying drawings, other objects and advantages of the present 
invention will become apparent to one skilled in the art.

DETAILED DESCRIPTION OF THE INVENTION 
A seat belt assembly for recording force exerted on the assembly is 
generally illustrated in FIGS. 1 and 2 and is designated with the 
reference numeral 10. The seat belt assembly 10 includes a first plate 12, 
a second plate 14 and a resilient biasing member 16. A pair of retainers 
18 are on the first plate 12 for maintaining the second plate 14 in a 
movable relationship with the first plate 12. 
The first plate 12 has an overall rectangular configuration as seen in FIG. 
2. The retainers 18 extend vertically from the plate 12 forming a pair of 
guide walls for positioning the second plate 14 in a substantially 
parallel plane relationship with the first plate 12. The first plate 12 
has an aperture 28, which has a tongue 30 projecting into the aperture 28, 
for positioning the biasing member 16 between the plates 12 and 14. The 
aperture 28 is preferably rectangular and is positioned between the 
retainers 18 on the first plate 12. A second aperture 29 is in the first 
plate 12 for securing the first plate 12 to a conventional automobile 
safety belt 32. The aperture 29 enables the safety belt 32 to be placed 
through the first plate 12 and attached to itself for permanently securing 
the first plate 12 on the belt 32. 
The retainers 18 have a flange 20, extending horizontally from the 
retainers 18, which is substantially parallel to the first plate 12. The 
flanges 20 have at least one or more fingers 24 projecting from the 
interior surface of the flange 20. The flanges 20 have a descending tit 22 
which substantially functions the same as the fingers 24 which will be 
further discussed herein. 
The fingers 24, on the interior surface of the flange 20, descend at a 
desired angle. The fingers 24 are generally formed by a U-shaped cut in 
the flanges 20. The material within U-cut is bent downward towards the 
first plate 12 forming the fingers 24. The fingers 24 have a back stop 34 
which enable one way movement of the second plate 14. The fingers 24 have 
an annular wall 36 which enable the second plate 14 to slide one way 
against the fingers 24 before the backstop 34 traps the second plate 14 
prohibiting movement of the second plate in a reverse direction. The 
fingers 24 enable the second plate 14 to move incrementally in the first 
plate 12. 
The tongue 30 projects annularly above the aperture 28. The tongue 30 acts 
as a stop to secure the biasing member 16 on the first plate 12 in the 
assembly 10. Also, if a force of extreme magnitude is applied to the 
assembly 10 the tongue 30 will come into contact with the second plate 14 
prohibiting further movement of the second plate 14. 
The second plate 14 has an overall rectangular configuration as best seen 
in FIG. 2. At least one or more fingers 40 project vertically from the 
second plate 14. The second plate 14 has an aperture 42 which has a tongue 
44 projecting into the aperture 42. The aperture 42 is preferably 
rectangular and enables the resilient biasing member 16 to communicate 
with the first and second plates 12 and 14. A second aperture 45 is in the 
second plate 14 for securing the assembly 10 to a conventional buckle (not 
shown). 
The fingers 40 include an inclined wall 48 and a backstop 46. The fingers 
40 intermesh with the fingers 24 enabling the second plate 14 to move, in 
the direction of arrow A, incrementally in the first plate 12. The 
incremental movement occurs as follows. The inclined wall 48 slides 
against the wall 36 until backstop 46 passes the wall 36, wherein the 
backstop 46 comes into contact with the backstop 34. This abutting of the 
backstops 34 and 46 prohibits movement of the second plate 14 in a reverse 
direction. The intermeshing of fingers 24 with fingers 40 provides the 
assembly 10 with a ratchet interface between the two plates 12 and 14. 
Thus, as the second plate 14 moves, the fingers 40 will ratchet along 
fingers 24 incrementally moving the second plate 14 in the first plate 12. 
The resilient biasing member 16, positioned between apertures 28 and 42, is 
in communication with the first and second plates 12 and 14, holding the 
plates 12 and 14 in a first relaxed position, as best seen in FIG. 1. The 
resilient biasing member 16 is preferably a helical spring. The biasing 
member 16 has a pair of caps 50, one on each end of the spring, for equal 
distribution of the spring force. The caps 50 have apertures 52 which 
enable the biasing member to be positioned on the tongues 30 and 44. The 
biasing member 16 supplies a resistive force to the plates 12 and 14 which 
keeps the fingers 24 and 40 in contact with one another. 
The time indicator 54, best seen in FIG. 5, may be an electrical means, 
mechanical means, or a chemical means which will determine when a force 
was exerted on the safety belt assembly 10. An electrical means could 
include a starting mechanism and a conventional digital watch assembly 
having an elapsed time counter. Preferably, a chemical device is used 
which decays at a determined measurable rate. This decay provides the 
analyst with a simple determination as to when the force occurred from 
knowing the initial concentration, the decay rate and the remaining 
concentration of the chemical. 
The time indicator 54 is positioned in communication with the plates 12 and 
14. Preferably, the time indicator 54 would be positioned between plates 
12 and 14 on one side of apertures 28 and 42. The time indicator 54 may be 
an encapsulated foam having an exterior coating and a predetermined amount 
of chemical within the foam. Once a force is exerted on the indicator 54, 
strong enough to break through the encapsulated coating, the chemical will 
begin to decay in the presence of atmospheric conditions. Thus, when 
analyzed, the time indicator 54 will determine when the excessive force 
was exerted on the safety belt assembly 10. 
In a second embodiment of the present invention, best seen in FIG. 6, the 
time indicator 7 is in communication with a biasing member 72. The biasing 
member 72, preferably a helical spring, has a housing 74 around its 
circumference. The housing 74 has a flange 76. In this embodiment the 
biasing member 72 returns to a relaxed position after every compression. 
The flange 76 is positioned in a line of contact with the time indicator 
70 as the biasing member 72 is compressed. The time indicator 70 includes 
several encapsulated pockets 78. A wall 80 separates the pockets 78 from 
one another. As the biasing member 72 is compressed the flange 76 slides 
over the encapsulated time indicator 70. As this happens, the flange 76 
breaks through the encapsulated coating, enabling individual pockets 78 of 
the time indicator 70 to decay. This breakthrough occurs through one 
pocket 78 at a time. Thus, as small forces are exerted on the assembly 10, 
the flange 76 may break through only one pocket 78. When an excessive 
force is exerted on the assembly 10, the flange 76 will break through 
several pockets 78. A decay analysis of the remaining chemicals in each 
pocket 78 will determine the time when each pocket 78 was broken. The more 
pockets 78 broken through at one time will indicate a large amount of 
force exerted on the assembly 10 at that time. Thus, the analyst will be 
able to determine when the force occurred. Also, the analyst will be able 
to determine the force exerted on the assembly by measuring the distance 
traveled by the biasing member 72 along the time indicator 70. 
In the present invention the assembly 10 is assembled as shown in FIG. 1. 
The second plate 14 is secured, by aperture 44, in a conventional safety 
belt buckle (not shown). A force is exerted on the assembly 10 which has a 
magnitude large enough to activate the assembly 10. The second plate 14 
slides, in the direction of arrow A, in the first plate 12. This slide 
measures the force exerted on the assembly and the point in time when the 
force was exerted. 
The slide occurs as follows. The second plate fingers 40 are intermeshed 
with the first plate fingers 24. As the force is exerted, the second plate 
fingers 40 ratchet on the first plate fingers 24 moving, in the direction 
of arrow A, in accordance with the force exerted. The second plate back 
stop 46 comes into contact with a first plate back stop 34 halting the 
movement of the second plate 14 in a reverse direction. As this happens, 
the biasing member 16 compresses between the tongues 30 and 44 trapping 
the biasing member 16 in a compressed state. This compressed state records 
the force exerted on the assembly 10. Also, as the second plate 14 
ratchets in the first plate 12, the time indicator 54 is activated. The 
second plate 14 compresses the encapsulated time indicator 54, breaking 
through the coating, exposing the chemical to atmospheric conditions, 
beginning chemical decay. The amount of decay is used to determine when 
the exertion of force occurred. 
The force exerted will be measured by conventional spring equations since 
the spring constant and the linear displacement of the spring will be 
known. The time when the force was exerted will be determined by an 
analysis of the amount of the chemical remaining with respect to its known 
dissipation rate and the original chemical concentration. 
Once the analyst has determined the amount of force exerted on the assembly 
10, and at what point in time the force was exerted on the assembly 10 he 
may reset the assembly 10 for further use. This is done by replacing the 
time indicator 54 and resetting the biasing means 16 and fingers 24 and 40 
back to their relaxed positions. Thus, the assembly 10 is ready to be 
reinstalled in a vehicle. 
FIGS. 7-9 illustrate further embodiments of the present invention. 
Corresponding elements of the invention will be marked with reference 
numerals having primes, which relates to the same element as previously 
described. 
Turning to FIGS. 7 and 8, another embodiment of a recording force seat belt 
assembly is illustrated and designated with the reference numeral 10'. The 
assembly includes a first plate member 110 associated with a second plate 
member 112, both of which, are, in turn, associated with a biasing member 
114. A belt 32' is secured to the biasing member 114 for securing the 
assembly 10; to the safety belt 32'. An aperture 45' is positioned in the 
biasing member 114 and plate member 112 for enabling the assembly 10' to 
be secured to a conventional seat belt buckle and/or anchor (not shown). 
The plate member 110 has an overall rectangular shape having a pair of 
guide walls 120 and 122 formed on the longitudinal edges of the plate 
member 110. A mechanism 124 projects from the plate 110 and couples the 
plate 110 with the biasing member 114. Generally, mechanism 124 is 
positioned on one of the lateral ends of the plate member 110. Also, the 
plate member 110 includes mechanisms 126 and 128 for restraining a timer 
member, described above, such as a chemical timer, which may also be used 
as a force indicator, or a force determining indicator 75, into the plate 
member 110. 
The guide walls 120 and 122 project substantially perpendicular to the 
plate member 110 and have extending flanges 130 and 132 projecting 
substantially parallel to the plate member 110. The guide walls 120 and 
122 enable the second plate member 112 to movably slide in the first plate 
member 110. The mechanism 124 is generally a projecting tab extending from 
the plate member 110 having a desired curvature for retainng the plate 
member 110 in an aperture 140 in the biasing member 114. The mechanisms 
126 and 128, retaining the timer member or the force determining indicator 
in the first plate member 110, project from the plate member 110 and 
include flanges 142 and 144 for securing the timer member or force 
determining indicator within the plate member 110. 
The plate member 112 includes guide members 150 and 152 projecting 
substantially perpendicular to the plate member 112 and having flanges 154 
and 156 extending substantially parallel to the plate member 112. The 
guide members 150 and 152 enable the second plate member 112 to movably 
slide in the first plate member 110. A member 160 projects at a desired 
curvature from the plate member 112 enabling securement of the plate 
member 112 to the biasing member 114 via aperture 141. 
The plate member 112 includes a wiper member 158 which strikes the force 
determining indicator or timer member of the first plate 110 for 
indicating the distance travelled by the biasing member 114 or starting 
the running of time when a force was applied to the assembly. The wiper 
member 158 depends from the bottom of the plate 112 and contacts the force 
indicator or timer member, as will be described herein. The biasing member 
114 may be formed with any suitable metallic sheet material having 
requisite strength and resilient characteristics. The biasing member 114 
has a desired width and thickness such that a desired spring constant may 
be obtained from the material. Generally, the width of the biasing member 
114 controls the stiffness of the biasing member 114 for a given material 
thickness. The length of the biasing member 114 controls the longitudinal 
deflection of the biasing member 114, which occurs in two primary modes 
prior to failure. To increase longitudinal deflection to the biasing 
member 114 without increasing the overall non-deflected length of the 
biasing member, the width of the biasing member 114 may be increased, 
which, in turn, enables an increase in longitudinal deflection while 
maintaining a constant spring length during non-deflection. The biasing 
means 114 generally employs a width to thickness cross-section ratio of 
three or more. The spring may include several spring constants. One of the 
spring constants may be used as a shock absorbing feature having a 
substantially lower spring constant than the other spring constants. This 
lower spring constant reduces the rate of energy absorption by the device 
and thereby reducing the stresses applied to the buckled-in occupant. 
Generally, the biasing member 114 has an overall flat, elongated, 
rectangular shape. The end portions 160 and 162 are integrally formed onto 
the ends of the biasing member 114. The end portions have means 164 and 
45' for attaching the biasing member to a belt and/or anchor buckle, 
respectively. The biasing member 114 may be formed from a metallic strip 
by stamping or otherwise achieving a serpentine configuration into the 
strip. The achieving of the serpentine configuration removes portions of 
the strip from in between the curved U-shaped members of the serpentine 
configuration. 
The serpentine configuration is formed from reversing U-shaped members 168 
and 170 sharing a common leg with the next reversing U-shaped member. The 
serpentine configuration enables the biasing member 114 to deflect in a 
longitudinal axial direction. The reversing U-shaped members 168 and 170 
include legs 172 and 174, base 176, and curvatures 178 and 180 connecting 
the legs 172 and 174 to the base 176. The width of the legs 172 and 174, 
base 176, and curvatures 178 and 180, along with the thickness of the 
strip, control the spring constant of the biasing member 114. Choosing the 
desired leg length, base, material, and thickness provides the spring with 
the desired spring constant pattern. A further explanation of the spring 
of the present invention is given in U.S. patent application Ser. No. 
916,155, filed Oct. 7, 1986, entitled "Serpentine Strip Spring", the 
disclosure of which is herein expressly incorporated by reference. 
FIG. 9 illustrates another embodiment of the present invention. In FIG. 9, 
the seat belt assembly 210 is modified to be secured by a fastening means 
212, such as a bolt, to a vehicle floor pan 216. The biasing member 114 
has an aperture for enabling the bolt 212 to pass therethrough securing 
the assembly 210 to vehicle floor pan 216. The assembly 210 is thus 
substantially the same as the assembly 10' above, and the element will be 
designated with the same reference numerals. 
The seat belt assemblies 10' and 210 generally function as follows. The 
assemblies 10' and 210 are secured between two portions of a seat belt. 
When a force is exerted on the assemblies, the biasing member 114, if the 
force is large enough, begins to extend in a longitudinal direction. As 
this extension occurs, the wiper member 158 contacts the force indicator 
and/or timer member 75. If only a force determining indicator is used, the 
wiper member 158 will contact the force determining indicator 75 and a 
mark will be etched onto the indicator, indicating the longitudinal 
distance travelled by the spring. As explained above, using conventional 
spring equations, knowing the distance travelled by and the spring 
constant of the biasing member 114, the force exerted on the belt can 
easily be determined. When a timer member 75 is used, the timer member is 
activated, starting the running of time as the wiper member 158 contacts 
the timer member 75. Also, the force exerted may be determined from the 
distance travelled by the wiper along the timer member. Thus, by using a 
timer member 75, both the point in time when force was exerted on the 
assemblies 10' and 210 and also the amount of force which was exerted on 
the assemblies 10' and 210 may be determined. 
While the above disclosure fulfills the embodiments of the present 
invention, it will become apparent to those skilled in the art that 
modifications, variations and alterations may be made without deviating 
from the scope and fair meaning of the subjoined claims.