Load measuring device

A load measuring device for use with a link formed as a loop and with the link having end portions for receiving a load on the link along a first axis, including a load cell for mounting across the link and within the loop and along a second axis substantially perpendicular to the first axis for providing an indirect measurement of the load on the link along the first axis in accordance with the force on the load cell along the second axis, the load cell including means responsive to the force on the load cell along the second axis for producing an output signal in accordance with the force on the load cell, and indicator means responsive to the output signal from the means included in the load cell for providing an output indication representative of the load on the link along the first axis.

The present invention is directed to a load measuring device for providing 
for the measurement of relatively high loads. The measuring device of the 
present invention provides for the measurement indirectly and may be 
smaller and more compact than prior art devices. 
The load measuring device of the present invention is used in combination 
with a chain link and may be used to provide for the measurement of the 
load to which the ends of the link are subjected. The load measuring 
device of the present invention may therefore be used to measure the load 
on an individual link, which link is part of an existing chain structure 
and with the entire chain subjected to the load being measured. 
Alternatively, the present invention may be used to provide for the 
measurements of the load at the ends of the link but with the link being 
specially inserted in line with the load to be measured. The link may be 
of a standard type or may be specially designed to operate with the 
measuring device. 
The load measuring device of the present invention provides for the 
measurement of the load on the ends of the link using an indirect method 
of measurement. Specifically, the load measuring device is located across 
an open portion of the link away from the ends of the link which receive 
the load. As the link receives the load at its ends, the load measuring 
device of the present invention is compressed. The compression to which 
the load measuring device is subjected is proportional to the load at the 
ends of the link. 
Generally the link is subjected to a load which is a small fraction of the 
maximum rated load for the link. In this way the metal in the link is 
within its elastic range so that the change in dimensions of the link in 
response to the load is proportional to the load. As indicated above, the 
link may be a standard link which is part of a line subject to the load 
being measured. Alternately, the link may be added to the line which is 
subject to the load so as to provide for the measurement of the load. In 
addition, the link may be specially formed to operate with the measuring 
device of the present invention to thereby provide for the measurement of 
a load. 
in the present application, the load measuring device provides for the 
measurement of the load at the ends of the link and in accordance with the 
measurements made by the load measuring device located across the open 
part of the link. Typically, the load on the link is along a first axis 
whereas the load on the load measuring device is along a second axis 
substantially perpendicular to the first axis for the load on the link. 
This provides for an indirect measurement of load as opposed to the prior 
art devices which provide for a direct measurement of load. 
The measurement of the load by the prior art devices is normally along the 
same axis as that for the load being measured. Since the prior art devices 
provide for the measurement of the load along the same axis as the load, 
the prior art devices must be capable of withstanding the full force of 
the load being measured. Therefore, the prior art devices must be 
relatively robust and are often quite large and heavy. In the present 
invention, since the measurement is indirect, the load measuring device 
does not have to have the same degree of strength and may be accordingly 
smaller in size and more compact. 
The load measuring device of the present invention also has the advantage 
of being able to be relatively portable so that it may be used to make 
measurements of loads in situ so as to allow the load measuring device of 
the present inventions an even greater flexibility in providing for the 
desired measurement of load.

In FIG. 1 a chain 10 is shown to be composed of a plurality of links and 
with a particular link 12 used for providing for the measurement of the 
load on the chain. A coupler 14 is connected to one end of the chain 10 
and a similar coupler may be connected to the other end and with the load 
on the chain 10 in accordance with the load on the couplers 14. It is to 
be appreciated that although the load measurement device of FIG. 1 is 
shown in use with a chain 10 having a number of links, the measurement may 
actually be made using only a single link, such as the link 12, and with 
this link being either normally a part of the load bearing line or 
specially incorporated in the load bearing line. Also the link 12 may be 
specifically designed just to provide for load measuring purposes. 
In any of the above cases, the link 12 receives the load at its opposite 
ends 16 and 18. In the specific example shown in FIG. 1, the load on the 
link 12 is coupled to this link 12 by the adjacent links and the load at 
the ends 16 and 18 of the link 12 should be uniform at both ends so as to 
provide for the proper operation of the load measuring device. 
With reference to FIG. 2, it can be seen that the load measuring device 
includes a load cell 20, which load cell is formed with a pair of interior 
beams 22. Oppositely positioned cantilevered members 24 and 26 provide for 
strain in the beams 22 in accordance with the load applied to center 
portions 28 and 30 of the canteliver members 24 and 26. In the particular 
example of the load measuring device of the present invention only one of 
the beams 22 is used to provide for measurements of load. However, it is 
to be appreciated that either one or both of the beams 22 may be used to 
provide for the measurement. 
The actual measurement of load is provided by a plurality of strain gauges 
32 through 38 mounted at opposite ends and opposite sides of one of the 
beams 22. As shown in FIG. 4, the strain gauges 32 through 38 are 
connected in a bridge circuit and with a source of voltage of 40 supplying 
power across one arm of the bridge. The output reading is taken across the 
other arm of the bridge and is supplied to a meter 42 which provides for 
digital output readout 44 of the load on the link 12. An electrical cable 
46 supplies the power to and receives the output signals from the bridge. 
A connector 48 located on the load cell 20 interconnects the cable to the 
bridge. It is to be appreciated that various auxiliary calibration 
resistors and zeroing resistors may be used to provide for the proper 
operation of the bridge circuit but such devices are commonly known and 
form no part of the present invention. 
In order to insure for the proper transmittal of the load on the ends 16 
and 18 of the link 12 across the load cell 20 and in a direction 
perpendicular to the direction of the load on the link 12, mounting 
couplers 50 and 52 are used. Each mounting coupler includes two half 
shells such as shells 54 and 56 of couplers 50 and 58 and 60 of coupler 
52. Each half shell has an internal curved configuration to match the 
external configuration of the link 12. The half shells are held together 
through the use of bolts 62 through 68 which pass through one half shell 
and engage threads in the other half shell. 
As can be seen in FIG. 3, the couplers 50 and 52 are mounted around the 
outside surface of the link 12 and provide for accurate inside surfaces 70 
and 72 between which the load cell 20 may be mounted. The use of the 
couplers 50 and 52 eliminates problems of mounting the load cells directly 
across the middle portion of the link 12 and compensates for any 
irregularities in the outer surfaces of the link 12. 
The load cell 20 includes a pin member 74 to be received within an opening 
76 in the half-shell 56 of the coupler 50. The pin member 74 and opening 
76 act as a guide to insure the proper positioning of the load cell 20 at 
its one end. The other end of the load cell 20 includes a screw member 78 
having a pin portion 80, which pin portion 80 is received in an opening 82 
in the half-shell 60 of the coupler 52. A nut member 84 is threaded onto 
the screw member 78. The pin portion 80 and the opening 82 also serve as a 
guide to properly position the other end of the load cell. The nut member 
84 may be adjusted to insure that the load cell is accurately positioned 
across the middle portion of the link 12 when there is no load on the ends 
16 and 18 of the link. In particular, the nut member 84 is tightened so 
that with no load on the link the load cell 20 is firmly positioned across 
the middle portion of the link and with the meter 42 providing for a 
reading representative of a zero load on the link 20. 
When a load is applied to the ends 16 and 18 of the link 12, this load 
produces a stretching of the elongated middle portion of the link as well 
as a bending of the elongated portions of the link around the end portions 
16 and 18. The link would be used within an elastic range wherein forces 
applied to the link provide for stretching and bending which are directly 
responsive to the application of a load an with the link returning to its 
initial configuration upon removal of the load. 
As the load is applied and the link stretches and bends around its ends, 
the middle portion of the link tends to close up and come together, 
thereby providing a force to the cantilevered members 24 and 26. This 
force is applied directly to the center portion 28 at one side of the load 
cell and through the nut 84 and the screw 78 at the other side of the load 
cell. As the cantilevered members 24 and 26 are forced towards each other, 
stress is produced in the beam members 22. Specifically, one side of each 
beam member is in tension while the other side is in compression which 
produces opposite effects in the strain gauges 32 and 36 as opposed to 
strain gauges 34 and 38. 
The changes in the strain gauges 32 through 38 are represented in FIG. 4 by 
changes in the resistance value of the stain gauges. Initially with no 
load, the resistance value of the strain gauges 32 through 38 were all 
substantially the same resistance value. This provides for a balanced 
condition in the bridge and therefore no output reading in the meter 42. 
As the load is increased the resistance values of the strain gauges 
change, thereby providing an unbalance in the bridge. This produces an 
output signal which provides for a direct indication by the meter 42 of a 
value representative of the load on the ends 16 and 18 of the link 12. 
It is to be appreciated that the actual load on the load cell 20 is a 
fraction of that applied to the ends 16 and 18 of the link 12, yet the 
load measured by the load cell 20, although an indirect measurement, is in 
proportion to the load applied to the ends of the link. The actual 
readings 44 on the meter 42 may be directly representative of the load or 
may be values which have been calibrated and with the actual load 
determined by reference to a calibrated chart. 
As was previously indicated, the link 12 may be part of an existing line or 
may be specially inserted into a line so as to provide for the measurement 
of a load. Also, the link 12 may be specifically designed to operate with 
the load cell 20 and in such a case the link may be provided with accurate 
surfaces so as to eliminate the need of the coupling members 50 and 52. As 
shown in FIG. 3, the load cell 20 also includes cover members 86 and 88 so 
as to shield and protect the interior of the load cell. It is noted, 
however, that these cover members are attached by screws 90 and 92 only at 
one end of the load cell 20 so as to allow for the proper movement of the 
interior members of the load cell to provide for the measurement of loads. 
Although the invention has been described with reference to a particular 
embodiment, it is to be appreciated that various adaptations and 
modifications may be made and the invention is only to be limited by the 
appended claims.