Method of reducing hysteresis in a spring scale

A method of improving the accuracy of scale readings featuring exciting the molecules of the supporting spring and clamping structure of the scale. The purpose of this excitation is to reduce the effects of hysteresis, creep and drift upon the measured load. Exciting the molecules of the support spring causes the scale to reach its stable state of stress much more rapidly. This results in obtaining more accurate weight readings for a load being weighed.

This invention pertains to weighing scales, and more particularly to a 
method of improving the accuracy of a spring supported weighing scale. 
BACKGROUND OF THE INVENTION 
Heretofore, weighing scales using support springs have experienced 
inaccuracies due to the molecular effects of the spring materials and 
clamping structure. It has been observed, that when a scale deflects under 
a load to be weighed a stable state of stress is not quickly achieved due 
to the effects of hysteresis, creep, and drift. These effects do not 
produce large errors in the weight readings and therefore, nothing has 
been done in the design of scales to compensate for them. 
Where high accuracy is not a criteria, the aforementioned molecular effects 
and their attendant errors do not generally present a problem. These 
molecular effects do not generally present a problem. These molecular 
effects can no longer be ignored however, because scale standards have now 
reached requirements of extreme accuracy. 
Usually, in any design, hysteresis, creep and drift are treated by means of 
prevention, i.e. a proper choice of materials is made to reduce (but not 
eliminate) these effects. 
This invention is concerned with the elimination of molecular effects in 
the load support springs of scales as a means of providing more accurate 
weight readings. 
SUMMARY OF THE INVENTION 
This invention relates to a method of increasing the accuracy of weighing 
scales using support springs in their design. The weight readings of these 
scales are improved by substantially reducing or eliminating the molecular 
effects causing hysteresis, creep and/or drift. The molecules of the 
support spring and clamping structure are excited by inducing a varying 
ultrasonic field in the spring. When a load to be weighed is supported 
upon the spring, the spring and its associated clamping structure will 
reach a stable state of stress more quickly as a result of this 
excitation. This will result in providing a more accurate weight reading. 
An alternate embodiment of the above method comprises the use of inducing a 
varying magnetic field in the support spring and clamping structure. 
It is an object of the invention to provide an improved weighing scale; 
It is another object of the invention to provide a weighing scale of 
improved accuracy; 
It is a further object of this invention to excite the supported springs of 
weighing scales in order to achieve a more rapid approach to a stable 
state of stress;

DETAILED DESCRIPTION 
Referring to FIG. 1, a deflectible load support member for a weighing scale 
is generally depicted by arrow 10. A load 11 to be weighed is placed upon 
a weighing platform or pan 12 of the scale. The pan 12 is connected to the 
deflectible load support member 10, and causes the load support 10 to 
deflect in response to weight 11 is shown by arrow 14. 
The load support member 10 is attached to a stationary frame member 15 by 
means of two pivot arms 16 and 17, respectively. 
A spring 18 substantially supports the deflectible member 10, and provides 
a substantially linear movement for the support member necessary to 
produce accurate weight readings. 
An ultrasonic transducer 19 is attached to spring 18 at its other end, as 
illustrated. 
An oscillating voltage power supply 20 is connected to the transducer 19 
via lines 21 and 22, respectively. 
As the deflectible member 10 moves (arrow 14) under the influence of weight 
11, an optical detector (not shown) converts the measured deflection into 
weight readings. 
In standard scales not employing the invention, the spring 18 will usually 
not reach a stable state of stress in the required time to provide an 
accurate weight reading. 
The invention seeks to eliminate this problem by substantially reducing or 
eliminating the molecular effects in the spring 18 and its associated 
clamping structure causing this condition. The molecular effects referred 
to are ones that cause hysteresis, creep or drift. As aforementioned, it 
is these effects that prevent the rapid attainment of a steady state 
condition, which in turn interferes with the accuracy of observed weight 
readings. 
OPERATION OF THE INVENTION 
The present invention substantially reduces or eliminates the molecular 
effects in the spring 18 by inducing an oscillating ultrasonic field 
therein. This field excites the molecules in the spring 18, which tends to 
eliminate the hysteresis, creep or drift conditions. 
The induced oscillating field is caused by the oscillating voltage power 
supply 20 which feeds the ultrasonic transducer 19. The transducer 19 
being connected to the spring 18, continuously excites the spring 
molecules. Thus, as the spring 18 is put in tension by the deflection of 
member 10, the excitation of the induced field will allow the spring to 
more quickly reach a stable state of stress. This in turn will provide for 
more accuracy in the weight readings. 
ALTERNATE EMBODIMENT 
Now referring to FIG. 2, an alterate embodiment of the invention is shown. 
Like designations refer to similar parts, components, and operations, for 
the sake of brevity. 
Deflectable member 10 is now made hollow as illustrated by the cut-away 
view, such that spring 18 fits inside and attaches to member 10 via pin 
25. Spring 10 can be made of material which is easily magnetizable if so 
desired. An electromagnetic coil 26 is constructed to surround the spring 
18 and its associated clamping structure. The spring 18 is now supported 
by the frame 15'. The coil 26 is fed with an oscillating current from 
power supply 27 via lines 29 and 30, respectively. 
The alternate embodiment of FIG. 2 operates in a similar fashion to the 
embodiment of FIG. 1. The spring 18 of FIG. 2 has its molecules excited by 
an induced oscillating magnetic field created by the coil 26. The induced 
oscillating field is created by feeding the oscillating current from power 
supply 27 into the electromagnetic coil 26. This oscillating field is 
induced in the spring 18 and its clamping structure. Thus, as the spring 
18 is put in tension by the deflecting member 10 in response to weight 11, 
the excitation of the induced field will allow the spring to more quickly 
reach a stable state of stress. This in turn will provide for more 
accurate weight readings. The induced magnetic field in the spring will 
excite the molecules in like fashion to that of the ultrasonic field. 
It is to be understood that many modifications can be made in the design of 
this invention consistent with the knowledge available to those skilled in 
this art. Such changes are deemed to be within those limits circumscribed 
for this invention by the appended claims. Having described the invention, 
what is desired to be covered by Letters Patent is as follows: