Load Introducing Device

1. Field of the Invention

The present invnetion relates to a load introducing device used as a part of a force gauge or as a part of a machine wherein measurement of tensile or compressive force is carried out in the normal course of operation.

2. Background Description

Force gauges or devices for measuring force are generally manufactured on a small scale and are accompanied by disadvantages due to the use of adhesive materials for attaching strain gauges. That is to say, the use of adhesive materials not only requires know-how and skill, but also requires troublesome adjustment of the electrical circuit. Further, there is a fear of an occurrence of error due to aging of adhesive materials. Therefore, it is desirable to avoid the use of a strain gauge as a force measuring device.

The foregoing illustrates limitations known to exist in present devices. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.

In one aspect of the invention this is accomplished by providing a load introducing device including a yoke having a pair of opposite flexible sides, a pair of opposite rigid sides and a cantilever portion extending from one of the rigid sides and between the flexible sides. A load introducing rod is fixed perpendicularly to the cantilever portion. An optical displacement sensor is provided between the cantilever portion and one of the rigid sides.

The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing. It is to be expressly understood, however, that the drawing is not intended as a definition of the invention but is for the purpose of illustration only.

In the drawing:

FIG. 1 is a cross-sectional view illustrating an embodiment of the load introducing device according to the present invention;

FIG. 2 is a side view of the device shown in FIG. 1.

FIG. 3 is a partial cross-sectional side view illustrating the load introducing device of FIG. 1 mounted in a force gauge;

FIG. 4 is a perspective view illustrating the load introducing device combined with a force gauge; and

FIG. 5 is a voltage vs. force graphical illustration.

In the figures, a load introducing device is generally designated 1 and includes a rectangular yoke comprising a pair of oppositely arranged flexible sides, 2, 3, a pair of oppositely arranged rigid sides 4, 5 connecting the ends of the flexible sides 2, 3, and an additionally provided cantilever portion 6 extending from one rigid side 4 in parallel with the flexible sides 2, 3. The flexibility of the side 2 is provided by a pair of low section-modulus portions 2a, 2b. Similarly, the flexibility of the side 3 is provided by a pair of low section-modulus portions 3a, 3b. One rigid side 5 opposing the other rigid side 4, on which the cantilever portion 6 is provided, is a portion for attaching the device 1, by means of a plurality of fitting holes 7 and screws 12, to a case 13 of an associated force gauge, see also FIGS. 3 and 4.

A load introducing rod 8 is fixed perpendicularly to the additionally provided cantilever portion 6. The load introducing rod 8 is movable axially by a force applied on it deflecting the sides 2, 3. The axial displacement of the load introducing rod 8 is detected by an optical displacement sensor 9 provided between the cantilever portion 6 and the rigid side 5.

The displacement sensor 9 is composed of a light source 10 and a semiconductor element 11. The signals issued by the displacement sensor 9 are amplified by an amplifier and operate an indicator on an associated force gauge, not shown.

One of the light source 10 and the semiconductor element 11 is attached to the cantilever portion 6 and the other is attached to the rigid side 5.

FIGS. 3 and 4 illustrate an example of force gauge 13 with which the load introducing device 1 of FIGS. 1 and 2 is used. Screws 12 pass through fitting holes 7 provided on rigid side 5 of the yoke of device 1. An adapter 8a is attached to an exposed end of load introducing rod 8. Several switches 14, 15 and 16 are provided in case 13 of the force gauge. Switch 14 is a measuring switch, switch 15 is a unit-selecting switch and switch 16 is a memory switch.

FIG. 5 illustrates, in diagrammatic form, an example of the relationship between output voltage and the force of the displacement sensor 9.

Electrical circuitry required to render the force gauge operative is well known to those skilled in the art and requires no detailed discussion.

The device according to the present invention provides a load detecting device using an electrical position sensor which is supplied at low cost. The constituents of this device can be assembled easily without requiring substantial skill.

In this device, an amount of axial movement of the load introducing rod is directly measured by the optical displacement sensor. The signals generated by the displacement sensor are utilized to operate an indicator of the digital or analogue type on a well known force gauge.