GB2064776A - Digital gauge - Google Patents

Abstract

A digital gauge has a casing containing a mechanical dial gauge assembly (10) converting linear displacement of a plunger (14) into rotational displacement of a shaft (16), a disc (18), having radial graduations formed by slots, secured to the shaft, a photoelectric converter having an emitter (20), and a receiver (22) arranged to count the disc graduations during rotation of the disc, a display instrument (30) providing a digital display of plunger displacement in response to signals from the photoelectric converter, a battery compartment (48) at the upper front section of the casing, and a plunger spindle clearance space 54 in the upper rear section of the casing. <IMAGE>

Description

SPECIFICATION Digital gauge The present invention relates to a digital gauge.

Dial gauges are well known which operate by changing linear displacement of a plunger or spindle having an end in engagement with an object to be measured into angular displacement of a shaft carrying a pointer movable over a scale marked on a dial. There has more recently been proposed a gauge displaying the indicated values in digital form and this has various advantages in respect of higher accuracy by reduction of reading error.

This type of digital gauge, however, has drawbacks arising from the complexity of the structure and the arrangement of its various parts due to the need to effect a digital display by electrical means from a spindle displacement converted into a rotation by mechanical dial gauge assembly. Also, a compartment for the battery needed to supply power to the electric circuit of the gauge is not efficiently located.

Accordingly, the present invention provides a digital gauge comprising a casing having a plunger protruding therefrom, a mechanical dial gauge assembly to convert linear displacement of the plunger into rotational displacement of a shaft, a slit disc secured to the shaft, a photoelectric converter having an emitter and a receiver positioned to co-operate with the slit disc, a display device providing a digital display of plunger displacement in response to signals from the photoelectric converter, a battery compartment in the casing at a position remote from the protruding plunger end, and an escape space for the plunger on displacement thereof located adjacent the battery compartment.

The gauge of the invention thus has its parts arranged to protect the escape space for the plunger from interference by other objects, and preferably the escape space is located behind the battery compartment. Moreover, the escape space can be wholly enclosed within the casing. The battery compartment can be defined in part by a wall of the casing through which the display device is displayed, and the battery compartment can then be accessible through the wall, so that the batteries are easily exchanged and without interference with the operation of the gauge in normal use.

The present invention is further described below, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a sectional side view of a dial gauge with a digital display embodying the invention; and Figure 2 is a front view of the gauge, with a casing thereof shown partly broken away.

The illustrated digital display dial gauge has a mechanical dial gauge assembly 10 and is provided with a bracket or holder 1 2 projecting from the badk thereof for attachment of the gauge to a support (not shown), so that the mechanical dial gauge assembly 10 is fixed at a predetermined position relative to an object to be measured. The mechanical dial gauge assembly 10 includes a plunger or a spindle 14 capable of moving up and down in the illustrated orientation of the gauge. The lower end of the spindle 1 LF is brought into contact with an object to be measured in use of the gauge and the resulting linear displacement of the spindle 14 is converted into an angular displacement of a main shaft 1 6.

In order to convert this rotational displacement of the main shaft 1 6 in the mechanical dial gauge assembly 10 into electrical signals, there is provided a photoelectric converter or transducer. The photoelectric converter includes a disc 18 fixed to the rotatable main shaft 1 6 of the mechanical dial gauge assembly 10, the disc comprising a thin metal or glass disc provided with light transmitting radial slits. An emitter 20 and a receiver 22 are positioned on axially opposed sides of the slit disc 18. The emitter 20 and the receiver 22 detect the amount of rotational displacement in the form of photoelectrically converted pulsed wave shapes. By counting the number of these pulses the angular displacement of the slit disc 1 8 is measured in the form of electrically detected signals.The emitter 20 can comprise a light emitting diode, for example, and the receiver 22 can comprise a photodiode, a photoelectric cell or the like.

Both the emitter and the receiver 22 are built into a photoelectric transducer block 24, in which an index slot, (not shown), is provided so that accurate photoelectric detection can be performed by reception of the slit disc 1 8 in this slot.

To the mechanical dial gauge assembly 10 are fixed a plurality of supports 26, on which is secured a printed cicuit board 28. On the printed circuit board 28 there is mounted a display instrument 30 including liquid crystal display elements. An on-off switch 32 for electric power and a selection switch 34 for selecting inch or metric units are also attached and electrically connected to the printed circuit board 28. A circuit device 36, preferably an IC circuit hence, is incorporated in the display instrument 30, and by this device the electrical output signals from the receiver 22 are amplified, modified so as to have a desired wave form, or divided into certain signals, or otherwise located in a predetermined manner, in order to effect a digital display of the value measured by the gauge on the display instrument 30.

After the completion of the sub-assembly comprising the mechanical dial gauge assembly 10 and the printed circuit board 28, a casing 38 is attached to the dial gauge as sembly. A reset switch 40 and a hold switch 42 have been first attached to the casing 38, and these switches 40 and 42 are electrically connected in circuit during the assembly with the casing 38. A transparent window 44 of glass or plastics material is installed on the casing 38 in the registry with the instrument 30 to enable the values displayed by the display instrument to be read in the assembled state of the gauge.

At the upper end of the casing 38, there is provided a partition 46 which divides off one part of the interior of the casing 38 for use as a battery compartment 48. Over the compartment 48, a detachable battery compartment lid 50 is releasably secured so that batteries 52 inserted in the battery compartment can be easily exchanged. It will be seen that the battery compartment 48 is located in such a position that the exchange of batteries does not obscure the digital display nor interfere with measurement of an object. As shown in Fig. 2, the illustrated digital gauge is given a front shape which gradually decreases in its width towards the battery compartment 48 from the region of the mechanical dial gauge assembly 10, and the display instrument 30 is located generally centrally so that a totally balanced and functional design can be achieved.

As mentioned above, the battery compartment 48 is not only located in the upper front section of the casing 38, but is also spaced from the upper back wall of the casing 38 to provide a spindle escape space 54. As illustrated in chain-dotted line in Fig. 1, the spindle escape space 54 offers an enclosed region for the upper end of the spindle 14 when it moves upwardly, which prevents the possibility of accident by collision of the upper end of the spindle 14 with an obstacle located in the vicinity of an object to be measured, such that it becomes impossible to measure the object.

Thus, without the protection for spindle escape 54 provided by the casing 38, there is a risk of collision with an obstacle which makes it impossible to measure an object until the entire equipment is reset, because the upper end of the spindle 14 would be exposed outside. Such a collision is reliably prevented by the arrangement whereby the spindle 14 moves up and down within the escape space 54.

If desired, a damper can be installed, in the spindle escape space 54 to regulate the speed of movement, especially downwardly, of the spindle 14. By limiting the speed of movement of the spindle 14 to below a certain speed, the production of error due to miscounting at the photoelectric converter can be prevented.

The illustrated gauge is fitted with a voltage drop alarm 56 constituted by a light emitting diode, for example, on the printed circuit board 28, so that the voltage level of the batteries 52 can be always checked. As shown in Fig. 2, there is provided on the side of the casing 38, an insert opening 58 for spindle lift cable, by which the spindle 14 can be upwardly moved. Also, on the side wall of the casing 38, there can be provided a detected signal monitor terminal 60. By means of this feature, the measured values are not only displayed on the display instrument 30, but can be conveyed out of the gauge through the terminal 60 to a central display instrument, an electronic computor, or the like in order to perform a desired operation or to permit the measured values to be stored.

The present invention can of course be embodied in a variety of ways other than as described and shown within its scope as defined by the following claims.

Claims (7)

1. A digital gauge comprising a casing having a plunger protruding therefrom, a mechanical dial gauge assembly arranged to convert linear displacement of the plunger into rotational displacement of a shaft, a slit disc secured to the shaft, a photoelectric converter having an emitter and a receiver positioned to co-operate with the slit disc, a display device providing a digital display of plunger displacement in response to signals from the photoelectric converter, a battery compartment in the casing at a position remote from the protruding plunger end, and an escape space for the plunger on displacement thereof located adjacent the battery compartment.

2. A digital gauge as claimed in claim 1 wherein the escape space is wholly enclosed within the casing.

3. A digital gauge as claimed in claim 1 or 2 wherein the battery compartment is defined in part by a wall of the casing through which the display device is displayed.

4. A digital gauge as claimed in claim 3 wherein the escape space is located behind the battery compartment.

5. A digital gauge as claimed in claim 3 or 4 wherein the battery compartment is accessible through the wall.

6. A digital gauge as claimed in any preceding claim having a damper for damping plunger movement located in the escape space.

7. A digital gauge substantially as herein described with reference to the accompanying drawing.