GB1596862A

GB1596862A - Fixed distance gauge

Info

Publication number: GB1596862A
Application number: GB863/78A
Authority: GB
Original assignee: Alfred Teves GmbH
Current assignee: Continental Teves AG and Co oHG
Priority date: 1977-01-19
Filing date: 1978-01-10
Publication date: 1981-09-03
Also published as: JPS5390962A; FR2378256B1; DE2701909A1; IT7819265A0; IT1109802B; SE7800533L; BR7800008A; DE2701909C2; ES233247U; ZA78155B; FR2378256A1; ES233247Y

Description

(54) FIXED DISTANCE GAUGE (71) We, ALFRED TEVES G.m.b.H. a joint stock Company of 7 Guerickestrasse, 6000 Frankfurt Am Main, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a one-part gauge with a fixed distance between the measuring surfaces.

Gauges of this type are known in various versions, for example as snap gauges or thickness gauges. In general, they serve to permit rapid measurements, for example when testing a large number of identical workpieces or for measuring at difficult locations. It is a disadvantage in the onepart gauge with a fixed distance between the measuring surfaces that its use is limited to where the gauge can approach the location of the work-piece where the measuring is to be made without being hindered by parts of the workpiece whose dimensions are larger or smaller than the gauge size, in the case of outside and inside measuring respectively. If measurements of this type are to be made using a gauge with a fixed distance between the measuring surfaces, this gauge might consist of several parts.Handling a multipart gauge is, however, substantially more difficult and timeconsuming.

When measuring undercuts, adjustable gauges such as slide caliper rules or micrometer calipers have the disadvantage that the measuring result must be read in the measuring position at the workpiece. Therefore, it is often not possible to use adjustable gauges for making measurements at workpieces that are installed in devices because the view to the scale of the gauge is obstructed.

According to the present invention, there is provided a one-part gauge comprising a U-shaped frame, rigid in the intended direction of measurement across the legs of the "U" and elastically deformable transverse to the direction of measurement, and measuring surfaces provided at projections extending beyond the edges of the legs of the U-shaped frame.

The result is a one-part gauge with fixed distance between the measuring surfaces in which, owing to elastic deformation of its legs transversely to the direction of measurement, the distance between the measuring surfaces may be enlarged or reduced so as to permit easy movement of the gauge over parts of a workpiece whose dimensions exceed or fall below the gauge size. As soon as the measuring surfaces of the leg ends of the gauge have reached the location of the workpiece to be measured, the gauge is allowed to relax and the workpiece size to be tested can be detected by feel. It is a particular advantage in this arrangement that the gauge, owing to its elastic design, conveys a clearly perceptible feel of whether the measured size exceeds or falls below the gauge size, because an "overtravel" effect occurs as the gauge is turned into the measuring position.By virtue of the fact that the gauge requires neither a joint nor a hinge, it permits particular ease of manufacture at relatively high accuracy of measurement and low susceptibility to wear. In view of its low production costs, the gauge of this invention is also suitable as an addition to replacement kits for machines or devices whose repair required prior testing of specific dimensions.

In an advantageous embodiment, the width of each of the legs of the frame, which is made from elastic material, is a multiple of its thickness. Particularly with gauges measuring dimensions below 50 millimetres it has proved an advantage if the width of each leg is ten to fifty times their thickness.

A favourable resistance against wear and high accuracy of measurement is achieved if the frame or at least the legs are made of spring steel sheet about 0.3 to 0.5 millimetres thick. It is an advantage hereby if the distance between the legs of the frame, except where the measuring surfaces project into the U, is 1.5 to 2 times the width of each leg.

Particular economy of manufacture of the gauge is achieved by blanking the gauge out from thin sheet metal. If the requirements as to life and accuracy of measurement are lower, the gauge may also be blanked out from a thin plate of elastic, inherently stable, plastics material.

In a gauge suitable for internal measurements, the gauge measuring surfaces are advantageously segments of a common cylinder envelope surface. In that case, canting of the gauge has no influence on the measuring result.

The rigidity of the legs of the gauge can be advantageously increased in the direction of measurement by the provision of beads.

The gauge is particularly useful for measuring the maximum permissible amount of wear of vehicular brake discs.

The frame width of such gauges is in the range 1.0 to 2.5 inches and is made smaller than the axial distance (normally not more than two and a half inches) between the brake-actuating members on either side of the brake disc, so that the gauge can be slid into the space provided on either side of the brake disc following removal of the brake pads for measuring the thickness of the brake disc.

The invention will be more clearly understood by reference to the embodiment of the invention illustrated in the accompanying drawings, in which: Figure 1 is a perspective view of a gauge according to an embodiment of the invention; Figure 2 is a plan view of a gauge according to another embodiment; Figure 3 shows the deformation of the gauge of Figure 1 being slid onto a brake disc; Figure 4 shows the gauge of Figure 1 in its measuring position at the brake disc of Figure 3.

The gauge illustrated in Figure 1 is for measuring an external dimension and has essentially a U-shaped frame 1 of rectangular circumferential contour, with a central slot 2 extending in the longitudinal direction and two legs 3, 4. At their free ends, the legs 3, 4 have circularly shaped measuring surfaces 5, 6 facing one another. The dual arrow 7 indicates the check gauge size as predetermined by the distance between the measuring surfaces 5, 6. The distance between the inner surfaces 8, 9 of the legs 3, 4 facing the slot 2 is greater than the distance between the measuring surfaces 5, 6.

The frame is preferably blanked out from thin spring-steel sheet. Owing to their form and the elasticity of the matenal from which the frame is made, its legs 3, 4 permit very easy bending in the direction indicated by the dual arrow 10, whilst they are of great stiffness in the measuring direction as indicated by arrow 7. This ensures that the gauge size is accurately maintained.

The embodiment illustrated in Figure 2 provides for measurement of an internal dimension. Its basic structure corresponds to that of the gauge of Figure 1. Therefore, like parts have been assigned like reference numerals. In the direction of view, the gauge is likewise very thin and may be blanked out from spring-steel sheet or a plastics plate.

The measuring surfaces 15, 16 are provided at the outside of the legs 3, 4 and turned away from one another. Further, they are curved in such a manner as to form part of the surface of a common cylinder, the axis 18 of which extends through the middle of the slot 2 perpendicularly to the plane of the drawing. Owing to this design of the measuring surfaces 15, 16, impairment of the measurement due to canting of the gauge is effectively avoided.

Handling and operation of the gauge of this invention will be described with reference to Figures 3 and 4, using, by way of example, the measurement of the thickness of a brake disc. In both Figures, the brake disc identified by reference numeral 19 is shown as a fragmentary view. The two friction surfaces 20, 21 of the brake disc 19 are worn down by long use to such an extent that the radially outer edges 22 of the brake disc 19 which lie outside the range of action of the brake pads form projections rendering it impossible for the brake disc thickness to be measured in the area of friction surfaces 20, 21 by means of a conventional one-part gauge.

As illustrated in Figure 3, the legs 3, 4 of the frame 1 of.the gauge of this invention, owing to their elastic deformability, can be twisted in opposite directions transverse to the measuring direction so that the leg ends, with their measuring surfaces 5, 6, can be easily slid over the projecting edges 22 of the brake disc. The frame 1 is then turned into the position illustrated in Figure 4 which results in the measuring surfaces 5, 6 of the legs 3, 4 approaching each other again. If the thickness of the brake disc is greater than the fixed distance between the measuring surfaces of the gauge in its relaxed state, the gauge will not straighten out completely but will remain twisted and will resist further turning. This resistance will be clearly perceptible even if the gauge size is exceeded to a minor extent, of the order of one tenth of a millimetre or less.

Only after this resistance has been overcome by the operator will the gauge allow further turning, but it will not remain in a measuring position perpendicular to the friction surfaces 20, 21 of the brake disc but will overtravel this position which may be compared to a dead centre, to assume the opposite twisted or crossed position. This overtravel effect can even be felt more clearly than the turning resistance caused by the gauge. Therefore, if this overtravel effect occurs, it can be easily ascertained, while turning the gauge to and fro about the dead centre, whether or not the brake disc or another workpiece to be measured exceeds the gauge size.

By virtue of its mode of operation, the gauge constructed in accordance with this invention is particularly suitable for measurements at difficult and hardly visible places, because the presence of the necessary limit size can be easily detected by feel by means of the overtravel effect. Further, the gauge of this invention is also suitable for use as a "go, no-go" gauge for rapid testing of a large number of workpieces.

WHAT WE CLAIM IS: 1. A one-part gauge comprising a U-shaped frame rigid in the intended direction of measurement across the legs of the "U" and elastically deformable transverse to the direction of measurement, and measuring surfaces provided at projections extending beyond the edges of the legs of the U-shaped frame.

2. A gauge as claimed in claim 1, wherein the width of each of the legs is a multiple of the thickness of the legs.

3. A gauge as claimed in claim 2, wherein the width of each leg is ten to fifty times its thickness.

4. A gauge as claimed in claim 1, wherein the frame and/or its legs is/are made of spring-steel sheet between 0.3 and 0.5 millimetres thick.

5. A gauge as claimed in claim 4, wherein the distance between the legs of the frame is 1.5 to 2 times the width of each leg.

6. A gauge as claimed in any one of the preceding claims, wherein the gauge has been blanked out from thin sheet metal.

7. A gauge as claimed in any one of the claims 1 to 5, wherein the gauge is blanked out from a thin plate of elastic, plastics material.

8. A gauge as claimed in any one of the preceding claims, wherein the measuring surfaces are circularly shaped.

9. A gauge as claimed in any one of the preceding claims and suitable for measuring an internal dimension, wherein the measuring surfaces lie on the surface of an imaginary common cylinder.

10. A gauge as claimed in any one of the preceding claims, wherein the legs are provided with beads.

11. A gauge as claimed in any one of the preceding claims, wherein for measuring the maximum permissible amount of wear of vehicular brake discs the width of the frame is in the range 1.0 to 2.5 inches and smaller than the axial distance (normally not more than two and a half inches) between the brake-actuating members on either side of the brake disc, with the distance between the inner surfaces of the legs being greater than the thickness of the brake disc when new.

12. A gauge substantially as hereinbefore described with reference to and as illustrated in Figures 1, 3 and 4 or Figure 2 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. effect occurs, it can be easily ascertained, while turning the gauge to and fro about the dead centre, whether or not the brake disc or another workpiece to be measured exceeds the gauge size. By virtue of its mode of operation, the gauge constructed in accordance with this invention is particularly suitable for measurements at difficult and hardly visible places, because the presence of the necessary limit size can be easily detected by feel by means of the overtravel effect. Further, the gauge of this invention is also suitable for use as a "go, no-go" gauge for rapid testing of a large number of workpieces. WHAT WE CLAIM IS:

1. A one-part gauge comprising a U-shaped frame rigid in the intended direction of measurement across the legs of the "U" and elastically deformable transverse to the direction of measurement, and measuring surfaces provided at projections extending beyond the edges of the legs of the U-shaped frame.