GB2355530A - Measuring callipers - Google Patents

Abstract

A measuring calliper has a planar base 42 having a first jaw 44 which is displaceable linearly to a plurality of predetermined positions, and a second jaw 46 pivotally connected thereto at a pivot pin 48. On the base 42 is a measuring scale 52 which indicates the internal diameter of a brake drum 40.

Description

2355530

DESCRIPTION MEASURING CALLIPERS

The present invention relates to measuring callipers and in particular, but not exclusively, to callipers for measuring vehicle brake linings, brake discs and brake drums to assess the degree of wear.

Currently, the thicknesses of brake linings, discs, drums and the like can be accurately measured by means of engineering instruments such as micrometer gauges, Vernier callipers and the like. However, whilst the output from such instruments is useful to a vehicle mechanic such measurements often do not mean a great deal to the general public. This is of concern in the growing number of "fast-fit" car centres which supply and fit the most commonly-required replacement vehicle components such as tyres, brake linings, exhausts and clutch linings.

There is thus a need for a measuring implement which is both easy and accurate to use and whose output may be readily interpreted by those having little or no technical skill.

In accordance with the present invention, a measuring calliper comprises a base, a first jaw secured or securable to the base, a second jaw pivotally mounted with respect to the base, a measuring scale secured to the base, and an indicator moveable adjacent to the measuring scale, the indicator being secured to, and moveable with, the second jaw and one of the jaws being moveable to a plurality of predetermined positions with respect to the base.

In this way pivotal movement of the second jaw is used essentially to -2display any deviation from the predetermined spacing.

Preferably, the distance between the pivot and the measuring scale is greater than the distance between the pivot and the tip of the second jaw. Using this arrangement, the movement of the indicator "magnifies" the movement of the jaws such that the measuring scale is easier to interpret.

The base and jaws are preferably generally planar.

By way of example only, a specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which:- Fig. 1 is a front view of an embodiment of measuring device in accordance with the present invention, shown measuring the diameter of a brake drum; and Fig. 2 is a view from the rear of the measuring device of Fig. 1.

The embodiment of the invention is illustrated in Figs. 1 and 2 and is suitable for measuring the internal diameter of a brake drum 40. The measuring device comprises a planar, generally rectangular base 42, a first jaw 44 which is displaceable linearly to a plurality of predetermined incremental positions with respect to the base and a second jaw 46 which is pivotally mounted to the base by means of pivot 48. The jaw 46 is generally L-shaped and the end of the jaw 46 on the opposite side of the pivot 48 is formed into an indicating pointer 50 which is located adjacent to an indicating scale 52 secured to the base. Calibration of the scale is permitted by securing the scale to the base by means of two screws S passing through a respective elongate slot 53 in the scale 52. The pivotally mounted jaw 46 is biassed outwardly (i.e. anti-clockwise in Fig. 1) by means of a -3spring 54 which is mounted on two bolts 56 secured to the base 42, the spring being located in a cut-out 58 in the jaw.

The non-pivoting jaw 46 is movable to a plurality of predetermined positions spaced apart from adjacent locations by predetermined amounts, in the present case 10mm.

With reference to Fig. 2, the jaw 44 is also generally L-shaped and the lower bar of the "L" comprises an elongate planar, generally rectangular guide portion 60 extending parallel to the longitudinal axis of the base 42. The guide portion 60 is provided with a longitudinally arranged guide track 62 and the plate 62 is held on the base 42 by means of a rectangular securing plate 64 which is held in place on the base 42 by means of the two aforementioned bolts 56 and two securing nuts 57. The undersurface of the plate 64 is rebated at two locations 64a,64b across its width to allow passage of the guide plate portion 60.

A leaf spring 66 located in the lower rebate 64b of the cover plate 64 engages the upper transverse face of the lower rebate 64b and the lower longitudinal edge of the rectangular guide track 62 and urges the lower edge of the guide portion 60 into engagement with the bolts 56. The bolts 56 are positioned 5cm apart and the lower edge of the guide portion 60 is provided with a series of recesses 68, adjacent recesses being spaced apart by a distance of lcm. Thus, the spring 66 urges the guide portion 60 into positions in which two recesses 68 in the lower edge of the guide portion 60 5cm apart engage the shank a respective one of the bolts 56. In order to move the base portion 60 the jaw 44 is moved in either direction, providing sufficient force to disengage the recesses 68 from the abutting bolts 56 and to engage two different recesses.

With reference to Fig. 1, it will be noted that the upper edge of the guide portion 60 protrudes above the level of the base plate 42 and is provided with a scale 70 which is graduated in one-centimetre steps. The scale is graduated such that a datum mark 72 indicates the spacing of the jaws in conjunction with the spacing indicated on the scale 52.

In use, the slidable jaw 44 is adjusted to lie at the predetermined position which is immediately below the anticipated or expected diameter of the brake drum to be measured. The pivoting jaw 46 is then pivoted clockwise as shown in Fig. 1 and the sliding jaw 44 is placed in contact with the inner surface of the brake drum. The pivoting jaw is then released and the force of the spring 54 causes the pivoting jaw 46 to engage the diametrically opposite region of the brake drum 40.

The scale 52 is calibrated such that the spacing of the points of the two jaws is given by adding the predetermined spacing indicated on the scale 70 with respect to the datum 72 and the "magnified" indication of the spacing shown on the scale 52.

The invention is not restricted to the details of the foregoing embodiment.

Claims (10)

1. A measuring calliper comprising a base, a first jaw secured or securable to the base, a second jaw pivotally mounted with respect to the base, a measuring scale secured to the base, and an indicator moveable adjacent to the measuring scale, the indicator being secured to, and moveable with, the second jaw and one of the jaws being moveable to a plurality of predetermined positions with respect to the base.

2. A measuring calliper as claimed in claim 1, wherein one of the jaws is moveable translationally to a plurality of predetermined positions.

3. A measuring calliper as claimed in claim 1 or claim 2, wherein the first jaw is moveable to a plurality of predetermined positions with respect to the base.

4. A measuring calliper as claimed in any of claims 1 to 3, further comprising biasing means for biasing the second jaw.

5. A measuring calliper as claimed in claim 4, wherein the second jaw is biased away from the first jaw.

6. A measuring calliper as claimed in any of claims I to 5, wherein the moveable jaw is slidably mounted with respect to the base.

7. A measuring calliper as claimed in any of the preceding claims, wherein the base and jaws are generally planar.

8. A measuring calliper as claimed in any of claims I to 7, wherein the distance between the pivot and the measuring scale is greater than the distance between the pivot and the end of the second jaw -

9. A measuring calliper as claimed in any of clainis 1 to 8, wherein the first and second jaws are each provided with an outturned nose.

10. A measuring calliper substantially as herein described, with reference to, and as illustrated in the accompanying drawings.