GB2479971A

GB2479971A - Measuring device for external diameters

Info

Publication number: GB2479971A
Application number: GB1106578A
Authority: GB
Inventors: Thomas Maxwell Parry
Original assignee: James Neill Holdings Ltd
Current assignee: James Neill Holdings Ltd
Priority date: 2010-04-28
Filing date: 2011-04-19
Publication date: 2011-11-02
Anticipated expiration: 2031-04-19
Also published as: GB201007059D0; GB2479971B; GB201106578D0

Abstract

The device 1 comprises a first frame member 2 and at least one second frame member 9 wherein a first end 10 of the second frame is attached to an end 4 of the first frame and the second end 12 of the second frame is free to adjust or move relative to the adjacent end of the first frame. The first frame has a test piece contact point 3 at the end 4 of the first frame. The opposite end 5 of the first frame has a bore 6 in axial alignment with the contact point 3 and an anvil 7 of a measuring device 8 extending through the bore 6. At the free end 12 of the second frame 9 there is disposed an actuating lever 13 attached to the anvil 7 of the measuring device 8 by a pivot pin 16 on the free end of the actuating lever engaging an aperture on the anvil 7; anvil actuating means 17,18,19 are provided on the second frame. There is described an arrangement wherein two second frame members are disposed on either side of the first frame member (figures 7 to 10). Reactive forces caused by urging the anvil of the measuring device against the test piece are taken by one or two of the second frame members to thereby ensure that the first frame member does not flex during the measuring process. This helps to provide greater accuracy in measurements.

Description

MEASURiNG DEVICE This invention relates to measuring devices and is particularly concerned with devices for measuring external dimensions, such as, for example, external diameters of circular or cylindrical objects.

Measuring instruments such as snap gauges, transducer probes and micrometers provide extreme degrees of accuracy even when measurement is at the micron level. However, where measurement of relatively large external dimensions are required, known constructions exhibit the disadvantage, particularly at the micron level, that there can be no guarantee that a reading is accurate, and there can be an inconsistency arising with repeat readings.

Ordinarily, such measuring instruments are formed by a frame supporting a measurement indicator, the anvil of which extends through an aperture on the frame, and the.frame having a means of contacting the workpiece in axial alignment with the anvil. Thus, with the anvil withdrawn, the frame can be positioned around the workpiece, and the anvil driven through the aperture and into contact with the workpiece which, consequently, is pressed against the aligned contact. The result of urging the anvil against the workpiece and the workpiece against the contact on the frame, is the establishment of a reactive force in the frame.

Particularly with measuring devices for relatively large external dimensions, the reactive force established in the frame can cause the frame to flex, the result of which can, at the micron level at least, cause an inaccuracy in the reading taken, and in addition can create considerable difficulties by causing inconsistencies between a first and subsequent repeat readings.

The objective of the present invention is to provide a measuring means that overcomes the disadvantage mentioned above.

According to a first aspect of the present invention a measuring device comprises a first frame member, a workpiece contact point internally of the first frame member, a bore through the first frame member at the opposite end to and in axial alignment with the contact point, a measuring means positioned externally of the first frame member, an anvil of the measuring means extending through the bore, and there being at least one second frame member lying alongside the first frame member, the second frame member being secured to the first frame member at its end opposite to the location of the measuring means, and the second frame member at its free end having a pivotally attached actuating lever the opposite end of which is pivotally attached to the end of the anvil emerging through the aperture with freedom for relative moment and there being an actuator means at the free end of the second frame member, in engagement with the actuating lever. The measuring means may be removably secured to the first frame member with its anvil extending through the bore, or the measuring means may be formed integrally with the first frame member. The attachment of the actuating lever to the anvil may be a pivotal connection, but desirably, an aperture through the anvil to accept the pivot pin provides clearance above and below the pivot pin to ensure that only axial forces are created that are transferred to the second frame member.

The first frame member and at least one second frame member may be secured at one end by screws, rivets or other mechanical fixing means, with or without the assistance of an appropriate adhesive. Equally, the first and second members may be formed integrally at one end.

With the actuator means in a withdrawn condition, the anvil of the measuring means is also withdrawn, allowing the first frame to be positioned around the workpiece to be measured and the actuator means activated to urge the anvil against the workpiece and engage the workpiece against the Thus, the reaction to the force of the anvil pressing on the workpiece is transferred to the second frame member by the actuating lever, and not to the first frame member on which the measurement means is mounted. As a consequence, the first frame member is free of such reactive forces as a measurement takes place, allowing extremely accurate measurement to take place, and for repeat measurement to be taken with a substantial guarantee that they will be equally accurate.

The first frame member may be of any suitable material having relatively high strength and relatively low. weight. It may be a solid plate-like member of, e.g. an aluminium alloy, or it may be a laminate of, e.g. aluminium/carbon fibre plates with a foam or honeycomb core. Preferably, the second frame member is a solid plate-like construction of an appropriate relatively light weight and high strength material, such as an aluminium alloy or carbon fibre.

The actuator means for the actuating lever may be a threaded rod or a spring-loaded cam lever extending through a corresponding hole in the free end of the second frame member to bear against the actuating lever. Thus, with a threaded rod, its rotation with the assistance of a screw knob at its outer end, drives it through a threaded hole, to pivot the actuating lever about its connection to the second frame member, to pull the anvil through the aperture in the first frame member and into contact with the workpiece.

According to a second aspect of the invention, a measuring device comprises a first frame member having a workpiece contact point at one end and a measuring means mounted at its opposite end, in axial alignment with the contact point, two second frame members lying to opposite sides of the first frame member, both of which are secured to the first frame member at the same end, the free ends of the second frame members being connected by a bridging piece that is clear of the adjacent end of the first frame member, an anvil on the measurement means extending through a bore in the first frame member, an actuating lever pivotally attached to the anvil and pivotally mounted on the second frame members, and an actuator means mounted on the bridging piece and extending through an aperture in the first frame member and into contact with the actuating lever. As with the first embodiment, the actuating lever may be pivotally attached to the anvil, the anvil having an aperture to receive a pivot pin, that provides clearance above and below the pivot pin to ensure that only axial forces are created and transferred to the second frame member.

Therefore, all reactive forces caused by urging the anvil of the measuring means against the workpiece and hence the workpiece against the contact point, are taken by the one or the two second frame members, thereby ensuring that the first frame member does not flex during the taking of measurements, thereby assuring the taking of accurate first and repeat measurements.

Three embodiments of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a perspective view of one embodiment of the invention; Figure 2 is an end elevation of Figure 1; Figure 3 is a side elevation of Figure 1; Figure 4 is a perspective view of a second embodiment of the invention; Figure 5 is an end elevation of Figure 4; Figure 6 is a side elevation of Figure 4; Figure 7 is a perspective view of a third embodiment of the invention; Figure 8 is an end elevation of Figure 7; Figure 9 is a side elevation of Figure 7; and Figure 10 corresponds to Figure 7 but shows one second frame member removed.

In Figures 1 to 3, a measuring device I has a first frame member 2 of generally U-shape, with a contact point 3 for a workpieôe, on one end 4. On the opposite end 5 is a bore 6 in axial alignment with the contact point 3, with the anvil 7 of a measuring device 8, extending through the bore 6.

Alongside the first frame member 2 is a second frame member 9 also of general U-shape, one end 10 of which is rigidly secured to the end 4 of the first frame member, such for example by four bolts 11. At its free end 12 the second frame member 9 has an actuating level 13 attached by a pivot 14, the opposite end 15 of the lever 13 being pivotally attached to the anvil 7 of the measuring device 8 by a pivot pin 16 on the free end of the actuating lever engaging in an aperture on the anvil 7 with clearance above and below to ensure that only axial forces are applied to the pivot pin and transferred to the second frame member.

Also provided on the end 12 of the second frame member is an actuator means 17 in the form of a threaded rod 18 extending through a correspondingly threaded hole in the end 12, the end of the rod bearing against the actuating lever 13. A screw knob 19 is provided on the outer end of the threaded rod 18 to facilitate the driving of the threaded rod 18 through the threaded hole.

In Figures 4 to 6, an essentially similar construction of measuring device is illustrated, and like parts are given the same reference numerals.

Here, an additional frame member 20 is provided, lying to the opposite side of the frame member 2 as the second frame member 9. At their free ends, the frame members 9 and 20 are connected by a yoke 21 extending around the end 5.

With a workpiece located within the first frame member 2, the anvil 7 of the measuring device 8 is urged against it by rotation of the threaded rod 18 and to trap the workpiece between the end of the anvil and the workpiece contact point 3. AU of the reactive forces that are created are transferred to either the second frame member 9 or the second frame members 9 and 20 thereby ensuring that the first frame member is not subjected to axial forces and caused to flex during the taking of a measurement reading, thereby substantially guaranteeing the accuracy of the reading taken.

In Figures 7 to 10, like parts are provided with the same reference numerals. Here, a first member 2 of an aluminium alloy, or a laminate of aluminium and carbon fibres, is shaped to be better able to receive a workpiece, the first member 2 having a stud 22 to bear against the workpiece.

The first member 2 also has an elongate hole 23 to enable the measuring device to be held by a user.

The second frame members 9 and 20 are any suitable material, such as for example a carbon fibre or an aluminium based material having high strength and low weight and each has an elongate hole 24 in alignment with the hole 23 in the member 2. In this embodiment the yolk to hold the outer ends of the second frame members 9 and 20 is a separate member 25 extending through the outer end of the sandwich of first and second plate members, and secured to the outer face of the respective second frame members by screws 26. Here again, the first member 2 and second members 9 and 20 are rigidly held together by bolts 11 and the end 4 of the first member.

On the end 4 of the first member 2 is the workpiece contact 3, in alignment with the anvil 7 of a measuring device 8. The anvil 7 is attached to the operating lever 13 pivotally mounted at 14, and is engaged by the threaded rod of the screw knob 19: As is shown in Figure 10, the first member 2, in addition to the bolts 11, has a number of spacer studs 27, to which the second members 9 and 20 are attached, and whereby the first and second members are held in close spaced relationship, but with the second members 9 and 20 able to move in relation to the member 2, at the end 5 bearing the measuring device 8.

As with the constructions of Figures 1 to 6, operation of the screw knob 19 to urge the anvil 7 against a workpiece resting in space provided, results in all of the reactive forces being transferred through the lever 13 and to the second members 9 and 20, thereby ensuring that the first member 2 is not subjected to axial forces, and hence will not flex, as a measurement reading is taken, thereby guaranteeing to a substantial degree that the readings taken are accurate.

Claims

Claims 1. A measuring device comprising a first frame member, a workpiece contact point internally of the first frame member, a bore through the first frame member at the opposite end to and in axial alignment with the contact point, a measuring means positioned externally of the first frame member, an anvil of the measuring means extending through the bore, and there being at least one second frame member lying alongside the first frame member, the second frame member being secured to the first frame member at its end opposite to the location of the measuring means, and the second frame member at its free end having an actuating (ever the opposite end of which is attached to the end of the anvil emerging through the aperture with freedom for relative moment and there being an actuator means at the free end of the second frame member, in engagement with the actuating lever.
2. A measuring device as in Claim 1, wherein the measuring means is removably secured to the first frame member with its anvil extending through the bore.
3. A measuring device as in Claim 1, wherein the measuring means is formed integrally with the first frame member.
4. A measuring device as in any of Claims I to 3, wherein the attachment of the actuating lever to the anvil is a pivotal connection.
5. A measuring device as in Claim 4, wherein an aperture through the anvil to accept the pivot pin provides clearance above and below the pivot pin to ensure that only axial forces are created that are transferred to the second frame member.
6. A measuring device as in any of Claims 1 to 5, wherein the first frame member and at least one second frame member are secured at one end by screws, rivets or other mechanical fixing means, with or without the assistance of an appropriate adhesive.
7. A measuring device as in any of Claims I to 5, wherein the first and second frame members are formed integrally at one end.
8. A measuring device as in any of Claims 1 to 7, wherein the first frame member is of any suitable material having relatively high strength and relatively low weight.
9. A measuring device as in any of Claims 1 to 8, wherein the actuator means for the actuating lever is a threaded rod extending through a corresponding threaded hole in the free end of the second frame member to bear against the actuating lever, rotation of the rod with the assistance of a screw knob at its outer end, driving it through the threaded hole, to pivot the actuating lever about its connection to the second frame member, to pull the anvil through the aperture in the first frame member and into contact with the
10. A measuring device as in any of Claims I to 8, wherein the actuator means for the actuating lever is a cam lever extending through a corresponding hole in the free end of the second frame member to bear against the actuating lever, linear movement of the cam lever driving it through the hole to pivot the actuating lever about its connection to the second frame member, to pull the anvil through the aperture in the first frame member and into contact with the workpiece.
11. A measuring device comprising a first frame member having a workpiece contact point at one end and a measuring means mounted at its opposite end, in axial alignment with the contact point, two second frame members lying to opposite sides of the first frame member, both of which are secured to the first frame member at the same end, the free ends of the second frame members being connected by a bridging piece that is clear of the adjacent end of the first frame member, an anvil on the measurement means extending through a bore in the first frame member, an actuating lever pivotally attached to the anvil and pivotally mounted on the second frame members, and an actuator means mounted on the bridging piece and extending through an aperture in the first frame member and into contact with the actuating lever.
12. A measuring device substantially as hereinbefore described with reference to Figures 1 to 3, Figures 4 to 6, or Figures 7 to 10 of the accompanying drawings.