GB2230095A - Measuring apparatus - Google Patents

Abstract

Measuring apparatus (10) comprises a base (12) having a surface (13) upon which an article to be measured can be disposed. The apparatus also comprises support means capable of carrying a sensing device for sensing the surface of the article. The support means comprises first and second members (16, 18) wherein the support members engage the base at said surface and are movable nearly relative to said base. A connecting member (22) is also provided to connect the first and second support members. The connecting member is disposed at the opposite side of the base to the surface (13) engaged by the support members. The base has sloping faces (12a)(12b) and air bearings (24), (25). <IMAGE>

Description

MEASURING APPARATUS This invention relates to measuring apparatus.

In the manufacture of goods where the dimensions of those goods are critical, it is necessary to be able to carry out strict quality control to ensure that the dimensions do not exceed acceptable tolerances. There are several types of measuring apparatus for this purpose currently commercially available.

One type of measuring apparatus consists of a four sided ring bridge structure having a base disposed within the ring bridge structure and where the bridge is movable along rails disposed beneath the base.

It is an object of this invention to provide improved measuring apparatus.

According to this invention there is provided measuring apparatus comprising: a base having a surface upon which an article to be measured can be disposed; support means capable of carrying a sensing device for sensing the surface of the article, said support means comprising first and second support members wherein the support members engage the base at said surface and are movable linearly relative to said base; and a connecting member to connect the first and second support members, said connecting member being disposed at the opposite side of the base to said surface engaged by said support members.

In one embodiment of the invention, the base has opposed sloping edges, and advantageously has a profile of a substantially dovetail configuration, wherein the support members engage a respective one of said sloping edges for movement relative to said base.

In the preferred embodiment, each support member engages the base at said surface and at said respective sloping edge by low friction bearings which may be air bearings.

This arrangement has the advantage that it provides for the apparatus a rigid stable structure and overcomes problems associated with distortion.

In the preferred embodiment of this invention, the support means comprises a gantry having an elongate guide member suitable for guiding the sensing device supported by said support members on the same side of said base as said planar surface. Preferably, the connecting member is in the form of a plate and may be attached at the bottom of each of said support members.

Usually, the apparatus is provided with a sensing device movable along said guide member parallel to said surface and perpendicular to the direction of movement of the support means, said sensing device being adapted to sense the surface of the article, thereby to determine the dimensions thereof.

The apparatus may also comprise a carriage adapted to be linearly movable along said support means; and carrying a sensing device movable linearly in relation to said carriage to sense the surface of an article disposed on said base.

An elongate holder may be provided to hold the sensing means at one end thereof and at the other end thereof is attached via an appropriate arrangement of pulleys to a weight to enable the probe to be positioned accurately.

T-he holder may be movable through said carriage and low friction bearing means may be provided further to ensure that the sensing means can be positioned accurately.

Preferably, a first housing is provided to house a first bearing for said holder. A second housing similar to said first housing may be provided on top of said carriage to house a second bearing for said holder.

A plurality of further low friction bearings may be provided to permit movement of said carriage. The further bearings may be appropriately arranged on said carriage and adapted to act against said support means. Preferably the bearings referred to above are air bearings.

Reference is now made to the accompanying drawings in which: Figure 1 is a perspective schematic view of apparatus according to one embodiment of the present invention.

Figure 2 is a side view of a support member according to one embodiment of the present invention.

Figure 3 is a front view of apparatus according to one embodiment of the present invention.

Figure 4 is a perspective view of a sensing device according to one embodiment of the present invention.

Figure 5 is a view along the lines V-V in Figure 4.

Figure 6 is a view along the lines VI-VI in Figure 4.

Referring to the drawings, measuring apparatus is shown.

The apparatus is generally designated 10 and comprises a base 12, support means in the form of a gantry 14 which is movable in the directions indicated by the arrows A.

As can be seen particularly from Figures 1 and 3, the base 12 has a planar surface 13 upon which an article (not shown) to be measured can be disposed. The base 12 has a profile which is of a dovetail configuration and has sloping edges 12a and 12b as shown in the drawings.

The gantry 14 comprises first and second support members 16,18 which are disposed at the opposed sloping edges 12a,12b of the base 12. The support members 16, 18 support a guide member 10. One end of the guide member 20 is attached to the top of the first support member 16 and the other end of the guide member 20 is attached to the top of the second support member 18.

A connecting member in the form of a plate 22 is provided to connect the support members 16,18. The plate 22 is disposed beneath the base 12. One end of the plate 22 is attached to the bottom of the first support member 16 and the other end of the plate 22 is attached to the bottom of the second support member 18.

A plurality of air bearings 24,25 are arranged on the support members 16, 18 to enable the gantry to be moved easily in the directions indicated by the arrow A and to be positioned accurately where desired. The air bearings 24,25 are operated pneumatically by means well known in the art and provide a cushion of air between the support members 16, 18 and the base 12.

The air bearings 24 engage the planar surface 13 of the base 12 and the air bearings 25 engage the sloping edges 12a,12b of the base 12.

A carriage 26 (see Figures 4 to 6) is also provided to carry a sensing device in the form of a probe 30 to sense the position of an article disposed on the base 12. The carriage 26 is supported by the gantry 14 and is movable along the guide member 20 in the direction indicated by the arrows B.

The guide member 20 passes through the carriage 26.

The probe 30 is held by an elongate holder 32 which is disposed perpendicular to the guide member 20 and is movable vertically in the directions indicated by the arrows C, so that the holder 32 can slide through the carriage 26. The probe 30 is movable in three mutually perpendicular directions.

A weight 34 is provided to facilitate movement of the holder 32 and thereby the probe 30. The weight 34 is attached to the holder 32 and by cords 36 which passes via a pulley arrangement 38. The weight 34 slides within a weight receiving member 40.

Attached to the underside of the carriage 28 is a first housing 42 for an air bearing 44. A second housing 46 is attached to the top of the carriage 28 and houses an air bearing 48. The air bearings 44, 48 can provide a cushion of air against the holder 32 further to facilitate movement of the holder 32 and to enable the probe 30 to be positioned accurately.

In operation, a first article (not shown) is disposed on the base 12. This first article is used to calibrate the apparatus 10. The gantry 14 can then be moved in relation to the base until the guide member 20 is disposed over the article. The carriage 26 can then be moved along the guide member 20 until the probe 30 is disposed above a first predetermined part of the article. Then the probe 30 is lowered until it contacts this first predetermined part and the position of the probe 30 at this point is recorded on a computer. The probe 30 will then be moved by appropriate movement of the gantry 14, the carriage 28 and the holder 32 until the probe 30 contacts another predetermined part of the article. This position of contact of the probe 30 is also recorded on the computer.This can be repeated until the position of the probe 30 at a desired number of predetermined parts of the article have been recorded on the computer. Since the probe 30 is movable in three mutually perpendicular directions its precise position in space can be determined.

In order to determine whether the dimensions of further articles are the same as those of the first article or are within acceptable tolerances, a further article is disposed on the base 12 in the same position as the first article. The probe 30 is then moved until it contacts the first predetermined part of the further article. The position of the probe 30 at this first predetermined part of the further article is then recorded and compared with the position of the probe at the first predetermined part of the first article. This probe is then moved until the position of the probe 30 at the predetermined part of the further article have been recorded. These positions are then compared against those for the first article and if any of them are outside acceptable tolerances, the article is rejected.

This process is repeated until all the further articles have been checked.

Claims (11)

rT.IMS

1. Measuring apparatus comprising: a base having a surface upon which an article to be measured can be disposed; support means capable of carrying a sensing device for sensing the surface of the article, said support means comprising first and second support members wherein the support members engage the base at said surface and- are movable linearly relative to said base; and a connecting member to connect the first and second support members, said connecting member being disposed at the opposite side of the base to said surface engaged by said support members.

2. Measuring apparatus according to Claim 1, wherein the base has opposed sloping edges, and a profile of a substantially dovetail configuration, wherein the support members further engage a respective one of said sloping edges for movement relative to said base.

3. Measuring apparatus according to Claim 2, wherein each support member engages the base at said surface and at said respective sloping edge by low friction bearings which may be air bearings.

4. Measuring apparatus according to any preceding claim, wherein the connecting member is in the form of a plate and may be attached at the bottom of each of said support members.

5. Measuring apparatus according to any preceding claim, wherein the support means comprises a gantry having an elongate guide member suitable for guiding the sensing device supported by said support members on the same side of said base as said surface.

6. Measuring apparatus according to Claim 5, comprising a sensing device movable along said guide member parallel to said surface and perpendicular to the direction of movement of the support means, said sensing device being adapted to sense the surface of the article, thereby to determine the dimensions thereof.

7. Measuring apparatus according to Claim 6, comprising a carriage adapted to be linearly movable along said support means; said carriage carrying said sensing device being movable linearly in relation to said carriage to sense the surface of an article disposed on said base.

8. Measuring apparatus according to Claim 7, comprising an elongate holder to hold the sensing means at one end of said holder and at the other end thereof said holder is attached via an appropriate arrangement of pulleys to a weight to enable the sensing device to be positioned accurately.

9. Measuring apparatus according to Claim 8, wherein the holder is movable through said carriage and low friction bearing means are provided further to ensure that the sensing means can be positioned accurately.

10. Measuring apparatus according to Claim 9, wherein a first housing is provided to house a first bearing for said holder; a second housing similar to said first housing is provided on top of said carriage to house a second bearing for said holder.

11. Measuring apparatus according to any preceding claim, wherein a plurality of low friction bearings are provided to permit movement of said carriage; the bearings being arranged on said carriage and adapted to act against said support means.