GB2191011A - Measuring or checking angle - Google Patents

Abstract

Apparatus for measuring the angle between two adjacent straight portions of a tube or rod has two supports 36 each angularly movable and about parallel axes, and each adapted to contact the said adjacent straight portions and to lie parallel to them. Each of the supports is connected to an optical encoder, which effectively counts the angular movement necessary in order to move the supports into contact with the adjacent straight portions which are to be measured, and that angular movement can be converted into a read-out in terms of for example degrees of arc. The supports can be adjusted towards and away from one another along the slots 12 to enable the apparatus to be used with a range of different tubes or rods to be checked, and the apparatus also includes a support 18 which is essentially contained in the same plane as the supports, so as to maintain the said adjacent straight portions in a plane perpendicular to the axes of rotation of the supports. <IMAGE>

Description

SPECIFICATION Measuring or checking angle.

In the manufacture of articles it is often necessary to produce tubes or rods which are bent, sometimes into complex shapes comprising a series of straight portions extending between successive bends.

The object of the invention is to facilitate the measurement or checking of the angle of any one or more of such bends.

According to a first aspect of the invention, a method of measuring or checking the angle between two adjacent straight portions of a tube, rod or the like part comprises locating the bend or a point on the article near the bend on a fixed support, locating part of each said straight portion on an angularly movable support, and turning the latter supports about parallel axes relative to one another in opposite directions until aligned with the straight portions, including the step of sensing the angular positions or sensing the smovement to the aligned positions and converting the same into a measurement.

It is preferred to use optical encoders connected to the angularly movable supports.

Two kinds of optical encoders are known, namely the absolute and the incremental types, but these differ (for the purposes of the present invention) primarily in the zeroing or calibration which is necessary after switching on and insofar as significant, this will be explained in the ensuing description.

It is preferred to use angularly movable supports which are L-shaped with the horizontal limbs lying in a plane containing a horizontal surface comprising the fixed support.

Essentially, and in the simplest version, the two angularly movable supports can be lined up so as to be parallel or zero, when an output reading, for example from a microprocessor connected to the encoders, may read 1800. If a tube bent to a generally V shape is then placed on the three supports and the two outer supports are turned clockwise and counterclockwise respectively until the vertical limb of each is aligned with one of the straight limbs, both encoders will be turned but possibly through different angles. Suppose that the actual angle between the two straight portions is 60". One encoder may be turned through 50 and the other through 70" before each is aligned with the corresponding straight portion.The outputs from the two encoders is summed and subtracted from the initial reading. To ensure that each movable support is accurately aligned with the corresponding straight portion, each carries a shoe preferably having contact surfaces provided along parallel edges which are as widely spaced as possible. Whilst it is preferred to use L-shaped shoes, Vee's could be employed especially if only a single diameter of tube or like is to be measured.

The third support which is a fixed one is merely used for the purpose of keeping the article with its axes in a plane truly parallel to the plane containing the support surfaces, may be a simple fixed bar. Additional supports, again to prevent any possibility of the article tilting out of the desired plane, may be provided on opposite sides of the first and third (angularly movable) supports and may themselves be pivotally carried on the apparatus so as to facilitate adjustment to suit different kinds of workpieces.

In its simplest form, the apparatus and its associated electronic circuitry and/or microprocessor may have a digital decimalised read-out in degrees. Thus a particular bend may be indicated as being 59.99 .

Alternatively, the microprocessor may have programmable memory enabling the desired angle to be inserted, for use in production so that an unskilled person can measure a series of articles with the read-out being expressed in terms of satisfactory or unsatisfactory, for example by signal lamps being lit. The parameters, for example the permissible variation from the preset reading would be memory stored for this purpose.

The apparatus can be made useful for articles of varying transverse dimensions, for example tubes of different diameters, most conveniently in the L-shoe version.

It is to be noted that precise location is unimportant in that if the apex of the bend does not lie precisely on the third and central support, then it is simply that one of the encoders will turn more than the other.

Where an article of complex shape is involved, possibly having successive bends lying in different planes as well as being at different angles, then the apparatus can be used successfully on these, with the operator either noting the direct read-out for each bend and comparing it with the desired value, or by using a more complex memory and checking the bends in a preset order. However, it is within the scope of the invention to provide a more complex apparatus in which several sets of encoders are provided.

The encoders are desirably adjustable along the length of a bed towards and away from one another. The minimum spacing between the two would be required when the bend has a particularly small included angle. For example if a 1800 bend were possible with the material concerned, so that the two lengths extend parallel to one another, then the separation between the contact surfaces of the two shoes when lying parallel to one another would only be the same as twice the external diameter of the article.

In general however and with bends of less than 1800 included angle it is preferred to measure the included angle at a greater distance from the bend so as to avoid errors in read-out because of the distortion in the cross-sectional shape of the article in the vicinity of the bend, which usually follows specially in mass production of articles from tubes.

The invention is more particularly described with reference to the accompanying drawings wherein: Figure 1 is a plan view of a first embodiment of the invention; Figure 2 is an elevation of the same; and Figures 3-7 show various components being measured in the apparatus.

Referring now to the drawings and particularly Fig. 1 thereof, the apparatus comprises a bed 10 provided with elongated slots 12 mounting (firstly) a pair of optical encoders 14, 26 (see Fig. 2). The encoders are slidable along the length of the slots and desirably are fixed in selected positions, for example by a spring loaded detent system or by clamp screws not shown.

The drawings show the encoders spaced apart symmetrically about a central support 18, aithough it is unnecessary that they are located symmetrically or with any precision.

The bed also supports a pair of mounting brackets 20 for additional supports 22, 24 carried on respective arms 26, 28 which as illustrated may be slotted at 30 with clamp nuts 32 so that these arms may be swung to position the supports 22, 24 at different locations to suit needs.

Each of the encoders comprises an Lshaped shoe having a horizontal limb 36 and a vertical limb. The edges of the limb are effective to contact the workpiece, and between those edges the shoes may be relieved, so that effectively they are of very shallow channel section.

Each of the shoes is angularly movable about the vertical axis of the corresponding encoder, these axes being parallel and contained in a common plane extending substantially along the length of the slots 12.

The fixed support 18 has its upper surface 40 lying in the same plane as the (effective) upper surfaces of the horizontal limbs 36. The support pads 22, 24 also have their surfaces lying in that same plane.

The effective surfaces (the edges) of the vertical limbs 38 of the two shoes are spaced from the pivotal axes of the shoes by a common distance.

The rotatable parts of the encoders may be provided with pegs 42 to encounter stops 44 in order to limit angular movement beyond a certain point.

If encoders of the absolute type are used, the read-out on a digital display unit connected to the encoders by an appropriate micro-processor may read 1800 when the two shoes are turned so that they are parallel with one another when a straight edge placed against the two shoes will be in contact with both of the effective edges of both of the shoes. In the case of an incremental encoder, any movement necessary to turn the shoes to that aligned position will give rise to a readout different from 1800 but this can be corrected so that the display does read 1800.

Fig. 3 illustrates a situation in which a simple small diameter tube bent to an obtuse angle of say 140 is placed on the apparatus for measurement. The apex of the bend is located generally on the fixed support, the encoders are generally symmetrically located about that support, and the shoes are turned to be in alignment with the two respective straight portions, whilst the pads 22, 24 are used to support the tube at more remote locations so as to prevent it turning to lift the apex 15 from the support which would give a false reading. This is because, for example, if the component was allowed to rotate until the two straight portions had their axes contained in a vertical plane containing the axes of rotation of the encoders, the two shoes would be returned to the parallel condition and the false reading of 1800 would result.

Fig. 4 shows a near right angle bend being measured at one end of a component, whilst Fig. 5 shows the opposite end of the same component being checked. It will be noted that in the cases of Figs. 4 and 5 only one of the support pads is in use. Further, Figs. 4 and 5 show the encoders at different locations relative to the central support. In general it is preferred to locate t encoders as far away as possible from the central support in order to avoid errors as mentioned earlier in the specification, but it may also be desirable to avoid repositioning of the encoders if a component is being checked at a number of different locations, in order to speed the whole operation.

The central support extends for a relatively large direction transversely of the bed in order to receive and support the apex of the bend when the included angle is particularly small and (also) the shoes are particularly far apart.

Figs. 6 and 7 illustrate different views of the same component having different bends measured, when two adjacent straight portions lie in one plane, and one of those straight portions and the next adjacent straight portion have their axes contained in a different plane.

In this situation it is particularly important that the support pads 22, 24 contact the same straight portions as that contacted by the adjacent shoe, in order to avoid errors being introduced.

Although it is expected that the invention will find its greatest applicability with bent tubes it can be used for measuring angles of components generally.

When the component is of uniform thickness, all 3 supports will be co-planar, but more variable articles can be accommodated by appropriate adjustments to the relative height of the supports.

Claims (9)

1. A method of measuring or checking the angle between two adjacent straight portions of a tube, rod or the like comprising locating the bend or a point near to the bend on a first support, locating part of each of said straight portion on respective second and third supports, and turning the latter supports about parallel axes relative to one another in opposite directions until aligned with the length of the straight portions, including the step of sensing the angular positions of the second and third members when so aligned, or sensing the movement to those aligned positions, and converting the same into the measurement.

2. A method as claimed in Claim 1 wherein the movement is expressed in terms of being within or without preset parameters.

3. A method as claimed in Claim 1 wherein the angles of movement of the two supports are added together and subtracted from 1800 and the result is expressed in terms of actual angle of the bend.

4. Apparatus for carrying out the method claimed in Claim 1 comprising a pair of encoders each comprising fixed and angularly movable parts, with electronic output proportional to the relative angular movement at any one time, arranged on opposite sides of a fixed support and each carrying a shoe for engagement and alignment with part of the straight portion on one or other side of the bend which is located in the vicinity of the third support.

5. Apparatus as claimed in Claim 4 wherein the encoders are mounted on a bed and are adjustable along the length of the bed towards and away from each other.

6. An apparatus as claimed in Claim 5 wherein the article engaging components are V-shaped supports.

7. Apparatus as claimed in claimed in Claim 5 wherein the article receiving components are L-shaped supports.

8. Apparatus as claimed in Claim 7 wherein the horizontal surface of each support is co-planar with the fixed support.

9. Apparatus as claimed in any preceding claim provided with additional article work supports lying in the same plane as the fixed support and at opposite ends of the bed.