GB2116705A - Handling of mechanical components - Google Patents

Abstract

Each of a series of identical components moving in line in a feed system has its orientation sensed by an optical test involving detection of light scattered and/or reflected by the component, and those components not having a wanted orientation are either removed from the line or appropriately re-orientated. For example, a phototransistor (4) may be arranged to detect light scattered and reflected by grub screws (10) as they pass through a light beam (14) while progressing endwise along the track (6) of a vibratory bowl feeder (1), the signals generated by the phototransistor (4) indicating whether a particular screw has its slotted end leading or trailing; a pneumatic device controlled by these signals blows screws with the slotted end trailing back into the well of the feeder bowl (5), while permitting those with the slotted end leading to reach the feeder outlet. <IMAGE>

Description

SPECIFICATION Handling of mechanical components In carrying out assembly operations it is frequently required to feed a series of identical mechanical components one at a time to a delivery point. In some cases it is necessary or desirable to ensure that all the components arrive at the delivery point with the same orientation, and the achievement of this may present difficulties where it is desired to utilise certain readily available types of feed system. In the case of a vibratory bowl feeder, for example, the mode of operation is such that for most types of component there are at least two different stable orientations which may be assumed by individual components as they progress along the track of the feeder.Hitherto, the problem which this presents has normally been dealt with by providing mechanical devices attached to the bowl and designated so that a component which has an undesired orientation will either be appropriately re-orientated or be returned from the track to the reservoir of components in the well of the bowl. Such devices must, however, be designed specifically for each type of component, and there are some types of component which cannot readily be catered for in this way.

The present invention is based on the realisation that the problem can be dealt with in an alternative way by using relatively simple and inexpensive optical techniques for sensing component orientation. These techniques offer considerable flexibility of application, and can be used with a wide variety of types of component, including those with only a small degree of asymmetry.

According to one aspect of the invention, a method of handling a series of identical mechanical components comprises feeding the components sequentially towards a delivery point in such a manner that each component can assume any one of a small number of different stable orientations, subjecting each component before it reaches the delivery point to an optical test in which the component is temporarily illuminated by a beam of light as a result of relative movement occurring between the component and the beam and in which an output is derived from a photo-electric detection system responsive to light from the beam which is scattered and/or reflected by the component, the arrangement being such that the form of said output will differ significantly according to whether or not the tested component has a given one of said orientations, and so treating the components in accordance with the results of the tests that all those components which arrive at the delivery point have said given one of said orientations.

The treatment of the tested components may involve either appropriate re-orientation of those ascertained not to have said given one of said orientations, or the prevention of such components reaching the delivery point.

According to another aspect of the invention there is provided an apparatus for use in handling mechanical components, comprising a vibratory bowl feeder, means for protecting a beam of light so as to illuminate components traversing a given portion of the track of the feeder as a result of the operation of the feeder, a photo-electric detection system responsiveto light from the beam which is scattered and/or reflected by such components, and means for utilising signals derived from said detection system to cause the removal from said track of any component of a given type which is orientated other than in a given manner while traversing said given portion of the track.

It is to be understood that in this specification the term light includes ultra-violet and infra-red radiation as well as visible radiation.

One arrangement in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which: Figures 1 and 2 are respectively somewhat diagrammatic side and plan views of part of an apparatus adapted for use in the handling of grub screws, the side view being partly cut away to show internal detail; Figure 3 is an explanatory diagram; and Figure 4 is a schematic diagram of an electrical circuit forming part of the apparatus illustrated in Figures 1 and 2.

Referring to Figures 1 and 2, the apparatus includes a vibratory bowl feeder 1 of substantially conventional form, and an associated optical system incorporating a low power continuous wave iaser source 2, a plane mirror 3 and a photo-transistor 4.

These components of the optical system are supported by a frame which is omitted from the drawings for the sake of clarity, the frame being fixed relative to the feeder 1. The feeder 1 has a cylindrical bowl 5 on the interior of which is mounted a track 6 whose upper face is coated with black rubber. The major part of the track 6 is in the form of a spiral extending upwards from the base of the bowl 5 at an inclination of 3 , but at its upper end the spiral merges with a straight track section 7 which extends horizontally through a gap formed in the cylindrical wall of the bowl 5 to provide the outlet of the feeder 1; the section 7 is bounded at one side by a vertical wall 8 which constitutes a continuation of the cylindrical wall of the bowl 5.

In use of the apparatus, a large number of identical grub screws are deposited randomly in the well of the bowl 5, and screws drawn from this supply are caused to progress up the track 6 in the usual way by virtue of vibratory motion of the bowl 5. Before reaching the section 7 the screws are reduced to a single file by means of a deflector device 9 (Figure 2) mounted above the track 6; as a result, those screws 10 which pass the device 9 proceed in turn along a path which extends initially adjacent the cylindrical wall of the bowl 5 and ultimately adjacent the wall 8.

In proceeding along this path the screws 10 have their longitudinal axes aligned with the length of the track 6, but of course some will have the slotted end leading and some will have the slotted end trailing.

The function of the optical system is to sense which of these two possible orientations applies in respect of each of the screws 10. As will be explained more fully below, only those of the screws 10 sensed as having a chosen one of these orientations are permitted to reach the outlet of the feeder 1, while the others are caused to be returned from the track 6 to the well of the bowl 5. The removal of each screw 10 having the unwanted orientation is effected by an air jet issuing from an orifice 11 (Figure 1) in the wall 8, the orifice 11 communicating with one end of the pipe 12 (Figure 2) whose other end is connected to a compressed air supply (not shown) and which is provided with an electrically operable pneumatic valve 13.

Considering now the arrangement of the optical system, the source 2 (which may suitably incorporate a helium-neon laser having a power rating of 0.5 mW) is arranged to project a light beam 14 (which may typically have a diameter of about 2 mm) horizontally in a vertical plane aligned with the straight portion, extending along the section 7, of the path traversed by the screws 10, the beam 14 being reflected by the mirror 3 so as to be directed downwardly at an angle of about 450 in the same plane and so that it will intersect the straight portion of the path traversed by the screws 10 at a point near that end of the section 7 adjacent the spiral part of the track 6; for the sake of clarity, only part of the horizontal portion of the beam 14 is indicated by Figure 2.As a result, each of the screws 10 is temporarily illuminated by the beam 14 shortly after it reaches the section 7, with the geometry being such that the leading end of the screw is illuminated.

Since the screws 10 speed up on reaching the horizontal track section 7, they will pass through the beam 14 with significant gaps between them even if they were touching on the spiral part of the track 6, so that the illumination of the leading end of the screw 10 is not interfered with by the presence of other screws on the section 7.

The phototransistor 4 detects light from the beam 14 which is returned from the screws 10 by scattering and reflection, and by appropriately positioning the phototransistor 4 it is readily possible to arrange that the variations in intensity of the detected light resulting from the passage of a particular screw 10 will differ significantly according to which of the two possible orientations applies for that screw, primarily as a result of the difference in shape between the two ends of the screw.For this purpose, it has been found that a particularly suitable arrangement is to dispose the phototransistor 4 at about the same level as, and 1 - 3 cm from, the point at which the leading end of a screw 10 will encounterthe beam 14, with the phototransistor 4 facing that end in a direction inclined at an angle of about 30 to the length of the section 7. Typical results obtainable with such an arrangement are illustrated in Figure 3, in which the output of a detector circuit incorporating the phototransistor 4 is plotted against time, the line A representing a background level corresponding to light scattered from the beam 14 by the track 6 in the absence of any screws 10, and the signals B and C corresponding to the passage of screws respectively having the slotted end leading and trailing.It will be seen that the signals B and C can readily be differentiated simply on the basis of amplitude.

To utilise such signals, there is provided an electrical circuit which is diagrammatically illustrated in Figure 4. In describing the circuit, it will be assumed for the sake of definiteness that the chosen orientation for those of the screws 10 which are to be permitted to reach the outlet of the feeder 1 is that with the slotted end leading, but it would of course be readily possible to arrange for the converse case if desired. Thus, the phototransistor 4 is incorporated in a conventional detector circuit 15 whose output is applied to a first input of a comparator 16, to the second input of which is applied a preset voltage derived from a constant voltage source 17.

The comparator 16 is operative to generate an output signal if, and only if, the voltage applied to the first input exceeds that applied to the second input, and the level of the voltage generated by the source 17 is set (e.g. as indicated by the line D in Figure 3) so that this will occur when a signal of the form C appears at the output of the circuit 15 as a result of the passage of a screw 10 having the slotted end trailing but will not occur when a signal of the form B appears at the output of the circuit 15 as a result of the passage of a screw 10 having the slotted end leading.The output signals generated by the comparator 16 are applied to the valve 13 via a timing circuit 18, the arrangement being such that the valve 13 will be opened to cause an air jet to issue from the orifice 11 whenever a screw 10 having the slotted end trailing reaches the orifice 11, but will otherwise remain closed.

Although the apparatus illustrated in the drawings has been described as specifically adpated for use in the handling of grub screws, it may be regarded as illustrative of a general type of apparatus which can be utilised in a similar way in the handling of various types of small mechanical component (not necessarily of generally cylindrical form). For use with a given type of component, it will of course normally be desirable to ensure the most favourable conditions for discrimination between different possible orientations of that type of component by virtue of the "signatures" constituted by the forms of the signals derived from the detection system and respectively corresponding to those orientations.This will commonly require the geometrical layout of the optical system to be varied from the specific form described above and illustrated in the drawings, and in some cases it may be appropriate to incorporate additional components in the optical system; for example lenses may be included to vary the shape of the illuminating beam and/or modify the field of view of the detection system, and it may be desirable to provide discrimination against the effects of ambient light by including in the detection system a filter having a narrow transmission bandwidth matched to the wavelength of the laser. Key features of the "signatures" are of course likely to depend on aspects of the shape of the relevant type of component which will give rise to differences in the intensity of light scattered and/or reflected in a given direction from a component for different attitudes of presentation to the light beam. It will usually be possible to optimise the differences by appropriate choice, after simple trial, of factors such as the direction of incidence and shape of the illuminating beam, and the viewing direction and field of view of the detection system.

For some types of component there will of course be more than two stable orientations which a component can assume in the feeder, but in such cases it will usually be found possible to arrange the optical system so that a given one of these orientations can readily be differentiated from all the others simply by virtue of amplitude differences in respect of the relevant "signatures". It will then normally be possible to utilise simple signal-processing techniques, such as are involved in the circuit illustrated in Figure 4, in order to control a system for rejecting or re-orientating those components which do not have the given orientation. In some cases, however, it may be necessary to utilise more sophisticated signal-processing techniques, involving for example the analysis of temporal features of the relevant "signatures".

Having regard to the considerations discussed above, it will be appreciated that it should be possible to provide an apparatus similar to that illustrated in the drawings which, by incorporating provision for adjustment of appropriate parameters of the optical system and the electrical circuit, is adaptable for use with a variety of types of component.

Claims (4)

1. A method of handling a series of identical mechanical components, comprising feeding the components sequentially towards a delivery point in such a manner that each component can assume any one of a small number of different stable orientations, subjecting each component before it reaches the delivery point to an optical test in which the component is temporarily illuminated by a beam of light as a result of relative movement occurring between the component and the beam and in which an output is derived from a photoelectric detection system responsive to light from the beam which is scattered and/or reflected by the component, the arrangement being such that the form of said output will differ significantly according to whether or not the tested component has a given one of said orientations, and so treating the components in accordance with the results of the tests that all those components which arrive at the delivery point have said given one of said orientations.

2. A method according to Claim 1, in which the feeding of the components is effected by means of a vibratory bowl feeder whose operation causes said relative movement to occur.

3. An apparatus for use in handling mechanical components, comprising a vibratory bowl feeder, means for projecting a beam of light so as to illuminate components traversing a given portion of the track of the feeder as a result of the operation of the feeder, a photoelectric detection system responsive to light from the beam which is scattered and/or reflected by such components, and means for utilising signals derived from said detection system to cause the removal from said track of any component of a given type which is orientated other than in a given manner while traversing said given portion of the track.

4. An apparatus for use in handling mechanical components, substantially as hereinbefore described with reference to the accompanying drawings.