GB2134090A - Feeder - Google Patents

Abstract

In order to feed diamonds 10 in succession with increasing gaps between the diamonds, a horizontal feed member 32 having a groove is oscillated both up and down and in a direction parallel to its discharge end portion 34. The receiving end portion 33 of the feed member 32 is curved through about 60 DEG . As the diamonds 10 progress along the groove, the amplitude of the horizontal component of oscillation increases whilst the vertical oscillation remains the same. There are suspension springs 36 arranged so that the diamonds 10 are lifted upwards and forwards and then jump as the feed member 32 is returned to its initial position. In this way, the diamonds 10 progress along the feed member, gradually opening up along the curved portion 33. In a development of the invention, a counterbalancing arrangement can be provided by fixing the power source or electromagnet 38 to the middle of the springs 36 and having a counterweight on the other side of the electromagnet 38 to the feed member 32 with the effective mass or effective moment of inertia equal to that of the feed member 32. <IMAGE>

Description

SPECIFICATION Feeder Background of the invention The present invention particularly relates to a feeder for feeding gemstones, e.g. diamonds, but it can be more generally applicable to any discrete objects. It is important for some operations, in particular where a high through-put is desired, that there should be no lengthy gaps in the feed.

A primary feeder is a device which separates goods (discrete objects) from bulk and provides a feed of the objects, whether continuous or single.

A single feed device may be connected downstream of the feeder to separate a continuous feed of objects into a feed of objects separated from one another, though in most single feed devices it is accepted that occasionally a multiple feed may occur. The single feed may be required for instance for automatic weighing, when it is important not to weigh two of the objects together.

The invention The present invention provides feeders as set forth in Claim 1, 14 or 18 and methods as set forth in Claim 20 or 21. The remaining Claims set forth optional features of the invention.

Even though there may be a device for supplying the objects in succession to the feeder, the feeder of Claim 1 can be called a primary feeder, the objects will tend to separate on the groove into groups or trains, all in contact, the leading object holding the others back. However, the feeder can be operated so that the objects then separate out and usually it is desirable to feed the objects singly and with increasing separation as they move along the groove. Nonetheless, it may in some circumstances be satsifactory even if no gaps are formed, provided the movement is slow and the objects can be released from the end of the groove one by one.

The feeder of Claim 1 can avoid feeding "doubles" whilst however ensuring that the gaps between the objects are relatively small with reasonable uniformity. Nonetheless, the feeder need not be very high, e.g. lower than a bowl feeder. Furthermore, the number of objects on the feeder need not be very great so that the feeder can be quickly emptied. For instance, one embodiment of the feeder can be emptied in one to two seconds after stopping delivery. A further consequence of this is that the total mass of objects carried by the feeder need not be very great so that there is not a great change in mass between "fully loaded" and "unloaded", making it easier to balance the feeder.

As the objects are relatively spread out along the groove, there is good access to the objects.

Furthermore, there is little churning so that delicate objects are not damaged and objects that are subject to contamination are not greatly contaminated.

If the groove has a plurality of turns, there can be a considerable length of track in a relatively small zone.

It is not essential that the groove should be curved-thus it would be possible to arrange a rectilinear groove with oscillating means for oscillating the feed member about an axis on a line passing through the delivery end of the groove and at right angles to the groove.

However, the groove preferably has at least a curved portion.

The feeder of Claim 1 is relatively easy to control. Thus motion can be halted, or the velocity can be regulated by changing the amplitude of oscillation.

The feeder of Claim 14 has more general appiication. The feeder may be a primary feeder or may just be a delivery path. The feeder reduces the amount of vibration which can be transmitted to other apparatus, such as a weighing machine, and also reduces the amount of noise.

Description of preferred embodiments The invention will be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a vertical section, along the line I-I in Figure 2, through a first primary feeder of the invention; Figure 2 is an isometric projection of the feed member or feeder disc in Figure 1; Figure 3 is a vertical section, looking in a radial direction, through the mounting of a suspension spring of the feeder of Figure 1; and Figure 4 is an isometric projection of a second primary feeder of the invention.

Figures 1 to 3 The primary feeder 1 has a generally horizontal feeder member or disc 2 with a spiral groove or track. The disc 2 is carried by three or four rod or ieaf suspension springs 3 which are equally spaced about the axis of the disc 1 and skewed with respect to the axis, for instance at an angle of about 200. The centre parts of the springs 3 are supported on a fixed mount 4 in any suitable manner, shown as being bonded to rubber sleeves 5. The other ends of the springs 3 are connected to a counterweight 6.

The feeder disc 2 carries an armature 7, and there is a like armature 8 on the counterweight 6.

Between the armatures 7 and 8 and horizontally between the springs 3, there is an electromagnet 9 which acts as a power source or prime mover for vibrating the feeder disc 2 and the counterweight 6, in synchronism in opposite directions. The mass and moment of inertia of the counterweight 6 and parts moving therewith are adjusted so as to be equal to the mass and moment of inertia of the feeder disc 2 and the parts moving therewith (this can also take account of the load of objects 10 on the feeder disc 2, if desircd), so that the effective masses and effective moments of inertia are substantially equal. In this way, harmful vibrations are reduced, as is noise. It will be noted that this principle could also be applied to other feeders, for instance linear feeders.It is helpful if the mount 4 is heavy, particularly in relation to the masses of the feeder disc 2 and associated parts and of the counterweight 6 and associated parts.

The gaps between the armatures 7, 8 and the electromagnet 9 is lightly larger than the maximum vertical amplitude. As the armature 7 is vibrated up and down, it also oscillates about its axis due to the restraint of the springs 3. As the armatures 7, 8 are drawn towards the electromagnet 9, the springs 3 assume a slight S configuration, acting as double cantilever springs.

An impetus is applied at right angles to the spring 3, i.e. upwards and forwards, and, if there is no slip, the objects 10 will initiate a small trajectory or jump in this direction, thereby progressing around the groove in the feeder disc 2. The direction can thus be controlled so that it is possible to supply the objects 10 to the centre of the feeder disc 2 and remove from the edge, or vice versa. The velocity of movement of the objects 10 around the groove depends upon the amplitude of movement of the armature 7. However, as the amplitude of movement of the feeder disc 2 in the horizontal plane is greater at greater radii, the objects 10 tend to move faster on the outer turns of the groove.It is also possible to arrange the spiral such that the angle between the tangent to the spiral and the tangent to a circle at the point in question decreases as you move outward along the spiral; as the horizontal movement of the feeder disc is strictly rotary, the resolved movement in the direction of the groove is proportionally greater at greater radii.

Nonetheless, the vertical oscillation remains constant for all parts of the groove. Thus supplying the objects 10 to the centre tends to open them up whilst supplying them to the edge tends to close them up-closing them up may be beneficial in some circumstances.

The actual amplitude chosen will depend upon the size of the objects 10. However, if the objects 10 are gemstones, small hops of about 0.1 mm are found desirable, and a maximum acceleration of the feeder disc 2 of 3 g is suitable. The frequency chosen depends upon the size of the objects 10 and also on the shape of the groove, the coefficient of friction, and the shapes, resonant frequencies and specific gravities of the objects 10. However, a frequency of 84 Hz has been found suitable for gemstones and seems to move stones of different shapes and sizes at substantially the same speed. Varying the frequency is also found to vary the way in which the objects 10 separate as they pass along the groove.

The groove itself can be in the form of an Archimedian spiral (razz where r is the radius, a is the constant and 0 is the angle) or a logarithmic spiral (r=aem, where m is another constant) or an involute; it appears that the objects 10 upon up more quickly with a logarithmic spiral and move faster.

The cross-sectional shape of the groove can be of any suitable form. As shown, it is preferably formed by two surfaces, both of which are inclined to the horizontal, one being inclined at a small angle, the other inclined at a large acute angle. The objects 10 lie on the low angle surface, which may be about 200 to the horizontal, just ensuring that the objects 10 also lie against the large angle surface. The angle of the large angle surface should be such that the stones 10 do not fly out, an angle of 800 to the horizontal being suitable. An angle between the two surfaces of 800, i.e. slightly acute, is found preferable, which gives good retention without any jamming. If the primary feeder is for separating gemstones for weighing, the size range could be from 4 mm up to 16 mm for low speed weighing or 1 mm up to 4 mm for high speed weighing.The depth of the groove may be 7 to 8 mm for these ranges, it being important that the top of the ridge should be above the centre of mass of the largest objects 10 in the range.

The choice of the pitch of the spiral depend upon the maximum dimension of the objects 10.

The pitch should be greater than the maximum dimension of the objects 10. For the high speed weighing range for gemstones (see above), the pitch may be 11 mm. The groove may be very short, for instance as short as one sixth of a turn (see Figure 4), but can be considerably longer, extending to a number of turns. A multi-turn groove is shown, and the diameter of the feeder disc 2 can be about 16 cm, the diameter of the centre being about 4 cm.

The groove may be strictly horizontal, or may drop slightly, or may have a slope which varies, for instance being steeper at the beginning, in the middie or the end; if desired, the groove can have steps (see Figure 4). The preferred arrangement is to have a slight, uniform drop throughout, say an inclination of 5 .

The feeder disc 2 can be made of any suitable material, and can be machined or pressed. A light section is shown, which requires less power and causes less noise. The material of the feeder disc 2 is not considered to be very critical, though it is preferred to have a fairly bouncy material.

Possibilities are steel or aluminium, possibly plastics-coated, particularly in the case of aluminium and gemstones, so as to avoid dirtying the gemstones with the aluminium. The top surface of the feeder disc 2 is preferably polished.

In the centre of the feeder disc 2, at the receiving end of the spiral groove, there is a central cone 11 to which the objects 10 are supplied by any suitable means, providing the means do not cause any damage to the objects 10; it may be desirable to include a hopper device, so as to avoid any heaping up on the central cone 11, but this is not essential. Thus, the means could be a hopper with a circular outlet, a low angle (say 3 to 50) ramp, for instance vibrated with an electromagnetic clapper and for instance with an electromagnetically-control flap, parallel plates between which the objects 10 pass, an adjustable wire over which the objects 10 fall or a tipping bowl.The means shown is purely by way of example, and is in the form of a compartmented wheel 1 2 which rotates in the direction indicated by the arrow at the bottom of a ramp 13.

At the discharge end of the spiral groove, there is a long, widening out arcuate (spiral) slot 14 so that "smalls" (undersized objects 10) drop down before they reach the delivery point of the primary feeder. The "smalls" can be passed along a reject path.

A linear fibre optic array 1 5 is associated with the spiral groove, about half way along the groove. The fibre optic array 1 5 is illuminated uniformly by any suitable arrangement, for instance an array of light emitting diodes. The arrangement shown includes an infra-red source 1 6 and a collimating lens 17. The fibre optic array 1 5 acts as a density monitor and gives an analogue signal for the supply means control, e.g.

for controlling the speed of rotation of the wheel 12. The position of the fibre optic array 1 5 is such that the objects 10 should be separated before they reach the array 15, the array 1 5 detecting the gaps between individual objects 10 or between trains of objects 10.

It will be noted that the density monitor does not ensure uniform spacing, but improves conditions as the next group of objects 10 passes along the groove. In order to give accurate control of the feed from the primary feeder, there is an emitter 1 8 and a sensor 19 of any suitable type right at the end of the groove, connected to an on/off control of the electromagnet 9. As indicated schematically in Figure 3, the sensor 19 is connected to a control device 20 which is fed by a signal from a succeeding piece of apparatus 21, such as a magazine.If the apparatus 21 feeds a "not ready" signal and the sensor 1 9 feeds an "object present" signal, the control device 20 switches off the electromagnet 9 and the object 10 waits at the end of the groove until the apparatus 21 sends a "ready" signal and the control device 20 switches on the electromagnet 9.

Figure 4 The primary feeder 31 has a generally horizontal feed member 32. In this case, the groove or track has a curved portion 33 curving through a substantial angle of preferably 600, but possibly up to 900. The curve may be a radial arc or for instance an involute. The groove also has a rectilinear portion 34 of short length, though this is not considered essential.

The feed member 32 is carried by an armature 35 which in turn is carried by two leaf suspension springs 36. The springs 36 are fixed to a base 37 which also mounts an electromagnet 38 which acts as a power source or prime mover. As the armature 35 is vibrated up and down, it executes a short arcuate (a parallel motion) path with a horizontal component parallel to the rectilinear groove portion 34, as indicated by the doubleheaded arrow. Thus the feed member 32 will rise when the horizontal component is in the feed direction and will fall when the horizontal component is in the reverse direction, so that the objects 10 will progress in small jumps.

The counterbalancing arrangement described above can be applied to this embodiment, as can the linear fibre optic array 1 5 and/or the widening-out slot 14 (though here it would be straight) and/or the emitter 18.

As above, any suitable means can be used for feeding to the receiving end of the feed member 32, here illustrated as a simple hopper 39.

As in the case of Figures 1 to 3, the groove may be strictly horizontal or can have an e.g.

varying slope. In the case shown, the bottom of the feed member 32 is strictly horizontal but the groove itself has small steps 40 and the runs between the steps are slightly inclined downwards in the feed direction, for instance at 50.

Claims (21)

Claims

1. A feeder for feeding discrete objects in succession, comprising: a generally horizontal feed member having a groove therein, along which the objects will travel from a receiving end to a discharge end; and means for oscillating the feed member so as to provide at least a component of horizontal oscillatory movement along the groove, the direction of oscillation and the shape of the groove being such that in one portion of the groove, said component has a smaller amplitude than in another portion of the groove so that the objects will travel at different speeds in said two portions.

2. The feeder of Claim 1, wherein said one portion is nearer the receiving end than said other portion.

3. The feeder of Claim 1 or 2, wherein, at least for the major part of the length of the groove, there is a continuous change in the amplitude of said component.

4. The feeder of any one of the preceding Claims, wherein said oscillating means also provide a vertical oscillation, the feed member rising when said component is in the feed direction and falling when said component is in the reverse direction, so that the objects progress by small jumps.

5. The feeder of any one of the preceding Claims, wherein the groove has at least a major part of generally spiral shape and the oscillating means is for oscillating the feed member about a substantially vertical axis.

6. The feeder of Claim 5, wherein said axis is substantially the axis of the spiral.

7. The feeder of Claim 5 or 6, wherein the groove is curved through at least 3600.

8. The feeder of any one of Claims 1 to 4, wherein the groove is curved through a substantial angle of 900 or less, the oscillating means being for oscillating the feed member substantially parallel to the discharge end of the groove.

9. The feeder of any one of Claims 1 to 4, wherein the groove has at least a portion of curved shape.

10. The feeder of any one of Claims 5 to 9, wherein the spiral or curved shape is an Archimedian spiral.

11. The feeder of any one of claims 5 to 9, wherein the spiral or curved shape is a logarithmic spiral.

12. The feeder of any one of Claims 5 to 9, wherein the spiral or curved shape is an involute.

13. The feeder of Claim 8 or 9, wherein the curve is a circular arc.

14. A feeder for feeding objects, comprising a feed member having a track and a power source for vibrating the feed member to feed the objects along the track, the feed member being on one side of the power source and a counterweight being on the other side of the power source, the arrangement being such that the feed member and counterweight move in synchronism in opposite directions during vibration, the effective mass of the counterweight being substantially equal to that of the feed member if the vibration has a linear component, and/or the effective moment of inertia of the counterweight being substantially equal to that of the feed member if the vibration has a rotary component.

1 5. The feeder of Claim 14, wherein the feed member is connected to the counterweight by at least two spring members with the power source between the spring members, the centre parts of the spring members being supported and the respective ends being connected to the feed member and to the counterweight.

16. The feeder of Claim 15, wherein there are at least three of the spring members, equally spaced around the axis of the power source and skewed with respect to the axis of the power source, thereby providing a rotary oscillatory motion.

17. The feeder of any one of Claims 14 to 16, and also being in accordance with any one of Claims 1 to 13.

1 8. A feeder, substantially as herein described with reference to, and as shown in, Figures 1 to 3 or Figure 4 of the accompanying drawings.

19. The feeder of any one of the preceding Claims, and associated with a magazine for feeding discrete objects.

20. A method of feeding discrete objects, comprising using the feeder of any one of the preceding Claims.

21. A method of feeding discrete objects, substantially as herein described with reference to Figures 1 to 3 or Figure 4 of the accompanying drawings.