GB2281604A

GB2281604A - Vibrator apparatus

Info

Publication number: GB2281604A
Application number: GB9417229A
Authority: GB
Inventors: Arthur Hamer; Beverley Hugh Pardoe
Original assignee: British Nuclear Fuels PLC
Current assignee: Sellafield Ltd
Priority date: 1993-09-03
Filing date: 1994-08-26
Publication date: 1995-03-08
Anticipated expiration: 2014-08-26
Also published as: GB9417229D0; GB2281604B

Abstract

A vibrator apparatus for vibrating an elongate beam 2 includes a reaction member 5 connected by resilient mounting assemblies to the beam. The source of the vibrations is preferably an electromagnetic device 16 located between the beam and the reaction member. At each end of the beam is a weight 13 which is positioned below the neutral axis of the vibrator axis and is adjustable in a direction normal to the length of the beam so as to modify the vibrational movement of the beam. On the upper surface of the beam a conveying surface for objects 33, for example, nuclear fuel pellets, is formed by a multiplicity of inclined fibres packed in a backing. In operation, vibration of the beam causes an object supported on the fibres to move along the beam in the direction of fibre inclination. <IMAGE>

Description

Vibrator Apparatus This invention relates to vibrator apparatus. More particularly, the invention relates to a vibrator apparatus for imparting vibrations to a conveyor of the type in which objects are transported on a vibrating conveyor surface comprising a fibrous pile surface.

An example of a conveyor of this type is disclosed in Applicant's GB Patent No. 2223998B. In the conveyors described in this patent objects to be transported are supported on a conveying surface having a multiplicity of extremely thin, short flexible fibres packed as an ultra high density pile in a backing. The fibres are inclined with respect to the backing so that when the conveying surface is vibrated the objects are transferred in the direction of fibre inclination.

It is known to vibrate the conveying surface by means of an eletromagnetic device and such an arrangement is shown in GB patent specification No. 2241685. This arrangement includes an electromagnetic induction coil which co-operates with an armature fixed to a support element or beam on the upper surface of which the pile conveying surface is attached. The support element is supported by two or more resilient plates arranged in a cantilever manner. In use, the electromagnetic device is energised thereby causing the support element, and hence the conveying surface, to vibrate. Objects placed on the vibrating conveying surface are moved therealong in the direction of inclination of the fibres forming the conveying surface.

A problem encountered when using this type of vibrator apparatus is that the support element tends to exhibit a rocking motion, particularly in a vertical plane in line with the beam. This rocking motion is particularly pronounced at the ends of support elements that are relatively short in length. As a result, the velocity of the objects being conveyed is adversely affected.

It is an object of this invention to provide a vibrator apparatus which overcomes, or at least minimises, the aforementioned problem.

According to the present invention there is provided a vibrator apparatus, said apparatus comprising a beam of elongate form, a reaction member, resilient means for mounting said beam on the reaction member, and vibration means adapted to impart vibrations to said beam, wherein a balance weight is suspended from the beam, the position of the balance weight being adjustable in a direction normal to the longitudinal direction of the beam so as to modify the vibrational movement of the beam.

Preferably the balance weight is located below the neutral axis of the vibrator apparatus.

Desirably, there is an adjustable balance weight suspended from each end of the beam. Each balance weight may be mounted for adjustment along a vertical rod depending from the beam.

In a preferred embodiment, the means for imparting vibrations to the beam comprises an electromagnetic device.

The reaction member may be of elongate form extending parallel to the beam, with the electromagnetic device being located between the beam and the reaction member.

The electromagnetic device preferably comprises an electromagnetic induction coil supported by the reaction member and an armature supported by the beam.

Preferably the resilient means for connecting said beam to said reaction member includes a resilient strip having a length which extends transversely with respect to the longitudinal direction of the beam and having a width extending in a plane normal to said longitudinal direction, the arrangement being such that, upon activation of the vibration means, the resilient strip moves in a directicn parallel to said longitudinal direction.

Conveniently, the resilient strip is connected at each of its ends to the beam and is connected at a region intermediate its two ends to the reaction member.

The resilient means may comprise two resilient mounting assemblies, one of said assemblies being located on one side of the vibration means and adjacent to one end of the reaction member and the other of said assemblies being located on the other side of the vibration means and adjacent to the other end of the reaction member.

The balance weights are preferably adjustable in a direction normal to the longitudinal direction of the beam, so as to cause the neutral axis of the vibrator apparatus to pass through the centres of the resilient strips.

Preferably the vibrator apparatus is supported on vibration isolating means which may comprise a plurality of coil springs of a generally frusto-conical form, the smallest uppermost coils of said springs being located under the reaction member and the largest lowermost coils resting on a baseplate.

The vibrator apparatus preferably includes a cushion element for supporting an object thereon, the cushion element being attached to an upper surface of the beam and comprising a multiplicity of fibres packed in a backing at an inclined orientation with respect to the backing, whereby upon activation of said vibration means vibrations are imparted to the beam so as to move the object along the beam in the direction of fibre inclination.

The cushion element may be an element as described and claimed in Applicant's prior patent specifications GB2223998 or GB2241685.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows a side elevation of a vibrator apparatus; Figure 2 shows an end elevation of the vibrator apparatus with a balance weight removed for clarity, and Figure 3 is a scrap plan view of a spring mounting on the line III-III of Figure 1.

Referring now to the drawings, a vibrator apparatus is shown and comprises an elongate, box-sectioned beam 2 which is resiliently supported by two spring mountings 3, 4, each arranged adjacent to an end of a reaction member 5. The reaction member 5 is in the form of an inverted channel section and is supported on a base plate 6 by means of four coil springs 7, which serve as antivibration mountings, arranged beneath the bottom corners of the reaction member 5. Each spring 7 is generally of frusto-conical form with its smallest uppermost coil fixedly attached to the underside of an L-shaped bracket 8, which forms part of the reaction member 5. The largest lowermost coils of the springs 7 rest in circular recesses 9 formed in the upper surface of the base plate 6.Thus, the vibrator apparatus 1 is free standing and can be readily removed from the base plate 6 and replaced by a similar unit if the need arises.

Extending along each of the side surfaces of the beam 2 at the upper region thereof are two elongate side plates 10, 11, the upper edges of which project above the upper surface of the beam 2. Between the side plates 10, 11 the upper surface of the beam 2 is covered with a cushion element 12 comprising a multiplicity of fibres. The fibres may consist of extremely fine synthetic polymer fibres, for example nylon 66, set at one end in a glass fibre reinforced vinyl base layer. Preferably, the fibres are packed to form an ultra high density pile in the base layer at an angle of inclination with respect to the base layer of between 700 and 80 . The packing density of the fibres is of the order of 80 x 106 fibres per square metre, and each fibre is between 43 to 45 microns thick and projects up to 2.5 mm above the base layer.The cushion element 12 is secured to the beam 2 by a suitable attachment, for example an adhesive, or by use of a magnetic strip attached to the beam 2 and having an adhesive backing to which the cushion element 12 can be attached.

As seen in Figure 1, each end of the beam 2 overhangs an end of the reaction member 5. Suspended from each overhanging end of the beam 2 is a balance weight 13.

Each balance weight 13 is mounted on a screw-threaded rod 14 passing centrally through the weight and fixed to the beam 2 by nuts 15. Each balance weight 13 is located on the rod 14 by means of nuts 15 above and below the weight.

The position of each balance weight 13 can be adjusted along the length of the rod 14 by loosening the nuts 15, moving the balance weight and nuts to the desired position, and then re-tightening nuts.

An electromagnetic device 16, which, in use, operates to impart vibrations to the beam 2, is arranged between the beam 2 and the reaction member 5 at a position substantially mid-way between the two spring mountings 3, 4. The electromagnetic device 16 comprises an armature 17 which is fixed to the vertical arm 18 of an L-shaped bracket 19. The other arm 20 of the bracket 19 is connected to the underside surface of the beam 2. An electromagnetic induction coil 21 is mounted on the upper surface of the reaction member 5 so as to define a required air gap, when in a de-energised state of the coil, with the armature 17.

Each spring mounting 3, 4, see Figure 3, comprises two outer L-shaped brackets 22 arranged with their longer arms 23, 24 fixed to the upper surface of the reaction member 5. Extending between the two brackets 22 and arranged transversely with respect to the length of the beam 2 is a resilient spring strip 25 which lies in a plane normal to the beam length. Each end of the spring strip 25 is attached to a respective one of the vertical shorter arms 26, 27 of tne brackets 22 by means of screws 28 and clamping plates 29. The spring strip 25 is connected to the beam 2 by a central L-shaped bracket 30.

The bracket 30 has a longer arm 31 fixed to the underside of the beam 2 and a shorter, vertically depending arm 32 to which a central portion of the spring strip 25 is attached by two pairs of screws 28 and clamping plates 29.

To function satisfactorily the balance weights 13 are positioned such that the neutral axis X-X of the vibrator apparatus 1, including the balance weights 13, passes through the horizontal centre lines of the spring strips 25. The length of each spring strip 25 in a direction transverse to the longitudinal direction of the beam 2 is greater than the width of the strip along a plane normal to the longitudinal direction. Preferably, the length of each resilient strip 25 is of the order of six times greater than the width.

In use of the vibrator apparatus 1, the electromagnetic device 16 is energised by an electrical supply of half-wave alternating current. This current causes the armature 17 to be attracted to the induction coil 21 against the tension of the spring strips 25 during the positive half cycle of the electric current, with a consequent reduction in the air gap between the induction coil 21 and armature 17. During the negative half cycle when no current exists, since it has been half-wave rectified, the armature 17 returns under tension in the spring strips 25 to a point where the air gap has increased from that existing at the de-energised position.

The movement of the armature 17 is repeated during the next half cycles of the electric current and causes vibration of the beam 2. Because of the inclination of the fibres in the cushion element 12 an object 33, for example, a nuclear fuel pellet, is transferred along the cushion element 12 during the positive half-cycle of the electric current. During the return motion of the beam 2 the fibres of the cushion element slide under the object 33. Suitably, the frequency of the electromagnetic device 16 may be between 50 and 100 Hz with, for example, a vertical peak-to-trough displacement of 0.Smm.

The vibrational characteristics of the beam 2 can be modified and finely tuned by appropriate adjustment of the balance weights 13 along their respective rods 14 in a direction normal to the longitudinal direction of the beam 2. In particular, adjustment of the balance weights 13 can be effected to eliminate any tendency of the beam 2 to exhibit a rocking motion along its length. The magnitude of the rocking motion is influenced by the material forces of the vibrator apparatus mass above the neutral axis and by the frequency of operation. Since the balance weights 13 are located below the neutral axis the tendency to rock can be eliminated by individual adjustment of the weights so that the neutral axis X-X passes through the centres of the spring strips 25, thereby countering both the coupling effect of the vibrating beam 2 and the asymmetry of the mass distribution.

It has also been found that the tendency of the beam 2 to rock in directions both longitudinally and transversely of the beam is minimised by arranging the mountings 3, 4 so that the spring strips 25 extend transversely with respect to the length of the beam 2. This provides the advantage that the movement of the spring strips 25 is in a direction parallel to the length of the beam 2 and, consequently, in a direction parallel to the movement of the object 33 being conveyed. In addition, the mountings 3, 4 serve to provide some degree of damping. By removing or reducing the tendency of the beam to rock, objects supported on the cushion element 12 are transported thereon more efficiently.

The cone type coil springs 7 on which the vibrator apparatus 1 stands effectively isolate the apparatus so that surrounding equipment is not adversely affected by the vibrations.

The aforementioned features of the invention have enabled the vibrator apparatus to be of lightweight design. An advantage of having a lightweight construction is that lower reaction forces are involved during operation. This enables a low reaction mass ratio between the reaction member 5 and the beam 2 to be achieved. For example, the mass of the reaction member 5 can be of the order of 5 times the mass of the beam 2. Satisfactory operation can be achieved with a reaction beam 5 having a mass which is of the order of 3 times the mass of the beam 2.

Other advantages provided by the lightweight construction are that it is easier to install and handle and floor loading is reduced.

The vibrator apparatus may form a modular unit in a series of similar units so that the cushion elements provide a continuous length of conveying surface. If, for any reason, a unit malfunctions it is a relatively simple matter to lift the unit from the base plate 6 and replace it by a fresh one.

The soft handling characteristics provided by the cushion elements have particular advantage for transporting a wide variety of light objects, especially objects with fragile surfaces. Thus the vibrator apparatus is particularly suitable for use in transferring nuclear fuel pellets where damage to the sides or corners of the pellets must be avoided or at least minimised.

Claims

1. A vibrator apparatus comprising a beam of elongate form, a reaction member, resilient means for mounting said beam on the reaction member, and vibration means adapted to impart vibrations to said beam, wherein a balance weight is suspended from the beam, the position of the balance weight being adjustable in a direction normal to the longitudinal direction of the beam so as to modify the vibrational movement of the beam.

2. A vibrator apparatus according to Claim 1, wherein the balance weight is located below the neutral axis of the vibrator apparatus.

3. A vibrator apparatus according to Claim 1 or Claim 2, wherein an adjustable balance weight is suspended from each end of the beam.

4. A vibrator apparatus according to Claim 3, wherein each balance weight is mounted for adjustment along a vertical rod depending from the beam.

5. A vibrator apparatus according to any one of the preceding Claims, wherein the vibrator means comprises an electromagnetic device.

6. A vibrator apparatus according to Claim 4, wherein the reaction member is of elongate form extending parallel to the beam, the electromagnetic device being arranged between the beam and the reaction member.

7. A vibrator apparatus according to Claim 5, wherein the electromagnetic device comprises an electromagnetic induction coil and an armature, and wherein the induction coil is supported by the reaction member and the armature is supported by the beam.

8. A vibrator apparatus according to any one of the preceding Claims, wherein the resilient means for connecting the beam to the reaction member includes a resilient strip having a length which extends transversely with respect to the longitudinal direction of the beam and having a width which extends in a plane normal to said longitudinal direction, the arrangement being such that, upon activation of the vibration means, the spring moves in a direction parallel to said longitudinal direction.

9. A vibrator apparatus according to Claim 7, wherein the resilient strip is connected at each of its ends to the beam and is connected at a region intermediate its two ends to the reaction member.

10. A vibrator apparatus according to Claim 8, wherein the resilient means comprises two resilient mounting assemblies, one of said assemblies being located on one side of the vibration means and adjacent to one end of the reaction member and the other of said assemblies being located on the other side of the vibration means and adjacent to the other end of the reaction member.

11. A vibrator apparatus according to any one of the Claims 7 to 9, wherein the balance weights are adjustable in said direction normal to the longitudinal direction of the beam, so as to cause the neutral axis to pass through the centres of the resilient strips.

12. A vibrator apparatus according to any one of the preceding Claims, wherein the apparatus is supported on vibration isolating means, said vibration isolating means comprising a plurality of coil springs of a generally frusto-conical form, the smaller uppermost coils of said springs being located under the reaction member and the largest lowermost coils being arranged to rest on a baseplate.

13. A vibrator apparatus according to any one of the preceding Claims, wherein the apparatus includes a cushion element for supporting an object thereon, the cushion element being attached to an upper surface of the beam and comprising a multiplicity of fibres packed in backing at an inclined orientation with respect to the backing, whereby upon activation of the vibrator means vibrations are imparted to the beam so as to move the object along the beam in the direction of fibre inclinat-lon.

14. A vibrator apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.