GB2167171A - Weighted drums - Google Patents

Abstract

In a method of manufacturing a drum suitable for use in a spin-drier, the drum is made by injection moulding from two drum-halves 11 and 12 subsequently joined together. In the moulding of drum-half 11, a channel is formed at one end by a flange 17 and inturned lip 18, which channel is subsequently filled with a relatively dense curable material, such as an epoxy resin loaded with finely-divided stone particles. The mass of the weight required for the drum is predetermined and resin is added to the channel until the total weight of the drum reaches a required value. Preferably the curable material employed is self-levelling. Alternatively a moving nozzle may be used to apply a viscous resin material, and controlled to form an even annular body. <IMAGE>

Description

SPECIFICATION Weighted drums This invention relates to a method of manufacturing a weighted drum, and also to a drum whenever made by the method of this inven ton.

Spin-driers for removing water from wet garments (or of course other fabric piece goods) conventionally have a drum disposed with its axis vertical, which drum is connected directly or indirectly by pulleys and belts to the shaft of an electric motor mounted beneath the drum and able to rotate the drum at a relatively high speed. The bearings supporting the drum are disposed beneath the drum and so it is necessary to provide a balance weight at the upper end of the drum, to ensure that the drum may be spun stably notwithstanding possible uneven loading of wet garments in the drum.

For many years now, spin-drier drums have been made either from stainless steel or other corrosion-resistant metal alloys, or from an enamelled metal. The balance weight in the form of an annulus which is affixed around the outer periphery of the drum adjacent the end thereof which is intended to be uppermost, and though the balance weight may be made from a variety of metals, it is usually manufactured as a zinc alloy diecasting. Such a weight is easy to manufacture, in that no turning is required, but zinc alloys are liable to corrode in the presence of water, especially if some .pa chemicals are present, such as may be encountered with wet washing.

More recently, spin-drier drums have been manufactured from plastics materials, usually by an injection moulding process utilising polypropylene or high density polyethylene. Such drums have been virtual copies of metal drums, but are cheaper to manufacture. The drums have to be weighted in the same manner as the metal drums used previously, and so annular metal weights, again in the form of zinc die-castings, have been used, which rings are attached to the moulded drum, around its outer periphery adjacent the end of the drum intended to be disposed uppermost.

The provision of a metal ring around a plastics drum has not been an entirely satisfactory solution to the problem of weighting the drum. Affixing the ring to the plastics material requires the heat staking of raised pegs through the whole of the ring and these may leave sharp edges on the inner surface of the drum which might snag clothes-it will be appreciated that the inner surface of the drum should be smooth in order to minimise damage to clothing. Also, due to differential thermal expansion rates, the annular weight can become loose on the drum.

In any event, the manufacture of a die-cast zinc alloy annulus is a relatively expensive process, especially when a post-treatment has to be applied in order to prevent corrosion. In addition, the adjustment of the mass of such an annulus is relatively expensive, in that the mould in which the die-casting is made has to be altered, to produce a annulus having a different mass of metal.

In an attempt to reduce the problems associated with the use of a die-cast metal ring of a plastics spin-drier drum, it has been suggested that a moulded plastics material annu us, formed of a relatively high density plastics material, could be used as a direct substitute for the metal weight. This solution however still presents the problems associated with the adjustment of the weight of the ring and also the fixing of the ring to the outer periphery of the drum.

Bearing in mind the problems associated with the known techniques for the manufacture of spin-drier drums, as set out above, it is an aim of this invention to provide a method for manufacturing a weighted drum suitable for use in a spin-drier, which drum is relatively cheap to produce and overcomes the disadvantages discussed above.

According to this invention, there is provided a method of manufacturing a weighted drum, which method comprises the steps of moulding a drum body to include a circular flange element at or adjacent one end of the drum thereby to define an annular channel between the flange element and a portion of the drum wall, supporting the drum with its axis substantially vertical and with said channel disposed such that the opening thereto faces upwardly, adding a pre-determined quantity of a curable material into said channel, and then causing or permitting the curable material to cure.

It will be appreciated that when manufacturing a drum suitable for use for example in a spin-drier in accordance with the method of this invention, no separate annulus for weighting the drum has to be manufactured, which annulus would then have to be affixed to the outer surface of the drum. Thus, not only are the number of operations required in the manufacture of the drum greatly reduced, but so also are the problems associated with fixing the annulus to the drum. The drum thus may offer a smooth inner surface whilst being weighted to the required extent.

It will also be appreciated that the mass of the provided weight easily may be adjusted, to suit the required circumstances of use of the drum. This may be achieved simply by adjusting the quantity of curable material added into the channel, during the manufacture of the drum.

The channel defined by the flange may be formed around the outer surface of the drum, over one end of the drum, or within the drum.

The preferred arrangement is for the flange to be generally L-shaped, and to be inturned so that the channel is within the drum, adjacent the-one end thereof and opening towards the other end of the drum. An alternative is for the channel to be defined by two cylindrical walls upstanding from the major part of the drum, the channel opening axially away from the major part of the drum. An annular lid may for this configuration be provided for the channel.

It is preferred for the added quantity of curable material to be determined on a weight basis. This conveniently may be done by supporting the drum on a suitable weighing machine, and then adding the curable material into the channel until the weighing machine detects an increase in drum weight of the required amount. It will however be appreciated that the added quantity of curable material could be determined on a volume basis, by an appropriate dispensing head for the material arranged to discharge a pre-determined quantity of material into the channel.

The curable material may be any relatively dense material which may be flowed into the channel and which then will cure or set to form a solid, dense mass. Though it would therefore be possible to use a material such as concrete, it is highly preferred to use a polymerisable resin material, which advantageously is loaded with particles of a relatively dense substance. For example, the preferred form of polymerisable resin material used in this invention comprises a mix of an epoxy resin together with finely ground stone material, a hardener being added to the resin immediately before the resin is added into the channel of the drum, so as subsequently to cause the resin material to cure. Such a resin material may have a density in the region of 3.5-4.0 g/cm3.

The viscosity of the curable material employed advantageously is such that it may be added to the channel and then display selflevelling characteristics, before curing has advanced too far. Depending upon the viscosity, the material either could be discharged at a single point in the channel to run therearound, or could be discharged for example from a nozzle which is arranged to move around the length of the channel. The latter arrangement could be employed for example in the case of a relatively "stiff" or viscous resin material.

Depending upon the plastics material from which the drum body is moulded and the resin material used for weighting the drum, it may be advantageous to employ a mechanical fixing for the cured resin material. For example, such a fixing may comprise pins passed through apertures provided in either the outer drum wall or the flange itself, to extend in a radial plane and become embedded in the resin material. Such pins may be in the form of round headed rivets, the shaft of each rivet being appropriately formed to permit the resin material securely to key thereto-for instance by providing apertures in the rivet shank.

As to the drum body itself, this preferably is moulded by an injection moulding process from a plastics material such as polypropelene or high density polyethylene. Conveniently, the drum body is formed in two halves joined to geth about a radial plane. For a spin-drier, the drum should be apertured as appropriate to permit the egress of water during a spinning operation, and the inner surface of the drum should be smooth so as to prevent damage to garments placed within the drum.

The end of the drum remote from the channel defined by the flange should be appropriately formed to permit the mounting of the completed drum on a drive boss secured to an electric motor drive shaft.

This invention extends to a weighted drum suitable for use in a spin-drier, whenever manufactured by a method according to this invention.

In order that this invention may better be understood, it will now be described in greater detail but only by way of example, reference being made to the accompanying drawings in which: Figure 1 is a diagrammatic longitudinal sectional view through a completed spin-drier drum manufactured in accordance with this invention; and Figure 2 is a diagrammatic longitudinal sectional view of an alternative form of drum.

Referring to Fig. 1 of the drawings, there is shown a moulded plastics spin-drier drum 10, formed from two drum parts 11 and 12 joined together about a radial plane 13. Each drum part 11 and 12 is manufactured by an injection moulding technique using polypropelene, and then the two parts are joined together by means of a precision friction welding process. Though not shown in the drawings, the drum parts 11 and 12 are suitably apertured to permit the egress of water when the drum is in use in a spin-drier. Also, the end 14 of drum part 12 should be suitably configured to permit the attachment thereof to a drive boss, appropriately mounted on a motor drive shaft. Thus, the end 14 may be recessed so as to receive therewithin the drive boss, and may be provided with fixing holes, to permit bolts to be passed therethrough.

End 15 of drum part 11 is open to define the loading mouth for the drum, and when the drum is in use, this end 15 will be uppermost, with the axis of the drum substantially vertical.

The drum part 11 is moulded so as to have an inturned flange 16, this flange comprising a first flange section 17 being directed generally radially inwardly of the outer wall of the drum, and a second flange section 18 being directed generally back towards end 14 of the drum.

In this way, the first and second flange sections 17 and 18 together with the adjacent wall portion 19 of the drum body define a channel 20 around the inner end 15 of the drum.

A number-and typically four-holes 21 are drilled through the wall portion 19 of drum part 11, opposed to the second flange section 18. Split rivets 22 of a diameter not less than that of the drilled holes are pressed through the holes, the length of each rivet 22 being such that the rivet engages the second flange section 18 and then partially collapses as the rivet is driven fully home to have its head bearing agairist wall portion 19 of the drum.

The rivets may for example be bifurcated, to permit such a collapse.

Once the two drum parts 11 and 12 as described above have been moulded and those two parts friction-welded together to define the overall drum 10, the drum is placed on a weighing machine with the axis of the drum substantially vertical and end 15 of the drum lowermost. A high density loaded resin material, premixed with a hardener, is then run into the channel 20 defined around the inside of end 15 of the drum, by means of a suitable nozzle which is arranged to be moved circularly around the length of channel 20, as the resin material is discharged therefrom.The discharge of material from the nozzle is controlled by the weighing machine: when the drum weight has increased due to the addition of the loaded resin material into the channel by the required amount, the flow of resin material from the nozzle is cut off, such that the amount of resin material in the channel 20 has a precisely controlled mass.

The resin material employed comprises an epoxy resin loaded with a finely ground stone material, the resin being mixed with a hardener immediately prior to the compound being discharged from the nozzle into the channel 20. The density of the resin material employed in this example is approximately 3.8 g/cm3 and the viscosity is such that the resin material displays a self-levelling property before curing is completed. The rate of polymerisation is adjusted such that the resin has cured sufficiently to become unworkable within five minutes.

As the resin is run into the channel 20, the resin forms around the partially collapsed rivets 22 pressed into the holes 21 drilled in the drum part in the region of the channel 20, the rivets then serving securely to hold the cured resin balance weight in the position illustrated in the drawing.

It will be appreciated that the weight of resin material added to the channel 20 easily can be adjusted so as to suit the parameters of any given drum. Such weight adjustment requires no more than an adjustment of the control of the resin discharge head, and so presents none of the problems associated with the use of a separate weight annulus around the outside of the drum. There is also the advantage that because the balance weight is located nearer the axis of the drum of this invention than would be the case were a balance weight attached to the drum around its outer periphery, the amount of weight re quired to obtain effective balancing of the drum is reduced.

Though the manufacturing process has been described with the step of joining the two drum halves together before running the epoxy resin material into the channel 20, the process may equally be performed by filling the chan nel 20 of drum half 10 after the manufacture of that half and before it is joined to drum half 11. Such a process may be easier to perform, in view of the simpler access to the channel 20.

Referring now to Fig. 2, there is shown an alternative form of drum, and like parts with those of Fig. 1 are given like reference charac ters; these parts will not be described again here. This alternative form of drum has a channel 20 provided at end 15 of the drum, to face away from the major part of the drum, the channel being defined by concentric cylin drical walls 25 and 26. Wall 25 is constituted by an extension of the side wall of the drum proper, whereas wall 26 is generally in the form of an L-shaped flange, extending within the wall 25. This wall 26 thus defines the mouth of the drum, as well as the channel 20.

A snap-on ring 27 is also provided, to cover the channel after the channel has been filled with a stone-loaded resin.

Apart from the foregoing differences, the drum of Fig. 2 is manufactured and weighted in the same manner as that of Fig. 1. The drum moreover possesses much the same ad vantages, but may be marginally easier to fill with the resin, in view of the accessibility of the channel.

Claims (17)

1. A method of manufacturing a weighted drum, which method comprises the steps of moulding a drum body to include a circular flange element at or adjacent one end of the drum thereby to define an annular channel be tween the flange element and a portion of the drum wall, supporting the drum with its axis substantially vertical and with said channel dis posed such that the opening thereto faces up wardly, adding a pre-determined quantity of a curable material into said channel, and then causing or permitting the curable material to cure.

2. A method according to claim 1, in which the flange element is formed to have a general L-shape in cross-section, the flange element being inturned with respect to the drum so that the channel is within the drum, adjacent the one end thereof and opening to wards the other end of the drum.

3. A method according to claim 2, in which the flange element is formed by a cylin drical wall, there being a second cylindrical wall arranged so that the two cylindrical walls upstand from the major part of the drum with the channel opening axially away from the major part of the drum.

4. A method according to claim 3, in which an annular lid is provided to close the opening between the two cylindrical walls.

5. A method according to any of the preceding claims, in which the predetermined quantity of curable material added is determined on a weight basis.

6. A method according to claim 5, in which the drum is supported on a suitable weighing machine, and then the curable material is added into the channel until the weighing machine detects an increase in drum weight of the required amount.

7. A method according to any one of claims 1 to 4, in which the predetermined quantity of curable material added is dispensed on a volume basis.

8. A method according to any of the preceding claims, in which the curable material used is a relatively dense material which will flow into the channel but which then will cure or set to form a solid, dense mass.

9. A method according to claim 8, in which the curable material used is a polymerisable resin material, loaded with particles of a relatively dense substance.

10. A method according to claim 9, in which the curable material used comprises a mix of an epoxy resin together with finely ground stone material, a hardener being added to the resin immediately before the resin is added into the channel of the drum, so as subsequently to cause the resin material to cure.

11. A method according to claim 10, in which the loaded resin material used has a density in the region of 3.5 to 4.0 g/cm3.

12. A method according to any of the preceding claims, in which the viscosity of the curable material employed is such that the material displays self-levelling characteristics after the material has been added to the channel but before curing has significantly advanced.

13. A method according to any of the pre ceding claims, in which a mechanical fixing ar rangement is employed for the cured resin material.

14. A method according to any of the pre ceding claims, in which the drum body is manufactured by an injection moulding process using a plastics material.

15. A method according to claim 14, in which the drum body is formed in two halves which are joined together about a radial plane, one end of the drum being provided with said flange element and the other end of the drum being appropriately formed to permit the mounting of the drum on a drive boss.

16. A method of manufacturing a weighted drum according to claim 1 and substantially as hereinbefore described with reference to the accompanying drawings.

17. A weighted drum suitable for use in a spin-drier, whenever manufactured by a method according to any of the preceding claims.