GB2070479A

GB2070479A - Apparatus for casting accumulator grids

Info

Publication number: GB2070479A
Application number: GB8007037A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-03-01
Filing date: 1980-03-01
Publication date: 1981-09-09
Also published as: DE3107175A1; DK89981A

Abstract

The apparatus includes a rotary cylinder (1) formed with a shaped die profile on its external surface and positioned close to a static concave cylindrical surface (3 and 10) or a moving flexible belt or another rotary cylinder. Molten metal is introduced at the entry and the solidified castings are removed from the exit. The two parts (3 and 10) of the static block are separated by a thermal insulating barrier (9) and the part (10) is provided with cooling passages (16). <IMAGE>

Description

SPECIFICATION Apparatus for casting accumulator grids This invention relates to the production of grids for accumulator plates but is also applicable to the formation of similar open mesh structures formed in any metal or alloy having a low melting point.

Conventionally accumulator grids are formed by die casting, the molten metal being poured into a die cavity between two mould blocks which are mechanically brought together to form the cavity, and moved apart after the metal has solidified. The cycle is repeated continually, the cast grids being removed one by one from the die and moved on to other finishing stations at which the grids are trimmed and "pasted", i.e. filled with the specific chemical compound required for use in the electrolyte of the accumulator.

Existing procedures and machines suffer from various disadvantages. The machines tend to be complicated and hence there is the possibility of malfunction. Also the cycle time is longer than would be desired due to the basic parameters of the casting process. There is also a possibility that the cast grids may be damaged on removal from the die and the method usually requires a controlled pouring valve to dispense a measured quantity of the molten metal into the die chamber.

Furthermore the dies themselves are subject to large temperature gradients with consequent problems in providing an effective closure and at the same time achieving the necessary high temperatures for pouring and lower temperatures for solidifying the metal.

Accordingly it is an object of the invention to provide an improved apparatus and process for producing accumulator grids or the like which will be an improvement on the existing methods.

Broadly stated the invention consists in apparatus for continuous casting of accumulator plate grids or like open mesh structures in lead alloy or other metal having a low melting point comprising a movable die member in the form of a rotary member or a continuously movable endless band, provided with a die surface and arranged to co-operate with a mating surface to define a mould or die cavity for the grid, means for introducing molten metal into the die cavity, and means for moving the movable die member continuously or intermittently in a direction parallel to its surface.

In one form of the invention the die formation is formed on a rotary member and extends around the greater part of the peripheral surface.

Conveniently the rotary die member co-operates with and lies adjacent to a static mating block having a concave internal surface matching the periphery of the die member, and the mating block preferably includes a molten metal pouring nozzle and means for cooling the block and hence the cast grids. The mating block may also include a thermal break or barrier between the pouring nozzle and the cooling means.

In another form of the invention the apparatus includes an endless flexible band arranged to contact the surface of the rotary die member for a limited arcuate travel and means for introducing molten metal between the die face of the rotary member and the said band. The band is preferably formed of stainless steel or like non-corroding refractory material.

The invention may be performed in various ways and two specific embodiments will now be described by way of example with reference to the accompanying drawings in which: Figure 1 illustrates a pair of typical accumulator plate grids, Figure 2 is a diagrammatic side elevation partly in section through one form of continuous casting machine according to the invention, and Figure 3 is a similar diagrammatic side elevation of the second embodiment.

In the first example the apparatus comprises a rotary drum or roller 1 having a diameter for example of about eight inches and mounted on a pair of movable trunnion blocks or bearings 2. The surface of the drum is engraved or otherwise formed with the required shallow die pattern to form the accumulator grids. A typical grid pattern is illustrated in Figure 1 which consists of two grids temporarily joined along the centre line and intended to be separated later. In this example there may be four such grid patterns spaced around the surface of the drum.

In a conventional grid casting machine the two mating dies are each formed with a die pattern of approximately half the full thickness. In the present invention however the pattern on the rotary drum is of the full depth.

The die drum co-operates with a static mating block which includes an upper part 3 and a lower part 10. The two parts are rigidly connected together with an intervening thermal break or barrier 9 and together they form a concave partcylindrical surface matching the periphery of the drum. The upper part 3 is formed with a molten metal supply trough 4 extending across the full width of the drum and this trough communicates with a transverse feed groove or slot 7 opening onto the concave face via a number of restricted supply ports 6. From this feed groove the molten metal is thus supplied to the die cavity defined between the drum and the block. The trough 4 is provided with a spill port 8 at a level above the groove 7 but preferably not appreciably higher than the point 1 5 where the drum first makes contact with the block. This has two effects.It causes continuous flow of molten metal into and out of the trough 4 via the supply pipe 5 from a centrifugal molten metal supply pump, delivering the metal from a heated tank. This has the desirable result of heating the whole of the upper part of the block 3 to maintain optimum flow conditions for the molten metal. The positioning of the spill port 8 also acts to prevent molten metal backing up and escaping at the point 1 5.

The lower part 10 of the block is provided with a number of cooling passages 1 6 which are designed to assist in cooling the metal in the die cavities so that at the lowest point of the drum the cast grids can be removed as a continuous solid web 18 between a pair of pinch rolls 14.

The rotary die drum 1 may be urged towards the mating block by a spring 13 acting between a static channel 12 and an enlarged head of a bolt connected to a rod 11 attached to the sliding trunnion block 2 at each end. Alternatively the rotary die may be fixed in position (though preferably adjustable) to give the required contact or fine clearance. Other methods may be used to control the clearance or contact pressure between the two members.

In the second embodiment illustrated in Figure 2 the rotary die member 20 is essentially of the same construction as in the first example. In this case however the static mating block is replaced by an endless flexible stainless steel band 21 guided by a series of rollers 22 so as to envelop part of the periphery of the drum. Molten metal is supplied at 23 into the entry trough between the drum and the band and a cooling system 24 is provided to cool the back of the band and hence the metal in the die formation of the drum. As in the previous example the solidified cast grids are moved as a continuous web by means of nip rolls 26.

In both examples it is necessary to seal or close off the ends of the supply groove or supply trough where the molten metal is actually brought into contact with the die surface of the drum.

In a possible further modification the rotary die member is arranged to co-operate with a mating rotary member to define the die cavity, the second member having either a plane cylindrical surface or a matching die formation. This may have certain advantages but it suffers from the fact that the surfaces of the two members are only in close engagement over a limited travel.

Claims

1. Apparatus for continuous casting of accumulator plate grids or like open mesh structures in lead alloy, or other metal having a low melting point, comprising a movable die member in the form of a rotary member or a continuously movable endless band, provided with a die surface and arranged to co-operate with a mating surface to define a mould or die cavity for the grid, means for introducing molten metal into the die cavity, end means for moving the movable die member continuously or intermittently in a direction parallel to its surface.

2. Apparatus according to claim 1, in which the die formation is formed on a rotary member and extends around the greater part of the peripheral surface.

3. Apparatus according to claim 1 or claim 2 in which the rotary die member co-operates with and lies adjacent to a static mating block having a concave internal surface matching the periphery of the die member.

4. Apparatus according to claim 3 in which the mating block includes a molten metal pouring nozzle.

5. Apparatus according to claim 3 or claim 4, in which the mating block includes means for cooling the block and hence the cast grids.

6. Apparatus according to any of claims 3 to 5, in which the mating block includes a thermal break or barrier between the pouring nozzle and the cooling means.

7. Apparatus according to claims 1 or 2, including an endless flexible band arranged to contact the surface of the rotary die member for a limited arcuate travel and means for introducing molten metal between the die face of the rotary member and the said band.

8. Apparatus according to claim 7 in which the band is formed of stainless steel or like noncorroding refractory material.

9. Apparatus for casting accumulator plate grids or like open mesh structures substantially in any of the forms described with reference to the accompanying drawings.