Metal founding – Means to shape metallic material – Including means to heat mold
Reexamination Certificate
1999-02-10
2001-01-09
Pyon, Harold (Department: 1722)
Metal founding
Means to shape metallic material
Including means to heat mold
C164S332000, C164S334000
Reexamination Certificate
active
06170559
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This is the 35 USC §371 National Stage of International application PCT/GB98/02008 filed on Jul. 6, 1998, which designated the United States of America.
FIELD OF THE INVENTION
This invention relates to methods and apparatus of casting a lead formation on the lug of a battery component
For the purposes of this Specification the term “lead” includes suitable lead alloys.
BACKGROUND OF THE INVENTION
It is well known to cast straps and other formations on the lugs of battery plates, for example to connect together each of the plates in a group. In almost all cases this is done by filling a mould cavity with lead and dipping the lugs into that cavity. In order for an acceptable connection to be made between the lead and the lug, the temperature of the lead at the interface needs to be above the freezing point of lead. In general this requires the lead block to be heated by a heat source, such as a gas flame, until the lugs are dipped into a cavity and then cooling has to occur so that the lead solidifies quickly. Most such heating arrangements are inefficient and expensive. Attempts have been made to dip the mould block into a pot of molten lead in order to achieve the desired result, but this precludes the use of ejector means for removing the cast on straps from the mould, because the lead would clog up and such moveable parts.
The more normal method of filling the mould cavities is to flow lead in channels to the side of the cavities and allow it to spill over weirs. This can require very great control of lead flow, if one is to ensure that the cavities are filled but the mould as a whole is not over filled.
SUMMARY OF THE INVENTION
From one aspect the invention consists in a method of casting a lead formation on the lug of a battery component, comprising streaming lead over a mould block defining a mould cavity to flood the cavity and maintaining the flow of the lead until the temperature of the mould block, at least adjacent the cavity, is raised by heat from the lead until an appropriate working temperature is reached.
This streaming of the lead over the mould block not only provides for very good filling of the cavity but also very efficient heating of the mould block, because there is good conduction between the molten lead and the mould block. Further as the lead moves over the mould block, rather than the mould block into the lead, mechanical parts such as an ejector system can be provided in a position which is permanently away from the lead stream.
In a particularly preferred arrangement, the heat from the molten lead provides substantially the only heat source for the mould, thus obviating the need for additional heaters.
The appropriate working temperature is that at which lugs can successfully be connected to the castings. It will usually be equal to or exceed the freezing temperature of the lead, but experiments have shown that in certain mould configurations at least slightly lower temperatures are operative.
An important feature of this method is that, where the mould temperature is above the freezing point of the lead, it acts as a positive heat reservoir acting to maintain the lead temperature if the lugs should take out too much heat from the molten lead in the cavity. This is particularly useful where the volume of the mould cavity, and thus the thermal energy of the lead, is low relative to the thermal capacity of the lugs. In other words, the method allows a positive net flow of heat from the mould to the lead in the cavity if the temperature of the molten lead drops.
The method may further include dipping the lugs into the cavity immediately after the stream has stopped, although preferably excess lead is scraped from around the top of the cavity prior to dipping.
The block may be cooled to cast the lead, in the cavity on to the lug and usually there would be a plurality of cavities and/or lugs.
From another aspect there is provided apparatus for casting a lead formation comprising a source of molten lead, a mould block having a mould cavity in an upper face thereof, retaining means for defining a lead pond over the upper face of the block, an inlet at one end of the pond and an outlet at the other, whereby lead can be streamed through the pond to flood the cavity and raise the temperature of the block, means for maintaining the flow of lead at least until the block is at the freezing temperature of lead and means for halting the flow of lead when the desired block temperature is reached.
Preferably the outlet is below the level of the upper surface (eg. in the manner of a weir) so that the lead drains off the upper surface. The apparatus may further include scraper means for removing excess lead from the upper surface and/or ejector means for ejecting a cast component from the cavity of cavities.
The apparatus may still further include means for lowering a battery plate group to dip the lugs of the group into the cavity. There may be multiple groups and multiple cavities.
Clamping means may be provided for laterally retaining the mould block.
Although the invention has been defined above it is to be understood it includes any inventive combination of the features set out above or in the following description.
REFERENCES:
patent: 3395748 (1968-08-01), Tiegel
patent: 4425959 (1984-01-01), Mund
patent: 4534401 (1985-08-01), Schaumburg et al.
patent: 5520238 (1996-05-01), Hopwood
patent: 24 27 639 (1975-07-01), None
patent: 2 023 471 (1980-01-01), None
patent: WO 94/16466 (1994-07-01), None
Lin I.-H.
Pyon Harold
TBS Engineering Limited
Young & Thompson
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