US2099449A - Method of making dry cells - Google Patents

Description

Nov. 16, 1937. o. METZGER- METHOD OF MAKING DRY CELLS Filed Nov. 26, 1934 0. j/[eiz Gttomeg Patented Nov. 16, 1937 UNITED STATES PATENT OFFICE METHOD OF MAKING DRY CELLS Germany Application November 26, 1934, Serial No. 754,805 In Germany November 14, 1931 4 Claims.

' This application is a continuation in part of applicant's copending applications Serial Nos. 600,753 filed March 23, 1933, and 659,021, filed February 28, 1933. 5 This invention relates to zinc containers for electrical cells for dry batteries, pocket lamps, anode batteries and the like and method of making same. Up to now such zinc containers have been made by bending a rectangular piece of zinc l0 sheet into a cylindrical form, soldering its longitudinal edges together and then soldering a circular end onto one end of the tube. Thezinc containers made in this way, however, have the disadvantage that they are very rapidly consumed by electrolytic actions. Zinc containers have also been made by a drawing process (that is containers drawn from a round disc). In this process however, the discs from which the containers are drawn have to be greased. This 0 grease adhering to the container, which is very disadvantageous for the electro-chemical use of the container, has to be carefully removed by washing so that a further operation is required which makes the containers considerably more expensive. Moreover, the drawn containers have very sharp bottom corners which also are found to have a detrimental effect on the life of the container.

The present invention consists in this, that the zinc container is made from a small plate of rolled zinc by the known cold extrusion process. The zinc containers made by this method have the advantages over other containers of greatly increased life and completely smooth inner and outer surfaces. The containers according to the invention are further characterized by the feature of being completely free from fat.

The so-called cold extrusion process for making tubes for pastes and similar cylindrical containers from aluminum, lead and tin is known but up to now it has not been proposed to use the cold extrusion process for making zinc containers from rolled zinc plates (for example zinc discs of circular or other shape) which, on account of the great homogeneity of the initial material and its increase on account of this meth- 0d of forming and the considerable compression of the crystalline structure of the zinc which are obtained by impact, have their electrolytic properties and their life improved to a very great extent and also have completely smooth inner and outer surfaces, which is very desirable. It is known to make zinc containers by a hot extrusion process. This process is, however, expensive and does not give the very good electrolytic properties which are obtained in the present process. The molecular structure of the zinc is altered with unsatisfactory results by the heating of the zinc.

Previous attempts in this direction have all 5 'given negative results. In particular, the industry concerned has not realized that rolled zinc plates as a starting material, which is homogeneous in itself, show an unexpected improve ment of the electrolytic properties when extrud- 10 ed in the cold.

Since the machines used for carrying out the cold extrusion process are known, it will not be necessary to show these in a drawing in order to make the invention clear.

In the accompanying drawing, Figs. 1 and 2 show the small rolled zinc plate used as the initial material in plan and side elevation and Figs. 3 and 4 show the zinc container made from this plate in partial longitudinal section and in plan.

The zinc container (1 is made from a circular disc-like plate b consisting of rolled zinc. This zinc plate has a diameter of about 18.5 mm. and a thickness of about 5 mm. The zinc at ordinary room temperature (i. e. 15-20 C.) is subjected to the action of the extruding mechanism which in lieu of applying a steady pressure applies a sudden impact of from 10,000 to 20,000 kg. per sq. cm, (142,000 to 284,000 lbs. per sq. inch). The plunger moves with a velocity of 150 mm. per second or more.

It is of course understood the extrusion of the zinc takes place backwardly, i. e. in a direction opposite the movement of the plunger.

The zinc plate in the above-described cold extrusion process is shaped by a very sudden impact on the press to a cylinder with a bottom 0 which has about the same'diameter as the plate, has walls of uniform thickness and is about 53 mm. high. i

The process is completed so speedily that the transforming process of the zinc is not visible with the naked eye. The zinc, however, shaped by the said very sudden impact shows-in a further increase of the homogeneous qualities of the starting material-an extraordinarily dense and homogeneous molecular structure, so that the zinc container made by this method has excellent electrolytic qualities and therefore a greatly increased life. In addition a rounded bottom edge d is obtained and the inner and outer surfaces are smooth and mirror-like.

In amodiflcation of the above process, the zinc is preheated to a point below 90 which latter is about the lower limit of recrystallization of zinc.

In this modification as in the first form described, lubrication is not necessary while the tools are not used up so rapidly.

What I claim is:

5 1. The cold, instantaneous, impact extrusion method of backwardly forming an integral hollow zinc container with a closed end which comprises placing a disc-like plate of rolled zinc in a closed cavity without preheating said plate, impacting said zinc plate in said cavity at room temperature of about C. to about C. with one blow of a solid plunger almost filling said cavity and only leaving a. small open annular space, said impacting being efiected without a lubricant and in- 15 stantaneously with an extremely high pressure of about 142,000 to about 284,000 pounds per square inch whereby the extrusion of zinc is effected in a direction opposite to the movement of the plunger so speedily that it is not visible with the 20 naked eye and whereby an integral hollow zinc container with a closed end and with smooth and mirror-like surfaces is formed with an extraordinarily dense and homogeneous structure and with excellent electrolytic qualities and greatly in- 29 crease life, and discontinuing the application of pressureafter said one sudden impact blow has been effected momentarily.

2. The cold, instantaneous, impact extrusion method of backwardly forming an integral hollow 30 zinc container with a closed end which comprises placing a disc-like plate of rolled zinc in a closed cavity without preheating said plate, subjecting said zinc plate at room temperature to an in- ,stantaneous impact with one sudden blow of a plunger moving with a velocity of at least mm.

per second, said sudden single impact blow being effected without a lubricant and with an extremely high pressure of about 142,000 to about 284,000

pounds per square inch whereby the extrusion of zinc is effected in a direction opposite to the movement of the plunger so speedily that it is not visible with the naked eye and whereby an integral hollow zinc container with a closed end and with smooth and mirror-like surfaces is formed with an extraordinarily.dense and homogeneous structure and with excellent electrolytic qualities and greatly increased life, and removing said plunger from said formed hollow zinc conaoi tainer without the application of pressure after said one sudden impact blow has been effected momentarily.

3. The cold, instantaneous, impact extrusion method of backwardly forming an integral hollow zinc container with a closed end which comprises placing a disc-like plate of rolled zinc in a closed cavity without preheating said plate above the lower recrystallization limit of zinc, subjecting said zinc plate below the temperature of the lower recrystallization limit of zinc to an instantaneous impact with one suddenblow of a plunger moving with a velocity of at least 150 mm. per second, said sudden single impact blow being effected without a lubricant and with an extremelyhigh pressure of about 142,000 to about 284,000 pounds per square inch whereby the extrusion of zinc is effected in a direction opposite to the movement of the plunger so speedily that it is not visible with, the naked eye and whereby an integral hollow zinc container with a closed end and with smooth and mirror-like surfaces is formed with an extraordinarily dense and homogeneous structure and with excellent electrolytic temperature of about 15 C. to about 20 C. with 'one blow of a solid plunger almost filling said cavity. and only leaving a small open annular space, said impacting being effected without a lubricant and instantaneously with an extremeiy high pressure of about 142,000 to about 284,000 pounds per square 'inch whereby the extrusion of zinc is effected in a direction opposite to the movement of the plunger so speedily that it is not visible with the naked eye and whereby an integral hollow zinc container with a closed end and with smooth and mirror-like surfaces is formed with an extraordinarily dense and homogeneous structure and with excellent electrolytic quantities and greatly increased life.

- O'I'IO METZGER.

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