An Improved Method of Stamping or Drawing Hollow Bodies or Vessels from Sheet Metal, and Apparatus therefor.
Year: 1895

page_text: Date of Application, 10th June, 1895-Accepted, 13th July, 1895
COMPLETE SPECIFICATION.
An Improved Method of Stamping or Drawing Hollow Bodies or
Vessels from Sheet Metal, and Apparatus therefor.
We, WILLIAM MCLAREN, of 70 Canfield Gardens, West Hampstead, in the
County of Middlesex, Manufacturer, and HARVEY EDWARD BROWN, of
18 Ballater Road, Clapham, in the County of Surrey, Engineer, do hereby
declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
This invention relates to an improved method of stamping or drawing hollow
bodies cups or vessels from sheet metal whereby we are enabled to produce seamless
articles of considerable depth suitable for a variety of uses, such as for lamp bodies,
preserve tins, buckets and the like.
In the ordinary method of stamping or drawing hollow bodies or cups from metal
blanks, the entire depth to which such blanks are to be drawn must be effected
practically at one operation, because when the edge of the blank has been once
turned up vertically, it is not possible to operate further upon said blank with the
ordinary dies. Furthermore the depth to which the blank can be at present drawn
is limited owing to the fact that when the mass of metal intended to form the
cylindrical part or sides of the hollow body or cup is great in proportion to the
mass of metal forming the bottom or end thereof, the resistance to a converging
movement of the mass of the metal forming the sides of the hollow body or cup is
greater than the strength of the bottom or end upon which the ram or punch bears
in forcing the blank through the die. In drawing hollow bodies or cups in the
ordinary manner, it is necessary to press the part of the blank that is to form the
sides of the hollow body or cup between the flat horizontal marginal parts of
the draw ring and the die in order to prevent the metal from wrinkling during the
time that the ram
or punch is forcing the blank through the die and while the
diameter of said blank is being steadily reduced to that of the hollow body or cup
required. It is therefore obvious that by this procedure it would not be possible to
produce hollow bodies or cups of great depth unless the strength of the bottom of
the cup were greater than the resistance to movement of the entire mass of metal
forming the sides thereof, which as already pointed out is not the case when the
drawing operation is effected in the ordinary manner.
Now according to our invention we overcome this difficulty by performing the
drawing or stamping in a series of operations in such a manner that the reduction
in diameter of the hollow body, cup, or vessel is effected in steps so that only a
comparatively small portion of the entire mass of the metal forming the sides of
the hollow body or cup is caused to converge or move inwardly at any given
moment during the drawing operations.
For this purpose we employ a number of dies gradually diminishing in size from
a little less than that of the blank or disc of metal first acted upon down to that of
the diameter of the hollow body, cup, or vessel to be produced. The diameter of
the ram or punch of the largest die is approximately equal to the diameter of the
draw-ring employed in the next die of the series, while the diameter of the ram or
punch of this latter die is approximately equal to the diameter of the draw-ring
employed in the next succeeding die, and so on until the last die is reached. In this
way the blank is first converted into a comparatively shallow dish by the die of

page_text: largest size, said dish being of such a diameter as to just fit the draw ring of the
next die, by which latter it is reduced in diameter and elongated so as to form
another dish or cup that just fits the draw-ring of the next die, the drawing
operation being continued in steps in this manner until a hollow body, cup, or
vessel of the requisite length and diameter is obtained.
In order that our said invention may be fully understood and readily carried
into effect we will describe the same more fully with reference to the accompanying
drawings.
Figure 1 is a vertical section shewing an advantageous construction of one of the
series of dies, and draw rings and rams, we employ.
Figure 2 is a similar view shewing the draw ring and ram in another position.
Figure 3 is likewise a similar view shewing the ram in the act of performing the
drawing operation.
Figures 4, 5 and 6 are sectional views shewing a cylindrical cup as it appears
when the draw-ring and ram are in the respective positions represented in the
preceding figures.
Figure 7 is a sectional view representing the cylindrical cup as it appears after
the ram has forced it completely through the die.
A is the draw-ring within which the ram or punch B is adapted to slide, and C is
the die through which the cup D under operation is drawn. We find it advantageous
although not absolutely necessary to make the lower edge a of the draw ring and
the upper edge c of the die with corresponding bevelled edges which enable the
metal to "flow more easily than would otherwise be the case if the respective
edges a and c were flat.
"
--
The drawing operation is as follows: We first set up the edge of the blank by
means of an ordinary die and draw ring so as to produce a shallow dish of the
requisite diameter to fit the draw ring of one or other of our series of dies. The
said dished blank is then placed between the die and draw ring in the position
represented in Figure 1. The draw ring A is then caused to descend and presses
the marginal portion d of the dished blank into the bevelled mouth of the die C as
shewn at Figure 2. This operation gives to the dished blank approximately the
shape illustrated in Figure 5. The ram B is next caused to descend and gradually
forces the dished blank through the aperture c¹ in the die. It is to be observed
that the actual drawing operation takes place only between the bevelled edges a
and c and consequently the converging movement of the molecules of the metal, at
any given moment during the drawing operation, takes place only in the com-
paratively small mass of metal existing in the annular portion located between the
vertical sides d', d² of the cup (Figure 6). The internal diameter of the cup
produced by this drawing operation and shewn in Figure 7 is such that the draw
ring of the next succeeding die of the series will just fit into it, and the same
operations taking place as above set forth, the cylindrical cup becomes still further
elongated and its diameter still further reduced to such an extent that the draw
ring of the next succeeding die of the series will just fit it. In this manner the
drawing operation is continued in successive steps until a cup or vessel of the desired
depth and diameter is obtained.
When it is desired to produce hollow bodies without a closed end or bottom we
cut out such end after the completion of the drawing operation.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. The improved method of stamping or drawing hollow bodies cups or vessels
from sheet metal blanks consisting in passing said blanks through a graduated
series of dies so constructed and arranged to operate that only a comparatively
small portion of the mass of metal forming the sides of the hollow bodies or cups
is moved inwardly at any given moment during the drawing operation substantially
as described.

page_text: 2. Stamping or drawing dies constructed substantially as described with reference
to the accompanying drawings and for the purpose specified.
Dated this 10th day of June 1895.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicants.