[0001] The invention relates to a method and apparatus for manufacturing steel drums.
[0002] In accordance with the state of the art steel drums are manufactured from steel plate
which is welded by seam-welding after being bent into a body.
[0003] The problem with this is the high costs connected with this non continuous production
technique and the associated quality problems such as start and end of the weld, at
the ends of the body.
[0004] The object of the invention is to provide a method and apparatus allowing drum bodies
to be produced in a continuous process.
[0005] In accordance with the invention this is achieved by a method for manufacturing steel
drums comprising the stages:
(1) uncoiling a steel strip from a coil
(2) manufacturing from the strip in a continuous process a spirally welded tube with
a diameter essentially equal to the diameter of the drum to be manufactured, whereby
the pitch angle is set in dependency of the width of the steep strip
(3) cutting off from the spirally welded tube pieces with a length essentially equal
to the body length of the drum to be manufactured
(4) providing the drum body with lids on both of its ends.
[0006] In a special embodiment of the method the subsequent coils have a varying width and
the coils are processed without slitting by setting the pitch in dependency of each
new width.
[0007] The invention is also embodied in an apparatus for manufacturing steel drums comprising:
- means for uncoiling a steel strip from a coil
- means for conveying the steel strip from the coil to means for bending the steel strip
- means for bending in a spiral fashion the steel strip into a tube shaped spiral comprising
means for setting the pitch angle
- means for welding the spiralled tube
- means for cutting off from the spiralled tube bodies for the steel drums
- means for providing the drum body with lids on both of its ends.
Preferably the means for setting the pitch angle comprise a turnable.
[0008] The advantages of this are:
- the steel is less expensive by the coil than by the plate
- less material handling of the coils is required than with the plates of the state
of the art
- with the invention variable material widths can be used allowing an inexpensive second
choice material to be used; slitting is no longer required
- there is no material loss
- the continuous welding process can be better controlled and produces a more consistent
quality than with the state of the art at the start and end of the weld
- the bodies are exactly cylindrical
- the spirally formed weld seam makes the drum stronger and stiffer.
[0009] The invention will now be illustrated by reference to the drawing.
[0010] The only drawing shows an apparatus in accordance with the invention.
[0011] Steel strip (1) is uncoiled for example on an uncoiling reel (not shown) from a coil
(not shown). The steel strip (1) is conveyed to means for bending the steel strip
and there bent in spiral fashion into a tube shaped spiral (6) having a pitch angle.
[0012] These means consist of for example the adjustable bending roll (2) and inner bending
roll (3) together with driven bending rolls (4) and (5). The steel strip is fed under
tension and at such a pitch angle that the strip edges abut seamlessly. The pitch
angle at which the steel strip arrives on the bending roll is critical and determines
whether the steel strip runs off or butts. This is adjusted with the turntable (9).
[0013] Then the tube shaped spiral (6) is welded with a welding unit (not drawn) at (7)
into a spirally welded tube. A high frequency welding module is excellent to use for
continuously welding the spirally welded tube. The spirally welded tube is conveyed
by the conveyor (10).
[0014] Pieces (8) with a length such as needed for the drum body are cut off from the spirally
welded tube for example with a shear blade rotationally, axially and radially driven
at (11), (12) and (13). Finally, after some intermediate processes such as applying
stiffening ribs and preparing the drum body ends, this drum body is provided with
lids at both ends.
[0015] A particular advantage of the invention is that compared to the state of the art
minimum material handling is required and the production line is very short.
1. Method for manufacturing steel drums comprising the stages:
(1) uncoiling a steel strip from a coil
(2) manufacturing from the strip in a continuous process a spirally welded tube with
a diameter mainly equal to the diameter of the drum to be manufactured, whereby the
pitch angle is set in dependency of the width of the steel strip
(3) cutting off from the spirally welded tube pieces with a length mainly equal to
the body length of the drum to be manufactured
(4) providing the drum body with lids on both of its ends.
2. Method in accordance with claim 1 whereby subsequent coils have a varying width and
whereby the coils are processed without slitting by setting the pitch angle in dependency
of each new width.
3. Apparatus for manufacturing steel drums comprising:
- means for uncoiling a steel strip from a coil
- means for conveying the steel strip from the coil to means for bending the steel
strip
- means for bending in a spiral fashion the steel strip into a tube shaped spiral
comprising means for setting the pitch angle
- means for welding the spiralled tube
- means for cutting off from the spiralled tube bodies for the steel drums
- means for providing the drum body with lids on both of its ends.
4. Apparatus in accordance with claim 3 whereby the means for setting the pitch angle
comprise a turnable (9).