Note: Descriptions are shown in the official language in which they were submitted.
A proco~ for th~ ~nufacture of on~-piec2 pl~stlc ~ads
for cartr1d ~s
The pre~nt 1nvention rel~te~ to ~ pr~ces~ for
the ~anufacture of oneop1~ce plastic ~ads for cartrid0es,
1n part1cular ~hot cartr~dges, each ~ad compr~sing a c~n
which is ~o receive the po~der, a shot cup servin~ ~o
receive the shot, and a ~hock absorber dispos2d bet~een
the can and the shot cup. The invention also relates to
the one~pieGe plastic ~ad manufactured by this process.
It is kno~n to those skilled ;n the art that such
plastic ~ads, used for the production of cartridges, are
manufactured by the ;nject;on-moulding process. Compared
~;th the parts to be manufactured, the mouLds requ;red
for th;s purpose have to be relatively large and are
correspondingly expensive. Moreover, the injection-
~oulding process is time-consum;ng and cannot be carr;ed
out continuously~
It is therefore the object of the present inven~
tion to propcse a process which not only considerably
simplifies the process hitherto used, but aLso makes
possible the use of substantially simpler moulds and con-
tinuous production~ This novel process is characterized in
that a parison i5 first made by extrusion and this parison
is then given the desired final form by blow-moulding and
is cooled.
According to another feature of this process, the
parison made by extrusion is continuously moved during
the blow-moulding step, and the blow mould surrounding
the parison in the forming region is moved along with the
parison flnd, after the end of the blow-moulding step and
after cooling, is moved back again into its starting
p 0 8 ition.
According to another feature of this process,
pressurised gas is blown into the parison, introduced
into the blow mould, at two points which are at a mutual
distance in the axial direceion of the parison, in such a
way that the connection between the powder can and the
shot cup can be sealed gas-tight even duri.ng the blow-
moulding step and subsequent sealing of these becomesunnecessary.
According to still another feature of this process
a vacuum is applied to the outer surface of the parison
located within the blow mould, and the parison is thus
pressed against the contours of the blow mould by the gas
pressure prevailing in the interior of the parison.
The one-piece plastic wad manufactured by this
process is characterised in that the shock absorber in a
virtually closed hGllow body filled with air.
.According to another feature of this plastic wad9
the connection between the can and the shot cup is
interrupted by a gas-tight seal at least one point
located between these two.
According to another feature of this plastic wad,
the hollow body has one end face, serving as a yielding
membrane, facing the can and one facing the shot cup,
the end faces each being connected, respectively, to the
can and the shot cup via one connecting element of smaller
diameter, the connecting element adjacent to the can being
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wrlded ga~-tight.
~ n illu~tr~tive embod~ment of the subject of the
~nventton is d~scribed belo~, ~ith refer~nce to the
attach~d drawing in which:
Figure 1 is a 5ectional representation of a de~ice used
for extruding the par;son and for blo~-moulding
the w~d,
Figure 2 dia~rammatically illustrates a continuous manu-
facturing process, and0 Figures 3 and 4 sho~, in a diagrammat;c perspective vie~,
t~o possible embodinlents of a ~ad manufactured
by the process according to the invention~
Figure 1 sho~s an extrusion die ~hich is marked
1 as a whole and ~hich, in a kno~n manner, comprises a
cylindrical cover 2, a mandrel (torpedo~ 3 coaxial to the
cover and a die orifice 4. The mandrel 3 is fixed via
radial ~ebs S to the inner wall of the die. The heated
and thus plastic;sed materi~l passes under the action of
a screw 3a to the die orifice 4 and emerges there in the
form of a parison 6 wh;ch is still at a reLat;vely high
temperature just belo~ the softening point.
As Figure 1 shows~ the front section of the mandrel
3 is prolonged in the form of a cylindrical extension 2b
in such a ~ay that 1t guides the emerging parison 4 until
the latter enters the region of a blo~ mould ~hich is
marked 7 as a whole and ~hich has the ha~ched cross-section
and is movably mounted and prov;ded ~ith drive means, in
such a way that the t~o mould halves 7a/7b are pressed
together in the d;rection of th@ arro~ and can also be
d~ 6 ~
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~p~r~ted a~n from one ano~1~r 1n the oppos~te direction.
Th~ two mould halves 7a~7b ~re closed as soon ss
the parlson 6 has been moved through the en~ire Len~h of
th~ mould. Immed'~ateLy after ~he mould has been closed,
5 compressed alr is blown v1a a needle 8 into the interior
of the cavity H, so that the entire urface of the par;-
son is laid ~galnst the inner swrfaces of the mould halYes
7a/7b. Since the mould is provided ~ith a cooling jacket
9, throu~h ~hich a coolant flo~s, the parison ~aterial
;s rap;dly cooled on contac~ ~ith ~he inner wall of the
mould and, on solidification, assu~es the desired form
g;ven by the contour of the mould halves~
The needle 8 is arranged and controlled in a bore
in the mouLd half 7a in such a ~ay that, at a suitable
lS moment, that is to say immediately after the mould has
been closed, it pierces the parison b, a valve being
opened and compressed air being admitt~d to the cavity H
through the needle 8.
If only one needle 8 is used~ the connecting
points of the shot cup 15 and the can 14 to the shock
absorber 22, ~hich are marked 16 and 17 in Figure 1, must
remain open during the blo~moulding step and are subse-
quently closed~ as necessary. To avoid this subsequent
~orking step~ a second needle 8a is preferably used ~hich
is controlled synchronously with the firs~men~ioned
needle 8 and ;s also ~ounted in a mouLd boreD at an axial
distan~e from the former. If these t~o needles are used,
the ~ould can then be shaped in such a ~ay that the Gon-
nect;on point 16 of the st;ll plastic parison material
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i~ ~eld~d 0as-tight.
The ~nd ~ect~ons of the blow~moulded partO ~hich
have been dama~ed by p;ersing ~lth th~ needle, are cut
off~ as shown in Fi~ure 1.
s T~o pa~rs of blades 10 3nd 11 .are also movably
arranged in the mould halves 7a/7b~ as shown ~n Figure 1,
and they are controlled in such a way that they sever
~he ~ad at t~o po;nts after blo~-moulding and cooLing.
The pairs of blades 10, 11 can be located either, as
10 accord7ns to F;gure 1, ~ithin the blow mould or QutSide
the blow mould. If severin~ is carr;ed out outs;de the
mould~ a s;ngle blade suff;ces~ Other severing ele~ents,
such as laser beams, ~ater ~ets~ saws and the llke can
of course also be used~
Due to the contoursO ~hich can be seen in Figure
1~ of the mould halves 7a/7b, the resulting shape of the
~ad 13 is as sho~n in Figure 3. This ~ad thus has a
cylindrical can 14 ~hich is to receive the po~der, a
cyLindrical, somewhat Longer shot cup 15 for the shot and,
between the can 14 and the shot cup 15~ a shock absorber
22~ This shock absorber 22 is a circuLar cylindrical~
virtually closed, air-filled hollo~ body ~hich has excel-
lent properties ~ith respect to damping the recoil occurr
ing on firing. The holloY body is connccted to the can
14 and ~he shot cup 15 via t~o tubular connecting elements
16, 17 respectively.
To ensure that a breakthrough of the po~der gases
formed in the can 14 is prevented, the t~o ~ubular connec~
in~ ele~ents 16 and 17 are preferably sealed g2s-tigh~.
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In ~ome ca5e8~ ho~ever~ 1t 3uf f i ces, ~s men~oned, to
~eal only one o~ these two conn~ct~n~ ele~ents ~as~ti~h~,
~h~l~t the other can have ~ throu~h-bore.
The mould shown in Figure 1 can be ~odified in
v~rious ~ays by those skilled in the art~ Thus, 1t
~ould al50 be possible to make the hollow body type shock
absorber 22 in a square shape or star shape ins~ead of a
circular cyl1ndrical shape. It ~ould aLso be possible
for the connecting elements 16 and 17 to have any desired
hollo~ shape which can be obtained by blow-moulding. As
Figure 4 also sho~s, a can 18 could also be connected to
a shot cup 19 via a straight cylindrical connecting piece
20.
The blo~-rnouldin~ proce~s described is advan-
ta~eously distinguished from the known injec~ion-moulding
technol4gy, inasmuch as the involved~ relatively Large
and expensive injection mould no~ becomes unnecessary
and the production process can be speeded up considerabLy.
Moreover, as diagrammat;cally ;Llustrated ;n Figure 20
the manufacturing process can also be carried out con-
t;nuously in a simple manner, in contrast to the existing
technology. The nould halves 7a/7b are here arranged to
be movable and are gu;ded by means of a drive on the
periphery of continuous belts 12 runn;ng over rollers R~
in such a ~ay that the ~ould haLves move along ~ith the
moved parison 6 on closing and subsequen~ly, after the
end of the blow-moulding step, are l;fted off the parison
and return again into their starting position. In Figure
2, the startin~ position is marked I~ the closing position
7~'~
1~ markcd II and the ~nd pos1t~on~ from ~h1ch the rever~al
of d1r~ct10n take3 pl~c~ m~rked III~
The expr~ss10n~ "blow-mould1n~" and "blow~mould;ng
3tep" used in the present CGnt@xt are to be understood
~n such a ~ay that they compr;se any manufactur;n0 proo
cess operat;n~ with a d1fference in gas pressure~ In
place of the provision of needles for applying pressurised
gas, it ~ould, for example, also be possible to arrange
a number of fine channels ;n the mould~ ~hich channels
are connected to a vacuum source and end on the inner
surface of the mould~ facing the parison. ~y applyin~ a
vacuum, the plastic parison ~ouLd then be pressed against
the contours of the mould, under the action of the gas
pressure prevailing in the cavity.
The device described can operate vertically or
horizontally.
The starting ~aterial used is a thermoplastic,
preferably polyethylene.
