Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The invention relates to an improved method for
manufacturing perforated pipes particularly corrugated thermo-
plastic pipe with perforated wave valleys by conveying a plastic
pipe continuously through a perforation zone and perforating the
pipe due to the action of at least one movable punch member.
According to known methods plastic pipes are passed
through a hollow guide, punching means being pressed, by means
of a cam disc, into or through the wall of the plas~ic pipes at
selected times, forming the desired openings.
As long as the perforating operation is carried out at
a rather low rate of pipe transportation the suitable elastic prop-
erties of the material used for the punches can be selected so
that during their engagement with the plastic pipes they are
capable of bending or deflecting so that they can be removed
from the plastic pipes later on without fracture or breakage.
A disadvantage is, however, that the punches which are mounted
only for radial movement contact pipes which are being conveyed
in a direction perpendicular thereto.
To increase the conveyance rates of plastic pipes is
clearly advantageous as extruders manufacturing plastic pipes
can at present operate at considerably faster rates. Hence the
problem occurs that on the one hand punches acting upon plastic
pipes are caused to bulge or bend, which gives rise to undesired
fractures of the punches and to disturbances in the production
process, while on the other hand the punches can be easily dam-
aged by the forces produced when plastic pipes and punch contact
each other.
The invention provides a method which overcomes the
aforementioned disadvantages.
The solution is attained according to the invention by the
arrangement that at least during the time of engagement with the
plastic pipes, a movement in the direction of conveyance is im-
parted to a punch member which equals the rate o~ conveyance of
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the plastic pipes and that during their penetrating action the
punches retain substantially a perpendicular position with res-
pect to the plastic pipes.
It is thus possible to operate at much faster rates
since the speed of movement of the punches enables an operating
structure which can stand considerable bulging without fracture.
When the punches are moving in the direction of convey-
ance of the plastic pipes they can moreover be conveyed very
quickly without having to adapt their properties to these much
faster rates of conveyance, which may surpass twice or three
times the speed which is possible with known devices.
The punch member is conveniently moved reciprocally
towards and away from the pipes by means of a punch holder mounted
on two eccentrics, the movement of the punch member being related
to the rate of conveyance of the pipes.
During the entire length of engagement of the punch
with the plastic pipes the punch should be conveyed in the di-
rection of conveyance of the pipe at a rate which is identical
to the rate of conveyance of the plastic pipes. In this manner
deformation of the punches as a result of engagement with the
plastic pipes is completely avoided.
Finally it is advisable to convey a punch at a rate
in the direction of conveyance of the plastic pipes which equals
the rate of conveyance of the plastic pipes in the area in which
~- the punch is retracted from its position of engagement with the
plastic pipes. In this way a binding or deformation of the
punch is avoided during its removal from the plastic pipes. -
The invention also relates to an imposed device for
~ continuously perforating pla~tic pipes, particularly corrugated
;~ 30 pIastic pipe, comprising a guide member for the plastic pipe, a
pipe conveying member for the transportation of the plastic pipe,
a punching~l~member for punching holes in the plastic pipe and an
~ operating member for causing the punching member to perforate
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the plastic pipe.
Such devices are generally known and have the afore-
mentioned disadvantages.
In order to obviate these difficulties and in particular
to provide a device which lends itself well for perforating plas-
tic pipe when much faster rates of conveyance of the pipe are
used, the device is provided with punch member actuators for
causing the punch members to move with the same speed as the
pipe conveying members at least when the punch members act upon
the pipes to be perforated, and in order to preserve a substan-
tially perpendicular position with respect to the conveyed pipes
when the punching members are in contact therewith.
Thus, the rate of conveyance of plastic pipes can be
considerably increased without the risk of fracture or distortion,
of the punching members and without the necessity of adapting
the bending properties thereof.
In a particularly convenient fashion the punch member
actuators for causing the punch members to move with the same
velocity as the pipe conveying members (at least when the punch-
ing members are acting upon the pipe to perforate same) consist
of a first eccentric member.
The device is efficiently provided with a punching
member disposed on a punching member holder being connected with
two eccentrics which can be actuated by one driving mechanism,
while the first eccentric member acts upon the two eccentrics.
Very good results are obtained by means of this device
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~-~ since it operates very uniformly during the perforation operation,
<~ even when the pipes to be perforated are moving at very fast
rates.
The invention will now be further described with ref-
erence to the accompanying drawings which illustrate apparatus for
performing the method according to the invention, and wherein:
Figure 1 shows a front view of a device for continuous-
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ly perforating plastic pipes; and
Figure 2 is a side elevation of the device shown in
Figure 1.
The drawings show a device for continuously perforating
the wave valleys of plastic pipes, particularly corrugated thermo-
plastic pipes such as polyvinylchloride. The device has a frame
1 with a drive motor 2 driving drive gear 3 through an inter- --
mediate shaft. This driving gear 3 drives gear wheels 22 and
23 which are connected with the eccentric discs 28 and 27 respect-
ively. During rotation of the driving gear wheel 3 and the gear
wheels 22 and 23 (the gear wheels rotating all at the same speed)
the eccentric shafts 19 and 20 of the eccentric discs 27 and 28
move according to the arrows 24 and 26, whereby a downward move-
ment is imparted to the driving rods 15 and 16.
The driving rods 15 and 16 are pivotally connected
through pivots 18 and 17 to connecting beam 12 in which is pro-
vided an elongate slot 13. In this elongate slot 13 is secured
by a screw 14, a supporting beam 8, carrying pairs of punches 9,
- 9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h, 9i, 9j, and 9k, so that, when the
driving rods move downwardly the punches 9, 9a, etc. also move
downwardly.
A conveying wheel 10 is mounted for conveying a corru-
gated plastic pipe 30, which pipe may be surrounded by an en-
velope 11 with an opening 29 through which the punches can act.
~t: The envelope 11 may be channel-shaped or consist of strips be-
¦~ -tween which are open areas.
When the eccentrics are caused to act in this way upon
the punches, it is necessary to use complicated mechanisms in
order to adapt the rate of conveyance of the plastic pipe to the
velocity of the punches 9 which vçlocity is defined by the eccen-
tric shafts 15 and 16. It is, however, almost impossible in prac-
l tice to precisely control the speed of pipe movement.
J- So as to overcome this difficulty applicant provides
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a first eccentric mechanism, consisting of a cam 5 having an ecc-
entric circumference 31, mounted on a shaft 6, the latter being
connected with a cam drive gear wheel 4 which cooperates with
drive gear wheel 3.
A cam roller 32, secured to an eccentric disc 28 by
rod 33 continuously cooperates with the circumference 31 of the
cam 5, due to the action of spring 34 cooperating with a saddle
member 25 provided on eccentric disc 28 and with a saddle member
21 provided on eccentric disc 27.
The cam 5 rotates with the same speed as the eccentric
discs 27 and 28 owing to an active drive gear wheel 3. When the
circumference of the cam disc 5 and the speed of rotation thereof
are suitably selected the punches 9, 9a, etc. are moved with
the same velocity as the plastic pipes 30 during the perforating
action.
During rotation of the cam 5 and due to the eccentric
circumference thereof, the eccentric driving rod 15 will not only
be subjected to a movement of the eccentric shaft 20 but also be
influenced by the cam 5, and as a result of spring 34 driving
rod 16 undergoes the same movement as driving rod 15. This means
that the supporting beam 8 together with the punches on account
of its fixed connection with the connecting rod 12 not only
undergoes a downwardly directed movement in order to cause the
punches to penetrate the pipe 30, but also a reciprocal backward-
forward movement, respectively, to keep the linear velocity of
the supporting beam 8 uniform in spite of the usual non-uniform
velocity of the supporting beam 8 caused by the eccentrics.
Should it be desired to impart an additional left-
ward directed movement to the punches 9 in a device according to
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the invention, this can be effected by increasing the diameter
of the cam 5 at the location of the cam roller 32; when the
diameter of the cam 5 is decreased, movement of the punches more
to the right is achieved.
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The motor 2 normally drives both drive gear wheel 3
and conveyor wheel 10 for moving punches 9 and pipes 30 at an
identical rate.
In the drawing twelve pairs of opposite punches 9,
9', etc. disposed on a supporting beam 8, are shown.
Although these punches 9, 9a, 9b could all simultan-
eously contact plastic pipe 30, it is advisable to perform
perforation in sequential manner. For that purpose the lengths
of the punches differ, so that first the longest pairs of punches
9d, 9e, 9j and 9k contact the plastic pipe and subsequently
pairs of punches 9b, 9c, 9h and 9i, whereafter the remaining
pairs of punches follow.
The pairs of punches 9, 9', etc., are disposed in
planes which may assume a position perpendicular to the axis of
envelope 11, their lateral spacing being selected, of course,
such that the punches contact the pipe 30.
When the pipes have a substantially helical profile
then the pairs of punches are arranged in such a way that they
perforate in two consecutive wave valleys.
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