Tube punching method

A method of cutting a hole in the wall of a pliable tube in which the tube is flattened and is held with the walls touching each other and in which a plug is cut in one of the sidewalls while the tube is in this flattened position.

INTRODUCTION 
My invention relates to a method of punching holes in plastic tubes. 
Certain devices such as, for example, flower or vegetable dusting 
containers require flexible tubes with openings in the sides of the tubes, 
which are placed in a container, the dusting powder being forced through 
the openings and through the tubes by squeezing the container. This 
produces an imbalance in pressure which forces air and dusting material 
through a nozzle of the container and onto the flower or vegetable in the 
form of a dust. 
It is an object of my invention to provide a method of punching holes in a 
plastic or pliable tube by cutting a plug in one side of the tube and in 
which the opposite side or sidewall of the tube acts as a pliable backup 
wall which receives the cutting edge of the punch, assuring a full, 
complete and clean cut in the one sidewall of the tube and assuring that 
the cutting edge will not engage any hard or metal surfaces which might 
dull or injure the same. 
It is a further object of my invention to provide a method of cutting a 
hole in the sidewall of the plastic tube in which the tube is first 
flattened and held in flattened position and in which the punch is forced 
through one sidewall to cut a plug in that sidewall and thus form an 
opening and in which the cutting edge of the punch is moved into the 
surface of the opposite sidewall of the tube, the opposite sidewall 
forming a pliable backup pad which prevents the cutting edge from being 
damaged. 
In my method, cuttings are performed in such a way as to assure that the 
cutting edge will move completely through the near wall of the tube and 
assure that the cut is complete and that it is a clean cut. This is 
assured if the cutting edge is moved far enough so that there is at least 
a slight penetration of the side of the tube which forms the backup pad. 
It is a still further object of my invention to provide a method for 
cutting openings in the sidewall of a tube in which, on completion of each 
cutting operation in which a hole is cut in the tube, the backup pad is 
continually replaced upon the cutting of another opening, this being 
accomplished by using the back wall of the tube as the backup pad, which 
assures that a new backup area will be provided with each punching 
operation. 
It is a further object of my invention to provide a method of cutting 
openings in a sidewall of a tube in which the tube is flattened against a 
base plate to form the tube into a front wall and a back wall, the 
surfaces in contact with each other and in which the back wall of the tube 
becomes a backup pad which may be penetrated by the cutting edge of the 
cutting tool, the backup pad protecting the cutting edge from coming into 
contact with the base plate.

Referring to FIG. 1, there is diagrammatically disclosed a large reel which 
constitutes a tube supply 10. The tube which is to be punched is 
designated by the numeral 11 and is moved toward and through the series of 
punches 12, the tube 11 being fed by means of feed rollers 14. The tube 11 
is cut in proper lengths by means of the cut off device 15. 
The punches perform identical functions and therefor may be of identical 
construction and operation. It should be understood, of course, that other 
forms of the apparatus and even manual operations may be substituted for 
the punch apparatus which I have shown as a preferred way of performing 
the method of my invention. 
The tube punching apparatus includes a base plate 20 having flat surface 
21. The tube 11 is shown in contact with this surface 21 and it should be 
understood that the feed rollers intermittently feed the tube across the 
flat surface bringing successive portions of the tube 11 in a position to 
have an opening punched in it. 
The first step in the process is to flatten the tube and this is done in 
the apparatus by flattening the tube against the surface 21. The tube, 
when flattened, has the wall of the tube divided into two sides or two 
walls 23 and 24 and, when flattened, has contacting surfaces 25 and 26. 
Looking at the flattened wall from a cross sectional angle, as shown in 
FIG. 4, the two parts or walls 23 and 24 are connected together by bends 
30 and 31. The step of flattening the tube is performed by a tube 
compressor or flattener element 33 which is forced upwardly against the 
tube. However, the operation of this particular step will be described 
shortly after a foundation is laid with respect to the punch and how it 
functions. 
The punch 35 is in the form of a cylinder or annulus and has a cutting edge 
36 formed by beveling the wall as indicated at 37. The punch 35 is hollow 
as shown and receives a stripper, the function of which will be described 
at the appropriate time. The punch 35 is mounted on a plate 39 which plate 
is in turn mounted on a shaft or similar support 40 which extends into 
apparatus 44, which is not shown in detail but merely diagrammatically 
indicated as being within the housing 44. This actuator mechanism includes 
a means for moving the punch 35 and its associated parts toward and away 
from the tube. Any sort of reciprocating mechanism could be used and, of 
course, this operation could be manually performed although it is much 
more efficient to have the power mechanism for performing this and other 
functions in the performance of the method. 
Getting back now to the compressor or tube flattener 33, this element 
surrounds the punch 35 and is axially movable with respect thereto. 
Between the plate 39 and the tube flattener 33 are springs 42 which 
normally hold the parts 39 and 33, spaced from each other as shown clearly 
in FIG. 3. The parts as spaced in FIG. 3 (and also in FIGS. 2a, 2b and 2e) 
is the position of the parts when they are at rest or when the tube 
flattener 33 has engaged and flattened the tube 11 but at which time the 
punch has not moved into the wall 24 of the tube. 
Now let us assume that the first step of the method has been performed, and 
the tube has been flattened and the parts of the apparatus and the parts 
of tube are in the position as shown in FIG. 3. FIG. 3, of course, 
illustrates only one of the punches 12. One or more openings can be formed 
in the tube at this time depending upon the requirements of the tube when 
in use in a piece of apparatus. 
The pressure of the part 33 against the tube is sufficient to hold it 
firmly in the position shown. 
At this time the pressure applied for the flattening of the tube holds the 
tube against the surface 21 of the base plate 20, the front wall 24 
constitutes the wall to be perforated and the back wall 23 constitutes a 
pliable or flexible backup pad for the cutting operation. 
The cutting operation is performed which constitutes the step in the method 
of cutting the opening in the wall 24 of the tube, performed as follows. 
The punch 35, as shown in FIG. 3, is moved upward into a dotted position 47 
and the plate 39 has moved upward into the dotted position 48. This 
movement is permitted because the force of the springs 42 is overcome and 
they become compressed. 
At this time the parts are now in the position shown in FIG. 4. The cutting 
edge of the punch has moved entirely through the lower wall 24 and the 
cutting edge 50 of the punch has penetrated the surface 25 and may enter 
the upper wall 23 a slight distance. However, it is only necessary that 
the cutting edge move beyond the surface 26 so that a complete clean cut 
is made. 
The second wall 23 of the tube as stated becomes a backup pad for the punch 
device and since it is a plastic material as distinguished from a hard 
metal surface, the cutting edge is not damaged and will last a relatively 
long time before need for resharpening. 
At this time the punch has cut a plug 52 which leaves an opening 53 in the 
tube. Also at this time the top end of the stripper 38 is in engagement 
with the lower surface of the plug. 
The opening 53 having been formed in the lower wall of the tube, the next 
step is to withdraw the plug cutter and this, of course, is done by moving 
the shaft 40 downward. 
However, at this time the stripper need not move but remains in place and 
holds the plug 53 in its hole, the plug remaining in the tube to be 
removed at a later time. 
When the operation of withdrawing the punch is performed, the first thing 
that happens is the downward movement of the punch 35. However, the tube 
flattener does not at this time move but the springs are allowed to expand 
and when the springs have expanded, then the entire punching device is 
lowered. 
The sequence of the steps of the method is illustrated in FIGS. 2a to 2e 
and are briefly explained as follows. In FIG. 2a the tube has been moved 
into position for perforating and movement is stopped and the first step 
in the method is ready to be performed. The first step is the flattening 
of the tube and this is done by the upward movement of the shaft 40 which 
brings the tube flattener 33 into contact with the tube and further upward 
movement flattens the tube so that it is in the position shown in FIG. 2b. 
With the tube flattened, there is a further upward movement of the shaft 
40 and this performs the step of forming the opening in the tube. It will 
be seen that in FIG. 2c the springs 42 have been compressed to allow the 
punch 33 to move upward, the cutting edge moving through the lower wall 
portion of the tube 24 and performing a cut as a result of the parts being 
in the position as shown in FIG. 4. 
Having made the cut the parts are then moved into the position shown in 
FIG. 2d. The tube flattener remains in place and the other parts move 
downward, the springs expanding as previously described. 
The next step in the process is to move all the parts into the position 
shown in FIG. 2e in which the tube has been allowed to expand into its 
normal cylindrical shape and the parts are now in a position in which the 
tube is released and can be moved so that a further sequence of operations 
can be performed. 
An important feature of the method is that the upper or second wall of the 
tube forms the backup pad for receiving the cutting edge when the cutting 
operation is performed. The cutting edge, as previously described, moves 
into the soft material of the backup wall or pad and does not strike any 
hard surface which might damage or dull the cutting edge. 
Since the tube moves after each hole is cut, the backup pad of the tube 
becomes a constantly renewing backup pad for the cutting device or punch 
35. 
If desired, the plug which is cut from the tube may be removed at the time 
the cutting tool or punch is withdrawn from the flattened tube. This step 
in the process can be performed by the apparatus shown in FIG. 5 in which 
all of the parts are the same except that the stripper 38 is removed and 
the inner wall 60 of the tubular punch is tapered so that the plugs 52 may 
move downwardly. 
The apparatus may be simplified by eliminating the tube flattener 33. With 
this modified apparatus, flattening of the tube would be accomplished by 
the punch 35. The tube would be flattened by the sharpened end of the 
punch engaging the near wall of the tube and pushing it against the 
opposite wall. When the two sidewalls are in engagement, the punch will 
then move relative to the near wall, passing through it and forming the 
cut which produces the removable plug.