The invention concerns a punch wheel for punching at least one continuously extending row of holes, such as tractor holes in an endless web of paper or similar material, in a hole punching apparatus having punch wheels which coope¬ rate in pairs and are arranged on their respective ones of two parallel shafts rotating in opposite directions in operation, said wheel having along the periphery an out¬ wardly protruding rim which is provided with radially ex¬ tending through-going reception holes with an angular dis¬ tance corresponding to the desired hole distance, each of said reception holes being adapted to receive a punch needle or die ring, respectively, associated with a punch tool.

In the past, such punch tools have usually always had punch needles of relatively soft steel and die rings of hardened steel, and it has hereby been possible to produce the tools at a reasonable low price. Nevertheless, the use of these tools has not been inexpensive, far from it, be¬ cause they have to be replaced with rather short intervals owing to the poor wear resistance of the materials used, which each time involves costs on quite new punch tools and the not insignificant amount of work necessitated by the replacement. To this should be added the production loss which is a consequence of the frequent stoppages, where major or minor parts of the overall plant stand idle. These circumstances have been rather dissatisfac¬ tory, and it has in fact been attempted recently to im¬ prove these by employing a new type of punch tools which, as regards both the punch needles and the die rings, are made of hard metal. These new tools have a considerably longer life than before, but on the other hand the tools are rather expensive because hard metal is an expensive

material which is also difficult to machine. It is there¬ fore important that these high tool costs are distributed over a production as large as possible, and the punch needles are therefore often provided with cutting edges at both ends so that the needles can be turned when the first cutting edge has been worn down. When conventional punch wheels with simple supports for the punch needles are used, the possibilities of using the needles additionally are thereby exhausted since the needles only engage with quite few tenths of a millimeter in the corresponding die rings and therefore quite simply become too short to be able to operate when they have been worn so far down by regrinding that new cutting edges are formed. To avoid having to reject the needles for this reason, punch wheels with variable supports to compensate for the shortening caused by the regrinding operation have been developed. The task consisting in the ability to use the same tools repeatedly after regrinding has hereby been solved as far as it goes. However, all the known structures used for this purpose are cumbersome and time- consuming to adapt to a new reground set of tools since, as far as some structures are concerned, such adaptation requires that the wheel is first removed fully or partly from the hole punching apparatus, while, as far as other structures are concerned, the support can only be varied steplessly such that the height of the punch needles with respect to the die rings cannot or not very well be adjusted with the necessary precision and certainty.

The object of the invention is therefore to provide a punch wheel of the type stated in the opening paragraph, which, in support of the punch needles or the die rings, have supports which can be changed stepwise and thereby adjust the punch wheel faster and safer than known before from one predetermined support depth to another.

This is achieved in that the punch wheel of the invention is characterized in that a plurality of support rings are arranged inside the rim, which are rotatably mounted on a cylinder face on the wheel or shaft disposed radially be- low the rim, and which serve to support the punch needles or die rings; that said rings all have an outer cylinder face which is fully or partly positioned between two radi¬ ally extending tangent planes of the reception holes; that one or more rings have an outside diameter which is greater than the outside diameter of the other rings; and that these larger rings are each provided with a plurality of cutouts which are arranged with the same mutual angular distance as the reception holes, and extend in a width of at least the same size as the clear of the reception holes inwardly to a diameter which is smaller than at least the greatest outside diameter of the outside diameters of the said other rings. The support depth can hereby be varied stepwise since the punch needles or die rings are sup¬ ported by the largest ring of those whose cutouts are not disposed below the reception holes.

Further, according to the invention, the punch wheel may be arranged such that at least the support rings provided with cutouts can detachably be locked in at least one first position in which the cutouts are present below the reception holes, and at least one second position in which the outer cylinder face segments left between the cutouts are present below the reception holes. This entails that the punch wheel can quickly and safely be adjusted to a new reground tool length merely by turning the support ring corresonding to this to its second position, while the other, larger rings are placed in their first position.

Moreover, in an advantageous embodiment according to the invention, the above-mentioned detachable locking of the

rings can take place by means of a first wire spring or leaf spring engaging with a free hook-shaped end part with a cutout in the respective ring in the first position thereof, and a second corresponding spring likewise engag- ing with a free hook-shaped end part with a cutout in the ring in the second position thereof.

Further, according to the invention, the punch wheel may be arranged such that the support rings are all provided with cutouts except the smallest one, which carries an ad¬ justment pin extending freely accessibly out through the side wall of the housing via an adjustment slot provided substantially co-axially in said side wall and having a separate locking means for each ring for releaseably lock- ing the adjustment pin in determined adjustment positions, which as regards the smallest ring are located in a pre¬ selected end of the adjustment slot, while the rest are distributed along it with equal angular distances which are half the angular distance of the reception holes; that the smallest ring moreover supports one driving pin extending through a driving hole in the next-to-the- smallest ring mating with the driving ring, as well as through co-axially arranged driving slots in the other rings, whereby the rearmost end of each driving slot, seen in the direction of rotation of the adjustment pin, is disposed in a corresponding angular position with respect to one of the cutouts of the ring as the driving hole of the next-to-the-smallest ring, and the angular distance between the slot ends of the third largest ring is equal to the greatest angular distance between two driving shoulders on the driving pin plus half the angular dis¬ tance of the slot ends, while the angular distance of the slot ends then increases by half the angular distance of the reception holes each time the number of rings is increased by another larger ring in addition to the three smallest ones; and that the adjustment slot moreover has

such an angular position with respect to one of the reception holes of the wheel that the cutouts of the next- to-the-smallest ring are positioned radially below a reception hole when the adjustment pin is kept locked by the locking means of the smallest ring. The punch wheel may then be adjusted in a single movement merely by turning the adjustment pin to the desired adjustment depth corresponding to the adjustment position in the adjustment slot.

In a particularly simple and advantageous embodiment the smallest ring may moreover be secured to the wheel or be an integral component of it, whereby the adjustment slot in the side wall of the wheel continues transversely in- wardly through this smallest ring, and the next-to-the- smallest ring carries both the adjustment pin and the driving pin.

Additionally, according to the invention, the above-men- tioned locking means may be lock notches which are pro¬ vided in the adjustment slot or in a locking plate arranged at it, and which serve to receive part of the adjustment pin, said adjustment pin being secured with a spring on the smallest ring so biassed as to force the adjustment pin radially resiliently into a lock notch associated with a desired adjustment position. This pro¬ vides a particularly simple and effective construction.

Moreover, according to the invention, the support rings may have a diameter which differs from the diameters of the other rings and which is just as much greater than the diameter of the sizewise preceding ring as the distance a punch needle or die ring is ground down when reground, whereby the correct distance between punch needles and die rings is always ensured with great precision.

To obtain a particularly well-arranged position of the support rings these may be placed in a row with stepwise increasing ring diameter according to the invention.

Moreover, with a view to obtaining effective function of punch wheel with die rings the gap between the two radial tangent planes to the holes of the die rings may be kept free from support rings according to the invention.

Finally, according to the invention, the punch tools may be given a marking colour which is changed to another marking colour for each regrinding operation, and the adjustment position corresponding to the new length may be marked with the same colour on the wheel to make it readi- ly apparent how the adjustment pin is to be adjusted to obtain the support depth corresponding to the colour in question and thereby to the tool length.

The invention will be explained more fully by the follow- ing description of an exemplary embodiment with reference to the drawing, in which

fig. 1 is a schematic top view of a hole punching appara¬ tus,

fig. 2 shows punch wheels cooperating in pairs for the hole punching apparatus shown in fig. 1,

fig. 3 is an enlarged view of a punch tool consisting of a punch needle and a die ring with associated shim,

fig. 4 shows the same, but after regrinding,

fig. 5 shows the same, but after another regrinding opera- tion,

fig. 6 is a perspective partially sectional view of a fraction of a punch wheel mounted with the punch needle shown in fig. 3,

fig. 7 shows the same, but in a second adjustment position and mounted with the punch needle shown in fig. 4,

fig. 8 shows the same, but in a third adjustment position and mounted with the punch needle shown in fig. 5,

fig. 9 is a side, partially sectional view of the punch wheel of fig. 2,

fig. 10 is a section along the line X-X in fig. 9, and

fig. 11 is a side view on an enlarged scale of a fraction of the wheel with an adjustment slot in which an adjust¬ ment pin associated with the wheel is placed in the start¬ ing position shown with position I in fig. 9.

Endless webs of paper or similar material are provided with continuously extending rows of holes in many cases. This is e.g. the case with the so-called Leporello paper, where a row of holes having a diameter of about 4 mm and a mutual distance of about 12.7 mm are punched along each of the edges of the web of paper. These holes are used as tractor holes for moving the paper web forwardly in a printer which is coupled to a computer and serves as a read-out unit for it.

The holes are usually punched by means of punch wheels co¬ operating in pairs, which are indicated by 1, 2 in the drawing and are mounted on their respective ones of two mutually parallel shafts 3, 4 placed one above the other.

Fig. 1 is a schematic top view of a hole punching appara¬ tus which is generally indicated by 5. The figure only shows the upper shaft 3, which is in this case provided with two sets of punch wheels 1, 2 punching two rows of holes 7 along the edges 8 on a paper web 6 when the shafts 3, 4 are caused to rotate by means of a motor 9 and two sets of cooperating gear wheels 10, 11, of which only the upper wheel is visible. The paper web is hereby moved through the hole punching apparatus 5 in the direction indicated by the arrow A, but this feed can also take place in that the wheels 1, 2 are rotated by the paper web 6, which is then itself pulled through the apparatus 5, or by a combination of these two methods.

The actual punching process is performed by means of punch tools 12, which, as shown in fig. 2, consist of punch needles 13 mounted along the periphery of the upper wheel 1 and corresponding die rings 14 mounted along the peri¬ phery of the lower wheel 2. The punch tools 12, which are shown on an enlarged scale in figs. 3, 4 and 5, are se¬ cured in reception holes 16, 17, which are shown best in figs. 9 and 10, and which are provided in rims 18, 19 ex¬ tending outwardly along the periphery of the upper and lower wheels 1, 2, respectively. Each of the punch needles 13 is secured in the associated reception hole 16 by means of a set screw 21, which is screwed inwardly against a milled face 22 in the punch needle 13, which moreover treads with the inner end on a cylinder face 20, which is disposed radially inside the rim 18 and whose diameter may be varied in a manner which will be explained more fully below. Each of the die rings 14 abuts an internal shoulder 23 in the reception hole 17 via a shim 15 and is kept fixed in it by means of a screw 24.

As shown by way of example in figs. 9 and 10, each punch needle 13 just extends quite slightly, e.g. less than 1/2

mm, down into the corresponding die ring 14, since this is sufficient for punching in such a thin material as paper, and since, otherwise, the tools would be subjected to ex¬ cessively great wear, said tools being disengaged during rotation in the same manner as gear wheel teeth, without having a corresponding favourable shape as the engagement faces of these teeth. Measured in the pitch circle, i.e. the circle where the punch needles and the die rings en¬ gage with one another, the tools 12 have a mutual distance or pitch a, whereby the holes 7 will be punched with this distance a in the paper web 6. All the reception holes 16, 17 in the rims 18, 19 extend radially inwardly towards the centre of the respective wheel and have a mutual angular distance corresponding to the pitch a.

The punch tools 12 may be made of any suitable material, but are preferably made of hard metal, which gives the tools a long life, but on the other hand they will be so expensive that it is desirable to use the tools once or several times after regrinding so that the high tool costs can be distributed over a production as large as possible.

When the tools have been worn so much that they can no longer perform satisfactorily, they are therefore ground as shown in figs. 3, 4 and 5, where fig. 3 shows a new tool, fig. 4 a tool ground once, and fig. 5 a tool ground twice. Grinding may e.g. be up to 0.75 mm per cutting edge, so that the length of the punch needles 13 is reduced by a total of 1% mm while the die rings 14 will be 0.75 mm shorter, i.e. a total of 2% mm. Since, as previously mentioned, the engagement depth of the tools is just a few tenths of a millimeter the punch needles and the die rings of the tools can no longer reach one another and therefore cannot operate if conventional punch wheels with simple supports are used. In order that the punch tools can nevertheless be used after having been ground

down, the punch wheel of the invention is provided with variable supports which, in the shown embodiment, consist of the washers 15 for the die rings and of three specially shaped support rings 25a, 25b, 25c for the punch needles.

As shown clearly in fig. 10, these rings are rotatably mounted, e.g. with a slide fit, on an inner cylinder face 16 provided on the upper wheel 1, and each ring 25a, 25b, 25c has an outer cylinder face 27a, 27b, 27c, respec- tively, which is disposed radially below the reception holes 16 and serves as a support for the punch needles 13. The outside diameter of the rings varies at intervals corresponding to the length reduction of the punch needles for each grinding. The outside diameter of the ring 25a thus mates with the punch needle 13a shown in fig. 3, the outside diameter of the ring 25b with the punch needle 13b shown in fig. 4, and the outside diameter of the ring 25c with the punch needle 13c shown in fig. 5.

The three support rings are aligned with the smallest ring 25a outermost. When the punch needles are new, they must, as appears from the foregoing, be supported by this smallest ring 25a, which may be in any position because is has an unbroken cylinder face 27a. In contrast the two larger rings 25b, 25c have cutouts 28b, 28c emanating from their respective outer cylinder face 27b, 27c and extend¬ ing radially inwardly in a slightly greater width than the diameter of the punch needles to a depth imparting to the bottom of the cutouts a diameter which is smaller than the outside diameter of the smallest ring 25a. These cutouts are positioned with the same mutual angular distance α as the reception holes 16, and the two largest support rings 25b, 25c can therefore always be turned to a position where the cutouts 28b, 28c, as shown in fig. 6, are in the same angular position as the punch needles 13 and there¬ fore allow these to be moved down to rest on the outer

cylinder face 27a of the smallest ring 25a. If the next- to-the-smallest ring 25b is now turned from this first position half the angular distance a to the second position shown in fig. 7, where the cylinder faces 27b left between the cutouts 28b are in the same position as the punch needles 13, these will rest on the outer cylin¬ der face 27b on the next-to-the-smallest ring 25b, so that the wheel 1 may be used for the punch needles 13 shown in fig. 4 which have been ground once. If the largest ring 25c is then turned to its second position, which is shown in fig. 8 and where the cylinder face segments 27c disposed on this ring between the respective cutouts 28c, have the same angular position as the punch needles 13, these will now rest on this ring 25c, so that the wheel can be used for the shortest punch needles shown in fig. 5 which have been ground twice.

All three adjustment positions are drawn on the same wheel 1 in fig. 9 where they are indicated by I, II and III. To facilitate the adjustment, two oppositely facing, uniform wire or leaf springs 29 are arranged inside the wheel, the ends of said springs being each bent to a hook 30 which can alternately engage with one of the cutouts 28c of the largest ring 25c, since the two hooks are placed with a mutual angular distance which is an uneven multiple of 1/2 a . During turning of the two smallest rings, the largest ring is therefore kept locked in the first position by the first hook 30, but may, if desired, easily be turned to the second position where the ring is now locked by the second hook 30.

As shown in e.g. fig. 10, the smallest ring 25a carries a support pin 31 extending out through the side wall 32 of the wheel via an adjustment slot 33 arranged concentri- cally with the wheel. As shown best in fig. 11, the upper edge of this is formed with three lock notches 34a, 34b,

34c with a mutual angular distance of 1/2 α. These lock notches serve to receive the adjustment pin 31 and to lock it in predetermined adjustment positions, each of which mates with one of the punch needles 13a, 13b, 13c, whereby the adjustment position of the smallest ring 25a is in the rear end of the slot 33, seen in the direction of rotation of the adjustment pin 31 during adjustment of the wheel. The smallest ring 25a moreover carries a driving pin 35, which extends transversely through a driving hole 36, mat- ing with the pin, in the next-to-the-smallest ring 25b, which therefore performs an angular rotation of 1/2 a when the adjustment pin 31 is shifted from the first notch 34a to the second notch 34b in the adjustment slot 33. The driving pin 35 extends further inwardly through the largest ring 25c via a driving slot 37 arranged concentri¬ cally in it, as shown best in figs. 6, 7 and 8. The angu¬ lar distance between its front end, seen in the direction of rotation, to the driving pin 35 when this is present in the rear end of the driving slot 37, is 1/2 α. When the adjustment pin 33 is therefore rotated from the central lock notch 34b to the last lock notch 34c in the adjust¬ ment slot 33, the largest ring 25c will now also be carried along in. the rotary movement and will perform an angular rotation of 1/2 a .

The rear end of the driving slot 37 of the largest ring 25c is placed in the same angular position with respect to one of the cutouts 28c of the ring as the driving hole 36 in the next-to-the-smallest ring 25b with respect to one of the cutouts 28b of this ring. The adjustment slot 33 is simultaneously placed in such an angular position with re¬ spect to one of the punch needles 13 that the cutouts 28b of the next-to-the-smallest ring 25b are placed radially below the reception holes 16 when the adjustment pin 31 is kept locked in the lock notch 34a of the smallest ring 25a.

When the punch wheel is now to be used with a set of new punch needles 13, i.e. punch needles which have not been reground, the adjustment pin 31 is placed in the first lock notch 34a of the adjustment slot 33. This entails that the cutouts of the two largest rings 25b, 25c will automatically be in their first position where they provide clearance for the punch needles 13, which then rest on the cylinder face 27a of the smallest ring 25a. When the adjustment pin 31 is then turned to the central lock notch 34b of the adjustment slot 33, the next-to-the- smallest ring 25b will simultanesouly be turned and automatically shift to the second position in which the wheel 1 now fits the punch needles 12b which have been ground once; the largest ring 25c will not be carried along in the rotary movement since the driving pin 35 merely performs a relative angular rotation of 1/2 a in the driving slot 37 of this ring 25c. However, the driving pin 35 has been turned so far as is possible in the driving slot 37 of the largest pin 25c so that this wheel too is turned when the adjustment pin 31 is turned further to the last notch 34c in the adjustment slot 33. Since the largest ring 25c will hereby be turned through an angle of 1/2 α, this ring will now also be in its second position, whereby the wheel can be used for the punch needles 13c which have been ground twice.

There are no more adjusting possibilities in this embodi¬ ment, and it is therefore necessary to reject the punch tools when they are worn out following two regrindings, but this embodiment has provided the considerable advantage that it has been possible to use the tools for a production three times as great as is the case when using conventional wheels with simple supports for the tools.

The adjustment pin 31 is turned back again to the first lock notch 34a, thereby turning all the rings back to

their starting positions. The wheel is now ready for mounting of a set of new tools, and then the above- mentioned adjustment process in connection with the regrinding of the tools can be carried out again.

As shown in fig. 10, the adjustment pin 31 is positioned on a leaf spring 38 secured to the smallest ring 25a with rivets 39 or in another manner so that the adjustment pin 31 is kept against the upper edge of the adjustment slot 33 by means of a biased spring force and is thereby auto¬ matically centered and retained in a desired lock notch 34a, 34b, 34c. When the adjustment pin is to be shifted to one of the other lock notches, it is pressed downwards against the spring force and can then readily be shifted along the adjustment slot.

In a particularly simple and advantageous embodiment of the punch wheel, the smallest ring 25a is firmly posi¬ tioned in the wheel or constitutes an integral part of it. In this case the adjustment slot 33 is provided in the smallest ring as well, and it is then the next-to-the- smallest ring 25b which carries both the adjustment pin and the driving pin 35. In this embodiment the wheel operates in quite the same manner as described above for the first embodiment.

The invention is described above on the assumption that the wheel was provided with three support rings. However, the wheel may have as many rings as is desired, since the number of these is substantially determined by the number of regrindings which it is expedient to perform in prac¬ tice. But, regard must also be had to the stability of the construction since the rings, if they get too thin, will not be able to withstand the loads to which they are subjected during the punching process. The driving slots of these additional rings are adapted such that the angu-

lar distance between their slot ends is increased by half the angular distance a of the reception holes each time the ring number is increased by another large ring in ad¬ dition to the three smallest ones.

The quite significant advantage is obtained in all cases that the punch needles are supported by the cylinder faces of the rings, which can be machined by a simple and inex¬ pensive turning and/or grinding process to dimensions within narrow tolerances, while the cutouts which have to be milled only require rough machining since they are only to serve as clearance for the punch needles.

The punch wheel of the invention can of course also be used for the die rings. It will be advantageous in this case to keep the gap between the two radial tangent planes to the openings of the die rings free from support rings so that the punched material can escape from the wheel.

Thus, the punch wheel according to the invention makes it possible to use expensive punch tools of hard metal several times, since the wheel for each regrinding can quickly and easily be adjusted to the new ground tool length merely by shifting the adjustment pin from one lock notch to the next, so that the support ring to be used in each individual case will automatically be placed in support position. The actual regrinding will frequently take place in special workshops where the tools are then provided with a specific colour code for each regrinding. For example, the new tools may thus be marked in white, which may then be changed to blue when the tools have been reground once, and then additionally to red when they have been reground twice. This colour code enables the operator to immediately decide how the wheel is to be adjusted without having to perform a cumbersome and time- consuming measurement of the tools. To facilitate the work

of the operator additionally, the adjustment positions on the wheel may be marked with the same colours as the associated tools.