Driving unit for the knife holders of cross cutters or the like

One of the two knife holder shafts in a cross cutter for webs of paper or the like is driven by a unit wherein a motor rotates the input shaft of a bevel gear drive whose output shaft drives or constitutes one shaft of a universal joint. The other shaft of the universal joint is driven by the one shaft and transmits torque to the knife holder shaft or shafts by way of a step-up gear transmission and a clutch which allows for changes in angular positions of the knife holder shafts with reference to the universal joint. An extension of the axis of the input shaft of the bevel gear drive intersects the axes of the shafts of the universal joint at the point where the axes of the shafts of the universal joint intersect each other. To this end, the other shaft of the universal joint contains an elastically deformable but torsion-resistant insert. The angle between the axes of the shafts in the universal joint can be changed by a carrier which is turnable about the axis of the input shaft of the bevel gear drive and rotatably supports the one shaft of the universal joint.

CROSS-REFERENCE TO RELATED CASES 
Apparatus which sever running webs of paper or the like at desired 
intervals to form a succession of discrete sheets are disclosed in U.S. 
Pat. Nos. 4,201,102 and 4,255,998 to Rudszinat respectively granted May 6, 
1980 and Mar. 17, 1981. 
BACKGROUND OF THE INVENTION 
The present invention relates to apparatus for severing one or more running 
webs, strips, tapes or bands of paper, textile material, cardboard, 
metallic foil, plastic foil or the like, and more particularly to 
improvements in driving units for so-called cross cutters which are 
utilized to repeatedly sever a running web, band, strip or tape at desired 
intervals so that the running material yields a file of discrete plates, 
panes, panels or sheets. As a rule, such cross cutters employ one or more 
orbiting knives which are adjacent to the path of lengthwise movement of 
the material to be severed and each of which severs the web, band, strip 
or tape once during each of its orbital movements. 
It is already known to drive the knife or knives of a cross cutter by a 
unit which employs universal joints serving to ensure that the knife or 
knives advance at the speed of the material to be severed in the course of 
the actual severing operation but that the knife or knives move or can 
move at a different speed during travel away from and back to the severing 
station. The angle between the axes of the input and output shafts of the 
universal joints can be varied by a mechanism which normally includes an 
angle drive and serves to change the inclination of the input shaft with 
reference to the output shaft. Reference may be had to East German Pat. 
No. 51,105 which discloses a driving unit having a drive shaft mounted in 
parallelism with the shaft for the knife of the cross cutter. The drive 
shaft is connected with a first bevel gear through the medium of a pair of 
universal joints and a telescoped shaft between the two joints. The first 
bevel gear mates with a second bevel gear which is movable lengthwise of a 
splined shaft. Furthermore, the two bevel gears are connected to each 
other by a bearing so that the first bevel gear is compelled to share the 
movements of the second bevel gear in the axial direction of the splined 
shaft. The latter extends transversely of the knife shaft and of the drive 
shaft and is connected with the knife shaft by a second pair of bevel 
gears. 
A drawback of the just described patented driving unit is that it is bulky, 
complex and expensive. Furthermore, the play between the parts which are 
movable with reference to each other is quite pronounced, especially if 
one compounds the clearances between all of the elements which are 
installed between the input element of the driving unit and the knife 
shaft. Such pronounced play is of no consequence in connection with the 
production of certain commodities, such as in bag making machines which 
are specifically referred to in the East German patent. However, an 
accurate and reproducible cutting operation is quite important in certain 
other fields, such as in the making of steno pads, exercise books, memo 
pads and like stationery products wherein the neighboring sheets and/or 
covers must overlie each other with a high degree of accuracy. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of the invention is to provide a novel and improved driving unit 
for the moving parts of a cross cutter and to construct and assemble the 
driving unit in such a way that it is simpler, more compact and less 
expensive than heretofore known driving units. 
Another object of the invention is to provide a driving unit whose 
versatility considerably exceeds that of heretofore known driving units 
and which can transmit motion to a cross cutter in such a way that the 
severing action is more reproducible than in machines utilizing cross 
cutters and conventional driving units therefor. 
An additional object of the invention is to provide the driving unit with 
novel and improved means for varying the length of sheets, plates, panes, 
panels or like products which are obtained in response to repeated 
severing of a running web, strip, tape or band of paper, cardboard, 
textile material, synthetic plastic material or metallic foil. 
Still another object of the invention is to provide the driving unit with 
novel and improved means for selecting the speed at which the knife or 
knives of the cross cutter move in the course of the actual severing 
operation. 
An ancillary object of the invention is to provide a novel and improved 
universal joint for use in a driving unit of the above outlined character. 
Still another object of the invention is to provide a novel combination of 
an angle drive and a universal joint for use in a driving unit of the 
above outlined character. 
A further object of the invention is to provide novel and improved torque 
transmitting means between the driving unit and the shaft or shafts of the 
knife holder or holders in the cross cutter. 
Still another object of the invention is to provide a novel and improved 
separable connection between the aforementioned driving unit and the cross 
cutter. 
The invention resides in the provision of a driving unit for a rotary 
member (e.g., a shaft which carries a drum-shaped knife holder) in a cross 
cutter for one or more running webs of paper or the like. The driving unit 
comprises an angle drive (e.g., a pair of mating bevel gears and their 
shafts) having a rotary input element (such as the shaft for one of the 
bevel gears) and a rotary output element (such as the shaft for the other 
bevel gear) receiving torque from the input element, a prime mover or 
other suitable means for rotating the input element of the angle drive, 
and a universal joint including a rotary input shaft which is driven by 
the angle drive, which may constitute the output element of the angle 
drive and which has a first axis, and a rotary output shaft which is 
driven by the input shaft and has a second axis intersecting the first 
axis at a predetermined point. One of the shafts is movable with reference 
to the other shaft to thereby change the angle between the first and 
second axes, and the input element of the angle drive has a third axis 
which intersects the first and second axes at the aforementioned point. 
The driving unit further comprises carrier means rotatably mounting the 
output element of the angle drive and the input shaft and being movable 
about the third axis to thereby change the aforementioned angle, and means 
for transmitting torque from the output shaft of the universal joint to 
the rotary member of the cross cutter. 
At least one of the shafts in the universal joint preferably includes at 
least one elastically bendable torsion-resistant element; such 
torsion-resistant element can be interposed between two normally coaxial 
portions of the output shaft. 
The torque transmitting means preferably comprises a transmission, 
especially a step-up gear transmission with a ratio of two-to-one. 
Furthermore, the torque transmitting means may comprise means for changing 
the angular position of the rotary member in the cross cutter with 
reference to the universal joint, and such changing means preferably 
comprises a device for turning the rotary member of the cross cutter 
through 90 degrees with reference to the universal joint. The just 
mentioned device preferably includes a clutch which is interposed between 
the step-up transmission and the rotary member of the cross cutter and 
comprises a first clutch element driven by the transmission and a coaxial 
second clutch element driving the rotary member of the cross cutter. One 
of the clutch elements is connectable to the other clutch element in two 
different positions at an angle of 180 degrees to one another. 
The driving unit can further comprise manually operated or motor driven 
means for turning the carrier means about the third axis to thereby change 
the aforementioned angle between the first and second axes, and such 
turning means can comprise mating gears (e.g., a gear segment on the 
carrier means and a pinion mating with the segment and being rotatable by 
hand or by a motor). 
The novel features which are considered as characteristic of the invention 
are set forth in particular in the appended claims. The improved driving 
unit itself, however, both as to its construction and its mode of 
operation, together with additional features and advantages thereof, will 
be best understood upon perusal of the following detailed description of 
certain specific embodiments with reference to the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, there is shown a cross cutter including two 
rotary drum-shaped knife holders 31, 33 for elongated knives 32, 34 which 
cooperate with one another to sever, at desired intervals, at least one 
running web W of paper or the like. The web W is transported through the 
nip of the holders 31, 33 at right angles to the plane of FIG. 1 in a 
manner not forming part of the present invention. Reference may be had to 
U.S. Pat. No. 4,157,821 granted June 12, 1979 to Paul Fabrig. The shafts 
26 and 36 of the respective knife holders 31, 33 are mounted in suitable 
bearings B which, in turn, are installed in the stationary frame 3 of the 
machine embodying the cross cutter. Such cross cutters are utilized in 
machines for the making of writing pads, exercise books, spiral bound 
steno pads or analogous stationery products. 
In accordance with a feature of the invention, the driving unit for the 
shafts 26, 36 (which are kinematically connected to each other by mating 
spur gears 37, 38 so that they rotate at the same speed but in opposite 
directions) comprises a novel combination of a universal joint 16 and an 
angle drive 12. The latter comprises two mating bevel gears 13, 14 whose 
axes intersect each other at a point P and whose shafts are respectively 
denoted by the reference characters 9 and 11. The shaft 9 is the input 
shaft of the angle drive 12 and receives torque from a prime mover PM, 
e.g., the main prime mover of the machine wherein the cross cutter is 
installed and which serves to turn out pads, exercise books or like 
commodities (or simply a succession of paper sheets, plastic sheets or 
other sheet-like products of desired size and shape). 
The shafts 9 and 11 for the bevel gears 13, 14 are journalled in a carrier 
1 which is a substantially U-shaped body and is turnable about an axis 2 
coinciding with the common axis of the input shaft 9 and bevel gear 13 and 
making an angle of 90 degrees with an axis 10 which is common to the shaft 
11 and bevel gear 14. The carrier 1 is turnable about the axis 2 in the 
aforementioned stationary frame 3. The shaft 9 of the angle drive 12 is 
rotatable in one of two bearings 4, and each of these bearings comprises a 
disc-shaped annular bearing member 6 which is caused to bear against the 
adjacent portion of the carrier 1 under the action of a hydraulic fluid 
(e.g., oil) which is admitted into and maintained in pressurized condition 
in a cylinder chamber 7 of the frame 3. Those portions of the frame 3 
which are formed with the chambers 7 constitute cylinders reciprocably 
receiving the corresponding bearing members 6. Each of these bearing 
members can be said to constitute an annular piston or plunger which is 
biased against the carrier 1 when the respective cylinder chamber 7 is 
filled with a pressurized hydraulic fluid. The carrier 1 has two collars 8 
which are held in abutment with the adjacent portions of the frame 3 when 
the chambers 7 are filled with pressurized fluid. The two bearings 4 are 
coaxial with one another, i.e., the axis 2 constitutes a common axis for 
these bearings. 
The output shaft 11 of the angle drive 12 constitutes the input shaft of 
the aforementioned universal joint 16 which further comprises an output 
shaft 19 carrying a gear 18. The connection between the shafts 11 and 19 
comprises an elastically flexible or bendable but torsion-resistant torque 
transmitting element 17, e.g., an element made entirely of steel and 
manufactured by the firm A. Friedrich Flender GmbH & Co. KG, Bocholt, 
Federal Republic Germany. The inclination of the axis of the shaft 11 with 
reference to the axis 10a of the shaft 19 can be changed by turning the 
carrier 1 about the axis 2. Irrespective of the selected angular position 
of the carrier 1 with reference to the shaft 2, the axes 2, 10, 10a of the 
shafts 9, 11, 19 invariably intersect each other at the point P. 
The gear 18 on the output shaft 19 of the universal joint 16 meshes with a 
gear 20 on an intermediate shaft 22 which is coaxial with the rotary 
member or shaft 26. The gears 18 and 20 constitute a step-up transmission 
21 with a ratio of two-to-one, i.e., the RPM of the intermediate shaft 22 
is twice that of the output shaft 19. The shaft 22 further carries the 
male element 24 of a clutch whose female element 28 is rigid with the 
shaft 26 for the knife holder 31. The male clutch element 24 has two pins 
23 which are disposed diametrically opposite each other with reference to 
the axis of the shaft 22 and can enter complementary recesses or bores 27 
of the clutch element 28. The shaft 22 is reciprocable in the directions 
indicated by a double-headed arrow 29 without necessarily moving the gear 
20 out of mesh with the gear 18 of the step-up transmission 21. Thus, the 
clutch including the clutch elements 24 and 28 can be engaged in two 
different angular positions of the clutch element 28 with reference to the 
clutch element 24, and the angular spacing between such positions equals 
180 degrees. 
The carrier 1 has a gear segment 39 or a complete gear which meshes with a 
pinion 41 on a shaft 42. The latter can be rotated by hand or by a 
suitable servomotor to thereby turn the carrier 1 about the axis 2 and 
change the inclination of the axis 10 of the input shaft 11 with reference 
to the axis 10a of the output shaft 19. In other words, angular 
adjustability of the carrier 1 renders it possible to change the angle 
between the axes 10, 10a, of the input and output shafts 11, 19 of the 
universal joint 16 while such axes continue to intersect each other and 
the axis 2 at the point P. 
The operation of the driving unit of FIG. 1 is as follows: 
The input shaft 9 of the angle drive 12 is rotated by the main prime mover 
of the machine embodying the cross cutter or by a discrete prime mover 
(such as the prime mover PM shown in FIG. 1) which is driven in 
synchronism with the main prime mover of the machine and rotates the input 
shaft 9 of the angle drive 12 at a constant angular speed. The bevel gears 
13, 14 cooperate to rotate the output shaft 11 of the angle drive 12 at a 
speed which is identical with or proportional to the speed of the input 
shaft 9, depending on the ratio of the gears 13, 14 (it is assumed that 
the gears 13 and 14 are identical). 
The angular velocity of the output shaft 19 of the universal joint 16 
varies periodically in dependency on inclination of the axis 10 of the 
input shaft 11 with reference to the axis 10a of the output shaft 19. Such 
angle can be adjusted by turning the carrier 1 about the axis 2. As 
mentioned above, the output shaft 11 of the angle drive 12 constitutes the 
input shaft of the universal joint 16. This contributes to simplicity, 
lower cost and compactness of the driving unit. The non-uniform angular 
velocity of the output shaft 19 is transmitted to the shaft 26 by way of 
the step-up transmission 21, i.e., at the ratio of two-to-one, and the 
shaft 26 drives the shaft 36 at the same speed by way of the gearing 38, 
37. The knives 32 and 34 cooperate to sever the web W when the angular 
velocity of their shafts 26 and 36 reaches the maximum or minimum value, 
i.e., when the angular velocity of the shaft 22 is highest or lowest. 
Whether the knives 32, 34 sever the web W while moving at the maximum 
speed or at the minimum speed depends on their angular positions with 
reference to the universal joint 16, and such angular positions can be 
changed by disengaging the clutch including the clutch elements 24, 28 
(i.e., by moving the intermediate shaft 22 to the left-hand end position 
which is shown in FIG. 1), by thereupon rotating the clutch element 28 and 
knife holder 31) through an angle of 180 degrees (which, in view of 
selected transmission ratio of the transmission 21, corresponds to an 
angular displacement of the shaft 26 through 90 degrees with reference to 
the shaft 19 of the universal joint 16), and by finally reengaging the 
clutch (i.e., by moving the shaft 22 to its right-hand end position so as 
to reconnect the clutch element 24 with the clutch element 28 but after an 
angular displacement of the clutch element 28 through one-half of a full 
revolution). In other words, an angular displacement of the shaft 26 (and 
hence also of the shaft 36, holders 31, 33 and knives 32, 34) through 180 
degrees entails an angular displacement of the knives 32, 34 through 90 
degrees with reference to the universal joint 16. 
The extent of lack uniformity of angular movement of the output shaft 19 
during movement between the two angular positions in which the RPM of this 
shaft matches the RPM of the input shaft 11 can be varied in the 
aforedescribed manner, i.e., by the simple expedient of changing the 
position of the carrier 1 with reference to the axis 2. In other words, 
the carrier 1 can be turned by the shaft 42 and pinion 41 to change the 
inclination of the axis 10 of the input shaft 11 with reference to the 
axis 10a of the output shaft 19 of the universal joint 16. 
It will be noted that the angle drive 12 is located upstream or ahead of 
the universal joint 16, as considered in the direction of power flow from 
the prime mover PM to the shafts 26, 36 of the cross cutter, and that the 
axis (2) of the input shaft 9 of the angle drive 12 intersects the axes 
10, 10a of the input and output shafts 11, 19 of the universal joint 16 at 
one and the same point P. This contributes to compactness of the improved 
driving unit and to substantial reduction of the overall number of 
component parts so as to reduce the likelihood of excessive or extensive 
wear, unnecessary play between moving parts and cost of the driving unit. 
The provision of the carrier 1 which is turnable about the axis 2 of the 
input shaft 9 renders it possible to change the angle between the axes 10, 
10a of the shafts 11, 19 (i.e., the angle between the axes of the shafts 
forming part of the universal joint 16 and hence the extent of deviation 
of angular velocity of the output shaft 19 from the angular velocity of 
the shaft 11 during certain stages of rotation of the shaft 19). The 
driving unit of the present invention employs a single angle drive and a 
single universal joint. This constitutes a substantial simplification when 
compared with the driving unit of the aforediscussed East German Pat. No. 
51,105 which employs two universal joints and two angle drives. 
Furthermore, the improved driving unit need not employ a splined shaft for 
axial movement of component parts of the angle drive and/or a composite 
(telescoped) cardanic shaft between a pair of universal joints. All this 
greatly reduces the space requirements, complexity and cost of the 
improved driving unit and reduces the likelihood of undesirable play 
between the articulately connected parts of the improved driving unit. 
The driving unit of FIG. 1 exhibits the additional advantage that the 
output shaft 11 of its angle drive 12 constitutes the input shaft of the 
universal joint 16. This further reduces the space requirements and 
enhances the simplicity of the driving unit. 
As stated above, the axes 10, 10a of the shafts 11, 19 of the universal 
joint 16 intersect each other at a point P where such axes also intersect 
the axis 2 of the input shaft 9 of the angle drive 12. As a rule, this 
requirement cannot always be satisfied with a maximum degree of accuracy 
owing to manufacturing and assembling tolerances. The aforementioned 
elastically bendable but torsion-resistant element 17 is provided in order 
to counteract the forces which develop as a result of possible presence of 
aforementioned tolerances, i.e., in the event of lack of intersection of 
all of the aforementioned axes (of the shafts 9, 11 and 19) at a single 
point. The element 17 can be installed between another pair of shafts 
including the shafts 9, 11 and 19, e.g., between the shafts 9 and 11. 
Actually, the element 17 is installed between two sections or portions of 
a composite output shaft of the universal joint 16, namely, between the 
shaft 19 which carries the gear 18 and the shaft 19a for the fork 16a 
which is articulately connected with the fork 16b on the shaft 11 by two 
pins 16c, 16d in a manner well known from the art of such types of 
universal joints. 
The output element of a universal joint exhibits a non-uniformity period of 
180 degrees for each angular displacement of its input element through 360 
degrees, i.e., each revolution of the input element entails two 
periodically recurring non-uniformities. Thus, the knife shaft 26 could 
carry two knives at an angle of 180 degrees to one another. By changing 
the angle between the axes 10, 10a of the shafts 11 and 19 between 0 and 
54 degrees, one can change the length of successively severed sheets 
within a range of 1 to 1.73. Instead of utilizing a cross cutter having a 
single shaft 26 with two knives on the respective holder 31, the 
illustrated driving unit employs the aforementioned step-up transmission 
21 which is interposed between the universal joint 16 and the knife shaft 
26 to double the length of the zone (as considered in the circumferential 
direction of the carrier 31) wherein the knife 32 and the web W move in 
synchronism with one another i.e., in which the speed of orbital movement 
of the knife 32 (and hence of the associated knife 34) matches the speed 
of lengthwise movement of the web W through the nip of the holders 31, 33. 
This enhances the quality of the severing operation. 
The provision of clutch means including the clutch elements 24 and 28 
enables an operator to change the orientation of the knives 32, 34 with 
reference to the universal joint 16 by 90 degrees. This results in a 
widening of the aforementioned format range to 1:3 because, by changing 
the angular positions of the knives relative to the universal joint 16, 
one can utilize both sinusoidal half waves of the periodical 
non-uniformity movement of the output shaft 19. 
FIG. 2 illustrates a cross cutter and a modified driving unit therefor. All 
such parts of the apparatus shown in FIG. 2 which are identical with or 
clearly analogous to corresponding parts of the structure shown in FIG. 1 
are denoted by similar reference characters plus 100. For example, the 
knives of the cross cutter are shown at 132 and 134, their holders at 131, 
133, the step-up gear transmission at 121, the flexible torsion-resistant 
torque transmitting element between the shafts 152, 119 of the universal 
joint 116 at 117, etc. The difference between the two driving units is 
that the carrier 151 of FIG. 2 rotatably mounts the output shaft 111 of 
the angle drive 112 as well as the discrete input shaft 152 of the 
universal joint 116. The shaft 152 is parallel to the shaft 111, and the 
latter is rotatable in a bearing 150 of the carrier 151. The shaft 111 
drives the shaft 152 through the medium of a gearing including mating 
gears 153, 154 having identical diameters. In all other respects, the 
driving unit of FIG. 2 is identical with or clearly analogous to the 
driving unit of FIG. 1. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic and specific aspects of our contribution to 
the art and, therefore, such adaptations should and are intended to be 
comprehended within the meaning and range of equivalence of the appended 
claims.