Device for conveying flat floppy products

A device for conveying flat floppy products has an inlet conveyor belt with a constant velocity, an intermediate conveyor belt with a periodically changing velocity and an outlet conveyor belt with constant velocity. The intermediate conveyor belt causes a deceleration or acceleration of the product to be conveyed. Transfer of the product between the conveyor belts takes place at respectively the same velocities of the affected belts. The drive of the intermediate conveyor belt is performed by a gear making periodic gear changes. The invention relates to the relationship between the shaft distance and the radius of the drive pulley of the intermediate conveyor belt and is particularly related to steps reducing the torque during acceleration or deceleration of the drive elements and assuring a slip-free conveyance of the products.

FIELD OF THE INVENTION 
The present invention relates to a first device intended to bring flat 
products of low flexural strength, such as sheets or sheet packages of 
paper or plastic, from a constant inlet velocity v.sub.E to a second 
constant outlet velocity v.sub.A. The conveyance of packages of printed 
sheets, which must be slowed from a high inlet velocity to a reduced 
outlet velocity in order to effect an adaptation to the processing speed 
of a folding apparatus, can be cited as an example. 
DESCRIPTION OF THE PRIOR ART 
DE 1 189 919 A1 describes a device consisting of an inlet conveyor belt of 
a constant velocity, an intermediate conveyor belt with a periodically 
changing velocity, and an outlet conveyor belt. The transfer of the 
product to be conveyed from one belt to the next belt respectively takes 
place at the same velocity of the involved belts. The intermediate 
conveyance causes an acceleration of the product to a higher velocity. It 
is driven by a gear making periodic gear changes. Periodic gears are 
known. The gear with non-circular wheels disclosed in DE 646 002 A can be 
cited as an example. 
In connection with products of a length L, which follow each other at a 
clock time T, the distance "a" between the shafts of the reversing pulleys 
of the intermediate conveyor belt is composed of the length L and the 
deceleration length L.sub.V in the case of a product deceleration and, in 
the case of a product acceleration, of the length L and the acceleration 
length L.sub.B. 
Relatively short clock times T require comparatively large accelerations 
and decelerations of the intermediate conveyor belt. Relatively large 
inertia forces are generated by this, which can result in the breakdown of 
drive elements. In addition, there is the danger that the products will 
slide, change their distance and in this way interfere with the clocked 
operation. 
SUMMARY OF THE INVENTION 
The object of the present invention is to disclose the relationship between 
the shaft spacing distance "a" between of the reversing pulleys and the 
radius of the drive pulley r of the intermediate conveyor belt, to keep 
the inertia forces as low as possible and to assure a slip-free conveyance 
of the products. 
In accordance with the invention, the shaft spacing distance "a" is 
considered to be a part of the circumference of a replacement or 
theoretical pulley with a radius R, parts of the circumference of which 
are the angle ranges .phi..sub.E for the constant inlet velocity v.sub.E, 
.phi..sub.V for the deceleration range, .phi..sub.A for the constant 
outlet velocity v.sub.A, and .phi..sub.B for the acceleration range, and 
which theoretical pulley makes one revolution during the clock time T, so 
that the relationship "a"=L+R.phi..sub.V applies in the case of product 
deceleration, or "a"=L+R.phi..sub.B for the case of product acceleration. 
An actual drive pulley of a radius R would be of too large a size and would 
therefore have too large mass moments of inertia. In order to keep the 
deceleration and acceleration torque as small as possible at a 
predetermined periodic movement cycle and shaft spacing distance "a" of 
the reversing pulleys of the intermediate conveyor belt, the invention 
provides a considerably smaller radius r of the actual drive pulley of the 
intermediate conveyor belt than that of the radius R of the theoretical or 
replacement pulley. This is achieved in that gear wheel stages, which 
provide gearing up to a faster speed, are disposed between the periodic 
gear and the drive pulley and as a whole have a total gear level in an 
amount of i&lt;1. Without a change in the speeds of the intermediate conveyor 
belt, the radius of the drive pulley then becomes r=iR. 
The gear wheels with the ratio i result in that, compared with drive 
pulleys of the radius R, the mass moment of inertia of drive pulleys of 
the radius r is less by the factor i.sup.5 and, reduced to the drive shaft 
of the periodic gear, is less by the factor i.sup.3, if it is assumed that 
the ratio of width to radius of the pulleys remains constant. 
Now, since in connection with a predetermined stress, drive pulleys for 
conveyor belts are of a considerably larger size than gear wheels, the 
mass moment of inertia reduced to the drive shaft of the periodic gear has 
a considerably lower value, even when the additional gear wheels are taken 
into consideration. Because of this, a lower torque is created for the 
deceleration and acceleration of the conveyor belt. 
In connection with products with relative small mass in particular, angle 
ranges .phi..sub.V and .phi..sub.B and symmetrical time-dependent cycles 
of the deceleration and acceleration of the power take-off shaft of the 
periodic gear result in the same size of the extreme values of 
deceleration and acceleration, and therefore in a minimum of the otherwise 
largest size of the extreme values. In such a case, the shaft spacing 
distance between the reversing pulleys of the intermediate conveyor belt 
must satisfy the relationship "a"=.pi.r/i. 
In order to transfer the products at the start and end of the intermediate 
conveyor belt without a gap, it is provided in accordance with the 
preferred embodiment of the invention that the conveyor belts have belts 
which are respectively disposed parallel at a distance, wherein reversing 
pulleys of the inlet conveyor belt are seated on the one side, and 
reversing pulleys of the outlet conveyor belt are seated on the other side 
between the spaces of the reversing pulleys at the ends of the 
intermediate conveyor belts. 
To prevent mutual displacement of the products to be transported because of 
the slipping of the conveyor belts, it is possible to use toothed belts, 
whose teeth are in engagement with toothed belt pulleys, wherein the 
toothed drive belt pulleys of the intermediate conveyor belt have 
reference circles with a radius r. 
Furthermore, in order to convey the products free of slippage with respect 
to the intermediate conveyor belt during an acceleration or deceleration 
phase, the intermediate conveyor belt can consist of a lower conveyor belt 
and, parallel with it, an upper conveyor belt, whose working sides, which 
face each other, move in the same direction and synchronously, wherein 
pulleys resiliently placed against them generate a frictional connection 
between the working side and the products. 
To prevent blows in the teeth because of flank changes of the teeth caused 
by the change between acceleration and deceleration phases as well as the 
reduction of the carrying capacity caused by this, gear wheel trains are 
provided in a further embodiment of the invention, which can be preset in 
accordance with the torque by means of couplings in such a way that no 
contact change of the tooth flanks occurs. Research has found that the 
additional mass required by this does not remove the advantage of small 
drive pulleys of the intermediate conveyor belt in respect to the reduced 
mass moment of inertia at the drive shaft of the periodic gear.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows the intermediate conveyor belt schematically, wherein the 
shaft spacing distance "a" between the reversing pulleys or the length of 
the intermediate conveyor is composed of the product length L and the 
deceleration path L.sub.V for decelerating the products. 
The theoretical or replacement pulley with the radius R is shown in FIG. 2. 
The angle range .phi..sub.E for the constant inlet velocity V.sub.E is a 
part of the arc of a circle of the length L. The angle range .phi..sub.V 
for the deceleration area is a part of the arc of a circle of the length 
L.sub.V. The angle range .phi..sub.A =.phi..sub.E for the constant outlet 
velocity v.sub.A is a part of the arc of a circle of the length L. The 
angle range .phi..sub.B for the acceleration area is a part of the arc of 
a circle of the length L.sub.B. FIG. 2 furthermore shows the arc of a 
circle of the length "a" of the shaft spacing distance between the 
reversing pulleys of the intermediate conveyor belt. This is the sum of 
the lengths L and Lv. 
FIG. 3 schematically shows a lateral view of the intermediate conveyor belt 
and of the pitch circles of gear wheels. 1 indicates the lower conveyor 
belt, 2 the upper conveyor belt, 3 the output gear wheel on the power 
take-off shaft B of the periodic gear, 4 and 5 gear wheels on the shaft C, 
6 the gear wheel on the shaft D, 7 an intermediate gear wheel and 8 the 
gear wheel on the shaft E. The shaft D is connected with the toothed drive 
belt pulleys 9 of the lower conveyor belts and the shaft E is connected 
with the toothed drive belt pulleys 10 of the upper conveyor belts. The 
toothed drive belt pulleys 9 and 10 have the geometrical radius r. The 
toothed belt pulleys 11 and 12 are used for reversing the toothed belts. 
The shaft spacing distance between the shaft D of the toothed belt drive 
pulley 9 and the shaft of the toothed belt reversing pulley 11, or between 
the shaft E of the toothed belt drive pulley 10 and the toothed belt 
reversing pulley 12 of the intermediate conveyor belts. omega.sub.D and 
omega.sub.E indicate the oppositely directed angular speeds of the same 
magnitude of the shafts D and E. The adjustable toothed belt pulleys 13 
and 14 generate the necessary prestress of the conveyor belts 1 and 2. 
Springs 15 press the toothed belt pulleys 17 seated in beams 16 against 
the sheet packages through the toothed belts 1 and 2, which packages are 
conveyed in this way in a frictionally connected manner. The vector 
v.sub.E identifies the velocity of the inlet conveyor belt and the vector 
v.sub.A identifies the velocity of the outlet conveyor belt. 
FIG. 4 represents the meshing of the toothed belts 18 of the lower conveyor 
belt 1 with the toothed belts 19 of the inlet conveyor belt and with the 
toothed belts 20 of the outlet conveyor belt, respectively at the transfer 
places for the sheet package. The toothed reversing belt pulleys 21 of the 
inlet conveyor belt are seated between the toothed drive belt pulleys 9, 
and the toothed reversing belt pulleys 22 of the outlet conveyor belt are 
seated between the toothed reversing belt pulleys 11. 
FIG. 5 schematically represents an axial section through the intermediate 
conveyor belt, of the gear wheels with the constant ratio i and of the 
periodic gear 23 and 23 with the drive shaft A and the periodic gear 24 
and 24' of the power take-off shaft B. The shafts A, B, C, D and E have 
angular speeds of omega.sub.A, omega.sub.B, omega.sub.C, omerga.sub.D and 
omega.sub.E. Two equal, parallel arranged wheel sets are provided in each 
gear step, wherein the torque of the gear periodic wheels 23, 24 and 23', 
24' can be prestressed by means of the coupling K.sub.1, the gear wheels 
3, 4 and 3', 4' by means of the coupling K.sub.2, the gear wheels 5, 6 and 
5', 6' by means of the coupling K.sub.3 and the gear wheels 5, 7, 8 and 
5', 7', 8' by means of the coupling K.sub.4. The coupling K.sub.5 is used 
to connect the shaft D and the coupling K.sub.6 for connecting the shaft E 
of the intermediate conveyor belt. 
For the required movement cycle of the intermediate conveyor belt, FIG. 6 
represents the cycles of the predetermined angular deceleration or 
acceleration .epsilon., the angular velocity omega and the angle of 
rotation .phi. as a function of the time t for one period, i.e. for the 
clock time T, which are to be realized by the periodic gear. omega is the 
result of the integration of .epsilon., and .phi. of the integration of 
omega. 
In the preferred embodiment the periodic gears consist of non-circular 
wheels which comply with the movement cycle in accordance with FIG. 6. 
FIG. 7 shows the contact curve of the periodic gear wheels 23 and 23' 
seated on the shaft A with the center O.sub.A, and the minimum radius of 
the contact curve r.sub.WAmin as well as the maximum radius of the contact 
curve r.sub.WAmax. The shaft A rotates at a constant angular speed. FIG. 8 
shows, analogously to FIG. 7, the contact curve of the periodic gear 
wheels 24 and 24' seated on the shaft B with the center O.sub.B, with 
r.sub.WBmin as the minimum and r.sub.WBmax as the maximum radius of the 
contact curve. In FIGS. 7 and 8, E' identifies the angle ranges for the 
constant velocity v.sub.E, V' the angle ranges for the deceleration phase, 
A' the angle ranges for the constant velocity v.sub.A and B' the angle 
ranges for the acceleration phase of the intermediate conveyor belts 1 and 
2. The contact curves of the non-circular periodic gear wheels 23 and 23' 
and 24 and 24' roll off on each other without sliding. The curve lengths 
which are part of the respective angular ranges are therefore all of the 
same length. The contact curves can be described by the coordinates 
X.sub.A, Y.sub.A and X.sub.B, Y.sub.B. 
Analogously to FIG. 5, FIG. 9 shows the axial section of the intermediate 
conveyor belt with a gear wherein, instead of the periodic gear with 
non-circular gear wheels, an also known periodic gear with round gear 
wheels in an arrangement of a planetary gear with the planetary gear 
support 25, the planetary gear wheels 26 and 26' and the sun gear wheels 
27 and 27' is provided. The torque of the wheels 26, 27 and 26', 27' can 
be prestressed by means of the coupling K.sub.7. The roller 28, seated 
eccentrically in the planetary wheel 26', rolls off the cam disk 29, 
supports the torque of the planetary wheels and superimposes the periodic 
movement cycle in accordance with FIG. 6 on the planetary gear wheels 26 
and 26' which transfer the movement to the shaft C, instead of to the 
shaft B in FIG. 5. The gear wheel-planetary gear already acts in the sense 
of the invention as a stage of the gear wheels, which must realize the 
constant gear ratio i=r/R. 
While a preferred embodiment of a device for conveying flat floppy products 
in accordance with the present invention has been set forth fully and 
completely hereinabove, it will be apparent to one of skill in the art 
that a number of changes in, for example, the specific product being 
conveyed, the number of individual conveying belts, the type of printing 
unit being used and the like may be made without departing from the true 
spirit and scope of the present invention which is accordingly to be 
limited only by the following claims.