Print sheet brake

Abstract

A device for braking and positioning a print sheet in a processing machine, wherein, along a feeding direction for the print sheet, at least one mechanism exerts a braking force onto the print sheet, to position the print sheet in connection with an operation of a downstream-arranged processing station. The device includes at least a first mechanism operative to release pneumatic, braking-force triggering pulses that act upon the print sheet. At least a second mechanism is operative to generate at last one frictional force that acts upon the print sheet, wherein with aid of at least one of the first mechanism and the second mechanism, intermittent, uniform or oscillating braking forces are generated that act upon the print sheet. A control unit controls the braking forces based on at least one of changeable control profiles resulting from queried operating parameters and stored control profiles.

Claims

1. A method for operating a device for braking and positioning a print sheet in a processing machine, wherein along the feeding direction for the print sheet at least one mechanism exerts a braking force onto the print sheet causing a positioning of the print sheet in connection with the operation of a downstream-arranged processing station, the method comprising: generating, with at least one first mechanism, pneumatic, braking-force triggering pulses to act upon a top of the print sheet to press an underside of the sheet against a table-type support to generate, as a result of friction between the table-type support and the print sheet, a braking force that is transferred to the print sheet; generating, with at least a second mechanism, a braking-force triggering frictional force to act upon the print sheet; acting upon the print sheet with intermittent, uniform or oscillating braking forces generated with the first and second mechanisms; and controlling the braking forces generated by the first and second mechanisms by a control unit which is operated with changeable control profiles based on at least one of queried operating parameters and on stored control profiles.

2. The method according to claim 1, including generating the intermittent, uniform, or oscillating braking forces acting upon the print sheet by mechanisms that are effective directly, semi-directly or indirectly.

3. The method according to claim 1, wherein the braking forces are mechanically, electronically, hydraulically, pneumatically activated forces and the acting step includes focusing the activated forces directly or indirectly onto the print sheet.

4. The method according to claim 1, wherein the generating with a second mechanism includes generating a vacuum that acts upon the underside of the print sheet in a feeding direction in order to increase the friction.

5. The method according to claim 1, including supplementing at least one of the braking forces acting upon the print sheet during the feeding of the print sheet with an additional braking force that acts upon a back edge or a region of the back edge of the print sheet.

6. The method according to claim 1, including using at least one braking force in connection with forming an overlapping flow or separating the sheets from the overlapping flow of sheets transported in the feeding direction.

7. The method according to claim 1, wherein at least one braking force used for braking the print sheet subsequently functions as a cross-folding brake for the print sheet during operation in the downstream arranged processing station.

8. The method according to claim 1, including controlling at least one pneumatically operated braking force by at least one nozzle of a switching valve, taking into consideration a feeding speed and composition of the print sheet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the invention is explained in further detail with reference to the drawings, to which we expressly refer for all details not emphasized further in the description. All elements not absolutely necessary for the direct understanding of the invention have been omitted. The same elements in different figures are provided with the same reference numbers.

(2) FIG. 1 is a perspective view of a complete overview of a longitudinal folding device, including a transport belt for supplying print sheets according to an embodiment of the invention.

(3) FIG. 2 is shows an enlarged area of FIG. 1 with a modification including an intermediary mechanical element used for braking and positioning of the print sheet in connection with applying an air pulse as braking force.

(4) FIG. 3 is shows an enlarged area of FIG. 2 and further including geometric conditions and resulting forces during a braking operation.

DETAILED DESCRIPTION

(5) FIG. 1 shows an area surrounding a longitudinal folding device 100, which essentially consists of a longitudinal folding device 101 which can be operated using a sword 102. FIG. 1 also shows the configuration of a folding roller pair 103. The operation of longitudinal folding device 101 is illustrated by a print sheet 104 that is folded in a longitudinal direction. Of course, the print sheets can also be folded inside a cross folding device, not shown further herein, wherein this device is operatively connected to the shown longitudinal folding device 101 or can be operated as an autonomous unit. The print sheet 105 is supplied via transport belts 106 and is stopped in the precise folding position 107, either with the aid of a first measure involving:

(6) 1) a precisely positioned stopping within the meaning of a standstill for the print sheet at a precise point, achieved solely through braking-force triggering pulses and/or by introducing additional braking forces, such as by generating a vacuum that acts upon the print sheet and/or the use of at least one mechanical element; or with aid of a second measure, involving:

(7) 2) a precisely positioned stopping within the meaning of a standstill of the print sheet at a precise point, owing to braking-force triggering pulses and/or the introduction of additional braking forces, as described in the above, which ensure that the feeding speed of the print sheet relative to the specified end position is slowed down enough so that it is near zero or tends toward zero. The final standstill at a precise point for the print sheet is then determined by taking into account an end stop that is not shown further in the figures and which the print sheet hits with the remaining speed.

(8) Since this remaining speed is microscopically small, there is no danger that the front edge of the print sheet is damaged in the feeding direction once it hits the stop surface or could bounce back or spring back from this stop surface. This soft arrival in the end position for the print sheet additionally has the advantage that the print sheet can adapt completely to the stop surface, thus resulting in a maximized, precise alignment of the front edge of the print sheet with the stop surface.

(9) The following steps are relevant with the latter measure:

(10) The speed of the print sheet is slowed down approximately 10 cm prior to reaching the end stop, which is not shown herein but is familiar to one skilled in the art. The speed is slowed enough so that the sheet only hits the end stop with low kinematic residual energy, wherein the speed of the print sheet is <1 m/s during the impact. With an end speed of this type, no damage can occur to the print sheet and the print sheet also does not spring back as a result of an excessively high impact speed.

(11) The course of the delay of the sheet feeding speed can advantageously be provided based on an e-function or quasi e-function (similar), wherein a truncating of the original course through other mathematical progressions is also possible. Truncating is understood to mean in general the cutting off or separating of something, mostly in a figurative sense. For an example, the course of the e-function may no longer be continued at one point and after which the breaking course is continued based on a different mathematical function.

(12) However, for both described measures it is important that the dynamic of the braking-force triggering measures must take into consideration the manner in which the print sheets are transported. If transport belts are used for transporting the sheets, then a control unit 117 of all braking-force triggering measures must be considered in an operative connection with the kinematic force which is exerted by the transport belts onto the print sheets. The braking effect resulting from the specified means basically should not collide with the kinematic forces of the transport belts, wherein with specific constellations it is not impossible to purposely strive for an at least partial super-imposition of the two forces (braking force and transport force).

(13) FIG. 1 furthermore shows a trailing print sheet 108, intended to show the operation with a clock speed of the longitudinal folding device 100.

(14) The operation of the longitudinal folding device in an operative connection with a precise positioning of the print sheet 105 is configured as follows:

(15) The air pressure needed for the braking is computed based on the specified production data such as folding pattern, paper weight, paper width and cut-off length. The information is then sent to an automatic controller, taking into consideration that depending on the folding pattern, the print sheet has different values on the left and the right side.

(16) Furthermore, based on the specified production data such as folding pattern, paper weight, paper width and cut-off length, the air pressure required for decelerating the print sheet 105 is computed and the information is then sent to the automatic pressure controller 109, taking into consideration that depending on the folding pattern, the print sheet may have different values for the left and the right side.

(17) The illustrated air nozzle 110 is used to blow an amount of air directly onto the print sheet. When computing the necessary amount of air, it is simultaneously taken into consideration that an additional amount of air may be necessary to neutralize the possibly occurring fluttering movements during the intake of the print sheet 105. Of course, it should also be considered that even after a complete stop of the print sheet 105, introducing additional amounts of air may be required for stabilizing the print sheet 105.

(18) Thus, the pressure reservoir 111, arranged in a flow direction in front of a pneumatic switching valve, is filled to a required pressure with the aid of a pressure controller 109.

(19) The print sheet 105 entering/fed into the folding region is detected at the back edge with the aid of a light barrier, not shown in further detail here, wherein this light barrier simultaneously functions to synchronize the clock speed of the folding sword 102, wherein the operation of the light barrier also detects irregularities within the belt transport of the print sheet 105 and compensates these via the control unit 117.

(20) As a result of an activated trigger signal, a signal for activating the pneumatic switching valve is triggered, taking into consideration the dead time and speed compensation.

(21) Following this, the air stored in the pressure reservoir 111 is released abruptly, whereupon the air nozzle 110 blows a pulse-type air jet onto the print sheet 105.

(22) The released air blast can act directly upon the print sheet 105, or upon a lever (see FIG. 2, Position 112) which transmits the air blast and the corresponding resulting force to the print sheet. Of course, a configuration is also conceivable for which the air blast acts upon the print sheet 105 as well as the lever 112, wherein the directly and the indirectly introduced braking force can also be controlled intermittently and with differing pulse strengths of the air pulses (see FIG. 2, Position 114).

(23) During the feeding operation and/or during the folding process, the print sheet 105 is pressed onto a table-type support owing to the pneumatically triggered forces, thus generating a braking force for the print sheet as a result of friction.

(24) If necessary, an additional braking force can be directed simultaneously or phase-displaced onto the back edge of the print sheet 105, wherein a material stretching triggered by the braking effect results in reinforcing the print sheet 105.

(25) The braking instant (see FIG. 3, Position 115) is selected such that the print sheet 105 is securely slowed to 0 and, in an imaginary sense, also when using a print sheet end stop, as described in the above. This specification can also be met if the slowing down of the print sheet 105 to 0 has reached the imaginary stopping point (FIG. 3, Position 113) where the folding sword 102 takes over the print sheet as intended. The takeover of the print sheet 105 by the folding sword 102 can thus be coordinated such that it coincides with the imaginary stopping point 113 for the print sheet end.

(26) One option for a braking at a precise position of the print sheet 105, which is not shown further, can be achieved by activating an additional braking force based on friction. This can be achieved advantageously through generating a vacuum that acts upon the underside of the print sheet, wherein this option can without problem also be used together with the other previously explained braking forces. FIG. 2 furthermore shows the folding position 116 of the print sheet 105.

(27) FIG. 3 shows the geometric conditions and the resulting forces during the course of the braking operation for the print sheet. These values, namely the distances 230 and 240, as well as the forces F.sub.pulse (200), F.sub.braking (210) and F.sub.normal (220), which occur during the braking operation, are of a qualitative nature and are used as a basis for a controlled braking operation, wherein it is also possible to parameterize these values for control/regulation of the braking operation.

(28) Following the release of the air pulses (FIG. 2, Position 114), the pneumatic switching valve is closed immediately and the pressure controller 109 again fills the compressed air reservoir 111 to the predetermined pressure, thus making it available for the next cycle.

(29) The invention has been described in detail with respect to exemplary embodiments, and it will now be apparent from the foregoing to those skilled in the art, that changes and modifications may be made without departing from the invention in its broader aspects, and the invention, therefore, as defined in the appended claims, is intended to cover all such changes and modifications that fall within the true spirit of the invention.