The present application is a 35 U.S.C. §§ 371 national phase conversion of PCT/EP2017/025116, filed May 10, 2017, which claims priority of German Patent Application No. 10 2016 109 920.1, filed May 30, 2016, the contents of which are incorporated by reference herein. The PCT International Application was published in the English language.
The invention relates to a detection system for detecting double sheets being supplied to a lateral positioning device for a sheet element in a sheet element processing machine, and to a sheet element processing machine.
Sheet element processing machines typically comprise an introduction station where sheets (usually paper sheets and/or cardboard sheets) are provided to a feed table. The feed table is situated upstream of a cutting machine or a platen press. The sheet element is advanced against one or more front tabs by first means such as endless belts or rollers, then delivered by second means against one or more lateral positioning tabs before the front edge of the sheet element is gripped by a series of grippers mounted on a gripper bar arranged on a chain system.
Such a device is used for precise lateral positioning of sheet elements which have already undergone one or more printing operations, wherein the subsequent operation may be either a stamping process, for example hot foil stamping in a platen press, or a cutting and waste discharge operation in such a press. This subsequent operation must be performed in strict accordance with the preceding printing.
Lateral positioning devices are today used for jogging the sheets. They comprise firstly a lower roller driven in rotation and arranged transversely to the direction of movement of a sheet, close to a lateral tab situated on the left side of the table as viewed also in the direction of movement of the sheet, which is normally known as the operators side. However there are two lateral positioning devices on a machine, one on the operator side and one on the opposite operator side. The operator is free to work with one or the other depending on the requirements of the layout of the final product. These devices then comprise an upper roller, vertically above the lower roller, and mounted at the end of an arm which is in the top position at rest. This arm is lowered regularly on arrival of a sheet element against the frontal tabs, such that the upper roller grips the sheet element against the lower motorized roller which, by traction on the sheet element, causes a correction movement of the sheet element as far as the lateral tab.
There are different approaches in the prior art for detecting an unwanted condition in which sheets are not supplied individually but in a superimposed condition.
Document EP 0669274 describes a lateral positioning device for a sheet element on a feed table, with elements for holding the sheet element (by traction or thrust) with extended surfaces. The aim is thus to avoid damaging the grip surfaces of the sheet element. The singularity of the sheet element engaging in the lateral positioning device is here verified by a complementary device, situated at the inlet to the positioning device and comprising an upper roller and a lower roller situated in the same vertical plane. The spacing of these rollers is set to the value of the thickness of a single sheet element.
Document JP 3426850 describes a positioning device wherein the sheet element is moved laterally in one or the other transverse direction by means of a guidance device comprising two pairs of upper and lower rollers situated in the same vertical plane, each mounted on different lateral sides of the device. Each pair of rollers may be disengaged and the direction of rotation of the rollers may be reversed in order to allow driving of the sheet element in the required direction to correct its positioning. However, this method of gripping tends to mark sheet elements of the corrugated cardboard type, which are more susceptible to crushing than is flat cardboard.
Document JPS 6047751U describes a device with a pivoting lever arm carrying, at its end directed towards the sheet element, a freely rotating roller situated above a drive wheel which is continuously rotated by an endless screw, in order to take the sheet element assembly and deliver it by traction against the lateral stop. The roller of the pivoting lever may be moved away or retracted to switch from the pull mode of moving the sheet element to the push mode of moving the sheet element.
Document JPH 0430203 (JPS62147642) describes a positioning device in which the sheet element is moved laterally in the one or the other transverse direction by means of a guidance device comprising a pair of upper and lower rollers situated in the same vertical plane. The upper roller is freely rotatably mounted, and the direction of rotation of the lower roller may be reversed to allow driving of the sheet element in the required direction in order to correct its positioning. The same guidance device is present on each lateral side of the positioning station.
The object of the invention is to propose a detection system which allows reliably detecting superimposed sheets while at the same time having a simple and economic design.
In order to achieve this object, the invention provides a detection system for detecting double sheets being supplied to a lateral positioning device for a sheet element in a sheet element processing machine. The sheet element processing machine has a drive system including a cam and a cam follower lever. The detection system comprises a detector lever mounted so as to be displaceable between a sheet receiving position and a detection position. The detector lever has a sheet sensing end for engagement with an upper surface of the sheet element when the detector lever is in the detection position, and has a position detector end for cooperating, when the detector lever is in the detection position, and has a position detector configured for generating a signal dependent on the thickness of the sheet element. The detector system further comprises a raising lever configured for raising the sheet sensing end of the detector lever. The raising lever is mounted on the cam follower lever of the sheet element processing machine. To achieve the above mentioned object, a sheet element processing machine comprises a detection system outlined above and mounted in an introduction station upstream of a processing station.
This detection system and the sheet element processing machine equipped with that system allow achieving a couple of advantages. First, it is mechanically simple, so that it can be implemented at low costs. Second, it is space-saving, so that it can be used in existing printing environments without many modifications to existing printing machines. Third, it allows reliable detection of the height of the sheet(s) present under the sheet sensing end of the detector lever.
Detection of a double thickness allows indication of the abnormal presence of two superposed sheet elements. More generally, the object is to propose a device which is able to detect an abnormally great thickness of the sheet element in order to identify the abnormal presence of more than one sheet element. In fact, despite the care taken upstream to ensure that the sheet elements arrive one by one, a pair of superposed sheet elements may be delivered instead of a single sheet element, in particular because of electrostatic forces which may be present between the facing sides of two superposed sheet elements.
Such detection allows the operation of the processing machine to be stopped before any jamming occurs, in order to extract the superfluous sheet element in the presence of a superposed pair of sheet elements, or more generally to extract any arrangement of sheet elements which does not conform to the expected thickness. This allows rapid resumption of operation of the machine. In this way, the machine stoppage time has been reduced to a minimum, which is advantageous in terms of machine efficiency.
Preferably, the raising lever cooperates with the detector lever by abutting at a raising abutment provided on the detector lever. It has been found that this mechanically simple way of coupling the raising lever to the detector lever leads to a reproducible actuation of the detector lever.
According to a preferred embodiment, a tangent to the raising abutment, at the point of contact of the raising lever, is inclined with respect to a line running through the pivot axis of the cam follower lever and the point of contact, at an angle which is between 30° and 80° and more preferably in the order of 10° to 30°. The angle of inclination allows setting the vertical speed of the sheet sensing end of the detector lever, resulting from a raising movement of the cooperating end of the raising lever, to a desired value in a mechanically very simple manner. In particular, the speed of movement of the detector lever can be set to values which are lower than the speed of movement of the raising lever.
Preferably, the raising lever cooperates with the raising abutment by means of a roller. This reduces friction in the detection system.
In order to assure that the sheet sensing end of the detector lever reliably comes into contact with the sheet(s) to be detected, a clearance is present between the raising lever and the detector lever when the detector lever is in the detection position.
Preferably, the position detector end of the detector lever is equipped with a metal target which cooperates with a detection head of the position detector fitted with an inductive proximity sensor. This design avoids any intermediate elements so that the position detector directly cooperates with the detector lever.
For ensuring in a mechanically simple manner that the detector lever is biased into the detection position, a return spring is provided for biasing the detector lever into the detection position.
The invention will be better understood and its various advantages and characteristics will arise more clearly from the description below of the non-limitative exemplary embodiment, with reference to the attached drawings. In the drawings,
The detector system for detecting two superimposed sheets of cardboard, paper or similar material used in printing operations is implemented as part of a sheet element processing machine and in particular as part of a lateral positioning device for a sheet element. The lateral positioning device will be described with reference to
In the present text, the term “lateral” designates a direction perpendicular to the direction of advance of sheet elements, such as paper sheets, in a processing machine, and in particular in an introduction station 10 partly visible
The lateral positioning device 100 in
The operating principle of the lateral positioning device 100 is explained in relation to
In
In
Thus, in the first configuration, the lateral positioning device 100 functions in pull mode, since the sheet is wedged in the desired lateral position by pulling the packaging element 20, gripping and advancing it between the support roller 114 and the delivery wheel 102 until the packaging element 20 comes to rest against the lateral feed stop 121.
The cam lever drives the main lever 110 in parallel, as explained above and the detector lever through the complementary part 170. This configuration gives a cadenced movement to both levers with approximately the same rhythm.
Further, a secondary detector lever 130 is situated next to and upstream of the main lever 110 relative to the direction of advance P of the sheet elements 20. The detector lever 130 swivels around the direction P on its pivot 131 of horizontal axis, and at its first end 132 (at the right in
The detector lever 130 can swivel between a sheet receiving position and a detection position. In the detection position, the first end 132 of the detector lever 130 has descended in order to enable the detector roller 134 to come to rest precisely against the upper face of the sheet 20, as shown in
In order to force down the first end 132 of the detector lever 130, the shaft 131 about which the detector lever 130 pivots is surrounded by a pre-stressed coil spring 137. This prestressing also allows generation of a support force guaranteeing the contact of the detector roller 134 on the sheet 20 and hence a correct thickness measurement.
By monitoring the value of the thickness e measured for each new packaging element 20 arriving at the lateral positioning device 100, where necessary, the processing machine can be stopped so that an operator can verify and extract the incorrect sheet 20 or set of sheets 20.
In
Also, the lateral positioning device 100 functions in a second configuration shown In
In this second configuration, the support roller 114 is raised relative to its position in the first configuration, so that it is not able to touch the upper surface of the sheet 20′ when the first end 112 of the main lever 110 is lowered.
The lateral feed stop acts as a pusher element 121 and is arranged just above the support surface 101 and on the other side of the delivery wheel 102 relative to the support roller 134. This pusher element 121 has a thrust face against which the lateral edge of the sheet 20′ comes to rest. This pusher 121 executes a horizontal translation movement (from left to right on
Thus in the second configuration, the lateral positioning device 100 functions in pusher mode, wherein the sheet 20′ is wedged in the desired lateral position by pushing this packaging element 20′, the pusher 121 is transferred from the retracted position to the advanced position until the packaging element 20′ is brought into the lateral position corresponding to the end of travel (advanced position) of the pusher 121.
In this second configuration, the thickness of the sheet present on the feed table is monitored in the same way as described above in relation to the first configuration. To explain the transition from the first configuration (pull mode) to the second configuration (push mode) and vice versa, reference is made to
As is shown in
The pusher 121 is fixedly attached to the slider 155, itself fixed to the roller of the cam 156 (see
Details of the construction and the operation of the detector system are now explained with reference to
The detector lever 130 is pivotable between the sheet sensing position shown in
In the sheet sensing position of
In the sheet receiving position of
The detector lever 130 is brought from the detection position (against the action of return spring 137) by means of the raising lever 170. The raising lever 170 is a generally rigid arm engaging with one end (referred to in the following as “the raising end”) at the detector lever 130 and being mounted with its other end to a cam follower lever 172 (see bolts 173).
Cam follower lever 172 is mounted pivotally on horizontal pivot axis 111 and engages with a cam roller 174 at the surface of a cam disk 175. Cam disk is driven by a motor (not shown) for achieving certain functions of the sheet element processing machine.
Cam follower lever 172 is connected via a spring mechanism 176 to main lever 110. This will not be explained in detail as this is not relevant for understanding the design and the mode of operation of the detection system.
It is only relevant to understand that cam follower lever 172 performs a pivoting movement under the control of the cam disk 175 and that accordingly the raising lever 170 simultaneously performs a pivoting movement as well (see arrow P in
At its raising end, raising lever 170 is provided with a roller 178 which cooperates with detector lever 130. To this end, detector lever 130 is provided with a raising abutment 180 at which roller 178 engages.
Raising abutment 180 is a relatively solid metal block having an outer surface 182 at which roller 178 engages. In the embodiment shown, outer surface 182 is straight.
Raising abutment 180 is connected to detector lever 130 by means of bolts 184 so that it can be easily replaced when necessary. In the exemplary embodiment, the bolts 184 are arranged in recesses, and bushes 186 are being fitted within the bores for the bolts 184 in raising abutment 180 for greater strength.
In
An important feature of the cooperation between the raising lever 170 and the detector lever 130 is the orientation of the outer surface 182 with respect to the direction of movement of the raising end of the raising lever 170.
In
It is possible to use a raising abutment 180 which has a curved surface 182. This introduces additional options for controlling the relation of movement of the raising lever 170 and the resulting movement of the detector lever 130.
Assuming that the angle α was 90°, the raising abutment 180 would be lifted at the same speed with which roller 178 would move upwardly. Using a smaller angle α reduces the speed of the detector lever 130 as compared to the speed of the raising lever. It is thus possible to very easily set the raising (and also lowering) speed of the detector lever 130 to desired values for a given speed of movement of the raising lever 170; cam follower lever 172 being primarily used for driving other elements of the sheet element processing machine, it is not possible to implement desired raising (and lowering) speeds of the detector lever 130 by changing the way the cam follower lever 172 is being pivoted.
During operation of the sheet element processing machine, the detector lever 130 is in its sheet receiving position for most of a revolution of cam disk 175. Only when cam follower lever 172 is pivoted in a counter clockwise direction when looking at
After a short delay which allows oscillations in the detection system to disappear, position detector 140 provides a signal which is indicative of the distance between target 135 and detection head 141. Knowing the thickness of the sheets currently being processed, the signal allows distinguishing between a single sheet being present or two superimposed sheets being present.
Afterwards, as a result of cam follower lever 172 returning to the lower portion of cam disk 175, detector lever 130 is again lifted, and the next sheet can be advanced.
Number | Date | Country | Kind |
---|---|---|---|
10 2016 109 920 | May 2016 | DE | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/EP2017/025116 | 5/10/2017 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2017/207111 | 12/7/2017 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
5203555 | Cannaverde et al. | Apr 1993 | A |
Number | Date | Country |
---|---|---|
0 669 274 | Aug 1995 | EP |
2 657 165 | Oct 2013 | EP |
S60-47751 | Apr 1985 | JP |
H04-30203 | Jul 1992 | JP |
3426850 | Jul 2003 | JP |
WO 2016062411 | Apr 2016 | WO |
Entry |
---|
International Search Report dated Aug. 29, 2017 in corresponding PCT International Application No. PCT/EP2017/025116. |
Written Opinion dated Aug. 29, 2017 in corresponding PCT International Application No. PCT/EP2017/025116. |
Number | Date | Country | |
---|---|---|---|
20190283996 A1 | Sep 2019 | US |