Patent Application
20220176579
The present invention relates to a cutting machine for the transversal cutting of logs of paper material.
It is known that rolls of toilet paper, kitchen paper and paper for similar uses are obtained by transversal cutting of rolls of greater length, commonly called “logs” and produced by machines called “rewinders” in which a predetermined amount of a web of paper material, consisting of one or more overlapping paper plies, is wrapped around itself, or around cardboard tubes called “cores”. Generally, the logs produced by the rewinders are conveyed to a buffer store and, from this, to machines, called “cutting-off machines” which perform the aforementioned transversal cut. Generally, the cutting machines have a platform on which are defined guide channels for logs and, downstream of said channels, a cutting unit which includes a disk blade suitably operated and moved to determine the transverse cutting of the logs with a programmed sequence depending on the length of the rolls that must be obtained from the logs. The blades are normally associated with grinding wheels which cyclically intervene to restore the cutting profile of the blades themselves. Periodically the blades of the cutting machines must be replaced due to wear which progressively reduces both the diameter and the cutting capacity. Whenever a worn blade is replaced with a new one, the position of the grinding wheels must be adjusted with respect to the blade.
EP3194128B1 discloses a machine for the transversal cutting of logs of paper material comprising a feed path for the logs to be cut, a cutting unit with a replaceable discoid blade and supported so that it can rotate around its axis while it is subject to a cyclic movement for cutting the logs and to allow the advancement of the logs along the said feed path, and a sharpening unit with two grinding wheels configured and controlled to intervene on the discoid blade when the latter must be sharpened. The grinding wheels are mounted on a support system which includes a controlled approach mechanism of the grinding wheels to the blade configured to move each grinding wheel in a direction substantially parallel to its rotation axis. Said mechanism acts so as to bring a support slide of each grinding wheel to a nominal position with respect to the blade, and to approach the grinding wheel to the blade in a controlled manner by moving the grinding wheel with respect to the respective slide which is kept in said nominal position.
The main purpose of the present invention is to propose a machine for cutting logs in which the positioning system of the grinding wheels on the blade integrates a mechanism for detecting the wear of the grinding wheels in order to always obtain the most correct execution of the cut.
A further object of the present invention is to propose a losg cutting machine in which the positioning of the grinding wheels with respect to the blade replaced from time to time is automated and in which this positioning is substantially independent of the diameter of the blade, by means of a mechanically simple and programmable system so as to also allow independent position adjustments for the two grinding wheels.
This result has been achieved, in accordance with the present invention, by adopting the idea of making a machine having the characteristics indicated in claim 1. Other features of the present invention are the subject of the dependent claims.
Thanks to the present invention, the degree of wear of the grinding wheels can be detected automatically, with the advantages further indicated below.
Furthermore, it is possible to position the grinding wheels automatically, in less time than the positioning performed manually and with greater operational safety since this operation does not require operators access to the area of the machine that houses the blade. Furthermore, a device for positioning the grinding wheels in a machine according to the present invention has a relatively simple structure and integrates an effective mechanism for recognizing the desired position for the grinding wheels. Further advantages are linked to the possibility of independently controlling the positions of the grinding wheels when they are approached to the blade to be sharpened.
These and further advantages and characteristics of the present invention will be more and better evident to each person skilled in the art thanks to the description that follows and the annexed drawings, provided by way of example but not to be considered in a limiting sense, in which:
Preliminarily, with reference to
In the example of
In practice, the blade (2) rotates around a respective axis (x-x) which is parallel to the axis of rotation of the plate (1).
With reference to
In accordance with the present invention, the aforementioned positioning device for the grinding wheel (3) comprises:
In practice, the primary direction of movement (PD) is a direction parallel to the plane (P2) of the blade (2), i.e. a radial direction with respect to the latter, while the secondary direction of movement (SD) is a direction parallel to the rotation axis (x-x) of the blade (2).
The primary carriage (4) can consist of two independent units (40, 41) to each of which a corresponding secondary carriage (42, 43) is attached. Alternatively, the primary carriage can consist of a single unit (400) on which both the secondary carriages (42, 43) are connected.
With reference to the embodiment shown in
Each of said bodies (40, 41) has a first side (4P) parallel to the internal side (F1) of the plate (1) and a second side (4H) orthogonal and underlying the first side (4P). The first side (4P) slides along the respective guide (LG). The second side (4H) constitutes a cantilever structure whose function is disclosed below. In practice, each of said bodies (40, 41), seen laterally, has a structure with a part (4P) parallel to the internal side (F1) of the plate (1) and a part (4H) orthogonal to the same internal side (F1) of the plate (1) and oriented towards the outside (E) so as to define a bracket above the blade (2). In the example described above, the movement of the bodies (40, 41), i.e. of the two units that make up the primary carriage (4), is a guided movement thanks to the presence of the guides (LG) that constrain the bodies (40, 41) to the internal side (F1) of the plate (1). The “PT” references denote two pads arranged at a predetermined distance from each other on the side (4P) of each body (40, 41) and intended to slide on said guides (LG).
Each of the secondary carriages (42, 43) has a first arm (PA) parallel to the bracket (4H) of the respective primary carriage, to which it is connected by means of a corresponding slide guide (G2, G3), and a second arm (SA) which is orthogonal to the first arm (PA) and, at its free end, supports the shaft (30) of a respective grinding wheel (3). The second arm (SA) passes through a slot (BL) formed in the bracket (4H), so that the grinding wheel (3) with the relative shaft (30) is below the bracket (4H) and that said second arm (SA) is free to move in the slot (BL) according to the direction of secondary movement (SD). On the first arm (PA) of each secondary carriage (42, 43) a connecting rod (B2, B3) is connected which, in turn, is enslaved to a corresponding electric motor (M2, M3). Each motor (M2, M3) is supported by a surface (SM) that each primary carriage (40, 41) has at a predetermined distance from its side (4P) parallel to the plate (1). Each connecting rod is connected to the first arm (PA) by means of a pin (PN) orthogonal to both the connecting rod and the first arm. Therefore, each motor (M2, M3) can move the respective secondary carriage (42, 43) according to the direction of secondary movement (SD). This movement is a guided movement since each secondary carriage is connected to the primary carriage by means of a respective slide (G2, G3) which, in fact, is oriented according to the direction (SD).
Thus, each grinding wheel (3) is supported by the cutting unit (CU) in such a way that it can be moved both according to the primary direction of movement (PD) and according to the secondary direction of movement (SD). In fact, the bodies (40, 41) of the primary carriage (4) can be moved according to the direction (PD) by means of the motors (M0, M1), while the secondary carriages (42, 43) can be moved on the primary carriage along the direction (SD) by means of the motors (M2, M3).
The grinding wheels (3) are oriented with the respective grinding surfaces (31) towards the plane (P2) of the blade (2).
The cutting unit has also an abutment surface (ST) which acts as an end stop for the secondary carriages (42, 43) as further described below.
For example, said abutment surface is defined by a plate with a side fixed to the horizontal part (4H) of the primary carriage and a side (ST) protruding downwards, i.e. towards the blade (2). The side (ST) projecting downwards defines the abutment surface. The surface (ST) is at a predetermined position with respect to the lying plane (P2) of the blade (2). More particularly, the surface (ST) is at a predetermined distance (d) from the plane (P2) of the blade (2) whose position is known. For example, the surface (ST) is at a distance of 0.5 mm from the plane (P2).
A possible mode of operation of the device described above is the following.
When a new blade is mounted on the cutting unit (CU), in a first phase of adjusting the position of the grinding wheels, the secondary carriages (42, 43) starting from a predetermined initial position, are moved along the direction (SD) by the motors (M2, M3) so that each grinding wheel (3) is brought with its respective surface (31) in contact with the surface (ST). The motors (M2, M3) detect a torque variation when the grinding wheels (3) come into contact with the surface (ST) and, in this phase, stop the movement of the grinding wheels whose position along the direction (SD), therefore, is defined by the contact with the surface (ST). At this point, the stroke of each secondary carriage (42, 43) is detected, i.e. the run of each secondary carriage (42, 43) is detected starting from the initial position up to the position of contact of the grinding wheels (3) with the surface (ST). This detection allows to estimate the degree of wear of the abrasive side (31) of each grinding wheel because the run of each secondary carriage (42, 43) directed towards the surface (ST) increases when the wear of the respective grinding wheel (3) increases. Said detection is performed by an encoder associated with each of the motors (M2, M3) driving the secondary carriages (42, 43). Subsequently, each grinding wheel (3) is moved in the opposite direction to that which has determined its contact with the surface (ST), causing them to run for a distance value equal to the aforementioned distance (d). In this way, the surface (31) of each grinding wheel (3) is brought in correspondence of the plane (P2) regardless of the state of wear of the surface itself. Then, the primary carriage is moved along the direction (PD), until the grinding wheels (3) come into contact with the blade (2) which is made to rotate around its axis (x-x). This contact is detected through the same blade (2) which, in fact, undergoes a slowdown as a consequence of the contact itself. Normally the motor (20) that operates the blade is controlled by a system equipped with a control function that guarantees a constant rotation speed of the blade around the axis (x-x) during the transverse cutting of the logs. When the grinding wheel positioning device is in operation, so that the grinding wheels are moved first along the direction (SD) and then along the direction (PD) as mentioned above, the aforementioned motor control function (20) is temporarily deactivated. The contact of the grinding wheels (3) with the blade (2) causes the latter to slow down and this condition is taken as an indicator of the contact between the grinding wheels and the blade. When this condition occurs, the run of the primary carriage along the direction (PD) is interrupted. In practice, the run of the primary carriage is interrupted when the grinding wheels (3) come into contact with the blade (2). Therefore, the grinding wheels (3) are always correctly positioned on the blade (2) regardless of the state of wear of the blade itself.
As previously mentioned, the primary carriage can consist of a single unit (400), instead of two independent units. In this case, as shown in
As said above, the grinding wheel positioning device can be configured so as to integrate within it a mechanism for detecting the state of wear of the grinding wheels. This provides the advantage of having an estimate of the degree of wear of the grinding wheels, with the possibility, therefore, to signal to the users of the machine the need to arrange the change of the grinding wheels when the estimated value of the degree of wear is greater than a pre-established limit. For this purpose, the mechanism for detecting the state of wear of the grinding wheels can be associated with an acoustic and/or visual indicator that alerts the users. Further advantages deriving from the integration of a grinding wheel wear detection mechanism derive from the fact that in this way the blade will always be correctly sharpened, as it will be possible to avoid the prolonged use of excessively worn grinding wheels and thus always ensure the correct transverse cutting of the logs. Another advantage offered by a mechanism for detecting the degree of wear of the grinding wheels integrated in the grinding wheels positioning device is that the use of the machine is facilitated even for operators who are not particularly expert since the replacement of the grinding wheels is no longer closely linked to the experience of the operators. In addition, there is the fact that the detection on the degree of wear of the grinding wheels can form a database of values that can be used for statistical purposes both to record the actual use of each grinding wheel according to the conditions of use, and for a predictive program of replacements of the grinding wheels.
With reference to the example shown in
wherein
In accordance with a preferred embodiment of the invention,
Furthermore, preferably, the degree of the wear of the grinding wheels (3) is detected as a function of the run of the secondary carriages (42, 43) in said first step of positioning the grinding wheels (3).
Again, preferably, the means for detecting the wear of the grinding wheels are associated to a respective acoustic and/or visual signaling device.
According to a further embodiment of the invention, the detections relating the wear of the grinding wheels form a database of values that can be used to record the actual use of each grinding wheel according to the conditions of use, and/or for a predictive programming of grinding wheel replacements.
In practice, the details of execution can however vary in an equivalent way as regards the individual elements described and illustrated without thereby abandoning the idea of the solution adopted and therefore remaining within the limits of the protection granted by this patent in accordance with the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102019000008493 | Jun 2019 | IT | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IT2020/050134 | 5/26/2020 | WO | 00 |
