Improved roller conveyor

Abstract

A roller conveyor includes: a plurality of driven rollers (2), each driven roller having a cylindrical outer surface (21) configured to support an object to be conveyed, the outer surface being tangent to a conveying plane (a) on which the object is conveyed; a motor (3); a transmission element (4) kinematically connecting the motor (3) to the driven rollers (2) and configured to contact the portion of the outer surface (21) tangent to the conveying plane (a); a plurality of pressure rollers (5) configured to contact the transmission element (4) on the side opposite to the driven rollers (2), each of the pressure rollers (5) being configured to abut against a corresponding driven roller (2) to press the transmission element (4) between itself and the corresponding driven roller (2).

Description

Technical Field

[0001] This invention relates to a roller conveyor.

[0002] The roller conveyor according to the invention is particularly suitable for conveying glass plates in inkjet decorating machines. However, the roller conveyor according to the invention is suitable for conveying any type of object along a predetermined direction of travel and for various purposes other than decoration. Background Technology

[0003] There are currently many types of roller conveyors.

[0004] Typically, a roller conveyor includes multiple rollers arranged tangentially to the conveying plane.

[0005] These rollers have outer surfaces designed to support objects to be conveyed. The outer surfaces of each roller are cylindrical and have the same diameter as each other, and the outer surfaces of each roller are tangent to the conveying plane.

[0006] To transport objects, these rollers are rotated by a motor. The motor is connected to the rollers via a transmission mechanism, which may include belts, chains, gear trains, etc.

[0007] A very common concept in drive systems is to use a belt to connect a motor to multiple rollers of a conveyor. In existing devices, the belt contacts the end portions of the rollers, which differ from the outer surface on which the object to be conveyed rests. These end portions have different diameters relative to the outer surface of the rollers. If, due to various manufacturing errors, the end portions of the rollers do not have the same diameter, or if the end portions of the rollers are eccentric relative to the outer surfaces of the individual rollers, the peripheral speeds of the outer surfaces of the multiple rollers will differ from each other. This means that the conveying speed of the object is not constant, and the object may also experience changes in orientation and unexpected and undesirable rotation.

[0008] The applicant has devised a highly effective solution to address the shortcomings summarized above. This solution, described in publication WO2020 / 079506, comprises a roller conveyor including multiple rollers, each having a cylindrical outer surface configured to support an object to be conveyed, the outer surface being tangential to a conveying plane on which the object is conveyed. A drive element kinematically connects a motor to these rollers. The drive element is configured to contact the portion of the outer surface tangential to the conveying plane. Multiple pressure rollers are configured to contact the drive element on the opposite side of the rollers to compress the drive element into contact with the outer surface. These pressure rollers are located in the portion of the drive element between two side-by-side rollers.

[0009] Thus, all the rollers are driven to rotate at substantially the same speed as each other.

[0010] The applicant has identified ways to further improve the above solution.

[0011] Specifically, each pressure roller located at a corresponding section between two side-by-side rollers on the transmission element causes the transmission element to elongate or stretch. This is because there is no opposite pressure roller on the other side of the transmission element. The elongation caused by the pressure rollers results in speed oscillations in the transmission element, especially when the transmission element is in the form of a belt. However, although this oscillation is small, it should be avoided as much as possible. Summary of the Invention

[0012] The purpose of this invention is to provide a roller conveyor that can overcome the shortcomings summarized above.

[0013] The advantage of the conveyor according to the invention is that it allows all rollers to obtain the same peripheral speed, so that the conveyed object moves forward in a constant and uniform manner without experiencing any speed variation. Attached Figure Description

[0014] Other features and advantages of the invention will become more apparent from the following detailed description of embodiments thereof, which are illustrated by way of non-limiting example in the accompanying drawings, in which:

[0015] Figure 1 A schematic isometric view of the conveyor according to the present invention is shown;

[0016] Figure 2 It shows Figure 1 Enlarged image;

[0017] Figure 3 It shows Figure 1 A side view of the conveyor in the image;

[0018] Figure 4 It shows Figure 2 Cross-sectional view of the circular region in the diagram;

[0019] Figure 5a and Figure 5b The diagram shows a comparison of two graphs, one with reference to the prior art and the other to the conveyor according to the invention; these graphs use time on the horizontal axis and the other, with the other, the circumferential speed of the rollers on the vertical axis. Detailed Implementation

[0020] The roller conveyor according to the invention includes a plurality of driven rollers 2, each driven roller having a cylindrical outer surface 21 configured to support an object to be conveyed.

[0021] Driven roller 2 is rotated by a rotating motor 3 (e.g., an electric motor). Motor 3 is connected to driven roller 2 via a transmission device that transmits the rotation of motor 3 to driven roller 2. The uniform rotation of driven roller 2 causes an object resting on driven roller 2 to move along the conveying direction on the conveying plane a.

[0022] The outer surface 21 of the driven roller 2 is tangent to the conveying plane a. The conveying plane a is preferably horizontal, but it can also have different angles of inclination relative to the horizontal direction. The conveying plane a is the plane on which the object is conveyed; that is, the conveying plane is the plane on which the object contacts the outer surface 21 of the driven roller 2 during its forward movement in the conveying direction. The driven roller 2 rotates about a corresponding axis of rotation located on a plane substantially parallel to the conveying plane a. The support frame F rotatably supports the driven roller 2 at its ends and also allows the conveyor to be placed on the ground.

[0023] The transmission device includes a transmission element 4 that kinematically connects the motor 3 to the driven roller 2. One or more idler wheels may be positioned between the motor 3 and the driven roller 2 to guide the transmission element 4 relative to the relative position between the motor 3 and the driven roller 2 and relative to the overall construction of the conveyor.

[0024] The contact between the transmission element 4 and the outer surface 21 occurs on the portion of the outer surface 21 that is tangent to the conveying plane a. In other words, the transmission element 4 is configured to contact the outer surface 21 of the driven roller 2, or the portion of the driven roller 2 that is tangent to the conveying plane a, which has the same diameter as the outer surface 21. In a preferred embodiment, the transmission element 4 is configured to contact the outer surface 21 of the driven roller 2 so as to transmit motion to the outer surface 21 itself. This means that the outer surfaces 21 of different driven rollers 2 must necessarily have a peripheral velocity equal to the velocity of the transmission element 4, and therefore have the same peripheral velocity as each other. This state of equal peripheral velocity can also occur between the outer surfaces 21 if the outer surfaces 21 do not have exactly the same diameter, or even have different diameters.

[0025] Therefore, the solution of arranging the transmission element 4 in contact with the outer surface 21 of the driven roller 2, or having the transmission element 4 interact with a portion of the driven roller 2 having the same diameter as the outer surface 21, allows for movement such that all driven rollers 2 have the same peripheral speed at the outer surface 21 tangent to the conveying plane a. This enables the forward conveying of objects with high precision without generating unwanted vibrations or rotations.

[0026] In the preferred but not exclusive embodiment shown, the transmission element 4 comprises a flat belt. The belt 4 is a closed loop along a path including: a drive pulley securely bound to the motor 3; one or more idler pulleys; and a driven roller 2. Specifically, the portion of the path followed by the belt 4 that is tangent to the outer surface 21 of the driven roller 2 lies substantially on the conveying plane a.

[0027] The conveyor includes a plurality of pressure rollers 5, which are arranged to contact the drive element 4 on opposite sides relative to the driven roller 2. Each pressure roller 5 is arranged to abut against a corresponding driven roller 2, such that the drive element 4 is compressed between the driven roller 2 and the corresponding pressure roller 5.

[0028] Specifically, each pressure roller 5 is configured such that its axis of rotation lies in a plane perpendicular to the conveying plane a, which also includes the axis of rotation of the driven roller 2 disposed opposite to the pressure roller 5 itself. In other words, the squeezing force exerted by the pressure roller 5 toward the transmission element 4 lies in a plane containing both the axis of rotation of the pressure roller 5 and the axis of rotation of the driven roller 2, and this plane is perpendicular to the conveying plane a. The squeezing force exerted by the pressure roller 5 is perpendicular to the conveying plane a and perpendicular to the portion of the transmission element 4 that is compressed between the pressure roller 5 and the driven roller 2. This applies to every pair of combinations formed by the driven roller 2 and the pressure roller 5.

[0029] In practice, the transmission element 4 is arranged among multiple pairs of combinations formed by the driven roller 2 and the pressure roller 5. Furthermore, the transmission element 4 is pressed into contact with each driven roller 2 by the corresponding pressure roller 5.

[0030] Due to the presence of the pressure rollers 5, the transmission element 4 is compressed into contact with the driven roller 2, remaining well attached to the driven roller without being stretched. This is because each pressure roller 5 is configured to abut against a corresponding driven roller 2. Therefore, the pressure exerted by each pressure roller 5 is counteracted by the driven roller 2, such that the transmission element 4 is compressed and substantially does not stretch. In practice, the pressure rollers 5 can be driven to abut against the driven roller 2 by an elastic element such as a spring known in the art, which will not be further described.

[0031] The pressure roller 5 is arranged substantially parallel to the driven roller 2. The outer surface of the pressure roller 5 is tangent to the conveying plane a. Therefore, the belt-type drive element 4 is arranged substantially on the conveying plane a according to a straight path. In other words, the pressure roller 5 can be stacked on top of the driven roller 2 at a point tangent to the conveying plane, i.e., each pressure roller 5 can be arranged such that its axis of rotation is coplanar with the axis of rotation of the corresponding driven roller 2. As already noted, the belt is positioned between the driven roller 2 and the pressure roller 5 stacked thereon.

[0032] The conveyor according to the invention can be used in machines for digital printing on glass plates or other materials. The machine includes at least one inkjet printhead of a type known in the art. The conveyor line is configured to forward transport the glass plate from an inlet area to an outlet area and pass under the printhead. The conveyor line includes the conveyor 1 according to the invention. In printing on glass plates, particularly for the production of car windows, very high precision printing is required to generate small text and codes and to produce opaque edge areas designed to protect the adhesive bonding the car window to the car body from solar radiation. The use of the conveyor 1 according to the invention ensures very precise and uniform transport of the glass plate, preventing undesirable rotation of the glass plate itself. This ensures that the glass plate is presented to the printhead in a very precise and predetermined position, allowing printing to be performed as intended to obtain the desired image.

[0033] Figure 5a and Figure 5b Experiments showed that the change in the peripheral speed of the roller was significantly reduced. Figure 5a The variation in the peripheral speed of the rollers in a prior art solution is shown. Figure 5b The variation of the peripheral speed of the rollers in the conveyor according to the present invention is shown.

Claims

1. A roller conveyor, comprising: Multiple driven rollers (2), each driven roller having a cylindrical outer surface (21) configured to support an object to be conveyed, the outer surface being tangent to a conveying plane (a) on which the object is conveyed; Motor (3); A transmission element (4) kinematically connects the motor (3) to the driven roller (2), and the transmission element is configured to contact the portion of the outer surface (21) that is tangent to the conveying plane (a); The roller conveyor is characterized in that it further includes a plurality of pressure rollers (5) arranged to contact the transmission element (4) on the side opposite to the driven roller (2), and each pressure roller (5) is arranged to abut against a corresponding driven roller (2) to press the transmission element (4) between the pressure roller and the corresponding driven roller (2).

2. The conveyor according to claim 1, wherein, The transmission element (4) includes a flat belt.

3. The conveyor according to claim 1, wherein, The axis of rotation of each of the pressure rollers (5) is set on a plane perpendicular to the conveying plane (a).

4. The conveyor according to claim 1, wherein, The rotation axis of the pressure roller (5) and the rotation axis of the driven roller (2) are located on the same plane, which is perpendicular to the conveying plane (a).

5. The conveyor according to claim 1, wherein, Each of the driven rollers (2) is provided with a pressure roller (5) configured to apply a squeezing force directly toward the drive element (4).

6. The conveyor according to claim 1, wherein, The transport plane (a) is substantially horizontal.

7. A machine for digitally printing glass plates, comprising a printing head and a conveyor line for the glass plates, the conveyor line being configured to guide the glass plates below the printing head, characterized in that, The conveyor line includes a roller conveyor (1) according to any one of claims 1 to 6.

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