Web film movement compensating device for a web film movement compensation between a continuous forward movement section and an intermittent forward movement section

Abstract

The present invention relates to a web film movement compensating device for a web film movement compensation between continuous forward movement section and intermittent forward movement section comprising two guide rollers (1, 2) rotating freely in stationary positions between a continuous driving device (5) and an intermittent driving device (6), two compensation rollers (3, 4) rotating freely on two respective pivoting arms (7, 8) oscillating about pivot shafts (11, 12), an elastic element (9) connected to one of the pivoting arms to actuate the corresponding compensation roller to move away from the guide rollers, and a movement transmission mechanism including lever arms and transmission rods (13, 14, 15) transmitting an oscillating movement from one of the pivoting arms (7, 8) to the other. A web film (50) moved by the driving devices is supported on the guide rollers (1, 2) and on the compensation rollers (3, 4) forming a meander.

Claims

1. A web film movement compensating device for a web film movement compensation between continuous forward movement section and intermittent forward movement section for an automatic horizontal bag-forming and -filling machine, comprising: first and second guide rollers (1, 2) parallel to one another arranged such that they can rotate freely in stationary positions between a continuous driving device (5) and an intermittent driving device (6); a first compensation roller (3) parallel to said first and second guide rollers (1, 2) installed such that it can rotate freely on a first pivoting arm (7) oscillating about a first pivot shaft (11) parallel to the first and second guide rollers (1, 2); a second compensation roller (4) parallel to the first and second guide rollers (1, 2) installed such that it can rotate freely on a second pivoting arm (8) oscillating about a second pivot shaft (12) parallel to the first and second guide rollers (1, 2); a movement transmission mechanism transmitting oscillating movements of the first pivoting arm (7) to said second pivoting arm (8) such that the first and second compensation rollers (3, 4) move closer to one another and to the first and second guide rollers (1, 2) and away from one another and from the first and second guide rollers (1, 2) simultaneously; and an elastic element connected to at least one of said first and second pivoting arms (7, 8) to actuate said first and second compensation rollers (3, 4) in a direction of moving away from one another and from the first and second guide rollers (1, 2); wherein a web film (50), which is moved continuously by said continuous driving device (5) and intermittently by said intermittent driving device (6), is supported on the first and second guide rollers (1, 2) and on the first and second compensation rollers (3, 4) forming a meander while said first and second pivoting arms (7, 8) performs oscillating movements between a maximum meander position and a minimum meander position, wherein said first pivot shaft (11) is closer to the first guide roller (1) than to the second guide roller (2) on a first side of a geometric plane containing the axes of the first and second guide rollers (1, 2) and said second pivot shaft (12) is closer to the second guide roller (2) than to the first guide roller (1) on a second side of said geometric plane containing the axes of the first and second guide rollers (1, 2); and wherein said movement transmission mechanism comprises a first lever arm (13) fixed to the first pivoting arm (7), a second lever arm (14) fixed to the second pivoting arm (8), and a connecting rod (15) having a first end connected to said first lever arm (13) by a first articulation (16) and a second end connected to said second lever arm (14) by a second articulation (17).

2. The web film movement compensating device according to claim 1, wherein the first and second guide rollers (1, 2) and the first and second pivot shafts (11, 12) are arranged in symmetrical positions with respect to an axis of symmetry that is parallel to and equidistant from the first and second guide rollers (1, 2) and contained in said geometric plane containing the axes of the first and second guide rollers (1, 2).

3. The web film movement compensating device according to claim 1, wherein the first and second compensation rollers (3, 4) have one and the same diameter, and the first and second pivoting arms (7, 8) have one and the same length.

4. The web film movement compensating device according to claim 1, wherein the first and second lever arms (13, 14) have one and the same length and said connecting rod (15) has a length equal to a distance between the first and second pivot shafts (11, 12).

5. The web film movement compensating device according to claim 1, wherein said elastic element is a first elastic element (9) connected to the first pivoting arm (7) to actuate the first compensation roller (3) in a first direction of moving away from the second compensation roller (4) and from the first and second guide rollers (1, 2), and wherein the device further comprises a second elastic element (10) connected to said second pivoting a (8) to actuate said second compensation roller (4) in a second direction of moving away from the first compensation roller (3) and from the first and second guide rollers (1, 2) opposite said first direction of moving away.

6. The web film movement compensating device according to claim 5, wherein the elastic element or each of said first and second elastic elements (9, 10) is selected among a pneumatic spring, a tension coil spring, a compression coil spring, and a torsion coil spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing and other features and advantages will be better understood based on the following detailed description of a merely illustrative and non-limiting embodiment in reference to the attached drawings, in which:

(2) FIG. 1 is a perspective view of a movement compensating device compensating for the movement of a web film between sections with continuous forward movement and intermittent forward movement according to an embodiment of the present invention; and

(3) FIGS. 2 and 3 are plan views of the movement compensating device of FIG. 1 in a maximum meander position and minimum meander position, respectively.

DETAILED DESCRIPTION OF AN EMBODIMENT

(4) First in reference to FIGS. 1, 2 and 3, reference number 25 indicates a structure on which there is installed a web film movement compensating device for a web film movement compensation between a continuous forward movement section and an intermittent forward movement section according to an embodiment of the present invention. The movement compensating device is useful for an automatic horizontal bag-forming and -filling machine, and comprises first and second guide rollers 1, 2 parallel to one another arranged such that they can rotate freely in stationary positions between a continuous driving device 5 and an intermittent driving device 6 (not shown in FIG. 1).

(5) The movement compensating device further comprises first and second pivoting arms 7, 8 arranged such that they can oscillate about respective pivot shafts 11, 12 parallel to the first and second guide rollers 1, 2, and first and second compensation rollers 3, 4 parallel to the first and second guide rollers 1, 2 installed such that they can rotate freely on the first and second pivoting arms 7, 8, respectively.

(6) In this embodiment, the first pivot shaft 11 is closer to the first guide roller 1 than to the second guide roller 2 on a first side of a geometric plane containing axes of the first and second guide rollers 1, 2, and the second pivot shaft 12 is closer to the second guide roller 2 than to the first guide roller 1 on a second side of the mentioned geometric plane.

(7) Furthermore, the first and second guide rollers 1, 2 and the first and second pivot shafts 11, 12 are arranged in symmetrical positions with respect to an axis of symmetry parallel to and equidistant from the first and second guide rollers 1, 2 and contained in the geometric plane defined above, the first and second compensation rollers 3, 4 have one and the same diameter, and the first and second pivoting arms 7, 8 have one and the same length.

(8) A first elastic element 9 is connected at one end to the structure 25 and at the other end to the first pivoting arm 7, and a second elastic element 10 is connected at one end to the structure 25 and at the other end to the second pivoting arm 8. In this embodiment, the first and second elastic elements 9, 10 are made up of devices with a pneumatic spring arranged such that they drive the first and second pivoting arms 7, 8 and the first and second compensation rollers 3, 4 in respective directions of moving away from the first and second guide rollers 1, 2, indicated by arrows 26 in FIG. 2.

(9) Alternatively, the first and second elastic elements 9, 10 could be made up of tension coil springs, compression coil springs, torsion coil springs, or springs of any other type. In any case, the first and second elastic elements 9, 10 are the same and are arranged symmetrically in relation to the mentioned axis of symmetry.

(10) The movement compensating device includes a movement transmission mechanism transmitting an oscillating movement of the first pivoting arm 7 to the second pivoting arm 8, such that the first and second compensation rollers 3, 4 move closer to one another and away from one another simultaneously. In the variant shown in FIGS. 1, 2 and 3, this movement transmission mechanism comprises first lever arms 13 fixed to the first pivoting arm 7, second lever arms 14 fixed to the second pivoting arm 8, and connecting rods 15 having a first end connected to the first lever arms 13 by first articulations 16 and a second end connected to the second lever arms 14 by second articulations 17.

(11) The first lever arms 13 and the second lever arms 14 have one and the same length, and the connecting rod 15 has a length equal to a distance between the first and second pivot shafts 11, 12. In other words, a distance between each of the first articulations 16 and the first pivot shaft 11 is equal to a distance between each of the second articulations 17 and the second pivot shaft 12, and a distance between the first articulations 16 and the second articulations 17 is equal to the distance between the first and second pivot shafts 11, 12.

(12) In an alternative embodiment (not shown), the movement transmission mechanism comprises a single first lever arm 13, a single second lever arm 14, and a single connecting rod 15, wherein the first and second lever arms 13, 14 have one and the same length and the connecting rod 15 has a length equal to the distance between the first and second pivot shafts 11, 12.

(13) As a result of the action of the movement transmission mechanism, only one of the first or second elastic elements 9, 10 is essential, so the other one can be omitted. However, the inclusion of both the first and second elastic elements 9, 10 is preferable for a more balanced operation.

(14) During operation, a web film 50 (FIGS. 1 and 2), which is moved continuously by the continuous driving device 5 and intermittently by the intermittent driving device 6, is supported on the first and second guide rollers 1, 2 and on the first and second compensation rollers 3, 4, forming a meander. The first and second pivoting arms 7, 8 perform oscillating movements between a maximum meander position (FIG. 2), in which the amount of web film 50 and a minimum meander position (FIG. 3).

(15) A transition between the minimum meander position (FIG. 3) and the maximum meander position (FIG. 2) occurs when the intermittent driving device 6 is stopped while the continuous driving device 5 is working, given that in such a circumstance the web film 50 loses tautness which is compensated for by the force exerted by the first and second elastic elements 9, 10.

(16) A transition between the maximum meander position (FIG. 2) and the minimum meander position (FIG. 3) occurs when both continuous and intermittent driving devices 5, 6 are working, with the intermittent driving device 6 working at a higher speed than the continuous driving device 5, given that in such a circumstance the web film 50 has increased tautness overcoming the force exerted by the first and second elastic elements 9, 10.

(17) The first and second compensation rollers 3, 4 comprise end plates supporting a cylindrical wall between them. Both the end plates of the first and second compensation rollers 3, 4 and the first and second pivoting arms 7, 8 have lightening openings provided for lightening the mass thereof and thereby reducing the inertial forces generated by intrinsic accelerations of the oscillating movement.

(18) The scope of the present invention is defined in the attached claims.