Patent Description:
More precisely, the invention relates to a transverse welding assembly for a flow-pack packaging machine.

Flow-pack packaging is one of the most widely used systems for packaging of a great variety of products, in particular food products, such as, for example, biscuits, snacks, bars, etc..

In flow-pack packaging systems, a continuous packaging film, typically of plastic material, is unwound from a reel and is folded into an element with a tubular shape that surrounds the products to be packaged and advances in a machine direction together with the flow of products to be packaged. The tubular element of packaging material is closed by a continuous longitudinal weld that joins the opposite longitudinal edges of the packaging film and by transverse welds spaced apart in the machine direction that seal the tubular element at opposite sides with respect to the products.

A horizontal flow-pack packaging machine typically comprises:.

The transverse welding assembly may comprise two welding elements that rotate around two axes parallel to each other. This solution has the drawback of a limited contact time between the welding elements and the film of packaging material.

In cases wherein to carry out the transverse welding it is necessary to keep the welding elements in contact with the packaging film for a longer time than it is possible with the rotating welding assemblies, a transverse welding assembly called box-motion is used, comprising a translating base, which is movable alternately along the machine direction between a rearward position and an advanced position and vice versa. The translating base carries two welding elements that are movable relative to each other between an open position and a closed position, in phase with the movement of the translating base.

In a box-motion transverse welding assembly, the reciprocating movement of the translating base is generally obtained starting from a rotary electric motor, connected to a transmission mechanism, for example, a connecting rod and crank, which transforms the rotary motion of the electric motor into an alternative straight movement of the translating base.

<CIT> discloses a transverse welding assembly comprising:.

In transverse box motion welding units there is the problem of ensuring that the translating base moves in the machine direction with a uniform speed (equal to the speed of the packaging film) without instantaneous disturbances introduced by the transmission mechanism.

The object of the present invention is to provide a transverse welding assembly for a flow-pack packaging machine that overcomes the problems of the prior art.

According to the present invention, this object is achieved by a transverse welding assembly having the characteristics forming the subject of claim <NUM>.

Preferred embodiments of the invention form the subject of the dependent claims.

The claims form an integral part of the disclosure provided here in relation to the invention.

The present invention will now be described in detail with reference to the attached drawings, given purely by way of non-limiting example, wherein:.

With reference to <FIG>, numeral <NUM> indicates a box-motion transverse welding assembly for a horizontal flow-pack packaging machine. The transverse welding assembly <NUM> comprises a stationary support structure <NUM> including a vertical plate <NUM> and feet <NUM> resting on the ground.

The transverse welding assembly <NUM> comprises a translating base <NUM> movable with respect to the support structure <NUM> along a horizontal straight direction A. The translating base <NUM> is movable alternately along the direction A between a rearward position and an advanced position and vice versa. The translating base <NUM> may be provided with shoes which engage two horizontal guides <NUM> carried by an adjustment plate <NUM>, which is adjustable in a vertical direction with respect to the vertical plate <NUM> of the support structure <NUM>. Adjustment in the vertical direction of the adjustment plate <NUM> allows the transverse welding assembly <NUM> to be adapted to the thickness of the products to be packaged.

With reference to <FIG>, the translating base <NUM> carries a first welding element <NUM> and a second welding element <NUM> movable relative to each other between an open position and a closed position, in phase with the movement of the translating base <NUM> in the direction A. Both the welding elements <NUM>, <NUM> may be movable with respect to the translating base <NUM> to vary their reciprocal distance between a closed position in which the welding elements <NUM>, <NUM> are in contact with each other, and an open position in which the welding elements <NUM>, <NUM> are detached from each other. The movement of the welding elements <NUM>, <NUM> is controlled by an actuator unit carried by the translating base <NUM>, which may be produced as in the box-motion transverse welding assembly according to the prior art.

With reference to <FIG>, the transverse welding assembly <NUM> comprises a transmission mechanism <NUM> configured to control the reciprocating movement of the translating base <NUM> along the direction A between a retracted position and an advanced position, and vice versa.

The transmission mechanism <NUM> comprises a cam oscillator device <NUM> connected to at least one oscillating arm <NUM> connected to the translating base <NUM> by means of a sliding coupling element.

With reference to <FIG>, the cam oscillator device <NUM> comprises a casing <NUM> (<FIG>) in which an inlet shaft <NUM> and an outlet shaft <NUM> are housed, rotatable, respectively, around a first axis B and a second axis C parallel to each other.

The inlet shaft <NUM> is connected to an electric motor (not illustrated) and, during operation, is driven in rotation at a constant speed and always in the same direction of rotation. At least one cam <NUM> is fixed on the inlet shaft <NUM>, which cooperates with at least one cam-follower <NUM> carried by the outlet shaft <NUM>. In the embodiment illustrated in the figures, the oscillator device <NUM> comprises two cams <NUM>, <NUM> with conjugated profiles fixed on the inlet shaft <NUM> and cooperating with respective cam-follower members <NUM>, <NUM> carried by the outlet shaft <NUM>. The cam-follower members <NUM>, <NUM> may consist of idle rollers carried by respective flanges <NUM>, <NUM> fixed to the outlet shaft <NUM>.

In principle, the oscillator device <NUM> could comprise a single cam <NUM> or <NUM>, and a single cam-follower member <NUM> or <NUM> pressed in contact with the respective cam <NUM> or <NUM> by a spring.

The profile of the cams <NUM>, <NUM> is configured to convert the continuous rotary movement of the inlet shaft <NUM> into an alternating pivoting movement of the outlet shaft <NUM> around the second axis C with a predetermined law of motion.

With reference to <FIG>, in a possible embodiment, the transmission mechanism <NUM> comprises two oscillating arms <NUM> parallel to each other, fixed to opposite ends of the outlet shaft <NUM>, and connected to the translating base <NUM> by means of respective sliding coupling elements.

In a possible embodiment, each of the two pivoting arms <NUM> has a guide <NUM>, which extends orthogonally to the axis C of the outlet shaft <NUM>, and carries a respective shoe <NUM> which engages the respective guide <NUM> in a sliding manner. The two shoes <NUM> are articulated at the translating base <NUM> around a third axis D parallel to the second axis C, and orthogonal to the straight direction A. Articulation of the shoes <NUM> at the translating base <NUM> may be carried out by means of respective bearings <NUM>. In a possible alternative embodiment, each pivoting arm <NUM> could have a guide slot orthogonal to the C axis within which a pin fixed to the translating base <NUM> slides.

During operation, the cam oscillator device <NUM> converts the continuous and unidirectional rotary motion of the inlet shaft <NUM> around the first axis B into an alternating pivoting motion of the outlet shaft <NUM> around the second axis C, which involves an alternating pivoting motion of the pivoting arms <NUM> around the same second axis C. Since the translating base <NUM> is constrained to move along the straight direction A, the shoes <NUM>, slidably engaged on the respective guides <NUM> and articulated to the translating base <NUM> around the third axis D, convert the reciprocating pivoting movement of the pivoting arms <NUM> into an alternating straight movement of the translating base <NUM> along the direction A.

Transmission of the movement to the translating base <NUM> by means of the shoes <NUM> sliding along the pivoting arms <NUM> allows obtainment of an absolutely constant speed of the translating base <NUM>, and free of perturbations in most of the stroke of the translating base <NUM>, with the sole exception of the end portions of the stroke, in which the inversion of the motion takes place. The speed of the translating base <NUM> is kept absolutely constant and free of perturbation during the period wherein the welding elements <NUM>, <NUM> are in the closed position. This allows considerable improvement of the quality of the weld.

Another particularly advantageous characteristic of the transmission mechanism <NUM> is the possibility of very quickly adjusting the amplitude of the stroke of the translating base <NUM> along the direction A. This adjustment is necessary when the format of the products to be packaged changes, in particular when the length of products in the direction A changes.

It can be noted that in the transmission mechanism <NUM> the amplitude of the stroke of the translating base <NUM> in the direction A is proportional to the distance between the second axis C and the third axis D. To vary the amplitude of the stroke of the translating base <NUM> along the direction A, it is therefore sufficient to vary the distance between the second axis C and the third axis D.

In a possible embodiment, the adjustment of the amplitude of the stroke of the translating base <NUM> may be carried out by adjusting the position of the oscillating cam device <NUM> with respect to the stationary base <NUM> in the vertical direction. With reference to <FIG>, the transmission mechanism <NUM> may comprise two actuators <NUM>, which allow adjustment of the position in the vertical direction of the oscillating cam device <NUM> with respect to the stationary base <NUM> in the vertical direction. The actuators <NUM> may be electrically or pneumatically operated. In a possible embodiment, the actuators may be manually operated.

With reference to <FIG>, the line A indicates the direction along which the translating base <NUM> is mobile. The lines <NUM>' <NUM>" indicate the extreme positions of the pivoting arms <NUM> in the fully lowered position of the oscillating cam device <NUM>, which corresponds to the maximum amplitude stroke of the translating base <NUM>. Points <NUM>', <NUM>" indicate the extreme points of the stroke of the translating base <NUM> in the condition of maximum stroke. The points <NUM>', <NUM>" indicate the points between which the speed of the translating base <NUM> has a constant speed without perturbations in the maximum stroke condition. The speed constancy of the translating base <NUM> may be guaranteed only in the forward stroke (when the welding elements <NUM>, <NUM> are in the closed position). In the return stroke, the constant speed of the translating base <NUM> may not be ensured.

The lines <NUM>', <NUM>" indicate the extreme positions of the pivoting arms <NUM> in the fully raised position of the cam oscillator device <NUM>, which corresponds to the minimum amplitude stroke of the translating base <NUM>. Points <NUM>', <NUM>" indicate the extreme points of the stroke of the translating base <NUM> in the condition of minimum stroke. The points <NUM>', <NUM>" indicate the points between which the speed of the translating base <NUM> has a constant speed without perturbations in the minimum stroke condition. In this case as well, the constancy of the speed of the translating base <NUM> may be guaranteed only in the forward stroke.

The oscillating cam device <NUM> may be arranged in any position between the completely lowered position and the completely raised position, so that it is possible to adjust the transmission mechanism <NUM> so as to obtain a stroke of the translating base <NUM> having any dimension included between the minimum stroke <NUM>'-<NUM>" and the maximum stroke <NUM>'-<NUM>".

Claim 1:
A transverse welding assembly for a flow-pack packaging machine comprising:
- a stationary support structure (<NUM>),
- a translating base (<NUM>) movable with respect to the stationary support structure (<NUM>) along a straight direction (A),
- a transmission mechanism (<NUM>) configured to command a reciprocating movement of the translating base (<NUM>) along said straight direction (A) between a rear position and an advanced position and vice versa, and
- first and second welding elements (<NUM>, <NUM>), carried by the translating base (<NUM>), and movable with respect to each other between an open position and a closed position in phase with the movement of the translating base (<NUM>),
characterized in that said transmission mechanism (<NUM>) comprises:
- a cam oscillator device (<NUM>), comprising an inlet shaft (<NUM>) rotatable around a first axis (B) and connected to an electric motor, at least one cam (<NUM>) fixed to said inlet shaft (<NUM>), an outlet shaft (<NUM>) oscillating around a second axis (C) parallel to said first axis (B), and at least one cam-follower member (<NUM>) carried by the outlet shaft (<NUM>) and cooperating with said at least one cam (<NUM>), wherein said cam (<NUM>) has a profile configured to convert a continuous rotary movement of the inlet shaft (<NUM>) into an alternating pivoting movement of the outlet shaft (<NUM>) around said second axis (C), and
- at least one pivoting arm (<NUM>) fixed to the outlet shaft (<NUM>) of the cam oscillator device (<NUM>) and connected to the translating base (<NUM>) by means of a sliding coupling element (<NUM>).