WO2000073045A1

WO2000073045A1 - A welding unit

Info

Publication number: WO2000073045A1
Application number: PCT/DK2000/000292
Authority: WO
Inventors: John Buk Jensen
Original assignee: Roll-O-Matic A/S
Priority date: 1999-06-01
Filing date: 2000-05-30
Publication date: 2000-12-07
Also published as: AU4911200A

Abstract

The invention relates to a welding station with two opposed conveyance elements, wherein at least one transversally extending welding string is coupled to said conveyance elements, and wherein there is - externally relative to the welding strings at each side - provided a cam conveyor defining a closed geometrical curve and having a cam follower connected to the welding string. The invention enables increased movement rate of the welding strings in that the cam follower comprises an element with at least three wheel means; that the cam follower comprises two opposed, continuous or discontinuous rail segments, wherein a first pair of wheel means consisting of two wheel means travels in succession on the one rail segment, and the remaining wheel means travel(s) on the second rail segment, wherein the two rail segments extend at a mutual distance that ensures that all wheel means are in contact with the respective rail segments all the way around the closed curve.

Description

A welding unit

The invention relates to a welding unit with two opposed conveyance elements wherein at least one transversally extending welding string is coupled to the conveyance elements, and wherein there is provided at each side, externally relative to the welding string (s), a cam conveyor comprising a cam follower connected to each welding string. Such welding unit is typically used for welding parallel-advanced sheets of film.

One example of such welding unit is known ia from EP 0,876,903 Al or DE Al 37,32,033. In the EP disclosure the elements of conveyance are toothed belts, and it is also taught in the disclosure that it is known to use chains to this end. Also articulations or toothed-wheel mechanisms are known to this end. The welding strings are to be conveyed in a closed curve, a part of which is rectilinear, the welding being accomplished by abutment on the film along the rectilinear part of the curve, frequently by abutment on a correspondingly conveyed retainer or welding string on the other side of the sheets of film that are to be joined by welding. The cam conveyor and the cam follower serve to ensure the orientation of the welding strings and the abutment pressure on the film. Different cam conveyors with associated cam followers are known; thus the above-mentioned EP patent teaches a carriage with two wheels that follow each other in a guide or a slide block that travels in a guide track. These so- lutions give rise to both wear and noise problems. If a two-wheeled carriage is used, the wheels change direction of revolution when switching between the rectilinear welding area and the arched area(s) of the closed curve, the plant switching - due to the mass forces - between the outside and the inside of the guide track. This gives rise to both noise and wear. A slide block will also be exposed to considerable wear that entails play with ensuing noise problems and problems regarding accuracy.

It is the object of the invention to provide a welding unit of the kind described above that enables movement of the welding strings at higher rates without significant wear or noise problems occurring, and to ensure that the constructive mass is kept at a minimum.

According to the invention this is accomplished in general by means of a welding unit comprising a cam follower that is conveyed by two rail segments, wherein the cam follower comprises an element with at least three wheel means arranged such that the individual wheel means do not at any point change direction of revolution, but are merely in contact with or are caused to contact the same rail segment whereby play-free conveyance is ensured.

Such welding unit is defined in claim 1. When more than three wheel means are used it is required that flexible or movable journaling of one or more wheel means is used, eg by means of bogies.

The above is accomplished in accordance with a first embodiment of the present invention in that the cam follower comprises an element with three wheel means, and that the cam conveyor comprises two opposed rail seg- ments, wherein a pair of wheels consisting of two wheel means travel in succession on the one rail segment, and the remaining wheel means travels on the other rail segment, the two rail segments extending at a mutual distance that ensures that all three wheel means are in con- tact with the respective rail segments all the way around the closed curve. Such embodiment is featured in claim 2.

When all three wheel means maintain the same direction of revolution all the way around the closed curve, additional wear and noise will not occur. It is hereby possible to achieve considerably increased rates of movement for the cam follower with ensuing increased rates for the welding unit. The point where the curve conveyor curves, the distance between the rail elements on which the two and the one wheel, respectively, travel (s) is changed to ensure uninterrupted contact between the rail elements and the wheels. Hereby completely play-free operation is obtained with ensuing minimal wear on wheels as well as rail elements.

According to a further embodiment of the present invention this is obtained by the cam follower comprising an element with four wheel means; that the curve conveyor comprises two opposed rail segments, wherein a pair of wheels consisting of two wheel means travel in succession of each other on the one rail segment and another pair of wheels travels on the other rail segment, said wheel means being journalled, and the two rail segments extend- ing at a mutual distance that ensures that all four wheel means are in contact with the respective rail segments all the way around the closed curve. In an embodiment featuring four wheel means, they can be arranged on one or two bogies as featured in claim 3 or 6.

The term "wheel means" is intended to designate an element that can comprise one or more individual wheels mounted rotatably on a shared axis. The term "conveyance element" is intended to designate an element capable of conveying a cam follower around along the cam conveyor. The conveyance element can be a chain, a toothed belt, an articulation or toothed-wheel mecha- nis as described above, or any other type of device that brings about the desired movement.

The rail segments can be continuous or discontinuous. Discontinuous rail segments are such that feature open- ings in the rail segment corresponding to the points where the wheel means of the cam conveyor are not loaded; this may correspond to inner as well as the outer rail conveyor. Hereby more ready servicing of the conveyance elements is ensured. When the claims define that the wheel means are in contact with the respective rail segments all the way around the closed curve, it goes without saying that this applies only to that part of the curve where the respective rail segment is present.

It is possible that - as featured in claims 4 and 7 - the two rail segments are configured and extend between said pair of wheels and the respective wheel means, or between the respective inner and outer wheel means. Hereby it becomes very uncomplicated to configure the rail segments like the two sides of a rail that can be eg machine- processed from the lateral parts of a welding unit that also accommodate the remaining parts of the unit.

It is a further option, as featured in claims 5 and 8, that the two rail segments extend externally of said pair of wheels and the remaining wheel means . Hereby it is possible to manufacture the cam conveyor as one single machine-processed guide track in each of the lateral parts of the welding unit. A convenient embodiment of the invention is obtained in that, as featured in claim 9, the cam conveyor comprises a rectilinear rail segment with a random curve-shape for the remainder of its length. This embodiment is particularly convenient if the conveyance element is a toothed belt that is taken around at least two belt wheels.

The invention will now be explained in detail with refer- ence to the figures, wherein

Figure 1 is a sectional view through a welding unit with two pairs of welding strings;

Figure 2 is a sectional view along the line AA shown in Figure 1;

Figures 3 through 6 are sketches of cam conveyor and associated cam follower in various embodiments thereof for a welding station with three wheels in accordance with the invention; and

Figures 7 and 8 are sketches of cam conveyor and associated cam follower in various embodiments thereof for a welding unit with four wheels in accordance with the invention.

The welding station shown in Figures 1 and 2 comprise a mounting plate la and lb at each side that are separated by a number of stays 22 that fixate the plates la and lb relative to each other. Figure 1 illustrates, on the inside of the mounting plate la, belt wheels 6,7,8 that form a triangle and belt wheels 16,17,18 that form a corresponding triangle that is, however, inversed relative thereto, wherein the triangles are arranged with one of their faces towards each other. Toothed belts 27 are conveyed around each three of the belt wheels whereby the toothed belt that is conveyed around the belt wheels 6, 7 and 8 forms the sides of the first triangle, and the toothed belt around the belt wheels 16, 17 and 18 form the sides of the other triangle. The toothed belt section 27c between the wheels 7 and 8 then extends parallel with the toothed belt section 27d between the wheels 17 and 18.

The conveyor elements in the form of toothed belts can advantageously be positioned in two planes arranged parallel relative to each other whereby a simple coupling can be used between a conveyance element and the individual welding strings.

On the opposite inside of the second support plate lb corresponding belt wheels are journalled that have toothed belts that are symmetrical in relation thereto. The sheets of film F that are to be joined by welding are conveyed between the two plates la and lb in a plane that extends centrally between the two parallel extending toothed belt sections 27c and 27d. The welding strings that are as a whole each designated by 28 are at each lateral plate la and lb connected to each their toothed belt. For further control of the course of the welding string, in particular in case of the parallel toothed- belt sections 27c and 27d, guides S are formed in the mounting plates la, lb in which curve rollers 15 travel. The curve rollers 15 are connected to the welding strings 28 by means of the element 29. Each welding string 28 has three curve rollers 15 at each side and the rollers 15 are able to rotate about their own axis which enables them to roll in abutment on the one or the other side of the conveyance path corresponding to the guide S .

On the outside of each mounting plate la and lb a drive wheel 19 is provided that are able to drive the toothed belts synchronously on each side of the film via shaft connections through the mounting plates. Hereby the welding string 28 is able to move around the triangular curve, and during passage of the toothed-belt sections 27c and 27d they will follow the sheets of film F in parallel at each side thereof. Control of the drive rate ensures that the welding strings 28 have the same rate as the sheets of film F along the toothed-belt sections 27c and 27d. The welding strings 28 are arranged such on the toothed belts that, simultaneously, to each side of the sheets of film F they follow the two parallel extending toothed-belt sections 27c and 27d. Adjustment of the temperature of the support faces in accordance with the time during which the faces are pressed against the sheets of film causes the sheets of film to be joined by welding between the support faces.

The welding strings can be rectilinear or curved; eg a welding can be configured such that it curves away from the welding unit proper. If such curved welding string is used against a retainer that is rectilinear or has a corresponding curvature it is ensured that the abutment pressure against the sheets of film decreases towards the rims thereof. The welding strings can also be conveyed by means of a curved curve conveyor whereby the abutment pressure can be varied during the welding process.

In operation the sheets of film F can be conveyed continuously and at high velocity through the welding unit, and when a welding is to be accomplished, the belt wheels of the welding unit are caused to rotate via the drive wheels by one or more servomotors 19 and the toothed belts 27 are moved and convey a welding string 28 on each side of the film for abutment on each their film face and press the strings 28 against each other.

Figure 3 illustrates an enlarged section of a mounting plate la, where two welding strings concur around the sheets of film F. The cam follower can be an element 29 with a suitable configuration, but herein it is configured as an actual carriage illustrated by a square to each side of the sheets of film F, and in accordance with the invention, three wheels hi, h2 and h3 are provided on the carriage that travel in the guide S formed by the rail segments Si and Sy. In the embodiment shown in fig. 3, two of the wheels hi and h2 extend on the inside Si of the guide, and the third wheel h3 extends on the outside Sy of the guide. The inside and outside of the guide thus form each their rail segment for one and two wheels, respectively. In the curve the distance between the inside and the outside of the guide must then be smaller than is the case at the rectilinear section if all three wheels along the entire guide are to be in contact with one of the sides of the guide. The carriage is shown with a dotted line at the rectilinear section to each side of the sheets of film F where the welding itself is performed. During the entire movement around the guide S, all three wheels hi, b-2 and h3 will keep the same direction of revolution since they each travel against the same side of the guide and thus against the same rail segment all the way. Hereby play-free course, reduced wear and less noise are obtained that combine to enable a substantial increase of the working rates of the welding station. Figure 4 shows an embodiment wherein the two of the carriage wheels hi and h2 run towards the outside Sy of the guide, and the third one runs towards the inside Si of the guide. Here it will be necessary to provide an increase in the guide width of the curve towards the rectilinear section.

In Figures 5 and 6 examples are shown of embodiments in which the guide S is replaced by a rail K on whose sides the wheels hl,h2,h3 travel against respective rail segments Si and Sy. When the two wheels hi and h2 travel on the inside Si of a curve and the wheel h3 travels on the outside Sy, as shown in Figure 5, the rail K in the curve must be narrower than is the case at the rectilinear stretch. Figure 6 shows an example of the two wheels hi and h2 travelling on the outside and the one wheel h3 travelling on the inside of a curve, and here the rail K must have an increased width in the curve compared to the width of the rectilinear stretch.

In the above-mentioned examples the one wheel h3 is arranged exactly between the centres of the two other wheels hi and h2 in the direction of movement of the car- riage, and hereby the best carriage stability is obtained and hence the most reliable control of the carriage orientation.

Now, Figure 7 shows an embodiment with four wheels, wherein two of the wheels hll and hl2 run on the inner rail segment Si of the guide and the two remaining wheels hl3 and hl4 on the outer rail segment Sy of the guide. Thus, the inner and outer sides of the guide form each their rail segment for an inner and an outer pair of wheels, respectively. The inner wheels hll and hl2 are arranged directly on the carriage 29, while the outer wheels hl3 and hl4 are arranged on a shared bogie 20 that, in turn, is arranged on the carriage 29. In order to ensure play-free conveyance of the carriage, the jour- nalling of the bogie on the carriage and the shape of the outer rail segment is selected to ensure that all four wheels are in contact with the respective rail segments all the way around the closed curve.

Now, Figure 8 illustrates an alternative embodiment with four wheels, wherein two of the wheels h21 and h22 run on an inner rail segment Si, and the two remaining wheels h23 and h24 travel on an outer rail segment Sy. Herein the guide is defined by a shared rail K, wherein the inner and outer sides thus form each their rail segment for an inner and an outer wheel pair, respectively. A first inner wheel h21 and a first outer wheel h23 forms a first, frontmost wheel pair arranged on a common first bogie 31 that is, in turn, arranged on the carriage 29. A second inner wheel h22 and a second outer wheel h24 form a second, rearmost wheel pair arranged on a common second bogie 32 that is, in turn, arranged on the carriage 29. This journalling of the wheels means that the inner rail segment Si and the outer rail segment Sy can be configured with constant mutual spacing, eg in the form of the sides on a shared rail K as shown.

Claims

C l a i m s

1. A welding unit with two opposed elements of conveyance (27) , wherein at least one transversally extending weld- ing string (28) is coupled to said elements of conveyance (27) , and wherein there is - externally relative to the welding strings (28) - to each side provided a cam conveyor (S) defining a closed geometrical curve and with a cam follower associated with the welding string (28) , characterised in that the cam follower comprises an element (29) with at least three wheel means (hl,h2,h3); that the cam conveyor comprises two opposed, continuous or discontinuous rail segments (Si,Sy), wherein a first pair of wheel means consisting of two wheel means (hl,h2) travel in succession on the one rail segment, and the remaining wheel means (h3) travel (s) on the other rail segment, the two rail segments extending at a mutual distance that ensures that all wheel means are in contact with respective rail segments all the way around the closed curve.

2. A welding unit according to claim 1, characterised in that the cam follower comprises an element (29) with three wheels (hl,h2,h3), wherein the first pair of wheel means consisting of two wheel means (hl,h2) travel in succession on the one rail segment, and the remaining wheel means (h3) travels on the other rail segment.

3. A welding unit according to claim 1, characterised in that the cam follower comprises an element (29) with four wheel means (hll, hl2, hl3,hl4) , wherein a first pair of wheel means consisting of two wheel means (hll,hl2) travel in succession on the one rail segment, an another pair of wheel means consisting of two wheel means (hl3,hl4) arranged on the element (29) by means of a common bogie (30) travel on the other rail segment, wherein the two rail segments extend at a mutual distance that ensures that all four wheel means are in contact with the respective rail segments all the way around the closed curve .

4. A welding unit according to any one of the preceding claims 1 through 3, characterised in that the two rail segments (Si,Sy) extend between said first pair of wheel means (hl,h2) and the remaining wheel (s) (h3) .

5. A welding unit according to any one of the preceding claims 1 through 3, characterised in that the two rail segments (Si,Sy) extend on the outside of said wheel pair (hl,h2) and the remaining wheel (s) (h3) .

6. A welding unit according to claim 1, characterised in that the cam follower comprises an element (29) with four wheel means (h21, h22, h23, h24 ) ; and wherein a first and a second inner wheel means (h21,h22) travel in succession on the one rail segment, and a first and a second outer wheel means (h23,h24) travel in succession on the second rail segment; wherein the first inner wheel means (h21) and the first outer wheel means (h23) form a first pair of wheel means arranged on a common first bogie (31) that is, in turn, arranged on the element (29); and wherein the second inner wheel means (h22) and the second outer wheel means (h24) form a second pair of wheel means ar- ranged on a common second bogie (32) that is, in turn, arranged on the carriage (29) ; wherein the two rail segments extend at a mutual distance that ensures that all four wheel means are in contact with the respective rail segments all the way around the closed curve.

7. A welding unit according to claim 6, characterised in that the two rail segments (Si,Sy) extend between said respective inner and outer wheel means (h21, h22, h23,h24) .

8. A welding unit according to claim 6, characterised in that the two rail segments (Si,Sy) extend on the outside of said respective inner and outer wheel means (h21,h22,h23,h24) .

9. A welding unit according to any one of the preceding claims 1 through 8, characterised in that the cam conveyor comprises a rectilinear rail segment with a random curve-shape for the remaining part of the stretch.

10. A welding unit according to any one of the preceding claims 1 through 9, characterised in that the conveyance elements (27) are arranged in two mutually parallel planes .