Method for head welding and head welding assembly

Abstract

The method is applicable in the production of tubes, bottles, cans, etc. It allows for work with new types of materials, provides increased welding quality and low scrap rate. Initially, the tubular body (4) is placed on the mandrel (1) so that its to-be-welded end is positioned at a distance from the head (2), which is greater than the distance that would be required to get into the final welded position, after forming. A forming and cooling element (6) and a nozzle (7) for heating gas are located coaxially to the mandrel (1), through which nozzle (7) the tubular body (4) and the head (2) are heated in the area intended for welding. After heating is completed, the tubular body (4) is moved in the opposite direction to the head (2) to a position where its to-be-welded end reaches the forming and welding position. With the help of a forming and cooling element (6), forming and welding are carried out.

Description

[0001] METHOD FOR HEAD WELDING AND

[0002] HEAD WELDING ASSEMBLY

[0003] FIELD OF THE INVENTION

[0004] The method and head welding assembly are intended for application in machines for head welding to tubular body made of foil, having one or more layers, especially for the manufacturing of tubulars, bottles, cans, etc.

[0005] BACKGROUND OF THE INVENTION

[0006] From EP 2279072 a method and an assembly for head welding are known, where on a mandrel, on which there is a head and a tubular body, put over in a typical manner, and the tubular body is in such a position relative to the head that, after heating and forming the tubular body around the head, the end of the tubular body overlaps the section of the head necessary for a reliable seam. Heating gas, usually air, is supplied to the chamber formed between the head and the to-be-welded part of the tubular body, and after reaching the required temperature in the respective sections of the tubular body and the head, with the help of an additional forming and cooling element FCE, the tubular body is bent and pressed against the head. After a certain amount of time, required for the welding, the FCE is taken away from the welding zone, with which the process is completed.

[0007] In this method, the main disadvantage is related to the shape and size of the chamber formed between the head and the to-be-welded part of the tubular body in the heating position. The distance between the tubular body and the head varies significantly with distance from the tubular body end. This leads to a variable resistance for the heating gas, hence decreasing, with increasing distance from the end of the tubular body, the amount of passing heating gas, and hence decreasing the transferred energy and thus, decreasing heating. Since the temperature range in which heating of the tubular body is acceptable is limited, sufficient heating cannot be provided in a range that is optimal for obtaining quality welding. SUMMARY OF THE INVENTION

[0008] The objective of the invention is to create a method for head welding that ensures maximum uniform heating of the tubular body in the welding area in order to achieve better quality welding.

[0009] Another objective of the invention is to create a head welding assembly working according to the method according to the invention.

[0010] The method, according to the invention, comprises the following steps:

[0011] - placement of a head and a tubular body of a manufactured product on a mandrel, whereby the tubular body is secured against movement relative to the mandrel. The tubular body is made of one or several layers of material, of which at least the one located on the side of the head is suitable for welding to the material of the head;

[0012] - positioning in the heating zone of forming and cooling element FCE and a nozzle, both located coaxially with related to the mandrel, with the nozzle being used to supply heating gas to the heating zone;

[0013] - heating the to-be-welded end of the tubular body and the corresponding part of the head to which the said end of the tubular body will be welded, by supplying heating gas to the heating zone through the nozzle;

[0014] - after the time required for sufficient heating has elapsed, the to-be-welded end of the tubular body is formed and pressed against the head by the forming and cooling element FCE;

[0015] - after the time required for the carrying out of the welding has elapsed, the forming and cooling element FCE and the nozzle are removed from the welding zone;

[0016] According to the invention, in the heating position, the to-be-welded end of the tubular body is positioned in an axial direction from the periphery of the head at a distance greater than the width of the section of the to-be-welded end of the tubular body, which will be welded to the head. Before forming and welding, the tubular body is moved in an axial direction opposite to the head, so that the section of the to-be-welded end of the tubular body, which will be welded to the head, is moved towards the head until forming and welding position is reached.

[0017] Preferably, in the heating position, the to-be-welded end of the tubular body is located in the forming area of the forming and cooling element FCE.

[0018] In an embodiment of the method, the movement of the tubular body to the forming and welding position begins before the heating is completed.

[0019] A head welding assembly is also provided, according to the invention, which consists of:

[0020] - a mandrel with a fixing element for a tubular body of a manufactured product, one end of the mandrel corresponding in shape and dimensions to the head of the manufactured product,

[0021] - a forming and cooling element FCE and a nozzle for supplying heating gas, both coaxially located to the mandrel, which are configured to move in the axial direction together or independently of each other, reciprocating to and from the mandrel,

[0022] The head welding assembly has the following positions of its components:

[0023] - an initial position at which the FCE together with the nozzle are in the farthest position from the mandrel in the axial direction;

[0024] - a heating position in which the FCE together with the nozzle are located adjacent to the mandrel, whereby the head, the tubular body, the FCE and the nozzle form a chamber into which a heating gas is supplied by means of the nozzle;

[0025] - a forming and welding position in which the FCE is in the closest position to the mandrel, for pressing and welding the heated end of the tubular body to the heated area of the head.

[0026] According to the invention, the mandrel also comprises a movable element located between the fixing element and the mandrel’s body, wherein the fixing element is configured with the ability to fix a tubular body to the movable element. The fixing element and the movable element are configured with the ability of reciprocating progressive movement relative to the mandrel in the axial direction.

[0027] The purpose of the invention is to ensure more uniform heating of the tubular body in the section which is to be welded. The main irregularity in the heating of the method from the state of the art is due to the fact that the distance between the tubular body and the head at the end of the tubular body (x2), shown in Fig. 6, is significantly larger than that at the other end of the to-be-welded section (xl), shown in Fig. 6, which leads to a significant difference in the amount of passing heating gas in different sections and, accordingly, different heating. With the proposed method, due to the changed position of the tubular body, the distance between the tubular body and the head at the end of the tubular body (x4), shown in Fig. 7, is approximately equal to that at the other end of the to-be-welded section (x3), shown in Fig. 7, and hence the amount of passing heating gas in different sections is almost the same, as a result of which the heating is much more uniform. Since the temperature range in which the process can be executed without underheating or overheating the components is limited, uniform heating is critical for obtaining a stable and good-looking weld.

[0028] The advantages of the method according to the invention are that due to the smaller variation in the distance between the tubular body and the head, the amount of gas passing through and in contact with the to-be-welded surfaces is more even, resulting in more uniform heating. During forming, uniform heating ensures uniform deformation of the to-be-welded end of the tubular body and thus reduces the risk of wrinkling in the weld area, thus improving the appearance of the final product. Also, more uniform heating allows work with much thinner materials, which, due to their lower mechanical stability, are more sensitive to uneven heating. This also provides reduction in defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The invention is explained in more detail, with an example of a head welding assembly in a machine for welding (not shown in the figures), where:

[0030] - Fig. 1 is a longitudinal section of the assembly in the initial position;

[0031] - Fig. 2 is a longitudinal section of the assembly in the heating position;

[0032] - Fig. 3 is a longitudinal section of the assembly in the pre-forming position;

[0033] - Fig. 4 is a longitudinal section of the assembly in the forming and welding position;

[0034] - Fig. 5 is a longitudinal section of the assembly in the final position;

[0035] - Fig. 6 is an enlarged image of the end of the mandrel with a portion of the head and the tubular body from the state of art, coinciding with the preforming position of the present invention;

[0036] - Fig. 7 is an enlarged image of the end of the mandrel with a portion of the head and the tubular body in the heating position according to the present invention.

[0037] DETAILED DESCRIPTION OF THE INVENTION

[0038] According to the method for head welding, initially, on a mandrel 1 of the head welding assembly, a head 2 and a tubular body 4 of the manufactured product are placed. The tubular body 4 shall be placed on the mandrel 1 so that its end, which is to be welded, is projected forward, and positioned at a distance from the head 2, which is greater than the width of the section of the tubular body 4 which is to be welded to the head 2. This is usually in the range of a few millimetres for the typical dimensions of the manufactured product. The terms 'forward' and 'backward' in this description are used in reference to the position of the tubular body 4 relative to the mandrel 1 , with 'forward' meaning the direction towards the end of the mandrel 1 on which the head 2 is positioned, and 'backward' being the opposite direction. In the state of art method, the position of the tubular body 4 relative to the head 2 in the heating position is the same as the arrangement of these two elements in the pre- forming position (as shown in Fig. 6), that is, the to-be-welded end of the tubular body 4 protrudes forward from the head 2 as much as the width of the to-be-welded section of the tubular body 4. In the present method, according to the invention, the relative positions of the tubular body 4 and the head 2 are different in the heating position (Fig. 2 and 7) and in the pre-forming position (Fig. 3 and 6).

[0039] After the initial positioning of the tubular body 4, it is pressed and fixed to the mandrel 1 by means of a movable fixing element 5 (Fig. 1). Then the heating nozzle 7 and the forming and cooling element FCE 6 are moved toward the mandrel 1 to the heating position (Fig. 2). The heated gas is supplied through the nozzle 7 for the time required to reach the required temperature of the head 2 and the tubular body 4 in the heating zone. Next, the fixing element 5 is moved together with the tubular body 4 in the opposite direction to the head 2, as a result of which the tubular body is moved in the same direction to the pre-forming position (Figs. 3 and 6), corresponding to the welding position, and the section of the to-be-welded end of the tubular body 4 is positioned in relation to the corresponding section of the head 2, to which it will be welded. Then the FCE 6 moves independently to the mandrel 1 to the forming and welding position (Fig. 4), at which the FCE 6 forms and presses the tubular body 4 against the head 2. After the time required for the welding elapses, the FCE 6 returns to the initial position (Fig. 5).

[0040] In the heating position (Fig. 2), when the to-be-welded end of the tubular body 4 protrudes forward from the head 2, a larger heating zone is formed between the two elements of the manufactured product (Fig. 7), in which a larger amount of heating gas circulates, which contributes to a more uniform heating of the tubular body 4 and the head 2. After pulling back the tubular body 4 to the forming and welding position (Fig. 4), due to the uniform heating, the to-be-welded end of the tubular body 4 is evenly deformed and the usual wrinkling of the welded end is not obtained, resulting in a better quality, stronger and improved appearance welding. The head welding assembly, according to the invention, consists of a mandrel 1 and a forming and cooling element 6 and a nozzle 7 for supplying heating gas.

[0041] The mandrel 1 has a body of cylindrical or other shape, and one of its ends having a shape and size corresponding to the head of the manufactured product. To the mandrel 1 there is a fixing element 5 for fixing the position of the tubular body 4 on the mandrel 1.

[0042] Figures 1 to 5 show an example design of a head welding assembly implementing the method of the invention. It should be noted that the method, according to the invention, can also be implemented through other assemblies for head welding known from the state of the art. The assembly shown in the figures consists of a mandrel 1 and a movable element 3 coaxial to the mandrel. The head 2 is placed on the mandrel 1 , and additionally, a movable element 3 is placed on the mandrel 1 , in a section with a reduced diameter, the movable element 3 being in the form of a sleeve, preferably cylindrical. The through opening of the movable element 3 is of such shape and size as to accommodate the body of the mandrel 1 , so that the movable element 3 can move freely and without jamming reciprocally in the axial direction relative to the body of the mandrel 1. The outer diameter of the movable element 3 is slightly smaller than the inner diameter of the tubular body 4, which must be placed on the mandrel 1. The tubular body 4 of the manufactured product is located on the movable element 3. A fixing element 5 is located around the movable element 3, configured for fixing the tubular body on the movable element 3, for example by pressing, thus maintaining the position of the tubular body 4 during heating and forming. The fixing element 5 and the movable element 3, together with the tubular body fixed between them, are configured to perform a reciprocal translational motion in an axial direction relative to the body of the mandrel 1 so as to move the tubular body relative to the end of the mandrel on which the head 2 is placed.

[0043] As shown in Figures 1 to 5, the forming and cooling element FCE 6 and the nozzle 7, known from the state of art, are coaxially arranged to the mandrel 1. The FCE 6 and the nozzle 7 are configured to move axially together or independently of each other reciprocating to and from the mandrel 1. The nozzle 7 is comprised of two parts, internal and external, which form channel 8 for the supply of heating gas. The temperature of the FCE 6 is maintained within the required range, for example, by means of a coolant that circulates in a cooling loop of channels in the FCE 6 (not shown on the figures). The side of the FCE 6 that performs the forming, has a surface that corresponds in shape and size to the head 2 and the tubular body 4 of the manufactured product.

[0044] The head welding assembly and its integral elements has the following positions:

[0045] - initial position at which the FCE 6 together with the nozzle 7 are in the position farthest from the mandrel 1 in the axial direction (Fig. 1);

[0046] - a heating position in which the FCE 6 together with the nozzle 7 are adjacent to the to-be-welded end of the mandrel, whereby the end of the mandrel 1, the FCE 6 and the nozzle 7 form a cavity in which the parts of the head 2 and the end of the tubular body 3 which are to be heated are located (Figure 2);

[0047] - a forming and welding position in which the FCE 6 is in the closest position to the mandrel 1 and presses the heated end of the tubular body 4 against the head 2 (Fig. 4).

[0048] The parts of the head welding assembly are made of permissible materials known from the state of art.

[0049] Operation of the head welding assembly

[0050] The head welding assembly, according to the invention, implementing the claimed method, works as follows:

[0051] A head 2 is placed on the mandrel 1 , and a tubular body 4 rests on the movable element 3. The to-be-welded end of the tubular body 4 is positioned in the required position, after which it is pressed against the movable element 3 using the fixing element 5. Then the forming and cooling element 6 together with the nozzle 7 are moved to the welding zone. Then the heating gas is supplied through the nozzle 7. After the time required for heating has elapsed, the fixing element 5 moves backwards in the opposite direction to the head 2, which also leads to the movement of the tubular body 4 and the movable element 3 in the same direction. The movement distance shall be such that the end of the tubular body 4 comes into a position relative to the head 2 corresponding to the required overlap between the tubular body 4 and the head 2 in the final welded position. Then the forming and cooling element 6 is fed to a position where the tubular body 4 is formed and pressed with the required force against the head 2. After the time required for cooling is elapsed, the forming and cooling element 6, together with the nozzle 7, are taken away from the welding zone.

Claims

AMENDED CLAIMS received by the International Bureau on 05 February 2025 (05.02.2025)CLAIMS1. Method for head welding, which includes the following stages:- arrangement of a head (2) and a tubular body (4) on a mandrel (1), whereby the tubular body (4) is secured against movement relative to the mandrel (1), which tubular body (4) has one or more layers of material of which at least the one located on the side of the head (2) is suitable for welding to the material of the head (2);- moving of a forming and cooling element (6) and a nozzle (7) used to supply heating gas, both arranged coaxially to the mandrel (1) towards a heating zone;- supply of heating gas through the nozzle (7) to the heating zone of the to- be-welded end of the tubular body (4) and the corresponding part of the head (2) to which the heated end of the tubular body (4) will be welded;- after the time required for heating is elapsed, with the help of the forming and cooling element (6), the to-be-welded end of the tubular body (4) is formed and pressed against the head (2);- after the time required for the welding is elapsed, the forming and cooling element (6) and the nozzle (7) are removed from the welding zone; characterized by that the arrangement of the tubular body relative to the head and the mandrel has two positions, respectively heating position and forming and welding position, wherein in the heating position, the to-be-welded end of the tubular body (4) is projected in an axial direction from the periphery of the head (2) at a distance that is greater than the width of the section of the to-be- welded end of the tubular body (4) which will be welded to the head (2) after the welding is carried out, wherein before forming and welding the tubular body (4) is moved back in an axial direction opposite to the head (2), so as the section of the to-be-welded end of the tubular body (4) which will be welded to the head (2) is moved in the direction of the head (2) until the forming and welding position is reached.

2. A method according to claim 1 characterized by that, in the heating position, the to-be-welded end of the tubular body (4) is located in the forming area of the forming and cooling element (6).

3. A method of claim 1 characterized by that the movement of the tubular body (4) to the forming and welding position begins before the heating is completed.

4. Head welding assembly consisting of- a mandrel (1) with a fixing element (5) for a tubular body (4), wherein one end of the mandrel (1) corresponding in shape and size to a head (2) of a manufactured product,- coaxial to the mandrel (1) a forming and cooling element FCE (6) and a nozzle (7) for supplying heating gas, which are configured with the ability to move in the axial direction together or independently of each other reciprocating to and from the mandrel (1), wherein the head welding assembly have the following positions of its integral parts:- an initial position at which the FCE (6) together with the nozzle (7) are in the position farthest from the mandrel (1) in axial direction;- a heating position in which the FCE (6) together with the nozzle (7) are adjacent to the mandrel (1), wherein the mandrel (1), the FCE (6) and the nozzle (7) form a chamber in which a nozzle opening for heating gas is located;- forming and welding position in which the FCE (6) is in the closest position to the mandrel (1), for pressing and welding the heated end of the tubular body (4) to the head (2), characterised in that the mandrel (1) also comprises a movable element (3) located between the fixing element (5) and the body of the mandrel (1), whereinthe fixing element (5) is configured with the ability of fixing a tubular body (4) to the movable element (3), the fixing element (5) and the movable element (3) being configured with the ability of reciprocating movement relative to the mandrel (1) in the axial direction.

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