GB2096038A

GB2096038A - Can body welder

Info

Publication number: GB2096038A
Application number: GB8209650A
Authority: GB
Original assignee: Daiwa Can Co Ltd
Current assignee: Daiwa Can Co Ltd
Priority date: 1981-04-02
Filing date: 1982-04-01
Publication date: 1982-10-13
Also published as: JPS57165187A; FR2503001A1; AU8172782A; CH654234A5; IT8248134A0; CA1175295A; JPH0144433B2; KR830008781A; DE3211781A1; IT1148904B

Abstract

A can body welder for welding the overlapped portion of a can body by passing said portion between upper and lower electrode rolls (1,2), is provided with a cooling means, for example passages for flow of cooling liquid or a nozzle for blowing cooling gas, for keeping the temperature of the tip portion (8) of a forward guide part (37), while welding, at a temperature at which the surface protective layer of the portion of the can body which comes in contact with and slides along said tip portion cannot be damaged. <IMAGE>

Description

SPECIFICATION Can body welder The present invention relates to a can body welder for welding the side seam of a can body made of a metal, for example, tinplate sheet, the welder having guide parts which guide the overlapped portion comprising the side seam of said can body between upper and lower electrode rolls.

The structure of the welded article-guiding parts combined with the related outer parts of a known can body welder is shown in the accompanying drawings in Figure 1 (side view) and Figure 2 (sectional view along the line ll-ll in Figure 1).

In these Figures, 1 denotes an upper electrode roll; 2 denotes a lower electrode roll positioned right under said upper electrode roll 1; 3 denotes a horizontal supporting part for supporting said lower electrode roll at its one end (which supports also the intermediate guide part mentioned below); 4 denotes a backward fixing part which is fixed to the body wall plate of the welder (not shown) and suspends and supports a backward guide part 5 which is in turn fixed to the upper portion of the hinder part 3a of the above-mentioned supporting part 3; 6 denotes an intermediate guide part positioned on the above-mentioned supporting part 3 and located just in front of the backward guide part 5; 7 denotes a forward guide part which is on the forward notch portion of said intermediate guide part 6 over the supporting part 3 and which has a tip portion 8 locating close to and between the upper and lower electrode rolls 1 and 2, where guide grooves 16 and 16' extend therethrough to the tip portion 8; 9 denotes a forward fixing part for fixing said forward guide part 7 and is rigidly connected to a horizontally projecting arm 11 fixed to the abovementioned body wall plate by means of a bolt 10 extending vertically through said projecting arm and a nut 12; 14 (Figure 2) denotes a bolt for attaching the forward guide part 7 to a plate 13 of the forward fixing part 9; and 15 and 15' are electric insulating plates for the insulation between the respective parts.

A denotes a can body, and the two edges of it B and C forming the side seam are inserted in the above-mentioned guide grooves 16 and 16' positioned in the forward guide part 7, respectively.

Here, said guide grooves 16 and 16' extend to guide grooves 18 and 18' (18' is not shown) positioned in the intermediate guide part 6 and to guide grooves 19 and 19' (19' is not shown) positioned in the backward guide part 5, respectively.

Figure 2 shows perforations 21,22 and 23 penetrating the supporting part 3 in its axial direction, 21 and 22 being passages for cooling water for cooling the supporting part 3 while 23 is a passage for an electrode wire. Left and right cuttings 24 and 25 are for wiring the pipes for paint and for detection of the quantity of paint, respectively.

In the above-mentioned system shown in Figures 1 and 2, a cylindrical can body made of a metaltic plate progresses from the left in Figure 1 to circle the supporting part 3 to insert the two edges B and C which become the side seam in the guide grooves 19 19' in the backward guide part 5, and then moves to the right in the Figure along the guide grooves 18 and 18' in the intermediate guide part 6 and then the guide grooves 16 and 16' in the forward guide part 7 and passes by the tip portion 8 of the forward guide part. The two edges B and C are sent one upon another between the upper and lower electrode rolls 1 and 2. The edges are heated because of electric resistance and pressurized with the two electrode rolls for welding while they pass between said two electrodes.Welding current passes through the upper electrode roll < can body -, lower electrode roll < supporting part.

Though not shown, another type of welder for tinplate sheet-made can body has also been used, which is provided with electrode wires which are coiled around the upper and lower electrode rolls, respectively and move as said electrode rolls rotate, where the overlapped portion of the can body is inserted in the two electrode wires for welding. This type of welder is also provided with the respective guide parts shown in Figure 1.

In either case, the welder for the side seam of a can body has a welding speed of 50 m/min. and a satisfactory welded can body side seam is obtained at a frequency of 420 HZ, a primary current of 120 A and a secondary current (welding current) of 3600 A.

The inventors of the present invention have looked for ways of improving the welding speed and the production efficiency using the prior art systems of the types mentioned above. In an experiment, the frequency was set at 600 HZ to increase the welding speed to 70m/min. and the primary current was set to 130 A to run the welder. As a result, in about 10 minutes after the start of the welding cans having poorly welded portions or cans having melted plating layers and/or peeled or burn coating layers on the two sides of the welded portion were observed. Then, the operation was stopped to find out the causes.Extraneous matter was found in the guide grooves of the guide parts, particularly in the guide grooves 16 and 16' in the tip portion 8 of the forward guide part 7, and the extraneous matter was found to comprise the tin for plating and the protective coatings separated from the can bodies.

As a result of experiments and study to find the causes for the phenomena mentioned above, it has been found that the temperature of the tip portion 8 of the forward guide part increases rapidly and that the relationship between the increase in the temperature and the time elapsed after the start of operation in the case where the frequency is 600 HZ, and the primary current is 130 A is illustrated by the graph Z shown in Figure 6 of the accompanying drawings.

From this graph, it is noted that the temperature reaches about 300 C within 10 minutes after the start of operation and is over 35000 in 20 minutes, and thus it is assumed that as the two edges of the can bodies come into contact with and slide along the walls of the grooves in the forward guide parts at such high temperature peeling off and/or melting of the coating and/or the applied tin on the surface occurs, thereby causing the deposits on the walls of said grooves.

Also, it has been found from the experiments and study that, where the frequency is 420 HZ and the primary current is 120 A, the forward guide part reaches about 1800C in about 20 minutes after the start of operation, and thereafter the temperature remains at around 1800C.

According to the present invention there is provided a can body welder for welding two overlapped edge portions of a can body which become the side seam upon welding by passing said overlapped portions between an upper electrode roll and a lower electrode roll, which welder is provided with a horizontal supporting partforsupporting said lower electrode roll at one end of said supporting part and with a forward guide part having a tip portion located in the neighbourhood of both of said upper and lower electrodes and guide grooves penetrating therethrough to said tip portion for guiding the two guide edge portions of said can body, respectively, where said forward guide part is placed above said supporting part, and welding current passes through the upper electrode roll, the can body, the lower electrode roll and the supporting part in that order, wherein the welder is provided with a cooling means adapted to keep the temperature of the tip portion of said forward guide part, while welding, at a temperature at which the surface protective layer of the portion of the can body which comes in contact with and slides along said tip portion cannot be damaged.

In the accompanying drawings: Figure 1, as mentioned above, is a side view of a known can body welder showing the structure of the combination of welded article-guiding parts and its related outer parts; Figure 2, as mentioned above, is a sectional view along the line ll-ll in Figure 1; Figure 3 is a side view showing the structure of the combination of welded article-guiding parts and its related outer parts according to an embodiment of the present invention; Figure 4 is a sectional view along the line IV-IV in Figure 4; Figure 5 is a partially enlarged view of Figure 3; and Figure 6 and 7 both are graphs showing the relationship between the time elapsed after the start of welding and the increase in the temperature of the tip portion of the forward guide part.

An embodiment of the present invention is described below with reference to Figures 3 to 5. As the present invention relates to an improvement in guide parts shown in Figures 1 and 2, those parts shown in Figures 3,4 and 5 have the same reference numerals as the corresponding ones shown in Figures 1 and 2. Those numbers include 1 ,2,3,3a,4,5,8,1 5,1 5',1 6,1 6',1 8,19,21 ,22,23,24,25,A B and C.

The improved parts are the intermediate guide part 36 and the forward guide part 37, and the newly added part is a fixing part 41 forfixing these intermediate and forward guide parts from above.

Numerals 42,43 and 44 denote bolts for fixing said portion to be fixed.

The improvement in the intermediate guide part 36 comprises, as is illustrated in Figures 4 and 5, inlet and outlet ports 46 and 47 for cooling liquid placed in the rear end rising portion 45 of said intermediate guide part 36 and provision of a vertical passage 48 for cooling liquid which communicates with said inlet port 46, an outward horizontal passage 49 leading to the tip portion 53 of said part 36, a passage 50 which is located at the end of said passage 49 vertically against the drawing sheet, a returning horizontal passage 51 positioned in parallel with the outward horizontal passage 49 mentioned above and a returning vertical passage 52 which communicates with the outlet port 47 so that the cooling liquid may flow back. The improvement in the forward guide part 37 is made by the combination with the newly added fixing part 41.

That is, said fixing part 41 is provided with an inlet port 61 and an outlet port 62 for cooling fluid at the rear end and further with an outward horizontal passage 63 which communicates with said inlet port 61 and leads to the neighbourhood of the front end of the fixing part 41, a passage 64 located at the end of said passage 63 vertically against the drawing sheet and a returning horizontal passage 65 positioned in parallel with the outward horizontal passage 63 mentioned above and communicating with the outlet port 62.The forward guide part 37 is provided with an outward horizontal passage 72 which communicates with an outward descending passage 71 which descends from the outward horizontal passage 63 in the fixing part 41, a vertical passage 73 located at the front end of said outward horizontal passage 72 vertically against the drawing sheet and a returning horizontal passage 74 which starts at the other end of said vertical passage 73 and is in parallel with the returning horizontal passage 72. The returning horizontal passage 74 communicates with a returning descending passage 75 which descends from the returning horizontal passage 65 in the fixing part 41. Thus, the cooling liquid which has entered the system through the inlet port 61 passes through the forward guide part 37 and flows back to the outlet port 62.

Employing the guide parts shown in Figures 3-5, water at 70C was sent to the insides of the above passages in the intermediate and forward guide parts under pressure and the welder was operated at a frequency of 600 HZ and a primary current of 130 A while cooling said two parts to weld can bodies at a rate of 500 cans per minute. No poorly welded can was produced in several hours of continuous operation.

The relationship between the time and the temperature of the tip portion of the forward guide part when the operation was made under the same conditions as the above is shown by the graph Yin Figure 6.

The inventors of the present invention have studied the relationship between the temperature of the tip portion 8 of the forward guide part and the operation time in the case where a forward guide part not provided with a cooling means according to the present invention is used at a variety of frequency and current values. The result is shown in Figure 7. Figure 7 shows that the temperature of the tip portion increases as either or both of the frequency and current value increases. On the other hand, as a result of experiments, it has been found that if the degree of heating of the welded article by its contact with the forward guide part is to such an extent that the applied metal and the protective coating on the surface are not damaged, peeling off of such protective layer and poor welding are not brought about.

For example, the critical temperature is about 2000C in the case of tinplate sheets. Accordingly, even where the production of poorly welded cans is expected from Figure 6 (the curve Z) and Figure 7 as no cooling means according to the present invention is provided, such production may be avoided by the application of the present invention.

In the above embodiment, cooling liquid was passed through all of the fixing part 41, intermediate guide part 36 and forward guide part 37 for cooling, but the point is that cooling is effected to such an extent that the temperature of the forward guide part, particularly the tip portion, does not reach the critical temperature. Therefore, the temperature of the tip portion 8 may also be controlled by well cooling the intermediate guide part and/or the fixing part which are in contact with said forward guide part and cooling the forward guide part with the cooled parts.

As Figure 7 shows, the degree of increase in the temperature of said tip portion changes depending on the frequencies and the current values. So, where both the frequency and the current value are low, the tip portion of the forward guide portion may be controlled to desired temperatures by cooling only the intermediate guide part.

In the above embodiment, cooling liquid was introduced into the forward guide part 37 via the fixing part 41 inevitably because of the structure of the welder, but cooling liquid may be introduced directly into the forward guide part if it is possible from a structural viewpoint.

Further, in the above embodiment passages for allowing cooling fluid flow as a means for cooling the forward guide part are provided in the forward guide part and the fixing part and the intermediate guide part which are in contact with the forward guide part. However, cooling gas, for example, liquid nitrogen, may be vaporized and blown against the intermediate guide part and the forward guide part through a nozzle to create a cooling atmosphere thereby limiting the temperature of the forward guide part to less than the critical temperature.

Claims

1. A can body welder for welding two overlapped edge portions of a can body which become the side seam upon welding by passing said overlapped portions between an upper electrode roll and a lower electrode roll, which welder is provided with a horizontal supporting partforsupporting said lower electrode roll at one end of said supporting part and with a forward guide part having a tip portion located in the neighbourhood of both of said upper and lower electrodes and guide grooves penetrating therethrouqh to said tip portion for guiding the two guide edge portions of said can body, respectively, where said forward guide part is placed above said supporting part, and welding current passes through the upper electrode roll, the can body, the lower electrode roll and the supporting part in that order wherein the welder is provided with a cooling means adapted to keep the temperature of the tip portion of said forward guide part, while welding, at a temperature at which the surface protective layer of the portion of the can body which comes in contact with and slides along said tip portion cannot be damaged.

2. A can body welder as claimed in claim 1, wherein the cooling means comprises a passage provided in said forward guide part for allowing cooling fluid flow therethrough.

3. A can body welder as claimed in claim 1 or 2, wherein the cooling means comprises passages for allowing cooling fluid flowtherethrough in an intermediate guide part and/or a fixing part which are in contact with said forward guide part.

4. A can body welder as claimed in any preceding claim, wherein the cooling means comprises a nozzle for blowing cooling gas against said forward guide part.

5. A can body welder substantially as herein described with reference to Figures 3 to 5 of the accompanying drawings.