JPS6124112B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to resistance seam welding of successive workpieces.

In the manufacture of cylinders and other containers, such as tinplates, which consist of an essentially cylindrical outer shell or jacket and a folded floor or bottom, so-called resistance roll seam welding is used to achieve airtight seams. is known to be adopted. Resistance roll seam welding is characterized by an overlapping welding of a series of welding points such that a welding point is added during each half-cycle of the alternating current used for this purpose. Each welding point has a predetermined length dimension when considered with respect to the direction of transport or feed of the workpieces to be welded, which length dimension is determined by the transport mechanism relative to a predetermined frequency of the alternating current. Considering a practical example, for a transport speed of 15 m/min and an alternating current of 50 Hz, the length dimension is approximately 2.5 mm. The welding points with the abovementioned lengths are arranged in line adjacent to each other along the overlapping edges of the workpieces to be welded.

However, in the case of conventional resistance seam welding techniques, a weld point appears exactly at one edge of the workpiece at the start of the weld seam and/or at the end of the weld seam, with the result that one such weld point of the workpieces to be welded, which on the other hand inevitably led to burnout of the edges of such workpieces. The workpiece to be welded is, for example, a so-called frame forming the jacket or outer shell surface of the tin iron to be produced in this way, which frame is subsequently subjected to a folding or inward flanging operation. The disadvantages of such burnt edges are particularly noticeable during the folding of such floors, as they create leakage points in the product.

According to a first feature of the invention, there is provided a method for resistance seam welding successive workpieces, the method comprising: transporting each workpiece in a predetermined direction at a constant nominal speed to a roll weld; In the roll weld, the workpieces are welded by applying to the workpiece half-cycles consisting of an integral number of half-cycles of alternating current to create a series of welding points, each welding point being The leading and trailing edges of the workpiece pass at said constant nominal speed through a measuring section which is created during each successive half-cycle of the group of AC half-cycles and which is arranged forward of the weld in the direction of transport of the workpiece. detecting a point in time and determining the value of the phase of the alternating current at the point in time; to ensure that the series of weld points are arranged on the workpiece such that the trailing edge of the last of the weld points is spaced inwardly from the trailing edge of the workpiece. , consisting of varying the transport speed of the workpiece according to the deviation of said determined phase value from the corresponding reference phase value, the distance between the leading edge of the first welding point and the leading edge of the workpiece and the last A method is provided in which the spacing between the trailing edge of the weld point and the trailing edge of the workpiece is adjustable.

According to a second feature of the invention, there is provided an apparatus for resistance seam welding successive workpieces, comprising a roll weld and a roll weld that moves the workpieces in a predetermined direction at a constant nominal speed. and a mechanism for welding the workpieces by applying to the workpieces half-cycles consisting of an integral number of half-cycles of alternating current to create a series of weld points. operatively, each weld point being made during each successive half-cycle of the group of AC half-cycles;
Furthermore, a measuring part is arranged in front of the welding part in the direction of transport of the work piece and is adapted to detect the time points when the leading and trailing edges of the work piece pass therethrough, and the phase of the alternating current at said time points. and varying the workpiece transport speed according to the deviation of the determined phase value from the corresponding reference phase value so that the leading edge of the first weld in the series of weld points is in front of the workpiece. a series of weld points spaced inwardly from the edges such that the trailing edge of the last weld point in the series is spaced inwardly from the trailing edge of the workpiece; and a control mechanism operative to ensure that a distance between the leading edge of the first weld point and the leading edge of the workpiece and the trailing edge of the last weld point is maintained on the workpiece. A device is provided which allows adjustment of the spacing between the workpiece and the trailing edge of the workpiece.

The present invention will now be described in more detail with reference to one embodiment thereof, with reference to the accompanying drawings.

FIG. 1 schematically shows a conventional roll welding machine having a pair of welding rollers, rolls 1 and 2, sometimes also referred to in the art as electrode rolls. The welding roller 2 is driven by a suitable drive motor 3. A transport or feed mechanism 4 arranged in front of, ie upstream of, the welding rollers 1 and 2 with respect to the direction of progress of the workpieces,
It has two sprocket gears 5 and 6.
The sprocket gear 5 is driven by a suitable drive motor 7. A conveyor or transfer chain 8 and/or equivalent structure is draped around both of these sprocket gears 5 and 6 and supports conveyor elements 9 at spaced locations along their length. 9 continuously transports or feeds the work piece 10 towards the welding rollers 1 and 2 in a predetermined direction of travel at a constant nominal speed.
The workpieces 10 to be welded are, by way of example, constituted by sheet metal strip materials whose overlapping contact edges are joined together by a roll seam welding operation to form an airtight seam. Assume that Each of the sheet metal strips welded together forms, for example, the jacket or shell of the chisel and the floor or shell of such chisel is formed by carrying out suitable folding movements during the next processing step. The bottom can be formed. For convenience, the body of the chisel to be welded may be referred to as the frame from now on.

The drive motor 3 of the welding roller 2 and the drive motor 7 of the transport or feeding mechanism 4 can be controlled independently of each other. The welding operation is performed by applying half-cycles consisting of an integral number of half-cycles of alternating current to each workpiece 10 to create a series of weld points as shown in FIG. is produced during each successive half-cycle of the AC half-cycle group. For a predetermined transport speed of the workpiece 10, it is possible to calculate the dimensions of each weld point in the transport direction. The number of weld points in each half-cycle group is such that for workpieces 10 of varying lengths, the series of weld points is between the leading and trailing edges of the workpiece as shown in FIG. selected for inclusion. However, the lengths of the individual workpieces or frames 10 have certain tolerances, so that for a given transport speed it is possible that their welding points may be placed in unfavorable positions. . The purpose of the apparatus described here is to prevent welding points from being applied directly to the leading or trailing edges of the frame at the edge of the sheet metal strip or strip material, so that the welding If a dot is applied directly to the leading or trailing edge, it may cause burnout of the material at such location.

In order to control the feeding or advancement of the workpiece or frame 10, a measuring device 11 is arranged between the welding rollers 1 and 2 and the sprocket gear 5 of the transport mechanism.
This measuring section 11 may be equipped with a conventional light source and light receiving device or suitable devices, through which the leading and trailing edges of each frame 10 pass. When the frame 10 passes the measuring section 11, the measuring section determines when the leading and trailing edges of the frame pass through the measuring section. For convenience, 2 is shown in Figure 1.
Calculator 12, shown as two separate blocks, receives the welding AC waveform as a reference signal from block 16 on the one hand, and its output signal from measuring section 11 on the other hand. The calculator 12 is the measurement unit 1
When a signal indicating passage of the leading edge of the work piece 10 is received from 1 to 1, it operates to determine the value of the phase of the alternating current signal at that time. At a constant nominal transport speed, the leading edge of the first weld spot in the series is spaced a distance A inwardly from the leading edge of the workpiece as shown in FIG. Thus, when the workpiece 10 is to reach the welding rollers 1, 2, such a determined phase value has a predetermined reference value. The calculator 12 compares the determined phase value with its reference value and, in response to any deviation between those values, corrects the constant nominal transport speed of the workpiece 10. and sends a control signal to the control unit 14 of the drive motor 7 of the transfer mechanism 4, so that the speed of the drive motor 7 is equal to the front end of the first welding point applied to the frame or workpiece 10. is changed so that it is located at a distance A from the leading edge of the frame. As soon as such a frame 10 is captured by the welding rollers 1 and 2, these welding rollers carry out the subsequent transport of the frame and the conveyor element 9 of the transport mechanism 4 no longer transfers the frame or workpiece. 10 and is not in operative engagement.

A similar operation occurs with the aid of the computer 12 when the trailing edge of the frame 10 passes through the measuring section 11, but in this case the trailing edge of the last welding point in the series of welding points As you can see by referring to the figure,
The speed of the drive motor 3 of the welding roller 2 is adjusted through the control unit 15 so that it is located at a distance A' from the trailing edge of the frame or workpiece 10.

The manner in which the speed of the drive motor 7 or 3 is controlled by the computer 12 and the control unit 4 or 15 after the leading or trailing edge of the frame body 10 has passed through the measuring section 11 as described above may be any conventionally known suitable method. Since the invention can be implemented in a variety of ways and in a variety of forms using conventional equipment and components available on the market, such as stepping motors, counters, microprocessors, etc. There is no limitation in any way.

However, in order to further facilitate understanding of the inventive idea of the present invention, an example of its embodiment will be described below.
That is, as previously explained, the feeding of each workpiece 10 is such that the welding current (50 Hz alternating current, the waveform of which is shown in block 16 as a reference signal) reaches its positive zero (i.e., negative amplitude). At the moment when the point B at a distance A from the front edge b of the workpiece 10 in FIG. 2 reaches the welding position D between the welding rollers 1 and 2 in FIG. , and the welding current is controlled to be supplied to the welding rollers 1 and 2 at that moment. A sensing element of the measuring part 11, which is sensitive to a light beam, for example, is placed at a position separated from the welding position D by a certain distance a (FIG. 1). Therefore, from the moment when the leading edge b of the workpiece 10 passes through its sensing element until the point B reaches the welding position D and at that moment the welding current is supplied from the zero point in the positive direction, the workpiece 10 has to be moved by a distance a+A and the workpiece has a nominal feed rate v ₀
When the object is being transported at a speed of 1, it takes a time of t ₀ =(a+A)/v ₀ to move that distance. Within that time, N ₀ =t ₀ · _w (where _w is the alternating current frequency of the welding current, for example 50 Hz) wave numbers of the welding current pass through the welding position D. Here, the wave number N ₀ consists of an integer part representing the number of complete waves and the remaining decimal part, and the latter decimal part can be called a "position error". The reason for this is that the leading edge b of the work piece 10 passes the sensing element of the measuring section 11 at the moment corresponding to the zero point in the positive direction of the welding current, and the work piece 10 moves at the above nominal speed v ₀
This is because the welding current has a phase angle (360°×[position error]) corresponding to the position error at the moment point B reaches the welding position D. Normally, the moment when the sensing element of the measuring unit 11 detects the leading edge b of the workpiece 10 does not coincide with the zero point in the positive direction of the welding current, and therefore the sensing element detects the leading edge b of the workpiece 10.
From the phase angle of the welding current at the moment of detection, divide it by 360° to produce what is called the phase error. These 〓position error〓 and 〓phase error〓
controls the feed rate of the workpiece and varies from the nominal feed rate v ₀ mentioned above. In detail, if the phase angle of the welding current at the moment when the leading edge b of the workpiece 10 passes the sensing element of the measuring part 11, and therefore the phase error, is determined, then the distances a and A mentioned above are given. , the supply speed v is changed from the above nominal supply speed v ₀ , and t=(a+A)/
Position error determined by v, N = t・w
If (decimal part of N) is made to be one's complement to the determined phase error, then at the moment the leading edge b of the work piece 10 reaches the welding position D, the "phase error" The sum with the "position error" is exactly 1,
The welding current will take a zero point in the positive direction.

The determination of these required feed rate changes (acceleration or deceleration) is based on a constant distance a, a variable distance A that can be adjusted arbitrarily, a frequency w of the welding current, a selected nominal feed rate v ₀ , and a determined value. The calculation is performed by the computer 12 based on the phase error. At this time, the calculator 12 supplies the set value, compares the measured value with the set value, and generates an error signal such as a DC signal whose amplitude is proportional to the amount of change in rotational speed required by the electric motor 7. Only simple processing such as generation of
It is added to the input of 4.

Many variations in how such control is implemented are possible, the details of which are well known. For example, in order to determine the phase error, the computer 1
2 includes a counter controlled by a reference frequency source 16, the counter is adapted to count from 0 to 1000 or from 0 to 10000 for each cycle of the welding current, and the counter is adapted to count from 0 to 10000 for each cycle of the welding current. 0 for each direction zero point
will be reset to The detection signal sent from the measurement unit 11 reads the count value of the counter at that moment, and the read count value is a digital value of the phase error, and the digital value is converted into an analog signal if necessary. . Various types of such devices are commercially available. Furthermore, since each step of the stepping motor corresponds to a uniform displacement of the work piece being moved, the use of a stepping motor as the drive motor 7 makes the control device extremely simple. It is clear that acceleration and deceleration are carried out by changing the drive pulse frequency, while the number of steps determines the distance traveled, so it is convenient to use a counter for processing. good. The control device for the electric motor 3 also has a similar configuration. The details of the method and apparatus for making the distance between the rear end of the last weld point and the rear edge of the workpiece 10 an adjustable value A' as shown in FIG. 2 can also be inferred from the above description. Therefore, its explanation will be omitted.

Furthermore, the apparatus shown in FIG. 1 is also equipped with another control device that is convenient to be placed in parallel when carrying out the present invention, although it does not reflect the gist of the present invention as described above. a second similar measuring section 13 arranged further forward of the measuring section 11 with respect to the transport direction of the work piece;
The detection signal from is fed to the block above the calculator 12. This control device controls the feed mechanism 4 in such a way that the workpieces 10, which are successively transferred by a number of conveyor elements 9 on the conveyor 8, are delivered one after another to the welding rolls 1, 2 at appropriate intervals as short as possible.
This is provided to control the speed of the drive motor and improve the working efficiency of the entire resistance seam welding device. The aforementioned second measuring section 13, like the first measuring section 11, detects the moment when the front edge of the workpiece 10 passes through the measuring section, and thereby detects the processing during a series of transfers. It is possible to detect the distance between the pieces 10, and if the distance is larger than the appropriate value, the workpiece 10 in front is captured by the welding rollers 1, 2 and its transport speed is reduced by the feeding mechanism. After the transfer speed of the supply mechanism 4 becomes independent of the transfer speed of the welding rollers 1 and 2, the transfer speed of the supply mechanism 4 is accelerated and the welding rollers 1 and 2 are
The distance between the work piece 10 captured by the feed mechanism 4 and the work piece 10 on the next feeding mechanism 4 is narrowed to an appropriate value. These operations are also performed by the computer 12 based on the detection signal of the second measuring section 13.
and control block 14.

With the device described above, it is possible to carry out resistance roll seam welding with a feed movement or forward movement controlled synchronously to the welding frequency, so that the first welding point and the last welding point can be The exact distance of the points from the edge of the workpiece to be welded can be maintained. This advantage is particularly advantageous for machining operations that follow welding operations, where it has hitherto been impossible to avoid defects caused by inaccurate welding. Ta.

The drive motors 3 and 7, which respectively constitute the drive mechanism for the welding rollers 1 and 2 and the drive mechanism for the transfer mechanism 4, can be constructed by electronically controlled stepping motors.

[Brief explanation of the drawing]

1 is a block diagram of a roll welding machine and associated control elements, and FIG. 2 is a plan view, on an enlarged scale, of a portion of a workpiece, with which resistance roll seam welding is performed by the roll welding machine. This shows the format that will be used. 1, 2... Welding roller, 3, 7... Drive motor, 4
... Supply mechanism, 5, 6... Sprocket gear, 8... Conveyor, 9... Conveyor element, 10... Processed piece (frame body), 11, 13... Measuring section, 12... Computer, 1
4, 15...Control unit, 16...Reference frequency source (welding current source).

Claims (1)

[Claims] 1. A method for controlling the start and end of welding when continuously performing resistance welding using alternating current with a roll welding machine, the method comprising: The temporal positions of the leading and trailing edges of the workpieces to be welded in the measuring section through which the workpieces to be welded are detected with respect to the frequency and phase state of the welding current, and the first and last welding points are always welded. located at an adjustable distance from the leading and trailing edges of the workpiece to be processed, respectively;
A control method, characterized in that the speed of the workpiece to be welded and the frequency and phase state of the welding current are adapted to each other by one of the computers processing the detected values. 2. A control device for implementing the method recited in claim 1 in a roll welding machine, comprising:
A mechanism 11 for determining the temporal position of the leading and trailing edges of the workpiece to be welded with respect to the frequency and phase state of the welding current in a measuring section in front of one of the welding zones and through which the workpiece to be welded passes; and further welded by the computer such that the first and last welding points are located at a certain adjustable distance from the leading and trailing edges, respectively, of the workpieces to be welded at any given time. A control device characterized in that it comprises a computer 12 by which the speed of the workpiece to be processed and the frequency and phase state of the welding current are matched.