EP0446499B1 - Method of lowering the drawing speed of drum drawing machines - Google Patents

Description

The invention relates to a method for lowering the drawing speed of drum drawing machines for pipes or the like before the drawing end of a tube bundle, wherein each of a plurality of tube bundles drawn in succession is collected after a pull through the drawing tool in a receiving basket, which in each case step by step after pulling the tube bundle into a Drain station is transported, from where another of several pulling processes in the same order is initiated.

Continuous drum drawing machines for pipes are often known under the name Spinner-Block. The pulling force in these drum drawing machines is applied by friction over five to ten pipe turns on the drum with the support of non-driven pressure rollers, the rising pipe turns continuously pushing down the turns sitting on the drum.

Arranged below the drawing drum is a container which is referred to as a receiving basket and is dimensioned such that the largest possible bob weights can be taken up in one length even with the smallest drawn tube dimensions.

Pipes are reduced in several passes, for example based on the dimensions 55 x 2.5 mm and a unit weight of 300 kg to 6 x 0.35 mm. The pipes are 5,450 m long. After each train, the receiving basket, which is filled with a complete length of pipe, is transported from its position below the drawing drum to the discharge station, from where the end of the pipe is fed to the drawing drum as the new beginning of the pipe for the next train, while a new free receiving basket is brought into the receiving station below the drawing drum . As a rule, several, about six to seven, baskets are on the way and are fed to the drawing drum one after the other.

If there are only a few turns left in the drain basket of the drain station, the pulling speed must be reduced, on the one hand so that the last pipe turns do not swing back and forth in the drain basket uncontrollably and the pipe end would whip out of the basket and on the other hand so that the relief shock that arises when the pipe end leaves the drawing ring and the drawing force collapses, is greatly reduced. The maximum achievable drawing speed is currently 1,200 m / min. A reduction of this drawing speed at the end of the train to approx. 60 m / min. is imperative.

In conventional systems, the lowering of the drive speed when there are only a certain number of turns in the drain basket is carried out by the operator, who has to observe the turns lying in the drain basket by means of one or more mirrors. If there are only a few turns left in the basket, he presses the slow-down button to reduce the speed. The remaining turns are then drawn at the reduced speed for the reasons mentioned above. This activity occupies the operator over part of the drawing time so that he cannot carry out other work.

The demand to automate the continuous drum drawing process has led to considerations of counting the turns falling into the receiving basket and recording them in a computer with a storage register. When this basket is again in the sequence station during the next drawing sequence, the falling turns are registered again by the computer and the drawing speed is reduced when a certain number of turns have fallen into the basket. The difference to the total number of turns is the number of turns that should be in the drain basket when braking. However, the computer must divide the number of turns by the lengthening that occurs when the tube is reduced in the drawing tool. Other influencing factors that cannot be taken into account in this method are the pipe weights per meter, which fluctuate within permissible limits and which depend on the condition of the drawing tools. Different pipe weights result in different pipe lengths and number of turns after the train. Assuming weight fluctuations of plus / minus 5% and a nominal length of 5,000 m, the deviations plus / minus would be 250 m. If these possible errors are taken into account by programming the computer to the smallest possible number of turns, an additional 500 m are drawn with a reduced drawing speed when the maximum pipe length occurs. The average drawing speed is thus greatly reduced and the drawing time extended accordingly. The cost of pulling increases.

 Another known method (DE-C 3708859) proposes to mark several turns of the tube behind the drawing ring by means of paint spraying. On the next train, this mark is recognized by sensors and used as a signal to reduce the speed of the drawing drum drive. This method takes advantage of the fact that the beginning of the pipe falling into the receiving basket becomes the end of the pipe on the next train. This method has so far not been successful in practice because there are no suitable marking colors on the market that do. Guarantee visual identification of the pipe end section.

Based on the problems described, the present invention has for its object to develop a method and an apparatus for reducing the pulling speed of drum drawing machines, which can be easily activated by the operator on the first move of each drawing game and then for other moves of this draw game is no longer changed.

To achieve the object, the method according to the characterizing part of the patent claim is proposed.

The method therefore suggests recording the pipe lengths during the first draws of all the pipe bundles and comparing them with the extension of the first pipe bundle after the second train. The constants Q and D that can be calculated from this are used to determine the switchover points for the following pipes of this draft game, without having to intervene again by hand.

The corresponding device works, for example, with pulse counters. After storing all lengths (impulses) of all (normally seven bundles of pipes), the operator observes the basket when pulling the first bundle of pipes of the second train and switches manually to low speed when there are only a few turns left in the basket. The impulses are counted and recorded from the start of drawing to the switchover point. In addition, the impulses from the start of drawing to the end of drawing this tube are counted and registered. The quotient Q from the counted pulses from the start of drawing to the end of drawing this drawn tube and the counted pulses to the end of drawing of the tube drawn in the first train is a measure of the extension of the pipe in the second train. The current diameter of the drawing ring and stopper are also taken into account, which also influence the length of the finished pipe.

The pulses counted until the switch to low speed are subtracted from the number of pulses which result between the start of pull and the end of pull of the second train. The difference D formed in this way represents a measure of the pipe length which has to be driven at a reduced drawing speed.

With the constants Q and D determined in this way, the switchover points for the following pipes (normally six pieces) of this train play are then calculated. The number of pulses corresponding to the new total pipe length is saved to determine the next switchover points. If a pipe ripper occurs, the automatic switchover is deactivated by pressing a button. When pulling the remainder, the switch to low speed is done by hand.

An exemplary embodiment of the invention is described below. The drawing shows the principle of a continuous drum drawing machine on which the method according to the invention can be carried out.

1 with the drawing drum is referred to, on which the tube turns, as indicated at 2, are wound in several revolutions in a known manner. A frictional force is thereby achieved which makes it possible to pull the tube 3 through the drawing tool 4 and thereby reduce it. During the drawing process, the pipe windings to be drawn lie in the drain basket 5 of the drain station (not shown in more detail), while the reduced, drawn pipe windings are thrown off by the drawing drum 1 into the receiving basket 7 arranged underneath. This is done in that the subsequent pipe coils 2 press the coils already on the drawing drum down so that they fall down when they come out of the area of the pressure roller 6.

As soon as the receiving basket 7 is filled with a complete tube length of, for example, 5,000 m, the receiving basket 7 is brought into the drain station and is there to the drain basket 5. The empty drain basket 5 is brought under the drum 1 as the drain basket 7. The end of a drawn tube turn is introduced as the beginning of a new tube to be drawn in the next train in the continuous drum drawing machine, so that a second and in the same way further trains can take place.

In the exemplary embodiment it is assumed that a measuring device on the drum drawing machine emits a pulse per m tube. With a pipe length of 200 m after the first train, 200 pulses would then be stored.

This tube length of 200 mm is called M₁. According to this example, after the second train the pipe is 286 m long, 286 pulses have been saved. The total length of this tube is designated M₃.

However, the operator has switched the machine to slow speed after a pipe length of M₂ = 250 m or 250 pulses so that the pipe end goes slowly through the drawing ring, ie. H. the 36 pulses to the end of the drawing correspond to the pipe length D = 36 m, which are driven at reduced speed.

$$\text{D = M₃ - M₂ = 286 - 250 = 36}$$

$${\text{L}}_{\text{A}}\text{= M₁' x Q - D = 300 x 1,43 - 36 = 393}$$

In the case of another pipe length, designated M₁ ', which is 300 m long after the first train, the pipe length L _A , in which a switch to a low drawing speed has to be carried out, was calculated as follows: $$\text{Q = M₃: M₂ = 286: 200 = 1.43}$$

$$\text{D = M₃ - M₂ = 286 - 250 = 36}$$

$${\text{L}}_{\text{A}}\text{= M₁ 'x Q - D = 300 x 1.43 - 36 = 393}$$

In the above example, the machine would accordingly have to be automatically switched to a slow drawing speed after 393 pulses corresponding to L _A = 393 m.

To determine the new drawn length, the number of pulses is counted from the start of the pull to the end of the pull and saved; this value serves as the basis for the calculation for the next drawing game.

Claims (1)

1. A method for lowering the drawing rate of drum drawing machines (1) for pipes (3) or the like before the end of drawing of a nest of pipes, in which each of a plurality of nests of pipes which are drawn in succession is collected in a receiving basket (7) after one pull through the drawing die (4), which basket is transported step by step into an uncoiling station each time after the nest of pipes has been drawn, whence another drawing operation of a plurality of drawing operations which take place in the same sequence is initiated,
   characterised in that
   the length of the drawn pipe of each nest of pipes which is circulating is measured (M₁) and recorded upon the first pull, that upon the second pull of the first nest of pipes the drawing rate is lowered manually towards the end of the pull and the length of the pipe which has been drawn up to the moment of lowering is measured (M₂) and recorded,
   that the total length of this pipe is measured (M₃) and recorded after the second pull,
   that the quotient $$\text{Q =}\frac{\text{M₃}}{\text{M₁}}$$

   

   is formed from the third measured value (M₃) and the first measured value (M₁), and the difference $$\text{D = M₃ - M₂}$$

   

   is formed from the third measured value (M₃) and the second measured value (M₂), and that for the subsequent second pulls of the following pipe lengths M₁' the drawing rates are lowered automatically after the length of the drawn pipe L_A, which is calculated according to the following formula: $${\text{L}}_{\text{A}}\text{= M₁' X Q - D,}$$

   

   has passed through.

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