GB2257072A - Control of drum drawing machine - Google Patents

Description

2 2 2-)70"4 1 Method for automatically lowering the drawinq rate of drum

drawinq machines The invention relates to the use of drum drawing machines in the production for example, of pipes. Particularly, it relates to the need to lower the speed of the machine before the end of drawing of a length of workpiece.

In the use of a known pipe drawing machine, each of a plurality of nests of pipes which are drawn in succession is collectedin a rotatable receiving basket located beneath the drawing drum after one pull through the drawing die. Each full basket is transported into an uncoiling station after each nest of pipes has been drawn, whence another of a plurality of drawing operations which take place in the same sequence is initiated.

Continuous drum drawing machines for pipes are frequently known by the name 'Spinner-Block'. The drawing force of these drum drawing machines is applied by friction on five to ten loops of pipe on the drum with support from non-driven pressure rolls, with the pipe loops being wound onto the drum constantly pushing the loops already there downwards and into a receiving basket, which is of such a size that the maximum possible billet weights can be received in one length even for the smallest drawn pipe dimensions.

In known drum drawing machines, pipes can be reduced in several pulls, for example, starting from the dimension 55 x 2.5 mm and an individual weight of 300 kg, to 6 x 0.35 mm. The drawn pipe after such a reduction becomes 5,450 m long. After each pull, the receiving basket which is occupied by a complete pipe length is transported from its position beneath the drawing drum to the uncoiling station, whence the pipe end is supplied for the next pull of the machine, while 2 is a new empty receiving basket is brought to the receiving station beneath the drawing drum. Generally, a plurality, such as six or seven, receiving baskets are in use and supplied successively to the drawing drum.

Towards the end of a pull, there are only a few loops in the uncoiling basket of the uncoiling station, and the drawing rate has to be reduced. The reason for this is to prevent the final pipe loops from lashing about uncontrolledly in the uncoiling basket and to keep it in the basket. Also, the load release shock which occurs when the pipe end leaves the drawing die is substantial. By lowering the drawing rate, this shock as the drawing force collapses is greatly reduced. A typical maximum achievable drawing rate is around 1,500 m/min. The recommended reduction in the drawing rate at the end of the pull is to about 90 m/min.

In known installations, the lowering of the speed of rotation when there is only a certain number of loops left in the uncoiling b4sket is effected by the operator. In one machine, the operator has to watch the loops lying in the uncoiling basket using one or more mirrors, and actuate the slow-down button where there are only a few loops remaining. This activity is time consuming, and occupies time the operator might use for other work.

Proposals have been made for the automation of the deceleration step in an otherwise continuous drum process. In one such proposal, the lengths of pipe are detected during the first pulls of all the nests of pipes and compared with the elongation of the first nest of pipes after the second pull. The values which can be calculated from this are used to determine the changeover points for the subsequent pipes of this-cycle of pulls, without once having to intervene manually.

3 In this proposal, after all the lengths of pipe (normally seven nests of pipes) lying in the baskets have been stored, the operator watches the drawing process during the drawing of the first nest of pipes of the second pull and then switches to low speed manually when only a few loops are left in the basket.

Then the time from the start of drawing to the changeover point is measured by counting pulses for example, and recorded. The entire time to the end of drawing of this pipe is measured in the same way, and recorded. The quotient of the counted pulses from the start of drawing to the.end of drawing and the counted pulses to the end of drawing of the pipe drawn in the first pull is a measurement of the elongation of the pipe in the second pull. The present diameter of the drawing die and the plug, which likewise affect the length of the finished pipe, are also taken into consideration.

The pulses counted until the change to low speed are deducted from the number of pulses yielded between the start of drawing and the end of drawing of the second pull. The difference thus formed represents a measurement for the pipe length which must be run at a reduced drawing rate.

In another known proposal, the pipe is marked behind the drawing die by spraying on paint after several loops of the pipes have been drawn. Upon the next pull, this marking is recognised by sensors and used as a signal to reduce the speed of rotation of the drive of the drawing drum. The process uses the fact that the start of the pipe which first falls into the receiving basket becomes the pipe end upon the next pull. However there are no suitable marking paints'on the market which would guarantee visual recognition of the pipe end section.

4 The present invention is directed at a process for automatically lowering the drawing rate of drum drawing machines which completely releases the operator from watching the drawing operation for the purpose of early recognition of the pipe end at least from the second cycle of pulls of a drawing sequence in a simple manner.

According to the invention the number of rotations of the receiving basket beneath the drum is counted and recorded from the start of drawing until the pipe end and upon the next pull of the pipe the basket located on the uncoiling table performs the same number of rotations as has been recorded, but reduced by a settable value, until the machine switches over from drawing speed to low speed.

The rotations of the receiving basket in either location are counted and stored in a suitable storage means from the start of'drawing until the end of drawing. If the workpiece is then drawn for the second time, the basket which is now located on the uncoiling table must perform the same rotations as have previously been recorded before the pipe end is reached.

In order then to change the drive of the drawing machine to slow speed, for example five is deducted from the recorded number of rotations-of the basket, in order to be able to reduce the speed of the machine to the required amount, in this case five rotations before the end of the pipe. During subsequent pulls, the machine then operates in the same sequence.

1 If the machine is charged with straight pipes upon the first pull, the reduction of the drawing rate during this pull can be brought about by a proximity switch which is located within the charging channel.

If the drawing machine is to be charged with prepared nests of pipes, according to another feature of the invention even upon the first pull the set value is from a previous process using similar nests can be entered into the control system. In this manner, no monitoring of the process is required in this stage either, and the machine is able to switch over automatically to low speed here as well.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawing, which illustrates the principle of a continuous drum drawing machine on which the process according to the invention can be performed.

As shown in the drawing drum, pipe loops are wound on the drawing drum 1 in several rotations in known manner, as indicated at 2. A frictional force is achieved which makes it possible to draw the pipe 3 through the drawing die 4 and in so doing to reduce it. During the drawing operation, the pipe loops which are to be drawn lie in the uncoiling basket 5 of the uncoiling station, which is not shown in greater detail, while the reduced, drawn pipe loops are discharged from the drawing drum 1 into the underlying receiving basket 7. This is achieved by the subsequent pipe loops 2 pushing loops already located on the drawing drum downwards, so that these fall down once they leave the region of the pressure roller 6.

As soon as the receiving basket 7 is filled with a complete pipe length of for instance 5,000 m, the receiving basket 7 is shifted to the uncoiling station and becomes the uncoiling basket 5 for a second pull. The empty uncoiling basket 5 is brought under the drawing drum 1 as the receiving basket 7. In the next pull, the end of a drawn pipe loop is introduced into the continuous drum drawing machine as the beginning of a new pipe which is to be drawn, so that a second pull and in the same way subsequent pulls can take place.

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Claims (4)

1. A method for automatically lowering the drawing rate of a drum drawing machine in which a plurality of nests of workpiece are drawn in succession, each being collected in a rotatable receiving basket located beneath the drawing drum after one pull through the drawing die, and each filled basket being shifted to an uncoiling station whence another drawing operation of a plurality of drawing operations which take place in the same sequence is initiated, wherein the number of rotations of the receiving basket beneath the drum is counted and recorded from the start of drawing for an entire length of workpiece, and upon the next pull thereof the same basket located at the uncoiling station is allowed to perform a number of rotations less than the recorded number by a settable value, at the end of which the machine switches over from drawing speed to low speed.
2. 2. A method for automatically lowering the drawing rate of a drum drawing machine in which a plurality of nests of workpiece are drawn in succession, each being collected in a rotatable receiving basket located beneath the drawing drum after one pull through the drawing die, and each filled basket being shifted to an uncoiling station whence another drawing operation of a plurality of drawing operations which take place in the same sequence is initiated, wherein the machine switches over from drawing speed to low speed in the first pull after a number of rotations of the basket at the uncoiling station set with reference to the previous conduct of a method according to Claim 1 with similar workpieces.

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3. 3. A method according to Claim 1 or Claim 2 including a control system for monitoring the counting of pulses and setting said value.
4. 4. A method of automatically lowering the drawing rate of a drum drawing mechanism according to Claim 1 and substantially as herein described.