The present invention refers to a sheet metal accumulator of the loop type with traction winding.

In the field of pipes and/or welded sections produced on continuous production lines, sheet metal accumulators which act as a reservoir to allow constant feeding of the production line situated downstream of the accumulator are well known to the art and normally used.

The accumulator is normally placed between at least one coil-carrying reel and the production line and accumulates a sufficient amount of sheet metal to allow an empty reel to be replaced with a reel bearing a coil of sheet metal and to join the sheet metal of the new coil with the "tail" of the sheet metal already unwound from the empty coil without having to stop the production line.

Many types of sheet metal accumulator are known to the art, amongst which can be cited, purely by way of example, pit accumulators (free loop) and accumulators of the loop type with thrust-type winding (known as floops) which have the great drawback of not operating correctly if the sheet metal is (too) thin and/or is made of (overly) ductile material.

A sheet metal accumulator of the loop type with traction winding is able to overcome the aforementioned drawback. Systems (such as, for example, coil winders) which accumulate sheet metal by traction are known to the art, but the Applicant is not aware of accumulators that accumulate sheet metal in loops by traction.

KR 2004 4039921 which forms the bain for the preamble of claim 1, discloses a sheet metal accumulator of the loop type which, to prevent the loosening of the loop(s) of sheet metal wound on the rolls of the rotatable turntable, provides strip laxity preventing means, comprising a plural links and a tightening roll, which acts on the outer surface of said sheet metal loop(s).

KR 2004 0039920 discloses a sheet metal accumulator of the loop type, comprising a mobile internal turntable and a fixed external one, having a plurality of winding roll and a lead roll, rotating forwards and backwards on the fixed turntable.

To avoid interference, if any, with the lead roll, each winding roll is supported by means tilting it of a certain angle towards the centre of the turntable when the lead roll arrives.

KR 2004 0039920 further comprises means rotating each winding roll around its axis.

Object of the present invention is to produce a sheet metal accumulator of the loop type with traction winding that does not present the drawbacks and limitations previously described; this object is achieved by means of a sheet metal accumulator of the loop type with traction winding having the features set forth in claim 1.

Further advantageous characteristics of the invention form the subject matter of the dependent claims.

The sheet metal accumulator of the loop type with traction winding is adapted to be placed between a source of sheet metal (preferably a coil-carrying reel) and a production line and comprises at least one inlet group, a pinch roll, an external mobile turntable, an internal fixed turntable coaxial with the mobile one, a helical path integral to the fixed turntable and adjustment means situated at the in-put and at the output of the accumulator.

The two turntables carry a plurality of rolls, suited to carry loops of sheet metal, which are mounted on swinging arms connected to one another by tie rods and moved by hydraulic or pneumatic means (or by other functionally equivalent hydraulic means), operation of which is managed by a logic unit that controls also adjustment means suited to control and adjust at least the tension of the sheet metal entering the accumulator.

The loops of sheet metal are traction wound on said rolls.

The invention will now be described with reference to purely exemplifying (and therefore non limiting) embodiments illustrated in the appended figures, wherein:

• Figure 1 shows diagrammatically a front view of a sheet metal accumulator of the loop type produced according to the invention, in a working condition;
• Figure 2 shows diagrammatically a side view of the sheet metal accumulator of Figure 1;
• Figure 3 shows diagrammatically a rear view of the sheet metal accumulator of Figure 1;
• Figure 4 shows diagrammatically the sheet metal accumulator of Figure 1 in a stand-by condition;
• Figure 5 shows diagrammatically the sheet metal accumulator of Figure 1 in a first step of winding of the sheet metal onto the fixed and mobile turntables;
• Figure 6 shows diagrammatically the sheet metal accumulator of Figure 1 in a second step of winding of the sheet metal, following that of Figure 5.

In the appended figures corresponding elements will by identified by the same reference numerals.

Figure 1 shows diagrammatically a front view of a sheet metal accumulator 1 produced according to the invention, which is carried by a metal structure 100 and which comprises at least one inlet group 2 suited to guide the sheet metal 20, a pinch roll 3, a mobile roll (dandy roll) 4 which controls the tension of the incoming sheet metal 20, a series of idle rolls 5, an external mobile turntable 6 carrying an idle traction roll 12, an internal fixed turntable 7 (coaxial with the turntable 6) carrying an idle transmission roll 13, a helical path 15 (seen better in Figure 2) integral with the fixed turntable 7 and a mobile roll (dandy roll) 18 which controls the tension of the sheet metal 20 exiting the accumulator 1.

The inlet group 2, the pinch roll 3, the mobile rolls (4, 18), the idle rolls (5, 12, 13) and the helical path 15 will not be described herein because they are known to a person skilled in the art.

The two turntables 6, 7 carry a plurality of rolls 8 suited to carry the loops of sheet metal traction wound on said rolls 8, which are mounted on swinging arms 9 connected to one another by tie rods 10 and driven by pistons 11 (or by other known hydraulic means; Figure 3), operation of which is managed by a logic unit which, preferably, also controls the pinch roll (̵3)̵ and the external turntable 6.

For the sake of simplicity of the graphic representation, the logic unit and its sensors and actuators have been omitted in the appended figures; moreover, in Figure 1 only one loop of sheet metal has been indicated on the mobile turntable 6 and on the fixed turntable 7.

In the working condition (Figure 1), the sheet metal 20 passes through the inlet group 2, the pinch roll 3, the mobile roll 4 and the idle rolls 5 to reach the traction roll 12 of the mobile turntable 6 which, rotating with the turntable 6, winds up the entering sheet metal 20 onto the loops of sheet metal present on the mobile turntable 6 and, at the same time, winds up onto the loops of sheet metal present on the fixed turntable 7 the sheet metal 20 coming from the loop of sheet metal in contact with the rolls 8 of the mobile turntable 6.

The sheet metal 20 coming from the fixed turntable 7 and from the helical path 15 passes beneath the mobile roll 18 before reaching the production line.

• Figure 2 shows diagrammatically a side view of the sheet metal accumulator 1 of Figure 1; for the sake of simplicity of the graphic representation, in Figure 2 only the metal structure 100, the mobile turntable 6, the helical path 15, one of the rollers 8, one of the swinging arms 9 and one of the tie rods 10 have been denoted by the respective reference numerals.
• Figure 3 shows diagrammatically a rear view of the sheet metal accumulator 1 of Figure 1; visible in Figure 3 are the metal structure 100, the inlet group 2, the pinch roll 3, the means 41 that control the mobile roll 4, the rear part of the mobile turntable 6 carrying the hydraulic cylinders 11 which act on the pins of the swinging arms 9 and the rear part of the fixed turntable 7.

In the embodiment illustrated in Figure 3, each hydraulic cylinder 11 acts on the pin of one of the swinging arms 9, mechanically coupled to the pins of the adjacent swinging arms 9 by means of the tie rods 10.

• Figure 4 shows diagrammatically the sheet metal accumulator 1 of Figure 1 in the stand-by condition: the sheet metal 20 passes only in the inlet group 2, in the pinch roll 3, on the mobile roll 4, on the idle rolls 5, on the idle transmission roll 13, on the helical path 15 and on the mobile roll 18 (which controls the tension of the sheet metal 20 exiting the accumulator 1) without involving the two turntables 6, 7.
• Figures 5 and 6 show diagrammatically the sheet metal accumulator 1 of Figure 1 in two successive steps of winding of the sheet metal 20 on the mobile and fixed turntables 6, 7.

Starting from the stand-by condition (Figure 4) in which the input speed of the sheet metal 20 is equal to the output speed, the mobile turntable 6 begins to turn in a counter-clockwise direction (in the embodiment described here) causing the input speed of the sheet metal 20 into the accumulator 1 to be greater than its output speed towards the production line. The traction roll 12, integral with the turntable 6, draws the sheet metal 20 against the transmission roll-13 of the fixed turntable 7 (Figure 5) and then onto the rolls 8 carried by the mobile turntable 6 and by the fixed turntable 7 (Figure 6) and continues to rotate at this speed until the pre-set number of loops has been formed on the two turntables 6, 7.

It should be remembered that the input speed of the sheet metal 20 into the accumulator 1 correlates with the rotation speed of the pinch roll 3 and that during formation of the loops on the two turntables 6, 7, the sheet metal 20 leaves the accumulator 1 at the speed required to feed the production line.

When the required number of loops has been formed on the two turntables (̵6, 7)̵, the mobile turntable 6 and the pinch roll 3 reduce their rotation speed so that when the mobile turntable 6 is at a standstill, the quantity of sheet metal (̵20)̵ that enters into the accumulator 1 is equal to that exiting towards the production line.

Once this situation has been reached, the pinch roll 3 gradually slows down until it stops (blocking the incoming sheet metal 20) while the mobile turntable 6 starts rotating in a direction opposite to the previous one to pay off the loops formed on the turntables 6 and 7 and feed the production line with the sheet metal 20 stored in the accumulator 1.

The fact that the pinch roll 3 blocks the incoming sheet metal 20 allows the sheet metal source to be replaced, joining another coil to the end of the incoming sheet metal 20.

When there is no more sheet metal 20 stored in the accumulator 1, the mobile turntable gradually slows down until it stops and, if the inflow of sheet metal 20 to the inlet thereof has been restored, it switches (or can switch) to the stand-by condition (Figure 4) and, subsequently, once again winds up (or can wind up) the sheet metal 20 onto the two turntables 6 and 7 (Figures 5 and 6).

Operation of the traction accumulator 1 of the present invention will not be described in greater detail because it is obvious to a person skilled in the art or in any case can be deduced from operation of thrust-type accumulators known to the art.

Without departing from the scope of the invention which is defined by the appended claims, a person skilled in the art can make to the sheet metal accumulator previously described all those modifications and improvements suggested by normal experience and/or by the natural evolution of the art.