STRIP ACCUMULATOR

Abstract: An accumulator (10) for a flexible strip (12) includes a frame and a plurality of strip feed means located side-by-side on the frame so that in use at least one suspended storage loop (26) of strip (12) can be formed, with the storage loop (26) being formed between a pair of strip feed means so that one of the feed means can feed strip (12) into the storage loop (26) and the other of the strip feed means can withdraw strip (12) from the storage loop (26).

Description: STRIP ACCUMULATOR FIELD OF THE INVENTION This invention relates to a strip accumulator. BACKGROUND TO THE INVENTION Strip accumulators are used in tube or pipe mills to accumulate strip. The accumulated strip is fed into the pipe mill whilst the head of a strip from a fresh coil is welded to the tail of a strip from a depleted coil. Thus the pipe mill can continue to produce pipe from the accumulated strip in the accumulator whilst the strips are being welded together. There are various types of prior art accumulators. These accumulators accumulate the strip in coil-form on large accumulator wheels, in a pit in a randomly folded fashion or in one or more loops. There are various types of accumulators which accumulate the strips in one or more loops. One type of loop accumulator accumulates strip on a large horizontal turntable which rotates about its vertical axis. Strip is fed in an upright fashion onto the turntable at its outer periphery, and is stored in abutting loops on the turntable, and is extracted from the inner periphery of the turntable. This type of accumulator requires a large amount of floor space and the strip has to be rotated from a horizontal position to a vertical position and then back to the horizontal position. Another type of loop accumulator, known as a Floop accumulator, utilizes a series of rollers which move relative to one another to increase or decrease the size of the loops. Both these loop accumulators are expensive and therefore generally only used to feed high speed tube mills where a large storage capacity is required. Yet another type of loop accumulator forms loops between pairs of fixed upper rollers with the bottom of each loop passing around a lower roller to which a weight is attached. The lower roller can move vertically downwards to increase the size of the loop and vertically upwards to decrease the size of the loop. SUMMARY OF THE INVENTION According to the invention an accumulator for a flexible strip includes a frame and a plurality of strip feed means located side-by-side on the frame so that in use at least one suspended storage loop of strip can be formed, with the storage loop being formed between a pair of strip feed means so that one of the feed means can feed strip into the storage loop and the other of the strip feed means can withdraw strip from the storage loop. Each strip feed means preferably includes two rollers between which the strip can pass. Drive means for driving one or both of the rollers to feed the strip into or from its storage loop is preferably provided. Each strip feed means preferably includes biassing means for biassing the two rollers towards one another to pinch the strip between the two rollers. The biassing means may be an actuator. The accumulator may include loop width increasing means for increasing the width of the storage loop to increase the storage capacity of the loop. The loop width increasing means preferably includes loop support means and displacing means for displacing the loop support means away from the strip feed means to increase the width of the storage loop. The displacing means may include carriage means supporting the loop support means, the carriage means being displacable away from and towards the strip feed means to increase or decrease the width of the storage loop. Alternatively the displacing means may include a pivotally mounted structure supporting the loop support means, the pivotally mounted structure being displacable away from and towards the strip feed means to increase or decrease the width of the storage loop. According to another aspect of the invention a method of operating a strip accumulator includes the steps of: forming at least one suspended spiral-like storage loop; increasing the size of the storage loop to accumulate strip within the accumulator; and decreasing the size of the storage loop to withdraw the accumulated strip from the accumulator. The method may include the step of increasing the size of the storage loop by increasing the depth and the width of the loop. The method may include the step of forming a plurality of suspended spiral-like storage loops. The width of the plurality of loops may be increased simultaneously. The storage loops are formed by the strip winding continually and advancing from one strip feed means to the next preferably along a common axis or at least in the same direction. Each storage loop is thus spiral-like and a plurality of such loops are referred to herein as a spiral-like formation. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a side view of part of a pipe mill including an accumulator according to a first embodiment of the invention; Figure 2 is a perspective view of part of the accumulator of figure 1 ; Figure 3 is a front view of the part of the accumulator of figure 2; Figure 4 is a side view of the part of the accumulator of figure 2; Figure 5 is a diagrammatic front view of the accumulator showing spirallike formations; Figure 6 is a diagrammatic imaginary view of the accumulator showing the accumulator in a substantially full configuration; Figure 7 is the same view as figure 5 but showing the accumulator in an empty position; Figure 8 is a diagrammatic side view of a second embodiment of an accumulator according to the invention; Figure 9 is a front view of the accumulator of figure 8; Figures 10 to 13 show the steps involved in creating a storage loop in the accumulator of figures 8 and 9; Figure 14 shows the steps, according to another embodiment of the invention, involved in creating a storage loop in the accumulator of figures 8 and 9; Figure 15 is a diagrammatic side view of a third embodiment of an accumulator according to the invention; Figure 16 is a diagrammatic side view of a fourth embodiment of an accumulator according to the invention; and Figure 17 is a diagrammatic side view of a fifth embodiment of an accumulator according to the invention. DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to figure 1, an accumulator 10 is fed a flexible steel strip 12 from a coil 14 located on a decoiler 16. The strip 12 from the decoiler 16 passes through a strip joiner 18 and a pinch roller 20 to the accumulator 10. As can be seen more clearly from figures 2 to 5, the strip 12 passes over support rollers 22 located on a common axis 24 to form a spiral-like formation. In figure 5 the spiral-like formation is shown diagrammatically and referred to by reference numeral 25. The spiral-like formation 25 consists of a number of suspended spiral-like storage loops 26. Typically the pitch of each storage loop is about 300 mm for an accumulator which is designed to accommodate a strip width of up to 200 mm. Each support roller 22 has a drive roller 28, between which drive roller 28 and its support roller 22 the strip 12 is sandwiched. The drive rollers 28 are driven by chains 29 connected to magnetic clutches 30 located on a common shaft 32 driven via a gearbox 34 by an electric motor 36. Each drive roller 28 has its own magnetic clutch 30 for engaging or disengaging the drive shaft 32, The diameters of the drive rollers 28 decrease along the drive shaft 32 so that the steel strip 12 will be fed faster into the accumulator 10 than it is removed from the accumulator 10. The drive rollers 28 are biassed downwardly onto their respective support rollers 22 by arms - 38 biassed downwardly and connected to plates 40. The chains 29 for each drive roller 28 are tensioned by arms 42 biassed downwardly and also connected to the plates 40. The arms 38 are biassed by rubber torsion bars 43 and the arms 42 are biassed by rubber torsion bars 45. The support rollers 22 are supported on a frame 44. The loops 26 are suspended under the influence of gravity from the support rollers 22 and adopt a catenary-like shape. In order to explain the operation of the accumulator, the support rollers 22 in figures 6 and 7 are shown having separate axes. In reality the support rollers 22 are located one behind the other. The accumulator could however be operated in the configuration shown in figures 6 and 7. The operation of the accumulator is described with reference to figures 6 and 7 in which the letters have the following meaning: Mp - pinch roll motor drive Ma - accumulator motor drive D1 to D5 - wheel drives 1 to 5 C1 to C5 - clutches 1 to 5 to engage wheel drives 1 to 5, respectively S1 - "strip join" selector switch (not shown) S2 - pinch roll "inch forward" switch (not shown) S3 - accumulator "fill" switch (not shown) P1 to P11 - proximity limit switches on accumulator PS1 to PS3 - proximity emergency stop limit switches on accumulator L1 - strip "entry" loop into accumulator from pinch roll feed L2 to L5 - "storage" loops in accumulator L6 - strip "exit" loop into mill from accumulator FEEDING IN STRIP ON COIL CHANGE 1.1 Switch accumulator to manual mode. 1.2 Strip joiner clamps up. 1.3 S1 in Position 2 to switch pinch roll drive Mp off. 1.4 Top pinch roll up. 1.5 Accumulator drive Ma off. 1.6 Clutches 01 to 05 disengaged (de-energised). 1.7 Manually feed strip through strip joiner, pinch roll and accumulator to mill entry, so that: - 1.7.1 Loop L1 is between P2 and P3. 1.7.2 Loops L2 to L5 are anywhere between Level 2 and Level 3. 1.8 Top pinch roll down. 1.9 Switch S1 to position 1 to re-connect pinch roll drive, Mp. 1.10 Press 'fill' button. 1.11 This simultaneously switches on pinch roll drive Mp, accumulator drive Ma and all clutches 01 to 04, with Ma running at 190% of rated speed (for 50 Hertz), or so-called 'fill' speed. NOTE: Pinch roll feed speed, Vpr, is indexed off accumulator wheel drive 1 feed speed, Vd1 , and must always be faster. Vpr = 1 ,05 X Vd1. So Mp will be running at 1 ,05 X 1 ,9 = 200%. 1.12 When Loop:- 1.12.1 L1 reaches P3, Mp stops. 1.12.2 L1 reaches P2, Mp starts. 1.12.3 L2 reaches P4 at Level 1 , C1 de-clutches. 1.12.4 L2 reaches Level 2*, C1 clutches. 1.12.5 L3 reaches P5 at Level 1 , C2 de-clutches. 1.12.6 L3 reaches Level 2*, C2 clutches. 12.7 L4 reaches P6 at Level 1 , 03 de-clutches. 12.8 L4 reaches Level 2*, 03 clutches. 12.9 L5 reaches P7 at Level 1 , 04 de-clutches. 12.10 L5 reaches Level 2*, 04 clutches. * There are no proximity switches at Level 2 for sensing Loops L2 to L5. Instead, Level 2 is estimated using an elapsed time interval for a loop leaving its respective proximity switch at Level 1 (viz. P4, P5, P6 and P7, respectively). 1.13 If, for any reason, any loop L2 to L4 reaches Level 3, then the respective proximity switch (viz. P8, P9 and P10) will de- energise its respective clutch, 02 to 04. In other words if/when: 1.13.1 L2 reaches Level 3, P8 de-energises 02. 1.13.2 L3 reaches Level 3, P9 de-energises 03. . 3.3 L4 reaches Level 3, P10 de-energises 04. 1.14 Emergency Stop. - If, due to any malfunction, Loop 1 reaches PSI or any of the Loops L2 to L4 reaches Level 4, then power to all clutches as well as motor drives Ma and Mp switches off. 1.15 When Loops L2 to L5 are at Level 1 (i.e. Full) Mp and Ma to switch off. STARTING UP FOR AND RUNNING IN NORMAL OPERATION 2.1 Strip joiner, pinch roll and accumulator to have status as at Clause H 5. 2.2 Switch accumulator to automatic mode. 2.2.1 This will link accumulator drive motor, Ma to Mill Forming Drive so that Ma switches on and off whenever the forming drive motor switches on and off. 2.2.2 All other status to remain as at clause 1.15. 2.2.3 Except that The speed of Ma must be set to enable wheel Drive 4 (D4), feed speed, Vd4 to be faster than mill take-off speed, Vm. Vd4 = 1 ,05 X Vm. 2.3 For the rest, the operation to be exactly as per Clause 1.12. 2.4 Emergency Stop :- If there is any malfunction. Causing:- Loop L1 to reach PSI and/or Loops L2 to L5 to reach PS2 at Level 4 and/or Loop L6 to reach PS3, then the mill must stop and all power to all clutches as well as the motor drives Ma and Mp must switch off. 3. OPERATION FOR STRIP JOINING 3.1 With accumulator still operating in automatic mode. 3.2 Switch S1 to Position 2 to switch Mp off. 3.3 Carry out strip joining operation. 3.4 P2 and P3 to have no influence on Mp. 3.5 01 to de-clutch. 3.6 P4 to have no influence on C1. 3.7 C2 to 04 to operate as before. 3.8 When L2 reaches P8 at Level 3, 02 de-clutches. 3.9 P5 to have no influence on C2. 3.10 03 and C4 operate as before. 3.11 When L3 reaches P9 at Level 3, 03 de-clutches. 3.12 P6 to have no influence on 03. 3.13 04 operates as before. 3.14 When L4 reaches P10 at Level 3, 04 de-clutches. 3.15 P7 to have no influence on 04. 3.16 If/when L5 reaches P11 at Level 3, then the Mill must stop. 3.17 Emergency Stop: - As per 2.4. 3.18 When the strip joining operation is complete switch selector S1 back to Position 1 to switch Mp on. 3.18.1 Mp to switch on. 3.18.2 Simultaneously all clutches that have been de clutched, must clutch in. 3.19 Press accumulator 'fill' button. 3.19.1 Ma must run at 190% rated speed (called 'fill' speed) to fill the accumulator. 3.19.2 Obviously Mp will be running at 1 ,05 X 1 ,9 = 200% rated speed. 3.20 The loops L2 to L5 will now fill and when:- 3.20.1 L5 reaches P7 at Level 1, C4 de-clutches and P7 controls C4 as per normal operation. 3.20.2 L4 reaches P6 at level 1 , 03 de-clutches and P6 controls 03 as per normal operation. 3.20.3 L3 reaches P5 at level 1 , 02 de-clutches and P5 controls C2 as per normal operation. 3.20.4 L2 reaches P4 at level 1, 01 de-clutches and P4 controls C1 as per normal operation. 3.20.5 When all the loops L2 to L5 are at Level 1, (that is, the accumulator is full) Ma must revert from fill speed back to normal operating speed (i.e. Vd4 = 1 ,05 x Vm) arid then operate as before in normal operation. 4. EXITING THE LAST STRIP TAIL OF A ROLL THROUGH THE ACCUMULATOR 4.1 When the tail of the last strip exits the pinch roll feed, it will fall away from the sensing range of proximity switch, P1. This must cause:- 4.1.1 A warning bell/light to ring/flash. 4.1.2 Mp to switch off. 4.1.3 01 to de-clutch; and 4.1.4 The rest of the accumulator to operate as per Clauses 3.6 through to Clause 3.15. 4.2 When L5 reaches P1 1 at Level 3, clutches C1 , C2, C3 and C4 must simultaneously clutch in, with none of the proximity switches having any influence. 4.3 The strip tail will thread through the drives and exit the accumulator. 4.4 The mill operator can now stop the mill at his convenience with the accumulator stopping at the same time. NOTE: Diameter of D1 = 1,01 5 X Diameter of D2 Diameter of D2 = 1 ,01 5 X Diameter of D3 Diameter of D3 = 1,01 5 X Diameter of D4 This gives a 1,5% "in speed" to "out speed" differential. As will be appreciated from the above description of the operation of the accumulator 10, in the normal operating mode the depth or height of each storage loop L2 to L5 is maintained between levels 1 and 2 as shown in figure 6 to maintain sufficient strip accumulated within the accumulator. When it is necessary to join the tail of the accumulated strip to the head of a strip on a fresh coil, the depth of each enlarged loop L2 to L5 is decreased sequentially from loop L2 to L5 until the configuration shown in figure 7 is attained. Referring now to figures 8 and 9, an accumulator 10.2 includes seven pinch roller stations supported side-by-side on a frame 52. For the sake of clarity only two pinch roller stations 50.1 and 50.2 are shown in figure 9. Each pinch roller station includes of an upper roller 54 and a lower roller 56. The upper roller 54 is mounted between brackets 58 which are pivotally connected via pivot points 60 to the frame 52. An actuator 62, mounted on the frame 52, biasses the upper roller 54 downwardly to pinch the strip between the upper roller 54 and the lower roller 56 so that the strip can be fed into a storage loop 26 by the rollers. The lower roller 56 is connected to a sprocket 64 which is driven by a chain 68 connected to a sprocket 70. The sprocket 70 is driven by an electric motor 72 via a gearbox 74. A gantry arrangement 76 is located at the front of and at the rear of the pinch roller stations. Each gantry arrangement includes a pair of opposed roller carriages 78. Each carriage 78 is supported by wheels 80 on a rail 82. Each carriage 78 has a body 84 with a bracket 86 supporting two horizontally extending rollers 88. A pair of vertical guide rollers 90 is located in line with each pair of pinch rollers 50 and mounted on the gantry arrangement 76. Each carriage 78 is connected at its front and rear ends to a chain 92 which passes over a sprocket 94 and is driven by a motor 96 to move the carriage 78 along its rail 82. Referring now to figures 10 to 13, entry strip 98 from a coil enters the first pinch roller station 50.1 and passes between the upper and lower pinch rollers 54 and 56, through both pairs of horizontal rollers 88 and then to the second pinch roller station 50.2 and so on to form suspended spiral-like storage loops 26. The strip exits the seventh pinch roller station (not shown) to the pipe mill (not shown) and is hereinafter referred to as the exiting strip 100. The accumulator 10.2 is operated in much the same way as the accumulator 10, except that when all the storage loops 26 have reached their maximum depth as shown in figure 11 , the carriages 78 are moved away from the pinch roller stations simultaneously to increase the width of the storage loops 26 as shown in figure 12. Further strip is then fed into each loop 26 to increase the depth of the storage loops 26. Figure 13 shows a loop 26 at its maximum depth and at its maximum width. It will be appreciated that each storage loop 26 is fed strip by its upstream pinch roller station and that strip is withdrawn from the loop by its downstream pinch roller station. Thus the accumulator requires one more pinch roller station than there are storage loops formed in the accumulator. In the drawings the pinch roller station 50.1 is the upstream pinch roller station and the pinch roller station 50.2 is the downstream pinch roller station for the storage loop 26 formed between the pinch roller stations 50.1 and 50.2. It will be appreciated that the pinch roller station 50.2 is the upstream pinch roller station for the next storage loop. Each pair of pinch roller station has its own drive motor 72 for its pinch rollers 54 and 56 as opposed to the common drive motor 36 and magnetic clutches of the accumulator 10. Figure 14 shows an arrangement in which the depth and the width of a storage loop 26 is increased in four stages. However it will be appreciated that its depth and width could be increased in any number of stages. Instead of utilizing the gantry arrangement 76 to increase the width of the storage loops 26, the horizontally extending rollers 88 may be supported on two pivotally mounted structures 102. Each pivotally mounted structure 102 consists of two beams 104 each pivotable about pivot points 106 and displaceable about their pivot points by an actuator 108 pivotally supported on a frame 110. The pairs of horizontal rollers 88 can thus move in arcs 112 to increase the width of the storage loops 26. The applicant believes that the accumulator 10.2 can store up to 70 m of strip and accommodate strips varying in width from 50 to 200 mm and in thickness from 0,7 mm to 3 mm in a space having a footprint of 5 m x 2,5 m and a height of 5,5 m. Referring now to figure 16, an accumulator 10.3 is the same as the accumulator 10.2 except that it has two horizontally extending rollers 114 supported in guides 1 16. The guides 116 are located between the pinch roller stations and the extended position of the rollers 88. The rollers 114 can move vertically downwardly in the direction of arrow 118 to create two secondary outer loops 120 in each of the main storage loops 26 to increase the amount of strip stored within the main storage loops 26. The rollers 114 contact all of the storage loops 26 and therefore simultaneously create the secondary outer loops in the main storage loops 26. The rollers 114 move vertically upwardly in the direction of arrow 118 to reduce the size of the secondary outer loops 120 when accumulated strip is required by the pipe mill, and thereafter the width of the main storage loops can be decreased to the position shown in figure 11. Referring now to figure 17, an accumulator 10.4 is the same as accumulator 10.2 except that it has a horizontally extending roller 122 contacting all of the main storage loops 26 and located within guides 124. The roller 122 can move vertically upwardly in the direction of arrow 126 to create a secondary inner loop 128 in each of the main storage loops 26 to increase the amount of strip stored within the main storage loops 26. The secondary inner loops 128 are created simultaneously in all of the main storage loops 26. The roller 122 is lowered to its bottom position shown in dotted lines when the accumulated strip is required by the pipe mill. The rollers 114 and 122 can be combined on a single accumulator so that each main storage loop 26 can have two secondary upper loops 120 and a secondary inner loop 128. It will be appreciated that many modifications and/or variations of the invention are possible without departing from the spirit or scope of the invention.

Claims: CLAIMS 1. An accumulator for a flexible strip including a frame and a plurality of strip feed means located side-by-side on the frame so that in use at least one suspended storage loop of strip can be formed, with the storage loop being formed between a pair of strip feed means so that one of the feed means can feed strip into the storage loop and the other of the strip feed means can withdraw strip from the storage loop. 2. The accumulator of claim 1 wherein each strip feed means includes two rollers between which the strip can pass. 3. The accumulator of claim 2 including drive means for driving one or both of the rollers to feed the strip into or from its storage loop. 4. The accumulator of claim 2 or claim 3 wherein each strip feed means includes biassing means for biassing the two rollers towards one another to pinch the strip between the two rollers. 5. The accumulator of claim 4 wherein the biassing means is an actuator. 6. The accumulator of any one of the above claims including loop width increasing means for increasing the width of the storage loop to increase the storage capacity of the storage loop. 7. The accumulator of claim 6 wherein the loop width increasing means includes loop support means and displacing means for displacing the loop support means away from the strip feed means to increase the width of the loop. 8. The accumulator of claim 7 wherein the displacing means includes carriage means supporting the loop support means, the carriage means being displacable away from and towards the strip feed means to increase or decrease the width of the storage loop. 9. The accumulator of claim 7 wherein the displacing means includes a pivotally mounted structure supporting the loop support means, the pivotally mounted structure being displacable away from and towards the strip feed means to increase or decrease the width of the storage loop. 10. An accumulator substantially as herein described and illustrated with reference to the drawings. 11. A method of operating a strip accumulator including the steps of: forming at least one suspended spiral-like storage loop; increasing the size of the storage loop to accumulate strip within the accumulator; and decreasing the size of the storage loop to withdraw the accumulated strip from the accumulator. 12. The method of claim 11 including the step of increasing the size of the storage loop by increasing the depth and the width of the loop. 13. The method of claim 11 including the step of forming a plurality of suspended spiral-like storage loops. 14. The method of claim 13 including the step of increasing the width of the plurality of storage loops simultaneously. 5. A method of operating a strip accumulator substantially as herein described and illustrated with reference to the accompanying drawings.

Inventors: PALLISTER GEOFFREY FLEMMER, PALLISTER, GEOFFREY, FLEMMER
Applicants: BARLOWORLD ROBOR PTY LTD, PALLISTER GEOFFREY FLEMMER, BARLOWORLD ROBOR (PTY) LTD., PALLISTER, GEOFFREY, FLEMMER
Application year: 2001
Main classification: B65H
IPC codes: B21C49, B65H83