US3669377A

US3669377A - Coiling apparatus

Info

Publication number: US3669377A
Application number: US96516A
Authority: US
Inventors: Martin Gilvar; Charles E Conlon; Alfred R Leger
Original assignee: Morgan Construction Co
Current assignee: Siemens Industry Inc
Priority date: 1970-12-09
Filing date: 1970-12-09
Publication date: 1972-06-13
Anticipated expiration: 1989-06-13
Also published as: JPS5014990B1; DE2158722A1; GB1364101A

Abstract

Apparatus and method for forming a coil by winding an axially advancing product length around a mandrel. The rotational speed of the winding means is initially adjusted relative to the axial speed of the product length to loosely encircle the mandrel with a relatively short leading section of the product. The leading section is then temporarily held against the mandrel and the speed of the winding means is increased while axially reciprocating the mandrel to produce an evenly distributed, closely packed and tightly wound coil. Upon completion of the coil forming operation, the mandrel is axially withdrawn from the coil, and the coil is discharged from the apparatus.

Description

United States Patent Gilvar et al.

[151 3,669,377 51 June 13, 1972 COILING APPARATUS [72] Inventors: Martin Gllvar, Westboro; Charles E. Conlon, Worcester; Alfred R. Leger, Leominster, all of Mass.

[73] Assignee: Morgan Construction Company, Worcester. Mass.

[22] Filed: Dec. 9, 1970 [21] Appl.No.: 96,516

F ORElGN PATENTS OR APPLICATIONS 966,563 8/1957 Germany ..242/82 Primary Examiner-Billy S. Taylor Attorney-Chittick, Pfund, Birch, Samuels 84 Gauthier 57 ABSTRACT Apparatus and method for forming a coil by winding an axially advancing product length around a mandrel. The rotational speed of the winding means is initially adjusted relative to the axial speed of the product length to loosely encircle the mandrel with a relatively short leading section of the product. The leading section is then temporarily held against the mandrel and the speed of the winding means is increased while axially reciprocating the mandrel to produce an evenly distributed, closely packed and tightly wound coil. Upon completion of the coil forming operation, the mandrel is axially withdrawn from the coil, and the coil is discharged from the apparatus.

8 China, 6 Drawing Figures PATFNTFnJuxm m2 SHEEI 2 OF 4 INVENTORS MARTIN GILVAR BY CHARLES E. CONLON ALFRED R. LEGER CLMWQJ PM; -Jfim ATTORNEYS PATENTEU JIIII I 3 I972 SHEET '4 BF 4 SPEED REFERENCE FROM M 235%" MILL TACHOMETER ,L- 76 POWER SUPPLY AND DRIVE s2 M RESGTJELEAQ'OR :3 MOTOR TENSION B4 REFERENCE L SPEED FEEDBACK I MANUALLY SET PRODUCT 9| FIG-4O OFF BEEF-FDR VARIABLE ON 21' DELAY TIME 94 'cR- g 95 ]TR OAR-3| 98 cR -z IoI CFI:-3|' I02 I v no oIL FLOW ACR-3 MUR-l I To .L I CYLINDER 52 II as I MUR-Z PRODUCT H8 MR4 Ioe DIAMETER PRODUCT CYLINDER oAR-I SPEED SPEED MDR "2 REFERENCE FEED BACK FROM MILL IL T 1. R 5: "g TACHOME ER MUR-Ea 1 fin F- CRX-3 AcR-5 K 11' ACR-4 STR I INVENTORS I24 MARTIN GILVAR BY CHARLES E. CONLON F|G.4C CRX-Z ALFRED R. LEGER Eu fwd, r' ATTORNEYS COILING APPARATUS DESCRIPTION OF THE INVENTION The present invention relates to a novel apparatus and method for forming an axially moving product length into a coil. The invention is especially useful in coiling rolling mill products such as for example rod or bar, although it will be appreciated from the following detailed description that other uses are also contemplated.

One of the principal objects of the present invention is to provide a unique apparatus and method for coiling an axially moving product length into a dense coil made up of rings which are evenly distributed, closely packed and tightly wound. Another object of the invention is to provide an apparatus and method for producing a coil by tightly winding an axially moving product length around a reciprocating mandrel, the resulting coil being made up of densely packed rings arranged in an orderly fashion. Another object of the invention is the provision of an apparatus which is especially suitable for, although not limited to, the coiling of product emerging from a rolling mill. A further object of the present invention is the provision of a relatively simple apparatus involving the use of a minimum number of operating components. Still another object of the present invention is the provision of an apparatus and method which achieves a dense coil by maintaining the produce in tension while it is being wound around a reciprocating mandrel. Additional objects will be apparent from the following detailed description of the invention.

Broadly stated, the present method comprises the steps of: passing an axially moving product length through a rotating laying head which operates to form the product into rings encircling a mandrel, the initial rotational speed of the laying head relative to the axial speed of the product being such that a relatively short leading section of the product length loosely encircles the mandrel; holding the leading section of the product length against the mandrel and then increasing the speed of the laying head while axially reciprocating the mandrel to tightly wind subsequent rings around the mandrel in a dense orderly arrangement, the aforesaid holding action being maintained for a brief interval; continuing the winding action until a coil of the desired weight has been produced, the said coil usually containing the entire length of a given product length; and, thereafter, retracting the mandrel from the coil prior to discharging the completed coil from the apparatus.

The invention is further described with reference to the accompanying drawings wherein:

FIG. I is a vertical sectional view taken through one embodiment of an apparatus embodying the concepts of the present invention, which apparatus is especially adapted to coil product, such as for example rod or bar, emerging from a rolling mill;

FIG. 2 is a sectional view taken along lines 2-2 of FIG. I;

FIG. 3 is a sectional view similar to FIG. I showing the reciprocating mandrel axially withdrawn from a completed coil; and,

FIGS. 4A, 4B and 4C are diagrammatic, block and schematic illustrations of the electrical control system employed with the apparatus shown in FIGS. I to 3.

Although the invention will hereinafter be described in connection with the coiling of a product length emerging from a rolling mill, it will be understood that any reference to a given product or product source is employed herein for illustrative purposes only, and is not intended nor should it be construed as a limitation upon the scope of the claims appended hereto.

Referring more particularly to the drawings, there is shown in FIGS. 1-3 a coil forming apparatus which includes a laying head assembly generally indicated at I overlying a mandrel 12. The laying head assembly is of generally known construction comprising a vertically disposed rotatable cylindrical shaft 14 supported by bearings I6 carried on a support structure l8. Shaft [4 may be driven in any known conventional manner, as for example by a plurality of belts extending between a pulley 22 on the shaft and another pulley 24 on a gear reducer 26. the latter being driven through shaft 28 by a variable speed drive motor (schematically shown in F IG. 4a at 76).

Although not shown in the accompanying drawings, it will be understood that suitable guide means are employed to direct the product to be coiled into the upper end 300 of a laying pipe 30 which is carried by the shaft I4 for rotation therewith. The laying pipe extends downwardly and axially through shaft 14 as at 306 before curving laterally and outwardly through an opening 32 in the shaft. Thereafter, the laying pipe takes on a curbed configuration as at 30c which extends around mandrel 12 with the exit end 30d of the laying pipe being located as shown in the drawings. The lower curbed section 30c of the laying pipe is preferably supported by attachment to a cylindrical skin 34 which is in turn supported by and attached to the main shaft 14 by radially extending braces 36. A joint 3| is provided between

sections

30b and 30c in order to facilitate assembly of the laying pipe 30 into the shaft 14.

Mandrel 12 includes a generally cylindrical wall 38 having an exterior surface which tapers slightly inwardly from bottom to top. Circumferentially spaced wear strips 39 may if desired be arranged around the exterior surface of the mandrel. The mandrel further includes a generally circular shelf 40a and an annular shelf 40b spaced vertically therebeneath. Both shelves 400 and 4015 are suitably apertured to accommodate positioning of stabilizing posts 42. The posts are secured by any suitable means, as for example by kee er plates 44 to shell 40b, with the lower sections of the posts slidably extending through bearings 46 in an underlying support structure 48.

An operating cylinder 52 is mounted on a pedestal 54 beneath support structure 48. The cylinder extends vertically through a suitable opening in support structure 48 and is provided with an extensible piston rod 56. Piston rod 56 is connected at its upper end as at 58 to the underside of shelf 400.

In light of the foregoing, it will be understood that when the piston rod 56 is reciprocated vertically, the mandrel 12 will undergo corresponding vertical movement. The stabilizing posts 42 will provide a vertical guiding action while at the same time preventing the mandrel from rotating.

A somewhat annularly shaped platen 62 surrounds the mandrel 12. In the operative position shown in FIG. 1, the platen 62 is supported as at 64 on a radial flange 66 at the bottom of mandrel I2. A pair of gripping

arms

68a and 68b are mounted on platen 62 for pivotal movement about axes 70 between inoperative positions shown in solid in FIG. 2 and operative positions shown by broken lines at 680 and 68b in FIG. 2. The gripping arms are manipulated between the aforesaid operative and inoperative positions by means of torque motors 72 mounted on the underside of platen 62.

The circular shelf 40a on mandrel I2 is spaced beneath the upper edge of wall 38, thus providing a recess 50 at the top of the mandrel. A pair of

cylinders

51a and 51b are located within recess 50 on shelf 40a. The cylinders are each provided with piston rods 51c which are connected to lugs 53 depending from the undersides of a pair of

plates

55a and 55b. The

plates

55a and 55b are each slidably mounted between guides 57 for movement under the influence of

cylinders

51a and 51b between extended operative positions as shown in FIGS. I and 2 and retracted inoperative positions as shown in FIG. 3.

The apparatus shown in FIGS. 1 to 3 operates in the following manner: prior to commencing the coiling operating, the rotational speed of laying pipe 30 is adjusted in relation to the axial speed of the product to be coiled such that the resulting product rings will be slightly larger in diameter than the outside diameter of mandrel 12 at the level defined by the upper surface of annular platform 62. Stated somewhat differently, the initial rotational speed of the laying pipe will be such that the leading product end will be caused to loosely encircle the mandrel. The mandrel I2 and the platform 62 will be in the uppermost position as shown in FIG. I, the gripping arms will be opened to their inoperative positions shown by the solid lines in FIG. 2, and the

plates

55a and 55b will be operatively extended.

With the apparatus thus adjusted, the leading end of the product length to be coiled will pass through the rotating laying pipe 30 and be formed into a circular pattern of one or more rings loosely encircling the mandrel 12. As soon as this has taken place, the torque motors 72 will be actuated to pivot gripping

arms

68a and 68b to their closed operative positions with the result that the initial loosely formed rings will be gripped and held against the exterior surface of the mandrel. With the gripping arms operatively positioned, the rotational speed of the laying pipe 30 is then increased to produce a predetermined tension in the product being coiled. At the same time, cylinder 52 is operated to being lowering mandrel 12 along with the platen 62 supported thereon. The rate at which cylinder 52 is operated is such as to cause the rings to be arranged side-by-side touching one another in densely packed layers. Operation of cylinder 52 will continue, first to lower and then to raise piston rod 58, with the result that the mandrel and platen 62 supported thereon will be vertically reciprocated between an uppermost position as shown in solid in FIG. I and a lower position shown by the dotted lines in FIG. 1. During the first upward stroke of the piston rod 56, the gripping members 68b will be opened to their inoperative positions. Vertical reciprocal movement of mandrel l2 and platform 62 will continue throughout the formation of the coil, with appropriate adjustments constantly being made to the rotational speed of the laying pipe in order to compensate for the gradually increasing diameter of the coil, thereby maintaining a predetermined substantially constant tension in the product being coiled. The

extended plates

55a and 55b define a ceiling against which the coil is formed. Upon completion of the coiling operation, the rotational speed of the laying pipe 30 will be returned to that prevailing during the start" condition, the

plates

55a and 55b will be retracted, and the piston rod 56 will be fully lowered as shown in FIG. 3 with the result that the mandrel 12 will be fully withdrawn from the completed coil C. As the mandrel 12 is dropped to the lowermost position shown in FIG. 3, platen 62 will come to rest on appropriately positioned support posts 74 extending vertically from structure 48. With the mandrel fully retracted from the completed coil, coil discharge may take place in the direction indicated schematically in FIG. 2.

FIGS. 4A, 4B and 4C illustrate in diagrammatic, block and schematic form an electrical control system for operating the apparatus shown in FIGS. 1-3. Referring initially to FIG. 4A, the speed of the variable speed laying head drive motor 76 is controlled by a combination power supply and speed regulator 78. The initial synchronization of the drive motor speed with the rolling mill speed is achieved by providing a mill speed signal from a mill tachometer as a reference input signal to the speed regulator 78. This adjusts motor armature voltage to maintain constant torque over mill speed range. Two feedback loops are provided for the power supply and speed regulator to control both laying head drive motor speed and tension on the product being coiled. A speed feedback loop 80 provides a feedback signal from drive motor tachometer 82. The current feedback loop 84 generates a signal representing the amount of current drawn by the laying head drive motor 76. The current feed back loop 84 provides a control of the tension on the coiled product and can be preset to produce a predetermined tension. This is done by adjusting motor field excitation to maintain constant horsepower over coil build-up range.

FIG. 48 illustrates in diagrammatic form the control circuitry for the operating speed of the reciprocating mandrel l2. Mandrel speed is controlled by varying the oil flow to the operating cylinder 52 through a servo-controlled variable valve 86. The reference inputs to valve servo 88 are product speed, product diameter. and a cylinder speed feedback signal. The product diameter input is present for the particular diameter of the product.

The operating sequence of the apparatus from an electrical standpoint is shown in schematic form in FIG. 4C. Overall control of the apparatus is provided by a master ON-OFF switch 90 which is wired in series with a product detector 92 and a variable drop out delay timer 9]. Timer 91 is used to provide an energization path for a master control relay 94 through timer contacts VDT-l. In the start" condition illustrated in FIGS. 1 and 2, the laying pipe 30 is rotating at a seed relative to the axial speed of the product to be coiled such that the resulting rings will loosely encircle mandrel 12. The mandrel, and hence the platen carried thereon are in the fully raised position and the gripping

arms

68a and 68b are in the then inoperative positions. When the leading end of the product is detected by product detector 92, the latter being appropriately located at some point along the path of product travel in advance of the laying head assembly l0, timer 91 is actuated and master control relay 94 is energized through the now closed variable delay timer contact VDT-l. The energization of another control relay 94 closes a normally open contact CR-l which in turn actuates timer 96. At the end of a predetermined timing cycle, timer 96 opens normally closed timer contact TR-l which interrupts the energization path for an open gripper solenoid 98. At the same time, normally open timer contacts TR-Z are closed thereby completing the energization path for a closed gripper arm solenoid 100.

The energization of master control relay 94 also closes the normally open contacts CR-Z which establishes an energizetion path for a solenoid I01. Solenoid 101 is used to control the movement of cylinders 51. With the solenoid energized, the cylinders 51a and 5lb will move the

plates

55a and 55b to their extended operative positions as shown in FIGS. I and 2. Conversely, when solenoid ml is de-energized, the cylinder will move the plates to their retracted inoperative positions as shown in FIG. 3.

A third set of normally open contacts (IR-3 is also closed by the energization of master control relay 94. Contacts CR-J provide control for a gripper arms closed relay 102, a mandrel down relay 104, a mandrel up relay I06 and an open gripper arms relay I08. When the

gripper arms

68a and 68b reach the closed position, gripper arms closed limit switch is momentarily closed completing the energization path for gripper arms closed relay I02. A holding path for the gripper arms closed relay is established through its own contact ACR-l. Referring back for the moment to FIG. 4A, a set of normally open gripper arm-closed relay contacts ACR-Z are used to provide a speed up signal to the power supply and speed regulator 78. The speed up signal causes the laying head drive motor 76 to speed up sufliciently to lay the rings slightly against the mandrel. The tension of the rings is sensed by the current feedback loop 84. The current drawn by the laying head drive motor 76 is a function of product tension, and hence the current feedback signal provides an indication of the tension. When the current drawn by motor 76 reaches a predetermined amount corresponding to the desired preset tension, motor speed is regulated to maintain the preset tension.

Referring back again to FIG. 4C, a normally opened set of gripper arms-closed relay contacts ACR-3 is used to complete the energization path through normally closed mandrel up contacts MUR-l to the mandrel down relay I04. The mandrel down relay controls the energization path for a mandrel down solenoid 2 through a set of contacts MDR-l. The mandrel down solenoid in turn controls the direction of oil flow to the mandrel cylinder 52 to start piston rod 56 in a downward direction. At the bottom of the mandrels reciprocating stroke (shown in dotted in FIG. 1) a limit switch I" is closed completing the energization path for the mandrel up relay I06. Energization of the mandrel up relay opens mandrel up relay contacts MUR-l, thereby interrupting the energization path for the mandrel down relay I04, while at the same time setting up a holding path through mandrel uprelay contacts MUR-Z. In addition, the mandrel up relay also completes the energization path for a mandrel up solenoid 116 through mandrel up relay contacts MUR-J. The mandrel up solenoid changes the direction of oil flow to the mandrel cylinder 52 causing the cylinder to start in an upward direction.

During the top half of the mandrels stroke, limit switch 118 is closed. Assuming that the mandrel is on its first upward stroke after starting the coiling operation, mandrel up relay contact MURA will be closed thereby completing the energization path for open arms relay 108. The open arms relay sets up its own holding path through contacts OAR-1. The energization of the open arm relay 108 interrupts the energization path for the closed arm solenoid 100 by opening relay contacts OAR-2. At the same time, normally open arms relay contacts OAR-3 are closed providing an energization path for the open arms solenoid 98. This circuitry allows the gripper arms to open during the first upwardly stroke in the reciprocating cycle of the mandrel. The open arms solenoid 98 will remain energized and therefore the arms will remain open as long as the product detector 92 detects product and provides the energization path for the master control relay 94.

When the mandrel reaches its top limit, limit switch 120 opens and interrupts the energization path to the mandrel up relay 106. The mandrel down relay 104 is then energized and the down-up reciprocating cycle of the mandrel is repeated again with the exception that the arms remain open as noted above.

The up and down reciprocating cycle of the mandrel continues as long as product is sensed by the product detector 92. When the tail end of the product length passes beyond detector 92, power is interrupted to timer 91, after a preset time delay to allow completion of the coiling operating, timer contacts VDF/are opened thereby breaking the energization path for master control relay 94 and causing relay contacts CR-l, CR-Z and CR-3 to open. With CR-l open, the timer 96 is reset and timer contacts TR-l and TR-2 return to their normal conditions.

The opening of contacts CR-2 de-energized solenoid 101 which in turn causes

cylinder

51a and 51b to move

plates

55a and 55b to their retracted inoperative positions as shown in FIG. 3. Mandrel 12 is now moved to its lowermost position beneath platen 62 as illustrated in FIG. 3, with the result that the fully formed coil is in effect stripped from the mandrel. The energization path for the mandrel down solenoid 112 is provided by a normally closed contact on the master control relay CR4 and a normally open relay contacts CRXl on a stripping control relay 122. The stripping control relay is initially energized through arms closed relay contacts ACR-4, and a normally closed switch 124. A holding path of stripping control relay 122 is provided through a set of contacts CRX-2. With the stripping control relay energized, the mandrel down solenoid 112 will be energized when the master control relay 94 is de-energized at the end of the rod sensing cycle. When the mandrel reaches its full down position, limit switch 125 closes to start the stripping operation. After the stripping operation is completed, the normally closed switch 124 is mechanically opened, thereby interrupting the energization path for the stripping control relay 122. With stripping control relay 122 de-energized, an energization path for the mandrel up solenoid 116 is set up through normally closed stripping relay contact CRX-3 and normally closed arms closed relay contacts ACR-S. The mandrel then returns to its full up position and is maintained there until the next product length is detected by product detector 92 at which point the entire cycle is repeated.

Having thus described a preferred embodiment of the invention, the advantages to be derived therefrom will now be more apparent to those skilled in the art. Of primary importance is the production of a dense coil made possible by tightly winding product rings in an ordered arrangement, rather than by relying on a somewhat random arrangement of loosely formed rings, as has generally been the custom in the past. Other advantages include a relatively simple and inexpensive apparatus employing a minimum number of operating Components.

It will be appreciated that various modifications may be made to the invention as described above. Thus, for example, the mandrel and the laying head may if desired be arranged horizontally rather than vertically as depicted in the drawings. The number and general design of the gripping arms may also be changed to suit particular operating conditions. While the method and apparatus of the present invention are particularly useful in coiling the product of a rolling mill, it will be appreciated from the foregoing that other types of products and elongated elements may be coiled by the same apparatus and method.

It is our intention to cover all changes and modifications to the embodiments herein disclosed which do not constitute departures from the spirit and scope of the invention.

We claim:

1. Apparatus for coiling an axially moving elongated element comprising: a platen having an opening therein; a mandrel protruding through the opening in said platen, laying means rotatable around said mandrel for receiving and forming the axially moving element into a continuous series of rings encircling said mandrel, means for varying the rotational speed of said laying means relative to the axial speed of the element, the initial rotational speed of said laying means being such that the leading section of the element contacts said platen and loosely encircles said mandrel, gripping means movable between an inoperative position spaced radially from said mandrel and an operative position gripping the leading section of the element against said mandrel, whereupon following adjustment of the gripping means to the operative position, the rotational speed of the laying means is increased to develop tension in the element which results in the element thereafter being tightly wound around said mandrel, operating means for axially reciprocating said mandrel and said platen relative to said laying means, thereby axially distributing the rings being tightly wound on said mandrel in radially arranged layers, the said gripping means being returned to the inoperative position prior to the leading element section being overlapped by subsequently wound rings, and means against which said platen may be held to permit axial withdrawal of said mandrel through said opening thereby freeing a completed coil for removal from the apparatus.

2. The apparatus as claimed in claim 1 further characterized by said mandrel being tapered in an axial direction to facilitate withdrawal thereof from a fully formed coil.

3. The apparatus as claimed in claim 1 wherein said gripping means is comprised of arm members pivotally mounted on said platen for movement between said inoperative and opera tive positions.

4. The apparatus as claimed in claim 1 further characterized by control means responsive to the presence of the element leading end for controlling the operation of said gripping means.

5. The apparatus as claimed in claim 4 further characterized by additional control means responsive to movement of said holding means to the operative position for increasing the rotational speed of said laying means while simultaneously commencing reciprocating axial movement of said mandrel.

6. Apparatus for coiling an axially moving element comprising: a horizontal platen having an opening therein, a mandrel protruding vertically through the opening in said platen, said mandrel including means for supporting said platen, rotating laying means overlying said platen for forming the axially moving element into a continuous series of rings encircling said mandrel, the initial rotational speed of said laying means relative to the axial speed of the moving element being such that the leading section of the element loosely encircles the mandrel and rests on said platen, gripping means carried by said platen for movement between an inoperative position radially spaced from said mandrel and an operative position gripping the leading section of the element against said mandrel, whereupon the rotational speed of the laying head is increased to develop tension in the element and to tightly wind subsequent rings around said mandrel, operating means for axially reciprocating said mandrel to axially distribute the rings being tightly wound thereon in radially arranged layers, the said gripping means being returned to the inoperative position prior to the leading section of the element being overlapped by subsequently wound rings, whereby upon completion of the coiling operation, the operating means is manipulated axially relative to said platen to withdraw the mandrel from the fully formed coil, thereby freeing the coil for lateral removal from the apparatus.

7. Apparatus for coiling an axially moving product length comprising: a mandrel; rotatable laying means for forming the axially moving product length into a continuous series of rings encircling said mandrel, the initial rotational speed of said laying means relative to the axial speed of the moving product length being such that the leading section of the product length loosely encircles said mandrel; gripping means cooperating with said mandrel to temporarily grip the leading section of the product length therebetween, thereby allowing the rotational speed of the laying means to be increased with the result that tension is developed in the product length and the remainder of the product length is tightly wound around said mandrel; and, operating means for reciprocating said mandrel in an axial direction to distribute the rings being wound thereon in radially arranged layers, the said operating means being further operative upon completion of the coil forming operation to axially withdraw the mandrel from the coil.

8. A method of coiling an axially moving product length comprising the steps of; passing the product length through a laying head to form the product into a continuous series of rings, each of which encircles a mandrel protruding vertically through an opening in a horizontal platen, initially controlling the rotational speed of the laying head so that the leading section of the product length loosely encircles the mandrel and rests on the platen, temporarily holding the leading section of the product length against the mandrel while simultaneously increasing the speed of the laying head and axially reciprocating the mandrel, thereby developing tension in the product length with the result that subsequently formed rings are tightly wound around the mandrel in radially arranged layers, and, upon completion of the coiling operation, withdrawing the mandrel from said coil through the opening in said platen, thus freeing the coil for subsequent lateral removal from the platen.

Claims

3. The apparatus as claimed in claim 1 wherein said gripping means is comprised of arm members pivotally mounted on said platen for movement between said inoperative and operative positions.