US3314619A - Tension distributing winding device - Google Patents

Description

April 18, 1967 D. R. KERSTETTER TENSION DISTRIBUTING WINDING DEVICE Original Filed July 25, 1962 2 Sheets$heet 1 8 R MY 0 E Td m 6% v K W m R A April 13, 1967 D. R. KERSTETTER 3,314,619

TENSION DISTRIBUTING WINDING DEVICE Original Filed July 23, 1962 2 Sheets-Sheet 2 TiNS/ONAL FORCE -GM5 ZWRAPPLED LENG TH 0f HfL/X 40 60 ZWRAFPED LENGTH OF HfL/X W/RE DEMAND b A A I A I I 0 1 .4

\JU UV DEFZECT/ON TURN INVENTOR Donald R Kersfezter iZ d/JM ATTORNEY United States Patent 3 Claims. (Cl. 242-9) The present invention is a division of Serial Number 211,818 filed July 23, 1962, now abandoned, and as signed to the same assignee as the subject application.

This invention generally relates to a process and apparatus for wrapping a support with a helix of wire and more particularly to the use of this process and apparatus in the manufacture of frame type grid electrodes for electron tubes.

In a process of winding a helix of wire about a support and especially in the manufacture of frame grid electrodes, it has become increasingly evident that the tension exerted between the side members and the wire helix traversing them is of utmost importance. When tube electrodes are closely spaced and small in size, the materials used in the structure lack the physical strength present in the former self-supporting type of electrodes. As a consequence, problems growing out of inwardly bowed side members, loose and sagging wires surrounding the side members, and broken wires both during and after the wrapping process have plagued the manufacture of frame grid electrodes. Although numerous variations and alterations have been made in the materials and wrapping process to improve the tension relationship between side members and the lateral wire, the control level thus far achieved has not been adequate.

One approach to the tension problem when using a self-supporting type electrode utilizes a fixed amount of back tension which is applied to the lateral wire as it is wrapped about the spaced side members. While the technique has proven satisfactory for heavier and physically stronger materials or wires, it has several disadvantages when lighter and more easily distorted materials are used. Those disadvantages will be appreciated when it is realized that since the lateral wire helix surrounding the side members is attached thereto only at the ends of the helix, the intermediate lateral turns are held in position only by the frictional force existing between the side members and the wire. Therefore, it is imperative that the wire have sufiicient back tension during the wrapping process to correctly position and retain each lateral wire turn on the side members.

It has been found that an insuflicient amount of fixed back tension or opposition to the pull on the wire during a wrapping process results in erratic and poor spacing between adjacent turns of the electrode. Further, if the back tension is insufficient during the wrapping process, the tension developed between the wire helix and the side members permits the wire turns to sag during tube operation. As a result, the desired electrical characteristics are lost and reliability of the electron discharge device is reduced. Additionally when the wire turns surrounding the side members are not taut, their vibration characteristics result in microphonic and uncontrollable noise factors which are again detrimental to product reliability.

Conversely, when the fixed back tension on the lateral wire during wrapping is increased to a level just below the breaking point of the lateral wire, the side members progressively bow inwardly as successive lateral wire turns are added to the helix. It is to be realized that when the spaced side members are rigidly held by cross straps outside of the helix area, the bending moment exerted on the side members increases as each turn of the helix is added. This condition occurs even though the actual back tension or force exerted. by each turn of the wire remains fixed. Therefore, the side members intermediate the rigid cross straps how more inwardly with each succeeding turn. As a result, the tension between the side member and the previous turn is lost and these turns become loose and sag from their original location.

In addition to the previously mentioned problems, it has also been found that the widely used non-circular type of wire helix grid requires a varying supply of lateral wire. It should be realized that when a pair of spaced side members for a non-circular grid are rotated to cause the lateral wire to wrap thereabout, the lateral wire will be demanded at a varying cyclic rate by the side members which may be rotating at a constant rate. This cyclic demand for lateral wire at the side rods causes unwanted varying back tension on the wire.

Attempts to correct this problem primarily have been directed toward providing a dampening device intermediate the lateral wire supply and the side member wrapping location. Various combinations of pulleys, weights, and springs have provided very limited success in attempts to eliminate cyclic back tension lateral wire variations. This limited success is believed to be based upon the fact that the inertia of the dampening apparatus itself prevents the rapid variations in response necessary to compensate for the rapid change in tension and lateral wire demand by the rotating side members.

Therefore, it is an object of the invention to improve the reliability of a helix wrapped support grid.

Another object of this invention is to reduce the variations along the helix in the tensional force between the wire turns and the spaced side members.

A further object of the invention is to improve the microphonic and random noise characteristics of an electrode for an electron discharge device.

A still further object is to reduce the cyclic back tension variations in Wire supplied to the spaced side members during a wrapping process.

An additional object of this invention is to program the wrapping process to provide a wrapped grid having multiple turns of wire with each turn exhibiting substantially the same tension characteristics.

The foregoing objects are achieved in one aspect of the invention by programming the variation in back tension on the lateral wire as it is wrapped about the support. The desired program varies the back tension on the wire as the turns of a wire helix wrap about the rotating side members in accordance with the cumulative deflection forces on the side members exerted by the summation of individual turn forces exerted during winding the completed helix. This tensional relationship is provided by synchronizing a programmed back tension cam with the side member rotating device. In addition, a low inertia dampening device is employed so that the varying rate of wire demand by the rotating side members during the wrapping of each turn may be substantially immediately met. The dampening device has low mass and low inertia to facilitate substantially instantaneous response to variations in wire demand by the rotating side members.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended'claims in connection with the accompanying drawings in which:

G. l is a perspective view of a strap frame;

FIG. 2 is a curve of the bending moment and the lateral turn tensional force of an electrode wrapped with a uniform back tensional force;

FIG. 3 is a curve of the programmed back tensional lback tension force on the lateral wire during the force applied to the wire and the resulting cumulative tensional force exerted by the lateral turns on the side members;

FIG. 4 is a curve of the wire demand by the side members during rotation and wire deflection by the low inertia dampening device;

FIG. 5 is a diagrammatic view of a programmed back tension wrapping apparatus and a low inertia dampening device; and

FIG. 6 is a diagrammatic view of a completed strap frame grid electrode with the wire turns wrapped thereabout and aifixed thereto.

The most frequently encountered prior art is that in which a strap frame which will be described later is wrapped with a wire helix to provide a strap frame electrode. During this wrapping process, a uniform back tensional force is applied to the wire from which the helix is formed. It is believed that the cumulative bending moment exerted upon the side members by the wire helix turns when applied with a uniform back tensional force on the wire varies substantially as shown in curve A of FIG. 2. Further, it has been found that the tensional force exerted between the side members and the lateral wire turns varies substantially as shown in curve B of FIG. 2. Accordingly, this process results in loose and sagging lateral wire turns especially in the areas where the tensional force is low which permit the electrical characteristics controlled by the grid electrode to vary and the microphonic and random noise values to increase.

A process which has substantially reduced these problems and aided greatly in the manufacture of reliable electrodes is the application of a programmed back tensional force to the lateral wire during the wrapping process. In this process the tension may be preselected for each turn of the wire helix and increased or decreased in substantially any prescribed manner desired. As is well known, when a force is applied to a wire within the elastic limit thereof, the wire will react in a substantially expected and predictable manner. Accordingly, a back tensional force, curve C of FIG. 3; is applied to the wire within the elastic limit thereof which is substantially proportional to the cumulative deflection force exerted by all of the completed helix turns on the side members and the tensional force desired on each turn upon completion of the helix. As a result, the side members bow sufficiently to relieve the tensional force added to each turn to compensate for this how and the desired uniform tension on each turn remains substantially as pre-selected, curve D of FIG. 3. Moreover, the back tensional force may be preselected to provide substantially any desired variation or level of tensional force between the helix and the side members. 1

Additionally, when a pair of spaced side members such as a strap frame is wrapped with a wire helix having a non-circular periphery, it has been found that intermittent period of increased wire demand by the rotating side members occur. Further, this increased wire demand occurs not at the frequency of rotation but at twice the frequency of rotation. Moreover, the periods of increased wire demand are interspersed with periods when the wire demand is not as great. Thus it has been found that the variation in wire demanded by the rotating side members varies substantially in a sinusoidal pattern throughout the longitudinal length of the helix as shown by curve E of FIG. 4.

Accordingly, a low inertia dampening device which will be described later is inserted intermediate the wire supply source and the rotating side members. This device provides a resilient elastic force such as a fluid force, electrostatic force, magnetic force or numerous other mediums which act upon the wire and cause a deflection thereof substantially as shown in curve F of FIG. 4. Thus, as the wire demand by the rotating side members increases, the deflection of the wire intermediate the supply source and the rotating side members decreases whereupon the increased demand is substantially immediately supplied. Further, when the wire demand decreases the 'wire deflection increases whereupon the supply of wire available at the rotating side members is decreased. Therefore, each turn of the wire helix has a substantially uniform tensional force exerted thereon throughout the entire winding length of the turn regardless of the speed at which the turns are applied to the side members.

In a process for wrapping the strap frame of FIG. 1 to form the strap frame electrode of FIG. 6, an apparatus as illustrated in FIG. 5 may be used. An automatic grid electrode winding machine having a rotating head portion 13 is synchronously operated with wire guide 15 and programmed tension means 17. Additionally, low inertia dampening apparatus 19 may be disposed adjacent to but not geared or synchronously connected with the grid electrode wrapping apparatus.

The rotating head portion 13 of the grid electrode machine is stationary in the loading position and the strap frame of FIG. 1 is loaded thereon. Rotating head portion 13 then moves to the operating position whereat it remains stationary until the wire which forms the wire helix is fed from a supply source affixed to back tension means 17 onto wire guide 15 and to the strap frame FIG. 1 positioned on rotating head portion 13 whereat the wire is attached. Rotating head portion 13 is then activated whereupon the wire attached thereto wraps about the strap frame of FIG. 1. Synchronously operated wire guide 15 acting through appropriate linkages and contoured cams directs the wire longitudinally along the strap frame at a rate and spacing between wrapped turns which may be preselected. Simultaneously, programmed back tension means 17 operating through the necessary linkages and contoured cams provides a predetermined varying tensional force in opposition to the flow of wire from the supply source to rotating head portion 13 whereat the wire forms the helix surrounding the strap frame. When the desired helix length has been wrapped upon the strap frame, the rotating head portion i stopped and the wire from the supply source is again attached to the strap frame and subsequently severed immediately adjacent thereto. Rotating head portion then returns to the loading position whereat a frame grid electrode as shown in FIG. 6 is removed therefrom. Accordingly, a rotating head portion 13, a programmed back tension means 17, and a wire guide 15 operating in synchronous relationship provide a process wherein the spacing between adjacent turns of a wire helix wrapped upon a strap frame may be preselected and the back tensional force exerted on the wire throughout the helix formation and consequently the tensional force exerted between each wire turn of the helix and the strap frame side members may be predetermined and controlled.

Additionally, low inertia dampening device 19 is used in conjunction with the above stated process and apparatus as shown in FIG. 2. Dampening device 19 may be disposed intermediate the wire supply source of programmed back tension means 17 and wire guide 15. As wire is demanded for wrapping the wire helix upon the strap frame at rotating head portion 13, the wire is withdrawn from programmed back tension means 17. Dampening device 19 provides an elastic resilient deflecting force normal to the wire intermediate the supply and the demand. When the demand for wire at rotating head portion decreases, the tensional pull on the wire decreases and the low inertia dampening force provides a substantially immediate increased deflection of the wire thereby decreasing the wire supply at the rotating head portion 13 and returning the tensional pull to its previous value. Further, when the wire demand at rotating head portion 13 increases, the tensional pull on the wire is increased and is met by an inversely proportional decrease in deflection by low inertia dampening device 19. Accordingly, low inertia dampening device 19 provides a force normal to the wire flow during the wrapping of the wire on a strap frame whereby a change in wire demand is met by an inversely proportional and substantially immediate change in wire deflection and as a result, each helix turn is wrapped with a substantially uniform tensional force throughout its length regardless of the variations in wire demand or rotational speed which occur during the wrapping process.

A programmed back tension apparatus is shown in FIG. 5 whereby the strap frame of FIG. 1 may be wrapped with a wire helix to form the frame grid electrode of FIG. 6. An automatic grid electrode wrapping machine is provided with a rotating head portion 13 which is synchronously operated with a wire guide 15 and programmed back tension means 17. Additionally, low inertia dampening means 19 is disposed adjacent the programmed back tension apparatus and operated in conjunction therewith but need not be attached thereto.

FIG. 1 shows a strap frame 5 prior to the addition of the wire helix. It is the turns of the wire helix wrapped upon the strap frame 5 which form a frame grid electrode as shown in FIG. 6. The side members 7 are rigidly spaced by pairs of supporting cross straps 9 at each end and may be round, rectangular, formed, or numerous other configurations. The cross straps 9 are attached to the side members 7 in numerous ways such as brazing, or fritting but in this specific instance, welding has proven most satisfactory. The inside surface of the cross straps 9 and the inside surface of the side members 7 form a channel 10 through which may be inserted a support means for holding the strap frame 5 while the helix of wire is wrapped as will hereafter be described.

FIG. 6 shows hte strap frame 5 of FIG. 1 with the wire helix 8 wrapped thereon to form a strap frame grid electrode. The wire helix 8 has It turns of lateral wire and each turn frictionally engages side members 7. Also the ends 12 of wire helix 8 are secured at longitudinally opposite ends of strap frame 5. Side members 7 have a maximum inward deflection at 12/2 position 14 due to the cumulative force of n turns acting thereon.

A rotating head portion 13 of a strap grid electrode winding machine is shown having diametrically opposing heads 21 and 23 which may be rotationally driven either individually or jointly during the strap frame wrapping process. Head 23 having a face portion 27 with mandrel 25 projecting therefrom has a loading position, shown by the dotted lines, and an operating position, shown by the full lines and means (not shown) whereby movement of head 23 from the loading position to the operating position is accomplished. Mandrel 25 is machined to provide a tightly fitting support for the frame 5 when telescoped through the channel 10 shown in FIG. 1. A tapered end 26 of mandrel 25 facilitates the loading of strap frame 5 thereon. Head 21 has a recessed portion (not shown) wherein the tapered end 26 of mandrel 25 is adapted to fit when head 23 moves forward the operating position, shown in full lines. The engagement of tapered end 26 of head 23 with the recessed portion (not shown) of head 21 during rotation provides a firm support for mandrel 25 and strap frame 5 telescoped thereon. While in the operating position, wire 41 is attached to strap frame 5 and upon rotation of heads 21 and 23 wraps about frame 5.

The wire guide is provided with wire guide arm 37 which is driven by drive means 31 through a shaft 33, guide cam 29, and guide cam follower 35. Further, a wire slot 39 is provided at the end of wire guide arm 37 for correctly positioning the wire 41 on wire guide arm 37 during operation. Wire guide cam 29 is contoured to provide any desired rate or variation in helix turn spacing as it longitudinally drives wire guide arm 27 and wire slot 39 through which wire 41 is directed onto strap frame 5. Wire guide spring 43 connecting wire guide arm 37 and fixed wire guide spring support 44 assures positive contact of guide cam follower 35 on guide cam 29 thereby insuring correct longitudinal positioning of each helix turn on frame 5.

The programmed back tension means 17 has a 400- cycle back tension motor 55 driven from a conventional power source through an amplifier 57 having a voltage control 59. A variable center tap arm 61 on the voltage control 59 is activated through a sliding arm 47, programmed cam follower 49, a programmed cam 45, a shaft 33, and drive means 31. A tension spring 53 and a fixed tension spring support 54 provides positive action be tween the programmed cam follower 49 and the pro grammed cam 45. The shaft of the back tension motor 55 is inserted within and frictionally holds a wire supply spool 63 from which wire 41 is withdrawn by strap frame 5 as it is rotated by rotating heads portion 13 to form the frame grid electrode of FIG. 6.

When the voltage on the back tension motor 55 is varied, the force exerted on the wire 41 through the shaft 65 and supply spool 63 is also varied. As a result, the back tension force or force opposing the withdrawal of wire 41 from the supply spool 63 may be controlled.

Therefore, when the center tap arm 61 is varied through the slide 47, and programmed cam follower 49 by rotation of the programmed cam 45, the back tension on wire 41 is also varied. Thus, the programmed cam 45 may be formed to provide the desired variations of the center tap arm 61 which essentially controls the amount of back tension opposing the withdrawal of wire 41 from the supply spool 63 and in turn the tension on wire 41 as the turns are applied to the strap frame of FIG. 1.

The low inertia dampening means 19, has an exhaust vent 79 which is supplied with air from a variable air supply 75 through an interconnecting pipe 77. This exhaust vent 79 is positioned directly beneath the wire 41 intermediate the wire supply spool 63 and the wire guide slot 39. A fiat thin gage foil 67 is aflixedl to a fixed support at one end 69' immediately adjacent the exhaust vent '79. The opposite curved portion 71 of the flat foil 67 is provided with a wire guiding groove 73 and is disposed immediately above the exhaust vent 79 with the wire guiding groove 73 contiguous with the wire 41. Therefore, the wire 41 and the curved portion 71 of the flat foil 67 are supported by the force of air issued from the exhaust vent 79. As pressure is exerted by the wire 41, flat foil 67 which is supported by the air emitted from the exhaust vent 79, is deflected. Hence any change in wire demand by the rotating strap frame 5 is substantially immediately met by a deflection of the flat: foil 67. Accordingly, an increased wire demand provides an increased tensional pull on the wire and results in a decreased wire deflection resulting in an increased supply to meet the increased demand. Since this deflection change is substantially immediate, the tension on the wire throughout the length of each turn remains substantially constant.

Accordingly, the proper selection of a programmed back tension cam profile has permitted a reduction in the forces exerted upon the wire and the side members during the wraping process of approximately 40% while producing an improved product. Further, the variations in tensional force exterted between the side members and the wire of the resulting strap frame electrode have been reduced by approximately Therefore, a pair of spaced side members wrapped with a wire helix having a substantially uniform tensional force exerted throughout the longitudinal length of the helix provides an electrode of greatly improved reliability. Additionally, the reduced tensional forces substantially obsolete the former requirements of strong, expensive and hard-to-work materials for strap-frame electrode manufacture. Rather, less strong, readily available, inexpensive, and more workable materials may now be used to provide a product of vastly improved reliability at a tremendously reduced cost. Furthermore, the uniformity of tensional forces has greatly improved the microphonic and random noise characteristics by virtually eliminating loose and vibrating lateral turns whereby the operational reliability of the strap-frame is enhanced. Additionally, a resilient elastic low inertia dampening device provides a uniform tensional force throughout the entire length of each helix turn during the wrapping thereof.

Although the back tension and dampening techniques described herein have been specifically illustrated in conjunction with a strap-frame electrode, it is to be understood that the invention is not limited thereto and may be used on any type construction wherein a support and wire strands or wire windings have a tensional relationship.

While there have been shown and described what are at present considered to be the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. An apparatus for wrapping a frame electrode With a helix of wire having a longitudinal axis wherein each turn of said wire helix has a substantially uniform tensional force comprising a spool containing a supply of wire mounted to allow relatively free wire withdrawal at a substantially constant rate, means for supporting a pair of spaced side members, means for rotating said side members to withdraw the wire from said spool and wrap the wire about said side members, said rotating side members demanding wire from a transverse direction relative to said longitudinal axis at a varying cyclic rate, a wire guide mounted adjacent said rotating side members and intermediate said side members and said spool formed to guide the wire longitudinally along said side members during rotation thereof, and a low inertia device positioned intermediate said Wire guide and said spool having means for deflecting said Wire normal to said wire flow, said deflecting means comprising a support, a thin foil having one end atfixed to said support with the opposite end being freely movable, said free end being formed to provide a curved portion having a groove on the convex side thereof for contacting said wire, a substantially constant pressure air supply means directing a flow of air onto the concave side of said curved portion of said foil to provide floating suspension and deflection thereof substantially immediately responsive and inversely proportional to the varying cyclic demand for said wire by said rotating side members.

2. Apparatus for providing Wire at substantially constant tension to a constantly varying demand pulling wire from a wire supply at a substantialy constant rate comprising means for providing a resilient elastic force and a wire deflecting means having relatively little mass and low inertia and located intermediate the wire supply and the wire demand, said means for providing a force being in the form of a substantially constant and alterable fluid supply source and said deflecting means being a thin-gage foil fixedly attached at one end to a support and freely movable at the opposite end, said freely movable opposite end of said foil being located intermediate to and in contact with said wire and said force and transmitting said force to said wire in a direction substantially normal to the pull thereon by said demand, said force and said deflecting means combining to provide a substantially instantaneous and proportional change in force applied normal to said wire in response to a change in pull thereon whereby an increase in wire demand is accompanied by a substantially equal increase in Wire supplied at substantially constant tension.

3. Apparatus for providing wire at substantially constant tension to a constantly varying demand pulling Wire from a wire supply at a substantially constant rate comprising means for providing a resilient elastic force and a wire deflecting means having relatively little mass and low inertia and located intermediate the wire supply and the wire demand, said force being in the form of an air column provided by a substantially constant and alterable air supply and said deflecting means comprising a thin-gage foil fixedly attached at one end to a support and freely movable at the opposite end, said freely movable opposite end of said foil being located intermediate to and in contact with said wire and said force and transmitting said force to said wire in a direction substantially normal to the pull thereon by said demand, said force and said deflecting means combining to provide a substantially instantaneous and proportional change in force applied normal to said wire in response to a change in pull thereon whereby an increase in wire demand is accompanied by a substantially equal increase in wire supplied at substantially constant tension.

References Cited by the Examiner UNITED STATES PATENTS 3,081,800 3/1963 Crosby et al -715 FOREIGN PATENTS 963,260 5/ 1957 Germany. 810,959 3/ 1959 Great Britain. 569,233 10/1957 Italy.

OTHER REFERENCES Reuter, German printed application 1,019,011, Novembet 7, 1957.

STANLEY N. GILREATH, Primary Examiner. FRANK J. COHEN, MERVIN STEIN, Examiner.

B. S. TAYLOR, Assistant Examiner.

Claims (1)

1. AN APPARATUS FOR WRAPPING A FRAME ELECTRODE WITH A HELIX OF WIRE HAVING A LONGITUDINAL AXIS WHEREIN EACH TURN OF SAID WIRE HELIX HAS A SUBSTANTIALLY UNIFORM TENSIONAL FORCE COMPRISING A SPOOL CONTAINING A SUPPLY OF WIRE MOUNTED TO ALLOW RELATIVELY FREE WIRE WITHDRAWL AT A SUBSTANTIALLY CONSTANT RATE, MEANS FOR SUPPORTING A PAIR OF SPACED SIDE MEMBERS, MEANS FOR ROTATING SAID SIDE MEMBERS TO WITHDRAW THE WIRE FROM SAID SPOOL AND WRAP THE WIRE ABOUT SAID SIDE MEMBERS, SAID ROTATING SIDE MEMBERS DEMANDING WIRE FROM A TRANSVERSE DIRECTION RELATIVE TO SAID LONGITUDINAL AXIS AT A VARYING CYCLIC RATE, A WIRE GUIDE MOUNTED ADJACENT SAID ROTATING SIDE MEMBERS AND INTERMEDIATE SAID SIDE MEMBERS AND SAID SPOOL FORMED TO GUIDE THE WIRE LONGITUDINALLY ALONG SAID SIDE MEMBERS DURING ROTATION THEREOF, AND A LOW INERTIA DEVICE POSITIONED INTERMEDIATE SAID WIRE GUIDE AND SAID SPOOL HAVING MEANS FOR DEFLECTING SAID WIRE NORMAL TO SAID WIRE FLOW, SAID DEFLECTING MEANS COMPRISING A SUPPORT, A THIN FOIL HAVING ONE END AFFIXED TO SAID SUPPORT WITH THE OPPOSITE END BEING FREELY MOVABLE, SAID FREE END BEING FORMED TO PROVIDE A CURVED PORTION HAVING A GROOVE ON THE CONVEX SIDE THEREOF FOR CONTACTING SAID WIRE, A SUBSTANTIALLY CONSTANT PRESSURE AIR SUPPLY MEANS DIRECTING A FLOW OF AIR ONTO THE CONCAVE SIDE OF SAID CURVED PORTION OF SAID FOIL TO PROVIDE FLOATING SUSPENSION AND DEFLECTION THEREOF SUBSTANTIALLY IMMEDIATELY RESPONSIVE AND INVERSELY PROPORTIONAL TO THE VARYING CYCLIC DEMAND FOR SAID WIRE BY SAID ROTATING SIDE MEMBERS.

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