US1970599A

US1970599A - Grid making machine

Info

Publication number: US1970599A
Application number: US676077A
Authority: US
Inventors: August J Franke
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1933-06-16
Filing date: 1933-06-16
Publication date: 1934-08-21
Anticipated expiration: 1951-08-21

Description

Aug. 2l, 1934. A J. FRANKE 1,970,599

GRID MAKING MACHINE Filed June 16, 1933 2 Sheets-Sheet 1 'IH HII:

' vINVENTOR y ,Mawr .7. FM4/KE BYy HHHII ATTORNEY Aug. 21, 1934- A. ,i FRANKE l 1,970,599

4GRID MAKING MACHINE Filedl June, 16,. 1955 2 shets-sneet 2 -36 n '9592 .for

g fd 27 INVENTOR 1406057' Z FA//ff ATTORNEY lill JPatented Aug. 2l, 1,934

' UNITED STATESl 1,970,599 GRID MAKING MACHINE August J. Franke, Harrison, N. J.,I assigner Radio Corporation of America,` a corporation of Delaware v Application June 16, 1933, Serial No. 676,077

My invention relates to4 windingI apparatus, more particularly to improvements in winding machines for winding 'grid electrodes such, for example, as are used in the construction oi eleotron discharge tubes K,and the like.

In the usual grid winding machine a supporting wire or wires have wound thereon and attached thereto a helical grid wire. This grid wire is usually fastened to the supporting wires of rods either by welding or by forming notches orslots in the supporting wires and laying the convolutions of the grid coil within these slots which are afterwards peened over to hold the grid Wire rmly to the supporting wire.

In certain types of tubes recently developed it is necessary to vary the pitch or spacing between the turns along the length of the grid. Heretofore, it has been impossible to make such a grid with vthe usual winding apparatus available. The method usually employed was to wind the grid with a constant pitch along the length of the supporting wire and remove by hand such turns as desired from the grid. This operation, of course, diminished 'production and increased the expense of making the grids. Besides grids a produced in this manner were not uniform.

fill

Furthermore, in the usual machine a plurality of grids are successively and continuously Wound on supporting wires duringa single winding operation, the turns being spaced uniformly along the 'entirelength of the supporting wire. These supporting wires are then cut to separate the individual grids. In forming the grids, turns between adjacent grids are notfastened to the supporting rods.` When the individual grids have been cut this loose wire is removed by hand. This loose wire is not only entirely wasted but production is diminished due to the necessity for removing these extra turns manually.A

Hence it is an object of my invention to produce an apparatus or machine for making variable pitch grid electrodes, by automaticallyvarying the pitch o! the grid wire in any desired degree as the grid is being wound. v

.Another object of my invention is to produce an apparatus or machine for making a gridelectrodes efliciently by reducing the waste to a minimum and by diminishing the time necessary tor making such grid electrodes.

Still another object of my invention is to provide an apparatus or machine of the type dev scribed without requiring radical changes in the construction thereof.-

These and other objects will appear hereinafter.

13 Claims. (Cl. 14o-71) Briefly, ina preferred embodiment of my invention supporting wires are fed longitudinally from a rotatable mandrel or arbor and the grid wire so guided that each turn of the helically wound grid wire crosses the supporting wires and is attached thereto. I'he supporting wires are moved continuously along the mandrel and are notched at each revolution thereof as theyare carried under a notching roller or similar device to engage the supporting wires at one point in the rotation of the mandrel. By the time the mandrel has completed another revolution, the supporting wires have moved a distance equal to the spacing between the notches. After a. notch is formed it is carried by the movement of the supporting wire and the rotation of the mandrel into such a position that the grid wire which is being bent around,the mandrel to make a. turn of grid coil falls into the notch. Afterwards the notch is closed by means of a peening roller to clamp the turn of the grid to the supporting wire.

A clamp connected to the supporting wires pulls the supporting wires through the mandrel to feed the same. This clamp rotates on a lead screw and advances on the lead screw the distance of the pitch between two adjacent threads on the lead screw in one revolution of the clamp. The grid wire would therefore normally be spaced -in accordance with the pitch on the lead screw but the lead screw is supported on a slide. This slide is connected to a lever which in turn cooperates witha cam whereby the lead screw may be shifted in accordance with the shape of the cam while the clamp is being rotated. By properly designing the cam it is possible to obtain a variable pitch grid and skip distance between individual grids, that is, a very wide pitch for one or two turns of the supporting wires can be y obtained thereby reducing the wire necessary to wind each set of grids. This, of course, reduces the waste of the grid wire and increases production. This is the result of moving the lead screw longitudinally toward and from the mandrel as the clamp rotates on the lead screw. In order to insure proper peening of the supporting wires to secure the grid wire to the supporting wires it is necessary to shift the peening roller in synchronism with the lead screw. is accomplished by means of a second cam mounted on the same shaft as the iirst cam and operating to shift the peening roller.

A better understanding of my invention will be obtained by referring to the accompanying drawings in whichFigure 1 is a side elevation partly in section of a grid winding machine em- Il. I

bodying my invention. Figure 2 is a plan viewv taken along the line 2-2 of Figure 1 and show-` ing that part of my invention for shifting the representation of a variable wound grid madeby means of my invention. Figure 6 is a detailed showing of the cam for shifting the lead screw slide.

` The particular form of grid making machine embodying my invention and disclosed in the drawings is constructed similar lto a lathe and comprises a bed p1ate'10 having at one end an.

end support 11 and being also provided with a. tail stock 12 and a head stock 13 at the right hand end thereof. A rotary head comprising a head spindle 14 is driven from a sprocket wheel 15 through a friction clutch 16 controlled by a clutch lever 17 actuated by a

link rod

26, 26" and 26. This rod is actuated in a manner to be described below by means of a stop lever A18 pivoted at 19 on the support 11. A tubular tail spindle 20 providedl at its inner end with a clamp 21 and on its outer end with a split nut 21 opened and closed by means of a handle 22 rotates in the tail stock 12 and also retreats from the head spindle 14 as it rotates. The spindle retreats because the split nut 21 is closed upon the feed screw 23 fixed to the arm 70. At the end of its travel along the feed screw the nut 21 encounters a stop 25 which abuts against the lever 18 and rotates the same about its pivot 19 in a counter clockwise direction to actuate the

link rod

26, 26" and 26 and lever 17 to open the friction clutch 16 which stops rotation of the head spindle 14.

The head spindle 14 and the tail spindle 20 rotate at the same speed as they are geared together through a gear 28 on the tail spindle and a gear 27 on the head spindle which are meshed with gears on the counter shaft 29. The gear 28 in the tail stock 12 is splined on the tail spindle to drive itand to permit it to move longitudinally through vthe gear.

The particular grid which the present machine is adapted to make has two supports and comprises a helix or coil of grid wire 30 with each turn in the grid firmly embedded in the two parallelsupporting wires 31 by notching or slotting each supporting wire at intervals corresponding to the spacing of the turns of the grid, placing.

each turn of the grid in the corresponding notch or slot, and then closing the notches or slots or so reducing their dimensions or displacing their edges as to clamp the grid wire in place.

Each supporting wire or side rod 31 is automatically fed in a continuous length from a spool 32 carried in a yoke 33 on the outer end of the head spindle 14. The two supporting wires or rods pass along two parallel channels 35 extending longitudinally through the head spindle 14 to a support for holding them properly positioned and spaced. The supporting wires preferably lie in grooves in the opposite edges of a fiat arbor or mandrel 40 which supports and holds them and which is mounted onthe inner end of the head spindle 14.. This arbor or mandrel is preferably held in place by a sleeve or cap 41` secured to the end of the spindle 14, for example, by being threaded thereon.

The means for -feeding the supporting wires along the mandrel is so constructed that the supporting wires are fed by being drawn along the mandrel. A suitable feed mechanism for doing this is one in which the projecting ends of the supporting wires are gripped by a member which moves away from the arbor such as the clamp 21 on the inner end of the tail spindle 20 so that as the tail spindle retreats the two supporting wires are drawn through the channels 35 and along the oppositeedges of the mandrel 40.

In order to form notches or slots in spaced re- 'lation along the supporting wires at the proper intervals some means for forming slots or notches is associated with the head spindle 14 such means being `a notching device such as the notching Wheel 42 which is mounted in such a position that its edge cuts a notch in the supporting wire as the supporting wire is carried bodily under the notching wheel by the rotation of the arbor 40.

The notching wheel or slot forming memberas best shown in Figure 4, has an edge which is rounded preferably on the same radius. as the radius of the grid wire and has a flat side perpendicular to`l its axis of rotation, the other side being at .an angle with the flat side. The notch produced in the supporting wire is rounded at the bottom to the curvature of the grid wire with one side perpendicular to the supporting wire and the other side inclined away at an angle so that the grid wire enters it freely and sets flrmly in the bottom of the notch.

The notch or slot forming vwheel is preferably carried in. a yoke 43 with a cylindrical shank which fits into a boss 44 on a standard 45 secured to the bed plate 10. The yoke held in vthe boss by a wing nut 46 can be rotated in the boss to set the notching wheel with its plane at an angle to the axis of the spindle. The notching wheel is set 'at such an angle that the notches are approximately parallel to the screw threads and can be locked in that position by a set screw 47. The edge of the notching wheel is set close to the edge of the mandrel so that as the supporting wire 31 passes under the notching wheel the edge of the wheel makes a notch of a depth somewhat greater than the diameter of the grid wire. The spacing of the notches in the supporting wire determines the pitch of the grid Wire helix and depends, in

the apparatus disclosed, both upon the pitch of the feed screw 23 and the distance the lead screw is shifted by a mechanism to be described, since the space between the notches depends upon the distance which the supporting wire moves along the mandrel during one revolution ofthe mandrel.

The wire grid is wound on the mandrel in a helix or coil with its convolutions or turns disposed in spaced relation the same as the notches in the supporting wire or side rods by feeding or guiding the grid wire to the mandrel substantially parallel to the plane of the notching kwheel so that the grid wire will lie straight in the notch of the supporting wire.

As shown in Figure 3 the grid wire is carried on a wire carrier such as the spool 50 and is drawn off the spool and wound over the two supby the rotation of f Aover the supporting As shown in Figure 4 1n one position of the mandrel a notch is made in one of the supporting wires by means of the notching roller 42. By the sult the notch is in such position that as the mandrel turns the grid wire which is being wound around the two supporting wires by the rotation of the mandrel enters'the notch and is rmly seated in it. The next half revolution brings this notch and thelgrid Wire in it under the notch or slot closing whee148, commonly termed a peening roller, which presses in or deforms the edge of the notch and closes the notch so that the grid wire is firmly secured to and embedded in the supporting wire. The peening roller is shifted simultaneously with the lead screw slide as will be more fully explained below so that the peening roller and the slot will register regardless of the movement of the supporting wires through the mandrel.

The notch closing Wheel 48 is mounted on the end of an arm 51 pivoted on a shaft 52 rotatably and slidably supported in

bearings

53 and 54 as most clearly shown in Figures 2 and 3. The .armv 51 carries at its other end a cam follower or roller 57 which engages a cam 58 mounted on a shaft 59 supported in bearings 81' and 82' on the bed plate 10. A spring 60 biases the lever 51 in a counter .clock-wise direction `so that the cam follower is pressed into. engagement with the cam 58. The cam normally permits this spring to hold the notch closing wheel against the supporting wires with sufficient force to close the notches. The cam 58 rotates the lever 51 in a clock-wise direction about theshaft 52 away from thesupportixngmwires at the predetermined intervals to provide" loose turns on the grid wire. The clearance betweenthe edge of the wheel 48 and the edge of thel mandrel is less than the distance the supporting wire projects from the mandrel so thatf'the edges of the notch are deformed and the grid wire is pressed home into the notch as the supporting wire passes under the closing Wheel. This clearance may be varied, for example, by providing a different diameter cam follower 57.

, Myiinvention especially provides an apparatus for making variable pitch grids. In order to do so it must be possible 'to vary the rate of the feeding of the supportingl Wires. If the nut 21 is only rotated on the lead screw the pitch betweensuccessive turns of the grid wire will be that of the lead screw 23. I, therefore, propose to shift the lead screw during the winding operation whereby the rate of movement of the supporting wires lmay be varied to provide a pitch in the grid winding either greater than or less than the pitch of the lead screw. The mechanism for accomplishing this result is most clearly shown in Figures 2 and 3.`

The lead screw 23 as pointed out above is securely fastened to an arm 70. This arm 701s in turn fastened to a slide 71 which slides back and forth in a bearing 72. Attached to the slide 71 is a lever 73 pivotally supported at 74 to the support 11. The lever 73 has pivotally cgnnected thereto a link or rod 75, the right hand end of which is pivotally connected to a bell crank 76 pivotally supported at 77. This bell `crank is provided with a cam follower 80 which engages the cam 80 xedly attached to shaft 59. The compression spring 79 supported on the stationary rod 79' abuts against the slide 71 to urge the lever 73 in a counter clock-wise direction. This acts through the link and bell crank 76 to resiliently force the cam follower 80 into engagement with the cam 80. It is obvious that as the cam rotates the cam follower moves in accordance with its surface and permits the slide 71 to move back and forth and thus shift the lead screw during the rotation of the spindle 20v to thereby varythe pitch. If the lever 73 is rotated .in a counter clock-wise direction the slide 71 and lead screw 23 will be shifted to the right, thereby decreasing the pitch of the grid since the travel of the clamp 21 and

spindle

20 and 85 thus the rate of feeding of the supporting rods will be reduced during a single revolution of the spindle. On the other hand, if the crank 73 is rotated in a clock-Wise direction the slide 71 and lead screw 23 will be shifted to the left, thereby increasing the travel of the clamp 21 and increasing the rate of feeding of the supporting wires thus increasing the pitch between successive turns of the grid wire. This operation will be discussed below inlconnection with the description of cam 80.

It is essential that the peeningv roller and notch to be engaged thereby should register during the peening operation. It is, therefore, necessary to shift the .peening roller in accordance with the shifting of the slide carrying the lead screw. This is accomplished by means of a second cam arrangement. Referring to Figure 2, it will be seen that the lever 51 carrying the peening roller 48 is rotatably mounted on the shaft 52 which 105 can slide longitudinally in the

bearings

53 and 54 as well as'rotate therein. The lever is fastened to the shaft 52 to prevent relative longitudinal movement therebetween by means of collars 55 and 55 secured to the shaft 52. The left hand end of shaft 52 carries the lever 83 non-rotatably secured thereto. This lever carries a cam follower or roller 82 whch engages the cam 81. A spring 56 biases the follower 82 against the cam 81. cam 81 is formed onone edge thereof instead of on its outer circumference as in cam 80 the contours on both cams are so shaped that the shaft 52 carrying the peening roller 48 and slide ,7.1. are shifted simultaneously and 'by equal 120 amounts during the grid winding operation.

Y 'I'he cam shaft driving mechanism is next described. The shaft 59 inadditicn to carrying thecams 80, 81 and 58 thereon also carries a ratchet 85 which is driven by means of pawls 125 86 and 87 held resiliently in contact therewith by means 'of

springs

89 and 90 as shown in Figures 2 and 3. The ends of these pawls are mounted on an eccentricmechanism 88 driven from countershaft 29, for causing .these pawls to drive the shaft 59 in a counter clock-wise direction as viewed in Figure 3. It will thus be apparent that the shaft 59 is driven in a series of small steps. A definite number of revolutions of the countershaft causes the cam shaft to move through a certain number of degrees for performing the shifting operation in a predetermined sequence as the grid supporting wires are fed from the mandrel.` f

In the usual grid Awinding machine 'a long grid 140 While the cam surface of 115` closing mechanism is so controlled by the cam 58 that it is temporarily inoperative at pre-determined intervals during the winding of the grid lWire. A definite number of revolutions of the on the bed plate 10 in front of the mandrel. This shear mechanism is normally biased open by spring 98. When the tail spindle reaches the limit of its travel and stops the machine, the motor (not shown) for driving .the socket 15 is stopped. The two supporting wires are cut by the shear jaws 95', the grid structure removed,

the split nut 21' opened, the tail spindle slid toward the head spindle and the-clamp 21 closed upon the end of the supporting wires, still on the mandrel. The split nut is tightened on the feed screw and the machine started again. While the means closing the notches is a preferred embodiment I may use other means such for example as a chisel or hammer in place of the closing grid.

The operation of the grid winding machine will be discussed in connection with the Figures 5 and 6. Assuming that the clutch 16 is engaged and that the tail and head spindles are rotating the tsplit nut will move along the lead screw 23 to the left, feeding the supporting wires 3l through the mandrel. Asthese spindles rotate the supporting wires are carried beneath the notching roller 42 and notches made therein. The grid wire is wound thereon, and as the wires are rotated the notch is brought under the peening roller and closed down as has been described.

As the countershaft 29 rotates the

pawls

86, 87 will rotate the shaft 59 through the ratchet 85. This, of course, varies the position of the cams 80, 81 and 58 to cause a shifting of the slide 'Il and of the peening roller 48, and movement of peening roller 48 all in proper sequence. It is, of course, obvious that the cams should not shift the slide and peening roller while thel supporting wire passes under the notching roller 42. Otherwise a clean cut notch would not result. It is also obvious that the peening roller 42 must be made inoperative at such a time as it is desired that the turns between grids will not be secured to the supporting rods 31.

In Figure 6 is shown the cam 80, looking at the same from the right hand side thereof, the cam rotating in a clockwise direction. Assume the cam to be'in such a position that the roller or cam follower and the point S on the cam are on the same line passing through the center of the shaft 59. This represents the point S' in the making of the grid as shown in Figure 5. As the supporting wires 31-31 are fed from the arbor to the left as shown by the arrow the cam moves through a certain number of degrees represented by the distance C during which time the portion of the grid' as shown by C in Figure 5 is wound. At this point the contour of-the cam changes and causes a different variation f the shifting of the slide 'I1 and results in that portion of the grid designated D. Similarly different ratios of movement of the slide are caused by slot to be peened. The length A in Figure 5 repdifferent portions ofthe cam surface, the portion of the grid represented by the various letters being made during the rotation of the cam through arcs designated by like letters on the Figure 6. It will be readily seen that between grids the slide is shifted rapidly dueto the cam contour as shown at H to provide the wide pitch as shown at H on the grid. It is during this portion of the rotation of the cams that the cam 58 moves the peening roller out of engagement with the supporting wires. Cam 81 for shifting ,the peening roller has a contour similar to the contour of the cam 8 0 so that the peening roller will be shifted to properly align the roller with the resents the length to which the grids are cut from the rods supporting a plurality of such grids. The length B represents the portion of grid wire securely fastened to the supporting rods.

'It is obvious that by changing the contour oi' cams 80 and 81 any desirable variation in the grid pitch can be obtained. It is also apparent that very little wire is wasted between grids on the supporting wire with the result that not only is waste reduced but production increased.

After a" set of grids is wound the supporting wires are cut as described aboveand the operation repeated.

The embodiment of the invention illustrated and described herein has been selected for the purpose of clearly setting forth the principles in` volved. It will be apparent, however, that the invention is susceptible of being modified to meet the different conditions encountered in its use and I, therefore, aim to cover by the appended claims all modifications within the true spirit and scope of my invention.

What is claimed is,

l. An apparatus for making grid electrodes including, feeding means for longitudinally feeding a supporting wire, means for helically winding a grid wire about said supporting wire, means for fastening the wound wire to said supporting wire, a driving mechanism for said feeding means including a lead screw connected to move said 120 feeding means uniformly and mounted for longitudinal movement, and means for moving said lead screw longitudinally to vary the rate of feeding of said supporting wire whereby the pitch of the turns of said wound wire is varied.

2. In a machine for making grid electrodes, means for feeding a supporting wire, means for helically winding a grid wire about the supporting wire, means for securing the turns of said grid wire to said supporting wire, and cam operated mechanism for moving said grid wire securing means and varying the speed of said supporting wire feeding means in proper time rela-4 tion thereto' to yvary thepitch of the turns of the grid Wire.

3. An apparatus for making grid electrodes including, means for holding a supporting wire,` means for forming slots on said supporting wire, means for helically winding a wire about said suppoitilig wire with the convolutions of the wound wire in said slots, means cooperating with said slot forming means for 'varying the spacings between the slots, means for closing said slots to secure said helically wound wire to said supporting wire, and other means for causing said closing means and'said slots to register when said closing means acts to secure said helically wound wire to said supporting wire.

4. An apparatus for securing a helically wound 150 wire to a supporting wire including, feeding means for uniformly feeding a supporting wire, means for fastening the helically wound wire to said supporting wire as said supporting wire is being fed, a driving mechanism for said feeding means, including a lead screw connected to move said feeding means uniformly, said lead screw being mounted for longitudinal movement and means for moving said lead screw longitudinally to vary the rate of feeding of said supporting wire to vary thev pitch between the convolutions of said helically wound wire.

5. An apparatus for making'grid electrodes including, means for holding a supporting wire,.

means for winding a grid wire helically about said supporting wire, means for fastening the helically wound Wire to said supporting wire, means cooperating with said winding means for varying the pitch between the turns of said helically wound wire, and other-means for causing said fastening means and said wound wire to register when said fastening means acts to fasten said wound wire to said supporting wire.

6. An apparatus for making grid electrodes including, means for feeding a supporting wire, means for winding a wire helically about said supporting wire, means for fastening the wound wire to said supportingvwire, means associated with said feeding means for varying the rate of feeding of said supporting wire whereby the pitch between the turns of the helically wound wire is varied, and means cooperating with said fastening means for causing said fastening means andvsaid wound wire to register when said fastening means operates to fasten said wound wire to said supporting wire.

'1. An apparatus for winding a plurality of grids successively in a single operation including, feeding means for feeding a supporting wire, means for winding a grid wire upon said supporting wire to form a helical coil thereon, means for fastening said helically wound wire to said supporting wire, a driving mechanism for said feeding means, including a lead screw connected to move said feeding means uniformly, said lead screw being mounted for longitudinal movement and means for moving said lead screw longitudinally while said grid wire is being wound on said supporting wire to provide a relatively large spacing between each grid.

8. An apparatus for winding grid electrodes including, means for supplying supporting wires,

means for engaging said supporting wires, means for supplying grid wire, moving means for simultaneously rotating and longitudinally moving said engaging means to wind said grid wire helically about said supporting wires, means for fastening said grid wire to said supporting wires, a lever operatively associated with said moving means, a cam for actuating said lever during the winding operation to vary the spacing between the turns of said helically wound wire, and a cam for actuating said fastening means to cause said fastening means to register with said wound wire during the fastening operation.

9. An apparatus for winding grids including,

means for supplying a supporting wire, a clamp for engaging said supporting wire, a lead screw, said clamp being mounted upon said lead screw, means for rotating said clamp upon said lead screw for longitudinally feeding said supporting wire for winding agrid Wire helically on said supporting wire, a movable support for said lead screw, a lever connected to said movable support and a cam for actuating said lever during tno Winding operation to vary the pitch of the turns of said helically wound Wire along the supporting wire.

10. An apparatus for making grids including a. clamp for engaging supporting wires, a lead screw for rotatably supporting said clamp, means for rotating said clamp on said lead screw for longitudinally feeding :the supporting wires to helically wind a grid Wire on said supporting wires, means for notching said supporting wires, means for laying the grid wire' in said notches as the supporting wires are fed longitudinally, means for peening oversaid notches to secure the grid wire to said supporting wires, a movable support for said lead screw, a movable support for said peening means, and cam operated means for simultaneously moving said movable supports for providing a variable pitch between vthe turns in the said grid winding. I

11. An apparatus for making grid electrodes including mechanism for winding a grid wire around a support wire into a helix and fastening the turns of the grid Wire to the support wire, and a support wire feeding means for feeding a. supsupport wire thru said mechanism including a support wire clamp movable relative to said mechanism, a lead screw movable longitudinally and operatively connected to said clamp for moving said clamp to pass a support wire thru said mechanismwith a movement dependent on the pitch of said lead screw and means for moving said lead screw longitudinally.

12. An apparatus-for winding grids including a clamp for feeding a supporting wire, means for helically winding and fastening a grid wire to the supporting wire, driving mechanism lfor said clamp including a lead screw connected' to uniformly move said clamp longitudinally with reference to said winding and fastening means, said lead screw being mounted to be movable longitudinally and means for moving said lead screw longitudinally during the winding operation to vary the pitch of the helically wound grid wire.

13. An apparatus for winding grids including means for supplying a supporting wire, a clamp for engaging said supporting wire, a driving mechanism for said clamp including a lead screw operatively associated with said clamp and having relativevrotation therewith for longitudinally feeding said supporting wire for winding grids helically on said supporting Wire, a movable supportassociated with said lead screw and said clamp and means for moving said movable support longitudinally during the winding operation to vary the pitch of the turns of said helically wound wire along the supporting wire.

AUGUST J. FRANKE.