US2834132A - Electrostatic applying and holding device - Google Patents

Description

May 13, 1958 J. o. TAYLOR ET AL 2,834,132

ELECTROSTATIC APPLYING AND HOLDING DEVICE Filed Dec. 14. 1954 Sheets-Sheet 1 04K j/mu/m flit. 0014/4.

INVENTORS May 13, 1958 J. o. TAYLOR ET AL ELECTROSTATIC APPLYING AND HOLDING DEVICE 2 Sheets-Sheet 2 Filed Dec. 14.

ATTORNEYZ United States Patent ELECTROSTATIC APPLYING AND HOLDING DEVICE John 0. Taylor, Pleasantville, and Ralph R. Bergman, New York, N. Y., assignors, by mesne assignments, to American Type Founders Co., Inc., Elizabeth, N. 1., a corporation of Delaware Application December 14, 1954, Serial No. 475,195

Claims. (CI. 40-125) This invention relates to new and improved apparatus for holding sheet material upon a supporting surface.

A principal object of this invention is to improve the smoothness of display of sheet materials.

Another object is to minimize the manual effort usually required in providing for a smooth display of sheet materials having a relatively large area.

Another object is to eliminate the mechanical and physical disfigurement of sheet material incurred during holding.

Another object is to provide a versatile sheeet applying and holding device capable of holding a sheet in any desired position with respect to a backing surface.

Heretofore most structures designed for holding sheet material in a desired fixed position with respect to a supporting surface have featured mechanical or adhesive arrangements. Many structures operative in accordance with these techniques have been unsatisfactory for the reason that it has been impossible to display or hold sheets having a relatively large area in a manner free from wrinkles and creases.

Electrostatic principles have also been applied in certain industrial applications for the purpose of holding sheet material in a desired position upon conveyor belts and other movable structure. In these applications, the necessary potentials are usually generated by the friction of moving components with a resulting attraction between a charged sheet and a conveyor belt or the like. Notwithstanding the fact that the application of electrostatic principles to sheet holders results in an advantageous mode of operation wherein large sheets may be displayed in a desired position completely free from creases and wrinkles, no one has heretofore suggested that these principles may be advantageously applied to a display board type sheet holder, and without a movement of components to generate a holding potential by friction.

In a preferred embodiment of this invention, a relatively fiat display board is utilized to support sheet material on one surface thereof. From a generic aspect, however, the supporting surface of the board may be formed so as to have a surface of considerable contour. With either construction, the sheet will be held with a minimum of unwanted wrinkles and creases. The purpose for which the sheet is to be supported is not material to this invention, and it may well be that the sheet is to be held for exposure such as may be required in photography, or for visual display, or so that information may be sketched or written thereon. In any event, with the application of the structure of this invention to a display board, it is possible to hold the sheet in any desired position relative to the surface of the board without the use of mechanical holding means such as clamps, thumb tacks, etc., and without the use of adhesives such as glue or paste.

This mode of operation is obtained herein by enclosing within the display board a relatively flat, sheet-like electrode generally parallel to the supporting surface of the board. Inasmuch as a relatively high voltage is to be connected to this electrode sheet during the holding op- ,7 2,834,132 Patented May 13, 1958 eration, the sheet supporting surface of the display board is formed of an insulating sheet of plastic or the like. The sheet which is to be held is manually placed upon the supporting surface of the board and is subjected to an electrostatic field of exceedingly high intensity by applying a potential to the exposed surface thereof by means of an electroconducting roller or the like. By continually rolling the energized roller over the surface of the sheet so that all areas thereof have been subjected to a relatively high electrostatic intensity, electrostatic attraction causes the sheet to adhere to the display board in a manner free from all wrinkles and creases and without necessity of mechanical or adhesive holding means.

In order that the structural features for attaining the objects of this invention may be readily understood, reference is herein made to the accompanying drawings wherein:

Figure l is a simplified diagrammatic representation of the basic structure employed in the electrostatic sheet applying and holding device of this invention;

Figure 2 is a schematic diagram of the electrical circuitry employed in a preferred commercial embodiment of this invention;

Figure 3 is a partially broken-away view of a highvoltage, roller-type applicator for applying an electrostatic charge to a sheet which is to be held;

Figure 4 is an end view of the applicator shown in Figure 3 with the roller guard cover in the safety position;

Figure 5 is a sectional view taken along line 5-5 of Figure 3 and showing the application of the roller type applicator to a sheet mounted on a display board shown in section;

Figure 6 is a sectional view taken along line 6-6 of Figure 3 and showing the roller guard cover in both the safety and operate positions; and

Figure 7 is a sectional view taken along line 7-7 of Figure 3 and showing the roller guard cover in the safety position.

Referring now to Figure 1, the basic elements of the electrostatic sheet applying and holding device of this invention comprise a high voltage energizing source 10, a display board 11, and an applicator 12. The input terminals of source 10 will in most installations be energized from a commercial volt alternating-current distribution line. The high-voltage output of source 10 is a direct-current potential of the order of several thousands of volts. The potential of one of the high-voltage output terminals is applied by conductor 14 to a sheet-like metallic electrode 46 (shown in Figure 5) positioned within or on the backside of display board 11 so as to be in a parallel plane with respect to sheet 13 which is to be held in a fixed position with respect to display board 11. The other high-voltage output terminal of source 10 is connected to a roller type applicator 12 by means of conductor 15. A high-voltage circuit path is provided within roller type applicator 12 as will be hereinafter explained in detail so that the surface of the roller assumes the high-voltage potential of conductor 15. If sheet 13 is manually held in the desired position upon display board 11 and applicator 12 is manually moved over the surface of sheet 13, the intense electrostatic field generated between applicator 12 and the electrode connected to conductor 14 will cause sheet 13 to adhere to the display surface of board 12 by electrostatic attraction in a manner free from all wrinkles and creases.

The amplitude of the direct-current output potential of source 10 necessary to effectuate optimum holding will vary in different situations. In the main, the magnitude of this potential is dependent upon the thickness and dielectric constant of sheet 13 and the thickness and 3 dielectric nstan f h ula in surf ce f, splay board 11 upon which sheet 13 is held. In any event, the optimum minimum potential for high voltage source may be readily determined by attempting to hold a sheet in place while working through a range of output potentials. In view of the high voltage employed it may be readily appreciated that the lowest voltage satisfactory for proper holding is desirable from a safety aspect.

In Figure 2, push-button type switch 16 and a solenoid 18 have been added to the circuitry to provide a commercial embodiment of the basic structure shown in Figure 1. Push-button switch 16 is advantageously located on the handle of roller type applicator 12 and is electrically connected in the input circuitry of high volt; age source 10 so that manual depression of the switch is required to close the energization circuit from the 110 volt A. C. line terminals through conductor 21, closed push-button switch 16, conductor 24, input of high voltage source 10, conductor 20 and conductor 19 to the line source. In the event high voltage source It) incorporates a filament type rectifier tube and a filter circuit having a relatively long time constant, some delay will be introduced in the time interval within which output will appear from high voltage source 10 after the depression of push-button switch 16. Should this delay be objectionable, a high voltage relay may be incorporated in the output circuitry of high voltage source It), and pushbutton switch 16 may be connected to a low voltage energizing coil for this relay. With this arrangement, filament heating and capacitor charging delays will be eliminated. However, the high voltage supply will be energized at all times and an additional switch will be required to deenergize sourcelt).

In a preferred construction for roller type applicator 12, roller 34 is enclosed within a metallic safety housing. This housing comprises a movable cover portion which is withdrawn by energizing toroidal solenoid 17 by'current flow in a circuit which includes conductor 21 closed switch 16, conductor 22, the winding of solenoid 17, con? ductor 23.and conductor 19. Armature 18 is rotatably moved in response to the energization of solenoidgl7, and as will be hereinafter described in detail this armature movement is translated into a corresponding movement of the safety cover for applicator 12. Accordingly, the depression of switch 16 energizes high voltage source 10 and thereby applies high voltage to applicator 12 and the electrode of display board 11, and also eflectuates the withdrawal of the safety cover for applicator 12.

Referring now to Figures 3 through '7, high voltage applicator 12 comprises a cylindrical roller 34 supported at the terminal ends thereof by trunnions 36m and 361') which matewith bearings 38a and 38b, respectively. The bearings are fabricated of any conventional insulating material suitable for withstanding relatively igh Voltages. -Roller 34 is housed within protective metallic covering structure comprisingroller guard 32' and roller guard extension 33. Each bearing 38a and 38b includes a flatbase portion which is screwed to the associated end wall portion of roller guard 32 and theprojectingfiange portionsof bracket 31 by means of screws 43.

The cylindrical surface 35 of roller 34 is processed with an .electroconducting film which may be, aquadag or silver paint, and the right-hand portion of roller. 34 is also processed with a corresponding conducting film whereby trunnion 36b is, electrically connected to the cylindrical surface 35 of roller 34. 7 Metallic slip ring 37 'is formed within bearing 38b and establishes a friction electrical contact with trunnion 36b. High voltage conductor 15'is soldered or otherwise connected to'the projecting lug of slip ring 37 and is clamped to the bottommost portion of roller guard 32 by means of clamps 44. Grommet 40 insulates high-voltage conductor 15 from roller guard 32, and the cable is fed through an axial hole located within handle 30. Grommet 39 insulates conductor 15 from metallic support bracket 31.

The terminal ends of roller guard extension 33 are formed with flanges 41a and 41b which bear against the base portion of bearings 38a and 38b, respectively. This coupling arrangement enables roller guard extension 33 to be relatively movable with respect to roller guard 32 whereby roller 34 may be partially exposed or fully enclosedby the protective metallic housing as desired. An exposed view of the roller is shown in Figure 5.

Toroidal solenoid 17 is fixedly positioned upon the projecting portion of roller support bearing 38;: and the motion of the movable armature 18 is transmitted to roller guard extension 33 by means of connector 42. With such an arrangement, the energization of solenoid 17 causes, the withdrawal of roller guard extension 33 at the desired times inresponse to the manual depression of push-button switch 16. Biasing springs (not shown) force armature 18 in a position which will cause roller guard extension 33 to envelop roller 34 whenever pushbutton switch 16 is in the open position. Figures 4, 6 and 7show the roller applicator 12 in the safety position in which guard extension 33 and guard 32 fully enclose roller 34. Figure 5 and the broken line positioning of components in Figure 6 show guard extension 33 in the withdrawn position.

The detailed construction of a preferred embodin en of a display board 11 is shown in Figure 5. The display board comprises a front cover 45 constructed of insulating material and a back cover 47 also constructed of insulating material. Metallic sheet 46 is fixedly positioned within thebox-like display board structure and conductor 14 provides an electrical path to electrode 46 from the high voltage source. As is shown in Figure 5, with roller guard extension 33 withdrawn in response to the energization of solenoid 17, the electroconducting Coating 35 of roller 34 creates a relatively intense electrostatic field in the shortest straight line distance between film 35 and electrode 46 whereby electrostatic attraction causes sheet 13 to adhere to the front section 45'of display-board 11. By manually moving applicator 12 over all surface portions of sheet 13 electrostatic attraction causes sheet 13 to adhere smoothly and firmly upon the front section of display board 11 without wrinkles and creases.

It is to be understood that the above-describedarrangements are illustrative of theapplications of the principles of this invention. Numerous other arrangements may be devised by those skilled in the art without departing from the scope of the invention Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. An electrostatic sheet applying and holding device comprising sheet holding means including a relatively smooth sheet supporting surface of electrical insulating material, a flat electrode supported on the back' of said sheet supporting surface, an instrument comprising an extended current carrying surface providing a second electrode, and a source at high voltage current connected with said electrode whereby when a sheet is placed upon the sheet supporting surface, the sheet is charged when the instrument is. moved thereover and the sheetis sustained upon the supporting surface by the electrostatic charge induced. onthe sheet. I

2. An electrostatic sheet applying and holding device in accordance with claim 1 wherein said instrument has a cylindrical shape.

3. An electrostatic sheet applyingand holding'device according to claim 2 where said instrument .is rotatably ounted,-

lectrosta c eet app yi an holdin devic comprising sheet holding means including a relatively moo h he prortins f e t al insula m e -a tar l ctrbde conformi g o the c nfi ur tion o nd. d sposed. adjacen o sai sheet uppor in r ace. an instrument comprising a current carrying surface providinga second electrode, and a source of highvoltage connected between said electrodes whereby when a sheet is placed upon the sheet supporting surface, the sheet is charged when the instrument is moved thereover and the sheet is sustained upon the supporting surface by the resulting electrostatic charge.

5. An electrostatic sheet applying and holding device in accordance with claim 4, wherein said instrument comprises a cylindrical roller and adjustable guard means mounted adjacent the periphery of said roller.

References Cited in the file of this patent UNITED STATES PATENTS Hutchinson July 29, 1913 Chamberlain Aug. 25, 1942 Walkup et al. Nov. 6, 1951 Ebert Aug. 4, 1953 Mayo et a1. July 27, 1954 Butterfield NOV. 2, 1954

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