US 2576882 A
Description (OCR text may contain errors)
NOV. 27, 1951 p KOQLE ET AL 2,576,882
DEVICE FOR CONVEYING PAPER AND SIMILAR SUBSTANCES Filed Dec. 4, 1947 IN VEN TORS. PZETEE KOOLE 10 ms EOURGONJON Y JZEZVDJZZKDEIANGE AGE VI Patented Nov. 27, 1951 DEVICE FOR CONVEYING PAPER AND SIMILAR SUBSTANCES Pieter Koole, Louis Raymond Bourgonjon, and
Hendrik de Lange, Eindhoven,
assignors to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application December 4, 1947, Serial No. 789,664 In the Netherlands September 4, 1946 Claims.
Several methods of conveying loose sheets of paper, such as letters, drawings and the like are known already. From the printing technique we know the method of picking up and feeding forward sheets of paper by means of suckers associated with a suction-device. It is, furthermore, common practice to cause a sheet of paper to bear upon a metal frame and to rapidly displace the latter; owing to the air resistance the paper is kept in place.
It occurs that a paper conveying device is desired, in which the surface of the paper lies completely free and in which clamps, bands, suctiondevices and the like are not needed. It should furthermore be possible to hold the paper in position against gravity. A paper-conveying device of this kind is desirable, for example, in facsimile devices and may be used in printing presses, stamping machines, sorting machines and the like.
After long experiments the applicant has sucseeded in realizing a conveying device of this type, in which the paper is held on the conveyor solely by electro-static forces. A sheet of paper held in this manner lies completely fiat and adheres to the conveyor, even against gravity or, in other words, the paper remains clinging to the conveyor.
Except for electrical dust and flying-ash collectors, electro-static measuring instruments and condenser loudspeakers (the latter having never been in common use), only few or no fields of application of electro-static forces are known in industry. This may be due to the fact that it is dimcult to separate the two kinds of charges occurring side by side in nature, since this leads to high, sometimes even to very high tensions. Yet in solving the problem initially mentioned it has surprisingly been found that, owing to the nature of the material the electro-static method leads to a very satisfactory result. It has been found that to this result contributes in the first place the fact that paper, even when very dry, still exhibits a slight conductivity, so that with respect to highly insulating substances it must be regarded as a conductor. It is furthermore possible to obtain the electro-static charges, for example,
either by friction or by connection to a source ing material loose sheets of paper or of similar substances are held on this conveyor by means of electro-static forces.
Moreover, a device should preferably be provided for neutralizing the elcctro-statlc forces by electrical means.
In one advantageous embodiment of the inven tion the conveyor of electrically insulating ma tcrial is caused to pass between two bodies, 01 which one. which primarily comes into contact with the paper, is provided with at least one earthed coating of electrically conductive material, whereas the other body, which is always solely in contact with the conveyor, is coated with a substance capable, upon friction against the electrically insulating material of the com veyor, of producing an electro static charge on this material. The substance referred to may be, for example, a cat-skin, felt, silk or a similar substance.
In this embodiment of the invention it is neces sary that all parts with which the conveyor contacts as long as the paper must be held in place, such as belt-tighteners, feeding mechanisms and the like should be mounted so as to be insulated with respect to earth or should be made of in-= sulating material, since otherwise the charge may flow away to earth on that side of the conveyor which is remote from the paper.
The body coated with a substance capable of producing, due to friction against an electrically insulating material, an electro-statlc charge on this material, preferably exhibits the shape of a cylinder the periphery of which has, with respect to the conveyor a speed which differs from zero a sufiicient amount of friction between the conveyor and the friction-substance being thus obtained.
In a further advantageous embodiment of the invention the conveyor of electrically insulating material is provided, on the side remote from the paper required to be conveyed, with narrow strips of thin, electrically conducting material which are electrically separated from one another in a direction at right angles to the direction of movement of the conveyor, the electrostatic charge being produced by successively connecting the strips to one terminal of a source of direct-current voltage, the other terminal of which is connected to a sheet of paper required to be conveyed and located on the other side of the conveyor.
In this embodiment of the invention it is fundamentally immaterial whether that side of the source of direct-current voltage which is not connected to earth is connected to the paper or to the strips of electrically conducting material. In this embodiment of the invention it is also desirable that all parts of the mechanism with which the strips of the conveyor come into contact as long as the paper must be held should be insulated with respect to earth. If that side of the highvoltage source which is not connected to earth is connected to the paper and if the earthed side of this source is connected to the strips, it will generally not be necessary to insulate the said parts from earth, but in general it is preferable, for practical reasons, to connect the side not connected to earth to the strips.
A further, preferahe embodiment of the invention consists in that that side of the conveyor which is remote from the paper required to be conveved is provided with an electrically conductive coating whilst that side of the paper which is remote from the conveyor is brou ht into contact with a body which is also provided with an electrically conductive coating, the electro-static charge being produced by connecting the coating of the conveyor to one terminal of a source of direct-current voltage, of which the other terminal is connected to the coating of the body which is in contact with the paper. Also in this embodiment it is fundamentally immaterial how the source of direct-current voltage is connected. In this case it is, however, preferable to connect the side which is not connected to 4 paper and the conveyer is thus correspondingly increased.
It is desirable to provide a device which automatically neutralizes, at a definite point, the
earth to the paper and the earthed side to the coating of th convevor. In t e latter case all guide rollers and similar mechanisms which do not come into contact with the paper during the conveyance. mav be earthed and need not be made of insulatin material.
It is sometimes desirable to further increase the adhesion between the conveyor and the substance to be conveyed. After the electro-static charge has been produced, an electric connection is established for this purpose, according to the invention. between the side of the conveyor remote from the paper and the side of the paper remote from the conveyor. Such a short-circuit surprisingly results, in a stronger adhesion. although it was to be expected that the adhesion would have become considerably less and even would have vanished altogether. The increased adhesion may be accounted for by the following.
Because of the essentially insulating properties of the paper sheet a charge of opposite polarity is initiallv induced in the surface of the paper adjacent to the conveyer surface. Similarly because of the insulating nature of the conveyer belt a charge of opposite polarity to the applied charge is induced on the surface adjacent to the paper. Thus the adjacent surfaces of the paper and conveyer have initially opposite charges which remain separated due to the air gap normally existing to a greater or lesser extent between paper and conveyer. In practice, the paper is not an absolute insulator so that the charge induced on the conveyer side of paper is neutralized to a greater or lesser extent because of the conduction throu h the paper. Thus the adjacent surfaces of the paper and the conveyer now assume the same polarity to a greater or lesser extent and the attraction forces between them are reduced. By short-circuiting the outer surfaces of the paper and the conveyer the charge on the conveyer outer surface is transferred to the paper and is distributed through the paper. Since the transferred charge is opposite in polarity to the charge on the inner surface of the conveyer the attraction b tween the adhesion between the conveyor and the paper to be conveyed. This is preferably effected, according to the invention, by electrical agency, in such manner that the conveyor together with the paper is passed between two bodies between which an alternating field prevails. After the passage through this alternating field, the peak voltage of which is preferably chosen to be of an order of magnitude such that between the coating and the paper a, now alternating, field strength eoual to that produced by the charging with direct-current voltage the'paper appears to be released by the conveyor. If desired use mav be made, in addition of a simple, mechanical device, for removing the paper.
It has also been found that a better adhesion between paper and conveyor can be obtained. if care is taken to ensure that the conveyor is as dry as possible. For this purpose, according to the invention, means of heating the conveyor are provided. This may be realized, for example, bv passing the conveyor over a simple radiation element. As an alternative. it is possible tainternally heat one of the guide rollers on which the conveyor runs.
Finally it has been found desirable to ensure that t e contact bet een conveyor and paper is as intimate as possible. According to the invention for this purpose means are provided to clear the convevor of dust before it receives the paper. This may be effected, for example by guidin the conveyor along a felt brush connected to a vacuum conduit or a vacuum cleaner.
In order that the invention mav be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, in which the embodiments shown in Figs. 1, 2 and 3 should be considered as examples.
Referring to Fi 1, I desi nates a conveyor of electrically insulating material, for example, rubber, or of flexible thermoplastic insulatin material, which is stretched in form of an endless belt between two cvlindersl and 3. Cylinder 2 is made of electrically insulating material such for example as synthetic resin. Above the conveyor is provided a guide 4 along which a sheet of paper 5 can slide on to the belt I. The
belt I is moved forward since one. of the cylinders 2 and 3 is driven.
This may, of course, also be effected by a separate set of cylinders, as shown in dotted lines and denoted ,by 6', the cylinders rotating in the direction of the arrows. The moving belt I carries the paper along with it and conveys it between the cylinders I and 8. The periphery of cylinder 1 is provided with a piece of cat-skin,
felt, silk or similar material and is separately driven in such manner that the peripheral speed of this cylinder is higher or lower than the speed of the belt, friction between the belt I and the coating of cylinder I being thus produced. Cylinder 8 which is made of metal, is earthed and is adapted to rotate freely. After having passed paper has to be removed again from the belt. For this purpose the cylinder 3 is made of metal and connected to an alternating-voltage source. of which the other terminal is connected to a metal cylinder II. The remaining adhesion is so slight that the paper cannot follow now the curvature of cylinder 3 and drops from the belt along a guide I2.
Before the point at which the paper arrives on the belt, the latter is provided with a simple device for removing dust, soil and the like, consisti'n'gof a brush l3 and a suction-pipe I4, the
latter communicating with a vacuum conduit,
for example the suction-pipe of a vacuum cleaner.
In Fig. 2 the reference numerals identical to those of Fig. 1 have the same meaning. Here,
however, the belt i is internally coated with strips of tin-foil 26 which extend'transversely to the direction of movement of the belt. A cylinder 2i presses against these tin-foil strips and is connected to the positive side of a source of direct-current voltage. The negative side is connected to an endless metal band 22 stretched around two cylinders 23. After a charge has thus been produced on belt and paper and consequently the paper adheres already to the belt, the force with which the paper adheres to the belt is increased by causing paper and belt to pass between two metal bodies 2d which are in contact with the belt and the paper respectively and which are electrically connected to one an other. Thus the tin-foil coating of the belt is short-circuited with respect to the paper and this short-circuit enhances the adhesion of the paper to the belt. Ii use is made of this short-circuit, the cylinder 2 may also be of metal and be earthed.
In order to neutralize the adhesion of the paper to the belt, they both, after having passed the scanning device 9, it, move between two metal bodies 25 and 2B which are again in con= tact with the paper and with the tin-foil coating of the belt. To these bodies, which, of course, may exhibit the shape of cylinders, an alternating voltage is applied. The force with which the paper adheres to the belt is thus reduced to such an extent that the paper drops from the belt, or again that the simple removing device i2 is capable of taking the'paper from the belt. The cylinder 3 may be made of metal and be earthed. If one of the terminals of the alternating-voltage source is likewise earthed, the body 26 may be dispensed with and the body 25 is arranged opposite the cylinder 3. In the interior of cylinder 3 is provided a simple heating tical to those of Figs. 1 and 2. The device for neutralizing the electro-static adhesive force consists of a body 34 connected to one terminal device constituted by a heating element 28 and a reflector ill, the cylinder 3 and the belt i being thus heated and dried, which is conducive to the adhesion of the paper to the belt.
In Fig. 3, in which the reference numerals corresponding to those of Figs. 1 and 2 again have the same meaning, the belt, which is coated on the side remote from the paper with a continuous layer 25 of tin-foil or is made conductive in any other manner, is now brought into contact with a metal body 35, which is connected to the earthed side of a source of direct-current voltage. The paper, on the contrary, comes into contact with a band 3i coated with tin-foil 32 and stretched between two cylinders 32 and 33. That side of the source of direct-current voltage which is not earthed is connected to the tin-foil band.
The other parts of this embodiment are idenof an alternating-voltage source, ofwhich'the other terminal is connected to the (metal) cylinder 3. 1
In this embodiment one of the terminals of the source of alternating voltage must be earthed and connected to the cylinder 3.
The heating element 21, 28 is now arranged in such manner that the belt is heated at the point at which the paper arrives on the belt.
What we claim is:
1. A device for conveying material in the form of sheets, comprising a conveyor belt member of electrically insulating material having a first exposed surface for receiving the said sheets on one side of the conveyor and having a second surface on an opposite side of said conveyor member, means to apply the sheets to be conveyed onto said first surface, an electrically conducting coating on a portion of said second surface, and means to apply electrostatic charges to the exposed surface of the sheets to be conveyed and to the said coating.
2. A device for conveying material in the form of sheets, comprising a conveyor belt member of electrically insulating material having a first exposed surface for receiving the said sheets on one side of the conveyor and having a second surface on an opposite side of said conveyor member, said conveyor member being movable in a given direction, means to apply the sheets to be conveyed onto said first surface, said second surface being provided with a plurality of electrically conducting coating spaced apart and ex tending in a direction transverse to the direction of movement of said conveyor, and means to apply electrostatic charges to the exposed surface of the sheets to be conveyed and to the said coatings successively.
3. A device for conveying material in the form of sheets, comprising a conveyor belt member of electrically insulating material having a first exposed surface for receiving the said sheets on one side of the conveyor and having a second surface on an opposite side of said conveyor member, said conveyor member being movable in a given direction, means to apply the sheets to be conveyed onto said first surface, an electrically conducting layer forming a layer forming a continuous coating on said second surface, and means to apply electrostatic charges to the exposed surface of the sheets to be conveyed and to the said conducting coating.
4. A device for conveying material in the form of sheets, comprising a conveyor belt member of electrically insulating material having a first exposed surface for receiving the said sheets on one side of the conveyor and having a second surface on the opposite side of said conveyor member, means to longitudinally move said conveyor member, means to apply the sheets to be conveyed onto said first surface, an electrically conducting coating on a portion of said second surface, means to apply electrostatic charges to the exposed surface of the sheets to be conveyed and to the of electrically insulating material having a first exposed surface for receiving the said sheets on one side of the conveyor and having a second surface on the opposite side of said conveyor member, means to longitudinally move said conveyor member, means .to apply the sheets to be conveyed onto said-first surface, an electrically conducting coating on a portion of said second surface, means to apply electrostatic charges to the exposed surface of the sheets to be conveyed and to the said conducting coating at a given point along the length of the conveyor, and means spaced from said given point in the direction of travel of the conveyor member to apply an alternating potential to the exposed surface of said sheets and the said coating to neutralize the said electrostatic charges.
LOUIS RAYMOND BOURGONJON.
HENDRIK m: LANGE.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS