US 3021817 A
Description (OCR text may contain errors)
Feb. 20, 1962 w. LIMBERGER COPYING OF DOCUMENTS Original Filed Aug. 16, 1957 Walter Limberqer INVENTOR M AGENT.
United States Patent I O 3,021,817 CQPYING OF DOCUMENTS Walter Limberger, Hamburg, Germany, assignor t Lumoprint Zindler K.G., Hamburg, Germany, a German company Original application Aug. 16, 1957, Ser. No. 678,685, now Patent No. 2,972,332, dated Feb. 21, 1961. Divided and this application Dec. 23, 1958, Ser. No. 782,603
8 Claims. (Cl. 118-637) My present invention relates to a device for rendering visible a latent electrostatic image by means of a toner by distributing pigment particles onto a xerographic layer in which the latent electrostatic image is located.
An apparatus for the preparation and the development of such images was described and claimed in my copending application Ser. No. 678,685, filed August 16, 1957, now Patent No. 2,972,332, of which this application is a division.
According to one aspect of the invention, a longitudinally loop-shaped open-topped container for receiving a pile of toner and guide devices for the layer support is provided whereby this support is guided under the toner pile with simultaneous agitation of the toner.
The invention provides the important advantage that an intensive and uniform covering of the latent electrostatic image With the toner is insured, whereby through the advance of the layer support a continuous agitation and movement of the particles of the toner lying directly upon the upwardly facing Xerographic layer are insured. By this agitation, unused particles of the toner, for example glass spheres which are provided with pigment particles, are continually supplied to the Xerographic layer. The agitating movement of the toner particles produced enhances transfer of the pigment particles to the xerographic-layer support.
According to the invention, an open-topped container is formed by a guide surface on which a toner pile is located and through which the layer support is guided under this pile.
Pursuant to a feature of the invention, the guide surface is inclined to the direction of the advance of the layer'support, which is guided over conveying rollers, for example, arranged so that the forward edge of the layer support is deflected by the guide surface in the direction towards the toner pile. It has been found that, by the inherent stiffness of the layer support, its forward edge slides along the guide surface so that the layer support is moved between the guide surface and the toner pile.
The guide surface is advantageously arched in a U shape and may be curved in a plane which lies perpendicular to the direction of advance of the layer support; in a particularly preferred embodiment, however, the plane in which the guide surface is curved lies perpendicular to the layer support and parallel to its direction of advance.
According to a further feature of the invention, the end of the guide surface over which the layer support is withdrawn is inclined upwardly. Advantageously, the guide surface has straight, upwardly diverging entrance and exit slopes inclined outwardly in different directions and connected by a preferably uniformly curved center part. This provides that the toner pile merely rests in the curved part of the guide surface, the upper edge of the pile preferably lying beneath the beginning of the curved section.
It is also possible to provide suitable directing surfaces at a distance above the guide surface in order to limit the accumulation of the toner to a particular region of the guide surface.
According to still another feature, the guide surface is perforated before and/or after the section on which "ice the toner pile is located. This construction has the advantage that foreign particles, particularly dust and the like, can fall downwardly during the advance of the layer support before the latter arrives at the toner pile. These perforations may be associated with a suction device adapted to urge the back of the layer support into firm contact with the guide surface, the suction device preferably acting on the layer support through one or more perforations of the guide surface located ahead of the toner pile.
In accordance with yet a further feature of the invention, the part of the guide surface which lies behind the toner pile as seen in the direction of advance of the layer support is made pivotable. The pivot point is preferably located beyond the toner pile. A periodic oscillation can be effected by an agitator, in order to return excess pigment particles to the pile.
Further advantages and features of the invention will appear from the description of certain embodiments thereof, of which only the parts essential to the invention are illustrated. In the accompanying drawing:
FIG. 1 shows a side view of an apparatus according to the invention in section; and
FIG. 2 shows a side view of another embodiment in section.
In FIG. 1, a guide surface 51, as seen in the direction of advance of the layer support, has a straight front part 52 and a likewise straight rear part 53. These two parts are inclined with their upper ends diverging. The lower ends are interconnected by a curved section 54. Within the guide surface, which is formed as an upwardly open shell, is located the toner pile 55. In the embodiment illustrated the toner substantially fills the curved section 54, so that the layer support guided along the upper side'of the guide surface 51 is pressed with its front edge continually onto the guide surface because of its stiffness.
The guide surface is itself supported in a frame 56. This frame carries Walls 57 which la.erally enclose the guide surface.
Above the guide surface 5.1, feed means 58, 59 are disposed. in this figure the feed means are merely indicated at the supply side of the layer support although they may be provided at either or both ends. They consist of rollers which may be yieldingly pressed together and guide the layer support 6% in a rredetermined direction perpendicular to the plane 61 connecting the axes of the rollers 58, 59. This direction, represented by a plane tangent to both rollers, is inclined towards the direction 62 of the front part 52 of the guide surface, so that the forward edge 63 of the layer support 69 contacting the guide surface is bent towards the toner pile 55. This insures that the layer support is guided directly along the guide surface and can push under the toner pile S5. The arrangement is such that the distance from the feed means 58, 59 along the guide surface 51 up to the feed means (not shown) behind the rear part 53 of the guide surface 51 is smaller than the length of the layer support, so that the layer support, after it has left the feed means 58, 59, is further advanced by the feeding devices located beyond the member 51. It will be understood that the entire system illustrated in the drawing will be enclosed in a larger casing (not shown) having slots for the insertion and the withdrawal of successive sheets 69, such casing usually also containing conventional means for producing a latent electrostatic image on the xerographic layer, by successively subiecting it to an electric field and a photographic exposure, and for fixing the developed image by a fusion process.
In the embodiment illustrated in FIG. 2, the guide surface 64 is curved in a vertical plane which runs parallel to the direction of advance. In this embodiment, the toner pile 65 is guided by directing surfaces 66, 67,
the rear directing surface 67 being curved to increase agitation of the toner. The agitation of the toner is also augmented by a stirrer element 68- projecting into the toner pile 65. p
In the direction of advance of the layer support corresponding to the arrow 69, the guide surface 64 includes a several apertures 70 in front of the toner pile 65 or in front of the directing surface 66. These apertures are so arranged that their axes on the upper side of the guide surface 64 do not intersect the toner pile 65. Furthermore, additional directing surfaces 71, 72 are provided beneath the guide surface as a means for directing the flow of air through the apertures 70 parallel to the axes of the apertures 70.
The channel formed by the directingsurfaces 71, 72 is connected to the suction side ofa fan 73. This fan may form part of the ventilation system of the apparatus, care being taken to prevent withdrawal of the total air volume through the channel formed by the directing surfaces 71, 72 so that merely a lower pressure is produced in this channel. This lower pressure serves to guide the layer support smoothly on the upper side of the guide surface 64 in the direction of the arrow 69,, whereby dust particles or the like, which may be located on the upper side of the guide surface 64, fall through the apertures 70. By the described arrangement of the apertures 70 in relation to the toner pile 65, the assurance is given that individual particles of the toner cannot be subject to the partial vacuum acting through the apertures 70 so that the back of the layer support can travel unhindered on the upper side of the guide surface 64.
1. An apparatus for developing electrostatic images on flexible sheets, comprising a trough-shaped stationary toner support with a pair'of side walls flanking a partly curved, upwardly concave stationary guide member having a continuous sheet-supporting upper surface, a pile of comminuted toner deposited in the concavity of said member and confined by said side walls, and feed means for moving a flexible sheet carrying an upwardly facing Xerographic layer across said upper surface and under said pile, thereby temporarily exposing said layer to the action of said toner, said guide member having a curved center portion merging into two substantially planar and upwardly sloping diverging end portions, said toner pile being substantially limited to said center portion, said feed means including sheet-driving means positioned above said guide member in a region between the planes of said end portions and forwardly of said center portion for directing said sheet downwardly onto the forward one of said end portions head of said toner pile.
2. An apparatus as described in claim 2, further comprising front and rear wall elements above said guide member preventing said pile from spreading onto said end portions, said wall elements being separated from said guide member by a distance sufficient to let said sheet ass. p 3. An apparatus as described in claim 1, further comprising agitator means for said toner positioned in the region of said center portion.
4. An apparatus as described in claim 1 wherein said forward one of said end portions is provided with perforations in the path of said sheet, further comprising suction means underneath said forward'end portion in operative alignment with said perforations, and wall means forming a channel connecting said suction means with said perforations, the axes of said channel and of said perforations diverging upwardly and forwardly from the vertical so as to be non-interse'ctingly positioned in regard to said toner pile.
5. An apparatus as described in claim 1 wherein said feed means comprises a pair of co-operating rollers positioned adjacent said forward one of said end portions, the latter including an acute angle with a plane tangent to both of said rollers whereby said sheet is deflected at said forward end portion toward said center portion.
6. An apparatus for developing electrostatic images on flexible sheets, comprising a stationary guide member having a continuous sheet-supporting upper surface, said surfacebeing formed with a curved, upwardly concave central portion and with two substantially rectilinear portions divergingly sloping upwardly from said curved portion and merging into the latter at the front and the rear thereof, respectively, a pair of co-operating transport rollers positioned adjacent the forward one of said sloping portions, said forward portion including an acute angle with a plane tangent to both of said rollers whereby a flexible sheet carrying on its upper face a latent electrostatic image can be directed by said rollers onto said sheet-supporting surface ahead of said curved portion, and stationary side walls flanking said curved portion for confining thereon a pile of comminuted toner adapted to develop a latent image on said sheet upon passage thereof between said surface and said pile.
7. An apparatus according to claim 6 wherein said forward portion is provided with perforations in the path of said sheet, further comprising suction means underneath said forward portion in operative alignment with said perforations, and wall means forming a channel connecting said suction means with said perforations, the axes of said channel and of said perforations diverging upwardly and forwardly from the vertical, thus being non-intersectingly positioned in regard to the space above said curved portion occupied by said toner pile.
8. An apparatus according to claim 7 wherein the axes of said perforations are parallel to the axis of said channel.
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