US 3152924 A
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Description (OCR text may contain errors)
Oct. 13, 1964 w.wAN|E| 1sTA ETAL 3,152,924
XEROGRAPHIC BRUSH Filed May 24. 1961 /0 ab 475 Ergl 50 IN VEN TORS` i@ @MQW United States Patent O 3,152,924 XEROGRAPHIC BRUSH Walter Wanielista, Westchester, and Charles l, Sippel, Jr., Villa Parli, Ill., assignors to Robertson PltotouMechanlx, Inc., Chicago, ill., .a corporation oi* illinois Filed May 24', i953, Ser. No. 112,283 3 Claims. (Si. 1l8-637) This invention relates to xerographic apparatus and processes, and more particularly to a xerographic brush adapted to present electroscopic developer powder from a mixture of such powder and magnetizable particles, onto a member bearing an electrostatic charge image.
In the art of xerography or electrostatic printing, a reproduction image is utilized which takes the form of a latent electrostatic charge image forming a magnetic pattern on a suitable matrix. Application of a developer mixture as described to the image-bearing matrix serves to develop this latent image. Typically, developer mixtures include a so-called toner powder or developer powder with magnetizable particles such as iron filings or the like interspersed therewith.
Various methods of applying the developer mixture to the latent image have been employed previously, including cascading the mixture over lthe image-bearing matrix or member to develop the image with the image-bearing member then being subjected to a lixing process. Other forms of apparatus include the use of polar members or magnetic held-producing means on which the brush-like tufts are formed directly with the result that the brush eventually constitutes a greater proportion of magnetizable particles or iron filings than toner powder so that an undesirable deposition of mixture is obtained. And in general, it has been dilicult to produce a brush having uniform characteristics dimensionally such as to provide an even deposition of the material or developer mixture on the image-bearing member.
The present invention overcomes these problems by the use of a magnetic field producing core and a nonmagnetic sleeve therearound. The mixture of developer is supplied to the non-magnetic sleeve from a source of supply through which the sleeve is rotated. And, in order to prevent uneven build-up of the brush on the sleeve, the invention provides for a differential rate of rotation of the non-magnetic sleeve and the inner magnetic held-producing means. In operation, therefore, the non-magnetic surface or sleeve is sequentially passed through the mixture and towards a presentation zone for brushing Contact with the image-bearing member. The differential rate of rotation of the sleeve and the core allords a uniform brush initially, and a doctor blade is positioned prior to the contact with the image-bearing member to further assure the uniformity of the brush at contact. After such brushing contact, the brush-like tufts or streamers are readily and conveniently removed to a predetermined depth by scraper means so that the nonmagnetic surface may be conditioned to taire on a new supply ot mixture ot the desired proportion of toner and magnetizable lings.
Accordingly, the present invention assures an optimum proportion of magnetizable particles and toner powder in the presentation Zone for brushing contact with the image-bearing member, and the brush itself assures an even contact with the image-bearing member. rlie application of the mixture to the image-bearing member is accomplished in such manner that the apparatus is free of objectionable projections and may accommodate image-bearing members of any commercially practicable size.
It is, therefore, an object of the present invention to provide an improved xerographic brush.
Another object of the invention is to provide an improved method and apparatus for atording a uniform contact of a brush of admixed powder and magnetizable particles with an image-bearing medium.
Another object of the invention is to provide a nonmagnetic presentation surface on which the brush is formed, which is moved at a differential rate with respect to magnetic means for holding the brush on the nonmagnetic surface, so as to produce an even brush surface.
Yet another object of the invention is to provide a method wherein an image-bearing member is sequentially subjected to a series ot separate brushing contacts of relatively uniform charaoteristic so as to reduce the quantum of magnetizable particle residue while increasing the quantum of powder deposited in the pattern of the charged image.
Other objects and advantages of the invention will become apparent as the description proceeds in accordance with the drawings in which:
FiGURE l is a vertical sectional View, taken along the lines l-l of FlGURE 2 and partly broken away, of a xerographic brush according to the present invention;
FIGURE 2 is a vertical sectional view taken along the lines ll-II of FEGURE l;
FIGURE 3 is an enlarged transverse vertical section taken along the line III-lll of FlGURE 4, of core and sleeve means for the xerographic brush of the present invention; and
FIGURE 4 is an enlarged front elevational view, partly in vertical section and broken away, of the structure shown in FIGURE 3.
Referring now to the drawings, the xerographic brush of the present invention is generally indicated by reference numeral 1t?, and it will be understood that the apparatus disclosed is utilized in conjunction with xerographic apparatus or may be used in connection with the practice of xerographic processes wherein an image bearing member is provided with an electroscopic charge pattern. A typical image-bearing member is indicated in FIGURE 2 at Means for moving the image-bearing member l1 are shown diagrammatically at 12 and are mechanically driven through suitable mechanical connection means 13 by a motor le.
The apparatus 10 thus establishes a presentation zone in which a developer mixture is presented to the imagebearing member for developing the latent electroscopic image. The apparatus l@ includes a non-magnetic shaft 15, a plurality equi-angularly spaced, longitudinally extending eld-producing means or magnets 16 arranged around the non-magnetic shaft 15, a coaxial non-magnetic sleeve i7 proximately radially spaced from the shaft 15 and the magnets 16 and a trough 1S for retaining a supply of developer mixture 19.
In accordance with the invention, the core 15 and sleeve 17 are journaled for diterential rotation in a support means 2t) having a pair of spaced bearing posts 26a.
The support means Zit may be positioned in a suitable framework of a erographic apparatus. A doctor blade 22 and a scraper 23 each having end brackets 47 and 4S, respectively, are carried by the bearing posts 2da in spaced relation to the sleeve 17.
The magnets 16 are preferably disposed end-to-end in multiples along the length of the core i5 and are etlective to pick up the mixture l and deposit it on the sleeve i7 as the sleeve is sequentially rotated through the trough 13. The magnets are aligned so that corresponding poles of adjacent magnets are lracing, for example, the north and south poles indicated at N and S of adjoining strip or bar form magnets confront one another, as seen in FIGURE 3. This longitudinal alignment ot the magnets is effective to create a high lux area which extends radially outwardly and between the magnets to assure that a sufliciently thick brush 25 is formed on the sleeve. Moreover, to prevent uneven buildup of mixture around the sleeve 17, it is contemplated the core and the sleeve 17 will be rotatively driven at relatively different rotational speeds.v For example, in the illustrative cmbodime'nt herein disclosed, both core and sleeve are driven in the same direction but at different speeds. Thus the magnets 16 constantly shift their position angularly with respect 'to the sleeve and tend to keep the deposit or brush portion adjacent thereto moving around the sleeve. This action continuously shifts the individual areas of the brush adjacent the magnets so that the tendency to build up deposits between the magnets is negated. A uniform thickness of the brush is afforded with good density and with excellent image developing characteristics.
To this end, the drive means 421 includes a lower gear shaft 26 journaled by bearings 27 and 28 which may be carried on lthe support means 20 or otherwise. The gear shaft 26 is driven b'y a suitable -prime mover (not shown) through a gear or the like 29. A relatively large diameter gear 30 is splined or otherwise secured to one end of the shaft 26 and drives a reduced diameter gear 31 which is connected coaxially by a journal shaft 32 and splined pin or the like 33 to the core shaft 15. Thereby, the' shaft 15 and the magnets 16 are rotated at a relatively high rate of speed, which may be, for example, approximately 228 r.p.m.
The other end of the lower gear shaft 26 has a gear or the like 34 secured thereto which is of smaller diameter than the gear 30' but which drives a gear 35 of larger diameter than the said gear 34 to afford a gear reduction means. The gear 35 in turn is connected b`y' a journal shaft 36 having a flange connected to the sleeve 17 so as to drive the sleeve at a much lower rate of rotation than the core 15 and the magnets 16 are driven and which may be, for example, 4l rpm. The right hand end of the sleeve 17 is supported on a bearing plate 38 which may have a reduced bearing surface 39, and the left hand end of the shaft 15 in turn may be supported by a journal pin 40 extending coaxially therefrom into a bearing 41 in the shaft 36.
Y It will be appreciated, however, that other relative rotational movement could be effected between the core and sleeve without departing from the spirit of our invention.
The respective journal shafts 32 and 36 may be mounted in the upright ends or bearing posts 20a of the support structure 20 by a 'bearing race 42 and a bearing race 43 respectively, and suitable O-rings may also be provided adjacent thereto, as designated by numerals 44 and 45, respectively.
Referring now to FIGURES 3 and 4, it will be seen that the magnets 16 may be set in the core 15 to extend radially outwardly therefrom to a predetermined extent, and into proximately radially spaced relationA with the sleeve 17. In the form shown, the magnets 16 are spaced approximately 36 from one another, angularly around the core 15, but variations in this relationship may be afforded within the scope of the invention, it being again noted, however, that the facing poles interact to effect a centration.
It willfalso be understood that the core 15 itself vmay be varied in construction, as may the mounting forrthe respective magnets 16, but in any event, the core is desirably of a non-magnetic material.
The sleeve 17 may be made of any suitable non-mag` netic material which can conveniently comprise a glass material, a plastic material or any of the non-magnetic metals such as brass, aluminum or copper. It is important, however, that the sleeve as well as the core 15 be suitably non-magnetic to develop the advantages and features herein contemplated.
The bore in the sleeve 17 is dimensioned to accommodate the outside dimension of themagnets 16, as described, and variation in this relationship is also encompassed within the scope of the invention and may be varied to alter the characteristics of the brush 25 as desired.
The developer mixture 19 within the trough 18 can comprise any suitable material used in the xerographic arts for developing latent electroscopi'c images, and it will be understood that one example of such a mixture comprises a developer or toner powder and a ferromagnetic carrier material such as iron filings. One edge of the trough 18 may be turned inwardly to form a flange 46 for reinforcing and retention of materials in the trough, the open area of the trough forming a presentation zone over which the image bearing member 11 is moved for brushing contact with the brush 25 carried on the nonm'agnetic sleeve 17.
In order to further assure an evenly projecting mass of mixture on the sleeve 17, the doctor blade 22 is carried on spaced supporting brackets 47 on the opposite walls of the support structure 20. It will be understood that adjustment in the radial position of the doctor blade 22 and the scraping blade 23 relative to the sleeve 17 may be afforded by the use of appropriate fastening means such as screws shown at 50. For example, the brackets 47 and 4S may be slotted to accommodate one lor more of the screws 50, thereby affording adjustability relative to the sleeve 17. Thus, as the sleeve 17 is sequentially moved through the supply of mixture 19 in the vtrough 18, in a counterclockwise direction in the example shown, the magnetic `field producing means or magnets 16 may form streamers or brush-like tufts on the surface of the brush to a slight extent and the doctor blade 22 `will trim this mass of developer mixture to uniform thickness. Because of the differential rotation between thev sleeve `1-7 and the magnetic means, however, lthere will be no tend enc'y to further build up after the sleeve has passed the blade 22 in any given cycle of rotation.
After brushing contact has been established between the image-bearing member 11 and the developer mixture or brush 25 on the sleeve, the sleeve moves past the scrap- `ing blade 23 which is similarly carried on brackets 48 on opposite walls of the support structure 20. Here again, the blade 23 may be radially adjusted with respect to the sleeve 17 withinv the scope of the invention. However, the blade 23 is positioned closer to the sleeve 17 than is thev blade 22, so that the sleeve will be conditioned to take on a new supply of a proper mixture of developer material. The developer removed will be returned to the trough 19 for reuse. For example, the doctor blade -22 may be set one-fourth inch radially from the sleeve, with the' scraper blade 23 being set one-eighth inch radially from the sleeve. The doctor blade 22 and the scraper blade 23 are of a non-magnetic material, as are other accessory components of the apparatus. v
It is to be noted that the preferred form of the invention entails the rotation of the core 15 and the mag- Vnets 16, as well as the sleeve 17, in the same direction in lany 'given sequence of operations.
3 medium, wherein any unevennesses in the brush surface presented to the medium are obviatecl automatically by relative rotation of the magnetizing means and the brush carrying means.
Although various minor modifications might be suggested by those versed in the art, it should be understood that We wish to embody Within the scope of the patent warranted thereon all such modifications as reasonably and properly come Within the scope of our contribution to the art.
We claim as our invention:
1. A Xerograplic brush for applying developer particles to an electrostatic image on a surface comprising a rotatable non-rnagnetic shaft forming a cylindrical core having a plurality of angularly spaced elongated magnets in the peripheral surface thereof and corotatable with said shaft, a rotatable cylindrical sleeve of non-magnetic material having an inside surface proximately radially spaced to said cylindrical core and said angularly spaced elongated magnets, said cylindrical sleeve having an outer peripheral surface adapted to support brush-like tufts of Xerographic magnetic developer mixture thereon, drive means to drive said core and said sleeve including separate means to rotate said core and said sleeve independently and to rotatably move said core and said sleeve in the same rotative direction but at dierent rotative speeds relative to one another, means adapted to contain a supply of Xerographic magnetic developer mixture subjacent said sleeve and into which said sleeve dips upon rotation thereof, and scraper means on one side of said sleeve for scraping the remaining mixture oli of said 6 sleeve after application of the developer particles to said surface and thereby conditioning said sleeve to take on a fresh supply of the magnetic developer mixture.
2. A Xerographic brush as defined in claim 1, wherein said magnets are supported at equal circumferential intervals in parallel relationship to the axis of the core and with their outer surfaces circumscrihing a cylindrical envelope.
3. A Xerographic brush as dened in claim 2, wherein said magnets are alicned and have corresponding jpml'es of circumerentially adjacent magnets in confronting relationship.
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