The present invention relates to the texturing of articles and more particularly to the conditioning and retexturing of articles for reuse. Specifically, the invention relates to the reconditioning of aluminium magnetic rollers used for transferring toner to an optical photoconductor (OPC) in a laser printer, photocopier or the like.

Magnetic rollers comprise a sleeve having a print surface and mounting ends, a permanent magnet disposed within the sleeve and at least one electrical contact. The print surface of the sleeve and the mounting ends which are held in bushings are prone to wear and are easily damaged during handling or cleaning with adverse effects on final print quality.

It is an object of the present invention to reduce waste by conditioning articles such as magnetic rollers for reuse and to provide a method and apparatus for texturing surfaces and to provide articles produced thereby. Particularly, it is an object of the present invention to provide reconditioned sleeves for magnetic rollers having comparable or improved toner transfer characteristics to new sleeves supplied by original equipment manufacturers (OEMs) .

Accordingly, the present invention provides a method for conditioning an elongate cylindrical metal article for reuse, said method comprising:

(a) mounting the article for rotation about its longitudinal axis (b) rotating the article at a substantially constant speed

(c) blasting the article with a particulate material of comparable hardness to produce a textured surface; and

(d) washing the article in a stream of dehumidified gas to remove settled particulate material.

Advantageously, the article is treated with a sealant to seal pores on the textured surface and to prevent corrosion or oxidation.

The article is mounted vertically so that the particulate material does not settle on the textured surface and become subsequently embedded into said surface. The particulate material is of comparable hardness to the article so that cleaning and texturing is efficiently effected.

To avoid surface contamination, the particulate material is similar to the constituent material of the metal article, for example, the particulate material may be the oxide of that metal.

The particle to be subjected to the method of the invention is usually a magnetic roller sleeve of substantially pure aluminium. In this case aluminium oxide (AI2O3) is used as the particulate material for air blasting. Other particulate mixtures are also suitable, for example, a mixture containing 12% Siθ2, 1.5% iθ2 together with the balance comprising AI2O3.

Conveniently, the dehumidified gas is air.

The sealant used on the article comprises a xylol, ethyl acetate, methanol, ethanol, hexone and aliphalic naphtha mixture.

Preferably, the article comprises a sleeve having mounting ends and the method comprises a preparation phase which includes polishing the ends and covering the ends with caps to protect the ends from subsequent blasting.

The mounting ends are polished to remove scratches and wear marks so that wear is prevented on the magnetic roller bushings which are usually Mylar* or Nylon*.

The present invention further provides an apparatus for conditioning an elongate cylindrical metal article for reuse, the apparatus comprising:

an enclosed cabinet having a rotatable mounting means for holding an article and rotating the article about its longitudinal axis;

at least one blasting pistol for blasting the article with particulate material;

a wash vent array for washing the article in a stream of dehumidified gas to remove settled particulate material;

a recovery unit for recovering the particulate material for reuse; and

a gas circuit, having a vacuum pump for extracting particulate material laden gas from the cabinet; a cyclone for separating the particulate material from the gas; and a refrigeration unit for cooling and dehumidifying the gas for recirculation, the recirculated gas being supplied to the or each blasting pistol and to the wash vent array in the cabinet to wash the article.

*Trade Mark.

The or each blasting pistol is provided with a nozzle of a hard material, preferably boron carbide, and is mounted on a platform which is movable parallel to the axis of rotation of the article.

The present invention yet further provides a reconditioned sleeve for use with a magnetic roller, said sleeve having a randomly textured toner transfer surface, said surface comprising an area subjected to pressurised particulate blasting.

The gas may be an inert gas or more conveniently may be air. Hereinafter, all references to "air" may be understood to include other gases .

The invention will now be described more particularly with reference to the accompanying drawings which show, by way of example only, one embodiment of apparatus according to the invention. In the drawings:

Figure 1 is a block diagram of the apparatus;

Figure 2 is a perspective view of the overall apparatus; and

Figure 3 is a detailed perspective view of the blasting arrangement.

Referring to the drawings, the apparatus comprises a blast cabinet 1 which houses a pair of blast pistols 3 mounted on a rack 5. A motor driven target turntable 7 is centrally disposed in the cabinet 1 in front of an air wash vent array 9.

Each blast pistol 3 is supplied by an air line 10 and a

96/31318 PCME96/00021

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particle line 12 for projecting particles towards a target R mounted vertically in a clamp 14 on the turntable 7. Exhausted air and particles are drawn from the cabinet 1 through a tube 15 into a cyclone separator 17 by a pump within cabinet 19. In the cyclone separator 17, particles and waste or undersized (broken) particles are separated and the particles are held in a collector 21 for reuse. The air is recirculated through a refrigeration plant comprising a dehumidifier 23 and cooler 25 to return to the blast pistols 3 and air wash vent array 9.

To recondition a used magnetic roller R, the print surface and mounting caps must first be inspected for excessive wear or damage. Dents or deep defects will render the roller useless. The caps are ground and soft polished to remove scratches, burrs, wear marks and grooves before the roller print surface is retextured. The polishing is achieved using a soft SCOTCHBRIT* polishing wheel revolving at approximately 1400 rpm.

Protective rubber caps C are then placed over the newly ground caps and the roller R is placed in the blasting cabinet 1. The roller is held vertically by the clamp 14 which grips one of the rubber caps C. The clamp 14 and roller R are then rotated by the motor driven turntable 7 at approximately 180 rpm.

To commence the retexturing process, the blast pistols 3 are moved to their uppermost position on the rack 5 by a motor drive arrangement 27 and cool dry air from the refrigeration plant is circulated to the pistols 3. Aluminium oxide particles or particle mixtures having aluminium oxide as their main constituent are introduced

*Trade Mark

into the air stream at the blast pistols 3 which, through blast nozzles 29, concentrate the air and particle stream onto the target roller R. The air and particle stream removes all traces of lacquers, carbon black coatings, previous retexturing and minor scratches and wear marks.

The rack 5 lowers the blast pistols 3 along the length of the target roller R as it rotates to effect total retexturing. The air wash vent array 9 provides a constant stream of cool dry air to remove particle and other debris from the roller R to prevent unwanted embedding of particles in the retextured surface. The retextured surface is then optionally coated in a sealant comprising a xylol, ethyl acetate, methanol, ethanol, hexone and aliphalic naphtha mixture (manufactured by Federal Mining and Manufacturing Company, USA) to seal pores in the surface and to prevent corrosion or oxidation. The used air, particle and debris mixture is drawn out of the cabinet (under negative pressure) through the tube 15 into the cyclone separator 17. The now warm, and often damp, air is circulated through the pump 19 into the dehumidifier 23 and chiller 25 of the refrigeration unit for reuse. The aluminium oxide particles and debris are separated and any aluminium oxide particles which have been broken into yet smaller particles are disposed of along with the debris. Useful particles are routed to the particle collector 21 for recirculation to the blast pistols 3.

Standard rollers R comprise a print surface of very pure (99.9%) aluminium and to avoid contamination the blast particles comprise an aluminium oxide mixture comprising 1.5% Ti0 , 12% Si0 ₂ and 86.5% Al ₂ 0 ₃ of average 180 mesh particle size. Alternatively, the particles comprise a

fused aluminium oxide mixture comprising: AI2O3 96.16%, Ti0 ₂ 2.58%, Si0 ₂ 0.49%, MgO 0.30%, Fe ₂ 0 ₃ 0.20%, CaO 0.14%, a2θ 0.07% and K2O 0.06%, in which the average particle size is 220 mesh. These blast particles are suitable for retexturing as they are sufficiently hard to remove scratches and old material and to retexture the surface but soft enough not to cause excessive damage. A softer material would clean the rollers but would fail to retexture them.

The nozzles 29 for the blast pistols 3 comprise a carbide material preferably, tungsten carbide or boron carbide for longevity. In the particular embodiment described the nozzles 29 have a 9.5mm bore and each carry an air volume of 0.594m^/min (21 cubic feet/min) at a pressure of 5.17 bars (75 p.s.i.). The full cycle takes 40 seconds and includes a 3 second air wash.

Using standard test procedures for evaluating toner efficiency and transfer rates the following results were obtain for a retextured roller transferring TURBON* SX toner (from Turbon International, Germany)

Toner efficiency rate: 93.6% 20% coverage : 19 gms/100 pages (5% coverage is preferred standard)

Thus, for an industrial standard toner, in a toner cartridge containing 280 gms of toner the yield exceeds 5000 pages. Additionally, print density, measured using a Di Nippon Screen Densitometer, remained consistent throughout an entire print yield run.

*Trade Mark.

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the appended claims.