METHOD OF AND MEANS FOR TESTING FLOW PROPERTIES OF MAGNETIC TONERS

Abstract: A method for testing electrostatic developer toners which comprises applying the toner to a stationary non-magnetic sleeve (4), moving the toner along the surface of the sleeve by an array of field lines generally normal to the surface produced by a multiple magnetic roll (1) rotating within the sleeve and determining the characteristics of the toner from the pattern (15) of the spread toner by reference to a calibrated scale (9) and stop line (5) on the surface of the sleeve.

Description: "METHOD OF AND MEANS FOR TESTING FLOW PROPERTIES OF MAGNETIC TONERS" BACKGROUND OF THE INVENTION It is well known to tone electrostatic latent images contained on photoconductive or dielectric surfaces by application thereto of so called mono- 5. component or single component electroscopic marking particles or toner which may be of the heat fixing or cold pressure fixing type. Single component toner particles contain magnetisable material such as for instance magnetite 10. whereby such toner can be applied for toning purposes to the latent image bearing surface by means of a magnetic applicator roll. It is customary to have the single component toner contained within a hopper or tank from which it is fed onto the • j ^ applicator roll. The applicator roll consists usually of a non magnetic stationary or rotating sleeve within which is contained a rotating multi-pole magnet roll. As such magnet roll rotates, the magnetic field lines associated with the poles 20. usually of alternating polarity attract toner to the non-magnetic outer sleeve and cause said toner to form a coating thereon, commonly referred to as the magnetic brush. A so called doctor blade is usually fitted to control the coating 25. thickness or the height of the magnetic brush. The magnetic brush is brought into close proximity to the latent image bearing surface to effect toner transfer over the so called toning gap by attraction to the latent image areas where the 30. electrostatic forces associated therewith overcome the magnetic forces holding the toner against the sleeve of the applicator roll. The machine performance that is image quality and stability of single component toners depends on a number of properties of the toner material such as electrical conductivity, tribocharging 5. characteristics, particle size and particle size distribution, etc. , as is well known in the art. One of the main factors affecting machine performance of the toner is related to its flow properties as is also well known. By good flow properties 10. is meant the ability of the toner to distribute itself uniformly and rapidly over the surface of the outer sleeve of the magnetic applicator roll so that imagewise removed toner material by the latent image bearing surface is instantly 15. replenished and thus the magnetic brush in the toning gap is of constant height and uniformity. Poor flow properties of a toner are indicated by uneven image density mainly in the form of streaks or bands along the copy, which are caused 20. by uneven toner distribution on the applicator roll or insufficient toner in localised portions thereof. In order to improve the flow properties of single component toners it is customary to admix 25. so-called flow improvers such as siliea powders and the like therewith in certain specific proportions A common test of toner flow characteristics is measurement of the angle of repose of the toner. However such measurement can give widely varying 30. results in repeat testing of one and the same sample due to variation in degree of aeration, amongst other things, and the test results thus obtained can not be directly related to actual machine performance. t_ RE O PI OBJECT OF THE INVENTION The object of this invention is to provide a method of and means for testing or measuring at least on a comparative basis in a reproducible manner the flow properties of magnetic toners where such flow properties as determined in accordance with this invention can be readily correlated with the flow of the toner on a magnetic applicator roll in actual machine operation. The novel apparatus or test device in accordance with this invention comprises in essence a multi-pole magnet member mounted in such manner that relative motion between the magnet member and a toner support at a predetermined speed results, the toner support being associated with a toner metering feed tube and scales measuring the rate at which the toner spreads over or coates the support. In its preferred form the apparatus for testing flow properties of magnetic toners consists in essence. The method of testing electrostatic developer toners comprises applying the toner to the surface of a toner support and moving it along the support and recording the pattern of movement and is characterised by applying the toner to one surface of the support, producing an array of magnetic field lines in a direction generally normal to the field lines, and determining the characteristics of the toner form the pattern of the toner particles spread along the surface of the toner support under influence of the relative movement the toner support surface and the magnetic field lines. OMPΪ BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional side elevation of a preferred embodiment showing the rotating multi- pole magnet, fixed sleeve and toner feed tube. 5. FIG. 2 is a front elevation of the fixed sleeve and toner feed tube showing the spread scale, drive mechanism and revolution counter, the fixed sleeve being part sectioned. DESCRIPTION OF THE PREFERRED EMBODIMENT 10. Referring now to FIG. 1 in detail, multi-pole magnet roll 1, which forms the array of fixed lines is mounted on axle 2 and arranged to revolve in the direction shown by arrow 3. The multi-pole which forms the toner support magnet roll 1 is 15. enclosed in stationary sleeve 4, fixed sleeve 4 has stop line 5 inscribed thereon. The toner feed tube 6 is mounted vertically above the normal to fixed sleeve 4, and spaced apart therefrom to form a feed aperture 7. When toner is fed 20. into toner feed tube 6 and allowed to flow through feed aperture 7, rotation of multi-pole magnet roll 1 in the direction shown causes toner to travel around fixed sleeve 4 in the direction shown by arrow 8. 25. Referring now to FIG. 2 in detail, multi- pole magnet 1 of FIG. 1 is mounted on axle 2 and enclosed in fixed sleeve 4. Toner feed tube 6 is mounted vertically by means not shown above OMPI and normal to fixed sleeve 4 to define toner feed aperture 7. Stop line 5 is engaged in the position shown on fixed sleeve 4. Calibrated spread scale 9 is engraved in the position shown on fixed sleeve 5. 4. Revolution counter 10 is frictionally engaged to one end of axle 2, and axle 2 is rotated by. being driven by motor 11 through pulleys 12 and 13 and drive belt 14, thus rotation multi-pole magnet roll 1 of FIG. 1. Curved line 15 represents 10. the position of the edges of a toner coating formed on sleeve 4 when this apparatus is used in the manner as hereinafter described. In a preferred embodiment of an apparatus constructed in accordance with FIGS. 1 and 2, 15. the fixed sleeve is an aluminium tube 30mm outside diameter, 0.5mm wall thickness, 110mm long. The fixed sleeve encloses a multi-pole magnet roll 28.5mm outside diameter and 110mm long, having 8 poles symmetrically placed, alternating polarity. 20. The magnetic strength is 1000 gauss maximum measured at the surface of the fixed sleeve. The toner feed tube is also of aluminium, 8mm inside diameter and 55mm long. The toner feed aperture is cut into the lower end of the 25. feed tube in both front and rear section, and is of rectangular cross section 5mm wide and 2mm high. The stop line is inscribed on the sleeve at a distance of 7mm from the upper vertical axis thereof. The spread scale as shown in FIG. 2 3 Q^ comprises eight 5mm divisions, that is 40mm overall. The multi-pole magnet roll is rotated at a fixed speed, normally 270 rpm. OMPΪ VJ Prior to conducting a test, the toner sample is normalized by storing for at least 24 hours at 20°C and 50% relative humidity. The tests are carried out under these same ambient conditions. 5. For the test, a fixed weight of toner is introduced into the feed aperture through the feed tube and the motor is switched on. A convenient quantity of toner is 70 milligrams, but more or less may be used as desired. The motor is switched off 10. when the leading edge of the toner coating reaches the stop line. The number of revolutions is read from the revolution counter and the spread is measured in terms of the total lateral width of the coating, in this instance about 25mm as shown 15.. in FIG. 2. In interpreting the test results, it can be said in general terms that the better the flow properties are of a toner, the less number of revolutions will be required to reach the stop 20. line and the greater will be the spread during these revolutions. Typically we have found in correlation with performance is a wide range of machines, that toners having good flow properties reach the stop line within 18 and 22 revolutions. 25. Toners with excellent flow properties reach the stop line in 17 or less revolutions, whereas toners with poor flow properties need 24 or more revolutions to reach the stop line. The total lateral spread of good toners is about 24 to 28mm, that of toners 30. with excellent flow properties is over 28mm, whereas the spread of toners having poor flow properties is 24mm or less. It will be realised that the flow properties of a toner depend on certain fixed characteristics thereof, such as magnetite content, frictional electrification particularly of low conductivity 5. toners, particle size distribution, particularly proportion of fines and mean particle size, also particle morphology, that is surface topography. In addition the flow properties can be affected by variables such as moisture content, which again 10. depends on the physical and chemical properties of the toner and appears to reach a constant level specific to particular toners after 24 hours of conditioning as referred to in the foregoing. Thus the figures given above of revolutions and 15. spread apply to test conditions as stated earlier, that is 20°C and 507 o relative humidity. Tests can be conducted of course under other ambient condition however the results will be different from those given here and will have to be interpreted 20. accordingly. We have found in general that there is a close correlation between the number of revolutions as measured in accordance with this invention and the capability of the toner in actual machine 25. operation to move under the doctor blade for replen¬ ishing the magnetic brush on the applicator roll, whereas good spread in accordance with the test procedure of this invention correlates to the ability of the toner in actual machine operation 30. to replenish the magnetic brush on the applicator roll in lateral direction that is along its axis. There has been described a method of and means for testing flow properties of magnetic toners. The test results obtainable in accordance with this invention can be directly related to 5. machine performance and can serve the purpose of assessing and comparing toners for suitability in specific applications. Configuration of test apparatus and operational data thereof found satis¬ factory in context of this invention have been 10. disclosed in detail, however such detail disclosure should be construed only in illustrative rather than restrictive sense because departures therefrom by one skilled in the art could equally well serve the desired purpose without departing from the 15. spirit of this invention.

Claims: THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: 1. Apparatus for testing electrostatic developer toners which comprises applying the toner to the surface of a support and moving it along a support and recording the pattern of movement, characterised by a non-magnetic toner support, - means to apply the toner to one surface of the said support, - means to produce an array of magnetic field 10. lines across the support alternating progressively in polarity, and - means for determining the characteristics of the toner from the pattern of the toner spread along the surface of the said support 15. under influence of the relative movement between the said surface and the said magnetic field lines. 2. Apparatus for testing flow properties of magnetic toners according to claim 1 consisting in essence of a cylindrical non-magnetic stationary sleeve which forms the said support and containing 5. therein a rotatably mounted multi-pole magnet roll which forms the said array, means to rotate said magnet roll at predetermined speeds, means adapted to feed a predetermined quantity of magnetic toner onto the surface of said stationary sleeve, 10. markings contained on the surface of said stationary sleeve adapted to define the circumferential and axial spread thereon of said predetermined quantity of magnetic toner fed thereto, wherein such spread OMPI Vy is caused by the rotation of said multi-pole magnet 15. roll and wherein the direction of such circumferential spread is opposite to the direction of rotation of said magnet roll, and means to count the number of revolutions of said multi-pole magnet roll in relation to the spread of said predetermined 20. quantity of magnetic toner as defined by said markings, whereby to determine the characteristic of the said toner. 3. Apparatus for testing flow properties of magnetic toners as in Claim 2, further charac¬ terized by said multi-pole magnet roll being of symmetrical construction comprising an equal number 5. of alternating magnet poles of at least 800 gauss total magnetic strength as measured on the surface of said stationary cylindrical non-magnetic sleeve. 4. Apparatus for testing flow properties of magnetic toners as in Claim 2, further charac¬ terized by said means adapted to feed a predetermined quantity of magnetic toner onto the surface of 5. said stationary sleeve being located a small distance above the uppermost center line thereof, whereby circumferential spread of said magnetic toner around said stationary sleeve is caused to commence at said uppermost center line 10. and towards one side thereof in a direction opposite to the direction of rotation of said magnet roll and to continue towards a marking out the surface of said sleeve defining circum¬ ferential spread of said magnetic toner, and 15. - whereby axial spread of said magnetic toner is caused to commence also at said uppermost center line of said stationary sleeve and to continue concurrently with the circum¬ ferential spread of said magnetic toner within 20. markings on the surface of said sleeve defining axial spread of said magnetic toner. OMPI 5. Apparatus for testing flow properties of magnetic toners as in Claim 4, further charac¬ terized by said marking on the surface of said stationary 5. sleeve defining the circumferential spread of said magnetic toner being located near said uppermost center line of said stationary sleeve but on that side thereof which is opposite to the side towards which circumferen- 10. tial spread of said magnetic toner commences whereby said marking defines a circumferential spread of said magnetic toner over a distance nearly equivalent to the circumference of said stationary sleeve, and 15. - said markings on the surface of said stationary sleeve defining the axial spread of said magnetic toner being located on the same side of said stationary sleeve which contains said marking defining the circumferential 20. spread of said magnetic toner near the uppermost center line thereof. 6. The method of testing flow properties of magnetic toners with apparatus constructed substan¬ tially as defined in claim 1 which comprises applying the toner to the surface of a support and moving it 5. along a support and recording the pattern of movement, characterised by the steps of - applying the toner to one surface of a non-mag¬ netic support producing an array of magnetic field lines across the support alternating 10. progressively in polarity causing relative movement between the said support and the array of magnetic field lines in a direction generally normal to the field lines, and 5. - determining the characteristics of the toner from the pattern of the toner particles spread along the surface of the support under influence of the relative movement between the surface and the magnetic field lines. 7. The method of claim 6 characterised in that the said toner support is cylindrical and the said magnetic field lasers are produced by rotatively a multi-polarity magnet roll within it 5. whereby to cause movement over the surface of the said support of magnetic toner, in a direction opposite to the rotation of the said roll of the toner over the said surface. 8. The method of testing flow properties of magnetic toners with apparatus constructed substantially as in Claim 2, said method consisting essentially of the steps of 5. — feeding a predetermined quantity of magnetic toner onto the uppermost center line of a non-magnetic stationary sleeve containing a rotatably mounted multi-pole magnet roll therein, 10. - commencing rotating said magnet roll by driving means in one direction to thereby cause circumfer¬ ential spread of said magnetic toner around said stationary sleeve to commence at said uppermost center line thereof in opposite direction as well 15. as to thereby cause axial spread of said magnetic toner on the surface of said stationary sleeve f OMH to commence also from said uppermost center line thereof and to continue concurrently with the circumferential spread of said magnetic 20. toner, - simultaneously with commencing rotating said magnet roll commencing counting the number of revolutions of said magnet roll, - ceasing rotating said magnet roll when said 25. circumferential spread of said magnetic toner around said stationary sleeve reaches a marking contained on the surface thereof defining a distance of circumferential spread nearly equivalent to the circumference of said station- 30. a r y sleeve, noting the number of revolutions of said magnet roll required to cause circumferential spread of said magnetic toner over a distance nearly equivalent to the circumference of 35. said stationary sleeve, - noting the distance between markings on said stationary sleeve defining the axial spread of said magnetic toner, and - defining the flow properties of said magnetic 40. toner in terms of number of revolutions required for a circumferential spread over a given distance and in terms of width of axial spread over a number of revolutions.

Inventors: LIMA-MARQUES LUIS, SPOONER ANTONY NIGEL, LIMA-MARQUES, LUIS, SPOONER, ANTONY, NIGEL
Applicants: AUSTRALIA RES LAB, RESEARCH LABORATORIES OF AUSTRALIA PTY. LIMITED
Application year: 1984
Main classification: G01N11
IPC codes: G01N11, G01N27, G01N33, G03G15