Powder dispensing apparatus with metering roll

Abstract

 A powder dispenser comprises a container (16) having therein a rotatable metering roll (32) which is engaged by lower wall portions (40) and (50) to provide a surface portion exposed below the container. A metering portion of the roll (45) entraps powder as the roll rotates past wall (40) to dispense it by gravity from the dispenser as the portion leaves wall (40). The roll is either eccentrically .mounted as shown, or has a non-circular cross section in order to vibrate the powder in the container as the roll rotates. This reduces powder caking.

Description

[0001] The present invention relates to methods and apparatus for metering powder from a container and is especially, but not exclusively, useful in xerographic copier/duplicator types of equipment.

[0002] It has been known for many years to transfer powder from a reservoir into a processing area by means of a rotating roller which has flexible plates engaging the peripheral surface of that roller to provide a dynamic seal. The powder can be entrapped or adhered to the roller surface as the roller surface passes through the material in the reservoir area, with this material being released by the roller after it has passed beyond the containment defined by the peripheral edge engaging seal plates. U.S. Patent Specification No. 3,114,482 shows such an arrangement.

[0003] Similar metering configurations have been adapted by the xerographic industry for the purpose of dispensing toner from a container to the active developer area of the copier. For instance, U.S. Patent Specification No. RE28,589 shows such an arrangement wherein the toner transporting element comprises a roller having a series of longitudinal peripheral grooves on its external surface. The toner is trapped in these grooves and transported past the flexible sealing plates so as to be dropped into the active developer sump for a copier. Various forms for entrapping toner on the surface of a metering roller for dispensing from a reserve chamber have also been known. For instance, metering rollers have been made with porous or other toner-absorbing material forming the basic roller elements or the surface thereof. Other metering rollers have included outwardly extending ridges, and even just a single inwardly directed groove along the roller surface.

[0004] Unfortunately, the toner in the reserve sump tends to form a cake-like consistency along the walls of the container above the dispenser. Thus, a surface monitoring mechanism associated with the toner in the reservoir either erroneously indicates that there is a minimum toner level because it fails to sense the presence of caked toner along the sides, or erroneously indicates the presence of plentiful toner by being held in an artificial level position by the caked toner. Techniques employed in the past in an effort to overcome this caking problem have enjoyed varying degrees of success. One method employed is to maintain continuously moving stir paddles along the container wall. Another is to employ vibratable screens or the like along the container wall, such as that shown in U.S. Patent Specification No. 3,840,156. The caking problem mentioned is discussed in U.S. Patent Specification No. 3,964,648 which endeavours to resolve it by an arrangement radically different from the present invention in that it employs rotating rod that pivots within the cylindrical storage container and in proximity to its walls so as to break up the cake and also to throw a portion of toner out of the reservoir into the sump of the developer.

[0005] U.S. Patent Specification No. 4,044,719 shows an arrangement wherein a grooved, rotating replenisher meter roll engages a spring-like plate so that the spring-like plate will scrape loose any toner that has caked into the metering roll, but does not address the resolution of the reservoir caking problem.

[0006] The present invention is directed to a system in which reservoir caking is reduced by employing a metering roll which itself agitates powder in a container. This system is simpler and, as it employs no extra devices apart from the roll, cheaper to produce than the prior art devices.

[0007] According to the invention, there is provided powder dispensing apparatus comprising a powder container including a lower wall portion biassed into sealing contact with the surface of a rotatable metering roll positioned within the container but having an exposed surface portion therebelow, the metering roll surface having a section configured to entrap a metered quantity of powder from the container as it passes the wall portion and to discharge the metered quantity by gravity from the dispensing apparatus as it leaves the wall portion, characterised in that the surface of the metering roll, relative to the axis of rotation thereof, is so shaped as to impart vibratory motion to the powder in the container as the roll rotates, thereby to agitate the powder to reduce caking therein.

[0008] The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

FIG. 1 is a partially sectioned side view of a developer for a copier/duplicator employing a toner power dispenser embodying the present invention;

FIG. 2 is a top view of the FIG. 1 apparatus;

FIG. 3 is an expanded detail view particularly showing the roll operation in the FIG. 1 and 2 structure;

FIG. 4 is a partially broken and sectioned view of the roll mounting and plate sealing arrangement of the FIGS. 1-3 embodiment;

FIG. 5 is a partially broken and sectioned view of another embodiment of the present invention;

FIG. 6 is a partially sectioned and broken view of yet another embodiment of the present invention;

FIG. 7 is an expanded view illustrating the metering operation of the FIG. 6 embodiment;

FIG. 8 is an isometric view of an alternative arrangement for sealing the edge of the flexible plates;

FIG. 9 is a sectioned and broken view of the flexible plate seal of FIG. 8 showing its interrelationship to a sidewall; and

FIG. 10 is a sectioned and broken view of an alternative metering roll sealing configuration.

[0009] The various embodiments of the invention will be shown and described in conjunction with the environment of the developer mechanism for a xerographic copier/duplicator. As will be more apparent from the subsequent description, the structure chosen for these examples cooperate to eliminate toner sticking or bridging to the sidewalls of a toner replenisher chamber for a copier, thereby allowing relatively complete evacuation of the toner from the replenisher chamber on demand by the developer.

[0010] In FIG. 1, a segment 10 of a photoconductive surfaced drum or a photoconductor belt guide is shown in its generally operative relationship to the developer 12. The housing for developer 12 includes an opening 15 in which a toner charging or loading device can be attached. Thus, the toner is initially loaded and stored in replenisher chamber 16. The toner is metered from chamber 16 into the auger chamber 18, where it is added to the developer mix which is transported along the lower portion of chamber 18 by auger 19. Each end of divider wall 20 has an opening such as 21 with the mix entering the developer chamber 22 through the opening at one end. Auger element 24 rotates oppositely from auger 19. so that toner is forced through the opening at the opposite end from chamber 22 through the opening at the opposite end of wall 20, thereby continuously recirculating the mix between chamber 18 and 22 through the interconnecting ports or openings such as 21.

[0011] The mix contained in chamber 22 is attracted to the surface of magnetic developer roll 25 for ultimate contact against the photoconductive surface'of drum or belt guide 10 to provide development of the image on the photoconductive surface of 10. The operation of this mechanism is conventional.

[0012] Inside replenisher chamber 16 is a metering roll 30, which is mounted on shaft 32 for rotation eccentrically relative to the central axis of roll 30. Chamber 16 also includes bar 35 which, as can be seen in FIGS. 1 and 2, extends through the sidewalls of chamber 16 with outer end 36 being positioned to ride on the upper surface of a cam 37 (see FIG. 2). Microswitch 38 is located so as to be actuated by arm 36 of rod 35 when the level of toner in chamber 16 has dropped below some minimum. Each time that shaft 32 is rotated, cam 37 likewise rotates, lifting arm 36 and allowing rod 35 to drop onto the upper surface of the toner contained in chamber 16, thereby ensuring that rod 35 is always following the surface level of the toner contained in chamber 16. Note that rod 35 functions as a combination toner level sensor and toner agitator in that the inner segment 39 pivots along the wall inside chamber 16, thus augmenting the loosening of toner from the housing sidewall as the toner level drops.

[0013] A flexible plate 40, fabricated from spring steel or the like, is mounted as shown in FIGS. 1 and 3. That is, plate 40 is formed with a bend so as to be insertable between the retainer 41 and nub 42 of centre wall 20. This arrangement ensures that plate 40 is biased toward the peripheral surface of roll 30 and maintains constant engagement therewith during full rotation of roll 30. The dashed position of plate 40 as shown at 44, is obtained as roll 30 rotates in the direction indicated by the arrows. Roll 30 has grooves or flat areas 45 separated by one or more peripheral bridges 46. In the example shown, two grooves 45A and 45B, formed by flat cuts, are separated by bridges 46A, 46B, and 46C. As roll 30 rotates eccentrically around shaft 32, the grooves 45 entrap toner which is transported past the outer edge of blade 40 and allowed to drop into the auger chamber 18. Bridges 46 prevent the outer edge of blade 40 from scraping the toner out of the entrapment areas 45 as it passes the leading edge 47 of plate 40.

[0014] On the opposite or outer wall 48, another flexible blade or plate 50 is mounted and retained within nubs 51 and 52 in a manner somewhat similar to blade 40. That is, the spring-like nature of blade 50 and its attachment between nubs 51 and 52 causes blade 50 to be continuously biased toward the peripheral surface of roll 30 so that outer edge 53 remains in continuous contact with the surface of roll 30. Accordingly, blade or plate 50 flexes to the position shown in dashed lines at 54, and outer edge 53 not only ensures that the toner contained in chamber 16 does not escape, but also provides a scrubbing function to loosen any toner adhering to the peripheral surface of roll 30 to cause it to drop into the auger sump 18. The result of the eccentric movement of roll 30 through chamber 16, as well as the flexing action of spring plates 40 and 50 in response to rotation of metering roll 30, is that the toner contained within replenisher chamber 16 undulates, thereby preventing it from sticking or bridging on the housing sidewalls 20 and 48. This augments complete evacuation of replenisher chamber 16. In effect, blade 40 acts as a metering spring in conjunction with roll 30, whereas blade 50 acts as a cleaning spring, although both provide continuous sealing.

[0015] FIG. 4 illustrates a typical arrangement for sealing the mechanical mounting of roll 30, relative to sidewall 55. Sidewall 55 is constructed with a slight depression therein, into which a sponge-like member 56 is bonded or otherwise secured with member 56 being fabricated from any acceptable closed cell material such as polyurethane or the like. Rotational power to roll 30 is coupled through shaft 32, which is further mounted within collar 57. The compressible nature of member 56 allows it to maintain a sealed relation with the end face of roll 30 so that toner will not migrate through the mounting hole for shaft 30 through sidewall 55 and collar assembly 57. The resilient sealing member 56 also engages the outer edges of flexible plates 40 and 50 to prevent escape of toner from chamber 16. That is, the bead on the outer edges of plates 40 and 50 somewhat compress member 56 in a manner similar to roll 30, thereby completing the seal of chamber 16 despite the flexing movement of plates 40 and 50. This interrelationship can be seen in FIGS. 1, 3, and 4.

[0016] In operation, power from a source (not shown) is applied to shaft 59 (note FIG. 2). Clutch 58 is operable in response to electrical or mechanical actuation to couple the rotary power from shaft 59 to shaft 32 and thus, to roll 30. The typical controls, having determined by whatever means that additional toner is to be metered from replenisher chamber 16, causes clutch 58 to be actuated and one or more rotations of roll 30 to be accomplished until the controls determine that adequate toner has been dispensed. In the course of rotation of roll 30, toner is entrapped in notches 45 on roll 30, transported past the sealing flexible wall 40, and disgorged into auger chamber 18 with the further assistance of scraper edge 53 on flexible wall 50. Walls 40 and 50 oscillate between the positions shown in FIG. 3, maintaining continuous jostling or jogging of the toner contained within chamber 16. Cam 37 likewise causes level sensor bar 35 to reciprocate to aid in sidewall build-up prevention and level sensing of the amount of toner contained within chamber 16.

[0017] A somewhat different embodiment of the present invention is illustrated in FIG. 5, wherein the replenisher chamber 70 is shown with a charge of toner 71 contained therein. The combination toner level sensor and toner agitator 72 is here shown with a somewhat open grid configuration, but pivotable around shaft 74, which has an arm external to chamber 70 for actuating a microswitch in response to a cam movement similar to that discussed previously for level sensor bar 35. The generally triangular shape of the lateral member such as 73 aids both in assuring that sensor 72 is brought to rest on the top of the toner and in breaking up the toner lumps as it is dropped into chamber 70.

[0018] The eccentrically mounted metering roll 75 is sealed with a metering spring-type of plate or blade 76 on one side, and a cleaning spring-type of blade 77 on the other, also in a manner somewhat analogous to that previously described, at least as far as mountings thereof relative to sidewalls 78 and 79. Roll 75 has a continuous longitudinal groove 80 therein, without any bridging since groove 80 will entrap toner within itself and blade plate 76 seals the mouth of groove 80 as it passes from chamber 70 to the auger chamber 81. In this case, the outer edge 82 of blade plate 77 is arranged so as to enter groove 80 and assure scrubbing of any toner from groove 80 before it reenters chamber 70.

[0019] Yet another arrangement is shown in FIGS. 6 and 7 wherein the toner within chamber 86 is sensed by toner level arm 88, having a single inverted V-shaped transverse arm 89 for resting on the top of the toner and also aiding in lump break-up. The eccentrically mounted metering roll 90 has an oval shaped cross-section in this example and interfaces with spring blades or plates 91 and 92 in a manner similar to that previously described. However, eccentrically mounted roll 90 has an outwardly extending ridge or raised metering boss 95 thereon for the purpose of metering-toner past sealing blade plate 91 with plate 92 acting as a scraper as is shown in detail in FIG. 7. The toner in reservoir chamber 86 oscillates vertically in accordance with arrows 96 and 97 in response to rotation of metering roll 90. The noncircular cross-section of metering roll 90 adds a churning effect to the toner in the replenisher chamber as roll 90 rotates. Note that the metering roll can be configured with a circular cross-section but offset rotational axis, or with a non- circular cross-section but central axis rotation, as long as an oscillatory motion is imparted to one or more of the peripheral sealing plates.

[0020] An alternative arrangement for sealing the replenisher storage chamber relative to the sidewalls is illustrated in FIGS. 8 and 9. Flexible plate 100 is similar in construction and operation to the metering and cleaning blades 40 and 50 of FIGS. 1 and 3. Blade 100 is sealed relative to sidewall 101 by a resilient sealing pad 102. Pad 102 is made of a compressible material such as polyurethane foam with a pressure sensitive adhesive surface for adhering in wrapped relation around the edge of plate 100. Thus, compression of the wrapped edge of pad 102 establishes a dynamic seal interface 103 with sidewall 101 to prevent escape of toner despite flexing movement of spring plate 100.

[0021] FIG. 10 shows a configuration for sealing the metering roll 104 relative to sidewall 101 in a manner suitable for use concurrently with FIGS. 8 and 9. Roll 104 is mounted for eccentric rotation by drive shaft 105 coupled to a power source (not shown) on the other side of sidewall 101. Sealing assembly 106 is formed of a compressible core 107 which is affixed to roll 104 by bonding or adhering at interface 108 as by a pressure sensitive adhesive or the like. The opposite side of seal assembly 106 is formed by a wear-resistant layer 109 such as Mylar (trademark of E. I. DuPont de Nemours & Co.). Seal assembly 106 is installed in a generally compressed relation on the end of metering roll 104 and remains in compressed relation between roll 104 and sidewall 101 during the full rotational operation of roll 104. Accordingly, toner is prevented from escaping from the storage chamber into either the developer sump or the mounting hole for drive shaft 105.

[0022] Note that the reciprocating motion of the metering roll surface as shown in the preferred embodiments imparts some pulsating motion to the reservoir toner independent of the flexible plates. Thus, the flexible walls can be implemented by relatively rigid plates mounted and biased for a plunger type of movement toward the metering roll surface. The combination of the spring-like flexible walls and the eccentric movement of the metering roll surface in accordance with the preferred embodiments is advantageous in that the greatest amount of agitation of the toner in the replenisher chamber is obtained.

Claims

1. Powder dispensing apparatus comprising a powder container including a lower wall portion biassed into sealing contact with the surface of a rotatable metering roll positioned within the container but having an exposed surface portion therebelow, the metering roll surface having a section configured to entrap a metered quantity of powder from the container as it passes the wall portion and to discharge the metered quantity by gravity from the dispensing apparatus as it leaves the wall portion, characterised in that the surface of the metering roll, relative to the axis of rotation thereof, is so shaped as to impart vibratory motion to the powder in the container as the roll rotates, thereby to agitate the powder to reduce caking therein.

2. Apparatus as claimed in claim 1 further characterised in that said roll has a substantially circular cross section and is mounted eccentrically about said axis to effect said vibratory motion.

3. Apparatus as claimed in claim 1 further characterised in said roll is mounted centrally about said axis but has a non-circular cross section to effect said vibratory motion.

4. Apparatus as claimed in any of claims 1 to 3 further characterised in that said lower wall portion is formed from resilient material and is biassed into contact with the roll such as to vibrate as the roll rotates to effect further vibratory motion to the powder in the container.

5. Apparatus as claimed in any of the previous claims further characterised by a further lower wall portion biassed into sealing contact with the surface of the roll, the wall portions defining the edges of said exposed surface portion of the roll, said further lower wall portion being of resilient material such as to vibrate as the roll rotates to effect further vibratory motion to the powder in the container.

6. Apparatus as claimed in any of the previous claims further characterised in that said section of the metering roll surface includes an identation to retain powder and a bridge over which the, or each, lower wall portion rides.

7. Apparatus as claimed in any of claims 1 to 5 further characterised in that said section of the metering roll includes a projection over which the, or each, lower wall portion rides.

8. Apparatus as claimed in any of the previous claims, further characterised in that the metering roll and the, or each, wall portion extend over substantially the length of the container.

9. Apparatus as claimed in any of the previous claims, further characterised in that said container comprises the toner dispenser of the developer unit of a xerographic copier, and toner is dispersed therefrom by the metering roll into the developer sump of the developer unit.

Drawing