Developing device and method for locating a toner restricting member at a developing device

Abstract: A developing device includes a movable toner carrier (14) having its surface deposited with a toner and toner restricting member (16) arranged parallel to the toner carrier. The toner restricting member comprises a retaining rod made of an elastic material and a contact unit (18) provided on the outer periphery of the retaining rod, extending in an axial direction of the retaining rod and having at least one contact area (18a) set in contact with the surface of the toner carrier.

Description: The present invention relates to a developing device as defined by the features of the preamble of claim 1 or 8, for an electrophotographic apparatus which utilizes a one-component toner developing method. The invention also relates to a method for setting a toner restricting member of a developing device. An electrostatic type electrophotographic apparatus for use, for example, in a copier, facsimile equipment and laser printer apparatus has a photosensitive drum with a photosensitive layer formed thereon. A charger, exposure device, developing device, transfer device and fixing device are located along and around the photosensitive drum. As the photosensitive drum is rotated, a charge is formed by the charger on the surface (photosensitive layer) of the photosensitive drum and a toner is supplied by the developing device on the surface of the photosensitive drum to form a toner image on the drum surface. Then a charge opposite in polarity to the charge on the toner image is applied to a recording paper sheet by the transfer device to allow the toner image on the drum surface to be transferred to the recording sheet under an electrostatic force. Finally, the toner image on the recording sheet is fixed by the fixing device. Further, a cleaning device has to be provided so as to continuously perform a recording process. The toner remaining on the drum surface after transfer is removed by the cleaning device. The charge remaining on the drum surface is removed by the discharger, followed by a charging step in a continuous cycle. Some developing device to be mounted on the electrophotographic apparatus utilizes a one-component toner developing method. In this type of device, a non-magnetic toner not containing any carrier is pressed by a toner restricting member against the surface of a toner carrier whereby the toner is formed as a thin layer on the carrier surface, while being triboelectrically charged. Fig. 40 shows this type of conventional developing device. This developing device is located parallel to a photosensitive drum 9 and has a casing 1, agitator 2, toner feed roller 3, collecting blade 5 and toner restricting member 6. The casing 1 has substantially the same length as that of the photosensitive drum and defines an inner space where a one-component toner T is stored. The casing 1 has an opening at which the developing roller 4 is located. The casing 1 is arranged parallel to the photosensitive drum 9. The toner feed roller 3 and developing roller 4 have substantially the same length as that of the photosensitive drum 9 and are arranged parallel to the photosensitive drum 9 such that they are rotatably supported at the casing 1 side. The developing roller 4 is placed in contact with the outer peripheral surface of the drum 9, noting that the developing roller 4 is formed of electroconductive rubber and fixed to the outer periphery of a metal shaft 4a. The toner restricting member 6 is located above the developing roller 4 in a manner to be parallel to the photosensitive drum 9. The toner restricting member 6 comprises a leaf spring 7 made of metal and a blade contact unit 8 made of an elastic material, such as rubber. The leaf spring and blade contact unit 8 have substantially the same length as that of the developing roller 4. The blade contact unit 8 is fixed to one side edge of the leaf spring 7 along its length. The other side edge of the leaf spring 7 is fixed to the casing 1. The blade contact 8 is placed, under an elastic force of the leaf spring 7, in contact with the outer periphery of the developing roller 4. The operation of the developing device is as follows: A nonmagnetic one-component toner T in a toner storage area of the casing 1 is fed to the toner feed roller 3 by the rotation of the agitator 2. The toner feed roller 3 and developing roller 4 are rotated by a rotation device, not shown. The toner is fed by the toner feed roller 3 onto the outer peripheral surface of the developing roller 4. The blade contact unit 8 of the toner restricting member 6 allows the toner T which is deposited on the peripheral surface of the developing roller 4 to be pressed against the outer periphery of the developing roller 4. By so doing, the blade contact unit 8 forms the toner T as a thin layer on the outer periphery of the developing roller 4 and, at the same time, the toner is tribo electrically charged. The charged toner T is deposited onto the outer periphery of the drum 9 to allow an electrostatic image which is formed on the outer periphery of the drum 9 to be developed into a visible image. Such a conventional developing device has drawbacks as will be set forth below. The toner restricting member 6 is of such a type that the contact unit 8 is fixed directly to the leaf spring 7. The leaf spring 7 performs a double function of holding the blade contact unit 8 in place and bringing the blade contact unit 8 in contact with the developing roller 4 by its spring force. For this reason, a varying state of the leaf spring 7 directly acts upon the blade contact unit 8, thus varying the state in which the blade contact unit 8 makes contact with the developing roller 4. That is, the leaf spring 7 has substantially the same length as that of the developing roller 4 and, because it is provided in a restricted space, is slender in configuration. For this reason, the spring constant is set to a larger value so as to obtain a predetermined spring force. If, however, the spring constant of the leaf spring 7 is set to a larger value, then the pressure force with which the blade contact unit 8 is pressed by the leaf spring 7 against the developing roller 4 varies greatly in accordance with the wear of the blade contact unit 8 caused by frictional contact with the developing roller 4. Further, the leaf spring 7, being longer in its lateral direction, is liable to be deformed in its longitudinal direction, thus causing a local variation of the pressure force with which the blade contact unit 8 is pressed by the leaf spring 7 against the developing roller 4. The force with and position in which the contact unit 8 is contacted with the developing roller 4 depend heavily upon the thickness of the toner layer on the developing roller 4 and amount of toner charged on the roller. The spring force of the leaf spring 7, being largely varied, causes a larger variation in the thickness of the toner layer on the developing roller 4 and in the amount of toner charged thereon. Therefore, an image of poor quality is formed on the recording sheet, thus failing to obtain a better-quality image. Further, the spring 7 is manufactured by a discharge machining method and hence involves more manufacturing cost. From EP-A-390 605 there is known a developing unit disclosing the features of the preamble of claim 1 or claim 8. This known developing device comprises a rotatable toner carrier on the surface of which the toner is deposited and a toner restricting member is arranged parallel to the toner carrier. The toner restricting member comprises a retaining rod made of a rigid substance and a contact unit which is made of an elastic material and which is provided on an outer periphery of the retaining rod so as to extend along the axial direction of the retaining rod. The forward end of the contact unit can be set in contact with the surface of the toner carrier and a spring is provided to directly press the contact unit onto said surface. Thus, the problem is posed that the pressure exerted on the toner carrier and a degree to which the contact unit contacts the toner carrier depends on the power of the spring elements so that variations in the power of the spring directly influence the pressure between the contact unit and the toner surface and the toner layer. A non-magnetic single component development device is known from JP-A-60 046 577. In this device a semi-cylindrical control member is adhered to the front edge of an elastic plate to constitute the layer forming member for a developer. Depending on the radius of curvature of the control member the developer feeding performance should be improved according to this device. A similar developing device is also disclosed in EP-A 270 104, in which a toner restricting member arranged parallel to a rotatable toner carrier and comprising retaining rods made of a rigid substance is provided to be in contact with the surface of the toner carrier in order to adjust the toner layer thickness thereon. Finally, a clearing device for an electro photographic printing device is described in JP-A-58 068 776. The cleaning device comprises a rotatable shaft arranged in parallel to the axis of a toner carrier. A plurality of cleaning blades are provided in radial directions extending from the shaft and the forward ends of the cleaning blades can be sequentially set in contact with the surface of the toner carrier upon rotation of the shaft. It is the object of the present invention to provide a developing device and a method for setting a toner restricting member of a developing device for an electro photographic apparatus which ensure a highly reliable developing operation through a stable contact with a developing roller. According to a further aspect of the present invention a developing device for an electro photographic apparatus should be provided which can use one toner restricting member for a prolonged period of time without the need of using a plurality of toner restricting members and, in this sense, is of economic advantage. According to the invention there is provided a developing device comprising: a casing; a toner carrier rotatably provided in the casing and having a surface for holding a one-component toner, for transferring the toner held by the surface of the toner carrier by rotation of the toner carrier ; and a toner restricting member non-rotatably provided in the casing in parallel to the toner carrier, the toner restricting member comprising: a retaining rod formed of a rigid substance; and a contact unit formed of synthetic resin having elasticity, and provided on an outer periphery of the retaining rod in such a manner as to extend in an axial direction of the retaining rod, the contact unit having a contact portion having a forward end for contacting the surface of the toner carrier ; characterized in that, the contact portion extends from the outer periphery of the retaining to the end of the contact portion to have a height smaller than a diameter of the retaining rod, said retaining rod having a circular cross section or a polygonal cross section and being held in the casing such that said forward end of said contact portion contacts the surface of the toner carrier. According to the invention there is also provided a developing device comprising: a casing; a toner carrier, rotatably provided in the casing and having a surface for holding a one-component toner, for transferring the toner held by the surface of the toner carrier by rotation of the toner carrier; and a toner restricting member non-rotatably provided in the casing in parallel to the toner carrier, the toner restricting member comprises: a retaining rod formed of a rigid substance; and a contact unit formed of synthetic resin having elasticity, and provided on an outer periphery of the retaining rod in such a manner as to extend in an axial direction of the retaining rod, characterized in that the contact unit has a plurality of contact portionseach having a forward end for contacting the surface of the toner carrier, each of the contact portions extending from the outer periphery of the retaining rod to the end of each contact portion to have a height smaller than a diameter of the retaining rod and said retaining rod having a circular cross section or a polygonal cross section and being held in the casing such that the forward end of one of said contact portions contacts the surface of the toner carrier. According to the invention there is also provided a method for setting a toner restricting member of a developing device, comprising the steps of: preparing a toner restricting member comprising: a retaining rod formed of a rigid substance and having a circular cross section or a polygonal cross section; and a contact unit formed of synthetic resin having elasticity, and provided on an outer periphery of the retaining rod in such a manner as to extend in an axial direction of the retaining rod, the contact unit having a contact portion having an end, which contacts a surface of a toner carrier, the contact portion extending from the outer periphery of the retaining rod to the end of the contact portion to have a height smaller than the diameter of the retaining rod; and locating the toner restricting member non-rotatably in a casing such that the toner restricting member is arranged in parallel to the toner carrier, and bringing the contact portion of the contact unit into contact with the surface of the toner carrier. According to the present invention, the rigid substance can be used for the blade retaining rod and the blade can be held in a stable way so that the blade can be stably set in contact with the toner carrier. Further, it is possible to obtain a high accurate toner restricting member using a combination of the retaining rod and contact unit of high dimensional accuracy and to obtain an image of excellent quality. Since one toner restricting member has a plurality of contact areas, it can be used over an extended period of time by switching one contact area to another in accordance with the extent of the latter's wear. The toner restricting member using such a single specific contact unit as already set out above ensures a higher economic advantage than a plurality of toner restricting members each equipped with a single contact unit have to be used to achieve the same advantage as that of the present invention. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Fig. 1 is an expanded, perspective view showing a developing device according to a first embodiment of the present invention; Fig. 2 is a cross-sectional view showing the developing device of Fig. 1; Fig. 3 is a cross-sectional view showing a toner restricting member for the developing device of Fig. 1; Fig. 4 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a round bar; Fig. 5 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a round bar; Fig. 6 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a round bar; Fig. 7 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a round bar; Fig. 8 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a circular cylinder; Fig. 9 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a circular cylinder; Fig. 10 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a circular cylinder; Fig. 11 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a circular cylinder; Fig. 12 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square rod; Fig. 13 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square rod; Fig. 14 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square rod; Fig. 15 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square bar; Fig. 16 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square cylinder; Fig. 17 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square cylinder; Fig. 18 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square cylinder; Fig. 19 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square cylinder; Fig. 20 is a cross-sectional view showing a developing device according to a second embodiment of the present invention; Fig. 21 is a perspective view showing a toner restricting member of the device of Fig. 20; Fig. 22A shows a toner restricting member whose position is switched to another position for setting; Fig. 22B shows a toner restricting member whose position is switched to another' position for setting; Fig. 23 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a round bar; Fig. 24 is a perspective view showing a toner restricting member using a retaining rod formed of a round bar; Fig. 25 is a cross-sectional view showing the toner restricting member of Fig. 24; Fig. 26A shows a toner restricting member whose position is switched to another position for setting; Fig. 26B shows a toner restricting member whose position is switched to another position for setting; Fig. 26C shows a toner restricting member whose position is switched to another position for setting; Fig. 27 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a round bar; Fig. 28 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a circular cylinder; Fig. 29 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a circular cylinder; Fig. 30 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a circular cylinder; Fig. 31 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a circular cylinder; Fig. 32 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square rod; Fig. 33 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square rod; Fig. 34 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a hexagonal rod; Fig. 35 is an end view showing a toner restricting member of Fig. 34; Fig. 36A is views showing the toner restricting member whose position is switched to another position for setting; Fig. 36B is views showing the toner restricting member whose position is switched to another position for setting; Fig. 36C is views showing the toner restricting member whose position is switched to another position for setting; Fig. 37 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square rod; Fig. 38 is a cross-sectional view showing a toner restricting member formed of a square cylinder; Fig. 39 is a cross-sectional view showing a toner restricting member using a retaining rod formed of a square rod; and Fig. 40 is a cross-sectional view showing a conventional developing device. A developing device according to a first embodiment of the present invention will be explained below. The developing device of the first embodiment is of such a type that a contact unit with one contact area is provided on a retaining rod of a toner restricting member. Now the first embodiment of the present invention will be explained below: In the embodiment shown in Figs. 1 to 3, a rod of a circular cross-section is employed as a retaining rod of a toner restricting member. Figs. 1 and 2 show a diagrammatic view showing a developing device. The developing device is located parallel to a photosensitive drum (image carrier) provided in a body of an electrophotographic apparatus. The developing device comprises a casing 11, agitator 12, toner feed roller 13, developing roller (toner carrier) 14, collection blade 15 and toner restricting member 16. The casing 11 has substantially the same length as that of a photosensitive drum 23 and defines a space where a nonmagnetic toner T not containing any carrier is stored and where the agitator 12 is located. An opening is provided at that area facing the photosensitive drum 23 where the toner feed roller 13 and developing roller 14 are located. The casing 11 is provided parallel to the photosensitive drum 23. The toner feed roller 13 and developing roller 14 have substantially the same length as that of the photosensitive drum 23. The developing roller 14 is made of electroconductive roller and fixed to the outer periphery of a metal shaft 14a. The toner feed roller 13 and developing roller 14 are located parallel to the drum 23 such that these rollers are rotatably supported. The developing roller 14 is located at an outer side relative to the toner feed roller 13 such that the roller 14 is set in contact with the outer periphery of the drum 23. The collection blade 15 is mounted on the casing 11 at an area below the developing roller 14 and set in contact with the developing roller 14 so that a toner T does not leak from between the developing roller 14 and the casing 11. The toner restricting member 16 has a retaining rod 17 and contact unit 18 as shown in Fig. 3. The retaining rod 17 has substantially the same length as that of the photosensitive drum 23, is made of a rigid substance, that is, a metal such as carbon steel and stainless steel, and is comprised of a rod whose cross-section is circular. The metal rod is manufactured by a cold-drawing method. The contact unit 18 is warkead-like in cross-section, that is, of a blade-like configuration, and has the same length as that of the retaining rod 17. The contact unit 18 is made of an elastic material, such as insulating rubber. The contact unit 18 is provided on the portion of the outer periphery of the retaining rod 17 and extends in the longitudinal direction of the retaining rod 17. The base end of the contact unit 18 is abutted against the outer periphery of the retaining rod 17 and thermocompression bonded to the retaining rod. The forward end of the contact unit 18 serves as a contact area 18a contacting with the outer periphery of the developing roller 14, that is, the contact unit 18 has a single contact area. The toner restricting member 16 is situated above the developing roller 14 and extends in a direction parallel to the photosensitive drum 23 with its contact unit down. Both the ends of the retaining rod 17 are so supported on the opposed walls of the casing 11 as to be displaceable in an up/down direction but not in a rotational direction. That is, caps 19A and 19B are fitted over the corresponding ends of the retaining rod 17 as shown in Fig. 1 and, each, have a circular configuration corresponding to the end portion of the retaining rod (round rod) 17 with a cutout provided to allow the cap (19A, 19B) to be fitted over the end of the retaining rod 17. Vertically extending ribs 20A and 20B are provided, as straight ribs, at both outer ends of the caps 19A and 19B in an up/down direction. A pair of vertically extending grooves 21A, 21B are provided at the opposed walls of the casing 11 and opened at the upper edges of the opposed walls of the casing 11. The straight ribs 20A and 20B of the caps 19A and 19B fitted over the ends of the retaining rod 17 are inserted into the associated grooves 21A and 21B of the casing 1 so that the retaining rod 17 is movably, but nonrotatably, supported on the casing 11. In this state, the contact area 18a of the contact unit 18 is placed, under an elastic force of the contact unit 18 by itself, on the outer periphery of the developing roller 14. When the retaining rod 17 is depressed by a spring 22 from above, then the retaining rod 17 is stably so supported as to allow the contact unit 18 to be placed in stable contact with the outer periphery of the developing roller 14. The operation of the developing device is as follows: A nonmagnetic toner T in a toner storage section of the casing 11 is fed onto the toner feed roller 13 by the rotation of the agitator 12. The toner feed roller 13 and developing roller 14 are rotated by a rotation device, not shown. The toner T is deposited by the toner feed roller 13 onto the outer periphery of the developing roller 14. The toner T on the outer periphery of the developing roller 14, upon being passed through the contact unit 18 of the toner restricting member 16, is pressed by the contact area 18a of the contact unit 18 against the outer periphery of the developing roller 14. By so doing, the toner T is deposited as a thin layer on the outer periphery of the developing roller 14 while, at the same time, being triboelectrically charged. Further, the toner T is deposited onto the outer periphery of the photosensitive drum 23. In the developing device, since the toner restricting member 16 includes the retaining rod 17, composed of a rigid substance, and the contact unit 18, composed of rubber, fixed to the retaining rod 17 and constituting a portion of the outer periphery of the retaining rod 17, an advantage is obtained as will be set out below. The retaining rod, being made of a rigid substance, is less likely to be deformed in the axial direction upon reception of any external force, thus allowing the contact area 18a of the contact unit 18 to be stably contacted with the outer periphery of the developing roller 14 in the axial direction of the developing roller. When the retaining rod 17 is depressed by the spring 22, then a spring force is borne by the retaining rod 17 and does not act upon the contact unit 18 directly. For this reason, the spring 22 for depressing the retaining rod 17 ensures an allowable specification without being restricted by the magnitude of the spring constant. Thus, there is no possibility that a contact force of the contact unit 18 on the developing roller 14 will vary in accordance with the extent of wear caused by the slide contact of the contact unit 18 with the developing roller 14. As a result, the thickness of the toner layer on the developing roller 14, as well as the amount of toner charged on the surface of the developing roller, can be stabilized to obtain a stable image of better quality. In the embodiment shown, as the retaining rod 17 is made of a rigid substance, such as metal, no larger warp occurs upon the manufacture of the retaining rod 17 and it is possible to manufacture the retaining rod 17 with high dimensional accuracy. It is, therefore, not necessary to straighten out the retaining device with a straightening device. Further, the contact unit 18 is not warped even if being thermocompression bonded to the retaining rod 17 and it is thus possible to prevent an increase in the number of steps required and in the manufacturing cost. When the toner feed roller 3 feeds the toner T to the developing roller 4, any excessive toner not passed through the contact unit 18 is readily moved along the outer periphery of the retaining rod 17 and readily back into the toner storage section of the casing 11. It is thus possible to prevent accumulation and aggregation of the toner T at an area between the retaining rod 17 and the developing roller 4 and to form the toner T as a thin film without causing any inconvenience. Those toner restricting members 16 as shown in Figs. 4 to 7 are each made of, for example, metal and have a retaining rod 17 circular in cross-section. The toner restricting member 16 as shown in Fig. 4 has a structure as will be set out below. A contact unit 18 is formed of an elastic member and has a contact area 18a and base seat 24. The base seat 24 has the same length as that of the contact are 18a and a width greater than that of the contact area 18a. The contact area 18a is projected from the base seat 24 such that the contact area 18a is integral with the base seat 24. The base seat 24 is provided at the base of the contact area 18a in which case the base seat 24 is projected on a downstream side with the contact area as a reference as viewed in a toner conveying direction, that is, in a rotation direction of the developing roller 4, with the contact area 18a as a reference. The base seat 24 is thermocompression bonded to the outer periphery of the retaining rod 17. In the structure, the contact area 18 can obtain a greater fixing area relative to the retaining rod 17 than a contact area is provided without the base seat. It is thus possible to increase the bond strength with which the contact 18 is fixed to the retaining rod 17. Upon the formation of the base seat 24, a resin injection opening can be provided at the projected area, thus eliminating the need to provide a resin injection opening at the forward end portion of the contact area 18a, that is, at the developing roller contacting area. As a result, the forward end portion of the contact area 18a becomes smoother. Since the contact unit 18 has, unlike the base seat 24, no projected area on the upstream side of the developing roller as viewed in the direction of the feed of the toner T, the toner T is smoothly flowed upon the feeding of the toner without the toner T being lodged at that area defined between the contact unit 18 and the developing roller 14. The toner restricting member 16 as shown in Fig. 5 has a structure as will be set out below. A contact unit 18 has a contact area 18a and a base seat 25 on which the contact area 18a is provided. The base seat 25 is projected at both the upstream and downstream sides of the contact area 18a with the contact area as a reference as viewed in the direction of the feed of a toner. This structure, like the structure as shown in Fig. 4, has an advantage from the standpoint of its strength and its formation. The toner restricting member 16 as shown in Fig. 6 has the following structure. A contact unit 18 has a contact area 18a and a base seat 26. The base seat is cylindrical in cross-section and has an inner diameter the same as the diameter of the retaining rod 17 and a length the same as that of the retaining rod 17. The contact area 18a is provided on the portion of an outer periphery of the base seat 26 along the full length of the base seat 26. The base seat 26 is fitted over the outer periphery of the retaining rod 17 along the full length of the latter. This arrangement can fix the contact unit 18 to the retaining rod 17 with a greater strength. A toner restricting member 16 as shown in Fig. 7 is a variant of the toner restricting member 16 as shown in Fig. 6. The toner restricting member 16 shown in Fig. 7 has a contact area 18a whose forward end is flattened and can be more stably contacted with the outer periphery of the photosensitive drum 23 than the contact area whose forward end is round. Figs. 8 to 11, each, show a toner restricting member 16 having a retaining rod 27 comprised of a cylinder whose cross-section is circular. The toner restricting member 16, having the retaining rod 27 of such a cylindrical configuration, can be made lighter in weight. In a toner restricting member 16 shown in Fig. 8, a contact unit 18 is fixed directly to a retaining rod 27 and has only a contact area 18a thereon as in the case of the toner restricting member 16 shown in Fig. 3. In a toner restricting member 16 shown in Fig. 9, a contact unit 18 is fixed to a retaining rod 27 and has a contact area 18a and base seat 24 as in the case of the toner restricting member 16 shown in Fig. 4. In a toner restricting member 16 shown in Fig. 10, a contact unit 18 is fixed to a retaining rod 27 and has a contact area 18a and base seat 24 as in the case of the toner restricting member 16 shown in Fig. 6. In a toner restricting member 16 shown in Fig. 11, a contact unit 18 is fixed to a retaining rod 27 and has a contact area 18a and base seat 26 as in the case of the toner restricting member 16 shown in Fig. 6. Toner restricting members 16 shown in Figs. 12 to 15, each, use a retaining rod 28 having a square cross-section. In the toner restricting member 16 shown in Fig. 12, a contact unit 18 is fixed directly to the retaining rod 28 and has only a contact area 18a as in the case of the toner restricting member 16 shown in Fig. 3. In the toner restricting member 16 shown in Fig. 13, a contact unit 18 is fixed to the retaining rod 28 and has a contact area 18a and base seat 24 as in the case of the toner restricting member 16. In a toner restricting member 16 shown in Fig. 14, a contact unit 18 is fixed to the retaining rod 28 and has a contact area 18a and base seat 25 as in the case of the toner restricting member 16 shown in Fig. 6. In a toner restricting member shown in Fig. 15, a contact unit 18 is fixed to the retaining rod 28 and has a contact area 18a and base seat 26 as in the case of the toner restricting member 16 shown in Fig. 6. Toner restricting members 16 shown in Figs. 16 to 19, each, use a retaining rod 29 whose cross-section is square-cylindrical. In the toner restricting member 16 shown in Fig. 16, a contact 18 is fixed directly to the retaining rod 29 and has only a contact area 18a as in the case of the toner restricting member 16 shown in Fig. 3. In the toner restricting member 16 shown in Fig. 17, a contact unit 18 is fixed to the retaining rod 29 and has a contact area 18a and base seat 24 as in the case of the toner restricting member 16 shown in Fig. 4. In the toner restricting member 16 shown in Fig. 18, a contact unit 18 is fixed to the retaining member 29 and has a contact area 18a and base seat 25 as in the case of the toner restricting member 16 shown in Fig. 5. In the toner restricting member 16 shown in Fig. 19, a contact unit 18 is fixed to the retaining rod 29 and has a contact area 18a and base seat 26 as in the case of the toner restricting member 16 shown in Fig. 6. The retaining rod of the toner restricting member 16 can be made of not only metal but also a rigid synthetic resin and the contact unit can be made of not only rubber but also other elastic materials. A means for supporting the retaining rod of the toner restricting member is not restricted to the one as set out above. A developing device according to a second embodiment of the present invention will be explained below. In the developing device of the second embodiment, one contact unit is provided at a retaining rod of a toner restricting member and has a plurality of contact areas. The second embodiment will be explained below with reference to Figs. 20 to 22. In the second embodiment, a rod circular in cross-section is provided as a retaining rod for the toner restricting member. Figs. 20 and 21 show a diagrammatic arrangement of the developing device. The developing device of Figs. 20 and 21 are of a nonmagnetic one-component developing type. The developing device is the same as that shown in Figs. 1 and 2 except for the toner restricting member and its support structure. The same reference numerals are employed in the second embodiment to designate component parts or elements corresponding to those shown in Fig. 2. That is, reference numeral 11 shows a casing; 12, an agitator; 13, a toner feed roller; 14, a developing roller; 15, a collection blade; 22, leaf spring; and 23, a photosensitive drum. In Fig. 20, reference numeral 41 shows a toner restricting member having a retaining rod 42 and contact unit 43. The retaining rod 42 is made of a rigid substance, such as carbon steel and stainless steel. The retaining rod 42 has a length greater than the photosensitive drum 12. The contact unit 43 has, for example, four contact areas 43A, 43B, 43C, and 43D which are mutually separated from each other. The contact areas 43A, 43B, 43C and 43D are made of an elastic material, such as insulating rubber, and are of a blade type and have the same length as that of the retaining rod 42 as in the case of the contact area 18a of the contact unit 18 in the first embodiment of the present invention. The contact area 43A, 43B, 43C and 43D are fixedly bonded on the outer periphery of the retaining rod 42 such that these contact areas are located at equal intervals along the axial direction of the retaining rod 42. A pair of right square members 44, 44 are mounted one at each end of the retaining rod 42 and adapted to position the contact areas 43A, 43B, 43C and 43D constituting the contact unit 43. The number of corners of the right square members is set to be equal to that of the contact areas 43A, 43B, 43C and 43D of the contact unit 43. The four sides of the right square member 44 correspond in position to the respective contact areas 43A, 43B, 43C and 43D. For example, externally threaded sections, for example, of the right square members 44 are inserted, in an aligned relation, into internally threaded portions of the opposed end portions of the retaining rod 42 at and along the center axis of the latter. A pair of support sections 45A, 46B are oppositely formed in those right and left side walls of the casing 11 so as to locate the toner restricting member 41. The respective support sections 45A and 45B are formed as corresponding square openings in the casing 11 so as to fixedly support the right square members on both the ends of the retaining rods 42 of the toner restricting member 41. That is, the respective support sections 45A and 45B are opened at the upper edges of the opposed side walls of the casing 11 so as to detachably insert the corresponding square members 44. In this connection it is to be noted that the support sections 45A and 45B, each, have a pair of opposed sides 45a, 45b corresponding to the vertically opposed sides of the right square member 44 and a bottom side 45c on which the lower side of the square member 44 is seated. The square members 44 on the retaining rod 42 are fitted from above into the support sections 45A and 45B of the casing 11 and supported there in which case each square member 44 has its opposed sides set vertically. " The opposed sides of each square member 44 are vertically fitted at that opening defined by the opposed sides 45a, 45b and bottom side of each support section so that the retaining rod 22 is fixed in place, that is, not rotated along its axis. Of those contact areas 43A, 43B, 43C and 43D of the contact unit 43 as shown in Fig. 22A, the lowest one as shown in Fig. 22B is set in contact with the outer periphery of the developing roller 14. The topmost contact area 43C for example of the retaining rod 22 is depressed by a leaf spring 22 as shown in Fig. 20. The leaf spring 22 is attached to a member, not shown, and, by so doing, the toner restricting member 41 is supported in a stable way. The developing operation of the developing device thus arranged will be carried out as follows: The contact area 43A of the toner restricting member 41 is set in contact with the outer periphery of the developing roller 14 as shown in Fig. 20, allowing a toner T which is deposited on the developing roller 14 to be pressed against the outer periphery of the developing roller 14. By so doing, the toner T is formed as a thin layer on the outer periphery of the developing roller 14 and triboelectrically charged there at that time. In this case, a rotational force is applied by the contact area 43A. Since, therefore, the retaining rod 42 is fixed in place, by each square member, in each support section of the casing 11, the retaining rod 42 is not rotated. The contact area 43A in contact with the developing roller 14 is worn by its slide contact with the rotating developing roller 14. If a thin toner layer is hard to form on the outer periphery of the developing roller 14 due to a progressed wear of the contact area 43A, the retaining rod 42 is detached away from the support sections 45 and 45B. The retaining rod 42 is rotated through an angle of 90° along its axis so that the contact area 43B faces the developing roller 14 in place of the contact area 43A. In this state, the retaining rod 42 is again set in the support sections 45A and 45B of the casing 11 so that the new contact area 42B is placed in contact with the outer periphery of the developing roller 4 as shown in Fig. 22B. In this way, the contact areas 43A, 43B, and 43C and 43D are set in contact with the developing roller 14 in a way that each is replaced with another contact area in accordance with an extent of its wear, that is, all the four contact areas 43A, 43B, 43C and 43D can be used, one at a time, for contact with the developing roller. It is thus possible to extend the life of the contact unit 43 a few times as long as that of a conventional contact unit. Another form of the toner restricting member 41 will be explained below. Those toner restricting members shown in Figs. 23 to 27 use a retaining rod 42 circular in cross-section. The toner restricting member 41 shown in Fig. 23 shows an improved one of the toner restricting member 41 shown in Fig. 22. The contact unit 43 in Fig. 23 has respective contact areas 43A, 43B, 43C and 43D and base seat 46 cylindrical in configuration. The contact areas 43A, 43B, 43C and 43D are fixedly bonded on the outer periphery of the retaining rod 41 such that these contact areas are arranged at and along the outer periphery of the base seat 46. The toner restricting member 41 as shown in Figs. 24 to 26 will be explained below. In Figs. 24 to 26 the same reference numerals are employed to designated parts or elements corresponding to those shown in Figs. 20 and 21. In Figs. 24 to 26, a cylindrical contact unit 47 is fitted over an outer periphery of a retaining rod (round rod) 42 in which case the contact unit 47 is formed into a cylindrical continuous configuration instead of forming those contact areas 43A, 43B, 43C and 43D separately on a contact unit 43. A pair of right hexagonal members 48, 48 are mounted one at each end of the retaining rod 42 such that these hexagonal members are fixed to the retaining rod 42 in the same method as the combination of the right square members 44 and retaining rod 42 shown in Figs. 20 and 21. A pair of support sections 49A, 49B are provided one at each upper side edge of a casing 11 so as to support the retaining rod. The respective support sections 49A and 49B are formed as square holes so as to support both ends of the a pair of right hexagonal members 48, 48 of a toner restricting member 41. These support sections are opened at those upper side edges of those opposed walls of the case 11 so that the retaining rod 42 is detachably inserted into these support sections. The support section is defined by a pair of opposed vertical side corresponding to a respective pair of opposed sides of the hexagonal member 48 and a bottom side 49c against which a given edge of the hexagonal member of the retaining rod abuts. Both ends of the retaining rod 42 are supported by the hexagonal members at the support sections 49A and 49B of the casing 11. The retaining rod 42 so supported by the support sections 49A and 49B that a given pair of opposed sides are vertically set relative to the corresponding opposed sides of the support sections 49A and 49B. As shown in Fig. 26A, a given pair of sides of the hexagonal members of the retaining rod 42 are vertically set relative to the opposed side 49a and 49b of the respective support sections 49A and 49B so that the retaining rod 42 is restricted against a rotation with its axis as a center. By so doing, a corresponding portion of the outer periphery of the contact unit 47 makes contact with the outer periphery of the developing roller 14. When the developing operation is done by the developing device, the contact unit is worn due to its slide contact with the rotating developing roller 14. If it is difficult to form a thin toner layer on the outer peripheral surface of the developing roller 14 due to a progressed wear of the contact unit 47 as shown in Fig. 26B, retaining rod 42 and hence the hexagonal member 48 is detached, as one unit, away from the support sections 49A and 49B of the casing 11. The retaining rod 42 is rotated through an angle of 60° with its axis as a center and then inserted into the support sections of the casing 11 so that, as shown in Fig. 26C, another new surface portion of the contact unit 47 is set in contact with the outer periphery of the developing roller 14 in which position the already worn surface portion of the contact unit 47 is situated away from the developing roller 4. In this way, an unworn surface portion of the contact unit 47 can be sequentially used as a contact portion contacting with the developing roller so that the whole outer periphery of the contact unit can be utilized as such a contact portion in accordance with an extent of its wear. In a toner restricting member 41 as shown in Fig. 27, a contact unit 50 of a right hexagonal cross-section is used stead of the contact unit of a circular cross-section as shown in Figs. 24 to 26. In this case, each edge 50a, or each side 50b, of the contact unit 50 is set in contact with the developing roller 14. In those toner restricting members 41 as shown in Figs. 28 to 31, use is made of a retaining rod 51 of a circular cross-section. The retaining rod, since being cylindrical in configuration, can be made lower in weight. In the toner restricting member 41 as shown in Fig. 28, four contact areas 43A, 43B, 43C and 43D of a contact unit 43 are fixed to the outer periphery of the retaining rod 51 as in the toner restricting member 41. In the toner restricting member 41 as shown in Fig. 29, a contact unit 43 has four contact areas 43A, 43B, 43C and 43D and base seat 46 as shown in Fig. 23 and fixed to the retaining rod 51 as in the toner restricting member 41 as shown in Fig. 23. In the toner restricting member 41 as shown in Fig. 30, a contact unit 47 is fitted over the retaining rod 51 as in the retaining rod 51 as shown in Fig. 25. The toner restricting member 41 as shown in Fig. 31 is of such a type that a contact unit 50 of a hexagonal cross-section is fitted over the retaining rod 51 as in the toner restricting member 41. The retaining rod of a toner restricting member 41 as shown in Figs. 28 to 31 is supported at the casing 11 and restricted against a rotation, but is movable toward and away from the developing roller 4. As such a means use is supported at the casing 11 and made of proper means whereby the square members 44 as shown in Fig. 21 and hexagonal members 48 as shown in Fig. 24 are provided on the retaining rod 51 so as to support the retaining rod 51 at the support sections of the casing 11. A toner restricting member 41 as shown in Figs. 32 and 33 are of such a type as to have a retaining rod 51 of a right square cross-section. In the toner restricting member 41 as shown in Fig. 32, a contact unit 43 is formed on the outer surface of the retaining rod 52 and has, for example, mutually separate contact areas 43A, 43B, 43D and 43D as in the toner restricting member 41. In the toner restricting member 41 as shown in Fig. 33, a contact unit 43 is formed on the retaining rod 52 and has contact areas 43A, 43B, 43C and 43D and base seat 46 as in the toner restricting member 41 as shown in Fig. 23. Toner retaining member 41 as shown in Figs. 34 to 36 will be explained below. The toner restricting member 41 is of such a type that a contact unit 54 of a right-hexagonal cross-section is fitted over a retaining rod 53 of a corresponding right-hexagonal cross-section and bonded there. Each edge 54a of the contact unit 54 can be set in contact with the outer periphery of the developing roller 14. Both the ends of the retaining rod 53 are projected from the contact unit 54 and suported at a pair of support sections 55A and 55B which are formed as openings at the upper edge portions of a casing 11. The combination of the retaining rod 53 and support sections 55A and 55B are used on the same principle as that of the right-hexagonal members 48 and support sections 49A and 49B as shown in Figs. 24 and 25. That is, a pair of opposed sides of the retaining rod 53 are so supported that these side are vertically set at the opposed sides of the supported sections 55a and 55b with a bottom edge 55c of the retaining rod 53 supported on a bottom side of each support section. When the toner restricting member 41 is supported by the casing 11, the edge 54a, for example, of the contact unit 54 is set in contact with the developing roller 14 as shown in Fig. 36A. When the edge 54a of the contact unit 54 is worn due to its contact with the developing roller 14 as shown in Fig. 36B, then both the ends of the retaining rod 54 are removed from the support sections of the casing 11. The retaining rod 53, being rotated through an angle of 60° with the axis as a center, is placed at the support sections of the causing 11 so that another edge 54a of the contact unit can be set in contact with the developing roller 114. In this way, the edge 54a of the contact unit 54 is so re-set in contact with the outer periphery of the developing roller 14 as shown in Fig. 36C. The edge 54a of the contact unit 54 can be sequentially set against the developing roller 14 in accordance with the progressed wear of the contact unit so that all the edges of the contact unit 54 can be employed relative to the developing roller. Although, in this embodiment, the edges of the contact unit 54 can be employed one by one relative to the developing roller 4, those six sides of the contact unit 54 each defined by the adjacent edges can also be set in contact with the outer surface of the developing roller 4. A toner restricting member 41 as shown in Figs. 37 and 38 uses a retaining rod 56 having a cylinder whose cross-section is a right square configuration. In the toner restricting member 41 as shown in Fig. 37, four separate contact areas 43A, 43B, 43C, and 43D are provided on the outer surface of the retaining rod 56 as in the toner restricting member 41 as shown in Fig. 22. In the toner restricting member 41 as shown in Fig. 38, a contact unit 43 is formed on the retaining rod 56 and has four contact areas 43A, 43B, 43C and 43D as in the toner restricting member 41 shown in Fig. 23. In a toner restricting member 41 as shown in Fig. 39, a contact unit 54 hexagonal in cross-section is fitted over a cylindrical retaining rod 57 hexagonal in cross-section as in the toner restricting member 41 as shown in Fig. 35. The retaining rod is made of not only metal but also other rigid substances including rigid synthetic resin. For a blade-like contact unit formed on the retaining rod, not only four but also three or more than four contact areas can be formed on the contact unit. If a plurality of contact areas of the contact unit are formed into a continuous unit, no restriction is made to its polygonal shape if it is properly selected.

Claims: A developing device comprising: a casing (11); a toner carrier (14) rotatably provided in the casing and having a surface for holding a one-component toner, for transferring the toner held by the surface of the toner carrier by rotation of the toner carrier (14); and a toner restricting member (16) non-rotatably provided in the casing (11) in parallel to the toner carrier (14), the toner restricting member (16) comprising: a retaining rod (17,27,28,29) formed of a rigid substance; and a contact unit (18) formed of synthetic resin having elasticity, and provided on an outer periphery of the retaining rod (17, 27,28,29) in such a manner as to extend in an axial direction of the retaining rod (17,27,28,29), the contact unit (18) having a contact portion (18a) having a forward end for contacting the surface of the toner carrier (14); characterized in that, the contact portion (18a) extends from the outer periphery of the retaining rod (17,27,28,29) to the end of the contact portion (18a) to have a height smaller than a diameter of the retaining rod (17,27,28,29), said retaining rod (17,27,28,29) having a circular cross section or a polygonal cross section and being held in the casing (11) such that said forward end of said contact portion (18a) contacts the surface of the toner carrier (14). The developing device according to claim 1, characterized in that the retaining rod (17) is a solid rod. The developing device according to claim 1, characterized in that the retaining rod (27) is a hollow cylindrical rod. The developing device according to one of claims 1 to 3, characterized in that the contact unit (18) has a portion which is directly fixed to the retaining rod. The developing device according to one of claims 1 to 3, characterized in that the contact unit (18) comprises a base seat (24) which is formed on a downstream side with respect to a direction in which the toner is transferred by the toner carrier (14), with reference to the end of the contact portion (18a), and which is fixed to the retaining rod. The developing device according to one of claims 1 to 3, characterized in that the contact unit (18) comprises base seats (25) fixed to the retaining rod and formed on an upstream side and a downstream side with respect to a direction in which the toner is transferred by the toner carrier (14), with reference to the end of the contact portion (18a) which contacts the surface of the toner carrier (14). The developing device according to one of claims 1 to 3, characterized in that the contact unit (18) comprises a cylindrical section in which the retaining rod is fixedly fitted and the contact portion (18) arranged on the outer periphery of the cylindrical section. A developing device comprising: a casing (11); a toner carrier (14), rotatably provided in the casing and having a surface for holding a one-component toner, for transferring the toner held by the surface of the toner carrier by rotation of the toner carrier (14); and a toner restricting member (41) non-rotatably provided in the casing (11) in parallel to the toner carrier (14), the toner restricting member comprises: a retaining rod (42,51,52,53,56,57) formed of a rigid substance; and a contact unit (43,47,50,54) formed of synthetic resin having elasticity, and provided on an outer periphery of the retaining rod in such a manner as to extend in an axial direction of the retaining rod, characterized in that the contact unit (18) has a plurality of contact portions (43A-43D) each having a forward end for contacting the surface of the toner carrier (14), each of the contact portions extending from the outer periphery of the retaining rod to the end of each contact portion to have a height smaller than a diameter of the retaining rod and said retaining rod (42,51,52,53,56,57) having a circular cross section or a polygonal cross section and being held in the casing (11) such that the forward end of one of said contact portions (43A-43D) contacts the surface of the toner carrier (14). The developing device according to claim 8,. characterized in that the retaining rod (42) is a solid rod. The developing device according to claim 8 characterized in that the retaining rod (51) is a hollow cylindrical rod. The developing device according to one of claims 8 to 10, characterized in that the contact unit (43) has the contact portions which are arranged separate from each other. The developing device according to one of claims 8 to 10, characterized in that the contact unit (43) comprises a cylindrical section in which the retaining rod is fixedly filted, and the contact portions arranged on the outer periphery of the cylindrical section in such a manner as to be circumferentially separate from each other. The developing device according to one of claims 8 to 10 characterized in that the contact unit (47,50,54) has the contact portions formed into a continuous unit. A method for setting a toner restricting member of a developing device, comprising the steps of: preparing a toner restricting member comprising: a retaining rod formed of a rigid substance and having a circular cross section or a polygonal cross section; and a contact unit formed of synthetic resin having elasticity, and provided on an outer periphery of the retaining rod in such a manner as to extend in an axial direction of the retaining rod, the contact unit (18) having a contact portion having an end, which contacts a surface of a toner carrier, the contact portion extending from the outer periphery of the retaining rod to the end of the contact portion to have a height smaller than the diameter of the retaining rod; and locating the toner restricting member non-rotatably in a casing such that the toner restricting member is arranged in parallel to the toner carrier, and bringing the contact portion of the contact unit into contact with the surface of the toner carrier.

Inventors: HASHIZUME HIROSHI, ISHIKAWA TAKASHI, HASHIZUME, HIROSHI, ISHIKAWA, TAKASHI, Hashizume, Hiroshi, c/o Intellectual Property Div., Ishikawa, Takashi, c/o Intellectual Property Div.
Applicants: TOKYO ELECTRIC CO LTD, TOSHIBA KK, KABUSHIKI KAISHA TEC, KABUSHIKI KAISHA TOSHIBA
Application year: 1992
Main classification: G03G15
IPC codes: G03G15