Corona discharge device

Abstract: A corona discharge device including a shield case (2) having a bottom wall (4), a pair of walls (8,12) extending perpendicularly from the bottom wall and a wire (20) stretched within the shield case. A plurality of guide members (122) for preventing entry of the sheet material into the shield case have one end portion fixed to one wall (108) of the shield case and the other end portion detachably anchored selectively at the one wall (108) and the other wall (110) of the shield case.

Description: This invention relates to a corona discharge device which can be utilized, for example, as a peeling corona discharge device in an electrostatic copying machine. Generally, a peeling corona discharge device is widely utilized in an electrostatic copying machine in order to peel a sheet material such as a copying paper kept in intimate contact with a rotating drum in a transfer zone. The peeling corona discharge device is provided with an electrically conductive shield case and a wire stretched within the shield case, and a corona discharge generated from the wire is applied to the sheet material through an opening in the shield case. The corona discharge device further comprises a guide means provided at the opening of the shield case to prevent entry of the sheet material through it. Such devices are, for example, known from JP-A- 59007969 and JP-A- 59007971. The guide means is made of, for example, a gut, a plastic film (see, for example, Japanese Laid-Open Utility Model Publication No. 120459/1985), or a plastics member (see, for example, Japanese Laid-Open Utility Model Publication No. 181456/1984). Conventional corona discharge devices, however, have the following problems to be solved in regard to the guide means. When the guide means is formed of a gut, it is troublesome to set it in a stretched state. When the wire is broken, it is troublesome and time-consuming to replace the wire. Cleaning of the wire is also not easy. When the guide means is formed of a plastic sheet material and set between a pair of side walls, the sheet material is likely to become displaced in the event that a relatively thick sheet material acts on it, or in the event of removing a jammed sheet. Cleaning of the wire is not easy, either. When the guide means is formed of a plastics member, deformation (so-called "warping") during moulding causes part of the plastics member to rise at the time of setting it in the shield case. If this rising is large, the sheet material may collide with it, and it fails to guide the sheet. It is a primary object of this invention to provide an improved corona discharge device which permits easy replacement of a wire and its cleaning, and can reliably prevent entry of a sheet material into a shield case. According to the present invention, there is provided a corona discharge device comprising an electrically conductive shield case having a first wall and a pair of opposed second walls which respectively define base and side walls of an elongate, open-mouthed cavity, a wire mounted in a stretched state within said cavity and a plurality of elongate guide members disposed in spaced-apart relationship longitudinally of the shield case for preventing entry of a sheet material into said cavity, wherein each guide member is formed of an elastically deformable sheet material, with one end portion of the guide member being fixed to one of said second walls and the other end portion being detachably anchored either at said one of said second walls or at the other of said second walls, such that when the other end portion of the guide member is anchored at said other one of said second walls, the guide member extends from the one wall to the other across the open mouth at said cavity, but when the other end portion of the guide member is anchored at said one of the second walls, the open mouth of the cavity is exposed. The invention is described further hereinafter, by way of example only, with reference to the accompanying drawings, in which:- Fig. 1 is a perspective view of a corona discharger embodying one example of a corona discharge device in accordance with the present invention; Fig. 2 is a top plan view of the corona discharge device of Fig. 1; and Fig. 3 is a perspective view showing part of a modified example of the corona discharge device of Fig. 1. In Figs. 1 and 2, the illustrated corona discharger is provided with an electrically conductive case 102 formed of a metallic material such as aluminum. The case 102 has a bottom wall 104 and side walls 106 and 108 projecting upwardly substantially vertically from both side ends of the bottom wall 104. Between the side walls 106 and 108 is disposed an electrically conductive partitioning wall 110 formed of a metallic material and the lower end of the partitioning wall 110 is fixed to the bottom wall 104 by such means as welding. With this arrangement, a shield case comprised of the bottom wall 104 (the lower portion in Fig. 2), the side wall 108 and the partitioning wall 110 functions as a shield case for one corona discharge device, and a shield case comprised of the bottom wall 104 (the upper portion in Fig. 2), the side wall 106 and the partitioning wall 110 functions as a shield case for the other corona discharge device. In this embodiment, the upper portion of one side wall 106 is slightly inwardly bent toward the partitioning wall 110, and a guide member 112 is fixed to the outside surface of the side wall 106 and its one side portion projects outwardly, as shown in Fig. 1. The opposed walls 108,110 and part of the bottom wall 104 thus define the side walls and base at a first elongate, open-mouthed cavity 103. Likewise, the opposed walls 110,112 and the other part of the bottom wall 104 define the side walls and base at a second, elongate, open-mouthed cavity 105. Supporting members 114 and 116 formed of an insulation material such as a synthetic resin material are attached to both end portions of the case 102, and wires 118 and 120 are stretched between the supporting members 114 and 116 (see Fig. 2). One wire 118 extends within cavity 105 along and between the side wall 106 and the partitioning wall 110, and the other wire 120 extends within cavity 103 along and between the side wall 108 and the partitioning wall 110. In use, the corona discharger is disposed in a transfer zone opposite to the rotating drum (not shown) of an electrostatic copying machine. One corona discharge device including a shield case composed of the bottom wall 104, the side wall 106 and the partitioning wall 110 and one wire 118 functions as a transfer corona discharge device, and the other corona discharge device including a shield case composed of the bottom wall 104, the side wall 108 and the partitioning wall 110 and the wire 120 functions as a peeling corona discharge device. A guide member 122 is further disposed in regard to the other corona discharge device in the corona discharger described. The guide member 122 is formed of sheet-like material which can be formed of a synthetic resin material such as a polyester or a vinyl chloride resin, and can be elastically deformed from a position shown in Fig. 1 and by a solid line in Fig. 2 to a position shown by a two-dot chain line in Fig. 2. In the illustrated embodiment, six guide members 122 in total are disposed in spaced-apart relationship longitudinally of the side wall 108 and the partitioning wall 110. With the longitudinally central part of the side wall 108 as a standard, three guide members 122 are provided on one side thereof (the left side in Fig. 2), and three guide members 122 are provided on the other side (the right side in Fig. 2) The guide members 122 are of substantially the same structure. Each of the guide members 122 has a fixed portion 124 provided at one end portion, a projecting portion 126 extending upwardly from the fixed portion 124, a guide portion 128 extending substantially horizontally from the upper end of the projecting portion 126, a suspending portion 130 extending downwardly from the end of the guide portion 128, and an anchoring projection 132 projecting nearly horizontally from the lower end of the suspending portion 130. The fixed portion 124 is fixed to the inside surface of the side wall 108 by an adhesive or a both-surface adhesive tape. A rectangular first hole 134 is formed in the partitioning wall 110 corresponding to each guide member 122. As shown in Figs. 1 and 2, first holes 134 provided correspondingly to the guide members 122 disposed on one side of the longitudinally central part of the side wall 108 are positioned inwardly of the fixed portions 124 of the guide members 122, namely to the right in Fig. 2. The first holes 134 provided correspondingly to the guide members 122 disposed on the other side of the aforesaid standard are positioned inwardly of the fixed portions 124 of the guide members 122, namely to the left in Fig.2. Furthermore, second holes 136 are formed in the side wall 108 correspondingly to the guide members 122. The second holes 136 are positioned further inwardly of the first holes 134. In this embodiment, the free end portion of each guide member 122 is adapted to be selectively anchored at the partitioning wall 110 and the side wall 108. Usually, in use, the anchoring projections 132 of the guide members 122 are anchored at the corresponding first holes 134, and in the anchored state, the forward ends of the anchoring projections 132 project slightly toward the side wall 106 through the partitioning wall 110. In this anchored state, as shown in Fig. 2, the guide portions 128 of the guide members 122 positioned on one side (the left hand side in Fig. 2) of the side wall 108 extend inclinedly from one end toward the other inwardly to the right in Fig. 2. The guide portions 128 of the guide members 122 positioned on the other side (on the right hand side in Fig. 2) of the side wall 108 extend inclinedly from one end toward the other inwardly to the left in Fig. 2. As shown in Fig. 1, the guide portions 128 of the guide members 122 cross the side walls 108 and 110 while slightly projecting beyond the upper ends of the partitioning wall 110 and the side wall 108. Accordingly, the guide members 122 guide the sheet member properly and accurately prevent entry of the sheet material into the shield case of the corona discharge device functioning as a peeling corona discharge device, i.e. into the cavity 103 between the partitioning wall 110 and the side wall 108. Furthermore, since one end portion of each guide member 122 is fixed to the side wall 108, the action of the sheet material, etc. on the guide members 122 does not result in detachment of the guide members 122 from the case 102. On the other hand, when the wire 120 is to be cleaned or replaced, the anchoring projections 132 of the guide members 122 are anchored at the corresponding second hole 136. As can be seen from Fig. 2, this anchoring can be achieved by detaching the anchoring projections 132 of the guide members 122 from the first holes 134, and then elastically deforming them inwardly (clockwise in Fig. 2 for the guide members 122 positioned on one side of the side wall 108, and counterclockwise in Fig. 2 for the guide members 122 positioned on the other side of the side wall 108) and anchoring them in the second holes 136. Consequently, the end portions of the anchoring projections 132 project slightly outwardly through the side wall 108. In this anchored state, the guide portions 128 of the guide members 122 extend nearly in the left-right direction in Fig. 2 inwardly of the side wall 108 along its inside surface to expose the overhead space of the wire 120. As a result, the wire can be cleaned and replaced easily. Fig. 3 shows a modified example of the corona discharger shown in Figs. 1 and 2. In this modified example, the height of the side wall 108′ of the case 102′ is slightly lower than that of the partitioning wall 110′, and the guide portion 128′ as a whole of the guide member 122′ projects upwardly beyond the upper edge of the side wall 108′. With this arrangement, in guiding the sheet material, the anchoring projection provided at the lower end of the suspending portion 130′ of the guide member 122′ is anchored at the hole 134′ formed in the partitioning wall 110′. When the space between the partitioning wall 110′ and the side wall 108′ is to be opened, the guide member 122′ is elastically deformed and its suspending portion 130′ is detachably anchored at the upper edge of the side wall 108′, as shown in Fig. 3. Accordingly, the second holes can be omitted. In this modified example, too, the fixing portion 124 of the guide member 122′ is fixed to the inside surface of the side wall 108′, and the same result as in the second embodiment can be achieved. While one preferred embodiment of the corona discharge device in accordance with this invention has been described, it should be understood that the invention is not limited to this specific embodiment, and various changes and modifications are possible without departing from the scope of the invention as defined by the appended claims. For example, the above embodiment has been described with reference to a corona discharger consisting of two corona discharge devices. This is not limitative, and the invention applies equally to a corona discharger consisting of a single corona discharge device.

Claims: A corona discharge device comprising an electrically conductive shield case (102) having a first wall (104) and a pair of opposed second walls (108,110) which respectively define base and side walls of an elongate, open-mouthed cavity (103), a wire (120) mounted in a stretched state within said cavity (103) and a plurality of elongate guide members (122) disposed in spaced-apart relationship longitudinally of the shield case for preventing entry of a sheet material into said cavity, characterised in that each guide member (122) is formed of an elastically deformable sheet material, with one end portion of the guide member being fixed to one (108) of said second walls and the other end portion being detachably anchored either at said one (108) of said second walls or at the other (110) of said second walls, such that when the other end portion of the guide member (122) is anchored at said other one (110) of said second walls, the guide member extends from the one wall (108) to the other (110) across the open mouth at said cavity (103) but when the other end portion of the guide member is anchored at said one (108) of the second walls, the open mouth at the cavity (103) is exposed. A corona discharge device as claimed in claim 1 in which the other (110) of said second walls has formed therein a first hole (134) at which the other end portion of the guide member is adapted to be detachably anchored. A corona discharge device as claimed in claim 1 or 2 in which, at a site on said one (108) of said second walls which is spaced from the mounting location for the one end portion of the guide member, a second hole (136) is formed at which the other end portion of the guide member (122) is adapted to be detachably anchored. A corona discharge device as claimed in claim 1 in which an anchoring suspending portion is provided in the other end portion of the guide member, and the suspending portion is anchored detachably at the upper edge of said one (108) of said second walls. A corona discharge device as claimed in any of claims 1 to 4 in which, with the longitudinally central part of the shield case as a reference, those of said guide members (122) which are disposed on one side of the reference and those which are arranged on the other side of the reference extend inclinedly from said one (108) of said second walls toward said other (110) of said second walls, inwardly towards said reference, but, when the mouth of the shield case cavity (103) is to be opened, the guide members arranged on one side of the reference and said guide members arranged on the other side of the reference are elastically deformed inwardly towards the reference and anchored at said one (108) of said second walls.

Inventors: KAMEDA KIYOSHIGE, KANO ATSUSHI, TANIGUCHI MASAMI, KAMEDA, KIYOSHIGE, KANO, ATSUSHI, TANIGUCHI, MASAMI
Applicants: MITA INDUSTRIAL CO LTD, MITA INDUSTRIAL CO. LTD.
Application year: 1988
Main classification: H01T19
IPC codes: H01T19, G03G15