CN1299312A - Insert molded end pins for developer magnet rollers - Google Patents

Abstract

The developing magnetic roller (1) is provided with an end pin shaft (2) which is formed by clamping and inserting molding at two ends. The end pin is insert molded into a ferrite and binder magnet roll to improve strength, flatness, handling and reduce cost.

Description

Insert molded end pins for developer magnet rollers

The present invention relates to electrophotography, in particular to a developing magnetic roller (MagnetRoll Developer) for electrophotography. The developer magnet roller is usually made of strontium ferrite with a nylon binder to form a cylindrical body that functions in the peripheral cylindrical developer sleeve.

The magnetic pole configuration contained in the magnetic core usually includes four or more staggered N-S poles formed along the longitudinal direction of the above-mentioned cylindrical body, which is similar to "back leaf clover configuration" when viewed from the end of the cylindrical body. The magnetic core is supported on the frame of the developing sleeve through the end shaft of the developing magnetic roller molded body.

Generally, such a developing magnet roller includes ferrite and an adhesive and is manufactured by the following method.

Assuming that the adhesive is a soft thermoplastic material such as extruded polyvinyl chloride (PVC), magnets are usually fitted to cold-rolled steel shafts during extrusion for reinforcement and longitudinal magnetization and form hollow cylinders, which are then Demagnetized and finally remagnetized into the final pole configuration with an electromagnet after assembly. This method is inherently expensive due to the multi-step process of extruding the magnetic compound, gluing the soft thermoplastic material to the shaft, and magnetizing the developer magnet into the final desired configuration.

Alternatively, a strong metal shaft clip can be molded into a ferrite and soft thermoplastic material such as ethylene-vinyl acetate adhesive and magnetized in the mold by permanent magnets or by electromagnets.

If the adhesive is a hard plastic such as nylon, the magnet is 100% molded including the small diameter end mounts. This magnetic roller with nylon adhesive is either magnetized with permanent magnets during the molding process, or partially magnetized with electromagnet coils within the mold and final magnetized after molding. Such nylon bonded magnets have acceptable performance and are inexpensive, but if the overlap-to-length ratio and/or magnet diameter-to-installation diameter ratio are large, the associated end shaft becomes brittle and prone to breakage. If the diameter of the end shaft is increased to increase the strength, qualified strength can be obtained. Such a mounting diameter size would be limited, however, due to surrounding geometry and the need for adequate clearance for adjoining components, such as the inner diameter of a developer sleeve end plug to allow passage of the end shaft. A perfect magnetic roller must be straight with only minimal radial fluctuations to ensure acceptable magnetic properties.

Numerous patents have been issued covering the design and manufacture of magnets. The following patents relate to unique shaft designs.

U.S. Patent 4557582 describes the attachment of magnet strips in planar form to an asymmetric polygonal support shaft of non-circular cross-section, the support shaft having the smallest end so that it is shaped to allow it to be mounted on a support . Glue the tape to this central shaft with adhesive. These magnet strips, when made separately, are difficult to assemble together on long cylindrical sleeves, whereas the shafts described above provide a mechanical means of mounting.

US Patent 4,580,121 describes ferrite magnets with a rubber adhesive held on an aluminum extruded shaft which is ribbed and held together by heat shrink sleeves. This non-magnetic aluminum extruded shaft provides a carrier for mounting the strip magnet.

U.S. Patent 4604092 describes an insert molding method where the central shaft is placed within bonded (nylon) ferrite magnets to compensate for large length-to-diameter ratios greater than 5, where the rare earth permanent magnets within the mold will result in The cylindrical magnetic roller is magnetized.

US Patent 4872418 describes a ferrite magnet with a nylon binder comprising at each end a segmented flat hammer or a polygonal projection at the longitudinal end.

US Patent 4954800 describes the use of electromagnets to magnetize roller magnets during the molding process to form longitudinal poles. The roll magnets thus obtained usually have only two poles, are then demagnetized and finally remagnetized to have four poles in the final configuration. This suggests an alternative approach to final magnetization. The shaft involved is still an integral part of the roller magnet.

US Patent No. 5,319,337 describes an insert molded shaft within a magnetic roller that also acts as a barrel. The metal magnetic shaft is preheated and welded with a thin layer of adhesive and thermoplastic resin. There are a total of 50 poles on the surface, and this magnetic axis provides the critical magnetic circuit in forming these surface poles.

US Patent No. 5,682,587 describes a generally applicable hollow magnet with metal filled resin bearings of various configurations, with a single end shaft forming a D-shape or a square shape. These support bearings are described as tapered end supports which also make electrical contact with the bias of the cartridge holder. These end shafts serve multiple purposes, including as supports, precision bearing surfaces, and electrical contacts.

US Patent 3,149,403 relates to a stub shaft that is plugged or insert molded into a non-magnetic core or body to which a magnetic assembly is attached. In short, such a magnet is a composite structure of magnetic parts and non-magnetic parts.

U.S. Patent 4142218 relates to a magnetic roller formed as a composite structure comprising non-magnetic bodies and/or end bushings with longitudinal magnet inserts in the latter, and the non-magnetic bodies/sleeves Insert the upper shaft after molding.

US Patent No. 5,383,473 discloses a first end shaft integrally molded as part of the magnet roller body and a second end shaft press fit after the magnet roller body/first end shaft is molded.

A first object of the present invention is to provide a developer magnet roller which has increased strength compared to a one-piece molded magnet having an integral end shaft.

A second object of the present invention is to provide a developing magnet roller with improved flatness.

A third object of the present invention is to provide a developing magnet roller which is possible to reduce the cost compared to the use of through-shaft magnets.

A fourth object of the present invention is to provide a developer magnet roller having insert molded non-magnetic end pins which facilitates handling for certain manufacturing methods.

According to the present invention, there is provided an improved developing magnet roller for a developing sleeve for electrophotography.

Developing magnet rollers, particularly those having a large overall magnet diameter to support shaft diameter ratio, are produced by a method that significantly improves roller strength, flatness, handling, and cost reduction.

Fig. 1 is a longitudinal sectional view showing a magnetic roller of the present invention.

The present invention will now be described in detail with reference to this drawing.

As shown in Figure 1, a magnet blank roller 1 is provided during the manufacture of the developing magnetic roller 5, and the roller body is composed of granular ferrite such as strontium ferrite material and adhesive, and the two ends of the roller 1 are respectively attached. End pin shaft 2. Such end pins are made, for example, of metal, ceramic or plastic. The end pin shaft 2 is inserted into the mold and the magnet blank roll 2 is formed by standard injection molding (ie injection molding of molten binder with ferrite pellets thoroughly mixed therein). Typical adhesives for this type of ferrite are hard thermoplastics such as Nylon 6 or Nylon 12.

Injection molded developer magnet rollers thus produced have improved strength, flatness, processability, and reduced cost, especially in the ratio of overall magnet diameter to support shaft diameter, by incorporating molded end shafts on inserts This is especially true when large.

The preferred form of the invention utilizes a non-magnetic material for the end shaft, such as a non-magnetic brand of stainless steel. This embodiment is ideal when the magnet rollers are produced using injection molding equipment containing permanent magnets. The inserting part of the shaft 2 has a certain textured structure (roughened treatment) to ensure effective locking. Alternatively, a more concave-convex locking surface may be used, such as machined dimples.

Although the present invention has been described with reference to the structure disclosed above, it should not be limited to the details described, and the application is intended to cover such modifications or variations within the purpose or scope of improvement in the following claims. of.

Claims (5)

1. include and in roller formation process, press from both sides the shafts for magnet roll developer of inserting molded end bearing pin.

2. the shafts for magnet roll developer of the described band edge bearing pin of claim 1, the base substrate of wherein said magnetic roll is included in the magnetisable ferrite pellet in the nylon binder.

3. the shafts for magnet roll developer of the described band edge bearing pin of claim 1, wherein said end bearing pin is to be made by metal, pottery or plastics.

4. the manufacture method of the shafts for magnet roll developer of the described band edge bearing pin of claim 1, wherein said end bearing pin are that folder is inserted and is molded on these two ends.

5. the manufacture method of the shafts for magnet roll developer of the described band edge bearing pin of claim 1, wherein said end bearing pin be non magnetic and be in including the injection molding of permanent magnet, press from both sides insert molded.