Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – Reshaping running or indefinite-length work
Reexamination Certificate
1998-06-16
2001-05-08
Dye, Rena L. (Department: 1772)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
Reshaping running or indefinite-length work
C264S292000, C264S295000, C264S322000, C264S327000, C264S339000, C264S516000, C428S035700, C428S036900, C425S394000
Reexamination Certificate
active
06228307
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method and a device for bending a component made of a thermoplastic material, particularly a sleeve-shaped component having a straight shank, and to the component itself that can be formed to shape by this method. The component finds application in a personal care appliance such as a dental care, a hair care, a kitchen apparatus or the like.
Plastic injection molding methods are conventionally used for the manufacture of large quantities of plastic components. The methods enable components of straightforward geometrical design to be manufactured with relative ease and economy. It is difficult or impractical, however, to use the known injection molding methods for the manufacture of geometrically elaborate components with several openings, undercuts or miniature dimensions, for example. An alternative way to manufacture such plastic components formed to an elaborate geometrical shape is to assemble them from several individual parts, each of which is injection-molded separately. However, this manufacturing approach is not only highly complex but also cost-intensive, particularly where large quantities are involved, hence the need to find an alternative to the multi-part manufacturing method for the production of tubular sleeve-shaped plastic parts, for example.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and a device for forming a component made of a thermoplastic material to shape, with the manufacture of an in particular sleeve-shaped component having a straight shank being intended. In the use of this method it is important that essential dimensions such as the cross section of the component or a bore with a diameter amounting to a few tenths of millimeters be maintained. It is a further object of the present invention to provide a component which is manufacturable in accordance with a method of the present invention and which meets the geometrical requirements referred to in the foregoing. The method, the device and the component to be provided should be such that they are economical to perform and manufacture respectively, making them suitable in particular for manufacturing products in very large quantities.
This object is accomplished by the present invention in that it provides a method for bending a component injection-molded as a one-piece construction, that the component to be formed to shape is supported on a holding means, and that the component's section to be formed is shapeable by at least two tools including, for example, an inner and an outer forming tool or a bending tool. The tools are arranged for movement relative to each other, holding the component in its condition as formed until it is subsequently heated to about softening point of the respective plastic by a heating unit. Advantageously, with this method the component to be formed is bent over a forming tool by a tool at room temperature or also at a slightly elevated ambient temperature “in cold condition”. To avoid snapback of the component thus bent after the tools are opened, the formed component is stress-relieved by the action of heat. This involves holding the component in the condition as formed and heating it to at least softening point by a heating unit. This advantageously produces a permanent deformation of the integrally made plastic component.
To manufacture a component bent through an angle of 90°, for example, an inner forming tool is used to advantage. The inner forming tool, which defines the inside radius of the component, is at least in partial engagement with the component to be formed when in a stop position. The advantage thereby obtained is that any component to be formed can be brought into a defined position relative to the forming tool.
Once the component to be formed is in engagement with the inner forming tool in a defined stop position, a bending tool advantageously operates to bend the component around the stationary inner forming tool, so that it is only necessary for the bending tool to be moved around the stationary inner forming tool.
Advantageously, the bent component is in contact with the inner forming tool on at least two engagement surfaces. This produces an accurate guidance of the component on the engagement surface, enabling good repeatability of the bending operation. Moreover, the provision of the two engagement surfaces at the beginning and end of the component's section to be formed is highly advantageous because it enables bending of the component to be performed reliably without buckling occurring.
It is an advantage that during the bending operation the bending tool or the outer forming tool executes a rolling motion on the component to be formed. This enables the component to be formed to shape to particular precision with zero wear.
As the forming operation proceeds, the tools execute a linear or arcuate movement. This makes it possible for the tools to travel a minimum amount, ensuring advantageously that the tools are at all times in contact with the component to be formed during the bending operation.
In a further step of the process, the outer forming tool which has not been used yet at this stage is moved up to the bent component.
Advantageously, the inner and the outer forming tool are brought into an essentially snug engagement with the formed component. This produces the advantage of a maximum possible engagement surface of the tools with the component.
Another advantage resides in that the formed component is heatable directly by a forming tool. To this effect, the forming tool is constructed as a heating unit.
By arranging for the holding means to engage on the straight shank of the component, the component is advantageously simply and securely held during the forming process.
In an advantageous further aspect of the present invention, which may also represent an independent invention, it is proposed providing a device for bending a component made of a thermoplastic material, in particular a sleeve-shaped component having a straight shank, particularly for a personal care appliance such as a dental care, hair care, kitchen apparatus or the like. This device includes holding means for supporting the component to be shaped, and the component is shapeable by at least two tools including, for example, an inner and an outer forming tool or a bending tool which are arranged for movement relative to each other. Still further, a heating unit is provided for heating the component in its condition as formed.
According to one aspect of this device, at least one forming tool includes an engagement surface for positioning the component to be formed. This engagement surface may be, for example, a plane surface that registers with an engagement surface of the component to be formed.
Still further, it is proposed providing the forming tools with guide grooves for receiving the component to be formed. By configuring the guide grooves so as to have only a small positive allowance relative to the outside dimension of the component's section to be formed, an accurate guidance of the component on this forming tool is obtained to advantage.
Particularly conveniently, the forming tool is configured as an inner or an outer forming tool, both forming tools having corresponding forming faces. These forming faces ensure accurate engagement of the component to be formed in the tool during the forming operation.
By configuring the corresponding forming faces as sections of a circular arc, forming the component with a circular-arc-shaped section is made possible to advantage.
Advantageously, the forming face of the inner forming tool has a smaller radius than the forming face of the outer forming tool. The radius of the inner forming face then corresponds to the inner radius of the component as formed to its final shape.
To obtain a stress-free condition of the cold formed component, at least one forming tool is heatable advantageously. Thus the inner forming tool, for example, is heated following cold forming, or the outer forming tool is heated and brought
Johne Karlheinz
Kastl Hans
Majthan Rudolf
Schenk Ulrich
Braun GmbH
Dye Rena L.
Fish & Richardson P.C.
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