EP2315956A1

EP2315956A1 - Plastic part, specifically a cage for a bearing, consisting of a radiation-crosslinkable plastic material, and method for the production thereof

Info

Publication number: EP2315956A1
Application number: EP09736106A
Authority: EP
Inventors: Arbogast Grunau; Sergej Schwarz
Original assignee: Schaeffler Technologies AG and Co KG
Current assignee: Schaeffler Technologies AG and Co KG
Priority date: 2008-08-20
Filing date: 2009-08-18
Publication date: 2011-05-04
Also published as: US8633271B2; US20110216994A1; CN102124239A; CN102124239B; DE102008038578A1; WO2010020238A1

Abstract

The invention relates to a plastic part, especially a bearing part, specifically a cage for receiving rolling bodies of a bearing, the body (1) of the plastic part consisting essentially of a radiation-crosslinkable plastic material. The aim of the invention is to provide a simple way of identifying the irradiation state of the radiation-crosslinkable plastic material during the production of the plastic parts, specifically of the cage for the rolling bearing. To this end, pigments (3, 4) that undergo a visible change during the irradiation are mixed in with the plastic material. The invention also relates to a method for producing a plastic part, especially a bearing part, specifically a cage for receiving rolling bodies of a bearing, the plastic part comprising a body (1) consisting of a radiation-crosslinkable plastic material.

Description

Name of the invention

Plastic part, especially cage for a bearing, made of a radiation-crosslinkable plastic, and method for its production

description

Field of the invention

The invention relates to a plastic part, in particular a bearing part, especially a cage for receiving rolling elements of a bearing, especially a rolling bearing, according to the preamble of claim 1, wherein the body of the plastic part consists essentially of a radiation-crosslinkable plastic. The invention further relates to a method according to claim 7 for producing a plastic part, in particular a bearing part, especially a cage for receiving rolling elements of a bearing, wherein the plastic part has a body made of a radiation-crosslinkable plastic.

If reference is made in the following to a cage made of a radiation-crosslinkable plastic or to a method for producing a cage in the description of the invention, it will be understood that instead of the cage also a bearing part, for example a bearing ring of a rolling or sliding bearing or a sliding lining of a sliding bearing or a lining of a sliding bearing track of a rolling bearing or a plastic seal, for example, for a bearing, or generally a plastic part is covered by the invention.

In the manufacture of a cage for a bearing, irradiation with high energy ionizing radiation, for example X-ray or UV radiation or by means of particle radiation (such as beta radiation) causes chemical cross-linking of the material of the body of the cage resulting as a result Radiation significantly improved in terms of wear resistance. In practice, it proves difficult to determine, without additional aids, whether sufficient radiation pretreatment of the material of the cage has taken place. The lack of ability to easily detect the irradiation state of the plastic, especially under the conditions of mass production, currently complicates the production of cages or more generally of plastic parts of a radiation-crosslinkable plastic. During the production complex and expensive measures in the process chain are required to be sure to determine whether the plastic is irradiated.

It is known from DE 10 2004 053 376 A1 and the publications cited therein and from JP 08276506 AA (abstract) to add laser-sensitive pigments to a plastic, so that the plastic provided with the pigments receives a marking or inscription during a laser treatment.

It is also known, for example from DE 103 51 813 B4 or DE 103 51 812 B4, the activation of plastics such as PTFE by means of ionizing radiation in order to couple to the activated plastic organic molecules such as polyamide to form a covalent bond.

EP 0 644 344 B1 describes a method for producing a rolling element receiving cage of a roller bearing, wherein the body of the cage from a under the action of radiation, in particular under the action of Beta radiation, crosslinkable plastic is provided, and wherein the body of the cage is fitted in the further course of the process with rolling elements. In carrying out the method it is provided that the provided body of the cage is first equipped with the rolling elements and then exposed to the radiation. It proves to be disadvantageous that the rolling elements received in the body partially shield the adjacent region of the body from the radiation, so that the solidification of the body is incomplete, especially in the vicinity of the rolling elements. The cage is not to be seen whether the irradiation has taken place, regardless of whether the cage is equipped with the rolling elements before or after the irradiation. The production of radiation-crosslinkable plastic cages therefore requires a complex control for quality assurance. It is also envisaged to apply a rather overdosed radiation dose to ensure that the cages are fully cross-linked throughout the body and therefore solidified. This goes against a requirement for the lowest possible radiation exposure.

Object of the invention

It is the object of the invention to provide a simple way to detect the irradiation state of the radiation-crosslinkable plastic in the production of plastic parts, especially the cage for the rolling bearing.

Summary of the invention

This object is achieved with the features of claim 1 and according to claim 6 and by a method according to claim 7.

The radiation-crosslinkable plastic of the body of the plastic part, especially of the cage, admixed pigments undergo during the irradiation a visually recognizable change that is easily detectable and can be detected quickly.

The optically detectable change in the pigments may be, for example, a color change which the pigments undergo due to the irradiation and which alters the color of the pigments and thus the color of the body of the cage. In this case, it is easy to determine whether the body of the cage has been sufficiently irradiated so that a required strength is achieved, as well as whether there are areas on the body of the cage that insufficient irradiation, for example due to shading of the radiation , have received. For example, it may be provided to subject critical areas, for example those which require particularly high mechanical strength or which were shaded during the first irradiation, to further targeted irradiation as aftertreatment.

There is also the possibility to carry out the irradiation targeted and in particular to select the radiation dose as low as possible and to adapt specifically to the manufacturing process.

The use of pigments in the production of plastic parts made of radiation-crosslinkable plastic as an indicator of irradiation can be easily integrated into a large-scale production and offers the further advantage that the pigments affect the mechanical properties of the plastic body at most low.

It is further understood that the pigments may also indicate whether the body of the cage has undergone a heat treatment. If necessary, two types of pigments may be provided, the first type indicating a color change upon irradiation with the high energy radiation, especially X-ray or UV radiation, and the second type of pigments having a color change upon heat input, for example a heat treatment after irradiation or a Heat input during operation of the cage. Due to the heat supply, the optical change of the pigments, for example the color change, can be reversed or the pigments can undergo a further optical change, for example a further color change.

The choice of pigments, the arrangement of the pigments on the surface or in the depth of the body of the cage and the conditions under which the pigments have the color change, further allows to enable a coding of the cage represented by the pigments such that a Certain cages or a certain batch of cages are easily identifiable and counterfeits are easily detectable, since a counterfeiter can simply mimic a color of the cage, however, the selection and arrangement of the pigments before the color change can be kept secret and in case of need in the short term and easy without the color of the cage changing significantly after the color change of the pigments.

It is preferred that the pigments comprise a powder of glasses, gemstones or semi-precious stones. The fine powder particles only insignificantly change the mechanical properties of the plastic of the body of the cage. However, it is known, for example, for glasses that they are cloudy under the action of high-energy, ionizing radiation such as X-ray, UV or particle radiation (if the glasses were transparent) and / or a discoloration, for example a darkening. Accordingly applies to a carcass of a cage, which was produced as an injection molded part and the body consists essentially of a radiation Vernetzetzbaren plastic, the fine particles of glasses were admixed that the body undergoes a change in color during irradiation, such as a gray color, the indicates at which point of the body the networking of the plastic has progressed to what extent. The same applies to powders of fine particles of a precious or semi-precious stone, such as beryl, diamond, quartz, sodium phir, spodumene, topaz, tourmaline or zirconium, which are either colorless before irradiation and obtained by the irradiation of a defined color or before irradiation have a color that deviates clearly recognizable from the color after irradiation.

As an alternative to the above-mentioned inorganic pigments, the pigments can also include organic pigments, for example, organic complexes, which are stable at temperatures up to about 100 ⁰ C and gene under irradiation of ionizing high-energy radiation a color change newspaper.

Further advantages and features of the invention will become apparent from the dependent claims and from the description of a preferred embodiment.

The invention will be described and explained in more detail below with reference to the accompanying drawings.

Brief description of the drawings

Fig. 1 shows a detail schematically an embodiment of a plastic part according to the invention.

Detailed description of the drawing

Fig. 1 shows a detail of a body 1 of a plastic part, not shown, in particular a bearing part, especially a cage for receiving rolling elements of a rolling bearing. The body 1 has a surface 2 and consists essentially of a radiation-crosslinkable plastic, such as PA66 with PTFE. Such a plastic is under the influence of high-energy radiation, preferably in particular X-radiation, crosslinkable, so that the body 1 of the cage is solidified with respect to the wear resistance.

The plastic of the body 1 of the cage pigments 3, 4 are mixed, which were selected so that these pigments 3, 4 perform a color change in the irradiation, compared to the rest of the material of the body 1 an externally visible change in the visual appearance of the body 1 of the cage, in particular a color change of the body 1 of the cage allows.

The plastic may be provided as a light, especially whitish plastic. The pigments 3, 4 are formed as particles of a powder of zirconium, wherein the size ratios in Fig. 1 for the dimensions of the particles are not to scale. Zircon is substantially colorless when unirradiated. The body 1 of the cage is substantially whitish-bright in the state before the X-ray irradiation. The irradiation gives the zirconium particles 3, 4 a color change to blue or brown, so that the body 1 becomes darker after the irradiation. The location-dependent darkening of the body 1 of the cage is a measure of the radiation dose produced at this location and thus an indicator of the degree of crosslinking of the plastic.

It is understood that the invention is not limited to the use of zirconium particles as pigments. As options for other pigments, especially inorganic pigments, offer particles of glasses, semi-precious stones or gems such as beryl (color change from pale yellow to pale pink by irradiation to green or dark blue), diamond (color change from yellowish, brownish or colorless by irradiation to blue, red, green or black), quartz (color change from colorless by irradiation to brown or black), sapphire (color change from colorless, pink or pale green by irradiation to green), spodumene (color change from pink by irradiation to yellow or green) or topaz (Color change from colorless by irradiation to blue, brown, green, or orange).

The invention is also not limited to the use of inorganic pigments; organic pigments could also be provided.

In the embodiment described above, the pigments 3 close to the surface 2 of the body 1 were made of the same material as the pigments 4 removed from the surface 2. It is understood that various pigments may be provided depending on the distance from the surface 2. As the intensity of the radiation decreases with the distance from the surface 2 in the body 1, that of the surface

2 nearby pigments 3 show first a color change, later then the surface 2 more distant pigments 4. For example, as pigments

3 zirconium particles of a zirconium powder can be provided and as particles 4 of a sapphire powder removed from the surface 2, wherein both the zirconium and the sapphire particles in the unirradiated state are substantially colorless and the body 1 of the plastic Cage whitish appears. During the irradiation, only the pigments 3 change their color from colorless to blue or brown, so that the body 1 of the cage as a whole becomes darker. As the irradiation progresses, the pigments 4 also change color from colorless to green, so that the body 1 of the cage as a whole becomes dark green.

It is further understood that various pigments 3, 4 may be present at different locations of the body 1 of the plastic part. The pigments 3, 4 can also be provided exclusively on those regions of the body 1 in which a sufficient strength is absolutely necessary, for example in the region of the cage webs of the body 1. The invention has been described above with reference to an embodiment in which the body 1 of the cage made of PA66 with PTFE. It is understood that other radiation-crosslinkable plastic, such as other polyamide types, polyether Etherketonarten, polypropylene, polyethylene or polyurethane or PTFE may be provided as plastic. It can further be provided that the radiation-crosslinkable plastic contains, in addition to the pigment 3, 4 plasticizers or crosslinking promoters as admixtures. Furthermore, it can also be provided that the plastic may contain other additives such as reinforcing fibers.

For the purposes of the present invention, the term .pigment ¹ does not only include those materials which on irradiation have a color change detectable in the visible light range. As pigments, it is also possible to provide those materials which do not undergo a color change directly upon irradiation, but exhibit luminescence, in particular can be excited by the irradiation to phosphorescence or fluorescence, in particular during subsequent illumination by means of UV radiation, for example. A corpus which has been treated with a fluorescent pigment need not have a color change which is significant in the area of visible light in the case of the irradiation causing the crosslinking of the plastic, but can make the previous irradiation optically detectable in the event of subsequent UV illumination.

LIST OF REFERENCE NUMBERS

Body surface pigment pigment

Claims

claims

1. plastic part, in particular bearing part, especially cage for receiving rolling elements of a bearing, wherein the body (1) of the plastic part consists essentially of a radiation-crosslinkable plastic, daduch characterized in that the plastic pigments (3, 4) are mixed, the undergo an optically detectable change during irradiation.

2. Plastic part according to claim 1, characterized in that the pigments (3, 4) comprise a powder of glasses, gemstones or semi-precious stones.

3. Plastic part according to claim 1, characterized in that the pigments comprise organic pigments.

4. Plastic part according to one of claims 1 to 3, characterized in that varies with the distance from the surface (2) of the body (1), the type of pigments (3, 4).

5. Plastic part according to one of claims 1 to 4, characterized records that the pigments can be excited by the irradiation for luminescence, in particular for phosphorescence or for fluorescence.

6. Use of pigments (3, 4) in the production of plastic parts, in particular bearing parts, especially cages of bearings, from radiation-crosslinkable plastic as an indicator of irradiation.

7. A method for producing a plastic part, in particular a bearing part, especially a cage for receiving rolling elements of a

Bearing, wherein the plastic part has a body (1) made of a radiation-crosslinkable plastic, comprising the steps

Providing a mixture of the radiation-crosslinkable plastic and a pigment (3, 4), and radiation crosslinking of the mixture.