Patent Application
20080070036
A ring collar 16 serving to lock the joint pin upon insertion into an associated joint connection (cf.
In the present case, the joint pin is made from a polyamide 6.6 material, which has a melting temperature of approximately 260° C.±5° C. The glass transition point in this material usually lies at approximately 70° C. to 50° C., depending on the moisture content of the material used.
The ideal working temperature here for the reshaping process lies above 110° C., in particular, in the range of 120 to 140° C., at which the reshaping step can be carried out without too great an expenditure of force.
Polyamide (PA) 6.6 shows a thermal, oxidative degradation only under extreme long-term exposure to temperatures above 140° C., where long-term exposure is to be understood as exposure over several days.
Since the holding time of the blank during and after the reshaping process can be limited to approximately 30 sec or even less (in dependence upon the diameter of the joint pin 10) it will be clear that the reshaping conditions in accordance with the method according to the invention are very remote from conditions under which thermal and oxidative degradation reactions are usually observed in the resin material PA 6.6. Only at temperatures of 220° C. are thermal and oxidative degradation reactions observed at holding times of longer than 1 h.
The expenditure of force for the described reshaping and formation of the functional elements 14 and 16 lies in the case of a blank having a diameter of 3 mm at approximately 40 to 200 MPa.
Very many different resin materials can, of course, be used for the manufacture of the joint pin 10, in particular, also such in which the glass transition temperature lies much lower than in the PA 6.6 discussed hereinabove.
Materials such as PA 11 and PA 12 are, for example, suitable. PA 11 has a glass transition temperature of approximately 43 C and a melting temperature of approximately 183° C. PA 12 has a glass transition temperature of approximately 45° C. and a melting temperature of approximately 175° C. The processing temperatures in conventional methods, at which the polymers are melted, lie at approximately 190 to 210° C. for both PA polymers.
A further material which demonstrates the range of materials that can be processed with the method according to the invention is polyoxymethylene (POM), which has a melting temperature of approximately 200° C., with a glass transition temperature which lies significantly under 0° C., namely at approximately −60 C.
In the case of such a material, that partial area or portion of the blank at which the reshaping or the formation of the functional element is to take place is determined by heating the portion of the blank that is to be reshaped to a temperature above room temperature. In principle, the reshaping could, of course, take place here without any heating to a temperature above room temperature, but there is then the problem that a change in the shape of the blank may also occur in the fixing tool and, in this case, the blank will then lose its previous perfectly cylindrical shape.
If, on the other hand, such materials with very low glass transition temperatures are heated in the area that is to be reshaped to a temperature significantly above room temperature, for example, to a temperature of 50° C., the reshaping process can then be limited very precisely to the heated portion of the blank.
Typical diameters of the rod-shaped components according to the invention range from 2 mm to 10 mm.
If an annular collar is desired as further functional element at a location spaced further from the head 14, this can also be accomplished in accordance with the invention, but this is then preferably performed in a separate reshaping step. This will be gone into in further detail hereinbelow in connection with the description of
The apparatus comprises a three-jaw chuck 64, which is mounted on a base plate 62, and through the center of which a continuous bore (not shown) extends, in which a rod-shaped blank can be received for manufacture of a rod-shaped component according to the invention.
The three-jaw chuck 64 comprises three radially displaceable jaws 66, which can be synchronously displaced in radial direction inwardly and outwardly, respectively.
In the assembled state, a guide ring 68 is supported on the three jaws 66 of the three-jaw chuck 64. At its end face 70 that faces the jaws 66, the guide ring 68 has three grooves 72 in which the jaws 66 slidingly engage.
A centering of the guide ring 68 relative to the center of the position defined by the three-jaw chuck for the fixed blank is thereby prescribed.
In the guide ring 68 there is axially displaceably held a swage plate 74 having a central cutout 76 which functions as negative mold for the formation of a spherical cap-shaped head on the blank that is to be processed.
Once the blank has been introduced into the three-jaw chuck and clamped in a centered manner by the latter, the blank can be heated (heating jacket 69) in the portion that is to be reshaped by the guide ring 68, which constitutes part of the reshaping tool, and once the blank has reached the reshaping temperature in this portion, the swage plate 74 is then displaced in axial direction against the jaw chuck 64, in the example shown here by means of a feed screw 78, which is received in a thread by an assembly plate 80. The assembly plate 80 is connected via tension rods 82 to the base plate 62, so that the force exerted by the feed screw 78 results in a compression of the portion of the blank raised to reshaping temperature.
If recesses (cf. description of
For release of the component, the pressure of the feed screw 78 is first taken away and the jaw chuck opened, whereupon the finished component can then be removed from the apparatus.
As is clearly apparent from the drawing of
The method according to the invention and the tool according to the invention also allow, in case of doubt, emergency repairs where, for example, in the case of breakage of a joint pin, only a portion of the latter needs to be replaced, which can then be inserted from the direction opposite to the still functioning remainder into and fixed in the joint of the chain belt.
In the description of the foregoing tool, a jaw chuck was used to fix the blank in the apparatus and to then cause the agglomeration of material in the portion to be reshaped using a reshaping tool in the form of a swage, thereby forming the desired functional elements.
This is achieved in the above-described manner at the free ends of the blank. If, however, a functional element is to be produced at a spacing from the ends of the blank, it is recommended that the reshaping tool be modified as shown schematically in
The apparatus in
Differently from the apparatus according to
It will be clear from this description that with the method according to the invention and the apparatus according to the invention, functional elements can be formed at any point on rod-shaped components of any length, a process which can, of course, also be performed a number of times on a blank 96.
The only precondition, in this connection, is that the jaw chucks provide a corresponding recess for functional elements that have already been formed or that the jaw chucks be of such dimensions in their axial extent that they avoid contact with functional elements already formed on the blank/rod-shaped component.
It will also be understood that as for the apparatus shown in and described in conjunction with
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 045 736.6 | Sep 2006 | DE | national |
