Pin

Abstract

A pin with at least one sleeve-shaped component (12, 22) having a longitudinal axis (L) and a bottom (24), characterized in that the wall thickness of the bottom (24) changes along a closed line (28) which lies on the surface of the bottom (24) facing the interior of the sleeve-shaped component (12, 22) and runs concentrically to the longitudinal axis (L).

Description

The invention relates to a pin having at least one sleeve-shaped component which has a longitudinal axis and a base.Pins of the type mentioned at the beginning are known. In this case, the sleeve-shaped component, which can be, for example, a protector or a shank, is produced from plastic by way of injection molding. In this case, methods with indirect core centering at the injection point are often used, the injection point lying at the base of the sleeve-shaped component. Due to the geometry used in this case, the core in the tool is stabilized during the injection process and is not pushed aside. However, constrictions occur, as a result of which the pressure increases. The result is a restricted to no process window and higher energy requirement. If higher viscosity plastic is used, the material can freeze during injection before a full filling of the mold is achieved. Especially in the case of PET (polyethylene terephthalate), streaks are frequently formed on the surface of the sleeve-shaped component.The object of the invention is to further develop the pin of the type mentioned at the beginning in such a way that the problems explained above in detail do not occur during injection molding, in particular a sufficiently large process window is achieved, the energy requirement is reduced and, in particular in the case of the use of PET, the formation of streaks on the surface of the sleeve-shaped component is restricted or even avoided.According to the invention, the object set is achieved with a pin of the type mentioned at the beginning in that the wall thickness of the base changes along a closed line which lies on the surface of the base facing the interior of the sleeve-shaped component and runs concentrically with respect to the longitudinal axis.In other words, the sleeve-shaped component is given a contour which solves the problems during injection molding explained in detail above. This is because the contour of the component corresponds to the contour of the casting mold.The invention is based on the finding that by changing the wall thickness of the base along the closed line, a better distribution of the material during injection can be achieved, whereby the pressure is lowered and the process window is enlarged. In addition, the energy requirement is lowered. It is also avoided that, in the case of the use of higher viscosity plastic, the material freezes during injection before complete filling of the mold is achieved. The formation of streaks is reduced or even avoided.Finally, the shaping according to the invention for the base of the sleeve-shaped component results in greater freedom in the selection of the ratio of wall thickness to length, in particular in the case of highly viscous plastic.The manner of varying the wall thickness of the base along the line mentioned can be chosen as desired in a suitable manner. According to the invention, it is preferably provided that the wall thickness of the base increases and decreases again two, three or more times along the line.In this case, the base can have two, three or more first regions along the line, the wall thickness of which is greater than in second regions lying between adjacent first regions in the circumferential direction.According to a further preferred embodiment of the invention, it is provided that the wall thicknesses of the first regions are of the same size.This achieves a particularly uniform distribution of the injected material.According to the invention, the first regions can in principle be attached at any desired locations on the floor, as long as the effects described above are achieved. However, it is preferred according to the invention to arrange the first regions such that an imaginary cylinder surface runs in the middle between the longitudinal axis and the inner wall of the sleeve through at least one of the first regions.With this arrangement, the first regions are very effective within the meaning of the invention.According to a particularly preferred embodiment of the invention, it is provided that the first regions are distributed uniformly along the line.Uniform distribution is understood here to mean that the angular distances between adjacent first regions along the line are of equal size. In the case of two first regions, the angular distances are thus 180°. In the case of three first regions, it is 120°.The uniform distribution of the first regions also achieves a uniform distribution of the material during injection.The wall thickness of the base in the first regions can in principle be chosen as desired, as long as the above-mentioned effects are achieved. According to the invention, the wall thickness of the base in the first regions is k times as great as in the second regions, with 1.5≤k≤2.5, preferably 1.7≤k≤2.3, more preferably 1.9≤k≤2.1.The above measures allow the most varied materials to be used for the production of the pin and in particular of the sleeve-shaped component. This applies in particular to PET. Therefore, according to the invention, it is preferably provided that the sleeve-shaped component is made of PET. Moreover, the entire pen can also be made exclusively of PET, which considerably simplifies its recycling.According to the invention, the PET is more preferably recycled PET.The sleeve-shaped component can be a protector or a shank of the pin according to the invention.Furthermore, the invention also provides a sleeve-shaped component of a pin of the type described above.Moreover, the invention also provides a mould for the sleeve-shaped component of the pin of the type described above.Finally, the invention also provides a casting core of the above casting mould.The invention is explained in more detail below on the basis of a preferred exemplary embodiment with reference to the accompanying drawing. Figure shows FIG. 1 is a schematic view, partly in section, of the bottom of a guard of a pin according to a preferred embodiment of the invention, FIG. 2 is a schematic longitudinal sectional view of the protector of FIG. 1, FIG. 3 shows a detail from FIG. 2, on an enlarged scale, FIG. 4 is a schematic longitudinal sectional view of the pin with the protector according to FIGS. 1 to 3, FIG. 5 shows a core of a casting mold for producing the protector according to FIGS. 1 to 3, and FIG. 6 shows a casting mould for producing the protector according to FIGS. 1 to 3.The pen 10 shown in the drawing includes a sleeve-shaped shaft 12 and a lead 14 which is disposed within a cartridge 16 and is supported by a lead holder 18. The advancement of the lead 14 is effected by the extension of the lead holder 18. By rotating the shaft 12 against the cartridge 16, a nut 20 held stationary in the shaft 12 is also rotated. The lead holder 18 has a threaded rod on the side facing away from the lead 14, which threaded rod is inserted into the screw nut 20. The cartridge 16 and the mine holder 18 are secured against relative rotation by ribs / webs on both components. Thus, the mine 14 can be extended or retracted by rotating the cartridge 16 and the shaft 12. The longitudinal axis of the pin 10 is denoted by the letter L. Finally, the pin 10 includes a protector 22.The protector 22 is sleeve-shaped and has a bottom wall 24.The wall thickness of the base 24 is not constant along a closed line 28 lying concentrically to the longitudinal axis L on the surface of the base 24 facing the interior of the protector 22. Instead, there are regions 30, 32, 34 in which the wall thickness of the base 24 is greater than in regions 31, 33, 36 lying therebetween.In the exemplary embodiment of the protector shown in the drawings, the wall thickness W 1 in the first regions 30, 32, 34 is 0.7 mm, whereas the wall thickness W 2 in the regions 31, 33, 36 lying therebetween is 0.35 mm. In other words, in the protector 22 shown in the drawings, the wall thickness W 1 is twice as large as the wall thickness W 2.As can be seen in particular from FIG. 1, three regions with the greater wall thickness W 1 are provided in the protector 22, which regions are distributed uniformly, i.e. with the same angular spacing of 120° along the line 28 about the longitudinal axis L. They all have the same wall thickness W 1. The same applies to the regions lying therebetween which likewise have the same wall thicknesses, although this is the smaller wall thickness W 2 in this case.An imaginary cylinder surface 38 in the middle between the longitudinal axis L and the inner wall 26 of the protector 22 runs through the regions 30, 32, 34 in the protector 22 illustrated in the drawings.The protector 22 shown in the drawings is made of recycled PET. The same applies to the other components of the pin 10, with the exception of the lead 14.The above discussion of the protector 22 also applies to the shaft 12.Figure 5 shows a core 40 having a recess 42 therein. the core 40 is used in injection molding the protector 22.Moreover, FIG. 6 shows a mold 44. Again, the mold 44 is a mold used for injection molding the protector 22. The core 40 is introduced into the casting mold 44 from the left in FIG. 6. As a result, a channel is formed at the right end of the cavity of the casting mold 44 between the recess 42 on the core 40 shown in FIG. 5 and the protrusion at the lower end part of the cavity; here, the melt is supplied. The injection point 46 is situated at the bottom right in FIG. 6.During casting of the protector 22 with the casting mold 44 and the core 40 therein, the channels 42 and 46 serve to form the regions 30, 32 and 34 respectively of the bottom 24 of the protector 22.A similar mould and core are used for injection moulding the shank 12.The features of the invention disclosed in the above description, the claims and the drawings can be essential both individually and in any combination for the realization of the invention in its various embodiments.

Claims

A pin having at least one sleeve-shaped component (12, 22) which has a longitudinal axis (L) and a base (24), characterized in that the wall thickness of the base (24) changes along a closed line (28) which lies on the surface of the base (24) facing the interior of the sleeve-shaped component (12, 22) and runs concentrically with respect to the longitudinal axis (L).Pin according to claim 1, characterised in that the wall thickness (W 1, W 2) of the base (24) increases and decreases again two, three or more times along the line (28).Pin according to claim 1 or 2, characterised in that the base (24) has two, three or more first regions (30, 32, 34) along the line (28), the wall thickness (W 1) of which is greater than in second regions (31, 33, 36) lying between adjacent first regions in the circumferential direction.Pin according to claim 3, characterised in that the wall thicknesses (W 1) of the first regions (30, 32, 34) are of the same size.Pin according to claim 3 or 4, characterised in that the first regions (30, 32, 34) are arranged in such a way that an imaginary cylinder surface (38) runs through at least one of the first regions in the middle between the longitudinal axis (L) and the inner wall (26) of the sleeve-shaped component (12, 22).The pen according to any one of claims 3 to 5, characterized in that the first zones (30, 32, 34) are evenly distributed along the line (28).Pin according to one of claims 3 to 6, characterised in that the wall thickness of the base (24) in the first regions (30, 32, 34) is k times as great as in the second regions (31, 33, 36), where k is 1.5 ≤ k ≤ 2.5, preferably 1.7 ≤ k ≤ 2.3, more preferably 1.9 ≤ k ≤ 2.1.Pin according to one of the preceding claims, characterized in that the sleeve-shaped component (12, 22) is made of PET.The pen according to claim 8, characterized in that the PET is recycled PET.Pin according to one of the preceding claims, characterized in that the sleeve-shaped component (12, 22) is a protector (22) or a shank (12) of the pin.Sleeve-shaped component of a pin (10) according to one of the preceding claims.A mould (44) for the sleeve-shaped component (12, 22) of the pin (10) according to any one of the preceding claims.The casting core (40) of the casting mold (44) of claim 12.

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