METHOD FOR MANUFACTURING AN IMPELLER

Abstract

A method for manufacturing an impeller with a number of impeller blades and a cover disc covering the impeller blades. Plastic is injected into an injection mold using a cascade injection molding process to form the impeller. The injection mold has a number of shut-off nozzles to feed the plastic at various joint positions and different opening times. The number of shut-off nozzles is determined as a function of the number of impeller blades.

Claims

1. A method for manufacturing an impeller with a number of impeller blades and a cover disc covering the impeller blades comprising: injection-molding the impeller blades from plastic into an injection mold using a cascade injection molding process; feeding the plastic into the injection mold via a number of shut-off nozzles at different joint positions with different opening times; and determining the number of shut-off nozzles as a function of the number of impeller blade.

2. The method as set forth in claim 1, further comprising correlating various joint positions with the cover disc.

3. The method as set forth in claim 2, further comprising correlating the various joint positions of the cover disc in such a way that, when viewed in a projection, the joint positions of the cover disc are each located between the impeller blades.

4. The method as set forth in claim 1, wherein if the number of impeller blades is even, the number of shut-off nozzles corresponds to the number of impeller blades.

5. The method as set forth in claim 1, wherein if the number of impeller blades is odd, the number of shut-off nozzles is greater than the number of impeller blades.

6. The method as set forth in claim 1, wherein if the number of impeller blades is odd, the number of shut-off nozzles is twice that of the impeller blades.

7. The method as set forth in claim 1, wherein a plurality of the shut-off nozzles are respectively divided into cascade groups, and the cascade groups have successive shut-off nozzle opening times.

8. The method as set forth in claim 7, further comprising positioning the shut-off nozzles of one of the cascade groups where the joint lines of the plastic fed from the shut-off nozzles of another cascade group are located.

9. The method as set forth in claim 1, wherein the impeller is a radial impeller.

10. The method as set forth in claim 1, wherein the plastic is a fiber-reinforced plastic.

11. An impeller manufactured according to the method as set forth in claim 1.

Description

DRAWINGS

[0019] Other advantageous refinements of the disclosure are depicted in greater detail below together with the description of the preferred embodiment of the disclosure with reference to the figures.

[0020] FIG. 1 is a perspective view of an impeller according to a first design variant.

[0021] FIG. 2 is a perspective view of an impeller according to a second design variant.

DETAILED DESCRIPTION

[0022] FIG. 1 shows a perspective view of an impeller 1 in a first design variant. It includes a bottom disc 4, a cover disc 3, and impeller blades 5, formed axially therebetween. This exemplary embodiment relates to an impeller 1 that is embodied as a radial fan with six impeller blades 5. Even though a bottom disc 4 is shown in FIG. 1, impellers without a bottom disc can also be produced.

[0023] The impeller 1 is manufactured from thermoplastic material using the method described in the injection mold using a cascade injection molding process. The impeller 1, with six impeller blades 5, includes six needle valve nozzles 6, 7 provided as joint positions to feed the plastic. Preferably, it is a hot runner system. The feed 9 is provided at joint positions that are equally spaced apart in the circumferential direction, via which the plastic is injected into the cavity of the injection mold.

[0024] The joint positions of the needle valve nozzles 6, 7 are correlated with the cover disc 3. This means that the liquid plastic is introduced into the region that forms the cover disc 3. When viewed in the circumferential direction, the joint positions of the needle valve nozzles 6, 7 are located between the impeller blades 5. They are adjacent to and not on the connecting lines of the impeller blades 5 and the cover disc 3, when viewed in an axial projection. During the manufacture of the impeller 1, the liquid plastic flows in the circumferential direction over the region of the cover disc 3. This represents the connecting lines of the impeller blades 5 and the cover disc 3.

[0025] The needle valve nozzles 6, 7 are divided into two cascade groups. The needle valve nozzles 6, provided with reference numeral 6, form the first group. The needle valve nozzles 7, provided with the reference numeral 7, form the second group. Both cascade groups of the needle valve nozzles 6, 7 have successive opening times. Thus, the melt front of liquid plastic from the needle valve nozzles 6, of the first cascade group, respectively, travels past the needle valve nozzles 7 of the second cascade group, when the needle valve nozzles 7 of the second cascade group are opened. The needle valve nozzles 7 of the second cascade group are positioned exactly where the joint lines of the plastic fed from the needle valve nozzles 6 of the first cascade group are located.

[0026] FIG. 2 shows an alternative exemplary embodiment of an impeller 1. The features of the embodiment from FIG. 1 are substantially identical, but the number of impeller blades 5 and joint positions with the needle valve nozzles 6, 7 varies. The impeller 1 does not have six, but only five impeller blades 5, an odd number. In order to eliminate the formation of joint lines in the same way as in the embodiment according to FIG. 1, the number of joints and needle valve nozzles 6, 7 is twice that of the impeller blades of FIG. 1. Here, the plastic is injected in temporal succession between the impeller blades 5 through cascade injection, via two cascade groups. The groups are composed of the needle valve nozzles 6 and the needle valve nozzles 7, thereby eliminating the joint lines.

[0027] The disclosure is not limited in its execution to the abovementioned preferred exemplary embodiments. Rather, a number of variants are conceivable that make use of the illustrated solution even in the form of fundamentally different embodiments. For example, the method can also be applied to axial fan impellers with and without a bottom disc. Fiber-reinforced thermoplastics can also be preferably used as plastics.

[0028] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.