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Vibration Damper for an Electric Motor

IP.com Disclosure Number: IPCOM000004388D
Publication Date: 2000-Oct-30
Document File: 3 page(s) / 3M

Publishing Venue

The IP.com Prior Art Database

Abstract

Herein is described an improved vibration damper for an electric motor. The resilient vibration damper has a modified shape that decreases the stresses on the surfaces when the material is formed into a curve. The V-shaped openings eliminate compressive and tensile forces within the material when it is formed into an arc. The position and shape of the openings can be varied to provide alignment with the support ribs.

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Vibration Damper for an Electric Motor

In devices using electric motors, such as string trimmers, the electric motor is supported inside a motor housing by a support structure. These support structures may take various forms. One type of support structure commonly used is a series of transverse support ribs which engage the sides of the electric motor and inhibit any transverse displacement of the electric motor relative to the housing. In many of these devices, the member driven by the electric motor is rotatively unbalanced and which upon rotation impart a vibration to the motor itself. The vibration of the motor produces a transverse force on the ends of the support ribs engaging the motor which, after a period of time, deforms the support ribs allowing the motor to vibrate independent of the motor housing. This may be alleviated by placing a resilient vibration damper between the ribs and the motor housing. In existing applications, this resilient vibration damper is a rectangular strip of rubber or polymeric plastic.

The rectangular strip of rubber used as a vibration damping element is curved to be roughly equal to the curvature of the motor housing, as is the support structure that holds it in place. For small diameter motors, as well as for thicker vibration damping elements, the curvature of the material, which begins as a flat piece, places compressive stresses on the inner surface and tensile stresses on the outer surface of the vibration damper, reducting the life of the damper. What is needed is a way to reduce these stresses by providing a more conformable dampening element which still provides the dampening characteristics needed to absorb motor vibration.

Figure 1: Schematic of typical motor housing and vibration damping system.

Figure 1 shows a typical example of a housing for a small electric motor 20 that might be used in an application such as a string trimmer. The vibration damper 92 is supported by ends 90 of a number of ribs 86 formed in the lower housing 12 and the upper housing 14.

Figure 1: Schematic of typical motor housing and vibration damping system.

Figure 2: Typical vibration damping element, prior to installation

Figure 2 shows a drawing of the resilient vibration damper 92 removed from the housing. It is a simple block of rubber or plastic material with the desired characteristics.

Figure 3: Modified vibration damping element

Figure 3 shows a modified shape for the resilient vibration damper that decreases the stresses on the surfaces when the material is formed into a curve. The V-shaped openings eliminate compressive and tensile forces within the material when it is formed into an arc. The position and shape of the openings can be varied to provide alignment with the support ribs 86.

Figure 4: Slotted vibration dampers in motor mount

Figure 4 shows the example of Figure 1 with the modified resilient vi...