GB2116430A - Massager with noise reduction - Google Patents

The invention is related to battery driven, hand held massagers. The firm connection between the motor unit (B & C) and the case (G) is replaced with modified suspension, the whole forming a low-pass mechanical filter. The required low frequency vibrations are transmitted to the case and the higher frequency components are attenuated. The ear being more sensitive to these higher frequencies, the effect is a considerable reduction in the audible noise. <IMAGE>

SPECIFICATION Massager with noise reduction The invention relates to the mechanical arrangements in battery driven, hand held massagers. The conventional massager has a thermoplastic case (G) containing batteries (A), and a motor (B) which drives a free eccentric cam (C). The motor is controlled by an on off switch an speed adjuster (H). The motor is fixed firmly to the case. The reaction of the motor to the rotation of the cam is transferred to the case to produce the required vibration. Due to the characteristics of the motor unit, the vibration in a fixed radial direction is not sinusoidal but of a complex waveform, giving rise to an unpleasant noise.

The invention reduces the audible noise by allowing the transmission of the low frequencies of vibration whilst attenuating the higher frequencies to which the ear is more sensitive.

This is carried out by any mechanical system interposed between the motor unit and the case, forming a low-passfiiter to the transmission of vibrations.

A simple embodiment of this principle is shown in the diagram. An elastic material (D) is used to suspend the motor unit in the case. The mass of the case together with that of the batteries held firmly by compressed foam plastic (E) and the elastic suspension form a resonant mechanical system. The wires (F) carrying current to the motor need to be flexible.

The resonant frequency (HZ) is made the same order as the motor speed (Revs/Sec). Above this frequency the velocity/frequency characteristic falls at a rate approaching 6db per octave. The amplitude of the vibrations is not appreciably affected and the noise is reduced to a slight hum.

Claim

The claim is that the noise emitted from a battery driven, hand held massager can be reduced to an acceptable volume by the introduction of a mechanical low-pass filter system to prevent the higher frequencies of vibration being transmitted from the motor unit to the case.

**WARNING** end of DESC field may overlap start of CLMS **.

1. **WARNING** start of CLMS field may overlap end of DESC **.

   SPECIFICATION Massager with noise reduction The invention relates to the mechanical arrangements in battery driven, hand held massagers. The conventional massager has a thermoplastic case (G) containing batteries (A), and a motor (B) which drives a free eccentric cam (C). The motor is controlled by an on off switch an speed adjuster (H). The motor is fixed firmly to the case. The reaction of the motor to the rotation of the cam is transferred to the case to produce the required vibration. Due to the characteristics of the motor unit, the vibration in a fixed radial direction is not sinusoidal but of a complex waveform, giving rise to an unpleasant noise.

   The invention reduces the audible noise by allowing the transmission of the low frequencies of vibration whilst attenuating the higher frequencies to which the ear is more sensitive.

   This is carried out by any mechanical system interposed between the motor unit and the case, forming a low-passfiiter to the transmission of vibrations.

   A simple embodiment of this principle is shown in the diagram. An elastic material (D) is used to suspend the motor unit in the case. The mass of the case together with that of the batteries held firmly by compressed foam plastic (E) and the elastic suspension form a resonant mechanical system. The wires (F) carrying current to the motor need to be flexible.

   The resonant frequency (HZ) is made the same order as the motor speed (Revs/Sec). Above this frequency the velocity/frequency characteristic falls at a rate approaching 6db per octave. The amplitude of the vibrations is not appreciably affected and the noise is reduced to a slight hum.

   Claim

   The claim is that the noise emitted from a battery driven, hand held massager can be reduced to an acceptable volume by the introduction of a mechanical low-pass filter system to prevent the higher frequencies of vibration being transmitted from the motor unit to the case.