This invention relates to piston suspension assemblies for small electrodynamic acoustical transducers and particularly to those utilizing a single piece of resilient plastic material for the sound radiating dome and the piston suspension.
Piston suspension assemblies of many different shapes have been devised for use in cone displacement electrodynamic acoustical transducers containing permanent magnets to provide the electromagnetic fields required for operation. Small acoustical transducers are inexpensive and are typically found in portable two-way radio communications devices or personal electronic radio receiving apparatus.
To allow adequate expansion of the sound radiating dome, which will result in improved linear excursions during operation, small electrodynamic acoustic transducers require much larger piston suspensions than exist today. The piston suspensions found in the prior art are frought with many different types of stresses which occur at different positions within the plane of the sound radiating dome and piston suspension during cone displacement. One such stress is a "bending" stress which occurs along the circumference of the sound radiating dome at the junction of the piston suspension; a second stress is found stretching along a plane, perpendicular to the radii of the piston suspension, in the sound radiating dome. During operation, these types of stresses result in continued wear and tear of the piston suspension and sound radiating dome, thereby causing a decrease in the performance of the transducer in its ability to produce linear excursions during operation. This will result in the acoustical transducer becoming less and less effective as operation continues over a period of time.
The piston suspensions which are common in the prior art utilize arcuate slots contained within a flat (not curved) piston suspension. Generally, these slots, while relieving some of the stresses discussed above, create "bending" type stresses elsewhere in the piston suspension (i.e. in the material between the slots) and concentric "stretching" type stresses within the arcuate slots of the flat suspensions, which occur by the twisting motion of the sound radiating dome or cone during its displacement.
The prior art also illustrates that the piston suspensions of acoustical transducers are generally made from any varied materials and from a material different from that which the sound radiating dome is made. The resiliency of such materials is varied, which affects the linearity of the resulting excursions. This difference in material will introduce an additional cost in the manufacturing of the end product.
The prior art also illustrates that the sound radiating dome of an acoustical transducer is smaller in size for a given linear excursion, than the sound radiating dome associated with the piston suspension of the present invention.