Description of the Request:
Design and Engineering Services company located in Ohio requested Polymer Technologies and Polymer Molded Products' assistance in redesigning the acoustical treatment package used in a hospital bed mattress inflator.
The Design and Engineering Service company's current hospital bed inflator consisted of a blower encased in a plastic housing. The housing was comprised of two injection molded halves joined together, that would then be mounted to the frame of a bed. The blower was installed in the housing by adhering it to a molded plastic blower mount. The existing acoustical treatment package consisted of ten die cut pieces of acoustical foam. Eight of the ten pieces were assembled together to form a tortuous air inlet path to the blower. The remaining pieces were installed below and above the blower itself with the pressure sensitive adhesive. Three separate dies were required to fabricate the ten foam parts. In all, the device consisted of thirteen pieces, not counting the blower or electronics.
Polymer Technologies' Solution:
The assessment of the inflator began by first testing the unit as-is in PTI's acoustical chamber in order to establish the baseline acoustical signature of the device. The testing done by Polymer was able to determine that the overall noise level measured at the inlet of the device was over 56 dBA with several significant spikes in the frequency spectrum. There also appeared to be a fundamental frequency of 315 Hz with additional spikes present at the 1st and 2nd harmonics (630 Hz and 1,250 Hz).
Using these specifications as a reference point, Polymer Technologies was able to redesign the device's acoustical treatment package. Polymer's redesign consisted of a two piece POLYFORM® molded foam insert set that totally encapsulated the blower. The new device also formed a redesigned tortuous air inlet path. The POLYFORM® insert set was produced from the PHDM-NS chemistry and provided:
- Acoustical treatment for the air inlet and for the blower
- Vibration isolation of the blower from the housing
- A means to mount the blower in the housing
- A simplified assembly process
- Reduced inventory parts from thirteen to four
Polymer's POLYFORM® molded foam insert provided a reduction of the overall noise level over 5 dBA. It also greatly reduced the 1st and 2nd harmonic spikes that were evident in the as-received condition, which resulted in a more "acceptable" sound quality.
The newly designed device was ultimately put into production by the Design and Engineering Service company after they were able to demonstrate to their customer the benefits of using engineered POLYFORM® molded foam inserts.
Due to the success of this project, Polymer's molded foam inserts are now a standard product in use in their hospital bed mattress inflator. This is yet another example of the success that can be realized by using the all-in-one acoustical, vibration isolation, and packaging solution provided by Polymer's custom engineered POLYFORM® molded foam inserts.
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