Automated sealing of vacuum cleaners

"A vacuum cleaner is only as good as its sealing system"

Sealing, adhesive and potting systems for high-quality household appliances such as vacuum cleaners have to meet a wide range of requirements that make a decisive contribution to functionality, safety and thus the satisfaction of appliance users. One of the most important requirements of a vacuum cleaner is that dust and dirt are sucked cleanly away from surfaces. To ensure that the dirt particles are collected with the sucked air in the dust bag for later disposal and cannot escape again from the housing, the vacuum cleaner housing and the seat of the HEPA filter for even finer dust separation must be tight. Vacuum cleaner manufacturers can use the soft-elastic polyurethane foam seals from Henkel's Sonderhoff portfolio for these seals, which seal by compressing the foam structure when installed.

In a commercial vacuum cleaner, the air drawn in is usually fed directly into an air-permeable dust bag. Commonly used are bags made of multilayer filter paper or, for example, non-woven bags, which filter the air and collect the dust for later disposal. After the dust bag, the air passes through a HEPA filter that separates even finer dust. The finer the paper filters or synthetic fibers, the greater the specific surface area and the better the separation effect. The smallest particles are separated from the air by the electrostatic attraction of the fibers.

But even the best fine dust filter cannot prevent air from flowing past the filter if the filter seat and the vacuum cleaner housing leak. Therefore, many vacuum cleaner manufacturers use Sonderhoff Fermapor K31 polyurethane foam gaskets for a tight filter seat and sealing of the housing, which seal by compressing the mixed-cell foam structure. The seal thus achieves a tight filter seat without leakage and prevents aspirated dust particles from escaping from the vacuum cleaner housing.

Contour-accurate, seamless sealing of vacuum cleaner housings with polyurethane foam gaskets

For sealing of vacuum cleaner housings (Fig. 2), Henkel offers the room-temperature-curing 2-component polyurethane foam Fermapor K31-A-4025-1 as a reference material and Fermapor K31-B-4 as a B-component for reaction curing.

The polyurethane sealing foam is applied to the component contour very precisely, safely and efficiently using a fully automated mixing and dosing machine with Formed-In-Place-Foam-Gasket (FIPFG) sealing technology. The chemical reaction of the Fermapor K31 material components generally results in good adhesion to the plastic of the vacuum cleaner housing.

Thanks to a mixed-cell foam structure, the closing forces when installing the foam seal are low.

In addition, the foam seal compensates for possible component tolerances of the filter frame or the housing contour. The Fermapor K31 foam seal has excellent long-term behavior and shows good recovery of the compressed foam after relief even after years. This allows frequent opening and re-closing of the housing flap for changing the dust bag while maintaining the sealing effect of the foam gasket.

Moreover, Henkel can adapt its seal formulations to the specific requirements of its customers, e.g. the pot life until foaming starts and the curing time, as well as the viscosity, hardness, density and adhesion properties.

Sealing and bonding of vacuum cleaner filters

Manufacturers of HEPA filters for vacuum cleaners also successfully use FIP(FG) technology when it comes to precise and efficient sealing foaming and bonding of their components. The 2-component polyurethane sealing foam Fermapor K31-A-4025-1 and the hardener B-4 (B-component) are used for sealing the filter frames of HEPA filters (Fig. 3).

Henkel's customers use Fermadur adhesive sealants from the Sonderhoff product portfolio to bond the filters in the filter frames.

The 2-component adhesive sealant Fermadur A-196-9-VP1 with the B component B-N for the crosslinking reaction is available for bonding the filter packs in the filter frames (Fig. 4).

The good flow properties of the Fermadur adhesive sealants ensure a full-surface adhesive application to the inside of the filter frame and the filter pack. The filter pack placed in the filter frame is thus optimally bonded and sealed on all sides.

The curing of the sealing foams and adhesive sealants takes place at room temperature, so that the costs of a tempering oven, which is required f.e. with 1K material processes, can be saved.

In addition to the compact FERMADUR adhesive sealants, Henkel also offers foamed filter adhesives for bonding the filter packs in the filter frames (Fig. 5).

The lower weight also additionally ensures lighter and thus easier parts handling. Both save money, while still meeting the requirements for high-quality filter bonding.

Customized system solutions

Leading manufacturers of vacuum cleaners and HEPA filters have relied for years on the Formed-In-Place (Foam-Gasket) sealing technology and the wide range of innovative material systems from Henkel's Sonderhoff portfolio. The liquid to paste-applied gaskets are very easy to adapt to the geometry of the component. They thus have the advantage of lower costs and more efficient material use compared to the seals commonly used in the past. Compared to gaskets produced by 2K injection molding, FIPFG technology do not incur the high tooling costs.

For sealing the contour of the vacuum cleaner housing with sealing foam and bonding the filter pack into the filter frame, users have at their disposal a mixing and dosing system for two or three material components with the new Sonderhoff DM 50x technology from Henkel (Figs. 6 and 7). The fully automatic dosing application is carried out by the MK 825 PRO precision mixing head, which is guided over the component with contour accuracy by a 3-axis linear robot. The rack and pinion drive of the robot is characterized by high rigidity and acceleration and enables dynamic application speeds.

Parts are fed for dosing application with a shuttle/sliding table in continuous shuttle operation either with pick-up plates in one plane or in two superimposed planes, if the component height permits. In a semi-automatic solution, a machine operator takes over the placement and quality inspection of the components. If a pick & place robot is used for part handling, an optionally installed camera system performs quality control.

The advantage of using the DM 503 mixing and dosing system for 3 material components is that both the sealing foam application for sealing the filter frame and the bonding of the filter into the inside of the frame can be carried out with the same dosing system (Fig. 7).

For frame sealing, the Fermapor K31 sealing foam is applied fully automatically to the pre-programmed contour of the filter frame with high dosing accuracy. There, the applied material foams up by several times its volume and forms an elastic soft foam seal at room temperature with the desired foam hardness. After the dosing cycle, the coupling point of the foam seal closes seamlessly and is thus almost invisible.

For filter frame bonding, the 2K Fermadur adhesive sealants are applied via the mixing head to the outer edges of the filter pack and the inner sides of the filter frame in a process-safe manner. This produces a full-surface bond, with which the filter pack is optimally bonded and sealed on all sides in the frame.

Summary

Vacuum cleaner manufacturers receive a sealing and bonding solution from Henkel that is perfectly matched to their requirements, with the appropriate material system and a dosing machine that ensures contour robot-controlled, fully automatic material application. The wide range of modular system configurations with different equipment options for semi-automatic or fully automatic production can be variably adapted by the user to his production conditions. In addition, a wide range of different material systems and Henkel's many years of automation and process expertise are available to him.

"In all our system solutions, our focus is on ensuring that the dispensing technology, material system and process automation are perfectly coordinated."