| 摘要 |
A dust shroud for a portable circular saw is described comprising an upper blade housing, a lower blade housing, an external connecting link connecting the two and aligned with the saw blade, and flexible sealing means attached to the upper part of the lower blade housing. The thickness of the connecting link is not greater than the thickness of the saw blade and since the link is aligned with the saw blade it follows the saw blade through the kerf created by the blade in the worksheet. The upper blade housing is attached directly to the saw's motor housing and moves therewith while the lower blade housing is attached to the upper blade housing through the connecting link and is thus kept aligned with the upper housing as the saw cuts through the workpiece. The flexible sealing means keeps dust from escaping from the lower blade housing since it continuously conforms to irregularities in the surface of the workpiece. The total area of openings into the blade housings is minimized in order to keep the air velocity as great as possible within the housings. The air entry area provided by the flexible sealing means is also minimized consistent with drag forces created, so that the saw may be smoothly moved across the workpiece. Different embodiments of the sealing means are disclosed for use with flat workpieces or those with only small to moderate irregularities and with workpieces of more highly irregular surfaces, such as corrugated sheets. Both upper and lower housings are connected through exhaust ducts to vacuum sources such that dust generated by the saw blade is confined within the housings from which it is withdrawn and collected by the exhaust ducts and vacuum system. Extremely low airborne dust counts in the vicinity of the saw in service are obtained with this device.
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