This invention relates to respirators, more especially powered respirators for use in a dusty environment.
At a Symposium entitled "Technical Measures of Dust Prevention in Mines" held in Luxembourg in October 1972, a powered respirator hood was described in which air was arranged to be drawn forward between the hood and an inner skin through a filter and down over the wearer's face. Such a hood has been found to be difficult to construct and hot to wear. The hood also had a flexible skirt at shoulder level so that the gap between the hood and the wearer's body was minimised, thus also minimising the risk of unfiltered, dusty air reaching the wearers face from below. However, the skirt may be disadvantageous in confined conditions when maximum freedom of movement of the head relative to the shoulders is required. A British patent application covering the hood was filed on May 9, 1972 as No 21584/72. .
It is an object of the present invention to overcome the above-listed disadvantages of the previously disclosed respirator hood.
According to the invention, a respirator comprises a hood having support means by which it can fit over the head of a wearer and be supported so as to leave a space between the hood and the wearer's head, sealing means attached to the hood and arranged so as to form, in use, a seal between the hood and the back and sides of the wearer's head, and means to supply filtered air which can pass over and in contact with the wearer's head and down over the wearer's face to escape at the lower forward edge of the hood. The hood generally conforms to the shape of the wearer's head and can be used without a shoulder length skirt so that the hood can be worn in confined working situations.
The sealing means may be, for example, a band of flexible expanded plastics material, and may also form a seal down the sides of the wearer's face.
The means to supply filtered air may comprise a filter fitted in said space between the hood and the wearer's head and an air displacing device by which, in use, air can be propelled through the filter. The filter may be of large surface area and occupy a major portion of the space between the hood and the top of the wearer's head, may be, for example, a bag filter, and may be made of any conventional filter material such as a resin-treated wood felt.
Optionally the filter may be of sufficiently large area to allow an adequate supply of air to be drawn or propelled through it by means of a low-power air displacing device such as an electrically driven fan powered by a cap lamp battery attached to the hood or to a belt round the wearer. Because the power required to drive the fan is low, the cap lamp battery may still provide power for a miner's cap lamp or similar lamp attached to the hood.
The air displacing device may be advantageously arranged at the rear of the hood so that it does not increase the height of the hood above the top of the head of the wearer, or project to any material extent beyond the rear of the hood.
The filter may have sound-absorptive properties to reduce the noise from the fan reaching the wearer. Additional sound absorptive material may be incorporated as a lining to the hood. The filter may be produced at a low cost, and further advantages are that the
filter may be protected from damage by the outer skin of the hood.
In another form, the means to supply filtered air may be an air supply hose connected to a remote source 5 the hose is preferably connected to the rear of the hood.
The hood may have a visor which can be opened if required, the outer skin of the hood may be a helmet which is sufficiently strong to protect the wearer from
10 falling or obstructing bodies, and the support means may be conventional helmet-supporting harness.
It is an advantage of a respirator according to the invention that it is relatively simple to construct, that the passage of air over the top of the wearer's head
15 provides a cooling effect and that there is minimum restriction of head movement. In the form utilising a battery driven air displacing device, the need for a trailing air hose or electric cable is eliminated. Such a respirator is particularly suitable for use in dusty envi
20 ronments such as a coal mine or foundry, especially in confined spaces.
When the sealing means is extended down the sides of the wearer's face, the gap at the lower edge of the hood through which air escapes can be very small , so
25 that the chance of dusty air entering the hood from below is minimised.. If required, an exhalation valve can be provided at the lower edge to further reduce the risk. Alternatively, a flexible skirt attached to the lower edge of the hood can be provided reducing the gap still
30 further although the skirt may restrict head movement somewhat.
The invention will now be described by way of example only with reference to the accompanying drawings in which:
35 FIG. 1 is a diagrammatic front to rear cross sectional view of one form of respirator as worn; and FIG. 2 is a similar view of an alternative respirator In FIG. 1, a hood indicated generally by reference numeral 30 comprises an outer rigid skin 31, a hood
40 supporting harness 32 and an air inlet 33. A fan 34 is situated near the air inlet 33 and is connected by lead 35 to a cap lamp battery (not shown). A bag filter 36 is attached at its mouth 37 to the outer skin 31 and to the supporting harness 32 and is arranged to lie between
45 the outer skin 31 and the top of the wearer's head. A band of expanded polyurethane 38 is attached to the outer skin 31 and forms a seal at the back and sides of the wearer's head and down the sides of the wearer's face. The hood has a visor 39 (which may be either
50 fixed or pivoted so as to be openable) and the outer skin is shaped at 40 to remain clear of the wearer's ear 41.
In operation, the fan 34 propels dusty air through the inlet 33, through the filter mouth 37, and through the
55 filter 36 as indicated by the arrows 42. The dust is retained by the filter 36 and clean air indicated by the arrow 43 flows past the face of the wearer and escapes at the bottom edge of the visor 39. The flexible band 38 prevents air from escaping at the sides or rear of the
60 wearer's head.
In FIG. 2, a hood indicated generally by reference numeral 44 has a support harness 45 and a band of expanded polyurethane 46. From a remote source of filtered air 52 an air hose 47 is connected by connect
65 ing means 48 to the rear of the hood. To the lower edge of the hood 44 and a fixed visor 49 is connected a flexible skirt 50. In use, air passes along the hose, over the top of the wearer's head, down past the wearer's