GB2063074A

GB2063074A - Protective respiratory helmet

Info

Publication number: GB2063074A
Application number: GB8034989A
Authority: GB
Original assignee: Martindale Protection Ltd
Current assignee: Martindale Protection Ltd
Priority date: 1979-10-30
Filing date: 1980-10-30
Publication date: 1981-06-03
Also published as: GB2063074B

Abstract

A protective respiratory helmets suitable for use in a polluted atmosphere comprises a head cover (11) which is secured to the head of the wearer by an internal head band and harness. A visor is pivotally mounted on the cover (11) by bearings. Filtered air is supplied to the visor via a duct (28) fitted to the inside of the head cover (11). A forehead seal is provided around the inside of the front of the cover comprising a flexible tube (20) with an internal flap (14). A motor and fan in a housing (33) draws ambient air into the duct (28) through a bag filter (42) located in a removable plastics filter case (43). <IMAGE>

Description

SPECIFICATION Protective respiratory helmet The present invention relates to a protective respiratory helmet, for example, a compact helmet which does not require external air lines, and is suitable for people working in a polluted atmosphere.

According to the present invention, a protective respiratory helmet includes a head cover, a filter, a motor driven fan arranged to cause ambient air to flow through the filter into the space within the head cover, and a case for the filter removably attached to the head cover over substantially the whole of the back wall of the head cover where it will be behind the head ofthewearer.

In a preferred embodiment, the case comprises a box containing the filter and adapted to fit at the entrance to the face. The filter is in the form of a bag possibly of electret material as described in British Patent Specification No. 1,469,740, with the wall area of filter material being substantially greater than the area of the entry to the case and the area of the exit from the case to the fan.

The helmet may have an internal duct leading air from the fan to an opening which will be at the front of the forehead of the wearer. The duct may also be removable from the head cover. The motor driven fan is preferably mounted at the inlet end of the internal duct.

The head cover may have a sealing element adapted to seal around the forehead of the wearer, and the duct may lead beyond the sealing element to the breathing area of the wearer.

Avisor may be adjustably mounted on the head cover and arranged when in the lowered position to effect an automatic seal around the region of the wearer's face established partly by the sealing element in the head cover, and partly by a second sealing element carried by the visor. The visor may include a non-return exhaust valve to allow air from inside the visor to be expelled.

In most environments, the visor will be made out of clear material but it may be preferred to replace this visor with a welding visor of a suitably dark material or it may be desirable to have a second welder's visor on top of the clear visor. This allows the welder working in a contaminated environment to selectively use the welder's visor while remaining protected from the ambient air.

It will be clear that the user can then only breathe air which has been filtered. Preferably there will be a flow-rate sensor arranged to give a warning if the rate of air flow is too low.

Thus the filter can be of large surface area so that a large air flow can be achieved, while yet it does not obscure the user's field of view because of its position at the back of the head cover.

The invention may be carried into practice in various ways, and one embodiment will now be described by way of example, with reference to the accompanying drawings; of which Figure 1 is a side elevation partly in section of a protective respiratory helmet for persons working in a contaminated atmosphere; Figure 2 is a sectional plan view; Figure 3 is a back view of the helmet of Figure 1; and Figure 4 is a exploded view of the helmet of Figure 1.

The helmet comprises a head cover 11 moulded from a hard plastics material, and fitted with an internal head band and harness secured around the inside of the head cover to enable it to be carried comfortably on the head of the wearer. Around the inside of the front of the cover, is a forehead seal 13 comprising a flexible tube 20 with an internal flap 14 on its cross section, which will be urged by its natural resilience against the head of the wearer when he puts the helmet on. The seal 13 terminates circumferentially in a downwardly facing surface at either side of the forehead.

A visor moulded from a hard transparent plastics material is hinged on external bosses moulded on opposite sides of the head cover 11. The visor is capable of being hinged between a lowered position and a raised position.

The upper edge of the visor is formed with a sealing member for sealing the visor around the edge of the head cover 11-in the lowered position. In that position a face seal clipped around an external rim on the visor makes a seal around the sides of the face and under the chin of the user and also butts against the downwardly facing surfaces so that the wearer's face is in a sealed chamber.

Filtered air is introduced into the space in front of the user's face through a duct 28 defined by a separate moulding 29 which is fitted into the inside of the head cover 11.

The moulding 29 defines the duct 28 which is of more-or-less constant cross sectional area throughout its length from above the back of the wearer's head to the front of his forehead, although that cross section changes shape from being circular at the inlet end 31 to being curved and elongate and long and narrow to conform to the wearer's forehead at the outlet 32. The change in cross sectional shape is smooth.

At the inlet end 31, the moulding 29 is fitted around a housing 33 for a motor and fan.

The complete assembly of the moulding 29 with the motor and fan housing 33 is fitted into the head cover 11 and secured in position by appropriate fastening means.

Air from outside is drawn into the duct 28 by the motor and fan through the rear surface of the head cover 11, by way of a circular entry 35 to the housing 33.

Thus, the rear surface of the cover 11 is open except for some spaced plates 36.

The components which make up the helmet are best illustrated in Figure 4.

Air entering the opening 35 is filtered by a bag filter 42 of a mat of electret material located in a removable moulded plastics filter case 43.

The filter case is easily attached to, and removed from the head cover 11 through a telescoping tube connection 41,so that the filter when choked can be discarded and be replaced by a fresh one.

The case 43 is almost as wide as the helmet cover 11 and deep enough to extend to the rear of the user's neck. The spacing between its front and back walls 44 can be sufficient to accommodate whatever filter is necessary.

There are external leads for supplying the motor 34 with power from a battery, which could conceivably be carried on the helmet, but in many applications will more conveniently be carried in a case on the wearer's belt.

The motor and fan 34 may be provided with a flow rate sensor which is conveniently as described in British Patent Specification No.79.14894 (Case 20) and which is arranged to give an audible or visual warning to the wearer if the rate at which air is flowing through the fan drops below a rate which has been previously calculated to be necessary for the wearer's breathing requirements.

It will be appreciated that the helmet can be quickly and easily assembled from premoulded components and can be easily put on by the wearer because there are no external skirts to be fitted to prevent the entry of contaminated air, and indeed no external connections apart from the possible electrical connections to a battery for the motor.

The mounting of the filter externally of the head cover 11 at the back means that it can be easily replaced when clogged and it can be of large cross sectional area without excessively increasing the size of the helmet, so that a large volume of air can be filtered, and it does not require any space within the head cover 11.

A coarse pre-filter 46 is pivotally attached to the filter case over the inlet of the case to remove the larger particles from the air before they reach the bag filter 42. The pre-filter is shown in two positions in Figure 1. In its first position it covers the inlet of the case, and in its second position it is swung clear of the inlet. It is apparent that the pre-filter may be readily pivoted away from the opening to the filter case to allow the filter bag to be replaced.

The front of the visor is smooth and may be covered by a replacable film of transparent material, which can protect the visor from scratching.

The preferred flow rate sensor is axially mounted in the airflow passage and comprises a rotor which is freely mounted for rotation. The flow of air in the passage causes the rotor to rotate, and a light source is directed at a surface of the rotor which is formed with alternate reflective and non-reflective surfaces.

A detector receives light reflected from surface and produces a pulse corresponding to the reflective and non-reflective surfaces and the frequency of the pulses are used to provide a measure of the flowrate.

Claims

1. A protective respiratory helmet including a head cover, a filter, a motor driven fan arranged to cause ambient air to flow through the filter into the space within the head cover, and a case for the filter removably attached to the head cover over substantially the whole of the back wall of the head cover where it will be behind the head of the wearer.

2. A helmet as claimed in Claim 1 in which the case comprises a box containing the filter and adapted to fit at the entrance to the fan.

3. A helmet as claimed in Claim 1 or Claim 2 including means defining an internal duct leading air from the fan to an opening which will be in front of the forehead of the wearer.

4. A helmet as claimed in Claim 3 in which the filter is in the form of a bag with a surface area substantially greater than the area of the entry to the case and the area of the exit from the case to the fan.

5. A helmet as claimed in any preceding claim in which the filter is of electret material.

6. A helmet as claimed in any of Claims 3-5 in which the motor driven fan is mounted in the inlet end of the internal duct.

7. A helmet as claimed in any of Claims 3-6 in which the head cover has a sealing element adapted to seal around the forehead of the wearer, and in which the duct leads beyond the sealing element to the region of the wearer's face.

8. A helmet as claimed in any preceding claim including a sealing element within the head cover arranged to form a seal around the forehead of the wearer, and a visor adjustably mounted on the head cover and arranged when in the lowered position, to effect an automatic seal around the region of the wearer's face established partly by the sealing element in the head cover, and partly by a second sealing element carried by the visor.

9. A helmet as claimed in Claim 8 in which the visor includes a non-return exhaust valve for air breathed out by the wearer.

10. A helmet as claimed in any preceding claim including a clear visor.

11. A helmet as claimed in any preceding claim including a welding visor.

12. A helmet as specifically described herein with reference to the accompanying drawings.