WO1986006643A1

WO1986006643A1 - Respirators

Info

Publication number: WO1986006643A1
Application number: PCT/GB1986/000239
Authority: WO
Inventors: John Robert Feeney
Original assignee: Protector Safety Limited
Priority date: 1985-05-04
Filing date: 1986-05-06
Publication date: 1986-11-20
Also published as: DK387A; GB2195545B; GB8725696D0; GB2195545A; DK387D0; AU5812186A

Abstract

A respirator (1) has a fan (5) operable at two speeds to permit the respirator to be used either with a first type of filter element (3G) for removing gases (or vapours) or with a second type of filter element (3P) for removing particulate matter. The speed of the fan is controlled by the position of a resiliently biased switch (10). One type of filter element (3G or 3P) is adapted to depress the switch so that the fan runs at one speed whereas the other type of filter element (3P or 3G) does not engage the switch so that the fan runs at the other speed.

Description

RESPIRATORS

The present invention relates to respirators.

Various types of powered respirators are used ⁵ for filtering contaminated air thus allowing a user of the respirator to breathe safely in an otherwise potentially harmful atmosphere, e.g. one containing a toxic gas or a harmful particulate substance (e.g. asbestos) . ¹⁰ In the U.K., Europe and the U.S.A. there are standards for "Positive Pressure Powered Respirators" in which air is supplied at a high flow rate - typically in excess of 120 litres per minute through a filter into a mask, hood or blouse to 15 maintain a slight positive pressure - typically l-2m bars - therein. Such respirators are used for removing particulate matter from air and for this purpose the filter will typically be of fluted paper. However these respirators have only limited

20 use for removing toxic gases and vapours (in which case the filter will typically be of activated carbon) because the high flow rate reduces the life of such a filter to an unacceptably low level.

A respirator for use in filtering toxic gases or

25 vapours will in fact generally be operated with a flow rate of 10-100 litres per minute and more usually 50-60 litres per minute.

Consequently, it has been the practice to produce two different types of respirator, namely one

30 operating at a 'high* flow rate for filtering particulate laden air and one operating at a 'low' flow rate for filtering toxic gases or vapours from air.

The need to produce two different types of ^⁵ respirator is obviously disadvantageous. There is however a potentially much more serious problem arising from the fact that the two types of respirator are frequently used on the same site and that the two types of filter elements are frequently of the same size and shape. A person about to enter an environment of toxic gases or vapours may inadvertantly use a respirator intended for filtering particulate material with a filter elment for removing toxic gases or vapours. If this happens, the filter element will have an unexpectedly short life (owing to the high operating speed of the respirator) and obviously this is potentially dangerous.

It is an object of the present invention to provide a respirator which may be used safely both for filtering particulate laden air and for removing toxic gases and vapours from air.

According to the present invention there is provided a respirator comprising a filter housing, an air inlet, an air outlet communicating with the inlet via the housing and powered fan means for drawing air through the inlet and passing it through a filter in the housing to the outlet wherein the fan is operable at first and second speeds to supply air at different flow rates and the filter housing is provided with an actuator element selectively operable by a filter element in the housing to switch the fan from one speed to the other.

The respirator of the invention is adapted to operate at two different flow rates and may be used with either filters for removing particulate matter or filters for removing toxic gases or vapours. One or other of these filter elements will be adapted (when located in the housing) to operate the actuator element so that the fan runs at the appropriate speed for that type of filter. .The other type of filter element will not operate the actuator element allowing the fan to run at the appropriate speed for that element. The actuator element is preferably a switch in parallel with a resistor in an electrical circuit which incorporates the fan.

The invention will be further described by way of example only with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of one embodiment of respirator in accordance with the invention showing the fitting of a filter element therein;

Fig. 2 is a perspective view of the respirator shown in Fig. 1 (but omitting details of the filter element) from an alternative angle;

Fig. 3 is a detail showing operation of the actuator element incorporated in the filter housing of the respirator shown in Fig. 1; and Figs. 4a and 4b are circuit diagrams showing control of the fan in the respirator by the actuator element.

It will be seen from Figs. 1 and 2 that the illustrated respirator 1 incorporates a cylindrical filter housing 2 in which a disc-like filter element

3 is intended to locate. Although not detailed in the drawing, the filter element 3 comprises a casing with a front face 3a in the form of a grill. Within the element 3 is the filter material, e.g. fluted paper or activated carbon. The element 3 is located in housing 2 with its face 3a outwards and is held in position by a screw-ring 4 which screws onto housing

2 and engages against the peripheral margin of face

3a. A fan 5 is provided in the respirator 1 and, in use, serves to draw air • (arrows A) through the grid-face 3a of filter element 3 and pass it via opening 6 through an outlet 7 which will be^' connected via a flexible hose (not shown) to a respirator mask, hood blouse or the like (not shown) worn by a user. The mask, hood or blouse may be of the positive pressure type.

The respirator 1 may be worn on a belt and the fan 5 powered by an external power source (not shown) which may also be worn on the belt and which supplies power via a connector 8 on the respirator 1. An on-off switch 9 is also provided for switching the fan 5 on or off as desired. The electrical circuitry connecting the fan 5 to connector 8 and switch 9 is conventional and is not illustrated.

The respirator 1 is intended for use with either filter elements 3P (for filtering particulate matter) or filter elements 3G (for filtering toxic gases or vapours). Consequently, fan 5 is required to run at two different speeds, i.e. a 'fast' speed for the former use and a 'slow* speed for the latter use. For this purpose, the speed of the fan 5 is controlled by a button switch 10 provided centrally within housing 2. Switch 10 is biased outwardly and, in its outer position, allows fan 5 to run at its fast speed whereas when pressed inwardly causes the fan to run at its slow speed.

The inner face of filter elements 3P include a centrally positioned cylindrical recess 11 whereas the inner face of elements 3G are flat (see Fig. 3). Consequently, when a filter element 3G is located in housing 2, the button switch 10 is automatically pushed inwards to provide for the slow fan speed. Alternatively, when a filter element 3P is located in housing 2, the switch 10 simply locates in recess 11 and remains in its outer position, thereby providing the fast fan speed.

Consequently, the fan speed is automatically selected depending on the type of filter element 3 located in housing 2.

The manner in which switch 10 controls the fan speed is illustrated in the circuit diagrams shown in Figs. 4a and 4b. As shown in Fig. 4a, the open position of switch 10 (i.e. when it is pushed inwards by filter 3G) causes current to pass to fan 5 via resistor R, thereby causing fan 5 to run at 'slow' speed. As illustrated in Fig. 4b, the closed position of switch 10 (i.e. when it is in its outer position) causes resistor R to be 'shorted' out so that fan 5 runs at the fast speed.

Claims

CLAIMS:

1. A respirator comprising a' filter housing, an air inlet, an air outlet communicating with the inlet

5 via the housing and powered fan means for drawing air through the inlet and passing it through a filter in the housing to the outlet wherein the fan is operable at first and second speeds to supply air at different flow rates and the filter housing is provided with an ° actuator element selectively operable by a filter element in the housing to switch the fan from one speed to the other.

2. A respirator as claimed in claim 1 wherein the actuator element comprises an electrical switch operable by a filter element.

3. A respirator as claimed in claim 2 wherein the switch is biased to a first position at which the fan runs at the first speed and is movable against the bias by a filter element to a second position at which the fan runs at the second speed.

4. A respirator as claimed in any one of claims 2 to 4 wherein the switch is part of an electrical circuit including the fan, power means, an a resistance positioned in the circuit to cause the fan to operate at the first or second speed depending on the position of the switch.

5. A respirator as claimed in claim 4 wherein the resistance is in parallel with the switch.

6. A respirator as claimed in any one of claims 2 to 5 wherein the switch is positioned centrally within the housing.

7. A respirator as claimed in any one of claims 1 to 6 wherein the housing is cylindrical.

8. A respirator as claimed in claim 7 provided with a screw threaded ring for location, on the housing for retaining a filter element therein in position.