Abstract:
A gas particulate filter system is provided for supplying clean heated airo an operator subjected to ambient environments containing nuclear, biological or chemical contaminants. The filter unit includes replaceable radial flow canister means, centrifugal blower/heater means, continuously variable electronic control means for regulating air temperature and air flow, and clamping means for easy assembly of the components under adverse field conditions.

Description:
GOVERNMENTAL INTEREST 
     The Government has rights in this invention pursuant to contract No. DAAK-11-81-C-0100 awarded by the Department of the Army. 
    
    
     BACKGROUND OF THE INVENTION 
     The One-man Gas Particulate Filter Unit (GPFU) relates to a device for providing breathable air to men in military vehicles which encounter nuclear, biological and or chemical (NBC) agents that are required to be removed for safety reasons from the air. The GPFU is designed to interface with a protective gas mask or ventilated face piece system. 
     In the past, prior art military vehicles air supply systems failed to protect personnel from accidental contamination during the handling and disposal of a contaminated filter. The present invention provides a replacement canister which can store an old contaminated filter while providing a new charcoal filter. 
     The present invention is capable of reliably operating under extreme environmental battlefield conditions. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a radial flow gas-particulate filter canister in axial alignment with a centrifugal blower, heater unit and dust pre-filter. A continuously variable power control module provides for heater activation, temperature control, and air flow from less than one cubic foot per minute to four cubic feet per minute at eleven inches of water head to a M25 type Protective Mask. 
     Accordingly, an object of the present invention is to provide a replaceable gas particulate filter unit for military personnel operating in a hostile NBC environment. 
     Another object of the present invention is to provide a gas particulate filter unit which can be easily reassembled under field conditions. 
     Another object of the present invention is to provide a gas particulate unit which has continuously variable temperature and airflow control. 
     A further object of the present invention is to provide a GPFU which is able to purify hazardous air by means of a pair of filters and able to heat and circulate clean air by means of a blower-heater module. 
     For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following descriptions taken in connection with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1A and 1B are isometric views of a One-man Gas Particulate Filter Unit (GPF) in as-shipped components state. FIG. 1A is a radial flow filter module and FIG. 1B is a radial flow blower-heater module. 
     FIG. 2 is an isometric exploded view showing the initial installation of the filter module to the blower-heater module. 
     FIG. 3 is an isometric exploded view showing the replacement sequence for a filter module. 
     FIG. 4 is an isometric additionally detailed exploded view of the One-man GPFU. 
     FIG. 5A is a cross-sectional view of the blower-heater module air inlet end showing the end cap in an open position. 
     FIG. 5B is a cross-sectional view of the blower-heater module air inlet end showing the end cap in a closed position. 
     FIG. 6 is an exploded view of the blower-heater module end cap assembly. 
     FIG. 7 is a partial cut-away cross-sectional isometric view of the filter module. 
     FIG. 8 is a schematic electrical diagram of the electrical control module for controlling motor speed, heater temperature and on-off switching. 
    
    
     Throughout the following description, like reference numerals are used to denote like parts of the drawings. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1A, the present invention comprises a sealed filter unit, having a cylindrical canister housing 10 which has an axially aligned hose connecting small flange end 12 and a flanged filter end 14. In the as-shipped state the aforementioned ends 12 and 14 are sealed by hose outlet end cap 16 and inlet filter end cap 18 respectively to the canister housing 10 by means of over-center &#34;V&#34; filter outlet clamps 20 and filter inlet body clamp 28 respectively. 
     Referring to FIG. 1B, a cylindrically shaped blower-heater module 24 has a flanged cylindrical center housing member 26 which is sealed to the rear end by a &#34;V&#34; clamp 28&#39; and on its opposite air inlet end by a manually adjustable open and closed pre-filter cover 30. 
     Referring now to FIG. 2 during the initial installation of the asshipped gas particulate filter canister 36 has outlet cap 16 and inlet cap 18 removed and discarded therefrom. Pre-formed packing &#34;O&#34; ring seals 32 and 34 are used to provide a simple and effective means to seal the filter canister 36 during storage handling, disposal and to seal the filter canister 36 to the power-precleaner blower-heater module 24. Filter outlet clamp 20 is used to connect the outlet protective cover 16 or to a connect hose pneumatically connected to a face mask, not shown, to the outlet end 38 of filter canister 36. Filter body clamp 28 is used to connect the filter inlet cover 18 to the gas-particulate filter canister 36 and to connect the filter canister 36 to the power blower-heater pre-cleaner 24. In addition, filter body clamp 28&#39; is used to connect cylindrically flanged center housing 40 to rear housing 42 of blower-heater module 24. The &#34;V&#34; clamps are commercially available and modified to allow opening and closing with an over-center lever mechanism. 
     Referring now to FIG. 3, the procedure for replacement of a filter module requires removal of contaminated filter canister 36&#39;, &#34;O&#34; rings 32 and 34, and clamps 20 and 28. The aforementioned elements are assembled with end caps 16 and 18 of replacement filter canister 36&#34; for disposal. The new filter 36&#34; with new &#34;O&#34; rings 32&#39; and 34&#39; and &#34;V&#34; clamps 20&#39; and 28&#39; are operatively attached to the center housing 40. The dual arrows coming out of the center housing 40 represent the removal step of the filter canister 36&#39; and the single arrow going into the rear end of the center housing represents the replacement sequence for the filter canister 36&#34;. 
     Referring now to FIG. 4, the exploded view of the GPFV shows the filter canister 36, &#34;O&#34; ring 34 and the &#34;V&#34; clamp 38 as previously described in alignment with the power/pre-cleaner blower-heater module which comprises an air intake dust cover assembly 42 which is operatively attached to the inlet end 44 of a flanged cylindrically shaped rear housing member 46. The rear housing unit 46 includes a rain shield 45 and a retaining member 47 to hold the air inlet dust cover 42 removably attached to the rear housing unit 46. A heater-blower assembly 48 and 50, 50&#39; respectively is operatively positioned intermediate of the rear end 52 of the center housing 40 and the flanged outlet end 54 by means of an &#34;O&#34; ring packing seal 34 and &#34;V&#34; clamp 28 which fixedly locks the flanged outlet end 54 of rear housing 46 to the rear flange 56 of the center housing 40. Blower assembly 50 is axially aligned with heater assembly 48. The blower is a backward curved centrifugal fan which is driven by a brushless 27.5 volt direct current motor 1 operating at 23,000 r.p.m. The centrifugal blower and centrifugal fan housing (2) are attached to a mounting plate (not show). Its fan inlet face is sealed to the plate and a hole in the plate matches the fan&#39;s inlet. The plate is sealed to the center housing 40 with a high temperature gasket. The blower&#39;s inlet faces the rear of the assembly and the tangential blower outlet discharges into the center housing. The control electronic module will be described more fully hereinafter in relation to FIG. 8. The control electronics module 66 has temperature and speed set cables 68 and 70 respectively which are connected to speed and temperature hand control knobs 72 and 74, respectively, which are located on rear housing member 46. The control electronics module also includes a power input cable 76. A pair of temperature control leads 78 and 80 are electrically connected to the heater assembly 48 mating temperature control leads 78&#39; and 80&#39; respectively. 
     Referring now to FIGS. 5A, 5B and 6, the end cap assembly comprises a cylindrical end cap cover 82 having a closed end 84 having peripherally disposed screw holes 86 therein and an open end 88. An air inlet seal member 90 is fixedly held next to the cap end 84. A coiled compression spring 92 is operatively positioned within cap cover 82 between cap end 84 and spring stop member 94. A sintered metal disc shaped prefilter member 96 is sandwiched. between a metal ring wiper member 98 and a rear ring support 100. A front ring support wiper 102 holds wiper ring 98 against the rear side of the prefilter 96. Screws 104 pass through holes in the end cap cover 82 and axially aligned holes of the front ring support, the prefilter 96, the wiper 98 and the rear ring support wiper 100. Nuts 106 threadly attached to screws 104 fixedly hold the prefilter member 96 attached to the cap closed end 88 and spaced therefrom by cylindrical spacer 108. The wiper member 98 is designed to slidably ride against the interior surface of rear housing 46. The coiled spring rests against the inside of the end cap closed end 84 and the spring stop 94 and is designed to provide some resistance when in the closed position shown in FIG. 5A. The unit is designed to provide protection from the rain and is a means to actuate the blower module on/off switch, not shown in these figures, and to mechanically link unit operation with the open and closing of the air intake cover assembly 42. 
     Referring now to FIG. 7 the filter module 36 comprises a three tiered cylindrical housing 110 having a flanged hose end 112 and a flanged rear end 114. An outer cylinder member 116 is fixedly attached to the inside surface of housing 110 at the flanged rear end 114 and protrudes therefrom to accept the inlet filter end cap 18 and the center housing member 40. A partially perforated hose outlet tube 118 is axially aligned with the longitudinal axis of housing 110 and fixedly held therein on the outlet side by the small cylinder section 120 of housing 110. The other end of hose outlet tube 118 is supported by a central boss 122 of a stamped filter end support member 124. Cylindrically shaped activated charcoal material 126 is operatively disposed in the space intermediate the outer circumference of hose tube 118 and the inner surface of a perforated middle cylinder member 128. The annular groove 130 of filter end cap 124 supports a compression pad 132 therein and also support the inlet end of middle cylinder 128. Disposed intermediate to the outer surface of perforated middle cylinder member 128 and the inner surface of outer housing cylinder 116 is a cylindrically shaped pleated particulate filter 134 which is supported therein by the flange of end cap 124. 
     Referring not to the block diagram of FIG. 8, the 27.5 VDC vehicle electrical power goes via input terminal x-x through a unit on/off switch S1. As previously stated the unit on/off switch S1 is located in the rear housing 46 portion of the GPFU and is activated by the air inlet cap 42. This arrangement interlocks the heater 142 with the motor/blower control assuring that the heater 142 cannot be activated without the GPFU operating. The speed of the high speed motor 64 is controlled through a potentiometer 136 whose output is set by an operator for a desired motor speed and air flow. The 27.5 VDC power is also supplied to heater circuit via an in series connected heat on/off switch S2. Both the heater and motor circuits use the same pulse width modulation system. An oscillator 138 is used to generate pulses at 1 kHz with the pulse width determined by the operator at selected positions of motor speed control potentiometer 136 and heater temperature potentiometer 140. The motor 64 senses a change in the pulse width and responds with a speed change. The 27.5 VDC is supplied to the motor 64 through a motor circuit protector 144 and to the heater 142 through heater circuit protector 146 via an in series connected safety thermostat 148, of the bimetalic type. The bimetal thermostat 148 provides for redundant over-temperature safety. This redundant feature assures the air temperature exiting the heater coil 142 will not exceed temperatures that will cause off-gassing of chemical agents. The 27.5 VDC power source is also used to power a control voltage regulator 150 having a 15 VDC regulated voltage output at terminal y&#39;. The motor control and heater control circuits are connected to this 15 VDC source at terminals at y&#34;, and y&#39; and y&#39;&#34; respectively. The heater control circuit shown within the dashed line box 152 essentially provides voltage to the heater element 142 at a level selected by the operator. Feedback to this control circuitry is provided by a thermistor 154. The switching frequency used in heater control circuit is determined by the triangular wave output 1 kHz oscillator 138. The triangular waveform output is one of the inputs to a differential comparator 156 via conductor 158. The other input to comparator 156 comes from the output of a summing amplifier 160 via conductor 162. Inputs to the summing amplifier 160 are from the temperature selected by the operator by his setting the heater potentiometer 140 output level and the feedback voltage from the thermistor temperature sensor 154. The heater control comparator 156 directly drives a transistor power switch 164. The transistor switch 164 supplies pulses of current to the heater element 142 at a 1 kHz rate. The pulse width determines the net heater voltage and thus the heater power output. This closed loop control circuit can control and maintain the temperature of 100°  F. The high switching rate of 1 kHz causes the heating element 142 to respond only to pulse width changes. This control minimizes the temperature excursions of the heating element 142 and results in a relaibel heating system. Another feature in the heater portion of the block diagram is the on/off switch S2 that is integral to the temperature select control potentiometer 140. Switch S2 shuts off the heater and a click-off position indicates to the user that he has turned the heater 142 off. 
     Referring now to motor control portion of FIG. 8, which is outside of dashed box 152, the motor speed control is an open loop controller that responds to the speed selected by the user. Both the heater circuitry and the motor speed controller circuitry use the same pulse width modulation system. A motor control comparator 166 generates output pulses 1 kHz with the pulse width determined by the user selected position of the speed control potentiometer 136. The output of the speed potentiometer 136 is fed to the input of the comparator 166, via conductor 168. The other input to the comparator 166 is fed by conductor 170 from the oscillator 138. The motor 64 senses a change in the pulse width output of comparator 166 through a motor transistor switch 172 and thereto with a speed change. The pulse width modulation system used in conjunction with the motor power transistor 172 switches the motor field windings and results in a simple and very efficient speed control. Maximum speed, limited by motor/blower characteristics, produces maximum rated airflow and minimum speed produces an airflow of approximately 1 cfm. 
     While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.