Mass loading monitor

The present invention provides a mass loading monitor for measuring in real time the particulate, i.e., powder, dust and the like, content of air inside an industrial or commercial processing facility and providing a warning signal indicating the existence of a potentially explosive atmosphere in the facility. In a first embodiment, the mass loading monitor comprises two parallel cylinders, one of which is charged with clean, ambient air and the other of which is charged with air from within the facility containing dust, powder or other particulate matter. A piston resides within each cylinder and the pistons are commonly accelerated for a short distance during which time the pressure at each piston face is measured. The time integrals of the pressures from each of the piston faces are evaluated over the period: from rest to the time of discharge from the open end of the cylinders. The ratio of these integrals defines the difference in the densities within the cylinders. In a second embodiment, a single piston and cylinder assembly is first calibrated with clean air and subsequently filled with particulate laden air and the time integrals of the pressures on the piston face are similarly evaluated.

FIELD

The present disclosure relates to devices for detecting concentrations of particulate matter in air and more particularly to a mass loading monitor for real time detection and warning of potentially explosive concentrations of dust, powder or particulate matter in air from industrial and commercial processes.

BACKGROUND

Airborne dust or powder of, for example, sugar, grain and wood, escaping from industrial process machinery in a sufficient concentration can support rapid combustion and explosions. Such explosions typically occur in a confined or semi-confined space although an unbounded cloud can also support an explosion. Agricultural processes which occur at grain handling facilities such as transfer and storage depots, grain mills and cereal plants are particularly prone to this phenomenon. The following table highlights the losses over a recent ten year period (1996 to 2005) attributed to dust explosions in agricultural processing facilities in the United States.

Spray dryers are particularly vulnerable to this problem since they purposefully concentrate the powdered material before transferring it. The current response to this problem is to accept the possibility of an explosive event and incorporate, for example, explosion panels. These may either be passive devices—simply a weak component of the confining surface that gives way upon an explosion—or active devices that sense pressure in the device and release a panel. Alternatively, a dust suppressant may be routinely deployed in the spray dryer chamber.

Consideration of the foregoing current solutions to this problem leads one to the conclusion that an apparatus and technique to avoid this problem rather than to mitigate its effects would be a welcome addition to these industrial and commercial enterprises. The following disclosed and claimed invention is so directed.

SUMMARY

The present invention provides a mass loading monitor for measuring in real time the particulate, i.e., powder, dust and the like, content of air inside an industrial or commercial processing facility and providing a warning signal indicating the existence of a potentially explosive atmosphere in the facility. Optionally, the mass loading monitor may be configured to indicate the sensed level of particulate matter and to shut down the facility until the level of particulates drops to a safe level.

In an first embodiment, the mass loading monitor comprises two parallel cylinders, one of which is charged with clean, ambient air and the other of which is charged with air from within the facility containing dust, powder or other particulate matter. A piston resides within each cylinder and the pistons are commonly accelerated for a short distance during which time the pressure at each piston face is measured. The time integrals of the pressures from each of the piston faces are evaluated over the period: from rest to the time of discharge from the open end of the cylinders. The ratio of these integrals defines the difference in the densities within the cylinders. Lookup tables keyed to the type of material and relative humidity within the facility are then utilized to determine the explosion potential and provide an alarm or other indication that a predetermined concentration has been exceeded.

In a second embodiment, the same theory of operation is applied but only a single piston and cylinder assembly is utilized. Here, the single piston and cylinder assembly is first calibrated by determining the time integral of pressure with clean air at known temperature and barometric pressure. The assembly is then filled with particulate laden air and the time integral of pressure is compared to the calibration data and the density of the particulate laden air and its explosion potential is determined.

Thus it is an object of the present invention to provide an apparatus for monitoring the concentration of particulate matter in air.

It is a still further object of the present invention to provide an apparatus for monitoring the concentration of particulate matter in air in a processing facility for sugar, grain, wood and similar dust or powder producing materials.

It is a still further object of the present invention to provide an apparatus for monitoring the concentration of particulate matter in air in a processing facility for sugar, grain, wood and similar dust or powder producing materials and providing an alarm or other indication that a threshold concentration level has been reached or exceeded.

It is a still further object of the present invention to provide an apparatus for monitoring the concentration of particulate matter in air by accelerating samples of clean and particulate laden air to determine their time integrals of pressure and comparing the computed densities of the clean and particulate laden air.

It is a still further object of the present invention to provide an apparatus for monitoring the concentration of particulate matter in air having a pair of parallel cylinders in which a respective pair of pistons accelerate samples of clean and particulate laden air.

It is a still further object of the present invention to provide an apparatus for monitoring the concentration of particulate matter in air having a single piston and cylinder assembly that is calibrated with clean air and charged with particulate laden air.

It is a still further object of the present invention to provide a method for monitoring the concentration of particulate matter in air.

It is a still further object of the present invention to provide a method for monitoring the concentration of particulate matter in air by accelerating samples of clean and particulate laden air, determining the time integrals of pressure and comparing the computed air densities.

It is a still further object of the present invention to provide a method for monitoring the concentration of particulate matter in air in a processing facility for sugar, grain, wood and similar dust or powder producing materials and providing an alarm or other indication that a threshold concentration level has been reached or exceeded.

DETAILED DESCRIPTION

With reference toFIG. 1, a typical and exemplary grain processing facility is illustrated and designated by the reference number10. At the outset, it should be understood that, for purposes of the present invention and description, the grain processing facility10is representative of any industrial or commercial facility such as a sawmill, furniture factory, sugar processing plant, cereal plant, or coal handing facility wherein dust, powder or other relatively fine particulate matter is generated and dispersed into the air.

The grain processing facility10includes a building or superstructure12which typically encloses the processing machinery which is installed on one or more floors14. Railway gondola cars16, trucks or other vehicles may supply raw material(s) to the facility10and dump their contents onto one or more horizontal conveyors18. The conveyors18carry the material to a bin or hopper20from where they are extracted by a vertical, bucket type conveyor22or similar device. Cooperating horizontal conveyors24then carry the material to, for example, grinding or milling equipment26for processing or to one or more silos30for storage. The silos30include controllable outlets32which selectively supply material to an additional conveyor or conveyors34which, for example, provide material to the bin or hopper20or other collecting points.

At eight locations within the grain processing facility10are preferably disposed a mass loading monitor40according to the present invention. It will be appreciated, however, that more or fewer mass loading monitors40may be suitable or desirable in this exemplary facility10, and that the actual number of monitors40preferred or necessary in a given facility will depend upon the construction and layout of the facility, upon its machinery, upon the nature of the material processed in the facility and other variables.

Referring now toFIG. 2A, the mass loading monitor40includes an elongate frame42which supports a pair of rigid, parallel, elongate cylinders50having a length of approximately one meter. The first cylinder50is a clean air or reference cylinder and is supplied with clean ambient temperature and humidity air from an air supply52that includes a filter54, a reservoir56and a check valve58to prevent backflow through the reservoir56and the filter54. The air supply52and specifically the reservoir56may also include one or more additional outlet ducts or conduits59to provide clean air to one or more additional mass loading monitors40, as, for example illustrated inFIG. 1. It should thus be appreciated that a single properly sized air supply52may service multiple mass loading monitors40or that individual air supplies52may by associated with and supply individual mass loading monitors40,

An open end of the first cylinder50is enclosed within a first valve or control box60. The air supply52communicates with the interior of the first control box60as does the open end of the first cylinder50. A first hinged panel62controlled by a first two position actuator64opens and closes the first hinged panel62which acts as a valve to allow the air within the first cylinder50to be exhausted to the ambient through the control box60.

The second cylinder70which is essentially identical to the first cylinder50is a measurement cylinder and is supplied with air that contains dust, powder or other particulate matter from a region of a facility such as the grain processing facility10. The open end of the second cylinder70is enclosed within a second valve or control box72. A second hinged panel74is controlled by a second two position actuator76. The second hinged panel74opens and closes to allow the particulate laden ambient air to be drawn into the second cylinder70through the control box72and to be exhausted (returned) to the ambient. A third hinged panel and two position actuator78provide selective communication between the first valve or control box62and the second valve or control box74to allow clean air into the second control box74and the second cylinder70.

Referring now toFIGS. 2A and 2B, within the cylinders50and70are disposed respective piston assemblies: a first piston assembly80within the first cylinder50and a second piston assembly120within the second cylinder70. Except for their dispositions in the first cylinder50and the second cylinder70, the first and second piston assemblies80and120are identical and thus only the first piston assembly80will be described, it being understood that the description applies with equal accuracy to the second piston assembly120.

As illustrated inFIG. 2B, the first piston assembly80includes a main or primary piston82which is preferably hollow to reduce weight and includes a flat face84at its front and a concentric drive tube or hollow shaft86at its rear. On the flat face84of the main piston82is a circular aperture or port88which communicates with an inlet passageway92. In fluid communication with the inlet passageway92and oriented parallel to the axis (of translation) of the main piston82is a diaphragm94of a MEMS pressure transducer100. The MEMS pressure transducer100preferably has a range of from 0.0 kPa to about 1.0 kPa and includes a multiple conductor output cable102which carries electrical energy and output signals or data from the transducer100. On the side of the diaphragm94opposite the inlet passageway92is a reservoir passageway104which communicates with a two position (on-off) valve106. A multiple conductor cable108provides electrical energy to the two position valve106to selectively operate it. On the opposite side of the two position valve106from the reservoir passageway104is an ambient pressure passageway and port110. When the two position valve106is energized and open, ambient (atmospheric) pressure is established within the reservoir passageway104. When the two position valve106is de-energized and closed, ambient (atmospheric) pressure is stored in the reservoir passageway104.

Disposed adjacent the flat face84of the main piston82in a rest or quiescent position but moveable axially relative thereto is a light or secondary piston112. The light piston112includes a circular aperture or port114which is preferably the same size as the circular aperture or port88on the main piston82and is aligned therewith as illustrated inFIG. 2B. Secured to the center of rear face of the light piston112, extending axially therefrom and through the main piston drive tube or hollow shaft86is a light piston drive rod or shaft116.

An annular band of a plurality of ports or apertures122extend around each of the cylinders50and70at an axial location just beyond the limit of translation of the main pistons82. The ports or apertures122may be round, as illustrated, rectangular or another configuration. Extending about the circumference of each of the cylinders50and70in general alignment with the ports or apertures122is an axially, bi-directionally movable sleeve124. In the position illustrated inFIG. 2B, the sleeve124closes off the ports or apertures122. A two position actuator126translates the sleeve124to the right inFIG. 2Band opens the ports or apertures122, allowing ambient air to enter or exit the cylinders50and70.

Referring again toFIG. 2A, the main piston drive tube or hollow shaft86and the light piston drive rod or shaft116of the first piston assembly80and the main piston drive tube or hollow shaft86and the light piston drive rod or shaft116of the second piston assembly120extend to a light piston drive assembly130. The main piston drive tube or hollow shaft86of the first piston assembly80and the main piston drive tube or hollow shaft86of the second piston assembly120are secured directly to and translate with the light piston drive assembly130. The light piston drive rod or shaft116from the first piston assembly80and the light piston drive rod or shaft116from the second piston assembly120, however, are connected to and translated in unison by one or a pair of bi-directional linear actuators or motors132. The linear actuators or motors132may be electrically, hydraulically or pneumatically powered and capable of translating the light pistons112and the light piston drive shafts116approximately 3 feet (1 meter). The light piston drive assembly130and the main pistons82are, in turn, translated by a linear drive motor140. The linear drive motor140may be any currently available linear energy source capable of accelerating the first and second pistons assemblies80and120at approximately 100 to 150 meters/sec/sec over a relatively short (approximately 1 inch (2 to 3 cm.)) distance such as a tension spring actuator, electric linear motor or hydraulic cylinder but is preferably a double acting pneumatic piston and cylinder assembly. As such, the linear drive motor140includes a single output rod or shaft142having a piston144secured thereto which is coupled to and bi-directionally drives the light piston drive assembly130and the main piston.

When the linear drive motor140is activated, the first and second main pistons82and the first and second light pistons112translate together in the respective first and second cylinders50and70. To translate only the light piston drive rod or shaft116and the light piston112of the first piston assembly80and the light piston drive rod or shaft116and the light piston112of the second piston assembly120, only the light piston drive assembly130is activated. The linear drive motor140also includes a control assembly148which directs pneumatic or hydraulic flow or the supply of electrical energy to the linear drive motor140to achieve such bi-directional translation as those skilled in the art will readily understand.

In an alternative construction illustrated inFIGS. 3A and 3B, the secondary pistons112, the drive shafts116, the light piston drive assembly130, the ports122, the sleeves124and the actuators126are eliminated. Accordingly, the first and second piston assemblies80′ and120′ which each include a main piston82which resides in the respective first and second cylinders50and70, the main piston drive tubes86′ (which can be solid shafts rather than hollow tubes) and the linear drive motor140are utilized. In this construction, the main pistons82which are coupled to the output shaft142of the linear drive motor140by a bar or member143traverse essentially the full length of the respective cylinders50and70to ingest and expel clean air and particulate laden air. Given this extent of piston travel, hard wiring the MEMS pressure sensor100and the valve106to a stationary external data storage device or computer is impractical and thus a memory device and battery power supply109may be located within each of the main pistons82to record and subsequently download data. Alternatively, a low power, i.e., Bluetooth, transmitter may be incorporated in each of the main pistons82to provide real time data acquisition. Electrical contacts111A on the pistons82which mate with aligned contacts111B when the pistons82are fully retracted can also provide a data transfer route as well as provide electrical energy to the valve106.

The mass loading monitor40is intended and designed to determine whether a particular concentration of particulate matter in the air of a facility such as the grain processing facility10is approaching the minimum explosive concentration (MEC). The MEC is specified as a density: X grams per cubic meter. The magnitude of X depends upon the material, for example, sugar, coal, sawdust, oats and wheat, and varies also with the relative humidity level. Nominal values are in the range of 30 to 80 grams per cubic meter. Typical sea level ambient density is on the order of 1.2 Kg per cubic meter and thus the resolution required is between 2.5 and 6.67%.

The measurement strategy of the mass loading monitor40follows from the recognition that a density difference (ρw−ρw/o) is sought and that discharging air with particulates (w) and without particulates (w/o) from a cylinder—by the action of an accelerating piston can yield (ρw−ρw/o). The following analysis illustrates how the pair of cylinders50and70can determine (ρw−ρw/o). Alternatively, a second embodiment200, illustrated inFIGS. 7 through 16B, having a single cylinder can be utilized for this measurement.

Referring now toFIG. 4, the theory of operation and particulate mass measurement will be described in connection with a deformable control volume150disposed within the cylinder70that bounds or envelopes the particulate material. The momentum equation for this deformable control volume150, unsteady flow condition, is

∑F→=ⅆⅆt⁢∫cv⁢ρ⁢⁢V→⁢⁢ⅆ∀+∫cs⁢ρ⁢⁢V→⁢⁢V→·n^⁢ⅆA(1)
which leads to

where ppis the pressure at the face of the piston, τwis the wall shear stress, u and ρ are the axial velocity and density of material within the cylinder70. Experimental data reveal that the initial motion of the piston assemblies80and120compress and displace the air in the cylinders50and70in a progressive manner. That is, there is a time lag (approximately 0.01 sec. as presented inFIG. 5) for the air to be expelled from the 0.965 meter long cylinders50and70. This time lag allows the spatially averaged density in the cylinders50and70to be assessed. Specifically, from Equation (2), the efflux term is zero for t<δt and Equation (2) can be integrated to provide (where T≦δt)

The “small” dust or powder loading (≦80 g/m3) with respect to the density of the ambient air (≈1.1 Kg/m3) makes it rational to assume that the term γ will be unaffected by the presence or absence of particulate matter in the cylinders50and70. In contrast, the basis for the measurement process is the dependence of the terms α and β on the presence or absence of particulate matter. The two conditions are designated by the symbols: with particulates ( )w: α, β and without particulates ( )w/o: α, β.

During calibration or at any time during its service life, the mass loading monitor40can be operated with clean air in both cylinders50and70to quantify minor differences in their operating characteristics. Specifically, the operating theory and computations presented herein do not require identical performances for (α), (β) and (γ) with identical cylinder charges of no particulates although this will be assumed for the analytical structure of the data processing. The correction scheme, to be utilized when the air only data are not the same for the cylinders50and70, is to first form the ratio: [β1/β2]*, where β2represents the cylinder70that ingests the particulate matter. Second, when the dust or powder loading is to be determined, the ratio of the measured β2and β1values will then be multiplied by [β1/β2]* as a correction coefficient. It is understood that β will represent the corrected β2value in the subsequent text.

The air in both cylinders50and70will be at the same temperature and pressure (hence the same density). From Equation 3, the ratio of the (α) terms can be equated to the ratio of the spatially averaged densities since the integrals have identical kinematic features. This is the key step in the mass loading monitor40data processing algorithm. It should be appreciated that the time lag to accelerate the airborne particulate matter within the cylinder70will not only be small, but evaluating α at the discrete time T also ensures that the acceleration period will not alter the α value.

The desired information: Δρ=<ρw>−<ρw/o>, can be obtained from the ratio α′/α=<ρw>/<ρw/o> and the separately measured ρ. That is, a barometric pressure reading (patm) and the ambient (absolute) temperature T can provide (ρw/o) as: ρw/o=patm/RT, and

From measured data (where βwrepresents the corrected β2* value)

The ratio γ/β is plausibly <1 since γ depends upon the viscosity of air and the large acceleration (about 15 g's) will create an inertially dominated flow field. With this condition, it is recognized that the bracketed term represents a converged series whereby the bracketed term can be expressed as

The coefficient K can be treated as a calibration constant. Known quantities of small particulates can be added to a vertically disposed cylinder70and the piston120accelerated before their “leading edge” reaches the piston face. Since (αw/αw/o) will therefore be known and (βw/βw/o) will be measured, K can be determined.

Referring now toFIG. 5, a graph illustrates the time difference between the acceleration of one of the main pistons82and the later air motion at the end of the associated cylinder50or70. The left vertical scale is the voltage output of an accelerometer and relates to the left plot162. The horizontal scale is time in seconds. The right plot164is data from a hot-wire anemometer located at the end of the same cylinder50or70, at the control box. The plot164indicates that motion of the air at the end of the cylinders50and70commences after the acceleration of the main pistons82(and measurement of air within the cylinders50and70) has been completed.

Referring now toFIGS. 2A,2B and6, an electronic circuit block diagram of a mass loading monitor40is illustrated and designated by the reference number170. At the outset, it should be appreciated that sequencing of the operation of the mass loading monitor40described herein as well as data acquisition and storage is preferably under the control of a personal computer or microprocessor200. In operation, the light piston drive assembly130is activated to translate the light pistons112to the left, the length of the cylinders50and70, and then to the right to charge the first cylinder50with clean air. The sleeve actuator126is also energized to translate the sleeve124and open the ports122to allow air behind the faces of the light pistons112. The actuator76is energized during the return stroke of the light piston drive assembly130to provide particulate laden ambient air into the second cylinder70. The linear drive motor140is then activated to rapidly accelerate the light pistons112and the main pistons82a short distance, i.e., two to three centimeters, along the cylinders50and70. During this time, the MEMS transducers100in the main pistons82in the first, clean air cylinder50and the second, measurement cylinder70sense the pressure at the face of the light pistons112and provide these data to an analog to digital converter172. The digital data are then provided to integrators174which integrate the pressure from the beginning of the accelerative run of the piston assemblies80and120(t=0) to the end (t=T).

The ratio of the integrands from the integrators174is then established in a comparator176and this value is multiplied by the constant K in a process (multiplier) step178. A programmable or read only memory or storage device182includes look up tables and other data utilized, for among other purposes, to calculate the minimum explosive concentration (MEC). The MEC, as noted above, varies with the type of material, for example, sugar, coal, sawdust, oats and wheat, and varies also with the relative humidity. This current, necessary information is provided to a computational comparator184in which the value of the stored MEC is multiplied by a safety factor δ to avoid a false negative indication and this value is subtracted from K(βw/βw/o). If the result is greater than or equal to one, a warning signal is provided by an annunciator186. If the result is less than one, no output or a null or safe signal may be provided by an annunciator188. Alternatively, as noted above, the warning signal may directly control operations within a processing facility and shut down the machinery generating the MEC without human intervention.

The mechanical cycle of the piston assemblies80and120of the embodiment illustrated inFIGS. 2A and 2Bis completed by retraction of the main pistons82through reverse operation of the linear drive motor140, opening the sleeves124, translation of the light pistons112to the ends of the cylinders50and70, reverse translation of the light pistons to draw in new air charges into the cylinders50and70and closing of the sleeves124, whereupon the mass loading monitor40is prepared for a new measurement. With regard to the embodiment illustrated inFIGS. 3A and 3B, the main pistons82may complete a traverse of the cylinders50and70to the left to expel the present charges and then translate to the right to ingest a fresh charge of clean air and particulate laden air, respectively.

Operation of the alternate construction illustrated inFIGS. 3A and 3Bis essentially the same. The control assembly148is activated to provide compressed air to the linear drive motor140to translate the piston144fully to the left inFIG. 3Aand then to the right to charge the cylinders50and70with clean and particulate laden air, respectively. The linear drive motor140is then activated to rapidly accelerate the main pistons82a short distance, i.e., two to three centimeters, along the cylinders50and70. During this time, the MEMS transducers100in the main pistons82in the first, clean air cylinder50and the second, measurement cylinder70sense the pressure at the face84of the main pistons82and provide these data to the memory device and battery power supply109.

Referring now toFIG. 7, a second embodiment of a mass loading monitor according to the present invention is illustrated and generally designated by the reference number200. The second embodiment of the mass loading monitor200includes a frame202which extends along and supports the components and assemblies of the mass loading monitor200including, an elongate cylinder210having a length and diameter like the cylinders50and70of the first embodiment mass loading monitor40, a cam and drive assembly220, a jet ejector assembly300and a sequencing assembly350housed in a plenum352. If desired, the mass loading monitor200may be enclosed in an outer housing204having suitable access and service panels (not illustrated).

Referring now toFIGS. 3B,7,8,9and10, the cylinder210includes a plurality of generally rectangular ports or access openings212which encircle the cylinder210proximate an end adjacent the cam and drive assembly220. At the opposite end of the cylinder210is the jet ejector assembly300. Closely fitting with the smooth walled interior of the cylinder210is a wireless piston assembly80′ including a piston82and the other components contained therein and illustrated inFIG. 3B. Alternatively, a hard wired piston assembly utilizing the piston assembly80′ but with hard wiring extending to remote equipment may be utilized in view of the relatively limited travel of the piston assembly80′ in the second embodiment mass loading monitor200. The piston82is secured to a connecting rod214which extends into a space between a first drive disc222and a second drive disc226of the cam and drive assembly220and terminates in a double cam follower assembly230.

The double cam follower assembly230, illustrated inFIG. 10, is an active, air powered device having a cylindrical housing232oriented perpendicularly to the axis of the connecting rod214which defines a first or lower cylinder234, accessed by a pair of spaced-apart ports236A and236B, which receives a first double acting piston238connected to a first, lower cam follower240which terminates in a friction reducing ball bearing assembly242. Similarly, the housing232defines a second or upper cylinder244, accessed by ports246A and246B, which receives a second double acting piston248connected to a second, upper cam follower250which terminates in a friction reducing ball bearing assembly252. A plurality of lugs or bosses254or similar structures at the ends of the cylinders234and244prevent the respective pistons238and248from bottoming out, closing off the ports236A,236B,246A and246B and inhibiting translation of the pistons238and248when compressed air is supplied to the ports236A,236B,246A and2466.

The first drive disc222includes a first complex cam track224utilized to rapidly accelerate the piston assembly80′ to undertake a measurement as will be more fully described subsequently. The second drive disc226includes a second, bell shaped cam track228A utilized to translate the piston assembly80′ in cooperation the jet ejector assembly300to draw particulate laden air into the cylinder210. When commanded, either the first, lower cam follower240is extended downwardly to engage the first complex cam track224to undertake a measurement of β or the second, upper cam follower250is extended upwardly to engage the second cam track228A to facilitate ingestion of particulate laden air into the cylinder210as will be more full described subsequently.

Referring now toFIGS. 7,11,12,13and14, the jet ejector assembly300includes an ejector nozzle302having an inlet end304defining an inside diameter equal to the inside diameter of the cylinder210such that, as illustrated inFIG. 7, the ejector nozzle302may be aligned and disposed at the end of the cylinder210with minimal flow disruption at their junction. The nozzle302has a venturi configuration and disposed proximate a throat306is a tabbed jet array310which generates streamwise vorticity and enhances mixing. The jet array310includes alternating larger, inwardly directed tabs312and smaller, outwardly directed tabs314, all having side angles of 45°. The jet array310is connected to, supported by and supplied pressurized air through a pipe or conduit320which extends perpendicularly through the wall of the ejector nozzle302and extends along the cylinder210to the cam and drive assembly220.

As illustrated inFIGS. 11 and 13, the pipe or conduit320is attached to a follower arm322which terminates in a first, single cam follower assembly230′. The first, single cam follower assembly230′ is similar to the double cam follower assembly230illustrated inFIG. 10except that it includes only the lower cylinder234, the ports236A and236B, the double acting piston238, a vertically moveable lower cam follower240′ and the ball bearing assembly242. The lower cam follower240′ selectively engages a third cam track228B on the upper side of the second drive disc226. If the first, single cam follower assembly230′ is activated such that the lower cam follower240′ is disposed in the third cam track228B, as the second drive disc226rotates, the ejector nozzle302moves into or out of position at the open end of the cylinder210as illustrated inFIG. 12and described more fully below.

Referring now toFIGS. 7 and 13, the jet ejector assembly300also includes a ball valve330in the pipe or conduit320which selectively opens to deliver compressed air to the tabbed jet array310in the ejector nozzle302. The ball valve320includes a shaft324which is secured to a crank326and a linkage arm328which terminates in a second, single cam follower assembly230″. The second, single cam follower assembly230″ is the same as the first, single cam follower assembly230′ and includes a vertically moveable cam follower240″. The cam follower240″ selectively engages a fourth cam track338on a third drive disc340. If the second, single cam follower230″ is activated, rotation of the third drive disc340opens or closes the ball valve330as described more fully below.

Referring again toFIG. 7, the cam and drive assembly220includes an electric motor260having an output shaft262that directly drives a first timing belt drive pulley264, a flywheel266and the first drive disc222. Both the motor260and the output shaft may be supported by the frame202. The first timing belt drive pulley264drives a larger, first driven timing belt pulley268through a first timing belt270. The sizes of the pulleys264and268accomplish a 4 to 1 speed reduction. The first driven timing belt pulley268is secured to an idler shaft272. Also secured to the idler shaft272is a second timing belt drive pulley274which drives a larger, second driven timing belt pulley276through a second timing belt278. The sizes of the pulleys274and276accomplish a 5 to 1 speed reduction. The second timing belt driven pulley276is secured to a drive shaft280which is part of the sequencing assembly350. The drive shaft280of the sequencing assembly350rotates at one-twentieth the speed of the electric motor260.

Secured to the upper end of the idler shaft272is a third timing belt drive pulley284which engages and drives a third timing belt286. The third timing belt286engages and drives a third driven timing belt pulley288. The sizes of the pulleys284and288are the same such that there is no speed increase or decrease between them. The third driven timing belt pulley288is secured to an upper shaft290which is coaxial with the output shaft262of the motor260and may be piloted therein in a suitable bearing assembly292. Secured to the upper shaft290for rotation therewith are the second drive disc226and the third drive disc340.

Referring now toFIGS. 7,15,16A and16B, the sequencing assembly350is disposed in the plenum352and driven by the drive shaft280. Secured to the drive shaft280is an actuator arm354upon which reside a pair of spaced-apart rollers356A and356B disposed adjacent a cam plate360. The inner roller356A aligns with an inner cam track362A and the outer roller356B aligns with an outer cam track362B. The inner and outer cam tracks362A and362B include a plurality of circularly arranged arcuate cams that are actuated (depressed) by the rollers356A and356B as the drive shaft280and the actuator arm354rotate.

Normally closed valves are associated with the inner cam track362A and normally open valves are associated with the outer cam track362B. InFIG. 16A, a normally closed valve linkage370is illustrated and includes a cam372disposed in an opening in the cam plate360. The cam372is coupled to a first link374which is coupled to a first class lever arm376having a pivot378and a second link382which is attached to a compression spring384at one end and a valve stem386at the other. A valve body388is attached to the valve stem386and seats within a valve seat392. When the cam372is depressed, the valve body388moves off the seat392and provides a flow of compressed air to a passageway or line394which communicates with a port in a cam follower assembly.

InFIG. 16B, a normally open valve linkage400is illustrated and includes a cam402disposed in an opening in the cam plate360. The cam402is coupled to a third class lever arm404having a pivot406and a link408that is connected at one end to a tension spring410and at the other end to a valve stem412. A valve body414is attached to the valve stem412and seats within a valve seat416. When the cam402is depressed, the valve body414moves against the seat416and terminates a flow of compressed air to a passageway or line418which communicates with a port in a cam follower assembly. The plenum352is preferably supplied with pressurized air, commonly referred to as “shop air” at pressures in the range of from 60 to 120 p.s.i. and more preferably in the range of 90 to 100 p.s.i.

The sequence of operation of the second embodiment mass loading monitor200will now be presented with reference to all of the drawing Figures, especiallyFIGS. 7 and 15. The cycle of operation starts with the piston80′ beyond, i.e., to the left of, the ports212, in the position illustrated inFIGS. 7 and 8, with a charge of particulate laden air in the cylinder210. From the start position at three o'clock inFIG. 15indicated by an “S”, the following events sequentially occur:

Rotationof DiscCamActuator222TrackMotionAction0.5224DownPiston 80′ accelerates to 10 g's,then retracts224UpPiston 80′ returns to start position1.0360° dwell before next event2.0228AUpRetract piston 80′ behind ports 212228ADownHold piston 80′ behind ports 2121.0360° dwell before next event2.0228BDownRotate pipe 320 to place ejectornozzle 302 on axis of cylinder 210228BUpRetain nozzle 302 on axis1.0360° dwell before next event5.5338DownOpen ball valve 330 to bring newparticulate laden air into cylinder 210338UpClose ball valve 3301.0360° dwell before next event2.0228BDownReturn nozzle 302 to off axis position228BUpHold nozzle 302 in off axis position1.0360° dwell before next event2.0228AUpMove piston 80′ to start position228ADownHold piston 80′ in start position1.0360° dwell before starting next cycle20.0Rotations of first drive disc 222

At the completion of a measurement cycle as described directly above, data from the MEMS pressure sensor100within the piston82is downloaded or read, the time integral of pressure is computed and compared with the stored reference or calibration data and the particulate content of the air is computed.

AsFIG. 15graphically illustrates, the roller356A sequentially activates cams such as the cam372in the inner cam track362A which is associated with the normally closed valve linkages370and the valves388. Likewise, the roller356B sequentially activates cams such as the cam402in the outer cam track362B which is associated with the normally open valve linkages400and the valves414. The valves388and414provide or terminate the flow of compressed air to the upper cylinder244of the double cam follower assembly230associated with the second cam track228A on the second drive disc226to advance and retract the upper cam follower250. As illustrated inFIG. 15, additional normally closed and normally open valve linkages370and400are associated with the first cam track224on the first drive disc222to provide compressed air to the lower cylinder234and translate the lower cam follower240, the third cam track228B on the second drive disc226and its cam follower assembly230′ and the fourth cam track338on the third drive disc340and its cam follower assembly230″.

It should be understood that the sequencing assembly350may be replaced by an electronic timing or sequencing device (not illustrated) having, for example, an optical or magnetic marker attached to the first disc222and a proximate compatible sensor which provides timing or synchronizing pulses to a programmed sequencer such as a microprocessor having a plurality of outputs which drive solenoid valves on a manifold supplied with shop air and which selectively provide compressed air to the cam follower assemblies230,230′ and230″ in accordance with the above described sequence of operation.

The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within its scope. Such variations are not to be regarded as a departure from the spirit and scope of the invention