Background of the Invention In the operation of copier/duplicator machines, it is necessary to provide a system for the recovery of particulate contaminants from inside the copier/duplicator machine. These contaminants may comprise particulate materials as varied as paper dust, toner, developer and the like. These particulate materials can vary substantially in their density and in other properties.

Such particulates are typically recovered from copier/duplicator machines by a vacuum system which passes the air streams recovered from the inside of the copier/duplicator machine to a cyclone separator where particulates are separated with the gaseous components of the stream being withdrawn and passed to further filtration and the like. The particulates recovered from the cyclone separator are typically deposited in a collection vessel beneath the cyclone separator, although in some instances it is possible to position a cyclone separator in other than a vertical position. These particulates accumulate in the collection vessel and are periodically dumped from the collection vessel. In the event that the particulates accumulate in the collection vessel to an unacceptably high level, the failure to empty the collection vessel can lead to a toner blow out condition that contaminates the machine and the machine site. Such contamination in the copier/duplicator machine is very undesirable and creates many problems.

Unfortunately, the composition of the particulates collected in the collection vessel can vary widely from paper particulates to toner to developer. There is a wide disparity in the behavior of these various types of solids as well as in their density. Accordingly, attempts to use level control or detection systems such as Piezo electric systems have been relatively unsuccessful because they are relatively fragile and provide very short service lives. Similarly optical systems have been unsuccessful because the paper dust tends to form clouds and create false readings at the selected level for monitoring the particulates level in the collection vessel. Further weight systems are relatively inaccurate and can result in overfilling because the weight may be determined based upon a mixture of particulates which is more dense than those in fact collected.

Further weight systems tend to be relatively inaccurate since they involve mechanical mounting and the like.

As a result, a continuing effort has been directed to the development of improved methods and apparatus for determining the level of particulate material in a particulate material collection vessel and for generating a signal to indicate the high level of particulates in the collection vessel.

Summary of the Invention According to the present invention, the level of particulate material in a particulate material collection vessel is readily determined by a method comprising: positioning a transmitter to transmit an acoustic wave signal through a particulate storage area in the vessel at a selected level to a receiver; providing electrical power to the transmitter; monitoring an acoustic wave signal received at the receiver to detect a change in the acoustic wave signal indicative of particulate material at the selected level in the particulate material storage area; and, generating a signal indicative of the presence of particulate material at the selected level in the particulate material storage area.

The present invention further comprises a level indicator particulate collection vessel and comprising: a vessel having a particulate material inlet, the inlet being configured for connection to a cyclone separator particulate material outlet ; a transmitter transducer acoustically coupled to the vessel or positioned inside the vessel at a selected level and adapted to transmit an acoustic wave signal across at least a portion of a particulate material storage area inside the vessel ; a receiver acoustically coupled to the vessel or positioned inside the vessel at the selected level and adapted to receive the transmitted acoustic wave signal ; and, a comparator connected to the receiver and adapted to generate a signal responsive to a change in the acoustic wave signal indicative of particulate material in the particu) ate materia) storage area at the selected level.

Description of the Drawings Figure 1 is a schematic diagram of a particulate solids collection system for a copier/duplicator machine; Figure 2 is a schematic diagram of a particulate material collection vessel according to the present invention; Figure 3 is a schematic diagram of a further variation of the vessel of the subject invention; Figure 4 is a schematic diagram of a further embodiment of the vessel of the present invention; Figure 5 is a schematic diagram of a further embodiment of the vessel of the present invention; and, Figure 6 is a schematic diagram of commonly occurring component parts of transducers suitable for use in the present invention.

Description of Preferred Embodiments In the discussion of the Figures, the same numbers will be used throughout to refer to the same or similar components.

In Figure 1 a typical particulates collection system 10 for a copier/duplicator machine is shown. A gaseous stream containing particulate materials is withdrawn from the copier/duplicator machine via a line 12 and passed to a cyclone separator 14. In cyclone separator 14, particulates are removed as well known to those skilled in the art and passed via a particulates outlet 18 to a particulate material collection vessel 20. The gaseous component of the stream in line 12 are recovered via a line 16 and passed to a blower 22 which generates a sufficient vacuum to withdrawn the gaseous stream in line 16 from cyclone separator 14. This vacuum is also is sufficient to draw the gaseous stream into line 12 and into cyclone separator 14. The gaseous stream discharged from blower 22 is passed via a line 24 to a proportioning valve 26 where it may be separated in to two streams or alternatively passed to a single further treatment zone. In a preferred embodiment, a portion of the gaseous stream is passed through a line 28 via a blower 30 into a chamber 32. Blower 30 creates a positive pressure in chamber 32 causing the gas to exhaust via a filter 34 into a line 36. The cleaned gas in line 36 may be used in the copier/duplicator machine or otherwise discharged.

A second portion of the stream in line 24 may be passed via a line 38 and a blower 40 into a second chamber 42 from which it is discharged via a filter 44 to a line 46 for discharge to the atmosphere or the like. Two chambers may be used as discussed or the entire gaseous stream may be directed to a single chamber for filtration as desired. Such variations are considered to be well known to those skilled in the art.

A continuing problem has been the determination of when the collection vessel 20 was filled. As indicated previously, the type of solids collected may vary considerably in density, bulk and the like. Vessel 20 is formed with an inlet 48, which is adapted to connect in fluid communication with the discharge from cyclone separator 14 at inlet 48 of vessel 20. Vessel 20 as shown comprises an upper reduced diameter portion 50 with a particulate storage area 52 beneath reduced portion 50.

As shown in Figure 2, the particulate solids have reached a level 54 in vessel 20. A transmitter transducer 56 is acoustically coupled to vessel 20 with power being supplied to transducer 56 through a line 58. Transducer 56 generates an acoustic wave signal which is a sinusoidal wave in the ultrasonic sound region which is transmitted to a receiver/transducer 60 which is acoustically coupled to the outside of vessel 20. The received signal is transmitted via a line 62 to a comparator 64 where, as known to those skilled in the art, it is processed to produce a signal 68 indicative of a below selected level signal and via a line 68 and an above selected signal 70. The selected line in vessel 20 as shown is dotted line 66, which corresponds to substantially the center of transducers 56 and 60.

The use of such transducers is considered to be well known to those skilled in the art and such transducers are commonly available commercially. A line of such transducers is marketed by Murata Erie North America, 2200 Lake Park Drive, Smyrna, Georgia 30080. These transducers are available in widely varied frequencies. The ultrasonic range is generally considered to extend from about 10 to about 400 kilohertz. Below about 20 kilohertz, the sounds are audible to the human ear and constitute an undesirable noise pollutant. Frequencies higher than about 200 kilohertz are also less. desirable for a variety of reasons. Accordingly, it is preferred that ultrasonic waves between about 20 and about 200 kilohertz be used.

Transducers capable of generating sound waves in this frequency are commonly available as indicated above. Such transducers are typically used by acoustically coupling the transducer to a surface from which a sound wave is to be transmitted or in an area in which the sound wave is to be received. With metal vessels, braising and the like are effective to acoustically couple the transducers to the vessel. With metal or plastic vessels various adhesives known to those skilled in the art are readily available to acoustically couple the transducers to the vessel.

In Figure 3, the transducers are shown positioned at a much higher level in vessel 20.

Positioning the vessels at this higher level results in a higher selected level 66 which permits more complete filling of vessel 20 but which prevents less time for the operator to note the overfull condition and empty or replace vessel 20.

In Figure 4, a similar vessel is shown with the transducers being positioned in the walls of vessel 20. Transducers 56 and 60 are readily positioned in the walls of vessel 20 and in this instance no acoustic coupling is necessary since the receiver and signal are in direct communication. Please note that in the embodiment shown in 54, a high solids level is shown since the solids level is above the selected level 66, vessel 20 is ready of emptying or replacement.

In Figure 5, a similar embodiment is shown except that the transducers 56 and 60 are positioned inside vessel 20. In this instance, only the lines providing power and transmitting the received signal need penetrate the sidewalls of vessel 20.

In Figure 6, a more detailed disclosure of components typically used in the transducers is shown. As shown the transmitter circuit comprises an oscillator with a 400-kilohertz sinusoidal output. Any desired frequency sinusoidal output could be selected. The signal generator is transmitted to an ultrasonic transmitter, which is shown schematically positioned within the collection vessel with the ultrasonic receiver being positioned to receive transmissions from the transmitter. The received signals are then passed to a receiver circuit where a high pass filter, high gain amplifier, signal clipping diode, comparator, a low pass filter and an output signal generator are included. A wide variety of components may be used to achieve the desired sound wave generation and reception. Such variations as indicated previously are well known to those skilled in the art and transducers and receivers of this type are readily available.

In the practice of the present invention as shown in Figure 6, a crystal-based oscillator is used to generate a controlled and stable signal to operate the transducers within a selected frequency range. A sinusoidal signal is provided.

The first stage of the receiver circuit is a high pass filter that blocks any direct current components. This precaution is taken because the next step is a high gain amplifier that produces a bipolar square wave. The negative part of the square wave is then clipped with a diode with the resulting signal being fed into a comparator. The reference voltage of the comparator is high enough to block the received signal when the transducers have toner or other particulates between them. The comparator feeds into a low pass filter that produces a voltage level when the comparator is passing the received signal. The filter feeds the driver that provides the system's output.

In the practice of the present invention, it has been found that the signal is reduced to an extent sufficient to permit the use of the reference voltage in the comparator to block the flow when the transducers have toner between them while permitting the flow when no particulates are between the transducers, transmitter and receiver. Voltage reductions from the received signal from one-third to one-half have been noted in the evaluation of the present invention.

This is a sufficient difference to permit dependable detection of solids at or above the selected level. This permits the operator to note that the vessel is full and then empty or replace the vessel prior to a spill of particulates into the copier/duplicator machine.

Accordingly, the present invention has provided a reliable and predictably reproducible method for determining the level of particulate solids in a collection vessel so that spills, blowouts and the like in the solid collection system can be avoided thereby improving the reliability and operability of copier/duplicator machines.

It is noted that the embodiments discussed above are illustrative in nature and that many modifications and variations are possible within the scope of the present invention. Many such modifications and variations may be considered obvious and desirable by those skilled in the art based upon the foregoing description of preferred embodiments.