Abstract:
A mechanical level sensor detects when a fluid material added to a chamber has reached a predetermined level and therefore comprises a predetermined particular volume. Material is added to a chamber until it has reached the predetermined level. Once this level is reached, additional material overflows into a level sensor. The overflow material causes a wheel having a plurality of wells to rotate. This rotation is detected by a control circuit that signals the cessation of addition of material to the chamber and the dispensing of the material present in the chamber. The sensor is highly sensitive due to the almost frictionless rotation of the wheel about its axle.

Description:
FIELD OF THE INVENTION 
   The present invention is directed to a mechanical fluid level sensing device. More specifically, the present invention is a mechanical device that determines when a liquid or fluid solid has reached a certain level in a chamber. 
   BACKGROUND OF THE INVENTION 
   It is often desirable to automatically and repeatedly dispense a predetermined volume of a material. This can be done manually by using a variety of measuring devices. Such devices include, but are not limited to, graduated cylinders, volumetric flasks, graduated pipettes, and weight scales. However, these methods must be performed manually by an individual and are both inefficient and time consuming. Therefore, several methods have been developed for automatically measuring and dispensing a predetermined amount of a material. 
   It is common to use a pump that is programmed to run for a predetermined length of time in order to dispense a set volume of material. Alternatively, piston-type pumps may be programmed to perform a single stroke when activated, thereby dispensing a volume of material equal to the volume displaced by the piston. 
   Dispensing chambers have also been developed that have an integrated weight scale. Material is added to the chamber until a particular, predetermined weight is reached. The material may then be dispensed from the chamber. 
   Direct volume measurement is also used in volumetric dispensing devices, particularly for measuring fluid materials. An accumulation chamber of a predetermined volume has a sensor at the top of the chamber. Material is added to the accumulation chamber until the level of the material reaches the level of the sensor and is detected. Upon detection, the addition of material to the chamber is halted and the material in the chamber is dispensed. 
   Volumetric dispensers have become increasingly common. However, a problem often encountered is finding a proper detection sensor for the top of the accumulation chamber. Photoelectric sensors are a common type of detector used. However, especially with granular solid material, they are not always accurate. Small granular material is often susceptible to both static electricity and caking due to ambient moisture. A small amount of the material may adhere to the sides of the accumulation chamber, thereby blocking the light emitted by the sensor. Thick liquids may also temporarily coat the walls of an accumulation chamber and make photoelectric measurement unreliable. 
   Electric current detection has also been used. When a conductive liquid reaches a sensor at the top of an accumulation chamber, a current may be detected at the level of the sensor. However, many materials are not conductive. Additionally, those that are may be damaged or altered by the application of an electric current. 
   Float type level switches have also been used. For example, toilets use a float type level switch to regulate the volume of water in its reservoir. However, float sensors are unusable for level detection of fluid solids. 
   It is therefore desirable to provide an accurate sensor for detecting when a fluid solid or a liquid has reached a certain point in an accumulation chamber. 
   SUMMARY OF THE INVENTION 
   The present invention provides a mechanical fluid level sensor that accurately determines when a liquid or fluid solid has reached the level of the sensor in an accumulation chamber of a volumetric fluid material dispenser. The sensor is housed in a sensor chamber attached to the side of an accumulation chamber. An inlet port at a predetermined level of the accumulation chamber places the top of the sensor chamber and the accumulation chamber in fluid communication with one another. When material being added to the accumulation chamber reaches the inlet port, a portion of it overflows out of the accumulation chamber and into the sensor chamber. Below the inlet port within the sensor chamber is a sensor wheel. The sensor wheel has a plurality of wells extending along its circumference. When the overflow material falls through the inlet port it drops into one of the wells of the sensor wheel. There is very little friction between the sensor wheel and the axle it rotates on. Therefore, only a very small amount of material needs to fall into a well of the sensor wheel in order for the weight to cause the wheel to rotate. The sensor wheel has a plurality of permanent magnets embedded within it. On one side of the sensing chamber is a reed switch integrated into a control circuit. As the sensor wheel rotates, one of its magnets will pass near the reed switch, thereby activating it. Triggering the reed switch causes the control circuit to send a signal to discontinue addition of material into the accumulation chamber. The material in the accumulation chamber is then dispensed. This may also be triggered by a signal from the control circuit. At the bottom of the sensor chamber is an outlet port which allows the material that actuated the sensor wheel to reenter the accumulation chamber and be dispensed with the material already in the chamber. When the sensor is used to measure the volume of a liquid, it is desirable to incorporate a check valve into the outlet port so that fluid rising in the accumulation chamber doesn&#39;t enter the sensor chamber prior to it reaching the inlet port. 
   After the material in the chamber has been dispensed, the exit port of the accumulation chamber is closed and the process may be repeated. Because the mechanism of the sensor is mechanical, it is very inexpensive to produce. In addition, the sensor has only one moving part making it reliable and easy to manufacture. 
   These and other features of the invention will become apparent from the following detailed description of the preferred embodiments of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of the invention. 
       FIG. 2  is a left side cross-sectional view of the invention. 
       FIG. 3  is a right side view of the invention. 
       FIG. 4  is a side view of an alternative embodiment of the sensor wheel of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The present invention is a mechanical level sensor for use with a volumetric fluid material dispenser. It may be used to detect when a liquid or fluid solid has filled an accumulation chamber or other container to a particular level. As used herein, the terms fluid and fluid material refer both to liquids and fluid solids. The invention is accurate, reliable, and easy to manufacture. 
     FIG. 1  shows the level sensor  24  integrated with a volumetric fluid material dispenser  10 . Volumetric fluid material dispenser  10  has a material entry port  12  attached to the top of accumulation chamber  18  by means of sleeve portion  16 . Material entry port  12  has flange  14  for attachment to a depositing mechanism (not shown) that deposits material into accumulation chamber  18 . At the bottom of accumulation chamber  18  exit valve  20  connects accumulation chamber  18  to exit conduit  22 . As is explained below, both the depositing mechanism attached to material entry port  12  and exit valve  20  may be controlled by the control circuit of level sensor  24 . 
   Entry port  12  may receive fluid that is deposited by means of either gravity or a pump. In this embodiment, entry port  12  is substantially conical in shape. Those skilled in the art will appreciate that port  12  may be any of a variety of shapes so long as it allows for transfer of a fluid from a depositing mechanism into the accumulation chamber  18 . Additionally sleeve portion  16  may provide permanent or removable attachment of port  12  to chamber  18 . It may be desirable for the port  12  to be removably attached to chamber  18  to facilitate cleaning or the interchanging of alternative entry ports having different structures. 
   Accumulation chamber  18  in this embodiment is cylindrical. However, accumulation chamber  18  may be of any of a variety of shapes. It is preferred that accumulation chamber  18  is relatively narrow, having a high height to width ratio. Those skilled in the art will appreciate that such a design allows for more accurate measurement of the volume of the accumulation chamber. 
   Exit valve  20  may be comprised of any of a variety of types of valves well known in the art, including but not limited to check valves, gate valves, ball valves and butterfly valves. 
   Level sensor  24  consists of sensor chamber  25 . Sensor chamber  25  houses sensor wheel  30 . Sensor wheel  30  rotates about axle  32 . Control circuit  40  is attached to the outside of sensor chamber  25 . Sensor chamber  25  is in fluid communication with accumulation chamber  18  by means of inlet conduit  28 . 
   In this embodiment, chamber  25  is substantially cylindrical. Although this is a preferred design, sensor chamber  25  may be of any shape as long as it adequately houses the sensor wheel and protects it from outside influences, such as air turbulence, that may inadvertently cause wheel  30  to rotate when not desired. 
     FIG. 2  shows a cross-sectional left side view of the fluid sensor integrated with the volumetric dispenser in order to more clearly illustrate the mechanism and functionality of the sensor. Here it can be seen that sensor wheel  30  has four wells  34  across the length of the circumference of wheel  30 . Inlet conduit  28  allows fluid communication between accumulation chamber  18  and sensor chamber  25  by means of inlet port  36 . Inlet conduit  28  and sensor wheel  30  are oriented such that material flowing into the sensor chamber  25  from the accumulation chamber  18  falls within one of the wells  34 . 
   In operation, material is added to accumulation chamber  18  through material entry port  12 . Valve  20  is closed so as to allow material to accumulate in the accumulation chamber. As the material accumulates it will pass the level of outlet port  38 , which provides fluid communication between chamber  18  and the bottom of sensor chamber  25  below inlet port  36 . To prevent the fluid from entering sensor chamber  25  through outlet port  38 , it is preferable that port  38  comprises a check valve, biased toward the closed position, only allowing movement of fluid material from the sensor chamber  25  into the accumulation chamber  18 . This prevents liquid or other material from entering sensor chamber  25  through outlet port  38 . A check valve incorporated into outlet port  38  is necessary when volumetrically dispensing liquids and certain fluid solids. However, some fluid solids have cohesive or other properties that substantially prevent them from entering outlet port  38  even when there is no valve incorporated into it. When volumetrically dispensing such fluid solids, outlet port  38  requires no valve. 
   Material continues to accumulate in chamber  18  until it reaches the level of inlet port  36 . At this point, material added through material entry cone  12  partially overflows into inlet port  36 , down inlet conduit  28  and into one of the wells  34  of sensor wheel  30 . Because there is extremely little friction between sensor wheel  30  and axle  32 , only a small amount of overflow material will cause sensor wheel  30  to rotate. Sensor wheel  30  continues to rotate at least until the well in which the overflow material has fallen is overturned such that the material within it falls to the bottom of sensor chamber  25  where outlet port  38  is located. 
   Sensor wheel  30  has embedded within its walls permanent bar magnets  35  extending radially outward from the axle  32 . When wheel  30  rotates as a result of material being deposited in one of its wells, one of embedded magnets  35  will pass reed switch  26 . Reed switch  26  is either located on the outside of sensor chamber  25  or is embedded within the wall of sensor chamber  25 . Those skilled in the art will appreciate that when a reed switch comes in close proximity of a magnetic field a circuit is completed within it. This provides a means for detecting the rotation of sensor wheel  30 . 
     FIG. 3  shows in better detail reed switch  26  located on the side of sensor chamber  25 . Reed switch  26  is an integral part of control circuit  40 . When the reed switch  26  is actuated by the passing of one of bar magnets  35 , control circuit  40  is activated. Control circuit  40  then sends a signal to stop material deposition into the accumulation chamber  18  through material entry port  12 . Control circuit  40  also optionally sends a signal to open valve  20 . Alternatively, another signal may actuate valve  20  causing it to open, or it may be done manually. Once valve  20  is opened, the material within the accumulation chamber  18  is dispensed through conduit  22  until accumulation chamber  18  is empty. The overflow material that has accumulated in the sensor chamber  25  at outlet port  38  returns to accumulation chamber  18  and is also dispensed through conduit  22 . Once all of the material has been dispensed, exit valve  20  is closed and the cycle may be repeated. 
   In the embodiment shown in  FIGS. 1 ,  2 , and  3  the sensor wheel has four concave wells. Those skilled in the art will appreciate that the wells may have other geometries and may be more or less than four in number.  FIG. 4  shows an alternative embodiment of the sensor wheel  45 . In this embodiment, three wells  42  are substantially V-shaped. Wheel  45  rotates about axle  46  and has embedded within it a series of permanent bar magnets  44  for actuation of a reed switch. 
   While the four well wheel  30  shown in  FIGS. 1 ,  2 , and  3  is preferred, other designs such as the three well design of  FIG. 4  may be used. Similarly, sensor wheels having 5 or more wells may also be used. 
   In the preferred embodiment, a reed switch is used to detect the rotation of the sensor wheel. This is the preferred method of detecting the rotation of the sensor wheel because it does not add friction to the wheel&#39;s rotation. Other sensor methods that would require the wheel to contact a tab or a switch upon rotation would add substantial friction to the wheel&#39;s rotation and decrease the sensitivity of the sensor. On a small scale this is not practical. However, those skilled in the art will appreciate that if the invention is used to measure relatively large scale liquid volumes or large scale fluid solids, such as gravel or the like, other methods of detecting the sensor wheel&#39;s rotation may be suitable. 
   While the invention has been shown and described in some detail with reference to specific exemplary embodiments, there is no intention that the invention be limited to such detail. On the contrary, the invention is intended to include any alternative or equivalent embodiments that fall within the spirit and scope of the invention as described above and as recited in the appended claims.