Abstract:
There is provided a method for monitoring a vacuum system such as that used in a dairy milking system. Several independent measurements are made whereby a long term degradation of the vacuum pump or other component in the vacuum system may be identified before system performance drops below acceptable limits. Baseline data generated when the vacuum system is known to be in good working order. The baseline data is used to compare operation of the vacuum system. An alarm signal or other indication may be generated to alert an operator that vacuum system performance has degraded beyond an acceptable limit. Such predictive failure techniques allow maintenance to be performed on the vacuum system long before performance degrades to a point where a system becomes inoperative.

Description:
FIELD OF THE INVENTION 
   The invention pertains to monitoring devices for vacuum systems and, more particularly, to a device which monitors a vacuum system and alerts an operator when degradation of the vacuum system is detected. 
   BACKGROUND OF THE INVENTION 
   Vacuum-operated devices generally require a minimum vacuum capacity, typically measured in volumetric flow of air per unit time, to ensure their proper operation. Consequently, vacuum systems supplying vacuum to such devices must likewise maintain sufficient vacuum capacity. 
   Typically vacuum within a vacuum system is produced by a vacuum pump, several types of vacuum pumps being well known to those of skill in the art. In a vacuum system, the vacuum pump must be designed and sized to ensure enough capacity. That is, the vacuum pump must be capable of providing more air flow than the system requires. 
   Vacuum systems typically include some means for regulating the vacuum level (i.e., holding the vacuum level between predetermined limits). This is typically accomplished either by using a regulator that admits air in a controlled manner or by varying the speed of the vacuum pump to produce the required instantaneous vacuum. 
   However, as vacuum pumps and other components in a vacuum system age, several problems may occur. These problems result in a decrease in vacuum capacity of the system. Problems such as mechanical wear and degradation of the pump, leaks in the system, or failure of the vacuum regulator are typical. The loss of vacuum capacity can occur gradually over time leading to slow erosion of the vacuum capacity margin of the system and subsequent degradation in the performance of vacuum-using devices attached to the system. 
   For example, one common usage of vacuum systems is in milking systems designed for milking dairy cows or other milk-producing animals. These milking systems consist of a vacuum pump, a regulator, and a collection of interconnecting pipes and milking machines that utilize the vacuum to milk cows. The process of milking the cows typically creates a widely varying vacuum demand. The vacuum pump must have the ability to respond to that changing demand in a timely manner. 
   If, however, the vacuum pump or other components of the vacuum system begin to degrade, then the performance of the milking system may be degraded. This degradation can occur over a period of time and may not be readily recognized by the operators until a catastrophic or near-catastrophic failure occurs. However, the result is generally poor milking performance of the milking system. 
   DISCUSSION OF THE RELATED ART 
   U.S. Pat. No. 4,616,215 for VACUUM MONITORING AND SIGNALING APPARATUS, issued Oct. 7, 1986 to Richard E. Maddalena teaches a vacuum monitoring apparatus having an alarm when a vacuum level falls outside a preset range. MADDALENA, however, makes no provision for monitoring trends over a period of time in an effort to detect degradation in a vacuum system. 
   It would, therefore, be extremely beneficial to the operators of such milking systems to become aware of the degradation of performance of the vacuum system before the degradation seriously affects milking performance. It would be beneficial to provide a system capable of monitoring the capacity of the vacuum system and notifying an operator of any reduction in capacity. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention there is provided a method for monitoring a vacuum system such as is used in a dairy milking system. Several independent measurements including, but not limited to mass flow, are made whereby long term degradation of the vacuum pump or other components in the vacuum system may be identified before system performance drops below acceptable limits. 
   It is, therefore, an object of the invention to provide a method of monitoring vacuum levels in a vacuum system. 
   It is a further object of the invention to provide a method of monitoring vacuum levels that is useful for operators of a dairy milking parlor. 
   It is another object of the invention to provide a method of monitoring vacuum wherein gradual degradation of a vacuum system may be detected. 
   It is a further object of the invention to provide a method of monitoring vacuum wherein historic ratios of pressures may be compared to present ratios of pressures to detect degradation in a vacuum system. 
   It is an additional object of the invention to provide a method of monitoring vacuum wherein the amount of time necessary to bring a vacuum level to a predetermined point at startup of the vacuum system is used to determine the health thereof. 
   It is a still further object of the invention to provide a method of monitoring vacuum wherein a difference in pressure in a regulated and a non-regulated portion of a vacuum system is used to assess the efficiency thereof. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A complete understanding of the present invention may be obtained by reference to the accompanying drawings, when considered in conjunction with the subsequent detailed description, in which: 
       FIG. 1  is a schematic diagram of a vacuum system of a typical dairy milking system; 
       FIG. 2  is a simplified schematic diagram of the vacuum system of  FIG. 1 , having vacuum monitoring devices in accordance with the present invention; and 
       FIG. 3  is a schematic view of a possible monitoring device for practicing the method of the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring first to  FIG. 1 , there is shown a system schematic diagram of a portion of a typical milking system, generally at reference number  100 . A vacuum pump  102  is connected to a vacuum regulator  104  and to a vacuum header or distribution manifold  106 . Vacuum pump  102  may be of any type well known to those of skill in the art of vacuum systems, such as Model No. M7.5, manufactured by Masport, Inc., the exact specification of vacuum pump  102  forming no part of the instant invention. Vacuum regulator  104  is shown schematically as a bypass regulator, such as Model No. 350, manufactured by Western Dairy Research, Inc., but any other form of vacuum regulator such as an in-line regulator or a variable-speed vacuum pump drive system may also be used. 
   A pulsator  108  is connected to header  106  by pulsation line  110 . Main vacuum line  112  connects header  106  to a milk receiver  116  via a moisture trap  114 . Milk receiver  116  is shown connected to a milk line  118  which is, in turn connected to milking machine  120  shown connected to the teats of an animal  122 . Milk pump  124  pumps milk from milk receiver  116  to a holding tank, not shown, for further processing. 
   A typical milking system such as that shown in  FIG. 1  may have hundreds of feet of vacuum lines and many interconnections. Consequently, there are numerous points where vacuum leakage may occur. While vacuum regulator  104  normally keeps the vacuum level within predetermined limits, no vacuum monitoring tracks either the instantaneous or long-term performance. Developing leaks or degradation of vacuum pump  102  or vacuum regulator  104 , therefore, can not be detected until the milking performance is badly degraded. 
   The method of the present invention provides comprehensive vacuum system monitoring to detect the earliest stages of system performance degradation, whether from developing leaks or from degradation of a system component. The vacuum system capacity is monitored and evaluated in a number of independent ways. 
   Referring now to  FIG. 2 , there is shown a simplified version of the milking system of  FIG. 1 , having vacuum monitoring devices in accordance with the present invention. Vacuum pump  102 , vacuum regulator  104 , header  106 , pulsator  108  and milk receiver  116  are still present in the same arrangement as described hereinabove. 
   A vacuum sensor  202  is shown disposed in vacuum line  214  adjacent vacuum pump  102  but before the point vacuum regulator  104  is connected. Another vacuum sensor  204  is placed leader  204 , typically relatively close to regulator  104 . Additional vacuum sensors  206 ,  208  are disposed in vacuum line  118 . Still another vacuum sensor  210  is placed in pulsation line  110 . Vacuum sensors are off-the-shelf commercial vacuum sensors adapted to produce an electrical output representative of a vacuum level present thereat. A model no. PX241 vacuum sensor, manufactured by Omega or equivalent, has been found satisfactory for the application. Although not specifically shown in  FIG. 2 , vacuum sensors  202 ,  204 ,  206 ,  208 ,  210  are each electrically connected to a monitor  300  ( FIG. 3 ) as described in detail hereinbelow. 
   An air admission device  212  is attached to vacuum line  214 , also adjacent vacuum pump  102  and before the point of attachment of vacuum regulator  104 . Air admission device  212  is designed to open vacuum line  214  to a predetermined amount of air and may be a solenoid-operated valve with a calibrated orifice, not shown. The orifice may have either a fixed or variable diameter, depending upon the actuation method used. Any other device through which a predetermined amount of air may be admitted to vacuum line  214  may be utilized. Air admission device  212  is also operatively connected to controller  300  as described hereinbelow. 
   It will be recognized that while five vacuum sensors have been shown for purposes of disclosure, other numbers of sensors, even as few as one sensor, may be required depending upon the size and complexity of the vacuum system installed in a particular milking parlor. In fact, no sensor is required when the system operates on the basis of mass flow. Also, while the vacuum system of a milking parlor has been chosen to describe the inventive methods, these methods are also applicable to vacuum systems in other environments. 
   Referring now to  FIG. 3 , there is shown a schematic diagram of a monitoring and control system suitable for practicing the method of the invention, generally at reference number  300 . A monitor/controller  302 , hereinafter controller, is schematically shown. As will be recognized by those of skill in the art, controller  302  may be implemented in many configurations and the invention is not considered limited to the exact controller  302  shown for purposes of disclosure. Controller  302  accepts electrical output signals from vacuum sensors  202 ,  204 ,  206 ,  208 ,  210  ( FIG. 2 ) and using signal conditioning and/or conversion circuitry, not shown, converts incoming electrical signals to actual vacuum readings. These readings may be selectively provided on a display  304 . A keypad  306  may be used to monitor individual ones of sensors  202 ,  204 ,  206 ,  208 ,  210  and/or a flow meter, not shown, placed, for example, between vacuum regulator  104  and vacuum pump  102 . 
   Key pad  304  or programming interface  310  may be used to preload acceptable ranges for each of vacuum sensors  202 ,  204 ,  206 ,  208 ,  210  typically when the vacuum system is first installed. 
   A control output  308  is provided to electrically actuate air intake device  212  ( FIG. 2 ) upon command from controller  302 . It will be recognized that while electrical actuation of air intake device  212  has been chosen for purposes of disclosure, mechanical, hydraulic, or pneumatic action could also be used to accomplish the actuation. 
   It is anticipated that controller  302  is a microprocessor-based controller utilizing non-volatile memory to store instructions, fixed data, and accumulated data from the vacuum sensors  202 ,  204 ,  206 ,  208 ,  210 . 
   Controller  302  implements several different monitoring functions. In a first monitoring method, air intake device  212  is periodically activated. The effect of this activation on the vacuum level at sensor  204  or another of vacuum sensors  206 ,  208 ,  210  (i.e., in the controlled section of the vacuum system) is observed. If measured vacuum at sensor  204 , etc. does not drop below a predetermined value, the capacity of the system is deemed to be acceptable. In other words, vacuum pump  102  and vacuum regulator  104  are probably both operating properly and it is likely that no significant leaks occur in the vacuum system. The acceptable vacuum level is predetermined, typically at the time the monitored system  200  is installed. 
   If, however, the actuation of air intake device  212  causes vacuum loss at sensor  204 , etc., an alarm is generated. This alarm may be a visual indicator  312  or an internal, audible alarm, not shown. In addition, an alarm signal line  314  may be used to actuate a remote alarm. 
   Another measurement of vacuum system status is performed by controller  302  as the vacuum system is first started. The time necessary for the vacuum level to rise from approximately 10% to approximately 90% of the nominal vacuum level can be measured. The measurement of this slew rate is another way of evaluating the overall health and integrity of the vacuum system. As described, an unacceptable slew rate at vacuum system startup may trigger an alarm. 
   Another way in which the inventive system may monitor vacuum system health is by developing statistics regarding normal vacuum excursions and establishing a baseline of normal vacuum system behavior and, optionally, evaluating the statistics to determine trends. Controller  302  may then monitor vacuum level excursions on an ongoing basis and evaluate excursions to determine the fall in an acceptable range of values. 
   Still another way the method of the invention uses to evaluate vacuum system health is to monitor total mass flow rate, which should remain within a predetermined set of limits. Mass flow rate is easily monitored by readily available commercial products. A typical mass flow measurement consists of a rotary vane placed in the air (or vacuum) stream to be measured. Rotation of the vane is easily monitored and correlated to the mass flow of the air stream causing the van rotation. 
   Another method of evaluating vacuum system performance is to compare the vacuum level at or near the vacuum pump  102  (e.g., at vacuum sensor  202 ) to the vacuum level on the regulated side of the system (e.g., at one of vacuum sensors  204 ,  208 ,  208 ,  210 ). That ratio should remain relatively constant if the capacity of vacuum pump  102  has not been reduced or if the vacuum system  200  otherwise has not been degraded. 
   Another method of assessing the performance of the vacuum system  200  is to compare the vacuum level of remote sections of the system (e.g., at vacuum sensors  206 ,  208 ,  210 ) to the area near the vacuum regulator (e.g., vacuum sensor  204 ). Again, that ratio should remain within specific limits if the vacuum system  200  is operating at a normal, acceptable capacity (i.e., vacuum system  200  is not degraded). 
   Since other modifications are changes varied to fit particular operating conditions and environments or designs will be apparent to those skilled in the art, the invention is not considered limited to the examples chosen for purposes of disclosure, and covers changes and modifications which do not constitute departures from the true scope of this invention. 
   Having thus described the invention, what is desired to be protected by letters patents is presented in the subsequently appended claims.