System and method for identifying and rejecting defective blow-molded plastic products

Abstract

A system and method for detecting and rejecting defective blow molded containers is provided. The invention includes a sound detector system for sensing the sound level from a mold during the blowing process, and outputting a sound level signal. If the sound level signal exceeds a predetermined set point, thereby indicating a discontinuous container, a kick mechanism rejects the defective container. The kick mechanism is sequenced with the sound detector system. A proximity switch may be employed to indicate the mold being in position in front of the sound detector.

We claim:  
     
         1 . A system for rejecting a defective discontinuous container from a container production line, the system comprising: 
 a blow molding carousel comprising at least two molds, each one of the at least two molds including an interior surface corresponding to a shape of the container and a nozzle coupled to the carousel and disposed proximate an opening in said mold, the carousel including a preform-loading point and a container-unloading point, each one of the molds receiving pressurized blow air into the mold through the nozzle;    a sound detector system that outputs a reject signal upon sensing a blow air sound level exceeding a predetermined sound level set point; and    a kick mechanism that ejects the discontinuous container in response to the reject signal being output from the sound detector,    whereby a preform contiguously expands within the mold interior surface in response to the pressurized blow air to form the container and a failure of a wall of the preform or the container during expansion forms said discontinuous container having a hole through which the blow air flows to form the blow air sound level exceeding the predetermined sound level set point.    
     
     
         2 . The system of  claim 1  wherein the predetermined sound level set point is less than a sound level of the pressurized blow air flowing outwardly through the container hole and the mold.  
     
     
         3 . The system of  claim 1  further comprising a container transfer wheel for transferring a plurality of the containers from the carousel at the container-unloading point, said kick mechanism disposed on the container transfer wheel.  
     
     
         4 . The system of  claim 1  wherein the kick mechanism includes a reject arm that strikes the discontinuous container from the container transfer wheel to eject the discontinuous container therefrom.  
     
     
         5 . The system of  claim 4  wherein the reject arm is actuated based on a signal from said sound detector after a time delay approximately equal to the time interval between the container moving from the sound detector to the reject arm such that the operation of the reject arm is sequenced with the sound detector.  
     
     
         6 . The system of  claim 4  wherein the reject arm is actuated based on a signal from said sound detector after a preset number of pulses from a proximity switch approximately corresponding to the number of containers between the sound detector and the kick mechanism such that the operation of the reject arm is sequenced with the sound detector, the proximity switch sensing the presence or absence of a mold at a position proximate the carousel.  
     
     
         7 . The system of  claim 4  wherein the kick mechanism includes a controller receiving a sound level signal from the sound detector and outputting a reject signal in response to the sound signal exceeding the predetermined set point.  
     
     
         8 . The system of  claim 7  wherein the controller outputs the reject signal after an interval to sequence the sound detector with the reject arm.  
     
     
         9 . The system of  claim 8  wherein the kick mechanism includes a valve that opens in response to receiving the reject signal.  
     
     
         10 . The system of  claim 9  wherein the valve is a pneumatic valve and the reject arm is air actuated.  
     
     
         11 . The system of  claim 1  further comprising a proximity switch that senses a position of any one of the molds of the carousel, the proximity sensor fixed relative to the carousel.  
     
     
         12 . The system of  claim 11  wherein the sound detector is activated in response to any one of the molds of the carousel being disposed at a first position relative to the proximity switch and is deactivated in response to said any one of the molds of the carousel being disposed at a second position relative to the proximity switch.  
     
     
         13 . The system of  claim 12  wherein the proximity switch is circumferentially aligned with the sound detector relative to the carousel.  
     
     
         14 . The system of  claim 12  wherein the carousel is rotatable and the sound detector includes a microphone that is disposed between 150 degrees and 210 degrees from the preform-loading point relative to the carousel.  
     
     
         15 . The system of  claim 14  wherein the microphone is disposed approximately 180 degrees from the preform-loading point relative to the carousel  
     
     
         16 . The system of  claim 1  further comprising a preform transfer wheel for transferring a preform to the carousel at the preform-loading point.  
     
     
         17 . The system of  claim 1  wherein the kick mechanism ejects the discontinuous container from the carousel between the preform-loading point and the container-unloading point.  
     
     
         18 . The system of  claim 1  wherein the pressurized blow air is applied substantially between the preform-loading point and the container-unloading point.  
     
     
         19 . The system of  claim 1  wherein the sound detector system includes a sound detector microphone housing having an inlet that is directed to the mold.  
     
     
         20 . The system of  claim 1  further comprising an acoustical enclosure substantially surrounding the carousel and the sound detector.  
     
     
         21 . The system of  claim 1  wherein mold includes vents through which blow air escapes while the mold houses the discontinuous container.  
     
     
         22 . A sound detection system for identifying a defective discontinuous container from a container production line, the sound detection system comprising: 
 a microphone for sensing a sound level proximate a container mold of the production line, the sound level varying according to whether pressurized blow air flows through a vent in the container mold; the microphone providing a sound level signal; and    a control system in communication with the microphone, the control system receiving the sound level signal and comparing the sound level signal to a predetermined sound level set point, the control system outputting a reject signal in response to said sound level signal exceeding the predetermined sound level set point, the sound level set point being less than a sound level signal corresponding to pressurized blow air flowing through the container mold vent.    
     
     
         23 . The sound detection system of  claim 22  further comprising a proximity switch for sensing the position of the mold relative to the microphone, wherein the sound level system is activated in response to the proximity switch indicating that the mold is within a predetermined sensing range of the microphone and deactivated in response to the proximity switch indicating that the mold is outside of the predetermined sensing range.  
     
     
         24 . The sound detection system of  claim 23  further comprising a controller that compares the sound level signal to the predetermined set point, the controller generating a reject signal in response to the sound level signal exceeding the predetermined set point, the controller delaying generating the reject signal according to a predetermined interval.  
     
     
         25 . The sound detection system of  claim 24  whereby a preform contiguously expands within the mold in response to a pressurized blow air to form the container, and a failure of a wall of the preform or the container during expansion forms the discontinuous container having a passage through which the blow air flows to form the blow air sound level signal exceeding the predetermined sound level set point.  
     
     
         26 . A method for rejecting a defective discontinuous container from a container production line comprising the steps of: 
 (a) sensing a sound level proximate a blow molding carousel comprising at least two molds, each one of the at least two molds including an interior surface corresponding to a shape of the container, each one of the molds receiving pressurized blow air into the mold;    (b) generating a sound level signal that corresponds to the sound level;    (c) comparing the sound level signal with a predetermined sound level set point;    (d) generating a reject signal in response to the sound signal exceeding the predetermined set point; and    (e) rejecting the discontinuous container from the production line in response to the reject signal;    whereby a preform contiguously expands within the mold interior surface in response to the pressurized blow air to form the container and a failure of a wall of the preform or the container during expansion forms the discontinuous container having a hole through which the blow air flows to form the blow air sound level exceeding the predetermined sound level set point.    
     
     
         27 . The method of  claim 26  further comprising a deactivating step and an activating step, the activating step including activating the method in response to the carousel being disposed in a first circumferential position; the deactivating step disabling at least one of the sensing step (a), the generating step (b), the comparing step (c), the generating step (d), and the rejecting step (e) in response to the carousel being disposed in a second circumferential position.  
     
     
         28 . The method of  claim 27  wherein the deactivating step includes deactivating at least one of the comparing step (d) and the generating step (d) in a controller.  
     
     
         29 . The method of  claim 26  wherein the generating step (d) includes delaying outputting the reject signal to sequence the rejecting step (e) with the sensing step (a).  
     
     
         30 . The method of  claim 29  wherein the sequencing step includes delaying the outputting of the reject signal approximately by a time interval approximately equal to the discontinuous container moving from a microphone that senses the sound level in step (a) to a reject arm that rejects the discontinuous container in the rejecting step (e).  
     
     
         31 . The method of  claim 29  wherein the sequencing step includes delaying the outputting of the reject signal by a preset number of pulses from a proximity switch approximately corresponding to the number of containers between a microphone that senses the sound level in step (a) and a reject arm that rejects the discontinuous container in the rejecting step (e).  
     
     
         32 . The method of  claim 26  wherein the sensing step (a) includes employing a microphone to sense the sound level and the generating step (b) includes generating the sound level signal with the microphone.  
     
     
         33 . The method of  claim 32  wherein the generating step (b) includes outputting the sound level signal to a control system, the comparing step (c) includes comparing the signal in the control system, and the generating step (d) includes generating the reject signal in the control system and outputting the reject signal from the control system to a kick mechanism.  
     
     
         34 . The method of  claim 33  wherein the rejecting step (e) includes receiving the signal in the kick mechanism and actuating a reject arm to reject the discontinuous container in response to the sound level exceeding the predetermined sound level set point.  
     
     
         35 . The method of  claim 26  wherein the predetermined sound level set point is less than a sound level of the pressurized blow air flowing outwardly through the mold.