METHOD FOR GRANULAR RESIN MATERIAL DELIVERY USING FILL TIME MONITORING AND ALARM FOR FILTER CHECK

Abstract

Apparatus for pneumatically supplying granular material from a supply to at least one receiver for temporary storage of the granular material prior to transfer to a process machine including a timer for measuring time required for loading the receiver and a microprocessor for comparing times measured by the timer and triggering an alarm when consecutively compared times increase by a preselected amount and a method and apparatus for determining when a filter of a granular material receiver providing granular material to an associated process machine, is at reduced filtering efficiency.

Claims

1. Apparatus for pneumatically supplying granular material from a supply to at least one receiver for temporary storage of the granular material prior to transfer to a process machine, comprising: a. a vacuum pump having a suction intake; b. a first conduit connecting the granular material supply to the receiver; c. a second conduit connecting the receiver to the vacuum pump suction intake; d. a timer for measuring time required for loading the receiver with granular material whenever process machine needs additional material and the receiver is loaded; e. a microprocessor for comparing times measured by the timer and triggering an alarm when consecutively compared times increase by a preselected amount.

2. Apparatus for determining when a filter, of a granular material receiver providing granular material to an associated process machine, is at reduced filtering efficiency comprising: a. a timer for measuring time required for loading the receiver with granular material whenever the associated process machine needs additional material and the receiver is loaded in response to that need; b. a microprocessor for comparing times measured by the timer and triggering an alarm when consecutively compared times increase by a preselected amount.

3. A method for determining when a filter, of a granular material receiver providing granular material to an associated process machine, is at reduced filtering efficiency, comprising: a. measuring time required for loading the receiver with granular material when the receiver is loaded in response to the associated process machine requiring granular material; and b. comparing the measured times and triggering an alarm upon a measured time increasing over a previously measured time by a predetermined amount.

4. The method of claim 3 wherein the measured times are consecutive times.

5. The method of claim 3 wherein measuring time further comprises: a. sensing when granular material in a receiver drops to a predetermined level; b. issuing a granular material refill signal upon granular material in a receiver dropping to the predetermined low level; c. initiating a timer in response to the granular material refill signal; d. sensing when granular material level in the receiver reaches a predetermined high level and providing a signal indicative thereof; e. stopping the timer in response to the sensor signaling that the granular material has reached the predetermined high level.

6. The method of claim 5 wherein sensing when granular material in a receiver drops to a predetermined level is performed optically.

7. The method of claim 5 wherein sensing when granular material level in a receiver drops to a predetermined level is performed mechanically.

8. The method of claim 5 wherein sensing when granular material in a receiver drops to a predetermined level is performed electrically.

9. The method of claim 5 wherein sensing when granular material in a receiver reaches a predetermined high level is performed optically.

10. The method of claim 5 wherein sensing when granular material in a receiver reaches a predetermined high level is performed mechanically

11. The method of claim 5 wherein sensing when granular material in a receiver reaches a predetermined high level is performed electrically.

12. Apparatus of claim 1 further comprising a sensor for signaling when granular material in the receiver has reached a predetermined high level.

13. Apparatus of claim 1 further comprising a sensor for signaling when granular material in the receiver has reached a predetermined low level.

14. Apparatus of claim 12 wherein the sensor is optically actuated.

15. Apparatus of claim 12 wherein the sensor is mechanically actuated.

16. Apparatus of claim 12 wherein the sensor is electrically actuated.

17. Apparatus of claim 13 wherein the sensor is optically actuated.

18. Apparatus of claim 13 wherein the sensor is mechanically actuated.

19. Apparatus of claim 13 wherein the sensor is electrically actuated.

Description

DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1 is a schematic representation of a resin delivery system manifesting aspects of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0048] In this application, unless otherwise apparent from the context it is to be understood that the use of the term vacuum means air at slightly below atmospheric pressure. The vacuum (meaning air at slightly below atmospheric pressure) provides a suction effect that is used to draw granular plastic resin material out of a supply and to convey that granular plastic resin material through various conduits to receivers where the granular resin material can be temporarily stored before being molded or extruded. Hence, it is useful for the reader mentally to equate the term vacuum with the term suction.

[0049] Referring to FIG. 1, apparatus for conveying granular plastic resin material from the supply to receivers that retain and then dispense the resin material when needed by a process machine is illustrated. The apparatus, which is designated generally 88 in FIG. 1, preferably includes a vacuum pump designated generally 92 and shown schematically in FIG. 1.

[0050] Still referring to FIG. 1, vacuum drawing conduit 100 is connected to a plurality of receivers 16, each of which receives, retains and dispenses, as needed, granular plastic resin material to a process machine, such as a gravimetric blender, or an extruder, or a molding press, as located preferably below a receiver 16. The process machines are not illustrated to enhance the clarity of the drawings.

[0051] Further illustrated in FIG. 1 is a hopper 18 for storage of granular plastic resin material therein and a resin conveying conduit 98, which serves to draw resin from hopper 18 and to deliver the resin through resin conveying conduit 98 to the respective receivers 16. This occurs in response to vacuum being drawn by the vacuum pump, with vacuum propagating through vacuum drawing conduit 100, the various receivers 16, and resin conveying conduit 98, to hopper 18. During operation of the resin conveying system shown schematically in FIG. 1, upon actuation of vacuum pump 92, vacuum is drawn at vacuum pump suction head 93. This vacuum, as it propagates to hopper 18, draws resin out of hopper 18 and into respective receivers 16.

[0052] Receivers are equipped with filters. The resin material delivered to a processing plant contains dust. As the resin pellets are pulled out of resin storage hopper 18, the resin pellets necessarily contact one another, thereby causing small chips of resin material to drop off the main resin pellets, creating additional dust. Moreover, as the resin is conveyed, tiny particles of resin drop off the larger resin pellets as the resin pellets glance against the wall of the conveying conduit, creating still more dust.

[0053] The dust cannot be permitted to enter a process machine, namely a molding press or an extruder, with the resin pellets. In the case of a clear plastic molded product, the dust would cause cloudiness in the product when clarity of the finished molded product is required. In all cases, for both clear and colored products, dust would interfere with the manufacturing process.

[0054] Dust is typically removed from the resin as the resin is conveyed from the resin supply to the process machine, by a filter positioned in the receiver. Each receiver conventionally has a filter. As resin material passes through the receiver, the filter gradually accumulates dust from the resin passing through the receiver. As dust accumulates in the filter, filter efficiency drops and, if the filter is not cleaned or changed, the filter eventually clogs with dust and no longer functions. If the filter no longer functions, dust may travel with the resin pellets and may enter the process machine, resulting in manufacture of defective, unacceptable parts. Alternatively, the dust may accumulate in the filter in such a way as to completely block the filter and thereby block or stop resin material from passing through the receiver and on to the process machine. In either case, it is important for the plant operator to know that the filters in the receivers are functioning properly and are not on the verge of being clogged with dust and hence ceasing to function.

[0055] As a receiver filter fills with dust, air flow through the receiver is necessarily impeded, thereby resulting in a slowdown of the resin filling process at the receiver. So, a slower receiver fill time indicates that the receiver filter is becoming filled with dust.

[0056] This invention addresses the problem of clogged receiver filters and maintaining receiver filters in a sufficiently open condition that conveyance of the granular resin material from the resin supply to the process machine may continue without substantial interruption. The invention monitors fill time for each receiver and compares fill time for that receiver to a known acceptable fill time for that receiver or a comparable receiver having an open, unclogged filter. As the fill time for the receiver drops to below a level corresponding to an acceptable fill time for that receiver or a comparable receiver having an acceptably open, unobstructed filter, the invention sounds an alarm, which may be audible or electronic, indicating that the filter in the receiver must be changed. Upon receiving the alarm, an operator may either manually change the filter or, in the case of self-cleaning receivers, the operator or a microprocessor may actuate a switch to energize the receiver filter cleaning function. Desirably, the fill times for each receiver as monitored are transmitted wirelessly to a central controller, where those fill times are compared to a known acceptable fill time for a receiver with an acceptably open filter. Alternatively, wires can be used to transmit the sensed fill time from a given receiver to a central microprocessor or other control device. If the fill time is excessively long, an operator or a microprocessor may shut down the receiver or even the entire system.

[0057] Referring to the drawings again, a receiver 16A is equipped with a high resin level sensor 150 for sensing when resin level within receiver 16A reaches a predetermined acceptable high level. Receiver 16A further includes a low resin level sensor 152 for determining when resin within receiver 16A reaches an unacceptably low level such that receiver 16A must be replenished with resin. As further illustrated schematically in FIG. 1, a timer 154 is connected to high level sensor 150 and to low level sensor 152 by unnumbered wires. A microprocessor 156 is connected by an unnumbered wire to timer 154. While wire connections have been illustrated in FIG. 1, wireless connectivity is preferable as between and among high and low level sensors 150, 152, and timer 154, and microprocessor 156.

[0058] High level sensor 150 may be optical in nature, or may be mechanical in nature, or may be electrical in nature. An optical sensor 150 employs a light beam or infrared beam passing across all or a portion of receiver 16A to detect when resin level in receiver 16A has reached an acceptably high level and receiver 16A is acceptably full of resin. Similarly, an optical sensor if used as low resin level sensor 152 employs a light beam or an infrared beam passing through a lower portion of receiver 16A to detect when resin within receiver 16A has reached an unacceptably low level and replenishment of receiver 16A is required.

[0059] Timer 154 receives signals from high level sensor 150 and low level sensor 152, regardless of the means by which those sensors detect resin level, and measures and records the time required for the resin level to rise from the predetermined low level to the predetermined high level. A microprocessor 156 processes the time interval, compares it to previous time intervals, and provides an alarm signal in the event the currently measured time level is inconsistent with previously measured time intervals required for fill of receiver 16A.

[0060] It is further within the scope of the invention to have timer 154 actuated by a signal coming from a central control system that regulates fill and refill of all receivers 16. This type of connection has not been illustrated in FIG. 1. Similarly, a signal coming from a central control station triggering shutoff of resin flow into a receiver 16 may be used as the trigger for the high resin level indication provided to timer 154.

[0061] Sensors 150, 152 may also be mechanical in nature, having reed switches or other switches that are physically moved by the resin in the receiver 16A and are spring loaded to return to a null position when those switches are not actuated. Sensors 150, 152 may also be electrical sensors which sense the electrical conductivity of any resin in the vicinity of the sensor and thereby provide a signal as to whether there is resin at the predetermined high or low level, according to the sensor of interest.

[0062] This invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. The disclosed embodiments are therefore to be considered in all respects as being illustrative and not restrictive with the scope of the invention being indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0063] As discussed above and from the foregoing description of the exemplary embodiments of the invention, it will be readily apparent to those skilled in the art to which the invention pertains that the principles and particularly the composition and methods disclosed herein can be used for applications other than those specifically mentioned. All such applications of the invention are intended to be covered by the appended claims unless expressly excluded therefrom.

[0064] As used in the claims below, comprising means including while consisting of means having only, and consisting essentially of means having the stated constituents plus trivial amounts of other reagents which do not materially affect the claimed invention or products embodying the same.

[0065] The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description and all changes which come within the range of equivalency of the claims are to be considered to be embraced within the scope of the claims. Additional objects, other advantages, and further novel features of the invention will become apparent from study of the appended claims as well as from study of the foregoing detailed discussion and description of the preferred embodiments of the invention, as that study proceeds.