US 2853155 A
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Description (OCR text may contain errors)
Sept. 23, .1958 I w. B. PE TE 2,853,155
FILTER APPARATUS CONTROL Filed April 1, 1955 INVENTOR.
W/LL/AM 8.1 5751? ATTORNEY United States Patent Qfiiice 2,853,155 Patented Sept. 23, 1958 FILTER APPARATUS CONTROL William B. Peter, Louisville, Ky., assignor to American Air Filter Company, Inc., Louisville, Ky., a corporation of Delaware Application April 1, 1955, Serial No. 498,711 1 Claim. (Cl. 183-62) Number 447,847 filed on August 4, 1954 and now U. S. Patent 2,807,330 for Method and Apparatus for Filtering Air, there is described and claimed a filter providing a compressed web rolled upon a spool, the web being unwound from the feed spool across an air stream and simultaneously expanded in condition to act as a filter; and the spent web is rewound in compressed condition upon a receiving spool. In a filter apparatus of this type at a given installation, the rate of feed of the web is correlated to the filter area, the feed being intermittent. The actuation of the web feed mechanism may be controlled by a differential pressure switch which actuates the feed mechanism when the pressure drop across the filter web reaches or exceeds a certain value, and which de-energizes the feed mechanism when the pressure drop falls below that value.
In some installations it is desirable to actuate the web feed means by a timer. The period of operation of the web feed mechanism is quite slow, on the order of about 6 /2 to 29 lineal inches per week of 70 hours, equivalent to about .09 in. per hour to .4 in. per hour. A timer for this purpose therefore must be exceedingly accurate, and must be adjustable through a wide time range. Such timers are commercially available but are relatively expensive.
It is an object of the present invention to provide an inexpensive automatic renewable type filter operated at timed intervals.
A further object is the provision of an inexpensive control mechanism for an automatic renewable filter in which the filter medium is advanced periodically in small increments.
Another object is the provision of a feed control mechanism tor a filter which is inexpensive and reliable in action.
The present invention employs a pair of continuous repeating cycle timers connected in series, so that the first timer operates the second timer at intervals, and the second timer accumulates operating time and actuates the feed mechanism intermittently. Repeating cycle timers of this type are commercially available and are relatively inexpensive. They operate in a continuously repeating cycle of opening and closing an electrical switch or contact. In such a timer the percentage of the time of a cycle during which the switch is closed is adjustable. However, in the arrangement of the present invention, it is preferred that the second timer which actuates the feed mechanism, is maintained at a fixed adjustment, and adjustment of the first timer is employed to vary the operating time of the second timer and of the feed mechanism. This structure has the advantage that the timer and feed time are easily adjustable and the apparatus employed is inexpensive.
The invention will be described in greater detail in the following specification taken in connection with the accompanying drawings illustrating a preferred embodiment by way of example,.'and wherein:
Figure 1 is a partly diagrammatic side elevation of a filter embodying the invention; and
Figure 2 is a wiring diagram to explain the operation of the invention.
Referring to the drawing, Figure 1, the type of filter,'
shown by way of example, comprises a frame 1 having an opening therethrough over which moves a filter web 3.
The web 3 may be of any suitable type, such as, for ex-' ample,.matted or interwoven glass fiber, and at the top, is
unwound from a supply roll 4, on which it has been wound in compressed condition. The web 3 is supported by a suitable perforate web or conveyor as it moves vertically across the opening, the arrangementallowing the web to fluff up on the conveyor, and at the bottom the web is rewound in tightly compressed condition on a rewind spool 5, which is driven, through suitable power transmission mechanism, by a motor 6. This structure is the subject matter of said Rivers patent, and as it forms no par-t of the present invention, it need not be described here in further detail.
In such filters, the operative area of the filter medium is a function of the height and width of the filter opening, and assuming a constant width, the area will vary as the height. The rate of feed of the web of such a filter is quite small, and may vary from about 6 /2 inches per week of seventy hours, to about 29 inches per week, for an equal width, depending on the height of the filter opening employed. The motor 6, which operates the rewind spool and thus determines the rate of feed, is operated at only short intervals.
Referring to Figure 2, the filter medium 3 is diagrammatically shown as driven by motor 6, and a fan or blower 7, driven by motor 8, maintains a stream of air to be filtered passing through the filter. This motor receives its power from electrical leads 9 and 10. Connected switches 11, 12 are provided, the switch 11 being closed so as to excite a lamp 13 which serves to indicate when the filter apparatus is not operating. A pressure sensitive vane 14 is so arranged that it is responsive to the stream of air, and when the blower is operating the vane 14 acts to shift switch 12 to closed position and open switch 11 to deenergize light 13. The first cycle control timer 15 has a synchronous motor 16 which drives a cam 17 that closes switch 18 for a predetermined period of a cycle, that can be varied. Thus, for example, the timer 15 may be set to hold switch 18 closed for seven seconds out of each twelve minutes.
When switch 18 is closed, the motor 19 of the second timer 20 is energized, and this motor in a similar way will keep switch 21 closed for a predetermined period out ofeach twelve minutes of operation. Motor 6 is operated when relay coil 22 is energized to close switch 23. This relay coil can be energized by a manually operated switch 24 which is provided for use in changing rolls. However, in operation, relay coil 22 is energized by closing of. timer switch 21. As each timer motor 16 and 19 has a cycle time of twelve minutes, and assuming timers 15 and 20 are each to close switches 18 and 21 for seven seconds on each cycle, it will require 713 seconds of operation of timer motor 16 before timer motor 19 is in position to close switch 21 for the first time. That is, when switch 18 completes closing and opening for the l02nd time it will have operated timer motor 19 fora total of 714 seconds. As 713 seconds of operation of motor 19 are necessary before switch 21 is closed, it will be seen switch 21 will be closed for one second, and therefore motor 6 is operated for one second. The next time switch 18 closes, which will be in 713 seconds, motor 19 will again be operated for 7 seconds, and during six of these seconds switch 21 will be closed to operate motor 6. Thus, at the end of about twenty and three fifths hours intervals, motor 6 is operated for seven seconds, and on the average, for each seventy hours of operation of the air filter, the filter web is advanced 6 /2 inches. The rate of advance of the filter web can be adjusted by varying timer 15 to provide a longer or shorter closing time for its switch 18. Thus, for example, by varying the setter of timer 15 from 7 to 29 seconds, the feed can be varied from 6 /2 inches per 70 hour week to 29 inches per week. That is, each second setting of timer 15 corresponds to one inch per week web feed. This ratio, of course, can be varied as desired.
When the blower 7 is stopped, the vane 14 opens switch 12 to stop the timer operation. The timers therefore accumulate time only while the filter is in operation.
I claim as my invention:
A filter medium feed control comprising normally inoperative motorized filter medium feeding means, first repeating cycle timing means operative in responseto air flow through said filter medium, first switching means controlled by said first repeating cycle timing means and arranged to be selectively actuated thereby during a predetermined portion of each of said repeating time cycles thereof, second repeating cycle timing means operative in response to and in accordance with the periods of actuation of said first switching means, second switching means controlled by said second repeating cycle timing means and arranged to be selectively actuated thereby during a predetermined portion of each of said repeating time cycles thereof and means responsive to the periods of actuation of said second switching means for rendering said motorized filter medium feeding means operative to advance filter medium during said periods of actuation.
' References Cited in the file of this patent UNITED STATES PATENTS 1,638,067 Szekely Aug. 9, 1927 2,152,900 Manning Apr. 4, 1939 2,626,012 Persons Jan. 20, 1953 2,687,173 Loft Aug. 24, 1954 2,722,998 Hall Nov. 8, 1955 i