RESTRICTION INDICATOR FOR AIR CLEANERS

Abstract: A restriction indicator (10) for an air cleaner of an internal combustion engine. A bellows-type diaphragm (40) is biased toward a retracted position by a first end of a compression spring (45). A calibration wheel (50) threadingly engaging the housing (12) supports a second end of the compression spring, such that the restriction indicator can be calibrated by rotation of the calibration wheel. An end of the compression spring is seated on a slanted seating surface (72) so that a plunger (63) is pushed off-center to engage a latch (62) and lock the restriction indicator.

Description: RESTRICTION INDICATOR FOR AIR CLEANERS Field of the Invention This invention relates generally to restriction indicators for air cleaner systems, and more particularly to a restriction indicator having a calibration mechanism and a novel spring seating arrangement. Background ofthe Invention Restriction indicators provide a signal indicating when it is necessary to service the air cleaner of an intemal combustion engine. They typically are connected to the air outlet of the air cleaner upstream of the intake of the engine. Most mechanical restriction indicators employ a bellows-type diaphragm vented to the atmosphere, which is resisted from expanding by a compression spring. As the air cleaner becomes more contaminated, the differential pressure between the "atmospheric"/high pressure side and the "negative'Vlow pressure side ofthe restriction indicator increases, tiiereby causing the diaphragm to expand. When the differential pressure has reached a certain level, the diaphragm typically becomes locked in an expanded position, and a constant warning signal is provided to the user that the air cleaner should be serviced. An example of such prior art restriction indicators is shown in U.S. Patent No. 3,443,365. A significant concem with restriction indicators is the accuracy with which they indicate that a particular differential pressure has been reached. Restriction indicators are designed to provide a warning indication at a specific design pressure differential. It is important that they are accurate because improper indication would result in the air cleaner being serviced earlier or later than intended. It is difficult, however, to consistently manufacture accurate restriction indicators due to the variability ofthe component parts which make up the assembly. Component parts such as the spring, diaphragm, housing and locking mechanism, even when manufactured to close tolerances, can affect the accuracy ofthe indicator. Current designs, however, do not provide a mechanism for calibrating and adjusting the restriction indicator to account for these manufacturing variations. Another problem associated with restriction indicators is providing a locking mechanism which will consistently lock and release after repeated use. In many designs, the locking mechanism includes a resettable plunger which engages a latch to lock the diaphragm in an expanded warning position. An example of this is shown by the '365 patent, in which the plunger is bent to engage the latch off-center. What has been needed is a restriction indicator for air cleaner systems with a simple mechanism for permitting calibration to adjust for manufacturing inconsistencies. What has also been needed is a simple mechanism for locking a plunger in a restriction indicator. Summary of the Invention According to the present invention, a restriction indicator for an air cleaner system is provided. In one aspect ofthe invention, the restriction indicator comprises a housing having high and low pressure chambers. The high pressure chamber is in communication with an inlet and the low pressure chamber is in communication with an outlet ofthe housing. A bellows-like diaphragm in the housing generally defines the high pressure chamber, and is moveable between expanded and retracted positions. A compression spring in the low pressure chamber has a first end biasing the diaphragm toward the retracted position. A mechanism cooperates with the diaphragm and compression spring to indicate when the diaphragm is in the expanded position. A calibration wheel supports a second end ofthe compression spring and has a portion which threadingly engages the housing. The threaded portion ofthe calibration wheel is rotatable so that a biasing force ofthe spring against the diaphragm can be varied, thereby permitting calibration of d e movement ofthe diaphragm to its expanded position at a predetermined differential between the high and low pressure chambers. In another aspect of die invention, an adjustable restriction indicator comprises a housing having high and low pressure chambers. The high pressure chamber is in communication with an inlet and the low pressure chamber is in communication with an outlet ofthe housing. A bellows-like diaphragm in the housing separates the chambers, and is moveable between expanded and retracted positions in response to pressure differences between the chambers. A compression spring in the low pressure chamber has a first end biasing the diaphragm toward d e retracted position. A platform supports a second end ofthe compression spring and has a portion which d readingly engages die housing. The threaded portion ofthe platform is rotatable so tiiat a biasing force ofthe spring against the diaphragm can be varied. In yet another aspect ofthe invention, the invention comprises an improvement in restriction indicators ofthe type where an expandable bellows-like diaphragm is biased by a compression spring toward a retracted position, and a resettable plunger engages a latch to lock the diaphragm in an expanded warning position. A member of the restriction indicator includes a slanted seating surface on which an end ofthe compression spring is seated. When the diaphragm expands to the expanded warning position, the spring pushes die plunger off-center to engage die latch. These and other advantages and features of novelty that characterize d e invention are pointed out with particularity in die claims annexed hereto. However, for a better understanding of d e invention and its advantages, reference should be made to the drawings which form a further part hereof, and to d e accompanying descriptive matter in which there is illustrated and described a preferred embodiment of tiie invention. Brief Description ofthe Figures Figure 1 is a cross-sectional view of a restriction indicator according to the present invention, with the indicator in a non-warning position; Figure 2 is a cross-sectional view ofthe restriction indicator shown in Figure 1 , with the indicator in a warning position; and Figure 3 is a cross-sectional view ofthe restriction indicator shown in Figure 2, as viewed generally from section 3-3. Detailed Description ofthe Preferred Embodiment Referring now to the drawings wherein like numerals designate like parts, a restriction indicator according to d e present invention is shown in Figures 1-3. The restriction indicator ofthe present invention can be used in conjunction with a variety of air cleaner systems for intemal combustion engines. In the preferred arrangement, restriction indicator 10 is connected to a tubular member at the outlet ofthe air cleaner upstream ofthe intake ofthe engine, not shown. Restriction indicator 10 is inserted into an aperture ofthe tubular member, with a rubber grommet (not shown) positioned around barb 16 to provide a press fit seal in the area between annular rings 18. Referring to Figure 1, restriction indicator 10 comprises housing 12 including casing 14 and cap 20 enclosing the open end of casing 14. Cap 20 is releasably connected to casing 14 by means of ramped ridge 15 which is snap fit into channel 21 of cap 20. Defined within housing 12 are high 30 and low 32 pressure chambers. High pressure chamber 30 is in communication witii the atmosphere via an inlet 31 defined by three apertures 22 in cap 20 spaced at 120E intervals. Low pressure chamber 32 is in communication with an outlet 33 formed in barb 16 which in turn is in communication with the negative pressure side of the air cleaner, not shown. Expandable diaphragm 40 generally defines high pressure chamber 30, which enlarges as diaphragm 40 expands. It is said herein that diaphragm 40 "generally" defines high pressure chamber 30 because chamber 30 also includes portions of die housing between the open end of diaphragm 40 and inlet 31. It will be understood that this area could be larger or smaller depending on the design. Diaphragm 40 is a flexible, expandable bellows-type diaphragm. It will be understood that a variety of diaphragms with similar characteristics could be employed widiin the principles ofthe invention. Diaphragm 40 includes lip 41 which is compressed between retainer 60 and a shoulder of casing 14, with cap 20 pushing downwardly on retainer 60. Interposed between cap 20 and retainer 60 is an annular filter 25 in recess 24 of cap 20. Filter 25 is made of DACRON polyester fiber or the like and prevents contaminants from entering high pressure chamber 30. Compression spring 45 biases diaphragm 40 toward a retracted position, as for example the position shown in Figure 1. Figure 2 shows diaphragm 40 in an expanded and locked position, with spring 45 being compressed by diaphragm 40. Spring 45 is seated as its upper end 46 with seating surface 72 of signal and at its lower end 48 with seating surface 53 of calibration wheel 50. Diaphragm 40 is connected to signal 70 by means of plunger 63 which is snap fit into a corresponding opening 74 in signal 70. Base 42 of diaphragm 40 is held and sealed between plate 64 of plunger 63 and signal 70. A raised portion 43 of base 42 assures proper sealing. Signal 70 moves downwardly and upwardly with the expansion and retraction of diaphragm 40. Outer screen 76 of signal 70 is visible dirough casing 14, which is transparent, in the portion forming a window 13 between the lower end of cap 20 and opaque covering 11 on casing 14. Altematively, opaque covering 11 could be removed. Screen 76 is color coded and includes the words "CHANGE AIR FILTER," becoming visible through window 13 when diaphragm 40 is in its expanded position, as shown in Figure 2. Signal 70 also includes tab 71 used to align witii apertures 61 in retainer 60 for consistent assembly. Restriction indicator 10 includes a locking assembly 69 which is largely known in prior designs. Although a locking mechanism is not absolutely necessary, it is preferable to provide a constant indication that the design pressure differential has been reached, so that a warning is provided when the engine is not operating. Locking mechanism 69 includes plunger 63 connected to move with signal 70 and with base 42 of diaphragm 40, and three circumferentially spaced latches 62 extending downwardly from retainer 60, best shown in Figure 3. Referring to Figure 2, when diaphragm 40 has expanded to its expanded position, plunger 63 is pushed off-center so that flange 65 of plunger 63 engages with latch 62, thereby locking diaphragm 40 and signal 70 in a warning position. Resetting the restriction indicator 10 is accomplished by manually depressing release button 67. Release button 67 has three fingers 68 which extend downwardly into three corresponding slots 66 between flanges 65, as shown in Figure 3. Fingers 68 and slots 66 are constructed to guide fingers 68 inwardly to recenter plunger 63 as release button 67 is depressed, thereby releasing plunger 63 from latch 62 and returning diaphragm 40 to its retracted position under the force of spring 45. It will be appreciated that d e locking and resetting mechanisms could be constructed in a number of other ways. A novel aspect of locking mechanism 69 is die slanted spring seating surface 72 on signal 70. Slanted seating surface 72 causes plunger 63 to be pushed off-center to securely engage latch 62. While slanted seating surface 72 is on signal 70 at upper end 46 of spring 45, it will be understood that the slanted surface could be on some other member ofthe device, and lower end 48 of spring 45 or both ends 46, 48 could be seated on a slanted surface. In the preferred arrangement, a single slanted seating surface 72 having an angle of approximately 15 degrees is employed. Slant angles of between 5E and 20E could also be beneficially employed. Spring 45 is of an appropriate strength and, when not deformed by slanted seating surface 72, is flat (not slanted) at both ends 46, 48. To ensure proper and consistent seating of spring 45 at upper end 46, a bent axial projection 47 of spring 45 is inserted into aperture 73 of seating surface 72. Calibration wheel 50 is provided to permit calibration of restriction indicator 10 by adjusting the biasing force of spring 45 against diaphragm 40. Calibration wheel 50, which defines a platform, includes plate 52 supporting spring 45, and shaft 54 extending downwardly into barb 16 of housing 12. Shaft 54 has external threads 55 which engage a corresponding intemal thread 17 of barb 16. It will be appreciated that calibration wheel could be configured in a number of other ways within the principles ofthe invention, as for example with a plate having extemal threads engaging an inner wall of the housing. Also, while the preferred calibration wheel 50 is molded as a single part, it could comprise two or more parts, as for example a stationery plate rotatably connected to a threaded shaft. Communication between low pressure chamber 32 and outlet 33 is provided by central passage 59 of calibration wheel 50, which includes orifice 56 and first 57 and second 58 portions. Orifice 56 is sized and configured to reduce the transmission of pressure pulses from the engine intake to low pressure chamber 32, which can cause premature restriction indication. Second portion 58 of passage 59 is shaped hexagonally in cross section to receive an Allen wrench (not shown) for threadingly rotating calibration wheel 50. Shaft 54 of calibration wheel 50 is provided with two flexible ears extending radially outwardly. When calibration wheel 50 is rotated, ears 51 "ratchet" against the inner wall of barb 16, also hexagonally shaped, and lock into position in two of six spaced slots 66 in barb 16. This prevents unintended rotation of calibration wheel 50, which could affect the calibration. Individual restriction indicators are calibrated as follows. A weight corresponding to the design pressure differential (in this case approximately 20 inches of water) is placed on the top of plunger 63. The calibration wheel 50 is then rotated counterclockwise with an Allen wrench until die plunger is lowered to a set point. The restriction indicator, now calibrated for improved accuracy, is ready to go into service. It should be understood that the present invention is not limited to the preferred embodiment discussed above, which is illustrative only. Changes may be made in detail, especially in matters of shape, size, arrangement of parts, or material of components within the principles ofthe invention, to the full extent indicated by the broad general meanings ofthe terms in which the appended claims are expressed.

Claims: WHAT IS CLAIMED IS: 1. A restriction indicator for an air cleaner system, comprising: (a) a housing having high and low pressure chambers, with said high pressure chamber in communication widi an inlet and said low pressure chamber in communication with an outlet of said housing; (b) a bellows-like diaphragm in said housing, generally defining said high pressure chamber and movable between expanded and retracted positions; (c) a compression spring in said low pressure chamber, having a first end biasing said diaphragm toward said retracted position; (d) means, in cooperation with said diaphragm and compression spring, for indicating when said diaphragm is in said expanded position; (e) a calibration wheel supporting a second end of said compression spring and having a portion threadingly engaging said housing; and (f) means for threadingly rotating said threaded portion of said calibration wheel relative to said housing, whereby a biasing force of said spring against said diaphragm can be varied so as to calibrate the movement of said diaphragm to said expanded position at a predetermined pressure differential between said high and low pressure chambers. 2. A restriction indicator according to claim 1 , wherein said calibration wheel includes an orifice in communication widi said outlet of said housing, said orifice being sized and configured to reduce the transmission of pressure pulses from said outlet to said low pressure chamber. 3. A restriction indicator according to claim 1 , wherein said calibration wheel includes a spring supporting plate and a shaft extending therefrom into said outlet of said housing, said shaft having extemal threads engaging at least one corresponding intemal thread of said outlet and having a central passage providing communication between said low pressure chamber and said outlet. 4. A restriction indicator according to claim 3, wherein said calibration wheel rotating means comprise a portion of said shaft of said calibration wheel shaped to receive a tool, whereby rotation of said tool threads said shaft of said calibration wheel relative to said outlet of said housing. 5. A restriction indicator according to claim 3, wherein said shaft of said calibration wheel includes a plurality of flexible ears extending radially outwardly from said shaft, and said housing includes a plurality of corresponding slots in an inner side of said outlet, such that said ears can be ratcheted relative to said outlet and locked into position in said slots to prevent unintended rotation of said calibration wheel. 6. A restriction indicator according to claim 1 , wherein said indicating means includes a signal element connected to move with said diaphragm and said first end of said spring, such that said signal element is visible through a window of said housing when said diaphragm expands to said expanded position. 7. A restriction indicator according to claim 1 , further including means for automatically locking said diaphragm in said expanded position so as to provide a constant indication tiiat the predetermined pressure differential has been reached, and means for manually resetting said locking means. 8. An adjustable restriction indicator for an air cleaner system, comprising: (a) a housing having high and low pressure chambers, with said high pressure chamber in communication with an inlet and said low pressure chamber in communication witii an outlet of said housing; (b) a bellows-like diaphragm in said housing separating said chambers and movable between expanded and retracted positions in response to pressure differences between said chambers; (c) a compression spring in said low pressure chamber, having a first end biasing said diaphragm toward said retracted position; and (d) a platform supporting a second end of said compression spring, having a portion threadingly engaging said housing, constructed and arranged so that a biasing force of said spring against said diaphragm can be varied by rotation of said threaded portion of said platform. 9. A restriction indicator according to claim 8, wherein said platform includes an orifice in communication with said outlet of said housing, said orifice being sized and configured to reduce the transmission of pressure pulses from said outlet to said low pressure chamber. 10. A restriction indicator according to claim 8, wherein said platform includes a spring supporting plate and a shaft extending therefrom into said outlet of said housing, said shaft having extemal threads engaging at least one corresponding intemal thread of said outlet and having a central passage providing communication between said low pressure chamber and said outlet. 11. A restriction indicator according to claim 10, wherein a portion of said shaft of said platform is shaped to receive a tool, whereby rotation of said tool threads said shaft relative to said outlet of said housing. 12. A restriction indicator according to claim 10, wherein said shaft of said platform includes a plurality of flexible ears extending radially outwardly from said shaft, and said housing includes a plurality of corresponding slots in an inner side of said outlet, such that said ears can be ratcheted relative to said outlet and locked into position in said slots to prevent unintended rotation of said platform. 13. A restriction indicator according to claim 8, further including signal element connected to move with said diaphragm and said first end of said spring, such tiiat said signal element is visible through a window of said housing when said diaphragm expands to said expanded position. 14. A restriction indicator according to claim 8, further including means for automatically locking said diaphragm in said expanded position so as to provide a constant indication that the predetermined pressure differential has been reached, and means for manually resetting said locking means. 15. A restriction indicator for an air cleaner system, in which an expandable bellows-like diaphragm is biased by a compression spring toward a retracted position, and a resettable plunger engages a latch to lock the diaphragm in an expanded warning position, wherein the improvement comprises: a member having a slanted seating surface on which an end ofthe compression spring is seated, such that the spring pushes the plunger off-center to engage the latch when the diaphragm expands to the expanded position. 16. A restriction indicator according to claim 15, wherein said member comprises a signal element to which the diaphragm and plunger are connected opposite the spring. 17. A restriction indicator according to claim 15, wherein said slanted seating surface includes an aperture for receiving an axial projection from said end ofthe compression spring, thereby assuring proper seating of said end ofthe spring. 18. A restriction indicator according to claim 15, wherein said slanted seating surface is slanted about between 5 and 20 degrees relative to an unslanted position.

Inventors: NEPSUND LARRY R, NEPSUND, LARRY, R.
Applicants: DONALDSON CO INC, DONALDSON, COMPANY, INC.
Application year: 1996
Main classification: F02M35
IPC codes: B01D35, B01D46, F02M35