Air Filter Condition Indicator Patents (Class 116/DIG25)
  • Patent number: 6074463
    Abstract: A fan filter unit has a blower, a motor, a filter and a charge induction sensor installed on the ceiling of a clean room. The charge induction sensor is movable between a drive stopped position at which the sensor can be seen with the naked eye and a normal drive position at which the sensor can not be discriminated from the bottom of the filter. The direction of air passing through the filter and static charges prevailing in the unit dictate the position assumed by the sensor.
    Type: Grant
    Filed: January 6, 1998
    Date of Patent: June 13, 2000
    Assignee: Samsung Electronics Co., Ltd.
    Inventors: Joung-sun Lee, Ki-whan Lim
  • Patent number: 5917141
    Abstract: An air filter monitoring device that includes an attachment mechanism for attaching the monitoring device to the cover grate of an air return of an air conditioning system and a first and a second air flow actuated switch wired electrically in series with an alerting device, such as a light emitting diode and/or an audible alarm, each having an air resistance plate positioned within an air flow chamber. The air flow chamber is formed within a housing having an adjustable air intake inlet in connection with the air flow chamber. Air flowing through the air flow chamber within a range between a first and a second predetermined value causes the first and second air flow actuated switches to activate the alerting device.
    Type: Grant
    Filed: January 12, 1998
    Date of Patent: June 29, 1999
    Inventor: Clyde J. Naquin, Jr.
  • Patent number: 5727498
    Abstract: A retractable indicator assembly 10 may be mounted on a container C which transmits air through the container and removes deleterious gases with an activated charcoal medium M in the container. An elongate indicator housing 12 has a chamber 20 therein. A male adaptor 14 has external threads 16 for sealing engagement with the container. A plug 40 is provided at the upper end of the housing 12. Housing 12 includes a transparent wall portion 28 for viewing at least a portion of the chamber 20. A litmus indicator 42 is moveable by a retractable rod 54 from a retracted position within the container to an extended position within the chamber 20 of the housing 12. An outer housing 64 is secured to the upper end of the rod 54, and protects the indicator housing 12 while the litmus indicator 42 is in its normally retracted position.
    Type: Grant
    Filed: February 13, 1996
    Date of Patent: March 17, 1998
    Assignee: The United States of America as represented by the Administrator of the National Aeronautics and Space Administration
    Inventors: George R. Hackler, Ronald J. Gamboa, Victor Dominquez
  • Patent number: 5616157
    Abstract: A filter indicator system for indicating when air flow through a filter is restricted includes an indicator mounted in a filter assembly downstream of the filter. The indicator includes a housing having a central space, a side wall, an end wall, an end inlet in the end wall, and a side outlet. A pop-up member is located in the central space and includes a signal portion which extends adjacent the end inlet. A moving device is then used for moving the pop-up member between a non-signalling position where the signal member does not extend noticeably through the end inlet and a signalling position where the signal portion extends noticeably through the end inlet.
    Type: Grant
    Filed: November 14, 1995
    Date of Patent: April 1, 1997
    Assignee: Florida Pneumatic Manufacturing Co.
    Inventors: Donald R. Mead, Deborah V. Beebe
  • Patent number: 5604306
    Abstract: An apparatus and method for detecting a plugged condition of an air filter uses a computer based model of the air restriction.
    Type: Grant
    Filed: July 28, 1995
    Date of Patent: February 18, 1997
    Assignee: Caterpillar Inc.
    Inventor: David R. Schricker
  • Patent number: 5352255
    Abstract: A noise maker having a housing with a hole formed on at least one surface of the housing and a weighted member in resilient relationship over the hole. The weighted member is movable between a first position closing the hole to a second position for allowing a desired volume of air to flow through the hole so as to produce an audible sound. The weighted member is slidably mounted on a dowel rod within the housing. A slider plate is provided with a plurality of hole sizes formed thereon. The slider plate is interposed between the hole and the weighted member. The hole is formed on a first planar surface of the housing. The housing has an opening formed on a second planar surface of the housing. The first and second planar surfaces are in parallel relationship. A chamber extends between these surfaces. The surfaces in the chamber are permanently coupled together. The chamber has a rectangular configuration.
    Type: Grant
    Filed: April 5, 1993
    Date of Patent: October 4, 1994
    Inventor: Andrew A. Taft
  • Patent number: 5351035
    Abstract: A self-contained sensing unit to be mounted on air duct between the filter and blower to monitor the condition of the filter. The sensor has a probe to be inserted into the duct downstream of the filter. The probe is in fluid communication with a bellows. When the filter becomes clogged, a negative pressure in the duct actuates the bellows which in turn closes a circuit from a battery to a signaling device.
    Type: Grant
    Filed: February 22, 1993
    Date of Patent: September 27, 1994
    Assignee: Ben A. Everson
    Inventor: Lonnie R. Chrisco
  • Patent number: 5325809
    Abstract: A warning system for a hair dryer to warn the user when the air inlet of the dryer has become clogged with hair or other particles, the dryer including an air filter in the inlet, an air-actuated whistle having an air inlet end and an air outlet end, the whistle being mounted in the air inlet with the air inlet end outside the filter and the air outlet end inside the filter. Air will pass through the whistle when the inlet has become clogged, causing it to blow, and thereby warning the user that the inlet has become clogged. This occurs when the air pressure differential between the two sides of the filter reaches a predetermined level.
    Type: Grant
    Filed: April 26, 1993
    Date of Patent: July 5, 1994
    Assignee: Conair Corporation
    Inventor: Theodore B. Mulle, Jr.
  • Patent number: 5315838
    Abstract: A filter monitor for indicating the condition of an air filter in a room air conditioner to determine whether the filter is clogged. The filter monitor assembly includes a shell mounted on the front of the air conditioner, with an air pressure equalization passage permitting air flow through the shell when a clogged air filter creates a negative air pressure inside the air conditioner housing. A signal flag within the shell is normally retracted by the force of gravity, but is visibly extended outside the shell by the pressure-induced air flow through the shell, indicating that the air filter is clogged.
    Type: Grant
    Filed: August 16, 1993
    Date of Patent: May 31, 1994
    Assignee: Whirlpool Corporation
    Inventor: Christopher M. Thompson
  • Patent number: 5150604
    Abstract: The present invention provides a process, and an apparatus for accomplishing that process, for indicating when an inert gas purifier is about to loose its required level of purification efficiency. The inert gas purifier can therefore be replaced before the impurity levels of its purified output gas reach undesirably high values.
    Type: Grant
    Filed: November 13, 1990
    Date of Patent: September 29, 1992
    Assignee: SAES Getters SpA
    Inventors: Marco Succi, Fabrizio Doni
  • Patent number: 5057821
    Abstract: An apparatus including a housing secured to a filter web, wherein the housing includes a reciprocating rod directed orthogonally through the housing relative to the filter web, whereupon plugging of the filter web permits the rod to be directed through the housing to effect actuation of a switch therewithin. The rod mounts a magnet to track a plurality of contacts of a switch within the housing to effect actuation of an audible and visual alarm.
    Type: Grant
    Filed: February 19, 1991
    Date of Patent: October 15, 1991
    Inventor: Gary C. Card
  • Patent number: 5036698
    Abstract: A method and apparatus for predicting the remaining service life of an air filter element reads the pressure drop across the filter element at regular usage intervals (such as engine run time or distance the vehicle has traveled). An approximation of the rate at which the pressure drop is increasing is made, which is used to calculate the usage at which the maximum pressure drop will be attained.
    Type: Grant
    Filed: May 4, 1990
    Date of Patent: August 6, 1991
    Assignee: Allied-Signal Inc.
    Inventor: Kenneth A. Conti
  • Patent number: 4987881
    Abstract: A fuel burning furnace includes a number of energy efficient features. The furnace includes a heat exchanger in which combustion air is preheated by hot discharge gases. Diverters are provided in the heat exchanger to continually urge hot combustion gases toward the interior portions of the heat exchanger to improve its heat transfer characteristics. The furnace incorporates a number of features to determine malfunction and indicate inefficient operation. A humidification control system for the humidification or dehumidification of circulated air also is provided. The furnace also includes a blower motor system which compensates for loss of tension in driving belts and makes correction for blower speed in response to temperature variations.
    Type: Grant
    Filed: March 16, 1990
    Date of Patent: January 29, 1991
    Inventor: Rajendra K. Narang
  • Patent number: 4922890
    Abstract: A fuel burning furnace includes a number of energy efficient features. The furnace includes a heat exchanger in which combustion air is preheated by hot discharge gases. Diverters are provided in the heat exchanger to continually urge hot combustion gases toward the interior portions of the heat exchanger to improve its heat transfer characteristics. The furnace incorporates a number of features to determine malfunction and indicate inefficient operation. A humidification control system for the humidification or dehumidification of circulated air also is provided. The furnace also includes a blower motor system which compensates for loss of tension in driving belts and makes correction for blower speed in response to temperature variations.
    Type: Grant
    Filed: June 12, 1989
    Date of Patent: May 8, 1990
    Inventor: Rajendra K. Narang
  • Patent number: 4867095
    Abstract: A cartridge style, pop up, differential pressure indicator includes a threaded body member, a cover structure and a cylindrical indicator button, which carries a magnet at its lower end, and is slidably supported in the cover for movement between a depressed, hidden position and an extended indicating position. The button is engaged at one side by a leaf spring which in the depressed position urges a lip on the button under a ledge in the cover to serve as a detent. A piston slidably supported in the body is subject to differential fluid pressures and carries a magnet at its upper end, poled in a manner to repel the magnet in the indicator button to urge the latter against the bias of the detent spring and upwardly to the extended, indicating position. A semicircular bimetal strip supported in the cover engages the detent spring at lower temperatures to prevent false release of the indicator button due to cold weather, high fluid viscosity situations.
    Type: Grant
    Filed: April 5, 1988
    Date of Patent: September 19, 1989
    Assignee: Parker Hannifin Corporation
    Inventors: Bruce E. Shane, Keith D. Leady, Wayne L. Conner, Albert F. Cella
  • Patent number: 4747364
    Abstract: A flow rate sensor for use with an air filter channels air flow to energize an audible sound generator upon development of an air pressure differential within the sensor above a settable threshold, which pressure differential results from a reduction in the air flow rate through the air filter due to clogging of the air filter by filtered matter.
    Type: Grant
    Filed: August 5, 1986
    Date of Patent: May 31, 1988
    Assignee: Filter Alert Corporation
    Inventor: Barry N. Horowitz
  • Patent number: 4610703
    Abstract: This invention is a pollution cleansing system inside a motor vehicle for the protection of the occupants. An "Air Purifier" is built into the vehicle's cowl plenum chamber of the heating-cooling system and in the vehicle's side vents. The "Air Purifier" prevents pollutants, such as exhaust fumes of the motor vehicle, including dust and smoke entering the motor vehicle interior. By installing the "Air Purifier" in motor vehicles we can be assured of breathing purer air.
    Type: Grant
    Filed: January 31, 1986
    Date of Patent: September 9, 1986
    Inventor: Thaddeus Kowalczyk
  • Patent number: 4520748
    Abstract: A differential-vacuum alarm device is disclosed. The device comprises a housing divided into three chambers by two walls. One wall isolates one chamber from the other two. The other wall, preferably transverse to the first wall and integral therewith, substantially isolates the second chamber from the third. The second wall preferably carries a vibratable reed which is activatable when air, moving via effects of differential vacuum, passes from the second chamber into the third. The housing further includes a cover, preferably snap engageable with the housing. The walls are preferably integral with, and depend from, the cover. Inner surface portions of the housing preferably include integral, U-shaped channels for receiving edge portions of the walls. With the wall edge portions engaged in the channels and the cover snap engaged with the housing, the three chambers are substantially isolated, one from the other. A housing bottom, forming a floor common to the three chambers, includes three through apertures.
    Type: Grant
    Filed: October 19, 1983
    Date of Patent: June 4, 1985
    Assignee: Illinois Tool Works Inc.
    Inventors: Francis G. Frano, William E. Ruehl
  • Patent number: 4365627
    Abstract: An improved canister for a filter-type respirator having an end-of-service life warning device which is located in a position such that all air flowing through the canister flows through the warning device after the air has flowed through at least about 50 volume percent of the filtering material contained in the respirator.
    Type: Grant
    Filed: September 22, 1980
    Date of Patent: December 28, 1982
    Assignee: The Dow Chemical Company
    Inventor: Richard E. Wing
  • Patent number: 4365582
    Abstract: A differential pressure signal device employing an audible vibratory reed assembly having the property of being activated automatically upon being subjected to a predetermined energy level. The assembly is preferably all plastic and includes a unique rockable flapper valve that is automatically activated when the differential in pressure between two chambers reaches a predetermined level. The opening of said valve provides a large inrush of air that activates and operates the audible vibration of said reed until the differential in pressure is lowered below said predetermined level.
    Type: Grant
    Filed: November 24, 1980
    Date of Patent: December 28, 1982
    Assignee: Illinois Tool Works Inc.
    Inventors: David C. Boyer, William E. Ruehl
  • Patent number: 4336038
    Abstract: A fibrous filter mat of which all or a part of the fibers are coated totally or at least in part with a mixture of at least two dye components which are insoluble in one another, one of said components being fat- and/or oil-soluble and of a color which contrasts with that of the fiber blend and/or of the other component, the other component being fat- and/or oil-insoluble. The mat is especially suited for kitchen exhaust hoods since entrapment of fats and oils causes a color change as the oil-soluble dye dissolves and spreads out.
    Type: Grant
    Filed: August 28, 1980
    Date of Patent: June 22, 1982
    Assignee: Firma Carl Freudenberg
    Inventors: Wolfram Schultheiss, Harald Hoffmann
  • Patent number: 4313743
    Abstract: An electrolytic device adapted for mounting on the interior wall of a container housing sorbent chemicals for detection and display of moisture content. A sandwich or tab-type probe includes superhydroscopic MgClO.sub.4 or CaSO.sub.4 particles which resist electrical current flow when dry and have a higher affinity for moisture than the sorbent chemicals in cartridges or filters. Moisture intrusion is drawn to the anhydrous MgClO.sub.4 or CaSO.sub.4 particles changing their ohmic resistance and thereby enabling visual and nondestructive detection of the moisture intrusion into the container or cartridge. The probe is spaced away from the sorbent chemicals avoiding the transfer of mechanical stresses and any additional pressure drop through the sorbents, thereby permitting the device to be used in combination with a wide range of sealed containers and air filters.
    Type: Grant
    Filed: March 24, 1980
    Date of Patent: February 2, 1982
    Inventor: Richard A. Wallace
  • Patent number: 4254731
    Abstract: An indicator device for indicating when a prechosen pressure difference has been exceeded comprises a casing having two ports separated by a resilient diaphragm with an aperture therein, and a movable member urged into sealing relation with said aperture so as to prevent leakage therethrough, the configuration of the member and the aperture being selected so that, in use, the application of a prechosen pressure differential between said ports will cause the member to partly pass through the aperture to a position whereat it is retained by the diaphragm, said member being provided with means for indicating that it has been so retained.
    Type: Grant
    Filed: May 22, 1979
    Date of Patent: March 10, 1981
    Assignee: Engineering Components Limited
    Inventor: Peter F. Taylor
  • Patent number: 4215646
    Abstract: A whistle audibly responsive to extremely small pressure differentials is described. The whistle has a cylindrical inlet portion, a cylindrical outlet portion and a cylindrical constriction that form a passageway between said inlet and outlet portions. The whistle produces audible sound having an intensity of about 80 DB in response to a pressure differential, across the inlet and outlet portions, that is in the range of about 0.005 to 0.02 psi.
    Type: Grant
    Filed: November 3, 1978
    Date of Patent: August 5, 1980
    Inventor: Douglas J. Williams
  • Patent number: 4193292
    Abstract: An indicating device for vacuum cleaners, or similar apparatus, utilizing a dust container. The indicating device such as a diaphragm, is under the influence of a pressure differential and is movable against a force of a spring to give a visual indication from the outside of the vacuum cleaner of the degree of filling of the dust container therein. The motor of the vacuum cleaner has a motor regulator and the overall arrangement is provided with a unit for continuously varying the tension of the spring against the force of which the indicating device is movable.This invention relates to an indicating device for vacuum cleaners or similar apparatus having dust container with means which under the influence of a pressure differential is movable against the force of a spring and has a signalling device visible from the outside of the means for continuous visual indication of the degree of clogging of the dust container.
    Type: Grant
    Filed: January 5, 1979
    Date of Patent: March 18, 1980
    Assignee: Aktiebolaget Electrolux
    Inventor: Sven B. Simonsson
  • Patent number: 4184376
    Abstract: A device (10) for metering discrete lengths of filament utilized in a flexible filament vegetation cutting device is disclosed. The line metering device (10) is preferably used in flexible filament lawn mowers. An electric motor (28) rotatively drives a drive shaft (32) about its axis. A driving mechanism, preferably a spool (36) is coupled to the drive shaft (32) for rotation therewith whenever the drive shaft (32) is rotated. A driven mechanism, preferably a guide drum (84), is selectively coupled for rotation to the driving mechanism (36). The spool (36) has the flexible filament (66) wound about it and is coupled to one of the driven and driving mechanisms (84, 32) for rotation therewith.
    Type: Grant
    Filed: December 13, 1978
    Date of Patent: January 22, 1980
    Assignee: Donaldson Company, Inc.
    Inventors: Timothy J. Thomas, Harold A. Manguson
  • Patent number: 4162660
    Abstract: A dirty filter indicator for use with an air filter for an internal combustion engine, the filter comprising a replacement for an ordinary wingnut used to hold the outer cover of the air cleaner in position. The replacement nut has a bypass passage through it which communicates with the interior of the filter so that if the filter becomes dirty and clogged, a lightweight ball which is located in this passage and is normally biased to one position moves to a second position to indicate that the filter is dirty.
    Type: Grant
    Filed: June 29, 1978
    Date of Patent: July 31, 1979
    Inventors: Robert V. Albertson, Edward P. Christian
  • Patent number: 4153003
    Abstract: A pressure differential indicator for indicating a change in a fluid pressure differential across a component in a fluid system, such as an oil filter, has piston means, means for communicating fluid pressures of said system upstream and downstream of said component to opposite sides of said piston means, respectively, and differential means associated with the piston means for normally balancing the resultant forces of said pressure on opposite sides of said piston means at a given predetermined pressure differential across said component whereby said piston means is responsive to an increase or decrease in the pressure differential above or below said predetermined differential pressure to indicate a clean or clogged filter condition. Means are provided for holding the piston means in its last position upon relief of said first and second pressures to indicate the operating filter condition when the system is not operating.
    Type: Grant
    Filed: November 29, 1974
    Date of Patent: May 8, 1979
    Assignees: Wm. M. & Isabel Willis, John W. & Dolores C. Adams, Edward T. & Charlotte L. Bradbury, Robert A. & Dorthy J. Lefevre, Carl L. & Colene Seeley, Gilbert & Dolores D. Contreras
    Inventor: William M. Willis
  • Patent number: 4117717
    Abstract: A device is provided for detecting the presence of solid impurities within a pressurized fluid. The device comprises a housing having a fluid passageway formed therein. One end of the fluid passageway is open to the pressurized fluid, preferably via a restricted port, while the other end of the fluid passageway is open to a low pressure fluid region. A filter element is disposed across and obstructs the fluid flow through the passageway at a point intermediate its ends so that the filter element removes solid particles from fluid flowing through the passageway. A pressure sensing means, such as a pressure transducer, communicates with the fluid passageway between the pressurized fluid and the flter element. An increase of fluid pressure sensed by the pressure sensing means is indicative of a clogged filter element which, in turn, indicates the presence of solid impurities within the pressurized fluid.
    Type: Grant
    Filed: June 23, 1977
    Date of Patent: October 3, 1978
    Assignee: Teledyne Industries, Inc.
    Inventor: Walter F. Isley
  • Patent number: 4091762
    Abstract: An audible vibratory biased reed assembly having the properties of being activated or commencing vibration upon being subjected to a predetermined energy level. This assembly utilizes a straight, flat, elongated, closed or clapping reed, to produce a clatter or buzzing sound, with the reed being biased through application of a bias force to one edge to distort its flatness adjacent its free extremity. The bias force is applied by an angular transverse bridge which substantially triples the frequency of the mechanical clatter.
    Type: Grant
    Filed: September 20, 1976
    Date of Patent: May 30, 1978
    Assignee: Illinois Tool Works Inc.
    Inventor: William E. Ruehl
  • Patent number: 4060050
    Abstract: An indicator device mounted on a vacuum cleaner housing which is under the influence of the pressure differnce between the inlet and outlet of a dust or dirt collector unit of the vacuum cleaner. The outer surface of the indicator device has markings that are continuously visible, and which show the amount of accumulated dust and dirt filling in the dust collector, at any given time.
    Type: Grant
    Filed: August 18, 1976
    Date of Patent: November 29, 1977
    Assignee: Aktiebolaget Electrolux
    Inventor: Sven Bertil Simonsson
  • Patent number: 4020783
    Abstract: A device for monitoring the condition of a filter element, comprising a combined clamping nut and differential pressure indicator. The body of the device is non-circular about an axis to facilitate its use as a wingnut, and has an outer surface and an inner surface through which passes an axial orifice, internally threaded to engage a threaded mounting rod. A differential pressure responsive device of novel design, including a slack diaphragm and an air-permeable translucent screen, is mounted in a further orifice in the outer surface for exposure of one side of the diaphragm to the pressure outside the filter, and a passage in the body connects the further aperture with the inner surface to supply to the other side of the pressure responsive device the pressure within the filter. The combination of such an arrangement with an air cleaner having a safety filter is also a part of the invention, as is the method of monitoring the filter conditions which the structure makes possible.
    Type: Grant
    Filed: June 19, 1975
    Date of Patent: May 3, 1977
    Assignee: Donaldson Company, Inc.
    Inventors: Erland D. Anderson, David S. Paulson, Bruce M. Sullivan
  • Patent number: 4014209
    Abstract: An air filter condition indicating device particularly adapted for use with an air filter positioned in an air flow path, such as in an air induction system of an internal combustion engine for continuously sensing and indicating flow condition of an air filter in the air induction system. The disclosed device includes a transparent tubular member having liquid therein and arranged in a generally U-shaped path with a first leg thereof positioned adjacent an indicia member and adjacent an observation aperture in one wall of a gauge housing. A first flow member communicates between an upstream side of the filter or an air intake portion of the air induction system and an upper end portion of the first leg of the tubular member.
    Type: Grant
    Filed: December 15, 1975
    Date of Patent: March 29, 1977
    Inventor: Wayne L. Emerick
  • Patent number: 3974795
    Abstract: A differential pressure indicating device includes a piston responsive to the differential between inlet and outlet pressures. The piston is retained in a normal position by the force of spring means, and which spring means releases the piston at a predetermined excessive differential pressure condition, whereupon the piston actuates an indicating member for indicating the condition. The device is reset by manually re-engaging the piston and the spring means subsequent to correcting the condition.
    Type: Grant
    Filed: June 18, 1975
    Date of Patent: August 17, 1976
    Assignee: Facet Enterprises, Inc. Filter Products Division
    Inventor: Robert L. Crisp, Jr.
  • Patent number: 3939457
    Abstract: An air filter restriction detection device communicating with the air stream passing from an air filter to the air intake of an internal combustion engine sensing a decrease in the supply of air being drawn through said air filter by said engine and the same being indicated by the linear movement of an indicating member in said device, said device indicating also when said air filter requires cleaning or replacement for lack of a sufficient supply of air being drawn therethrough.
    Type: Grant
    Filed: November 7, 1974
    Date of Patent: February 17, 1976
    Inventor: Richard Donald Nelson
  • Patent number: 3936284
    Abstract: An air filtering apparatus is disclosed utilizing a prefilter at the inlet side and a HEPA type filter at the outlet side. The interior chamber of the apparatus is divided into two subchambers with a blower forceably pumping air from the inlet chamber to the outlet chamber. A first indicator means is responsive to a predetermined decrease in pressure in the inlet chamber for indicating when the prefilter needs changing, and a second indicator means is responsive to a predetermined increase in pressure in the outlet chamber indicating when the HEPA type filter requires changing. A plurality of the apparatuses may be utilized in an air filtering system controlled remotely by radio transmitting and receiving devices.
    Type: Grant
    Filed: August 16, 1974
    Date of Patent: February 3, 1976
    Assignee: Mason Engineering and Designing Corporation
    Inventor: Donald G. Mason
  • Patent number: 3934543
    Abstract: An apparatus for monitoring the condition of a fluid filter comprises a flexible diaphragm exposed to the upstream, downstream or differential pressure acting on the filter and indicator means for monitoring the condition of the filter as a function of movement of the diaphragm in response to said pressures. A unique, low friction indicator mechanism, means for adjusting the sensitivity of the device and means for resetting the device are also disclosed.
    Type: Grant
    Filed: December 23, 1974
    Date of Patent: January 27, 1976
    Assignee: Sherwood Products Corporation
    Inventor: Durrell U. Howard