Patent Publication Number: US-3874859-A

Title: Automatic drain device for deliquescent gas dryers

Description:
United States Patent 1 Krause Apr. 1,1975  
 [ AUTOMATIC DRAIN DEVICE FOR DELIQUESCENT GAS DRYERS [75] Inventor: Martin C. Krause, Wattsburgh, Pa.  
 [73] Assignee: Van-Air Incorporated, Erie, Pa.  
 [22] Filed: Dec. 19, 1973 [21] Appl. No.: 426,076  
 [52] US. Cl 55/218, 55/432, 55/433, 137/624.l3, 251/129, 251/292 [51] Int. Cl BOld 33/38 [58] Field of Search 55/218, 430, 438, 432; 137/624.l3; 251/291, 292, 129  
 [56] References Cited UNITED STATES PATENTS 975.292 11/1910 Schramm 251/292 X 2.827.913 3/1958 Wagner 251/291 X 3,096,787 7/1963 Kaylcr l37/624.l3 3.483.673 12/1964 Wcllman 55/218 FOREIGN PATENTS OR APPLlCATlONS 1.550391) 7/1969 Germany 251/292 Primary E.\&#39;antt&#39;nerFrank W. Lutter Assistant lirantinerWilliam A. Cuchlinski Attorney, Agent, or FirmBaldwin, Egan, Walling &amp; Fetzer [57] ABSTRACT An automatic control device for use, for instance, in automatically draining solution from a pressurized vessel, such as for instance a deliquescent desiccant type air or gas dryer. The control device is adapted to periodically exhaust waste liquid which collects in, for instance, a dryer vessel from the latter. The device comprises a motor power operated valve coacting with fluid conveying means which is adapted to be disposed in a drainage line leading from the vessel. The motor operated valve is automatically actuated to open position at predetermined periods whereupon the waste liquid is drained from the vessel, and then the valve is automatically closed until the next actuation thereof. The valve and the fluid conveying means is disposed exteriorly of the motor power unit for the valve and is rapidly disassemblable therefrom, for permitting rapid removal and reassembly of the power unit from the valve and fluid conveying subassembly, and rapid replacement of worn parts from the valve body. Thus, in the event that a malfunction occurs in the power system, the latter can be rapidly removed and replaced without depressurizing the system, or the valving can be manually operated, to prevent flooding or loss of pressure in the dryer system.  
 9 Claims, 5 Drawing Figures m m nAPR&#39; 1191s 3, 74, 59 slimlqgz acqy 46 K 1 AUTOMATIC DRAIN DEVICE FOR DELIQIJESCENT GAS DRYERS The invention relates to liquid level control devices such as for instance automatic drain devices, and more particularly to an automatic drain device adapted for automatically exhausting solution at periodic intervals from a pressurized vessel, such as for instance a deliquescent desiccant type air and/or gas dryer, and a drain device which is especially easy to service and maintain BACKGROUND OF THE INVENTION Automatic mechanism for automatically controlling the flow of fluid into or from a pressurized vessel, are known in the prior art U.S. Pat. No. 3,483,673 dated Dec. 16. 1969 to Frederick Wellman and entitled Automatic Drain Device For Deliquescent Gas Dryers discloses one arrangement of automatic device ofthe general nature with which the present invention is concerned.  
  Reliability and ease of servicing of such devices are of great importance in order to prevent flooding of the system if the control mechanism malfunctions with the valve portion in a closed position, and in order to prevent loss of pressure in the system if the valve portion malfunctions in open position.  
 SUMMARY OF THE INVENTION The present invention provides a compact automatic liquid level control device for automatically controlling flow of fluid into or from a vessel, and which includes means for rapidly removing and/or reassembling the power unit and control circuit for the mechanism to and from the fluid conveying conduit and valve subassembly thereof. so that servicing of the device can be expeditiously accomplished. The mechanism includes means for manually operating the valve in the event of malfunction of the motor mechanism, and for electrically overriding the control mechanism.  
  Accordingly, an object of the invention is to provide an automatic control device for controlling the emptying or filling of a predetermined amount of fluid or liquid at predetermined intervals into or from a tank or vessel.  
  Another object of the invention is to provide a novel automatic drain device for use with a deliquescent des&#39; iccant type of air or gas dryer. for automatically draining waste solution coming from the deliquescent desiccant in the dryer. from the dryer tank.  
  A still further object of the invention is to provide a compact automatic drain device for use in a deliquescent desiccant type air or gas dryer comprising fluid conveying conduit means assembled with a valve mechanism. and with the power unit and control circuit arrangement for automatically operating the valve at predetermined intervals of time being coupled in a simplified manner to the fluid conveying conduit and valve subassembly, and by fastener means which can be rapidly actuated to quickly remove and/or replace the power unit from the fluid conveying conduit and valve subassembly. and a device which permits manual actuation of the valve in the event of malfunctioning of the device. thus providing for reliability and ease of servicing of the drain mechanism.  
  A still further object of the invention is to provide a compact automatic drain device for use in an air or gas dryer having a fluid conveying conduit and valve assembly in which the valve can be quickly disassembled and any worn parts replaced without disturbing the threaded fluid conveying conduit portions.  
  A still further object of the invention is to provide in combination with a deliquescent desiccant type air and/or gas drying device comprising an enclosure tank adapted to hold a quantity of deliquescent chemical desiccant therein. which desiccant is adapted to remove moisture from air and/or gas placed in contact with the desiccant, a compact automatic reliable drain device so constructed and arranged that maintenance thereon and servicing thereof is facilitated.  
  Other objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings wherein:  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a generally diagrammatic, partially broken, elevational view of a compressed air and/or gas dryer with the compact automatic drain control device of the invention coupled thereto, for controlling periodic removal of desiccant waste solution from the dryer;  
  FIG. 2 is an enlarged, side-elevational view of the control device of FIG. 1;  
  FIG. 3 is an end elevational view of FIG. 2 taken generally from the right-hand end thereof;  
  FIG. 4 is a top plan, generally diagrammatic illustration of the motor housing of the control device with the top thereof removed;  
  FIG. 5 is a generally perspective, exploded illustration of the control device of FIG. 2.  
 DESCRIPTION OF PREFERRED EMBODIMENT Referring now again to the drawings and in particular to FIG. I, the gas and/or air dryer illustrated comprises an enclosure or tank 10. The dryer tank has an air or gas inlet 12 through which pressurized inlet air or gas to be dried or treated is inserted into the enclosure tank, and an air or gas outlet 14 through which the air or gas is withdrawn from the enclosure. The use of the term gas hereinafter will be understood to also include air since the latter is, of course, a gas.  
  Disposed intermediate the inlet 12 and outlet 14 of the enclosure may be a gas pervious supporting means 16, such as for instance a grid. on which is disposed a bed of deliquescent chemical desiccant 18. The deliquescent desiccant is a chemical composition which is adapted to attract moisture from the air or gas as the latter engages the bed and passes therethrough. Such attracted moisture causes dissolving or Iiquifying of the desiccant material in the bed, with the liquid flowing down through the bed into the bottom of the dryer enclosure where such waste liquid is adapted to be periodically removed through the drain opening 19 in the enclosure.  
  Drain opening 19 may be coupled to a drain line 20 which is adapted to be directed to, for instance, a sewer system or any other suitable disposal area, for disposing of the drain solution. The gas entering the dryer is generally under pressure and passes through the desiccant bed 18 and out the outlet 14 as dry, clean gas. Reference may be had to US. Pat. No. 3,246,453 issued Apr. 19, 1966 in the name of Philip S. Becker and US. Pat. No. 3,303,621 issued Feb. 14, 1967 to W. E. Hill, for disclosures of deliquescent desiccant types of gas dryers of the general above-discussed nature.  
  Disposed in the drain line 20 is a compact control device 22 for automatically controlling draining of the waste solution in the bottom of dryer from the latter, at predetermined intervals of time. Mechanism 22 in the embodiment illustrated comprises a motor power unit, such as for instance a conventional compact electrical motor 26 (FIGS. 4 and 5), having a magnetic mechanical brake and a gear train (not shown) associated therewith, and a power output shaft or stem 30, which is adapted for coupling to a valve means 32, which valve means controls the passage of fluid through the fluid conveying means 34 of the automatic drain control mechanism 22.  
  Motor unit 26 and associated brake and gear train are preferably enclosed in a housing 36 which may include a top section 36a and a bottom section 36b. A gasket member 38 is provided for sealing the housing sections when disposed in assembled relation, so that the motor and associated components are protected from mechanical injury and moisture. The aforementioned power stem 30 of the motor unit depends from the underside of housing 36, preferably in moisture proof relation thereto, and is rotatable with respect to the housing.  
 A compact control circuit package 40 which preferably includes solid state electronic circuit components,  
 is provided for detachable mounting in housing 36, and which is adapted for connection to the motor unit, for controlling the opening and closing cycle of the valve means 32, and the time interval between each cycle, and thus automatically controlling the periodic flow of waste fluid from enclosure 10. Control circuit package 40 is of commercially available type.  
  Circuit board 41a of package 40 may be conveniently removably mounted as by means of fasteners 42, in the housing 36, and therefore can be easily and quickly replaced for expediting servicing. As can be best seen in FIG. 4, such control circuit package is positioned in the housing to one side of the motor unit 26, with such circuitry preferably including potentiometers 44,44a as part of the control circuit, and which are accessible for adjustment from exteriorly of housing 36. Openings 46,461! are provided in the upper section 36a of the housing 36, to enable such potentiometer elements to be adjusted, for a purpose to be hereinafter set forth. Openings 46,46a may be provided with removable covers 47 for preventing entry of dirt and other contaminants. Junction block 48 in circuit package 40 (FIG. 4) is coupled to motor 26 and also is coupled by electrical plug and line 48a to a conventional source of current, which source may be either conventional A.C. current or DC current depending on what is available and on whether motor 26 is an AC. or DC. motor.  
  The aforemetioned valve means 32 includes a valve body member 50 having a passageway 50a (FIG. 5) wherein a ball valve member 54 is seated, providing for passage of fluid through opening 54a in the ball member. Body member 50 has flanges 5012 which are apertured as at 51 for coupling the valve means in fluid passing condition with the aforementioned fluid conveying conduit means 34. The outer side surfaces 52 of valve body 50 are preferably generally planar as shown in FIG. 5.  
  A valve stem member 55 projects into the passageway 50a in valve body 50 and into assembled coaction with ball valve member 54, for rotating the latter upon rotary movementof stem 55. Stem 55 preferably has circumferential recesses 55a formed therein, for receiving O-ring seal members 55b which prevent the discharge of fluid along the stem member, which as will be understood, projects exteriorly of valve body member.  
  The lower preferably polygonal shaped (in cross section) end 56a of the valve stem member 55 projects into slot 58 in the ball member, and the upper preferably polygonal shaped (in cross section) end 56 projects up through hub 60 of the valve body 50. Accordingly,  
 it will be understood that valve stem 55 is rotatable.  
 with respect to the valve body and with respect to hub 60, and during rotation thereof causes corresponding rotation of the ball valve member 54 with respect to the valve body. Valve member 54 coats with valve seats 59 7 disposed in passageway a, for controlling the flow of fluid through the valve means 32. Portion 56 of the valve stem extends into coacting relationship with slotted connector 62.  
 Connector 62 is preferably slotted at both of its ends I in a direction generally transverse with respect to one another, with the lower slotted portion 64 receiving the.  
 aforementioned upper end portion of the valve stem therein. Set screw members 66 extend through openings 68 in the connector member, to anchor the connector member to the valve stem. While connector 62&#39; is anchored to a stem portion 56 as aforedescribed. possible pivotal movement of connector 62 with respect to stem 55 is provided about an axis passing through set screw members 66, and as can be seen from FIG. 3.  
 The upper end of connector 62 is likewise slotted, as  
 aforementioned and as at 70, and receives therein the rectangular shaped (in horizontal cross section) power stem or shaft 30 from motor unit 26. Accordingly, it will be seen that upon energization of the power unit 26, and rotation of stem 30, the latter causes rotation, of connector 62 and thus rotational movement of valve stem 55, which in turn rotates ball valve member 54 to cause opening and closing of the valve.  
 An attaching bracket member 72 is provided which 7 includes a generally planar base portion 72a, side panels 72b and depending leg portions 72c. Leg portion 720 are adapted to straddle the fluid conveying and bracket with respect to the housing 36, so that the power shaft 30 of motor unit 26 can be properly positioned through opening 74 without interference. A-  
 tube-like cover member .80 (FIGS. 2 and 3) may be provided which slips over the aforementioned embossments 79 and conceals the attachment of the bracket 3 to the embossments 79.  
 Fluid conveying means 34 in the embodiment illustrated comprises spaced threaded end conduits 82 including laterally extending flange portions 82a which have openings 84 therethrough, for a purposeto be hereinafter set forth. The conduit sections may bein ternallythreaded as at 86, for threaded attachment in drain pipe of the dryer 10. The inner surface 87 of flange portion 82a of each conduit 82 is generally planar as illustrated in FIG. 5, while the confronting surface 52 of the valve body preferably has a recess 88 formed therein, with the recess being adapted to receive an O-ring seal 90, which seals the juncture between the conduit means 34 and the valve body 50. it will be seen therefore that with such an arrangement, the internal size of the conduit sections 82 can be varied from say, for instance, one-half inch up to, for instance, 1 inch pipe diameter without the necessity of changing the valve structure, so that the drain mechanism can be conveniently attached to different sizes of drain pipe without use of bushings or adapters.  
  Conduit sections 82 may be expeditiously held in assembled relation with the valve means 32 by means of threaded studs 94, which extend through openings 84 in the conduit sections and openings 51 in the valve body. Threaded fasteners such as, for instance, nut 96, provide for securing the conduit sections 82 to the valve body in tight, sealed condition. It will be seen that the studs are of sufficient length so that the distal ends thereof are spaced apart a distance greater than the distance between the respective leg sections 720 of bracket 72, so that the threaded studs project out vvardly of such legs (FIG. 2). Fasteners, which in the embodiment illustrated are nuts 98, coact with the studs 94, to support the fluid conveying conduit and valve assembly on the bracket 72. While housing 36 and attached bracket 72 are shown as being disposed above the fluid conducting conduit and valve assembly, such could be installed below such conduit and valve assembly by rotating the latter 180 about the longitudinal axis. Thus. the control device can be installed in inverted position, or any intermediate angular position, where interference or lack of adequate space prevents upright installation.  
  It will be seen that merely by loosening fasteners 98 from their holding coaction with the legs 72c of bracket 72. the housing 36 encasing the motor unit and the attaching bracket 72, can be readily lifted off of the fluid conveying conduit and valve assembly, due to the open ended slots 100 in the legs of bracket 72, to thus rapidly provide for separation of the control circuit and motor unit from the fluid conveying conduit and valve assembly. It will be seen that during such lifting off of the motor unit and control circuit disposed in housing 36, the power stem on the motor unit is merely lifted from its coaction with slotted end 70 of the connector 62, and readily exposes the connector 62 for manual turning to open or close the valve 32. Thus, in the event of malfunction ofthe drain mechanism, the housing encasing the motor and control circuit, and the associated attaching bracket 72, can be readily removed for either rapid replacement by another &#34;on hand&#34; spare part unit, or the valve means can be manually operated if such a spare part is not immediately available, and without interference with the fluid conveying conduit means and valve assembly.  
  The aforementioned potentiometer 44a in the control circuit package 40 is for adjusting the time cycle of operation of the device, for opening and closing the valve means 32 to periodically, automatically exhaust fluid from the enclosure 10 to which the device is attached. while the other potentiometer 44 is available for adjusting the time delay in which the valve remains open prior to its automatically closing during the exhaust cycle. Access to the potentiometers from exteriorly of the housing 36 is available through aforementioned openings 46, 46a (after removal of the associated cap closure 47) by merely inserting a tool, such as a screwdriver, through the respective opening into coaction with the potentiometer for turning adjustment thereof. For example, the potentiometer 44 for controlling the time delay from full open to full closed position of the valve mechanism during its periodic cycle of exhausting fluid from the enclosure, can be adjusted through a range of, for instance, 4 seconds to 40 seconds, or in other words through a 10 to 1 maximum ratio. Moreover, the periodic time for causing cycling of the drain mechanism to exhaust fluid from the enclosure can be adjusted by means of for instance potentiometer 44a through a range of, for instance, every 15 minutes to, for instance, every 2% hours, for again a ratio of 10 to 1 maximum. It will be understood, of course, that other ratios can be incorporated into the control.  
  There also may be provided a control button 102 on the housing which is adapted for selectively causing cycling of the valve means 32 from full close to full open condition. By pressing the override button 102, the workman can open the valve means from closed to full open condition. Whereupon after a predetermined time delay, the valve means automatically moves back to closed position. This enables a convenient check on the time delay length of the valve in open condition. and provides for adjustment of such time delay. This also enables the workmen to check that the valve is operating satisfactorily.  
  In the event that the drain mechanism is to be used in an environment where the source of current is D.C. current, the actuator motor 26 can be changed from an A.C. motor to a D.C. motor or vice versa to permit use of the mechanism in either A.C. or DC. current environments. Such change of motors would not necessi tate changing of the control circuit package 40.  
  Form the foregoing discussion and accompanying drawings, it will be seen that the invention provides a novel control mechanism for use with different sizes of drain pipe, and in different power source arrangements, and one wherein a motor unit and control package arrangement is readily separable from a fluid conveying conduit and valve assembly, so that in the event of malfunction or failure of the device, the mechanism can be readily serviced and the drive motor and control circuit package therefor can be&#39;readily replaced by new units, thus insuring minimum down time for the device. Moreover, when the power unit and control circuit is removed from the fluid conveying conduit and valve assembly, means is provided for convenient manual operation of the valve, so that the valve can be actuated even though the power section of the control mechanism malfunctions. Also, this eliminates the necessity of having an additional manually operated valve installed in the drain pipe for operation if the automatic control device should malfunction.  
  The terms and expressions which have been used are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of any ofthe features shown, or described, or portions thereof, and it is recognized that various modifications are possible within the scope of the invention.  
 What is claimed is:  
  l. A compact control unit operative for automatically controlling a flow of liquid in combination with an enclosed vessel, said vessel including means adapted for removing moisture from pressurized gas passed through said vessel, said vessel having a drain opening in the lower portion thereof for draining liquid therefrom, means connecting said control unit in liquid transmitting relation with said drain opening, for controlling the egress of liquid from said vessel, said control unit comprising liquid conveying means, said liquid conveying means comprising an inlet communicating with said connecting means and an outlet, and valve means coacting with said liquid conveying means for controlling the flow of liquid through said liquid conveying means, electrically powered motor means for actuating said valve means to move said valve means from a closed position to an open position and then back to a closed position upon predetermined energization of said motor means, means including electrical circuitry for automatically controlling energization of said motor means at predetermined intervals of time, a housing for said energization controlling means, means releasably coupling said motor means to said valve means for actuation of the latter by said motor means. said valve means and liquid conveying means being spaced from and disposed exteriorly of said housing whereby said valve means and said liquid conveying means are readily accessible, exteriorly accessible attaching means holding said liquid conveying means and valve means assembly in assembled relation with said motor means and associated energization controlling means, said attaching means being readily accessible and operable for quickly removing said motor means and said energization controlling means from said liquid conveying means and valve means assembly, said releasable coupling means providing for convenient manual actuation of said valve means in the event of removal of said motor means from coupled coaction with said valve means, and said attaching means including means which not only holds said motor means and associated energization controlling means to said liquid conveying means and valve means assembly but also is operable to hold the latter in assembled relation and which upon predetermined actuation permits quick removal and replacement of said valve means said liquid conveying means without disconnecting the latter from said drain opening connecting means.  
  2. The combination in accordance with claim 1 wherein said vessel moisture removing means includes a gas pervious support in said vessel adapted to receive thereon a bed of deliquescent chemical material for removing moisture from the pressurized gas passing through said bed. the removed moisture being adapted to move downwardly in said vessel toward said drain opening.  
  3. The combination in accordance with claim 2 wherein said vessel has a gas inlet disposed below said gas pervious support and a gas outlet disposed above said gas pervious support.  
  4. The combination in accordance with claim 3 wherein said valve means includes a laterally projecting valve actuating stem constructed and arranged manual actuation to manually actuate said valve means to open or closed position in the event of removal of said housing and motor means from coupled coaction with said liquid conveying means and valve means assembly.  
  5. The combination in accordance with claim 1 wherein said liquid conveying means comprises spaced conduit sections defining respectively said inlet and said outlet, each of said conduit sections including lat{ eral flanges, said valve means being disposed intermediate said conduit sections and including flanges formed generally complementary to the first mentioned flanges, said attaching means including a bracket comprising generally vertically oriented, spaced arms having open ended, generally vertically extending slots therein, threaded studs extending through apertures in said flanges and through said arm slots, and actuateable fastener means coacting with said studs and with said arms and said conduit section flanges for not only hold ing said motor means and associated energization controlling means to said liquid conveying means and valve means assembly, but also operable to hold the latter in assembled relation, and wherein said connecting means includes a pipe coupled at one end thereof to said drain. opening and at the other end thereof to one of said conduit sections defining said inlet for passage of waste solution from said vessel to said valve means, said valve means being detachable from said one conduit section upon predetermined deactuation of said fastener means and separation of said studs from at least certain of said flanges, and without disturbing the connection of said one conduit section to said pipe.  
  6. The combination in accordance with claim 1 wherein said motor means includes a rotatable power stem releasably coupled to said valve means by said coupling means, for actuating said valve means upon actuation of said motor means, said motor means being disposed in said housing with said stem extending exte-, riorly of said housing and being detachable from said valve means as a unit with said energization control means.  
 &#39;7. The combination in accordance with claim 6 wherein said valve means includes a laterally projecting stem, said coupling means comprising a connector member connected at one end thereof with said valve stem and at the other end thereof with said motor power stem for coupling the motor stem to said valve member for powered actuation of the latter member, said connector member comprising slots extending therethrough at opposite ends thereof, said slots being generally aligned with one another in a direction axially of said connector member except that one of said slots is rotated with respect to the direction of the other slot, so that the latter extends transverse of said one slot. 7  
 8. The combination in accordance with claim 1,  
 wherein said attaching meansincludes a bracket member secured to said housing and generally depending therefrom, said bracket member comprising a generally flat base portion attached to said housing and down wardly projecting generally flexible arm portions depending from said base portion, said arm portionshavi ing openended generally vertically extending slots therein, means detachably securing said bracket member to said housing, said liquid conveying means including spaced conduit sections having lateral flanges, said valve means including a valve body disposed intermediate said conduit sections, said attaching means also in cluding studs extending through apertures in said flanges and through said arm slots in said bracket mem ber, and fastener means coacting with said studs and said arm portions of said bracket member to releasably anchor said bracket member to said liquid conveying means and said valve means assembly, said fastener means upon predetermined loosening actuation thereof permitting separation of said bracket member and attached motor means and energization controlling means from said conduit sections and said valve body, said arm slots providing for unrestricted removal movement of said bracket member and attached housing linearly away from said studs upon said predetermined loosening actuation of said fastener means.  
  9. The combination in accordance with claim 1 wherein said valve means comprises a valve body, a valve member and at least one seat with which said valve member coacts in said body, to control the flow of fluid through said valve body, a valve stem coupled to said valve member and projecting exteriorly of said valve body, said coupling means comprising a connector member coacting at one end thereof with said valve stem and at the other end thereof with a motor stem of said motor means for coupling the motor stem to said valve member for powered actuation of the latter member. said motor means being disposed in said housing with said motor stem projecting exteriorly of said housing, said attaching means including a pair of threaded rod-like members extending through openings in said valve body, said liquid conveying means comprising spaced end conduit members between which is disposed said valve body, said conduit members having lateral flanges with openings aligned with said openings in said valve body and through which said rod-like members extend, exteriorly accessible fastener means coacting with said rod-like members and said flanges to connect the end conduit members to said central valve body in liquid tight relation, said attaching means also including a bracket attached to said housing and having open ended generally vertically oriented slots therein through which said rod-like members extend, said fastener means coacting with said rod-like members and said bracket at said slots to releasably secure said bracket and attached housing to said rod-like members, said valve member comprising a ball valve in said valve body, a removable valve seat disposed in said valve body and coacting with said ball valve to control the flow of fluid through said conduit members and said valve body, said ball valve having a slot therein receiving a portion of said valve stem, sealing means coacting with said valve stem to prevent liquid leakage along said valve stem, said ball valve being rotatable with rotation of said valve stem, said housing being sealed and separate from said valve means and said liquid conveying means so that any leakage of liquid at said valve means cannot have any detrimental effect on said energization controlling means and said motor means.  
  l l l l UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION P t nt 3,874,859 Dated April 1, 1975 Inventor(s) Martin C. Krause It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:  
 Column 7, line 46, after &#34;means&#34;, insert -from--.  
 Column 7, line 63, after &#34;arranged&#34;, insert -for-.  
 Signed and sealed this 17th day of June 1975.  
  S EAL) At t e S t C MARSHALL DANN RUTH C. IASON Commissioner of Patents Attesting Officer and Trademarks FORM PO-1O5O (10-59) USCOMM-DC 60376-P69 UIS. GOVERNMENT PRINTING OFFICE 2 I959 0-355&#39;3Jl