AU635696B1 - Apparatus for determining the position of a moveable structure along a track - Google Patents

Description

PATENTS ACT 1990 C 0 M P L E T E SP EC I FI CA TIO N FOR A STANDARD PATENT OR I GI NA L .0.

see weS be Name of Applicant: Actual Inventors: LANDIS GYR POWERS, INC.

David A. Egbers and Steven D. Jacob Address for Service: 0*S 4:00 lnvention Title: SHELSTON WATERS Clarence Stieet SYDNEY NSW 2000 "APPARATUS FOR DETERMING THE POSITION OF A MOVEABLE STRUCTURE ALONG A TRACK" 0 OSeSOe 0 0 OgS*0S 0 The fallowing statement is a full description of this invention, including the best method of performing it known to us:la 1 2 0' 4 4 6 7 8 9 10 11 12 13 14 16 17 18 19 21 22 23 APPARATUS FOR DETERMINING THE POSITION OF A MOVEABLE STRUCTURE ALONG A TRACK Cross Reference to Related Applications 1. Title: Inventors: Serial No.: 2. Title: Inventors: Serial No.: 3. Title: Inventors: Serial No.: 4. Title: Inventors: Serial No.: Apparatus for Controlling the Ventilation of Laboratory Fume Hoods Osman Ahmed, Steve Bradley, Steve Fritsche and Steve Jacob 590,195 A System for Controlling the Differential Pressure of a Room Having Laboratory Fume Hoods Osman Ahmed and Steve Bradley 589,931 A Method and Apparatus for Determining the Uncovered Size of an Opening Adapted to be Covered by Multiple Moveable Doors Osman Ahmed, Steve Bradley and Steve Fritsche 590,194 Laboratory Fume Hood Control Apparatus Having Improved Safety Considerations Osman A2,med 509,952 The present invention generally relates to an apparatus which determines the position of one or more structures such as sliding doors or windows mounted in tracks, and more particularly relates to determining the position of one or more sash doors that are moveable in associated tracks of a laboratory fume hood.

Fume hoods are ut.Oized in various laboratory environments for providing a work place where potentially dangerous chemicals are used, with the hoods coaprising an -2- 1 enclosure having moveable doors at the front portion 2 thereof which can be opened in various amounts to permit a 3 person to gain access to the interior of the enclosure for 4 the purpose of conducting experiments and the like. The enclosure is typically connected to an exhaust system for 6 removing any noxious fumes so that the person will not be 7 exposed to them while performing work in the hood.

8 Fume hood controllers which control the flow of 9 ai- through the fume hood have become more sophisticated in recent years, and are now able to more accurately maintain 11 the desired flow characteristics to efficiently exhaust the 12 fumes from the enclosure as a function of the desired 13 average face velocity of the opening of the fume hood. The 14 average face velocity is generally defined as the flow of Ogee 15 air into the fume hood per square foot of open face area of 16 the fume hood, with the size of the open face area being 17 dependent upon the position of one or more moveable sash *4 18 doors that are provided on the front of the enclosure or S 19 fume hood, and in most types of enclosures, the amount of bypass opening that is provided when the door or doors are 21 closed.

22 The fume hoods are exhausted by an exhaust system 23 that generally include a blower that is capable of being 24 driven at variable speeds to increase or decrease the flow of air from the fume hood to compensate for the varying 26 size of the opening or face. Alternatively, there may be 27 a single blower connected to the exhaust manifold that is 28 in turn connected to the individual ducts of multiple fume 29 hoods, and dampers may be provided in the individual ducts to control the flow from th- individual ducts to thereby 31 modulate the flow to maintain the desired average face 32 velocity. There may also be a combination of both of the 33 above described systems.

34 The doors of such fume hoods can be opened by raising them vertically, often referred to as the sash 36 position, or some fume hoods have a number of doors that 37 are mounted for sliding movement in typically two sets of 38 tracks. There are even doors that can be moved 1 horizontally and vertically, with the tracks being mounted 2 in a frame assembly that is vertically moveable.

3 Prior art fume hood controllers have included 4 sensing means for measuring the absolute position of vertical doors or the relative positions of horizontal 6 doors and then using a signal proportional to the sensed 7 position to thereby vary the speed of the blowers or to 8 vary the position of the dampers.

9 It is a primary object of the present invention to provide an improved sensing means for measuring the 11 absolute position of moveable structures along a track.

12 Another object is to provide an improved sensing 13 means for determining the absolute position of sash doors 14 in a laboratory fume hood, wherein there may be one or 15 several sash doors that are moveable along sets of tracks.

16 A related object is to provide such an improved 17 sensing means that is universally adapted to provide 18 absolute position indicating signals for doors that are S 19 moveable in either the vertical or horizontal direction.

e 20 Another object is to provide such an improved 21 sensing means that is adapted to provide a single elongated 22 switching means that can be placed along the track in which 23 one or two sash doors are moveable, and wherein separate 24 signals are generated that are indicative of the absolute 25 position of each of the one or two doors.

26 Yet another object of the present invention is to 600009 S 27 provide such an improved sensing means that provides such 28 separate signals that are indicative of the absolute posi- 29 tion of each of two doors that are moveable in a single set S 30 of tracks, and which sensing means is sufficiently small in 31 cross section and simple in its construction that it can be 32 unobtrusively placed in the track without interfering with 33 the movement of the sash doors.

34 These and other objects will become apparent upon reading the following detailed description of the present 36 invention, while referring to the attached drawings, in 37 which: 38 FIGURE 1 is a schematic block diagram of 1 apparatus of the present invention shown integrated with a 2 room controller of a heating, ventilating and air con- 3 ditioning monitoring and control system of a building; 4 FIG. 2 is a block diagram of a fume hood controller, shown connected to an perator panel, the latter 6 being shown in front elevation; 7 FIG. 3 is a diagrammatic elevation of the front 8 of a representative fume hood having vertically operable 9 sash doors; FIG. 4 is a diagrammatic elevation of the front 11 of a representative fume hood having horizontally operable 12 sash doors; 13 FIG. 5 is a cross section taken generally along 0, 14 the line 5-5 of FIG. 4; FIG. 6 is a diagrammatic elevation of the front 16 of a representative combination sash fume hood having 17 horizontally and vertically operable sash doors; 18 FIG. 7 is an electrical schematic diagram of a 19 plurality of door sash position indicating switching means; FIG. 8 is a cross section of the door sash 21 position switching means; and, 22 FIG. 9 is a schematic diagram of electrical 23 circuitry for determining the position of sash doors of a 24 fume hood.

o 25 Detailed Description 26 It should be generally understood that a fume 27 hood controller controls the flow of air through the fume 28 hood in a manner whereby the effective size of the total 29 opening to the fume hood, including the portion of the 30 opening that is not covered by one or more sash doors will 31 have a relatively constant average face velocity of air 32 moving into the fume hood. This means that regardless of 33 the area of the uncovered opening, an average volume of air 34 per unit of surface area of the uncovered portion will be moved into the fume hood. This protects the persons in the 36 laboratory from being exposed to noxious fumes or the like 37 because air is always flowing into the fume hood, and out 1 of the exhaust duct, and the flow is preferably controlled 2 at a predetermined rate of approximately 75 to 125 cubic 3 feet per minute per square feet of effective surface area 4 of the uncovered opening. In other words, if the sash door or doors are moved to the maximum open position whereby an 6 operator has the maximum access to the inside of the fume 7 hood for conducting experiments or the like, then the flow 8 of air will most likely have to be increased to maintain 9 the average face velocity at the predetermined desired lvl. The capabilities and effectiveness of various 11 controllers of the prior art varies considerably.

12 Broadly stated, the present invention is directed 13 to a sensing means that is adapted to determine the 14 absolute position of one or more structures such as doors, 15 windows or the like that are moveable in sets of tracks.

-e ;16 The invention is not limited to doors or windows, however, S 17 inasmuch as the sensing means may be used with many types 18 of structures that are moveable along a predetermined path.

19 However, the present invention is particularly adapted for use with laboratory fume hoods of the type which have a 21 controller for accurately controlling the flow of air 22 through the fume hood to maintain an average face velocity *r 23 air moving into the fume hood, which is a function of 24 t size or area of the openings, which in turn is in part 25 a function of the positions of the sash doors of the fume 26 hood. Since it is highly desirable for fume hood S 27 controller apparatus to provide extremely rapid and S 28 effective control of the average face velocity of the fume S 29 hood, and to achieve and maintain the desired average face

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30 velocity within a few seconds after one or more doors which S 31 cover the front opening of the fume hood have been moved, 32 it is necessary that the position of the door,? be rapidly 33 and accurately determined, and to that end, the present 34 invention provides generally continuous voltage signals that are input to a fume hood controller, which uses the 36 signals to control the flow of air into and out of the fume 37 hood.

38 Turning now to the drawings, and particularly -6- 1 FIG. 1, a block diagram is shown of several fume hood 2 controllers 20 interconnected with a room controller 22, an 3 exhaust controller 24 that may be part of the room 4 controller itself and a main control console 26. The fume hood controllers 20 are interconnected with the room 6 controller 22 and with the exhaust controller 24 and the 7 main control console 26 in a local area network illustrated 8 by line 28 which may be a multiconductor cable or the like.

9 The room controller, the exhaust controller 24 and the main control console 26 are typically part of the building main 11 HVAC system in which the laboratory rooms containing the 12 fume hoods are located. The fume hood controllers 20 are 13 provided with power through line 30, which is at the proper 14 voltage via a transformer 32 or the like.

15 Referring to FIG. 2, a fume hood controller 20 is 16 illustrated with its input and output connector ports being 17 identified, and the fume hood controller 20 is connected to 18 an operator panel 34. It should be understood that each 19 fume hood will have a fume hood coh.troller 20 and that an operator panel will be provided with each fume hood con- 21 troller. The operator panel 34 is provided for each of the 22 fume hoods and it is interconnected with the fume hood 0 23 controller 20 by a line 36 which preferably comprises a 24 multi-conductor cable having eight conductors. The 25 operator panel has a connector 38, such as a 6 wire RJ111 26 type telephone jack for example, into which a lap top 27 personal computer or the like may be crnnected for the 28 purpose of inputting information relating to the 29 configuration or operation of the fume hood during initial 30 installation, or to change certain operating parameters if 31 necessary. The operator panel 34 is preferably mounted to 32 the fume hood in a convenient location adapted to be easily 33 observed by a person who is working with the fume hood.

34 The fume hood controller operator panel 34 includes a liquid crystal display 40 which when selectively 36 activated provides the visual indication of various aspects 37 of the operation of the fume hood, including three digits 38 42 which provide the average face velocity. The display -7- 1 illustrates other conditions such as low face velocity, 2 high face velocity and emergency condition and an 3 indication of controller failure. The operator panel may 4 have an alarm 44, an emergency purge pushbutton 46 which an operator can press to purge the fume hood in the event of 6 an accident. The operator panel has two auxiliary switches 7 48 which can be used for various customer needs, including 8 day/night modes of operation. It is contemplated that 9 night time mode of operation would have a different and preferably reduced average face velocity, presumably 11 because no one would be working in the area and such a 12 lower average face velocity would conserve energy. An 13 alarm silence switch 50 is also preferably provided.

14 Fume hoods come in many different styles, sizes and configurations, including those which have a single 16 sash door or a number of sash doors, with the sash doors 17 being moveable vertically, horizontally or in both direc- 18 tions. Additionally, various fume hoods have different 19 amounts of by-pass flow, the amount of flow permitting opening that exists even when all of the sash doors 21 are as completely closed as their design permits.

22 Referring to FIG. 3, there is shown a fume hood, 23 indicated generally at 60, which has a vertically operated 24 sash door 62 which can be moved to gain access to the fume 25 hood and which can be moved to the substantially closed 26 position as shown. Some types of fume hoods have a bypass 27 opening that is located above the door sash while others 28 are below the same. In some fume hoods, the first amount 29 of movement of a sash door will increase the opening at the bottom of the door shown in FIG. 3, for example, but as the 31 door is raised, it will merely cut off the bypass opening 32 so that the effective size of the total opening of the fume 33 hood is maintained relatively constant for perhaps the 34 first one-fourth amount of movement of the sash door 62 through its course of travel.

36 Other types of fume hoods may include several 37 horizontally moveable sash doors 66 such as shown in FIGS.

38 4 and 5, with the doors being movable in upper and lower -8- 1 pairs of adjacent tracks 68. When the doors are positioned 2 as shown in FIGS. 4 and 5, the fume hood opening is 3 completely closed and an operator may move the doors in the 4 horizontal direction to gain access to the fume hood. Both of the fumes hoods 60 and 64 have an exhaust duct 70 which 6 generally extends to an exhaust system which may be that of 7 the HVAC apparatus previously described. The fume hood 64 8 also includes a filtering structure shown diagrammatically 9 at 72 which filtering structure is intended to keep noxious fumes and other contaminants from exiting the fume hood 11 into the exhaust system. Referring to FIG. 6, there is 12 shown a combination fume hood which has horizontally 13 movable doors 76 which are similar to the doors 66, with 14 the fume hood 74 having a frame structure 78 which carries ee 15 the doors 76 in suitable tracks and the frame structure 78 16 is also vertically movable in the opening of the fume hood.

17 The illustration of FIG. 6 has portions removed 18 as shown by the break lines 73 which is intended to 19 illustrate that the height of the fume hood may be greater than is otherwise shown so that the frame structure 78 may 21 be raised sufficiently to permit adequate access to the 00904 22 interior of the fume hood by a person. There is generally :23 a by-pass area which is identified as the vertical area to 0 24 and there is typically a top lip portion 77 which may be 25 approximately 2 inches wide. This dimension is preferably 2 26 defined so that its effect on the calculation of the open 27 face area can be taken into consideration.

28 While not specifically illustrated, other 29 combinations are also possible, including multiple sets of vertically moveable sash doors positioned adjacent one 31 another along the width of the fume hood opening, with two 32 or more sash doors being vertically moveable in adjacent 33 tracks, much the same as residential casement windows.

34 The fume hood controller is adapted to control virtually any of the various kinds and styles of fume hoods 36 that are commercially available, and to this end, it has a 37 number of input and output ports (lines, connectors or 38 connections, all consiered to be equivalent for the -9- 1 purposes of describing the present invention) that can be 2 connected to various sensors that may be used with the 3 controller. As shown in FIG. 2, there are five sash 4 position sensor ports for use in sensing the position of both horizontally and vertically moveable sashes.

6 To determine the position of the sash doors, a 7 sash position sensing means embodying the present invention 8 is provided adjacent each movable sash door and is 9 generally illustrated in FIGS. 7, S and 9. Referring to FIG. 8, the door sash position sensing means comprises an 11 elongated switch mechanism 80 of relatively simple 12 mechanical design which preferably consists of a relatively 13 thin polyester base layer 82 upon which is printed a strip es 14 of electrically resistive ink 84 of a known constant Sees resistance per unit length. Another polyester base layer 16 86 is provided and it has a strip of electrically

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17 conductive ink 88 printed on it. The two base layers 82 e 18 and 86 are adhesively bonded to one another by two beads of

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19 adhesive 90 located on opposite sides of the strip. The base layers are preferably approximately five-thousandths 21 of an inch thick and the beads are approximately two- 22 thousandths of an inch thick, with the beads providing a 23 spaced area between the conductive and resistive layers 88 24 and 84. The switching mechanism 80 is preferably applied 25 to the fume hood by a layer of adhesive 92.

26 The polyester material is sufficiently flexible 27 to enable one layer to be moved toward the other so that 28 contact is made in response to a preferably spring biased 29 actuator 94 carried by the appropriate sash door to which the strip is placed adjacent to so that when the sash door 31 is moved, the actuator 94 moves along the switching 32 mechanism 80 and provides contact between the resistive and 33 conductive layers which are then sensed by electrical 34 circuitry to be described which provides a voltage output that is indicative of the position of the actuator 94 along 36 the length of the switching means. Stated in other words, 37 the actuator 94 is carried by the door and therefore 38 provides an electrical voltage that is indicative of the 1 2 3 4 6 7 555* 9 12 13 14 16 17 19 21 22 sofa 23 24 26 27 28 29 31 32 33 34 P7 6 ~ThA~v37 38 position of the sash door.

The actuator 94 is preferably spring biased toward the switching mechanism 80 so that as the door is moved, sufficient pressure is applied to the switching means to bring the two base layers together so that the resistive and conductive layers make electrical contact with one another and if this is done, the voltage level is provided. By having the switching means 80 of sufficient length so that the full extent of the travel of the sash door is provided as shown in FIG. 3, then an accurate determination of the absolute sash position can be made.

It should be understood that the illustration of the switching mechanism 80 in FIGS. 3 and 5 is intended to be diagraimmatic, in that the switching mechanism is preferably actually located within the sash frame itself and accordingly would not be visible as shown. The width and thickness dimensions of the switching mechanism are so small that interference with the operation of the sash door is virtually no problem. The actuator 94 can also be placed in a small hole that may be drilled in the sash door or it may be attached externally at one end thereof so that it can be in position to operate the switch 80. In the vertical moveable sash doors shown in FIGS. 3 and 6, a switching mechanism 80 is preferably provided in one or the other of the sides of the sash frame, whereas in the fume hoods having horizontally movable doors, it is preferred that the switching mechanism 80 be placed in the top of the tracks 68 so that the weight of the movable doors do not operate the switching mechanism 80 or otherwise damage the same. It is also preferred that the actuator 94 be located at one end of each of the doors f or reasons that are described in the cross-referenced application entitled A method and apparatus for determining the uncovered size of an op:--ing adapted to be covered by multiple moveable doors by Ahmed et al., Serial NJo- 590,194.

Turning to FIG. 9, the preferred electrical circuitry which generates the position indicating voltage is illustrated, and this circuitry is adapted to provide -11- 1 two separate voltages indicating the position of two sash 2 doors in a single track. With respect to the cross-section 3 shown in FIG. 5, there are two horizontal tracks, each of 4 which carries two sash doors and a switching mechanism is provided for each of the tracks as is a circuit as shown 6 in FIG. 9, thereby providing a distinct voltage for each of 7 the four sash doors as shown.

8 The switching means is preferably applied to the 9 fume hood with a layer of adhesive 92 and the actuator 94 is adapted to bear upon the switching means at locations 11 along the lei.-jth thereof. Referring to FIG. 7, a 12 diagrammatic illustration of a pair of switching means is 13 illustrated such as may occur with respect to the two 14 tracks shown in FIG. 5. A switching mechanism 80 is 15 provided with each track and the four arrows illustrated 16 represent the point of contact created by the actuators 94 17 which result in a signal being applied on each of the ends 18 of each switching means, with the magnitude of the signal Re 19 representing a voltage that is proportional to the distance between the end and the nearest arrow. Thus, a single 21 switching mechanism 80 is adapted to provide position 22 indicating signals for two doors located in each track.

23 The circuitry that is used to accomplish the voltage 24 generation is shown in FIG. 9 and includes one of these 25 circuits for each track. The resistive element is shown at 26 84 and the conductive element 88 is also illustrated being 27 connected to ground with two arrows being illustrated, and 28 represented the point of contact between the resistive and 29 conductive elements caused by each of the actuators 94 30 associated with the two iseparate doors. The circuitry 31 includes an operational amplifier 100 which has its output 32 connected to the base of a PNP transistor 102, the emitter 33 of which is connected to a source of positive voltage 34 through resistor 104 into the negative input of the operational amplifier, the positive input of which is also 36 connected to a source of positive voltage of preferably 37 approximately five volts. The collector of the transistor 38 102 is connected to one end of the resistive element 84 and -12- 1 has an output line 106 on which the voltage is produced 2 that is indicative of the position of the door.

3 The circuit operates to provide a constant 4 current directed into the resistive element 84 and this current results in a voltage on line 106 that is 6 proportional to the resistance value between the collect 7 and ground which changes as the nearest point of contact 8 along the resistance changes. The operational amplifier 9 operates to attempt to drive the negative input to equal the voltage level on the positive input and this results in 11 the current applied at the output of' the operational 12 amplifier varying in direct proportion to the effective 13 length of the resistance strip 84. The lower portion of 14 the circuitry operates the same way as that which has been 15 described and it similarly produces a voltage on an output 16 line 108 that is proportional to the distance between the 17 connected end of the resistance element 84 and the point of 18 contact that is made by the actuator 94 associated with the 19 other sash door in the track.

From the foregoing description, an improved 21 sensing means for determining the position of sash doors is 22 provided that offers advantages over the prior art. Even 23 though one switching means 80 is provided for each track, 24 the unique circuitry enables position indicating voltages 25 for two sash doors that are moveable in a single set of 26 tracks to be produced. The apparatus is simple to install 27 and generates the signals utilizing a minimum of components 28 which contributes to its extremely good cost effectiveness 29 in terms of its manufacture.

While various embodiments of the present inven- 31 tion have been shown and described, it should be understood 32 that various alternatives, substitutions and equivalents 33 can be used, and the present invention should only be 34 limited by the claims and equivalents thereof.

Various features of the present invention are set 36 forth in the following claims.

Claims (1)

1. 4. 2 wherein two sash doors are moveable in one set of tracks, 3 said circuit means providing a substantially constant 4 4 electrical current through a portion of said resistance means between opposite end portions of said resistaice 6 means and the nearest switch location, said circuit means 7 thereby providing voltage signals that are proportional to ~8 the distance between each end portion of said resistance 4 9 means and the ne- .est switch location. 1 Claim 15. Apparatus as defined in claim 14 2 wherein the fume hood has at least four sash doors, two 3 sash doors being moveable in each set of tracks, each of ,06eue 4 said circuit means providing a substantially constant ~5 electrical current through a portion of said resistance 6 means between opposite end portions of said resistance 7 means and the nearest switch location, said circuit means 8 thereby providing voltage signals that are proportional to 9 the distance between each end portion of said resistance means and the nearest switch location. 1 Claim 16. Apparatus as defined in claim 2 wherein one of said actuating means is attached to each 3 sash door at a predetermined known position along its 4 width. 1 Claim 17. Apparatus as defined in claim 18 wherein each of said sets of tracks are located in a common frame means, said frame means being vertically moveable relative to the opening of the fume hood. DATED this 4th day of JANUARY, 1993. LANDIS GYR POWERS, INC Attorney: LEON K. ALLEN Fellow Institute of Patent Attorneys of Australia of SHELSTON WATERS *go Si S S.. -19- ABSTRACT OF THE DISCLOSURE A sensing means for determining the absolute position of one or more structures such as doors, windows or the like that are moveable in sets of tracks. Apparatus comprises an electrical switching means having an elongated electrical resistance means with a predetermined resistance value per unit length located adjacent to one of the sash doors actuator means oe* (94) associated with the sash doors for operating said switching means, circuit means adapted to provide a or 10 substantially constant electrical current through a portion of said resistance means (84) between an end e, portion of said resistance means (84) and the nearest 60 switch location, said circuit means thereby providing a voltage signal having a magnitude that is proportional to the distance between said end portion of said resistance ao means and the switch location. 0