CA1113278A - Air velocity gauge - Google Patents

Abstract

AIR VELOCITY GAUGE
Abstract of the Disclosure An air velocity gauge for direct measurement of low air flow or draft rates in the range of 20-400 feet per minute comprising a generally flat housing of quadrilateral shape defining a draft way therethrough and a set of opposed draft way inlet and outlet openings that are aligned with the plane of the housing that approximate the size and general shape of the way. A vane formed from a strip of Mylar*polyester film is suspended pendulum fashion from the upper portion of the housing adjacent the draft way inlet and is creased longitudinally of same to ridgify the vane to act as such rather than as a flexible flap. The housing itself is in the form of an open centered center frame with open sides, to each side of which is applied a transparent side plate held in place by an adhesively backed opaque scale or scale plate that adheres to lands defined by the housing center frame for this purpose. The scale plates are formed with mirror image windows struck on the arc of movement of the vane that are calibrated to directly read air flow velocity in proportion to the vane deflection about its pivot axis. The housing end plates are formed with cooperating ports for housing a level bubble vial for leveling the gauge; the housing side plates are also formed to define fastener receiving sleeves for mounting the gauge in use.

* - Trade Mark

Description

~3Z78 This is a division of copending Canadian Patent Application Serial No. 314, 430, filed October 26, 1978 and assigned to the present assignee.

This inven~ion relates to an air velocity gauge, and more particularly, to an air velocity gauge for measuring low air flow rates, such as those in the 20-400 feet per minute range.
The Occupational Safety & Health Administration (OSHA) regulations and other sources of ventilation and safety standards now in general use have made it important to be able to accurately measure low air flow rates so as to be able to show compliance with standards that have been set.
As an example of the problems presented, OSHA
regulations dealing with the operation of spray painting booths require that the minimum maintained air flow velocity or draft through the booth be in the 75-250 foot per minute ;
rage, depending on the design of the booth and other factors.
Where the painting operation in the booth is electrostatic and without air guns, and no operatcr is present, the minimum maintained air flow velocity or draft through the booth may be in the 50-75 feet per minute range.
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~ H~wever, conventional air velocity measuring devic~s ~,, .
are expensive, and are not particularly suited for measuring air flow at the very low flow rates indicated, due to such factors as multiple and intricate moving parts, inertial loàds to be overcome, and actuating power requirements.
One conventional air velocity measuring device is the so-called hot wire anemometer, which requires electrical power to opera~e and costs in the $300.00 to ~500.00 range.

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A less expensive mechanical device available is of the rotational vane type that involves a number of intricate moving parts and costs in the neighborhood of $150.00 or more.
~ lowever, the Applicants are not aware of the availa-bility of air velocity gauges selling for under $50.00 that function reliably in the ultra low 20-400 foot per minute range.
A principal object of this invention is to provide a low cost air velocity gauge of simplified and trouble free nature that reliably measures air ve]ocity or draft movement in the low air flow 20-400 feet per minute rate range.
- An~ther principal object of the invention is to provide a si~plifed but accurate air velocity gauge having only one moving part, and that relies only upon the impetus of the air m~vement itself to operate the vane, and thus has no external power requirements.
~ _ An~ther principal object o the invention is to : provide an air velocity gauge arrang~ment in which the read out is provided by direct action of the air movement on a free swinging vane of ultra low inertial resistance, to provide an air velocity gauge that is formed from inexpensive ~ plastic materials with metal parts as such minimized, and -~ - comprise an air velocity gauge arrangement that can be . readily understood and used by those with minimal experience with air flow measurement devices.
. Yet another principal object of the invention is to provide a pendulously mounted vane type gauge in which the : . 2.

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vane is of special construction that is particularly suited for accurate air velocity measurement in the ultra low flow rate ranges indicated.
Still other objects of the invention are to provide an air velocity gauge arrangement in which the housing is free of mechanical fasteners, that is designed for easy fit-together assembly with minimal tool requirements, and employs a pendulously mounted vane formed from wear and handling resistant light weight plastic material of film dimension thickness that is especially arranged for precluding fle~ing of the vane, and to provide an air velocity gauge that is inexpensive and simple to manufacture and assemble and is accurate and has long life in use.
Applicant's above referenced copending Canadian patent application is directed to one aspect of an air velocity gauge constructed in accordance with the teachings of the present invention. Another aspect of the present invention is directed to the improvement in an air velocity gauge which includes a flat housing of generally quadrilateral configuration defining a draft way therethrough between opposite sides of the housing that is coplanar with the housing and having a vane mounted in the housing extending across and transversely of the draft way for movement under the impetus of air flow through the draft way and scale indicia formed on the housing for read-ing an air velocity flow through the draft way. The improvement comprises: an open centered center frame of quadrilateral configuration having two of its opposed ends ported to form the inlet and out~et ends of the draft way, with the frame beang op~n at either side of the frame. The frame at both of the sides ;' ' dm:\~ \ -3-, .

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~L~13Z`^~8 defines dual level abutment surfacing comprising a first series of lands spaced from the frame and coplanar with a first plane paralleling the housing and a second series of lands spaced about the frame and coplanar with the second plane paralleling the housing and spaced outwardly of the first plane.
A pair of side plates are positioned one at either side of the frame with the respective side plates abutting the first series of lands and being interrupted to receive the lands of the second series of lands. A pair of scale plates are positioned one at either side of the frame adjacent and outwardly of the respective side plates. Each scale plate has its inwardly facing sides adhesively coated and adhered to the second series of lands to secure the side plate and scale plate at either side of the frame to the frame. The vane is pivotally mounted adjacent one end thereof in the frame adjacent the draft way inlet and hangs in an operative position pendulum style across the draft way for free swinging movement about an axis disposed crosswise of the housing under the impetus of air flow through the draft way. The scale plates define coinciding mirror image arcuate windows strùck on a radius centered on the vane pivotal axis and having a length no greater than the length of the vane. The windows are calibrated to read air flow rate through the way in proportion to the ; deflection of the vane under the impetus of the air flow ; through the way. The side plates are transparent at the portions of same underlying the respective scale plate windows Other objects, uses, and advantages will be obvious or become apparent from a consideration of the following detailed description and the ~application drawIn~s in which like reference numerals indicat~ like parts throughout the several views.

dm~ 4-Z7~3 , In the drawings:
Figure 1 is a diagrammatic frontal perspective view :~
illustrating a preferred embodiment of the invention;
Figure 2 is an exploded perspective view diagram-matically illustrating the basic components of the device and their manner of assembly;
Figure 3 is a fragmental top plan view of the device with the center frame omitted, illustrating the manner in which the two side plates of the housing assembly are formed to cooperate to receive and mount the level bubble -vial of the device;
Figure 4 is a top plan view of the vane mounting bracket that is diagrammatically illustrated in Figure 2 (where it is shown displaced from its vane mounting position within the housing center frame);
Figure 5 is a plan view of the special vane,employed ', in accordance with the invention;
. .Figure 6 is an end view of the vane shown in Figure . 5, taken su~stantially along line 6--6 of Figure S and on an ~, enlarged scale; and . . Figure 7 is a fragmental elevational view of a ,~
portion of one of the housing side plates illustratlng the . , vane bracket slideway that is definecl by the housing side , pla~es. , , However, it is to be distinctly understood that the - specific drawing illustrations provided are supplied primarily .
`. to comply with the requirements of the Patent Laws, and that the invention is susceptible of other embodiments which will . ~ .

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1~327~3 be obvious to those skilled in the art, and which are intended to be covered by the appended claims.
GENERAL DESCRIPTION
Refer~nce numeral 10 of Figures 1 and 2 generally indicate a preferred embodiment of the invention which comprises a housing 12 formed by a central open centered frame 14 which is open at either side 16 and 18 of same for application thereto of side plates 20 and 22 that are preferably formed from a suitable transparent material.
The outwardly facing surfaces 24 and 26 of the respective side plates 20 and 22 each have applied to same the respective gauge or scale plates 28 and 29. Plates 28 and Z9 are formed from a suitable opaque material (aluminum in the ill~strated embodiment), and are formed to define the respective arcuate slots 30 and 31 in mirror image relation to form th.~ respective window openings 33 and 33A that provide for visibility through the respective side plates 20 and 22 to the other :;ide of the housing 10 for purposes of reading th~
gauge, The respective gauge plates 28 and 29 on the inwardLy facing sides of same each bear an adhesive backing 35 coexten-sive there~ith for adherence to cooperating parts of both the respective side pla'tes 20 and 22 and the housing frame 14 to secure the components of the housing 12 together without employing mechanical fastening de~ices.
For this purpose! the'central frame 14 at both sides 16 and 18 o~ same is formed with a first set of lug or abutment structures 32 spaced thereabout each'defining surfacing 36 ' ~;. , .
~` against which the inwardly facing sides 24A and 26A of the ~.

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~327~3 respective side plates 2Q and 22 seat at either side of the frame 14. The frame 14 is also formed with a second set of lug or abutment structures indicated-at 34 each defining an abutment surfaci~ng 38 that is to be engaged by the adhesive coating 35 for adhering the respective scale plates 28 and 29 to the frame 14.
The surfacings 36 of the respective lug structures ' 32 at either side of frame 14 are in coplanar relation with the surfacings 36 being coplanar with the respective planes 37 at either side of frame 14 (see Figure 3).
. ~he surfacings 38 on either side of the frame 14, ; on the other hand, are coplanar with the respective planes 39, at either side 16 and 18 of the frame 14, disposed outwardly of the resFective planes 37, and are to be coplanar with the outer surf2ces 24 and 26 of the respective side plates 20 and 22 in the assembled relation of the frame. The planes 37 and 39 are indicated in broken lines in Figure 3. :
~or this purpose, the respective side plates 20 ar:d 22 ar~ notched as indicated at 41 in ~igures 2 and 7 about ,~ their re~p~ctive sides or marginal edgings to receive the lug or abutment structures 34 that define the respective abutme~t surfacings 38 in the assembled relation of the housing. Th~
notches 41 are o~ yarient configurations complimenting the .' outline of the abutment or lug structures 34 they are to receive.
~.~ ' It wi,ll thus be seen that in accordance with the l present invention, the side plates 20 and 22 are applied I ,within the respective sides 16 and 18 of the housing center : 7.
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1113Z7~3 frame 14 to have their respective surfaces 24A and 26A seat against the respective surfacings 36, which thus act as locating stops for mounting the side plates 20 and 22 in place within the frame 14. The surfacings 36 are thus set bacK
within the frame 14 approximately the thickness of the respective side plates 20 and 22 so that the adhesive coatings 35 of the respective gauge plates 28 and 29 will seat against both the side plate surfaces 24 and 26 (of the respective side plates 20 and 22) as well as the abutment surfacings 38, when the respective gauge plates 28 and 29 are appliea within the sides 16 and:18 cf housing 14.
Further in accordance with the invention, the side plates 20 and 22 are each formed with the respective receptacl~
' segments 4C that are of complemental segment form to define in the assembled relation of the housing 12 the chamber 42 in which a familiar form of level bubble capsule or vial 43 is mounted for leveling the gauge 10.
qhe respective side plate~ 20 and 22 also each define' an ~pper sleeYe segment 44 and a lower sleeve segment 46. The rçspective sleeve segments 44 and 46 are proportioned such that when the side plates 20 and 22 are in assembled ~' relation ir the hous'ing 12, the sleeYe segments 44 and the sleeve segn.ents 46 are at or near substantial abutting relation wit'h'out effecting the firm seating of the side plates 20 and , 22 against the surfacings 36, these,aligned sleeye segments ,define the respective sleeve structures 45 and 47 (see Pigure 1~ through which suitable attachment screws may be applied for securing the gauge in operating position. The sleeve .. ~ .

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segments 46 are of oblong configuration in transverse cross ~ection corresponding to the horiæontal axis Df same to permit the gauge to be leveled by observing the bubble of the level vial through suitable window 48 formed in the center frame 14 or the windows 49 defined by the openings 51 formed in the respective gauge plates 28 and 29.
The gauge plates 28 and 29 are each apertured as indicated at 44A and 44B, respectively, to receive the outwardly protruding portions of sleeve segments 44 and 46 at either side of the housing section 14. ' As indicated in Figure 2, the center frame 14 defin,es opposing end walls 50 and 52 which are respectively formed to define the respective window openings 54 and 56 that form the inlet and outlet openings to the housing draf:
way 55 through which the air flow to be measured passes through the gauge. The gauge inlet 54 and outlet 56 each have a size and configuration roughly approximating the dra-'t way 55 in ~ertical section so that the air flo~ through the gauge passes therethrough in a substantially unimpeded manner.
,3pplied above the window opening 54 is a slide in type mounti,n~ bracket 58 that mounts a novel vane 70 in its ' ~-operati,ng position ~ithin the gauge 10. It is a feature of ~ , -the invention that the side plates 20 and 22 are formed on ' thei~ respectiVe ~ide surfaces 24A and 26A to define the respective slide ways 60 t~at are shaped to slidably receive and accurately position the bracket,58 and its vane 70 so that the Vane 70 will be positioned vertically above and in al~gnment with the'datum zero marking 72 of the respective gauge plates 28 and 29 when in its at rest position.

~13Z7~3 As indicated, the vane 70 is of special significance.
In accordance with a preferred embodiment of the invention, it is formed from a polyester stripping having a thickness of approximately one mil ~0.001 inch), and thus the stripping is of film thickness dimensions. In a highly successful embodiment the stripping is formed from Mylar polyester film having a thickness of one mil. Mylar is a trademark of E. I. Du Pont de Nemours & Co. for its polyester plastic film. Vane 70 is also proportioned widthwise and lengthwise to effectively partition off the sides of the draft way 55 that are ()n either side of same.
The vane 70, further in ~ccordance with the invention, is imperforate below its pivotal mounting, and is formed with indentation means 73 extending along its longitudinal axis for sufficiently rigidifying the vane 70 so that when acting to measuro air flow through the gauge 10, it will remain ir: a substanti.llly planar or rectilinear configuration longitudinally of same, rather than flex laterally thereof in the manner cf a fréely :-lexing ribbon. In the form shown, the indentatien means 73 ~:omprises a center apex f~rming crease 74 and a pair ~ ', of apex forming creases 75 and 77 equally spaced from, and on either side of the center crease 74, with the creases 74, 75 and 77 having approximateiy the angulations indicated in Figure 6. The indentation means 73 thus defines a center ridge structure 76 along the mid portion of the vane 70 that extends in alignment with its longitudinal axis for maintaining the vane in a rectilinear substantially planar configuration while acting as a~measuring vane in the gauge.
~ he vane 70 is journalled on the mounting bracket 58 by having a journalling pin 84 applied to the upper end 86 of the vane 70. It is a feature of the invention that the .

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~13278 journalling pin 84 be of as small a diameter as reasonably possible to minimize the adverse effect of static friction, with the pin being .015 inch in a commercial embodiment. The pin at its outwardly projecting end portions 87 and 88 rests in the respective journalling slots 89 and 91 (see Figures 2 ;
and 4) of the bracket 58 that are vertically disposed when the gauge 10 is mounted in its operating position. The vane 70 is preferably oriented with respect to its bracket 58 within the housing 12 so that the ridge structure 76 faces in the direction of air movement into the housing 12, as indicated by the arrows 90 of Figures 1 and 2.
The vane 70 is thus char~cterized by being in the form of a light weight but tough, -~ear resistant material cf film thickness dimensions, in elongate strip form, in whic~
the film stripping involved is creased or crimped longitudinally thereof to define the indentation means 73 that holds the vane 70 auainst flexture laterally of its plane. While th~
vane 70 is of flat angulation configuration in transverse section, it is substantially planar within the rather thin transverse dimension range indicated in Figure 6.
The gauge 10 is employed by mounting same in the air flo~ to be measured, with the instrument draft way 55 aligned with the direction of air flow so that the air flow enters inlet opening 54 and leaves outlet opening 56. This may be done by applying suitable fastening devices to the sleeve structures 45 and 47, with the instrument being leveled by observance of the level bubble vial 43 to align the vane 70 with the zero datum marking 72 of the gauge plates 28 and , 11. ' ~ ~ 3Z7a 29 for the condition of zero air flow through the gauge.
When the air movement to be measured is generated by operation of the ventilating equipment or the like that is involved, the resulting air movement or draft through the gauge 10, and specifically through its draft way 55, impinges on the suspended vane 70, which is thus deflected to the left..of the showing of Figures 1 and 2, in proportion to the flow rate involved, about its pivotal mounting, to read directly on the instrument scale defined by the gauge plates 28 and 29 the velocity of the air flow in question. The vane, of course, is of sufficient length so that its pendant end 75 extends across, and thus is visible through, the windows 33 and 35 of the instrument 10.
SPECIFIC DESCRIPTI~N
The frame 14 and bracket 53 may be formed from a suitable opcque plastic material, such as white ABS.
As indicated in Figures.l and 2, the frame 14 is of generally q~adrilateral configuration and preer~ably is of one piece construction,:top wall 100 and bottom wall 102 in ..
addition to the end walls 50 and 52. The window opening 48 is appropriately centered with the location that the level bubble vial receiving chamber 42 is to have ih the assembled relation of the housing 12.
. The lug or abutment structures 32 and 34 may be of any convenient configuration and location, the important .~ . . .
. thing being that they define the surfacings 36 and 38 that are respectively oriented in coplanar planes.in the manner ` indicat.ed such that the surfacings 36 are coplanar in plane 12.

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37 while the sur~acings 38 are coplanar in plane 39 (see Figure 3). It is also desirablc that the surfacings 36 and 38 be in more or less alternate relation about the respective sides 16 and 18 of frame 14. In the form shown, at the upper corners of the frame 14, the surfacings 36 and 38 are defined by the oppositely oriented cells 104 and 106 that are closed at one side of the frame 14 to define surfacings 38, and are open at the other side of same to define surfacings 36. Thus, the cell 104 at one corner of the frame 14 opens at its side 16 while the cell 10~ at the other corner of the frame opens at its slde 18, and the cells 106 are similarly arranged. The remaining surfacings 36 and 38 are formed by the lugs 108 and ribs 110 that have been diagrammatically illustrated in Figure 2. Ihis specific arrangement however, is a manner of choice and design, and the designer may use any abutment forming configurations he considers appropriate consistent with the objectives of the invention and an appropriate manner of mzking frame ~4, which preferably is by a suitable injection molding procedure.
T~e side plates 20 and 22 are preferably each of one.
piece COnStlUCtiOn formed by employing a suitable injection molding procedure and arranged so that they are interchangeable.
Thus, the plates 20 and 22 are each ~ormed with a set of slide ways 60 on either side of same (on the respective surfaces 24~ and 26A), as indicated for side plate 22 in Figure 2. The side plates 20 and 22 are preferably formed from plexiglas or a suitable high impact acrylic plastic material, but are totally or substantially transparent for .'`, .
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good visual viewing of the vane 70 through the windows 33 and 33A.
The vial receiving receptacle segments 40 each comprise an upper wall segment 120, a lower wall segment 122 (see Figure 2), and side wall segments 124 and 126. The wall segments 124 and 126 are recessed as at 128 and 129 to receive the ends of the vial 43 in substantial abutting relation thereto. The lower wall 122 is formed with a central ridge 130 which engages under the back of the normally arched vial 43 for orienting purposes.
In applying the vial 43 to the gauge, after ~ne side plate 20 oc 22 has been mounted in its operative position within the frame 14, the frame is eriented to dispose the inside sur~acing 24A or 26A of the side plate in question upwardly, ~nd the vial 43 is placed in its operative positi~n within the then upwardly facing receptacle section 40 defined by the sid~ plate in question. The vial 43 may then be secured in place by applying a drop or two of the adhesive at either end of same, after which the second side plate is secured to the frame in the indicated manner to mount the ~ial in it3 operative position.
,~s indicated, the sleeve sections 44 and 46 are proportioned so that when the side plates are assembled to frame 14, the aligned sections 44 and 46 of each frame are at or near substantial abutting relation, while leaving the side plates 20 and 22 to seat firmly against frame surfacings 36, whereby the correct spacing between the slideways 60 is : ., ~ provided to slidably accommodate the vane bracket 58.
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32~8 Por each side plate 20 and 22, the slide ways 60 comprise a pair of,upstanding opposed flanges 140 and 142 integral with an upstanding end wall 144, with the ~lide way being open as at 146 to receive bracket 58. The slide ways 60 are each formed to define adjacent the open end 146 thereof an indentation or socket 148 for both keying the bracket 58 to the frame 14 in its mounted position, and properly locating the vane 70 with respect to the datum zero marking 72 of the ~ ' gauge plates 28 and 29.
The gauge plates 28 and 29 are suitably formed from aluminu~ plate of a suitable gauge. The slots 30 and 31 are of mirror image relation and the outer surfaces 150 and 152 of the respective plates 28 and 29,are formed to have the scale indicia indicated for plate 28 in Figures 1 and 2. The sIots 30 and 31 are thus struck on an arc that is coaxial with the axis of pivotal movement of the vane 70. The gauge plates 28 and 29 are suitably formed with the windows 44A and 44B to receive the projecting ends of the respective sleeve segment's 44 ~nd 46, and to define the respective windows 51 .
that expose for,~iewing from'the sides of frame 14 the level vial 43, and specifically its bubble 154 in its positioning ' - between the usual level locating lin'es 156 and 158 that are indicated in the drawings.
The vane mounting bracket 58 is more specifically illustrated in Figure 4 wherein it will be seen that the ' bracket 58 comprises the frame 160 of generally H shaped '; configuration defining elongate frame members 162 and 164 , that are connected by cross frame p,ortion 166. The frame .. ..

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members 162 and 164 at their like ends 168 are each suitably shape~ to define the respective mounting slots 89 and 91 that pivotally mount the vane pivot pin 84. The vane pin 84 rests within the slots 89 and 91 to pivot same about pivot axis 170.
The bracket frame members 162 and 164 at their like ends 172 are each formed to define the respective protuberances 174 that are round in configuration for snap fitting into the respective recesses 148 formed in the respective slide ways 60.
. The bracket 58 is formed with tab portion 176 extendin~ f~om cross frame portion 166 and bearing handle portion 178 that is formed to fit flush within the slide way opening 180 defined by the housing frame 14 end wall 50 when the bracket 58 is received in its indicated operative positicn within the frame 14. The housing 12 ~nd bracket 58 are arran~ed so that wher. the gauge is mounted ln its "level" position, as indicated by vial bubble 154, and the vane bracket protuberances : ,~
174 are seat.ed in slidway sockets 14~, the vane pivot axis 170,.the vane ? and the zero datum markings i2 are coplanar : in a verticcl plane (assuming zero f.Luid flow through draft ~ way 55, which is the.at rest position of vane 70).
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: fundamental aspect of the invention is that the vane 70 must . be of sufficiently light weight, low mass and inertia characteristics to be fully responsive to air velocities on the low order indîcated, and yet be sufficiently tough to resist normal : handling for cleaning purposes. It is also essential for 16.
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reading accuracy purposes that the vane have sufficient stiffness or rigidity to act as an elongate rectilinear member, rather than flex in the familiar flap like manner under the air movements through the gauge.
The Mylar polyester film material having a thickness -of 1 mil was finally hit upon as providing the light weight, low insertia, and toughness characteristics desired, but the polyester material in question ha~ing that thickness is highly flexible. The Applicants in their experimental work with reference to the vane 70 hit upon the utilization of the indent~tion of the vane along its longitudinal center to provide the stiffness or rigidity r~quired.
"he showing of Figure 6 illustrates the indentation arrangement that is preferred including the angulations employed in a successful commercial em~odiment of the invention.
As a matter of practice, the angulation of the apexes 74, 75 and 77 may lie in the range of from approximately 120 degrees to approxirlately 140 degrees and provide the vane with the requisite rigidity along its mid po~tion that will resist flexing of the vane laterally thereof.

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.s indicated in Figure 6, the vane 70 contemplates that the st:rip 73 wiil be slightly bowed along the length thereof in the direction of the apex i4, within a plane measuring (l.032 inch in thickness. It is preferred that the ~ane 70 be mounted within the gauge to dispose the vane 70 such that the apex 74 faces in the direction of air movement toward the vane, as this presents the generally concave side of the vane for engagement by the air flow to be measured.

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~ 17-, - . -1~3278 Vane 70 as so oriented seems ~o have maximized stiffness characteristics. However, the vane will provide satisfactory results if positioned so that the apex 74 faces in the opposite direction.
As indicated, the pivot pin 84 for the vane should be of minimal diameter to minimize stick friction problems.
In the form shown, the pin is applied to the vane by slitting the vane where indicated at l90 and l9l and p~ssing the pin through such slits in the manner indicated in Figure 5, after which the pin is bonded to the vane by applying a drop of a suitable ad~esive to one or both of the slits l90 and l9l.
Vane 70 is ?roportioned widthwise and lengthwise to substantially partition off draft ~ay 55 in its at rest position for maximum sensitivity when air movement through draft way 55 occurs.
In the form shown, the upper end 86 of the vane 7~ is of reduced width to clear the inner ends of the slide ways 60 under maximized air velocity reading conditions.
- It will therefore be seen that the invention provides an air velo-ity gauge of simplified and inexpensive construction in which th_ fr~me is composed of few and simple parts that are secured together without requiring mechanical fastening devices. The only moving part in the device is the vane that is suspended pendulum fashion for pivoting movement about an axis that extends crosswise of the gauge housing and transversely of the direction of movement of the air through the gauge.
The vane itself is of special significance in being :
arranged to be sufficiently light weight and low insertia so as to be responsive to air movements of the low order indicated, .~ .
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The foregoing description and the drawings are given merely to explain and illustrate the invention and the invention is not to be limited thereto, except insofar as the appended claims are so limited, since those skilled in the art who have the. disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.
. WE CLAIM:

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Claims (6)

1. In an air velocity gauge including a flat housing of generally quadrilateral configuration defining a draft way therethrough between opposite sides of the housing that is coplanar with the housing and having a vane mounted in the housing extending across and transversely of the draft way for movement under the impetus of air flow through the draft way and scale indicia formed on the housing for reading of air velocity flow through the draft way, the improvement wherein said housing comprises:
an open centered center frame of quadrilateral configuration having two of its opposed ends ported to form the inlet and outlet ends of the draft way, with said frame being open at either side of said frame, said frame at both said sides thereof defining dual level abutment surfacing comprising a first series of lands spaced about said frame and coplanar with a first plane paralleling the housing, and a second series of lands spaced about said frame and coplanar with a second plane paralleling the housing and spaced outwardly of said first plane, a pair of side plates positioned one at either side of said frame, with the respective side plates abutting said first series of lands and being interrupted to receive the lands of said second series of lands, a pair of scale plates positioned one at either side of said frame adjacent and outwardly of the respective side plates, said scale plates each having their inwardly facing sides adhesively coated and adhering to said second series of lands to secure the side plate and scale plate at either side of said frame to said frame, said vane being pivotally mounted adjacent one end thereof in said frame adjacent the draft way inlet and hanging in an operative position pendulum style across said draft way for free swinging movement about an axis disposed crosswise of the housing under the impetus of air flow through said draft way, said scale plates defining coinciding mirror image arcuate windows struck on a radius centered on said axis and having a length no greater than the length of said vane, with said windows being calibrated to read air flow rate through said way in proportion to the deflection of said vane under the impetus of said air flow through the way, said side plates being transparent at the portions of same underlying the respective scale plate windows.

2. The improvement set forth in claim 1 including:
means for removably mounting said vane in its said operative position;
said vane mounting means comprising:
a removable bracket, slidably mounted between said side plates, in which said vane is pivoted, said bracket and said side plates including snap fit means for setting said bracket within the housing to dispose said vane in its said operative position.

3. The improvement set forth in claim 1 wherein:
said side plates include aligned sleeves above and below said way for receiving fastener means for mounting the housing on a support.

4. The improvement set forth in claim 3 wherein:
said sleeves below said way are of elliptical configuration for adjusting the housing to position said vane at the zero datum calibration of said windows.

5. The improvement set forth in claim 1 wherein:
said side plates above said way are formed to define a level bubble vial receiving chamber, and a level bubble vial mounted in said chamber, said frame being apertured for reading of said vial.

6. The improvement set forth in claim 1 wherein said vane comprises:
a length of polyester of film dimensions having indentation means extending longitudinally thereof for holding said vane length against flexure.