USRE21127E - boyle - Google Patents

Description

June 27, 1939. J, BOYLE Re. 21,127

AIR VELOCITY METER Original Filed Dec. 23, 1933 3 Sheets-Sheet l June 27, 1939. J, R, BOYL: Re. 21,127

AIR VELOCITY METER I Original Fil ed Dec. 25, 1953 3 Sheets-Sheet 2 J n T M' MM June 27, 1939.

J. R. BOYLE AIR VELOCITY METER 5 Sheets-Sheet 5 Original F'iled Dec. 23, 1953 imQshock will not injure these .Reiesued June 27, 1939 Joann. 'Boylefc'hicago, 111., assignor .tolllinoia I Testing Laboratories, Inc., Chioagm'IlL, a corporation in Illinois Original No. z,oao,s4s, dated November 17, 193s, Serial No. 703,753, December-'23, 1933. Application for 149,918

3'! Claims. (Cl. 73-4802) The present, invention relates to an air velocity meter. Y i

One of the principal objects of the invention is to provide an, improved construction of small,-

5 compact, portable meter which can be conven iently carried from place to place for measur-.

ing air velocities. In this regard, it is a further object of the invention to provide an improved I meter which is constructed and balanced for accurate operation in any plane, 1. e.,' it can be held or setvertically, horizontally, or at any interinediate angular position for measuring the velocity of an air stream flowing in any direction. This feature is of decided advantage for ll enabling one to determine accurately the angle or direction of a low velocity air flow by merely comparing readings with theinstrument held at di fl'erent angles. 3

Another object of the invention is to provide .1 an improved construction of .meter of extreme sensitivity, capable of accurately measuring air currents of very low velocities. For example, meters which I have heretofore constructed embodying my invention are capable of accurately measgg uring such ve'ry feeble air currents as may be induced in the free air of a room by heated air rising from a radiator, or as may be set up by window ventilation or byconditioned. air circulated through the room by air conditioning, ducts. Thus, my improved meteris of-marked utility for heatingand ventilating engineers, in that it enables accurate determination to be made of ,the direction and velocity of air currents in different parts of a room or otherenclosure, and gg to determine the velocities of air currents passing through inlet or exhaust ducts associated with an air conditioning system, etc.

, ,Another'object of the invention is to provide ,a meterof the above cliaracteristics which is 4o also rugged and durable so that it can withstand without injury the most severe shocks and jars to which a portable instrument is ordinarily subjected. Inthis regard, it is an object Oftheinvention' to provide improved. means which is operative when the meter is not in use to imposea locking'force on the moving system so as to prevent movement thereof, and which is also 5perative to relieve relatively delicate bearings of the load ,of the moving system so that jar or bearings or other parts. The efllcacy of this improved construction has been demonstrated by meters 'constructed in accordance with mydnvention which have been dropped from the height of a table without g -in;|u ry; I

reissue June 23, 1937, Serial No.

My improved meter is preferably constructed as a direct reading instrument calibrated to indicate directly the air velocity in feet per minute, and it is another object of the invention to provide improved damping means which will prevent objec- 5 tionable oscillation or fluttering of the indicating pointer when reading rapidly pulsating air currents. The prior direct reading meters with which I am familiar have utilized air'vanes and other like damping devices-but these damping in devices do. not prevent the aforesaid objectionable oscillation of the indicator, which oscillation may be so wide and rapid under some conditions as to make the reading of the instrument impossible. This has been completely avoided 16 in my improved construction by employing improved magnetic damping means. which results in the meter giving substantially a dead beat in-- .dication even when operating under the most adverse conditions. In my improved meters embodying this magnetic damping means, the inan improved construction which will enable the the air or gas velocity within a closed duct or pipe. This attachment apparatus comprises tubes whch can be inserted through a hole in the side of the ma air or gas duct, and which tubes communicate at their other ends witiithe meter.

1 Thus, the instrument may be readily converted into a flow meter adapted for measuring the velocity' of an air or gas within a closed conduit through the instrument-silty of Pitot tubes or the like. In this regard, while most of the aforementioned features of my invention'have greatest utility in a portable'air velocity meter such as I have described, nevertheless it will be underinstrument;

stood that some of these features can be embodied with advantage in stationary flow meters and other like instruments for'measuring the volume or velocity of a fluid flow. Accordingly, my invention is not to be limited in its entirety to a portable, air velocity meter.

Other objects and advantages of my invention will appear from the following detail description of a preferred embodiment thereof. In the accompanying drawings illustrating such embodiment:-

Figure 1 is a front elevational view of theimproved instrument;

Figure 2'is a side elevational view, illustrating the side through which the air stream enters the Figure 3 is a similar view of the opposite side, illustrating the side from which the air stream is discharged from the instrument;

Figure 4 is the front view with the front cover removed, and some of the parts illustrated in section; a

Figure 5 is a transverse sectional view taken approximately on the plane of the line 5-5 of Figure 4 and looking in the direction indicated by the arrows; I

, Figure 6 is a view taken approximately on the same plane, but looking in the opposite direction, as indicated by the arrows 5-6;

Figure 7 is a perspective view looking at the open front of the instrument, but with the plate which defines the bottom and front side of the air channel removed;

Figure 8 is a perspective view of this plate;

Figure 9 is a detail sectional view of one of the improved bearings for the moving system;

Figure 10 is a diagrammatic view illustrating the use of the instrument for measuring the velocity of unconfined or ambient air;

Figure 11 is a similar view illustrating the use of the instrument for-measuring the velocity of an 'air stream issuing from a duct;

Figure 1 2 is a diagrammatic view illustrating the use of the instrument for measuring the velocity of an air or gas flow through a duct;

' Figure 13 is a fragmentary sectional view showing one arrangement by which my improved meframe and having its ends secured to ether as in-.

dicated at 24. The front and back coverplates 2| and 22 have grooves25 and 26 formed around their inner edges for receiving the edge portions of the sheet metal strip 23. A. block 21, serving primarily for mounting or attachment purposes,

is extended across the upper portion of the housi 18, substantially from side to side thereof, this lock being of lessendepth than the depth of the casing, as illustrated in Figures 5 and 6. This block is secured fast against the back cover plate 22, the cover plateand block being fastened together by the 23 (Figs. 5 and 6). The

' front cover plate 2l'is detachably secured in place by .screws 23, which pass through the upper corcover plate are connected by screws 3| extending through both plates and receiving nuts 32 on their rear ends. It will be understood that the housing can be constructed in other ways than that above described. For example, the back 22, the peripheral portion 23 and the mounting block portion 21 may be molded as a unitary piece, omposed of a phenolic condensation produ t, or aluminum or any other preferred material.

Defined below the block 21 is the air channel or passageway 34 in which the air vane 35 oscillates in response to the velocity of the air passing through said channel. the channel passes through upper and lower apertures 36, 36' provided in the lefthand vertical side 231 of the sheet metal frame structure 23. The air leaving the channel or passageway 34 passes out through a somewhat similar arrangement of apertures 31, 31', 31" provided in the righthand wall 231' of this sheet metal casing portion 23. As I shall hereinafter describe, shutters are preferably associated with these difierent sets The air entering of holes for restricting one of the sets and for ing its righthand end fixedly secured to the attachment block 21, as by having the end of this strip bent upwardly and secured to the top .of-

the block around the end thereof; or such attachment may be effected in any other desired manner. The other end of thesheet metal strip 38 is arranged so that it canfbe adjusted upwardly or downwardly to vary the size and shape of the air channel 34. This adjustment is effected by a screw ll which passes down through the mounting block 21 and has its lower end threading through a threaded bushing 42 which is suitably anchored to the top side of the strip 38; The left extremity of the strip 33 is left free so that it can move up and down in the adjustments effected by the screw ll. The head of the screw II is accessible through an" aperture 43 in the top wall 23f of the sheet metal housing portion. This hole 43 may be smaller than the head of the screw ll "so as to hold the screw against upward movement, the screw being mounted in the block 21 before said blockis enclosed within the perimetrical housing portion 23. If desired, a compression spring 4| may encircle the screw and the threaded bushing 42, such spring thrusting the strip 38 downwardly to the adjusted position established by the screw 4 I The air vane 35 swings about the axis of a pintle-or arbor 45, the are 46 designating the path of movement of the upper edge of said vane. When the vane is in its zero position, it lies substantially in the full line position illustrated in Fig. 4. Directly above the arc-l6,-the under side of the sheet metal strip 38 is formed with a curvature 41 extending substantially from thisvzero'position of the vane to the righthand extremity of the air channel 34. The curve 41 may be a'true are or may be a parab-' ola or other generated curve, depending principally on the manner in which it is desired to subdivide the indicating scale on the instrument.

With the scale graduated as shown in Figure 1, I

preferably form the curve 41 as a true arc. The

relation betweenthearc 46 of the vane and the curve 41 issuch that an aperture a is constantly defined between thesecurves, this aperture being position, and constantly increasing in. height and size as the .vane swings towards its position of I of minimum height'when the vane is in'its zero maximum air velocity. The adjustment afforded by the screw 4i enables the size of the aperture a to be increased or decreased with the vane disposed in its zero position. Such adjustment also 5 enables the height and shape of the curve 41 to be varied for securing scale corrections.

The bottom of the air channel or passageway 34 is defined by a plate 49, illustrated in per-, spective in Figure 8. This plate comprises a vertical front portion, 49a from which the bottom wall portions 49b and 49care bent rearwardly. Attaching flanges 49d are bent downwardly from the rear edges of the bottom wall portions 491), 48c. Screws or other suitable fastening members 5| 5 pass through apertures in these'fianges 49d and engage in the back coverplate 22.

front portion 49a is provided with apertures 48c for receiving screws 52 which fasten in the at: tachment block 21. An aperture 49! is provided between the bottom wall portions 491) and 490,

and the vane 35 extends upwardly through this. aperture. The lower portion of the vane is formed with a cylindrically curved portion 35a which is arranged just out'of-contact with the inner-edge 49g of the bottom wall portion 49b.

The very narrow slot affording mechanical clearance between this edge andthe curved portion, 35a remains of the same size throughout the entire throw of the vane so that the leakage around the under side of the vane at this point is maintained at a constant throughout the entire movement of the vane. The slope of the bottom wall portions 4% and 49c, substantially as shown, accommodates a greater range of movement of the vane and affords other advan:

tages. The front wall of the air channel 34 is defined by the vertical front portion 49a. of the plate 49, and the back wall of the air channel is defined by the rear cover plate 22, the front and rear edges of the vane being spaced slightly from,

these walls, as illustrated in Figure 6.

Mounted horizontally in the lower portion of the casing is a U-shaped permanent magnet 54.

The mounting of said magnet is preferably established through a bracket 55 (Figure 6) which is secured to the back cover plate 22 ,by screws 5.6.

The bracket 55 'is secured to the side of the magnet by lugs, screws or soldering. In the preferred embodiment shown, the moving system of the meter is mounted on the magnet-54 and bracket 55, although it will be understood that difierent arrangements of mounting brackets may be employed. The moving sys em comprises the vane 35, vcurved lower portion 35a, spindle 45 55 and damping segment 58. The lower end of the curved portion 35a is formed withan inwardly extending tongue portion 8517 which is crimped around the spindle 45 or otherwise fixedly secured thereto. The dampingsegment 56 is dis- 30 posed to swing between the closely disposed pole extremities of the magnet 54,as best shownin Figure 7. This segment has an upwardly extending tongue portion 58a which is apertured for 75 made of other materials, if desired.

The vertical .front leg of the magnet 54.

spindle .on said boss.

1 provided in the front cover plate'2l.

permitting the spindle 46 to pass therethrough.

The opposite ends of the spindle 45 are formed with pointed extremities 45a, as illustrated in the enlarged section of Figure 9 These extremities ,extend into tapered sockets 6| formed within jewel bearings 62 which are mounted within the 5 bearing bushings 63. In the preferred construction of these bearings, the socket 6| is formed on Y a more gradual taper than the spindle extremity 45a so that the bearing contact occurs primarily at the larger end of the socket, substantially at 10 the point indicated at Gla. This portion of the. 1 socket is slightly larger than the adjacent portion of the spindle extremity so that the, spindle can be moved upwardly to contact with the top portion of. the socket 6| when the weight of the 15 moving system is taken oil of the bearings. The bearing construction is the same at both ends of the spindle The rear bearing bushing 53 screws through a bracket 64 which is attached either to the mounting bracket 55 or to the upper 20 edge of the magnet 54 .(see Fig. 7). Thefront bearing bushing 63 screws through a front bearing bracket 65which is suitably fastened to the Referring again to Figure 9, a lock nut 66 screws over the outer 25- 7 end of the bearing bushing 63 and abuts against the outer side of the bracket 65." This lock nut has an annular shoulder or boss 66a projecting inwardly therefrom. Said shoulder or boss defines an annular bearing for an arm 61 (Figurefi) 30 which is pivoted to oscillate about the axis of the- The swinging end of this arm is provided with aninwardly projecting ex- ,tre'mity 61a, and to this extremity is suitably J fastened the outer end of the hairspring 68; The 35 inner end of the hair spring is suitably secured to the spindle 45. The hair spring is preferably arranged as shown in Figure 4, whereby the convolutions of the spiral are wound up as the vane 35 swingsto the right, although this arrangement '40 of the hair spring is not essential. The tension of l the hair spring can be increased or diminished for thepurpose of accurately setting the pointer on its zero position, by the rotation of a small screw II which has threaded mounting in the 45 frontcover plate 2|, and the front of which screw is accessible from the front of the instrument. The rear end of this screw has an L'- shaped arm I! secured thereto (Figure 6), and

the inwardly projecting end of thisarm or lever =50 extends through an aperture in the armli'l, whereby rotation of the screw 11 is operative to oscillate the arm 61 and thereby increase or decrease the tension on thespring 68. 7

The dial is printed one. card ,or plate 14, which 55 is suitably secured to the front side of the vertical wall portion 49a of the plate 49. The dial markings are visible through asight window 15 A glass 161s mounted in this sight window l5.' The pointer 11 consists of a rod or wire which is Secured j to the movable system in any suitable manner,

preferably by, bending a portion of the rod'in' wardly below theverticalwall 49a, the'nepassin'g the rod downwardly through an aperture in the 05 curved vane extension 35a and through an' aperture in the spindle 45, and th n bending the extremity of the' rod inwardly seat in g notch in the'lower portion of the damping segment extension No, as shown in Figures 6 and 4-. 'm

Devices are provided for adjusting the balance -or center of mass of the moving system in two different directions. Referring to Figures! and '7, one of these devices consists of a small angleshaped clip or arm ll which is pivoted at- 19 to 15 to this flange 58c, said latter balancing device being capable of pivotal adjustment in a plane defined by the top surface of the flange 58c and affording center of gravity adjustment in another line of direction. By shifting the position of one of these two adjustable balancing members the center of gravity of the moving system can be shifted in one direction, as for instance vertically towards or away from the horizontal plane of the pivot axis; and by shifting the position of the other balancing member the center of gravity can be shifted in another direction, as for instance horizontally towards or away from the vertical plane of the pivot axis. Convenient access may be had to these adjustable balancing members 18 and 8| by merely removing the front cover plate 2i. p

The concentrated flux field of the magnet 54 is primarily in the narrow gap 54g defined between the closely disposeed pole extremities 54a of the magnet. Referring to Figure 4, I have found it preferable to shape and arrange theadjacent edge of the damping segment 58 substantially as shown, with the diagonal edge 58c 01' the segment intersecting a limited portion of this concentrated flux field when the pointer 11 is'in its zero position. Certain advantages accrue to this formation of the adjacent edge of the damping segment and to this relation of the segment to the concentrated flux field. For instance, the restoring forces which are necessarily exerted by the balance of the-moving system and by the tension of the hair spring, for the purpose of returningthe pointer to zero position, can be reduced to a minimum or can be made practical- 1y nil when the pointer arrives in its zero position,

because the magnetic damping action is exerting very little motion retarding force substantially at the time that the pointer is approaching or arriving at its zero position. on the other hand, as soon as the vane 85 starts its oscillation to the right in response to a current of air, the damping action becomes increasingly effective as the. diagonal edge 58e oi the damping segment swings upwardly through the concentrated ilux field, whereby a maximum damping action iseffec'tive at the higher air velocities.

The device for imposing a locking and elevating force on the moving system when the meter is not' in use comprises a, resilient wire 88 which has a U-shaped resilient loop 880 at one end. as shown in Figure 4. The front bearing bracket 88 has an extension portion 88a projecting downwardly on the inner side of the magnet '88, and the upper end'of the loop 88:; is soldered or otherwise suitably secured to the lower-end of this extension-portion 88a. The wire is bent to have a rearwardly extending portion 88b passing below the circular outer periphery of the damp ing' segment l8 (Figure 8). and this portionot the wire has a U-shaped bend 88c therein for engaging the peripheral edge of the segment. The wire continues diagonally upwardly andto the Anotherbalancing device 8| of 86. When the latter shutter is in either of its open positions for permitting the passage of air through the channel ll, the wire is pressed downwardly to remove'all restraint from the damping segment 58, but when the shutter is moved upwardly to its closed position, the wire is carried.

upwardly thereby to impose an upward force against the bottom edge of the damping segment, thereby locking the moving system against motion and also lifting the moving system so that the weight thereof is not carried by the tapered spindle ends 45aand bearing jewels 82. When the moving system :is thus locked against motion, and its weight removed from the bearings, it is capable of withstanding very severe jars.

The shutter which controls the inlet apertures 38, 36' comprises a plate 85 which is arranged for vertical sliding movement along the inner side of the lefthand housing wall 231. The plate has laterally bent stiffening flanges 85a along its vertical margins. ISuitable provision is made for guiding the plate for vertical sliding movement, which guiding arrangement may be of any desired form, although in the preferred construction. shown I have illustrated resilient rods or wires 88 which have their upper ends anchored.

in the mounting block 21 (Figure and which have their lower ends pressing frictionally against the inner surface of the plate at points just inside of the marginal stiffening flanges 85a, where the rods serve to guide the vertical motion of the plate. Referring to Figure 4, said rods are formed with hump-shaped or rounded lower ends 86a which are adapted to snap into slots 85b in the p the lower portion of the shutter plate.

shutter plate 85. The plate is reciprocated by the rotation of a thumb wheel 81 which is mcunted at the lefthand side of the instrument. A shaft 88 projects from this wheel through the housing wall 281 and has a rod 89 anchored to its inner end and projecting rearwardly therefrom. Said rod extends through an aperture 850 which is provided in a flange 85d projecting from Rotation of the thumb wheel 81 is thus operative to reciptop of this recess ll.

- left, as indicated stud: for attachment to the shutter which controls the, leithsnd apertures-88.

ro'cate the shutter plate upwardly or downwardly. The downward motion thereof is limited by the lower diagonal edge 85s of the plate engaging the thumb wheel-shaft 88. The upper edge of the plate is adapted to slide up into a recess 9| between the attachment block 21 and casing wall 28!, and the upward motion of the plate is limitedby the engagement of said plate with the Provided in the plate 85 is a row of relatively large apertures 92, as large as the apertures 88, 88' in the casing wall, and upper and lower rows of'relatively small apertures 88 and 88'. The apertures in the shutter plate and in the casing wall are so related that when the shutter plate is in the lowermost position as illustrated in Figure 5, the top' edge of the plate is below the'upper row of easing apertures 38 and the row of shutter apertures 82 is in'registration with the lower row of easing apertures 38. This leaves the casing apertures entirely unobstructedgfor a maximum flow of air therethrough.

, Whentiie shutter plate is moved upwardly to its intermediate position, as determined by the action of the detent humps 88a snapping into the intermediate apertures 85b, the top row of 1 small shutter apertures is brought into registration with the top row of casing apertures 36 and the bottom row of shutter apertures 93' is brought into registration with the bottom row of casing apertures 38'. This reduces the total effective area of the openings through which the air can enter the instrument, such area bearing a predetermined relation to the total effective area of the casing apertures 36, 36' when unrestricted, whereby the instrument can be used to measure air velocities which would exceed the capacity of the instrument if the air flow were through the unrestricted casing apertures 36, 36'.

When the shutter plate is raisedto its uppermost position, the solid portion of the plate directly below the top row of small apertures 93 closes 58 and thereby lift and lock the moving system to place the moving system in inoperative condition as well. This is accomplished by extending the end 83d of the lifting spring into an aperture in the lower portion of the shutter plate 85, as

shown in Figure 5, whereby the lifting spring is caused to move upwardly against the peripheral edge of the damping segment when the shutter slide is in its uppermost position.

The dial 14 is provided with two concentric scales Stand 95, so arranged that the pointer 'ii swings over both scales. The inner "scale 94 is shown as being calibrated to read from 0 to 400 feet per minute, and is the scale which is read when the inlet apertures 36, 36' are opened wide, corresponding to relatively feeble air currents. The outer scale 95 is calibrated to read from approximately 0 to 2500 feet per minute,

and is the scale which is read when the air enters through the restricted apertures 93, 93', corresponding to relatively high air velocities. tongue 85 is bent laterally from the forward edge of the shutter plate 85 in position to extend over the front of the dial ll, this tongue moving up and down with the shutter plate and serving as an indicator for designating whether the inner scale 94 or the outer scale 85 is to be read. It will be apparent that the indicator is in position v to designate the inner scale 84 when the apertures 36, 36' are unrestricted, and will be in position to designate the outer scale 95 when the air flow is through the restricted apertures 93, 93".

Figure diagrammatically illustrates the use of the meter for measuring the velocity of an unconfined air flow, such as the circulation of air in a room or enclosure. By reason of the straight through flow of the air in the instrument-its entrance through the inlet apertures 36, 36' at one side of the casing, its substantially straight line flow through the channel 34, and its discharge through the outlet apertures 81, 31', 31" at the oppositeside of the casingthe' instrument is made more emcient and more sensitive and can be used to'better advantage for determining accurately the direction of an unconfined air flow by merely tilting or turning the instrument to difierent'angular positions and noting any variation in the readings. The substantially straight I in Figure 13,

line flow of the air through the instrument, as distinguished from a sinuous, tortuous or reversing path,'greatly reduces the inertia losses and side wall air friction. By minimizing these losses,

and particularly the inertia losses, the maximum kinetic energy of very feeble air currents is imparted to the vane. It will be noted from Figure 6; that the vane closes almost the entire rosssectional area of the channel when in its ero position, there-being only small clearance areas betweenthe channel walls and'the side and top edges of the vane. It will also be noted from Figure 4 that in all positions of the vane it closes the major cross-sectional area of the channel. These factors greatly increase the sensitivity and accuracy of the instrument to low velocity air flows.

Figure 11 diagrammatically illustrates the use of the instrument for determining the velocity of an air current issuing from a duct D. In each of the uses illustrated in Figures 10 and 11, the out? let ordischarge apertures 31-41" at the outlet side of the casing ,are maintained open. For

obtaining an average of the velocities issuing from the diil'erent radii of such a duct D, it is customary to take readings while moving the meter laterally across the end of the duct. This transverse movement of the meter in a direction perpendicular to the direction of air flowdoes not disturb the accuracy of the readings because of the fact that the inlet and outlet openings 36-35 and 31-31" are in opposite side walls of the meter casing, and hence any effect which such lateral or transverse movement of the casing may have on one opening is counterbalanced by the similar effect on the other opening. a

.;Figure 12 diagrammatically illustrates the use of a modified form of my improved meter for measuring the velocity of an air or gas flow occurring within a closed duct D. or other region of air flow removed from the-meter casing. In adapting the meter to this utility, an attachment 91 is connected with the meter for conducting the air or gas from the duct D throughthe meter and back into the duct. This attachment comprises two pipes 98 and 99 having apertures 98' and 99' in their, upper ends. The apertures 98'- are arranged to face in opposition to the direction of the flow and the apertures 99 are arrangedto face in the direction of flow, whereby the pipes or pressure tubes'i'or conducting a portion of the flow down through the meter. The two pipes are perferably arranged back to back so that they can be inserted through a. relatively small aperture III in the wall of aduct D; The lower ends of the two pipes are spread apart, as illustrated nd these ends have tapered extremities 98" and 99" for effecting tight seating in the upwardly directed tapered ends of the two passageways I02 and I03. A circular collar I is secured fast to the separated lower portions of the two pipes and is adapted to iit within a circular,

threaded boss I" which is secured to the top of the. meter housing. A clamping nut I" is arranged to screw down over the boss I05, this nut having an inwardly extending flange which overlies the edge of the collar I. It will be'evident that by screwing this nut I" downwardly, the

tapered extremities of the two pipes can be forced into tight seating contact with the tapered ends of 70 the passageways I02, I03. When the pipe attach-' ment 81 is disconnected from the instrument, the upper ends of these passageways are closedby I a closure attachment I08, illustrated in Figure 14. The latter comprises two solid plugs I and 7s l l I extending down from a block I lland adapted to seat in the upper ends oi the passageways I02, I N13 for closing the same. A screw cap H3 has swiveled connection with the block H2 through 5 the swivel pin ill, whereby the screw cap can be screwed downwardly over the threaded boss I05 for forcing the plugs illil, Ill down into the passageways. when an instrument of the construction illustrated in Figures 12 and 13 is provided with a top carrying strap 5, one end of the strap is made releasable to facilit te connecting the attachment 91 to the instrum t.

The two passageways I02, III! are formed within the mounting block 21 and communicate with 15 the inlet and outlet ends respectively 0! the air channel. The adjustable top wall 38 oi the air channel is preferably arranged so that these passageways open into the channel beyond the ends of said adjustable top wall. When thus employing the instrument in conjunction with the attachment 91 for measuring the velocity of a flow within a closed conduit, it is desirable that, the outlet apertures 31, 31', 31" in the righthand side of the casing be closed. This is accomplished by the provision of a shutter 'plate Ht which is arranged for sliding movement insideof the righthand casing wall 231', corresponding substantially to the slidable arrangement of-the shutter plate 85 at'the opposite side of the casing. For example, the plate Hi may be provided with laterally extending marginal flanges Ilia which cooperate with spring rods lll tor guiding the motion of the plate, similarly to the guiding relation previousiy described between the flanges 85a and the spring rods IS. The plate H6 is provided with three rows of relatively large apertures lilwhich are adapted to register with the three rows of casing apertures l1, I1, 31" when the plate is in its lower position. The movement oi the plate to its upper position closes all rows 0! casing apertures. Such movement is eflected by an arm III which extends across the casing adjacent to the bottom thereof, The leithand end of this arm isrigidiy secured to the lowerportion of the shutter slide 85 so as to move directly therewith. The arm is disposed adjacent to the back wall of the casing, as shown in Figures 5 and 6, so that it can have the required range of movement in a plane in back of the permanent magnet N. The righthand and 01 said arm isadapted to engage w a flange I lib which is punched laterally from the lower portion of the shutter plate H8. One or more tension springs I21, connected between the flanges l Ito and the bottom wall portion 48c, nornially tend to pull the shutter slide H6 down to its open position; The arrangement is such that the latter slide will remain in this (open position, with theoutlet apertures, 31, 81', ll" completely open, as long as the inlet shutter 85 is either down in itswide open position or in its intermediate restricted position with the resti'ic ted apertures 93, 83 in register with the apertures.

However, as soon as theinlet opening'shutter 85 V is moved upwardly to its completely closed posi- ,;tlon, the corresponding upward movement of the 51m in will eil'ect engagement with the flange i Ito and move the outlet shutter 8 up to its closed position, thereby closing both sides of the casing. As soon as the inlet shutter is mpved back to its intermediate position or to its lower position, the springs in restore the outlet shutter m to its open position. Thus, the two shutters are capable of completely closing the instrument housing, Wvhieh is particuiar-1y desirable when the instrument is to 'struction-adapted for the. use of the attachment have the attachment 9! adapted thereto for measuring the velocity of a flowthroug'h a closed conduit, as illustrated in Figure 12. Even where the instrument is not intended or designed for this latter adaptability, the closing of the outlet 5 apertures 31, 3.1, 31", when the instrument is locked against operation, is 01 advantage for preventing any possibility of the vane 35 being subjected to any air pressure. In the modified con- 10 81, the locking wire 83 may be dispensed with so that the moving system is still movable with both shutter slides elevated to their closed positions; or this locking wire is retained by giving each of 1 the slides still another higher ,position, beyond the closed positions, in which higher position the casing will still be closed and the wire will be brought into action for locking and elevating the moving system. It will be noted that when the conduit attachment 91 is coupled to the meter casing it constitutes a self-supporting extension from the casing whereby the casing can be employed as a supporting handle for maneuvering the orifice end of the conduit into diilerent positions in the air stream. Also, the use of the extension conduit is advantageous in situations where the presence oi! the meter casing directly in the air stream would cause such turbulence and blocking effects in the air flow as to result in erroneous readings, the relatively small size or the extension conduit not causing such obiectionable turbulence or blocking eilect.

I have found that the magnetic damping mechanism, constructed and arranged substantially as herein described, is ei'llcacious to dampen .the motion of the moving system when low velocity air currents are admitted through the unrestricted apertures 36, 36' or when the restrictedapertures 93, 93' are interposed for higher velocity currents. The eddy currents that are set up in the damping segment 5! upon any tendency of the segment to oscillate quickly, oppose sufllcient retarding force to such quick motion that a dead beat indication is obtained even when the air velocities are rapidly pulsating. In the case of a rapidly pulsating air flow, the indication is substantially the mean 01" the diflerent velocities. This magnetic damping operation creates noririctional retardation and does not decrease the sensitivity of the instrument. Also, this magnetic damping operation if enables the indicating pointer to follow such slow surges or changes in velocity as can be read directly without inconvenience, which is often desirable Furthermore, such magnetic damping also damps the indicating-means against any 5-5 vibration or motion which may arise from holding the meter in the hand during the taking oi' velocity measurements. i

. While I have illustrated and described what I regard to be the preferred embodiment of my 00 invention, nevertheless it will be understood that such is merely exemplary and that numerous modifications and-rearrangements may be made therein without departing from the essence oi the invention. 7

I claim:-- s

1. In an air yelocity meter of the class described, the combination of a casing, 6 air channel defined in said casing for directing an airflow therethrough, a moving system comprising a vane, indicating means and a balancing segment, .said vane extending into said air channel in position to be deflected through a limited range of oscillatory movement by the velocity of the air flow through said channel, said indicating means indicating the stantially at right angles thereto and balancing said vane and indicating means, and a permanent magnet comprisin pole extremities defining an air gap, said balancing segment moving through said air gap.

2. In a portable air velocity meter 01 the class I described, the combination of a casing, inlet and outlet openings in opposite side walls of said casing, an air channel in said casing extending in a substantially straight. line between said openings, whereby said openings can be aligned with free atmospheric, air currents and said currents can have substantially unidirectional flow throughsaid casing, a moving system comprising a vane, indicating means and a balancing segment, said vane extending into said air channel in position to be deflected through a limited range of oscillatory, movement by the velocity of the air flow through said channel, said indicating means indicating the range of deflection. of said vane, said balancing segment depending below said vane and lying substantially at, right angles thereto and substantially balancing said vane and indicating means, and a permanent magnet comprising pole extremities defining an air gap, said balancing segment moving through said air gap.

3. In a portable air velocity meter of the class described, the combination of a casing, inlet and outlet openings in opposite side walls of said casing, an air channel in said casing extending in a substantially-straight line between said openings, whereby said openings can be aligned with free atmospheric air currents and said currents can have substantially unidirectional flow through said casing, a moving system comprising a vane, indicating means and a damping segment, said moving system being pivoted for, oscillatory movement about an, axis extending substantially at right angles to the direction of flow' of the air through said, channel, said vane extending into said channel and being disposed substantially transversely thereof in position to be deflected through a limited range of oscillatory movement by the velocity of the air flow through said chan-- nel, said indicating means indicating the range of deflection of said vane, said damping segment depending below said vane and lying substantially at right angles thereto, and permanent magnet means comprising pole extremities defining an air gap, said damping segment moving through said air gap.

4. In a portable air velocity meter of the class described, the combination of a substantially rectangular casing which can be held in the hand or rested on a supporting surface for operation, inlet and outlet openings in opposite side wallso! the upper portion of said casing, an approximately horizontal air channel in the upper portion of said casing extending in a substantially straight line between said openings, whereby said openings can be aligned with free atmospheric air currents and said currents can have substantially unidirectional flow through Said casing, a spindle in said casing below said air channel and extending substantially at right angles to the direction of flow of the air through-said channel, a U-shaped permanent magnet disposed substantially horizon-.

tally in said casing belowsaid spindle, and a moving system comprising a vane, indicating means.

and a balancing segment pivotally mounted on said spindle, said vane extending into said channel and being disposed substantially transversely .thereof and closing the major portion of said channel when in "zero position, said indicating a means indicating the range of deflection of said vane, said balancing segment depending below. said vane and lying substantially at right angles thereto and moving between the pole extremities of said permanent magnet.

5. In a portable air velocity meter of the class described, the combination of a casing, an air channel defined in said casing for directing an air flow therethrough, means for controlling the air flow through said channel, a moving system commeans, and a permanent magnet comprising pole extremities defining an air gap, said balancing segment moving through said air gap.

6. In a portable air velocity meter of.,the class described, the combination of a casing, inlet and outlet openings in said casing, an air channel in said casing extending between said openings, adjustable means actuatable from the exterior of said "casing for controlling the efiective area of one ofsaid openings to adapt the meter to different ranges of velocities, a moving system comprising a vane and indicating means, said moving system being pivotedfor oscillatory move ment about an axis extending substantially at right angles to the direction of flow of the air through said channel, said vane extending into said channel and being disposed substantially transversely thereof and closing the major portion of said channel when in zero position, said indicating means indicating the range ofdeflection of said vane, said indicating means having multiple scale means cooperating therewith for described, the combination of a casing, an air channel defined in said casing for directing an air flow therethrough, adjustable means controlling the air flow through said channel foradapting the meter to different ranges of velocities, a moving system in said casing comprising a vane and indicating means, said vane having osc1l-- latory movement in said air channelabout a. pivot axis extending substantially at right angles to the direction of flow of the air through said channel, said indicating means indicating the range of deflection of said vane and comprising multiple scale means forgiving different readings for different ranges of velocities, a designating device operating in conjunction with said adjustable controlling means for designating the scale of said multiple scale means to be read, and magnetic means for damping the motion of said moving system.

ings, whereby said openings can be aligned with freeatmospheric-air currents. for substantially unidirectionalflow through said casing, a moving system comprising a pivoted vane, indicating means and a damping member on'opposite sides of the pivot axis of the vane, said vane extending into. said air channel in position to be deflected through a limited range of oscillatory movement by the velocity of the air fiow through said channel and the general axis of said channel being.

spaced to one side of the pivot axis oi said vane, said indicating means indicating the range 01 deflection of said vane, permanent magnet means comprising pole extremities defining an air gap and disposed on the side of said pivot axis opposite side air channel, said damping member moving through said air gap,-a hair spring opposing motion of said moving system in one direction, and means for adjusting the zero position of said indicating means through said hair spring;

9. In a portableair velocity meter of the class described, the combination/of a casing, an air channel defined in said casing for directing an air flow therethrough, a moving system in said casing comprising a vane, indicating means and a damping member, said vane being disposed substantially transversely in said air channel and having oscillatory movement therein about a pivot axis extending substantially at right angles to the direction of flow of the air through said channel, said indicating means indicating the range of deflection of said vane, a hair spring for restoring said moving system to zero position, and permanent magnet means in said casing comprising pole extremities defining an air gap,

said damping member moving through said air gap and being constructed to exert diiIerent degrees oimagnetic retardation to motion of sal d, moving system in difierent angular positions of said moving system, whereby said ,damping member exerts minimum magnetic retardation when said moving system is in close proximity to its zero position. g

10. In a. portable air velocity meter of the class described, the combination of a casing, an air channel definedin said] casing for directing an air fiow therethrough, a moving system comprising a vane and indicating means, said moving system being pivoted for oscillatory movement about an axis extending substantially at right angles to the direction of flow of the air through said channel, said vane extending into said channel and being disposed substantially transversely thereof, said indicating means indicating the angular deflection of said vane, mag- 'netic means for damping the motion of said moving system, including a partxmovable with said vane, and locking means for holding the moving system against motion comprising a member movable into engagement with the movable part of said magnetic damping means,

11. Infan airvelocity meter of the class de-'- scribed, the combination of a casing, an air channel defined in said casing for directing an air flow therethrough, a moving system'comprising a vane, indicating means: and a balancing segment, said vane extending into said air'channel and positioned tobe deflected through aiimited range of'oscillatory movement by'the velocity of the air now through said channel, said indicating means indicating the range or deflection of said vane, said balancing segment depending below said vane and lying substantially at right angles thereto and substantially'balancing said vane and indicating means, apermanentmagnet comprising pole extremities defining an air g'ap said balancing segment moving through said air gap, and a movable wall defining a part of said air channel movable to different positions for changing one of the dimensions oi said channel.

. 12. In a portable 'air velocity meter of the class described, the combination of acasing, an air channel defined in said casing for directing an air flow therethrough, a moving system in said casing comprising a vane, indicating means and a balancing segment, said vane extending into said air channel in position to be deflected through a limited range or oscillatory movement by the velocity of the air flo'w through said channel, said channelvarying in cross-sectional area between different points of its length, ,whereby said vane in a low velocity'position closes a greater proportion of said channel than it does in a high velocity position, said indicating means indicating the range of deflection of said vane, said valancing segmentdepending below said vane and lying substantially at right angles thereto and substantially balancing said vane and indicating means, and a permanent magnet in said casing comprising pole extremities defin-v moving ancing segment, said moving system being pivcited for oscillatory movement about an axis extending substantially at rightangles to the direction of flow oi the air through said channel,

said vane extending into said channel and being disposed substantially transversely thereof and closingthe major portion of said channel in all positions thereof, said air channel varying incross-sectional area between different points of its length, whereby said vane closes a greater proportion 01 the channel-in a low velocity position than it does in a high velocity position, said indicating means indicating the range of de-- fiection of said vane, said balancing segment depending below said vane and lying substantially at right angles thereto and. substantially balancing said vane and indicating means, and a permanent magnet in, said casing comprising pole extremities defining an air gap, said balancing segment moving through said air; gap.

14. In a portable air velocity meter of the class described, the. combination of a casing, inlet and outlet openings in opposite side walls of said cats-- ing, an air channel in saidcasing extending in a substantially straight line between said openings, whereby said-openings can be aligned with free atmospheric air currents and said currentscan.

havesubstantlally uni-directional flow through said casing, av ne pivoted for oscillatory movement about ain'axis extending substantially-at right angles to thedirection of flow of the air through said channel, said vane being disposed substantially transversely insaid channel and closing approximatelrthe entire cross-sectio area oi said channel when in its zero position,v

said vane 61051118112118 maior-cross1sectional area 01' said channel in all posltions thereof; said channel increasing in cross-sectional area to-' wards the position 0! maximum deflection of said vane, indicating means indicating the angular deflection of said ,vane and comprising diflerent 'scale dataior diflerent ranges of velocities, ad-

Justable means for controlling the eil'ective area of one of said openings to adapt the meter to diflerent ranges of velocities, and designating -means operating therewith for designating the ing, an air channel in said casing extending in a conduit.

substantially straight'line between said openings, whereby said openings can be aligned with free atmospheric aircurrents and said currents can have substantially uni-directional flow through said casing, a vane pivoted for oscillatory movement about an axis extending substantially at right angles to the direction of flow of the air through said channel, said vane being disposed substantially transversely in said channel and closing approximately the entire cross-sectional area of said channel when in its zero position, said vane closing the major cross-sectional area of said channel in all positions thereof, said channel increasing in cross-sectional area towards the position of maximum deflection of said vane, indicating means indicating the angular deflection of said vane, a conduit for adapting the meter to the measurement of fluid flow at a point removed from the meter, said conduit having anorifice at one end adapted to be inserted into the region of flow to be measured, detachable coupling means for coupling the other end of said conduit to said casing, the latter end of said conduit; communicating with the inlet end of said channel when so coupled to the meter, and means for closing theremainderof the inlet end of said channel from communication with atmosphere when the meter is thus adapted to the measurement of flow conditions through said detachable 16. In a portable air velocity, meter ofthe class described, the combination of a casing, inlet and outlet openings in opposite side walls of said casing, an air channel in said casing-extending in a substantially straight line between said openings,

whereby said openingscan be aligned with free atmospheric air currents and said currents can have substantially uni-directional flow through said casing, a vane'pivoted Ior oscillatory movement about an axisextendi'ng substantially at right angles to the direction of flow oi the air through said. channel, said vane being disposed substantially transversely in said channel and closing approximately the'entire crossrsectional area 01' said channel when in its zero position, said vane closing the major cross-sectional area oi said channel in all positions thereof, said channel increasing in stress-sectional area towards the position'of maximum deflectioh of said vane, indicating means indicating the angular de-- ilection oi said vane, adjustable means actuatable from the exterior of said casing for controlling the effective area 01 one of said openings to adapt the meter to different ranges of velocities, a con-- duit i'or adapting the meter to the measurement oLfluid now at a point removed from the meter, said conduit having, an orifice at one end adapted to be inserted into the region of flow to be measatmosphere when the meter is thus adapted to the measurement of flowconditions through said detachable conduit. I

17. In a portable air velocity meter of the class described, the combination of a casing an air channel in said casing for directing an,a.ir flow therethrough, a vane disposed substantially transversely in said channel and having limited oscillatory movement thereinabout a pivot axis extending substantially at right angles to that portion of the channel through which said vane swings, said'vane in its zeroposition being inclined from the vertical and closing approximately the entire cross-sectional area or said channel, said vane closing the major crosssectional area of'said channel in all positions,

, said channel increasing in cross-sectional area towards the position of maximum deflection o1 said vane, indicating means indicating the angular deflection of said vane, magnetic means for damping the motion of said indicating means,

an extension conduit, means for detachably coupling one end of said conduit to said casing in communication with the inlet end of said channel, the other end of said conduit having an orifice therein for conducting exploring operations in velocity regions remote from said meter,

and means for closing the remainder of the inlet portion of said channel from communication with atmosphere when the meter is thus used for the to be deflected through a limited range of oscillatory movement bythe velocity of the airy flow through said channel, said indicating means indicating the range of deflection of said vane, said balancing segment depending below both said vane and said air channel and lying substantially at rightanglesthereto and substantially balancing said vane and indicating means, and a' permanent magnet comprising pole extremities defining an air gap, said'balancing segment moving through said air gap.

19.'.In a portable air velocitymeter of the class described, the combination of a casing, inlet and outlet openings in opposite side walls of said casing, an air-channel in said casing extending in a substantially straight line between said openings, whereby said openings can be aligned with i'ree atmospheric air currents and said currents can have substantially uni-direetional'flow through said a moving system in said casing comprising a vane and indicating means, and means for adapting the meter to the measurement or fluid flow within a closed duct or the like comprising a'conduit adapted'to have communication at one end with the inlet portion of said air chan- Y nel and having its other end adapted to open into 7 said duct, and means for closing the inlet' open ing 01 said casing from communication with atmosphere when the meter is thus adapted to the measurement thelike. i

20. In a portable air velocity meter of the class described, the combination of a casing, an air channel extending in a substantially straight line through said casing, whereby said channel can be aligned with free atmospheric air currents and said currents can have. substantially r fluid fiow within a closed duct or 1 tlonal flow through said casing, a vane in said charmel pivoted i'or oscillatory movement about an axis extending substantially at right angles to the direction 01 flow of' the air through said 5 channel, indicatingmeans indicating the angular deflection oi-said vane, said vane responding to free atmospheric air currents of relatively low velocity passing through said channel, ex-r tension means for adapting the meter to the 10 measurement of fluid flow within a closed duct or in othervelocity regions removed Jrom the meter, comprising two conduits communicating with opposite ends oi! said channel. the other'ends of said conduit-shaving orifices therein adapted g to be presented in diflerent angular relationsto the fluid flow in the velocity region being measured, and means for closing the inlet and outlet ends of said channel from communication with atmosphere when the meter is thus adapted to go the measurement of fluid flow through said extengg of said casing, an air. channel in said casing sion means.

21. In a portable air velocity meter of theclass described, the combination 01' a casing, inlet and outlet openings in opposite side walls extending in a substantially straight line he: tween said openings, whereby said openings can be aligned with tree atmospheric air currents and said currents can have substantiallyuni- I so directional flow through said casing, a moving system in said casing comprising a vane and indicating means, means for adapting the meter to the measurement 0! fluid flow with a closed duct or the like comprising a conduit adapted 35 to havecommunication at one end with the inlet portion of said air channel and having its other end adapted to open'into said duct, and means carried by the casing for closing the inlet open-- ing of said casing from communication with 0 atmosphere when the meter isthus adaptedto the measurement of fluid flow within a closed duct or the like.

22. In a portable air velocity meter oi the class described, the combination 0! a casing, I 45 inlet and outlet openings in opposite side walls of said casing, an air channel in said casing .extending in a' substantially straight line between said .openings, whereby said openings can be aligned with i'reeatmosphericair currents and go said currents can have substantially unidirecment of fluid tional flow through said casing, a moving system in said casing comprising a vane and indicating means, means for adapting the meter to the" measurement of fluid flow within a closed duct .55 or the like comprising a conduit adapted to have communication at one end with the inlet portion of said air channel and having its other end adapted to open into said duct. and means carried by the casing against'said opposite side walls for closingboth said inlet and outlet openings oi the casing trom communication with atmosphere when the meter isthus adapted to the measureflow within a closed duct or the 23. In a portable air velocity meter of the class described, the combination oi a casing,

inlet and outlet openings in opposite side walls of 1811113881215!!! air channel inisald casing extending in a substantially straight line between said openings, whereby said openings can be aligned with tree atmospheric air currents and said currents can have substantially-unidirectionai new through'said casing, means carried by the casing and serving as a-lower wall for the inlet 1 portion or said air channel, amoving system in said casing comprising a vane and indicating means pivoted for movement about an axis spaced below said wall means, and a curved partcarried by said vane and arcuate about said axis so as to cooperate with said wall means so as to restrict air leakage from he inlet portion or said air channel.

24. In a portable air' velocity meter of the class described, the combination of a casing, inlet arid outlet openings in opposite. side walls of said casing, an air channel in said casing extending in a substantially straight line between said openings, whereby said openings can be aligned with tree atmospheric air currents and said currents can have: substantially unidirectional flow through said casing, means serving as a lower wall 'ior the inlet portion of said air channel, a moving system in'said casing comprising a'vane and indicating means pivoted for swinging movement about an axis below said wall means, said vane including a substantially flat section closing approximately the entire cross-sectional area of said air channel and-having a laterally bent sec-r tion with a portion curved arcuately about said pivot axis and cooperating with the inner end 01' said wall means in all positions of the vane for the purpose of preventing air leakage at this point, and balancing means for (said vane.

25. In an air velocity meter oi the class described, the combination of a casing, an air ing said vane and indicating means, means ior closing the ends of said air channel, and means operable therewith and movable into and out of engagement with said balancing segment for holding the moving system against, motion.

26. In an air-velocity meter of the class de -f scribed, the combination oi a casing, an air cha neldeflnedin the upper portion of said casing for directingan air flow therethrough, a

moving system comprising a vane, indicating means and a balancing segment, said vaneextending into said air 'channel "and positioned to be deflected through a limited range oi'oscillatory movement ,by the velocity of the air flow.

through said channehsaid indicating means indicating the range of deflection or said vane, said balancing segment depending below said mile and lying substantially at right angles thereto and substantially balancing said vane and indicatlng means, shutter means for closing the inlet end of said air channel and including a portion extending into thelower part of said casing, and a locking, member in the lower portion of said casing and movable into elfgagement with said balancing segment, said locking mber being operatively connected with the lower portion of said shutter i 27. In a portable air velocity meter of the class described, the combination oi a 'casingyall 31;- channel in said casing increasing in area towards its outlet end, a moving 'systemcomprising a vane closing-the niaior portion of said channel and movablejbout a Pivot axis disposed substantially at right angles to the channel for deflection by the air now therethrough, a spring opposing such motion of the vane, an indicating device associated with said moving-system for giving direct readings in terms of air velocity from the deflection of said moving 'system, inlet and outlet means comprising apertures in opposite side walls of said casing and the air channel being disposed so as to extend in a substantially straight line between said apertures whereby the latter can be aligned with free atmospheric air currents and a substantially uni-directional air flow provided through the meter, said inlet and outlet means being of relatively large efiective area for rendering said meter responsive to relatively feeble air currents, an extension conduit attachment comprising a stem portion having orifice means at the outer end thereof for introduction into a closed .duct or other region of air flow removed from the meter and adapted to have its other end placed in communication with said air channel, said stem portion being of substantially uniform cross ,section throughout its length for movement through a relatively small aperture in the wall of said duct and comprising two passageways,

one leading from the region of air flow to the T deflection by the airflow therethrough, a spring opposing such motion of the vane, an indicating inlet end of said air channel and the other leading from the outlet end of said air'channel back to said region of air flow, whereby said air channel may be selectively placed in communication through said inlet and outlet means directly with 'fre'e atmospheric air currents in whichthe meter itself is situated or through said extension con 'duit with an air flow at a point removed from the meter, and means for preventing free atmospheric air currents in which the meter itself may be, situated from passing through said air channel when said extension conduit is placed in communication with the meter.-

' 28. In a portable air velocity meter of the class described, the combination of a casing, an air channel in said casing, afmoving system comprising a vane movable in said air channel for device associated with said moving system for giving direct readings in terms of air velocity from the deflection of said moving system, inlet and outlet means in said casing for passing air through said channel from the immediate external vicinity of said meter, an extension conduit attachment having orifice means at one end for introduction into a,closed duct or other re-, vgion-ofair flow removed from the meter and adapted to have its other end placed in communication with said, air channel, said extension conduit attachment comprising two ducts, one leading from the region or, air now to the inlet end of said air channel and the other leading irom' the outlet end oi said air channel back to said'region of air flow, whereby said air channel may be selectively placed in communication through said extension conduit with an air flow 'at a point removed from the meter or through,

said inlet and outlet means directly with an air flow in which themeter itseli'is situated, and means for preventing an air flow in which the meter itself may'be situated from passing through said air channel when said extension conduit is,

placed in communication with the, meter.

29. In a portable air velocity-meter oi the class described, the combination oi" a. casingfia'n'air 7 channel in said casing, a moving system compriiinrrvanembvable in said air channel for deflection by the air flow therethrongh, a spring which the meter itself may class described, the. combination of opposing such motion of the vane, an indicating device associated with said moving system for giving direct readings in terms of air .velocity from the deflection of said moving system, inlet and outlet means comprising apertures in the opposite side walls of said casing and the air channel being disposed so as to extend in a sub-- stantially straight line between said apertures whereby the'latter can be aligned with free atoutlet m eans directly with free atmospheric air currents'in which the meter itself ,issituated orv through said extension conduit with an air flow at a point removed from the meter, and means for preventing free atmospheric air currents in which the meter itself may be situated from passing through said air channel when said extension conduit is placed in communication with the meter.

30. In a portable air velocity meter of the class I described, the combination of acasing, an air channel in said casing, a moving system comprising a vane movable in said air channel for deflection by the air flow there 'hrough, a spring opposing such'motion of the vane, an indicating device associated with said moving system for giving direct readings in terms of air velocity from the deflection of said moving system, inlet and outlet means in said casing for passing air through said channel from ithe immediate external vicinity of said meter, an extension conduit attachment having; orifice means at one end for introduction intog a closed duct or other region of air flow removed from the meter and adapted to have its other end placed in communication with said air channel, wherebysaid air channel may be'selectively placed in communication through said extension conduit with an air flow at a point removed from the meter or through said inlet and, outlet means directly with an air flow in which the meter itself is situated, and means for preventing an air flow in be situated from passingthroughsaid air channel when said extension conduit is placed'in communication with the meter.

31. In a portable air velocity meter :of the a casing, an air channel in said casing, a moving system comprising a vane movable in said air .c'hannel for deflection by the air-flow therethrough, a spring opposing such motion 01 the vanefmeans for substantially balancing said vane to maintain the accuracy of the meterv when held at diiferent angles, an indicating device associated with said moving system for giving direct readings in terms of air velocity from the deflection of said moving sy tem permanent magnet damping means for damping the motion of saidindicating device, an

extension conduit attachment having orifice means at one end for introduction into a closed duct or other region' of air flow removed from thd meter, and coupling means for placing the other end of said extension conduit in commuchannel may be selectively placed irr communi- Q nication with said air channel, whereby said air,-

air flow at a point removed from the meter or directly with anair flow in which the meter itself is situated.

moving system comprising a vane movable in saidair channel for deflection by the air flow therethrough, a spring opposing suchmotion of the vane, said moving system being substantially .line between said apertures whereby the latter can bealig-ned with free atmospheric air currents and a substantially uni-directional air flow provided through the meter, an extension conduit attachment having orifice means at one end for introduction into a closed duct or other region of air flow removed from the meter, and quick detachable coupling means for coupling the other end of said extensionconduit in communication with said air channel, whereby said air channel may be selectively placed in communication through said inlet and outlet means directly with free.atmospheric air currents in which the meter itself is situated or through said extension conduit with an air flow at a point removed from the meter. g 33. A portable air velocity meter of theclass described comprising a casing, an .air channel in said casing increasing in cross-sectional area toward the outlet end thereof, a moving system comprising a vane movable in said air channel for deflection bythe air flow therethrough, a spring opposing such motion of the vane, an indicating device actuated by said moving system for giving direct readings in terms of air velocity from the deflection of said moving system, a substantially rigid conduit attachment comprising a stem portion having orifice means at its outer end for introduction into a closed duct or other region of air flow removed from the meter and formed with two passageways communicating with said orifice means, and releasable coupling means for detachably'coupling the other end of.

a said conduit attachmentto the meter casing with end of said stem, portion into different positions said two passageways communicating with opposite ends of said air channel, said conduitattach-z ment constituting a substantially rigid seli-supporting extension ,when coupled to said meter casing whereby said casing can function as a the meter is'operated in different angular positions, velocity indicating means actuated by said moving system, and an extensionconduit having orifice means at one end for introduction into a a self-supporting extension from the m'etercasf ing whereby said casing conjunction as a supporting handle for maneuvering the. orifice end of said extension conduit into different positions in the air stream. I

35. A portable air velocity meter of the class described comprising a casing, an air channel in said casing, a moving system comprising a: vane movable in said air channel for deflection by the air flow therethrough, said vane moving about an axis disposed substantially at right angles to the direction of flow of the air through said channel, a spring opposing the motion of said moving system, an indicating device associated with said moving system for giving direct readings in terms of air velocity from the deflection of said moving system, inlet-and outlet aperture means in opposite side walls of said casing for passing air through said channel, and a shutter member movably carried by said casing and actuatable' movable into predetermined relation to one of. said aperture means in the casing for reducing by 'a predetermined extent the eflective area of said latter aperture means for adapting the meter to the measurement of a higher range of velocities. 36. In a portable air velocity meter capable of being held in the hand and of being inclined at diflerent operating angles during use, the combinationof a casing, an air channel insaid cas-' ing, a moving system comprising a vane movable in said air channel for deflection by the air now 7 therethrough, spring means opposing such motion of the vane, indicating means adapted to give direct'readings in terms of ,air velocity from the deflection of said moving system, a conduit having one end connecting with said air channel and having orifice means at its other end adapted for introduction into a closed duct or other region of air flow relatively remote from said casing so that velocity measurements can be taken at points inaccessible to said casing and so that inaccura cies arising from, the turbulence created by disposing the casing in the air stream are avoided, means for substantially balancing said moving system to maintain the accuracy of the meter when held at different angles, and damping means equally eflective in any position of the meter for damping said indicatingmeans, said balancing means and said damping means cooperating to maintain the accuracy of the meter whendisposed in or moved to different angles orpositions as may be required to secure the desired readings. 37; A portable air velocity meter'comprising a casing, an air channel in said casing, inlet and outlet apertures for said channel in opposite side swalls of said casing i'or'passing air substantially in adirect straight line through said channel from one side of the casing to the other side, said hannel increasing in cross sectional area toward the outlet end thereof, a moving system comprising a vane movable in said air channel generally longitudinally thereof for deflection by the air flow therethrough, means yieldingly opposing "such motion 01' the vane and operative torestore the" latter to normal position after cessation of air flow, means fox-substantially balancingsaid moving system to maintain the accuracy of the meter when held at different; angles and when moved during the use thereof, said opposing nected to'said meter casing in communication closed duct or other region of air flow removed means being q eflective i i POB t Ori o from the meter and having its other end conthe meter, an indicating device associated with with said air channelfisaid conduit constituting terms of air velocity from the deflection oi said said moving system for giving direct readings in moving system, and damping means for damping the movements of said moving system, said damp ing means being equally efiective in'any position of the meter, the arrangement of the inlet and out-iet openings in opposite side walls of the casing providing for movement of the meter transv rsely oi the air iiow be g measured Withc'ut

Images