US3744092A

US3744092A - Apparatus for controlling the density of a fiber feed mat

Info

Publication number: US3744092A
Application number: US00150281A
Authority: US
Inventors: C Auten
Original assignee: Curlator Corp
Current assignee: Curlator Corp
Priority date: 1971-06-07
Filing date: 1971-06-07
Publication date: 1973-07-10
Anticipated expiration: 1990-07-10
Also published as: DE2227506B2; DE2227506C3; DE2227506A1; JPS513833B1; BE784465A; ATA485372A; CH547376A; AT333629B; CA945726A; GB1351413A

Abstract

For controlling its fiber density during formation of a mat that is to be fed to the lickerin of a card or web forming machine, a pressure gauge is connected to the inlet duct of the suction fan that causes fibers to be drawn from a feed mechanism and laid down on a condenser to form the mat; and this gauge is geared to a pivoted or reciprocable damper in the duct to control air flow in the duct, thereby to control the density of the mat. The control damper may be positioned either at the inlet or the outlet side of the fan.

Description

Auten 1 11 3,744,092 1451 July 10,1973

APPARATUS FOR CONTROLLING THE DENSITY OF A FIBER FEED MAT Charles R. Auten, Charlotte, NC.

Curlator Corporation, East Rochester, N .Y.

Filed: June 7, 1971 Appl. No.: 150,281

Inventor:

Assignee:

us. 01 19/1563, 19/89, 302 35 1111. C1 D0lg 25/00 Field of Search ..l9/l56-l56.4,

References Cited UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONS 684,810 12/1952 Great Britain ..302/35 811,578 8/1951 Germany ..302/35 Primary ExamineF-Dorsey Newton Attorney-Shlesinger, Fitzsimmons & Shlesinger [5 7 ABSTRACT For controlling its fiber density during formation of a mat that is to be fed to the lickerin of a card or web forming machine, a pressure gauge is connected to the inlet duct of the suction fan that causes fibers to be drawn from a feed mechanism and laid down on a condenser to form the mat; and this gauge is geared to a pivoted or reciprocable damper in the duct to control air flow in the duct, thereby to control the density of the mat. The control damper may be positioned either at the inlet or the outlet side of the fan.

6 Claims, 6 Drawing Figures Pmmmm 1 0 w SHEEIINS INVENTOR. I CHARLES R. AUTEN QML ZZ ZW ATTORNEYS PAIENIED ("973 SHED 3 0F 5 nmu/ OON INVENTOR. CHARLES R. AUTEN ATTORNEYS Pmtmzuim I 3.744.092

ME '6 0F 5 FIG. 5

INVENTOR.

CHARLES R. AUTEN ATTORNEYS PAIENIEflJmwm SBEEYSIIS FIG. 6

INVENTOR CHARLES R. AUTEN ATTORNEYS APPARATUS FOR CONTROLLING THE DENSITY OF A FIBER FEED MAT The present invention relates to apparatus for controlling the fiber density of a mat such as is to be fed into a card or into a machine for making random fiber webs.

ln a more specific aspect, the invention relates to apparatus for controlling the thickness of feed mats such as may be formed in the fiber feeding mechanism of the machine disclosed in the Langdon et al. U. S. Pat. No. 2,890,497, granted June 16, 1959.

In the feeder of US. Pat. No. 2,890,497, small tufts of fiber are carried upwardly from the bottom of a hopper by an elevating apron to .be delivered by an air stream in the space between a rotating condenser and a cooperating set of rollers to be formed into a feed mat that is fed over a feed plate by a feed roller into the lickerin of a card or web forming machine. The tufts, which are not picked off the elevating apron by the air stream, are recycled to the hopper. The air bridge is operated by means of a fan connected to the suction side of the rotating condenser. When the fan is running, the air bridge fills with tufts of fiber which are compacted by the suction of the fan; and this compaction of the fiber in the. trumpet-like or converging-walled duct would close off the air flow to the condenser, thereby halting stripping of the tufts of fibers from the apron pins, except for the fact that the condenser rotates. This rotation, along with the rotation of the rollers on the undercarriage, that cooperates with the condenser, moves the fiber feed mat forward, so that stripping of the tufts of fibers from the apron can continue. The action is immediate and continuous provided the air flow is of sufficient strength to remove tuftsof fibers from the elevating apron pins. Because of the forward movement of fiber to the air bridge, a variable air pressure is established; and the tufts are stripped and packed into the air bridge as needed to make up the feed mat which is to be delivered to the web-forming equipment.

With a fiber feed mechanism such as described, at any point across the width of the air bridge, where a weak packing of fiber might occur in the trumpet, a strong air flow is established, and the tufts are immediately pulled into the weak area to build it up. Thus, a feed mat of uniform thickness is formed across the condenser.

The air bridge in feeders such as described, measures the output of fibers on a volumetric basis, and causes the individual fiber tufts to be packed in between the condenser and the undercarriage under steady flow conditions. The packing pressure is dependent on the intensity of the suction pressure existing in the suction chamber and is directly related to the RPM of the fan.

In such feeder equipment, a constant speed fan is used, thus normally causing constant air velocity at a constant pressure head. However, when used with a variable opening and a variable flow of air through the feed mat being built up in the air bridge, a variable static pressure is created against which the fan has to work. This variable static pressure causes variation in the uniformity of the feed mat developed, which, in turn, will cause non-uniformity in the resulting product. The higher the static pressure, the more .compact the fiber in the air bridgebecomes, which in turn increases the static pressure still more. Hence, the static pressure will continue to increase until the feed mat is cleared from the formation chamber. The pressure, of course,

drops rapidly when the high density feed mat has been cleared. The build-up of pressure and the rapid decrease thereof giVes rise to a wide variation inthe lengthwise uniformity of the feed mat, and affects the next processing step, such as the formation of a sliver on the card or of a random fiber web on the web forming machine, with which the feeding mechanism is cooperating.

The variation in weight of the sliver or of the random fiber web should be kept to a minimum. The greater the deviation, the lower the quality of the sliver or web as regards further processing.

The prime purpose of the present invention is to continuously monitor static pressure within the feed con denser and limit its rise and fall so that the web density lengthwise is controlled within certain limits and as nearly as possible not to exceed 2 percent. With such a deviation, a much smaller deviation from the actual required mean weight of the sliver or web is obtained.

In order to overcome the variation, the air fiow can be monitored within the feed mat forming section of the feeder mechanism, and either the fan speed or the static pressure can be regulated to compensate for the differential air flow differences due to the air bridge tuft formation. A monitor might be positioned within the suction chamber of the feeder. This monitor would be a device for measuring static pressure; and any change in static pressure within the chamber measured by the monitor could be converted to an electrical signal to cause either a change in speed of the fan by a variable speed motor, or to cause a damper to be actuated to change the amount of air flow through the fan.

Variable speed motors are usually expensive and the circuitry required is complicated.

The present invention relates to a control for changing the amount of air flow employing a damper. The damper control is less expensive, and can be used in setups where a plurality of cards or similar machines are to be fed from a single source of fibers.

ln operation, with air being drawn through the condenser via the feed fan, a static pressure is developed, as stated above, sufficient to form a feed mat. As the feed mat is moved forward, a variable pressure flow is also developed, as stated, due to the variable filtering of the air through the tufts of fibers forming the feed mat, and the open area caused by the rotating condenser. As the feed mat accumulates in the air bridge increasing the density, the static pressure is likewise increased. If this increase in pressure rises above the predetermined level, due to the density of the fiber accumulated in the air bridge, to be above the required maximum, the monitor operates a switch moving thedamper in a direction to restrict somewhat the air flow from the suction chamber to the fan. This decreases the packing pressure of the fiber. On the other hand, should the feed mat decrease in density, the monitor would actuate another switch which would open the fan damper, hence increasing the flow to the vacuum chamber and causing more fiber tufts to be drawn into the air bridge, thus increasing the packing pressure and the density of the feed mat being formed. This constant alteration of air flow and pressure operates to keep the fiber density in the air bridge within a predetermined tolerance, and hence operates to produce more uniform feed mats.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims particularly when read in conjunction with the accompanying drawings.

In the drawings:

FIG. 1 is a somewhat diagrammatic longitudinal vertical section showing a conventional feeder mechanism as modified in accordance with one embodiment of this invention;

FIG. 2 is a fragmentary vertical sectional view on an enlarged scale showing particularly a modified form of feed control;

FIG. 3 is a schematic diagram showing how a conventional pressure gauge may be modified to operate in conjunction with the mechanism of the present invention;

FIG. 4 is a diagrammatic view, showing another way in which the pressure gauge may be electrically coupled to a damper to control the air fiow from the condenser;

FIG. 5 is a greatly enlarged view showing another form of damper and the control therefor; and

FIG. 6 is a sectional view taken at right angles to FIG. 5.

Referring now to FIG. 1, denotes generally how a conventional feeder mechanism may be modified in accordance with the present invention. This feeder, which is basically constructed as disclosed in U.S. Pat. No. 2,890,497, issued June 16, I959, comprises a hopper that has an opening or mouth at 26 into which the textile or other stock material, which is to be fed, is dumped. Mounted in the base of the hopper is an endless floor apron or conveyor belt 27, that travels over

pulleys

29 and 30 which are joumaled in the hopper.

This floor apron or conveyor 27 carriesthe stock material from opening 26 to an elevating apron or conveyor 40, which is mounted to travel over pulleys 41 and 42. This apron, as shown in FIG. 2, and in U.S. Pat. No. 2,890,497, isprovided with a plurality of straps in which are embedded pins 45 that are inclined in the direction of travel of the belt. The pins 45 pick up bunches of the stock material, which are carried to the elevating apron by the floor apron 27, and carry the tufts of fibers upwardly toward the top of the hopper as the belt itself travels upwardly.

Mounted in the upper portion of the hopper to cooperate with the elevating apron 40, is a stripping apron 50. This apron travels over

pulleys

51 and 52; and it carries pins 55. The stripping apron reduces the tufts of material, which are carried upwardly by the pins of the elevating apron, to a size suitable for use in the manufacture of a mat or web; and it removes excess material from the elevating apron and returns this material to the body of the hopper itself. This stripping apron leaves only small bunches or tufts on the individual pins 45.

These aprons may be driven in the same manner as described in U.S. Pat. No. 2,890,497.

The tufts carried by the pins 45 are stripped from these pins by suction. A suction fan 70 is mounted on top of the hopper 25. This fan is driven by a motor 72, which is also mounted on the top of the hopper, through pulleys and a belt 75, that connect the armature shaft of the motor with the fan drive shaft 74. The fan exhausts to atmosphere through outlet 76. Its intake is through a conduit 77 that is connected with an upright duct 78. The lower end of this duct 78 communicates with a screen box 80.

.lournaled in the screen box is a rotary foraminous condenser 85. This condenser may comprise a single cylindrical screen 86, or two coaxial such screens. A duct 89 extends diametrically through the condenser and is bounded by

spacers

90 and 91. The

duct spacers

90 and 91 are secured at opposite ends to opposite sides of the screen box 80. The duct 89 is thus fixed relative to the rotary condenser and forms an extension of the duct 78.

The condenser may be driven as described in Pat. No. 2,890,497.

Adjacent the condenser and below it is a roll carriage in which are joumaled a plurality of

rollers

101, 102, 103 and 104. These are feed rollers and may be driven in the same manner as described in the abovementioned patent. Idler rollers 105 and 106 (FIG. 2) may be mounted between the

feed rollers

101 and 102 and 102 and 103, respectively. The roll carriage is connected to the hopper 25 by a plate 110 which constitutes the lower surface of a duct or conduit 112 which forms an air bridge between the hopper and the screen box. The upper side of the duct is bounded by the rear seal plate 115 which is bolted to the screen box.

The roller 103 is closer radially to the axis 121 (FIG. 2) of the condenser than the roller 106 or the roller 102. In fact, the distance of the several rollers from the axis of the condenser gradually decreases so that fibers carried through the conduit or air bridge 112 to the condenser by suction are compacted between the rotating condenser and the rollers to form a mat; and as the condenser rotates, this mat is fed forward. It passes onto a feed plate 130, over which it is fed by the feed roll 152 into the rotating lickerin 155 of the card, or random fiber webber, or other machine, with which the feed mechanism of this invention is used.

In one embodiment of the invention, the mechanism for controlling the thickness longitudinally of the mat that is to be fed into the processing machine, may include a rotary damper, such as shown at 200 in FIG. 4, and a pressure gauge for measuring differential pressures, such as shown at 201 (FIG. 3). This pressure gauge is connected by a duct, indicated diagrammatically at 202, with the suction duct 77 so that suction in duct 77 will operate the gauge.

This pressure gauge may be of conventional manufacture, and include two electrically

conductive pins

203 and 204 set in predetermined position to restrict the movement of the gauge needle 205 to the left or right. The gauge needle is connected by a lead 207 to the main supply line L,.

The high and

low pins

203, 204 are connected to solenoids or relays 212, 225, respectively (FIG. 3), which operate when the gauge needle 205 makes contact with either the high or low limit pins. The closing of a relay operates a switch which completes the circuit to a drive motor 222, such as a three-wire reversible gear motor having two pole four coil construction and a permanent split capacitor. The motor 222 is connected by gearing, including the gear 230, and by an electro-magnetically operated clutch 232 with a shaft 233 to which the damper 200 is secured, so that the motor operates the damper to either its closed or open position, depending upon the signal generated by the monitoring gauge 201.

The right-hand pin 204 is connected by theline 210 with the relay or solenoid 212, which in turn is connected with the main line L The relay or solenoid 212 operates the switch 214 which serves to connect the line 216 with the line 218, which connects the main line L with the clockwise rotating coil of motor 222. The left-hand pin 203 is connected by line 223 with the relay or solenoid 225, which operates the switch 227 that connects line 216 with line 229 that controls the left-hand rotating coil of the motor 222, for causing motor 222 to operate counterclockwise.

In FIG. 3, a butterfly type damper 200 is shown in the suction-duct 77 between the suction side of the fan and the condenser chamber. The electromagnetic clutch 232 is normally closed for continuous monitoring. However, the clutch may be opened by a manually operated switch so that the damper may be adjusted to compensate for changes in fibers and the materials being processed through the feeder mechanism. Changes in fibrous materials cause a different quality of air flow through the feed mat, since higher denier, for instance, has a lower resistance to air; whereas fine deniers have a higher resistance due to the increased felting action within the feed mat.

The solenoid for operating the clutch 232 is indicated at 240. It is connected by the

lines

220 and 242, respectively, with the main lines L and L respectively. Manual operation of the clutch may be effected through a manually movable switch 243. manual operation of the motor 222 may be effected through operation of a push pull member 245 which is connected to reed member 246 to move that member selectively into contact with contact 248, which is connected with line 218, or with contact 249 which is connected with line 229. Reed 246 is connected to main line L While butterfly dampers are simple in construction, they do have a detrimental effect on air flow itself due to turbulence pockets. This type of damper causes the air stream to fluctuate. Also, when processing short fibrous material, such as pulp fibers and the like, these fibers tend to accumulate on the damper face, and over a period of time reduce the effectiveness of the damper control and its response time.

The preferred method of monitoring changes in static pressure is via a light-sensitive electric switch which is also responsive to changes in pressure. Such a device is disclosed in the U. S. Pat. No. 3,397,319 of J. P. Locke, granted Aug. 13, I968.

Gauges, such as described in US. Pat. No. 3,397,319, can be adapted to act as both pressure indicators and pressure control switches by mounting a light-interrupting element on the magnetizable helical core that is incorporated in the gauge and that is caused to rotate by reason of a permanent magnet mounted on the free end of a cantilever spring which is actuated by a pressure diaphragm. The light-interrupting element is mounted on the helical core in position to interrupt, or to allow passage of light from, a light source to a photosensitive cell adjustably mounted so as to permit the interruption and passage of light at predetermined pressures. The photosensitive device is connected in a relay circuit to open an electrically actuated switch and close this switch at predetermined pressures, thereby controlling absolute or differential fluid pressure. By connecting the photoelectric gauge into a relay circuit an electrically activated switch can be made to open and close at a predetermined pressure, and thereby control the variation in static pressure in a condenser chamber via a damper or the like. Such a gauge is shown so connected in FIG. 4.

In FIG. 4, the pressure gauge is indicated at 250. It has a needle 252, which is connected through a control circuit denoted diagrammatically at 254 with the supply lines L and L The needle is moved in one direction or the other by pressure through operation of the diaphragm of the gauges The diaphragm is connected by a duct 255 with the suction duct 80 of a fan 70. The needle is connected by the line 254 with the supply line L,. The

pins

256 and 258 are connected by

lines

260 and 262, respectively, with the control circuit, which is designated as a whole at 264. The control circuit is connected by a common line 266 with the motor 270 which operates the damper 200. The coil of the motor, which controls its clockwise rotation, is connected by line 272 with the control circuit 264. The counterclockwise movement of the motor is effected by a coil which is connected by the line 274 with the control circuit.

If the pressure in the condenser chamber 80 rises, the gauge needle 252 is thrown toward the high side of the gauge. If this rise is more than a predetermined pressure, the needle moves far enough for the light source within the gauge to be interrupted, activating the photoelectric cell 280, which in turn, actuates a relay or solenoid (not shown) to cause the switch 281 to close the contacts 283 to supply current to the relay 285 and activate the associated switch 287 through line 274 and common line 266 to allow current to be supplied to the motor 270 and turn this in a clockwise direction, thus closing the damper 200. This reduces the static pres sure in the condenser chamber; and, as the pressure drops, the light beam once more activates the photoelectric cell 280, thus breaking the circuit and stopping the motor, and hence maintaining the pressure within the chamber 80.

A drop in pressure activates the low side of the circuit since the needle will then close a contact through the pin 256 and the photoelectric cell 290 will operate to shift the switch 291 and close the contacts 293, which causes the relay 295 to be energized to close the switch Y297 and allow current to be supplied to the motor through

lines

272 and 266 and turn the motor in counterclockwise direction, thus opening the damper and allowing the condenser pressure to rise.

It will be seen that this continuous monitoring holds the static pressure at the condenser within certain limits, thus causing a more even web density at the air bridge 112 (FIG. 1) of-the feeder mechanism.

FIG. 1 shows an embodiment of the invention in which an axially-reciprocable tapered plug 300, instead of a pivotal damper, is used to vary the pressure in duct 77. Here the plug dampens the inlet or suction side of the fan just as in the case of the dampers already described. The mechanism for actuating this plug is substantially the same as shown in FIG. 2, and will, therefore, be described in connection with the latter figure.

FIG. 2 shows an embodiment of the invention in which the outlet of the fan is dampened rather than its suction side. The effect is the same. Here again a tapered plug 300 is used as the damper. It is moved toward or away from the orifice 302 in a duct or pipe 77 which is aligned with the axis of the outlet duct 77. This plug is connected to a shaft 304 in a position to reciprocate in a bearing or bushing 305 in a box or chamber 307, whose top is perforated, as denoted at 309. The shaft 304 is connected by a linkage, including the link 310, wormwheel 312, and worm 314 with a reversible motor 215, whose direction of rotation is determined by the pressure gauge 250 and the control circuit 254 in a manner similar to that described with reference to the embodiment of the invention shown in FIG. 4. When the motor rotates in one direction or the other, the gear wheel 312 is rotated correspondingly and the plug damper 300 is moved rectilinearly. Perforated baffles 306, 308 may be positioned on opposite sides, respectively, of the plug 300. This arrangement reduces the output velocity of the fan, and hence reduces the noise level by baffling the air flow.

FIGS. and 6 illustrate details of another arrangementof the preferred plug type baffle system. Here the plug is disposed between the suction chamber and the fan. The cross-sectional area of the duct 70', which leads from the suction chamber, is equivalent to the cross-sectional area of the plug chamber 320, the difference in area between the chamber 320 and the area of the duct 78 equaling the area of the plug at its maximum dimension.

The plug has a cylindrical portion 314' and a tapered nose 3l6 fitting the tapered internal conical surface 318 at the confronting end of the duct 78.

In this embodiment of the invention, the plug is moved to and from operative position through operation of a motor 325, which drives through a gear reduction unit 326 a sprocket 328 that is connected by a chain 330 with a sprocket 332. The sprocket 332 is secured to the shaft 334 on which is fastened a pinion 336 that meshes with a rack 338 that is connected by a bar 340 to the plug 300. The bar 340 passes through a chamber 342 which operates to reduce any air loss from the duct due to movement of the bar 340. The operation of the motor 325 is, of course, under control of avpressure gauge, as in the previouslydescribed embodiments of the invention.

The thickness controlling mechanism of the present invention has particular advantage in a multiple feeding system such as that disclosed in the Auten and Langdon U.S. Pat. No. 3,326,609, issued June 20, 1967, for with a plug or damper arrangement, such as disclosed in the present application, one suction fan may be used in a common condenser suction line, thus eliminating the need for individual feeder fans and motors, but still retaining the individual static pressure control at each card via the automaticidamper control device disclosed herein.

While in the described embodiments of the invention, the pressure gauge has been described as operating through contact of its needle with pins in the gauge to cause clockwise or counterclockwise operation of the motor that actuates the damper, it will be understood that the needle movement could be used in other ways, as will be obvious to those skilled in the art, to effect movement of the dampers selectively in opposite directions.

Furthermore, while the invention has been described in connection with use of a pressure gauge to monitor air flow to or from the fan, it will be understood that a flowmeter, or other suitable measuring instrument might be used instead.

While the invention has been described in connection with several different embodiments thereof, then it will be understood that the invention is capable of further modification, and this aspplication is intended to cover any embodiments of the invention that fall within the scope of the invention, or the limits of the appended claims.

I claim:

1. In a machine for forming a fiber mat,

a movable foraminous condenser,

a conduit for conducting a stream of fibers suspended in air onto said condenser,

a suction fan,

means for actuating said fan,

a duct connected at one end to said condenser and at its opposite end to the suction side of said fan to draw air through said condenser across the whole width thereof, upon actuation of said fan, to cause fibers to be deposited from said conduit on said condenser across its width,

a pressure gauge operatively connected to said duct between said condenser and said fan to monitor air flow through said duct to said fan,

a single movable damper mounted operatively at one side of said fan in the air stream flowing through said fan to vary, with its movement, the amount of air flow through said fan from the suction side of said fan to the exhaust side thereof, and

means operatively connecting said pressure gauge to said damper to vary the position of said damper with variation in pressure in said duct.

2. A machine as claimed in claim 1, wherein said damper is movably mounted on the exhaust side of said fan to throttle flow of exhaust air from said fan.

3. In a machine for forming a fiber mat,

a movable foraminous condenser,

a suction fan,

means for actuating said fan,

a pressure gauge mounted in said duct between said condenser and said fan to monitor air flow through said duct to said fan,

-- a single movable damper disposed to vary, with its movement, the amount of air flow through said fan, and

means operatively connecting said pressure gauge to said damper to vary the position of said damper with variation in pressure in said duct,

said damper being disposed in said duct between said gauge and said fan.

4. In a machine for forming a fiber mat,

a movable foraminous condenser,

a suction fan,

means for actuating'said fan,

a single movable damper disposed to vary, with its movement, the amount of air flow through said fan,

said damper being pivotally mounted in said duct.

5. In a machine for forming a fiber mat,

a movable foraminous condenser,

a suction fan,

means for actuating said fan,

a single movable damper disposed to vary, with its movement, the amount of air flow through said fan, and a means operatively connecting said pressure gauge to said damper to vary the position of said damper with variation in pressure in said duct,

said damper being rectilinearly reciprocably mounted in said duct and having a conical portion operative to close off the bore of said duct to a variable extent as said damper is moved rectilinearly.

6. In a machine for forming a fiber mat,

a movable foraminous condenser,

a suction fan,

means for actuating said fan,

a single movable damper disposed to vary, with its movement, the amount of air flow through said fan, and

said damper being movably mounted on the exhaust side of said fan to throttle flow of exhaust air from said fan,

an exhaust box connected to the exhaust side of said fan, and

a duct forming said connection,

said damper being an axially reciprocable tapered plug mounted in said box with its smaller end in confronting relation to the last-named duct to vary the opening of said duct with variation in pressure in the first-named duct, and

said box being perforated for exhaust of air therefrom.

Claims

1. In a machine for forming a fiber mat, a movable foraminous condenser, a conduit for conducting a stream of fibers suspended in air onto said condenser, a suction fan, means for actuating said fan, a duct connected at one end to said condenser and at its opposite end to the suction side of said fan to draw air through said condenser across the whole width thereof, upon actuation of said fan, to cause fibers to be deposited from said conduit on said condenser across its width, a pressure gauge operatively connected to said duct between said condenser and said fan to monitor air flow through said duct to said fan, a single movable damper mounted operatively at one side of said fan in the air stream flowing through said fan to vary, with its movement, the amount of air flow through said fan from the suction side of said fan to the exhaust side thereof, and means operatively connecting said pressure gauge to said damper to vary the position of said damper with variation in pressure in said duct.

3. In a machine for forming a fiber mat, a movable foraminous condenser, a conduit for conducting a stream of fibers suspended in air onto said condenser, a suction fan, means for actuating said fan, a duct connected at one end to said condenser and at its opposite end to the suction side of said fan to draw air through said condenser across the whole width thereof, upon actuation of said fan, to cause fibers to be deposited from said conduit on said condenser across its width, a pressure gauge mounted in said duct between said condenser and said fan to monitor air flow through said duct to said fan, a single movable damper disposed to vary, with its movement, the amount of air flow through said fan, and means operatively connecting said pressure gauge to said damper to vary the position of said damper with variation in pressure in said duct, said damper being disposed in said duct between said gauge and said fan.

4. In a machine for forming a fiber mat, a movable foraminous condenser, a conduit for conducting a stream of fibers suspended in air onto said condenser, a suction fan, means for actuating said fan, a duct connected at one end to said condenser and at its opposite end to the suction side of said fan to draw air through said condenser across the whole width thereof, upon actuation of said faN, to cause fibers to be deposited from said conduit on said condenser across its width, a pressure gauge mounted in said duct between said condenser and said fan to monitor air flow through said duct to said fan, a single movable damper disposed to vary, with its movement, the amount of air flow through said fan, means operatively connecting said pressure gauge to said damper to vary the position of said damper with variation in pressure in said duct, said damper being pivotally mounted in said duct.

5. In a machine for forming a fiber mat, a movable foraminous condenser, a conduit for conducting a stream of fibers suspended in air onto said condenser, a suction fan, means for actuating said fan, a duct connected at one end to said condenser and at its opposite end to the suction side of said fan to draw air through said condenser across the whole width thereof, upon actuation of said fan, to cause fibers to be deposited from said conduit on said condenser across its width, a pressure gauge mounted in said duct between said condenser and said fan to monitor air flow through said duct to said fan, a single movable damper disposed to vary, with its movement, the amount of air flow through said fan, and means operatively connecting said pressure gauge to said damper to vary the position of said damper with variation in pressure in said duct, said damper being rectilinearly reciprocably mounted in said duct and having a conical portion operative to close off the bore of said duct to a variable extent as said damper is moved rectilinearly.

6. In a machine for forming a fiber mat, a movable foraminous condenser, a conduit for conducting a stream of fibers suspended in air onto said condenser, a suction fan, means for actuating said fan, a duct connected at one end to said condenser and at its opposite end to the suction side of said fan to draw air through said condenser across the whole width thereof, upon actuation of said fan, to cause fibers to be deposited from said conduit on said condenser across its width, a pressure gauge mounted in said duct between said condenser and said fan to monitor air flow through said duct to said fan, a single movable damper disposed to vary, with its movement, the amount of air flow through said fan, and means operatively connecting said pressure gauge to said damper to vary the position of said damper with variation in pressure in said duct, said damper being movably mounted on the exhaust side of said fan to throttle flow of exhaust air from said fan, an exhaust box connected to the exhaust side of said fan, and a duct forming said connection, said damper being an axially reciprocable tapered plug mounted in said box with its smaller end in confronting relation to the last-named duct to vary the opening of said duct with variation in pressure in the first-named duct, and said box being perforated for exhaust of air therefrom.