US3670778A

US3670778A - Pneumatic warp thread monitoring apparatus

Info

Publication number: US3670778A
Application number: US104554A
Authority: US
Inventors: Ghert Meier
Original assignee: Oerlikon Contraves AG
Current assignee: Rheinmetall Air Defence AG
Priority date: 1970-02-27
Filing date: 1971-01-07
Publication date: 1972-06-20
Anticipated expiration: 1989-06-20
Also published as: CH520218A; DE2060908C3; FR2094910A5; JPS4826824B1; DE2060908A1; CA929832A; DE2060908B2; SE368040B; GB1298312A

Abstract

A warp thread monitoring apparatus for looms wherein each properly tensioned warp thread passes through an associated thread monitoring lamella or blade and retains such in an elevated position, and upon rupture of the relevant warp thread this lamella then drops into a lower position, thereby activating a release or triggering mechanism for sounding an alarm or stopping the loom. According to important aspects of the invention, a channel system is arranged beneath each row of thread monitoring lamellae and upon rupture of the relevant warp thread the corresponding lamella drops into this channel system to interrupt the flow of an air current forced from the inlet side of the channel system to the outlet side thereof. This in turn affects the operation of a pneumatic flow sensing device influencing the trigger mechanism for sounding the alarm or stopping the loom.

Description

[ June 20, 1972 n m w m j.

a mm mm PNEUMATIC WARP THREAD MONITORING APPARATUS ABSTRACT [72] Inventor: Ghert Meier, Stadel, Switzerland A warp thread monitoring apparatus for looms wherein each [73] Assignee: Contraves AG, Zurich, Switzerland [22] Filed: Jan. 7, 1971 properly tensioned warp thread passes through an associated thread monitoring lamella or blade and retains such in an [21] APPLNO'Z elevated position, and upon rupture of the relevant warp thread this lamella then drops into a lower position, thereby [30] Foreign Application Priority Data activating a release or triggering mechanism for sounding an Feb. 27, 1970 Switzerland alarm or stopping the loom. According to important aspects of .2894/70 the invention, a channel system 18 arranged beneath each row 52 uses 157 thread mnitring and upon rupture relevant warp thread the corresponding lamella drops into this [58] Field of139/336, 349, 350, 353, 358,

511 Int.Cl.

channel system to interrupt the flow of an air current forced from the inlet side of the channel system to the outlet side thereof. This in turn affects the operation of a pneumatic flow [56) References Cited sensing device influencing the trigger mechanism for sounding the alarm or stopping the loom. UNITED STATES PATENTS FOREIGN PATENTS OR APPLICATIONS 6 Claims, 3 Drawing Figures .llfflif .lfflflillllllf Vlillfll s 7ffllllllI/Illfl VIIIIIII r .lll/l/IlllllIl/l YIIIIII 7lIlflIlIIll/l l ,IIIIIIII .lI/lI/IIIIIIIII VIII/III 7IIIII/l/Illl/ll ill/Ill! a I/lIl/lllllll/l/ VIIIIIIJ VIIIIIIIIIIIII II/IIIII vtlllrllllrflllv It'll/I VIIIIIIIIIIIII' PKTENTEnmao I972 IN VENTOR GHERT VIE/ER PNEUMATIC WARP THREAD MONITORING APPARATUS BACKGROUND OF THE INVENTION The present invention broadly relates to loom stop motions, and, more particularly. concerns itself with a new and improved warp thread monitoring device for looms which is of the type wherein each properly tensioned warp thread piercingly extends through an associated thread monitoring lamella or blade and retains such lamella in an elevated position, and upon rupture of the relevant warp thread this lamella drops into a lower position. thereby placing into operation a triggering mechanism for indicating a fault condition of the loom, as by sounding an alarm or stopping the loom.

In known prior art stop motion devices of this general type, the lamella consist of sheet metal equipped with an elongate hole or aperture at the portion thereof disposed above the threading eyelet for the warp thread. A rail or bar piercingly extends through the elongate hole. This rail consists of three parallel electrically insulated metal strips, the outer ones of which are electrically coupled to one pole or terminal source and the inner one of which is connected to the other pole or terminal of an electrical current circuit controlling the triggering mechanism. If owing to rupture of the associated warp thread the corresponding lamella drops, then this falling down of such lamella closes the previously open alarm or current control by electrically coupling the intermediate metal strip, which protrudes from the rail profile and is provided with teeth at its upper end, with one of the lateral metal strips. The entire rail is continuously moved back and forth in its longitudinal direction. Its tooth arrangement entrains each lamella which has dropped and therefore forms a gap or passageway to both sides of the relevant lamella between the other lamella. so that the location of the ruptured warp thread, after triggering the alarm or stopping the loom, can be quickly ascertained. Additionally, this toand -fro movement of each lamella which has dropped, together with the movement of the aforementioned rail favors the bridging of the metal strips at the rail by the relevant lamella. Nonetheless, owing to the marked dust contamination of the air within a weaving mill it oftentimes occurs that the corresponding contamination of the electrical contact locations of the aforementioned rails and/or lamellae and which should close the alarm or current control circuit, owing to such contamination of the contact locations, and following dropping of a lamella, either fails to immediately close the alarm or current control circuit, and if the contamination is intensive enough, fails to close such circuit at all, so that a faulty fabric is continued to be woven. Upon dropping of such lamella following warp thread rupture, it can also happen that owing to loose shifting or displacement of the dropped lamella, sparks are produced at the electrical contact locations resulting in the danger that the dust or other contaminants which are present are explosively ignited.

SUMMARY OF THE INVENTION Hence there is a real need still existing in the art for warp thread monitoring equipment which is not associated with the aforementioned drawbacks of the prior art constructions. Accordingly, a primary objective of the instant invention is directed to the provision of warp thread monitoring apparatus which effectively and reliably fulfils the existing need and is not associated with the aforenoted disadvantages existing in prior art stop motion equipment.

Another more specific object of the present invention relates to a stop motion device for looms, particularly for shutting down the loom and/or indicating an alarm condition upon rupture of one or more of the warp threads, wherein operation of the stop motion equipment itself is extremely rapid, after occurrence of the fault condition, and positively and reliably indicates malfunction of the loom.

Yet a further significant object relates to an improved stop motion device for monitoring warp threads at looms, which device is relatively simple in construction, extremely reliable in operation, provides for rapid monitoring of the momentarily existing operating conditions of the loom, and affords nondelayed triggering of an alarm and/or shutdown of the loom upon occurrence of a malfunction thereat.

The unreliable monitoring function noted in the prior art equipment is intended to be avoided with the present invention in that a channel arrangement is advantageously disposed beneath the row of thread monitoring lamellae, a longitudinally directed air current being forced through such channel arrangement. Each lamella when no longer supported by its associated warp thread drops into the channel arrangement, causing interruption of the air flow to the outlet end of such channel arrangement so that through the use of a flow controlled-pneumatic element, upon interruption of the flow of air through the channel arrangement, each warp thread rupture can be ascertained most reliably and used to activate the associated triggering mechanism.

Now, in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the inventive warp thread monitoring apparatus contemplates the provision of a channel arranged beneath each row of thread monitoring lamellae. Upon occurence of a defective condition of a warp thread, typically rupture, the associated lamella drops into the channel, interrupting an air current forced from the inlet side of such channel towards the outlet side thereof. This in turn controls operation of an associated pneumatic flow sensing device which influences a trigger mechanism.

BRIEF DESCRIPTION OF THE DRAWING The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawing wherein:

FIG. I is a schematic side view in cross-section of a preferred embodiment of warp thread monitoring device for a group of warp threads, the sectional view being taken substantially along the line II of FIG. 2.

FIG. 2 is an elevational view of the warp thread monitoring device depicted in FIG. I as viewed substantially along the line IIII thereof; and

FIG. 3 schematically illustrates details of a fluidic sensing device with a subsequently arranged pneumatic OR-gate for evaluation of the operating conditions of the equipment depicted in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Considering now the drawings there is illustrated therein an exemplary embodiment of warp thread monitoring device used in conjunction with textile equipment, particularly a loom. By referring now specifically to FIGS. I and 2 there will be recognized a channel system I consisting of a plurality of substantially aligned linearly extending

channel members

11, 12, I3, etc.,each of which possesses a substantially U-shaped configuration in cross-section. Between each two neighboring channel members, such as channels ll, 12, and 12, 13 there is arranged an intermediate tubular member or pipe 2, the construction and operation of which will be more fully considered hereinafter. A lamellae support rail 3 is mounted above the channel system I and in substantial parallelism with respect thereto. This support rail 3 piercingly extends through the upper elongate holes or slots 40 of a multiplicity of warp thread lamellae or blades 4 of known construction.

Now the warp thread apertures 41 of all the lamellae 4 are pierced by a respective warp thread K. All of the warp threads K extend in parallelism to one another between the support rail 3 and the channel system I and specifically in a transverse direction with respect to these components, as best indicated by referring to FIG. I. As long as each warp thread K is properly tensioned then such warp threads will retain the associated lamella 4 in its corresponding raised or elevated position. On the other hand, once a warp thread has ruptured, for instance as indicated in FIG. 1 at the location designated by reference character KB, the relevant lamella 4 will then drop down until it remains suspended between two neighboring teeth of the row of teeth 30 provided at the upper side of the support rail 3, which rail can be moved toand -fro in its lengthwise direction, as indicated by the double-headed arrow appearing at the right of FIG. I. When this happens the lower portion of the corresponding lamella 4 blocks the flow of an air current through the relevant channel member of the channel system 1.

Now as best indicated by again referring to FIG. I an air current is forced or blown through each channel member 11, I2, 13 and so forth from the left towards the right of the channel system 1. This air current can move freely from the inlet side of the channel system, at the left of FIG. I, to the outlet side thereof, at the right of FIG. 1, so long as none of the lamellae 4 associated with the corresponding channel member drop into their lowered position because of thread rupture, to thus block or impede air flow through such channel member. The air needed to produce the moving air current can be furnished from any suitable compressed air container or source, which for convenience in illustration has not been particularly depicted in the drawings, the air then moving through the intermediate air supply tubes 2, the upper respective ends of which are conveniently connected to such compressed air supply container means or to compressed air supply conduits through the agency of a suitable connection, such as a hose or equivalent device.

An intermediate wall 21 arranged at the lower portion of each intermediate hollow tube 2 sub-divides each such supply tube 2 into a first chamber or compartment 22 and a second chamber or compartment 23. The left-hand side compartment 21 of each intermediate tube 2 communicates by means of an aperture or bore 24 with the flow region of the

corresponding channel member

11, 12 or 13 located to the left of such intermediate supply tube. The

compartments

22 and 23 will be seen to extend substantially transversely with respect to the direction of air flow through the channel system 1.

Additionally it will be seen that leading from the compartment 23 at the right-hand side of each intermediate air supply tube 2 is an appropriately configured aperture or hole 25 communicating with the downstream arranged channel member 12 or 13, and so forth. located at the right side of each such intermediate tube 2 in the arrangement of FIG. I. Compressed air flows continuously out of the supply source through the upper portion of the air supply tube 2 and then initially through the compartment 23, through the associated discharge opening 25 and then into the portion of the channel system I located to the right of the corresponding intermediate supply tube 2. On the other hand, in the left-hand compartment 22 of each intermediate tube 2 there is only present a downward flow of air from the infeed opening 24 provided that none of the lamellae 4 arranged to the left of the corresponding intermediate tube 2 and associated with the corresponding portion of the channel system I have dropped because of rupture of a warp thread. The air discharged from the left-hand compartment 22 arranged at the intermediate tube 2 flows into the surrounding atmosphere, as clearly shown in FIG. 1. Below the lower boundary line of the channel system I each intermediate tube member 2 is provided at its outer walls with the openings or

apertures

26 and 28, as shown, and at the intermediate partition wall 21 with the further opening or aperture 27. At least the

apertures

26 and 27 are aligned with one another. Again as best seen by referring to FIG. 1, between the aperture 28 leading from the righthand compartment 23 of the first intermediate tube 2 at the left of the arrangement of FIG. 1 and the aperture 26 appearing at the left-hand compartment 22 of the next successive downstream located intermediate tube member 2 there is provided an air flow conduit 5. Moreover, a respective nozzle-like constricted portion 50 is provided or mounted approximately before the outlet side of each such connection conduit 5 leading from one such hollow tube member to the next successive tube member 2.

Now as clearly indicated in FIG. 1 behind or downstream of each such constricted portion 50 there is provided a transversely extending line or channel 51 which leads to a sensing outlet line or conduit 52. The jet of air emanating from the nozzle-like constricted portion 50 is thus ejected or blown out of the conduit 5 through the confronting aperture or hole 26 into the compartment 22 of the next arranged tube member 2 as appear in the direction of air flow. A counter aircurrent or jet is ejected or blown from the opposite side of the nozzle-like constricted portion 50, in other words downstream thereof, and specifically, through the aperture 27 at the intermediate wall 21 and into the compartment 22. Now as long as the flow of air in the channel system 1 consisting of the

channel members

11, 12, I3 and so forth, can freely move from the inlet side of the channel system to the outlet side thereof, that is, from the left towards the right of FIG. I, and such air flow is not blocked or impeded by a detached lamella 4, in other words one which has dropped, then the air current in the compartment 22 of the corresponding intermediate tube member 2 will move from the top towards the bottom and thus deflect the two air currents moving in countercurrent flow out and through the apertures or holes 26 and 27, as clearly indicated by the arrows appearing at the left-hand arranged tube member 2 of the system of FIG. I.

However, as soon as the flow of air through the channel system 1 has been interrupted owing to the presence of a defective or ruptured warp thread, then it will be recognized and understood that the compartment 22 of the next successive intermediate tube member 2 located downstream of the lamella which has dropped into the channel because of thread rupture will no longer conduct an air flow downwardly through the compartment 22. As a result the air jet emanating from the aperture or hole 27, blocks or dams up the flow of the air jet coming out of the other aperture 26. Thus, while during normal conditions of operation the sensor outlet conduit 52 and the transverse channel 51 are subjected to a negative pressure condition at the region behind or downstream of the injector nozzle-like arrangement 50, now at the outlet conduit 52 there prevails an over-pressure owing to such rupture of the warp thread. Such overpressure condition can then be used to activate a triggering device as will now be explained.

FIG. 3 illustrates at the left side thereof a flow controlledfluidic element or component 6 equipped with a supply line or conduit 60 and two outlet lines or

conduits

61 and 62, as well as a control conduit 52 merging at the branch-ohlocation of the

outlet conduits

61 and 62, that is, such control conduit representing the sensor outlet conduit 52 of the arrangement of FIG. 1. As long as no overpressure condition prevails in this sensor outlet, conduit 52, rather a negative pressure, then in the fluidic element 6 the air will flow from the supply conduit 60 to the outlet conduit 61. However, as soon as, and for such time as, an overpressure condition exists in the associated sensor outlet conduit 52, then the air flow from the supply conduit 60 of the corresponding fluidic element 6 will be deflected into outlet conduit 62.

Now all of the outlet conduits 61 of each of the fluidic elements 6 are in communication with one of the inputs of a pneumatic OR-gate 7, at the output 70 of which there is coupled a triggering or evaluation device A, Triggering or evaluation device A serves to indicate a disturbance condition at the loom, for instance by initiating stopping of the loom and/or triggering of an alarm owing to rupture of a warp thread, as soon as one of the control conduits no longer carries an underpressure.

It should be apparent that a number of devices of the type shown in FIG. 1 could be arranged in parallel juxtaposed relationship to one another in order to be able to accommodate in staggered relationship closely adjacently situated warp threads K.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

Accordingly, what is claimed is:

l. A warp thread monitoring apparatus for textile machines, especially looms, comprising a plurality of thread monitoring lamellae through each of which there piercingly extends an associated warp thread to retain the corresponding lamella in a raised position and upon rupture of any one of the warp threads the associated lamella drops into a lowered position, channel means having an inlet side and an outlet side and disposed beneath said plurality of thread monitoring lamellae, means for causing an air current flow between said inlet side and outlet side of said channel means, pneumatic flow-sensing means operatively connected with said channel means and responsive to the air flow conditions prevailing at said channel means, and a trigger mechanism operated by said pneumatic flow-sensing means for indicating the presence of a defect condition at the textile machine, each said thread monitoring lamella dropping into said channel means upon rupture of its associated warp thread to thereby at least impede the flow of air through said channel means which is then monitored by said pneumatic flow sensing means.

2. A warp thread monitoring apparatus as defined in claim 1, wherein said means for causing an air current flow between said inlet side and outlet side of said channel means incorporates air infeed means extending substantially transverse to the direction of air flow through said channel means and embodying at least one pair of substantially aligned oppositely situated air flow apertures and an air flow passageway for deflecting the air flow emanating from said aligned air flow apertures when the plurality of lamellae are in their raised position and the air flow through said channel means is undisturbed, whereas upon rupture of the warp thread and corresponding dropping of the associated lamellae into the channel means the air flow through said air flow passageway is interrupted so that the air flow emanating from said aligned apertures tends to dam up, causing a build-up of pressure at one of said aligned apertures which is then sensed by said pneumatic flow-sensing means.

3. A warp thread monitoring apparatus for textile machines, especially looms, comprising a plurality of thread monitoring lamellae through each of which there piercingly extends an associated warp thread to retain the corresponding lamella in a raised position and upon rupture of any one of the warp threads the associated lamella drops into a lowered position, channel means having an inlet side and an outlet side and disposed beneath said plurality of thread monitoring lamellae, means for causing an air current flow between said inlet side and outlet side of said channel means, pneumatic flow-sensing means operatively connected with said channel means and responsive to the air flow conditions prevailing at said channel means, and a trigger mechanism operated by said pneumatic flow-sensing means for indicating the presence of a defect condition at the textile machine, each said thread monitoring lamella dropping into said channel means upon rupture of its associated warp thread to thereby at least impede the flow of air through said channel means which is then monitored by said pneumatic flow-sensing means, said means for causing an air current flow between said inlet side and outlet side of said channel means incorporates air infeed means extending substantially transverse to the direction of air flow through said channel means and embodying at least one pair of substantially aligned oppositely situated air flow apertures and an air flow passageway for deflecting the air flow emanating from said aligned air flow apertures when the plurality of lamellae are in their raised position and the air flow through said channel means is undisturbed, whereas upon rupture of a warp thread and corresponding dropping of the associated lamellae into the channel means the air flow through said air flow passa eway is interrupted so that the air flowemanatin from said igned apertures tends to dam up. causing a buil -up of pressure at one of said aligned apertures which is then sensed by said pneumatic flow-sensing means, and wherein said pneumatic flow-sensing means incorporates an air flow conduit arranged in front of each pair of aligned air flow apertures and a sensor outlet conduit communicating via a transverse conduit with said air supply conduit, each said air supply conduit possessing a nozzle-like constricted portion, said transverse conduit being arranged downstream of said nozzle-like constricted portion with respect to the direction of air flow, so that a negative pressure condition prevails in said transverse conduit during such time as the air flow through said channel means is not interrupted by virtue of rupture of a warp thread, whereas upon rupture of a warp thread an overpressure condition prevails at said transverse conduit.

4. A warp thread monitoring apparatus as defined in claim 3, wherein said pneumatic flow-sensing means further includes a flow controlled-fluidic component for evaluating sensing the presence of an overpressure condition, said sensor outlet conduit serving as the control conduit for said fluidic component.

5 A warp thread monitoring apparatus as defined in claim 3, wherein said channel means comprises a respective channel member associated with a given group of thread monitoring lamellae, each channel member having an inlet side and an outlet side for the flow of air, said air infeed means including a respective intermediate tubular member arranged between the outlet side of one channel member and the inlet side of the next successive channel member, each said intermediate tubular member being equipped with two compartments, one compartment defining said air flow passageway and serving to receive the outflow of air from an adjacent channel member arranged upstream therefrom with respect to the direction of flow of the air through said channel means, said intermediate tubular member being provided with said air flow apertures, said pneumatic flow-sensing means communicating with said one compartment, the other compartment being provided with an air discharge opening, said other compartment serving for the infeed of a supply of air via said air discharge opening into the associated channel member and in a direction towards the next successive intermediate tubular member arranged downstream in the direction of the air flow through said channel means, said other compartment further serving to supply air via the other of said air flow apertures into said one compartment.

6. A warp thread monitoring apparatus for textile equipment, especially looms, comprising a plurality of warp thread monitoring lamellae each of which is operably associated with a given warp thread and retained in a raised position when the warp thread associated therewith is intact and movable into a lowered position when the warp thread associated therewith is defective, an air flow channel means disposed beneath said plurality of warp thread monitoring lamellae, means for producing an air flow through said channel means, means for sensing the flow of air through said channel means and responsive to impedance of such air flow through said channel means when a given lamella drops into said channel means upon rupture of its associated warp thread.

a r va s

Claims

1. A warp thread monitoring apparatus for textile machines, especially looms, comprising a plurality of thread monitoring lamellae through each of which there piercingly extends an associated warp thread to retain the corresponding lamella in a raised position and upon rupture of any one of the warp threads the associated lamella drops into a lowered position, channel means having an inlet side and an outlet side and disposed beneath said plurality of thread monitoring lamellae, means for causing an air current flow between said inlet side and outlet side of said channel means, pneumatic flow-sensing means operatively connected with said channel means and responsive to the air flow conditions prevailing at said channel means, and a trigger mechanism operated by said pneumatic flow-sensing means for indicating the presence of a defect condition at the textile machine, each said thread monitoring lamella dropping into said channel means upon rupture of its associated warp thread to thereby at least impede the flow of air through said channel means which is then monitored by said pneumatic flow sensing means.

3. A warp thread monitoring apparatus for textile machines, especially looms, comprising a plurality of thread monitoring lamellae through each of which there piercingly extends an associated warp thread to retain the corresponding lamella in a raised position and upon rupture of any one of the warp threads the associated lamella drops into a lowered position, channel means having an inlet side and an outlet side and disposed beneath said plurality of thread monitoring lamellae, means for causing an air current flow between said inlet side and outlet side of said channel means, pneumatic flow-sensing means operatively connected with said channel means and responsive to the air flow conditions prevailing at said channel means, and a trigger mechanism operated by said pneumatic flow-sensing means for indicating the presence of a defect condition at the textile machine, each said thread monitoring lamella dropping into said channel means upon rupture of its associated warp thread to thereby at least impede the flow of air through said channel means which is then monitored by said pneumatic flow-sensing means, said means for causing an air current flow between said inlet side and outlet side of said channel means incorporates air infeed means extending substantially transverse to the direction of air flow through said channel means and embodying at least one pair of substantially aligned oppositely situated air flow apertures and an air flow passageway for deflecting the air flow emanating from said aligned air flow apertures when the plurality of lamellae are in their raised position and the air flow through said channel means is undisturbed, whereas upon rupture of a warp thread and corresponding dropping of the associated lamellae into the channel means the air flow through said air flow passageway is interrupted so that the air flow emanating from said aligned apertures tends to dam up, causing a build-up of pressure at one of said aligned apertures which is then sensed by said pneumatic flow-sensing means, and wherein said pneumatic flow-sensing means incorporates an air flow conduit arranged in front of each pair of aligned air flow apertures and a sensor outlet conduit communicating via a transverse conduit with said air supply conduit, each said air supply conduit possessing a nozzle-like constricted portion, said transverse conduit being arranged downstream of said nozzle-like constricted portion with respect to the direction of air flow, so that a negative pressure condition prevails in said transverse conduit during such time as the air flow through said channel means is not interrupted by virtue of rupture of a warp thread, whereas upon rupture of a warp thread an overpressure condition prevails at said transverse conduit.

5. A warp thread monitoring apparatus as defined in claim 3, wherein said channel means comprises a respective channel member associated with a given group of thread monitoring lamellae, each channel member having an inlet side and an outlet side for the flow of air, said air infeed means including a respective intermediate tubular member arranged between the outlet side of one channel member and the inlet side of the next successive channel member, each said intermediate tubular member being equipped with two compartments, one compartment defining said air flow passageway and serving to receive the outflow of air from an adjacent channel member arranged upstream therefrom with respect to the direction of flow of the air through said channel means, Said intermediate tubular member being provided with said air flow apertures, said pneumatic flow-sensing means communicating with said one compartment, the other compartment being provided with an air discharge opening, said other compartment serving for the infeed of a supply of air via said air discharge opening into the associated channel member and in a direction towards the next successive intermediate tubular member arranged downstream in the direction of the air flow through said channel means, said other compartment further serving to supply air via the other of said air flow apertures into said one compartment.