US3870250A

US3870250A - Process and plant for pneumatic transport

Info

Publication number: US3870250A
Application number: US345722A
Authority: US
Inventors: Constantin Gh Teodorescu; Stefan P Ardeleanu
Original assignee: INST PENTRU CREATIE STINTIFICA
Current assignee: INST PENTRU CREATIE STINTIFICA; INSTITUTUL PENTRU CREATIE STINTIFICA SI TECHNICA-INCREST
Priority date: 1972-03-31
Filing date: 1973-03-28
Publication date: 1975-03-11
Anticipated expiration: 1992-03-11
Also published as: FR2178864B1; RO55679A2; GB1423305A; DD101638A5; DE2306847A1; IT979111B; JPS497978A; SU583731A3; JPS533556B2; CS194672B2; FR2178864A1; DE2306847B2

Abstract

An object (e.g., an elongated vehicle) is displaced through a plurality of end-to-end tube sections each provided at a location adjacent its downstream end with an exhauster which continuously draws air out of the respective section. The downstream end of each tube section is normally closed by a flap-type check-valve arrangement that opens as the object in the tube inertially approaches this downstream end, drawn along by a low-pressure zone created ahead of the vehicle by the exhauster. The presence of the object or vehicle in the tube is detected and an enabling force is applied to the check valve to open the downstream end of the tube and, as the object passes the inlet of the exhauster, it compresses the air captured between its leading end and the check valve. The combined effect of the opening force applied to the valve by the detector as well as the air pressure built up behind it suffice to open this check valve and allow the object to exit from its downstream end of the one tube section and enter the upstream end of the following one, thereby entering the pneumatic-force field of the next exhauster whereupon the cycle is repeated.

Description

United States Eatent n91 Teodorescu et al.

[ PROCESS AND PLANT FOR PNEUMATIC TRANSPORT [75] Inventors: Constantin Gh. Teodorescu; Stefan R Ardeieanu, both of Bucharest, Romania [73] Assignee: lps titut llientru Creatie Stintifica Si Technica-llncrest, Bucharest, Romania 22 Filed: Mar. 28, 1973 21 Appl. No.: 345,722

[30] Foreign Application Priority Data Mar. 31, 1972 Romania 70354 [52] 11.5. C1 243/6, 243/4, 243/38 [51] int. Ci. B65g 51/04 [58] Field of Search 243/1, 2, 4, 6, 29,30, 243/32, 38, 39; 104/138, 139, 155, 156; 105/365 [56] References Cited UNITED STATES PATENTS 461,535 10/1891 Johnson 243/6 683,141 9/1901 Pikc 243/38 2,601,391 6/1952 Halpern 243/32 X 2,784,922 3/1957 Richert 243/38 3,332,639 7/1967 Joy 243/29 X 3,404,638 10/1968 Edwards 104/156 3,438,337 4/1969 Edwards 243/1 X 1 Mar. 11, 1975 305,395 5/1918 Germany 243/30 Primary ExaminerEvon C. Blunk Assistant Examiner.lames L. Rowland Attorney, Agent, or Firm-Karl F. Ross; Herbert Dubno [57] ABSTRACT An object (e.g., an elongated vehicle) is displaced through a plurality of end-to-end tube sections each provided at a location adjacent its downstream end with an exhauster which continuously draws air out of the respective section. The downstream end of each tube section is normally closed by a flap-type checkvalve arrangement that opens as the object in the tube inertially approaches this downstream end, drawn along by a low-pressure zone created ahead of the vehicle by the exhauster. The presence of the object or vehicle in the tube is detected and an enabling force is applied to the check valve to open the downstream end of the tube and, as the object passes the inlet of the exhauster, it compresses the air captured between its leading end and the check valve. The combined effect of the opening force applied to the valve by the detector as well as the air pressure built up behind it suffice to open this check valve and allow the object to exit from its downstream end of the one tube section and enter the upstream end of the following one, thereby entering the pneumaticforce field of the next exhauster whereupon the cycle is repeated.

sum 3 5 4} Fig.7

PROCESS AND PLANT FOR PNEUMATIC TRANSPORT FIELD OF THE INVENTION The present invention relates to a system for transporting an object, e.g., a freight, message or passenger vehicle, through a tube. More particularly this invention concerns a method of and an apparatus for the pneumatic transport of a container, vessel or the like through an elongated tube.

BACKGROUND OF THE INVENTION A process is known for pneumatic transport inside a tubular passage using vehicles or containers carrying passengers or goods. Gases under pressure are fed into the passage which is formed of tube sections having suction-delivery nozzles of convergent-divergent shape, and each provided with an annular slot located at a small distance upstream the nozzle neck such that the fluid jet, on leaving the slot with great speed, generates along the wall of the neck a low-pressure zone which forces the stream to curve towards this wall. An air suction of considerably greater capacity is created so as to generate a pressure differential on the one and the other side of the annular slot which draws the vehicle downstream while forming around it an enveloping rapidly moving air layer which in turn forms a fluid torus penetrating inside the tube and supporting the vehicle and preventing it from touching the walls of the tubular passage. The excess fluid escapes through the space between the outer wall of the tube and the divergent wall of the nozzle. The successive feeding with gas under pressure by the various nozzles along the passage is effected so that the vehicle moves on by receiving successive impulses.

This process has the drawback of a reduced stability of the vehicle and due to the fact that the fluid torus surrounding the vehicle does not support the vehicle when the latter exceeds a certain weight, there is the possibility of blocking the vehicle inside the tube.

A pneumatic device is known for the transport of loads in tubes, by means of a container provided with six rollers, two of which are mounted at the lower part, one at each end, to support the weight and transmit it to a central rail mounted at the lower part of the tube, and four lateral rollers, two at each end, serving to guide the container directly on the walls of the same tube in its straight portions. On curves, the tube is also provided with rails for lateral guiding. The propulsion of the container is carried out by a mass of compressed air which is circulated through the tube to entrain the vehicle, and the braking is electrodynamic.

The device described above has the drawback that the construction of the container is complicated and the vehicle is very heavy so that a great deal of energy is wasted simply in displacing the container rather than its payload.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide an improved pneumatic transport system.

Another object of this invention is a transport system wherein the weight ratio of the container to its payload that it can be used to transport people, freight and messages.

SUMMARY OF THE INVENTION These objects are attained according to the present invention in a system wherein a plurality of end-to-end (preferably spaced-apart) tube sections are each provided with a respective exhauster. The air in each tube section is continuously evacuated therefrom at a location slightly upstream of the downstream end of the section. An openable check valve or gate is provided at the downstream end of each such section so that a current of air from upstream to downstream is created by the exhauster. An object such as a freight container or passenger vehicle is thus drawn toward the downstream end of the section by the low-pressure zone in front of it, which is substantially lower than the ambient pressure behind it, the upstream end of the tube being open to the atmosphere.

According to another feature of this invention the proximity of the container or vehicle near the downstream end of the tube is detected by a sensor which operates mechanism to apply an opening force to the gate at the downstream end. This force is, however, insufficient to overcome the pressure differential and spring biasing that hold the gate closed. Only when the container passes the exhauster location (i.e., the location at which the exhauster or suction blower communicates with the tube) and starts to act as a ram to compress the mass of air captured between its leading end and the gate is this force sufficient to open the gate. Since the container develops a relatively rapid rate of advance, it has considerable inertia such that it flies past the exhauster to compress the air downstream of it. In this manner the downstream gate will open only when the container approaches it, thereby insuring that a malfunction will not open this gate and leave the container stranded in the tube due to a failure of pressure i.e., a pressure differential insufficient to move it along.

In accordance with yet another feature of this inventionthe container is supported in the tubes by rollers spaced along the tubes but not carried on the container, so that this container can be a simple shell.

According to yet another feature of this invention the sensor can be an electromagnetic coil which coacts with the steel shell of the container to detect its presence. Alternatively or, in addition, a simple mechanical lever system having an arm extending into the tube can be actuated on passage of the container to detect the presence of the container. It has been found to be advantageous to use this mechanical arrangement to back up the electromagnetic one so that a safe system iscreated.

BRIEF DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a schematic diagram of the apparatus according to the invention with two transport tubes;

FIG. 2 is a longitudinal vertical section through one of the transport tubes;

FIG. 3 is a cross-section taken along line A A, of FIG. 2;

FIG. 4 is a longitudinal horizontal section through the transport tube at the suction chamber;

FIG. is a cross-section through the transport tube and the container at the electromagnetic control unit; FIG. 6 is a longitudinal section through the transport tube showing in enlarged scale the electromagnetic and the mechanical control units;

FIG. 7 is a longitudinal section through the force accumulator; and

FIG. 8 is a longitudinal horizontal section through the transport tube at its downstream end.

SPECIFIC DESCRIPTION The apparatus according to the invention consists, as shown in FIG. 1, of a plurality of transport sections 1 arranged is series after one another. Each section 1 consists of a tube 11 on which are mounted a suction chamber 2 connected through a conduit 3 to the suction mouth of an exhaust fan 4, a check valve 5 operated by the intermediary of two force accumulators 6 and electromagnets 7 which are in turn controlled by an electromagnetic control unit 8. The operation of check valve 5 by means of the same force accumulators 6 may also be performed by two mechanical control units 9, actuatable by a container 10 directly. The mechanical controls 9 ensure the opening of check valve 5, if the electromagnetic unit 8 fails to operate owing to some accident.

The transport section 1 has a tube 11 formed of a number of commercial conduits or pipes connected end-to-end in any convenient airtight fashion, for instance with sleeve joints, so as to form a single tube 11 in which a plurality of rollers 12 are mounted by means of bolts 13 and airtight housings 14, as shown in FIGS. 2 and 3. The housings 14 are secured to tube 11 by means of screws. Each of the rollers 12 projects through a hole a formed in the wall of tube 11 and extends beyond the inner surface of this tube by a distance h so that the container, while running inside the tube 11, only engages the rollers 12 without touching the tube wall. The rollers 12 are mounted in sets of three arranged in mutually orthogonal planes, one roller at the base of the tube 11 for supporting the weight of container 10, and two lateral ones'for guiding the container 10. The spacing l between the sets of rollers 12 along the tube 11 is chosen dependent on the length l of the cylindrical portion of container 10 and is at most one half this length. The tube 11 is further provided with a plurality of slots b at the suction chamber 2 so that air can be sucked out of this tube therethrough by the exhaust fan 4 for the requisite lowpressure zone at the tubes downstream end.

As shown in FIG. 8, the check valve 5 is formed of a fixed part consisting of a pipe 15, a front wall 16 and two triangular walls 17 which are secured to one end of the tube 11 by means of screws. The triangular walls 17 are welded to the front-wall 16, in horizontal position one above the other and spaced so as to allow the container 10 to pass between them. Both the front wall 16 and the triangular walls 17 have bent edges provided with rubber packings 18. The triangular walls are stiffened in the position shown by a rectangular frame 19.

The check valve 5 also contains two flaps 20 pivoted on respective axles 21, journaled in supports 22.

Normally the movable flaps 20 are biased into contact with the packings 18 by two springs 23 and by the low-pressure zone created at the downstream end of the section 1 by the exhaust fan 4.

. In the open position, shown in dot-dash lines in FIG. 8 and brought about by traction on cables 24, the movable flaps 20 leave an aperture s sufficient to let the container pass without hitting them. The maximum size of the opening s is defined by rubber stops 25 which are fastened by screws to the rectangular frame 19.

The force accumulator 6, shown in FIG. 7, consists of a tubular housing 26 receiving a spring 27 and an end of a rod or bar 28 and connected to an eye 29. The spring 27 is precompressed between the base of the element 26 and a disk carried on the element 28, the rest position being determined by the latter being locked be means of a countersunk screw 30 spanning a notch C out laterally in the threaded boss of the eye 29. The tubular housing 26 is formed with a hole d which allows air to escape on a sudden tensioning of the spring 27.

The electromagnet or solenoid 7, as shown in FIG. 6,

consists of a core 31 having a movable armature 32 and two coils 33, the whole assembly being covered by a protective housing 34 on which the two terminals e and fare mounted.

The electromagnetic sensor 8 which is shown in FIG. 5, consists of a transformer having a primary coil 35 whose terminals i and j are connected to a power source, a secondary coil 36, whose terminals k and m are connected to the terminals e and fof the electromagnet 7, and a U-shaped core 37. Thus, when container 10 (ferromagnetic object) passes in front of the core 37, the magnetic circuit is closed and a substantial increase in the voltage in the secondary winding 36 takes place. The core 37 extends through a hole It formed in the tube 11, so that the container 10 may pass very near its ends. The whole assembly is covered by an airtight housing 38.

The mechanical control unit 9, shown in FIG. 6, consists of a two-arm lever 39 having at one end a roller 40. The lever 39 pivots around a bolt 41, the pivoting angle being limited by two rubber stops 42. The bolt 41 as well as the rubber stops 42 are fastened to a support 43 which is screwed to tube 11, the whole assembly being covered by another airtight housing 44.

The connection between the movable armature 32 of electromagnet 7 and lever 39 is made by a cable 45, and between lever 39 and the bar 28 of force accumulator 6 by another cable 46.

The lever 39 extends inside transport tube 11 with roller 40 through a hole p so that container 10 engages and actuates it when passing thereunder.

The operation of the system, according to the invention, takes place as follows:

The loaded container 10 is inserted in the upstream tube end.

Exhaust pumps 4 are operated to suck up the air from transport tubes 11, compelling it to circulate through the tube in a single sense from the open upstream end toward the suction chamber 2 and exhauster 4, this downstream end being closed by check valves 5.

When introduction of the container 10 into the interior of transport tube 11 effectively blocks off its free upstream end too, the exhauster evacuates the air in the tube between the container and the check valve 5, thus producing and maintaining a low-pressure zone therebetween.

To the upstream side of the container 10 atmospheric pressure will push this object 10 into the interior of transport tube 11 toward the suction chamber 2, this differential force having to overcome the inertia of container 10, the friction forces between the container 10 and the rollers 12 of the transport tube 11, and the resisting forces caused by the running of the same container 10 due to the level differences of the soil on which the tube is laid out. Due to the fact that the transport tube ill is provided with rollers 12, the friction forces are a minimum regardless of the total weight of container it). in this way, the container 19 runs through the transport tube 11 and arrives in front of the electromagnetic control unit 8 at a relatively high speed. Container l closes through its steel wall the magnetic circuit without touching the core 37, and due to the fact that the primary coil 35 is connected to line an increase in voltage will be obtained in the secondary coil 36 which will actuate the electromagnets 7.

The movable armatures 32 of electromagnets 7 will be attracted and will operate by means of

cables

45 and 46 upon force accumulators 6, compressing spring 27 by means of bar 28. At the same time, the lever 39 of the mechanical sensor 9 will also rotate up to the rubber stop 42. The spring 27 will act through the tubular housing 26 on the eyebolt 29 and therethrough on the cable 24 to pivot the flap 20 into the open position. The flaps will not open up suddenly due to their relatively high inertia as well as to the low-pressure zone existing in transport tube 11 between the check valve and the container 10 at the moment when this latter is detected by electromagnetic sensor 8 and mechanical sensor 9.

The front or downstream end of container 10, after passing the electromagnetic control circuit 8, passes rapidly in front of the slots b of the suction chamber 2 and covers and blocks them.

Due to its high inertia, the container 10 compresses the air captured in the transport tube 11 between the suction chamber 2 and the check valve 5, acting like a piston. Then the container will pass under without touching the rollers 40, since lever 39 is rotated by solenoid 31. As the pressure of the air compressed by the container rises toward atmospheric pressure to a level such that the force exerted by spring 27 can overcome the resistance of the flaps 20, these flaps will open and the front end of the container 10 will arrive at the level of the flaps, so that these latter will no longer be able to close. After the container passes entirely, the flaps 20 will close, firstly due to springs 23 which exert a relatively small closing force, and owing to the low pressure inside the transport tube ll permanently generated by exhauster 4. After the container passes the flaps 20, it will enter the following transport section 1 of the same system, starting again the cycle described above, but having by this time the initial speed reached on leaving the first tube. The mechanical control unit 9 backs up the opening control of flaps 2G, in case of an accidental deficiency of the electric parts. Container 10, by hitting with its conical front end against the rollers 40 of lever 39, rotates this lever 39 to tension the spring 27 by means of cable 46 and bar 28. In order to increase the opening safety of flaps 20, the check valve 5 is formed such that the flaps 20 in the closed position lie at an angle equal to the conicity of the containers front to that if the container hits them with its conical portion without previous control, they open up without damage and allow the passage of the container.

The plant, according to the invention, presents the following advantages: It allows the transport with high speed of large weights of materials and goods; the useful conveyed quantity is a maximal one since the container is of simple construction and relatively light. Medium power stations instead of a single high-power station are used. In the construction of the plant it allows the use of helically welded tubes of large diameter. It presents a high degree of safety in transport. It does not pollute the atmosphere. It eliminates the influence of meterological factors in the transport. it contributes to decongesting the existing transport means and, finally, it allows the complete automation of the auxiliary loading and unloading operations.

Each tube 11 may have, as illustrated, a rearwardly flared entry bell disposed just ahead of the check valve of the preceding tube. The vehicle 10 is preferably elongated with a bullet-shaped or streamlined end, the length of the vehicle exceeding the distance between the bell of a downstream tube and the check valve end of the preceding or upstream tube. As illustrated, the outer periphery of the vehicle is geometrically similar to the cross-section of the tube in which it is received and this cross-section can be circular, rectangular or square. Sleeve joints may mechanically connect the adjoining ends of successive tubes. The suction chamber 2 surrounds each tube 11 and opens into the latter via axially extending slots angularly spaced about the tube.

We claim:

1. A system for transporting an object comprising:

a plurality of in-line tube sections, each including:

an elongated tube having an upstream end and a downstream end,

a plurality of rollers mounted at a lower portion and- /or opposite lateral portions of each tube along the interior thereof and uniformly spaced along the entire length of the tube,

two flaps extending from the exterior toward one another to normally close said downstream of said tube by sealing engagement with one another, said tube being open at its upstream end;

an elongated objectadapted to traverse said tubes riding on said rollers;

a device proximal to but spaced from the downstream end of each of said tubes for creating a lowpressure zone between said downstream end and said object for drawing said object from each upstream end toward the respective downstream end of each tube;

means adjacent said device for detecting the proximity of said object for applying to each pair of flaps an opening force insufficient to swing said flaps apart and open said downstream end in the absence of an additional force, but sufficient upon the generation of an over-pressure ahead of said object to open said flaps and permit the object to pass into the upstream end of the next following tube, said rollers being each sealingly mounted in housings external to said tubes with each roller penetrating through a hole formed along the wall of the tube, each tube comprises a pair of triangular walls which define with the respective flaps a normally closed gate, said walls being mounted on the downstream end of the respective tube, and means for pivoting each pair of flaps on the respective downstream end of a tube.

2. A system for transporting an object comprising:

a plurality of in-line tube sections, each including:

an elongated tube having an upstream end and a downstream end,

a plurality of rollers mounted at a lower portion and- /or opposite lateral portions of each tube along the interior thereof and uniformly spaced along the entire length of the tube, two flaps extending from the exterior toward one another to normally close said downstream of said tube by sealing engagement with one another, said tube being open at its upstream end;

an elongated object adapted to traverse said tubes riding on said rollers;

a device proximal to but spaced from the downstream end of each of said tubes and creating a low-pressure zone between said downstream end and said object for drawing said object from each upstream end toward the respective downstream end of each tube;

means adjacent said device for detecting the proximity of said object for applying to each pair of flaps an opening force insufficient to swing said flaps apart and open said downstream end in the absence of an additional force, but sufficeint upon the generation of an over-pressure ahead of said object to open said flaps and permit the object to pass into the upstream end of the next following tube,

a solenoid having an armature;

a first element connected to said armature;

a force storing device connected to said first element, a secondelement connecting said force storing device to said flaps; and

a pivotal lever engageable with a leading portion of said object and connected to one of said elements for displacing same.

3. A system for transporting an object comprising a plurality of in-line tube sections each including:

an elongated tube having an upstream end and a downstream end;

at least one outwardly pivotal flap sealingly engageable over said downstream end;

means for exhausting air from said tube at a location spacedly adjacent said downstream end thereby creating a low-pressure zone at said downstream end for drawing said object from said upstream end toward said downstream end; and

means adjacent said location for detecting the proximity of said object and on such detection for applying to said flap an opening force insufficient to open up said downstream end whereby said object on passing said location builds up a relatively highpressure zone adjacent said flap which along with said force suffices to open said flap and permit exit of said object from said downstream end, the detecting means including:

at least one electromagnet mounted on said tube and generating a field extending into said tube, said object being at least partially ferromagnetic,

a solenoid energizable in response to said electromagnet and having an armature acting upon said flap, and a force accumulator between said solenoid and said flap and including a first element connected to said armature operatively and a second element connected to said flap. 4. The system defined in claim 3 wherein said tubes are each provided with a plurality of rollers supportingly engageable with said object on passage of same through said tubes.

5. The system defined in claim 3 wherein each tube is provided with a pair of such flaps and a pair of triangular walls coating therewith to form a gate, both of said flaps being connected to the detecting means.

6. The apparatus defined in claim 5 wherein said flaps normally lie at an angle to each other, said object having a generally conical leading end of an apex angle generally corresponding to said angle.

7. The apparatus defined in claim 3 wherein said force accumulator includes spring prestressed between said elements.

8. The apparatus defined in claim 3 wherein the detecting means includes a two-arm lever pivoted on said tube and having one arm extending into said tube into the path of said object and another arm operatively connected to said flap.

Claims

1. A system for transporting an object comprising: a plurality of in-line tube sections, each including: an elongated tube having an upstream end and a downstream end, a plurality of rollers mounted at a lower portion and/or opposite lateral portions of each tube along the interior thereof and uniformly spaced along the entire length of the tube, two flaps extending from the exterior toward one another to normally close said downstream of said tube by sealing engagement with one another, said tube being open at its upstream end; an elongated object adapted to traverse said tubes riding on said rollers; a device proximal to but spaced from the downstream end of each of said tubes for creating a low-pressure zone between said downstream end and said object for drawing said object from each upstream end toward the respective downstream end of each tube; means adjacent said device for detecting the proximity of said object for applying to each pair of flaps an opening force insufficient to swing said flaps apart and open said downstream end in the absence of an additional force, but sufficient upon the generation of an over-pressure ahead of said object to open said flaps and permit the object to pass into the upstream end of the next following tube, said rollers being each sealingly mounted in housings external to said tubes with each roller penetrating through a hole formed along the wall of the tube, each tube comprises a pair of triangular walls which define with the respective flaps a normally closed gate, said walls being mounted on the downstream end of the respective tube, and means for pivoting each pair of flaps on the respective downstream end of a tube.

2. A system for transporting an object comprising: a plurality of in-line tube sections, each including: an elongated tube having an upstream end and a downstream end, a plurality of rollers mounted at a lower portion and/or opposite lateral portions of each tube along the interior thereof and uniformly spaced along the entire length of the tube, two flaps extending from the exterior toward one another to normally close said downstream of said tube by sealing engagement with one another, said tube being open at its upstream end; an elongated object adapted to traverse said tubes riding on said rollers; a device proximal to but spaced from the downstream end of each of said tubes and creating a low-pressure zone between said downstream end and said object for drawing said object from each upstream end toward the respective downstream end of each tube; means adjacent said device for detecting the proximity of said object for applying to each pair of flaps an opening force insufficient to swing said flaps apart and open said downstream end in the absence of an additional force, but sufficeint upon the generation of an over-pressure ahead of said object to open said flaps and permit the object to pass into the upstream end of the next following tube, a solenoid having an armature; a first element connected to said armature; a force storing device connected to said first element, a second element connecting said force storing device to said flaps; and a pivotal lever engageable with a leading portion of said object and connected to one of said elements for displacing same.

3. A system for transporting an object comprising a plurality of in-line tube sections each including: an elongated tube having an upstream end and a downstream end; at least one outwardly pivotal flap sealingly engageable over said downstream end; means for exhausting air from said tube at a location spacedly adjacenT said downstream end thereby creating a low-pressure zone at said downstream end for drawing said object from said upstream end toward said downstream end; and means adjacent said location for detecting the proximity of said object and on such detection for applying to said flap an opening force insufficient to open up said downstream end whereby said object on passing said location builds up a relatively high-pressure zone adjacent said flap which along with said force suffices to open said flap and permit exit of said object from said downstream end, the detecting means including: at least one electromagnet mounted on said tube and generating a field extending into said tube, said object being at least partially ferromagnetic, a solenoid energizable in response to said electromagnet and having an armature acting upon said flap, and a force accumulator between said solenoid and said flap and including a first element connected to said armature operatively and a second element connected to said flap.

4. The system defined in claim 3 wherein said tubes are each provided with a plurality of rollers supportingly engageable with said object on passage of same through said tubes.