US 3408113 A
Description (OCR text may contain errors)
M 91 N GE m mm \Q UT V x P in w n Oct. 29, 1968 G. BOULADON PNEUMATIC TRANSPORT MEANS Filed Aug. 25, 1967 United States Patent 3,408,113 PNEUMATIC TRANSPORT MEANS Gabriel Bouladon, Chanteoiseau, Rte. de Saint-Loup, Versoix, Geneva, Switzerland Filed Aug. 23, 1967, Ser. No. 662,654 Claims priority, application Switzerland, Aug. 24, 1966, 12,368/ 66 8 Claims. (Cl. 302-2) ABSTRACT OF THE DISCLOSURE Pneumatic transport means comprising a tube divided by a. longitudinally extending floor into an upper segment along which may slide a transport unit and into a lower segment divided up into a succession of chambers provided with reversably acting fans operating either to supply air under pressure into the upper segment behind the transport unit or to extract air from the upper segment in front of the transport unit through pressure responsive valves in said floor, thereby to propel the transport unit along said upper segment under the action of the pressure difference created or opposite ends of the transport unit.
Disclosure This invention relates to pneumatic transport means.
Pneumatic transport means in which a transport unit is moved within a tube under the action of an upstream pressure, a downstream vacuum, or a combination of both, have been known for some time. The transport unit behaves like a movable piston within the tube. Such a system requires the play between the transport unit body and the tube wall to be very small so as to restrict leakage. But this gives rise to friction which generates a parasitic resistance hindering displacement.
Further, because the compressed air supply required to set up a pressure upstream and/or the suction required to set up a vacuum downstream are applied at the end to the line, the useful length of the tube and speed at which the transport unit moves are necessarily limited for the pressure losses due to air displacement within the tube quickly become substantial when the length of the tube and/or the speed of the air exceed certain limits.
An object of the present invention is to provide pneumatic transport means in which these drawbacks are obviated. The pneumatic transport means provided by the present invention comprise a propulsion tube, a longitudinally extending floor dividing said tube into an upper segment and a lower segment, a transport unit movably mounted in said upper segment for sliding motion therealong and having a cross-section similar to that of said upper segment, a series of spaced, gastight, transverse partition walls dividing said lower segment into a succession of adjacent chambers, and a propulsion system for setting up a pressure difference between air at the back and air at the front of said transport unit and including supply means able to give to the pressure prevailing within the chambers located behind and beneath said transport unit a value greater than that prevailing within the chambers located ahead of said transport unit, control means for cancelling, as said transport unit progresses along said upper segment, the pressure difference between two adjacent chambers, and a plurality of valves distributed within said floor and adapted to enable air to flow from said lower segment to said upper segment when the ratio between the pressure prevailing within said upper segment and the pressure prevailing within the lower segment has a value less than one but greater than a given threshold, to enable air to flow from said upper segment to said lower segment when said ratio has a value greater than one, and to stop all flow of air between said segments when said ratio has a value below said threshold.
In the accompanying diagrammatic drawings:
FIGURE 1 is an axial section of a portion of one embodiment of transport means according to the invention;
FIGURE 2 is a cross-section along line 11-11 of FIG- URE l;
FIGURE 3 is a diagram illustrating the operation of a component of the transport means shown in FIGURES l and 2; and
FIGURE 4 is a sectional view of this component.
The pneumatic transport means shown in FIGURES 1 and 2 comprises a tube 1 in which moves a transport unit 2 and which is divided by a longitudinally extending floor 3 into two segments of unequal cross-section. The first segment, of larger cross-section S (FIGURE 2), is travelled along by the transport unit 2 and constitutes a transport segment 4 (FIGURE 1); the second segment, of small cross-section s, is located below the transport segment and constitutes a supply segment 5.
This supply segment is divided up into a series of supply chambers, such as supply chambers 6 6 6 (FIG- URE 1), by spaced gastight partitions 7. Each of the ends of a supply chamber is connected by a duct to a reversible fan. Thus, supply chamber 6 has one of its ends connected by a duct 8,, to a fan 10 and its other end connected by a duct 9 to a fan 11,,. Similarly, chamber 6 has its ends connected by ducts 8 and 9 to fans 10 and 11 respectively. It is possible to use the walls of adjacent ducts as supporting arches for the tube 1, these arches merging to form a tubular pillar, as is apparent with pillar 16 into which merge the ducts 9 and 8 The floor 3 is fitted with a plurality of valves 17 which are distributed over its entire area and which govern the flow of air between the trasnport segment and the supply segment. These valves are all alike and are adapted each to satisfy the following operating conditions:
(a) When the pressure in the transport segment is greater than a reference pressure but less than the pressure in the supply segment, i.e. when the ratio R=P /P between the pressure P in the transport segment and the pressure P in the supply segment is less than one but greater than a given threshold k, the valve opens and lets air flow out of the supply section into the transport segment;
(b) When the pressure in the transport segment is less than the reference pressure by an amount Ap while the pressure in the supply segment is equal to or greater than the reference pressure, i.e. when the ratio R=P /P is less than the threshold k, the valve closes and stops all flow between these two sections; and
(c) When the pressure in the transport segment is greater than the pressure in the supply segment, i.e. when the ratio R P /P is greater than one, the valve opens and lets air fiow from the transport segment into the supply section.
These operating conditions are schematically illustrated by the FIGURE 3 diagram: the cross-hatched zone to the left of boundary 30 is that in which the ratio R is less than the threshold k, i.e. that in which the valve is closed, this being the condition corresponding to operating condition (b), whereas the zone to the right of boundary 30 is made up of two portions: the first, in which R l, corresponds to operating condition (a) schematically illustrated by upwardly directed arrows 31, and the second, in which R 1, corresponds to operating condition (c) schematically illustrated by downwardly directed arrows 32.
Valves which satisfy these operating conditions are known and FIGURE 4 shows, by way of example, one constructional form which is assumed to be fitted in the longitudinal floor 3. For each valve, floor 3 is formed with an opening 35 made up of two portions: a lower portion 36, which is located on the supply segment side, and an upper portion 37, which is located on the transport segment side. The diameter of the upper portion 37 is larger than that of the lower portion 36. A cup-shaped member 38 formed in its bottom with a hole 39 is held centered in opening 35, by two deformable gastight diaphrams 40 and 41 secured to the walls of the lower and upper portions 36 and 37 respectively. A valve member 42, having the shape of an inverted cone and cooperating with the hole 39, is fixedly mounted on a stem 43 which is itself secured to a cross-member 44 fixed to the longitudinal floor 3. The space 45, lying between the deformable diaphragms 40 and 41, communicates with the atmosphcre via a channel 46. The diameters of the opening portions 36 and 37 are so chosen that the force exerted upwardly on the deformable diaphragm 40 by the pressure P of the air contained in the supply segment 5 is greater than the sum of the weight of the cup-shaped member 38 and of the force exerted downwardly by the pressure P of the air contained in the transport segment 4. Consequently, the bottom of the cup-shaped member 38 is pressed against the valve member 42 to close the passage provided by the hole 39, thereby corresponding to operating condition (c). If the pressure P in the transport segment exceeds a reference valve, which is less than pressure P and which depends on the diameters of diaphragms 40 and 41 and on the weight of the cupshaped member 38, the equilibrium is broken and the cup-shaped member 38 is caused to move away from the valve member 42 so that the passage provided by the hole 39 opens. As long as the ratio R'=P /P remains below one, while remaining above the threshold k corresponding to the equilibrium breakage point, air flows from the supply segment into the transport segment. When the ratio R becomes greater than one, the direction of flow is reversed, i.e. it flows from the transport segment into the supply segment.
The transport segment is fitted with detectors 18 18 18 (FIGURE 1) with one detector per supply chamber, such detectors being capable of responding to the passage of the transport unit 2. Each detector is electrically connected to the two fans associated with the following supply chamber, i.e. with the supply chamber over which the transport unit will pass after having caused the detector to respond, and is adapted to reverse the direction of the air flow in the ducts housing the two associated fans. Thus detector 18,,, located opposite supply chamber 6,,, controls via a switch 19 whose function will become apparent later, and a line 20 connected to a line 22 connecting together fans and 11 the direction of the air flow in the ducts 8 and 9 associated with the chamber 6 over which the transport unit 2, which is assumed to move from left to right, will pass after having caused this detector 18 to respond. This change in direction of the air flow can be achieved by reversing the direction of rotation of the fan motors or by reversing the pitch of the fan blades, or further by resorting to a valve arrangement. The detectors may be of any suitable kind, either of the type that is responsive to direct mechanical contact with the object to be detected (for instance a tumbler switch), or of the proximity detection type (for instance optical, pneumatic, magnetic or capacitive); the only condition they have to satisfy is that of being bistable.
The illustrated transport means operate as follows:
With the transport unit 2 located in the position shown in FIGURE 1, i.e. opposite supply chamber 6 and moving in the direction of the arrow, the supply chambers 6 6, and the preceding chambers are supplied with air under pressure, whereas a vacuum is set up in chamber 6 and the following chambers under the action of their fans operating as extractors. The valves of chamber 6 and of the preceding chambers operate in accordance with conditions (a) so that the portion of the transport segment lying behind the transport unit becomes pressurized. The valves of chamber 6 and of the following chambers operate in accordance with conditions (c) so that a vacuum is set up in the portion of the transport segment lying in front of the transport unit. The transport unit 2 is thus propelled from left to right by this pressure difference which, although remaining slight, can give rise to a relatively large force in view of the large cross-section S of the unit. Of the valves as sociated with chamber 6,,, those which lie behind the transport unit 2 operate under conditions (a) and allow air to flow into the transport segment. The same applies to those lying beneath the transport unit. But the valves of chamber 6 which lie ahead of the transport unit operate under conditions (b); they are thus closed. The air which escapes from beneath the transport unit 2 into the space 23 (FIG- URE 2) lying between the floor 3 and the bottom of the unit, whether this air issues from the subjacent valves or is due to leakage from the rear of the unit, sets up an air blade which supports the unit and reduces friction to a large extent. The air which leaks past the transport unit from the rear forwards through the space 24 between the unit body and the wall of tube 1 forms a film of air acting as a lubrifying layer which facilitates the sliding motion of the transport unit. As the unit progresses, the various detectors are actuated and the pressure or vacuum conditions prevailing in the various chambers becomes reversed. Thus when the unit travels past detector 18,,, the latter reverses the direction of operation of the fans 10,, and 11 associated with the next supply chamber 6,,, The latter, in which a vacuum was previously prevailing, becomes pressurized when the unit passes over it. Upon the unit travelling past detector 18 the latter will reverse the direction of operation of the fans associated with chamber 6 and so forth with the following detectors. It will be observed that the boundary between the pressurized chambers and the chambers in which prevail a vacuum progresses in a discontinuous manner and accompanies the transport unit in the course of its motion.
When the unit moves in the opposite direction, i.e. from right to left, the detector located opposite a supply chamber must act in this instance, on the fans of the adjacent chamber to the left. That is why each detector is associated with a switch 19 whose function is to direct the signal generated by this detector either to the fans of the adjacent chamber to the right, e.g. via lines 20 20 or 20 or to those of the adjacent chamber to the left, e.g. via lines 21 21 or 21 These switches must therefore be remote controlled by any suitable means not shown, each time the transport unit is made to move off again in the opposite direction after having reached one end of the tube.
Such transport means are able to cover very long distances, of up to several tens, or even several hundreds, of kilometers. In such a case, it is preferred to divide the transport segment into sections, say of about 1 to 2 kilometers long, by means of mobile doors such as doors 25 and 26 (FIGURE 1). By so dividing up the transport segment, several transport units can be made to travel one behind another, with one section never being occupied by more than one unit at a time, since each door separates the pressurized air that is propelling the unit along one section from the vacuum in front of the unit in the preceding section. Each section thus constitutes an autonomous transport element and the transport means as such are made up by juxtaposing these elements end to end, which sections have a length greater than that of three consecutive supply chambers.
Clearly the reversal of the direction of operation of the fans is not instantaneous so that if a transport unit is moving at high speed, a certain reversal advance must be provided for, in the same way that a certain ignition advance must be given to a petrol engine when operating at high speed. It may thus be possible to associate the passage detector of order n not with the fans of the supply chamber of order n+1 but with those of the supply chamber of order n+2 or n+3, or more generally with the fans of the supply chamber of order n+1+p, the value of p depending on the speed of the transport unit and on the time constant involved by the reversal of the direction of operation of these fans.
Instead of providing one passage detector per supply chamber, it is preferred to provide two, and to associate with these two detectors a discriminating circuit able to determine the direction in which the transport unit is being propelled on the basis of the order in which the detectors of the pair are being actuated. This discriminating circuit can then itself control the feeding in of the signal for reversing the direction of operation in the appropriate direction, i.e. take over the function of the corresponding switch, which then no longer has to be man ually operated.
Further, several detectors may be provided per supply chamber. This makes it then possible automatically to adapt the value of the reversal advance, ie the value of p referred to earlier, to the instantaneous speed of the transport unit.
1. Pneumatic transport means comprising a propulsion tube, a longitudinally extending floor dividing said tube into an upper segment and a lower segment, a transport unit movably mounted in said upper segment for sliding motion therealong and having a cross-section similar to that of said upper segment, a series of spaces, gastight, transverse partition walls dividing said lower segment into a succession of adjacent chambers, and a propulsion system for setting up a pressure difference between air at the back and air at the front of said transport unit and including supply means able to give to the pressure prevailing within the chambers located behind and beneath said transport unit a value greater than that prevailing within the chambers located ahead of said transport unit, control means for cancelling, as said transport unit progresses along said upper segment, the pressure difference between two adjacent chambers, and a plurality of valves distributed within said floor and adapted to enable air to flow from said lower segment to said upper segment when the ratio between the pressure prevailing within said upper segment and the pressure prevailing within the lower segment has a value less than one but greater than a given threshold, to enable air to flow from said upper segment to said lower segment when said ratio has a value greater than one, and to stop all flow of air between said segments when said ratio has a value below said threshold.
2. Transport means according to claim 1, wherein said supply means include for each of said chambers a pair of reversible fans both working in tandem chamber and located at opposite ends of the associated chamber, and wherein said control means are adapted selectively to reverse their common direction of operation.
3. Transport means according to claim 2, wherein each of said fans comprises reversible-pitch blades, the hand of said pitch being controlled by said control means.
4. Transport means according to claim 2, wherein each of said fans comprises a reversible rotation motor, the direction of rotation of said motor being controlled by said control means.
5. Transport means according to claim 2, wherein said control means include a plurality of passage detectors which are distributed along said upper segment with at least one detector opposite each of said chambers and which are each adapted to deliver, as said transport unit passes by, a reversal signal for causing said direction of operation reversal.
6. Transport means according to claim 5, wherein smd control means include at least two passage detectors per chamber, said detectors being connected to a discriminator capable of determining the direction in which said transport unit moves and to feed said reversal signal to the fans associated with a chamber ahead of said transport unit, whatever its direction of movement.
7. Transport means according to claim 6, wherein said discriminator is adapted to measure the instantaneous speed of said transport unit and to select that of said chambers to whose fans said reversal signal should be fed whereby the latter may have an advance such, in relation to the position of said transport unit, that said cancellation of the pressure difference will occur in the selected chamber when said transport unit comes to be located thereover, whatever the speed at which said transport unit is travelling.
8. Transport means according to claim 1, which comprise at least two transport units and at least one door dividing said upper segment into two sections, said door being adapted to open upon the arrival of a transport unit and to close again when said transport unit has passed therethrough, whereby said transport units may travel simultaneously along said upper segment at the rate of one transport unit per section, said sections having a length at least equal to three consecutive chambers.
References Cited UNITED STATES PATENTS 1,813,625 7/1931 Knox 243-6 3,148,845 9/1964 Buchwald et al. 243-6 3,265,324 8/1966 Mach et al. 2436 3,305,191 2/1967 Buchwald 2436 3,352,512 11/1967 James 104155 ANDRES H. NIELSEN, Primary Examiner.