US3672159A - Apparatus for crane jibs adapted to be extended and retracted telescopically - Google Patents

Abstract

A crane jib for attachment to a crane column including in combination a jib inner section pivotally attached to the crane column, a jib central section telescopically disposed with respect to the inner section, a jib outer section telescopically disposed with respect to the central section, first and second hydraulic cylinders disposed within the central section and having their rods attached respectively to the inner and outer sections, valve means and control means for applying fluid pressure through the valve means to the hydraulic cylinders for telescoping said sections substantially simultaneously for extension and retraction of the jib.

Description

United States Patent Sundin [151 3,672,159 1 51 June 27, 1972 [s41 APPARATUS FOR (IRANE JIBS 2,984,373 5/1961 Przybylski ..214/141 ADAPTED TO BE EXTENDED AND 3,212,604 /1965 Gamett ..9l/l73 X RETRACTED TELESCQPICALLY 3,240,008 3/1966 McMullen ..60/ 10.5

3,250,182 5/1966 Mansel ..9l/l67 [72-] inventor: Anders Erlk Sundln, Forsa, Sweden 3 300 050 /19 7 Lado I 212 3 5 [73] Assignees 1 A. E. Sundln Produkter AB, Delsbo, 3'407947 10/1968 vaua "91/41 1 X Sweden Primary Examiner-Martin P. Schwadron [22] Flled: 1 1970 Assistant Examiner-Irwin C. Cohen [21] APPL No: 13,991 Attorney-Kane, Dalsimer, Kane, Sullivan and Kurucz [57] ABSTRACT Foreign Application Priority Data A crane jib for attachment to a crane column including in Feb. 28, I969 Sweden ..2764/69 combination a jib inner section pivotally attached to the crane column, a jib central section telescopically disposed with [52] US. Cl 60/105, 91/4] 1, 9211/3/35? respect to the inner section a j outer section telescopically 58 Field ofSeai-ch....; ..60/10.5- 187/9-91/167 168 y I 91/4 I 436 2 2 havmg the1r rods attached respectlvely to the 1nner and outer sections, valve means and control means for applying fluid [56] keferencescned tpressure through the valve means to the hvdraulic cylinders or telescoplng said sect1ons substantially s1multaneously for UNITED STATES PATENTS extension and retraction of the jib.

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INVEN TOR ANpERs ER\K suuom augzilfi z wwa ATTORNE Y5 APPARATUS FOR CRANE JIBS ADAP'IED TO BE EXTENDED AND RETRACTED TELESCOPICALLY BACKGROUND OF THE INVENTION It is very difficult in the case of crane jibs adapted to be extended and retracted telescopically, more particularly in the case of crane lorries, to obtain a satisfactory association of the displacement movements of the individual telescopic sections, more particularly if the crane jib comprises at least three telescopic sections. It is not possible to achieve a mutual co-ordination between the extended telescopic sections of telescopically extensible and retractable crane jibs in advance, whose telescopic units comprise only one common pressure container to which a hydraulic fluid is supplied. Also, the telescopic sections are extended individually, which often results in unnecessary high bearing pressure in the individual sections and at the same time causes a non-uniform extending movement.

In order to obtain uniform load distribution over the bearings of the individual telescopic sections, it is desirable to have a substantially simultaneously occurring extension or retraction of the telescopic sections, and in some cases this is even necessary, and yet their speed of extension and length of travel may be different.

It has already been attempted to solve this problem by a number of different constructions, but all of these more or less involve disadvantages and defects. For example there has been provided a crane jib which is telescopically extensible and comprises a double-acting hydraulic cylinder, but the latter only operates directly one of the telescopic sections at a time. The retracting and extending movement of the other telescopic sections is brought about by means of a very complicated rope system with running wheels arranged at the outside of the crane jib. However, the tractive force when extending or shortening the jib by means only a short working life, since it is easily damaged.

It is also already known to provide each individual telescopic section with a hydraulic unit, these hydraulic units being connected in parallel with one another and connected to an actuating device. But parallel arrangement of the hydraulic units involves the disadvantage that both the magnitude of the force and the rate of movement of the hydraulic cylinders are different in the two directions of movement. Accordingly, the telescopic sections are not extended simultaneously, and instead the section which has the least frictional resistance is extended first. Since the sequence in which the telescopic sections are extended is not correctly predetermined, the guiding of the hose for the hydraulic fluid within the crane jib is made substantially more difficult. If for example the foremost jib section is extended first, the hydraulic fluid hoses must be capable of being extended in order not to be fractured at the rear edge of the central section.

SUMMARY OF THE INVENTION Both for the solution of these problems and in order to obviate the aforesaid disadvantages, an apparatus has been provided which is characterized in that the two hydraulic cylinders are secured to an end wall and situated within the central telescopic section, the piston rod of the one (first) hydraulic cylinder being secured to the end of the inner telescopic section pivotably arranged on the crane column and the piston rod of the second hydraulic cylinder being secured to the end wall of the outer telescopic section, and in that the hydraulic cylinders are connected in series in a pressure fluid system.

The apparatus according to the invention is also characterized by elements which, for extension of the crane jib, conduct a pressure fluid from a pressure source by way of a first pressure fluid supply conduit directly into the inner pressure chamber i.e. the pressure chamber situated at that end of the second hydraulic cylinder which is nearest to the crane column, the piston and the piston rod of this hydraulic cylinder being displaced outwardly and pressure fluid present in the outer pressure chamber of this second pressure cylinder being pressed out through an outer communicating conduit and supplied to the outer pressure chamber of the first hydraulic cylinder, whereby this cylinder is displaced relatively to its piston and by means of the said piston pressure fluid present in the inner chamber of the first hydraulic cylinder is pressed by way of an inner communicating conduit, through a valve arrangement and a pressure fluid duct and then introduced into the inner pressure chamber of the second hydraulic cylinder.

The apparatus according to the invention is also characterized by elements which in order to shorten the crane jib, introduce a pressure fluid from a pressure source by way of a second pressure fluid supply conduit, through the valve arrangement and the forward communicating conduit and into the inner pressure chamber of the first hydraulic cylinder that is displaced inwards relatively to its piston and pressing pressure fluid through the outer communicating conduit into the outer pressure chamber of the second hydraulic cylinder, whereby the piston of this hydraulic cylinder is displaced inwards relatively to its cylinder, and pressure fluid present in the inner pressure chamber is pressed through the first pressure fluid supply conduit, serving as an inlet when the jib is extended, and supplying it to a pressure fluid container of the pressure source.

Further features of the invention will become apparent from the following.

An apparatus according to the present invention makes it possible to effect a substantially simultaneous extension and also a substantially simultaneous retraction of the individual telescopic sections, and furthermore e.g. the outer most telescopic section can be given, by special choice of dimensions, a greater travel length and a higher speed of displacement than the telescopic section adjacent it. As a result, the pressure produced by the lifted load and acting on the bearing parts of the hydraulic section is uniformly distributed, so that at the extension or retraction of the jib the bearing pressure is kept as low as possible in every section. Owing to the fact that the outermost telescopic section is given a greater travel length, the telescopic sections situated nearer the crane column are given larger bearing surfaces, so that a still more uniform distribution of the bearing pressure in the sections is achieved.

Owing to the direct action of force by the hydraulic cylinders on the telescopic sections and the symmetry thereof in mechanical movement, a considerable tractive force is obtained in the longitudinal direction of the crane jib both at extension and at retraction of the jib. Also the movement during extension or retraction of the jib is-very uniform in all telescopic sections.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view, partly in section, of a crane jib according to the invention with the telescopic sections fully extended,

FIG. 2 shows a longitudinal sectional view through the crane jib in the retracted state,

FIG. 3 shows the hydraulic system during the extension of the jib, in a diagrammatic view,

FIG. 4 is again a diagrammatic view, showing the hydraulic system during the retraction of the crane jib and FIG. 5 shows a partial elevational view of a further form of embodiment, illustrating the bearing or mounting of the pressure cylinders on one of the telescopic sections.

DETAILED DESCRIPTlON OF A PREFERRED EMBODIMENT According to FIG. 1, in one example of embodiment of the apparatus according to the invention the crane jib l is mounted to be pivotable on a crane column 2 which is arranged to be rotatable for example on the back of a lorry for pivoting the crane jib 1 in the horizontal plane. The crane jib l is adapted to be lifted and lowered by means of a hydraulic cylinder 3 and consists of three telescopic sections 4,5,6 which are conveniently of rectangular crosssection and of which the inner telescopic section 4, mounted pivotably on the crane column 2, is not mobile in the longitudinal direction of the crane jib l. The two telescopic sections and 6 are arranged to be displaceable whithin one another and to be capable of being contracted into extended from the telescopic section 4. The outer telescopic section 6 is provided at its end wall 21 with a load hook 17 on which the load to be lifted is suspended either directly or by means of a rope, to be then loaded for example on to a motor lorry. The inner and central telescopic sections 4 and 5 are provided within their outer end respectively both above and below with shoulders 43, 43', 44, 44' which serve together with shoulders 45, 45', 46, 46' (see FIG.2) arranged on the inner end of the central and outer telescopic sections 5, 6 above and below and extending radially outwardly, as supporting surfaces, guide shoulders and end stops. However, these may also be mounted supporting rollers. The extending and retracting movements of the crane jib are carried out by means of a hydraulic system comprising chiefly two hydraulic cylinders 7,8, pressure fluid being supplied to the said hydraulic cylinders at the extension and retraction of the crane jib l by means of a hydraulic pump 9 from a pressure fluid container 10 by way of a changeover device 11 and a valve arrangement 12 (see FIG. 2). FIG. 2 of the drawings also shows that the two hydraulic cylinders 7, 8 are arranged with their end nearest to the crane column 2 at the end wall 13 of the central telescopic section 5. The hydraulic cylinder 7 (in future referred to as the first hydraulic cylinder) is provided with a piston 14 and a piston rod 15 which extends through the end wall 13 of the central telescopic section 5 and at its inner end, nearest the crane column 2, is secured to the end 16 of the inner telescopic section 4 ar ranged pivotably on the crane column 2. The securing element 18'for the hydraulic cylinder 7,- serving as a support, must, owing to the unavoidable deflection of the telescopic sections 5,6 when the crane jib is subjected to considerable load, be made to be somewhat yieldable in a plane transversely to the direction of displacement of the crane jib 1. The second hydraulic cylinder 8 is provided with a piston 19 and a piston rod 20 whose outer end is secured to the end wall 21 of the outer telescopic section 6. The inner end, nearest to the crane column 2, of the hydraulic cylinder 8 (designated hereinafter as the second hydraulic cylinder") is also mounted in the end wall 13 of the central telescopic section 5, as shown in FIG. 2.

As for example FIGS.3 and 4 show diagrammatically, the hydraulic system comprises the aforesaid pressure fluid container 10, from which the pressure fluid is conveyed by means of the hydraulic pump 9 to the change-over device 11, which changeover device is adjustable to three different positions, namely one position for extension of the crane jib 1, one position for retraction of the said jib, and an intermediate position wherein the pressure fluid is returned directly to the pressure fluid container 10 without influencing the two hydraulic cylinders 7,8. From the change-over device 11, two pressure fluid supply conduits 22, 23 lead to the crane jib 1, the first of which 22 is connected directly to the second hydraulic cylinder 8 and the second 23 to a double-acting non-retum valve 24, which valve is arranged in an inner end portion 25 of the second hydraulic cylinder 8 which is nearest the crane jib 2. This double-acting non-return valve is formed by a valve ball 27 which is mobile in a valve chamber 26 and which blocks the second pressure fluid supply conduit 23 and a pressure fluid duct 28 situated between the valve chamber 26 and the first pressure fluid supply conduit 22. Leading to the valve chamber 26 is a further pressure fluid conduit which is referred to hereinafter as the inner communicating conduit 29, which is constantly open and connects the valve chamber 26 to the inner pressure chamber 30, nearest to the crane column 2, of the first hydraulic cylinder 7. The two outer pressure chambers 31, 32, nearest to the load hook 17 (see FIG. 2), of the hydraulic cylinders 7,8 are connected by a pressure fluid conduit, in future referred to as the outer communicating conduit 33, to one another. The piston 14 of the first hydraulic cylinder 7 is also provided with a throughflow duct 34 in the outer end of which there is arranged a spring-loaded valve 35 with a projection 36 which, when the piston 14 has reached its outer end position, abuts against the end wall 37 of the hydraulic cylinder 7 and holds the valve 35 open. At the inward displacement of the hydraulic cylinder 7, the valve 35 is closed by the action of the pressure spring 38 associated therewith.

FIG. 5 shows a partial view, shown in longitudinal section, of the mounting or securing of the hydraulic cylinders according to a further form of embodiment, which has a few constructional advantages relatively to the form of embodiment described hereinbefore. In this form of embodiment the inner end portion 18, 25, nearest to the crane column 2, of the two hydraulic cylinders 7, 8 is constructed as a single end portion 39 and provided with a common mounting portion 40 which is arranged in the end wall 13 of the central telescopic section 5 and is mobile in a plane transversely to the longitudinal direction of the crane jib 1. The pressure fluid duct 28 opens directly into the inner pressure chamber 41 of the hydraulic cylinder 8 and the non-return valve 24 with the connections is so arranged that the valve ball 27 carries out a horizontal movement.

By way of a summary, the course of the extension operation (se FIG. 3) and the retraction operation (see FIG. 4) of the crane jib 1 will be described hereinafler,

When using the crane and when the crane jib 1 is not extended or retracted, the change-over device 11 is at neutral, the hydraulic pump 9 delivering the pressure fluid directly back to the pressure fluid container 10. When it is necessary to extend the crane jib I, the operating lever 42 of the changeover device 1 l is swung to the position shown in FIG. 3. In this position, the pressure fluid is conducted through the first pressure fluid supply conduit 22 and into the inner pressure chamber 41 of the second hydraulic cylinder 8, whereby the piston 19 is pressed outwards. The piston rod 20 arranged in a stationary position on this piston and the outer telescopic section 6 are now shifted outwards. At the same time pressure fluid is also conducted through the outer communicating conduit 33 and into the outer pressure chamber 31 of the first hydraulic cylinder 7. Since the piston 14 of the first hydraulic cylinder 7 is situated in the end position, the valve is open and the pressure fluid can consequently pass through the throughflow duct 34. As a result, a delay is achieved in the extension of the central telescopic section 5, but this depends on the size of the cross-sectional area of the throughflow duct 34. With a relatively small cross-sectional area the two cylinders 7,8 are set in motion substantially simultaneously, the first cylinder 7 also being displaced relatively to the piston 14 associated therewith. Since the piston rod 15 with its inner end, directed towards the crane column 2, is secured to the end 16 of the inner telescopic section 4, which is not mobile in the direction of prolongation of the jib, the central telescopic section 5 is moved outwards. In this case pressure fluid is pressed into the inner pressure chamber 30 of the first hydraulic cylinder 7, through the inner communicating conduit 29 and introduced into the valve chamber 26 of the non-return valve 24, the valve ball 27 blocking the second pressure fluid supply conduit 23, which is thus completely inoperative. The pressure fluid is therefore conducted through the pressure fluid duct 28 and into the inner pressure chamber 41 of the second hydraulic cylinder 8 again.

At retraction of the crane jib l, the operating lever 42 of the change-over device I 1 is swung to the position shown in FIG. 4. When this happens, pressure fluid is introduced through the second pressure fluid supply conduit 23 and into the valve chamber 26 of the non-return valve 24, the valve ball 27 blocking the pressure fluid duct 28 and the pressure fluid consequently being introduced through the inner communicating conduit 29 and into the inner pressure chamber 30 of the first hydraulic cylinder 7. Since the piston rod 15 is securely arranged at one of its ends on the end of the telescopic section 4 pivotably mounted on the crane column 2, the cylinder 7 is displaced inwards relatively to its piston i.e. the central telescopic section 5 is retracted. Pressure fluid is introduced through the outer communicating conduit 33 into the outer pressure chamber 32 of the second hydraulic cylinder 8, whereby the piston 19 with the piston rod 20 associated therewith and with it also the outer telescopic section 6 are shifted inwards i.e. retracted. The pressure fluid present in the inner pressure chamber 41 of this hydraulic cylinder 8 is conveyed through the first pressure fluid supply conduit 22, which is connected by the change-over device 11 to the pressure fluid container 10, back into the pressure fluid container which itself communicates with the hydraulic pump 9. As soon as the piston 14 of the first hydraulic cylinder 7 has reached its outer end position, the valve 35 is opened, the pressure fluid being pressed through the throughflow duct 34 and flowing into the second hydraulic cylinder 8 until the piston 19 thereof has reached its inner end position. The travel length of the hydraulic cylinders 7,8 and their effective cross-sectional areas can be so chosen that the piston 14 of the first hydraulic cylinder 7 reaches its end position before the piston 19 of the second hydraulic cylinder 8 has reached its end position i.e. the central telescopic section 5 has already run in before the running-in movement of the outer telescopic section 6 terminates. If the apparatus is so dimensioned that the pistons 14, 19 reachtheir particular end positions simultaneously, relatively small displacements may occur in time owing to leakage at the piston seals. But the valve 35 guarantees that the two pistons 14, 19 actually occupy their relevant end positions. Since the two outer pressure chambers 31, 32 of the hydraulic cylinders 7, 8 form with the outer communicating conduit 39 a closed hydraulic system, the valve 35 is extremely important for the filling of the system with pressure fluid.

in order to enable the apparatus according to the invention to be suitably dimensioned for obtaining a predetermined travel length for the two hydraulic cylinders 7,8, a mathematical relationship is necessary between on the one hand the cross-sectional areas of the cylinders and the piston rods and on the other hand their travel length, which is explained hereinafter in more detail:

a the inner cross-sectional area of the first hydraulic cylinder 7 b cross-sectional area of the piston rod c the inner cross-sectional area of the second hydraulic cylinder 8 d cross-sectional area of the piston rod 20 e travel length of the first hydraulic cylinder 7 f= travel length of the second hydraulic cylinder 8.

If no pressure fluid leaves the pressure fluid system during the extension of the jib, the introduced quantity of pressure fluid is identical with the decrease in the volume of the parts of the piston rods situated in the cylinders, from which the following equation follows (d f b e).

In order that during retraction, with the same pressure, a tractive force can be obtained in the piston rods 15, 20 which is equal in magnitude to the compressive force thereof during extension, the same quantity of fluid must be supplied. During retraction, in addition to the stored quantity of fluid the quantity of fluid displaced by the moved-in piston rods 15, 20 must also leave the hydraulic cylinders 7,8. Therefore the following equation is obtained:

A certain deviation from the dimensional relationships is permitted in practice in order to adapt to existing standard dimensions and auxiliary means used in production.

If both hydraulic cylinders have the same travel length (e f) and the piston rod cross-sectional areas are the same in magnitude (b d), there is obtained The decrease in the quantity of fluid in the outer pressure chamber 32 of the second hydraulic cylinder 8 is the same as the increase in the fluid quantity in the outer pressure chamber 31 of the first hydraulic cylinder 7, i.e.

(c d) f a e But if there is the same travel length (e =f) and piston rod cross-sectional area (b =d), then according to the foregoing c 4d. The introduction of these values into the previous equation gives Since the difl'erence between the travel length of the two cylinders is generally not greater than about 10 20 percent of the travel length in order to subject the bearings of the crane jib 1 to loads of equal magnitude, the last-indicated equations can be used in a preliminary calculation for computing the measurements of the apparatus.

The apparatus according to the invention provides a crane jib which is very compact in the retracted position in relation to its operating circle, which is very advantageous when used for example in the case of crane lorries, since cranes used in these are usually arranged, during transport, behind the drivers cab transversely to the longitudinal direction of the lorry, and for this reason should be somewhat less than the overall width of the vehicle.

The forms of embodiment illustrated and described should only be regarded as examples and can be varied construc tionally in various ways within the framework of the following claims. For example the piston of the second hydraulic cylinder can be provided with a throughflow duct and a valve. Finally, several apparatus according to the present invention can be connected following one another in a telescopically reu'actable and extensible crane jib, in which case, for shifting for example six telescopic units, a hydraulic cylinder pair according to the present invention is arranged in the second telescopic section and a further pair of hydraulic cylinders within the fifth telescopic section.

I claim:

1. A crane jib for attachment to a crane column including in combination a jib inner section pivotally attached to said crane column, a jib central section telescopically disposed with respect to said inner section, a jib outer section telescopically disposed with respect to said central section, first, second and third interior walls of said jib inner, central and outer sections respectively, first and second hydraulic cylinders rigidly attached to said second wall, first and second piston rods respectively of said first and second hydraulic cylinders attached respectively to said first and third walls, a first piston head mounted on said first piston rod within said first cylinder, inner and outer first cylinder chambers separated by said first piston head, a second piston head mounted on said second piston rod within said second cylinder, inner and outer second cylinder chambers separated by said second piston head, an outer communicating conduit connecting said outer cylinder chambers, a flow-through duct in said first piston head connecting said inner and outer first cylinder chambers, a valve within said flow-through duct, a double-acting non-retum valve, a valve chamber of said double-acting valve, an inner communicating conduit connecting said inner chambers through said valve chamber, a fluid pressure source, a first pressure fluid conduit connecting said inner second cylinder chamber through said valve chamber with said pressure source, a second pressure fluid conduit connecting said inner first cylinder chamber with said pressure source through said valve chamber, control means selectively determining the entry of pressure into said pressure fluid conduits from said pressure source whereby upon extension of said jib pressure is conducted by said first pressure fluid conduit into said inner second cylinder chamber displacing said second piston head and pressing pressure from said outer second cylinder chamber through said outer communicating conduit into said outer first cylinder chamber displacing said first piston head and fluid present in said inner first cylinder chamber is pressed into said inner second cylinder chamber through said inner communicating conduit and said valve chamber and whereby upon retraction of said jib pressure is conducted by said second pressure fluid supply into said inner first cylinder chamber through said valve chamber and said inner communicating conduit displacing said first piston head and pressing pressure through said outer communicating conduit into said hydraulic cylinders are rigidly attached and said member is pivotally attached to said second wall mobile in a plane transversely to the longitudinal direction of said crane jib.

3. A crane jib in accordance with claim 1 in which the valve within said flow-through spring loaded member so that at the outer end position of said piston head said inner and outer first cylinder chambers are connected through said flow-through duct.

Claims (3)

1. A crane jib for attachment to a crane column including in combination a jib inner section pivotally attached to said crane column, a jib central section telescopically disposed with respect to said inner section, a jib outer section telescopically disposed with respect to said central section, first, second and third interior walls of said jib inner, central and outer sections respectively, first and second hydraulic cylinders rigidly attached to said second wall, first and second piston rods respectively of said first and second hydraulic cylinders attached respectively to said first and third walls, a first piston head mounted on said first piston rod within said first cylinder, inner and outer first cylinder chambers separated by said first piston head, a second piston head mounted on said second piston rod within said second cylinder, inner and outer second cylinder chambers separated by said second piston head, an outer communicating conduit connecting said outer cylinder chambers, a flow-through duct in said first piston head connecting said inner and outer first cylinder chambers, a valve within said flow-through duct, a double-acting non-return valve, a valve chamber of said double-acting valve, an inner communicating conduit connecting said inner chambers through said valve chamber, a fluid pressure source, a first pressure fluid conduit connecting said inner second cylinder chamber through said valve chamber with said pressure source, a second pressure fluid conduit connecting said inner first cylinder chamber with said pressure source through said valve chamber, control means selectively determining the entry of pressure into said pressure fluid conduits from said pressure source whereby upon extension of said jib pressure is conducted by said first pressure fluid conduit into said inner second cylinder chamber displacing said second piston head and pressing pressure from said outer second cylinder chamber through said outer communicating conduit into said outer first cylinder chamber displacing said first piston head and fluid present in said inner first cylinder chamber is pressed into said inner second cylinder chamber through said inner communicating conduit and said valve chamber and whereby upon retraction of said jib pressure is conducted by said second pressure fluid supply into said inner first cylinder chamber through said valve chamber and said inner communicating conduit displacing said first piston head and pressing pressure through said outer communicating conduit into said outer second cylinder chamber displacing said second piston head, and said non-return valve including a free-moving valve means in said valve chamber, said free moving valve means alternatively blocking said first and second pressure fluid supply conduits communicating with said valve chamber and constantly main-taining the inner communicating conduit open.

2. A crane jib in accordance with claim 1 in which a member is provided in which said valve chamber and said inner communicating conduit are formed and to which said hydraulic cylinders are rigidly attached and said member is pivotally attached to said second wall mobile in a plane transversely to the longitudinal direction of said crane jib.

3. A crane jib in accordance with claim 1 in which the valve within said flow-through spring loaded member so that at the outer end position of said piston head said inner and outer first cylinder chambers are connected through said flow-through duct.

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