A screw drilling device

Description

[0001] The present invention relates to a screw drilling device particularly for producing concrete foundation piles, of the type comprising a spiral screw integral with a central tubular element in which a duct is formed for the supply of a fluid to be injected into the borehole formed by the device.

[0002] Screw boring devices of the aforementioned type, in which the lower end of the duct is closed by a plug, are known (see for instance EP-A-0 378 348). During drilling, the earth is broken up and caused to rise along the turns of the screw whereas, in the closed position, the plug prevents earth from blocking the concrete-supply duct. Upon completion of the drilling, concrete is pumped through the duct; the concrete under pressure expels the plug and fills the cavity of the hole bored whilst the screw full of debris is extracted therefrom.

[0003] Extraction is effected with the screw kept stationary, that is, not rotating, or rotating slowly clockwise; anticlockwise rotation would cause the debris to fall from the screw, contaminating the concrete and compromising the quality of the product. Upon completion of the extraction and before the next drilling operation, the plug, which is connected to the screw by a chain, is usually replaced manually. This operation requires the presence of an operator at the bottom of the screw in a position which is dangerous because debris may fall from the screw.

[0004] To improve the quality of the concrete injected into the borehole, a device has been proposed which, at the beginning of the pumping stage, provides for a second, coaxial tubular element, extending throughout the length of the screw and connected to suitable lifting and lowering members, to extend telescopically from the lower end of the central tubular element. The lower end of the second tubular element admits the fluid into the mass of fluid previously injected, beneath any debris and contaminants which, since they have a lower specific weight than concrete, tend to float and can therefore be removed upon completion of the pour.

[0005] Problems inherent in this technique are the vertical dimensions of the members for moving the second tubular element which reduce the depth of boring which can be achieved by a given machine, as well as complications in the mounting of the screw and of the second tubular element which are formed by several connectible elements.

[0006] The object of the present invention is to provide an improved screw drilling device which can prevent the problems mentioned above.

[0007] This object is achieved, according to the present invention, by a device having the characteristics set out in Claim 1.

[0008] A further object of the present invention is to provide a device which can produce a borehole with a diameter larger than that of a conventional tube used to line the first metres of the hole.

[0009] This object is achieved, also according to the invention, by a device having the characteristics recited in Claim 6.

[0010] Further important characteristics are recited in the other dependent claims.

[0011] Further characteristics and advantages of the invention will become clearer from the detailed description of an embodiment thereof, given with reference to the appended drawings, provided by way of non-limiting example, in which:

Figure 1 is a partially axially sectioned elevational view of a device according to the present invention in a first operative condition,

Figure 2 is a partially axially sectioned elevational view of the device of Figure 1 in a second operative condition,

Figure 3 is a transverse section taken on the line III-III of Figure 1, and

Figure 4 is a transverse section taken on the line IV-IV of Figure 2.

[0012] With reference first of all to Figures 1 and 2, a screw boring device according to the present invention is generally indicated 1. The device 1 comprises a spiral screw 2 welded around a tubular core 3 in which a central duct 4 is formed for the supply of concrete or other mixtures to be injected into the borehole 5 formed by the device 1.

[0013] The boring device 1 is rotated and translated vertically about and along the central axis x in known manner and is preferably guided in the first metres of the drilling by a coaxial cylindrical outer tube 6 having the main function of lining the upper or initial portion of the borehole 5.

[0014] The lower end of the screw, which terminates in a sharp radial cutting edge 2a, is firmly attached to a horizontal plate 7 in the form of a disk sector extending through an angle greater than 180°, that is, in the embodiment shown, an angle of about 240°. The plate 7 which is referred to herein as the fixed plate, defines a circular-sector-shaped opening 8 extending through the complement to 360° of the above- mentioned angle, that is, through about 120° in the embodiment shown.

[0015] The terms "radial" and "axial" as used herein, should be interpreted as relating to the axis x of the borehole unless stated otherwise.

[0016] The tubular core 3 extends below the level of the plate 7 forming a lower end portion 3a of predetermined length "L", preferably of between 50 and 100 cm and generally comparable to the diameter of the screw.

[0017] As shown in Figure 1, the lower portion 3a has a cylindrical outer surface 3b which is preferably offset from the central axis x by an eccentricity "e".

[0018] Inside the tube portion 3a, the central duct 4 bends outwardly forming an inclined end duct portion 4a which opens in the outer cylindrical wall 3b with a lateral opening 4b.

[0019] A rotatable unit, preferably formed as a single body, generally indicated 9, is fitted on the lower tube portion 3a and forms a plate-like portion 10 in the shape of a disk sector the shape and size of which correspond to those of the fixed plate 7, and a cylindrical bush-like portion 11.

[0020] As can be seen in Figures 1 and 3, the plate 10, which is referred to herein as the rotatable plate, defines a circular-sector-shaped axial opening 12 complementing the plate to 360°, and having a geometrical shape corresponding to that of the opening 8 in the fixed plate 7. The lower surface of the rotatable plate 10 bears a plurality of members 13 for breaking up the ground.

[0021] On one of the radial sides which define the opening 12, the rotatable plate 10 forms an abutment 14 which projects axially in order to come into abutment alternatively with one of the two sides 8a, 8b of the opening 8 in the fixed plate 7, as will be explained further below.

[0022] The bush-like portion 11 has an eccentric inner cylindrical surface 15 and an eccentric outer cylindrical surface 16; the internal surface 15 which houses the lower tube portion 3a has the same eccentricity "e" as that tube portion and the outer surface 16 has a diameter corresponding to that of a conical tip 17 situated at the lower end of the device and fixed to the bottom of the tube 3a at 18 so as to clamp the rotatable body 9 axially relative to the tube 3a and hence to the screw. The conical tip 17 bears a further set of breaking-up members 20.

[0023] The bush-like portion 11 has a lateral or radial hole 19 situated at the same level as the opening 4b in the tube portion 3a and preferably inclined in the same manner as the final portion of the duct 4a in order to be joined thereto in one of the two working conditions of the device, as shown in Figures 2 and 4.

[0024] The relative orientations of the radial hole 19 and of the axial opening 12 are such that, in the first working condition which the device adopts during the boring stage (Figures 1 and 3), the angular openings 8 and 12 of the respective plate-like portions 7 and 10 are aligned axially and the opening 4b of the duct 4, 4a is blocked by the bush-like portion 11 whereas, in the second working condition, which is adopted at the stage of the injection of concrete and simultaneous extraction of the device from the borehole (Figures 2 and 4), the angular opening 8 is closed by the rotatable plate 10 and the radial hole 19 meets the opening 4b.

[0025] The device of the present invention operates as follows.

[0026] As shown in Figure 1, during the boring stage, the screw device performs a combined clockwise rotational and vertical downward translational movement, as indicated by the arrow A. During rotation in this direction, the side 8a of the "fixed" plate 7 abuts the abutment 14 of the rotatable body 9 causing the body 9 to rotate (Figure 3). In this condition, as stated, the angular openings 8 and 12 coincide and allow ground debris broken up by the members 13 to enter and rise between the turns of the screw 2. The rotatable body 9 is oriented in a manner such that the cylindrical outer surface 16 of the bush-like portion 11 coincides with the circular profile of the base of the conical tip 17. The duct 4, 4a, is closed by the bush-like portion 11.

[0027] When the desired depth of bore has been reached, a reverse rotation is imparted to the screw; the friction generated by the contact of the rotatable body 9, particularly its breaking-up members 13, with the ground, restrains the body 9 whilst the screw and the plate 7 rotate relative to the body 9 (anticlockwise, Figure 4) until the side 8b abuts the abutment 14. In this condition, the bottom of the screw is closed by the plate 10 which prevents the debris accumulated between turns of the screw from falling into the borehole (Figures 2 and 4). The holes 4b and 19 coincide, allowing concrete to be admitted to the borehole through the duct 4, 4a.

[0028] In the preferred embodiment, as shown in Figure 2, the hole 19 is located in the vicinity of the lower end of the bush-like portion 11 at an axial distance L' slightly shorter than the above-mentioned length L. This facilitates the injection of the fluid beneath the free surface 21 of the cast fluid; any floating waste is therefore not covered and trapped in the cast fluid but will rise and remain on the surface and can be removed, thus improving the quality of the concrete constituting the product.

[0029] The eccentric configuration of the rotatable body 9 relative to the axis of the screw is particularly advantageous since it enables a borehole of a diameter considerably larger than that of the screw and of the outer covering tube 6 to be produced. As can be seen in Figures 1 and 3, the plate-like portion 10 also carries breaking-up members 13 on its peripheral portion which, in the boring condition, extends radially beyond the screw and the tube 6. This enables the borehole produced to have a diameter larger than that of the lining tube which can easily be fitted in the hole without having to be rotated; simpler machinery can therefore be used for moving the tube. In the casting and extraction position (Figures 2 and 4), the plate-like portion 10 is included within the shape of the fixed plate 7 so that the entire device can be extracted from the tube to permit subsequent operations such as the positioning of reinforcement for strengthening the concrete.

[0030] Naturally, the principle of the invention remaining the same, the forms of embodiment and details of construction may be varied widely with respect to those described and illustrated purely by way of non-limiting example, without departing from the scope of the invention as defined in the appended claims.

Claims

1. A screw drilling device, particularly for producing concrete foundation piles, of the type comprising a spiral screw (2) integral with a central tubular element (3) in which a duct (4) is formed for the supply of a fluid to be injected into the borehole (5) formed by the device, characterized in that it comprises a unit (9) forming a first wall (10) having a first axial opening (12) and a second wall (11) having a first radial opening (19), the unit (9) being mounted rotatably on a lower portion (3a) of the tubular element (3) and being able to adopt two alternative operative positions:

a first position, in a boring configuration, in which the first wall (10) is oriented so as to afford access for debris between the turns of the screw through the first axial opening (12) and the second wall (11) is oriented so as to close a second radial opening (4b) formed in the lower tubular portion (3a) for discharging the fluid from the duct (4), and

a second position, in a fluid-injection configuration, in which the first wall (10) is oriented so as to close the screw at the bottom and the second wall (11) is oriented so as to put the first and second radial openings (19, 4b) into communication.

2. A device according to Claim 1, characterized in that the rotatable unit (9) comprises:

- a radial plate (10) constituting the first wall, parallel to and facing the underside of a radial plate (7) fixed to the screw, the plate (10) bearing breaking-up members (13) on its underside, and the plates (10, 7) forming respective axial openings (8, 12) which can be superimposed in the first position, and

- a cylindrical bush-like portion (11) forming the second wall in which the second radial opening (4b) is formed.

3. A device according to Claim 2, characterized in that the plates (7, 10) are shaped as disk sectors extending through angles greater than 180° and the axial openings (8, 12) are circular-sector-shaped openings formed in the respective plates.

4. A device according to Claim 3, characterized in that the plates (7, 10) are shaped as disk sectors extending through angles of about 240°.

5. A device according to Claim 2, characterized in that the rotatable unit (9) forms an abutment means (14) for abutting alternatively, in the first and second positions, respective opposed end surfaces (8a, 8b) fixed for rotation with the screw.

6. A device according to any one of the preceding claims, characterized in that the lower tubular portion (3a) is eccentric relative to the axis (x) of the screw and the rotatable unit (9) also bears breaking-up members (13) on the peripheral part of its plate-like portion (10) so that, in the first operative position, at least one of these members extends radially at least up to a distance from the central axis substantially corresponding to the radius of a tube (6) for lining the borehole (5).

7. A device according to Claim 6, characterized in that the bush-like portion (11) has an eccentric, cylindrical surface (15) in which the lower tubular portion (3a) can be fitted.

8. A device according to Claim 6, characterized in that the bush-like portion (11) has an outer cylindrical surface (16) having a diameter corresponding to that of a conical tip (17) which is fixed (18) to the lower end of the tubular portion (3a) so as to clamp the rotatable unit (9) axially to the screw.

9. A device according to Claim 1, characterized in that the radial openings (4b, 19) are formed at an axial distance (L') no less than approximately 50 cm from the radial plate (10).

Ansprüche

1. Schneckenbohrvorrichtung, besonders zur Herstellung von Betonfundamentpfeilern, wobei die Vorrichtung eine Schneckenspindel (2) enthält, die mit einem zentralen Rohrelement (3) gemeinsam aufgebaut ist, in dem ein Kanal (4) ausgebildet ist, um ein Fluid einzuleiten, das in das Bohrloch (5) gespritzt werden soll, das die Vorrichtung ausbildet, dadurch gekennzeichnet, dass die Vorrichtung eine Einheit (9) enthält, die eine erste Wand (10) bildet, die eine erste axiale Öffnung (12) besitzt, sowie eine zweite Wand (11) bildet, die eine erste radiale Öffnung (19) besitzt, wobei die Einheit (9) drehbar an einem unteren Teil (3a) des Rohrelements (3) befestigt ist und zwei alternative Arbeitstellungen einnehmen kann:

eine erste Stellung in einem Bohrzustand, in der die erste Wand (10) so ausgerichtet ist, dass Bohrklein durch die erste axiale Öffnung (12) zwischen die Windungen der Schnecke gelangen kann, und in der die zweite Wand (11) so ausgerichtet ist, dass sie eine zweite radiale Öffnung (4b) verschließt, die im unteren Rohrteil (3a) ausgebildet ist, um das Fluid vom Kanal (4) abzugeben, sowie

eine zweite Stellung in einem Zustand, in dem das Fluid eingespritzt wird, in der die erste Wand (10) so ausgerichtet ist, dass sie die Schnecke am Boden verschließt, und in der die zweite Wand (11) so ausgerichtet ist, dass die erste und die zweite radiale Öffnung (19, 4b) miteinander in Verbindung stehen.

2. Vorrichtung gemäß Anspruch 1, dadurch gekennzeichnet, dass die drehbare Einheit (9) enthält:

- eine radiale Platte (10), die die erste Wand bildet und parallel zu einer radialen Platte (7) und gegenüber von deren Unterseite liegt, die an der Schnecke befestigt ist, wobei die Platte (10) an ihrer Unterseite Aufbrechelemente (13) trägt, und wobei die Platten (10, 7) entsprechende a-xiale Öffnungen (8, 12) bilden, die in der ersten Stellung überlagert werden können, sowie

- einen zylindrischen, buchsenartigen Teil (11), der die zweite Wand bildet, in der die zweite radiale Öffnung (4b) ausgebildet ist.

3. Vorrichtung gemäß Anspruch 2, dadurch gekennzeichnet, dass die Platten (7, 10) als sektorförmige Scheiben ausgebildet sind, die über Winkel von mehr als 180° verlaufen, und die axialen Öffnungen (8, 12) kreissektorförmige Öffnungen sind, die in den entsprechenden Platten ausgebildet sind.

4. Vorrichtung gemäß Anspruch 3, dadurch gekennzeichnet, dass die Platten (7, 10) als scheibenförmige Sektoren ausgebildet sind, die über Winkel von etwa 240° verlaufen.

5. Vorrichtung gemäß Anspruch 2, dadurch gekennzeichnet, dass die drehbare Einheit (9) eine Aufnahmeeinrichtung (14) bildet, um alternativ in der ersten und zweiten Stellung entsprechend gegenüberliegende Endflächen (8a, 8b) aufzunehmen, die für eine Drehung mit der Schnecke befestigt sind.

6. Vorrichtung gemäß irgendeinem der bisherigen Ansprüche, dadurch gekennzeichnet, dass der untere Rohrteil (3a) relativ zur Achse (x) der Schnecke exzentrisch liegt, und dass die drehbare Einheit (9) weiters auf dem Randteil ihres plattenartigen Teils (10) Aufbrechelemente (13) trägt, so dass in der ersten Betriebsstellung zumindest eines dieser Elemente radial zumindest um einen Abstand von der Mittelachse verläuft, der im Wesentlichen dem Radius eines Rohres (6) entspricht, um das Bohrloch (5) auszukleiden.

7. Vorrichtung gemäß Anspruch 6, dadurch gekennzeichnet, dass der buchsenartige Teil (11) eine exzentrische, zylindrische Fläche (15) besitzt, in die der untere Rohrteil (3a) eingesetzt werden kann.

8. Vorrichtung gemäß Anspruch 6, dadurch gekennzeichnet, dass der buchsenartige Teil (11) eine zylindrische Außenfläche (16) besitzt, die einen Durchmesser besitzt, der dem Durchmesser einer konischen Spitze (17) entspricht, die am unteren Ende des Rohrteils (3a) befestigt (18) ist, um die drehbare Einheit (9) an der Schnecke axial einzuspannen.

9. Vorrichtung gemäß Anspruch 1, dadurch gekennzeichnet, dass die radialen Öffnungen (4b, 19) in einem axialen Abstand (L') ausgebildet sind, der nicht weniger als etwa 50 cm von der radialen Platte (10) beträgt.

Revendications

1. Dispositif de forage par vis hélicoïdale, particulièrement destiné à la production de piles de fondation en béton, comprenant une vis hélicoïdale (2) venue de matière avec un élément tubulaire central (3) dans lequel est formé un conduit (4) d'alimentation d'un fluide à injecter dans le trou de forage (5) formé par le dispositif, caractérisé en ce qu'il comprend un organe (9) formant une première paroi (10) possédant une première ouverture axiale (12) et une deuxième paroi (11) possédant une première ouverture radiale (19), l'organe (9) étant monté de manière rotative sur une partie inférieure (3a) de l'élément tubulaire (3) et pouvant prendre deux positions de fonctionnement alternatives :

une première position, en configuration de forage, dans laquelle la première paroi (10) est orientée de façon à permettre l'accès aux débris entre les pas de l'hélice à travers la première ouverture axiale (12) et où la deuxième paroi (11) est orientée de façon à fermer une deuxième ouverture radiale (4b) ménagée dans la partie tubulaire inférieure (3a) pour assurer l'évacuation du fluide provenant du conduit (4), et

une deuxième position, en configuration d'injection de fluide, dans laquelle la première paroi (10) est orientée de façon à fermer la vis hélicoïdale dans sa partie inférieure et où la deuxième paroi (11) est orientée de façon à mettre en communication les première et deuxième ouvertures (19, 4b).

2. Dispositif selon la revendication 1, caractérisé en ce que l'organe rotatif (9) comprend :

- une plaque radiale (10) constituant la première paroi qui est parallèle et fait face au-dessous d'une plaque radiale (7) fixée à la vis hélicoïdale, la plaque (10) supportant des éléments de rupture (13) sur sa face inférieure, et les plaques (10, 7) formant des ouvertures axiales respectives (8, 12) qui peuvent être superposées dans la première position, et

- une partie cylindrique en forme de boîte (11) qui forme la deuxième paroi et dans laquelle la deuxième ouverture radiale (4b) est formée.

3. Dispositif selon la revendication 2, caractérisée en ce que les plaques (7, 10) ont des formes de secteurs de disque s'étendant sur des angles supérieurs à 180°, et les ouvertures axiales (8, 12) sont des ouvertures en forme de secteurs circulaires qui sont formées dans les plaques respectives.

4. Dispositif selon la revendication 3, caractérisé en ce que les plaques (7, 10) ont des formes de secteurs de disque s'étendant sur des angles d'environ 240°.

5. Dispositif selon la revendication 2, caractérisé en ce que l'organe rotatif (9) constitue un moyen d'aboutement (14) permettant d'abouter alternativement, dans les première et deuxième positions, les surfaces d'extrémité opposées (8a, 8b) qui sont fixées pour tourner avec la vis hélicoïdale.

6. Dispositif selon l'une quelconque des revendications précédentes, caractérisé en ce que la partie tubulaire inférieure (3a) est excentrique par rapport à l'axe (x) de la vis hélicoïdale et l'organe rotatif (9) supporte également des éléments de rupture (13) sur la partie périphérique de sa partie en forme de plaque (10) de façon que, dans la première position de fonctionnement, un au moins de ces éléments s'étend radialement au moins jusqu'à une distance de l'axe central qui correspond sensiblement au rayon d'un tube (6) qui est destiné à centrer le trou de forage (5).

7. Dispositif selon la revendication 6, caractérisé en ce que la partie en forme de boîte (11) possède une surface cylindrique excentrique (15) dans laquelle la partie tubulaire inférieure (3a) peut être emboîtée.

8. Dispositif selon la revendication 6, caractérisé en ce que la partie en forme de boîte (11) possède une surface cylindrique extérieure (16) dont le diamètre correspond à celui d'un embout conique (17) qui est fixé (18) à l'extrémité inférieure de la partie tubulaire (3a) afin de verrouiller axialement l'organe rotatif (9) sur la vis hélicoïdale.

9. Dispositif selon la revendication 1, caractérisé en ce que les ouvertures radiales (4b, 19) sont formées à une distance axiale (L') qui n'est pas inférieure à approximativement 50 cm de la plaque radiale (10).

Drawing