Abstract
Disclosed is a method for driving a screwable foundation, which comprises a thread-type external helix that has a pitch on the outer contour thereof, into the ground. In said method, a striking force is applied to the screwable foundation in the driving direction in alternation with or at least temporarily simultaneously with a torque when the screwable foundation is driven into the ground.
Claims
1. An apparatus for driving ground screw foundations into the ground, which have a sleeve body and on the exterior thereof an external helix with a thread-like pitch, which has a. a rotation apparatus for the screwing in of the ground screw foundation, a striking apparatus for generating a striking-in force in the driving direction of the ground screw foundation, b. at least one of the following devices from the group which comprises a rotation rate measurement device for determining the current rotation rate of the ground screw foundation during its driving, a distance measurement device for determining the driving distance of the ground screw foundation and a device for limiting the torque, and c. a regulating apparatus adapted for regulating the rotation apparatus and/or the striking apparatus and the switching on or off thereof with the aid of the values determined under b., by means of which the rotation apparatus and the striking apparatus are able to be operated in alternation or at least temporarily simultaneously during the driving; in which the torque is transferable from the motor of the rotation apparatus via at least one pair of contact surfaces arranged on a predetermined diameter to a drive shaft and to the ground screw foundation, wherein the at least one pair of contact surfaces are movable relative to one another, and wherein the diameter in which the at least one pair of contact surfaces is arranged on is at least two times greater than the diameter of the drive shaft.
2. The apparatus as claimed in claim 1, in which the regulating apparatus defines the slip value from the current rotation rate, the pitch of the external helix and the driving distance of the ground screw foundation, which slip value is compared with a predefined amount of a slip value.
3. The apparatus as claimed in claim 1, in which the regulating apparatus acts on the rotation apparatus in a rotation rate reducing manner and switches on the striking apparatus, when the ground screw foundation impinges on a stone or on hard ground, and the actual driving distance is less than a driving distance corresponding to the current rotation rate, until the amount of a predetermined slip value is reached.
4. The apparatus as claimed in claim 1, in which the striking apparatus is constructed as an acoustic source emitting ultra-high-frequency oscillations having a frequency of up to 40 Hz.
5. The apparatus as claimed in claim 1, in which the striking apparatus is constructed as an apparatus emitting high-frequency mechanical oscillations having a frequency of up to 40 Hz.
6. The apparatus as claimed in claim 1, in which the rotation apparatus is able to be switched off or limits the torque on reaching the maximum torque on the basis of a signal provided by a torque sensor.
7. The apparatus as claimed in claim 1, wherein the diameter in which the at least one pair of contact surfaces is arranged on is at least five times greater than the diameter of the drive shaft.
8. The apparatus as claimed in claim 1, in which the pair of contact surfaces are movable relative to each other in a direction of a rotation axis of the rotation apparatus.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Further features and advantages of the invention will emerge from the following example embodiments in connection with the figures. There are shown here:
(2) FIG. 1: an embodiment of a screwable foundation driving apparatus according to the invention,
(3) FIG. 2: the screwable foundation in a first position during screwing in,
(4) FIG. 3: the screwable foundation in a second position during screwing in,
(5) FIG. 4: a flow chart of a method according to the invention for driving a screwable foundation,
(6) FIG. 5: a second embodiment of a screwable foundation driving apparatus according to the invention,
(7) FIG. 6a, b: a third embodiment of a screwable foundation driving apparatus according to the invention, and
(8) FIG. 7a, b, c: various developments of a screwable foundation in side view and bottom view, which is able to be driven into the ground by the method according to the invention or respectively by the apparatus according to the invention.
DETAILED DESCRIPTION
(9) FIG. 1 shows a driving apparatus 1 according to the invention for driving a screwable foundation 10 into the ground 20. The screwable foundation 10 has at least in partial regions a screw helix 11. The driving apparatus 1 has a carriage 2, in which a drive head 3 is displaceably arranged. Through the relative movement of the drive head 3 relative to the carriage 2, which generally takes place substantially in vertical direction, the advance V is provided for the driving of the screwable foundation 10. The advance V is able to be provided by the dead weight in particular of the drive head 3 or by an active drive with predetermined propelling force and/or propulsion speed. The drive head 3 has a coupling 7, which is able to be connected in a torsionally rigid manner with the screwable foundation 10. The coupling 7 is rotatable by the drive head 3 both in rotation direction R and also in translation direction T, in order to exert a percussion drilling process. On the drive head 3 or respectively on the driving apparatus 1 both a rotation rate sensor 4 and a torque sensor 5 for measuring the driving rotation rate or respectively the driving moment, and also a distance sensor 6 for determining the distance of advance and the speed of advance are provided.
(10) FIG. 2 shows a portion of the screwable foundation 10 in a first position during the driving into the ground 20. The screwable foundation has in this portion a thin-walled cylindrical sleeve 14 and the screw helix 11 arranged on its exterior. In an idealized screwing-in process, in which the speed of advance corresponds to the screwing-in speed of advance, i.e. screwing-in rotation rate n times the thread pitch p, the screw helix 11 cuts into the ground 20 such that both the upper and also the lower flank 12 or respectively 13 are in contact in the ground 20. In actual screwing-in processes, however, the speed of advance frequently does not coincide with the screwing-in speed of advance. In the case shown in FIG. 2, the speed of advance v is too little or respectively the rotation rate n is too great. This is also designated as a positive slip, so that the factor s for the slip is greater than 1. With a positive slip, a cavity 21 is produced beneath the lower flank 13 of the screwable foundation 10 during the driving. This occurs for example when the driving resistance, for example by a stone, is increased. The formation of such cavities 21 has a negative effect, however, on the stability (holding power) of the screwable foundation 10 in the ground 20. In the present application, the slip is defined as follows: s=(n.Math.p)/v.
(11) The cavity 21 is produced in that the actual advance lags behind the ideal advance by the lag N.
(12) Through the method according to the invention, by the use of an in particular combined rotational- and striking- or respectively ramming movement, the lag N is to be reduced, as is shown in FIG. 3.
(13) In FIG. 4 a flow chart is presented diagrammatically for a driving process according to the invention. The screwing-in process is started at step 100. After the start of the screwing-in process, the screwing-in process is monitored by means of the sensors for rotation rate, torque and advance (4, 5 and 6). Via these sensors in particular a stone detection 110, a thread protection 120 and a screwable foundation protection 130 are realized. The screwing-in depth is monitored via the advance sensor 6 as a switch-off condition for the driving process. When the screwing-in depth is reached, the driving process is terminated in step 150. The monitoring processes 110, 120 and 130 generally run parallel to one another. However, the individual types of regulation are also able to be implemented individually or in various combinations. For each of the monitoring operations there is a condition in column 101, by which the respective status is detected. In column 102, the striking apparatus or respectively the striking force is then switched on and the further driving is regulated according to column 103. On reaching an exit condition according to column 104, the striking mechanism is switched off according to column 105.
(14) The stone detection 110 has as detection condition that an intrusion of the speed of advance takes place. In particular the current slip exceeds a predetermined threshold slip value, because for example the screwable foundation impinges onto a rock and the advance is abruptly reduced. By switching on the striking mechanism it is guaranteed that an advance also takes place in hard subsoil, for example in rock or stone. After switching on the striking mechanism, the rotation rate is regulated by means of the speed of advance and a positive slip, for example with s=1.1. Through the positive slip, after penetrating the rock, the advance is speedily accelerated again. The exceeding of a predetermined threshold rotation rate, for example 20 min.sup.1, applies as exit condition here. With the occurrence of the exit condition, the striking mechanism is switched off, and the rotation rate regulation is terminated.
(15) For the thread protection 120, the detection 121 is determined by means of the covered advance distance and the distance ideally covered on the basis of the number of revolutions u and the thread pitch p. Consequently, the lag N applies as detection criterion. When the lag exceeds a predefined value, for example half a thread pitch p, then the striking mechanism switches on, and a rotation rate regulation also takes place. In the above-mentioned case, the slip s is regulated, however, to a value <1, for example 0.9, i.e. to negative slip. Thereby, the further destruction of the structure in the ground is counteracted, in particular that a conveying of earth to the surface by the screwable foundation 10 or respectively the screw helix 11 takes place. According to step 124, when the lag is reduced or falls below a predefined value, this applies as exit condition. On reaching the exit condition, the striking mechanism is switched off, and the rotation rate regulation is terminated.
(16) A third type of regulation is represented by the screwable foundation protection according to 130. According to step 131, when a predefined maximum torque or respectively a limit torque is reached, this applies as detection criterion. For example, the torsional rigidity of the screwable foundation 10 or the nominal output of the drive head 3 can serve as limit torque. By activation of the striking mechanism, the screwing-in resistance of the screwable foundation 10 is reduced, by the ground being loosened. When the screwable foundation protection becomes active, the torque is regulated to the limit torque which is reduced if applicable by a safety factor, according to step 133. The falling below of the predetermined rotation rate threshold by a predefined value with maximum rotation rate serves here in particular as exit condition according to step 134. When, for example, the maximum torque lies at 3500 Nm, a value of 3000 Nm can function as limit torque for switching on. On occurrence of the exit condition according to step 134 the striking mechanism is switched off and the torque regulation according to step 133 is likewise terminated.
(17) When in the three regulation types 110, 120 and 130 the exit condition occurs according to column 104, the program loop between steps 100 and the monitorings 110, 120 and 130 is returned, i.e. a monitoring still takes place according to steps 110, 120 and 130. Furthermore, the possibility exists that the monitorings 110, 120 and 130 are also active during a regulation according to column 103.
(18) FIG. 5 shows a second embodiment of the driving apparatus 1 according to the invention, in particular of the drive of the driving apparatus 1 according to the invention, in which by means of an oscillation movement an oscillation is able to be introduced into the coupling 7. A sleeve 30 is rotatably mounted between drive head 3 and coupling 7. The sleeve 30 is arranged concentrically to the shaft. A mass 31 is arranged as unbalanced mass on the sleeve. Furthermore, the sleeve is able to be driven via a drive 32, for example an electric motor. By a setting of the mass 31 in rotation, an oscillation is exerted on the coupling 7 and therefore also on the screwable foundation 10. The rotation direction of the sleeve takes place here preferably in opposition to the rotation direction of the coupling. This apparatus can be arranged in addition to the percussion boring machine shown in example embodiment 1 on the driving machine 1 or only in combination with a boring machine. The introduction of oscillations, in particular vibrations, is advantageous in particular in the screwable foundation protection regulation or respectively in the overload protection according to step 130 in FIG. 4. However, it is also able to be used for example for the penetrating of stone in the stone detection according to step 110 in FIG. 4. The rotation axis of the mass 31 is alternatively also able to be arranged perpendicularly to the longitudinal axis of the screwable foundation. The rotation speed of the mass 31 is preferably between 1000 and 10000 min.sup.1.
(19) In FIGS. 6a, b a second embodiment of the driving apparatus 1 according to the invention, in particular of the drive of the driving apparatus 1 according to the invention, is shown. The motor 8 of the drive head 3 is constructed with a central feed-through 33, through which a hollow shaft 34 is guided and is driven by the motor 8. A drive shaft 35 is constructed concentrically to the hollow shaft 34 and is guided through the hollow shaft 34. On a first side of the motor 8 a striking pin 36 is arranged, via which striking energy is able to be introduced into the drive shaft 35. On the opposite second side of the motor 8, the hollow shaft 34 has two carriers 37, which form pairs of contact surfaces 39a, b with wings 38 arranged on the drive shaft. The torque of the motor 8 is transferred to the drive shaft 35 via the hollow shaft 34 and the pairs of contact surfaces 39a, b. The pairs of contact surfaces 39a, b are constructed here such that in the striking operation they permit a relative movement between hollow shaft 34 and drive shaft 35 in the direction of the longitudinal extent thereof. In addition, the pairs of contact surfaces 39a, b are arranged on a diameter which is distinctly greater than the diameter of the two shafts. The diameter on which the pairs of contact surfaces 39a, b are arranged corresponds approximately to 6 times the diameter of the drive shaft 35. Thereby, the surface pressure in the pairs of contact surfaces 39a, b is reduced, so that the friction and also the wear owing to the relative movement are reduced.
(20) FIG. 7a shows a screwable foundation 10, which consists of a cylindrical, thin-walled sleeve 14. The screwable foundation 10 according to FIG. 7b has in the lower region a tapered portion and is open toward the bottom. The screwable foundation according to FIG. 7c has in the upper region a thin-walled cylindrical portion and in the lower region a cone-shaped portion, which terminates in a closed screwable foundation tip. In firm types of ground such as sandstone, preferably downwardly-open screwable foundations are used, because in contrast to closed screwable foundations, practically only the volume of the tube wall, but not the volume of the entire screwable foundation must displace. Owing to the ground which is firm in any case, a sufficient stability is guaranteed. In the screwable foundations which are shown, the screw helix 11 can be arranged over the entire length of the screwable foundation or only in partial regions.
