Boring or penetrating the earth – With signaling – indicating – testing or measuring
Reexamination Certificate
1999-06-29
2001-01-23
Pezzuto, Robert E. (Department: 3671)
Boring or penetrating the earth
With signaling, indicating, testing or measuring
C175S296000
Reexamination Certificate
active
06176324
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a drilling device used in particular for the drilling of holes intended for the extraction of rocks and ores, in which a rotary movement is imparted to the drilling tool, this assembly being mounted on an advancing device which enables a thrust to be exerted on the tool during drilling.
It is known that the torque created by the contact of the tool or drilling head with the ground increases with the thrust applied.
It is therefore necessary to provide regulating devices enabling the thrust exerted on the tool to be adapted to the maximum torque admissible by the drive device, in order to protect the tool from risks of jamming in the drilled ground.
FIGS. 1 and 2
represent, very schematically, a rotary percussion drilling device of known type, in two operating positions. These figures show a hammer drill
1
equipped with a tool
2
associated on the one hand with an impact device
3
and on the other hand with a rotary drive device
4
. The hammer drill is mounted to be displaceable relative to the ground
5
in which a bore is to be made with the aid of an advancing system
6
mounted on a slideway
7
. The advancing system comprises a hydraulic ram
8
whose body is solidly fixed to the device
6
and whose column
9
bears on a fixed point. The various movements are obtained from a hydraulic pump
10
which feeds, via three distributors,
12
,
13
and
14
respectively, the impact device
3
, a hydraulic motor
15
and the ram
8
. The connections are embodied by way of a series of hoses,
16
,
17
and
18
respectively. The feed circuit of the hydraulic motor for driving the tool in rotation comprises the hoses between the hydraulic pump
10
and the distributor
13
, the distributor
13
, the hose
17
a
, the rotary motor
15
, the return hose
17
b
and the hose between the distributor
13
and the return to atmosphere. A circuit reversing device
19
is placed in the circuit situated between the distributor
14
and the ram
8
for advancing the drilling device. The reversing system
19
is controlled by the pressure of rotation of the motor
15
, ensuring the rotational drive of the drill. The maximum admissible rotational pressure at which the reversing system reacts is adjustable. The information pick-up of this system is, nevertheless, very distant from the inlet of the motor
15
, for reasons of bulk, which results in very substantial hose lengths.
Below the maximum admissible rotational pressure, the fluid feed of the various motor members takes place, as shown in
FIG. 1
, via the hoses shown in solid lines. The reversing system
19
is in its position of rest and does not act on the advancing circuit. In the event that the tool
2
becomes jammed in the ground, the rotational pressure increases. If the pressure exceeds a predetermined value, set on the reversing system
19
, the latter reverses the feed direction of the ram
8
, as shown in
FIG. 2
, allowing the tool to move back.
In such a case, the hydraulic rotational pressure of the motor is not measured directly, and the drill is very remote from the control system. The measured pressure is the sum of the rotational pressure of the motor and the losses of line head within the circuit formed by the hose
17
. However, the losses of head within a circuit are very variable as a function of temperature, which influences viscosity, and of the hydraulic fluid flow.
In order to work in all conditions, it is necessary to adjust the reversing switch device
19
to a value such that the maximum admissible rotational pressure is equal to the rotational pressure plus the maximum loss of head.
The rotational pressure due to mechanical torque being constant, the losses of head are for their part variable as a function of temperature. The measured pressure is therefore variable as a function of temperature. This type of device does not allow fine adjustment of the reversing system.
SUMMARY OF THE INVENTION
In order to remedy these disadvantages, the Applicant uses a drill in which the output of the motor is directed towards the intake of the part providing the impact. An identical flow is directed towards the part providing the impact and is accumulated with the output of the motor providing the rotation of the tool. The torque is measured by differential measurement of the pressure between the intake and output of the rotation motor. In this case, the measured rotational pressure is equal to the rotational pressure at the boundaries of the motor, excluding the losses of head in the rotation circuit.
This solution enables the reversing system to be actuated correctly. However, incorporating it complicates the implementation of the other hydraulic functions, because of the dependence of the rotation and impact circuits on the drill.
The object of the invention is to provide a drilling device which makes it possible to avoid the losses of head in the hydraulic circuit feeding the motor which drives the tool in rotation, by virtue of the variable nature of these losses of head as a function of temperature and of the hydraulic fluid flow, while making it possible to retain optimum adjustment of the maximum value of the admissible torque over the entire operating range of the device, without requiring complex technical solutions, especially from a hydraulic point of view.
To this end, the drilling device to which the invention relates, of the type possessing a drilling unit of which the tool is driven to rotate from a hydraulic motor associated with an advancing device enabling a bearing force of the drilling unit on the ground to be created, the various actuating members being driven from at least one hydraulic pump via a set of hydraulic distributors and a set of tubes, such as hoses, the two feed tubes of the advancing device of the drilling system being equipped with a switch for reversing the direction of circulation of the fluid in the advancing device, is characterized in that mounted on one of the branches of the feed circuit of the hydraulic motor for driving the tool in rotation is a fluid characteristics measurement device constantly supplying information to a compensation device for subtracting the calculated loss of head created by all the members of the circuit between two known points in that circuit, situated on either side of the motor, from the pressure difference measured between those same two points, the result of this operation actuating the switch for reversing the direction of circulation of the advancing fluid if the value exceeds a given value.
Such a device enables the direction of displacement of the drill on its slideway to be reversed automatically in order to prevent the jamming of the drilling tool in the soil if the rotational pressure exceeds the maximum admissible rotational pressure.
The measuring device sends to the compensation device a measurement of the loss of head proportional to that of the rotation circuit.
The compensation device uses this information to actuate the reversing system if the increase in rotational pressure is due to an increase in the mechanical torque.
If the increase in rotational pressure is due to a variation in the losses of head in the rotation circuit, the reversing system is not actuated.
The measuring device, the compensation device and the reversing switch, and the transmission of information between these various members, may be mechanical, hydraulic, pneumatic, electronic or electrical.
The advantage of this structure lies in the fact that variations in the pressure of the fluid driving the motor which drives the drilling system in rotation that are due to variations in the loss of head in the circuit do not affect the value of the maximum admissible rotational pressure. Only a variation in the pressure of rotation due to contact between the tool and the ground triggers a reaction by the reversing system.
According to a feature of the invention, this device comprises a device for measuring the flow rate and viscosity of the hydraulic fluid whose head loss characteristics are proportional to
Etablissements Montabert
Oliff & Berridg,e PLC
Pezzuto Robert E.
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