GB2400811A

GB2400811A - Drilling appliance with automatic position detection

Info

Publication number: GB2400811A
Application number: GB0408999A
Authority: GB
Inventors: Andreas Strasser; Markus Leupert
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-04-25
Filing date: 2004-04-22
Publication date: 2004-10-27
Anticipated expiration: 2024-04-22
Also published as: DE10318798B4; GB0408999D0; DE10318798A1; CN1539584A; GB2400811B; CN100455389C

Abstract

The invention relates to a drilling appliance (2), in particular a hand-held percussion drilling machine or a hand-held drilling hammer with electric drive motor. It is provided that the drilling appliance (2) has a sensor (24) for detecting the orientation of a drilling axis (B) and a sensor system (26, 28 fig 5) for detecting at least one drilling parameter, and also a device (52, fig 5) for evaluating output signals of the sensor (24) and the sensor system (26, 28) and for altering a movement of a drilling tool (10) of the drilling appliance (2) in response to the evaluation of the output signals. The drilling parameter may be rotational speed, torque, current supplied or power consumed.

Description

240081 1 Drilling appliance with automatic position detection The

invention relates to a drilling appliance, in particular a hand-held percussion drilling machine or a hand-held drilling hammer with electric drive motor.

Prior art

Such hand-held electric tools or drilling tools in the form of percussion drilling machines and drilling hammers are well known and are sold in large quantities both for professional use and for do-it-yourself use. These kinds of hand-held drilling appliances are generally used to drill masonry, concrete or stone, the drilling taking place either vertically or horizontally. For drilling, normally drilling tools in the form of socalled twist drills are used, these possessing a helical twisted flute which runs along the drilling tool and by means of which the drillings or drilling dust detached in the drill hole by the drilling tool tip are or is conveyed out of the drill hole.

If such drilling appliances are used to drill vertically or obliquely downwards, the drillings or drilling dust detached in the drill hole are or is conveyed more slowly by the drilling tool through the twisted flute to the mouth of the drill hole than in the case of horizontal drilling or vertically upward drilling. This leads to an increase in the rotational resistance acting on the drilling tool in the drill hole and hence in the energy consumption for the drilling operation. In unfavourable circumstances, sticking or blocking of the drilling tool in the drill hole may even occur, and, if the operator of the drilling appliance is inattentive, this may result in the drilling appliance rotating and freeing itself from the operator's grasp, which quite often causes injury to the operator.

If, on the other hand, such drilling appliances are used to drill through a wall or another workpiece made of concrete or stone, a generally undesirable chipping-off of relatively large pieces of the concrete or stone around the drill hole quite often occurs as the drilling tool emerges from the wall or the workpiece.

Advantages of the invention The drilling appliance according to the invention having the features of Claim 1 has, in contrast, the advantage that, when drilling downwards, sticking of the drill bit and thus the risk of injury to the operator resulting therefrom is avoided. The sensor for detecting the orientation of the drilling axis of the drilling appliance makes it possible to ascertain whether substantially downward or substantially horizontal drilling is taking place, while the sensor system for detecting at least one drilling parameter, for example the rotational speed or the torque of the drilling appliance, makes it possible to detect changes in the behaviour of the drilling appliance in operation, so that the output signals of the sensor system which are indicative of these changes can be evaluated, while taking into account the signals from the sensor, in order to alter the movement of the drilling tool in response to the evaluation of the output signals. This alteration may consist, for example, in temporarily switching off a percussion mechanism of the drilling appliance if the sensor system indicates an increase in the rotational resistance and the sensor indicates a vertically or steeply downwardly inclined orientation of the drilling axis, which is regarded by the evaluation circuit as a sign that drillings or drilling dust are or is being inadequately conveyed away out of the drill hole, or in reducing the rotational speed of the drive motor of the drilling appliance if the sensor system detects a decrease in the rotational resistance and the sensor indicates a substantially horizontal orientation of the drilling axis, which is interpreted by the evaluation circuit as a sign that the drilling tool is just about to emerge from a wall after drilling through it.

In a preferred configuration of the invention, it is provided that the sensor for detecting the orientation of the drilling axis of the drilling appliance is an inclination sensor or at least one so-called acceleration sensor, with the help of which the orientation of the drilling appliance can be detected by the evaluation circuit before the drilling has started or while it is taking place.

A further preferred configuration of the invention provides that the sensor system for detecting parameters of the drilling comprises a rotational-speed sensor, which, as the parameters, picks up the instantaneous rotational speed of the drilling tool or a drive motor of the drilling appliance and compares it with a predetermined minimum rotational speed or a rotational-speed value picked up a short time beforehand, in order to detect changes in the rotational speed which are, for example, a sign of imminent sticking of the drilling tool or that the same is just about to break through a wall. Since the rotational speed of the drilling tool is adjustable in most drilling appliances in order to adapt it to different drilling-tool diameters and workpiece materials, the aforementioned predetermined minimum rotational speed is expediently dependent on the set rotational speed. Alternatively, a torque sensor could also be used, in which case the evaluation device expediently compares the torque detected by the torque sensor with a torque value detected by the sensor a short time beforehand. A comparison with a predetermined torque value would, in principle, also be conceivable, although the drilling appliance would then have to have a device for inputting or measuring the diameter of the drilling tool, since the measured torque is greatly dependent thereon.

A torque sensor is particularly suitable, however, for detecting when the drilling tool is just about to break through a wall or the like, since a noticeable reduction in the resistance torque of the drilling tool occurs just before the tool breaks through. By comparing the instantaneous torque at the drive motor, or alternatively the current or power consumption of the drive motor of the drilling appliance dependent on the torque, with a torque determined a short time beforehand, this torque decrease can be ascertained.

Further advantageous configurations of the invention emerge from the rest of the features mentioned in the subalaims.

Drawings The invention is explained in more detail below in an exemplary embodiment with reference to the associated drawings, in which: Figure 1 shows a partially cutaway side view of a percussion drilling machine; Figure 2 shows an enlarged view of an inclination sensor of the percussion drilling machine with a vertical orientation of the drilling axis of the percussion drilling machine; Figure 3 shows an enlarged view of an inclination sensor of the percussion drilling machine with an oblique orientation of the drilling axis; Figure 4 shows an enlarged view of an inclination sensor of the percussion drilling machine with a horizontal orientation of the drilling axis; Figure 5 shows a block diagram of components of the percussion drilling machine.

Description of the exemplary embodiment

The percussion drilling machine 2 illustrated in the drawing consists essentially of a housing 4 with a handle part 6, and a drill chuck 8 projecting beyond the housing 4 for clamping a drill bit or another drilling tool 10.

As with most commercially available percussion drilling machines, the housing 4 is provided, on the handle part 6, with an on/off switch 12, an adjusting wheel 14 integrated in the on/off switch 12 for adjusting the rotational speed of the drill chuck 8, a locking button 16 for continuous operation of the drilling machine 2, and a switch 18 for changing over the direction of rotation of the drill chuck 8. Located on the top side of the housing 4 is a slide switch 20 for changing over from pure drilling mode to percussion drilling mode and vice versa. The housing 4 encloses an electric drive motor and gearing (not illustrated) and is provided with ventilation slits 22 on its side faces and its top side, for ventilating the motor.

Besides the motor and gearing, the housing further encloses an inclination sensor 24 for detecting the orientation of a drilling axis of the drilling tool 10, a rotational-speed sensor 26 for measuring the rotational speed of the drilling tool 10 or the drive motor of the drilling machine 2, and a torque sensor 28 for detecting the resistance torque exerted on the drill chuck and the drive motor by a workpiece, of which only the inclination sensor 24 is illustrated, schematically, in Fig. 1.

As is best illustrated in Fig. 2, this inclination sensor 24 comprises a closed housing 30, for example an ampoule made of glass, roughly a quarter of which is filled with mercury or another electrically conductive liquid 32.

The housing 30 is substantially rotationally symmetrical about an axis A parallel to a drilling axis B of the drilling machine 2 and has, at its end facing the drill chuck 8, an outwardly tapered projection 34. A total of four contacts 36, 38, 40, 42 lead into the housing 30.

Three of the contacts 36, 40, 42 are of wire-shaped design and are welded into a wall 44 of the housing 30 in such a way that their free ends lead into the interior of the housing. Of these three contacts 36, 40, 42, the first 36 is arranged at the outermost end of the tapered projection 34, while the other two are arranged at opposite faces 46, 48 of the housing 30, to be precise both on the side of the housing 30 adjacent to the handle part 6 of the drilling machine 2. The fourth contact 38 is of ring-shaped design, surrounds the inner side of the tapered projection 34 and is led to the outside via a connecting wire 50 welded into the wall 44 of the housing 30.

This arrangement ensures that the first and fourth contact 36, 38 are always electrically connected by the conductive liquid 30 when the drilling axis B of the drilling machine 2 is oriented at an angle of more than 45 degrees to the horizontal H. as illustrated in Fig. 2 for an angle of 90 degrees. However, when the drilling axis B is inclined at a shallower angle than 45 degrees, the liquid 32 flows completely out of the protruding projection 34 and interrupts the connection between the first and fourth contact 36, 38, as illustrated in Fig. 3 for an angle of 30 degrees. On the other hand, the second and third contact 40, 42 are always connected by the electrically conductive liquid 32 when the drilling axis BA is oriented at an angle of less than 15 to 20 degrees to the horizontal H and the handle part 6 of the drilling machine 2 points downwards, as illustrated in Fig. 4 for an angle of O degrees.

As is best illustrated in Fig. 5, the four contacts 36, 38, 40, 42 are connected to an evaluation circuit 52, the contacts 36 and 40 further being connected to a current source 58, so that, through a current signal at the contacts 38, 42, it is possible to ascertain in the evaluation circuit 52 whether one of the two respective pairs of contacts 36, 38 and 40, 42 is jointly immersed in the liquid 32 and hence one of the two previously described orientations of the drilling machine 2 is signalled. The evaluation circuit 52 is connected to a controller 54 for the drive motor of the drilling machine 2, which enables a percussion mechanism (not illustrated) of the drilling machine 2 to be switched off or on or the rotational speed of the drive motor to be altered, in dependence on the result of the evaluation in the evaluation circuit 52.

Instead of the above-described inclination sensor 24, it is also possible to use a so-called linear acceleration sensor with a plurality of active axes, which instead of the electrically conductive liquid contains movable spheres whose position, which is dependent on the orientation of the drilling axis B. is detected by suitable means.

The rotational-speed sensor 26 can be designed, in a known manner, as an analogue tachogenerator or as an optical or electromagnetic tachometer which picks up the rotational speed of the drive motor of the drilling machine 2 or of an output shaft of the machine's reduction gearing. The rotational-speed sensor 26 is likewise connected to the evaluation circuit 52, which ascertains whether the rotational speed has fallen below a predetermined minimum value. This predetermined minimum rotational speed depends, however, on the rotational speed of the drill chuck 8 set at the adjusting wheel 14 and increases in step with the set rotational speed. Thus, it is actually ascertained whether the quotient from the measured rotational speed of the drill chuck 8 or of the rotational speed of the drill chuck 8 calculated from the rotational speed of the drive motor, on the one hand, and from the rotational speed of the drill chuck 8 set at the adjusting wheel 14, on the other hand, has fallen below a predetermined minimum value.

The torque sensor 28 measures, for example, the current flow to the drive motor of the drilling machine 2 at short time intervals and is likewise connected to the evaluation circuit 52, which compares the output signals of the torque sensor 28 over certain short time intervals and can thereby detect a decrease in the resistance torque during drilling.

The evaluation circuit 52 additionally receives information on the position of the slide switch 20, so that it can also ascertain whether the percussion drilling machine 2 is in pure drilling mode or in percussion drilling mode.

If it is ascertained in the evaluation circuit 52 that firstly the contact 38 is carrying current, i.e. substantially downward drilling is taking place, and that secondly there has been a fall below the predetermined minimum rotational speed or the predetermined minimum value for the quotient from the measured and the set rotational speed of the drill chuck 8, this is a sign that the drilling tool 10 is no longer capable of properly conveying the drillings away out of the drill hole. If in this case it is ascertained, through the information on the position of the slide switch 20, that the drilling machine is operating in percussion drilling mode and its percussion mechanism is switched on, the latter is temporarily switched off by a signal from the evaluation circuit 52 and drilling is continued in pure drilling mode until the rotational speed lies above the predetermined minimum rotational speed again. A changeover to the percussion drilling mode again then takes place. In this way, sticking of the drilling tool 10 and hence rotation of the drilling machine 2 about the drilling axis B can be prevented.

If, on the other hand, it is ascertained in the evaluation circuit 52 that firstly the contact 42 is carrying current, i.e. substantially horizontal drilling is taking place, and that secondly the resistance torque decreases suddenly during drilling, this may be a sign that the drilling tool 10 has just penetrated the workpiece and is emerging from it on the opposite side. In this case, the evaluation circuit 52 brings about an immediate reduction of the rotational speed of the drive motor, with the result that the impact energy also falls and pronounced chipping- off of parts of the workpiece at the emergence of the drilling tool 10 can be prevented.

Claims

Claims 1. Drilling appliance, in particular hand-held percussion drilling

machine or hand-held drilling hammer with electric drive motor, characterized by a sensor (24) for detecting the orientation of a drilling axis (B) of the drilling appliance (2) and a sensor system (26, 28) for detecting at least one drilling parameter, and also by a device (52) for evaluating output signals of the sensor (24) and the sensor system (26, 28) and for altering a movement of a drilling tool (10) of the drilling appliance (2) in response to the evaluation of the output signals.
2. Drilling appliance according to Claim 1, characterized in that the sensor (24) distinguishes between a vertical or steeply downwardly inclined orientation of the drilling axis (B) and a horizontal or shallowly inclined orientation of the drilling axis (B).
3. Drilling appliance according to Claim 1 or 2, characterized in that the sensor is an inclination sensor (24).
4. Drilling appliance according to Claim 1 or 2, characterized in that the sensor is an acceleration sensor.
5. Drilling appliance according to Claim 4, characterized in that the acceleration sensor is a linear acceleration sensor with one or more active axes.
6. Drilling appliance according to one of the preceding claims, characterized in that the sensor system (26, 28) comprises a rotationalspeed sensor (26), which detects, as the drilling parameter, a rotational speed of the drilling tool (10), a drive motor of the drilling appliance (2) or a drive shaft arranged therebetween.
7. Drilling appliance according to one of the preceding claims, characterized in that the sensor system (26, 28) comprises a torque sensor (28), which indirectly or directly detects, as the drilling parameter, a torque acting on the drilling tool (10), a drive motor of the drilling appliance (2) or a drive shaft arranged therebetween.
8. Drilling appliance according to one of the preceding claims, characterized in that the sensor system (26, 28) comprises a current sensor, which detects, as the drilling parameter, the current strength of a current supplied to a drive motor of the drilling appliance (2).
9. Drilling appliance according to one of the preceding claims, characterized in that the sensor system (26, 28) detects the power consumed by a drive motor of the drilling appliance (2).
10. Drilling appliance according to one of the preceding claims, characterized in that the device (52) compares the rotational speed detected by the sensor system (26, 28) or the torque detected by the sensor system (26, 28) with a predetermined rotational-speed or torque value.
11. Drilling appliance according to one of the preceding claims, characterized in that the device (52) compares the rotational speed detected by the sensor system (26, 28) or the torque detected by the sensor system (26, 28) with a rotational-speed or torque value detected a short time beforehand.
12. Drilling appliance according to one of the preceding claims, characterized in that, in the comparison, a rotational speed set at the drilling appliance (2) and/or a diameter of the drilling tool (10) is taken into account.
13. Drilling appliance according to one of the preceding claims, characterized in that the devices effect a changeover from a combined percussion drilling mode to a pure drilling mode if the evaluation of the output signal of the inclination sensor indicates a vertical or steeply inclined orientation of the drilling axis and the evaluation of the output signal of the sensor system indicates an increase in the rotational resistance.
14. Drilling appliance according to one of the preceding claims, characterized in that the devices effect a reduction in the rotational speed of the drive or the drilling tool if the evaluation of the output signal of the inclination sensor indicates a horizontal or shallowly inclined orientation of the drilling axis and the evaluation of the output signal of the sensor system indicates a decrease in the rotational resistance.
15. A drilling appliance substantially as herein described with reference to the accompanying drawings.