GB2217480A

GB2217480A - Speed setting for electric hand tool

Info

Publication number: GB2217480A
Application number: GB8906186A
Authority: GB
Inventors: N Rittmannsberger; W Suchowerskyj
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1988-04-16
Filing date: 1989-03-17
Publication date: 1989-10-25
Also published as: JPH01306110A; DE3812771A1; GB8906186D0

Description

2 17 4 8 0 Speed setting for electric hand -tool

Prior art

The invention is based on an eLec-tric hand tooL of the generic type of the main claim. Electric hand tools, particularly drilling machines, are known which exhibit a key panel for preseLecting- tooL diameter and material to be machined. The key panel is connected to a microcomputer which acts on control electronics and sets the required motor speed. The microcomputer furthermore enables the speed and the gear speed to be set to be displayed on an LCD display panel.

However, an electric hand tooL constructed in manner is expensive since, in addition to the control electronics, microcomputer, main memory and read only memory are also needed which, on the one hand, store the program and, on the other hand, are used for processing arithmetic values. Furthermore, further expenditure is necessary for setting the work programs.

The electronics of drilling machines equipped in _this manner are extremely costly and highly susceptibLe to faults due to the characteristics of the components used.

Advantages of the invention 2 By comparison, the electric hand tool according to the invention, having the characterizing features of the main claim, has the advantage that a speed is presetected and the operating conditions such as speed are displayed by indicators in a matrix array in a simple manner. The indicators and setting switches are arranged clearly and compactly in a panel. As a result, the machine can be inexpensively constructed and easily monitored. In particular, the circuit arrangement according to the invention does not need any centraL eLectronic controL unit such as microcomputer and corresponding main memory so that it is aLso to a hi.gh extent insensitive to eLectric interference.

Due to the measures Listed in the subcLaims, advantageous further cleveLopments and improvements of the eLectric hand tooL specified in the main cLaim are pos sibLe. It is advantageous that no Limitation of the traveL of the trigger is required, for exampLe by means of a knurLed wheeL, so that the entire Length of-the pres.sing traveL of the trigger potentiometer is avaiLabLe at any speed and a manuaL start-up of the eLectric hand tooL is ensured which can be fineLy proportioned. It must be considered as a further advantage that the entire circuit arrangement can be used for cli.fferent hand tooLs or types of machines, no speciaL adaptation being required. The connection to the controL eLectronics is effected via onLy three feed Lines.

It is furthermore advantages if an unfavourabLy seLected speed of the gear is indicated to the operator by fLashing indicators, for exampLe, Light-emitting diodes. This is possibLe, in particuLar, if an eLectric information on the speed set at the gear is avaiLabLe.

Furthermore an advantageous further cleveLopment must be seen in the fact that additionaL indicators specify the gear speed to be set. In the inclividuaL case, it may be necessary for the operator to require a differ ent speed Limitation than the one which wouLd be set by the eLectronics. Due to the fact that the gear speed is set manuaLLy, the operator is LargeLy independent of the eLectronic speed setting. A manuaL intervention in the controL is in most cases not possibLe with eLectric hand tooLs exhibiting a microcomputer-controL.

Drawing Two iLLustrative embodiments of the invention are shown in the drawing and expLained in greater cletaiL in the description foLLowing. Figure 1 shows a first illustrative embodiment fo keys and the indicators, F with the display matrix a tive embodiment, Figure 3 variable speed limitation, of the second illustrative r the arrangement of the input igure 2 shows a block diagram ccording to the first illustrashows families of curves for a Figure 4 shows a block diagram embodiment.

Description of the illustrative embodiments Figure 1 shows an example of an arrangement of input keys 3 and 4 and of labelling for the speed of the motor in a matrix array 1 as used for a hand drilling' machine.. For inputting the type of materials such as, for example, wood, aluminium, steel, concrete, four keys 3 are arranged on the side at the edge of the matrix array 1 with the identification 10, 20, 30 and 40 which are in each case associated with one row 6 of the matrix array 1. Below the matrix array 1, four keys 4 are arranged which are in each case associated with a column 7 of the matrix array 1. The keys 4 specified, for example, the maximum drill diameter to be mounted. The switching points of the matrix array 1 are constructed as light-emitting diodes 5. At the free sides of the matrix array 1 not occupied by the keys 3 and 4, values for the speed of the motor are specified in the illustrative embodiment. 'To make the programming as simple as possible, a limited number of speed graduations was provided so that, for example, the speed for drilling operations in steel up to 3 mm 0 is the same as Jor drilling operations in wood up to 9 mm 0 thickness, namely 1500 rpm. The opera.tor is informed of 0 this by the diagonal marking 20. The speed of the electric motor is determined by the fact that in each case a key 3 for the type of material and a key 4 for the drill diameter are pressed. The matrix array 1 is connected in such a manner that, when these keys 3, 4 are pressed, the light-emitting diode associated with the switching point lights up. In this arrangement, it is necessary that the keys 3, 4 are provided with storage means or exhibit latching arrangements so that the associated light-emitting - 4 diode 5 continues to be lit and the speed set for the electric motor can be read off. It should be possible to reset the previously pressed keys by pressing one of.the other keys of each group. This arrangement of the matrix array 1 as described for a hand drilling machine can also be used, for example,_for an electric saw. In this ca.se, for example saw blade diameters must then be allocated to the keys 4.

In Figure 2, an electric block diagram with the associated matrix of the light-emitting diodes- is shown-. The keys 3 for the selection of material are connected.to the supply voltage with one terminal. The other terminal is in each case connected to one conductor of the rows 6. The free end of-the conductor leads to a logic memory 2 w h i c h e a c h handles the functions of Latching or storing and in casethe row-by-row and coLumn-by-coLumn mutual releasing of the keys 3 and 4, driving of the digitaL/ analog converter 8 and driving of the associated Light emitting diode 5.

The keys 4 are also connected to one another on o.ne side and Lead to the other pole of the voltage source.

Their second terminal part is connected to conductors of the columns 7. The free end of these conductors also Leads to the Logic memory 2. The outputs of the Logic memory 2 are connected to the inputs of a digitaL/anaLog converter 8. It emits to the trigger potentiometer 9 a voltage UM which is proportional to the preset maximum speed of-the motor. A control voltage USt is pi. cked up at the slider of the trigger potentiometer 9 and supplied to the control electronics which set a speed of the electric motor which corresponds to the parameters set. The controL voltage USt can reach a maximum value preset by the voltage UM set.

The Light-emitting diodes 5 are in each case con- nected to the conductors of the rows 6 and columns 7 in such a manner that, after a key 3 for the type of material and a key 4 for the drill diameter have been pressed, the associated Light-emitting diode 5-Lights up. When one of 1 the keys 3 and 4 has been pressed in each case, the current is Limited by a resistor R in the feed Line.

Figure 3 shows famiLies of curves for the speed Limitation arrangement. Figure 3a shows that the traveL of the trigger switch is mechanicaLLy Limited and the speed of the eLectric motor is determined by the maximum avaiLabLe traveL of the trigger switch in conventionaL eLectric hand tooLs. In the circuit arrangement according to the invention, the avaiLabLe traveL of the trigger 0 switch is aLways constant (3b). The famiLy of-curves specifies that the maxiumum speed of the eLectric motor is determined by the potentiometer suppLy voLtage UM, inclepenclentLy of the maximum traveL of the trigger switch. This is particuLarLy advantageous for sensitiveLy start- ing the eLectric hand tooL.

In Figure 4, a second iLLustrative embodiment of the circuit arrangement according to the invention is given. The conductors of the rows 6 and the coLumns 7 are not connected to the Logic memory 2 but directLy to the inputsof the cligitaL/anaLog converter 8 via the code converter 12. In this circuit arrangement, it is necessary that the keys 3, 4 are LatchabLe and are mutuaLLy reLeased when pressed again. This makes it possibLe that, when in each case one of the keys 3 and one of the keys 4 is pressed, the associated Light-emitting diode 5 remains switched on and the Logic information for the seLection of the type of materiaL and the driLL diameter is directLy suppLied_permanentLy to the digitaL/anaLog converter 8. The resistors 13, which are connected to the voLtage suppLy between the inputs of the code converter 12, cletermine the input LeveL whiLst the resistors 14, which are connected in series with the Light-emitting diodes 5, Limit the current in the active state. The digitaL/anaLog converter 8 forms an anaLog output voLtage UM which corresponds to the vaLue of the input parameters and which it suppLies to the trigger potentiometer 9 as information for the maximum speed Limitation. At the sLider of the trigger potentiometer 9, the voLtage USt for the controL 6 electronics is available which produces a particular motor speed corresponding to the pressing travel of the trigger switch.9.

This circuit, too, can be used for various elec- tric tools such as, for example, saws, band grinders, angle grinders or screwdrivers in which variable motor speeds must be set.

7 !7 1. Electric hand tool such as a drilling machine com prising a speed control device, with an input device for a first variable relevant to the machining, such as type of material, and for a second variable relevant to the machining such as tool diameter, and with a device which acts on a switching devi-ce_for speed control on the basis of the values of the input device, characterized in that indicators (5) are mounted in a matrix form on the elec tric hand tool and that at the edge of the matrix array (1) keys (3, 4) corresponding to the first and second variable relevant to the machining and associated with the rows (6) and columns (7) are arranged and that after one key (3, 4) each of the rows (6) and columns (7) is operated, the indicator (5) located at the intersection i.s switched on and that, due to the operation of the keys (3, 4), the maximum speed of the electric hand tool is limited to a value preset by this operation.

Claims

2. Electric hand tool according to Claim 1, charac terized in that keys

(3, 4) are constructed as latchable switches which in each case can be mutually released row by row and column by column.

3. Electric hand tool according to Claim 2, charac terized in that the terminals of the switches (3) and (4) are connected to a code convert?r (12).

4. Electric hand tool according to Claim 1, charac terized in that the terminals of the switches (3, 4 connected to a logic memory (2) and that its outpu connected to a digital/analog converter (8).

5. Electric hand tool according to at least one of the preceding claims, characterized in that the digital/ analog converter (8) supplies an output voltage (UM) to the trigger potentiometer (9) and that the tap of the are ts are 8 - trigger potentiometer (9) emits to controL eLectronics a voLtage (USt) which reaches a maximum vaLue of (UM).

6. ELectric hand tooL according to one of the pre ceding cLaims, characterized in that the maximum pres3ing distance of the trigger 'potentiometer (9) is constant.

7. ELectric hand tooL comprising a switchabLe gear according to one of the preceding cLaims, characterized in that, if a gear speed is not optimaLLy seLected, the indicator (5) seLected by the keys (3, 4) fLashes._ 8. ELectric hand tooL according to one of the pre ceding cLaims, characterized in that the matrix array (1)_ is arranged on the side of the housing facing the user.

9. ELectric hand tooL according to one of the pre ceding cLaims, characterized in that the matrix array (1) exhibits conductors associated with the rows (6) and coLumns (7), each conductor of one row (6) being connec ted to each conductor of one coLumn (7) by in each case one indicator (5).

10. ELectric hand tooL according to one of the pre ceding cLaims, characterized in that the indicators (5) exhibit Light-emitting diodes.

Either of the electric hand tools substantially as herein described with reference to the accomnanying drawings.

Published 1989 atThePatent Office. State House, 68"71 IlighRolbom. LondonWCIR4TP.Ftirther copies maybe obtained from The PatentOffice. Sales Branch, St Mary Cray. Orpington, Rent BRS 3RD. Printed by I'Zultiplex techniques ltd, St Mary Cray, Kent. Con. 1/87 k