Handleable working device, in particular pressing device

Details Handleable working device, in particular pressing device Handleable working device, in particular pressing device

2000-08-17

2002-04-09

Patel, Rajnikant B. (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

C320S136000, C388S921000

Reexamination Certificate

active

06369560

ABSTRACT:

FIELD OF THE INVENTION
The invention concerns a handleable working device, in particular a pressing device, having a tool, in particular a pressing tool; an electric motor for driving the tool; a battery, in particular rechargeable, for supplying energy to the electric motor; and having a control device which has a voltage comparison element that performs a voltage comparison between the present battery voltage and a limit voltage, such that the control device generates an attention signal and/or limits activation of the electric motor so as to spare the battery if the voltage comparison indicates that the present battery voltage is equal to or less than the limit voltage.
DESCRIPTION OF THE RELATED ART
For assembly purposes or for processing purposes, handleable working devices that substantially comprise a tool and an electric motor for driving the tool are known. For joining pipes, for example, pressing devices are used with which a press fitting, which is slid over the pipe ends in order to create the pipe join, is radially compressed. Pressing devices of this kind are known, for example, from EP-A-0 627 273. Handleable working devices of fundamentally the same design, as is evident for example from EP-A-0 676 835, are also used to install cable lugs onto cable ends. The electric motor need not act directly on the tool. Its energy can also be converted into a hydraulic drive system which then acts on the tool.
As EP-A-0 676 835 further shows, energy can also be supplied to the electric motor via a replaceable and also rechargeable battery, so that the working device can be used even in places where no electrical power system exists. With such battery-driven devices, it is important to know whether the energy content still available in the battery is sufficient to perform a further operation (in the case of a pressing tool, a further pressing cycle). In modem batteries based on nickel-cadmium or nickel-metal hydride, the residual energy content is difficult to observe, since these batteries have a characteristic curve with an almost constant voltage level over a long period, the voltage decreasing relatively steeply only toward the end. The result of this can be that one working cycle still proceeds entirely normally, while the subsequent working cycle cannot be completed because the battery is discharged.
In EP-A-0 676 835, it is proposed to equip the working device—in this case a cable lug crimping device—with a voltage measurement device to sense the particular battery voltage, and with a voltage comparison element having at least one memory for at least one limit voltage. The voltage comparison element is activated before the electric motor is switched on, and performs a voltage comparison between the present battery voltage and the limit voltage. If the voltage comparison indicates that the present battery voltage is equal to or less than the limit voltage, the electric motor is not started. At the same time, a visual indication is given. EP-A-0 676 835 contains no information as to how the battery voltage is measured.
BRIEF SUMMARY OF THE INVENTION
It is the object of the invention to configure a working device of the kind cited initially in such a way that working cycles are started only if sufficient battery capacity is still present for the working cycle in question.
According to the present invention, this object is achieved in that the control device has an interval element with at least one stored interval; and that a load element is present by way of which the battery can be acted upon by a load cycle that generates a voltage curve with a varying battery voltage, the interval element being activated at least once after the load element is switched on, and the voltage comparison being performed within the interval.
The basic idea of the invention is consequently to act upon the battery with a load cycle that generates a voltage curve with a changing battery voltage, and then to perform the voltage comparison within at least one interval having a characteristic voltage curve. If the voltage remains below a limit voltage within the interval, an attention signal is generated, for example an electrical or audible alarm, and/or activation of the electric motor is limited or the electric motor is immediately inhibited, so that complete discharge of the battery does not occur.
The load element can be the electric motor itself, i.e. in this case the electric motor is switched on, and the voltage comparison is performed within at least one interval having a characteristic voltage curve. The load element can instead also be an adjustable resistor in the form of a potentiometer, with which the load cycle is generated. This version is advantageous if the battery is separate from the working device and is joined to it only via a cable. In this case the charge state of the battery can be checked independently of the working device and thus also without any connection to it, if the corresponding circuit is arranged in the housing for the battery. The two types of circuit can, however, also be combined with one another, by the fact that the resistor is arranged electrically in parallel with the electric motor and by way of a two-way switch either the resistor or the electric motor is selectably switched in as the load element.
In a particularly advantageous embodiment of the invention, it is proposed that the is voltage comparison element be configured as an analog comparator to which the battery voltage on the one hand and the limit voltage on the other hand are applied. The limit voltage can be generated by an auxiliary battery. The comparator switches logic states if the present battery voltage either exceeds or falls below the limit voltage. The circuit described above requires no current measurement system or parts that define current measurements, and is thus notable for its simplicity. In the case in which the load element is the electric motor itself, the voltage comparison places no load on the battery.
The interval element is preferably configured as a timing element. The interval can instead also be defined in a different manner, for example by sensing a specific number of revolutions of the electric motor or the like.
In one embodiment, the interval element is activated as the load element is switched on, i.e. the interval begins with actuation of the load element. Alternatively, there also exists the possibility that the voltage comparison element performs a voltage comparison after the load element is switched on, and the interval element is activated only when it is determined that the present battery voltage has reached, or falls below or exceeds, a second limit voltage. In this context, the first and the second limit voltage are preferably identical.
The load element should produce a start-up phase with a voltage drop, and then a subsequent voltage recovery, as is the case in most situations (in particular with pressing devices) when the electric motor is the load element. The voltage drop results from the high current consumption caused by the fact that the parts driven by the electric motor must be accelerated to its idle speed. In this case the interval element should be activated in such a way that the interval lies within the start-up phase.
If the interval lies within a phase of a very pronounced voltage change, for example within the start-up phase described above, the activation of one interval is sufficient to obtain a reliable indication as to the charge state of the battery and to take countermeasures if the risk exists that the battery charge is no longer sufficient for the present or future load cycle. An improvement can be achieved in this context, however, by the fact that the interval element is activated more than once, at separate times, within the load cycle; here again, it is advantageous to activate the interval element only in regions of the load cycle where a voltage drop and a subsequent voltage recovery take place. Alternatively, however, provision can be made for the intervals to be directly adjacent to one another at least over a por

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