# Patent

## Title
Frequency converter for an immersion vibrator

## Abstract

The invention relates to a frequency converter for an immersion vibrator, comprising a mobile converter housing, and a converter circuit disposed in said converter housing and adapted to convert an electrical supply voltage to a special voltage. The converter is further provided with a feed line that is mechanically linked with the converter housing and electrically connected to the converter circuit. At the end of said feed line facing away from the converter housing a plug part is disposed. The converter circuit feeds a connector with the special voltage, a plug part of the immersion vibrator being insertable into said connector.

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a frequency converter for an immersion vibrator.
2. Description of the Related Art
Immersion vibrators are used for compressing concrete while it is still liquid. To do this, a vibrator bottle which is part of the immersion vibrator is immersed in the concrete, and an electric motor and an imbalance, which is driven by this electric motor at a high rotation speed, are accommodated in this vibration bottle. In order to achieve the required motor rotation speed and hence compression frequency, the motor must be supplied with a special voltage, whose frequency (for example, 200 Hz) is greater than the mains frequency provided by the public mains system.
It is known for the special voltage to be provided by a special voltage network or by a frequency converter, which is either provided on site in the form of a large stationary unit, or is an integrated component of the immersion vibrator. An immersion vibrator with an integrated frequency converter is known from DE G 92 17 854.5.
CH 689598 A5, describes an immersion vibrator in which a converter can be disconnected from a protective sleeve which is fitted with a vibration bottle. The protective sleeve is coupled to the converter via a specially designed electromechanical plug and socket structure, so that not only is it possible to transfer the special voltage, but this also ensures a mechanically firm connection between the protective sleeve and the converter housing. The specific configuration of the electromechanical coupling means that the elements to be coupled must be accurately matched to one another. It is impossible to use components which are not equipped for the specific coupling.
Immersion vibrators with an integrated frequency converter have proven to be excellent in practice. However, as before, immersion vibrators which do not have their own frequency converter and must be fed by an external frequency converter are still used on building sites. These immersion vibrators are primarily distinguished by their cheaper procurement costs. However, on building sites, they require either an appropriate special voltage network at a low voltage level and a high voltage frequency, or a conventional frequency converter, which must be provided where the work is being carried out in the form of a very heavy box. This makes it very difficult to operate such an immersion vibrator.
Objects and Summary of the Invention
The invention is based on the object of specifying a frequency converter which also makes it possible for immersion vibrators without their own integrated frequency converters to utilize the advantages of immersion vibrators with their own frequency converter, when desired.
The object is achieved, by a frequency converter as in accordance with the present invention.
A frequency converter according to the invention has a mobile converter housing with a converter circuit, and is characterized in that a plug socket is provided which is fed with the special voltage from the converter circuit and into which a plug part of the immersion vibrator can be inserted. According to the invention, it is thus possible to plug the mains plug, which is used as the plug part, of an immersion vibrator which does not have its own frequency converter into the plug socket of the frequency converter, with the plug socket being integrated in the converter housing, or being capable of being connected to the converter housing via a further supply cable. It is thus possible, without incurring any particular additional costs and without having to accept any particular physical complexity, to convert an immersion vibrator without its own frequency converter to an immersion vibrator with a frequency converter.
One advantageous embodiment of the invention is characterized in that the plug socket can be fed with the mains voltage as an alternative to the special voltage, and in that a changeover switch is provided for switching between the special voltage and the mains voltage. The immersion vibrator can thus—as before—also be connected to a special voltage network without the frequency converter having to be removed from it. This has the advantage that the frequency converter cannot be lost during the busy operations on a building site. In a further advantageous embodiment of the invention a securing device is provided in the region of the plug socket, by means of which the plug part of the immersion vibrator is held in the plug socket. The securing device is thus used for strain relief and allows the operator to pull the frequency converter behind him on the immersion vibrator. For this purpose, the converter housing advantageously has an elongated external shape with minimized transverse dimensions, which makes it considerably easier for the converter housing to slide on the building site, which generally has numerous pieces of reinforcing ironwork. The mobile handling of the frequency converter is additionally improved by the converter housing having a smooth outer skin.



BRIEF DESCRIPTION OF THE DRAWING
These and further advantages and features of the invention will be explained in more detail in the following text using an example and with the assistance of the accompanying figures. The single FIGURE shows a frequency converter according to the invention, with an immersion vibrator connected.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An immersion vibrator 1 which is known per se has a vibration bottle 2, in which an elongated electric motor and an imbalance, which is driven by the electric motor, are accommodated. The vibration bottle 2 is connected to a switch housing 4 via a protective sleeve 3, which may be up to several meters long. The protective sleeve 3 is also used as an operating sleeve, by means of which the vibration bottle 2 is dunked by the operator into the concrete which is to be compressed. A switch 5 is arranged in the switch housing 4, and allows the electric motor in the vibration bottle 2 to be switched on and off. An electrical supply cable 6 passes out of the switch housing 4 and opens into a mains plug 7. Such an immersion vibrator 1, which is known per se, is normally connected by means of the mains plug 7 to a special voltage network provided on the building site or to a stationary frequency converter.
However, according to the invention, a frequency converter 8 is provided, into which the mains plug 7 is inserted.
The frequency converter 8 has a converter housing 9 in which an electronic converter circuit, which is known per se, is accommodated. An additional switch may also be provided, by means of which the power supply can be interrupted.
A supply cable 10 is passed out of the converter housing 9 to a mains plug 11. The mains plug 11 can be inserted into a conventional public mains system, as provided on the building site.
A plug socket 12, into which the mains plug 7 of the immersion vibrator 1 can be inserted, is integrated in the converter housing 9 on the side of the converter housing 9 facing away from the mains plug 11 and the supply cable 10.
The frequency converter 8 draws a conventional mains voltage (230 V or 400 V, 50 Hz) via the mains plug 11, and this is passed via the supply cable 10 to the converter circuit in the converter housing 9. There, the mains voltage is converted to a special voltage, which may be, for example, 42 V at 200 Hz. The special voltage is connected to the plug socket 12, where it can be passed to the immersion vibrator 1 via the mains plug 7.
As an alternative to the embodiment shown in the FIGURE, it is also possible to arrange the plug socket 12 separately from the converter housing 9, and to connect it to the converter housing 9 by means of an additional supply cable.
It is particularly expedient for the mains plug 7 of the immersion vibrator 1 to be held in the plug socket 12 by means of a preferably mechanical securing device. It is thus possible for the operator to pull the immersion vibrator 1 together with the frequency converter 8 behind him using the protective sleeve 3, without the connection between the mains plug 7 and the frequency converter 8 becoming detached.
The converter housing 9 has an elongated slim external shape with minimized transverse dimensions and a smooth outer skin, so that it can be pulled through concrete reinforcement with as little resistance as possible. Oblique end walls 13 on the converter housing 9 further assist the capability to slide.
The electronic design of the converter circuit and the slim shape of the converter housing allow the frequency converter 8 to be handled particularly easily when mobile. The handling capability is further assisted if the converter housing 9 does not have any handle which could adversely affect the sliding capability.
Since the frequency converter 8 together with the immersion vibrator 1 forms a compact unit which can easily be moved by the operator, even conventional immersion vibrators without an integrated frequency converter are provided with the operational advantages which until now have been the exclusive domain of immersion vibrators with an integrated frequency converter.
Another embodiment of the invention which is not illustrated in the FIGURE, allows the frequency converter to not only convert the mains voltage to the special voltage, but also to receive and pass through the special voltage. To do this, a changeover switch is provided on the converter housing 9, for switching between passing the special voltage through the converter circuit or converting the mains voltage to the special voltage. While the power for producing the special voltage is supplied by the converter circuit, whilst the changeover switch is being operated, it is just passed directly from the supply cable 10 to the plug socket 12, that is to say it just passes through the frequency converter 8. This makes it possible for the combination of the immersion vibrator 1 and the frequency converter 8 to be at least briefly connected to existing special voltage networks as well, without the immersion vibrator 1 needing to be disconnected from the frequency converter 8.

## Claims

1. In combination:
an immersion vibrator, including:
a vibration bottle that houses an electric motor and an imbalance, the imbalance being driven by the electric motor,
a switch housing connected to the vibration bottle and bearing an on-off switch that is electrically coupled to the electric motor, and
a first mains plug configured to plug into a socket of at least one of 1) a special voltage network and 2) a stationary frequency converter so as to receive a special voltage and to supply the special voltage to the electric motor via the switch; and

a frequency converter, including:
a mobile converter housing;
a converter circuit that is arranged in the converter housing and that converts an electrical mains voltage to the special voltage, the mains voltage having a frequency level lower than the special voltage;
a second mains plug configured to be plugged into a public mains system so as to supply public mains power to the converter circuit;
a plug socket which is fed with the special voltage from the converter circuit, wherein the first mains plug plugs into the plug socket; and
a manually operated changeover switch having a first position so as to cause the converter circuit to convert the mains voltage received at the second mains plug of the frequency converter to the special voltage for communication to the second mains plug, and a second position so as to cause the converter circuit to pass through the special voltage received at the second mains plug of the frequency converter to the first mains plug without modifying the special voltage.

2. The combination as claimed in claim 1, wherein the frequency converter further comprises a mechanical securing device in the region of the plug socket, via which the first mains plug is held in the plug socket.

3. The combination as claimed in claim 1, wherein the converter housing has an elongated external shape with minimized transverse dimensions configured to withstand immersion in a liquid concrete.

4. The combination as claimed in claim 1, wherein the converter housing has a smooth outer skin, and allows mobile handling of the frequency converter.

5. The combination as claimed in claim 1, wherein the second mains plug is connected to the housing of the converter via a supply cable.

6. In combination:
an immersion vibrator, including an electric motor, an imbalance driven by the electric motor, an on-off switch that is electrically coupled to the electric motor, and a first mains plug configured to plug into a socket of at least one of 1) a special voltage network and 2) a stationary frequency converter so as to receive a special voltage and to supply the special voltage to the electric motor; and
a frequency converter, including:
a mobile converter housing;
a converter circuit which is arranged in the converter housing and which converts an electrical mains voltage to the special voltage, the mains voltage having a frequency level lower than the special voltage;
a second mains plug which is configured to be plugged into a public mains system so as to supply public mains power to the converter circuit; and
a plug socket which is fed with the special voltage from the converter circuit, wherein the first mains plug plugs into the plug socket.

7. The combination of claim 6, further comprising a manually operated changeover switch having a first position so as to cause the converter circuit to convert the mains voltage received at the second mains plug of the special voltage for communication to the first mains plug, and a second position so as to cause the converter circuit to pass through the special voltage received at the second mains plug to the first main plug without modifying the special voltage.

8. The combination as claimed in claim 6, wherein the frequency converter further comprises a mechanical securing device in the region of the plug socket, via which the first mains plug is held in the plug socket.

9. The combination as claimed in claim 6, wherein the converter housing has an elongated external shape with minimized transverse dimensions configured to withstand immersion in a liquid concrete.

10. The combination as claimed in claim 6, wherein the converter housing has a smooth outer skin, and allows mobile handling of the frequency converter.

11. The combination as claimed in claim 6, wherein the second mains plug is connected to the housing of the converter via a supply cable.

12. The combination of claim 11, wherein the switch housing is connected to the first mains plug by a supply cable.

13. The combination as claimed in claim 6, wherein the immersion vibrator further comprises
a vibration bottle that houses the electric motor and the imbalance, and
a switch housing that is connected to the vibration bottle and that bears the on-off switch.

14. In combination:
a hand operated tool including an electric motor, a working device driven by the electric motor, an on-off switch that is electrically coupled to the electric motor, and a first mains plug configured to plug into a socket of at least one of 1) a special voltage network and 2) a stationary frequency converter so as to receive a special voltage and to supply the special voltage to the electric motor; and
a frequency converter, including:
a mobile converter housing;
a converter circuit which is arranged in the converter housing and which converts an electrical mains voltage to the special voltage, the mains voltage having a frequency level lower than the special voltage; and
a second mains plug which is configured to be plugged into a public mains system so as to supply public mains power to the converter circuit;
a plug socket which is fed with the special voltage from the converter circuit, wherein the first mains plug plugs into the plug socket.