FIELD OF THE INVENTION

The present invention relates to a construction machine guidance system for guiding the operator of a construction machine. BACKGROUND OF THE INVENTION

Today, both 2D and 3D models are used in public and private infrastructure projects. Such an infrastructure project may be the construction of one or several buildings, roads, railroads, an airport, mines, tunnels etc. or refurbishing of such constructions. During the building phase, it is important that the final design is identical with, or within predetermined tolerances of, the model. It is also important that the final design is located correctly in the terrain.

Hence, construction machines, such as excavators, bulldozers, front end loaders etc., are equipped with high-end GNSS systems (Global Navigation Satellite System - such as GPS, Glonass, Galileo etc) in order to establish the foundation of the construction at the correct location. The GNSS system has a sensor for receiving satellite signals and a sensor for receiving satellite corrections signals from other sources, such as local base stations or the Internet, to increase the accuracy to centimeter level.

It is increasingly important to document the working progress during the

construction phase. The project owner wants information about the quality of the work (i.e. is the work performed according to the project agreement), the time (i.e. information about any delay) etc. The contractor wants to document that his work is performed as according to the project agreement. The contractor also wants documentation of work needed to be done which is outside of the scope of the project agreement. It is often crucial for the contractor to provide sufficient documentation in order to receive the money entitled for their completed work.

The prior art vehicle-mounted GNSS systems can be cumbersome to mount on construction machines. Often, the antenna of the GNSS system is mounted on top of the cabin of the machine. In addition, there are sensors on different moving parts of the machine. As is known, a typical excavator has several moving parts, at least two arms and three joints are used to connect the grab to the machine. In order to use the grab as a position indicator, the position of the grab in relation to the antenna of the GNSS system must be calibrated. If there is a desire to move the GNSS system from one construction machine to another construction machine, a recalibration process is needed. The position (longitude, latitude, altitude) of the grab can be shown to the operator on a display inside the cabin of the machine. The grab is used as a position indicator by the operator of the excavator to control progress (i.e. to compare the depth and position of the grab with the intended depth and position of the model). The grab is also used as a position indicator for documentation purposes, for example by taking images of the grab and store the image together with information about its position. In practice, this is cumbersome for the operator, and is often not performed. The result is lack of documentation.

Hence, documentation is often performed separately by a person with a portable GNSS system. It is also increasingly popular to perform a drone survey by means of a drone flying above the construction site and using photogrammetry to create a 3D model of the construction site by means of data from the digital camera and the GNSS system and fixed control points on the ground. This 3D model is then compared with the planned 3D model. There are several disadvantages with these drone surveys. First of all, the use of drones often require that personnel and construction machines are removed from the construction site for safety reasons and for obtaining a correct 3D model. Moreover, the drone survey is expensive, as it is increasingly common that certificates and permissions are needed to fly them.

Consequently, the drone survey is performed only once a week or maximum once a day. Moreover, under rainy/foggy/snowy conditions it is not possible to obtain a 3D model, or the 3D will be unreliable (20 - 40 cm of snow above ground will influence the 3D model created by a drone considerably). As the construction works often is moving very fast forward it is important to measure and document objects before it gets buried under other materials. Therefore, it is quite important for the contractor to be able to provide documentation at frequent intervals.

One object of the invention is to provide a construction machine guidance system for guiding the operator of a construction machine. The system comprises a measuring system, where one object is that the measuring system can be moved in an easy way from one construction machine to another construction machine.

Preferably, the entire construction machine guidance system can be easy to move between different construction machines, by avoiding or simplifying the calibration process needed by prior art systems.

Another object of the invention is to provide a construction machine guidance system which enables the operator of the machine to control the operation of the construction machine according to plan, i.e. as accurate as needed according to the 3D model and as efficient as the schedule requires.

Another object of the invention is to provide construction machine guidance system where it is easy for the operator to produce documentation of the progress on the construction site.

Another object of the invention is to provide a construction machine guidance system which is cheaper than present systems. SUMMARY OF THE INVENTION

The present invention relates to a construction machine guidance system for guiding the operator of a construction machine on a construction site, where the system comprises:

- a time-of-flight sensor system comprising a time-of-flight camera for measuring a distance to an object of the construction site within a measuring range of the time- of-flight camera;

- a satellite-based positioning system;

- a signal processing system comprising a connection interface, where the time-of- flight sensor system and the satellite-based positioning system are provided in communication with the signal processing system via its connection interface;

where the time-of-flight sensor system, the satellite-based positioning system and the signal processing system are mechanically connected to a housing structure; where the housing structure is mountable to the construction machine;

where the signal processing system is configured to process the signals from the time-of-flight sensor system and the satellite-based positioning system, thereby producing an image representing the object of the construction site within the measuring range;

where the signal processing system is configured to output the image via the communication interface.

In one aspect, the housing structure comprises a protective wall structure and a protective bottom structure, where a top surface of the housing structure is formed by an antenna unit of the satellite-based positioning system.

In one aspect, the signal processing system and the motion sensor system are provided inside the housing structure.

In one aspect, the construction machine guidance system further comprises a display and communication unit mountable inside an operator cabin of the construction machine, where the signal processing system is configured to output the image to the display and communication unit via the communication interface.

The display and communication unit comprises a display and a user interface. By means of the user interface, the operator may select what to view. By means of the user interface, the operator may also choose to store the present status as

documentation. Here, the“present status” may comprise the image shown on the display, a time stamp, the current position and orientation, and possibly also other raw or processed data from the different subsystems of the guidance system. In one embodiment, the guidance system itself is configured to store information automatically, for example based on time or position.

The connection interface may be a wireless connection interface. The connection interface may be a wired connection interface, where a communication wire is provided from signal processing system through the protective wall or the protective bottom of the housing structure and further to the display and communication unit. Preferably, wires between the inside of the housing structure and the outside of the housing structure are connected via an external connection interface provided in the wall or bottom of the housing structure itself. In this way, it is not necessary to open the housing structure to connect it for example to a power source or to the display and communication unit.

The construction machine guidance system may further comprise a power supply system. The power supply system may comprise a rechargeable battery supplying electric power to the different subsystems of the system. Alternatively, the power supply system comprises an electric cable provided from the inside of the housing structure, through the protective wall or the protective bottom of the housing structure and to the outside of the housing structure. Here, the cable could be terminated with a connection interface connectable to a power supply system of the construction machine.

In one aspect, the time-of-flight sensor system is connected to brackets protruding from the outside of the housing structure.

In one aspect, the housing structure is releasably connectable to a mounting bracket of the construction machine.

In one aspect, the signal processing system comprises a storage system in which a planned 3D model of the construction site is stored, where the signal processing system is configured to provide an image from the 3D model, where the image from the 3D model has an outline corresponding to an outline of the measuring range of the time-of-flight sensor system.

In one aspect, the time-of-flight sensor system comprises a digital camera for taking images having a capture range corresponding to the measuring range of the time-of- flight camera.

The digital camera is capable of registering light visible for human beings. Hence, the system can store images from the planned 3D model, the 3D image generated from data from the time-of-flight camera and ordinary images taken from the substantially the same point of view. In one aspect, where the system comprises a motion sensor system for sensing the motion of the construction machine; where the motion sensor system are provided in communication with the signal processing system via its connection interface.

In one aspect, the housing structure is mountable to an elevated position of the construction machine. Preferably, the housing structure is mountable to a roof of an operator cabin.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will now be described in detail with reference to the enclosed drawings, where:

Fig. 1 illustrates an perspective side view of a construction machine with a construction machine guidance system;

Fig. 2 corresponds to fig. 1, where the working area in front of the construction machine is more visible;

Fig. 3 illustrates a perspective front view of the system in fig. 1;

Fig. 4 illustrates a perspective side view of the system in fig. 1;

Fig. 5 illustrates a top view of the system in fig. 1;

Fig. 6 illustrates the measuring system of the construction machine guidance system mounted to the roof of the cabin of the machine;

Fig. 7a and 7b illustrate a perspective side view of a first side of the measuring system;

fig. 8a and 8b illustrate a perspective side view of a second side of the measuring system;

Fig. 9a illustrates a first embodiment of the system where the display and communication unit is not considered a part of the system itself, and where the system does not comprise a motion sensor system;

Fig. 9b illustrates a second embodiment where the system comprises a motion sensor system;

Fig. 9c illustrates a third embodiment where the system where the display and communication unit is considered a part of the system itself;

Fig. lOa illustrates data from a time-of-flight sensor and data from a 3D model in the same view;

Fig. lOb illustrates the view of fig. lOa from above;

Fig. 11 and 12 illustrate a further embodiment;

Fig. 13 illustrates yet a further embodiment.

First, it is referred to fig. 1 and 2. Here, a construction machine CM is shown on a construction site CS. In this example, the construction machine CM has dug a trench TR, in which a pipeline PL has been installed. Thereafter, a first gravel layer GL1 has been partially supplied to the trench TR around the pipeline PL and then a second gravel layer GL2 has been partially supplied above the first gravel layer GL1.

The position of the different sections of the trench, i.e. depth, width, length, has been modelled in a 3D model in the planning phase. The 3d model also contains information about the position and type of pipeline PL, the position and types of gravel used to fill the trench.

The construction machine CM is here an excavator with three arm sections Al, A2, A3 and a grab tool GT. The construction machine CM has an operator cabin OC.

A construction machine guidance system generally referred to with reference number 10 is mounted to the construction machine CM. The main purpose of the construction machine guidance system 10 is to guide the operator of the

construction machine CM, in order to control the operation of the construction machine CM on the construction site CS according to plan, i.e. as accurate as needed according to the 3D model and as efficient as the schedule requires.

The construction machine guidance system 10 comprises a housing structure 12 mounted to the construction machine CM. In fig. 1 and 2, the housing structure 12 is mounted to a roof OCR of the construction machine OC.

The construction machine guidance system 10 further comprises a time-of-flight sensor system 20, a satellite-based positioning system 30, a signal processing system 40 and a motion sensor system 50. These systems 20, 30, 40 and 50 are mechanically connected to the housing structure 12.

It is now referred to fig. 6, 7a, 7b, 8a, 8b and fig. 9a. It should be noted that in fig. 7a, 7b, 8a and 8b, a side wall structure of the housing structure 12 are drawn transparent, in order to view the subsystems inside the housing section 12.

Time-of-flight sensor system 20

The time-of-flight sensor system 20 comprises a time-of-flight camera 25 for measuring a distance to one or several objects of the construction site CS within a measuring range 29 of the time-of-flight camera 25. In the drawings, the measuring range 29 is indicated as a pyramid-shaped object. In fig. 1, the measuring range is non-transparent and white, while in fig. 2, the measuring range 29 is semi transparent. In fig. 1 there are several so-called objects of the construction site CS. These objects are the trench TR itself, the pipeline PL, the first gravel layer GL1 and the second gravel layer GL2.

A time-of-flight camera 25 is often referred to as a ToF camera and is a range imaging camera system that resolves distance based on the known speed of light, measuring the time-of-flight of a light signal between the camera and the subject for each point of the image. The time-of-flight camera is a class of scannerless LIDAR, in which the entire scene is captured with each laser or light pulse, as opposed to point-by-point with a laser beam such as in scanning LIDAR systems. Such time-of- flight cameras are commercially available. One such commercially available time- of-flight sensor system 20 which has been used in the prototype of the present invention is IFM 03M251 with an IFM O3M950 IR illumination unit.

The time-of-flight sensor system 20 may comprise a digital camera 24 for taking images having a capture range corresponding to the measuring range 29 of the time- of-flight camera 25. The digital camera 24 is capable of registering light visible for human beings. The above-mentioned system 20 (IFM 03M251) comprises such a digital camera 24. In fig. 6, 7a, 7b, 8a, 8b, the time-of-flight sensor system 20 is shown as a rectangular box 21 connected in an inclined position to the housing structure 12, thereby causing the area in front of the construction machine CM to be within the range 29 of the time-of-flight sensor system 20.

In fig. 7a, it is shown that the rectangular box 21 is connected to brackets 16 protruding from the outside of the housing structure 12. A pin 17 is used to connect the rectangular box 21 to the brackets 16. The pin 17 is also used to adjust an angle a (indicated in fig. 6) between the housing structure 12 and the time-of-flight sensor system 20. This adjustment is typically performed when the system 10 is moved to another height above ground HAG (indicated in fig. 1), for example when moved to another construction machine. In this way, the range 29 of the time-of-flight sensor system 20 can be adjusted at different heights.

No calibration is necessary when the angle a is adjusted, as this angle is detected and outputted from the time-of-flight sensor system 20 of the above-mentioned type.

Satellite-based positioning system 30

The satellite-based positioning system 30 is for example a system corresponding to the GNSS system mentioned in the introduction above. The system 30 comprises a sensor for receiving satellite signals from a satellite SA and a sensor for receiving satellite corrections signals from other sources, such as a local base station BS or the Internet, to increase the accuracy of the position information. It should also be noted that such a GNSS system typically has two satellite sensors. In this way, both position information (represented by longitude, latitude, altitude) and direction information (represented as a vector in a three dimensional space) are available from the system 30. Such satellite-based positioning systems 30 are commercially available. One such commercially available satellite-based positioning system 30 is the GNSS COMPASS manufactured by Advanced Navigation

(http ://www. advancednavi gation com au). which was used in the prototype of the present invention.

In fig. 7a, 7b, 8a, 8b, the satellite-based positioning system 30 is shown with an antenna unit 32 which is forming a top surface l2c of the housing structure 12. The antenna unit 32 is receiving signals to the two satellite sensors.

Signal processing system 40

The signal processing system 40 is typically a computer or similar, which comprises or is connectable to a data storage.

The data storage may be a physical storage unit 42 provided within the computer forming the signal processing system 40. Alternatively, the physical storage unit 42 is provided as a separate unit of the construction machine guidance system 10, either within or outside of the housing structure 12. The physical storage unit 42 may be a hard disc, a hard drive etc. connected by means of a wire or by means of a wireless communication protocol to the signal processing system 40. In such an embodiment, the physical storage unit 42 typically will be located on the

construction machine CM itself. Alternatively, the data storage may be provided as a storage service illustrated as a cloud 44 in fig. 9a.

The 3D model of the construction site CS is typically stored on this data storage. The signal processing system 40 is capable of retrieving information from the 3D model based on the position and direction information, for example position and direction information received from the satellite-based positioning system 30.

Preferably, the signal processing system 40 is configured to provide an image from the 3D model, where the image from the 3D model has an outline corresponding to the outline of the measuring range 29 of the time-of-flight sensor system 20.

The signal processing system 40 is also capable of retrieving information from the time-of-flight camera 25 and the digital camera 24.

The time-of-flight sensor system 20 may be configured to send data to the signal processing system 40 periodically. Alternatively, the signal processing system 40 may send requests for data to the time-of-flight sensor system 20. These requests can be sent periodically, or based on an instruction sent by the operator of the construction machine via a user interface. The user interface may be a display and communication unit 70, which will be described further in detail below.

In fig. 7a, 7b, 8a, 8b, the signal processing system 40 is shown as a rectangular box 41 provided inside the housing structure 12.

Motion sensor system 50

The motion sensor system 50 comprises a sensor for sensing the motion of the construction machine CM. Typically, the motion sensor system 50 comprises one or more accelerometers or gyroscopes. Data from the motion sensor system 50 is used by the signal processing system 40 to improve the accuracy of the position information and the direction information received from the satellite-based positioning system 30.

In fig. 7a, 7b, 8a, 8b, the motion sensor system 50 is shown as a box 51 provided inside the housing structure 12.

Display and communication unit 70

In fig. 9a, it is shown that the construction machine guidance system 10 is connectable to a display and communication unit 70. Hence, in this embodiment, the unit 70 is not considered to be a part of the system 10.

In fig. 9a and 9c, it is shown that the display and communication unit 70 is a part of the construction machine guidance system 10.

The display and communication system 70 is connected via a wire or wirelessly to the signal processing system 40. The operator of the construction machine CM may send instructions to the signal processing system 40 via the display and

communication system 70 and may choose which data to be displayed on the display of the display and communication system 70. These views and options will be described in detail further below.

The display and communication unit 70 may be an iOS-based or Android-based tablet, or it may a tablet or computer running the Windows operating system or one of the Linux operating systems.

In fig. 1, the display and communication unit 70 is shown as a rectangle provided inside the operator cabin OC of the construction machine CM.

Assembly of the construction machine guidance system 10 The housing structure 12 comprises a protective wall structure l2a and a protective bottom structure l2b. As described above, the antenna unit 32 of the satellite-based positioning system 30 forms the roof structure of the housing structure 12.

Moreover, the signal processing system 40 and the motion sensor system 50 together with other parts of the satellite-based positioning system 30 are located within the housing structure 12 and are hence protected by the protective wall structures l2a and l2b against loads caused by weather conditions, dirt and dust from the construction site etc.

The time-of-flight sensor system 20, the satellite-based positioning system 30 and the motion sensor system 50 are provided in communication with the signal processing system 40. In fig. 8a, it is shown a connection interface 43 on the rear side of the signal processing system 40, to which the subsystems 20, 30, 50 are connected, for example by means of a ethernet communication bus wire, or another suitable communication wire. As the time-of-flight sensor system 20 is located on the outside of the housing structure 12, the wire between the system 20 and the system 40 is guided through an opening in the housing structure 12. The connection interface 43 is provided inside the housing structure and can be referred to as an internal connection interface.

In the present embodiment, the construction machine guidance system 10 also comprises a power supply system 60 inside the housing structure 12, as shown in fig. 7a, 7b, 8a, 8b. The power supply system 60 may comprise a rechargeable battery supplying electric power to the different subsystems of the system 10.

Alternatively, or in addition to the rechargeable battery, the power supply system 60 may be supplied with electric power from the construction machine CM via an electric cable through an opening in the housing structure 12.

A external connection interface 18 may be provided on the outside of the housing structure 12, to simplify the connection of wires to the construction machine guidance system 10. The connection interface 18 may comprise one connector for connecting a wire from the display and communication unit 70 to the construction machine guidance system 10, i.e. to the signal processing system 40 of the construction machine guidance system 10. This connector may comprise

communication connectors to enable communication with the unit 70, alternately, the connector may comprise communication and power connectors to enable communication with and to supply electric power to the unit 70. The connection interface 18 may also comprise a power connector for supplying power to the system 10 from the construction machine CM. In case the power supply system 60 comprises a rechargeable battery, the power connector is used to charge the rechargeable battery. It should be noted that also a wire between the signal processing system 40 and the time-of-flight system 20 can be connected via the external connection interface 18.

Preferably, the housing structure 12 is mounted to an elevated part of the

construction machine CM, for example on a roof OCR of the operator cabin OC.

The housing structure 12 may be releasably clamped to a base fixed to the construction machine CM, or may be releasably mounted to the construction machine by means of screws and bolts etc.

In fig. 6, it is shown that the housing structure 12 is connected to a mounting bracket MB of the construction machine CM. In one embodiment, the mounting bracket is fixed to the construction machine. In another and preferred embodiment, a rail or guiding system is provided between the mounting bracket and the construction machine. In this way, it is possible to move the housing structure 12 of the system 10 linearly forward in certain situations, for example if there is a relatively deep trench at a relatively short distance from the machine. In the rear position, it will be difficult to provide documentation of the entire trench due, as parts of the trench will be outside of the range 29 (too close to the construction machine). In this forward position, at least parts of the housing structure 12 will be protruding from the construction machine. It is preferred that the housing structure 12 can be moved linearly back to the rear position during normal use, as the housing structure 12 will be less exposed to moving part of the construction machine or other construction machines in this rear position. The housing structure 12 may be manually movable between the forward and rear positions, alternatively an linear actuator controlled from the display and communication unit 70 can be used to move the housing structure.

Hence, in order to move the construction machine guidance system 10 from a first construction machine to a second construction machine, the following steps must be performed:

- disconnect any wires from the connection interface 18 (this step may be optional, since the system 10 may comprise a rechargeable battery charged with sufficient capacity and since the display and communication unit 70 can be wirelessly connected to the signal processing system 40)

- disconnect the housing structure 12 from the first construction machine;

- move the construction machine guidance system 10 to the second construction machine;

- connect the housing structure 12 to the second construction machine;

- connect necessary wires to the connection interface 18.

One additional step can be to move the display and communication unit 70 from the first construction machine to the second construction machine. The unit 70 can itself be connectable to and disconnectable from a mount or bracket, in order to simplify the movement of the unit 70. The mount or bracket, and optionally the wire between the mount or bracket and the connection interface 18, will typically be fixed to each construction machine. In many cases it is believed that also the display and communication unit 70 will be fixed inside the operator cabin of each construction machine, as such units 70 can be relatively cheap. Hence, only the housing structure 12 with its subsystems 20, 30, 40, 50 will be moved between construction machines.

Operation of the construction machine guidance system 10

The operation of the construction machine guidance system 10 will now be described in detail.

The signal processing system 40 is configured to process the signals from the time- of-flight sensor system 20, the satellite-based positioning system 30, and the motion sensor system 50, resulting in an image representing the objects of the construction site CS within the measuring range 29.

By means of the display and communication unit 70, the operator can select between the following views generated by the signal processing system 40:

1) construction site as retrieved from the 3D model (of course based on position and direction information from the satellite-based positioning system 30);

2) construction site as seen by the camera 24;

3) construction site as seen by the time-of-flight camera 25;

4) two or three of the above views combined;

5) profile view

6) Plan view with optional background maps, as rasters and digital building drawings. The construction machine may also be indicated in this plan view

It should be noted that during operation, the operator will typically select to view only the current layer on which the operator is working with from the 3D model, for example one specific gravel layer, one specific crushed stone layer, a fabric layer, an asphalt layer, etc. This will simplify the view on the display, where only one layer from the 3D model is shown, possibly also with the present status based on data from the construction machine guidance system 10 adjacent to, or overlaid, the layer from the 3D model.

Of course, the grab tool GT of the construction machine CM should first be moved to a position outside of the range 29.

The selected view is then displayed on the display of the unit 70. Alternatively, it can be possible to display two or three of these views next to each other. In a preferred embodiment, it is also possible to display these views above each other. By means of the display and communication unit 70, the operator can also select to document present status. Based on such an instruction, the system 10 will store an image generated from the planned 3D model together with an image generated from data from the time-of-flight camera 25 and an image taken from the digital camera 24 together with the position and direction information and a time stamp. The system 10 may store the present status as ready-to-view images, and/or as raw data which can be used for later post-processing. It will also be possible to adjust the ray of the ToF in terms of resolution and area, for example you can choose a smaller area to collect data from rather than saving the whole view. This can be convenient when you only want to measure the top of a pipeline or similar.

In fig. lOa, it is shown a first test of the construction machine guidance system 10, Here, a 3D model of a trench is shown together with data from the time-of-flight sensor 25, seen from the same location, i.e. based on position and direction information. To the left in fig. lOa, a scale of distances is shown together with different colors. These colors represent the depth of the trench. As shown in fig. lOa, the time-of-flight data indicates a larger depth (blue) at locations where the trench is deep, and the time-of-flight data indicates a smaller depth (green - yellow - red) at the edge of the trench. The dark grey area is indicating the terrain which are outside of the range of the time-of-flight system 20.

From the description above, it is apparent that the above system 10 can be used to guide the operator of the construction machine, by selecting a layer from the 3D model and by comparing the view of the 3D model with a view of the present status generated by data from the time-of-flight system 20. Hence, it is for example possible for the operator to observe which areas of the trench which have not been filled sufficiently, which areas of the trench which has been filled sufficiently and which areas of the trench which has been filled too much. This information can be used as guidance for the operator to fill more gravel material in some areas and to remove gravel material from other areas.

The above construction machine guidance system 10 is relatively simple and can be moved between construction machines without the cumbersome calibration process needed with prior art. Moreover, the system 10 can be used on different types of machines.

It is easy for the operator to provide documentation via the display and

communication unit 70. It could also be possible to send notices from the signal processing system 40 to the display and communication unit 70 as a reminder to the operator to document progress. These notices can be time-based (for example can they be sent from the system 40 every 10 minutes) or they can be position-based (for example can they be sent from the system when the construction machine has moved 5 meters from the last position on which documentation was stored). An alternative embodiment is disclosed in fig. 11 and 12. Here, the time-of-flight sensor system 20 is a scanner-type of LIDAR. One such commercially available time-of-flight sensor system 20 is the Velodyne LIDAR sold under the name PUCK. The time-of-flight sensor system 20 may be connected to the housing 12 by means of the pin 17 in a similar way as the above embodiment.

In fig. 11 and 12, the side wall section l2a and the bottom section l2b of the housing section 12 have been partially removed to view the subsystems inside the housing. The brackets 16 for the pin 17 is still shown. It should be noted that some electrical and/or communication wires are also not shown in fig. 1 1 and 12. As in the above embodiment, a housing section 12 will also here be used as protection against the environment.

The embodiment in fig. 13 corresponds to that of fig. 1 1 and 12, but here, the pin 17 is connected directly to the side wall section of the housing 12, i.e. there are no protruding brackets 16.