Abstract:
Disclosed is a pivotable horn antenna intended for a radar level indicator and includes a ball joint, the joint socket of which can be screwed into a threaded hole in the container. This allows for optimization of the echo signal and correction of slanted installation of the horn antenna.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date of EP Patent Applications Serial No. 13 191 577.9 filed on 5 Nov. 2013, the disclosure of which is hereby incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to radar level indication technology. In particular, the invention relates to a pivotable horn antenna for a radar level indicator and to a radar level indicator comprising a horn antenna of this type. 
     TECHNICAL BACKGROUND 
     Radar level measurement devices (radar level indicators) can be attached to the flanges of containers. The container flanges are openings in the container lid having typical diameters of several inches. The radar level indicators are then screwed onto said flange by means of a plurality of screws. 
     To improve the quality of the echo signal detected by the radar level measurement device, it can be useful to pivot the radar level measurement device following the installation thereof in the container and to orientate said measurement device towards the level surface in order to correct slanted installation of the device for example. 
     SUMMARY OF THE INVENTION 
     According to a first aspect of the invention, a pivotable antenna arrangement for a radar level indicator is specified. The pivotable antenna arrangement comprises an antenna, for example in the form of an antenna horn, which emits the transmitted signal. 
     In addition, a region in the form of a ball joint head is provided. The ball joint head can be a part of the antenna or arranged above the antenna so that the ball joint head is located between the electronics of the radar level indicator, which electronics generates the transmitted signal, and the antenna. It can also fundamentally be provided to arrange the ball joint head at the lower end of the antenna. 
     Further provided is a housing having a joint socket in which the ball joint head can rotate. The housing comprises an external thread in order to screw the antenna into a threaded hole in a container, in which the filling material of which the fill level is to be measured is located. 
     The ball joint head may be a part of the antenna, e.g. the antenna horn, or may be arranged above the antenna (e.g. the antenna horn) and connected to the antenna. The lower region of the housing surrounds at least a part of the ball joint head and the antenna, and has an outer diameter which decreases towards the lower end of the housing. For example, the outer diameter of the lower region of the housing may decrease in a stepped manner. 
     A flange connection between the container and the radar level indicator is thus not required. Instead, the radar level measurement device is screwed into a threaded hole in the container in a very simple manner. 
     This type of attachment is simple and effective. A complex flange connection between the radar level measuring device and container is not necessary. It is also possible to make a hole in a thin sheet wall, to thread the external thread of the housing through said hole and to fasten using a nut. 
     The threaded hole has, for example, a diameter of 1 inch, 1.5 inches or 2 inches. 
     According to one embodiment of the invention, the joint socket comprises a lower region and an upper region that can be attached in a lower region. The lower region allows the antenna horn to be guided through from above so that said horn protrudes out from the joint socket on the other side of the lower region. Once the antenna horn has been guided through the lower region, the upper region is attached to the lower region. 
     This can take place for example by screwing the upper region onto the lower region. For this purpose, the upper region comprises for example one or more holes, through which it is possible to guide screws which are screwed into corresponding threaded holes in the lower region. 
     Alternatively or in addition, it can be provided that the upper region comprises an external thread which is screwed into a corresponding internal thread of the lower region. 
     By tightening the screw connection between the upper region and the lower region, the ball joint head can be clamped in the joint socket so that the horn antenna can no longer pivot. Releasing one of the for example three screws is sufficient to release the ball joint head so that the antenna can be pivoted. The remaining screws can comprise a different screw head or other marking, so that the user identifies which screw has to be released to pivot the antenna. 
     According to another embodiment of the invention, the lower region of the housing of the joint socket comprises an external thread in order to screw the horn antenna into the threaded hole in the container. 
     Fundamentally, the outer thread can also be attached to the upper region of the housing. In this case, the horn antenna would in fact be screwed into the threaded hole from the inside of the container. 
     According to another embodiment of the invention, the pivotable antenna arrangement is configured as a waveguide, to the end of which an antenna horn is attached. 
     The transmitted signal generated by the signal generation electronics of the radar level indicator is thus conducted through the waveguide of the ball joint head and then fed into the horn of the antenna arrangement. 
     According to another embodiment of the invention, the ball joint head is screwed onto the antenna horn. The connection is flange-like, for example. 
     According to another aspect of the invention, a radar level indicator is specified having a pivotable horn antenna described above and below. 
     In the following, embodiments of the invention will be described with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A, 1B and 1C  show a pivotable antenna arrangement according to a first embodiment of the invention. 
         FIGS. 2A and 2B  show a pivotable antenna arrangement according to another embodiment of the invention. 
         FIGS. 3A and 3B  show a pivotable antenna arrangement according to another embodiment of the invention. 
         FIGS. 4A and 4B  show a pivotable antenna arrangement according to another embodiment of the invention. 
         FIG. 5  shows a ball joint of a pivotable antenna arrangement according to another embodiment of the invention. 
         FIG. 6  shows a level measuring device in a container according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The drawings are schematic and not to scale. 
     Where identical reference numerals are used in the following description of the drawings, they denote like or similar elements. However, like or similar elements may also be denoted by different reference numerals. 
       FIGS. 1A, 1B and 1C  are a sectional view, a side view and perspective view, respectively, of a pivotable antenna arrangement according to an embodiment of the invention. The antenna arrangement can be configured as a horn antenna. Other antenna shapes are also possible however, for example rod antennas. 
     The pivotable antenna arrangement comprises an antenna horn  101 , the upper end of which comprises a flange  110  which is attached by a plurality of screws  111 ,  112  to a corresponding mating flange of a ball joint head  102  adjacent to the antenna horn. The ball joint head  102  comprises a spherical region which is supported by a two-part joint socket  103 ,  104 . 
     The two-part joint socket is a part of a housing and comprises an upper region  103  which can for example be plate- or disc-like and has a round cross section. This upper region  103  comprises a plurality of holes, for example three holes, through which the screws  106 ,  107 ,  108  can be guided. One of these holes  114  is visible in  FIG. 1A . 
     The three screws can be bonded at the factory and, in order to tilt the antenna, the user simply releases the screw  106  that has a different screw head to the two other screws. 
     The lower region  104  is housing-like and surrounds parts of the ball joint head  102  and the antenna horn  101  of the pivotable horn antenna. 
     At the lower end of the lower region  104  of the joint socket there is an external thread  105  which can be screwed into a corresponding threaded hole of the container. The external thread has a diameter of for example 1.5 inches or 1 inch. 
     An additional external thread can also be attached to the middle section  116  of the lower region  104  of the joint socket. 
     Above the external thread  105  there is a narrowing  124  in the housing, adjacent to which is a contact surface  125  which hits the outer surface of the container when the antenna arrangement is screwed in. 
     Below the ball joint head  102  there is a bulge  117  which forms the flange for flange-mounting the antenna horn  101  and in which internal threaded holes can be provided for screwing on (flange-mounting) the antenna horn  101 . 
     The internal region of the ball joint head  102  is designed as a waveguide and is used to transmit transmitted signals to the horn antenna and to transmit the received signal picked up by the horn antenna to the interface  109 , from which the received signal is relayed further to the electronics of the radar level indicator. 
     As can be seen in the drawings, the external cross section of the lower region  104  of the housing becomes smaller in steps. For example three steps are provided, it being possible for the lower third to comprise the outer thread  105  and the upper third  113  to have for example a hexagonal cross section, so that a spanner can be placed thereon to screw the horn antenna into the container hole. 
     The embodiment of  FIG. 1A to 1C  has for example a 1½ inch external thread  105 , whereas the embodiment of  FIGS. 2A and 2B  can have an 2 inch external thread  105 . In this embodiment, the cross section of the lower region of the joint socket  104  is not formed in three steps, but rather in two. 
     The opening  201  in the lower region of the joint socket, in which opening both the flange-like region of the ball joint and the upper region of the horn antenna move, is cylindrical. 
       FIGS. 3A and 3B  show a pivotable horn antenna having an external thread  105  of for example 1½ inches, the horn antenna comprising an antenna extension  301 . This antenna extension  301  can be arranged between the flange  110  of the horn antenna  101  and the flange  117  of the joint socket. 
       FIGS. 4A and 4B  show a pivotable horn antenna also having a 1½ inch external thread of the housing and having a rinsing connector to pump air through the antenna into the container. 
       FIG. 5  shows a ball joint head  102  of a pivotable horn antenna, which ball joint head is located in a housing having a joint socket  103 ,  104 . The upper region  103  of the housing comprises an external thread  501  which can be screwed into the lower region  104  of the housing. The lower region  104  of the housing can likewise comprise an external thread  105  which can be screwed into a threaded hole in the container lid. 
       FIG. 6  shows a pivotable horn antenna  100  of a radar level indicator installed in a container  601 . For this purpose, the container  601  comprises a threaded hole  603  in the cover region, into which hole the pivotable antenna arrangement can be screwed. In the container there is a filling material  602 , the level of which is to be measured. 
     The pivotable antenna arrangement is inexpensive to produce and easily assembled by the customer. Very little effort is required at the point of assembly. In this manner, the level measuring device can be mounted in the screw-in connection piece such as to be pivotable and orientable. The screw-in connection piece is constructed such that the basic individual parts of the device can be used in all variants having a rinsing connector and antenna extension. A flange connection between the antenna arrangement or radar level indicator and container is not required. 
     The thread size of the screw-in connection piece limits the maximum usable pivot angle of the antenna arrangement. For example, the maximum usable pivot angle with a thread size of 1½ inches is up to −8°, and up to −10° with a thread size of 2 inches. In order to maximise the maximum pivot angle, the threaded connection piece (screw-in connection piece, also referred to above as the lower region of the housing of the joint socket) is hollowed out as much as possible. In other words, said connection piece is as thin-walled as possible. 
     As can be seen in the 1½ inch thread version in  FIG. 1A to 1C , in order to maximise the pivot angle it can be provided that the lower region of the joint socket housing  104  first has a cylindrical opening  120  at its lower end, which opening then widens in a conical manner towards the end of the lower region in the region  121 . 
     The outer surface of the antenna horn is also designed to have a constant wall thickness in the upper region  122  thereof near the flange connection  110 . However, in the region where the antenna horn touches the internal wall  121  of the lower part  104  of the joint socket at the maximum pivot angle, the wall thickness of the antenna horn becomes narrower (see region  123 ). In this way, the maximum pivot angle can be increased. 
     This geometry can also be seen in the embodiment in  FIGS. 4A and 4B . 
     Moreover, it should be noted that “comprising” and “having” do not exclude the possibility of other elements or steps, and “one” or “a” does not exclude the possibility of a plurality. It should further be noted that features or steps which have been described with reference to one of the above embodiments may also be used in combination with other features or steps of other above-described embodiments. Reference numerals in the claims should not be treated as limiting.