Abstract:
A suspension device for rotatable appliances, such as antennas, of the type which for rotation is connectible with a frame-mounted shaft which extends through a power operated disk or a similar antenna mounting and which, beyond the antenna mounting, has a free end mounted in a stationary part, which is capable of limited motion generated rated by insufficient concentricity between the antenna mounting and the shaft. An angle-transducing device is provided for said shaft. A connector is arranged adjacent to or round the shaft and directs components of force on the stationary part which have arisen owing to sufficient concentricity to merely displacement in the X-Y direction in a plane perpendicular to the shaft, by the connector being displaceably fixed in the X direction to the stationary part and displaceably fixed in the Y direction to the frame, or by the connector being displaceably fixed in the X direction to the shaft and displaceably fixed in the Y direction to the antenna mounting.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a suspension device for rotating appliances, such as antennas, of the type which for rotation is connectible with a frame-mounted shaft which extends through a power operated disk or a similar antenna mounting and which, beyond the antenna mounting, has a free end mounted in a stationary part, which is capable of limited motion generated by insufficient concentricity between the antenna mounting and the shaft, for which an angle-transducing device is arranged. 
     BACKGROUND ART 
     From frame-mounted rotatable antennas, signals are transmitted to a stationary installation for processing and evaluation. In, for instance, radar antennas, the rotational angular position of the antenna is relevant for the evaluation of the signals. The transmission occurs via a transmitter, a rotating member, which is theoretically coaxial with the axis of rotation of the antenna, to a stationary installation for processing the signals. Therefore, in such antennas there is at least one angle-transducing device connected to one of the rotary parts of the antenna. 
     The prior-art technique of suspending the rotating member is inaccurate owing to the fact that in actual practice it is very difficult to mount the shaft of the rotating member concentrically with the antenna shaft, so that the angle-transducing device provides correct information on the rotational angular position of the antenna. There will always be a certain eccentric and inclination error between the antenna shaft and the mounting of the shaft, which causes errors in the angle transducing. 
     If the stationary part is rigidly fixed to the frame, forces will arise, which are a great stress on the components included in the antenna suspension. This results in a short service life, short service intervals and great expenses for repair and spare parts. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to eliminate the above deficiency in connection with angle transducing of the prior-art suspension devices for rotatable appliances and to achieve the extremely great accuracy in angle reproduction that is necessary for, for instance, modern radar systems, and to keep the expenses down for repair, maintenance and spare parts. 
     According to the invention, this object is achieved by a device according to the introductory part, which comprises a connector which is arranged adjacent to or round the rotating member and directs components of force on the stationary part, which have arisen owing to insufficient concentricity, to merely displacement in the X-Y direction in a plane perpendicular to the shaft by the connector being displaceably fixed in the X direction to the stationary part and displaceably fixed in the Y direction of the frame, or by the connector being displaceably fixed in the X direction to the antenna shaft and displaceably fixed in the Y direction to the antenna mounting. 
     Further developments of the invention are evident from the features that are stated in the dependent claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention will now be illustrated for the purpose of exemplification and with reference to the accompanying drawings, in which 
     FIG. 1 is a side view of prior-art technique; 
     FIG. 2 is a bottom view of prior-art technique; 
     FIG. 3 is a schematic view of a suspension device according to a preferred embodiment of the present invention; 
     FIG. 4 is a bottom view of the preferred embodiment; 
     FIG. 5 is a perspective view of a connector; 
     FIG. 6 illustrates a further embodiment of the present invention; 
     FIG. 7 illustrates one more embodiment of the present invention; 
     FIG. 8 is a perspective view of the preferred embodiment according to FIGS. 3 and 4; 
     FIG. 9 illustrates yet another embodiment of the present invention; 
     FIG. 10 illustrates a variant of the embodiment in FIG. 9; 
     FIG. 11 shows one more variant of the embodiment in FIG. 9 
     FIG. 12 shows a further variant of the embodiment in FIG. 9; and 
     FIG. 13 shows one more embodiment of the present invention. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     A prior-art suspension device for a rotatable antenna comprises a frame  1 , in which an antenna  2  is rotatably mounted. From the antenna, signals are transmitted via a transmitter, a rotating member  3 , which is theoretically coaxial with the axis of rotation of the antenna, to a stationary installation (not shown) for processing the signals. The rotational angular position of the antenna is read by means of an angle-transducing device  4 , which is fixed to the rotating member  3 . 
     The rotating member  3  is divided into a rotating part and a stationary part. The rotating part comprises a shaft  5 , which is non-rotationally connected to the antenna  2  and comprises cables C both to the antenna  2  and to the stationary installation and a power operated disk  6  for rotating the shaft  5  of the rotating member  3 . 
     The power operated disk  6  is on its circumference mounted in the frame  1  by means of a rotation bearing  7 , and the shaft  5  of the rotating member  3  is permanently fixed to the disk  6 . The stationary part comprises a casing  8  for an arrangement of said transmission of signals to the stationary installation and for rotational mounting of the lower end of the shaft, see the bearing  8 ′. The angle-transducing device  4  is fixedly connected to the casing  8  and engages the shaft  5  of the rotating member  3  by means of a gear  9 . 
     The shaft  5  of the rotating member  3  is intended to be orthogonal to an X-Y plane. As mentioned above, there will, however, in practice be a certain eccentric and inclination error between the shaft  5  of the rotating member  3  and the center axis of the disk  6 . This error causes the shaft  5  of the rotating member  3  not to rotate perfectly about the center axis of the disk  6 . Since the shaft  5  is permanently fixed to the disk, the lower end of the shaft  5  will instead move in a circle about the center axis of the disk  6 . The casing  8  is connected to the frame  1  by means of a strut  15 , see FIGS. 1 and 2, which however allows motions, generated by the eccentric and inclination error, of the casing  8  about the strut mounting, see FIG.  2 . This motion results in the angle transducer  4  cyclically supplying incorrect information on the rotational angular position of the antenna  2 . 
     According to the invention, instead of the strut  15  there is arranged adjacent to or round the rotating member  3  a connector  10 , which is displaceably fixed in the X direction to the casing  8  and displaceably fixed in the Y direction to the frame  1  and is torsionally rigid in respect of the rotation about the antenna shaft  5 . The X-Y directions are perpendicular to each other and to the antenna shaft  5 . 
     As a result, the connector  10  prevents rotation of the rotating member outside the center axis of the antenna, which rotation would cause errors in the angle transducing. The connector  10  directs the motions caused by the forces to merely motions in the X-Y direction in a plane perpendicular to the antenna shaft. Motions in the X-Y direction do not affect the angle transducing. The resulting forces get an outlet, and the stress on the suspension device decreases. Thus, the invention allows merely motion in the X-Y direction and prevents rotational displacement of the stationary part, so that angle errors do not arise. 
     The connector  10  can be a rigid ring or a polygonal peripheral member, i.e. with a hole for receiving the rotating member  3 , see FIG. 5, or a portion of a peripheral member, see FIGS. 10 and 12, or a separate member, see FIG.  11 . 
     In a first embodiment of the present invention, said displaceable mounting is accomplished by means of pins  12  sliding in grooves  13 . See FIGS. 3 and 4. A pair of pins  12  are diametrically arranged on the connector  10  and slide in grooves  13  arranged on the casing  8  in the X direction, and one more pair of diametrically arranged pins  12 , which are offset 90 degrees from the first pair, slide in grooves  13  which are arranged in the frame  1  in the Y direction. Alternatively, the pins  12  can be arranged on the frame  1  and the casing  8 , respectively, and the grooves in the X-Y direction on the connector  10 . It goes without saying that the groove-pin arrangements can also be formed in a mixed manner, for instance, the pins  12  in the X direction are arranged on the connector  10  with corresponding grooves  13  in the frame  1 , and the pins  12  in the Y direction are arranged on the casing  8  with corresponding grooves  13  in the connector  10 , or one pin  12  is arranged in the X direction on the connector  10  and the other pin  12  in the X direction on the frame  1 . The pins  12  can be directed upwards or downwards depending on which construction is best suited for each individual construction with regard to the surroundings. The number of pins  12  with corresponding grooves  13  is not limited to that mentioned and shown in this embodiment. 
     The grooves  13  themselves need not be without play as long as the antenna  2  rotates in one direction only since the pins  12  then always move along the same side of the groove  13 . 
     In another embodiment, the displaceable mounting, which besides is without play, is provided by arranging linear bearings (not shown) between the connector  10  and the casing  8  in the X direction and between the connector  10  and the frame  1  in the Y direction. Then the antenna  2  can rotate in both directions without any angle deviation arising owing to play. At least one bearing for each direction is required. 
     In a third embodiment, see FIGS. 5 and 6, metal plates  14 , which are fixed between the connector  10  and the casing  8 , can flex in the X direction (their transverse extent is in the X direction), and metal plates  14 , which are likewise fixed between the connector  10  and the frame  1 , can flex in the Y direction (their transverse extent is in the Y direction). The metal plates are fixed by means of, for instance, screw or rivet joints. 
     FIG. 9 illustrates a fourth embodiment, in which the connector  10  is fixed to the casing  8  by means of a pair of pivotable link arms  16  which are arranged orthogonally to the direction of displacement in the X direction, the connector  10  further being fixed to the frame  1  by means of a pair of pivotable link arms  16  which are arranged orthogonally to the direction of displacement in the Y direction. The second pair of link arms  16  are off-set 90 degrees from the first pair. 
     In FIGS. 10 and 11, the connector  10  has a shape different from that described above. In FIG. 10, the connector consists merely of part of a peripheral member and has the shape of an L, and in FIG. 11 the connector consists of a rectangular plate, but it goes without saying that the connector can have any shape whatever. With such designs of the connector  10 , it can be mounted without having to be slipped over the casing  8  or the shaft  5 , but it is necessary to have an increased material thickness or a material with increased rigidity so that a rigidity like in a closed ring is obtained. The connector  10  is fixed to the casing  8  by means of a pair of pivotable link arms  16 , as shown in FIG.  9 . Moreover, the connector  10  is fixed to the frame  1  by means of a pair of pivotable link arms  16 , as shown in FIG.  9 . 
     FIG. 12 shows a simplified variant of the embodiment according to FIG. 9 where the connector  10  is fixed to the casing  8  by means of a pair of pivotable link arms  16  of different length, which are arranged orthogonally to the direction of displacement in the X direction, the connector  10  further being fixed to the frame  1  by means of a pair of pivotable link arms  16  which are arranged orthogonally to the direction of displacement in the Y direction. The points of fixation for the link arms  16  at the connector  10  coincide so that only two points of fixation is provided at the connector  10 . 
     FIG. 13 shows a connector  10  similar to the one in FIG.  10 . In this fifth embodiment, pivotable link arms  16  are used to fix the connector  10  to the casing  8 , so that the connector  10  is displaceable in the X direction, as explained above in connection with FIG.  9 . Furthermore, the connector  10  is displaceably fixed in the Y direction by means of two grooves  17  extending in the Y direction and cooperating with a pair of pins  12  which are arranged in the frame. The grooves  17  can be arranged in alignment or in parallel with each other or can be formed as a single groove  17 . Of course, the grooves can be arranged in the frame  1  instead, and the pins in the connector  10 . As understood by a person skilled in the art, a pin and groove arrangement can be arranged in the X direction instead of the link arms  16 , similar to the arrangement in the Y direction. 
     FIG. 7 illustrates a sixth embodiment, in which the stationary part is fixedly mounted in the frame  1 , the connector  10  being displaceably fixed in the X direction to the shaft  5  of the rotating member  3  and displaceably fixed in the Y direction to a power operated antenna mounting  11 , which corresponds to the disk  6  in the embodiment described above. 
     The shaft  5 , the connector  10  and the antenna mounting  11  rotate as a single unit, the X-Y plane being defined in relation to the shaft  5 , i.e. the X-Y plane is not stationary but rotates with the shaft  5 . 
     The antenna mounting  11  or the disk  6  is then mounted with a play between itself and the shaft  5  of the rotating member  3  to allow instead motion of the shaft  5  relative to the disk  6  or the antenna mounting  11  in the X-Y plane. 
     The displaceable mounting in this embodiment can be carried out according to one of the methods described above. 
     The Figures illustrate an angle transducer  4  which is arranged on the housing  8  and connected to the shaft  5  of the rotating member  3  by means of a gear  9 . The angle transducing can also be carried out by means of an apertured disk arranged on the shaft  5  of the rotating member  3  and an optical reader is arranged on the casing  8  for reading the apertured disk and, thus, the roational angular position. Alternatively, the apertured disk can be an electromagnetic reader, for instance a resolver. One or two angle transducers  4  can engage the shaft  5  of the rotating member  3  by means of a gear. It goes without saying that also other methods can be used. 
     The invention is not limited to that described above and shown in the drawings but can be modified within the scope of the claims.