Abstract:
The invention relates to a joystick having a hand-grip, which is mounted with two degrees of freedom in a mounting in a housing and which may be deflected in different directions out of an initial position, the grip being biased by a spring mechanism towards its initial position and sensor apparatus being provided to sense the different positions of the grip and to generate an output signal which may be used to control machine and/or vehicle functions. A housing cover ( 5 ) is provided having its upper side directed towards the grip, while on the underside, there is pivotally mounted a cardan joint center portion ( 6 ) on whose underside there is pivotally mounted a cardan joint inner portion ( 7 ), whose underside is provided with spherical segments, which are mounted in complementary bearing cup-portions provided on a receiving support ( 8 ).

Description:
CROSS-REFERENCE 
     Applicant claims priority from German patent application 19838004.6 filed Aug. 21, 1998. 
    
    
     The present invention relates to a joystick having a hand-grip, which is mounted with two degrees of freedom in a mounting in a housing and which may be deflected in different directions out of an initial position, the grip being biased by a spring mechanism back towards its initial position and the different positions of the grip being sensed by sensor apparatus which outputs a signal which is used to control machine and/or vehicle functions. 
     As regards the mounting, use may be made of a ball-and-socket joint or a cardan joint. A cardan joint comprises three joint portions, which are pivotally connected by means of guides. These guides consist of a large number of individual parts. Moreover, the effort required for assembly is great. Ball-and-socket joints have three degrees of freedom. However, in the case of joysticks, rotation about the grip axis is not required. On that account, such rotation is prevented by a pin which is fastened to the socket and engages in a vertical groove in the ball. This arrangement, however, is susceptible to wear and is only capable of bearing light stresses. The problem on which the present invention is based is to provide a joystick which overcomes or mitigates the aforementioned disadvantages. In particular, it is desirable that the joystick should be economic to manufacture and easy to install. 
     In regard to a joystick having a grip, which is mounted with two degrees of freedom in a mounting in a housing and which may be deflected in different directions out of an initial position, the grip being biased by a spring mechanism back towards its initial position and in which the different positions of the grip are sensed by sensor apparatus which outputs a signal which is used to control machine and/or vehicle functions, it is proposed that on the underside of a housing cover which has its upper side directed towards the grip, there should be pivotally mounted a cardan joint centre portion on whose underside there is pivotally mounted a cardan joint inner portion, whose underside is provided with spherical segments, which are mounted in complementary bearing cup-portions provided on a receiving support. In regard to the device according to the invention, there may be employed a cardan joint in which the bottom half is cut away. Because of this, the joint can easily be assembled by engaging the parts together. The receiving support prevents the elements of the cardan joint from coming apart. 
     A particular embodiment of the invention is characterised in that on the side of the cardan joint inner portion which is directed away from the grip, there is provided a magnet whose movement is recorded by a sensor carried by a printed-circuit board which is mounted in the housing. By this means it is readily guaranteed that the deflection of the grip will be accurately sensed. In addition, the number of individual parts of the joystick is kept small. 
     Another particular embodiment of the invention is characterised in that the grip comprises a grip tube having a stop for a spring, which is biased against a plate which engages on the housing cover. The spring ensures that after the grip is deflected, it is restored to its initial position. The joint portions are pulled upwards by the force of the spring. 
     In regard to the joystick described at the beginning, the position of the joystick is sensed by sensors which provide an output in the form of an electrical signal. This signal is used to control machine and vehicle functions. In most cases, several switches are disposed in the grip of the joystick. The cables for these switches may possibly be led through a corresponding recess in the joint. If the joystick is used in agricultural and construction machines, it must be capable of withstanding high loadings. The mounting of the joystick must therefore be dimensioned correspondingly sturdily. The provision of the recess for the cables which are led through the mounting also leads to the dimensions of the joystick being increased. In conventional joysticks, the sensors are attached outside the mounting. When using Hall sensors, there is fastened to the grip tube a magnet which is disposed in proximity to a sensor which is fastened to the housing. Depending on the position of the grip and of the magnet, the voltage at the sensor varies. The attachment of magnet and sensor outside the mounting leads to a relatively large spacing between magnet and sensor. This has the result that very large magnets must be used in order to guarantee effective functioning of the joystick. 
     A further problem which the invention seeks to solve is therefore that of reducing the dimensions of the housing of the joystick. In particular, it is desirable that the spacing between magnet and sensor should to be reduced. 
     In regard to a joystick having a grip, which is mounted with two degrees of freedom in a mounting in a housing and which may be deflected in different directions out of an initial position, the grip being moved by a spring mechanism back into its initial position and the different positions of the grip being sensed by a sensor apparatus which outputs a signal which is used to control machine and/or vehicle functions, it is proposed in a preferred embodiment of the invention, that the sensor apparatus should be arranged inside the mounting. This has the advantage that when using Hall sensors, the spacing between magnet and sensor is reduced. Moreover, the susceptibility to interference as a result of electromagnetic influences from outside the housing of the joystick is reduced. 
     One particular embodiment of the invention is characterised in that the mounting is provided by a cardan joint having a substantially annular cardan joint centre portion which is mounted in the housing, and a cardan joint inner portion which is mounted by means of a rotary guide in the cardan joint centre portion and is fork-shaped. As a result of the fork-shaped construction of the cardan joint inner portion, space for a sensor apparatus is provided in the cardan joint. 
     Another particular embodiment of the invention is characterised in that the rotary guide comprises bearing pins which are attached to the cardan joint inner portion and are guided in slide bushes which are fastened in the cardan joint centre portion. The guiding of the bearing pins in the slide bushes guarantees smooth working and virtually wear-free functioning of the joystick. 
     Another particular embodiment of the invention is characterised in that on the cardan joint inner portion, there is mounted a ring magnet which cooperates with sensors which are attached to a printed-circuit board, which is fastened to the housing, underneath the ring magnet, with the aid of a support. In the event of a deflection of the grip, the ring magnet mounted on the cardan joint inner portion executes a movement corresponding to the deflection of the grip. The movement of the ring magnet is sensed with the aid of the sensors arranged in the vicinity. 
     Another particular embodiment of the invention is characterised in that the printed-circuit board cooperates with an electronic analysis circuit which is accommodated in the housing. Damage to individual elements of the sensor apparatus on account of improper operation or the effect of dirt is reliably prevented by the arrangement of the complete sensor apparatus inside the housing of the joystick. 
     Another particular embodiment is characterised in that the grip comprises a grip tube which is formed on the cardan joint inner portion. Because of this, it is achieved that even very great forces may be applied to the grip without damage occurring. 
     Another particular embodiment of the invention is characterised in that on the grip, there is mounted at least one switch which serves to control machine and/or vehicle functions and is connected by means of at least one cable, which is led through the grip tube, the ring magnet and the support, to the electronic analysis circuit. The guiding of the cable through the ring magnet guarantees reliable functioning of the joystick in every desired configuration. 
     Another particular embodiment of the invention is characterised in that the deflection region of the joystick comprises a first region, in which the restoring force of the grip increases only comparatively slightly, and a second so-called dwell-pressure region in which the grip, having passed a pressure-point, can move a little further, and in that at least one arcuately shaped leaf spring is fastened to the grip tube with the aid of a mounting. In one known device, a spring-mounted locking ram is fastened to each axis. This locking ram is pressed by a spring against a ramp fastened to the housing. The behaviour of the grip during return to its position can be influenced by the shape of the ramp. The restoring force of the grip changes as a function of the angle of the ramp in relation to the direction of movement of the ram. This conventional solution requires a separation of the axes of movement of the grip. Moreover, it is necessary to provide space for the ramp in the vicinity of the axes of movement. The assembly dimensions of the joystick are increased because of this. These disadvantages are avoided in one particular embodiment of the invention, by means of an arcuately shaped leaf spring which may be attached to the grip tube. Moreover, the invention makes it possible to manage with fewer individual parts than is the case in known devices. 
     A further particular embodiment of the invention is characterised in that in the mounting, a recess is provided for the purpose of receiving the deformed leaf spring. The movement of the spring may then be limited by the size of the recess. Deformation of the spring in the reverse direction is prevented by this limitation of the movement of the spring. 
     Another particular embodiment of the invention is characterised in that the deflection region of the joystick comprises a first region, in which the restoring force of the grip increases only comparatively slightly, and a second so-called dwell-pressure region in which the grip, having passed a pressure point, can move a little further, and in that on the grip, there is displaceably mounted at least one spring-biased ram which cooperates with a detent contour provided at the edge of a connecting member, which detent contour limits the deflection of the grip. 
     The geometric configuration of the detent contour may be chosen so as to determine whether the grip will engage in the end position or will spring back. 
     Other advantages, features and details of the invention are disclosed in the following description, given with reference to the drawings, in which different embodiments of the invention are shown, by way of example only. In this connection, the features mentioned in the description and in the appended claims may be relevant to the invention either individually or in combination. In the drawings: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a 
     joystick according to a first embodiment of the invention; 
     FIG. 2 is a longitudinal sectional view through the joystick shown in FIG. 1; 
     FIG. 3 is a longitudinal sectional view through the joystick shown in FIG. 1, displaced through 90° relative to the representation shown in FIG. 2; 
     FIGS. 4 and 5 are longitudinal sectional views, offset from one another by 90°, through a joystick according to a second embodiment of the invention; 
     FIG. 6 shows a longitudinal section through a joystick according to a third embodiment of the invention; and 
     FIG. 7 shows a longitudinal section through a joystick according to a fourth embodiment of the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The joystick shown in FIGS. 1 to  3  comprises a lever in the form of a tube  1 , which carries a hand-grip or handle  24  on its upper portion  26 . The grip tube  1  serves to receive a ring  2  which, when in position on the grip tube  1 , forms a stop for a spring  4 . The spring (represented only in FIGS. 2 and 3) is pressed against a plate  3 . The plate engages against a cover  5 , which forms part of a housing which surrounds the articulated mounting of the grip tube  1 . The housing also includes a receiving support  8 . 
     On the underside of the housing cover  5  there are provided two semi-cylindrical shaped recesses, of which one is identified by the reference number  10  in FIG.  1 . The semi-cylindrical shaped recesses  10  serve to receive bearing pins  11  and  12 , which are formed on the centre portion  6  of cardan joint. By this means it is provided that the cardan joint centre portion  6  may tilt about an axis EW extending in East E and West W directions, which passes longitudinally through the bearing pins  11  and  12 . Two semi-cylindrical shaped recesses  13  and  14  are provided on the underside of the cardan joint centre portion  6 , offset through 90° in relation to the bearing pins  11  and  12 . The semi-cylindrical shaped recesses  13  and  14  serve to receive two bearing pins  15  and  16  which are provided on the inner portion  7  of the cardan joint. The inner position  7  can pivot about an axis NS extending in North N and South S direction. 
     As is to be seen in FIGS. 2 and 3, the cardan joint inner portion  7  is formed with spherical segments. The spherical segments serve for mounting the cardan joint inner portion  7  in a receiving support  8 . For this purpose, bearing cup-portions complementary to the spherical sections of the cardan joint inner portion  7  are constructed in the receiving support  8 . The receiving support  8 , which is formed with an internal opening extending through it, rests on a printed-circuit board  9 . Into the opening of the receiving support  8  there extends a magnet in the shape of a right parallelepiped which is formed on the cardan joint inner portion  7  at the lower end  30  of the lever. 
     In the assembled state, the grip tube  1  extends through the cardan joint inner portion  7 . The cardan joint inner portion  7  is fastened to a lower portion  28  of the grip tube  1  by a pin. Because of this, it is provided that the cardan joint inner portion  7  shall execute the same movements as the grip tube  1 . After deflection of the grip tube  1 , the spring  4  ensures that the grip tube  1  is restored to its initial position. The spring  4  engages by means of the plate  3  against the housing cover  5 . The joint is a cardan joint in which the bottom half is cut away. The recesses serving as bearing points in the cardan shaft centre portion  6  and the cardan shaft inner portion  7  are open to the bottom. Because at this, the joint can easily be assembled by engaging the parts together. The individual joint portions are pulled upwards by the force of the spring  4 . This prevents the components of the joint from coming apart. However, it would be possible to press the joint downwards by overcoming the spring force. This is prevented by the receiving support  8 , which supports the joint from underneath. Sensing of the position of the grip is achieved by Hall sensors which are arranged on the printed-circuit board  9 . These Hall sensors react to the position of the magnet which provided on the inner sensors position  7  of the cardan joint. 
     The joystick represented in FIGS. 4 and 5 comprises a grip tube  41  which is a mounted in a cardan joint. The cardan joint comprises an annular centre portion  46  and a forked inner portion  47 , which are accommodated in a housing  45 . The cardan joint centre portion  46  is pivotally mounted in the housing  45  by means of a rotary guide. The rotatary guide is formed by two bearing pins  55  and  56 , which are attached to the cardan joint centre portion and are guided in slide bushes  53  and  54 . The bearing pins  55  and  56  as well as the slide bushes  53  and  54  are arranged on an axis which is perpendicular to the longitudinal axis of the grip tube  41 . 
     As is to be seen in FIG. 5, two slide bushes  49  and  50  are arranged in the cardan joint centre portion  46  on an axis which is perpendicular to the longitudinal axis of the grip tube  41  and perpendicular to the axis which passes through the bearing pins  55  and  56 . The slide bushes  49  and  50  serve to receive two bearing pins  51  and  52 , which are attached to the cardan joint inner portion  47 . The cardan joint inner portion  47  is joined rigidly to the grip tube  41 . By this means it is guaranteed that the cardan joint inner portion  47  executes the same movements as the grip tube  41  when the latter is deflected. 
     The cardan joint inner portion  47  is in the form of a fork. A ring magnet  48  is mounted inside the cardan joint inner portion  47 , concentrically with the grip tube  41 . The ring magnet  48  moves together with the grip tube  41  when the latter is deflected. The movement of the ring magnet  48  is detected by Hall sensors which are arranged on a printed-circuit board  59 . The spacing between the ring magnet  48  and the Hall sensors on the printed-circuit board  59  is small, as is to be seen in FIGS. 4 and 5. The printed-circuit board  59  is fastened to the housing  45  by means of a support  58 . 
     Cables which, for the sake of clarity, are not shown in the drawings are led through the grip tube  41 , the cardan joint inner portion  47 , the ring magnet  48 , the cardan joint centre portion  46 , the annular printed circuit board  59  and the support  58  to an electronic analysing circuit  44 . 
     The deflection of the grip tube  41  is limited by a connecting link  57  which is mounted on the housing  45 . 
     In FIG. 6, a joystick is shown which has two different regions of deflection. In the first region, the restoring force of the grip increases only slightly. A stop should be noticeable at the end of this region. In the second region, the grip should move onwards a little, following application of a substantial force. At the end of the second region, a digital signal is generated. The restoring force of the grip should decrease again after a sharp rise. 
     In the case of the joystick shown in FIG. 6, the pressure function between the two deflection regions is achieved by an arcuately biased leaf spring  60 , which is fastened by means of a support  62  to the grip tube  61  of the joystick. On the housing  65  of the joystick there is fastened a connecting member  67  which limits the deflection of the grip tube  61 . The leaf spring  60  is arched outwards away from the grip tube  61 . At a particular deflection of the grip tube  61 , the leaf spring  50  touches the edge of the connecting member  67 . Upon further deflection of the grip tube  61 , the spring force of the leaf spring  60  must be overcome. The spring force of the leaf spring  60  which acts against a further deflection increases until the leaf spring  60  is deflected in the region of the edge of the connecting link  67 , into a recess  63  which is provided on the support  62 . The resilient deformation the leaf spring  60  is limited by this means. Without such limitation of its deformation the leaf spring  60  might be deformed so far that the deformation at its lower end would become greater than the deformation at its upper end. In such a case, the deformation of the leaf spring  60  would be reversed. It could not then spring back of its own accord out of the reversed position. 
     In regard to the joystick shown in FIG. 7, a ram  72  for each direction of deflection is mounted displacpably on the grip tube  71 . The ram  72  is biased by a spring  73 . The travel of the ram  72  is limited by stops. The tip of the ram  72  cooperates with the edge of a connecting member  74 . The edge of the connecting member  74  has a particular contour, which may be identified by the angles α and β. The ram is spring-deflected as a function of the angle α, by which means the deflecting force of the grip tube  71  is increased. When the ram  72  is moved over the edge of the detent contour of the connecting member  74 , the force falls off again. The magnitude of the angle β determines whether the grip tube  71  will engage in the end position or will spring back.