Abstract:
A joystick controller has a lever mounted for pivotal movement relative to a housing, a seat member affixed to the housing, and a slider member biased towards the seat member. The seat member has a profiled surface that cooperates with a corresponding surface of the slider member. In one aspect, the profiled surface includes at least one lock position for engaging the slider member at a predetermined angle of pivotal displacement of the lever about a first axis. The slider member is shaped to allow pivotal movement of the lever about a second axis, without movement of the slider member, but to prevent movement of the lever about the first axis when engaged in the lock position. In another aspect, the profiled surface has a profile in a first direction whereby the biasing force remains substantially constant when the lever is pivotally displaced about a first axis, and a profile in a second direction whereby displacement of the lever about a second axis displaces the slider member so as to alter the biasing force.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application relates to and claims priority to corresponding Great Britain Patent Application No. 0503663.7, which was filed on Feb. 23, 2005, and which is incorporated by reference herein. 
   TECHNICAL FIELD 
   The present invention relates to Joystick controllers. 
   BACKGROUND OF THE INVENTION 
   Joystick controllers are used in a wide variety of control applications. One example is in the control of an excavator bucket. Movement of the bucket is actuated by hydraulic pistons, which are controlled by electrical signals provided by the joystick. The joystick has a lever, which is mounted for pivotal movement relative to a fixed body. Movement of the lever in one direction, by pivoting the lever about a first axis, controls the raising and lowering of the bucket. Movement of the lever in a second direction, by pivoting about a second axis (usually orthogonal to the first axis), controls orientation of the bucket (i.e. moves the bucket by turning it to the left or the right). 
   When excavating earth it is frequently required to place the bucket controls into a so-called float configuration, in which the raising and lowering controls are over-ridden so that the bucket drops under its own weight to the ground. In the float configuration, the bucket stays at the ground and rests on the terrain. There is no hydraulic influence over its vertical position. However, it is still desirable that an operator of the excavator should be able to control the left-right orientation of the bucket using the joystick while leaving the bucket level free to move with terrain change. A float configuration can be achieved with a joystick that has a lock facility to prevent movement of the joystick lever in the direction that controls vertical movement of the bucket. When the joystick is locked, the vertical controls are over-ridden. 
   One such joystick controller has been described in GB 2,313,175. This joystick has a bush that can slide up and down a shaft of the lever and is biased by a spring against a cradle mounted on the joystick body. The cradle has a recess, which engages a shoulder of the bush when the joystick lever has been displaced by a certain angle about a first axis (say the x-axis), to hold the lever at that angle. 
   A problem with this arrangement is that, when in the locked position, pivotal movement of the joystick in the other direction about the orthogonal y-axis can only be achieved by a corresponding pivotal movement of the bush and cradle. This means that the cradle must be mounted to the joystick body in such a way that it is allowed to pivot about the y-axis. Furthermore, this joystick uses a gimbal arrangement by which the joystick lever is mounted to the body for pivotal movement. Nowadays it is often preferable to use a ball and socket arrangement for mounting the joystick lever. 
   Many known joystick controllers include a return-to-centre arrangement, so that when the lever is displaced and subsequently released it is biased back towards a central position. The degree of biasing force also provides a tactile feedback by which the operator can sense the extent of displacement. However, there are many applications where it may be required to keep the joystick at a displacement in one (e.g. x) direction. It is a problem to achieve this while still retaining the return-to-centre feature in the orthogonal y direction. 
   SUMMARY 
   It is an aim of the present invention to provide a joystick controller that alleviates the aforementioned problems. 
   According to a first aspect of the present invention there is provided a joystick controller having: a lever mounted for pivotal movement relative to a housing; a seat member affixed to the housing; and a slider member biased towards the seat member, wherein the seat member has a profiled surface that cooperates with a corresponding surface of the slider member, the profiled surface including at least one lock position for engaging the slider member at a predetermined angle of pivotal displacement of the lever about a first axis, and wherein the slider member is shaped to allow pivotal movement of the lever about a second axis, without movement of the slider member, but to prevent movement of the lever about the first axis when engaged in the lock position. 
   Preferably, the slider member has an opening through which the lever extends, the opening in the slider member being elongated to allow pivotal movement of the lever about the second axis. The second axis may be orthogonal to the first axis. 
   Preferably, the seat member and the housing are formed as a single integral component. 
   In embodiments of the invention, the lock position is at or close to a maximum extent of displacement of the lever. The lock position may be defined by a raised portion that engages in a corresponding recess in the corresponding surface of the slider member. Alternatively, the lock position may be defined by an outward facing lip or rim, the slider member having a corresponding inward facing lip that drops over the outward facing lip to lock the lever. 
   Embodiments may include a plurality of lock positions at different angular displacements of the lever about the first axis. An advantage of this arrangement is that it allows the joystick lever to be used for the dual function of left-right movement control (when moved about the second axis) and as a multi-position selector when moved about the first axis. In one embodiment the joystick has three lock positions providing a three-position selector, which may be used, for example, for defining forwards, neutral and reverse positions. Alternatively, the plurality of lock positions may be used as a gear selector for a multi-speed gearbox. 
   It will be appreciated that the biasing of the slider member ensures that the lever is always pressed against the seat member. When the slider member engages the seat member in the lock position the biasing action provides an additional force of engagement that holds the lever in the lock position. The lever may be taken out of the lock position by overcoming this additional engagement force to move the slider member out of engagement with the seat member. 
   The profiled surface of the seat member may have a profile that has a wave-like form. The wave-like form may approximate to a sine wave. The corresponding surface of the slider member may include at least a portion having a corresponding profile. It is an advantage that the wave-like form provides lock positions defined by the troughs of the waves. 
   Preferably, the wave-like form of the profiled surface of the seat member has a plurality of troughs defining a plurality of lock positions. It is a further advantage that the wave-like forms provide continuous smooth contacting surfaces between the slider member and the seat member so that movement of the lever out of a lock position, or from one lock position to another, can be done smoothly. 
   According to a second aspect of the present invention there is provided a joystick controller having: a lever mounted for pivotal movement relative to a housing; a seat member affixed to the housing; and a slider member biased by a biasing force towards the seat member, 
   wherein the seat member has a profiled surface that cooperates with a corresponding surface of the slider member, the profiled surface having a profile in a first direction whereby the biasing force remains substantially constant when the lever is pivotally displaced about a first axis, and a profile in a second direction whereby displacement of the lever about a second axis displaces the slider member so as to alter the biasing force. 
   In a preferred embodiment the profiled surface of the seat member has a convex part-circular profile in the first direction. The cooperating surface of the slider member may have a corresponding concave part-circular profile in the first direction. The profile in the second direction may be uniform such that the entire profiled surface is part-cylindrical. Preferably, the seat member and the housing are formed as a single integral component. 
   In embodiments of this aspect of the invention, the substantially constant biasing force ensures that when the lever is pivotally displaced about the first axis, there is no change to this force so the lever will remain at the displaced angle until it is moved to a different angle. This aspect is known as “put and stay”. When the lever is displaced about the second axis, the change to the biasing force may be used to provide a force that returns the lever to a central position. 
   Embodiments of this aspect may include a brake means for providing a frictional force to resist movement of the lever about the first axis. It is an advantage that the frictional force adds to the biasing force to help ensure that the joystick lever stays at the “put and stay” angle until moved to a different angle by the operator. 
   The brake means may comprise a spring and a pivoted lever for applying a brake force against a yoke member that is moved by displacement of the lever. Preferably, the lever carries a roller that bears against a cam surface of the yoke member to provide the frictional force. An advantage of this arrangement is that the frictional force is applied through the roller, but there is no sliding or rubbing of the surfaces when the joystick lever is moved to a different angle. 
   In embodiments of either aspect of the invention, the joystick controller further comprises an over-press feature, wherein an increase in biasing action of the slider member is provided when pivotal movement of the lever about the second axis is close to its maximum displacement. The over-press feature comprises a ramp profile on the slider member, or on the seat member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention will now be described with reference to the following drawings. 
       FIG. 1  is a cross-sectional elevation of parts of a joystick controller according to a first embodiment of the first aspect of the invention. 
       FIG. 2  is a plan view showing a slider member and seat member of the joystick of  FIG. 1 . 
       FIG. 2   a  is an elevational view of the slider member of  FIG. 2 . 
       FIG. 3  is an isometric view of parts of a joystick controller according to a second embodiment of the first aspect of the invention. 
       FIG. 4  is a sectional elevation of part of the joystick controller of  FIG. 3 . 
       FIG. 5   a  is an elevation of a joystick controller according to an embodiment of the second aspect of the invention. 
       FIG. 5   b  is a sectional elevation of the joystick controller of  FIG. 5   a.    
       FIG. 5   c  is a sectional elevation of the joystick controller of  FIGS. 5   a  and  5   b  in an orthogonal plane. 
       FIG. 5   d  is an elevation of the joystick controller of  FIGS. 5   a  to  5   c , in which the joystick lever is pivotally displaced. 
       FIG. 5   e  is a sectional elevation of the joystick controller of  FIG. 5   d.    
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , a joystick controller  10  of the ball and socket type, has a lever  12  mounted to a ball  14 , which is located in a part-spherical socket  16 , allowing universal pivotal movement between the ball  14  and the socket  16  about a pivot centre  18 . The pivot centre  18  is at the intersection of a first axis A—A, orthogonal to the plane of the page of  FIG. 1 , a second axis B—B, and a third axis C—C that defines an axis of the lever  12 . The lever  12  extends past the pivot centre  18  to an armature  20 . The armature  20  carries part of one or more movement detection devices (not shown) for providing output signals indicative of the pivotal movement of the lever  12 . Examples of suitable movement detection devices include potentiometers or non-contact devices such as Hall effect sensors. 
   The socket  16  forms part of a housing, of which only a top portion  22  is shown in  FIG. 1 . The top portion  22  has a central opening  24  through which the lever  12  extends. The central opening  24  limits the maximum pivotal displacements of the lever  12  about the first axis A—A and the second axis B—B. A seat member  26  is mounted atop the top portion  22  of the housing. The seat member  26  has a profiled upper surface  28 . In the embodiment shown in  FIG. 1 , the profiled surface  28  has a central portion  30  having a shallow angle, either side of which is a raised lip portion  32   a ,  32   b.    
   A slider member  34  has a central opening  36  through which the lever  12  extends. The slider member  34  has a contact surface  38 , which includes an inner portion  40  having a shallow angled profile of the same or similar angle to that of the central portion  30  of the profiled surface  28  of the seat member  26 . Either side of the inner portion  40 , the contact surface  38  includes a recess  42   a ,  42   b . The recesses  42   a ,  42   b  are of a size to fit over and engage the corresponding raised lip portion  32   a ,  32   b  of the seat member  26 . 
   A bush  44  is slideably mounted around the lever  12  and engages a top surface  46  of the slider member  34 . The bush  44  is biased downwards against the top surface  46  by means of a compression spring (not shown). The compression spring is mounted around the lever  12  above the bush  44  and between the bush  44  and a stop (not shown) on the lever  12 . The biasing action of the compression spring is transmitted through the bush to the slider member  34 , so as to maintain a contacting force between the slider member  34  and the seat member  26 . 
   Referring to  FIG. 2 , in which corresponding features have the same reference numerals as used in  FIG. 1 , the seat member  26  has a central opening  27 , through which the lever  12  (not shown) extends. The slider member  34  extends either side of the opening  27  such that there is always contact between surfaces of the slider member  34  and the seat member  26 . The central opening  36  in the slider member  34  is elongated in the direction of the first axis A—A. 
   In use, when the lever  12  is close to its central, upright position, a small displacement of the lever  12  about the first axis A—A results in displacement of the slider member, causing sliding between the contacting angled surface  30  of the seat member  26 , and the corresponding angled surface  40  of the slider member. This displacement urges the slider member  34  upwards, pushing the sliding bush  44  upwards against the biasing action of the spring. Further displacement of the lever about the first axis A—A in, say, a direction towards the top of the page of  FIG. 2 , causes further sliding movement, until the slider member  34  reaches the raised lip  32   a  on the seat member  26 . Further displacement of the lever  12  causes the slider member  34  to lift up over the lip  32   a  until the recess  42   a  in the contacting surface of the slider member  34  engages onto the raised lip  32   a . The biasing action of the spring causes increased resistance due to compression of the spring as the slider member is displaced upwards. This increased biasing action provides an increased force that serves to lock the slider member  34  onto the seat member  26 . 
   At any stage, the lever  12  may be displaced in the orthogonal direction by pivoting about the second axis B—B without causing any movement of the slider member  34 . The lever  12  is free to move in this direction due to the elongated shape of the opening  36  in the slider member  34 . However, displacement of the lever in this second orthogonal direction causes the bush  44  to tilt with respect to the slider member  34  and in doing so the bush is displaced up the lever  12 , compressing the spring. Thus movement of the lever in either direction causes compression of the spring, thereby retaining an important feature of the joystick, which is to return it to its central, or null position when it is released. 
   When used as a controller for an excavator bucket, the lever  12  controls the height of the bucket when it is pivoted about the first axis A—A, and controls the left-right angular position of the bucket when pivoted about the second axis B—B. However, if the lever  12  is pushed rapidly and firmly to the lock position where the recess  42   a  in the slider member engages with the lip  32   a , the hydraulic system is configured to release hydraulic pressure so that the excavator bucket drops to the ground under its own weight. This places the excavator in the float configuration, in which the bucket stays at the ground and rests on the terrain. There is no hydraulic influence over its vertical position. However, an operator of the excavator can still use the joystick to control the left-right angular position of the bucket. 
   Referring to  FIG. 2   a , the slider member  34  is shown in elevation and includes raised ramp portions  44   a ,  44   b  at each end. These ramps provide an over-press feature whereby, when pivotal movement of the lever about the second axis B—B is close to its maximum displacement in either direction, there is an increase in the biasing action of the bush  44  against the slider member  34 . This provides a useful tactile feedback to the operator, to indicate that the joystick lever is nearing its limit of displacement. 
     FIGS. 3 and 4  show a joystick controller  50  having another form of profiled seat.  FIG. 3  shows part of the joystick controller  50 , including a lever  52  and a top portion  54  of a housing. A seat member  56  is fixed to the top portion  54  by way of fastener screws  58 . The lever  52  extends through a central opening  60  in the seat member  56 . The seat member  56  has a profiled upper surface  62 , which has a waveform. In this case the waveform is based on a sine wave that has been shaped to follow a curved overall profile. The waveform includes three trough positions  63 ,  64 ,  65  and four wave peaks  66 ,  67 ,  68 ,  69 . 
   Referring to  FIG. 4 , the joystick controller  50  includes a slider member  70 , and a sliding bush  72 , similar to those described above in relation to  FIGS. 1 and 2 . However, in this case the slider member has a contacting surface  74 , which contacts the profiled surface  62  of the seat member  56  in two contact regions  75 ,  76  which are shaped to have a portion of a waveform that corresponds to the waveform of the profiled surface  62 . 
   In this arrangement, the joystick  50  has three distinct lock positions with respect to its displacement about the first axis, as will be described in more detail below. As for the embodiment shown in  FIGS. 1 and 2 , displacement about the second axis is not affected. 
   The position of the joystick shown in  FIG. 4  is the central position of the three. In this position, the contact regions  75 ,  76  of the slider member  70  contact the seat member at the two outer trough positions  63 ,  65  of the profiled surface. Displacement of the lever in one direction (for example to the left as shown in  FIG. 4 ) by pivoting about the first axis will cause the contact regions  75 ,  76  of the slider member  70  to ride up the sides of the troughs  63 ,  65  of the profiled surface  62  and over two of the peaks. The contact  75  slides over the outer peak  66  and then drops down to rest beyond the peak  66 . The contact region  76  slides over an inner peak  68  (see  FIG. 3 ) and then drops down to rest in the central trough  64  (see  FIG. 3 ). It will be appreciated that the biasing action of the spring causes the lever to be held in the lock position. However, the waveform profile means that the lever can be moved from one lock position to another in a smooth sliding movement between the correspondingly profiled surfaces. 
   The three lock positions of the joystick  50 , allow it to be used as both a positional controller (when moved forwards or backwards in the orientation depicted in  FIGS. 3 and 4 ), and a selector when moved into one of the three lock positions. For example, the three lock positions may correspond to forward, neutral and reverse positions for selecting a direction of movement (or to up, neutral and down, for raising or lowering applications). Clearly, the number of lock positions need not be limited to three. A greater (or smaller) number of lock positions could be provided for selection, for example, of gears in a multi-speed gearbox. 
   Referring now to  FIGS. 5   a  to  5   e , a joystick controller  100  has a lever  102  mounted for pivotal movement relative to a body  104 , by means of a ball and socket arrangement  106 . A first yoke  108  is pivotally mounted on a first axis X—X. A second yoke  110  is pivotally mounted on a second axis Y—Y, orthogonal to the first axis X—X. The first axis X—X and the second axis Y—Y cross at the pivot centre  111  of the ball and socket arrangement  106 . 
   As shown in  FIG. 5   a , and in cross-section in  FIG. 5   c , the first yoke  108  has a pair of armatures  112  extending downwards from the first axis X—X. The lower end of each armature  112  defines a cam surface  114 , which abuts a roller  116  carried in a centrally aligned position by a lever arm  118 . Each lever arm  118  is supported at one end on a pivot mounting  120 , and at the other on a spring mounting  122 . The spring mounting  122  biases the lever arm  118  upwards so that the roller  116  is biased into abutment with the cam surface  114 . 
   As shown in  FIG. 5   b , the body  104  has a top surface that forms a seat  124 . The seat  124  has a convex cross-section profile that includes part of a circle centred on the pivot centre  111  of the ball and socket  106 . A slider member  126  of generally conical shape has a bore through which the lever  102  extends. A spring  128  biases the slider member down the lever  102  into contact with the seat  124 . The surface of the slider member  126 , which is in contact with the seat  124  has a corresponding concave profile. In  FIGS. 5   a  and  5   b  the lever  102  is in its central position and so the biasing action of the spring is symmetrical around the lever  102 . 
   The seat  124  extends uniformly parallel to the first axis X—X such that the entire profiled surface is part-cylindrical. This means that when the lever  102  is displaced so as to pivot about the second axis Y—Y, one side is urged against the seat  124 , while the opposing side lifts clear of the seat  124 . The slider member  126  is urged to slide up the lever  102  so as to compress the spring  128 . At the same time the biasing force against the lever  102  is no longer symmetrical, and so creates a moment that acts to return the lever to its central position. 
   On the other hand, as shown in  FIGS. 5   d  and  5   e , when the lever  102  is displaced so as to pivot about the first axis X—X, the profile of the seat  124  means that there is no corresponding urging of the slider member  126  against the seat. The slider member  126  is not urged to slide up the lever, and there is no change to the biasing action of the spring  128  and no moment created on the lever  102 . Consequently, the lever  102  will remain in the displaced position (angle) until moved to a new position. 
   Moreover, the cam surface  114  on the armature  112  is moved (as shown in  FIG. 5   d ) and this acts against the roller  116  pushing down on the lever arm  118 , which pivots on the pivot mounting  120  and compresses the spring mounting  122 . This increases the reaction force between the roller  116  and the cam surface  114  and increases the frictional resistance to further movement, thereby creating a brake effect. As a consequence the lever  102  will remain in the displaced position until such time as the operator moves it by overcoming the increased frictional force. This produces the aforementioned “put and stay” capability. Note that, although providing a frictional brake effect, there is no sliding or rubbing of mating surfaces, thereby avoiding frictional wearing of the surfaces. 
   It will be appreciated that it is possible to vary the profile of the seat  124  in the direction parallel to the first axis X—X, so as to vary the amount displacement of the slider member (and in consequence the size of the biasing force). In one embodiment, the seat  124  has a part spherical profile so that the “put-and-stay” facility applies when the lever  102  is displaced in any direction. In this embodiment additional brake arrangements may be included for applying an increased reaction force to the second yoke  110 . The additional brake arrangements may include a further pair of pivotal and spring mounted levers carrying rollers that bear against cam surfaces on armatures of the second yoke  110 . 
   As can be seen in  FIG. 5   e , further pivotal displacement of the joystick lever  102  will cause the conical slider member  126  to come into contact with an outer flat portion  130  beyond the convex seat  124 . The conical slider member  126  will be urged up the shaft of the lever  102  to compress the spring  128 . This results in an eccentric reaction force on the lever, tending to urge it back towards its central position, and provides an over-press feature, similar to that described above for the joystick of  FIGS. 1 to 2   a , to present a tactile feedback to the operator indicating that the joystick lever is nearing its limit of displacement.