Abstract:
The invention relates to an improved snow grooming vehicle featuring a multifunction joystick adapted to selectively control a plurality of independent functions of various work implements installed on the snow grooming vehicle. More specifically, the multifunction joystick is adapted to select specific functions of a work implements and apply the movements of the joystick to these specific functions. If a new function is selected, the movements of the joystick are applied to the newly selected function while disabling the previously selected function From a single joystick, the operator may control a wide array of functions of the work implements installed on the snow grooming vehicle.

Description:
This application is the National Phase of International Application PCT/CA99/00019 filed Jan. 8, 1999 which designated the U.S. and that International Application was published under PCT Article 21(2) in English. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to snow groomers and to implement controls for snow groomers and for other utilitarian motorized vehicle. 
     BACKGROUND OF THE INVENTION 
     Snow groomers are tracked vehicles used for preparing snow surfaces such as ski slopes, cross-country ski trails, snow mobile trails and the like to obtain a smooth compacted snow covered surface of a desired configuration to facilitate the practice of winter sports and reduce the risks of accidents while practicing these winter sports. Snow groomers are normally equipped with a variety of snow grooming and conditioning implements which are operated from the operator&#39;s cabin enabling the operator to control these implements while the snow groomer is moving. 
     Joysticks are commonly used to control work implements on snow groomers and on a variety of utilitarian vehicles. The lateral motion and the fore and aft motion of the joystick normally control the hydraulic system of a single work implement. In some instances, the joystick will be adapted to control a second implement by rotating the joystick clockwise or counterclockwise while still controlling the primary implements. 
     Joysticks are also constructed with a base featuring a cardan joint or universal joint to provide motion of the stick in all directions and feature electric position sensors linked to the shaft of the joystick as is disclosed U.S. Pat. No. 5,576,704 to Baker et al. The relative position of the joystick in relation to the position sensors is translated by a control means into motion of a specific work implement and in some instances, the joystick affords some degree of control over the acceleration and deceleration of the specific work implement. U.S. Pat. No. 4,574,651 to Lennart et al. discloses a control stick for a fighter aircraft that controls a plurality of functions. An array of selector switches and buttons are disposed either on the handle or in close proximity of the handle enabling the pilot to control many functions without removing his hand from the control stick. The control stick has two separate portions. The lower portion only moves fore and aft along a single axis and controls the engine throttle. The upper portion of the control stick is swingable along two axes similar to a conventional joystick and its sole purpose is to control the radar orientation and range. Buttons and switches on the control stick unit operate control instrumentalities and radar mode selection while the joystick maintains radar control. 
     UK Patent Application GB 2 244 742A discloses a joystick for controlling a cleaning vehicle. The joystick uses a first microswitch 170 and a second microswitch 190, both connected to a control module 198 to control various cleaning implements and operations. 
     In the presence of a plurality of independent work implements requiring joystick controls, a plurality of joysticks are usually installed, one for each implement. It is not uncommon to see up to five joysticks in a single operator&#39;s cabin. This array of joystick controls is cumbersome and less than efficient in a small operator&#39;s cabin. 
     OBJECTS AND STATEMENT OF THE INVENTION 
     It is thus an object of the invention to provide an improved snow grooming vehicle. 
     It is another object of the invention to provide a multifunction joystick control system adapted to selectively control a plurality of independent functions. 
     It is another object of the invention to provide a multifunction joystick control system adapted to combine hydraulic control for some implement functions with electrical control for other implement functions. 
     Yet another object of the invention is to provide improved implements controls for utilitarian vehicles. 
     It is also an object of the invention an improved snow grooming vehicle adapted to selectively control a plurality of independent functions using a single multifunction joystick. 
     As embodied and broadly described herein, the invention provides a snow grooming vehicle having a frame supported and propelled by ground engaging tracks, an operator&#39;s cabin mounted to the frame, implement coupling means for at least one snow working implement carried by the frame, and at least two sets of implement actuators which are subject to operational control by the operator from within the operator&#39;s cabin. Each set of implement actuators being controllable by a joystick independently of the control of any other set of implement actuators. The snow grooming vehicle has an engine for driving the ground engaging tracks, the joystick has a hand grip portion positioned for convenient manipulation by the operator when sitting into the operator&#39;s cabin in a normal command position. Electrical transducer means are operatively associated with the joystick for generating an electrical signal representative of the position of the joystick. Manual control switching means operable by the operator from its normal command position are provided for selecting a set of implement actuators of which the operator desires to change the condition by means of the joystick thereby adjusting the position or setting of an implement according to the position of the joystick. There is a controller having at least two inputs and one output and generating an output signal representative of the position of the joystick for operatively controlling the set of implement actuators selected by the operator. The manual control switching means are coupled to a first input of said controller; the electrical signal produced by the electrical transducer means are coupled to a second input of the controller, whereby while the manual control switching means is actuated, the controller generates an output signal representative of the position of the joystick which is used to operatively control a predetermined set of implement actuators; the joystick being adapted to control at least one other set of implement actuators when the manual control switching means is not actuated. 
     Preferably, one snow grooming implement is a front snow blade and the other set of implement actuators which are controlled by the joystick when the manual control switching means is not actuated consists of a first hydraulic cylinder which sets the height of the front snow blade and a second hydraulic cylinder which sets the tilt angle of the front snow blade. 
     Advantageously, the first and second hydraulic cylinders are controlled by a set of hydraulic control valves which are mechanically linked to, and controlled by the joystick and rendered inoperative whenever the manual control switching means is actuated. 
     As embodied and broadly described the invention also provides a snowgrooming vehicle having an internal combustion engine, a frame, an operator&#39;s cabin supported by the frame, a set of ground engaging tracks, a drive mechanism linking the engine to the ground engaging tracks enabling the vehicle to move on snow, implement coupling means for at least one implement, the implement being subject to functional control by the operator from within the operator&#39;s cabin, a multifunction joystick control system for selectively controlling an implement carried by the implement coupling means. The multifunction joystick control system comprises a joystick having a hand grip portion positioned for convenient manipulation by the operator when sitting into the operator&#39;s cabin in a normal command position, manual control switching means operable by the operator from the normal command position for selecting a function of an implement that the operator desires to control by normal bi-axial manipulation of the joystick, a controller for generating an output signal which is used for effecting the operational control of the function of an implement selected by the operator whenever the manual control switching means is actuated. The multifunction joystick control system is adapted to also control the operation of at least one other function of an implement by normal bi-axial manipulation of the joystick while the manual control switching means is not actuated. 
     Preferably, the multifunction joystick control system further comprises a set of electrical transducers operatively associated with the joystick for generating an electrical signal representative of the position of the joystick, the electrical signal generated by the set of electrical transducers being coupled to a second input of the controller. 
     Advantageously, the manual control switching means generates an electrical signal representative of the selected function of an implement, and this electrical signal generated by the manual control switching means is coupled to a first input of the controller. 
     The invention also provides a multifunction joystick control system for a snow grooming vehicle which has a frame, ground engaging tracks, an operator&#39;s cabin, an engine for driving the vehicle, implement coupling means for at least one snow grooming implement and at least two sets of implement actuators separately controlled by the operator, each set of implement actuators being controllable by a joystick. The multifunction joystick control system has a joystick having a hand grip portion positioned for convenient manipulation by the operator when sitting into the operator&#39;s cabin in a normal command position, a set of electrical transducers operatively associated with the joystick for generating an electrical signal representative of the position of the joystick, a first manual control switching means operable by the operator from the normal command position for selecting a first set of implement actuators that the operator desires to operationally control, the first manual control switching means generating an electrical signal representative of the first set of implement actuators, and a controller having at least two inputs and one output and generating an output signal for effecting the operational control of the set of implement actuators selected by the operator. The electrical signal generated by the first manual control switching means is coupled to a first input of the controller. The electrical signal generated by the set of electrical transducers is coupled to a second input of the controller. The controller generates a first output signal when the first manual control switching means is actuated, the first output signal being representative of the position of the joystick and being used to control the operation of the first set of implement actuators. The multifunction joystick control system is adapted to control the operation of at least one other set of implement actuators as a function of the position of the joystick when the first manual control switching means is not actuated. 
     Preferably, the other set of implement actuators consists of a set of hydraulic cylinders which require control by the operator for proper operation of the utilitarian vehicle. The multifunction joystick control system also comprises a hydraulic circuit for operating the hydraulic cylinders, control valve means operatively associated with the joystick for controlling hydraulic fluid supply through said hydraulic circuit to the hydraulic cylinders as a function of the position of said joystick and disabling means for disabling the control valve means when the first manual control switching means is actuated. 
     Advantageously, the manual control switching means comprises at least one push button located on the hand grip portion of the joystick. 
     As embodied and broadly described, the invention also provides a multifunction joystick control system for a utilitarian vehicle having at least one implement and at least two sets of implement actuators which are subject to operational control by the operator from within an operator&#39;s cabin in the utilitarian vehicle. Each set of implement actuators is controllable by a joystick independently of the control of any other set of implement actuators. The multifunction joystick control system features a joystick having a hand grip portion positioned for convenient manipulation by the operator when sitting into the operator&#39;s cabin in a normal command position, a set of electrical transducers operatively associated with the joystick for generating an electrical signal representative of the position of the joystick, a first manual control switching means operable by the operator from the normal command position for selecting a first set of implement actuators that the operator desires to operationally control, the first manual control switching means generating an electrical signal representative of the first set of implement actuators, a controller having at least two inputs and one output and generating an output signal for effecting the operational control of the set of implement actuators selected by the operator. The electrical signal generated by the first manual control switching means is applied to a first input of the controller. The electrical signal generated by the set of electrical transducers being applied to a second input of the controller. The controller generates a first output signal when the first manual control switching means is actuated, the first output signal being representative of the position of said joystick and being used to control the operation of the first set of implement actuators. The multifunction joystick control system is adapted to control the operation of at least one other set of implement actuators when the first manual control switching means is not actuated. 
     Other objects and features of the invention will become apparent by reference to the following description and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A detailed description of a preferred embodiment of the present invention is provided herein below, by way of example only, with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view illustrating a multifunction joystick according to the invention, installed in an operator&#39;s cabin; 
     FIG. 2 is a front elevational view of the multifunction joystick illustrated in FIG. 1; 
     FIG. 3 is a rear elevational view of the multifunction joystick illustrated in FIG. 1; 
     FIG. 4 is a side elevational view illustrating a typical snow groomer with a front snow blade and a rear snow grooming accessory; 
     FIG. 5 is a top plan view illustrating the snow groomer shown in FIG. 4; 
     FIG. 6 is a perspective view illustrating a the multifunction joystick according to the invention with the handle portion removed; 
     FIG. 7 is a top plan view of the multifunction joystick as shown in FIG. 6; 
     FIG. 8 is a side elevational view of the multifunction joystick as shown in FIG. 6 and 7. 
     FIG. 9 is block diagram depicting the controller of the multifunction joystick according to the invention. 
    
    
     In the drawings, preferred embodiments of the invention are illustrated by way of examples. It is to be expressly understood that the description and drawings are only for the purpose of illustration and are an aid for understanding. They are not intended to be a definition of the limits of the invention. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to FIG. 1,  2  and  3 , a novel multifunction joystick is designated generally by reference numeral  10 . Joystick  10  has a handle portion  14  which can be manipulated by the operator from its normal position. Joystick  10  is adjustably mounted to a side arm  52  of the operator seat in a snow groomer cabin and all work implements of the snow groomer are controlled and, in accordance with the invention, actuated by the operator via the multifunction joystick  10 . Although the invention is described in relation with tracked vehicles used for grooming snow trails, ski slopes and the like, control system in accordance with this invention may find application in any type of utilitarian vehicles featuring work implements that require segregated joystick control. 
     Referring to FIGS. 4 and 5, a conventional snow groomer  60  is illustrated. The snow groomer  60  is constructed around a narrow frame  110  on which the operator&#39;s cabin  66  is mounted. An internal combustion engine is positioned in the mid-section of snow groomer  60  and a muffler  67  is provided to evacuate the exhaust gas produced by the internal combustion engine. At the rear of snow groomer  60  is a utility compartment  112  provided to carry tools and equipment. Snow groomer  60  is supported and propelled by a pair of wide snow engaging tracks  65  and their associated tandem wheels  69 , single wheels  68  and suspension system (not shown) on frame  110  in accordance with conventional practice. 
     Snow groomer  60  is shown with a front work implement  62  and rear work implement  64 . Front work implement  62  consists of a large front snow blade  72  with adjustable wings  71  and  73 . Front blade  72  is coupled to frame  110  by means of a single-arm frame  70  on an attachment point  120  consisting of a balljoint which enables partial rotation of front blade  120  about a vertical axis, a transverse axis and a longitudinal axis. Front blade  72  may be raised or lowered by a hydraulic cylinder  76  connected at one end to the upper part of the frame  110  of the snow groomer  60  and at the other end to the lower part of the front blade  72 . Blade  72  may be pivoted about the snow groomer&#39;s longitudinal axis so that one side of the blade  72  is higher than the other. This is accomplished by actuating a tilt hydraulic cylinder  77  connected between the frontal extremity of the single-arm frame  70  and an attachment point  122  of blade  72 . Tilt hydraulic cylinder  77  imparts a rotary motion to the front blade  72  about a longitudinal axis of the snow groomer  60 . This adjustment of the front blade  72  is referred to, in the industry, as tilting the front blade  72 . 
     The angle of the front blade  72  in relation to the longitudinal axis of the snow groomer  60  is also adjustable using a pair of angler hydraulic cylinders  78 A and  78 B located on both sides of the single-arm frame  70  which imparts rotational motion to the blade  72  around a vertical axis. The pitch angle of the blade  72  is adjustable by a pitch hydraulic cylinder  79  linking the upper part of the frame  110  with the upper part of the blade  72 . Finally, the angle of the blade wings  71  and  73  may be adjusted by left-wing hydraulic cylinder  81  and right-wing hydraulic cylinder  83  which open or close the angle of the blade wings  71  and  73 . 
     The rear work implement  64  is mounted to the snow groomer  60  by means of a conventional double-arm frame  85  acting as a implement coupling means. Rearwork implement  64  consists of a tiller  90  provided with a variety of hydraulic adjustments. A first hydraulic cylinder  86  serves to raise and lower the double-arm frame  85  thereby raising and lowering tiller  90  relative to the ground. A second hydraulic cylinder  87 , positioned diagonally between the two arms of the double-arm frame  85 , is provided to laterally displace the tiller  90  in relation to the snow groomer  60 . A third hydraulic cylinder  88  attached directly to the tiller  90  on one side and to the frame  110  of the snow groomer  60  on the other side provides depth control of the tiller  90 . When actuated, the hydraulic cylinder  88  imparts a rotation of the tiller  90  about the axis defined by the two attachment points  91  of tiller  90  to the rear double-arm frame  85 . This rotation of tiller  90  either increases the depth of tilling of the snow or reduces it. Finally, a pair of hydraulic cylinders  89 , positioned atop tiller  90 , actuate the tiller rear flap  94  which increases or decreases the volume of the snow chamber  95 . 
     As noted above, the illustrated work implements are well known in the art and can be found in commercially available snow groomers. Otherwork implements are also available, such as front snow blowers or compactors. These work implements are normally controlled by the same hydraulic system using separate manual controls, one for each implement. Most of these work implements require joystick control in that they cannot be fully controlled merely with a single direction lever or control switch. In other words, they are controllable as a function of the bi-axial position or motion of a joystick. 
     An improved snow groomer, in accordance with this invention uses instead a central system which has a multifunction joystick  10  for all implements. As shown in FIGS. 1,  2 , and  3 , joystick  10  is swingable relative to the base  12  about mutually perpendicular axes that intersect near the base  12 . The multifunction joystick  10  is, in this case, swingable about a fore-and-aft extending axis and a laterally extending axis. The joystick  10  may be configured for right hand or left hand actuation depending on where it will be located relative to the operator. In this example, a right hand multifunction joystick is illustrated. 
     The joystick  10  actuates, as a primary function, a conventional four-way hydraulic valve which controls the flow of hydraulic fluid to a set of hydraulic cylinders thereby controlling the actions of these implement actuators. In addition to joystick  10 , the control system uses one or more push buttons or other type of manual control switching means to select a given function. In the illustrated embodiment, seven push buttons are shown numbered  21  to  27  which are mounted to the upper part of joystick  10 . Out of these seven push buttons, four are used to select a function which requires inputs from the movements of joystick  10 . The other three buttons select functions that do not require input from joystick  10 . Four buttons numbered  21 ,  22 ,  23 , and  24 , are located on the portion of joystick  10  facing the operator (FIG. 2) and are positioned to be easily reachable by the thumb of the right hand of the operator; and three buttons, numbered  25 ,  26 , and  27 , are positioned on the portion of the multifunction joystick  10  facing away from the operator (FIG.  3 ). Buttons  24  and  25  are preferably actuated by the forefingers while button  27  may be actuated by either the forefingers or the thumb. The multifunction joystick  10  also features a knob  28  provided for setting the engine power output which overrides the gas pedal or the directional levers of the snow groomer  60 . Rotating knob  28  counterclockwise or upwards with the right hand thumb increases the engine power output while rotating it clockwise or downwards decreases engine power output. 
     By default, that is when none of the four buttons requiring inputs from the movements of joystick  10  are actuated, joystick  10  controls the movements of front blade  72 . Pushing forward on joystick  10  will actuate hydraulic cylinder  76  and lower front blade  72  while pulling on joystick  10  backward will actuate hydraulic cylinder  76  in the opposite direction and raise front blade  72 . Moving joystick  10  laterally to the right or to the left actuates tilt hydraulic cylinder  77  thereby tilting front blade  72  by raising or lowering the left side of blade  72  which rotates about its attachment point  120  to the single-arm frame  70 . Needless to say, moving joystick  10  to the left side, lowers the left end of blade  72 , and vice versa. 
     Push button  24  is dedicated to blade angle adjustment and pitch angle adjustment. Pressing button  24  and keeping it pressed disables the default function of the multifunction joystick  10 , namely the raising and lowering and the tilting of the front blade  72  by actuating an electro-mechanical valve which cuts off the supply of hydraulic fluid to four-way hydraulic valve of joystick  10 . With button  24  pressed, the movements of joystick  10  will act upon a pair of angler hydraulic cylinders  78 A and  78 B and to pitch hydraulic cylinder  79 . Electrical transducers located at the base  12  of joystick  10  send signals representative of the position of joystick  10  to controller  100  (FIG. 9) which send a signal representative of the bi-axial position of joystick  10  to an electro-mechanical four-way hydraulic valve which controls the supply of hydraulic fluid to hydraulic cylinders  78 A,  78 B and  79 . This transfer of function of the multifunction joystick  10  will hereafter be described in greater detail with reference to FIGS. 6 to  9 . A lateral motion of joystick  10  to the right or to the left, acts upon hydraulic cylinders  78 A and  78 B to adjust the angle of front blade  72  in relation to the longitudinal axis of the snow groomer  60 . The pair of hydraulic cylinders  78 A and  78 B are part of the same hydraulic circuit and work in tandem. When cylinder  78 A extends, cylinder  78 B retracts, thereby creating a rotational displacement of front blade  72  which changes its angle in relation to the longitudinal axis of the snow groomer  60 . Hence when button  24  is maintained actuated, a forward or backward motion of the multifunction joystick  10  actuates pitch hydraulic cylinder  79  which controls the pitch angle of front blade  72 . A forward motion of the multifunction joystick  10  extends pitch hydraulic cylinder  79  and increases the pitch angle of front blade  72  while a rearward motion of the multifunction joystick  10  retracts pitch hydraulic cylinder  79  and decreases the pitch angle of front blade  72 . When button  24  is released, the default mode of the control system is resumed and joystick  10  automatically provides control of the height and tilt angle of front blade  72 . 
     Pressing button  27  and keeping it pressed disables the default mode of the multifunction joystick  10  as previously described. With button  27  pressed, the movements of joystick  10  serve to the adjustment of the two blade wings  71  and  73 . A lateral motion of joystick  10  either retracts or extends hydraulic cylinder  83  thereby opening or closing the right blade wing  73 . A fore-and-aft motion of joystick  10  either retracts or extends hydraulic cylinder  81  thereby opening or closing the left blade wing  71 . Releasing button  27  reinstates the default mode of the control system. 
     The default mode of the control system and related joystick  10  and the modes associated with buttons  24  and  27  enable the operatorto control all the hydraulic cylinders necessary to manipulate and adjust the front blade  72 . 
     In accordance with the present invention, the same control system and its multifunction joystick  10  are used to also control the rear work implements  64 . Pressing button  23  and maintaining it pressed, disables the default rmode of multifunction joystick  10  and transfers the joystick controls to hydraulic cylinder  88  for the fore-and-aft motion of joystick  10  and to hydraulic cylinders  89  for the lateral motion of joystick  10 . A forward motion of joystick  10  retracts the hydraulic cylinder  88  thereby increasing the depth of tilling of tiller  90 . A rearward motion of joystick  10  extends the hydraulic cylinder  88  thereby decreasing the depth of tilling. A lateral motion of joystick  10  extends or retracts the two hydraulic cylinders  89  positioned atop tiller  90  thereby actuating the tiller rear flap  94  upward or downward to adjust the snow chamber  95  by increasing or decreasing its volume. 
     Pressing button  22  and maintaining it pressed, disables the default mode of joystick  10  and transfers the joystick controls to hydraulic cylinder  86  for fore-and-aft movement of joystick  10  and to the diagonally positioned hydraulic cylinder  87  for the lateral movement of joystick  10 . Therefore, in this condition, a lateral movement of joystick  10  actuates hydraulic cylinder  87  and displaces tiller  90  towards the right or the left according to the motion of joystick  10 . A fore-and-aft movement of joystick  10  raises or lowers tiller  90  and the rotation of tiller  90  is automatically stopped. If tiller  90  is not in the central position, when the raising command is given, tiller  90  will be automatically returned to the central position before it is raised. 
     By pressing button  26 , tiller  90  is lowered onto the snow by its own weight by releasing the hydraulic pressure of hydraulic cylinder  86  and tiller  90  assumes a vertical floating mode which simply means that it is resting on the snow and will follow the vertical contours of the terrain. Tiller  90  starts rotating as it reaches the snow. Button  26  does not require to remain pressed and is not associated with any movements of joystick  10 . The vertical floating mode will remain until button  26  is pressed again. 
     As part of the floating mode of tiller  90  previously mentioned, button  21  is provided to control the pressure of tiller  90  on the snow. Button  21  is coupled with an “up-down” selector switch on the dashboard of the snow grooming vehicle and to hydraulic cylinder  86 . If the operator wishes to increase the pressure exerted by tiller  90  on the snow surface, he verifies that the “up-down” selector switch is at the “down” position, and presses button  21  until the pressure has built up sufficiently. Maintaining button  21  pressed builds up pressure in the hydraulic cylinder  86  to pull on tiller  90 . In order to decrease the pressure exerted by tiller  90  on the snow surface, the “up-down” selector switch must be at the “up” position and then button  21  can be pressed to build pressure in hydraulic cylinder  86  in the opposite direction to push on tiller  90  thereby decreasing the pressure exerted by tiller  90  on the snow surface. Button  21  does not disable the default mode of multifunction joystick  10 . 
     A further floating mode of tiller  90  is available. Button  25  is provided to render tiller  90  laterally floating which means that tiller  90  is free to move sideways and follow the various contours of the terrain. Button  25  in effect opens the hydraulic circuit of hydraulic cylinder  87  which enables the double-arm frame  85  to freely move laterally. This function of button  25  will remain “on” until a contradictory command is given. A lateral displacement command of tiller  90  or a raising command of tiller  90  with button  23  will disable the function of button  25 . Button  25  does not disable the default mode of joystick  10 . 
     Multifunction joystick  10  has therefore a default function which consist of raising and lowering front blade  72  and tilting it. Other functions previously described and associated with motion of multifunction joystick  10  could become the default function as may be required for proper functioning of snow groomer  60 . 
     Referring now to FIGS. 6,  7 , and  8  which show joystick  10  with its handle removed from the shank  36 , joystick  10  comprises an annular base  30  adjustably mounted to a fork-like support member  50 . Joystick  10  comprises an hydraulic section  32  and an electrical section  34 . The hydraulic section  32  comprises a standard four-way hydraulic valve (not shown) to which is mounted the shank  36 . The four-way hydraulic valve is actuated when shank  36  is moved from its central neutral position and hydraulic fluid is directed in four possible directions. Hydraulic fluid enters the four-way hydraulic valve through an supply line  38  and exits the four-way hydraulic valve through at least one of four hydraulic lines  37  or through a drain line  39 . When shank  36  remains in its neutral position, hydraulic fluid circulates from the supply line  38  to the drain line  39 . If the shank  36  is moved in any direction, the four-way hydraulic valve directs hydraulic fluid towards an hydraulic cylinder either on the piston side to extend the hydraulic cylinder or on the shaft side to retract the hydraulic cylinder depending on the movement of the shank  36 . In this particular embodiment of the invention, the hydraulic section of multifunction joystick  10  is the default function referred to earlier. 
     The electrical section  34  is mounted above the annular base  30  and comprises, in this example, four electrical transducers  41 ,  42 ,  43 , and  44  positioned radially around shank  36  at equal angular spacing from each other. Shank  36  features a circular conical portion  40  provided to actuate the electrical transducers  41 ,  42 ,  43 , and  44  as soon as shank  36  is moved from its central neutral position. A series of electrical wires  46  link each push buttons  21 ,  22 ,  23 ,  24 ,  25 ,  26 , and  27  to the controller  100  (shown schematically in FIG. 9) so that when one of the push buttons is actuated, the electrical signal produces by this push button is receives as an input by the controller  100 . 
     Electro-mechanical four-way hydraulic valves are used to control the various sets of implement actuators of the front work implement  62  or of the rear work implement  64  of the snow groomer. Controller  100  generates an output signal representative of the position of the multifunction joystick  10  which is sent to a specific electro-mechanical four-way hydraulic valve selected by one of the push buttons  22 ,  23 ,  24  or  27 , which then directs the flow of hydraulic fluid to the specific set of hydraulic cylinders according to this output signal. 
     When any of the buttons  22 ,  23 ,  24  or  27  is pressed, the hydraulic fluid supply to supply line  38  is cut off by an electro-mechanical valve  105  (shown in FIG. 9) located upstream from multifunction joystick  10  thereby disabling the four-way hydraulic valve located in section  32  of multifunction joystick  10 . When any of the buttons  22 ,  23 ,  24  or  27  is pressed, the electric signal produced by the actuation of any of the electrical transducers  41 ,  42 ,  43 , or  44 , is sent to the specific electro-mechanical four-way hydraulic valve associated with the button being pressed. Electrical transducers  41  and  43  will translate fore-and-aft motions of multifunction joystick  10 , electrical transducers  42  and  44  will translate lateral displacement of multifunction joystick  10 . 
     Buttons  21 ,  25 , and  26  are more directly linked to the various electro-mechanical hydraulic valve since the function they perform is not dependant on the electrical transducers  41 ,  42 ,  43 , and  44 . They perform on-off functions of a rear hydraulic circuits and do not disable the default function of the multifunction joystick  10 . 
     FIG. 9 represents a block diagram of a controller  100  adapted to receive signals generated by the electric transducers  41 ,  42 ,  43  and  44  and by buttons  22 ,  23 ,  24  and  27 , and in response thereto generate an output signal which will actuate the various electro-mechanical valves controlling hydraulic cylinders  78  and  79 ,  81  and  83 ,  88  and  89 ,  86  and  87 , and  105 . As soon as one of the buttons  22 ,  23 ,  24 , or  27  is actuated an output signal is sent to electro-mechanical valve  105  to disable the default mode of the multifunction joystick  10 . Pressing one of the buttons  22 ,  23 ,  24  and  27  also selects one of the electro-mechanical valve controlling the hydraulic cylinders  78  and  79 ,  81  and  83 ,  88  and  89 ,  86  and  87 . Controller  100  applies an output signal to the selected electro-mechanical valve which is representative of the electrical signal received from the electrical transducers  41 ,  42 ,  43 ,  44 . For example, when push button  22  is pressed, an input signal  220  is sent to controller  100  which generates an output signal  510  to electro-mechanical valve  105  to disable the default mode. Input signal  220  is further interpreted by controller  100  to generate an output signal  504  representative of any input signals  410 ,  420 ,  430 , and  440  or combinations thereof received from electric transducers  41 ,  42 ,  43  and  44  and to apply output signal  504  to the electro-mechanical valve controlling hydraulic cylinders  86  and  87 . Controller  100  generates an output signal  510  as soon as any one of push buttons  22 ,  23 ,  24 , and  27  is actuated. Controller  100  generates an output signal  503  to the electro-mechanical valve controlling the hydraulic cylinders  88  and  89  from an input signal  230  generated when button  23  is actuated. An output signal  501  to the electro-mechanical valve controlling the hydraulic cylinders  78  and  79  is generated by controller  100  from input signal  240  generated when button  24  is actuated. Controller  100  generates an output signal  502  to the electro-mechanical valve controlling the hydraulic cylinders  81  and  83  from input signal  270  generated when button  27  is actuated. 
     Controller  100  may made of a series of standard relays which are energized upon pressing any one of buttons  22 ,  23 ,  24 , and  27 . These relays respond to the condition of electrical transducers  41 ,  42 ,  43 , and  44  and apply an electrical signal which actuates the various electro-mechanical four-way hydraulic valves. Controller  100  could also be easily achieved using a suitable micro processor relaying the various commands of multifunction joystick  10  to the various electro-mechanical four-way hydraulic valves. 
     In a particular embodiment of the invention, standard electrical transducers are use for translating joystick movement into signals to the electro-mechanical valves but other means are just as suitable. Position sensors, proximity sensors, hall-effect sensors, magnetic switches and so on may be used to perform the same tasks. Also, the electrical transducers are actuated by the circular conical portion  40  of shank  36 . They could easily be positioned underneath a surface projecting from the shank  36  and actuated by this surface when the multifunction joystick  10  is moved in any direction. Other obvious means to produce a usable signal are possible without departing from the spirit of the invention. 
     The above description of preferred embodiments should not be interpreted in a limiting manner since other variations, modifications and refinements are possible within the spirit and scope of the present invention. The scope of the invention is defined in the appended claims and their equivalents.