Abstract:
A control lever ( 10 ) is provided with a grip ( 12 ), which in a joint ( 14 ) having two degrees of freedom is supported in a housing ( 11 ) and can be switched from an initial position in various directions for activating shift elements ( 18, 19 ), whereby spring elements ( 41, 42 ) are provided for returning the grip ( 12 ) to its initial position, and with a functional device for overcoming a pressure point during the activation and/or for retaining a desired shift position. In order to provide functional devices in greater numbers in a gearshift lever of this type without requiring substantially more installation space or substantially higher costs, provision is made that the functional device is constituted by an electrically controllable hydraulic arrangement ( 35 ), which connects to diametrically opposing shift elements ( 18, 19 ), which can be activated by the grip ( 12 ) in two opposing directions of motion.

Description:
CROSS-REFERENCE 
     Applicant claims priority from German patent application 10 2006 042 629.0-26 filed Sep. 5, 2006. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to a gearshift lever such as are used in construction vehicles. 
     Controls such as gearshift levers are known that have a universal joint and a spring mechanism for returning the grip to the central position. Arranged about said universal joint, generally speaking, are four pin-shaped shift elements which are pressed by a pressure spring against a limit stop and which extend to the pivot point of said universal joint. The limit stop has a shoulder on the pin-shaped shift element which presses against the housing. Mounted on the grip is a plate that extends to the pin-shaped shift elements. If the grip is shifted, the plate presses against a shift element, and a return force is exerted. In order to make additional functions in the controlled device perceptible to the user in a gearshift lever of this type, additional functional devices are realized for sudden changes in the return force (overcoming the pressure point) and/or retaining (locking) the shift element in a predetermined position. In the case of familiar, purely mechanical gearshift levers, functional devices of this type are realized by additional spring-activated pins or by ball thrust bearings. 
     The disadvantage herein is that realizing a pressure point or a locking function purely mechanically is often not possible in unlimited numbers because each additional mechanical element requires installation space and generates higher costs. Furthermore, the service life is limited by the wear and tear on these mechanical elements. Variable engagement of components is hardly possible. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is therefore to provide a control lever of the type cited above in which functional devices can be provided in greater numbers without requiring substantially more installation space or substantially higher costs. 
     As a result of the measures proposed according to the present invention, a gearshift lever can be realized in which functional devices for overcoming a pressure point during activation and/or for retaining a selected shift position can be achieved in a way that reduces wear and tear. 
     According to a first embodiment of the present invention, an electromagnetic, controllable valve that functions to choke and/or block a through flow is provided in a simple and economical manner. 
     In a preferred, second exemplary embodiment of the present invention, a magneto rheological fluid is used that is subject to a magnetic field in a simple manner for choking or blocking flow from one shift element to another. 
     Further details of the invention can be seen from the following description, in which the invention is described and explained in greater detail on the basis of the exemplary embodiment that is depicted in the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal section view of a gearshift lever in accordance with a preferred exemplary embodiment of the present invention in a resting or initial position. 
         FIG. 2  depicts the gearshift lever according to  FIG. 1  in one of many shift positions. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Limited Description Of The Invention 
     The lever  10 , which can be used to control various machinery includes a handgrip  12  that can be pivoted to operate electrical switches at  15 , and to depress selected shift element(s)  18 ,  19  (and two others, not shown). When a shift element is depressed, it depresses a disc  45  against the force of a spring  41 ,  42 , and pushes hydraulic fluid that lies in line  51 , out of the chamber, such as from one sleeve such as  41  to an opposite sleeve  42 . The hydraulic fluid can be magneto rheological fluid whose viscosity can be greatly increased by a magnetic field produced by an electromagnet  55 . If a moderate level magnetic field is applied, it requires more force to pivot the handgrip, while a large force can prevent pivoting. 
     In an example, the lever is used to control an excavator. A circuit that energizes the electromagnet  55  is programmed so when the excavator approaches a wall that should not be damaged, a low level of current is applied to the magnet  55  so the operator feels the increased resistance to pivoting of the hand grip. If the operator operates the handgrip to move the excavator closer to the wall, a higher current is applied to the magnet to more clearly warn the operator. Instead of using magneto rheologic fluid, applicant can place a valve along the connecting line  51 , that has a variable valve opening. When there is a small opening, it requires more force to pivot the handgrip at a reasonable rate. In both of the systems, the operator receives a feedback indicating that the controlled equipment should not move rapidly in a predetermined direction. 
     Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents. 
     More Detailed Description 
     Control lever  10 , which is depicted in the drawing in accordance with a preferred exemplary embodiment and is also known as a joystick, can serve to control construction vehicles and devices, for example. 
     Lever  10  has a housing  11  and a handgrip  12  that can move or swivel in multiple, for example, two degrees of freedom. Housing  11 , which is essentially cylindrical, is centrally located and is provided with a fixed part  13  of a universal joint  14 , whose movable part  15  is arranged on the lower side of a plate  16  of handgrip  12 . Fixed part  13  of universal joint  14  is attached at the upper, open end of a central blind-hole opening  17  formed in housing  11 . Pivoting of the plate in different direction s closes different electrical switches. 
     Lever  10  in the depicted exemplary embodiment is provided with shift elements that are arranged uniformly distributed over the periphery, whereby in the sectional representation only two shift elements  18  and  19  are represented, which are diametrically opposite each other. The two other shift elements are arranged diametrically opposite each other and are rotated 90° with respect to shift elements  18  and  19 . Shift elements  18  and  19 , like the other, undepicted shift elements, are configured in a pin-shaped manner and protrude in the axial direction into part  25  of housing  11  that surrounds blindhole opening  17 , whereby with their upper free ends  22 ,  23  they are situated opposite an annular surface  21  of the lower side of plate  16  of grip  12 , or they contact said annular surface in the initial position ( FIG. 1 ) in an axially biased manner. 
     Starting from its annular surface  24  that is opposite handgrip  12 , housing part  25  is provided with boreholes that extend axially and that, like the shift elements, are arranged uniformly distributed over the periphery, of which only boreholes  26 ,  27  are depicted, which are diametrically opposite each other. In the upper part of boreholes  26 ,  27  bearing sleeves  28 ,  29  are introduced that are axially fixed, protrude beyond annular surface  24 , and are sealingly held against a shoulder of the borehole at their inner ends by a sealing ring  31 . Bearing sleeves  28 ,  29  accommodate shift elements  18 ,  19  so that the latter are axially movable. Shift elements  18 ,  19  are directly guided within segments  32  of boreholes  26 ,  27 , which are connected to said bearing sleeves and are smaller in diameter. Attached thereto and larger in diameter is a hydraulic chamber  33 ,  34  of a hydraulic arrangement  35 . Hydraulic chambers  33 ,  34  are open to boreholes  26 ,  27  at the lower end of housing  11  and are each provided with an interior threaded borehole. 
     Screwed into each hydraulic chamber  33 ,  34  is an elongated sleeve  36 ,  37 , whose interior end  38  in hydraulic chamber  33 ,  34  is smaller in diameter and is surrounded there by a pressure spring  41 ,  42 , which at one end is supported at a shoulder, and at the other end is supported on a disk  45 , which is supported on an annular shoulder between hydraulic chamber  33 ,  34  and borehole part  32 . Engaging in this disk  45  is an end  44  of shift element  18 ,  19  that is smaller in diameter. Therefore, each shift element  18 ,  19  is acted upon by pressure spring  41 ,  42  such that, in the idle or initial position, shift elements  18 ,  19  are pressed against handgrip  12 . 
     Lower ends  39  of elongated sleeves  36 ,  37  protrude from housing  11 , which is supported on a pot-like element  47 , into whose hollow space elongated sleeves  36 ,  37  extend, which are connected to each other by a connecting line  51 . The Figures at least partially also indicate a connecting line  52  which is provided in the corresponding hydraulic chambers between the elongated sleeves that are rotated by 90°. 
     Hydraulic arrangement  35  is filled with a hydraulic fluid within hydraulic chambers  33 ,  34 , and within elongated sleeves  36 ,  37 , and their connecting line  51 . This means that when handgrip  12  is turned in the direction of arrow A in accordance with  FIG. 2 , shift element  18  is axially pressed downwards. Because end  44  of shift element  18  engages in disk  45  and moves along with it, these two elements act as hydraulic pistons in hydraulic chamber  33 , so that, at the other end of hydraulic arrangement  35 , the hydraulic fluid presses through disk  45  onto shift element  19  moving it upwards in the direction of arrow B. 
     In the exemplary embodiment depicted, the hydraulic fluid is a magneto rheological fluid within hydraulic arrangement  35  as well as within the hydraulic arrangement that is rotated 90° with respect to the former. For controlling the flow rate of the hydraulic fluid within hydraulic arrangement  35 , an electromagnet  55  is arranged, for example, on the right-hand side, about lower end  39  of elongated sleeve  37  of hydraulic arrangement  35 , the electromagnet partly or entirely surrounding sleeve  37 ,  36  or another area of hydraulic arrangement  35 . The viscosity of the magneto rheological fluid can be altered by the magnetic field of electromagnet  55 . In other words, the functional device that results from the interaction of the magnetic field that is generated by electromagnet  55  and the magneto rheological fluid within hydraulic arrangement  35  can be controlled such that, during the activation of handgrip  12 , by setting up an electromagnetic field the viscosity can be modified so that an artificial pressure point is produced. A further possibility of electromagnetically influencing the magneto rheological fluid consists in increasing the electromagnetic field so powerfully that the fluid in the area of electromagnet  55  is practically stationary or fixed, which amounts to blocking the flow through hydraulic arrangement  35 . In this way, the selected shift position (for example, in accordance with  FIG. 2 ) is retained, because pressure spring  41 , here shown on the left side, is not capable of pressing shift element  18  into the initial position. Shift elements  18 ,  19  and therefore handgrip  12  can only reach their initial position when the electromagnetic field is no longer present. 
     It is obvious that this can also be achieved in an opposite motion of handgrip  12  or a motion of handgrip  12  that is rotated by 90°, as can be seen from partially depicted electromagnet  56  situated around connecting line  52  or its elongated sleeve. 
     According to one undepicted exemplary embodiment of the present invention, a customary hydraulic fluid in the form of a hydraulic oil is used within hydraulic arrangement  35 . In place of an electromagnet  55 ,  56  in connecting line  51 ,  52 , a throttling valve and/or a blocking valve is provided, which can either generate a pressure point by narrowing the through flow or retain a shift position by blocking the connecting line. 
     Obviously, the depiction in the drawing remains the same in a section that is rotated by 90° from the depicted section with respect to the arrangement of shift elements, hydraulic arrangements, and the like. 
     It is also obvious that, as is not depicted, specific machine and/or vehicle functions are accomplished using signals that are derived from sensor devices and that this also applies to the electrical driving of functional devices such as electromagnets, throttling or blocking valves, and the like.