Abstract:
A transmission shift lever assembly has a manually operated shift lever that can be moved in a longitudinal direction and in a transverse direction. The shift lever operates upon transmitting elements in order to transmit information to the vehicle gearbox or a gearbox control corresponding to the movement of the lever. The shift lever is coupled to a retainer, and a plurality of arms form four-bar linkages which couple the retainer to housing members so that the lever pivots about a virtual pivot axis which is repositioned remote from the lever, and so that the shift lever moves with little tilting motion.

Description:
FIELD OF THE INVENTION 
     The invention relates to a transmission shift lever assembly which has a lever which can be moved in longitudinal and transverse directions. 
     BACKGROUND OF THE INVENTION 
     It is well known to provide an agricultural tractor with a manually operable transmission shift lever. Such a lever cooperates with transmission elements to transmit information corresponding to the movement of the lever to a vehicle gearbox or to a gearbox control. Such a shift lever can be used to select differing gear ratios or groups of the vehicle gearbox. The shift lever can also be used to engage neutral positions or a park position. 
     Shift levers can be pivoted in two directions about two perpendicular axis along a shift path established by a shift gate. The shift gate may have a double “H” shape, which has a central neutral channel and two or three transverse channels. By moving the shift lever in an end region of one of the transverse channels, a gear ratio or a group of the gearbox can be selected and engaged. With such shift levers, the lever must be tilted during shifting. 
     DE-A-199 22 010 shows a sliding block which is fastened to a shift lever which interacts with quadrants of two transmission elements. By pivoting the shift lever in the longitudinal direction the sliding block can be moved from one quadrant to another quadrant, in order to select one of the quadrants. By pivoting the shift lever in the transverse direction the sliding block acts upon the selected quadrant and shifts the associated transmission element that is connected to the vehicle gearbox, whereby a gear ratio or a group of the vehicle gearbox is engaged. 
     It would be desirable to have a shift lever which is ergonomically designed and which has a compact configuration. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a shift lever which is ergonomically designed and which has a compact configuration. 
     This and other objects are achieved by the present invention wherein a manually operated shift lever or selector lever is movable in a longitudinal direction and a transverse direction to select and engage differing gear ratios and/or gearbox groups and to select a park position. Transmitting levers transmit signals to a vehicle gearbox corresponding to the movement of the lever. The shift lever is coupled to a retainer or a bridge, and a pair of arms form four bar linkage which connects the retainer with a pair of plates. 
     A pair of rods interconnect and extend between the plates The shift lever is pivotally coupled to the rods by pairs of arms which form four-bar linkages. By varying the spacing between the ends of the arms, the pivot center or virtual pivot axis of rotation of the shift lever can be positioned near to or far from the shift lever in either direction, from minus infinity to plus infinity. If the arms are equally long and parallel to each other, then the pivot center will be located at infinity. 
     The virtual pivot axis of the shift lever can be positioned so that the shift lever moves with little or no tilting. Despite a relatively short lever length and relatively small longitudinal movement of the shift lever, comparatively large actuating movements are possible. Therefore, the shift lever assembly can be relatively small and compact and with improved ergonomics. The compact configuration and the reduced lateral movement of the shift lever permits a favorable positioning on a vehicle platform. The lever movements are short and uncomfortable tilting of the hand during shifting is avoided. 
     Preferably, one end of each arm is pivotally coupled to the retainer so that each arm is pivotal in a longitudinal direction with respect to the retainer. Preferably, the other end of each arm is pivotally coupled to one of the rods so that each arm is pivotal in a longitudinal direction with respect to rods and with respect to the housing. All these pivot axes are therefore parallel to each other. 
     Preferably, the shift lever is fixed to a central region of a bridge-shaped retainer, and a pair of arms are coupled to each side of the retainer. The resulting assembly has substantially symmetrical configuration and has an optimum force distribution, so that assembly can be relatively small and compact. A thrust piece is fastened on each side of the retainer. The thrust pieces interact with contact pieces of transmitting levers which are arranged between the thrust pieces. 
     Several transmitting levers are pivoted about a pivot pin which interconnects the housing members, each of which can transmit a corresponding signal to another device, such as the vehicle gearbox. Each of the transmitting levers has a contact piece which have contact surfaces thereon. A thrust piece is carried on by shift lever or by the retainer. By moving the shift lever in the longitudinal direction the thrust piece is brought into a position next to and opposite a contact surface of a selected transmitting lever. When the shift lever is moved in the transverse direction, the thrust piece engages contact surface and pivots the selected transmitting lever out of its neutral position, for example, into a gear ratio position. 
     Preferably, a plurality of transmitting levers are arranged between the two housing plates. For compactness, the transmitting levers are pivoted on a central longitudinal pivot pin which interconnects the housing plates. Each contact piece has two contact surfaces located opposite each other, each of which interacts with an associated thrust piece. 
     Preferably, the transmitting levers are provided with legs which can be connected with linkages which can be coupled to a vehicle gearbox. For example, shifting control cables can be hooked into openings in the legs. Also, sensors or switches may be arranged near to the legs, for transmitting shift signals to a gearbox control. Electrical switches could be integrated into the spacing elements 
     Spacing elements are positioned between each adjacent pairs of transmitting levers. The spacing elements do not pivot with the transmitting levers, but are fixed to the housing members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a perspective view of a shift lever assembly according to the invention. 
     FIG. 2 shows the shift lever assembly according to FIG. 1 in the transverse direction. 
     FIG. 3 shows the shift lever assembly according to FIG. 1 in the longitudinal direction. 
     FIG. 4 shows the scheme of a shift gate. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A shift lever  10  is mounted in the central region of a bridge or retainer  12  between two spaced apart housing plates  14 , 16 . The plates are connected to each other by two spacing rods  18 ,  20 . Four transmitting levers  22 ,  24 ,  26 ,  28  and four sheet metal spacers  30 ,  32 ,  34 ,  36  are stacked in alternating layers between the plates  14 , 16 . The spacers  30 ,  32 ,  34 ,  36  have longitudinal bores  37  that are aligned with each other, through which a pin (not shown) is inserted, in order to fasten the spacers  30 ,  32 ,  34 ,  36  to a housing (not shown). The plates  14 , 16  and the transmitting levers  22 ,  24 ,  26 ,  28  are pivotally supported in bearings, on a longitudinally extending pivot pin  38 , the ends of which are received by the plates  14 ,  16 . Because the plates  14  and  16  are connected to each other by rods  18  and  20 , the plates  14 ,  16  are constrained to pivot together about the longitudinal axis of pin  38 . 
     Arms  40 ,  42 ,  44 ,  46  are coupled between the ends of the bridge  12  and the spacing rods  18 ,  20 . A first end of each arms  40 ,  42 ,  44 ,  46  is pivotally coupled the bridge  12  by pivot pins  48 ,  50 . A second end of each arms  40 ,  42 ,  44 ,  46  is pivotally coupled a corresponding rod  18 ,  20  by pivot pins  52 ,  54 . All the pivot pins  48 ,  50 ,  52 ,  54  have axes which are parallel to each other and transverse to the axes of the rods  18 ,  20 . 
     Each pair of arms  40 ,  42 ,  44 ,  46  form a four-bar linkage together with the bridge  12  and a corresponding one of the rods  18 ,  20 . As best seen in FIG. 2, the two arms  44 ,  46  are not parallel to each other because the spacing between pivot pins  48 ,  50  is greater than the spacing between the pivot pins  52 ,  54 . The longitudinal axes of the two arms  44 ,  46  intersect at a virtual pivot axis (not shown) which is positioned downwardly and beyond the field of view of FIG. 2, and which is below the pin  38 . Upon a movement of the shift lever  10  in the longitudinal direction L, the lever is pivoted about the virtual pivot axis, and because this point is located far away, the lever  10  and the handgrip  56  tilt only slightly. Alternatively, if the arms are parallel to each other, then the shift lever  10  translates without tilting. 
     The transmitting levers  22 ,  24 ,  26 ,  28  are all identical, and each includes a first leg  58  and a second leg  70 . The first leg  58  extends from the pin  38  towards the lever  10 . An end of each first leg  58  includes a contact piece or shift block  60 , which has two contact surfaces  62  located opposite each other. Between each pair of adjacent contact pieces  60  there is a fixed spacer piece  64  connected to a corresponding one of spacers  30 ,  32 ,  34   36 . At each end of the bridge  12  a thrust piece  66 ,  68  is fastened that is oriented in the transverse direction Q. The ends of the thrust pieces  66 ,  68  face towards the contact surfaces  62 . By pivoting the shift lever  10  in the longitudinal direction L, the ends of the two thrust pieces  66 ,  68  can be located next to a selected contact piece  60 . If the shift lever  10  is then pivoted together with plates  14 ,  16  in the transverse direction Q about pin  38 , then one of the thrust pieces  66 ,  68  engages the corresponding contact surface  62  and pivots the associated transmitting lever  22 ,  24 ,  26 ,  28 . 
     The second leg  70  of each transmitting lever  22 ,  24 ,  26 ,  28  is oriented at an angle relative to the first leg  58  and projects laterally away from pin  38 , as best seen in FIG.  3 . Each second leg  70  includes three transverse bores  72 . Control cables (not shown), such as push-pull cables, can be selectively hooked In the bores  72  and connected to a shift mechanism (not shown) of a vehicle gearbox (not shown). Each second leg  70  is rigidly connected to and moves in response to movement of the associated first leg  58 . Upon a transverse deflection of the shift lever  10  the selected first leg  58  is pivoted and thereby pivots the associated second leg  70 . This can cause a push-pull cable (not shown) to transmit the movement of the leg  70  to another device (not shown). 
     Referring now to FIG. 2, a detent arrangement  74  is fastened to plate  14  and includes a ball  76  which is urged by a spring (not shown), against a detent profile  78  fastened to the bridge  12 . The detent profile  78  defines detent positions of the shift lever  10  in which the thrust pieces  66 ,  68  are located opposite a selected contact surface  62 . 
     Referring now to FIG. 4, the shift gate includes a neutral slot or channel N extending in the longitudinal direction from which three transverse channels branch off, each of whose end points corresponds to a group A, B, C, D, E, F of a vehicle gearbox (not shown). A hook-shaped transverse channel branches off from an end region of the neutral channel N, and corresponds to a park position P. The shift gate is mounted to receive the shift lever  10 . 
     The resulting assembly has substantially symmetrical configuration and has an optimum force distribution, so that assembly can be relatively small and compact. 
     While the present invention has been described in conjunction with a specific embodiment, it is understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims. For example, the arms could be arranged four-bar linkages employed for both directions of movement. For another example, a first pair of arms could be arranged for a first direction of movement between the lever retainer and an intermediate housing and a second pair of arms could be arranged for a second direction of movement between the intermediate housing and a final housing fixed to the vehicle. In general, however, a single arm arrangement is sufficient for the longitudinal movement, in which the shift lever is moved in a neutral channel.