GB2129074A

GB2129074A - A steering column mounted gear change mechanism

Info

Publication number: GB2129074A
Application number: GB08328500A
Authority: GB
Inventors: Ronald Proctor; William Dixon
Original assignee: Robert Hudson
Current assignee: Robert Hudson
Priority date: 1982-10-26
Filing date: 1983-10-25
Publication date: 1984-05-10
Also published as: GB8328500D0

Abstract

A column gear change mechanism is proposed which has a H-shaped shift pattern, which shift pattern is achieved by making the gear lever (2) pivotable about two axes and having two levers (8, 10) for operating a respective selector fork. Linking means are provided between the gear lever and the levers for effecting movement thereof. One of the links comprises a shaft (4) which is journal led for rotation about its axis which axis defines one of the two pivot axes of the gear lever. The shaft (4) carries one of the levers (8) and has the gear lever (2) secured thereto. Movement of the other lever (10) is controlled by angular movement of a second shaft (6) to which the lever (10) is attached. Said movement being effected by means of a bell- crank (20) and two operating rods (24, 30) which interconnect the gear lever (2) and second shaft (6). In another embodiment (Fig. 3), the lever equivalent to lever (10) is carried by a crank (116) whose movement is effected by a rod linking the gear lever and crank. Spring return means acts on the crank to centre the gear lever when in neutral. <IMAGE>

Description

SPECIFICATION Improvements in or relating to a gear change mechanism The present invention reiates to a gear change mechanism and in particular to a column-type gear change mechanism for use with an agricultural tractor gear box.

A known gear change mechanism of the column-type has a single shaft which is movable axially and pivotable by means of a gear lever attached to its upper end. The lower end of the shaft carries a lever whose end is adapted to engage selectively with first and second selector forks of the gear box. When the gear box, to which the known gear change mechanism is fitted, is in neutral, both the selector forks are in the neutral position and the lever co-operates with the first selector fork. In order to select a gear to transmit drive to the output from the gear box, the first selector fork has to be moved to engage one of two gears and then, the second selector fork has to be moved to engage one of two other gears.In the known mechanism, employing a single shaft, the lever disposed at the end of the shaft has to be physically moved from out of engagement with the first selector fork and into engagement with the second selector fork. When moving from neutral this is achieved by displacing the shaft axially once the first selector fork has been shifted to select one of the two gears. This results in a complicated gear lever movement which is illustrated in Figure 1. The Figure illustrates the position of the gear lever when in the gear indicated and the path that the gear lever has to travel. Movement in the neutral plane controls movement of a first selector fork whilst movement between 1 and 2 or 3 and 4 controls movement of a second selector fork.

Thus it will be seen that when it is required to move between, for example gears 2 and 3, the gear lever first moves said second selector fork into neutral to disengage the gear, the lever is displaced from engagement with said second selector fork into engagement with said first selector fork; this being achieved by downward movement (a) as viewed at the lever, so that the first selector fork can be shifted from engagement with one gear to engagement with the other gear, and then finally the lever is taken out of engagement with said first selector fork and engaged with said second selector fork, whereupon the appropriate one of the two gears may be selected.The complicated nature of the gear lever movement makes the gear changing operation slow and in certain circumstances, the vehicle speed may have dropped by such an amount during the changing operation that a higher gear cannot be pulled.

It is an aim of the present invention to provide a gear change mechanism which has a simpler gear lever movement and which thereby avoids the problems associated with the known mechanism.

According to the present invention then there is provided a column gear change mechanism comprising a gear lever, first and second angularly movable levers adapted to co-operate with respective first and second selectors for gear selection, angular movement of the first and second levers being controlled by movement of the gear lever by way of linking means connecting the gear lever to the first and second levers.

The gear lever has an H-shaped shift pattern, when viewed from the end of the gear lever, with the neutral position in the centre of the H. In the neutral position of the gear lever, both the first and second selectors are moved to their respective neutral positions, and when an output gear is required both the first and second selectors are moved from the neutral positions by the respective shaft levers controlled by the gear lever.

In use, the gear lever is positioned adjacent to the steering wheel.

In one embodiment the levers are carried by respective first and second shafts which are disposed substantially parallel to one another. The gear lever is pivotable about two axes which are normal to one another. The first pivot axis is defined by the first shaft whilst the second pivot axis is defined by a spindle by means of which the gear lever is pivotally secured to that end of the first shaft remote from the first selector. Thus, angular movement of the gear lever about the first pivot axis causes the first selector to be moved.

Movement of the gear lever about the second pivot axis gives rise to angular movement of the second shaft, whereby the second selector is operated. Pivotal movement of the gear lever is translated to angular movement of the second shaft by way of a bell-crank lever and two operating rods which interconnect the gear lever with one arm of the bell-crank, and the other arm of the bell-crank with a lever secured to the second shaft at a position remote from the second selector.

In another embodiment the second lever is carried by a crank which is moveable angularly by a rod or link which is pivotally secured to the gear lever at one end and to the crank at the other. The crank is journalled in a casing which is adapted to be secured to the gear box casing. A spring bias is applied to the crank to return the gear lever to a central position in the gate when in neutral.

By employing a mechanism in accordance with the invention having two shafts, a H-shaped gear lever movement is achieved and gear selection is made easier.

The present invention will now be described further, by way of example only, with reference to the accompanying drawings, in which: Figure 1 illustrates the gear change gate configuration with the prior art single shaft column change; Figure 2 illustrates a simplified perspective view of the the gear change mechanism in accordance with the present invention, and Figure 3 illustrates an alternative embodiment of gear change mechanism in accordance with the present invention.

Referring now to the embodiment of Figure 2 there is shown a gear change mechanism having a gear lever 2 and first and second shafts 4, 6. The shafts 4, 6 are adapted to operate first and second selector levers (not illustrated) of the gear box, for which operation each shaft has a respective lever 8, 10 secured to the end thereof. The first and second shafts 4, 6 are disposed generally parallel to one another and are angularly moveable such that the ends of the levers 8, 10 describe an arcuate movement.

The gear lever 2 is secured to the first shaft 4 at a position remote from the lever 8, i.e. at the upper end of the shaft 4. The shaft 4 defines a first pivot axis for the gear lever. The gear lever 2 is secured to the first shaft 4 so that it is angularly moveable with respect thereto about a spindle 12 which defines a second pivot axis for the gear lever. The first and second pivot axes of the gear lever are normal to one another. The shaft 4 is journalled for rotation in a mounting block 14 which is secured to any convenient member, but preferably the steering column casing. Journals are provided for locating the shaft 6 for rotation.

A bell-crank 16 is journalled about a pin 18 which is secured to any convenient member, but preferably the steering column. The second shaft 6 carries a gear selector arm 22 which is connected to one arm 20 of the bell-crank 16 by an operating rod 24. The connection with the arm 20 and the arm 22 is by way of a respective ball and socket joint which ensures play-free movement.

The gear lever 2 carries an extension 26 which is connected to the other arm 28 of the bell-crank 1 6 by an operating rod 30. A respective ball and socket joint connects each end of the operating rod 30 to the gear lever and bellcrank.

Thus it will be seen that movement of the gear lever 2 about the first axis causes angular movement of the selector operating lever 8 and movement of the gear lever about the second pivot axis causes angular movement of the selector operating lever 1 0. It will be seen that movement about the second axis corresponds to movement of the gear lever between the two parallel limbs of the H-shaped gate.

The gear change mechanism according to the invention is intended for use with a gear box in which selecting a gear requires two sets of gears in the box to be engaged. That is to say, both selectors have to be actuated. The gear change mechanism illustrated in Figure 2 is shown in the neutral position. An example of the mode of operation for the embodiment of Figure 2 will be described below. When it is required to select say 1 st gear, the lever is first moved from the neutral position (illustrated) toward the 1-2 limb of the change gate. This downward pivotal movement of the gear lever 2 about the second pivot axis 12 causes the second shaft 6 to be displaced angularly by way of the operating rods 24, 30 and the bell-crank 1 6. Thus, the lever 10 is moved toward A to select one of the two gears controlled by the selector operated.Next, the gear lever 2 is moved to the position 1 whereupon the first shaft 4 is rotated and the lever 8 moved to position C to engage one of the two gears controlled by the first selector. A change to position 2 merely moves the lever 8 to position D to engage the other of the two gears controlled by the first selector.

When it is required to move between say position 2 and position 3 both selectors have to be moved at least once. Movement of the gear lever from position 2 to x causes the lever 8 to move from D to neutral, and movement of the gear lever between x and y causes the lever 10 to be moved from position A, through neutral to position B in which the other of the two gears controlled by the second selector is engaged. The gear lever may then be moved from y to 3 thereby moving the lever 8 to position C. Movement of the gear lever from position 3 to position 4 moves the lever 8 from Cto D.

Another embodiment of gear change mechanism is described with reference to Figure 3. The mechanism comprises a gear lever 102 which is pivotable about first and second axes.

The first axis is defined by a first shaft 104 to which the gear lever is connected and which is journalled for rotation about its longitudinal axis as is the corresponding first shaft 4 of the Figure 2 embodiment. Similarly the first shaft 104 carries a lever 108 referred to as the first lever for engagement with one of the selector forks in the gear box. The gear lever 1 02 is pivotable with respect to the first shaft 104 about an axis 112 which defines the second axis and which is perpendicuiar to the axis of the first shaft.On the opposite side of the pivot axis 112 from the connection of the shaft 104, a connecting link 106 is secured to the gear lever, and the other end of the link is secured to one arm 128 of a crank 116 which is journalled for angular movement in a casing 11 7 which is adapted to be secured to the casing of the gear box. The axis of the crank is disposed substantially perpendicular to the first and second axis. An arm 1 20 is secured to the crank 11 6 at approximately 90O to the arm 128 and carries a lever 110, referred to as the second lever, which is arranged to cooperate with the other gear box selector fork. The crank 11 6 carries a further arm 121 disposed parallel to the arm 128 and extending in the same direction.The arm 1 21 carries a link 123 which is slidably received in brackets 125, 127 carried by the casing 117. The link carries two springs 129, 131, which serves as return springs to return the linkage to a central position when in neutral. The springs abut the bracket 125 and respective abutments carried on the link 123, which abutments may be adjustable to vary the spring rate. The spring 131 may have a higher rate than the spring 129.

The mechanism operates in a similar manner to that described with reference to Fig. 2 but the first/second and third/fourth branches of the gate are transposed to a preferred arrangement in which the first/second branch is uppermost and closest to the steering wheel.

Movement of the gear lever from the neutral position towards the first/second branch causes the lever to pivot about the second axis 112 which is accompanied by movement of the link 106 and angular movement of the crank 116 such that the lever 110 moves to position A. Subsequent movement of the lever from Y to first rotates the shaft 104 and moves the lever 108 to C. Thus, first gear is engaged. Movement of the lever through the gate is accompanied by corresponding movement of either lever 108 or both levers 108 and 110. The springs return the levers to the illustrated positions when the gear lever is moved to the neutral plane of the gate.

Claims

1. A column gear change mechanism comprising a gear lever, first and second angularly moveable levers adapted to cooperate with respective first and second selectors for gear selection, angular movement of the first and second levers being controlled by movement of the gear lever by way of linking means connecting the gear lever to the first and second levers.

2. A column gear change mechanism as claimed in claim 1 in which the gear lever is pivotable about first and second axes which are disposed substantially perpendicularly with respect to one another, and the first axis is defined by a first shaft which is journalled for rotation about its axis and to which the gear lever is secured, the first lever is secured to the first shaft for angular movement therewith.

3. A column gear change mechanism as claimed in claim 1 or 2 in which the second lever is carried on the arm of a crank, which crank is moveable by a link which connects the crank to the gear lever.

4. A column gear change mechanism as claimed in claim 3 in which the crank is journalled for rotation in a casing which is adapted to be secured to the gear box.

5. A column gear change mechanism as claimed in claim 3 or 4 in which the crank is subject to spring force to bias the gear lever into a central position when in neutral.

6. A column gear change mechanism as claimed in claim 5 in which the spring force is generated by two springs which take their abutment at one end on the casing and at their other ends on a link secured to an arm of the crank.

7. A column gear change mechanism as claimed in claim 1 or 2 in which the second lever is secured to a second shaft which is journalled for angular movement about its axis and which angular movement is effected by means of a bellcrank and two operating rods which interconnect the gear lever and the second shaft whereby pivotal movement of the gear lever about the second axis effects angular movement of the second lever.

8. A column gear change mechanism constructed and arranged substantially as hereinbefore described with reference to and as illustrated in Figs. 2 or 3 of the accompanying drawings.

9. A column gear change mechanism adapted to operate substantially as hereinbefore described with reference to and as illustrated in Figs. 2 and 3 of the accompanying drawings.