Techni cal Field

This invention relates to power take-off (PTO) drive lines used on agricultural or industrial tractors to drive implements such as spinner broadcasters _/ mowers, balers etc.

Such PTO drive lines conventionally include a clutch which allows drive to the implement to be disconnected. When the clutch is disengaged drag within the clutch may continue to result in unwanted rotation of the drive line output shaft. As will be appreciated this unwanted output shaft rotation due to clutch drag is of particular concern when the PTO clutch is oil cooled and thus has more internal drag.

Also in some installations the PTO drive line may for example, pass down the centre of a tractor transmission drive shaft and drag may occur between the concentric shafts aga n resulting in unwanted rotation of the PTO drive line output shaft.

Disclosure of the Invention

It is an object of the present invention to provide an improved form of PTO drive line which mitigates the above problem of unwanted rotation of the drive line output shaft.

Thus according to the present invention there is provided a PTO drive line including:-

- a dri e shaft;

- a driven shaft with which an implement may be connected;

- a disengageable PTO clutch for connecting/disconnecting drive between the dr~ive end driven shafts;

- bearing means for supporting the driven shaft for rotation, and

- brake means comprising means to increase the frictional resistance of the bearing means to inhibit any tendency of the driven shaft to rotate when the clutch is disengaged due to drag in the clutch elsewhere in the drive line

As will be appreciated, when the brake .means of the above drive line is engaged the rotation of the driven shaft is inhibited thus mitigating the problem of unwanted drive shaft rotation. For example if the drive line is powering a low inertia implement such as a spinner broadcaster, unwanted rotation of the output shaft would result in unwanted distribution of the material being spread by the broadcaster.

It will be apprec ated "that τtte~bτake means of the present invention is not intended to arrest any high inertia implement which may be connected to the driven shaft.

In a preferred arrangement the bearing means includes a roLLer hearing .with rollers disposed -between inner end αuter cages and means are provided to axially displace one of the cages to increase bearing friction to provide the desired braking effect.

Conveniently the cage may be displaced by a fluid pressure operated piston.

The drive line clutch and brake means may conveniently be controlled by a single lever having three positions, a first position in which the clutch is engaged _/ and the brake is disengaged _/ a second position in which the brake means is engaged and the clutch is disengaged and a third position in which both the clutch and brake means are disengaged.

The clutch and brake means may both be fluid pressure operated _/ for example using solenoid operated fluid flow cont rol va Ives .

Description of the Drawings

One embodiment of the present invention wi ll now be described, by way of example only _/ with reference to the accompanying drawings in which:-

Figure 1 is a diagrammatic _/ partly sectioned _/ side view of a PTO drive line embodying the present invention applied to an agriculture tractor _/ and

Figure 2 is a sectional view of the braking arrangement of Figure 1 on a larger scale.

Best Mode of Carrying out the Invention

Referring to Figure 1 _/ the PTO drive line is disposed in a back axle housing 30 and comprises a drive shaft 10 driven directly from the tractor engine (not shown) and a driven shaft 11 which can be driven from shaft 10 via an hydrauli cal ly engaged PTO clutch C which is oi l-cooled. The supply of oi l coolant to the clutch is controlled in the known manner so that coolant flow is disconnected when the clutch is disengaged. Since the constructional detai ls of clutch C and its associated coolant system form no part of the present invention (and suitable forms wi ll be well known

to persons skilled in the art), no further details of the clutch C will be given in the present application.

Driven shaft 11 carries gear wheels 12 and 13 which are formed as a single casting which is splined onto the end of shaft 11 at 14. The rearward end of shaft 11 is supported from housing 30 via angled roller bearings 15 and 16. Gear wheels 12 and 13 mesh with gears 17 and 18 respecti ely. Gear 17 may be engaged via spline 20 with a PTO output shaft 19 (half of which is shown in Figure 1) while alternatively gear 18 may be engaged via spline 21 with an alternative PTO output shaft 22 (half of which is shown in Figure 1).

Thus, for example, by fitting PTO output shaft 19, drive from shaft 11 is obtained at say 540 r.p.m. via gears 12 and 17 and by fitting PTO output shaft 22 drive from shaft 11 is obtained via gears 13 and 18 at 1000 r.p.m. at the appropriate rated engine speed.

In accordance with the present invention a braking means is provided for ..shaft 11 to .pr&vent natation of this shaft when clutch C is disengaged. This braking arrangement is best seen in Figure 2 and comprises a piston 23 with a lip 24 which bears against the outer cage 16' of bearing 16. Piston 23 is displaceable in a blind bore 25 by admitting pressurised fluid into chamber 26 via connection 27 in housing 30.

A lubrication passageway 28 is also provided in housing 30 which communicates a flow of lubricating oil to an annular groove 40 cut in blind bore 25. Piston lip 24 is proved with a series of drillings 29 through which the Lubricating oil can lubricate bearing 16 (as shown by arrows X3 or can travel down the centre of gearwheels 12 and 13 ⁽ as shown by arrows Y) to lubricate other bearings not shown.

Figure 1 shows one form of hydraulic circuit for operating clutch C and displacing the braking piston 23. This comprises a pivoting lever 31 which can be moved between three positions 31C,31N,31B to control two solenoid operated hydraulic valves 32 and 33 which receive pressured fluid from a pump 34 and direct this fluid to the brake piston 23 and clutch C via lines 35 and 36 respectively. The lever 31 when in positions 31B and 31C operates switches 32' and 33 ' respectively, which in turn energise solenoids 32" and 33" associated with valves 32 and 33.

With the lever 31 in its neutral position 31N shown in Figure 1, neither switch 32' nor switch 33' is operated and valves 32 and 33 are both in the positions shown in Figure 1 where both the brake chamber 26 and the actuator of clutch C are connected with sump 38.

If the tractor operator moves lever 31 to position 31C, switch 33' is operated to energise solenoid 33" and hence displace valve 33 against spring loading 40 to pressurise the actuator of clutch C via Line 36 and thus engage clutch C.

If the tractor operator moves the lever 31 to the position 31B _/ switch 32* is operated to energise solenoid 32" and hence displace valve 32 against spring loading 39 to pressurise chamber 26 and hence move piston 23 to the left _/ as viewed in Figure 2, thus increasing the end loading on the outer cage 16' of bearing 16 and hence generating sufficient friction within bearing 16 to overcome any drag in clutch C and prevent rotation of shaft 11 when clutch C di sengaged .

It will be appreciated that the Lever arrangement described ahøve ensures that the braking, piston, 23 cannot „be actuated unless the clutch C is disengaged _/ since when the Lever 31 operates switch 32' switch 33' is not operated and clutch C is therefore disengaged being connected to sump 38.

The present invention thus provides a simple arrangement for overcoming the above described problem of PTO shaft rotation due to unwanted drag whether this drag occurs in the clutch or in a concentric drive shaft arrangement as referred to above.