Vehicle PTO drive line system

Abstract

A vehicle PTO drive line system has an output shaft (20) with a socket (21) to drivingly receive a removable PTO stub shaft (16). The stub shaft is retained in the socket by a retention disc (23) mounted about the stub shaft. The retention disc (23) is rotationally driven by the output shaft and is operative to axially locate the stub shaft within the socket in an operative position. The retention disc (23) is held in the operative position by a fastener (32) detachably mounted on the output shaft. The retention disc (23) cooperates with a sensor (25, FIG. 3) to generate a signal indicative of a rated speed of the stub shaft. The system may comprise several PTO stub shafts (16, 16') interchangeable mountable to the output shaft, each designed to be used at a different rated speed. Each stub shaft (16, 16') is mounted using a corresponding retention disc (23, 23') configured to generate a signal indicative of the rated speed of the stub shaft.

Description

TITLEVEHICLE PTO DRIVE LINE SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not applicable.FIELD

[0002] Embodiments of the present disclosure relate generally to a vehicle Power Take- Off (PTO) drive line system in which a PTO stub shaft projects from a vehicle, such as a tractor, to drive implements. Typically, the PTO stub shaft projects from the front or rear of the vehicle to drive implements located in front of or behind the vehicle.BACKGROUND

[0003] Utility vehicles such as agricultural tractors are often provided with a PTO drive line system having a stub shaft with driving splines which can be drivingly coupled to an implement, often through a PTO shaft. Agricultural implements have been developed which are designed to be driven at one of several standardised rotational speeds and power. Standard speeds commonly in use at present include 540 r.p.m, 1000 r.p.m, and 1,300 r.p.m. To ensure that an implement is not driven at the wrong speed and / or power, a standardised range of PTO stub shafts have been developed with different diameters and / or driving spline arrangements. ISO 500-1 , for example, defines 4 types of PTO, each having a rated speed (rotational frequency) the stub shaft is designed to operate at, or at least not above. The stub shafts for each of the four types have different configurations:• PTO Type 1 stub shaft has six straight driving splines, a nominal diameter of 35mm, a nominal rated speed of 540r.p.m, and a recommended PTO power of less than 65 kW.• PTO Type 2 stub shaft has twenty-one involute driving splines, a nominal diameter of 35mm, a nominal rated speed of 1000 r.p.m, and a recommended PTO power of less than 130 kW.• PTO Type 3 stub shaft has twenty involute driving splines, a nominal diameter of 45mm, a nominal rated speed of 1000 r.p.m, and a recommended PTO power of less than 300 kW.• PTO Type 4 stub shaft has twenty-two involute driving splines, a nominal diameter of 57.5 mm, a nominal rated speed of 1300 r.p.m, and a recommended PTO power of less than 450 kW.

[0004] Implements to be driven from a PTO have a drive coupling configured to engage a stub shaft for the PTO type they are designed to be driven by. Typically, implements, or a PTO shaft for connection therewith, are provided with a splined drive socket configured to receive the correct PTO stub shaft type. This helps to ensure that implements are driven at the correct operating speed and / or PTO power ranges.

[0005] Often it is desirable for a vehicle to be capable of selectively providing a PTO output at more than one of the rated speeds so that the vehicle can be used with a broader range of implements. To allow for this, it is known to provide a PTO drive line system having two output shafts, each being rotated at one of the rated speeds and to each of which is mounted the appropriate PTO stub shaft for the speed rating. US patent No. 3513712 to ALLIS CHALMERS MFG CO, discloses a modification in which a single reversable stub shaft having two differently configured sets of driving splines projecting either side of central flange. The central flange is arranged so that it can be bolted to either output shaft using different bolt patterns for each so that it can only be attached to an output shaft with the correct drive spline for the rotational speed of the output shaft projecting outwardly for connection with an implement. However, many vehicles do not have the space required to accommodate two PTO output shafts and the reversable stub shaft is expensive to manufacture and difficult to assemble.

[0006] To address this issue, PTO drive line systems have been developed in which a single PTO output shaft can be selectively driven at more than one of the standard rated speeds. Such a PTO drive line may have a speed change gearbox. Different PTO stub shafts corresponding to the selectable rotational speeds are detachably and interchangeably mountable to the output shaft. This arrangement requires a user to attach the appropriate PTO stub shaft for theimplement to be driven and to select the correct rated speed for the implement and stub shaft. WO 2010 / 026183 A2 to AGCO SA and CLAAS Tractors SAS discloses one such arrangement in which two different stub shafts are interchangeably mountable in a socket defined in the PTO output shaft. The stub shafts are locked in the socket by spring biased locking balls mounted in radially extending bores in the output shaft and which engage in an annular groove formed in each stub shaft. The locking balls are held in a locking position by an actuating sleeve which is moved to different positions to lock each of the stub shafts to the output shaft.

[0007] Where the PTO output can be selectively driven at different speeds, it is generally a requirement that the system includes measures to ensure that the PTO output shaft is not accidentally driven at the wrong speed for the stub shaft and implement attached. The system should aim to prevent the PTO output shaft being driven at a higher rotational speed than the rated speed of the implement and stub shaft. This is to ensure, for example, that a Type 1 stub shaft and implement are not operated with a speed higher than 540 r.p.m.. WO 2010 / 026183 A2 addresses this by providing first and second PTO speed indicating formations on the sleeve. Depending on which stub shaft is fitted, one or other of the speed indicating formations align with a sensor to generate a signal which is indicative of the rated speed for the stub shaft fitted (e.g., of the type of stub shaft). This signal is provided to a controller which also monitors the rotational speed of the output shaft. In the event the controller determines that the output shaft is being driven at a rotational speed higher than the rated speed of the detected stub shaft, a warning can be provided to a user.

[0008] Whilst the PTO drive line of WO 2010 / 026183 A2 works well, the mechanism for attaching the stub shafts is relatively complex and can only distinguish between two different types of stub shaft.

[0009] It is an object of the present invention to provide an improved form of PTO drive line system which has easily interchangeable stub shafts designed to be driven at different rated speeds and / or PTO power ranges and which provides an indication of the rated speed / type of the stub shaft fitted.BRIEF SUMMARY

[0010] In an aspect of the invention, there is provided a PTO drive line system having an output shaft with a socket arranged to drivingly receive a removable PTO stub shaft, the stub shaft being retained in the socket by a retention disc mounted to, and extending radially outwardly from, the stub shaft, the retention disc being rotationally driven by the output shaft and operative to axially locate the stub shaft within the socket when in an operative position relative to the output shaft, the retention disc being held in the operative position by a fastener detachably mounted on the output shaft, the retention disc configured for cooperation with a sensor located adjacent the retention disc when in the operative position to generate a signal indicative of a rated speed of the stub shaft in use.

[0011] The retention disc provides a simple method of axially locating the stub shaft which is easy to manufacture and assemble. The system also provides a feedback signal indicative of the type of PTO shaft fitted to allow for automatic monitoring to ensure a PTO stub shaft is not operated above its rated sped.

[0012] The retention disc may be driven from the output shaft by circumferentially spaced axially extending drive formations on the output shaft which extend through circumferentially spaced apertures in the retention disc.

[0013] In an embodiment, the system comprises a plurality of interchangeable removable PTO stub shafts, each being drivingly receivable in the socket, and a plurality of retention discs, wherein at least two of the PTO stub shafts have different rated speeds, each PTO stub shaft being retained in the socket by a corresponding retention disc configured to generate a signal indicative of the rated speed of that stub shaft. In embodiments the retention discs are separably mountable to corresponding stub shafts and the system may be configured such that for each stub shaft, only a corresponding retention disc configured to generate a signal indicative of the correct rated speed for that stub shaft can be mounted to the stub shaft in the operative position.

[0014] In an embodiment, each retention disc has a central aperture dimensioned to receive an outer circumferential surface region of a corresponding stub shaft when in the operative position, the retention disc engaging with a radially outwardly extending abutment onthe stub shaft in the operative position to locate the stub shaft axially in the socket, the arrangement being such that for each stub shaft, only a corresponding retention disc having the correctly dimensioned central aperture and the correct thickness can be mounted in the operative position.

[0015] In an embodiment, the at least two stub shafts with different rated speeds have outer circumferential surface regions of differing diameters and are configured such that the axial spacing between the radially extending abutment and the axial position of the fastener when mounted to the output shaft is different, each retention disc being dimensioned for use only with a corresponding stub shaft having a rated speed corresponding to the signal generated by that retention disc.

[0016] In an alternative embodiment, each retention disc has a central aperture which locates about an outer circumferential surface region of a corresponding stub shaft when in the operative position, the stub shafts having circumferentially spaced recesses in their outer circumferential surface regions, the central apertures of the retention discs being provided with corresponding radially inwardly extending and circumferentially spaced protrusions for location in the recesses, the circumferential spacing of the recesses and projections being different for stub shafts of different rated speeds and their corresponding retention discs, such that only a corresponding retention disc configured to generate a signal indicative of the correct rated speed can be mounted to each stub shaft.

[0017] In a further alternative embodiment, each retention disc has a central aperture which locates about an outer circumferential surface region of a corresponding stub shaft when in the operative position, the stub shafts each having external driving splines axially outboard of the circumferential surface region, the driving splines having an outer diameter larger than that of the circumferential surface region, stub shafts with different rated speeds having driving splines comprising a different configuration of driving splines (e.g., number and / or type of splines), the central apertures of the retention discs being provided with corresponding spline formations designed to slide axially along the external driving splines of corresponding stub shafts onto the circumferential surface region, the arrangement configured such that theretention discs can be rotated about their corresponding stub shaft when located about the circumferential surface region.

[0018] The output shaft may be assembled in a chamber of the drive line and the retention disc may be operative to close an axially outer end region of the chamber, at least partially, when in the operative position.

[0019] In an embodiment, the retention disc and stub shaft are undetachably (e.g. without damaging either the disc or shaft) connected to each other prior to assembly. The retention disc may be welded to the stub shaft.

[0020] In an embodiment, toothed indicating formations are provided around the outer periphery of the retention disc for cooperation with the sensor. The number and spacing of the toothed indicating formations determining the signal generated by the sensor. The toothed indicating formations of the retention discs may be encased in a ring of polymeric material, and wherein, optionally, the ring is injection moulded onto the retention disc. The protective ring may be provided with a visual identifier (e.g., colour coding, text, and / or symbol) indicative of the rated speed the signal generated by the retention disc in use is indicative of and hence the rated speed of the stub shaft to which the retention disc is intended to be assembled to.

[0021] In an embodiment, the detachable fastening comprises a circlip which engages in a groove formed in an outer circumferential surface of the output shaft axially outboard of the retention disc when the retention disc is in the operative position and wherein, optionally, where the output shaft is provided with circumferentially spaced axially extending drive formations, the circlip may engage in a groove formed in outer circumferential surface regions of the drive formations axially outboard of the retention disc when the retention disc is in the operative position.

[0022] In an embodiment, the detachable fastening comprises a locking nut and locking washer which are mounted on a threaded potion of the output shaft axially outboard of the retention disc when the retention disc is in the operative position and wherein, optionally, where the output shaft is provided with circumferentially spaced axially extending drive formations the locking nut and locking washer may be mounted on a threaded portions of the drive formations axially outboard of the retention disc when the retention disc is in the operative position.

[0023] The vehicle may be an agricultural tractor.

[0024] Within the scope of this application, it should be understood that the various aspects, embodiments, examples and alternatives set out herein, and individual features thereof may be taken independently or in any possible and compatible combination. Where features are described with reference to a single aspect or embodiment, it should be understood that such features are applicable to all aspects and embodiments unless otherwise stated or where such features are incompatible.BRIEF DESCRIPTION OF THE DRAWINGS

[0025] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0026] FIG. 1 shows a diagrammatic side view of a tractor having a rear PTO driveline system with an interchangeable PTO stub shaft arrangement;

[0027] FIG. 2 shows a vertical longitudinal section through part of the PTO drive line system fitted to the tractor shown in FIG .1;

[0028] FIG. 3 shows on a larger scale view of part of FIG.2;

[0029] FIG. 4 shows a retention disc for use with a corresponding PTO stub shaft having a rated speed of 1000 r.p.m.in a PTO drive line system in accordance with the present invention;

[0030] FIG. 5 shows a section on line C-C of FIG.4;

[0031] FIG. 6 shows a retention disc for use with a corresponding PTO stub shaft having a rated speed 540 r.p.m.in a PTO drive line system in accordance with the present invention;

[0032] FIG. 7 shows on a larger scale a section through a retention disc locked in its operating position holding a stub shaft in a socket of a PTO output shaft in a PTO drive line system in accordance with the present invention;

[0033] FIG. 8 shows a perspective view illustrating diagrammatically how two different stub shafts having rated speeds of 540 r.p.m. and 1000 r.p.m. are locked in the socket of a PTO output shaft by a circlip in a PTO drive line system in accordance with the present invention;

[0034] FIG. 9 shows a retention disc which uses an alternative categorizing formation between the retention disc and a corresponding stub shaft;

[0035] FIG. 10 is a fragmentary view of the area Y of FIG.9;

[0036] FIG. 11 is a section on the line D-D of FIG.9;

[0037] FIG. 12 shows a retention disc which uses a further alternative categorizing formation between the retention disc and a corresponding stub shaft;

[0038] FIG. 13 is a section on the line E-E of FIG.12, and

[0039] FIG. 14 and 15 show details of an alternative detachable fastening in the form of a locking nut and washer.DETAILED DESCRIPTION

[0040] The illustrations presented herein are not actual views of any machine, sensor, or portion thereof, but are merely idealized representations that are employed to describe example embodiments of the present disclosure. Additionally, elements common between figures may retain the same numerical designation.

[0041] The following description provides specific details of embodiments of the present disclosure to provide a thorough description thereof. However, a person of ordinary skill in the art will understand that the embodiments of the disclosure may be practiced without employing many such specific details. Indeed, the embodiments of the disclosure may be practiced in conjunction with conventional techniques employed in the industry. In addition, the description provided below does not include all elements to form a complete structure or assembly. Only those process acts and structures necessary to understand the embodiments of the disclosure are described in detail below. Additional conventional acts and structures may beused. The drawings accompanying the application are for illustrative purposes only and are thus not drawn to scale.

[0042] As used herein, the terms "comprising," "including," "containing," "characterized by," and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps, but also include the more restrictive terms "consisting of" and "consisting essentially of" and grammatical equivalents thereof.

[0043] As used herein, the term "may" with respect to a material, structure, feature, or method act indicates that such is contemplated for use in implementation of an embodiment of the disclosure, and such term is used in preference to the more restrictive term "is" so as to avoid any implication that other, compatible materials, structures, features, and methods usable in combination therewith should or must be excluded.

[0044] As used herein, the term "configured" refers to a size, shape, material composition, and arrangement of one or more of at least one structure and at least one apparatus facilitating operation of one or more of the structure and the apparatus in a predetermined way.

[0045] As used herein, the singular forms following "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0046] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0047] As used herein, spatially relative terms, such as "beneath," "below," "lower," "bottom," "above," "upper," "top," "front," "rear," "left," "right," and the like, may be used for ease of description to describe one element's or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Unless otherwise specified, the spatially relative terms are intended to encompass different orientations of the materials in addition to the orientation depicted in the figures.

[0048] As used herein, the term "substantially" in reference to a given parameter, property, or condition means and includes to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a degree of variance,such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least 90.0% met, at least 95.0% met, at least 99.0% met, or even at least 99.9% met.

[0049] As used herein, the term "about" used in reference to a given parameter is inclusive of the stated value and has the meaning dictated by the context (e.g., it includes the degree of error associated with measurement of the given parameter).

[0050] Referring to the drawings, a tractor 10 is shown diagrammatically in FIG.l. The tractor has wheels 11 and an engine 12 which provides drive to a back axle housing 13 via an interconnecting clutch and / or transmission housing 14. The central portion of the back axle housing 13 includes a PTO drive line system 15 from which external drive is provided via a PTO stub shaft 16.

[0051] The PTO drive line 15 is driven from the engine 12 via a shaft 17 (see FIG.2) which provides a driving connection to a PTO output shaft 20 via gears 18, 19, and 101. PTO output shaft 20 includes a socket 21 in which an operative stub shaft 16 is secured as will be described below.

[0052] The output shaft 20 can be driven at two different speeds. In the present embodiment, the output shaft can be driven at 540 r.p.m via either of gears 18 or 19. Gear 18 is engaged by moving coupling collar 22 to the left (as shown) from a central position to couple output shaft 20 to gear 18 or gear 19 can be engaged by moving coupling collar 22 to the right (as shown) from the central position to couple output shaft to shaft 17 to gear 19. Engagement of either gear 18 or gear 19 drives the output shaft at 540 r.p.m. However, gears 18 and 19 provide different ratios so that engagement of gear 18 enables the output shaft 20 to be driven 540 r.p.m with the shaft 17 (and hence the engine) rotating at a lower speed than that required when gear 19 is engaged. Engagement of gear 18 therefore enables the PTO to be operated at 540 r.p.m in a more fuel-efficient manner. This is typically designated as PTO speed 540E to distinguish over PTO speed 540 obtained when gear 19 is engaged. Both PTO speeds 540 and 540E require the use of a PTO shaft of Type 1 (according to ISO 500-1) and can be regarded as the same PTO rated speed of 540 for the purposes of the present invention.

[0053] The output shaft 20 can be driven at lOOOr.p.m (known as PTO rated speed 1000) by moving coupling collar 102 to the left to connect output shaft 20 to shaft 17 via gear 101. In this mode of operation, coupling collar 22 must be brought in the mid position shown in FIG.2 to disengage driving connection of gears 18 and 19 with output shaft 20. A PTO rated speed of 1000 r.p.m. requires the use of a PTO shaft of Type 2 (according to ISO 500-1).

[0054] Drive passes from output shaft 20 to the stub shaft 16 held in socket 21 via engaging splines 21a formed in socket 21 and driven splines 16a formed on each respective stub shaft 16. In the embodiment shown in FIG. 2, the operative stub shaft 16 is a Type 2 stub shaft having a rated speed of 1000 r.p.m.

[0055] FIG. 3 shows stub shaft 16 held in the socket 21 of output shaft 20 by a retention disc 23 which rotates with the output shaft 20 and the stub shaft 16. The retention disc 23 is provided with a stub shaft type indicating formation, which in the present case is in the form of teeth 24 spaced around its outer periphery (see FIGs. 4 and 5). These teeth 24 cooperate with an adjacent first Hall effect sensor 25 as the retention disc is rotated to provide a PTO stub shaft signal (in form of evenly spaced pulses) to a PTO control system to identify the type of PTO stub shaft held in the socket 21, e.g., Type 2 in this case. The number, size and spacing of the teeth 24 on the retention disc results in a pulsed signal being generated by the Hall sensor when the retention disc is rotated. This signal can be identified by the control system as being indicative of the type of PTO shaft and / or the rated speed of the PTO stub shaft mounted in the output shaft 21. To this end, a retention disc 23 can only be used in the system with a stub shaft 16 having a rated speed which corresponds to the signal generated by the retention disc 16. Where a retention disc 23 and stub shaft 16 are matched in this way, they are referred to herein as "corresponding". In the arrangement shown in FIG. 2, where the PTO stub shaft is a Type 2 with a designated speed of 1000 r.p.m, the system will recognise the signal generated by the corresponding retention disc 23 as being indicative of a Type 2 stub shaft and / or a rated speed of 1000 r.p.m. For use with a different stub shaft for a different PTO Type / rated speed (say a Type 1 PTO stub shaft) a different number and / or spacing of teeth 24' can be provided to generate a differently pulsed signal in cooperation with the Hall sensor in use and which is associated by the control system with that type of PTO stub shaft / rated speed. In the present embodiment, theretention disc 23 for use with a Type 2 stub shaft 16 has 24 teeth evenly spaced about is periphery. As discussed below with reference to FIG. 6, a retention disc 23' for use with a Type 1 stub shaft having a rated speed of 540 may be provided with four teeth, for example. It should be appreciated that number, size and spacing of the teeth 24, 24' can be varied provided that the retention discs 23, 23' generate a uniquely identifiable signal which can be associated by the system with a particular Type and / or rated speed of a PTO stub shaft to which it is mounted.

[0056] In an embodiment, the teeth 24, 24' are encased in a protective ring 24a of plastics or similar material for safety reasons and to help prevent the ingress of dirt etc into the drive line. The protective ring 24a is preferably manufactured by extrusion-coating with plastic wherein the retention disc 23, 23' is inserted into a moulding machine with the plastic mould being injected around teeth 24, 24'. Alternatively, protective ring 24a may be a separately moulded part being clipped or clued to retention disc 23, 23'. Regardless of how it is manufactured, protective ring 24a may be colour coded or provided with text and / or one or more symbols to visually indicate the type / rated speed of PTO stub shaft that the retention disc is intended to be used with. In this way, the protective ring 24a can provide visual indication of the PTO stub shaft type held in the socket 21.

[0057] In an alternative embodiment, Hall sensor 25 may be replaced with a sensor capable of determining a distance, the teeth 24, 24' may be omitted and retention disc 23, 23' provided with dedicated diameter unique for a certain PTO stub shaft type / rated speed. Each PTO stub shaft is used with a corresponding retention disc having a predetermined diameter which correlates to its Type and / or rated speed.

[0058] With reference to FIG.2, a second Hall effect sensor 105 is provided to cooperate with cut-outs (not shown) in gear 19 which is always driven by shaft 17 to derive the current PTO speed. By comparison of the signals derived from first and second Hall sensors 25, 105 the control system can determine whether the actual PTO rotational speed exceeds the rated speed of the operative stub shaft 16. If the actual PTO rotational speed is higher than the rated speed of the operative PTO stub shaft 16, the control system may generate a warning and / or stops the PTO operation by e.g., disengaging a PTO drive clutch (not shown) so that the shaft 17 is not driven. In use where the retention disc 23, 23' is configured to generate a pulsed signal, the controlsystem can use the signal from second Hall effect sensor 105 to determine the rotational speed of the output shaft, and hence the retention disc, and count the number of pulses per revolution generated by the retention disc in cooperation with the first Hall effect sensor to identify the Type and / or rated speed of the operative stub shaft.

[0059] The retention disc 23 is driven by the output shaft 20 via circumferentially spaced axially extending drive formations 26 on the output shaft which extend through circumferentially spaced apertures 27 surrounding a central aperture 28 of the retention disc through which the stub shaft 16 passes (see FIGs. 3 and 4).

[0060] The retention disc 23 axially locates the stub shaft 16 within the socket 21 by engagement of one side 29 of the retention disc with a first radially outwardly extending abutment 30 on the stub shaft and on the other side 31 of the retention disc by engagement with a detachable fastening in the form of a circlip 32, which engages a second radially outwardly extending abutment on the axially extending drive formations 26 of output shaft 20. To this end, the circlip 32 is engaged in a circumferential groove defined in the radially outer surfaces of the drive formations 26.

[0061] FIG. 7 shows retention disc 23 designed to be fitted to a Type 2 stub shaft 16 with a rated speed of 1000 r.p.m. This retention disc 23 has a thickness of T1 with the distance between abutments 30 and 33 set to receive the circlip 32 and retention disc 23. The central aperture 28 is sized to receive the diameter DI of a circumferential surface region of the stub shaft 16 about which the retention disc 16 locates when in its operative position.

[0062] An alternative retention disc 23', shown in FIG.6, is provided for use with a Type 1 stub shaft 16' having a rated speed of 540 r.p.m (540 or 540E). Retention disc 23' has four circumferentially spaced teeth 24' which cooperate with sensor 25 to provide a signal indicative that a Type 1 stub shaft 16' with a rated speed of 540 / 540E is fitted. Retention disc 23' has apertures 27' for receiving the drive formations 26 of the output shaft and a smaller diameter central aperture 28' which is sized to receive a smaller diameter D2 (see FIG.5) circumferential surface region of the stub shaft 16'. Retention disc 23' has a thickness T2 which is thinner than retention disc 23 by thickness T3 (see dotted detail in FIG.7). The abutment 30' on the stub shaft16' is positioned so that the distance between abutments 30 and 33' is set to receive the thinner retention disc 23'.

[0063] The 540 r.p.m. retention disc 23' with its smaller diameter central aperture 28'cannot fit on the 1000 r.p.m. stub shaft 16 which has a larger diameter circumferential surface region DI. Whilst the 1000 r.p.m. retention disc 23 with its larger diameter central aperture 28 can fit on the smaller diameter D2 of stub shaft 16', the circlip 32 cannot be engaged since the thicker retention disc 23 will not fit between the closer abutments 33 and 30'. Looked at another way, the axial spacing between the circlip 32 when attached to the output shaft and the first radial abutment 30, 30' is set to receive a retention disc 23, 23' of the appropriate thickness Tl, T2.

[0064] Thus, the retention discs 23 and 23' can only be fitted to the correct, corresponding stub shafts 16 and 16' respectively due to the two identifying / categorizing formations provided by the central aperture diameters and the retention disc thicknesses needing to match as described above.

[0065] For distinguishing the retention discs 23 and 23'prior to assembly, with the teeth 24, 24' being covered by protective ring 24a, the protective ring 24a may be provided with a different colour so that the worker can easily identify the correct retention disc prior to assembly. In a further alternative, the protective ring 24a may be provided with an imprint or overprint textually / symbolically indicating the right assignment of corresponding PTO stub shaft 16, 16' and retention disc 23, 23', e.g. by the text "For use with PTO stub shaft Type 1 only" in respect of the retention disc 23'. This helps to avoid a worker trying to assembly an unsuitable combination.

[0066] FIG. 8 shows diagrammatically how the retention disc 23 can be used to locate its corresponding Type 2 stub shaft 16 in the socket 21 of PTO output shaft 20 or alternatively how retention disc 23' can be used to locate its corresponding Type 1 stub shaft 16' in the socket 21 of PTO output shaft 20.

[0067] The above-described arrangement is not limited to the use of Type 1 and Type 2 PTO stub shafts but can be modified to accommodate a PTO stub shaft of Type 3 or Type 4 as discussed above. Retention discs for use with Type 3 or Type 4 PTO stub shafts may be providedwith a unique configuration of indicating formations (e.g., teeth) to provide a uniquely identifiable PTO stub shaft signal.

[0068] As Type 2, Type 3 and Type 4 allow the operation of the PTO at or above a PTO speed of 1000 r.p.m., it may be sufficient for the system to be capable of identifying when a Type 1 stub shaft is mounted in the output shaft 20 as this requires a reduced PTO speed of 540 r.p.m. Therefore, the PTO stub shaft and the respective retention disc for Type 3 and Type 4 may share the same geometrical provisions as described for Type 2 PTO stub shaft 16 and the corresponding retention disc 23 (e.g., with diameter DI and thickness of Tl).

[0069] Furthermore, in the above embodiments, PTO stub shaft 16, 16' and retention disc 23, 23' are separable parts. In an alternative arrangement, it is envisaged that a retention disc may be fixedly connected to a corresponding PTO stub shaft prior to assembly to the output shaft, e.g. by, for example, welding.

[0070] In the above embodiment where two different categorizing formations are operative between the stub shaft and their corresponding retention disc, the system can be used to ensure that retentions discs for two different PTO rated speeds can only be fitted to their corresponding stub shafts. For most vehicle applications this will be sufficient as in most applications a vehicle PTO system will only be required to drive the PTO output shaft at two of the standard rated speeds. A common combination for an agricultural tractor is the provision of a PTO drive line which can drive the output shaft at 540 r.p.m and 1,000 r.p.m. However, other combinations are possible and a tactor could be configured to be selectively operative to provide Type 3 and Type 4 PTO outputs. Nevertheless, in some applications it may be desirable to be able to drive the PTO at more than two rated PTO speeds, say 540 r.pm, 1000 r.p.m, and 1,300 r.p.m. In this case it may be necessary to use three different types of retention disc to produce signals corresponding to the three rated speeds and to ensure that the retention discs can only be mounted in the operative position with a corresponding stub shaft of the correct rated speed.

[0071] FIGs. 9 to 11 illustrate an alternative arrangement for ensuring a retention disc can only be mounted to a corresponding stub shaft. In this embodiment, each retention disc 40 has a central aperture 41 having a diameter for receiving the outer circumferential region of the stub shaft 42 it is to be used with and has indicating teeth 45 which may be encased in aprotective cover 40a (see FIG.11). The central aperture 41 has radially inwardly extending projections 43 which are received in cut outs 44 in the stub shaft 42 which are spaced circumferentially at an angle TA. By using different spacing angles for each different required stub shaft Type / rated speed, it can be arranged that a particular retention disc 40 can only be fitted on a corresponding stub shaft which uses the same angle spacing TA. This arrangement enables the system to accommodate stub shafts with three or more different rated speeds with each retention disc located between a circlip 32 and an abutment on the stub shaft. In this embodiment, the circumferential surface region where the retention disc sits in its operative position can be the same for all the interchangeable stub shafts 42 and all the retention discs 40 can have a central aperture of the same diameter, although this is not essential. The circumferential surface regions of the stub shafts will have a larger diameter than the driving splines so that the retention discs can be slid axially over the driving splines to engage the inwardly extending projections 43 in the cut outs 44. The retention discs 40 can all be of the same thickness with a similar axial spacing between the between abutments 30 and 33 or between abutment 30 and the circlip 32.

[0072] In this embodiment it is necessary when mounting a stub shaft 42 to the output shaft 20 to align the inner driven splines 16a of stub shaft with the driving splines 21a in the socket 21, the driving formations 26 on the output shaft 20 with the apertures 46 in the retention disc, and the projections 43 with the cut outs 44. This is a more complex fitting procedure compare with the previously described arrangement.

[0073] FIGs. 12 and 13 show a yet further arrangement for ensuring that each retention disc can only be mounted to a corresponding PTO stub shaft. In this embodiment, each retention disc 50 has indicating teeth 56 which may be encased a protective ring 50a and a central aperture 51 provided with radially inwardly extending teeth 52 which match the external driving splines 53 on the corresponding stub shaft 54 to which the retention disc 50 is to be connected. This provides a simple mounting arrangement in which the retention disc 50 can be moved axially along the external driving splines 53 of its matching / corresponding stub shaft 54 until it reaches a reduced diameter circumferential surface region 57 of the stub shaft located adjacent the ends of the projections 26 (see dotted detail in FIG.13) when the stub shaft is mounted in the outputshaft 20. The reduced diameter circumferential surface region 57 may be provided with a larger diameter compared to the root circle 53a of the driving splines 53 to avoid weakening the PTO stub shaft while still enabling part engagement of the inwardly extending teeth 52 in the driving splines 53 as the retention disc is moved along the driving splines and onto the circumferential surface region. The inner diameter of the teeth 52 is dimensioned so that the ring is a sliding fit over the circumferential surface region 57 so that once the retention disc is moved on to the circumferential surface region, it can be rotated to align the apertures 55 with the driving projections 26 of the output shaft 20 to allow the retention disc to be slid to its operative position as shown in FIG.13. This arrangement provides a simple and quick mounting procedure for the retention disc, which is located between circlip 32 and an abutment 58 on the stub shaft to hold the associated stub shaft in the PTO output shaft socket. In this embodiment, the radially inwardly extending teeth 52 on each retention disc are configured so that they can only be engaged in and slid along the driving splines 53 of a corresponding PTO stub shaft. This embodiment can be used to mount PTO stub shafts with three or more rated speeds to the PTO output shaft 20 where each retention disc can only be mounted to a corresponding stub shaft of the correct rated speed.

[0074] In the embodiments described so far, the retention discs 23, 23', 40, 50 are held in the operative position on the stub shaft 16, 16', 42, 54 by a fastener in the form of an external circlip 32. The external circlip may be a clip in accordance with DIN 471 standard designed to be used on a shaft. The circlip 32 may be designed for use with circlip pliers or designed so that it can be fitted and removed without requiring circlip pliers and may be an E-Type circlip according to DIN 6799. A circlip for bores could be used in a similar manner Furthermore, any other axial securing means may be used such as a locking nut with an axial locking washer. Such an arrangement is shown in FIGs. 14 and 15 in which a Locking nut 60 is screwed on threaded portion 26a of extending drive formations 26 with a locking washer 61 in between lock nut 60 and retention disc 50. During assembly, nut 60 is adjusted to ensure there is no axial play between retention disc 50 and abutment 30 on the stub shaft 54. As shown in FIG. 15, the locking washer 61 is secured against rotation by an inwardly extending projection 61b on the locking washer 61 which extends into an axial groove 26b in a drive formation 26. When the correct axial positionof lock nut 60 is reached, one of a number of radially outwardly extending tabs 61a around the outer periphery of locking washer 61 is bent into one of several grooves 60a spaced circumferentially in the outer periphery of the locking nut 60 to prevent unscrewing of the locking nut. Other locking tab arrangements can be adopted.

[0075] The present invention thus provides a PTO drive line system in which the operative stub shaft can be easily changed, and an indication is provided as to which type of stub shaft is fitted and / or its rated speed so that the necessary warnings can be provided or corrective action taken if an operative stub shaft is operated at a speed higher than its permitted / rated speed.

[0076] In the embodiment illustrated, drive for the PTO output shaft is provided by an internal combustion engine 12 via a speed change gearbox. However, in other embodiments drive for the PTO output shaft may be provided by other means, such as an electric motor. In this case, the PTO drive system may not require a speed change gear box if the electric motor can be controlled to drive the PTO output shaft at an appropriate speed depending on the type of PTO stub shaft fitted.

[0077] A PTO drive line system in accordance with the invention may be configured to drive the output shaft 20 constantly at one of the rated speeds and / or it may be capable of selectively driving the output shaft at a speed which varies in dependence on the ground speed of the vehicle. It should also be appreciated that a PTO drive line system according to the invention is not limited to use with PTOs and / or PTO stub shafts configured in accordance with ISO 500-1 but can be adapted for use with any system of PTO stub shafts operable at different speed.

[0078] In the embodiment illustrated in FIG. 1, the PTO drive line system is located at the rear of a tractor but a PTO drive line system according to the invention can alternatively, or additionally, be located at the front of a tractor or indeed at any suitable location. Further a PTO drive line system according to the invention can be used with other types of vehicles, such as construction and other types of utility vehicle. Indeed, a PTO drive line system according to the invention can also be adapted for use with non-vehicular machines which are required to provide a PTO facility.

[0079] All references cited herein are incorporated herein in their entireties. If there is a conflict between definitions herein and in an incorporated reference, the definition herein shall control.

Claims

CLAIMSWhat is claimed is:

1. A vehicle PTO drive line system having an output shaft with a socket arranged to drivingly receive a removable PTO stub shaft, the stub shaft being retained in the socket by a retention disc mounted to the stub shaft, the retention disc being rotationally driven by the output shaft and operative to axially locate the stub shaft within the socket when in an operative position, the retention disc being held in the operative position by a fastener detachably mounted on the output shaft, the retention disc configured for cooperation with a sensor when in the operative position to generate a signal indicative of a rated speed of the stub shaft.

2. A vehicle PTO drive line system according to claim 1, wherein the retention disc is driven from the output shaft by circumferentially spaced axially extending drive formations on the output shaft which extend through circumferentially spaced apertures in the retention disc.

3. A vehicle PTO drive line system according to claim 1 or claim 2, the system comprising a plurality of interchangeable removable PTO stub shafts, each being drivingly receivable in the socket, and a plurality of retention discs, wherein at least two of the PTO stub shafts have different rated speeds, each PTO stub shaft being retained in the socket by a corresponding retention disc configured to generate a signal indicative of the rated speed of that stub shaft.

4. A vehicle PTO drive line system according to claim 3, wherein the retention discs are separably mountable to corresponding stub shafts, the system being configured such that for each stub shaft, only a corresponding retention disc configured to generate a signal indicative of the correct rated speed for that stub shaft can be mounted to the stub shaft in the operative position.

5. A vehicle PTO drive line system according to claim 3 or claim 4, wherein each retention disc has a central aperture which locates about an outer circumferential surface region of a corresponding stub shaft when in the operative position, the stub shafts each having external driving splines axially outboard of the circumferential surface region, the driving splines havingan outer diameter larger than that of the circumferential surface region, stub shafts with different rated speeds having driving splines comprising a different configuration of driving splines (e.g., number and / or type of splines), the central apertures of the retention discs being provided with corresponding spline formations designed to slide axially along the external driving splines of corresponding stub shafts onto the circumferential surface region, the arrangement configured such that the retention discs can be rotated about their corresponding stub shaft when located about the circumferential surface region.

6. A vehicle PTO drive line system according to claim 3 or claim 4, wherein each retention disc has a central aperture dimensioned to receive an outer circumferential surface region of a corresponding stub shaft when in the operative position, the retention disc engaging with a radially outwardly extending abutment on the stub shaft in the operative position to locate the stub shaft axially in the socket, the arrangement being such that for each stub shaft, only a corresponding retention disc having the correctly dimensioned central aperture and the correct thickness can be mounted in the operative position.

7. A vehicle PTO drive line system according to claim 6, wherein the at least two stub shafts with different rated speeds have outer circumferential surface regions of differing diameters and are configured such that the axial spacing between the radially extending abutment and the axial position of the fastener when mounted to the output shaft is different, each retention disc being dimensioned for use only with a corresponding stub shaft having a rated speed corresponding to the signal generated by that retention disc.

8. A vehicle PTO drive line system according to claim 3 or claim 4, wherein each retention disc has a central aperture which locates about an outer circumferential surface region of a corresponding stub shaft when in the operative position, the stub shafts having circumferentially spaced recesses in their outer circumferential surface regions, the central apertures of the retention discs being provided with corresponding radially inwardly extending and circumferentially spaced protrusions for location in the recesses, the circumferential spacing of the recesses and projections being different for stub shafts of different rated speeds and theircorresponding retention discs, such that only a corresponding retention disc configured to generate a signal indicative of the correct rated speed can be mounted to each stub shaft.

9. A vehicle PTO drive line system according to any one of the preceding claims, wherein the output shaft is assembled in a chamber of the drive line and the retention disc is operative to close an axially outer end region of the chamber, at least partially, when in the operative position.

10. A vehicle PTO drive line system according to any one of claims 1 to 3, wherein the retention disc and stub shaft are undetachably connected to each other prior to assembly.

11. A vehicle PTO drive line system according to any one of the preceding claims, wherein toothed indicating formations are provided around the outer periphery of the retention disc for cooperation with the sensor, the number and spacing of the toothed indicating formations determining the signal generated by the sensor.

12. A vehicle PTO drive line system according to claim 11, wherein the toothed indicating formations of the retention discs are encased in a ring of polymeric material, and wherein, optionally, the ring is injection moulded onto the retention disc.

13. A vehicle PTO drive line system according to claim 11 or claim 12, wherein the protective ring is provided with a visual identifier indicative of the rated speed the signal generated by the retention disc is indicative of and hence the rated speed of the stub shaft to which the retention disc is intended to be assembled to.

14. A vehicle PTO drive line system according to any one of the preceding claims, wherein the detachable fastening comprises a circlip which engages in a groove formed in an outer circumferential surface of the output shaft axially outboard of the retention disc when the retention disc is in the operative position and wherein, optionally, where the output shaft is provided with circumferentially spaced axially extending drive formations according to claim 2, the circlip engages in a groove formed in outer circumferential surface regions of the driveformations axially outboard of the retention disc when the retention disc is in the operative position.

15. A vehicle PTO drive line system according to any one of claims 1 to 13, wherein the detachable fastening comprises a locking nut and locking washer which are mounted on a threaded potion of the output shaft axially outboard of the retention disc when the retention disc is in the operative position and wherein, optionally, where the output shaft is provided with circumferentially spaced axially extending drive formations according to claim 2, the locking nut and locking washer are mounted on a threaded portions of the drive formations axially outboard of the retention disc when the retention disc is in the operative position.

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