TECHNICAL FIELD

The present subject matter, in general, relates to an independent power take-off (IPTO) unit and in particular, relates to a clutch system and a braking system implemented in the IPTO unit.

BACKGROUND

Heavy vehicles, like trucks or tractors, have load-handling equipment or implements attached to them to operate certain devices connected thereto, for example, pumps, cranes, air compressors, ploughs, lifting mechanisms, etc. These implements utilize power of an engine of the vehicle for their operation. The transfer of power from the engine to these implements is commonly done by a power take-off unit. For certain implements, it is desired that the implements keep operating irrespective of whether the vehicle is moving or is at rest. For such situations, it is desired that a rotation of the implement should be independent of a rotation of the shaft of the engine. A power take-off unit that serves this purpose is termed an independent power take-off (IPTO) unit.

A typical power take-off unit includes an input shaft, which is driven by the engine, an output shaft connected to the implement, and an intermediate set of meshing gears to transfer power from the input shaft to the output shaft. A typical IPTO unit, on the other hand, includes a clutch assembly in addition to the components of the typical power take-off unit. The clutch assembly allows the output shaft of the IPTO unit to be connected or disconnected to the input shaft and thus allows an intermittent operation of the implement. When the implement needs to be operated, the clutch assembly is engaged, thereby transferring power from the engine via the input shaft to the output shaft, causing the output shaft to rotate. When the clutch assembly is disengaged, transfer of power from the engine to the output shaft is discontinued.

Disengagement of the clutch assembly, however, does not result in a complete stoppage of the output shaft. This may occur due to various reasons, for example, inertia or the frictional drag induced by viscous nature of a lubricating fluid that is provided in between the input and output shaft to reduce heat and friction. In order to completely halt the rotation of the output shaft, a braking system is provided in the IPTO unit. The braking system is actuated when the clutch assembly is disengaged. Actuation of both the clutch assembly and the braking system is done by delivering a hydraulic fluid to the respective system, by means of a hydraulic pump.

Further, in a conventional braking system, there is a time lag for the hydraulic pump to build up a pressure to be utilized for the operation of the braking system. This causes an initial drag in the IPTO unit. Further, the IPTO unit requires the hydraulic pump to build a constant pressure either to engage the clutch assembly when the IPTO is in use or to engage the braking system when the IPTO is not in use. Also, when the braking system is engaged, a back-pressure gets built up inside the hydraulic pump. Maintaining constant pressure and withstanding back pressure result in wastage of a substantial portion of the engine power. This eventually leads to a reduction in the efficiency of the engine and the hydraulic pump.

In addition, the aforementioned hydraulic braking system used in conventional IPTO units is complex in structure and occupy a significantly large space. Further, the braking system employs a large number of components, thereby increasing the manufacturing cost. Moreover, the braking system does not ensure the complete rotational stoppage of the output shaft under all operating conditions.

SUMMARY

The subject matter as described herein is directed to an independent power take-off (IPTO) unit used in a vehicle, such as utility vehicles, for driving an implement attached to the vehicle. In one embodiment, the IPTO unit includes an input shaft, an output shaft, and a clutch-brake assembly. The input shaft is coupled to a crankshaft of the engine and operates independently from a transmission system of the vehicle, thereby making the operation of the IPTO unit independent of the transmission system. The output shaft can be attached to the implement for the transmission of power to the implement.

The clutch-brake assembly includes a clutch assembly and a braking system. The clutch assembly operationally engages and disengages the input shaft with the output shaft. The clutch assembly is engaged when power is required by the implement and remains disengaged otherwise. The clutch assembly is actuated hydraulically by a hydraulic system. The brake assembly engages to operationally retard the rotation of the output shaft when the clutch assembly is disengaged and disengages to free the output shaft when the clutch assembly is engaged. The brake assembly can be actuated mechanically and hence does not depend upon the hydraulic system that controls the clutch assembly, for its operation.

The hydraulic system is utilized when the clutch assembly is engaged. Consequently, a hydraulic pump of the hydraulic system builds pressure for the engagement of the clutch assembly. Hence, the durability of both the hydraulic pump and the IPTO unit are higher than that of a conventional IPTO unit, which uses the hydraulic system for the retardation of the output shaft.

In addition, the IPTO unit of the present subject matter has a stopper assembly to provide a free rotation, that is of a preset angle, of the output shaft in a direction opposite to its normal rotation. This helps in the alignment of the output shaft with the implement when the braking system is engaged.

These and other features, aspects, and advantages of the present subject matter will be better understood with reference to the following description and appended claims. This summary is provided to introduce a selection of concepts in a simplified form. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The above and other features, aspects, and advantages of the subject matter will become better understood with regard to the following description, appended claims, and accompanying drawings where:

Fig. 1 illustrates an exemplary independent power take-off (IPTO) unit in a vehicle, in accordance with an embodiment of present subject matter.

Fig. 2 depicts a sectional view along a section AA' of a clutch-brake assembly of the IPTO unit of Fig. 1, comprising a clutch assembly and an a braking system, with the clutch assembly in an engaged position and the braking system in a disengaged position, according to an embodiment of the present subject matter.

Fig. 3 depicts a sectional view along the section AA' of the clutch-brake assembly of Fig. 1, comprising a clutch assembly and an a braking system, with the clutch assembly in a disengaged position and the braking system in an engaged position, according to an embodiment of the present subject matter.

Fig. 4 illustrates an exemplary stopper assembly of the IPTO unit of Fig. 1, according to an embodiment of the present subject matter.

Fig. 5 illustrates an exemplary hydraulic system employed in the IPTO unit of Fig. 1 , according to an embodiment of the present subject matter.

DETAILED DESCRIPTION

The subject matter described herein is directed to an independent power take-off (IPTO) unit in utility vehicles, such as trucks or tractors, for driving an implement, which operated devices such as a hydraulic pump, blower, etc., attached to the vehicle.

According to one embodiment of the subject matter, the IPTO unit includes an input shaft, a clutch-brake assembly, and an output shaft. The input shaft is directly coupled to a crankshaft of the engine and is independent of a transmission system of the vehicle.

Thus the input shaft is in a continuous rotation as long as the engine runs, irrespective of whether the vehicle is moving or is stationary. The clutch-brake assembly controls the rotation of the output shaft. The output shaft may be connected to the implement to drive the implement. The coupling of the input shaft with the engine is achieved by an intermediate set of meshing gears.

Further, the clutch-brake assembly includes a clutch assembly and a braking system. The clutch assembly transmits power from the input shaft to the output shaft. The clutch assembly is engaged to connect the input shaft with the output shaft when power is required by the IPTO unit to drive the implement. The clutch assembly disengages the output shaft from the input shaft when the IPTO unit is not in use. The braking system operationally retards rotation of the output shaft when the output shaft is disengaged from the input shaft by the clutch assembly and finally stops the output shaft.

The clutch assembly is hydraulically actuated through a hydraulic system. The hydraulic system may include a fluid compressing device, for example, a gear pump, which is driven by the input shaft, and a fluid pressure regulator, for example, a solenoid valve, along with other hydraulic components like a filter, a check valve, etc. The fluid pressure regulator maintains a constant pressure of a hydraulic fluid flowing through the hydraulic system. The fluid pressure regulator may further include devices for direction control and to facilitate modulation of the hydraulic fluid. Such an arrangement results in a smooth and steady operation of the clutch assembly.

The braking system implemented herein is mechanically actuated. This mechanical actuation can be done via a plurality of springs present in the braking system. Further, the output shaft is provided with a preset degree of free rotation by a stopper assembly of the IPTO unit. This free rotation is in a direction opposite to the direction of normal rotation of the output shaft and this helps in the alignment of the output shaft and the implement even if the braking system is engaged.

Fig. 1 illustrates an independent power take-off (IPTO) unit 100 in a vehicle, such as utility vehicles, in accordance with an embodiment of the present subject matter. The IPTO unit 100 includes an input shaft 105, a clutch-brake assembly 110, and an output shaft 115. The input shaft 105 is directly coupled to a crankshaft 120 of an engine of the vehicle through a reduction gear set 125. The reduction gear set 125 continuously provides rotational power from the crankshaft 120 to the input shaft 105. The input shaft 105 in turn can drive an implement through the output shaft 115. The power from the input shaft 105 is transferred to the output shaft 115 through the clutch-brake assembly 110. Hence, the IPTO unit 100 is capable of receiving rotational power independent of a transmission system of the vehicle. This means that the IPTO unit 100 can function or draw power irrespective of the state of motion of the vehicle. Further, the crankshaft 120 drives a transmission shaft 130 through a transmission clutch 135 and a gear box 140.

The transmission shaft 130 in turn drives wheels of the vehicle.

Furthermore, in one implementation, the IPTO unit 100 is provided with a three-point linkage scotch yoke hydraulic pump 145, interchangeably referred to as scotch yoke hydraulic pump 145 hereinafter, mounted on the input shaft 105 and driven by the input shaft 105. The scotch yoke hydraulic pump 145 drives a three-point linkage (not shown in figure) and is completely immersed in a hydraulic fluid (not shown in Fig. 1), such as oil, flowing through the IPTO unit. The scotch yoke hydraulic pump 145 supplies the hydraulic fluid to a fluid compressing device 150, which can be an auxiliary gear pump.

The fluid compressing device 150 is driven by the input shaft 105. Both the scotch yoke hydraulic pump 145 and the fluid compressing device 150 receive power from the engine when the crankshaft 120 is rotating.

The fluid compressing device 150 builds up pressure and supplies the hydraulic fluid at high pressure required for the operation of the clutch-brake assembly 110 through a hydraulic system, which is described later in the description of Fig. 5.

Fig. 2 illustrates a sectional view of the clutch-brake assembly 110 of the IPTO unit 100 along a section AA'. The clutch-brake assembly 110 includes a hydraulically actuated clutch assembly 202, hereafter referred to as the clutch assembly 202, and a mechanically actuated braking system 204, hereafter referred to as the braking system 204. The clutch assembly 202 operationally engages or disengages the input shaft 105 with the output shaft 115. The braking system 204 operationally retards and then completely stops the output shaft 115 when the output shaft 115 is disengaged from the input shaft 105.

The clutch assembly 202 includes a hub 205 operationally mounted on the input shaft 105 such that the hub 205 rotates along with the input shaft 105. In addition, in one implementation, the hub 205 can also slide axially along the axis of the input shaft 105. The hub 205 has one or more hub spring(s) (not shown in figure), which oppose the axial motion of the hub 205. Also, the hub 205 has a plurality of friction discs 210 attached along its periphery. The clutch assembly 202 also has a plurality of intermediate plates 215, which are positioned in an alternate manner with respect to the friction discs 210.

The intermediate plates 215 are attached to a clutch housing 220. The clutch housing 220 can be mounted on the input shaft 105 using rolling elements (not shown in the figure), for example, roller bearings, ball bearings, etc., to enable a relative rotation between the clutch housing 220 and die input shaft 105.

The clutch assembly 202 further includes a pressure plate 225, the pressure plate 225 being mounted on the output shaft 115. The output shaft 115 is rotated by the pressure plate 225. The pressure plate 225 rests against the clutch housing 220 and bears the pressure of the friction discs 210 and the intermediate plates 215 whenever the friction discs 210 and the intermediate plates 215 are engaged.

The clutch housing 220 includes a cylinder 230 with a piston 235 free to reciprocate in the cylinder 230. The reciprocating motion of the piston 235 is controlled by a hydraulic fluid 240, which is supplied by a hydraulic system (not shown in figure). The hydraulic system directs the hydraulic fluid 240 to a feed ring 245, which in turn supplies the hydraulic fluid 240 to the cylinder 230.

Further, the braking system 204 is mechanically actuated and includes a brake plate 250, a brake disc 255, and a plurality of brake springs 260. The brake plate 250 has a plurality of flanges (not shown) at its periphery. These flanges rest in a plurality of slots (not shown) present on the clutch housing 220 such that the brake plate 250 can move in a direction axial to the input shaft 105. The brake disc 255 rests in the clutch housing 220 in such a way that the clutch housing 220 can rotate relative to the brake disc 255 when the braking system 204 is disengaged. Furthermore, the brake disc 255 has a brake lug 265 at its periphery, which rest on a brake bracket (not shown in figure). Further, one end of each of the brake springs 260 is attached to the brake plate 250 while the other end is attached to the pressure plate 225. The brake springs 260 provide mechanical actuation to the braking system 204. This method of mechanical actuation will be described in detail later in the description of Fig. 3.

As illustrated herein in Fig. 2, the sectional view along the section AA' of the clutch-brake assembly 110 depicts the clutch assembly 202 in an engaged position and the braking system 204 in a disengaged position. Whenever rotational power is required by the implement, the input shaft 105 is engaged to the output shaft 115 by engaging the clutch assembly 202 and disengaging the braking system 204.

In the present embodiment, the input shaft 105 and the hub 205 rotate whenever the crankshaft 120 rotates. When power is to be delivered to the implement, the clutch assembly 202 is engaged by a IPTO control mechanism, which can be a switch or a lever provided to operate the IPTO unit 100. The clutch assembly 202 is engaged by hydraulically moving the piston 235 inside the cylinder 230. To move the piston 235, the hydraulic system (not shown in figure) supplies the hydraulic fluid 240 to the cylinder 230 through the feed ring 245. The hydraulic fluid 240 builds up pressure inside the cylinder 230 and moves the piston 235 towards the pressure plate 225.

The piston 235 then moves the brake plate 250 away from the brake disc 255 and, as a result, the brake springs 260 are compressed and the braking system 204 is disengaged.

The brake plate 250 also moves the friction discs 210 towards the alternatively arranged intermediate plates 215. The movement of the friction discs 210 moves the hub 205, which in turn compresses the hub springs (not shown in figure) towards the pressure plate 225. The friction discs 210 and the intermediate plates 215 collectively apply pressure against the pressure plate 225. Consequently, the input shaft 105, the hub 205, the clutch housing 220, the brake plate 250, and the pressure plate 225 form one unit and rotate together.

As the pressure plate 225 is attached to the output shaft 115, the output shaft 115 also rotates with the input shaft 105. However, as the brake lug 265 rests against the brake bracket (not shown in figure), the brake lug 265 does not rotate with the clutch housing 220. The torque or rotational power from the input shaft 105 gets transferred to the output shaft 115 through the hub 205, the friction discs 210, the intermediate plates 215, the clutch housing 220, and the pressure plate 225. The flow of the torque is depicted by a network of arrows 270. In this way, the rotational power is delivered to the implement through the IPTO unit 100.

Fig. 3 illustrates a sectional view along a section AA' of the clutch-brake assembly 110, with the clutch assembly 202 in a disengaged position and the braking system 204 in an engaged position. When no rotational power is required for the implement, the clutch assembly 202 is disengaged and the braking system 204 is engaged to operationally retard and finally stop the output shaft 115. In the present embodiment, in order to disengage the clutch assembly 202, the IPTO control mechanism is operated. This directs the hydraulic system to withdraw the hydraulic fluid 240 out of the cylinder 230.

When the pressure inside the cylinder 230 reduces, the brake springs 260 expand and push the brake plate 250 towards the brake disc 255, which is supported by the clutch housing 220 on the side opposite to the pressure plate 225. The brake plate 250 comes in contact with brake disc 255 and the braking system 204 is engaged. The movement of the brake plate 250 moves the piston 235 into the cylinder 230. Thus, the pressure applied by the piston 235 on the friction discs 210 ceases and the hub spring(s) (not shown in the figure.) expand and push the hub 205 away from the pressure plate 225. Consequently, the friction discs 210 and the intermediate plates 215 get separated, thus resulting in the disengagement of the clutch assembly 202.

The engagement of the braking system 204 operationally combines the output shaft 115, the pressure plate 225, the brake springs 260, the brake plate 250, the brake disc 255, and the clutch housing 220 as a single unit. The brake lug 265 resting against the brake bracket (not shown in figure) provides a resistance to the rotation of the brake disc 255 and to the single unit formed due to engagement of the braking system 204. This resistance operationally retards the rotation of the single unit formed due to engagement of the braking system 204 and finally brings the single unit to rest. However, the input shaft 105, the hub 205, and the friction discs 210 rotate as long as the crankshaft 120 rotates. The flow of the torque or rotational power is depicted by the network of arrows 270. The braking system 204 remains disengaged as long as the clutch assembly 202 is engaged to drive the output shaft 115.

In the present implementation, the braking system 204 is mechanically actuated by virtue of energy stored in the compressed brake springs 260. The braking system 204 remains engaged even if the crankshaft 120 stops. Moreover the braking system 204 has a lesser response time as compared to known hydraulically actuated braking systems. Thus, the braking system 204 ensures a complete rotational stoppage of the output shaft 115 under all operating conditions.

Fig. 4 illustrates an exemplary stopper assembly 400 of the IPTO unit 100. The stopper assembly 400 includes the brake lug 265 and a brake bracket 405. The brake lug 265 rests against the brake bracket 405. During the engaged position of the clutch assembly 202, the brake bracket 405 prevents the rotation of the brake disc 255 despite the fact that the clutch housing 220 is rotating. The brake bracket 405 also helps to operationally retard the output shaft 115 during the engagement of the braking system 204.

In one embodiment, the brake bracket 405 has a first stopper 410 and a second stopper 415. When the braking system 204 is engaged, the braking system allows the output shaft 115 to rotate freely through an angle having a preset value and in a direction opposite to the direction of normal rotation of the output shaft 115. This rotation occurs between the first stopper 410 and the second stopper 415. This free rotation of the output shaft 115 helps in the alignment of the output shaft 115 with the implement. In one implementation, this preset value of angle of free rotation is about 60 degrees. In another one implementation, the preset value of angle of free rotation may be varied.

Fig. 5 illustrates an exemplary hydraulic system 500 employed in the IPTO unit 100. The hydraulic system 500 supplies the hydraulic fluid 240 for the operation of the clutch-brake assembly 110. In one embodiment, the hydraulic system 500 includes the fluid compressing device 150, a reservoir 505, a flow control device 510, a fluid pressure regulator 515, and a filter 520. In one example, the fluid compressing device 150 may be an auxiliary gear pump and the flow control device 510 can be implemented as a flow control valve. The fluid pressure regulator 515, in one implementation, is a solenoid valve.

The reservoir 505 stores the hydraulic fluid 240. The fluid compressing device 150 draws the hydraulic fluid 240 from the reservoir 505 though a fluid transport line. While flowing through the fluid transport line, the hydraulic fluid 240 first passes the filter 520 before entering the fluid compressing device 150. The fluid compressing device 150 has an inbuilt safety valve 525, which normally remains closed. However, when the pressure inside the line increases to a certain preset pressure value, the inbuilt safety valve bypasses the hydraulic fluid 240 to the reservoir 505 through a first bypass 530.

During the operation of the clutch-brake assembly 110, the fluid compressing device 150 pumps the hydraulic fluid 240 to the clutch-brake assembly 110 through the flow control device 510 and the fluid pressure regulator 515. The flow control device 510 supplies the hydraulic fluid 240, at a preset flow, to the fluid pressure regulator 515 and bypasses the rest of the hydraulic fluid 240 to the reservoir 505 through the first bypass 530.

In one implementation, the fluid pressure regulator 515 may include sub-valves such as a direction control valve 545, a pressure limiting valve 555, a modulation valve 565 etc. The direction control valve 545 controls the direction of the hydraulic fluid 240 by allowing the hydraulic fluid 240 to flow from the reservoir 505 to the clutch-brake assembly 110 during the engagement of the clutch assembly. The direction control valve 545 also lets the hydraulic fluid 240 to bypass, through a second bypass 535, while flowing back from the clutch-brake assembly 110 to the reservoir 505 during the disengagement of the clutch assembly 202.

The pressure limiting valve 555 maintains the hydraulic fluid 240 supplied to the clutch-brake assembly 110 at a certain predetermined constant pressure. Likewise, the modulation valve 565 controls the time of engagement of the clutch assembly 202 by controlling the flow of the hydraulic fluid 240 to the clutch assembly 202. The modulation valve 565 ensures a safe engagement of the clutch assembly 202 and prevents any damage to the implement or the IPTO unit 100. In an implementation, the fluid pressure regulator 515 comprising aforementioned sub-valves can be electrically actuated. For example, the actuation may be achieved by a direct current power source (not shown in figure) such as the battery of the vehicle, along with a double-pole double-throw switch 540 to control the power supply to the fluid pressure regulator 515.

As said earlier, the IPTO unit 100 of the present subject matter has the mechanically actuated braking system 204, which provides a complete stoppage of the output shaft 115 under all operating conditions. The brake springs 260 ensures that the braking system 204 is engaged even when the crankshaft 120 is not rotating, thus eliminating initial drag caused due to a hydraulically actuated braking system employed in conventional IPTO units. Due to this, the life of the hydraulic system 500 is increased as it is used only for actuation of clutch assembly 202 and not during engagement of braking system 204. The IPTO unit 100 also helps in better alignment of the output shaft 115 with the implement due to free rotation provided to the output shaft 115.

Although the subject matter has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are possible. As such, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiment contained therein.

I/we claim:
1. An independent power take off unit (100) comprising:

an input shaft (105);

an output shaft (115); and

a clutch-brake assembly (110) operably coupled to the input shaft (105) and the output shaft (115) to control rotation of the output shaft (115);

characterized in that,

the clutch-brake assembly (110) comprises:

a hydraulically actuated clutch assembly (202) to transmit power from the input shaft (105) to the output shaft (115), during an engaged condition of the clutch assembly (202); and

a mechanically actuated braking system (204) to stop rotation of the output shaft (205), during a disengagement of the clutch assembly (202).

2. The independent power take off unit (100) as claimed in claim 1, wherein the
hydraulically actuated clutch assembly (202) is actuated by a hydraulic system comprising:

a fluid compressing device (150) to supply a hydraulic fluid;

a flow control device (510) to maintain a constant rate of flow of the hydraulic fluid; and

a fluid pressure regulator (515) to regulate a constant pressure of the hydraulic fluid.

3. The independent power take off unit (100) as claimed in claim 2, wherein the fluid compressing device (150) is a gear pump.

4. The independent power take off unit (100) as claimed in claim 2, wherein the flow control device (510) is a flow control valve.

5. The independent power take off unit (100) as claimed in claim 2, wherein the fluid pressure regulator (515) comprises a solenoid valve.

6. The independent power take off unit (100) as claimed in claim 5, wherein the solenoid valve houses a modulation valve to control a rate of the engagement of the clutch assembly (202).

7. The independent power take off unit (100) as claimed in claim 5, wherein the solenoid valve includes a direction control valve to allow the hydraulic fluid to flow to the clutch assembly (202) during the engagement of the clutch assembly (202).

8. The independent power take off unit (100) as claimed in claim 1, wherein the braking system comprises (204) a stopper assembly (400) that allows the output shaft (115) to rotate through a preset value of free rotation, during the engagement of the braking system (204).

9. The independent power take off unit (100) as claimed in claim 8, wherein the preset value of free rotation is about 60 degrees.

10. The independent power take off unit (100) as claimed in claim 1, wherein the input shaft (105) is powered by an engine through a transmission drive line comprising:

a transmission clutch (135) connected to a crankshaft (120) of the engine;

an input pump shaft;

a reduction gear set (125) transmitting power from the transmission clutch (135) to the input pump shaft such that the input pump shaft rotates continuously when the engine is running; and

a three-point linkage scotch yoke hydraulic pump (145), rotated by the input pump shaft.

11. The independent power take off unit (100) as claimed in claim 10, wherein the three-point linkage scotch yoke hydraulic pump (145) is fully immersed in oil.

12. A system to drive an implement, utilizing power of an engine of a vehicle, the transmission of power from the engine to the load-handling unit being achieved by an independent power take off unit (100) as claimed in any of the preceding claims.

13. A vehicle comprising a independent power take off unit (100) as claimed in any of the claims 1-11.