Power take-off with bell housing cooling system

Abstract

The power take-off device includes a bell housing disposed about an axis and configured to be coupled to a housing of an engine or other driving device at a first axial end and to a housing of a driven device at a second axial end. The bell housing defines an air flow inlet and an air flow outlet between the first axial end and the second axial end. A clutch is disposed within the bell housing and configured to transfer torque from an input member coupled to the engine to an output member coupled to the driven device. A fan is configured to rotate with the input member to draw air into the bell housing through the air flow inlet, move the air generally radially through the bell housing from the air flow inlet to the air flow outlet across the clutch, and exhaust the air from the bell housing through the air flow outlet.

Description

[Technical field]

[0001] The present invention relates to a power take-off device, and more particularly to a power take-off device including means for cooling the interior of a bell housing of the power take-off device to facilitate the use of an electromagnetic clutch and brake. [Background technology]

[0002] A conventional power take-off includes a clutch that is used to transfer torque from an engine flywheel to a driven device, such as a shaft, gear, or pulley. The clutch is coupled to the engine and housed within a bell housing that may also house the engine flywheel. Many conventional power take-offs employ a mechanical clutch, such as a multi-plate clutch, that is actuated using a lever that allows an individual to manually engage or disengage the clutch. However, mechanical clutches have several drawbacks. The lever and other components of the actuation mechanism for the mechanical clutch increase part count and create packaging / space issues. Mechanical clutches also cannot be actuated remotely, i.e., from a distance. Mechanical clutches also require relatively frequent adjustments.

[0003] The use of an electromagnetic clutch instead of a mechanical clutch in a power take-off device may overcome many of the disadvantages associated with the use of a mechanical clutch. However, an electromagnetic clutch generates more heat than a mechanical clutch due to the transmission of electrical current through conductors in the clutch. The interior of the bellhousing is already exposed to relatively high air temperatures due to heat generated by the engine to which the bellhousing is mounted. The additional heat generated by the electromagnetic clutch further increases the air temperature within the bellhousing, which may result in premature wear or failure of the clutch, bearings, seals, and other components contained within the bellhousing. Summary of the Invention [Problem to be solved by the invention]

[0004] The present inventors have recognized a need for a power take-off device that minimizes and / or eliminates one or more of the above-mentioned disadvantages.

[0005] The present invention relates to a power take-off device, and more particularly to a power take-off device including means for cooling the interior of a bell housing of the power take-off device to facilitate the use of an electromagnetic clutch and brake. [Means for solving the problem]

[0006] A power take-off device according to one embodiment includes a bell housing disposed about an axis and configured to be coupled to a housing of a driving device at a first axial end and to a housing of a driven device at a second axial end. The bell housing defines an air flow inlet and an air flow outlet between the first axial end and the second axial end. The power take-off device further includes a clutch disposed within the bell housing and configured to transfer torque from an input member coupled to the driving device to an output member coupled to the driven device. The power take-off device further includes a fan configured to rotate with the input member to draw air into the bell housing through the air flow inlet, move the air generally radially through the bell housing from the air flow inlet to the air flow outlet across the clutch, and exhaust the air from the bell housing through the air flow outlet.

[0007] A power take-off device according to another embodiment includes a bell housing disposed about an axis and configured to be coupled to a housing of a driving device at a first axial end and to a housing of a driven device at a second axial end. The bell housing defines an air flow inlet and an air flow outlet between the first axial end and the second axial end. The power take-off device further includes an electromagnetic clutch disposed within the bell housing and configured to transfer torque from an input member coupled to the driving device to an output member coupled to the driven device. The power take-off device further includes an electromagnetic brake disposed within the bell housing and configured to apply a braking torque to the output member. The power take-off device further includes a fan configured to rotate with the input member to draw air into the bell housing through the air flow inlet, move the air in a generally radial direction across the electromagnetic clutch and the electromagnetic brake through the bell housing from the air flow inlet to the air flow outlet, and exhaust the air from the bell housing through the air flow outlet.

[0008] The power take-off device according to the present teachings represents an improvement over conventional power take-off devices. In particular, the power take-off device includes means for drawing outside air into the bell housing, moving the air through a heat generating element within the bell housing, and exhausting the heated air from the bell housing to reduce the temperature within the bell housing. As a result, the power take-off device facilitates the replacement of a mechanical clutch with an electromagnetic clutch, thereby overcoming the disadvantages associated with the use of a mechanical clutch. Whereas conventional power take-off devices, when proposed, locate a brake outside the bell housing, the power take-off device of the present invention also facilitates the use of an electromagnetic brake within the bell housing in combination with an electromagnetic clutch.

[0009] The foregoing and other aspects, features, details, utilities, and advantages of the present invention will become apparent from a reading of the following description and claims, and a review of the accompanying drawings.

[0010]

[0011]

[0012]

[0013]

[0014]

[0015] [Brief description of the drawings]

[0016] [Figure 1] 1 is a cross-sectional view of a power take-off device according to one embodiment of the present teachings for transmitting power from an engine to a driven device. [Diagram 2] FIG. 2 is a perspective view of a bell housing of a portion of the power take-off device of FIG. 1 showing the air inlet of the bell housing. [Diagram 3] FIG. 2 is a perspective view of a bell housing of a portion of the power take-off device of FIG. 1 showing a portion of the bell housing airflow outlet and a fan. [Figure 4] FIG. 2 is a perspective view of the power take-off device of FIG. 1 showing a fluid diffuser for exhausting air from the bell housing. [Diagram 5] FIG. 2 is a perspective view of a portion of the power take-off device of FIG. 1 showing air flow through the bell housing. [Figure 6] FIG. 2 is a perspective view of one embodiment of a fan blade for use in the power take-off device of FIG. [Figure 7] FIG. 2 is a perspective view of one embodiment of a fan for use in the power take-off device of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Referring now to the drawings, where like reference numbers are used to identify identical components in the various views, FIG. 1 shows a power take off (PTO) 10 for transmitting power from a driving device 12 to a driven device 14. The PTO 10 transmits power from an input member coupled to the driving device 12 to an output member coupled to the driven device 14. The driving device 12 may comprise, for example, a gasoline or diesel powered engine, and the input member coupled to the driving device 12 may comprise, for example, a flywheel 16. However, it should be understood that the driving device 12 may comprise another type of prime mover. The driven device 14 may comprise any of a wide variety of devices including, for example, an oil well pump jack, a stump grinder, a brush chipper, a fluid pump, a blower, a winch, or a gearbox. The exact configuration of the driven device 14 will vary depending on the application, but will include an output member (not shown), such as a shaft, gear, or pulley, coupled to the driven device 14 through which the PTO 10 transfers power from a flywheel 16 or another input member coupled to the drive device 12. The PTO 10 may include a bell housing 18, a screen 20, a fluid diffuser 22, an output shaft assembly 24, a coupling 26, a clutch 28, a brake 30, and a fan 32.

[0018] The bell housing 18 houses many of the other components of the PTO 10 and protects them from external objects and elements. The housing 18 may be made from conventional metals, metal alloys, and non-metallic composite materials. The housing 18 may be disposed about and centered on an axis 34 that may include a rotating shaft for the flywheel 16, the output shaft assembly 24, the coupling 26, the clutch 28 and brake 30 elements, and the fan 32. The housing 18 is tubular and generally bell-shaped, having a tarred diameter and generally tapering from one axial end 36 to an opposite axial end 38 of the housing 18. The end 36 of the housing 18 may define a flange 42 configured for coupling to a housing 40 of the device 12 and configured to engage a corresponding flange 44 on the housing 40. Referring to FIGS. 2-4, fasteners 46, such as bolts, may extend through the flanges 42, 44 to couple the bell housing 18 to the device housing 40. Referring again to FIG. 1, the end 38 of the housing 18 is configured for coupling to the housing 48 of the driven device 14. Referring to FIGS. 2 and 4, fasteners 50, such as bolts, may extend through an end flange 52 of the housing 48 of the driven device 14 and into an axial end face of the bell housing 18 for coupling the bell housing 18 to the housing 48 of the driven device 14. Referring again to FIG. 1, the bell housing 18 further defines an air flow inlet 54 and an air flow outlet 56. The outlets 54, 56 are disposed between the ends 36 and 38 of the housing 18. The geometric centers of the outlets 54, 56 may be diametrically opposed from one another on the housing 18. In use, the housing 18 is preferably positioned such that the air flow inlet 54 faces towards the ground while the air flow outlet 56 faces away from the ground to take advantage of the fact that air within the bell housing 18 rises within the housing 18 as it heats and expands, becoming less dense. However, it should be understood that the location and spacing of the apertures 54, 56 may vary.In particular, the ports 54, 56 need not be located at different circumferential positions on the bell housing 18 than shown in the illustrated embodiment, and the ports 54, 56 may be spaced circumferentially closer to one another (i.e., such that the geometric centers of the ports 54, 56 are spaced less than 180 degrees apart from one another).

[0019] A screen 20 is provided to prevent foreign objects and impurities from entering the interior of the bell housing 18 as air is drawn through the air inlet 54. With reference to FIGURE 2, the screen 20 may include a frame 58 that is coupled to the housing 18 using conventional fasteners and surrounds the air inlet 54. The frame 58 supports a mesh filter 60 through which air is drawn into the bell housing 18 via the air inlet 54, the mesh filter 60 preventing larger objects and impurities from entering.

[0020] Referring again to FIG. 1, the fluid diffuser 22 is provided to distribute the air exhausted from the interior of the bell housing 18 through the air outlet 56 over a wider area while also cooling it. The fluid diffuser 22 also prevents water and other external objects and elements from entering the interior of the bell housing 18 through the air outlet 56. Referring to FIG. 4, the diffuser 22 includes a body 62 that is coupled using conventional fasteners to mounting pads formed in the bell housing 18 and the surrounding air outlet port 56. The body 62 is generally rectangular in shape but tapers away from the bell housing 18 such that one or both sets of opposing side walls of the body 62 are angled relative to each end wall of the body 62. The body 62 surrounds the outlet 56, and a conventional seal (not shown) may be disposed between the body 62 and the bell housing 18 around the mouth 56. The body 62 includes an inlet (not shown) that is aligned with the airflow outlet 56 of the bell housing 18 and through which fluid discharged from the bell housing 18 enters the body 62 of the diffuser 22. The body 62 further defines a plurality of outlet passages 64 in fluid communication with the inlet of the body 62 and the airflow outlet 56 of the bell housing 18, which are configured to discharge air from the body 62 of the diffuser 22. In the illustrated embodiment, the outlet passages 64 terminate in some or all of the side walls of the body 62. Furthermore, some or all of the outlet passages 64 may be configured with a downward slope or angle such that one end of the outlet passage 64 (the inlet) where air from the airflow outlet 56 of the housing 18 and the inlet of the body 62 enters the passage 64 is farther from the axis 34 than the opposite end (the outlet) of the outlet passage 64 where air exits the outlet passage 64 and the diffuser 22. In this context, the diffuser 22 prevents water and other impurities from entering the interior of the bell housing 18 through the airflow outlet 56. Although a particular configuration for the diffuser 22 is shown in the illustrated embodiment, it should be understood that the configuration of the diffuser 22 may vary.

[0021] 1, output shaft assembly 24 is provided for transmitting both (i) a driving torque provided by flywheel 16 or another input member coupled to driving device 12, and (ii) a braking torque provided by brake 30 to an output member coupled to driven device 14. Shaft assembly 24 includes shaft 66, hubs 68, 70, and means, such as spacers 72 and fasteners 74, for preventing movement of hubs 68, 70 relative to shaft 66 along axis 34.

[0022] The shaft 66 is provided for coupling to an output member coupled to the driven device 14. The shaft 66 may be disposed about and centered on the axis 34. One axial end of the shaft 66 is configured for coupling to an output member coupled to the driven device 14. It should be understood that the configuration of this axial end of the shaft 66 depends on the nature and configuration of the output member coupled to the driven device 14. The other axial end of the shaft 66 defines a bore configured to receive a fastener 74. The radially outer surface of the shaft 66 may define a plurality of splines for purposes described below.

[0023] The hub 68 is provided to support a portion of the clutch 28 for rotation therewith. The hub 68 is tubular and disposed about a portion of the shaft 66. The hub 68 may be disposed about and centered on the axis 34. A radially inner surface of the hub 68 may define a number of splines configured to engage corresponding splines on the shaft 66 to couple the hub 68 to the shaft 66 for rotation therewith. It should be understood that the shaft 66 and the hub 68 may be rotatably coupled in other manners, including by use of keys and keyways and interlocking lugs. A radially outer surface of the hub 68 is configured to support a number of bearings 76, 78, 80 configured to enable relative rotation of the shaft assembly 24 and components of the coupling 26, the clutch 28, the brake 30, and the fan 32, as discussed in more detail below. One axial end of the hub 68 defines a number of bores configured to receive fasteners 82 used for the hub 70 coupled to the hub 68. Hub 68 further defines a radially outwardly extending flange 84 for purposes discussed below.

[0024] The hub 70 is provided to support a portion of the brake 30 for rotation with the hub 70 and the shaft 66. The hub 70 is tubular and disposed about a portion of the shaft 66. The hub 70 may be disposed about and centered on the axis 34. One axial end of the hub 70 defines a radially outwardly extending flange 86 configured for coupling to a portion of the brake 30, as discussed in more detail below. The other axial end of the hub 70 faces a corresponding axial end of the hub 68. The hub 70 defines a plurality of axially extending bores configured to receive fasteners 82 used to couple the hub 70 to the hub 68 for rotation with the hub 68 and the shaft 66.

[0025] The spacer 72 and fastener 74 provide a means for preventing movement of the hubs 68, 70 relative to the shaft 66 in one direction (to the right in FIG. 1) along the axis 34. Movement of the hubs 68, 70 relative to the shaft 66 in the opposite direction along the axis 34 is restrained by the bell housing 18. The spacer 72 is disposed at one axial end of the shaft 66 and hub 68 and defines a bore configured to receive the fastener 74. The fastener 74 extends through the bore in the spacer 72 and into a matching bore in the shaft 66 and may be secured within the bore via mating threads on the fastener 74 and in the bore.

[0026] Coupling 26 is provided to permit the transfer of torque from flywheel 16, or another input member coupled to drive device 12, through clutch 28 to output shaft assembly 24 and an output member coupled to driven device 14, while at the same time allowing for some misalignment between flywheel 16 and output shaft assembly 24. Coupling 26 includes a driving ring 88, a driven ring 90, and an elastomeric body 92 disposed between driving ring 88 and driven ring 90.

[0027] The drive ring 88 is provided for coupling to the flywheel 16 and may be coupled to the flywheel 16 using conventional fasteners 94, such as bolts, extending through aligned bores in the drive ring 88 and the flywheel 16. The drive ring 88 may be disposed about and centered on the axis 34 for rotation thereabout. With reference to FIG. 3, the drive ring 88 may define a plurality of radially inwardly projecting teeth or lugs 96 configured to engage the elastomeric body 92.

[0028] Referring again to FIG. 1 , the driven ring 90 is disposed radially inward of the drive ring 88. Similarly, the driven ring 90 may be disposed about and centered on the axis 34 for rotation about the axis 34. The driven ring 90 may include two members 98, 100 coupled together by a number of fasteners 102. The member 98 is disposed radially outward of the member 100 and is dimensioned to receive and support the elastomeric body 92 thereon, which may be bonded to the member 98 through vulcanization. The member 100 is disposed radially inward of the member 98. The member 100 is dimensioned to receive the bearings 76, 78 disposed between the hub 68 of the output shaft assembly 24 and the driven ring 90. The member 100 also provides a means for supporting components of the clutch 28, as will be described in more detail below.

[0029] The body 92 is provided for transmitting force from the drive ring 88 to the driven ring 90 while allowing a degree of relative movement between the drive ring 88 and the driven ring 90 to account for misalignment between the flywheel 16 and the output shaft assembly 24 and the transmission elements therebetween. The body 92 is made from an elastomeric material. With reference to FIG. 3, the body 92 defines a plurality of radially outwardly projecting teeth on lugs 104 configured to engage the lugs 96 of the drive ring 88 to couple the body 92 and the driven ring 90 to the drive ring 88 for rotation therewith.

[0030] Referring again to FIG. 1, the clutch 28 is provided for selective transfer of torque from the flywheel 16 or another input member coupled to the drive device 12 to the output shaft assembly 24 and, consequently, to the output member coupled to the driven device 14. In accordance with one aspect of the present teachings, the clutch 28 comprises an electromagnetic clutch. As a result, the clutch 28 can be actuated remotely, i.e., from a distance, without the need for a lever or other mechanical actuator. The clutch 28 is also smaller in size, thereby improving the packaging of the PTO 10, and does not require adjustment, unlike mechanical clutches found in many conventional power take-off devices. The clutch 28 includes an electromagnet 106, a rotor 108, and an armature 110.

[0031] The electromagnet 106 creates an electromagnetic circuit between the electromagnet 106, the rotor 108, and the armature 110 to cause the armature 110 to move toward and engage the rotor 108 and transmit torque from the armature 110 to the rotor 108. The electromagnet 106 is disposed on one axial side of the rotor 108 and includes a hub 112, a field shell 114, and a conductor 116.

[0032] The hub 112 is provided to support and orient the field shell 114 and the conductors 116. The hub 112 may be annular in shape and disposed about and centered on the axis 34. The hub 112 is configured to receive the output shaft assembly 24 extending through a bearing 80 disposed between the hub 112 and the output shaft assembly 24 to permit rotation of the output shaft assembly 24 relative to the hub 112. The hub 112 may be fixed for rotation within the bell housing 18. The hub 112 defines a radially extending flange configured to support and position the field shell 114 and the conductors 116.

[0033] The field shell 114 is configured to house the conductors 116. The field shell 114 also forms part of an electromagnetic circuit that causes selective engagement between the rotor 108 and the armature 110. The field shell 114 may be made from conventional metals and metal alloys, including steel. The field shell 114 is generally U-shaped in cross section and includes axially extending, radially aligned inner poles 118 and outer poles 120. The field shell 114 may define holes through which electrical current can be provided to the conductors 116 from an external power source.

[0034] The conductor 116 is provided to create an electromagnetic circuit between the field shell 114, the rotor 108, and the armature 110 to cause movement of the armature 110 and engage the rotor 108 to enable transmission of torque from the coupling 26 to the output shaft assembly 24. The conductor 116 is generally annular and disposed within the field shell 114 about the axis 34. In particular, the conductor 116 is disposed between an inner pole 118 and an outer pole 120 of the field shell 114. The conductor 116 may comprise a conventional copper coil, although other known conductors may alternatively be used. The conductor 116 may be electrically connected to a power source (not shown), such as a battery. When the conductor 116 is energized, an electromagnetic circuit is formed between the field shell 114, the rotor 108, and the armature 110.

[0035] The rotor 108 is provided for selective engagement with the armature 110 to transmit torque from the shaft coupling 26 to the output shaft assembly 24. The rotor 108 may be disposed about the shaft 34 and is coupled to the output shaft assembly 24 for rotation therewith. The rotor 108 defines a central bore through which the output shaft assembly 24 extends. A radially inner portion of the rotor 108 defines a recess configured to receive a flange 84 of the hub 68 of the output shaft assembly 24. A fastener 122 extends through the rotor 108 and the flange 84 of the hub 68 to couple the rotor 108 and the output shaft assembly 24 for rotation. A radially outer portion of the rotor 108 defines radially aligned inner and outer poles 124 and 126 extending axially, and a radially extending wall 128 extending therebetween. The poles 124, 126 and the wall 128 together define a recess configured to receive the field shell 114 and the conductor 116. In the field shell 114, the poles 124, 126 are aligned with the poles 118, 120 to provide a path for magnetic flux between the field shell 114 and the rotor 108 when the electromagnet 106 is energized and current is provided to the conductor 116. The wall 128 defines a clutch-engagement surface that faces the armature 110. The wall 128 may include a plurality of radially spaced rows of angularly spaced grooves 130, which may be empty or machined with a non-magnetic material. When the electromagnet 106 is energized, the grooves 130 allow magnetic flux to travel back and forth between the rotor 108 and the armature 110 across the air gap between the rotor 108 and the armature 110 , enabling high torque engagement between the rotor 108 and the armature 110 .

[0036] The armature 110 is provided to transmit torque from the coupling 26 to the rotor 108, and consequently from the flywheel 16 or another input member coupled to the drive device 12, to the output shaft assembly 24 and to the output member coupled to the output shaft assembly 24 and the driven device 14. The armature 110 may be made from a variety of conventional metals and metal alloys, including steel. The armature 110 may be annular in structure and disposed about and centered on the shaft 34. The armature 110 is disposed axially on one side of the rotor 108 opposite the electromagnet 106 and defines a clutch engagement surface facing the rotor 108. The armature 110 is axially spaced from the rotor 108 by an air gap. Similar to the rotor 108, the armature 110 may include one or more radially spaced rows of angularly spaced grooves 132, which may be empty or filled with magnetic material, to facilitate the shuttling of magnetic flux between the rotor 108 and the armature 110 upon operation of the electromagnet. The armature 110 is coupled to the driven ring 90 of the coupling 26. In particular, the armature 110 may be coupled to the member 100 of the driven ring 90 by a number of leaf springs 134 extending between the armature 110 and the member 100 of the driven ring 90 that bias the armature 110 away from the rotor 108 towards the coupling 26.

[0037] Although clutch 28 comprises an electromagnetic clutch in the illustrated embodiment, and PTO 10 in accordance with the present teachings facilitates the use of an electromagnetic clutch, it should be understood that a mechanical clutch or an electromechanical clutch may alternatively be used in place of electromagnetic clutch 28. In one embodiment with a mechanical clutch, for example, rotor 108 and armature 110 may be replaced by conventional disks that are biased into engagement by a mechanical actuator instead of electromagnet 106.

[0038] The brake 30 is provided to stop rotation of the output shaft assembly 24 and, consequently, the output member coupled to the driven device 14. In accordance with one aspect of the present teachings, the brake 30 comprises an electromagnetic brake housed within the bell housing 18. Brakes used in conjunction with conventional power take-offs often must be mounted in part outside the bell housing due to frictional heat generated during braking. However, the disclosed PTO 10 facilitates positioning and use of an electromagnetic brake within the bell housing, despite the additional heat generated by electromagnetic brakes compared to other types of brakes. The brake 30 includes an electromagnet 136, a friction disc 138, and an armature 140.

[0039] The electromagnet 136 creates an electromagnetic circuit between the electromagnet 136 and the armature 140 to cause movement of the armature 140 toward and engagement with the friction disc 138 and transfer of a braking torque from the friction disc 138 to the armature 140. The electromagnet 136 includes a hub 112, a field shell 142, and a conductor 144. According to one aspect of the inventive PTO 10, the hub 112 is shared between the electromagnets 106, 136 which form part of the clutch 28 and the brake 30. Further description of the hub 112 can be found above.

[0040] The field shell 142 is configured to receive the conductor 144. The field shell 142 also forms part of an electromagnetic circuit that causes selective engagement between the friction disc 138 and the armature 140. The field shell 142 may be made from conventional metals and metal alloys, including steel. The field shell 142 is generally U-shaped in cross section and includes axially extending, radially aligned inner pole 146 and outer pole 148. The field shell 142 may define a hole through which electrical current can be provided to the conductor 144 from an external power source.

[0041] A conductor 144 is provided to create an electromagnetic circuit between the field shell 142 and the armature 140 to cause movement of the armature 140 toward and engagement with the friction disc 138 and transmission of a braking torque from the friction disc 138 to the armature 140 and, therefore, to an output member coupled to the output shaft assembly 24 and the driven device 14. The conductor 144 is generally annular and disposed within the field shell 142 about the shaft 34. In particular, the conductor 144 is disposed between an inner pole 146 and an outer pole 148 of the field shell 142. The conductor 144 may comprise a conventional copper coil, although other known conductors may alternatively be used. The conductor 144 may be electrically connected to a power source (not shown), such as a battery. When the conductor 144 is energized, an electromagnetic circuit is formed between the field shell 142 and the armature 140.

[0042] The friction disc 138 provides a brake-engaging surface facing the armature 140 and is configured for selective engagement with the armature 140 to brake rotation of the armature 140 and the output shaft assembly 24, and consequently, the output member coupled to the driven device 14. The friction disc 138 may be made from a conventional friction material having a relatively high magnetic reluctance. The disc 138 is annular in shape and configured to be received between and fixed against rotation by the poles 146 and 148 of the field shell 142. The disc 138 may project outwardly slightly beyond the poles 146, 148 such that the disc 138 is closer to the armature 140 than the axial ends of the poles 146, 148.

[0043] The armature 140 is provided to transmit braking torque from the friction disc 138 to the output shaft assembly 24 and, consequently, to an output member coupled to the driven device 14. The armature 140 may be made from a variety of conventional metals and metal alloys, including steel. The armature 140 may be annular in structure and disposed about and centered on the shaft 34. The armature 140 defines a brake-engaging surface that faces the friction disc 138. The armature 140 is axially spaced from the friction disc 138 by an air gap. The armature 140 is coupled to the output shaft assembly 24. In particular, the armature 140 may be coupled to the flange 86 of the hub 70 of the output shaft assembly 24 by a number of leaf springs 150 extending between the armature 140 and the flange 86 that bias the armature 140 toward and away from the flange 86.

[0044] Fan 32 provides a means for drawing air into bell housing 18 through air inlet 54, moving the air through bell housing 18 to air outlet 56, and exhausting the air from bell housing 18 through air outlet 56. Referring to FIGURE 5, in accordance with one aspect of the invention, fan 32 moves air generally radially (with respect to axis 34) directly through bell housing 18 such that the air moves across clutch 28 and brake 30 for both cooling clutch 28 and brake 30 and removing heat from bell housing 18 generated by clutch 28 and brake 30 (in addition to heat generated within bell housing 18 from other sources, such as drive 12).

[0045] According to one embodiment, the fan 32 comprises a plurality of blades 152 formed or attached to a rotating element within the bell housing 18. Although the blades 152 may be formed or attached to any component of the PTO 10 that rotates within the bell housing 18, the blades 152 are preferably configured to rotate with the flywheel 16 or another input member coupled to the drive 12 such that the fan 32 operates continuously. Thus, the blades 152 are preferably formed or attached to a component of the PTO 10 that rotates continuously with the flywheel 16. For example, the blades 152 may be formed or attached to a member of the coupling 26, such as the drive ring 88, as shown in FIGS. 1 and 5. Alternatively, the blades 152 may be formed or attached to another component of the coupling 26 or to the armature 110 of the clutch 28. In the case of a mechanical clutch, the blades 152 may be formed or attached to a friction disk configured to rotate with the flywheel 16 or other input member. As noted above, the blades 152 may alternatively be formed on or attached to components of the PTO 10 that only intermittently rotate within the bell housing 18. These components may include, for example, the rotor 108 of the clutch 28 or the armature 140 of the brake 30.

[0046] 6, the blades 152 may be configured for attachment to a rotating element of the PTO 10, such as the drive-in 88 of the coupling 26. Each blade 152 may include a first portion 154 defining a generally L-shaped bracket configured to engage the drive ring 88. One leg 156 of the portion 154 is configured to engage a radially outer surface of the drive ring 88. The other leg 158 of the portion 154 is configured to engage an axial end face of the drive ring 88 and defines a bore 160 configured to receive a fastener for coupling the blade 152 to the drive ring 88. As shown in FIGS. 1 and 5, the fastener may comprise the same fastener 94 used to couple the drive ring 88 to the flywheel 16. Referring again to FIG. 6, each blade 152 further includes a second portion 162 extending from the leg 158 of the portion 154 in a direction opposite the leg 156 of the portion 154. As shown in Figures 1 and 5, the portion 162 of the blade 152 extends in a generally axial direction (relative to the axis 34). As shown in Figure 5, upon rotation of the drive ring 88, the configuration of the portion 162 of the blade 152 creates a force that draws air inwardly through the air inlet 54 of the bell housing 18, moves the air through the housing 18 in a generally radial direction across the clutch 28 and the brake 30 from the air inlet 54 to the air outlet 56, and expels the air from the housing 18 through the air outlet 56. In the illustrated embodiment, the portion 162 of the blade 152 is generally rectangular in shape, but at the end of the blade 152 remote from the portion 154, it is semicircular in shape. The portion 162 is also generally flat. However, it should be understood that the shape of the portion 162 of the blade 152 may vary. With reference to Figure 3, for example, according to another embodiment, the blade 152' is curved rather than flat. In particular, the blade 152' forms an arc. Blade 152' is preferably oriented such that the center of curvature of the arc is disposed on the front side of the arc relative to the direction of rotation of flywheel 16 or other input member coupled to drive 12 (and to components of PTO 10, such as drive ring 88 coupled to flywheel 16). Thus, in the embodiment shown in FIGURE 3, flywheel 16 and drive ring 88 (along with other components of coupling 26 and armature 110 of clutch 28) rotate in a counterclockwise direction.This orientation of the blades 152 ′ may enhance airflow within the bell housing 18 .

[0047] 1, 3, and 5, the blades 152 and 152' are separate components that are attached to the drive ring 88 or another rotating element within the PTO 10. With reference to FIGURE 7, in an alternative embodiment, the fan 32'' may include blades 152'' that are integrally formed with the drive ring 88'' or another rotating element within the PTO 10, such that the blades 152'' and the drive ring 88'' form a unitary (integral) structure and no fasteners such as bolts, welds, adhesives, or the like are required to connect the blades 152'' and the drive ring 88''.

[0048] The power take-off device 10 according to the present teachings represents an improvement over conventional power take-off devices. In particular, the power take-off device 10 includes means 32 for drawing outside air into the bell housing 18, moving the air through the heating elements 28, 30 within the bell housing 18, and exhausting the heated air from the bell housing 18 to reduce the temperature therein. As a result, the power take-off device 10 facilitates the replacement of a mechanical clutch with an electromagnetic clutch 28, thereby overcoming the disadvantages associated with the use of a mechanical clutch. Whereas conventional power take-off devices propose a brake located outside the bell housing, the power take-off device 10 according to the present teachings also facilitates the use of an electromagnetic brake 30 within the bell housing 18 in combination with the electromagnetic clutch 28.

[0049] While the invention has been shown and described with respect to one or more specific embodiments thereof, it will be understood by those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

Claims

1. a bell housing disposed about an axis and configured to be coupled to a driving device housing at a first axial end and to a driven device housing at a second axial end, the bell housing defining an air inlet and an air outlet between the first axial end and the second axial end; a clutch disposed within the bell housing and configured to transfer torque from an input member coupled to the driving device to an output member coupled to the driven device; a fan configured to rotate with the input member to draw air into the bell housing through the air inlet, move air generally radially through the bell housing from the air inlet to the air outlet across the clutch, and exhaust air from the bell housing through the air outlet; A power take-off device comprising:

2. 2. The power take-off device of claim 1, wherein the center of the inlet is diametrically opposite the center of the outlet.

3. 2. The power take-off device of claim 1, further comprising a diffuser coupled to said bell housing, said diffuser defining a plurality of outlet passages in fluid communication with said air flow outlet of said bell housing.

4. 4. The power take-off device of claim 3, wherein a first of the plurality of outlet passages is configured with a downward angle such that a first end of the first outlet passage where air from the airflow outlet enters the first outlet passage is farther from the axis than a second end of the first outlet passage where air exits the first outlet passage.

5. 2. The power take-off device of claim 1, wherein the clutch comprises an electromagnetic clutch.

6. 2. The power take-off device of claim 1, wherein the fan comprises a plurality of blades formed on or attached to a drive ring of a shaft coupling configured for coupling to the input member for rotation therewith.

7. 2. The power take-off device of claim 1, wherein the fan comprises a plurality of blades formed on or attached to a disk of the clutch, the disk being configured to couple to the input member for rotation therewith.

8. The power take-off device of claim 1 , wherein the fan comprises a plurality of individual blades configured to rotate with the input member.

9. 9. The power take-off device of claim 8, wherein one of said plurality of blades defines an arc and is oriented such that a center of curvature of said arc is disposed on a leading side of said arc relative to the direction of rotation of said input member.

10. a bell housing disposed about an axis and configured to be coupled to a driving device housing at a first axial end and to a driven device housing at a second axial end, the bell housing defining an air inlet and an air outlet between the first axial end and the second axial end; an electromagnetic clutch disposed within the bell housing and configured to transfer torque from an input member coupled to the driving device to an output member coupled to the driven device; an electromagnetic brake disposed within the bell housing and configured to apply a braking torque to the output member; a fan configured to rotate with the input member to draw air into the bell housing through the air inlet, to move the air generally radially through the bell housing from the air inlet to the air outlet across the electromagnetic clutch and the electromagnetic brake, and to exhaust the air from the bell housing through the air outlet; A power take-off device comprising:

11. The power capture of claim 10 , further comprising a coupling having a drive ring configured to be coupled to the input member and a driven ring configured to be coupled to the armature of the electromagnetic clutch.

12. 12. A power take-off device according to claim 11, wherein the fan comprises a plurality of blades formed on or attached to the drive ring of the shaft coupling.

13. 11. A power take-off device according to claim 10, wherein the centre of the inlet is diametrically opposite the centre of the outlet.

14. 11. The power take-off device of claim 10, further comprising a diffuser coupled to the bell housing, the diffuser defining a plurality of outlet passages in fluid communication with the airflow outlet of the bell housing.

15. 15. A power take-off device as claimed in claim 14, wherein a first of the plurality of outlet passages is configured with a downward angle such that a first end of the first outlet passage where air from the airflow outlet enters the first outlet passage is farther from the axis than a second end of the first outlet passage where air exits the first outlet passage.

16. 11. The power take-off device of claim 10, wherein the fan comprises a plurality of blades formed on or attached to a drive ring of a shaft coupling configured for coupling to the input member for rotation therewith.

17. 11. The power take-off device of claim 10, wherein the fan comprises a plurality of blades formed on or attached to an armature of the electromagnetic clutch, the armature being configured to be coupled to the input member for rotation therewith.

18. The power take-off device of claim 10 , wherein the fan comprises a plurality of individual blades configured to rotate with the input member.

19. 20. The power take-off device of claim 18, wherein one of the plurality of blades defines an arc and is oriented such that a center of curvature of the arc is disposed on a leading side of the arc relative to the direction of rotation of the input member.

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