Accessory drive and particle trap

TECHNICAL FIELD

The present invention relates to a combination drive assembly and particle trap for operatively engaging a plurality of accessory units and providing filtered fluid to the accessories under a positive head condition.

BACKGROUND

Pump drive assemblies for mechanically powering an accessory pump such as a steering pump and/or implement pump are well known. One type of known pump drive assembly includes a gear assembly support housing externally mounted to a transmission casing of a transmission with the input gear of the transmission utilized to drive the pump drive assembly. The accessory pump, as it is driven by the transmission, pumps transmission fluid through a dedicated line connected between the accessory pump and a flanged suction port provided on the transmission casing. The dedicated line may include a screen assembly spliced into the dedicated line to trap particles entrained in the transmission fluid before the fluid reaches the accessory pump.

The accessory drive assembly is typically mounted on the transmission casing at a position above the fluid level in the transmission so that the fluid does not unduly restrict rotation of the drive assembly in contact with the fluid. The gears of the accessory drive assembly are often pre-lubricated, during assembly, for example, with grease so that additional lubrication by the transmission fluid is not required. If fluid does enter the accessory drive assembly housing for any reason an amount of fluid may be trapped within the accessory drive housing and become significantly elevated in temperature which is known to cause gear failure or premature wear of the gears and bearings. To avoid compromising the accessory drive assembly, the accessory drive assembly is generally positioned away from the fluid to prevent problems caused by the interaction between the stagnant fluid and the gears.

The installation of the accessory drive assembly to the transmission generally includes, first, attaching the various drive assemblies so that the accessory pump is activated corresponding to rotation of the input shaft of the transmission. Second, at least one transmission fluid line must be installed between a flange on the transmission casing, below the level of fluid contained in the transmission casing, and the flange or connector on the accessory pump. Furthermore, a particle trap or filter screen is generally introduced within the transmission fluid to ensure that particles and debris entrained in the fluid are prevented from entering the accessory pump. Hence, installing an accessory pump and drive system requires multiple components and significant labor to equip a transmission with such a system.

The present invention is directed to overcoming one or more of the problems as set forth above.

SUMMARY OF THE INVENTION

In one aspect of the present invention an accessory drive system to provide engagement between a driving input source and a driven accessory unit is provided and includes a housing attachable to the input source. A fluid suction port and a discharge port are defined by the housing and the suction port is in fluid communication with a fluid reservoir of the input source. The fluid discharge port is in fluid communication with the suction port and a gear assembly is rotatably supported by the housing. The accessory unit is operably engaged by the input source through the gear assembly and the gear assembly is structured and arranged within the housing to urge fluid away from the housing in response to movement of the gear assembly.

In another aspect of the present invention a method for operably engaging a fluid circulating accessory unit to an input source is provided and the method includes driving a gear assembly attached to the input source through a housing; circulating fluid from a reservoir to the accessory unit through the housing; and removing substantially all of the fluid entering a gear chamber of the housing through movement of the gear assembly within the housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a perspective view of an accessory drive system according to the present invention;

FIG. 2

is an exploded view of the input source and the accessory drive assembly of

FIG. 1

;

FIG. 3

is a plan view of the accessory drive unit of

FIG. 1

;

FIG. 4

is a sectional view of the accessory drive unit of

FIG. 1

, taken along line

4

—

4

of

FIG. 3

;

FIG. 5

is a perspective view of the accessory drive unit of

FIG. 1

illustrating the idler gear and suction port;

FIG. 6

is a sectional view of the accessory drive unit of

FIG. 1

, taken along line

6

—

6

of

FIG. 3

, showing the particle trap assembly contained therein; and

FIG. 7

is a sectional view of the accessory drive unit of

FIG. 1

, taken along line

7

—

7

of

FIG. 4

, showing the gear assembly within the housing.

DETAILED DESCRIPTION

Referring to

FIG. 1

, an accessory drive system

9

is shown which includes input source

10

, such as transmission, for example, in driving engagement with an accessory drive assembly

12

. Accessory drive assembly

12

includes housing

14

attached to casing

16

of input source

10

. Accessory drive assembly

12

supports a first accessory unit

18

and a second accessory unit

20

which may be steering and implement pumps, for example.

Referring to

FIG. 2

, housing

14

includes a flange portion

24

and a projecting portion

22

extended from the flange portion

24

. The projecting portion

22

includes an opening

23

from which an idler gear

42

extends therefrom. Flange portion

24

includes a flange face

26

which overlays face

28

of casing

16

. Projecting portion

22

extends into slot

32

within casing

16

. As best shown in

FIG. 5

, housing

14

includes a suction port

30

which overlays port

34

extended through casing

16

of input source

10

. Referring to

FIG. 3

, bolts

36

extend through flange portion

24

of housing

14

and engage threaded holes

38

(

FIG. 2

) in casing

16

.

Referring to

FIG. 4

, accessory drive assembly

12

includes a gear assembly

40

including the idler gear

42

and an output gear

44

. Idler gear

42

meshes with an input gear (not shown) enclosed within the casing

16

and is driven by the input source

10

. The output gear

44

is meshed with the idler gear

42

and both output and idler gears

44

,

42

are rotatably supported by the housing

14

. In an exemplary embodiment, the idler gear includes thirty-six teeth and is respectively meshed with a transmission gear having thirty-five teeth and an output gear having thirty-nine teeth. As best shown in

FIG. 4

, output gear

44

includes a first spline portion

46

which accordingly engages with a splined shaft (not shown) of first accessory unit

18

(FIG.

1

). Similarly, a second spline portion

48

is provided in output gear

44

and accordingly engages with a splined shaft (not shown) provided by second accessory unit

20

(FIG.

1

).

Referring again to

FIG. 4

, housing

14

includes first housing portion

52

sealably attached with housing cover

54

by conventional bolting means. Output gear

44

is rotatably supported by first housing portion

52

and housing cover

54

through respective bearing assemblies

56

,

58

. First bearing assembly

56

includes an outer surface

60

which is engaged by inner bore

62

of first housing portion

52

. Bearing assembly

56

includes an inner surface

64

engaged by collar portion

66

of output gear

44

. Similarly, second bearing assembly

58

includes an outer surface

68

engaged by inner bore surface

70

of housing cover

54

. Bearing assembly

58

includes an inner surface

72

engaged by collar portion

74

of output gear

44

.

Idler gear

42

is rotatably supported by housing

14

as hereinafter described. Pin

76

and bearing

77

extend through hole

78

in idler gear

42

to generally center gear

42

about outer surface

80

of pin

76

. Pin

76

is accordingly sized in relation to holes

82

,

84

within housing

14

to hold pin

76

stationary as idler gear

42

rotates thereabout.

Referring to

FIGS. 4 and 7

, output gear

44

includes a periphery portion

86

which is closely arranged with an inner surface

88

of housing

14

, forming clearance

90

therebetween. Clearance

90

, which may also be referred to as a “draft”, uniformly extends along each lateral surface

91

,

93

and along the periphery portion

86

of output gear

44

within a gear chamber

95

of housing

14

. In an exemplary embodiment, clearance or draft

90

may be 1.5 mm, for example. A discharge chute

92

is provided radially outside output gear

44

within the housing

14

which receives fluid purged from gear chamber

95

of housing

14

by output gear

44

as hereinafter described. An opening

97

is provided in flange

24

of housing

14

so that fluid directed through discharge chute

92

may exit the accessory drive assembly

12

(FIG.

7

).

As best shown in

FIG. 4

, the accessory units

18

,

20

(

FIG. 1

) respectively mount to faces

45

,

47

of housing

14

. Housing

14

includes a pair of intake openings

49

,

50

which respectively receive fluid from the accessory units

18

,

20

.

Referring to

FIG. 6

, a particle trap assembly

96

is provided within suction chamber

94

of housing

14

to trap particles and debris entrained within the fluid entering the accessory drive assembly

12

from a fluid reservoir (not shown) formed within the casing

16

. The particle trap assembly

96

may include a cylindrical screen assembly

98

which is impregnated, circumferentially along portions of each end

100

,

104

with a resilient elastomer or other screen-to-casting-seal structure known to those having ordinary skill in the art. Furthermore, it is envisioned that the screen assembly

98

may be made of an alternative material such as corrugated cellulose, for example, or any other alternative material known to those having ordinary skill in the art.

Screen assembly

98

includes end

100

projecting into, and circumferentially sealed within, counterbore

102

of housing

14

. Similarly, end

104

of screen assembly

98

engages circumferential rim portion

106

of housing

14

. End

104

of screen assembly

98

includes end wall

105

which encloses end

104

and is preferably constructed of either the filter material itself or by the seal extending over end

104

of the screen assembly

98

. In contrast, end

100

of screen assembly

98

includes opening

107

to allow the clean fluid, which has passed through the screen assembly, to pass through the discharge port

99

and be accordingly directed to the accessory units. A retaining member

108

, such as a wave spring or arched retaining ring, for example, is positioned between end wall

105

of screen assembly

98

and a service cover

110

to secure the screen assembly

98

such that it is sealed within suction chamber

94

of housing

14

. Cover

110

is sealed to housing

14

through an O-ring seal

114

and is secured to housing

14

by fasteners

112

(FIG.

3

).

Referring to

FIGS. 1 and 5

, discharge port

99

includes an inner surface

116

, preferably machined, to sealably receive a tube end (not shown) fitted with an O-ring seal (not shown) to form a conventional pipe-to-port, or “slip-joint” type sealing arrangement. Alternatively, it is envisioned that the pipe may include an integral flange which may abuttingly interface with a complementary flange provided by the housing, such as a four-bolt flange for example. Accordingly, fluid passing through discharge port

99

is directed to respective charge pumps (not shown) fluidly connected to accessory units

18

,

20

(FIG.

1

).

Industrial Applicability

Referring to

FIG. 2

, in an exemplary embodiment accessory drive system

9

is driven by input source

10

which may be a transmission including a rotatable drive gear (not shown) meshed with idler gear

42

which urges rotation of output gear

44

(FIG.

7

). The transmission includes a reservoir having a level of fluid contained within casing

16

which is generally above the port

34

within casing

16

. Since the port

34

is generally below the level of fluid within the casing, the fluid flows into, and is continuously present within, the suction chamber

94

of the housing

14

. Fluid enters the gear chamber

95

from the accessory units

18

,

20

through intake openings

49

,

50

within the housing

14

(FIG.

4

).

Referring to

FIG. 7

, operation of the gear assembly

40

will now be described. Accessory units

18

,

20

(

FIG. 1

) direct fluid to the gear assembly

40

through bearing assemblies

56

,

58

(FIG.

4

and

FIG. 7

, however only bearing assembly

56

is shown in

FIG. 7

) rotatably supporting idler gear

42

. As the fluid travels through the bearings and across the idler gear, the fluid is urged from the idler gear to the output gear. The respective rotational motion of the idler and output gears is shown by arrows

118

,

120

. Fluid may enter opening

23

in projecting portion

22

of housing

14

, possibly subjecting gear

42

to partial immersion in fluid, however it is envisioned that the gear assembly

40

would be effective to remove even significant amounts of fluid which may have entered into housing

14

.

Since the output gear

44

is closely fitted within the gear chamber

95

substantially all of the fluid entering the gear chamber

95

is urged out of the gear chamber

95

by the output gear

44

. Arrows

122

, which are in proximity to the periphery portion

86

of the output gear

44

, indicate the fluid path as fluid passes through the gear chamber

95

. It may be seen that the fluid moves through the discharge chute

92

and exits the accessory drive assembly

12

through discharge opening

97

. The output gear

44

urges fluid away from the accessory drive assembly and back into the transmission casing

16

through the discharge chute

92

and then through the opening

97

within projection portion

22

of housing

14

. As a result, an insignificant amount of fluid resides within the housing, and consequently, the input and idler gears experience little if any resistance due to fluid.

Since the suction port

30

(

FIG. 5

) of the housing

14

is submersed in fluid within the fluid reservoir and generally below a fluid level of the reservoir, a positive fluid pressure or “head” is established at the site of the input of the accessory unit (not shown). As a result, a positive head is experienced by accessory units which increase the performance, controllability and responsiveness of the accessory units.

Other aspects, objects and advantages of the invention can be obtained from a study of the drawings, the disclosure and the appended claims.