Description

Background of the Invention

This invention relates to hydraulic motors, particularly those used as vehicle wheel motors or those incorporated into heavy machinery requiring mechanical braking systems.

A commonly used form of hydraulic motor consists of internal gear or gerotor sets consisting of inner and outer members which have radially projecting teeth that engage with each other to form expanding and contracting chambers. These chambers provide a means of circulating fluid through the gear set in a manner which utilizes fluid pressure _. for producing shaft rotation. Conversely, in a pump, shaft rotation is used to produce fluid pressure. In this way, such gear sets can be used as either hydraulic motors or pumps.

In a common gear or gerotor type motor, a central inner gear member is made to rotate eccentrically within a housing shaped for reciprocal contact with the gear member , to cause the creation of the expanding and contracting chambers. The eccentric rotational movement of the inner member is transmitted through a coupling called a "dog-bone" to a centrally rotating drive shaft from which machinery movement is powered. This can be seen, for example, in U.S. Patent 3,549,284. The dog-bone coupling is required because central

rotation about a fixed axis is needed in machinery drive shafts.

The dog-bone coupling may only be used to pro¬ duce central rotation at one end of the device motor housing. At the dog-bone end of a gerotor the central shaft rotates and provides the machinery drive. The centrally rotating shaft upon a fixed axis is generally supported by bearings in the relatively small area between the dog-bone coupling and the end of the housing. Th --eccentrically rotating dog-bone shaft cannot be supported by bearings at all and acts as a level applying undesirable force to the central drive shaft.

In common practice, mechanical brakes are added to machinery drive trains either between the hydraulic motor and the operating machinery or somewhere within the operating mechanical system itself. Mechanical brakes are required when hydraulic motors are used to propel heavy machinery or elevate platforms, since their locked position must be assured. Any hydraulic fluid leakage which allows the hydraulic motor to turn once hydraulic pressure is turned off, causes inad¬ vertent back movement of machinery. This back move¬ ment is highly dangerous in many machinery applications. It is for this reason that hydraulic motors are either limited in use or equipped with mechanical shaft locking devices. When hydraulic motors are used as wheel motors to propel vehicles, mechanical shaft locking devices serve as parking brakes.

In a common gerotor motor as described above, a mechanical brake must be installed on the central shaft. This results in the brake being located in series with the motor and the machinery to be pro- pelled. Thus, the brake is forced to carry the torque load of the motor as applied to the machinery. Such an arrangement extends the overall length of the motor-brake system and increases the motor and brake system's weight and cost. Additionally, mounting a brake between the machinery to be driven and the hydraulic motor drive places further undesirable bending and torque loads upon the central motor shaft and its bearings. This is because hydraulic actuation and mechanical locking operations cannot be so timed in practical use that they will not, from time to time, be opposing forces. Any misalignment of the braking action and the central motor shaft magnifies bending and torque loads upon that shaft and the bearing which supports it. Bearing and shaft failures are unfortunately quite common when such motors are used in high torque operations requiring mechanical brakings.

Some gear motors, however, have been designed with centrally rotating through-shafts. In these style motors, an orbiting outer member moves eccentrically while an inner member rotates centrally ^* about a fixed axis. See, for example, U. S. Patent 2,989,951.

In hydraulic motors with through-shafts rotating about a fixed axis, the shaft may project out both ends of the motor and be used for propulsion or braking purposes at either end along its fixed axis of rotation.

The creation of a fixed axis of rotation is generally accomplished by allowing the outer member of the gerotor set to orbit about the center of rotation of the fixed axis of the inner member. The outer member does not rotate about its own axis but merely orbits in a non-rotational manner around the fixed axis of the rotating inner member. This motion is a type of circular shuttle motion in which the entire outer member moves in a circle at a small radial distance from the axis of the inner member. This radial distance is the eccentricity required for the motor or pump to operate by forming expanding and contrac¬ ting chambers between the inner and outer members. The through-shaft motors represent an improve- ent over gerotor type motors discussed above but have been unable to overcome certain deficiencies when used in heavy duty operations which generate high torque loads. These devices have been limited by both the valving and bearing arrangements in their designs.

U. S. Patent 4,025,243 by Stephens discloses an orbit motor with a central shaft as described above. The shaft is supported by three needle bearings. A motor of this type would not be able to withstand high thrust loads as needle bearings primarily control shaft bending and are not capable of withstanding thrust loads along their longitudinal axis. The Stephens motor can only use needle bearings adjacent to its gear set because of its dual valving arrangment. The chambers formed between the inner and

outer members are ^' in fluid communication with valve ports on each side of the orbiting member in order to achieve efficient valve flow. This arrangement limits the amount of room surrounding the shaft, proximate to the gear set, in which a bearing may be placed and, therefore, restricts this type device to light thrust load operations.

U. S. Patent 2,989,951 to Charlson discloses an orbit motor wi ^* y ^* ι. a. gerotor. set of rotating inner ^' and orbiting outer members.- These are fed by valving on both sides of the gerotor set. This is required as in the Stephens motor to maintain efficient valving of the gerotor set. When valving of this type is only at one end of the gerotor, the chambers would fill too slowly with fluid to properly support normal motor speeds.

U.S. Patent 3,151,526 to Hoene reveals a gear motor shaft supported by three bearings. The device also has a complex valve arrangement which necessitates placement of bearings at a significant axial distance away from the central rotating gear where bearing support is most useful in preventing shaft bending.

An alternate method of supporting a shaft close to the operating members than those discussed above is to narrow the shaft diameter sufficiently to allow bearing placement adjacent to those members. Where this has been done, central shafts have failed under high torque loads.

The embodiment discussed below represents an improvement over hydraulic motors previously manu¬ factured . The.prior art ^" mo or- described in

U. S. Patent 3,623,829 is not adapted for use in the heavy machinery industry. High torque low speed motors have in the past retained the bearing arrangement of high speed gerotor motors and have not been able to take advantage of the through shaft characteristics possible within this new design for heavy duty uses.

A need therefore exists for a compact through- shaft motor which resists bearing failure and shaft breakage under high torque conditions. A motor of this type would allow for more efficient and less dis¬ ruptive replacement of mechanical brakes in hydraulic motor systems.

Summary of the Invention

In accordance with the principles of this invention the device disclosed comprises a fluid displacing apparatus with inlet and outlet ports for the entry and exit of hydraulic fluid. Inside a motor housing an inner member is mounted on a central shaft for rotation about a longitudinal fixed axis of the shaft. Fluid is displaced betwen the inner member and an outer member which is mounted within the apparatus housing for eccentric orbital movement about the fixed axis of the shaft.

The shaft projects externally to the motor housing at one end and is supported by three bearings adjacent to the .inner and outer members. Two of the bearings are thrust resistant tapered roller bearings while one of the bearings is a needle bearing. The bearings serve to accommodate thrust, bending and side loads that are applied to the apparatus shaft during operation of attached heavy machinery.

In the preferred embodiment, the outer and inner members define a plurality of circumferentiaily spaced fluid chambers which vary in size in response to the rotation of the inner member and the orbital movement of the outer member. Additionally, the inner member has a number of semicircular shaped teeth which in the preferred embodiment are formed by rollers held within pockets of said inner member. The outer member has multiple arcuately generated radial teeth on its inner diametric surface. The generated teeth number one greater than the number of semicircular teeth present on the inner member. The generated teeth are non-circular in order to provide for continuous reciprocal interaction with the semicircular teeth of the inner member in response to the nonrotational orbital movement of the outer member and the rotation of the inner member about a fixed axis.

The preferred embodiment further comprises a mechan¬ ical brake mounted upon the central shaft within the motor housing. The brake contains a brake disk mounted upon the shaft, and a non-rotatable brake pad is mounted within the motor housing; with means provided for moving the brake pad into contact with the rotatable brake disk to arrest or prevent rotation of the central shaft. A second preferred embodiment comprises a motor housing having a central rotatable shaft which projects external to the housing at both longitudinal ends of the housing. An inner and outer member are disposed in that housing as in the first embodiment above. One end of said shaft, however, is used for mounting of an external brake identical to the internal brake described above. The second end of said shaft is used to drive machinery with the rotational movement pro¬ vided by the motor.

Both embodiments provide for a compact hydraulic fluid displacing apparatus capable of supporting heavy thrust and bending loads. The invention also provides for mechanical braking at a point removed from the end of the central shaft used as the drive shaft for machinery.

Brief Description of the Drawings

Figure 1 is a cross -section of a hydraulic motor embodying this invention. The cross section is taken along the length of the central shaft.. Figure 2 is a cross section of the hydraulic motor taken along line 2-2 of Figure 1 showing the internal gear set.

Figure 3 is a cross section of the hydraulic motor taken along line 3-3 of Figure 1 showing the internal valving.

Figure 4 is a partial section of the hydraulic • motor showing the working relationship of the gear set, commutator and valve.

Figure 5 is a partial section of the motor as shown ^* in Figure 4 after a slight clockwise rotation of the inner member

Figure 6 is a partial section of the motor as shown in Figure 5 after an additional slight clockwise rotation of the inner member. Figure 7 is a plane view of a second embodiment of the invention with an external brake.

Figure .8 is a cross section of the second embodiment of Figure 7 taken along line 8-8 o± Figure 7.

Detailed Description of the Invention

Figure 1 is a lengthwise cross-section of a hydraulic motor 8 embodying the invention. The motor 8 contains an integral brake shown generally at 20 and three bearings 14, 16, and 18 for accommo¬ dation of large bending and thrust loads.

The hydraulic device of Figure 1 as described below utilizes pressurized fluid to produce shaft rotation. The device may also be used to produce pressurized fluid if shaft rotation is supplied to the unit. Therefore, the device may be considered as either a hydraulic motor or pump.

The hydraulic motor shown in Figure 1 is enclosed in a housing 9 in which a central shaft 12 is supported to rotate about a fixed axis. The shaft 12 is held in rotatable position about its longitudinal axis by two tapered roller bearings 14 and 16, and a needle bearing 18.

The motor housing is constructed in four pieces for ease of construction and access to internal parts. Motor mount housing 11 contains the tapered roller bearings 14 and 16 and the shaft exit area from which the extended shaft 12 is attached to machinery. A mounting flange 72 allows for the affixing of the motor to a machinery frame during motor usage and serves to transmit reaction forces generated by motor operations. Gear set housing 10 contains the two -gear members 30, 32 as well as the valve plate 48. The housing is designed, as discussed below, to prevent outer member 32 from rotating.

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Commuta or housing 13 houses a commutator 57 which serves to conduct fluid from the inlet port 46 and outlet port to the valve plate 48. The commutator housing 13 also supports needle bearing 18 which supports the shaft in the brake area 20.

Brake housing 21 supports the brake 20 used to lock the shaft 12 and prevent rotation as required for safe machinery operations.

Access to the brake area is achieved by removal of bolts 40. Further internal access to valve and gear set may be achieved by removing bolts 62 which are on bolt circle 68 (Figures 2 and 3) . Tapered roller bearings 14 and 16 are maintained within the motor mount housing 11 and in position by snap rings 15 and 17 mounted on the shaft 12 on each side of bearings 14 and 16 _. . Seal 19 prevents loss of hydraulic- fluid forward of the shaft near tapered bearing 14. Retainer 21 holds the seal in position next to snap ring 15. . Figure 2 is a cross section of the motor of

Figure- 1 which shows the fluid chambers 52 in which hydraulic fluid is circulated. As will be described below, high pressure fluid causes rotation of an inner member 30 as the chambers get larger and smaller due to the eccentric movement of outer member 32.

The path of hydraulic fluid used in this device may be better understood with reference to Figures 1, 2, and 3. High pressure fluid enters the hydraulic motor at inlet port 46 (Figure 1) . At the base of the inlet 46 is gallery 47, which serves to conduct fluid to eight inlet commutator ports 54 (also shown

in Figure 3 in dotted lines) . The gallery or plenum 47 is an open annulus in the commutator 57 connecting all the high pressure ports 54 and equalizing fluid pressure amongst them. High pressure fluid flows through a valve plate 48 which is affixed to shaft 12 and rotates with it. Plate 48 has a plurality of fluid transmission ports 56. The valve plate 48 and ports 56 are shown in detail in Figure 3 in solid lines. The valve plate selectively allows fluid from the commutator ports to enter the chambers between the rotating inner member 30 and non-rotating outer member 32 shown in Figure 2. The high pressure fluid upon entering chambers 52 causes the chambers to expand and thereby rotate the central motor shaft 12. - Fluid which has lost pressure by propelling the central shaft 12 remains in some of the chambers 52. This fluid is removed from the motor chambers 52 through valve plate 48 which selectively opens passages from the contracting chambers to the low pressure commutator ports 49. As shown in Figure 1, these ports 49 are also connected together with a gallery or plenum 51. This annular plenum equalizes fluid pressure and conducts the fluid to an outlet port similar to the inlet port 46. From this outlet port fluid is discharged from the motor and returned to a fluid source.

The inner member 30 (Figure 2) is mounted upon shaft 12 which rotates about a fixed center. The inner member 30 comprises a plurality of circumferen- tially spaced semicircular gear teeth 61. In the preferred embodiment of Figure 2, the teeth 61 consist of circular cylinders, or rollers, 61 which are _. held

at a uniform radius from the center of rotation. The outer member 32 has a non-circular, or generated, inner surface 33 with teeth 35 numbering one greater (eight) than the number of teeth (seven) on the inner member.

The outer member 32 moves eccentrically within the housing 10 but does not rotate about its axis 92. The center point of the outer member, axis 92, moves in a circular orbit about the axis of rotation 90 of the inner gear 30. The radius E of the circle made by the outer gear's center in its movement defines the amount of the outer member's eccentric movement.

Rotational movement of outer member 32 is pre¬ vented by rollers 73 mounted in the housing 10. These rollers are trapped in gear housing 10 in order to prevent rotation of the outer member 32 but do allow for the eccentric movement, or orbiting of the outer gear center, around the fixed center 90 of the inner member 30 shaft 12. The ^" inner peripheral surface of the outer, or inter¬ nally generated member (IGR) 32 is precisesly generated by a grinding or other shaping mechanism in a sinusoidal- like shape which utilizes the eccentric movement of the outer member 32 to provide for continuous contact of the outer member with the teeth of the rotating inner member. The teeth of the inner member are main¬ tained in constant contact thereby with the outer member 32. In this manner the inner and outer rotors create circumferentiaily spaced sealed chambers 52 (Figure 2) of varying volume in response to the eccen¬ tric non-rotational (orbital) movement of the outer me ber 32 and the central rotation of the inner member.30. Each of the rollers, or rolls, 61 is disposed at the appropriate

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radius with respect the generated inner surface 33 of the outer member 32 to create seven hydraulically sealed chambers 52. The smooth generated surface 33 is a low friction working surface which allows easy rotation of the inner member 30.

To operate the motor high pressure fluid is provided at inlet port 46. At the base of inlet 46 is gallery 47, and the gallery or plenum serves to conduct the fluid to eight stationary commutator inlet ports 54 shown in Figure 3 in dotted lines. The plenum 47 is an open annulus in the commutator connecting all the high pressure ports 54 and equalizing pressure amongst them.

Valve plate 48 is fixedly attached to shaft 12 adjacent to an inner member 30 as shown in Figures 1 and 3. The valve plate 48 therefore rotates in con¬ junction with the inner member 30. Depending on the rotational position of the valve plate 48 with respect to stationary commutator ports 49 and 54, seven valve ports 56 (shown in solid lines in Figure 3) open passages from the gear set chambers 52 to the commu¬ tator at high and low pressure ports, 49 and 54 respec¬ tively.

Figures 4, 5, and.6 show the relationships of the gear set, valving and commutator ports as the motor operates. The gear set is shown in phantom and the commutator ports in dotted lines.

Figure 4 is a cross-section of the gear set and valving in which the motor is shown operating in a clockwise direction. Chamber 52A is shown to be in¬ creasing in size as it is being filled with high pressure fluid from commutator port 54A through valve port 56A.. Chamber 52B as at its maximum volume and is not in communication with any commutator port.

Figure 5 shows the same elements as Figure 4 after the motor has rotated a small fraction of a turn from the position shown in Figure 4. The outer member 32 axis 92 has continued on its orbit about the inner member 30 axis 90. As a consequence, chamber 52A has raeached maximum dimensions. Chamber 52A as shown is now sealed and out of fluid communication with the commutator due to the rotation of the valve port 56A. Chamber 52B has begun to decrease in size, and the valve plate allows lower pressure luid to be withdrawn from the chamber 52B through valve port 56B, by commutator port 49C.

Figure 6 shows a further progression of the motor as chamber 52A and 52B both become smaller and have their low pressure fluid withdrawn through valve ports 56A- ^* and 56B.

In all cases, when a maximum chamber 52 size is reached in the movement of the inner and outer members, the valve plate 48 acts to open that chamber only to the low pressure commutator ports 49 until the chamber volume reaches its minimum and the low pressure fluid has departed, at which point the valving ^" switches the connection back to high pressure only so that the chamber may refill to maximum si-ze. High pressure and low pressure fluid is thereby intermittently fed and released from chambers 52 between the inner rotor 30 and the outer 32.

High pressure fluid entering into the gear set chambers pushes the teeth formed by the roller 61 towards the low pressure areas as the chambers 52 become larger in response to the high pressure. This use

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of fluid pressure to supply rotational energy decreases the hydrostatic pressure of the fluid. Low pressure fluid is then withdrawn from between the outer and inner rotors back through the valve plate 48 which opens the passage to the low pressure commutator ports 49, To reverse rotation of the motor, high pressure and low pressure fluid may be reversed at the inlet and outlet, and the motor will work as efficiently in the opposite direction from that detailed above.

The seven valve ports 56, or field elements, on the valve plate 56 are activated eight times per revolution. This continual release of fluid pressure for rotational energy in each of the seven chambers ^" 52 provides high torque for a small amount of rotation. Given a similar fluid input pressure, a traditional gerotor set with only two valve ports would spin at a much faster speed and lower torque than a motor valved as above. It is for this reason that this motor is considered a high torque low speed motor. An additional advantage of the rotating valve plate 48 is that it permits a high level of fluid volume to pass in and out of the opening and closing chambers 52 of the gear set at a very rapid rate. Shallow depressions 80 (Figure 3) on the surface of the valve permit fluid from the commutator 48 to be positioned between the commutator housing 13 and the rotating valve plate. These shallow depres¬ sions 80 prevent chafing between the commutator housing and the rotating valve plate and aid in balancing of the valve plate. As with any rotating

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part, unbalance tends to cause eccentric movement and wear. Since the valve plate rotates with the centrally rotating inner gear 30, such eccentric movement is to be avoided. It is thus shown that the chambers 52 created by the reciprocal members 30 and 32 are driven into rota¬ tional movement by the injection of high pressure fluid and the withdrawal of low pressure fluid. The fluid energy is thereby used to produce shaft rotation and work. Since the inner gear rotates centrally, valving may be accomplished with a centrally located valve plate and commutator that need not accommodate any eccentrically moving characteristics of the motor...

The use of such valving allows for the placement of valve and commutator ports at a larger radial dis¬ tance from the shaft than was ever before possible. This allows for the placement of large support bear¬ ings 14, 16, and 18 in the unused annulus surrounding the shaft adjacent to the working members 30, 32 and . the valve plate 48 in order to more fully support the central shaft 12. This arrangement is in sharp divergence from previous valving arrangements of common gear and gerotor motors. Commonly known gerotor motors have a generated outer peripheral surface on their inner members. This ^' shaping requires valving at a closer radius to the central shaft than in the present invention; as a result, bearings cannot be placed adjacent to the rotating members.

An important part of the present invention which enables use of the motor 8 in high torque load operations, relates to the type of bearings utilized and the placement of such bearings. Bearings 14 and 16 are opposed tapered roller bearings which permit heavy radial and thrust loads. The bearings are placed adjacent to the gear set member 30, 32 for maximum motor support. Each tapered roller bearing is composed of an outer race 34, rollers 36 in a cage (not shown) and an inner race

38. The rollers in the cage rotate against the inner race and the outer race as the shaft 12 rotates. Inner race 38 is affixed to the shaft 12 so that the movement of the race 38 follows the shaft movement. Outer race 34 is mounted to the stationary motor mount housing 11.

In addition to the tapered roller bearings, a needle bearing 18 in the commutator housing 13 sup¬ ports the shaft. Particularly, the needle bearing 18 supports the shaft 12 in the brake area 20. Needle bearings 18 permit moderate rotational speeds in this application. Rotational speeds are maintained at less tha -2000 RPM with a minimum of friction. The needle bearing accommodates shaft bending and side loads. In some applications a sleeve bearing may be preferred instead of the needle bearing shown.

The needle bearing 18 consists of needle rollers 100 which rotate between the rotating shaft 12 and the stationary commutator 57 surrounding the shaft 12. The roller 100 rotates against a hardened portion of the central shaft 12 as an inner race and ^* the commu¬ tator housing 13 as an outer race. Needle rollers 100 are held within a cage (not shown) as they rotate.

In the preferred embodiment, bearings 14, 16 and 18 are oil fed bearings that utilize the hydraulic fluid of the internal gear set for lubri¬ cation. Check valve 50 permits the tapered roller bearings 14 and 16 to be lubricated from the inlet port 46 by way of the gear set. The pressure from the inlet port 46 is normally higher than the hydraulic. fluid pressure in the roller bearing area. This pressure normally holds the check valve 50 in the closed position. If fluid pressure near the bearings exceeds fluid inlet pressure or if motor rotation is reversed, the valve 50 automatically opens to prevent over-pressurization of roller bearings 14 and 16 by allowing fluid to be released ^* by way of passage 67. Vent port 58 is normally plugged with plug 60 except when high back pressure must be removed from seal 19. Needle bearing 18 is lubricated with hydraulic fluid which is allowed to seep past valve plate 48. In addition to the bearings already described, the solution to the problem of high shaft loads and bearing failure resides in the inclusion of. an integral shaft locking brake 20. In the first embodiment shown in Figure 1, the brake 20 is provided adjacent to the motor and disposed within the same housing assembly.

The brake 20 is a multidisk ^' type, having three rotary disks 22. The disks are permanently affixed to shaft 12 by close tolerance spline 105. When the disks 22 are brought into contact with non-rotating braking elements 24, shaft rotation is arrested or prevented.

Normally, the non-contacting position of braking element 24 is maintained by springs 26. In this posi¬ tion the disks 22 are free to rotate with the shaft 12. When shaft locking or braking is required, piston plate 28 is moved into position to push the brake pads 24 against the disks 22 and thereby arrest any motion of the shaft 12.

In the preferred embodiment, fluid applied at port 110 flows to annular cavity 112 and maintains fluid pressure on the piston 28 which releases the brake and unlocks the shaft. Alternately, the cavity 112 may be connected to inlet port 46 by a channel so that the pressurized fluid used for motor operation would maintain the brake in the un- locked position. In this method removal of inlet pressure acts as a failsafe to automatically lock the shaft.

Access to the brake is afforded by removal of bolts 40 which allows the brake housing 21 to he removed from the hydraulic motor. Hydraulic fluid is sealed from leakage into the brake area by seals 42 and 44. Seal 42 seals fluid from the mechanical piston plate 28. Seal 44 prevents fluid from the motor elements and needle bearing 18 from leaking into the brake.

It can be seen that the integral brake arrange¬ ment eliminates misalignment since the brake is mounted directly upon the central rotating shaft of the hydraulic motor. Also eliminated are stresses generated by machinery which are transmitted directly to the motor without prior transmission through the brake. The brake in the preferred embodiment is of a standard ultidisk design. However, several different mechanical designs could be used for the same purpose, such as drum brakes or single disk brakes.

It should be noted that the brake described above is intended for use as a parking brake. Use of this brake for arresting or slowing motion of the hydraulic motor during operations might result in overheating. Provisions have not been made for extensive brake cooling in this design. It is possible, however, to add a cooling arrangement to the housing and thereby increase the scope of brake usage, but this is not the intent in this preferred ^* embodiment which fulfills a particular market need. The use of an integral brake is made possible by use of a through shaft hydraulic- motor with multi¬ ple bearing support. The advantages of this design may be more carefully considered when viewing the internal gear set in Figures 1, 2, and 3. Figure 2 is a cross-section of the hydraulic motor at the gear set across the line 2-2 of Figure 1. Figure 3 is a cross-section across line 3-3 of Figure 1 at the valve 48 of the hydraulic motor. The novel bearing and valving arrangement and the compact internal integral brake are made possible by use of the through shaft and IGR arrangement. Most common hydraulic motors use an internal dogbone member to allow for the inner member to rotate eccentrically rather than about a fixed center. The invention shown here takes advantage of an outer orbiting member, a com¬ pact valving arrangement, and non-generated inner member 30 which rotates about a fixed axis.

Figures 7 and 8 display a second embodiment of the invention. In this embodiment a brake 76 is mounted externally to the heavy duty motor. The hydraulically activated portions of the heavy duty motor in Figures 7 and 8 are identical to the hydraul¬ ically activated portions of the motor shown in Figures

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1 an ^d 2. The embodiment shown in Figures 7 an _d 8 also utilizes the advantages of the through shaft, compact valving and heavy duty bearing arrangement of the first embodiment to allow for an improved external mechanical brake mounting arrangement. upon which is mounted a mechanical brake 76 similar to the type manufactured by Ausco and detailed in the first embodiment. This type brake is fully described in U. S. Patent 3,863,038 to Kreitner et al. The through shaft 12 extends external to the motor 78, both through the motor mount housing 11 where it may be connected to machinery and ^" through commutator housing 103 where the shaft is used by the brake 76. Brake 76 is used to lock the shaft 12 as required in machinery operation.

Figure 8 is a cross-section along line 8-8 of Figure 7. The cross-section is along the shaft and shows the same bearing arrangement adjacent to the gear set as discussed in the first embodiment above to support the central shaft 12.

As in the first embodiment, bearings 14 and 16 are tapered roller bearings. Bearing 18 is a needle bearing. Bearings 14 and 16 permit heavy radial, and thrust loads, and bearing 18 prevents shaft bending and is specially adapted for use in high torque low speed motors. The valving arrangement is the same as discussed in reference to Figures 4-6 above and allows the placement of the bearings adja¬ cent to the gear set.

The assembled motor housing consists of three pieces. The motor mount housing 11 and the gear set housing 10 are identical to those discussed in the first embodiment. The commutator housing 102

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in this embodiment is formed as a motor end suitable for attachment of an independent brake 78. Except for the extension of the shaft 12 beyond the motor housing for the mounting of independent brake 78, this embodiment is in all respects the same as that previously discussed.

Use of the through-shaft 12 allows for external braking with minimal misalignment. The motor-brake system requires only minimal additional space in the machinery or apparatus to which the motor is attached beyond that needed for use in the embodiment of Figures 1-6. Drive train problems in that machinery are avoided by placing the brake on the motor shaft itself, at a position removed from the drive train. Previous devices place the brake in series with the drive train such that the brake must withstand machinery loads.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as described in the appended claims. For example, different types of brake arrange¬ ments can be included in this device. The use of a through-shaft and heavy duty bearings adjacent to the gear set allow for "improved braking; the parti¬ cular mechanical brake used is of less importance. Furthermore, various mounting arrangements may be designed without affecting the basic nature of the invention. It must be further noted that this type of fluid power device can be used as a pump

by supplying shaft rotation to produce hydraulic pressure. In such uses, a mechanical brake is not generally required.