Patent Description:
Gear pumps are operable to pump fluid from an inlet to an outlet. Fluid enters the inlet and travels between the teeth of the gears and the surrounding housing. As the gears turn, the fluid is pulled towards the outlet and squeezed out of the pump. Both the drive gear and the driven gear are supported within the gear pump by respective gear shafts. Each gear shaft is in turn supported by both a pressure loaded journal bearing and a stationary journal bearing, both of which react the load of the gear shaft.

In gear pumps with this type of bearing configuration, a known physical phenomenon sometimes occurs called radial clamping. When no pressure differential exists across the gear pump (and therefore around the outer perimeter of the bearings), there is no hydraulic force that causes the bearings to be pushed together on the flats of the bearings. Accordingly, until sufficient pressure builds across the pump and around the bearings, the two independent bearings, such as the two stationary journal bearings or the two pressure loaded journal bearings, remain separated from each other along the flat surfaces thereof. This separation may result in increased leakage internal to the pump and decreased volumetric efficiency. <CIT> relates to a bearing plate. <CIT> relates to a pressure loaded pump. The document <CIT> discloses a bearing assembly according to the preamble of claim <NUM>.

According to an embodiment, a bearing assembly is provided in claim <NUM> and includes a first gear shaft aligned with a first axis and a second gear shaft aligned with a second axis. The second axis is oriented parallel to the first axis. A first bearing is supported on the first gear shaft and a second bearing is supported on the second gear shaft. A coupling mechanism extends between and radially clamps the first bearing to the second bearing. The coupling mechanism is operable to restrict relative radial movement between the first bearing and the second bearing.

In addition to one or more of the features described above, or as an alternative, in further embodiments the first bearing includes a first flat bearing surface and the second bearing includes a second flat bearing surface, the coupling mechanism being operable to restrict radial movement between the first flat bearing surface and the second flat bearing surface.

In addition to one or more of the features described above, or as an alternative, in further embodiments the coupling mechanism extends between the first flat bearing surface and the second flat bearing surface.

In addition to one or more of the features described above, or as an alternative, in further embodiments the coupling mechanism is spring-loaded.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a biasing member having a biasing force acting on the key and a retaining clip movable relative to the key between an engaged position and a disengaged position. In the engaged position, the retaining clip opposes the biasing force of the biasing member.

In addition to one or more of the features described above, or as an alternative, in further embodiments the retaining clip is in the engaged position when the key is inserted into a first end of the keyhole.

In addition to one or more of the features described above, or as an alternative, in further embodiments the first portion includes a tenon and the second portion includes a mortise.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a fastener rigidly affixing the tenon to the mortise.

In addition to one or more of the features described above, or as an alternative, in further embodiments the first portion includes a protrusion and the second portion includes a clevis having a clearance, the protrusion being receivable within the clearance.

In addition to one or more of the features described above, or as an alternative, in further embodiments comprising a fastener coupling the protrusion to the clevis.

In addition to one or more of the features described above, or as an alternative, in further embodiments the first portion includes an expanding pin.

In addition to one or more of the features described above, or as an alternative, in further embodiments the first bearing and the second bearing are stationary bearings.

In addition to one or more of the features described above, or as an alternative, in further embodiments the first bearing and the second bearing are pressure loaded bearings.

According to an embodiment, a gear pump includes a housing having an inlet and an outlet, a first gear mounted within the housing to a first gear shaft, a second gear mounted within the housing to a second gear shaft, a first bearing supported on the first gear shaft, a second bearing supported on the second gear shaft, and a coupling mechanism extending between and radially clamping the first bearing to the second bearing. The coupling mechanism is operable to restrict relative radial movement between the first bearing and the second bearing.

In addition to one or more of the features described above, or as an alternative, in further embodiments the first bearing includes a first flat bearing surface and the second bearing includes a second flat bearing surface, the coupling mechanism being operable to restrict relative radial movement between the first flat bearing surface and the second flat bearing surface.

<FIG> is a schematic, cross-sectional view of an example of a gear pump <NUM> according to an embodiment. As shown, the gear pump <NUM> includes a housing <NUM> having a gear pump inlet <NUM> and a gear pump outlet <NUM>. Although the inlet <NUM> and the outlet <NUM> are arranged at opposite sides of the housing <NUM>, embodiments where the inlet <NUM> and outlet <NUM> are arranged in another configuration relative to the housing <NUM> are also contemplated herein. A first gear or drive gear <NUM> and a corresponding second gear or driven gear <NUM> are mounted within the interior of the housing <NUM> between the inlet <NUM> and the outlet <NUM>.

The gear pump is operable to pump a fluid at a constant rate between the inlet <NUM> and the outlet <NUM>. As shown a fluid F enters the housing <NUM> of the gear pump <NUM> at the inlet <NUM>. Using a relatively low supplied inlet pressure, the fluid F fills into the gaps between the teeth of drive gear <NUM> and the housing <NUM> and between the teeth of the driven gear <NUM> and the housing <NUM>. The drive gear <NUM> is rotated in a first direction about a first axis, such as counterclockwise for example, and the driven gear <NUM> is in turn rotated in a second, opposite direction, such as clockwise for example, about a second axis. As the gears <NUM> and <NUM> turn, the fluid F is moved from the relative low pressure inlet <NUM> towards the relatively high pressure outlet <NUM>. In an embodiment, the fluid F is squeezed form the outlet of the housing <NUM> as a high pressure fluid FH.

With reference now to <FIG>, an exploded, perspective view of drive gear <NUM> and driven gear <NUM> is shown. As was also shown in <FIG>, drive gear <NUM> is meshable with driven gear <NUM>, which are mounted to a drive gear shaft <NUM> and a driven gear shaft <NUM>, respectively. The drive gear has axially opposed gear faces 34A, 34B, and is mounted to a first (or drive) gear shaft <NUM>. Similarly, driven gear <NUM> has axially opposed gear faces 36A, 36B and is mounted to a second (or driven) gear shaft <NUM>. To form one journal bearing assembly, one or both longitudinal ends of first, or drive-side, gear shaft <NUM>, can be respectively received in central recesses of a drive-side stationary journal bearing <NUM> and drive-side pressure loaded journal bearing <NUM>. Another journal bearing assembly can include one or both longitudinal ends of second, or driven-side, gear shaft <NUM>, which are in turn respectively received by driven-side stationary journal bearing <NUM> and driven-side pressure loaded journal bearing <NUM>. Each pair of journal bearings can thus respectively support drive-side gear shaft <NUM> and/or driven-side gear shaft <NUM>.

Stationary journal bearings <NUM>, <NUM> are each fixed in place, for example, against housing <NUM> (shown in <FIG>), whereas pressure loaded (or "floating") journal bearings <NUM>, <NUM> can translate axially relative to respective gear shafts <NUM>, <NUM>. Loads experienced by drive gear <NUM> are transferred to gear shaft <NUM>. Since drive-side stationary journal bearing <NUM> and drive-side pressure loaded journal bearing <NUM> react the loads experienced by gear shaft <NUM>, bearings <NUM> and <NUM> also react many of the loads experienced by drive gear <NUM>. Similarly, loads experienced by driven gear <NUM> are transferred to gear shaft <NUM>. Since driven-side stationary journal bearing <NUM> and driven-side pressure loaded journal bearing <NUM> react the loads second gear shaft <NUM>, bearings <NUM> and <NUM> also react many of the loads experienced by driven gear <NUM>.

Each of bearings <NUM>, <NUM>, <NUM>, <NUM> comprises a ring-like structure that has a flat bearing surface, 38A, 40A, 42A, 44A. Thus, such bearing surfaces 38A, 40A, 42A, 44A extend substantially parallel to the direction of the corresponding gear shaft <NUM>, <NUM> passing therethrough.

With reference now to <FIG>-<NUM>, in an embodiment, the bearings within at least one of the pair of stationary journal bearings <NUM>, <NUM> and the pair of pressure loaded journal bearings <NUM>, <NUM> are connected by a coupling mechanism <NUM> to restrict relative radial movement therebetween. The coupling mechanism <NUM> is configured to restrict the clearance between the flat surfaces on the pair of bearings <NUM>, <NUM>, or <NUM>, <NUM>, even when no pressure differential exists across the gear pump <NUM>. In each of the illustrated, non-limiting embodiments, the coupling mechanism <NUM> includes a first portion <NUM> mounted to a first bearing, such as bearing <NUM> for example, and a complementary second portion <NUM> mounted to the second bearing of the bearing pair, such as bearing <NUM> for example.

In the non-limiting embodiment illustrated in <FIG>, the first portion <NUM> of the coupling mechanism <NUM> includes a key <NUM> and the second portion <NUM> of the coupling mechanism <NUM> includes a corresponding keyhole <NUM>. As shown, the key <NUM> extends at an angle from the flat surface 44A of bearing <NUM>. The key <NUM> may be attached to the bearing in any suitable manner, such as via threaded engagement or press-fit for example. The key <NUM> has a non-uniform configuration over its length. In the illustrated, non-limiting embodiment, a diameter of the distal or free end <NUM> of the key <NUM> is greater than the diameter of the key <NUM> adjacent to the bearing surface 4A. For example, the key <NUM> may include a radially outwardly extending flange <NUM> located at or near the distal end <NUM> thereof.

A plate <NUM> having an opening or keyhole <NUM> formed therein is mounted to the flat surface 40A of the other bearing <NUM> of the bearing pair. The plate <NUM> may be mounted in any suitable manner, such as via an adhesive, a plurality of fasteners, such as a screw or bolt for example, or alternatively, may be press fit about the bearing. In an embodiment, a groove (not shown) corresponding to the keyhole <NUM> may be formed in the surface of the bearing 40A underneath the keyhole <NUM> as needed. As shown, the keyhole <NUM> also has a non-uniform configuration. Near a first end <NUM>, the dimensions of the keyhole <NUM> are sized to receive the distal end <NUM> of the key <NUM> therein. However, at least one dimension of the keyhole <NUM> reduces, such as over an axial length of the keyhole <NUM> for example. Accordingly, the dimensions of the keyhole <NUM> adjacent to a second end <NUM> are substantially smaller than the dimensions of the keyhole <NUM> adjacent to the first end <NUM>. Although a specific configuration of the keyhole <NUM> is illustrated in the FIGS. , it should be understood that embodiments where the keyhole <NUM> has another suitable configuration are within the scope of the disclosure. Furthermore, although the first and second ends <NUM>,<NUM> are illustrated as being opposite one another along an axis, embodiments where the second end <NUM> is arranged at an angle to the first end <NUM> are also contemplated herein.

Once the distal end <NUM> of the key <NUM> including the flange <NUM> is installed within the keyhole <NUM>, the key <NUM> may be translated within the keyhole <NUM>, towards the second opposite end <NUM> thereof. Because the keyhole <NUM> adjacent the second end <NUM> is smaller than the diameter of the flange <NUM>, the engagement therebetween restricts axial movement of the key <NUM> relative to the keyhole <NUM>, and therefore movement between the bearings <NUM>, <NUM>. Use of a coupling mechanism including a key <NUM> and a keyhole <NUM> as described herein will hold the bearings together more tightly than absent the coupling mechanism <NUM>, while still allowing the bearings <NUM>, <NUM> to retain all degrees of freedom. Further, the amount of radial clamping or unclamping may be controller by a tight tolerance stack-up from the key <NUM> to the keyhole <NUM>.

With reference now to <FIG>, the first portion <NUM> of the coupling mechanism <NUM> may be spring loaded. In the illustrated, non-limiting embodiment, the key <NUM> protruding from the surface 44A of a bearing <NUM> is spring loaded. As shown, a biasing member <NUM>, such as a coil spring for example, may be mounted about the body of the key <NUM> and extend between the surface 44A of the bearing <NUM> and a surface <NUM> of the flange <NUM>. The first portion <NUM> may additionally include a retaining clip <NUM> movable relative to the bearing <NUM>, the key <NUM>, and the biasing member <NUM> between an engaged or active position (<FIG>) and a disengaged or inactive position. When the retaining clip <NUM> is in the engaged position, a portion of the retaining clip <NUM> is configured to contact or engage the distal end <NUM> of the key <NUM>. Accordingly, the retaining clip <NUM> can be used not only to compress the biasing member <NUM>, but also to retain the biasing member <NUM> in a compressed position.

Inclusion of the retaining clip <NUM> may facilitate installation of the key <NUM> within the keyhole <NUM>. In such embodiments, the retaining clip <NUM> will remain in an engaged position during the initial insertion of the key <NUM> into the keyhole <NUM>. For example, as the key <NUM> is inserted into the keyhole <NUM>, the retaining clip <NUM> may apply a force to the biasing member <NUM> to compress the biasing member <NUM>. During translation of the key <NUM> within the keyhole <NUM>, the retaining clip <NUM> would engage a surface of the plate <NUM>. This contact may cause the retaining clip <NUM> to slide relative to the key <NUM>, thereby removing the force opposing the biasing member <NUM>. With the retaining clip <NUM> removed, the biasing force of the biasing member <NUM> is configured to presses against the adjacent keyhole plate <NUM>. However, it should be understood that in other embodiments, the retaining clip <NUM> need not separate from the key <NUM> and the biasing member <NUM>. In an embodiment, the keyhole <NUM> includes a feature (not shown), such as a chamfer or radius formed at the leading edge thereof for example. This feature may be included to facilitate movement of the key <NUM> while maintaining a positive load on the biasing member <NUM> to restrict relative movement of the bearings.

In an embodiment, to enable the separation of the retaining clip <NUM> from the key <NUM> and biasing member <NUM>, the retaining clip <NUM> may be slightly larger than the depth of the keyhole <NUM> plus the thickness of part of the plate <NUM>. When in the disengaged position, the retaining clip <NUM> would still be retained in position within the keyhole <NUM> because of the connection formed between the bearings <NUM>, <NUM> by the coupling mechanism <NUM>. The spring load of the biasing member <NUM> forcing the bearings <NUM>, <NUM> together prevents the retaining clip <NUM> from becoming loose and dislodging from the keyhole <NUM>.

With reference now to FIS. 5A and 5B, in another embodiment the coupling mechanism <NUM> includes a joint, such as a mortise and tenon joint for example. In the illustrated, non-limiting embodiment, the first portion <NUM> of the coupling mechanism <NUM> includes a protrusion or tenon <NUM> extending therefrom, such as from the flat surface 44A or bearing <NUM>. A protrusion <NUM> having any suitable shape, such as a protrusion that is uniform over its length, or varies over its length (as show), is contemplated herein. The second portion <NUM> of the coupling mechanism <NUM> includes a mortise, or an inwardly extending groove or opening <NUM> formed in the flat surface 40A of the other bearing <NUM>. In such embodiments, the first portion <NUM> is insertable into or in overlapping arrangement with the second portion <NUM> such that a minimum clearance is defined between the adjacent flat surfaces 40A, 44A of the bearings <NUM>. To maintain the bearings <NUM>, <NUM> in this configuration, a fastener <NUM>, such as a pin for example, may extend through both the first portion <NUM> and the second portion <NUM> to maintain a rigid connection therebetween. Although a mortise and tenon are described herein, embodiments where the joint has another configuration are also contemplated herein. For example, one of the first portion <NUM> and the second portion <NUM> may have a clevis configuration with two parallel arms, and the other of the first portion <NUM> and the second portion <NUM> may have a protrusion receivable within the clearance defined between the two parallel arms. Similar to the mortise and tenon joint, a fastener, such as a clevis pin for example, may be receivable within the corresponding and aligned openings formed in the clevis arms and the protrusion. To restrict relative movement between the clevis and the protrusion.

In yet another embodiment, best shown in <FIG> and <FIG>, the first portion <NUM> of the coupling mechanism <NUM> includes an expanding pin <NUM>. In the illustrated, non-limiting embodiment, the expanding pin <NUM> includes a base <NUM> and a plurality of legs <NUM> extending outwardly from the base <NUM> towards the opposite bearing <NUM>. The plurality of legs <NUM> may be resilient and configured to bias radially outwardly. The second portion <NUM> of the coupling mechanism <NUM> may include an opening <NUM> formed in the flat surface 40A of the bearing <NUM>. The expanding pin <NUM> is receivable within the opening or slot <NUM> formed in the bearing <NUM>. During installation of the expanding pin <NUM> within the opening <NUM>, a compressive force may be applied to the legs <NUM> opposing the biasing force thereof, such that the outer diameter defined by the plurality of legs <NUM> is less than a diameter of the opening <NUM>. As shown, when the plurality of legs <NUM> are arranged within the opening <NUM>, the resiliency of the legs <NUM> causes the plurality of legs <NUM> to flex or bend outwardly resulting in an outer diameter that is greater than the diameter of the opening <NUM>. This increased dimension limits movement of the expanding pin <NUM>, and therefore the bearing <NUM> relative to the opening <NUM> and bearing <NUM>.

Claim 1:
A bearing assembly comprising:
a first gear shaft aligned with a first axis;
a second gear shaft aligned with a second axis, the second axis being oriented parallel to the first axis;
a first bearing (<NUM>) supported on the first gear shaft;
a second bearing (<NUM>) supported on the second gear shaft; and
a coupling mechanism (<NUM>) extending between and radially clamping the first bearing to the second bearing, wherein the coupling mechanism is operable to restrict relative radial movement between the first bearing and the second bearing;
wherein the coupling mechanism (<NUM>) further comprises:
a first portion (<NUM>) mounted to the first bearing (<NUM>) and protruding radially outwardly from the first bearing towards the second bearing; and
a second portion (<NUM>) located at the second bearing, the second portion being configured to receive the first portion;
wherein the first portion includes a key (<NUM>) and the second portion includes a plate having a keyhole (<NUM>) formed therein, the key being receivable within the keyhole; and characterized in that:
the key (<NUM>) has a body and a radial flange arranged near an end of the body, and the keyhole (<NUM>) has a non-uniform configuration extending between a first end and a second end thereof, the flange being receivable within the first end of the keyhole but not the second end of the keyhole.