Patent Application
20180051696
The present disclosure relates to gear pumps, more specifically to bearing structures for gear pumps.
The process of cavitation in a gear pump is where, in operation, localized depressions in static pressure cause the pumped fluid to fall below the vapor pressure of the liquid (e.g., which creates bubbles). Cavitation is caused by sealing a volume and expanding the fixed volume. When the pressure of the vaporized fluid increases, collapse of the vapor can be damaging to the pump hardware which can negatively impact service life. Face cuts made to a bearing of the gear pump have been shown to have an impact on the realization of fluid cavitation in a gear pump. However, existing face cut geometries are insufficient.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved bearing structures for gear pumps. The present disclosure provides a solution for this need.
A bearing structure for abutting a pair of gears of a gear pump includes a body including a face on which the gears rotate, an inlet defined in the body, and an outlet defined in the body. The bearing structure includes a sealing portion of the face configured to fluidly seal the inlet from the outlet, the sealing portion being defined as a portion of the face in sealing engagement with the gears at a rotational position of the gears wherein a volume contained by teeth of the gears and the face is constant or about constant as the gears rotate. The structure can include pair of apertures defined by the body and configured to receive a gear shaft.
The sealing portion can include a point symmetric shape about a midpoint of the body. The sealing portion can include a main portion having a main portion width. In certain embodiments, the main portion width can be about equal to a root pocket arc length of gear teeth in the pair of gears and wherein the main portion is straight.
Two 90 degree corners can extend from the main portion of the sealing portion on opposite sides of the main portion, the corners defining a first edge and a second edge. The first edge and the second edge can be flat, for example.
In certain embodiments, the first edge of each corner can be defined parallel to a line of action of the gears. The second edge of each corner can be defined parallel to a contact length line.
In certain embodiments, the sealing portion can be defined in the face by machining (e.g., cutting). However, the bearing structure can be additively manufactured or made in any other suitable manner to form the sealing portion.
A method can include determining a shape of a sealing portion of a bearing structure for gears of a gear pump based on gear geometry such that a sealed portion only exists where volume between gear teeth is substantially constant. Determining a shape of the sealing portion can include using a contact length of the gears.
Determining a shape of the sealing portion can include using a line of action of the gears. Determining a shape of the sealing portion can include using a root arc length of the gears.
A method for pumping a fluid with a gear pump can include sealing a volume defined between gear teeth, an inlet, and an outlet only at angles of rotation of the gears where the volume remains constant.
These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description taken in conjunction with the drawings.
So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, embodiments thereof will be described in detail herein below with reference to certain figures, wherein:
Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, an illustrative view of an embodiment of a structure in accordance with the disclosure is shown in
Referring to
The bearing structure 100 includes a sealing portion 109 defined by the face 103 and configured to fluidly seal the inlet 105 from the outlet 107 (e.g., when the gears are assembled in the gear pump). Referring additionally to
The term “about constant” can be defined as a change in volume that is understood by those having ordinary skill in the art to have a negligible effect on cavitation and/or to account for manufacturing tolerances. While disclosed in certain embodiments, it is not necessary that the volume be exactly constant where the sealing portion 109 seals.
As appreciated by those having ordinary skill in the art, the structure 100 can include pair of apertures 115 defined by the body 101 and configured to receive a gear shaft 212 of a gear 210. It is also contemplated that the structure 100 can be any suitable number of parts (e.g., split in half at a midline 317) or can be a single piece. Any other suitable structure is contemplated herein, so long as the structure 100 is configured to allow two gears to rotate on the face 103 thereof.
Referring additionally to
Two 90 degree corners 109b can extend from the main portion 109a of the sealing portion 109 on opposite sides of the main portion 109. The corners 109b can define a first edge 109c and a second edge 109d. The first edge 109c and the second edge 109d can be flat, for example, or any other suitable shape.
Referring additionally to
The second edge 109d of each corner can be defined parallel to a contact length line 321, for example. The contact length lines 321 are the lines that define the length over which two gear teeth 211 are in contact when contact points on symmetrically located gear teeth 211 are equidistant of center point of contact 323. The lines of contact 321 can also be perpendicular to the line of action 319 and/or tangent to the involute profile of the gear teeth 211 at point of contact. Irrespective of the geometry of the gear teeth 211, the corners 109b can have 90 degree turns from the first face 109c to the second face 109d. However, the perpendicularity to the line of action can be varied in any suitable manner as appreciated by those having ordinary skill in the art in view of this disclosure.
While the embodiments of
In certain embodiments, the sealing portion 109 can be defined in the face by machining (e.g., cutting), which may limit designs (e.g., to those with curved roots 131 due to cutting radius). However, the bearing structure 100 can be additively manufactured or made in any other suitable manner to form the sealing portion 109 in any suitable configuration (e.g., with straight edges 531).
A method can include determining a shape of a sealing portion of a bearing structure for gears of a gear pump based on gear geometry such that a sealed portion only exists where volume between gear teeth is substantially constant. Determining a shape of the sealing portion can include using a contact length of the gears. Determining a shape of the sealing portion can include using a line of action of the gears. Determining a shape of the sealing portion can include using a root arc length of the gears.
As described above, embodiments allow determination of sealing geometry of a bearing structure as a function of given gear geometry. Therefore, embodiments allow application to any gear geometry to prevent cavitation. Traditional face cuts have been arranged in a way where the layout has been application specific and without consideration to the actual volume rate of change within the trapped volumes of the gear pump elements.
The methods and systems of the present disclosure, as described above and shown in the drawings, provide for bearing structures for gear pumps with superior properties including cavitation prevention and/or elimination. While the apparatus and methods of the subject disclosure have been shown and described with reference to embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the spirit and scope of the subject disclosure.
