Keyless gear timing assembly for a reciprocating pump

A keyless timing gear assembly for securing a bull gear to a crankshaft of a power end of a reciprocating pump assembly, the keyless timing gear assembly including at least one actuator, an expansion member and at least one wedge member disposed between the at least one actuator and the expansion member, the wedge member having a sloped surface to slideably engage a corresponding sloped surface on the expansion member such that, in response to actuation of the at least one actuator, the at least one wedge member exerts a force on the expansion member for securing a bull gear to a crankshaft.

FIELD

This disclosure relates to reciprocating pump assemblies, in particular, to a power end of a reciprocating pump assembly, and even more particularly, to a keyless gear timing assembly for a power end of a reciprocating pump assembly.

BACKGROUND

Large pumps are commonly used in mining and oilfield applications, such as during hydraulic fracturing and stimulation operations. During a hydraulic fracturing operation, fracturing fluid (i.e., water, mud, frac sand or proppant, and other materials) is pumped at high pressures into a wellbore to cause the producing formation to fracture. High pressure reciprocating pumps, like the SPM® QW2500 XL or EXL frac pump, the Destiny™ TWS 2500 frac pump, or the SPM® QEM 3000 Continuous Duty Frac Pump, manufactured by S.P.M. Flow Control, Inc. of Fort Worth, Texas, are favored due to their capability to produce high pressure and high volume flow. In operation, the fracturing fluid is caused to flow into and out of a pump fluid chamber as a consequence of the reciprocation of a piston-like plunger respectively moving away from and toward the fluid chamber. As the plunger (aka plunger rod) moves away from the fluid chamber, the pressure inside the chamber decreases, creating a differential pressure across an inlet valve, drawing the fracturing fluid through the inlet valve into the chamber. When the plunger changes direction and begins to move towards the fluid chamber, the pressure inside the chamber substantially increases until the differential pressure across an outlet valve causes the outlet valve to open, enabling the highly pressurized fracturing fluid to discharge through the outlet valve into the wellbore.

In many reciprocating pumps, multiple plungers are used to smooth the output flow rate and pressure, and to improve power efficiency. The multiple plungers are often driven by a common crankshaft, with the plungers positioned at different axial locations of the crankshaft. The load resistance and bending moments vary along the length of the crankshaft, leading to mechanical stress. To minimize the stress within the crankshaft, it is desirable to power both ends of the crankshaft in synchrony, which more evenly distributes power and thereby minimizes the different bending moments or load resistance along the crankshaft.

This may be accomplished by employing a bull gear on each end of the crankshaft. However, due to the manufacturing tolerances involved in the creation of each part of a pump, each pump is unique and the small differences in part sizes must be accounted for. In such an arrangement, the two bull gears must be carefully synchronized to avoid creating the stresses with the crankshaft this arrangement seeks to avoid. Timing the bull gears accurately can be a difficult and time consuming process. Therefore there is a need for a keyless gear timing device that will facilitate the synchronizing of bull gears without costly manual correction.

SUMMARY

According to a first aspect, there is provided a keyless timing gear assembly for securing a bull gear to a crankshaft of a power end of a reciprocating pump assembly. The crankshaft is configured to drive one or more plungers in a fluid end of the reciprocating pump assembly, with a first bull gear connected to a first end of the crankshaft and a second bull gear connected to a second and opposed end of the crankshaft. A pinion shaft is mechanically coupled to the first bull gear and the second bull gear via first and second pinion gears, respectively, the pinion shaft operable to rotate the pinion gears, and in turn, rotate the first and second bull gears to rotate the crankshaft. The keyless timing gear assembly including at least one actuator, an expansion member and at least one wedge member disposed between the at least one actuator and the expansion member, the wedge member having a surface to slideably engage a corresponding surface on the expansion member such that, in response to actuation of the at least one actuator, the at least one wedge member exerts a force on the expansion member for securing the first bull gear to the crankshaft.

In some embodiments of the keyless timing gear assembly, the wedge member may be a ring.

According to other embodiments, the at least one actuator is a threaded fastener threadedly coupled to the wedge member.

In still other embodiments, the keyless timing gear assembly includes a second wedge member, the second wedge member having a surface to slideably engage a corresponding surface on the expansion member such that, in response to actuation of the at least one actuator, the second wedge member exerts a force on the expansion member for securing the first bull gear to the crankshaft.

In some embodiments, in response to actuation of the at least one actuator, the distance between the wedge members decreases.

In still other embodiments, at least a portion of the expansion member is integrally formed with either the bull gear or the crankshaft.

In yet other embodiments, the at least one actuator is three actuators symmetrically positioned around a center axis of crankshaft.

According to some embodiments, the at least one actuator comprises a hydraulic actuator having a channel in fluid communication with the wedge member such that, in response to fluid pressure in the hydraulic channel, the wedge member slidably engages the expansion member to cause the bull gear to frictionally engage the crankshaft.

In yet other embodiments, the expansion member is a second wedge ring hydraulically coupled to the hydraulic actuator through the fluid channel.

According to a second aspect, there is provided a power end for a reciprocating pump assembly where the power end includes a crankshaft configured to drive one or more plungers in a fluid end. A first bull gear is connected to a first end of the crankshaft and a second bull gear connected to the crankshaft spaced apart from the first bull gear. A pinion shaft is mechanically coupled to the first bull gear and the second bull gear via first and second pinion gears, respectively, the pinion shaft operable to rotate the pinion gears, and in turn, rotate the first and second bull gears to rotate the crankshaft. A keyless timing gear assembly is provided for securing the first bull gear to the crankshaft, in which the keyless timing gear assembly includes at least one actuator, an expansion member, and at least one wedge member disposed between the at least one actuator and the expansion member. The wedge member has a surface to slideably engage a corresponding surface on the expansion member such that in response to actuation of the at least one actuator, the at least one wedge member exerts a force on the expansion member for securing the first bull gear to the crankshaft.

According to some embodiments, a shaft key is configured to couple a second bull gear to the crankshaft, wherein the first bull gear is synchronized to the second bull gear and locked onto the crankshaft after the second bull gear is fastened onto the crankshaft using the shaft key. The first bull gear and the second bull gear are of the same diameter and are synchronized to provide even power input to the crankshaft.

In other embodiments, the at least one actuator is a fastener threadedly coupled to the wedge member.

According to other embodiments, the wedge member is a ring.

In still other embodiments, a second wedge member is provided that has a surface to slideably engage a corresponding surface on the expansion member such that, in response to actuation of the at least one actuator, the second wedge member exerts a force on the expansion member for securing the first bull gear to the crankshaft.

In still other embodiments, in response to actuation of the at least one actuator, the distance between the wedge members decreases.

According to yet another embodiment, at least a portion of the expansion member is integrally formed with either the bull gear or the crankshaft.

In still other embodiments, the at least one actuator is a threaded fastener threadedly coupled to the wedge member.

According to a third aspect of the present invention, there is provided a method for synchronizing two bull gears spaced apart on a crankshaft in a power end of a reciprocating pump assembly. The method includes, having a reciprocating pump having a crankshaft and a pinion shaft installed, securing a first bull gear to the crankshaft and securing a second bull gear to the crankshaft spaced apart from the first bull gear, wherein securing the second bull gear includes actuating at least one actuator of a keyless gear timing assembly such that in response to actuation, at least one wedge member exerts a radial force on an expansion member for securing the second bull gear to the crankshaft to enable the first bull gear to rotate in synchrony with the second bull gear.

According to some embodiments, securing the first bull gear to the crankshaft also includes installing the first bull gear onto the crankshaft using a key. In some embodiments, the first bull gear is installed onto the drive side of the crankshaft and the second bull gear is installed on the non-drive side of the crankshaft.

Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of the inventions hereof.

Like numerals refer to like elements.

DETAILED DESCRIPTION

FIGS.1and2are perspective views of a portion of a reciprocating pump assembly102, such as, for example, a reciprocating plunger pump, in which a keyless timing gear assembly150is employed to advantage. According to embodiments disclosed herein, the keyless timing gear assembly150is operable to, as explained in greater detail below, lock a bull gear onto a crankshaft such that no manual offset of the bull gear is required.

Referring toFIGS.1and2, the pump assembly102includes a power end housing105coupled to a fluid end housing (not illustrated) via a plurality of stay rods132. The power end housing105includes a crankshaft122that is mechanically connected to a power source/motor (not shown), which in operation, rotates the crankshaft122in order to drive the reciprocating pump assembly102. In particular, rotation of the crankshaft122causes a plunger assembly130to reciprocate toward and away from the fluid end housing. In one embodiment, the crankshaft122is cammed so that fluid is pumped from a plurality of cylinders in the fluid end housing to minimize the primary, secondary and tertiary forces associated with reciprocating pumps.

In one or more embodiments, the power end100includes a pinion gear assembly134and generally extends at least partially between a first side101(i.e., a drive side) and a second side102(the non-drive side) of the power end housing105. In operation, the pinion gear assembly134is coupled to the power source/motor (not shown) to drive the power end100, as explained in greater detail below.

Referring specifically toFIG.3, the pinion gear assembly134is illustrated having a pinion shaft120and includes a pinion gear126and128on each end thereof (e.g., on the drive side end and the non-drive side end, respectively, or otherwise spaced apart on the pinion shaft120) that are configured to mesh with a bull gear110and112, respectively, thereby forming a gear assembly116and118. As illustrated, the gears110and112are bull gears mounted on the crankshaft122. In the embodiment illustrated inFIGS.1-3, a gearbox housing106and thus, gear assemblies116and118, are disposed on each side101and102of the power end housing105. In operation, the bull gears110and112are driven by the pinion gears126and128so as to, as explained in further detail below, rotate the crankshaft122.

With continued reference toFIGS.1-3, the power end100further includes a pinion shaft120mechanically coupled to the pinion gears126and128, and thus, the bull gears110and112via the pinion gears126and128. In the embodiment illustrated inFIGS.1-3, the pinion gears126and128have opposing gear teeth configured to mesh with corresponding teeth on the bull gears110and112. In some embodiments, the pinion gear126and bull gear110include a helical profile in an opposite direction of the same helical profile of the bull gear112and pinion gear128in order to reduce or substantially eliminate axial forces at high load conditions. During operation of the power end100, the pinion gears126and128rotate via the pinion shaft120, which in turn rotate the bull gears110and112thereby causing the crankshaft122to rotate to move the one or more plungers130as previously described. With continued reference toFIG.3, the pinion shaft120is mounted within the housing via one or more bearing assemblies136, which may include one or more ball bearings705(FIG.4).

In order to provide an even distribution of driving power to the crankshaft120, the bull gears110and112are disposed on each end of the crankshaft122to receive input rotation power from the pinion shaft120and pinion gears126and128. Conventionally, both bull gears110and112use keys to connect to the crankshaft120to minimize slippage. However, such configuration requires the keys to be manufactured with high precision to account for the manufacturing variations in the system. For example, errors may build up due to the manufacturing tolerances of the specific bull gears, pinion shaft and pinion gears, crankshaft, and the housing, meaning the keys connecting the bull gears110and112to the crankshaft may require precise individual manual adjustments or must be precisely machined keys with specific offsets on the key or keyway upon the final assembly. Accordingly, the keyless gear timing assembly150is used to address and otherwise minimize these associated problems.

According to one embodiment, the keyless timing gear assembly150employs expansion of components to cause compressive stresses to secure the bull gears110and/or112to the crankshaft122in a friction joint to prevent relative rotation therebetween. Thus, the torque transmission is not limited by a shearing limit (e.g., size and material strength) of a key or the keyway. For example and with particular reference toFIG.6, the bull gear110is securely fastened to the crankshaft122via at least one actuator750that is operable to press a first wedge ring930(or simply a wedge, in some embodiments) in and otherwise against an expansion member910for securing the bull gear110(or112) to the crankshaft122. In particular, the actuator750causes the wedge ring930to move in the direction of arrow960relative to the expansion member910and press against it, causing it to deform radially (in the direction of arrow970), simultaneously reducing the inner diameter of the expansion member910and increasing the outer diameter of the expansion member910. In some embodiments, the wedge ring930may include individual wedges evenly and radially distributed around a separate ring component. In other embodiments, the wedge ring930may have a gap or space in the ring, allowing it to dilate or constrict in response to the forces applied by the actuator750and the expansion member910.

In the embodiment illustrated inFIG.5, the power end100further includes a shaft key800configured to couple the bull gear112to the crankshaft122. The bull gear110is synchronized to the second bull gear112and locked onto the crankshaft122after the bull gear112is rotatably fastened onto the crankshaft122using the shaft key800. It should be understood that although a square cross-section shaft key800is illustrated, other keys having different cross-sections and other features, such as providing a shear limitation, may be used in the place of a square cross-section shaft key800.

In use, the first bull gear110and the second bull gear112are of the same diameter and are synchronized to provide even power input to the crankshaft122and to reduce the internal stresses within the crankshaft122. The synchronization may be achieved by adjusting the first bull gear110using the keyless timing gear assembly150during assembly to accommodate the combined fitting variations of the second bull gear112, the pinion gears126and128, and the relative positions between the crankshaft122, the pinion shaft120, and the housing105.

In the embodiment illustrated inFIG.6, the actuators750of the keyless gear timing assembly150are fasteners that may be threadedly coupled to the first wedge ring930at the threaded hole942. For example, when the fasteners750are turned, the threads of the fasteners750pull the first wedge ring930in the direction of arrow960to slidably engage the expansion member910along the mating sloped surfaces, causing the expansion member to exert a force radially in the direction of arrow970into the interior surface of the first bull gear110and in the opposite direction into the exterior surface of the crankshaft122, thereby creating a friction joint between them and preventing relative movement therebetween.

According to some embodiments, the keyless gear timing assembly150may also include a second wedge ring920disposed between the fastener750and the first wedge ring930. This configuration causes the second wedge ring920to be pressed into the expansion member910in the direction of arrow960to slidably engage the expansion member910along the corresponding sloped surfaces when the fastener750is turned. Together with the first wedge ring930, the second wedge ring920thereby pinches the expansion member910causing it to expand radially in the direction of arrow970against the bull gear110and the crankshaft122, creating a friction joint between and preventing relative movement therebetween.

In some embodiments the actuators750are supported by the second wedge ring920. In such cases, for example, the second wedge ring920includes corresponding through holes940to receive the actuators750therein in order to pass through. Additionally or alternatively, the wedge ring920may include other types of openings for the actuators750, such as a slot.

According to some embodiments, the expansion member910may include both an inner portion in contact with the exterior surface124of the crankshaft122and an outer portion in contact with the interior surface111of the first bull gear110. In operation, the expansion of the expansion member910may produce compression stresses and create static friction to secure the first bull gear110to the crankshaft122. In some embodiments, at least a portion of the expansion member910is integrally formed from the interior surface111of the first bull gear110. In other embodiments, at least a portion of the expansion member910is integrally formed from exterior surface124of the crankshaft122. The integrally formed expansion member910reduces the number of moving parts in the keyless gear timing device and may increase the strength of the connection between the crankshaft122and the first bull gear110. In other embodiments, a groove is present in the inner surface of the first bull gear110and the expansion member910has a corresponding tongue that fits into the groove, securing the expansion member axially to the bull gear110. In some embodiments, a similar groove and tongue arrangement secures the expansion member910to the exterior surface of the crankshaft122.

FIG.7illustrates a hydraulically activated keyless gear timing device150for securing a bull gear1020to a crankshaft1010. In the embodiment illustrated inFIG.7, a fluid channel1024is formed in a portion of the bull gear1020to provide fluid communication between the fluid opening1022and a first and second fluid chamber1040and1030. As illustrated, the first fluid chamber1040is in fluid communication with a first wedge ring1060. Similarly, the second fluid chamber1030is in fluid communication with a second wedge ring1050. In operation, the first and second fluid chambers1040and1030and the fluid channel1024are filled with a hydraulic fluid such as water or oil, by way of example. Pressure is applied on the hydraulic fluid by an actuator750through the fluid opening1022, and the pressure is translated to the first and second fluid chambers1040and1030, causing the first wedge ring1060to move in the direction of the arrow1080to press against and/or otherwise slideably engage the second wedge ring1050. The first and second wedge rings1060and1050in turn act against the bull gear1020and the crankshaft1010respectively in the direction of the arrow1070to frictionally secure the bull gear110to the crankshaft122. The hydraulic fluid is controlled and otherwise contained by the placement of seal rings in grooves1064located in the first wedge ring1060, one or more grooves1052and1054located in the second wedge ring1050, and grooves1032and1042located in the bull gear1020. Additionally, a valve, such as a one-way check valve (not shown), may be secured at the fluid opening1022to control and otherwise prevent the hydraulic fluid from leaking out of the keyless gear timing assembly150after fluid pressure is removed. Although not illustrated, the keyless gear timing assembly150using hydraulic actuation may also employ an expansion member to secure the bull gear to the crankshaft, similar to the expansion member910shown inFIG.6.

The keyless gear timing assembly150illustrated inFIG.4includes eight actuators750symmetrically distributed around a center of rotation. However, different numbers of actuators750may be used. For example, the keyless gear timing assembly150may include one, two, three, four, five, six, seven, or more actuators750. In other embodiments, nine, ten, twelve, fourteen, or twenty actuators750may be used. The actuators750illustrated inFIG.7are symmetrically arranged around the center of rotation, but in other embodiments the placement of the actuators750may be asymmetrical.

In some embodiments, the interior surface111of the bull gear110and the exterior surface124of the crankshaft122are tapered at an angle. Tapering the exterior surface124of the crankshaft122and the interior surface111of the bull gear110serves to increase the surface area available for contact by the first wedge ring930and the second wedge ring920, thereby increasing the strength of the connection between the bull gear110and the crankshaft122.

In other embodiments, the interior surface111of the bull gear110is textured to provide greater friction between the bull gear110and the first and second wedge rings930and920and the expansion member910. In some embodiments, the exterior surface124of the crankshaft122may be textured to similar effect. For example, the surfaces may be knurled, banded, grooved, dimpled, bumpy, or otherwise textured.

FIG.8is a flow chart1100showing a method of synchronizing two bull gears, such as the first and the second bull gears110and112. At1110, a crankshaft and pinion shaft are installed in a reciprocating pump. The crankshaft122may be supported or installed on bearings in a housing of a power end105. At block1120, a first bull gear110is installed onto a first end of the crankshaft using a key800. At block1130, a second bull gear112is installed onto a second end of the crankshaft122using a keyless gear timing assembly150as described above. At blocks1140and1150, the pinion shaft120is centered so as to ensure proper contact between the pinion gears126and128and the bull gears110and112and the keyless gear timing assembly150is tightened.

In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose.

In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive.