Patent Application
20130243609
This invention relates to pumps, and more particularly to an expansible chamber pump of a type which may be referred to as a lance pump or drum pump, particularly adapted for pumping lubricant, including grease, from a supply thereof (e.g., lubricant in a drum).
The pump of this invention is in the same field as the pumps shown in the following U.S. Pat. Nos. 2,187,684; 2,636,441; 2,787,225; 3,469,532; 3,502,029; 3,945,772; 4,487,340; 4,762,474; and 6,102,676. Of particular interest is U.S. Pat. No. 2,787,225, which is directed to a lance pump sold by Lincoln Industrial Corporation of St. Louis, Mo., under the designation Series 20. Although lance pumps such as those identified above have been commercially successful, there is a need for a pump that provides a selectively variable output pressure and reduces disassembly and assembly complexity.
In one aspect, the present invention includes a pump for pumping a viscous liquid from a reservoir. The pump comprises a pump body adapted for positioning above the reservoir and an elongate tube extending downward from an upper end connected to the body, past an upper portion and a lower portion, to a lower end when the body is positioned above the reservoir. An elongate core slidably received in the tube extends vertically downward from the body into the liquid when the body is in position above the reservoir. The core has a longitudinal axis extending between an upper end mounted on the body for vertical reciprocating motion and a lower end opposite the upper end. Further, the pump includes a stepper motor mounted on the body having a selectively rotatable output shaft extending vertically above the liquid in the reservoir when the body is in position and a transmission operatively connected to the stepper motor output shaft. The transmission effects reciprocating relative motion between the tube and the core so the elongate core moves between a relative raised position and a relative lowered position as the stepper motor output shaft rotates in one direction to effect an upward pumping stroke and in an opposite direction to effect a downward pumping stroke. In addition, the pump has an inlet check valve mounted inside the core defining with the core an expansible and contractible lower pump chamber. The inlet check valve is oriented to open during each upward pumping stroke permitting viscous liquid to enter the lower pump chamber. The pump also comprises an annular upper chamber defined in part by the tube and the core above the lower pump chamber and a lateral passage in the core connecting the lower pump chamber to the annular upper chamber. The lateral passage has a check valve oriented to open during each downward pumping stroke. The pump includes an outlet passage connected to the annular upper chamber permitting viscous liquid to flow from the annular upper chamber to the outlet passage on each upward and downward pumping stroke.
In another aspect, the present invention includes a pump for pumping a viscous liquid from a reservoir. The pump comprises a pump body adapted for positioning above the reservoir and an elongate tube extending downward from an upper end connected to the body to a lower end below the upper end when the body is positioned above the reservoir. The pump also includes an elongate core slidably received in the tube and extending vertically downward from the body into the liquid when the body is in position above the reservoir. The core has a longitudinal axis extending between an upper end mounted on the body and a lower end opposite the upper end. In addition, the pump comprises an electric motor mounted on the body having a selectively rotatable output shaft for effecting relative reciprocating motion between the core and the elongate tube so the core moves between a relative raised position and a relative lowered position as the motor output shaft rotates in one direction to drive the pump through an upward pumping stroke and in an opposite direction to drive the pump through a downward pumping stroke. The pump also includes a control operatively connected to the electric motor for controlling operation of the motor and an inlet check valve mounted inside the core defining with the tube an expansible and contractible lower pump chamber. The inlet check valve is oriented to open during each upward pumping stroke permitting viscous liquid to enter the lower pump chamber. Further, the pump includes an annular upper chamber defined in part by the tube and the core above the lower pump chamber and a lateral passage in the core connecting the lower pump chamber to the annular upper chamber. The lateral passage has a check valve oriented to open during each downward pumping stroke to deliver viscous liquid from the lower pump chamber to the annular upper chamber. The pump comprises an outlet passage connected to the annular upper chamber permitting viscous liquid to flow from the annular upper chamber.
Other objects and features will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the drawings.
Referring to
Referring to
As illustrated in
As further shown in
As shown in
The lower end portion 55 of the pump core 51 comprises a plunger 81 slidingly and sealingly received in the intermediate tubular member 37. The plunger 81 includes a longitudinal passage 83 extending between an upper lateral passage 85 and a lower lateral passage 87. A check valve ball 89 is located below the upper lateral passage 85 and rests in a seat 91. Another check valve ball 93 is located above the lower lateral passage 87 and rests in a seat 95. A shovel rod 101 extends downward from the lower end of the plunger 81 through a priming or inlet check valve 103 located in the tubular extension member 39 and into the priming tube 41. The space between the seat of the inlet check valve 103 and the lower end of the pump core 51 defines a lower chamber 104. The shovel rod 101 is slidable with respect to the inlet check valve 103. A shovel 105 is attached to a lower end of the shovel rod 101 and is configured for reciprocating movement with the shovel rod within the priming tube 41.
As will be described hereinafter, the upper and lower chambers 77, 104 are expansible and contractible chambers which expand and contract during upstrokes and downstrokes of the piston rod 65 and pump core 51. (The lower chamber 104 contracts and the upper chamber 77 expands during a downstroke; the lower chamber expands and the upper chamber contracts during an upstroke.) As a result, fluid is delivered through the outlet passage 43 during both upstrokes and downstrokes of the pump.
A motor-driven transmission, indicated generally at 109, is mounted on the body 23 for reciprocating the pump core 51 through a pump stroke. The transmission 109 reciprocates the pump core 51 between a raised position relative to the fixed pump tube 31 and a lowered position relative to the pump tube. The pump core 51 moves toward the raised position during an upstroke, as illustrated in
As illustrated in
The pump core 51 is movable through up and down pumping strokes by reciprocating movement of the piston rod 65. The piston rod 65 is movable in a reciprocating manner by a linear position drive mechanism comprising a stepper motor 115 having a vertical output shaft 117 connected to a co-axial lead screw, generally designated by 119, rotatable in a follower housing portion 121 of the body 23. The lead screw 119 comprises a lead screw body 123 having a bore 125 that receives the output shaft 117 of the stepper motor 115, and a threaded shaft 127 extending downward from the lead screw body. The shaft 127 has external threads 129 configured to mate with the internal threads 113 of the piston body 111. The stepper motor output shaft 117 engages the body 123 of the lead screw (e.g., with a spline connection) so that the shaft and the lead screw turn in unison. Desirably, the mating threads on the piston body and lead screw are constructed for the efficient transmission of power. By way of example, the threads 113, 129 may be full ACME threads capable of carrying a substantial load for pumping liquid at high pressures. Thrust loads exerted on the piston and the lead screw are carried by angular contact bearings 135. The angular contact bearings 135 support loads in both directions, i.e., during both the upstroke and the downstroke.
A follower, generally designated by 137, is secured to the piston body 111 for back and forth linear movement of the follower and the piston body in a cavity 139 in the follower housing portion 121 of the body 23. The longitudinal centerline of the cavity 139 is generally co-axial with the longitudinal centerlines of the piston body 111 and the lead screw 119. The longitudinal centerline of the cavity 139 is also co-axial with the longitudinal centerline of the piston rod 65 and the bore 35 extending through the hollow body 23. The piston rod 65 extends from a location within the cavity 139 through the bore 35 and into the pump tube 31.
The follower 137 comprises a follower body 141 having a central opening 143 that receives an upper end portion of the piston body 111. Desirably, the follower body 141 has a non-circular peripheral shape conforming to a non-circular cross-sectional shape of the cavity 139 to prevent rotational movement of the follower as it reciprocates in the cavity. The central opening 143 of the follower bore and the upper end portion of the piston body 111 can be non-circular in shape (e.g., rectangular) to prevent relative rotational movement between the piston and the follower. The follower 137 is held in place against a shoulder on the piston body 111 by a retaining clip 149. Other constructions may be used to prevent relative rotation and linear movement between the piston and the follower without departing from the scope of the present invention. Rotation of the motor output shaft 117 and lead screw 119 in one direction causes the piston rod 65 to move linearly in the bore 35 through a pumping upstroke, and rotation of the output shaft and lead screw in the opposite direction causes the piston rod to move linearly in the bore through a pumping downstroke. The lengths of the pumping upstrokes and downstrokes are controlled by operation of the stepper motor 115, which is under the control of a control, as will be described further below. Desirably, the cavity 139 functions as a reservoir for holding a lubricant (e.g., oil) suitable for lubricating the threads 113, 129 on the piston body 111 and the lead screw 119.
A calibration mechanism generally designated 161 is provided for calibrating operation of the stepper motor 115 relative to the position of the piston body 111 in the cavity 139. In the illustrated embodiment, this mechanism 161 comprises a magnet 163 on the follower 137 movable with the piston body 111, and at least one and desirably two magnetic field sensors 165, 167 mounted on the follower housing portion 121 at spaced-apart locations corresponding to the piston movement. The control receives signals from the calibration mechanism 161 and calibrates operation of the stepper motor relative to the position of the piston.
The pump body 23 can be contained in a housing 221. Furthermore, as illustrated in
To begin an upstroke, the control operates the stepper motor 109 to rotate its output shaft 117 in one direction, causing the piston rod 65 and pump core 51 to move upward from the position shown in
Upon completion of an upstroke, the control signals the stepper motor 115 to reverse direction, causing the piston rod 65 and pump core 51 to move through a downstroke. As the pump core 51 moves in a downward direction from the position shown in
Providing the same amount of lubricant during each stroke enables the pump to be used to meter predetermined measured quantities of lubricant. For example, if particular circumstances necessitate delivering a quantity of lubricant equal to that delivered by one stroke of the piston rod 65, the control 291 signals motor 115 to drive the piston rod through one stroke. If twenty times that quantity is desired, the control signals the motor to operate through twenty strokes to deliver the increased amount.
Referring to
In an embodiment in which the motor comprises a stepper motor, the control 312 selectively applies PWM (pulse width modulated) pulses via a power supply 320 to the stepper motor to vary speed and torque of the stepper motor as a function of the target pressure condition compared to the sensed pressure condition.
In one embodiment, the 312 applies PWM pulses to the stepper motor such that the speed of the stepper motor is a first speed and a first torque when the pressure signal is within a first range. In addition, the control 312 applies PWM pulses to the stepper motor such that the speed of the stepper motor is a second speed less than the first speed and at a second torque greater than the first torque when the pressure signal is within a second range higher than the first range.
In one embodiment, the motor comprises a servo motor and the control 312 selectively applies a varying voltage to the servo motor to vary the speed of the servo motor as a function of the target pressure condition compared to the sensed pressure condition.
For example, the control 312 may apply a voltage and/or current to the servo motor such that the speed of the servo motor is a first speed and at a first torque when the pressure signal is within a first range, and the control 312 applies a voltage and/or current to the servo motor such that the speed of the servo motor is a second speed less than the first speed and at a second torque greater than the first torque when the pressure signal is within a second range higher than the first range.
It is also contemplated as an alternative that a profile as illustrated in
When the drive mechanism 310 includes a stepper motor, one embodiment includes control instructions in memory 318 executed by control 312 resulting in the frequency of PWM pulses applied to the stepper motor decreasing and the pulse width increasing to decrease speed and increase torque as the pressure of the lubricant increases, as indicated by pressure signal 316. The frequency of the pulses applied to the stepper motor would be maintained above a minimum and the width of the pulses would be maintained below a maximum to prevent stalling and to minimize motor temperature. When the drive mechanism 310 includes a servo motor, one embodiment includes control instructions in memory 318 executed by control 312 resulting in decreasing the voltage applied to the servo motor and increasing the current applied to the servo motor as the pressure increases. The servo motor may have an encoder which provides feedback to the control 312 indicative of the speed of the servo motor. The voltage applied to the servo motor would be maintained above a minimum and the current applied would be maintained below a maximum to prevent stalling and to maintain the motor temperature within its operating range.
When the motor comprises a stepper motor, PWM pulses are selectively applied to the stepper motor to vary speed and torque of the stepper motor as a function of the target pressure condition compared to the sensed pressure condition.
In one embodiment, when a difference between the sensed pressure at 402 compared to the target pressure at 404 is within a first range at 406, the PWM pulses are applied to the stepper motor at 408 such that the stepper motor is at a first speed and at a first torque. When the difference at 410 is within a second range higher than the first range, PWM pulses are applied to the stepper motor at 412 such that the stepper motor is at a second speed less than the first speed and at a second torque greater than the first torque.
When the motor comprises a servo motor, the control 312 selectively applies a varying voltage to the servo motor to vary speed of the servo motor as a function of the target pressure condition stored in memory 318 compared to the sensed pressure condition 316. In particular, a voltage is applied to the servo motor such that the speed of the servo motor is a first speed and at a first torque when the pressure signal is within a first range, and a voltage to the servo motor such that the speed of the servo motor is a second speed less than the first speed and at a second torque greater than the first torque when the pressure signal is within a second range higher than the first range.
As a result of the motor operation as described above, the pressure of lubricant supplied to a system via output 308 is ramped up and maintained close or slightly below the target pressure stored in memory 318. Simultaneously, the volume of lubricant pumped over time is decreased as the pressure increases to avoid excessive pressure and to minimize the release of lubricant via a safety or relief valve of the system. This inhibits excessive back pressure, minimizes motor stalls and promotes more lubricant to be quickly and effectively supplied to the system. As a result, the system and its components are effectively lubricated and the risk of failure due to improperly lubricated components of the system is minimized.
As will be appreciated by those skilled in the art, the lance pump 21 described above has several advantages over many prior commercially available lance pumps. Because the lance pump 21 is driven by a stepper motor capable of turning its output shaft at variable speeds, the output pressure and flow rate provided by the pump can be varied to conform to demand or specific operating conditions and environments. The lance pump is capable of providing viscous liquids at desired pressures on demand. Further, because the motor can run at lower speeds, complicated reduction gearing such as found in some prior commercial lance pumps can be eliminated. It is envisioned that by eliminating the reduction gearing, the cost and complexity of the lance pump may be reduced compared to lance pumps having reduction gearing.
As will be appreciated by those skilled in the art, the lance pump described above may be used in place of other types of lubricant pumps such as those described in U.S. patent application Ser. No. 13/271,862 filed Oct. 12, 2011, entitled, “Pump having Stepper Motor and Overdrive Control,” which is incorporated by reference. In such an application the pump can be to provide substantial lubricant flow (e.g., 150 cc/min) during system start up when pressures are low (e.g., 0 psi) and reduced flow after start up (e.g., 10 cc/min) when lubricant pressures are higher (e.g., 5000 psi).
As will also be appreciated by those skilled in the art, the motor may be a servo motor rather than a stepper motor and the control can be modified accordingly.
Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.
As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
