Abstract
A tri-chamber nutating pump is disclosed which includes two pump chambers disposed within a pump housing that accommodates a nutating piston. A reciprocating compensating piston is also provided with its own compensating housing that is connected to the outlet. As a cumulative output from the first two pump chambers reaches its maximum level, the compensating piston is pushed into the outlet or through a passage to reduce the output of the first two chambers and avoid splashing. As the output from the first two chambers reaches its minimum level, the compensating piston is withdrawn from the outlet or through a passage thereby increasing the output of the third chamber to its maximum level when the output from the first two pump chambers reaches its minimum level.
Claims
1. A nutating pump, comprising: a nutating piston disposed in a pump housing, the pump housing comprising an inlet and an outlet, the pump housing further comprising a middle passage extending through the pump housing and intersecting the inlet and the outlet, the middle passage including a middle section disposed between the inlet and the outlet and a distal section disposed opposite the inlet from the outlet and terminating at an enclosure, the nutating piston comprising a proximal section and a distal end with a pump section disposed therebetween, the pump section at least partially and slidably accommodated in the middle section of the middle passage with the pump section extending at least partially across the inlet to the distal section of the middle passage, the proximal section of the nutating piston extending at least partially across the outlet, the pump section of the nutating piston comprising a recess extending across at least part of the pump section to the distal end of the nutating piston, the proximal section of the nutating piston having a first maximum outer diameter, the pump section of the nutating piston having a second maximum outer diameter that is greater than the first maximum outer diameter, the proximal section connected to the pump section at a transition section, the proximal section of the nutating piston coupled to a drive shaft, the pump housing and the nutating piston defining two pump chambers including a first pump chamber and a second pump chamber, the first pump chamber defined by the distal end and the recess of the nutating piston and the distal section of the middle passage, the second pump chamber defined by the transition section and a portion of the proximal section of the nutating piston that extends across the outlet of the pump housing and between the outer passage and the outlet, the outlet in communication with a through passage of a compensating housing, the through passage extending past a compensating piston at a third pump chamber disposed in the through passage, the compensating piston being slidably and sealably accommodated in the compensating housing, the compensating piston including a distal end directed towards the through passage and a proximal end engaging a bearing, the bearing engaging a cam, the cam coupled to the drive shaft, wherein rotation of the drive shaft causing rotation of the cam, which imparts reciprocating movement to the bearing and the nutating piston thereby causing reciprocating movement of the distal end of the nutating piston into and out of the through passage.
2. The nutating pump of claim 1 wherein the middle passage of the pump housing extends at least substantially perpendicular to the inlet and the outlet and the outer passage of the pump housing extends at least substantially parallel to the middle passage.
3. The nutating pump of claim 1 wherein the outlet of the pump housing is connected to an outlet housing disposed between the outlet and the compensating housing, the outlet housing having an outlet passage providing communication between the outlet and the through passage.
4. The nutating pump of claim 1 wherein the compensating piston is slidably accommodated in a liner, the liner having a distal end facing the through passage of the compensating housing and a proximal end engaging a primary seal for inhibiting leakage between the compensating piston and the liner.
5. The nutating pump of claim 4 wherein the primary seal is annular and has an outer periphery, the outer periphery comprising a slot for accommodating an O-ring, the O-ring sandwiched between the outer periphery of the seal and a seal retainer, the seal retainer including a proximal end with an opening through which the compensating piston passes, the proximal end connected to a distal end by a continuous sidewall, the distal end of the seal retainer being biased against the compensating housing by a spring, the spring also biasing the proximal end of the compensating piston against the bearing.
6. The nutating pump of claim 1 wherein the cam, the compensating piston and the nutating piston are arranged so that when a cumulative output from the first and second pump chambers is at a maximum, a compensating output from the third pump chamber is at a minimum.
7. The nutating pump of claim 1 wherein the cam, the compensating piston and the nutating piston are arranged so that when a cumulative output from the first and second pump chambers is at a minimum, a compensating output from the third pump chamber is at a maximum.
8. The nutating pump of claim 1 wherein the drive shaft is coupled to a stepper motor.
9. The nutating pump of claim 1 wherein the pump housing and the compensating housing are molded from a plastic material.
10. A method for providing a steady state output flow from a nutating pump that is operating at a constant motor speed, the method comprising: providing a nutating pump with a first pump chamber, a second pump chamber, and a nutating piston, the first pump chamber producing a first output in response to a first 180° of rotation of the nutating piston, the second pump chamber producing a second output in response to a second 180° of rotation of the nutating piston, the nutating pump including an outlet, providing a compensating piston with a distal end that faces the outlet when the compensating piston is in a retracted position and that extends into the outlet when the compensating piston is in an extended position, extending the compensating piston into the outlet when a cumulative output from the first and second pump chambers approaches a maximum level, and retracting the compensating piston from the outlet when the cumulative output from the first and second pump chambers approaches a minimum level.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The disclosed embodiments are illustrated more or less diagrammatically in the accompanying drawings, wherein:
(2) FIG. 1 illustrates, graphically, a prior art dispense/fill profile for a prior art nutating pump operated at a fixed motor speed;
(3) FIG. 2 is a rendering from a photograph illustrating the pulsating dispense stream of the prior art nutating pump, the operation of which is graphically depicted in FIG. 1;
(4) FIG. 3 is another rendering of a photograph of an output stream of the prior art nutating pump of FIG. 1, operated at a constant, but slower motor speed than the motor speed of FIG. 2;
(5) FIG. 4 graphically illustrates a dispense and fill cycle for the prior art nutating pump of FIG. 1, when operated at variable speeds to reduce pulsing;
(6) FIG. 5 is a sectional view of a prior art dual-chamber nutating pump 20 showing the piston 10 at a mid-portion of its dispense stroke with the stepped transition 31 between the smaller proximal section 28 of the piston 10 and the larger pump section 29 of the piston 10 moving away from the “second” chamber 44 and with the distal end 33 of the piston 10 entering the first chamber 42;
(7) FIG. 6 is another sectional view of the prior art dual-chamber nutating pump 20 illustrated in FIG. 5 but with the piston 10 rotated and moving away from the first chamber 42 and the housing enclosure 22 as the piston 10 moves to the middle of its down stroke, and further illustrating fluid entering the first chamber 42 and exiting the second chamber 44 as the stepped transition 31 enters the second chamber 44;
(8) FIG. 7 graphically illustrates the dispense profile for the prior art dual-chamber nutating pump 20 of FIGS. 5-6 operating at a constant motor speed of 800 rpm to provide two modified dispense profiles 1d, 1e, the first of which occurs during the dispense portion of the cycle and the second of which occurs during the fill portion of the cycle;
(9) FIG. 8 is a perspective view of a disclosed tri-chamber nutating pump 120;
(10) FIG. 9 is a sectional view of the tri-chamber nutating pump 120 of FIG. 8;
(11) FIG. 10 is a side plan view of the compensating piston 110 of the nutating pump 120 shown in FIGS. 8-9;
(12) FIG. 11 is a plan view of the sleeve 212 that accommodates the compensating piston 209 shown in FIGS. 9-10;
(13) FIG. 12 is a perspective view of the O-ring retainer 221 that protects against leakage from the proximal end of the sleeve 212 shown in FIGS. 9 and 11;
(14) FIG. 13 is a perspective view of the retainer seal 222 that surrounds the O-ring retainer 221, the sleeve 212 and part of the compensating piston 209 of the pump 120 as shown in FIG. 9;
(15) FIG. 14 is another perspective view of the retainer seal 222 shown in FIG. 13;
(16) FIG. 15 is a perspective view of the spring 223 that surrounds the retainer seal 222 shown in FIGS. 13-14;
(17) FIG. 16 is a perspective view of the seal 214 through which the compensating piston 209 passes and that is sandwiched between the proximal end of the sleeve 212 and the proximal end of the retainer seal 222 as shown in FIG. 9;
(18) FIG. 17 is a perspective view of the bearing assembly 234 that extends between the proximal end of the compensating piston 209 and the cam 201 of the pump 120;
(19) FIG. 18 is a perspective view of the cam follower 226 through which the proximal end of the compensating piston 209 passes and which is partially received in the follower guide 228 illustrated in FIGS. 20-21;
(20) FIG. 19 is another perspective view of the cam follower 226 shown in FIG. 18;
(21) FIG. 20 is a perspective view of the follower guide 228, which receives the proximal portion 227 of the cam follower 226 illustrated in FIGS. 18-19;
(22) FIG. 21 is another perspective view of the follower guide 228 illustrated in FIG. 20;
(23) FIG. 22 is a perspective view of the cam 201, which is coupled to the drive shaft 125 as illustrated in FIG. 9 and which engages the bearing 234, which is illustrated in FIGS. 8 and 17;
(24) FIG. 23 is another perspective view of the cam 201 illustrated in FIG. 22;
(25) FIG. 24 illustrates, graphically, the non-pulsating flow of the tri-chamber nutating pump 120 disclosed herein.
(26) It will be noted that the drawings are not necessarily to scale and that the disclosed embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details may have been omitted which are not necessary for an understanding of the disclosed embodiments or which render other details difficult to perceive. It should be understood, of course, that this disclosure is not limited to the particular embodiments illustrated herein.
DETAILED DESCRIPTION OF THE DISCLOSURE
(27) A nutating pump 120 is illustrated in FIGS. 8-9. The nutating pump 120 includes the basic features of the nutating pump as shown in FIGS. 5-6 and these features are identified using the reference numerals of FIGS. 5-6 with the prefix “1”, e.g., the pump housing 121 as opposed to the pump housing “21”. The nutating pump 120 includes a pump housing 121 that is coupled to an enclosure 122. The nutating pump 120 also includes an intermediate housing 123, which encloses the coupling 124, the proximal end 126 of the nutating piston 110 and the cam 201, which is also illustrated in FIGS. 22-23.
(28) The intermediate housing 123 also encloses a shroud 202, which provides dust protection for the various mechanical components disposed in the intermediate housing 123. The shroud 202 is utilized because the nutating pump 120 may be used to dispense colorants. For example, tints or colorants used to add color the white base material of a paint mixture can generate dust if the solvent evaporates. This dust causes damage to mechanical components and must be cleaned, thereby leading to increased maintenance requirements.
(29) The proximal end 126 of the nutating piston 110 is coupled to the upwardly extending tab 203 of the cam 201 by way of the link 127. Like the piston FIGS. 5-6, the nutating piston 110 also includes a proximal section 128 that has a smaller diameter than a distal pump section 129. The proximal section 128 passes through a bushing 204 as well as a seal 138. The proximal section 128 and the transition section 131 of the nutating piston 110 also pass through the second pump chamber 144. The pump section 129 is received in the middle seal 132 of the pump housing 121 and the distal end 133 of the nutating piston 110 is received in the distal seal 134. The first pump chamber 142 is barely visible in FIG. 9 as the distal end 133 of the nutating piston 110 is close to an abutting engagement with the enclosure 122. The position of the first pump chamber 142 is substantially the same as the first pump chamber “42” of FIGS. 5-6.
(30) Thus, like the nutating pump shown in FIGS. 5-6, fluid enters the nutating pump 120 through the inlet 135 before being pushed into the first pump chamber 142 by the axial movement of the nutating piston 110 towards the enclosure 122 as well as the rotation of the nutating piston 110 and the engagement of fluid disposed in the first pump chamber 142 by a recess 113 in the pump section 129 of the nutating piston 110. The nutating pump 120 also includes an outer passage 143 that connects the first pump chamber 142 to the second pump chamber 144. The transition section 131, which is not beveled in the embodiment shown in FIG. 9, generates displacement through the second pump chamber 144 when the nutating piston 110 is retracted in a proximal direction away from the enclosure 122 as discussed above in connection with FIGS. 5-6. For the direction of flow, the reader is directed to FIGS. 5-6 and the explanation thereof.
(31) The second pump chamber 144 is in communication with the outlet 136, which may be defined by an outlet housing 205 and the compensating housing 206. In the embodiment shown in FIG. 9, the compensating housing 206 may also partly define the third pump chamber 207 with the distal end 208 of the compensating piston 209 (see also FIG. 10), the distal end 312 of the liner 212 (see also FIG. 11), and the primary seal 214 (see also FIG. 16). The engagement between the proximal end 412 of the liner 212 and the primary seal 214 help to prevent leakage from the outlet 136 into the compensating housing 206. The primary seal 214 may include an outer periphery 314 with a peripheral slot 216 (FIG. 16) that may accommodate an additional O-ring 217 (FIG. 9). In addition, another O-ring 218 may be disposed between the primary seal 214 and an O-ring retainer 221 (see also FIG. 12). The O-ring retainer 221, O-ring 218, O-ring 217, and the primary seal 214 may all be accommodated within a seal retainer 222 (see also FIGS. 13-14). The seal retainer 221 includes a proximal end 322 with an opening 422 for accommodating the compensating piston 209. A continuous sidewall 522 connects the proximal end 322 to the distal flange 224. The seal retainer 222, in turn, may be accommodated within a spring 223 (see also FIG. 15) or other biasing element. The spring 223 may be trapped between the distal flange 224 (FIGS. 13-14) of the seal retainer 222 and the flange 225 of the cam follower 226 (see also FIGS. 18-19). The distal flange 224 may also include a slot 220 (FIG. 13) for accommodating the O-ring 230 (FIG. 9).
(32) The cam follower 226 may be prevented from rotation by passing the proximal forked end 227 of the cam follower 226 through the follower guide 228, which is shown in FIGS. 20-21 as well as FIG. 9. The follower guide 228 includes a rectangular proximal section 229, which is received in a similarly configured rectangular opening 231 in the compensating housing 206, which in turn, prevents rotation of the cam follower 226 and rotation of the compensating piston 209. The proximal forked end 227 of the cam follower 226 may pass through the rectangular proximal section 229 of the follower guide 228 before it is linked to the proximal end 232 of the compensating piston 209 (see also FIG. 10) by passing a pin (not shown) through the openings 233 in the proximal forked end of 227 of the cam follower 226 (FIGS. 18-19) and the opening 332 in the proximal end 232 of the compensating piston 209. The proximal forked end 227 of the cam follower 226 also engages the bearing 234 (see also FIG. 17) or a roller, which in turn engages the cam 201 or, more specifically, the proximal section 235 of the cam 201 (see FIGS. 22-23). The proximal section 235 is coupled for rotation with the drive shaft 125 by way of a pin, set screw or other type of connection that will be apparent to those skilled in the art. As shown in FIG. 9, the proximal section 235 of the cam 201 is hollow for receiving the distal end 240 of the drive shaft 125.
(33) FIG. 24 graphically illustrates the output flow per individual step of the stepper motor 326 where each 360° of rotation of the drive shaft 125 equals 400 individual steps of the stepper motor 326. The linearized shape of the proximal section 235 of the cam 201 is illustrated by the line 301. The output from the third pump chamber 207 is illustrated by the line 302. Further, the normalized output of the first and second pump chambers 142, 144 is illustrated by the line 303. Finally, the normalized output or combined tri-chamber output is illustrated by the line 304. Starting from the left side of FIG. 24, the output from the first and second pump chambers 142, 144 as represented by the line 303 begins at zero and begins to approach its maximum output at about 100 motor steps, which has a normalized output value of about 0.6. Contemporaneously, because the compensating piston 209 has not been pushed out into the outlet 136 or through passage 307, the output through the third pump chamber 207 begins at its maximum normalized value of about 0.4 and initially declines to its lowest value of less than −0.2 at about 100 motor steps. Thus, the output of the first and second pump chambers 142, 144 is at its maximum at 100 motor steps when the output through the third pump chamber 207 has reached a negative value. Thus, the combined output from the nutating pump 120 as represented by the line 304 remains steady at slightly less than about 0.4. This pattern continues throughout the rest of the dispense profile. Whenever the output from the first and second pump chambers 142, 144 reaches its maximum, the compensating piston 209 has been pushed into the outlet 136 to thereby impede the output from the first and second pump chambers 142, 144.
(34) Then, as the compensating piston 209 is retracted back towards the position shown in FIG. 9, the output from the third pump chamber 207 increases towards its maximum normalized output of close to 0.4 at 200 steps. Contemporaneously, the output from the first and second pump chambers 142, 144 decreases from its maximum after step 100 and the cumulative output from all three pump chambers 142, 144, 207 is maintained at the steady normalized value of about 0.4 (line 304). At about motor step 200, the output through the third pump chamber 207 is at its maximum and the output from the first and second pump chambers 142, 144 reaches about 0. This pattern is repeated for the second dispense portion of the profile (motor steps 200-400), which is identical to the first dispense portion of the profile (motor steps 0-200). After motor step 200, the nutating pump 120 also begins the fill portion of its profile, which is not shown in FIG. 24 (see the line number 1f of FIG. 7).
INDUSTRIAL APPLICABILITY
(35) The disclosed tri-chamber nutating pump 120 is useful for dispensing liquids, especially viscous liquids, with precision, accuracy and speed. The nutating pump 120 is particularly useful for dispensing paints and cosmetics and is especially useful for dispensing tints or colorants into a receptacle that may already include a liquid such as a base material for a paint or cosmetics product. Specifically most paints include a white base material, which is colored by adding concentrated tints or colorants to the base material. These tints or colorants must be accurately dispensed so that each can of paint has the same color. Any splashing of the tint dispensed onto the base in the paint receptacle will cause inaccuracies in the dispense and compromise the quality of the final product. Further, any splashing of tints or colorants must be cleaned up by maintenance personnel which is time consuming and costly. In addition to paint and cosmetics dispensing, the nutating pump 120 is useful for any application where the dispensing of viscous liquid materials is required with precision, accuracy and speed.
(36) The tri-chamber nutating pump 120 represents a substantial improvement over the nutating pump 120 illustrated in FIGS. 5-7 above. Specifically, the normalized combined output from the first, second and third pump chambers 142, 144, 207 remains steady through a complete 360° rotation of the drive shaft 125.
(37) While only certain embodiments have been set forth, alternative embodiments and various modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered to fall within the spirit and scope of this disclosure.
