Rotary Pump
A rotary pump is provided having a chamber arranged in a body and a displacement member disposed in the chamber for reciprocating therein. A drive member is used to move the displacement member within the chamber in response to relative rotation between the body and the drive member. A radial valve arrangement may be used to time when the chamber is in fluid communication with inlet and outlet ports on the pump.
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This application claims the benefit of U.S. provisional patent application Ser. Nos. 60/622,742 for ROTARY PISTON PUMP filed Oct. 28, 2004, the entire disclosure of which is fully incorporated herein by reference.
BACKGROUND OF THE INVENTIONReciprocating piston pumps having a single reciprocating piston, such a shot meters, are well known. The operation of these pumps consists of an intake stroke and a discharge stroke. During the intake stroke, a piston moves within a cylinder bore to allowing fluid to enter the pump. During the discharge stroke, the piston moves in the opposite direction forcing the fluid out of the cylinder. Typically, check valves are used to ensure fluid only enters the cylinder bore during the intake stroke and only exits the cylinder during the discharge stroke. As such, shot meters do not produce a continuous flow of material but rather a pulsed flow because the piston chamber must be refilled after each discharge stroke.
A shot meter also tends to have volumetric limitations since it can only discharge the amount of fluid that fits within its cylinder bore. As a result, for large volume dispensing operations, a rather large piston chamber and drive mechanism is needed. Due to the large size, the unit must be remotely located from the application site, thus requiring long hoses which can cause supply hose swelling and surge effects. Should the same large system be used for a smaller volume dispensing operation, the shot meter would have a larger than necessary volume of material. Thus, during low volume dispensing operations, residual material will be left in the piston cylinder. As a result, the first material into the chamber is not necessarily the first material out and some material may reside within the piston chamber longer than desired.
Gear pumps are a form of continuous flow positive displacement pumps that can be used in some shot meter applications. Gear pumps, however, cannot be used with many materials, especially those materials that can be damaged or otherwise compromised by the crushing nature of the gear pump operation. Gear pumps also do not survive highly abrasive materials and can experience a limited degree of blow-by, thereby making them less appropriate for high precision metering applications.
SUMMARY OF THE INVENTIONThe invention contemplates a pump concept that provides positive displacement pump operation. In one embodiment, the pump is realized in the form of a rotary pump having a chamber arranged in a body and a displacement member disposed in the chamber for reciprocating therein. A drive member is used to move the displacement member within the chamber in response to relative rotation between the body and the drive member. A valve arrangement may be used to time when the chamber is in fluid communication with inlet and outlet ports on the pump.
In the accompanying drawing, which are incorporated in and constitute a part of the specification, embodiments of the invention are illustrated, which, together with a general description of the invention given above, and the detailed description given below, serve to exemplify embodiments of the invention.
The invention relates generally to positive displacement fluid pumps. More particularly, the invention relates to a rotary, positive displacement pump that provides an alternative to known shot meters. In an exemplary embodiment, the pump includes one or more displacement members, such as for example pistons, that are disposed in a body and driven by a drive member, such as for example a cam. Timing of the intake and discharge cycles of the pump is controlled by a valve arrangement, such as for example a radial spool valve.
The pump concepts presented in this application may apply to other pump applications besides a shot meter. The pump design, in the exemplary embodiment, provides a true positive displacement, continuous flow, metering pump; thus, the pump is suitable for a wide variety of pump applications. For example, the pump may be used in a variety of applications in the automotive industry to dispense viscous liquids, which may resist flowing or self leveling, such as adhesives, sealants, or caulks, onto a surface. Examples of this type of application include applying a seam sealant along the seam on lap jointed and spot-welded underbody sections; applying epoxy around the seam at the rim or perimeter of a door member; and applying Urethane adhesive to bond a windshield to the car body.
While various aspects and concepts of the invention are described and illustrated herein as embodied in combination in the exemplary embodiments, these various aspects and concepts may be realized in many alternative embodiments, either individually or in various combinations and sub-combinations thereof. Unless expressly excluded herein all such combinations and sub-combinations are intended to be within the scope of the present invention. Still further, while various alternative embodiments as to the various aspects and features of the invention, such as alternative materials, structures, configurations, methods, devices, software, hardware, control logic and so on may be described herein, such descriptions are not intended to be a complete or exhaustive list of available alternative embodiments, whether presently known or later developed. Those skilled in the art may readily adopt one or more of the aspects, concepts or features of the invention into additional embodiments within the scope of the present invention even if such embodiments are not expressly disclosed herein. Additionally, even though some features, concepts or aspects of the invention may be described herein as being a preferred arrangement or method, such description is not intended to suggest that such feature is required or necessary unless expressly so stated. Still further, exemplary or representative values and ranges may be included to assist in understanding the present invention however, such values and ranges are not to be construed in a limiting sense and are intended to be critical values or ranges only if so expressly stated.
The pump 10 is generally, a rotary pump in which there is relative rotation between the cylinder block 18 and the cam 16. In
During relative rotation between the piston cylinder 12 and the cam 16 about the axis 20, the piston 14 reciprocates within the cylinder 12 between a first or inner position and a second or outer position. During the discharge stroke, the piston 14 is moved radially inward, within its piston cylinder 12, by following the profile of the cam 16. During the intake stroke, fluid pressure from fluid entering the cylinder 12 forces the piston 14 radially outward, within its cylinder 12. The generally elliptical profile of the cam surface 23 provides for the movement of the pistons and achieves two complete intake strokes and two complete discharge strokes with 360 degrees of relative rotation between the cam 16 and cylinder block 18.
The pump 10 includes a valve arrangement 22 for controlling the timing of fluid flow into and out of the cylinders 12. In the example shown in
In the example in
With reference to
A bracket 38 may mount to the base 32 to support the motor 36. Alternative support configurations, however, may be used for the drive mechanism 36 and pump 10. For example, the motor can mount onto the pump via a C-face mount, as is known in the art.
The pump 10 has a main housing that includes a hub 40 and a front cover 42 that is assembled to the hub by a series of bolts 44 or other suitable means. The pump has a first or inlet side 46 and a second or outlet side 48. A sensor assembly 50 may be provided for purposes that will be further described hereinafter and may mount to the hub 40 or other convenient location.
Referring to
The drive shaft assembly 52 connects to the inlet side 46 of the pump 10 via a series of bolts 66. Dowel pins or drive keys 68 may be provided on the drive shaft 54 to impart positive drive from the drive mechanism 36. A series of bolt holes 70 may be provided for mounting the pump 10 on the support frame 32, such as by the vertical mounting plate 34 (
With reference to
The driven gear 80 rotatably mounts on a roller bearing assembly 94 that journals a bearing shaft 96. A thrust bearing 98 is provided between the back face 100 of the driven gear 80 and an inner wall bearing surface 102 of the hub 40. The thrust bearing 98 prevents contact between the driven gear 80 and the hub 40 resulting from axial movement of the gear. The mounting of the gears, bearings, and bearing shaft in the manner described, minimizes axial load on the pump 10. Moreover, by separating the gear drive function from the cylinder block 18, via use of the drive pins 84, radial loads on the cylinder block 18 are avoided.
The hub 40 forms an oil cavity 104 that holds oil to lubricate pump components, such as for example, the roller bearing assembly 94 and the drive and driven gears 78, 80. Seal elements may be provided within the pump at various locations to seal against loss of oil. For example, seals 106 located at the interface between the cylinder block 18 and a valve arrangement 22 prevent against loss of oil through the valve arrangement 22. In addition, an end cap 108 retains a seal 110 to prevent loss of oil around the drive shaft 54. The various seals within the pump 10 can be made from a variety of seal materials, such as for example, polyethylene and most other polymers.
The inlet bolt 56 includes an elongated stem 112 having a threaded end 114 that extends into and mates with a threaded hole 116 in the cap 58. Thus, the inlet bolt 56 and the cap 58 axially hold the cylinder block 18, the bearing shaft 96, the roller bearing assembly 94 and the hub 40 together.
The inlet bolt 56 also includes a fluid passageway 116 formed in the elongated stem 112. At the inlet side 46 of the pump 10, the passageway 116 opens to an inlet port 118 that can receive a coupling or other connection to the fluid supply. Internal to the pump 10, the fluid passageway 116 opens to a set of cross-bores 118 formed in the stem 112. The cross-bores 118 open to a common annulus 120 that communicates with the valve arrangement 22.
Referring to
As shown in
The first portion 144 may include a seal post 149 that extends from the body 134 of the piston 14. The post 149 can be used to retain the sealing element 142 to provide a seal with the cylinder 12 during pump operations. The seal 142 can be made from a wide variety of sealing materials, such as for example, polyethylene and most other polymers.
The second portion 146 includes two radially extending arms 150 adapted to receive the roller 136 between them. The roller 136 rotatably mounts onto the roller pin 138, which mounts to the arms 150 via bores 152 located in the arms. Other methods of rotatably mounting the roller may be realized according to the invention by one of ordinary skill in the art. The roller 136 provides a low friction engagement with the cam 16. Low friction between the pistons 14 and cam surface 16 reduces power consumption of the pump 10 as well as reducing heat generation and likelihood of the pump seizing up.
The second portion 146 also includes the alignment pin 140 extending generally perpendicular from the second portion 146. The slot 128 of the cylinder block 18 receives the pin 140 to prevent rotation of the piston 14 within the cylinder 12 during operation and ensure proper orientation of the pistons during installation.
As a result of the relative rotation between the cylinder block 18 and the cam 16, the cam 16 moves the piston 14 radially inward. The shoulder 126 on the block 18 provides a positive stop for the shoulder 148 on the piston 14 to ensure the post 149 on the piston 14 does not contact the valve arrangement 22. As the piston 14 moves radially inward, fluid in the cylinder 12 is discharged into the outlet opening 26 in the valve arrangement 22.
The outlet opening 26 opens to a pair of outlet passageways 154 formed in the cap 58. The outlet passageways 154 communicate with the outlet 60 via cross-bores 156 allowing fluid to be discharged from the pump 10. Thus, the two dispense slots 26 discharge into a common outlet 60. If desired, each dispense slot 26 may be in fluid communication with its own outlet so that the pump can feed two dispensing systems. Fluid pressure in the two outlet lines, however, may need to be kept equal in some applications in order to avoid radial loads on the spool valve 22.
During the intake stroke, the fluid travels from the passageway 116, through the cross bores 118 and into the inlet slots 24. Four cross-bores 118 are provided to assure free flow from the fluid passageway 116 into the inlet slots 24. This eliminates alignment issues between the bores 118 and the slots 24 when the stem 112 is screwed into the hole 116 (see
The piston 14, at the end of the discharge stroke, is positioned substantially at the radially innermost edge of the cylinder 12. Thus, substantially all of the fluid is discharged from the piston cylinder 12 after the completion of a discharge stroke. In this way, the pump 10 generally achieves a first-in-first-out (FIFO) operation since little or no fluid in the cylinder will carry over to from the discharge stroke to the next intake stroke.
The spool valve 22 thus controls the inlet and discharge timing of fluid flow into and from the piston cylinders 12 without the use of check valves. The cam 16 controls the speed and timing of the intake and discharge strokes of the pistons 14 as the cylinder block 18 rotates. The cam 16 is matched to the geometry of the spool valve 22 so that the inlet slots 24 are open to the cylinders 12 during the intake stroke portions of the cam profile and the dispense slots 26 are open to the cylinders during the dispense or discharge portions of the cam profile. Thus, the pump has a timed port concept.
The spool valve 22 serves to completely isolate the inlet and outlet flow paths during operation of the pump 10. The lands 121 of the spool valve 22 are wider than the width of each cylinder 14. Thus, each cylinder 14 will not be exposed to both the inlet and outlet openings 24, 26 at the same time.
In this manner the pump 10 operates as a true positive displacement pump in which the dispense flow is independent of the inlet pressure and is thus a function of the speed with which the pistons 14 move during the discharge stroke. The speed of the pistons 14 during the discharge stroke is determined by the selected profile of the cam 16 and the speed that the cylinder block 18 is rotated by the drive mechanism 36. Accordingly, very precise flow rates can be achieved even at very low flow rates.
As shown in
In particular, in reference to pistons A-C in
The exemplary embodiment in
The pistons 14 can be designed with a close fit within the cylinders 12 to prevent oil seepage into the discharge slots 26. In addition, the lands 121 of the valve arrangement 22 can have a close fit with the interior surface of the opening 132 in the cylinder head 18 so as to prevent or minimize cross-over of fluid from an inlet slot 24 to a discharge slot 26. Due to the close machining tolerances and clearances between moving metal parts, it is expected that oil lubrication alone may not be enough to reduce the coefficient of sliding friction between closely spaced metal parts, such as for example between the pistons 14 and cylinders 12 and between the spool valve 22 and cylinder block 18. Therefore, the surfaces that are exposed to potentially high frictional contact with other surfaces may be treated as required to reduce the coefficient of friction. For example, a solid surface treatment such as, for example, Amorphous Diamond Like Coating (ADLC) may be used. This process involves the application of a coating to the surface by a plasma assisted chemical vapor deposition process and is known to those skilled in the art and is a commercially available process. Other processes or coatings may be used as required, such as for example a MOST™ process available from Ion Bond. Some pump designs and applications, however, may be able to rely on oil lubrication alone.
With reference to
The sensor 170 can be used to detect that each piston 14 fully radially extends towards the cam 16 during the intake stroke. When fully extended, the proximity sensor 170 detects the outer distal end of each piston 14 as it rotates past the sensor 170. The sensor 170 signal (typically “counts”) can then be compared to the rotational speed of the pump 10, measured by conventional means, such as for example, a tachometer (not shown) or other speed indicator, to detect if any pistons 14 are not functioning properly. Missed “counts” can indicate, for example, that the inlet pressure is insufficient to fill the cylinders 12 or that there is a leak or other anomaly within the pump 10. Alternatively, an inlet pressure sensor (not shown) may be used in combination with the sensor 170 to provide an inlet fluid pressure measurement. Proper pump operation can be confirmed when the “counts” of the sensor 170 are consistent with the pump rotational speed and inlet pressure is verified to be sufficient.
The second end portion 202 includes an axially extending slot 204 that forms an alignment lip 206. The alignment lip 206 forms part of an alignment mechanism 207 that will be described hereinafter. The piston 14′ also includes a curved “follower” surface 208. This surface 208 is selected to provide a low friction contact with the cam 16, preferably although not necessarily a line contact.
In this example, however, the piston cylinders 200 do not include a shoulder similar to the shoulder 126 of the cylinders 12 of
When each piston 14′ is properly inserted into its cylinder 200, the lip 206 must align with the notch 218. A piston retaining ring 222 (
The alignment mechanism 207 of this exemplary embodiment, therefore, can include the piston slot 204, the cylinder notch 218, and the retaining ring 222. This arrangement assures proper alignment of the pistons 14′ with the cam 16 during pump operation.
The invention has been described with reference to the preferred embodiments. Modification and alterations will occur to others upon a reading and understanding of this specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims
1-47. (canceled)
48. A rotary pump, comprising:
- a body rotatable about an axis;
- a plurality of radially extending chambers arranged in the body;
- a plurality of displacement members, each displacement member disposed in one of said plurality of chambers for reciprocating therein;
- a drive member that moves the plurality of displacement members within the chambers in response to relative rotation between the body and the drive member; and
- a radial valve arrangement presenting a fluid inlet opening during intake and an outlet opening during discharge to the plurality of displacement members, the drive member comprising a surface having a radial profile relative to the rotation axis of the body, the radial profile comprising a plurality of portions with different radius characteristics so that, when there is relative rotation between the drive member and the body, the displacement members in radially extending chambers that are discharging to the outlet opening move at different speed relative to each other according to the radial profile, the cumulative speed of the moving displacement members in the radially extending chambers that are discharging to the outlet opening being generally constant according to the radial profile, producing a generally constant fluid discharge rate during discharge.
49. The rotary pump of claim 48 wherein the plurality of displacement members move from a first position to a second position in response to sufficient inlet pressure from a fluid entering each of the plurality of chambers.
50. The rotary pump of claim 48 wherein the displacement members reciprocate between a first position and a second position and wherein the radial profile of the drive member surface during intake of the displacement members is steeper than the radial profile during discharge so that movement of the displacement members from the second position to the first position is slower than movement of the displacement member from the first position to the second position.
51. The rotary pump according to claim 48 wherein each of the displacement members includes an alignment device that prevents rotation of the displacement members in the chambers.
52. The rotary pump according to claim 51 wherein the alignment device includes an alignment pin received in a radial slot in the body.
53. The rotary pump according to claim 48 wherein the valve arrangement defines a pair of diametrically opposed inlet openings and a pair of diametrically opposed outlet openings.
54. The rotary pump according to claim 53 wherein the outlet openings are larger than the inlet openings.
55. The rotary pump according to claim 48 wherein the drive member comprises a cam having a radially inner drive surface that engages the plurality of displacement members, said inner drive surface comprises the radial profile having an accelerating portion, a decelerating portion and a generally constant velocity portion for discharge.
56. The rotary pump according to claim 48 wherein the outlet opening is sized to receive fluid from at least three chambers during discharge, wherein during discharge a first displacement member is accelerating, a second displacement member is decelerating and a third displacement member has a generally constant velocity.
57. The rotary pump according to claim 49 further comprising means for verifying that each of the plurality of displacement members has moved to the second position primarily in response to sufficient inlet pressure.
58. A rotary pump, comprising:
- a body rotatable about an axis;
- a plurality of radially extending chambers arranged in the body;
- a plurality of displacement members, each displacement member disposed in one of said plurality of chambers for reciprocating therein;
- an annular cam having a cam profile along a radially inner surface that moves the plurality of displacement members within the chambers in response to relative rotation between the body and the cam; and
- a radial valve arrangement defining an outlet opening, the outlet opening being configured to be in fluid communication with at least three chambers simultaneously, wherein during operation, the displacement member in at least two of the at least three chambers is changing speed and the displacement member in at least one of the at least three chambers is at a constant speed, and wherein the cumulative speed of the displacement members that are changing speed is equal the speed of the displacement member that is at a constant speed according to the cam profile.
59. The rotary pump of claim 58 wherein the plurality of displacement members move from a first position to a second position in response to sufficient inlet pressure from a fluid entering each of the plurality of chambers.
60. The rotary pump of claim 58 wherein the displacement members reciprocate between a first position and a second position and wherein the radial profile of the drive member surface during an intake stroke of the displacement members is steeper than the radial profile during a discharge stroke so that movement of the displacement members from the second position to the first position is slower than movement of the displacement member from the first position to the second position.
61. The rotary pump of claim 58 wherein the valve arrangement further defines an inlet opening, and wherein the inlet opening is smaller than the outlet opening.
62. A rotary pump, comprising:
- a body;
- radially extending chambers arranged in the body;
- displacement members, each displacement member disposed in one of said chambers for reciprocating therein;
- a valve arrangement defining an outlet opening presented to a plurality of the chambers during discharge;
- a drive member that moves the displacement members in the discharging chambers at different speeds with a cumulative speed that is generally constant during discharge so that fluid enters the outlet opening from the discharging chambers at a cumulative generally constant rate when the speed of relative rotation between the body and the radial valve arrangement is generally constant.
63. A rotary pump, comprising:
- a chamber arranged in a body rotatable about an axis;
- a displacement member disposed in the chamber for reciprocating therein between a first position and a second position, wherein the displacement member moves from the first position to the second position primarily in response to sufficient inlet pressure from a fluid entering the chamber;
- a drive member that moves the plurality of displacement members within the chambers in response to relative rotation between the body and the drive member; and
- a sensor positioned in the drive member for detecting when the displacement member is in the second position to indicate there is sufficient inlet pressure.
64. The rotary pump of claim 63 wherein the sensor is an inductive proximity sensor.
65. The rotary pump of claim 48 wherein said radial valve arrangement comprises two outlet openings with each outlet opening being in fluid communication with a respective dispensing outlet of the pump.
66. The rotary pump of claim 48 wherein the fluid inlet opening is isolated from the outlet opening so that each of the plurality of radially extending chambers are prevented from being in fluid communication with the fluid inlet opening and outlet opening at the same time.
67. The rotary pump of claim 66 wherein the inlet opening and the outlet opening are isolated by a land therebetween, and the radial profile of the drive member comprises a generally constant radius portion to produce a dwell time during which a displacement member is stationary within its chamber between an intake stroke and a discharge stroke.
68. (canceled)
Type: Application
Filed: Oct 28, 2005
Publication Date: Nov 24, 2011
Applicant: NORDSON CORPORATION (Westlake, OH)
Inventor: Mario Romanin (Valley City, OH)
Application Number: 11/718,116
International Classification: F04B 1/107 (20060101); F04B 49/12 (20060101);