FIELD OF INVENTION
The invention generally relates to the field of Mechanical Engineering. More specifically, it relates to high efficient maintenance in place progressive cavity pump.
BACKGROUND OF THE INVENTION
Definitions
Progressive Cavity Pump- A progressive cavity (PC) pump is a type of positive displacement pump and is also known as a progressing cavity pump, progg cavity pump, eccentric screw pump or cavity pump. (Ref:https://en.wikipedia.org/wiki/Progressive_cavity_pump) Helical rotor pump, eccentric screw pump etc.
Stator and Rotor - The stator is the stationary part of the pump and it is molded from an elastomeric material that is permanently bonded inside a steel tube. The cross-section is that of two semi-circles connected by two parallel straight lines. The centers of the semi-circles also lie along a helical path. As used in the context of the present invention, the stator refers to the stationary part of the progressive cavity pump, in which the rotor turns. The stator has a hole which is helical in shape, in which the helical rotor rotates.
The Rotor is usually made from metal with a polished surface finish and fits accurately into one of the two helices of the stator.

Progressive Cavity (PC) pump and its mode of operation
As can be seen in Fig. 6, the PC pump consists of single- helix rotor inserted in a double- helix stator, usually twice the wavelength of the helical hole in the stator and a powerful electrical motor which rotates the rotor. The rotor seals tightly against the stator as it rotates, forming a set of fixed-size cavities in between. The cavities move when the rotor is rotated but their shape or volume does not change. The Rotor is usually made from metal with a polished surface finish and fits accurately into one of the two helices of the stator.

End cover assembly - Used in the context of the present invention, end cover assembly refers to various arrangements of the casing of the pumps, which allow easy opening/dismantling of the pump and removal of the stator, rotor and universal joint for repair and maintenance on site, without the need for removal of the pump and transportation to workshop for repair and also without removing the suction and delivery pipes.

Working of PC pump:
The PC pump comprises of a precision machined single external helix metallic rotor, and a double internal helix elastomer stator. Due to the special profile of the rotor and stator set, a sealing line is formed along the axis of the rotor which is maintained at both static and dynamic conditions. The rotor seals tightly against the stator as it rotates, forming a set of fixed-size cavities in between. As the rotor turns within the stator, these cavities progress from the suction to the discharge end of the pump carrying the fluid.

Unique Features- Pumping is not due to the dynamic effect caused by drag, or friction against the moving teeth of the screw rotor but due to the sealed cavities, like a piston pump, and so has similar operational characteristics, such as being able to pump at extremely low rates, even to high pressure, revealing the effect to be purely positive displacement. The rotor moves in the inner cavity in an orbital manner.
At a high enough pressure the sliding seals between cavities will leak some fluid rather than pumping it, so when pumping against high pressures, a longer pump with more cavities is more effective, since each seal has only to deal with the pressure difference between adjacent cavities. Pump design begins with two (to three) cavities per stage. The number of stages (currently up to 12) is only limited by the ability to machine the tooling.

Different rotor shapes and rotor/stator pitch ratios exist, but are specialized in that they don't generally allow complete sealing, so reducing low speed pressure and flow rate linearity, but improving actual flow rates, for a given pump size, and/or the pump's solids handling ability.
(Volk, Michael W. (2005). Pump characteristics and applications (2nd ed.). CRC Press. pp. 27–28)
Applications of PC pumps in Industry
PC pumps have application in fluid metering and pumping of thin, viscous or shear-sensitive materials. Applications of PC pumps in industries thus include but are not limited to handling of waste water, waste water treatment, chemical and petrochemical, paper and cellulose, soap and fats, paint and lacquer, food and beverage, ceramics, agriculture, sugar, and shipbuilding industries. Typical PC pumps may handle many types of fluids from thin to highly viscous, neutral to corrosive, and contaminated or uncontaminated. Progressive cavity pumps may also typically handle fluids having solid matter, and fluids including a combination of liquid and gases.
Repair and maintenance of PC pumps- Challenges and Solutions/Innovative Approaches
As is evident from their mechanism of action, PC pumps undergo constant motion with natural consequence of wear and tear, which necessitates repair and maintenance, after a time period. This may involve replacement of the stator or the rotor or general cleaning to remove obstructive material/s. The challenges involved in the repair and maintenance of PC pumps are elaborated below:
Challenges:
i. Cumbersome process- Repair and maintenance of these PC pumps require extensive disassembly to access internal components, such as seals, rotors, stators, and the like.
ii. Removal and transport to workshop for repairs- In many cases the pump is required to be removed from the piping system and repaired in a workshop. This involves arranging transport, materials and resources, which makes the process tedious and slow.
iii. Long system downtimes during the time when repair is taking place- Repair operations take time and result in long system downtimes, which brings the industry operations to a halt, while the repair is going on
Solutions/Innovative Approaches
To address the cumbersome issues associated with repair and maintenance of PC pumps, industry has come out with various solutions/innovative approaches. These have their advantages and disadvantages as discussed below:
i. Split casing of the pump - Some PC pumps may include a split casing e.g. a split stator casing or split suction casing, for accessing the stator and rotor without removing the pump. However, such split casing arrangements are disadvantageous as the multi-piece stator is more susceptible to leaks and can only handle lower discharge pressures. Additionally, full disassembly may still be required for repair or maintenance of seals and joints.
ii. Coupling rod assembly of the pump- In some PC pumps, the coupling rod is made of two pieces and clamped together with the help of a split ring tightened with screws. In this case the torque is being taken only by the screws resulting in more load effect on the screws which may influence in the decrease of life of the clamping assembly.
iii. Design improvement to permit ‘maintenance-in-place’ – Design improvement to permit casing to be opened, the stator and rotor removed and overall disassembling to be done easily and quickly, without removing the pumps from site, thus drastically reducing downtime, maintenance cost and labor involved.
Commercially available PC pumps with maintenance-in-place (M I P) feature: A number of PC pumps are available commercially which permit easy maintenance-in-place owing to design improvements. Same are discussed below:
EP 3473856 A1 (Prior art Fig 1) of Circor Pumps North America LLC, discloses a PC pump entitled “Dismounting device for progressive cavity pumps” in which the pump can be dismounted and repaired easily. The disclosure provides for quick access to the internal pump components while still allowing the PC pump to remain substantially intact (e.g. substantial disassembly is not required) and maintaining a robust design. The dismount casing is configured for easy connection and removal, to the pump to provide access to the desired components, while still maintaining structural integrity and seals for use in high pressure environments, thus reducing system downtime for maintenance and repair of the PC pump. According to embodiments of the disclosure, the pump comprises a housing having a first end and a second end and a longitudinal axis, and a discharge casing having a first end coupleable to the second end of the housing, the discharge casing extending along the longitudinal axis coaxial to the housing. The pump further comprises a dismounting device including a first dismount casing and a second dismount casing disposed between the discharge casing and the second end of the housing. The dismounting device is configured to extend along the longitudinal axis coaxial with the housing and the discharge casing. The first dismount casing and the second dismount casing having variable thickness so that the first dismount casing can easily mate with second dismount casing. The dismounting device has a cylindrical shape. The casings are either sliding type or tapered.
Since the first dismount casing and the second dismount casing having variable thickness, it is likely to have precision issues in manufacturing this dismounting device and very fine accuracy is in tapering is required. In case, it is not achieved, there are ample chances of leakage at discharge casing and the second end of the housing. Also since precision and accuracy are must in this design, it may result in increasing the production cost as well.
Moreover, the primary components of this dismantling assembly are first dismount casing and the second dismount casing and O-Ring or gasket for sealing the assembly. The maximum Pressure limit is 10 bar for this pump.
Wangen PC Pump (Prior art Fig 2a and 2b) is a commercially available pump manufactured by the company ‘Wangen’, in which repair can be carried out easily, at site and assembling and disassembling of the pump is easy.
The dismounting device of this pump consists of a Spacer and a Gasket. The maximum Pressure limit is 6 bar for this pump.
(http://www.wangen.com/en/products/application/shipbuilding/WANGEN-Xpress)
EZ Strip PC pump (Prior art Fig 3) discloses an improved PC pump which can be dis-assembled using minimal tools and repaired onsite. The dismounting device of this pump comprises a two-piece casing. The maximum Pressure limit is 12 bar for this pump.
(http://www.mono-pumps.com/EZstrip)
Seepex PC pump (Prior art Fig 4a and 4b) discloses an improved PC pump is disclosed in which maintenance is easy due to the two-piece Smart Stator and quick release Smart Rotor, which leaves the joint in place and eliminates the need to remove pipe work.
(https://www.seepex.com/en/pumps-and-control-systems/smart-conveying-technology/)
Netzsch PC Pump (Prior art Fig 5a and 5b) discloses a pump with a tapered device arrangement for maintenance at connecting rod location. The maximum Pressure limit is 12 bar for this pump. (https://netzschindia.com/)

Limitations of existing PC pumps
Progressive Cavity (PC) pumps are used in a wide number of industries such as waste water, waste water treatment, chemical and petrochemical, paper and cellulose, soap and fats, paint and lacquer, food and beverage, plastics, ceramics, agriculture, sugar, and shipbuilding industries. The pump consists of a single-helix rotor inserted in a double-helix stator. Owing to wear and tear the pump requires regular maintenance. This involves removal of pump from the site, dismantling, repair and installation, which is a time consuming and cumbersome activity which increases downtime.
Existing PC pumps with dismounting devices for easy repair and maintenance, can handle up to maximum 12 bar pressure. Such pumps use a dismounting device in form of a split casing which is of sliding type or tapered type and permits easy dismantling for repair and maintenance of the pump. Such dismounting devices use O-rings for sealing the pump. Sliding type or tapered casing type arrangements are disadvantageous when pumps have to handle pressures more than 10 -15 bar, because they are susceptible to leaks at high pressures. Also, tapered face requires very accurate machining to avoid damage to O-ring and also ensure better fitment. Accurate machining is naturally expensive and increases overall cost of such pumps.
Therefore , it can be said that all the prior art pumps disclose split casing design, due to which none of the above pumps can withstand high pressures. Maximum pressures which such pumps can withstand are 10-15 bar.

Present invention and its advantages

The present invention discloses an improved Progressive Cavity (PC) pump, with unique and innovative features relating to high pressure limit along with maintenance-in-place/easy maintenance by permitting easy dismounting of the pump and access to rotor and stator quickly. These features are neither anticipated nor disclosed in the prior art PC pumps.
OBJECT OF THE PRESENT INVENTION
The primary object of the present invention is to disclose high efficient maintenance-in-place (M I P) Progressive Cavity (PC) pump which offers high pressure capacity of more than 48 bar and also permits easy maintenance in place owing to easy rotor, stator and universal joint removal.
Another object is to disclose high efficient maintenance-in-place (M I P) Progressive Cavity (PC) pump which can withstand high pressures without any leakage.
One more object is to disclose high efficient maintenance-in-place (M I P) Progressive Cavity (PC) pump which permits easy maintenance in place in a cost effective manner without using any specially machined tapering casing parts/dismounting devices.
One more objective is to disclose high efficient maintenance-in-place (MIP) progressive Cavity (PC) pump which enables better torque transmission and hydraulic thrust with standing capacity.

SUMMARY OF THE PRESENT INVENTION
The present invention makes innovative use of clamp rubber seal (5310-D) for the pump which enables the pump to withstand high pressures without any leakage. Easy maintenance in place feature of the pump has been achieved in a very cost-effective but efficient manner by eliminating specially machined tapered casings.
Instead a unique design of end cover assembly is provided in which two flanges are provided in the end cover - stator flange (5310-B) and end cover flange (5310-A). These two flanges are joined with clamp rubber seal (5310-D). This clamp rubber seal (5310-D) is further clamped with two metallic halves clamps (5310-C). Space is provided between the end cover - stator flange (5310-B) and end cover flange (5310-A), which permits easy removal of stator (2220). Coupling rod (2610-A, 2610-B) is made of two pieces tightened together with high tensile bolts (45) and an integral key is provided which can withstand more hydraulic thrust and also provide the better torque transmission. Seal ring (2610-C) has been provided to protect the accumulation of pumping fluid i.e. solid particles on the screw head (45) of the coupling rod joint, there by the smooth flow over the coupling rod can be achieved. Due to ease of use, the time to replace Stator (2220) and Rotor (2500) in pump of present invention is almost 70% less than the time required for the same in existing/conventional pumps.
BRIEF DESCRIPTION OF DRAWINGS
Fig 1- Fig 5 are prior art figures of existing commercial PC pumps with various mechanisms for MIP.
Fig. 6 is a sectional view illustrating an archetype of a pump in accordance with the present disclosure in an assembled condition
Fig.6A is a detailed sectional view of the pump of FIG. 6 illustrating an archetype of coupling rod assembly in attached position
Fig. 6B is a detailed sectional view of pump of FIG. 6 illustrating an archetype of coupling rod assembly in detached position
Fig. 7 is a sectional view illustrating an archetype of the pump shown in FIG.6 in a disassembled condition
Fig. 8A & 8B are perspective and side views, respectively illustrating an archetype of End cover assembly of the pump shown in Fig.1
Fig. 9 is a Partial sectional view illustrating another archetype of dismounting casing of a pump in accordance with the present disclosure
Numbering Details:
5010: Pump housing
20-A, 20-B: Second and First universal joints
2610-C: Seal ring
45: hex socket head cap screw
5310-A: End cover flange
5310-B: Stator flange
5310-C: Metallic half clamps
5310-D: Clamp rubber seal
2220: Stator
2500: Rotor
2610-A, 2610-B: Two parts of coupling rod
3200: Drive shaft
2500: Rotor
45: Tensile bolts
Other parts of the pump remaining the same as in existing pumps.
The pump is now disclosed in detail with reference to the accompanying drawings.
DETAILED DESCRIPTION OF INVENTION
The present invention discloses high efficient maintenance-in-place (M I P) Progressive Cavity (PC) pump which offers low to high pressure capacity of more than 48 bar and also permits easy maintenance in place owing to easy rotor, stator and universal joint removal. This pump can withstand high pressures without any leakage. This has been achieved by unique design of End cover assembly. Specially machined tapering casing parts/dismounting devices are not used in the invention.
Constructional and operational details: The design of connecting rod assembly is altered such that better torque transmission and hydraulic thrust with standing capacity is achieved.

In a preferred embodiment, the present invention consists of two major design changes for achieving high pressure withstanding capacity with easier maintenance and repair of the pump.
First is changing the design of end cover assembly of the pump in which End cover stator flange 5310-B, End cover flange 5310-A, Clamp rubber seal 5310-D, and two halves clamps 5310-C are provided to achieve the high pressure withstanding capacity. Space is created between the stator flange and end cover for easy removal of stator.

Second is making the coupling rod assembly split into two halves i.e first coupling rod portion (2610-B), a second coupling rod portion (2610-A) and other usual components of the pump remaining the same.

Keeping the above in mind, the present invention is described as below in detail.

As shown in Fig. 6, Pump may include a pump housing (5010) for housing the universal joints (20-A, 20-B), and a coupling rod assembly having a first coupling rod portion (2610-B) , a second coupling rod portion (2610-A), a Seal ring (2610-C) and hex socket head cap screw (45).
The first coupling rod portion (2610-B) may be connected to the drive shaft (3200) at a first universal joint 20-B, and the second coupling rod portion 2610-A may be connected to a rotor 2500 at a second universal joint (20-A).
The first and second universal joints (20-B, 20-A) may allow the coupling rod assembly to move with multiple degrees of freedom about the drive shaft 3200 and rotor (2500).
Coupling rod assembly, having a first coupling rod portion 2610-B, a second coupling rod portion 2610-A, a Seal ring 2610-C and hex socket head cap screw 45, may allow for easier maintenance and repair of the pump.

As shown in Fig. 6A and 6B, a detail view of the rotor 2500, the universal joint 20-A, and the first and second coupling rod portions 2610-B, 2610-A along with a seal ring 2610-C and hex socket head cap screw 45 are illustrated in an attached and detached position, respectively.

In an attached position, the rotor 2500 and the second coupling rod portion 2610-A at the universal joint 20-A may be coupled to the first coupling rod portion 2610-B.
When the rotor 2500 and the universal joint 20-A need to be removed for repair and/or replacement, the second coupling rod portion 2610-A may be detached from the first coupling rod portion 2610-B by unscrewing fasteners 45.

As shown Fig. 7, the end cover assembly of the pump is illustrated in a disassembled condition in which End cover stator flange 5310-B, End cover flange 5310-A, Clamp rubber seal 5310-D and two halves clamps 5310-C removed. Space is created between the stator flange and end cover for easy removal of stator.This allows the rotor 2500 and stator 2220 and other internal pump components easily accessible to an operator for repair and maintenance without detaching the suction & delivery pipe line from pump.
As shown Figs. 8A, 8B & 9, end cover assembly having end cover flange 5310-A, Stator flange 5310-B, clamp rubber seal 5310-D and clamp 5310-C.
The clamp rubber seal (5310-D) is a combination of flat & O ring sealing due to which pump can bear higher pressure range, of more than 48 bar without leakage.
THIS END COVER ASSEMBLY IS THE HEART OF THE INVENTION

The unique features of improved PC pump of present invention over prior art, are given in Table 1 below:
Table 1: Unique features of improved PC pump of present invention

S. No. Technical Feature Pump of Present Invention Prior Art Pumps

1. Maximum pressure From low pressures to 48 bar and above Achieved in a very innovative manner by use of clamp rubber sealing (combination of flat & O ring sealing) due to which pump can bear higher pressure range, of upto 48 bar and above pressure without leakage. 12 bar is the maximum pressure which these PC pumps can withstand, owing to their inherent design which involves use of first end casing and second end casing in which sealing is done using only O-ring.
2. Casing Design Easy to manufacture, owing to absence of taper face and no need for machining
Less cost. Needs accurate machining owing to tapered face design. Hence costly.
3. Dismounting Easy dismounting mechanism without use of any dismount casings. Instead, space is created between the stator flange and end cover for easy removal of stator. Two dismount casings are used, to join the stator flange and end cover flange.
4. Coupling rod Coupling rod is made of two pieces tightened together with high tensile bolts and an integral key is provided which can with stand more hydraulic thrust and also better torque transmission. In some PC pumps, the coupling rod is made of two pieces and clamped together with the help of a split ring tightened with screws. In this case the torque is being taken only by the screws resulting in more load effect on the screws which may influence in the decrease of life of the clamping assembly.
The pump of present invention also offers significant savings of time as evident from the comparison given in Table 2 below:
Table 2: Time Comparison to replace Stator & Rotor in conventional pump vs
pump of present invention

S. No. Description Current Invention
(Approximate time in Minutes) Standard Pump
(Approximate time in Minutes)
1 Stator Removal 14-20 28-30
2 Stator Assembly 20-25 56-60
3 Rotor Removal 14-20 50-55
4 Rotor Assembly 20-25 100-120
5 Total time 68-85 234-265

Novelty, Inventive Step and Industrial Application
Novelty
The present invention discloses a MIP Progressive Cavity Pump which can withstand high pressures of more than 48 bar without any leakage along with easy maintenance in place, has not been disclosed in the prior art. Maintenance in place has been made fast and cost-effective by eliminating use of specially machined, tapering dismount casings. Time to replace Stator and Rotor in pump of present invention is almost 65-75% less than in existing/conventional pumps and also with the special coupling rod assembly, better torque transmission and hydraulic thrust with standing capacity has been achieved.
Inventive Step
The technical advancement of knowledge lies in disclosing a design of end cover assembly of the pump in which End cover stator flange 5310-B, End cover flange 5310-A, Clamp rubber seal 5310-D and two halves clamps 5310-C are provided. Space is created between the stator flange and end cover for easy removal of stator. The clamp rubber seal (5310-D) is a combination of flat & O ring sealing due to which pump can bear higher pressure range of more than 48 bar without leakage.
Due to these features, the PC pump can not only withstand high pressures of upto 48 bar and above but also permits easy maintenance in place, in which repair and maintenance can be done in a fast manner.
The economic benefit of the present invention lies in reducing the down time of the pump to one fourth of normal time taken during maintenance, as the process of removal of stator assembly/ stator and rotor assembly/rotor is faster than usual as is evident from the TABLE 1 above.

The technical advancement of knowledge also lies in disclosing a coupling rod assembly split into two halves i.e first coupling rod portion (2610-B), a second coupling rod portion (2610-A).

Two halves of the split coupling rod assembly are tightened together with high tensile bolts and an integral key is provided which can with stand more hydraulic thrust and also better torque transmission.

Industrial Application
The PC pump of the present invention can be easily manufactured on commercial scale and has widespread applications in industries which include but are not limited to handling of waste water, waste water treatment, chemical and petrochemical, paper and cellulose, soap and fats, paint and lacquer, food and beverage, plastics, ceramics, agriculture, sugar, and shipbuilding industries and several others.
As used herein, the word "a" or "an" should be understood as not excluding plural elements or operations, unless such exclusion is explicitly recited. Furthermore, references to "one embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.
The present disclosure is not to be limited in scope by the specific embodiments described herein. Other embodiments and modifications apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings are intended to fall within the scope of the present disclosure. Furthermore, although the present disclosure has been described herein in the context of above, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any pump for similar purpose.

CLAIMS:WE CLAIM:
1. Highly efficient maintenance in place progressive cavity pump WHEREIN the same consists of :
- a pump housing (5010) for housing rotor (2500), stator (2220) and the universal joints (20-A, 20-B) which allow the coupling rod assembly to move with multiple degrees of freedom about the drive shaft (3200);
- a coupling rod assembly having a first coupling rod portion (2610-B) connected to the drive shaft (3200) at a first universal joint (20-B) and a second coupling rod portion (2610-A) connected to the rotor (2500) at a second universal joint (20-A), a Seal ring (2610-C) and hex socket head cap screw (45);
- end cover assembly consisting of stator flange (5310-B), end cover flange (5310-A), clamp rubber seal (5310-D) and two halves clamps (5310-C); and
WHEREIN:
- the clamp rubber seal (5310-D) is a combination of flat & O ring sealing due to which pump can bear higher pressure range of more than 48 bar without leakage;
- space is created between the stator flange and end cover for easy removal of stator and to allow the rotor (2500) and stator (2220) and other internal pump components to be easily accessible to an operator for repair and maintenance without detaching the suction & delivery pipe line from pump.

2. The highly efficient maintenance in place progressive cavity pump as claimed in claim 1 WHEREIN:
- the rotor (2500) and the second coupling rod portion (2610-A) at the universal joint (20-A) is coupled to the first coupling rod portion (2610-B) in an attached position,; and
- The second coupling rod portion (2610-A) is detachable from the first coupling rod portion (2610-B) by unscrewing fasteners (45) in order to remove the rotor (2500) and the universal joint (20-A) for repair and/or replacement.

3. The highly efficient maintenance in place progressive cavity pump as claimed in claim 1 WHEREIN the two halves of the split coupling rod assembly i.e first coupling rod portion (2610-B) and second coupling rod portion (2610-A) are tightened together with high tensile bolts and an integral key is provided.

4. The highly efficient maintenance in place progressive cavity pump as claimed in claim 1 WHEREIN the time to replace Stator and Rotor in pump of present invention is 68-85 minutes which is 65-75% less than in existing/conventional pumps.

5. The highly efficient maintenance in place progressive cavity pump as claimed in claim 1 WHEREIN the coupling rod assembly split into two halves i.e first coupling rod portion (2610-B), a second coupling rod portion (2610-A) is fitted in existing pump to convert it into high efficient maintenance in place progressive cavity pump.