Description:FIELD OF THE INVENTION
This invention relates to mechanical seals which are employed on rotating equipment in various industry sectors from food and chemical to pharmaceutical and oil and gas. Typical rotating equipment includes Pumps, Mixers, Agitators, Dryers and Reactors and specifically equipment such as ANFD’s (AGITATED NUTSCHE FILTER DRIERS) that have large movement capabilities along their longitudinal shaft axis in addition to their rotational movement.

BACKGROUND TO THE INVENTION
Mechanical seals are employed across all industry sectors on rotating equipment such as pumps, mixers and reactors. Some industry sectors such as the food, fine chemical and the pharmaceutical industries require technically sophisticated equipment which, in addition to its rotational mixing capabilities incorporates longitudinal movement mixing capabilities. Agitated filter dryers, such as ANFD’s, are an example of such equipment.

Agitated filter dryers are typically vertically orientated and designed for solid-liquid separation processes using filtration under pressure and vacuum drying and consist of a closed vessel incorporating a shaft connected to a paddle or agitation device. Materials and ingredients, herewith termed process media, are placed inside the vessel and essentially mixed by the paddle in a rotational and longitudinal manner. The vessel incorporates temperature control and uses filtration under pressure or vacuum to isolate process media solids from liquids, to produce a finished, dried and substantially solid process media herewith termed cake.

Towards the end of the operational cycle, as the paddle is rotated, typically in a clockwise direction, it pushes the dry cake towards the vessel wall during each rotation, thus expelling product intermittently out through the side discharge valve for collection in containers/bags or onto a subsequent in-line process.
At the heart of the Agitated filter drying equipment is a mechanical seal which seals the counter-rotational interface between the equipment shaft and housing.
If the mechanical seal functions correctly, the closed system of the Agitated filter dryer maintains high cake product quality and hygiene by providing odourless, contamination-free, and non-polluting operating conditions.
Unfortunately, given the extensive movement and operations of the Agitated filter dryer mechanical seals typically fail prematurely given:
- intermittent shaft stop/starts,
- cyclic vessel temperatures,
- cyclic vessel pressures from vacuum to high pressure,
- rotational and counter-rotational shaft movement,
- extensive longitudinal shaft movement, typically up to 1.5m (5 feet)

Along with a series of static elastomer components or o-rings, the seal faces of the mechanical seal are primarily designed to prevent the process fluid escaping the process equipment / vessel.
The create a seal, the counter-rotational seal faces of the mechanical seal are typically very flat and spring biased together and hence they generate frictional heat as they interact. To help keep the seal faces cool, mechanical seals can be hydraulically balanced in that, by design, a fluid film is formed between the two counter rotational seal faces. This fluid film is very small, often only microns (tens of thousands of an inch) thick, but it helps to cool and lubricate the seal faces allowing them operate in a leak free nature. However, if the fluid film is not stable because of varying equipment operational conditions, it will seize to act in a cooling and lubricating manner and cause the seal faces to dry run, grind together, chip, wear and leak.
For this reason, the condition of the fluid film is therefore vitally important to the success of the mechanical seal in service. A poor fluid film, in terms of thickness and temperature, will ultimately damage the seal faces and cause the mechanical seal to leak.
Needless to state, a leaking mechanical seal is not only an environmental hazard, it is a health and safety hazard and it can have a huge commercial impact to the processing plant in lost process fluid costs, clean up costs and failed equipment costs. In the case of Agitated filter drying equipment, contamination into the processed media and cake can result in the batch being rejected costs tens of thousands of £, $ or Euros.
Creating a stable fluid film in such arduous operating conditions as the Agitated filter drying equipment, is therefore highly desirable.
Furthermore, the experienced reader will understand the issues around hygiene when operating such equipment, specifically the elimination of harmful bacterial growth and breeding, viruses, or other microorganisms inside the vessel.
At the end of an operational shift or between process media batches, typically the Agitated filter drying equipment is taken through an in-cycle steam sterilising or cleaning regime.
Cleaning-In-Place (CIP) and Sterilization-In-Place (SIP) systems are designed for the automatic cleaning and disinfecting of the equipment.
However, processed media entrapment areas, closed cavities and non-accessible areas within the vessel, which are difficult to clean, create a huge concern of plant operators as they can lead to a whole host of health and wellness issues.
One of the main areas of concern for such entrapment areas is in and around the mechanical seal, specifically the mechanical seal components which contact the process media.
Clearly an aseptic mechanical seal design which minimises or eliminates said bacterial, virus and microorganism entrapment areas is highly desirable.
STATEMENTS OF THE INVENTION
First embodiment
A mechanical seal which contains at least one rotary seal face and at least one stationary seal face, wherein both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member, and said rotary face is connected to a longitudinal spring-like movement member forming rotary assembly, wherein said rotary and stationary sealing interface, and specifically the fluid film between said counter-rotational members, is longitudinally inwardly positioned from the equipment housing/gland plate, towards the equipment agitation/paddle device.
Second embodiment
A mechanical seal which contains at least one rotary seal face and at least one stationary seal face, wherein both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member, and said rotary face is connected to a longitudinal spring-like movement member forming rotary assembly, wherein said rotary assembly has a substantially aseptic outer most surface.
Said mechanical seal is connected to an item of rotating equipment, such as an Agitated filter dryer and said rotary assembly is substantially adjacent and/or in contact with the process media contained within the equipment.
Said mechanical seal rotary seal face is connected to the longitudinal spring-like movement member by one or more fasteners, such as a screw, which is positioned at the non-process media contact side of the mechanical seal.
Third embodiment
A mechanical seal which contains at least one rotary seal face and at least one stationary seal face, wherein both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member and said rotary face is connected to a longitudinal spring-like movement member and said longitudinal spring-like movement member is connected to the equipment shaft and/or agitating device/paddle, forming the equipment rotary assembly, wherein said equipment rotary assembly has a substantially aseptic outer most surface.
Said longitudinal spring-like movement member is connected to the equipment shaft and/or agitating device/paddle by one or more fasteners, such as a screw, which is positioned at the non-process media contact side of the longitudinal spring-like movement member.
Fourth embodiment
A mechanical seal which contains at least one rotary seal face and at least one stationary seal face, wherein both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member, wherein the spring like member is a bellows member that is substantially in contact with the process media.
Said bellows member comprises of a series of uninterrupted convolutions characterised with a seal face insert at one longitudinal end of bellows member and a gland attachment and/or clamping attachment with gland sealing means at the other longitudinal end of bellows member.
Said bellows member is preferably manufactured from an Alloy C276 material or a Glass Filled/Reinforced PTFE material.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
The accompanying drawings are as follows:
Figure 1 shows a longitudinal section of a prior-art double cartridge mechanical seal connected to an item of rotating equipment such as ANFD (Agitated Nutsche Filter Drier).
Figure 2 shows a longitudinal section of a single cartridge mechanical seal of the first embodiment of the current invention, again connected to an item of rotating equipment such as a ANFD (Agitated Nutsche Filter Drier) wherein the agitator/paddle element is raised.
Figure 3 corresponds to Figure 2 and shows a longitudinal section of the first embodiment of the current invention, wherein the agitator/paddle element is lowered.
Figure 4 shows a longitudinal section through a double cartridge mechanical seal of the first embodiment of the current invention.
Figure 5 corresponds to Figure 4 and shows an enlarged partial longitudinal section of a double cartridge mechanical seal of the first embodiment of the current invention.
Figure 6 corresponds to Figure 2 and shows a longitudinal section of a single cartridge mechanical seal the second embodiment of the current invention, wherein the agitator/paddle element is raised.
Figure 7 corresponds to Figure 6 and shows a longitudinal section of the second embodiment of the current invention, wherein the agitator/paddle element is lowered.
Figure 8 corresponds to Figure 6 and shows an enlarged partial longitudinal section of a single cartridge mechanical seal of the second embodiment of the current invention.
Figure 9 corresponds to Figure 7 and shows an enlarged partial longitudinal section of a single cartridge mechanical seal of the third embodiment of the current invention.
Figure 10 corresponds to Figure 7 and shows an enlarged partial longitudinal section of a single cartridge mechanical seal showing a spring biased monolithic stationary seal face design of the current invention.
Figure 11 corresponds to Figure 10 and shows an alternate enlarged partial longitudinal section of a single cartridge mechanical seal showing a bellows biased stationary seal face design of the fourth embodiment of the current invention.
Figure 12 corresponds to Figure 7 and shows an enlarged partial longitudinal section of the agitating/paddle member connected to the equipment shaft of the third embodiment of the current invention.
Figure 13 corresponds to Figure 12 and shows an alternate enlarged partial longitudinal section of the agitating/paddle member connected to the equipment shaft of the third embodiment of the current invention.

DETAILED DESCRIPTION OF THE INVENTION
The invention will now be described, by way of examples only, with reference to the accompanying drawings.
Figure 1 shows a longitudinal section of a prior-art double cartridge mechanical seal (10) installed on an item of rotating equipment (11) such as an Agitated Filter Drier, herewith termed an Agitated Nutsche Filter Drier (ANFD).
Said rotating equipment (11) comprises of an ANFD housing (12) and an ANFD shaft (13) which in operation create a counter-rotational interface area (14) which requires sealing to prevent the process media (15) contained in the ANFD vessel (16) from escaping into the atmosphere (17)
From Figure 1, the mechanical seal (10) has a rotary seal face (18) which is substantially connected to the rotating pump shaft (13) by cartridge seal sleeve (19) and clamp ring (20) assembly. The mechanical seal (10) also has a stationary seal face (21) which is substantially connected to the ANFD housing (12) by seal gland (22) and bolt (23).
The rotary seal face (18) is biased to the stationary seal face (21) by one or more spring members (24). The counter-rotational surface where the rotary seal face (18) and stationary seal face (21) meet is the primary sealing interface containing the fluid film (25).
The fluid film (25) helps to lubricate and cool the set of mechanical seal faces (18 & 21) in operation. In certain arduous equipment conditions, including rotating stop/start, longitudinal movement, high/low temperature changes and high/low pressure changes, as typically found in ANFD operations, the fluid film (25) breaks down and overheats / vapourises and/or dry runs. This causes the mechanical seal faces (18 & 21) to deteriorate and leak.
From Figure 1, the ANFD agitating/paddle member (26) is connected to the shaft (13) so that it rotates with said shaft (13), which is driven by a motor and typically gearbox, not shown.
A longitudinal bellows member (27) is connected to the ANFD agitating/paddle member (26) by multiple screws (28) substantially positioned in the process media (15).
A longitudinal bellows member (27) is also connected to the seal cartridge sleeve (19) by multiple screws (29) substantially positioned in the process media (15).
The other elements of the mechanical seal and equipment of Figure 1 will be understood by the reader and not further discussed.
From Figure 1, the reader will note the small radial gap (30) between the rotating cartridge sleeve (19) and stationary seal gland (22).
As the seal faces (18 & 21) and specifically the fluid film (25) is positioned outwardly of equipment housing (12) in a direction which is longitudinally oppose the agitation/paddle assembly (26), it can be understood that this area is extremely difficult to clean and remove process media contamination and batch particles.
Furthermore, the reader can see that the inclusion of stationary seal face anti-rotation pins (31) positioned in seal face slots (32) create further areas which are difficult if not impossible to clean thoroughly.
Lastly, the reader will note that the position of the screws (28) and (29) in the process media (15) is far from ideal in terms of hygiene as the screws (28) and (29) contain cavities in the screw head for Allen key tightening, and process media exposed threads (33) which again are difficult if not impossible to clean thoroughly.
As a result of the prior-art mechanical seal design (10) of Figure 1, the likelihood of harmful bacterial growth and breeding, viruses, or other microorganisms inside the vessel in and around said cavities is significantly high.
Figure 2 shows a longitudinal section of a single cartridge mechanical seal (40) of the first embodiment of the current invention, again connected to an item of rotating equipment (41) such as a ANFD (Agitated Nutsche Filter Drier) wherein the agitator/paddle (42) element is longitudinally raised inside the ANFD vessel (43) which contains process media (44).
As shown in Figure 2, the rotary seal face (45) and stationary seal face (46) are spring biased with one or more spring members (47). Between the two seal faces (45 and 46) is seal fluid film (48) is positioned longitudinally inwardly of the ANFD housing (46) towards the ANFD paddle (42).
This counter-rotational sealing interface and thereby fluid film (48) positioning below the ANFD housing inner most longitudinal surface eliminates the small radial cavity design between rotary and stationary members of Figure 1 and is therefore substantially easier to clean than the prior-art mechanical seal design of Figure 1.
This design of Figure 2 and the first embodiment of the current invention thereby offers a significant advantage for the plant operators responsible for cleaning and sterilising the inside surfaces of the rotating equipment (41).
Figure 3 corresponds to Figure 2 and shows a longitudinal section of the single cartridge mechanical seal (50) of the first embodiment of the current invention, wherein the agitator/paddle (51) of the ANFD (52) element is in its lowered position and substantially adjacent to the lower surface (53) of the ANFD vessel (54).
The reader will note that the position of sealing interface (55) of the mechanical seal (50) remains unchanged to that of Figure 2, as the shaft (56) and connected agitator/paddle (51) longitudinal movement is absorbed by the longitudinal bellows (57).
From Figure 3, the reader will note that the mechanical seal (50) incorporates a bearing (58) which radially and longitudinally supports the static position of the sealing interface and fluid film (55) during the shaft movement.
Figure 4 shows a longitudinal section through a double cartridge mechanical seal (60) of the first embodiment of the current invention. Said mechanical seal (60) comprises of a first set of inboard mechanical seal faces and fluid film (61) and a second set of outboard mechanical seal faces and fluid film (62).
From Figure 4, the inboard mechanical seal faces and fluid film (61) is longitudinally below the inner most surface of the ANFD housing (63) in the direction towards the agitator/paddle (64). Again, this facilitates cleaning and sterilisation of the mechanical seal surfaces within the vessel (not shown).
Figure 5 corresponds to Figure 4 and shows an enlarged partial longitudinal section of a double cartridge mechanical seal (70) of the first embodiment of the current invention.
From Figure 5, the double mechanical cartridge seal (70) has a first set of inboard seal faces (71) and a second set of outboard seal faces and fluid film (72). The substantially closed cavity between the two sets of seal faces inboard (71) and outboard (72) is termed the barrier chamber (73).
A cooling and lubricating barrier fluid enters the mechanical seal barrier chamber (73) and is preferably directed by the use of a deflector (74), by which the barrier fluid in the current invention travels in a cavity (75) along the outer most surface of said deflector (74) towards the inboard seal faces and fluid film (71) and then the barrier fluid travels along the inner most surface (76) of the deflector (74) towards the outboard seal faces (72).
The directed barrier fluid circulation by the use of the deflector (74) facilitates the ideal fluid film (71 and 72) conditions in both sets of seal faces thereby increasing mechanical seal (40) life longevity.
Figure 6 corresponds to Figure 2 and shows a longitudinal section of a single cartridge mechanical seal (80) of the second embodiment of the current invention, wherein the agitator/paddle (81) element is raised in vessel (82) of the item of ANFD rotating equipment (83).
Figure 7 corresponds to Figure 6 and shows a longitudinal section of a single cartridge mechanical seal (90) of the second embodiment of the current invention, wherein the agitator/paddle (91) element is raised in vessel (92) of the item of ANFD rotating equipment (83).
Figure 8 corresponds to Figure 6 and shows an enlarged partial longitudinal section of a single cartridge mechanical seal (100) of the second embodiment of the current invention.
From Figure 8, the stationary seal face (101) is spring biased to the rotary seal face (102) by one or more spring members (103) thereby creating counter-rotational sealing interface and fluid film (104).
One or more Elastomers (105) provides a seal between the rotary seal face (102) and the rotary cartridge sleeve assembly (106).
One or more Elastomers (107) provides a seal between the stationary seal face (101) and the seal gland (108).
From Figure 8, screws (109) secure the cartridge sleeve assembly (106) to the longitudinal bellows (110). Said screws (109) are sealed from the process media (111) by seal (112).
The reader will therefore note that as screws (109) are not in the process media (111) the mechanical seal (100) of the second embodiment of the current invention is inherently more hygienic compared to the prior-art seal of Figure 1.
This hygienic profile creates an aseptic mechanical seal design (100) offering significant advantages for the process operators and ANFD equipment (113) cleaning and sterilisation.
Figure 9 corresponds to Figure 7 and shows an enlarged partial longitudinal section of a single cartridge mechanical seal (120) of the third embodiment of the current invention.
From Figure 9, longitudinal bellows assembly (121) is connected to the end cap (119) by one or more screws (118).
Said end cap (119) is connected to the equipment shaft (122) by one or more screws (123) and agitator/paddle (124) is also connected to the shaft (122) and sealed with seal (125) and seal (126).
The reader will therefore note that as screws (118) and (123) are not in the process media (127) the mechanical seal (120) of the third embodiment of the current invention is inherently more hygienic compared to the prior-art seal of Figure 1.
Once again, this hygienic profile creates an aseptic mechanical seal design (120) offering significant advantages for the process operators and ANFD equipment cleaning and sterilisation.
Figure 10 corresponds to Figure 7 and shows an enlarged partial longitudinal section of a single cartridge mechanical seal (130) showing a spring biased monolithic stationary seal face (131) design of the current invention.
Figure 11 corresponds to Figure 10 and shows an alternate enlarged partial longitudinal section of a single cartridge mechanical seal (140) showing a bellows biased stationary seal face assembly (141) design of the fourth embodiment of the current invention.
The bellows stationary seal face assembly (141) provides an integral spring and sealing member (142) therefore eliminating the requirement for a stationary elastomeric seal as shown in Figure 10.
This fourth embodiment of the current invention provides a further enhancement to the aseptic mechanical seal (140) and ANFD equipment (143) cleaning and sterilisation.
Figure 12 corresponds to Figure 7 and shows an enlarged partial longitudinal section of the agitating/paddle member (150) connected to the equipment shaft (151) by means of a central paddle thread (152) of an item of rotating equipment (153) of the third embodiment of the current invention.
Figure 13 corresponds to Figure 12 and shows an alternate enlarged partial longitudinal section of the agitating/paddle member (160) connected to the equipment shaft (161) by one or more screws (162) of the third embodiment of the current invention.
From Figure 13, said screw (162) is not in contact with the process media (163) because of cover (164) which is seal threaded (165) into the agitating/paddle member (160) of an item of rotating equipment (166).
Once again, this provides an hygienic solution for paddle to shaft connection which has significant operational advantages as aforementioned.
The foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration by way of examples and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.
, Claims:

1. A mechanical seal which contains at least one rotary seal face and at least one stationary seal face, characterized in that both rotary and stationary seal faces are biased together to form a counter-rotational sealing interface by at least one spring member, and said rotary face is connected to a longitudinal spring-like movement member forming rotary assembly;
wherein said rotary face is connected to a longitudinal spring-like movement member forming rotary assembly, and said rotary and stationary sealing interface, the fluid film between said counter-rotational members, is longitudinally inwardly positioned from the equipment housing/gland plate, towards the equipment agitation/paddle device; and
wherein, said rotary assembly has an aseptic outer most surface.

2. The mechanical seal as claimed in claim 1, wherein said mechanical seal is connected to an item of rotating equipment, such as an Agitated filter dryer; and wherein said rotary assembly is substantially adjacent and/or in contact with the process media contained within the rotating equipment.

3. The mechanical seal as claimed in claim 2, wherein said rotary seal face is connected to the longitudinal spring-like movement member by one or more fasteners, such as a screw, which is positioned at the non-process media contact side of the mechanical seal.

4. The mechanical seal as claimed in claim 1, wherein said mechanical seal is connected to an item of rotating equipment, such as an agitated filter dryer and said rotary assembly is substantially adjacent and/or in contact with the process media contained within the equipment; and
wherein said mechanical seal rotary seal face is connected to the longitudinal spring-like movement member by one or more fasteners, such as a screw, which is positioned at the non-process media contact side of the mechanical seal.

5. The mechanical seal as claimed in claim 4, wherein said longitudinal spring-like movement member is connected to the equipment shaft and/or agitating device/paddle by one or more fasteners, such as a screw, which is positioned at the non-process media contact side of the longitudinal spring-like movement member.

6. The mechanical seal as claimed in claim 1, wherein said at least one rotary seal face and at least one stationary seal face, are biased together to form a counter-rotational sealing interface by at least one spring member; and

wherein the spring like member is a bellows member that is substantially in contact with the process media.

7. The mechanical seal as claimed in claim 6, wherein said bellows member comprises of a series of uninterrupted convolutions with a seal face insert at one longitudinal end of bellows member and a gland attachment and/or clamping attachment with gland sealing means at the other longitudinal end of bellows member.
8. The mechanical seal as claimed in claim 6, wherein said bellows member include bellows stationary seal face assembly which provides an integral spring and sealing member thereby eliminating the requirement for a stationary elastomeric seal.

9. The mechanical seal as claimed in claim 7, wherein said bellows member is preferably manufactured from an Alloy C276 material or Glass Filled/Reinforced PTFE material.

10. The mechanical seal as claimed in claim 6, wherein said longitudinal bellows assembly is connected to an end cap by one or more screws;
wherein said end cap is connected to the equipment shaft by one or more screws and agitator/paddle is also connected to the shaft and sealed such that no screws are present in the process media providing aseptic mechanical seal.