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Title:
REINFORCED HIGH PRESSURE NOZZLE SEAT ASSEMBLY
Document Type and Number:
WIPO Patent Application WO/2018/148781
Kind Code:
A1
Abstract:
A seat holding assembly for a water delivery nozzle assembly of the type comprising a body defining an internal space which receives and retains therein a water delivery nozzle. The housing has a first part which retains therein a water delivery nozzle which is capable of delivering a water stream; and a second part engaging with the first part; the seat holding assembly comprising a seat holder which includes a recess which retains a seat therein; characterised in that the seat retainer is arranged between the first and second parts of the housing to protect the seat from unwanted displacement from debris entering an outlet of the nozzle assembly.

Inventors:
PARIS, Jim (14 Marden Street, Georges Hall, New South Wales 2198, AU)
Application Number:
AU2018/000021
Publication Date:
August 23, 2018
Filing Date:
February 14, 2018
Export Citation:
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Assignee:
PARIS, Jim (14 Marden Street, Georges Hall, New South Wales 2198, AU)
International Classes:
B05B3/04; B05B15/16; E03C1/304; E21B7/18
Attorney, Agent or Firm:
WALSH, John (Walsh & Associates, Locked Bag 2011Glebe, New South Wales 2037, AU)
Download PDF:
Claims:
THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A water delivery nozzle assembly comprising:

a housing having a first part and a second part, the first part defining an internal space which receives and retains therein at least part of the water delivery nozzle, the second part capable of engagement with the first part and including a recess wrhich retains therein a seat holder;

the seat holder including a recess which retains a seat therein;

wherein the seat holder is arranged to protect the seat from unwanted displacement from debris entering the housing and towards an outlet of the nozzle.

2. A water delivery nozzle assembly according to claim 1 wherein, the first and second parts of the housing, co operate to retain the nozzle and the seat holder;

3. An assembly according to claim 2 wherein the seat holder is held between the first and second parts of the housing

4. An assembly according to claim 3 wherein, the seat holder is retained in a recess in the second part of the housing.

5. An assembly according to claim 4 wherein, the first part of the housing has a plurality of shoulder formations which co- operate with corresponding formations in the seat holder.

6. An assembly according to claim 5 wherein the shoulder formations are annular and decrease in diameter as they move distally away from the seat.

7. An assembly according to claim 6 wherein, the seat holder is sandwiched between the first and second parts of the housing.

8. An assembly according to claim 7 wherein the seat holder has an annular proximal formation which receives therein a leading end part of the nozzle.

9. An assembly according to claim 8 wherein the leading end part of the nozzle is a cylinder which defines an internal recess.

10. An assembly according to claim 9 wherein the nozzle recess includes a fluid entry and exit orifice which lies at the base of the nozzle recess.

11. An assembly according to claim 10 wherein the base of the recess opposes a first surface of the seal.

12. An assembly according to claim 11 wherein a second surface of the seal opposes a base of the recess in the seat holder. 13. An assembly according to claim 12 wherein, the seat is integrally attached to the seat holder.

14. An assembly according to claim 13 wherein, the second part of the housing is threadably connected to the first part of the housing.

15. An assembly according to claim 14 wherein, the seat is manufactured from tungsten carbide

16. An assembly according to claim 15 wherein, the seal is glued into the recess in the seat holder.

17. An assembly according to claim 16 wherein, the recess in the seat holder is cylindrical.

18. An assembly according to claim 17 wherein, the seat is cylindrical and has a hollow core.

19. An assembly according to claim 18 wherein, the seat holder includes a peripheral annular recess which retains an O ring.

20. An assembly according to claim 19 wherein, the O ring provides a seal between the seat h older and an inn er wall of the second part of th e housing.

21. An assembly according to claim 20 wherein, the first part of the housing includes a peripheral recess which retains a sealing O ring.

22. An assembly according to claim 21 wherein, the second part of the housing, includes a distal splayed recess

23. An assembly according to claim 22 wherein the splayed recess tapers inwardly towards a secondary recess in the seat holder.

24. An assembly according to claim 23 wherein the seat holder is manufactured from material selected from the group: stainless steel, tungsten carbide, plastics, metal.

25. A seat holding assembly for a water delivery nozzle assembly of the type comprising a body defining an internal space which receives and retains therein a water delivery nozzle,

a housing having a first part which retains therein a water delivery nozzle which is capable of delivering a water stream; and a second part engaging with the first part; the seat holding assembly comprising a seat holder which includes a recess which retains a seat therein; characterised in that the seat retainer is arranged between the first and second parts of the housing to protect the seat from unwanted displacement from debris entering an outlet of the nozzle assembly.

26. A seat holding assembly according to claim 25 wherein the seat holder is annular and includes formations which engage corresponding formations on an inner surface of the housing.

27. A seat holding assembly according to claim 26 wherein the seat holder includes an annular recess which receives a seat.

28. A seat holding assembly according to claim 27 wherein the seat holder includes an annular recess which retains therein an O ring.

29. A seat holding assembly according to claim 28 wherein the annular formations comprise a series of stepped shoulders.

30. A seat holding assembly according to claim 29 wherein the seat holder includes a bearing surface which opposes a surface on the first part of the housing.

31. A seat holding assembly according to claim 29 wherein the seat holder is manufactured from materials selected from flexible plastics, including polypropylene, polyethylene, rubbers including silicon, tungsten carbide, metals, stainless steel.

32. An assembly according to claim 31 wherein, the seat is manufactured from tungsten carbide

33. An assembly according to claim 32 wherein, the seal is glued into the recess in the seat holder.

34. An assembly according to claim 33 wherein, the recess in the seat holder is cylindrical.

35. An assembly according to claim 34 wherein, the seat is cylindrical and has a hollow core.

Description:
REINFORCED HIGH PRESSURE NOZZLE SEAT ASSEMBLY BACKGROUND

[0001 ] The present invention relates to high pressure water jet nozzles and more particularly relates to a nozzle assembly which has an improved seat support and improved sealing. The invention also relates to improvements in a nozzle assembly in which there is provided a secure nozzle seat. More particularly the present invention relates to improvements in the durability of high pressure nozzle seating assemblies to better resist impact damage during use and improve retention of the protective seal. The invention further relates to an assembly for a leading end of high pressure nozzles used in pipe cleaning which tightly retains a nozzle seat which protects the nozzle exit orifice from debris and unwanted . The invention further relates to a method for assembly of a leading end of a high pressure nozzle to reinforce the seat of the nozzle.

PRIOR ART:

[0002] Various apparatus and methods have been employed in the past for removing unwanted tree roots in water, sewerage or drainage pipes. Tree roots can destroy pipes and block the passage of water or sewage therethrough. Various pipe materials have been used in the past for sewerage, drainage and water reticulation networks. For sewage pipe networks materials such as cast iron, galvanised iron, clay and plastics have been used. The weakest part of a pipe network is usually the location of the pipe joins. Tree roots are opportunistic and are likely to be encountered where a pipe leaks, or at a faulty join. Water deli very pipes tend to be less susceptible to root penetration, as they are usually formed from continuous copper lines which have few joins. Drainage pipes which carry sewage or drainage water are particularly vulnerable to root penetration if a join is compromised, as roots can more easily detect the presence of water. Roots can also damage pipe joins and enter the pipe via that join. Plant and tree roots found in pipes are usually the fibrous variety. They can be very hard to dislodge especially as they are alive having been fed by water in the pipes. [0003] Various apparatuses have been employed for root removal from pipes.

One such method employs an electrically driven spinning cutter which is located on a free end of a long feed line. The feed line which is fed into a pipe, terminates at a drive motor and spins the feed line about a longitudinal axis and at the same time advancing the line along the pipe. As the cutters rotate and advance, they cut through roots and any other blockage. Other methods have been used such as feeding rods through a pipe and attempting to push the blockage away manually. Another method has been to feed a hose into the pipe and send high pressure water along the pipe in an attempt to flush the blockage. [0004] The plumbing industry has employed high pressure nozzles operating around 200 bar ( 5000psi), which are fed into pipes on the end of a high pressure water supply line. Typically, these high pressure nozzles have strategically placed openings which direct water in fine jets to create a high energy impact on a pipe wall to remove scale and mineral build up. The purpose of these nozzles is to deliver water at such high pressure that the roots inside the blocked pipe are eroded away by shredding or breaking. These high pressure nozzles are also used in sewer system clearing works and in hydro excavation. In hydro excavation a nozzle is used to excavate ground material assisted by a high pressure water jet. . [0005] There is a long felt want in the field to provide an improvement to the existing nozzles to ensure that the nozzle seat is not damaged or dislodged by unwanted particulate matter and debris entering the outlet orifice. This often occurs when a user improperly uses a nozzle to assist in loosening the excavation material. [0006] Furthermore there is a need to provide an alternative nozzle assembly and in particular a nozzle sealing seat which is simple to operate, is adaptable to existing water jet nozzles, , is relatively inexpensive to manufacture, can be mass produced, retrofitted, is durable, does not significantly increase the volume of the nozzle and requires a minimum of mental and physical effort to set up. There is also a need to provide an apparatus which allows a user to use the nozzle aggressively in hydro excavation but without the risk of dislodgement of the seat from impact from debris, small stones and particular matter. INVENTION:

[0007] The present invention provides a high pressure water jet nozzle including a leading end seat holder which prevents a nozzle seal from unwanted dislodgement and /or damage during use. More particularly the present invention provides a more durabile high pressure nozzle seating assembly to better resist impact damage during use and improve retention of a protective seal retained by a seat h older. The invention further provides a seat holder for a seal used in a leading end of high pressure nozzles used in such non limiting applications as sewer cleaning and hydro excavation. The seat holder tightly retains a seal and protects the nozzle exit orifice. The invention further relates to a method for assembly of a leading end of a high pressure nozzle which includes a seat holder co operating with a water jet nozzle housing and which prevents damage to the water jet nozzle. [0008] In one broad form the present invention comprises:

a water delivery nozzle assembly comprising:

a housing having a first part and a second part, the first part defining an internal space which receives and retains therein at least part of the water delivery nozzle, the second part capable of engagement with the first part and including a recess which retains therein a seat holder;

the seat holder including a recess which retains a seat therein; wherein the seat holder is arranged to protect the seat from unwanted displacement from debris entering the housing and towards an outlet of the nozzle.

[0009] According to a preferred embodiment, the first and second parts of the housing, co operate to retain the nozzle and the seat holder. The first part preferably houses most of the nozzle and the second part acts as a closure cap. Preferably the seat holder is held between the first and second parts of the housing and retained in a recess in the second part of the housing.

[0010] According to one embodiment, the first part of the housing has a plurality of shoulder formations which co- operate with corresponding formations in the seat holder, wherein the shoulder formations decrease in diameter as they move away from the seat. This allows the seat holder to be sandwiched between the first and second parts of the housing. The seat holder has a proximal annular formation which receives therein a leading end part of the nozzle. Preferably the leading end part of the nozzle is a cylinder which defines an internal recess. The nozzle recess includes a fluid entry and exit orifice which lies at the base of the nozzle recess. The base of the recess opposes a first surface of the seal. A second surface of the seal opposes a base of the recess in the seat holder.

[001 1 ] According to one embodiment, the seal is cylindrical in shape with an cylindrical opening therethrough and is integrally attached to the seat holder. This may be effected by friction fitting but a strong glue is preferred. The second part of the housing forming the closure cap is threadably connected to the first part of the housing. The seal is preferably manufactured from tungsten carbide According to a preferred embodiment the second part of the housing is a screw on cap. [0012] According to a preferred embodiment, the seat holder has an annular ring which receives and retains therein an O ring which provides a seal between the seat holder and an inner wall of the second part of the housing. Also, the first part of the housing includes a peripheral recess which retains another sealing O ring. The second part of the housing, according to one embodiment, includes a distal splayed recess which tapers inwardly towards a secondary recess in the seat holder. The water delivery nozzle is fully contained in the housing. The seat holder is preferably manufactured from stainless steel, but it will be appreciated that the seat holder/retainer may be manufactured from alternative resilient materials, such as but not limited to heavy duty plastics.

[0013] In another broad form the present invention comprises:

a water delivery nozzle assembly comprising a body defining an internal space which receives and retains therein a water delivery nozzle,

a housing having a first part which retains therein a water delivery nozzle which is capable of delivering a water stream; a second part engaging with the first part and retaining therebetween a seat retainer which includes a recess which retains a seat therein; characterised in that the seat retainer is arranged to protect the seat from unwanted displacement from debris entering an outlet of the nozzle assembly.

[0014] According to a preferred embodiment the second part releasably engages the first part and retains the seat retainer in the housing by engagement between bearing surfaces on the first and second parts and respective opposing bearing surface on the seat retainer.

[0015] In another broad form the present invention comprises:

a seat retaining assembly for a water delivery nozzle assembly including a housing defining an internal space which receives and retains therein at least one water delivery nozzle, the housing having a first part which retains therein a water delivery nozzle which is capable of delivering a water stream; a second part engaging with the first part and retaining therebetween the seat retaining assembly, the seat retaining assembly including a recess which retains a seat therein; characterised in that the seat retainer is arranged to protect the seat from unwanted displacement from debris entering an outlet of the water delivery nozzle assembly.

[0016] In its broadest form the present invention comprises: '

a water delivery nozzle assembly comprising a body defining an internal space which receives and retains therein a water delivery nozzle,

a housing having a first part which retains therein a water delivery nozzle which is capable of delivering a water stream; a second part engaging with the first part and retaining therebetween a seat retainer which includes a recess which retains a seat therein; characterised in that the seat retainer is arranged to protect the seat from unwanted displacement from debris entering an outlet of the nozzle assembly and is in integral non releasable engagement with the seat retainer.

[0017] According to one embodiment the seat is retained in the seat retainer by a strong glue. The seat retaining member is sandwiched between a part of the housing and another co -operating part of the housing. The seat retainer may be manufactured from metals fit for the purpose or in a mould from a flexible plastics material which may be selected from materials including polypropylene, polyethylene, tungsten carbide, rubbers including silicon. Preferably, the material is sufficiently strong to ensure that the seat is maintained in the correct position.

[0018] The present invention provides an alternative to the known prior art and the shortcomings identified. The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying representations, which forms a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practised. These embodiments will be described in sufficient detail to enable those skilled in the art to practise the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying illustrations, like reference characters designate the same or similar parts throughout the several views.

[0019] The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 shows a cross sectional view of a known/prior art nozzle assembly indicating at a leading end of the nozzle assembly, a nozzle housing, a nozzle seat and a nozzle seat holder.

Figure 2 shows a cross sectional view of another known/prior art nozzle assembly indicating at a leading end of the nozzle assembly, a nozzle housing, a nozzle seat and a nozzle seat holder.

Figure 3 shows a cross sectional view of a nozzle assembly having a housing which retains a nozzle seat holder including a seat according to one embodiment.

Figure 4 shows an exploded elevation view of a high pressure water jet nozzle and including a seat retention assembly according to one embodiment.

Figure 5 shows an exploded cross sectional view the high pressure water jet nozzle of figure 4 and shows the seat retention assembly.

Figure 6 shows a partially assembled elevation view of the nozzle assembly of figure 4.

Figure 7 shows a fully assembled elevation view of a high pressure water jet nozzle and including a seat retention assembly retained/concealed therein. Figure 8 shows the sewer nozzle assembly of figure 4 fully assembled and with a high pressure water delivery jet nozzle retained inside a housing.

Figure 9 shows an enlarged elevation view of a primary housing body according to a preferred embodiment.

Figure 10 shows an isometric view of the primary housing of figure 9.

Figure 11 shows an enlarged elevation view of a secondary housing body. Figure 12 shows an isometric view of the enlarged secondary housing of figure 1 1.

Figure 13 shows an enlarged elevation view of a tertiary housing body

Figure 14 shows an isometric view of the tertiary housing of figure 13.

Figure 15 shows an enlarged elevation view of a seat holder according to a preferred embodiment.

Figure 16 shows an enlarged view of a seat holder according to a preferred embodiment.

Figure 17 shows a cross sectional exploded elevation view of a hydro excavation nozzle assembly including a seat retaining assembly according to an alternative embodiment.

Figure 18 shows an elevation view of the nozzle assembly of figure 17 partially assembled.

Figure 19 shows a partially assembled view of the hydro excavation nozzle assembly of figure 17

Figure 20 shows a cross sectional view of the full assembled hydro excavation nozzle assembly.

Figure 21 shows a cross sectional view of a seat holder isolated from the nozzle assembly according to an alternative embodiment.

Figure 22 shows a seat holder of the type described earlier in conjunction with each embodiment for comparison.

DETAILED DESCRIPTION [0021 ] The examples referred to herein are illustrative and are not to be regarded as limiting the scope of the invention. While various embodiments of the invention have been described herein, it will be appreciated that these are capable of modification, and therefore the disclosures herein are not to be construed as limiting of the precise details set forth, but to avail such changes and alterati ons as fall within the purview of the description.

[0022] Throughout the specification a reference to a seat holder can be taken to mean a formation of any geometry which co operates with a nozzle assembly and includes a recess which accommodates a sealing or protective seat. Throughout the specification a reference to a seat can be taken to mean a surface or formation having a surface on which a leading end of a water jet nozzle bears during use. Throughout the specification a reference to a housing can be taken to mean a reference to a unitary or multi part body which provides an internal space in which fits various components of a nozzle assembly. .

[0023 ] Figure 1 shows a cross sectional view of a known/prior art nozzle assembly 1 comprising a leading end 2 of a nozzle housing 3. Housing 3 terminates in a recess 4 which accommodates a nozzle seat holder 5 which receives a seat 6. . Seat holder 5 which fits into recess 4 is defined by peripheral shoulder 7 and wall 8. Seat holder 5 as shown, is friction fitted along wall 8 via o- ring 9. If seat holder 5 is subject to sudden impact during use, applied in the general direction of arrow 10, seat holder 5 can be dislodged potentially causing damage to a high pressure water jet nozzle (not shown) but retained in space 11 within housing 3. Under impact to seat holder 4, o ring 9 does not have sufficient friction grip to resist unwanted dislodgement of seat holder 4.

[0024] Figure 2 shows a cross sectional view of another known/prior art nozzle assembly 15 indicating at a leading end 16 of the nozzle assembly 15 , a nozzle housing 17, a nozzle seat 18 and a nozzle seat holder 14. Seat 18 fits in a recess 19 defined by shoulder 20 and wall 21. Seat holder 14 as shown, allows seat 18 to be friction fitted along wall 21 via o- ring 22. If seat holder 14 is subject to sudden impact during use, applied in the general direction of arrow 23 seat holder 14 and/or seat 18 can be dislodged potentially causing damage to a high pressure water jet nozzle ( not shown) but which would in use be retained in housing 17.

[0025] Figure 3 shows a cross sectional view of a nozzle assembly 30 having a housing 31 which retains a nozzle 32 therein. Housing 31 is preferably provided in two parts, a first body part 33 which substantially envelops nozzle 32 and a second part 34 which forms an end cap which is threadably retained by housing part 33. These two parts could be integrally attached as one part but it is convenient for cap 34 to be detachable from housing part 33 to enable ease of access to seat holder 35. Thus seat holder 35 locates between first and second parts 33, 34 and engages seat holder via annular formation 44. Seat holder/retainer 35 includes a recess 36 which receives and retains therein a seat 37. Seat retainer 35 is annular includes an annular bearing surface 38 comprising a series of stepped shoulders 39 which are accommodated in corresponding opposing stepped shoulders 40 of housing cap 34 which oppose shoulders 39. The series of stepped annular shoulders 39 of seat holder/retainer 35 which engaged a corresponding stepped shoulders 40 enables transfer of any impact loading on either the seat holder 35 (which would occur at bridge 41) or on second housing part 34 via to bearing surface 42. Any debris which enters in the direction of arrow 43 is inhibited from entry into seat holder 35 reducing or preventing impact on seat holder 35 thereby avoiding displacement of seat 37.

[0026] There are broadly two types of nozzle assemblies which accommodate the seat retaining assembly contemplated by the present invention. The first is a sewer nozzle and the second are hydro excavation nozzles. The nozzle described in Figure 3 is based on the hydro excavation nozzles. [0027] Figure 4 shows an exploded elevation view of a high pressure water jet sewer nozzle 50 having a housing 51 provided in two parts, a first body part 52 and second body part 53 which comprises a screw on cap which in use engages housing part 52. Located between first and second parts 52, 53 is a seat holder/retainer 54 having a seat body 55 defining a recess 56 which receives and retains therein a seat 57. Seat retainer 54 includes an annular bearing surface 63 which opposes annular bearing surface 58 of first housing part 52. Seat retainer 54 includes a series of stepped annular shoulders 59 which engage a corresponding formation of stepped shoulders 60 ( see figure 5) .

[0028] Figure 5 shows with corresponding numbering an exploded cross sectional view the high pressure water jet nozzle assembly 50 of figure 4 and shows the seat retainer assembly 54. The location of the seal retainer 54 transfers of any impact loading on either the seat retainer 54 (which would occur at bridge 61) or on second housing part 53. Any debris which enters in the direction of arrow 64 is inhibited from entry into seat retainer/holder 54 reducing or preventing impact on seat 57 thereby avoiding displacement of seat 57.

[0029] In the representations of figures 4 and 5 it can be seen that housing part 52 includes annular recess 66 which receives and retains an O- ring ( not shown). In addition, retainer 54 includes an annular recess 67 which also receives an o ring (not shown).

[0030] Figure 6 shows with corresponding numbering a partially assembled elevation view of the nozzle assembly 50 of figure 4. In this representation, seat retainer 54 is engaging housing part 52. [0031 ] Figure 7 shows with corresponding numbering a fully assembled elevation view of a high pressure water jet nozzle 50 and including a seat retention assembly retained/concealed therein. [0032] Figure 8 shows the sewer nozzle assembly 30 of figure 3 fully assembled and with a high pressure water delivery jet nozzle 70 retained inside a housing. In addition to the representation of figure 3 the assembly of figure 8 is shown with an outer cover 71 which is screwed into housing part 33 of housing 31 via thread 72. Jet nozzle 70 includes a leading end 73 which engages recess 44 of seat holder 37. Tn use, nozzle 70 rotates inside housing 3 1 and delivers high pressure water through an exit opening. Seat retainer 35 holds seat 37 in place so that should leading end 73 of nozzle 70 be subject to damage should seat 37 be urged out of recess 76. Seat 37 is preferably retained in recess 76 by a strong glue. Cover 71 has a generally curved leading end 77 which renders the assembly useful in sewer clearing/cleaning because the radiused geometry of the leading end rides over the debris. Housing part 33 includes at its distal end an abutment surface 80 which opposes abutment surface 81 of seat holder 35. Also included at its distal end of housing part 33 is an annular recess 82 which retains an O ring 83. Likewise, seat holder 35 includes an annular recess 84 which accommodates an O ring 85. Housing part 34 is attached to housing part 33 via threaded connection 86

[0033] Figure 9 shows an enlarged elevation view of a part 33 of primary housing body 31 according to a preferred embodiment. Part 33 includes joining threads 72 and 86 and annular recess 82 which in use receives and retains therein an O ring. Figure 10 shows with corresponding numbering an isometric view of the part 33 of primary housing of figure 9.

[0034] Figure 1 1 shows an enlarged elevation view of a secondary part 34 of a housing body housing body 31 . Figure 12 shows an isometric view of the enlarged secondary part 34 of housing of figure 1 1 . Figure 13 shows an enlarged elevation view of a tertiary outer cover 71 which provides a protective cover over housing parts 33 and 34. Figure 14 shows an isometric view of the tertiary cover 71 of figure 13 and shows connecting thread 72.

[0035] Figure 15 shows with corresponding numbering an enlarged elevation view of an isolated seat holder 35 according to a preferred embodiment. Seat holder 35 comprises abutment surface 81 recess 76 which receives seat 37 ( see figure 8) and annular recess 84 which accommodates O ring 85 ( see figure 8).

[0036] Figure 16 shows an enlarged view of the seat holder 37 of figure 15. Seat retainer 35 is a stepped annular member having upper surface 81 and a recess 76 for receiving and retaining a seat 37. Annular recess 84 when in use, receives and retains an o- ring 85 ( see figure 8)

[0037 ]Figure 17 shows a cross sectional exploded elevation view of a high pressure water jet sewer nozzle assembly 90 having a housing 91 preferably provided in two parts, including a first body part 92 and second body part 93. Body part 93 is utilised as a retaining cover which houses seat retainer 94. Located between first and second parts 92 and 93 is sat holder/retainer 94 which comprises a seat body 95 defining a recess 96 which receives and retains therein a seat 97. Seat retainer 94 includes an annular bearing surface 98 which opposes annular bearing surface 99 of first housing part 92. Seat retainer 94 includes a series of stepped annular shoulders 100 which engage a corresponding formation of stepped shoulders 101 on cover 93. This enables transfer of any impact loading on either the seat retainer 94 which would occur at bridge 102 or on second housing cover part 93 to bearing surface 103. Any debris which enters in the direction of arrow 104 is inhibited from entry into seat holder 94 reducing or preventing impact on seat 97 thereby avoiding displacement of seat 97. The nozzle assembly of figure 17 also includes a screw on housing protector 105 which engages housing part 92 via threaded connection 106. [0038] Figure 18 shows with corresponding numbering an elevation view of the nozzle assembly of figure 17. In the representations of figures 17 and 18 it can be seen that seat holder 94 retained by the second part 93 includes annular recess 107 which receives and retains an o ring 108 In addition, first part 92 of housing 91 includes an annular recess 109 which also receives a sealing o ring 1 10.

[0039] Figure 19 shows with corresponding numbering a partially assembled elevation view of the nozzle assembly 90 of figure 1 8. In this representation, seat retainer 94 is engaging housing part 92. In this view it can be seen that annular recess 108 receives and retains sealing O ring 109 and annular recess 1 1 1 receives and retains sealing O ring 1 1 1 . Figure 20 shows with corresponding numbering a cross sectional view of the fully assembled hydro excavation nozzle assembly according to a preferred embodiment.

[0040] Figure 20 shows a cross sectional view of a hydro exaction nozzle assembly 129 and including a nozzle 120 retained inside the housing 123. Outer cover 121 which is screwed onto part 125 of housing 1 1 1 via thread 132. Jet nozzle 120 includes a leading end 133 which engages recess 134 of seat 127 . In use, jet nozzle 130 rotates inside housing part 125 and delivers high pressure water through an exit opening. Seat retainer 1 14 holds seat 127 in place so that leading end 133 of nozzle 120 is protected from damage and to resist movement of seat 127 out of recess 134. Seat 127 is preferably retained in recess 134 by a strong glue. Cover 121 provides a strong leading end to accommodate cyclic impact during the working life of the assembly 129. Assembly 129 is preferred for use in hydro excavation.

[0041 ] Figure 21 shows a cross sectional view of a seat holder 150 isolated from a nozzle assembly ( not shown) according to an alternative embodiment.

The cross sectional profile is similar to the seat holders described earlier except that the embodiment shows an alternative method for inserting a seat 151 into the seat holder 150. Seat holder 150 includes an annular recess 152 which in use retains therein an O ring ( not shown) for sealing against an inner wall of a housing to which the seat holder is fitted. Holder 150 also comprises a series of shoulder formations 153 which as described earlier engage corresponding inner shoulders on a nozzle assembly housing. Annular recess 154 receives a leading end of a nozzle formation in a similar manner to that described earlier. According to this embodiment the seat 151 is installed into recess 158 in the direction of arrow 155. Seat 151 includes annular shoulder 156 which engages corresponding shoulder 1 57 on seat holder 150 to secure the seat in position. If a load is applied in the direction of arrow 155, an engagement between the respective shoulders 156 and 157 contribute to resistance to dislodgement of the seat 151 . This provides an alternative to the arrangement described in Figure 22,

[0042] Figure 22 shows by way of a comparison a seat holder 160 of the type described earlier in conjunction with each embodiment. Seat holder 160 includes an annular recess 162 which in use retains therein an O ring ( not shown) for sealing against an inner wall of a housing to which the seat holder is fitted. Holder 160 also comprises a series of shoulder formations 163 which as described earlier engage corresponding inner shoulders on a nozzle assembly housing. Annular recess 164 receives a leading end of a nozzle formation in a similar manner to that described earlier. According to this embodiment the seat 161 is installed in the direction of arrow 165 and nests in recess 167. In each case described, the seats 151 and 161 are preferably glued into the respective recesses 158 and 167.

[0043] Means for securing the rotor seat against dislodgement from a seat holder have been described above but it will be appreciated that other seat retainers having the same or similar capability to resist unwanted dislodgement of the seal to achieve the strength and resilience required are contemplated. One advantage of the present invention is that the life of the nozzle assembly and more particularly the seat and seat holder is prolonged due to the isolation of the seat from unwanted impact damage. This reduces the costs of maintenance of a nozzle assembly. Another advantage is that the seat holder can be retrofitted to existing nozzle assemblies to prolong their life. Materials which may be selected for the seat holder may include metals, polypropylene, silicon, urethane tungsten carbide or other suitable mouldable materials. The assembly described herein in various non limiting embodiments improve the life span of a seat holder and rotor seat which is preferably glued into the seat holder. This is particularly beneficial for the reverse turbo nozzles used as a front or back nozzle assembly in drain clearing work or in front hydro excavation nozzle. The seat holder holds the seat in a fixed position to avoid the unwanted prior art problem of seat holder dislodgement and seat dislodgement. This could occur by the nozzle assembly hitting a dislodged pipe.

[0044] It will be recognised by persons skilled in the art that numerous variations and modifications may be made to the invention broadly described herein without departing from the overall spirit and scope of the invention.