Patent Publication Number: US-11660725-B2

Title: Abrasive blasting nozzle noise reduction shroud and safety system

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit under Title 35 United States Code § 119(e) of U.S. Provisional Patent Application Ser. No. 62/869,437; Filed: Jul. 1, 2019; the full disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to abrasive blasting systems. The present invention relates more specifically to devices for reducing noise and user fatigue associated with the operation of an abrasive blasting system. 
     2. Description of the Related Art 
     Various types of wet and dry abrasive blasting systems are known in the art. Most such systems use standard components terminating in nozzles with a variety of apertures, depending on the object being blasted and the type of abrasive being used. Whatever the system and material, the high pressure air flows with entrained abrasive particles generate significant forces and acoustic waves, both of which can have severe detrimental effects on the user/operator of such systems. 
     Efforts have been made to improve the efficiency of the blasting process, balancing the force required to effectively do the job with the ability of the operator to safely and securely hold and manipulate the blasting nozzle over a period of time. Despite such efforts, efficiency is often achieved at the cost of safety and safety can often only be achieved with reduced efficiency. There are, in addition, long term safety issues, such as hearing loss and musculoskeletal vibration injuries, that must be considered apart from the immediate safety issues associated with direct injury to the muscles, tendons, skin, ears, and eyes of the user/operator. Efficiency with abrasive blasting systems must also take into consideration how fast the operator can move across a surface and how long the user/operator can work the surface before requiring some rest. Other factors that affect efficiency include the type of surface being worked, the type of abrasive being used, and the pressure at which the system is operating. Most existing abrasive blasting systems sacrifice long-term and short-term safety for the immediate concerns of operational efficiency. 
     It would be desirable to have an abrasive blasting system that provided a safer working environment without dramatically reducing operational efficiency. It would be desirable to have a system that reduced the likelihood of direct contact between the abrasive stream and the operator without significantly reducing the ability of the operator to easily handle and manipulate the nozzle of the system. It would be desirable to have a system that reduced the noise generated by the typical abrasive blasting nozzle without significantly reducing the force provided by the abrasive stream or the ability of the operator to accurately direct the abrasive stream. It would be desirable to have a system that also reduced noise and improved safety for the benefit of bystanders. It would be beneficial if such an improved abrasive blasting system did not significantly increase the cost of the overall system or significantly alter the manner of using the overall system. That is, it would be desirable if such improvements could be easily implemented in connection with most standard abrasive blasting systems currently in use. 
     SUMMARY OF THE INVENTION 
     In fulfillment of the above and further objectives the present invention provides a shroud that may be affixed to an abrasive blasting nozzle to create a limited physical barrier to protect the user/operator and acoustic dampening components to reduce damage to the hearing of the operator. The device additionally provides a variety of features that improve safety and reduce fatigue during the use and operation of the abrasive blasting system. A preferred embodiment includes a partial end closure made up of flat acoustic panels is described as well as an alternate embodiment with an end opening having peripheral chevron shaped acoustic panel edges. The system includes a mechanism for attachment of the shroud to the abrasive blasting nozzle, a dead man switch handle, a second extended handle, a peripheral air envelope generator at the forward opening, and nested layers of one or more types of acoustic material(s). The shroud may be coupled to standard abrasive blasting nozzles or may include a built-in nozzle attachable to a standard abrasive blasting whip hose. The shroud system has connectors for operation of the incorporated dead man switch and may use an optional belt and/or shoulder harness to assist with the handling of the shroud and nozzle. While the system of the present invention is directed primarily to dry abrasive streams, the structures and principles involved can be applied to wet abrasive streams with minimal modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side elevational view of a first preferred embodiment of the nozzle shroud and safety device of the present invention showing the exterior enclosure and external structures of the device. 
         FIG.  2    is a cross-sectional view of the first preferred embodiment of the nozzle shroud and safety device of the present invention disclosed in  FIG.  1    and taken on Section Line A-A′ in  FIG.  3    and showing the interior layers of noise reduction materials and structures. 
         FIG.  3    is a front elevational view of the preferred embodiment of the nozzle shroud and safety device of the present invention as shown in  FIG.  1    with the front cover in place, showing the central abrasive blasting outlet aperture. 
         FIG.  4    is a front elevational view of the preferred embodiment of the nozzle shroud and safety device of the present invention as shown in  FIG.  1    with the front cover and front layered baffle removed to show the interior layers of noise reduction materials. 
         FIG.  5    is a schematic diagram showing use of the nozzle shroud and safety device of the present invention with a typical abrasive blasting system. 
         FIG.  6    is a cross-sectional view of a second preferred embodiment of the nozzle shroud and safety device of the present invention showing the interior layers of noise reduction materials and structures. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Reference is made first to  FIG.  1    which is a side elevational view of a first preferred embodiment of the nozzle shroud and safety device of the present invention showing the exterior enclosure and external structures of the device. In  FIG.  1   , nozzle shroud assembly  10  is shown connected to blasting material supply hose (whip hose)  12  through hose nozzle coupler  14  which connects to shroud nozzle attachment collar  20  by way of shroud collar hose threaded attachment  22 . In the preferred embodiment, the blasting nozzle (not seen in  FIG.  1   ) which terminates nozzle coupler  14 , is secured to the shroud of the present invention using threaded attachment hand tightening fins  23  positioned on threaded attachment  22  which rotates captively on attachment collar  20 . 
     Shroud cone collar  24  is fixed on attachment collar  20  and supports outer cone shell  42  which forms the overall enclosure for the noise dampening structures of the present invention (see  FIG.  2   ). The dimensions of the outer cone shell  42 , and therefore of the internal structures of the device, are primarily determined relative to the size of the blast nozzle. The length of the shroud is preferably about two to four times the length of the typical constrictive blast nozzle of the type shown in  FIG.  2   . Other nozzle dimensions, such as the nozzle orifice diameter, can be a factor in optimizing the length of the shroud. It has been found, for example, that a shroud length (measured from the end of the nozzle) of at least thirty-two times the diameter of the orifice nozzle, can appropriately balance the safety and efficiency objectives of the present invention. The width and taper of the outer cone shell  42  are also dependent upon the size of the blast nozzle and are limited by the need of the operator to view the work area where the abrasive stream is directed. 
     The nozzle shroud assembly  10  is preferably held by the operator using two hands with one hand holding rear control handle (anti-vibration)  28 , and a second hand holding forward grip handle  44  with anti-vibration grip cushion  45 . Rear control handle  28  operates with dead man switch  30  which is a standard electrical or pneumatic safety switch that cuts the blast stream off if the operator lets go of the device or the switch. The manner in which the operator holds and manipulates the device of the present invention is seen more clearly in  FIG.  5   . 
     An optional, but preferable, ancillary air curtain system is incorporated on the exterior of the shroud to provide a cylindrical air curtain around the exit port of the device. Peripheral air curtain nozzles  46  are positioned peripherally around the forward edge of the device and direct jets of air (without entrained particles) forward to surround the outlet and to provide additional noise dampening. Peripheral air curtain distribution hose  48  is secured to the forward rim of outer cone shell  42  and supports the array of nozzles  46 . Peripheral air curtain supply conduit  50  is fixed to the side of outer cone shell  42  and directs a flow of pressurized air to distribution hose  48  from peripheral air curtain supply hose  52 . Pressurized air for this ancillary air curtain system is preferably supplied by the same air compressor system (see  FIG.  5   ) as supplies the abrasive blasting air, albeit at a regulated reduced pressure and flow. The objective of the air curtain is not to add to the forward force exerted by the blast nozzle but rather to create a cylindrical “soft extension” of the shroud that facilitates the retention of the sound waves within the cone created. Further, the air curtain can assist with the containment of dust generated during the blasting process. 
     In the first preferred embodiment of the present invention, outer cone shell  42  is closed on the rearward end by the connection to the whip hose  12  terminating in the blast nozzle (see  FIG.  2   ). Outer cone shell  42  is partially closed on the forward end of the device by forward shroud cover  56 . A central opening (see  FIG.  2   ) allows for the unimpeded passage of the abrasive blast stream through to the surface being worked. Again, the internal and external components of nozzle shroud assembly  10  are not meant to impede the blast stream, but rather to capture and reduce the acoustic waves that expand outward from the blast nozzle when the high-pressure air flow (with entrained particles) exits the nozzle. 
     Reference is next made to  FIG.  2    which is a partial cross-sectional view of the first preferred embodiment of the nozzle shroud and safety device of the present invention showing the interior layers of noise reduction materials and structures. Once again, the cross-sectional view of  FIG.  2    is that taken along Section Line A-A′ shown in  FIG.  3   . The views of  FIGS.  2  &amp;  4    therefore provide the best descriptions of the improvements that constitute the present invention. 
     In  FIG.  2   , nozzle shroud assembly  10  is again shown connected to whip hose  12  through hose nozzle coupler  14  which connects to shroud nozzle attachment collar  20  by way of shroud collar hose threaded attachment  22 . In the preferred embodiment, blasting nozzle  16 , which terminates nozzle coupler  14 , is secured to the shroud of the present invention using threaded attachment hand tightening fins  23  positioned on threaded attachment  22  which, as more clearly seen in  FIG.  2   , rotates captively on attachment collar  20 . In this manner, nozzle  16  at the end of whip hose  12  is tightly secured into the receptacle collar components at the rearward end of shroud assembly  10 . Once again, shroud cone collar  24  is fixed on attachment collar  20  and supports outer cone shell  42  which forms the overall enclosure for the noise dampening structures of the present invention. 
     Blasting nozzle  16  presents its nozzle outlet port  18  in the axial center of metal mesh blast column  26 . Mesh blast column  26  is the forward extension of shroud nozzle attachment collar  20  and is preferably constructed of a rigid metal cylinder perforated with an array of apertures as shown. These apertures provide the initial disruption of the acoustic waves coming off nozzle outlet port  18 . Surrounding mesh blast column  26 , but preferably spaced therefrom, is inner acoustic dampener material  36 . In the preferred embodiment, inner acoustic dampener material  36  is constructed from open cell dimensional acoustic foam. This second layer of acoustic wave disruption is not intended to provide a barrier to the acoustic waves as much as it serves to further attenuate the waves and disperse their energy. 
     Intermediate air gap  38  separates inner acoustic dampener material  36  from the next noise reduction layer made up of outer acoustic dampener material  40 . In the preferred embodiment, outer acoustic dampener material  40  is constructed from a layer of dense acoustic panel that in turn provides further attenuation of the expanding acoustic waves. Outer acoustic dampener material  40 , while still not impermeable, does provide a dense fibrous material of the type used for acoustic panels and the like. This outer acoustic material is confined and shaped by outer cone shell  42 , which does provide the final side barrier to the expanding acoustic waves generated by the abrasive blast emanating from the blast nozzle. 
     Although the path immediately forward from the blast nozzle  16  through mesh blast column  26  is clear through forward shroud cover  56 , the peripheral volume associated with the concentric layers of acoustic material are capped with forward acoustic material layered baffle  54  as shown in  FIG.  2   . With from one to six or more layers, preferably made up of the same dense acoustic material as outer acoustic dampener material  40 , the layered baffle  54  provides yet another material into which the expanding acoustic waves are captured and attenuated. The most effective arrangement for this layered baffle  54  is as an array of donut shaped disks with spacers establishing air gaps between the layers of dense acoustic panels. Not until the acoustic waves (now well attenuated) encounter the forward shroud cover  56  do they hit a rigid structure (as with outer cone shell  42 ) that tends to reflect the waves back rather than attenuate them further. While some acoustic waves still escape the system through the axial opening that allows the unimpeded passage of the abrasive blast stream, significant reductions in the acoustic energy generated at the abrasive nozzle are achieved by the multi-layer, multi-material structures provided by the present invention. 
     Reference is next made to  FIG.  3    for a front elevational view of the preferred embodiment of the nozzle shroud and safety device of the present invention as shown in  FIG.  1    with the front cover in place, showing the central abrasive blasting outlet aperture. As indicated above, Section Line A-A′ in  FIG.  3    identifies the cross-section view shown in  FIG.  2   . 
     In the view of  FIG.  3   , blasting nozzle  16  presents its nozzle outlet port  18  in the axial center of metal mesh blast column  26 . Once again, mesh blast column  26  is the forward extension of shroud nozzle attachment collar  20 . These components are viewed through the central aperture in forward shroud cover  56  which extends to the peripheral edge of outer cone shell  42 . The ancillary air curtain system, described above, is shown incorporated on the exterior of the shroud to provide the cylindrical air curtain around the exit port of the device. Peripheral air curtain nozzles  46  (eight in the embodiment shown) are radially arrayed on peripheral air curtain distribution hose  48  that is secured to the forward rim of outer cone shell  42 . The forward end of forward grip handle  44  with anti-vibration grip cushion  45  is also seen in the view of  FIG.  3    although its point of attachment to outer cone shell  42  is hidden behind one of the peripheral air curtain nozzles  46 . 
       FIG.  4    is a front elevational view of the preferred embodiment of the nozzle shroud and safety device of the present invention as shown in  FIG.  1    with the front cover and front layered baffle removed to show the interior layers of noise reduction materials. In the view of  FIG.  4   , blasting nozzle  16  presents its nozzle outlet port  18  in the axial center of metal mesh blast column  26  which is the forward extension of shroud nozzle attachment collar  20 . 
     Surrounding mesh blast column  26 , but preferably spaced therefrom, is inner acoustic dampener material  36 . Once again, in the preferred embodiment, inner acoustic dampener material  36  is constructed from open cell dimensional acoustic foam. This second layer of acoustic wave disruption is shaped (dimensioned) with inward directed peaks separated by air gap valleys that capture and “trap” the disrupted acoustic waves that have moved through mesh blast column  26 . Other configurations for the geometry of dimensional acoustic material  36  are anticipated with the objective of the layer being to receive and attenuate the acoustic waves rather than to reflect them back. 
     As described above, intermediate air gap  38  separates inner acoustic dampener material  36  from the next noise reduction layer made up of outer acoustic dampener material  40 . In the preferred embodiment, outer acoustic dampener material  40  is constructed from one or more layers of dense acoustic panel that provide further attenuation of the expanding acoustic waves. Outer acoustic dampener material  40  is preferably composed of a dense fibrous material of the type used for acoustic panels and the like. This outer acoustic material is confined and shaped by outer cone shell  42 , which provides the final side barrier to the expanding acoustic waves generated by the abrasive blast emanating from the blast nozzle. The acoustic waves that reach the rigid surface of outer cone shell  42  are reflected back inward into the layers of acoustic dampening material or are directed forward into the layered baffle (removed in  FIG.  4   , but see  FIG.  2   ) where they are further attenuated. 
     The ancillary air curtain system described above that is incorporated on the exterior of the shroud provides a final “barrier” to the sideways expansion of the acoustic waves emanating from the blast nozzle  16 . As seen in  FIG.  4   , peripheral air curtain nozzles  46  are positioned to direct jets of air forward to surround the forward shroud cover (removed in  FIG.  4   ) and the central outlet aperture to provide additional noise dampening. In the preferred embodiment of the present invention shown in  FIGS.  1 - 4   , four layers of acoustic wave disruption are provided to significantly reduce the noise typically generated with the flow of abrasive entrained high pressure air from the blast nozzle. These layers include: (a) mesh blast column  26 ; (b) inner acoustic dampener material  36 ; (c) outer acoustic dampener material  40 ; and (d) the ancillary air curtain system provided by peripheral air curtain nozzles  46 . While the above are the primary active layers achieving the noise reduction functionality of the present invention, the air gaps described and the rigid shell components described, shaped and positioned as they are in the preferred embodiments, are not insignificant in facilitating the noise reduction. 
     Reference is next made to  FIG.  5    which is a schematic diagram showing use of the nozzle shroud and safety device of the present invention with a typical abrasive blasting system. As indicated above, the device of the present invention is structured to be used in connection with standard abrasive blasting systems and to require little or no modification to such systems to achieve optimal functionality. The standard abrasive blasting system shown schematically in  FIG.  5    includes abrasive blasting system air compressor  60  with compressed air reservoir tank  62 . It should be noted that some systems operate directly off of an air compressor without the need for a reservoir. Compressed air flow from the compressor/reservoir is regulated initially with compressed air supply valve  64 . 
     Compressed air flow in the system is directed to the abrasive media tank  68  where the flow is split (and further regulated) at manifold valve  65 . A flow of air is directed into abrasive media tank  68  through abrasive media tank compressed air inlet  66 . This flow of air mixes with the reservoir of abrasive material in abrasive media tank  68  to create an air—abrasive slurry that will more readily flow out from the tank by gravity feed at the tank bottom funnel outlet. 
     The primary flow of compressed air is directed around abrasive media tank  68  by way of compressed air supply line  70  to abrasive metering valve  72 . It should be noted that operational control of the flow of high pressure air with entrained abrasive material is achieved by way of the connection shown between the dead man switch (described above) and metering valve  72  as well as manifold valve  65 . This control is provided through electrical or pneumatic control line  75  which parallels flexible supply line  74  and high pressure supply line (whip hose)  76  from the device of the present invention. 
     The operator  86  (preferably wearing a protection suit as shown) holds the nozzle shroud assembly  80  of the present invention using forward grip handle  82  and rear control handle (hidden in this view) as described above. Shroud nozzle attachment collar  78  (an assembly of the components described above with  FIG.  2   ) connects shroud assembly  80  to the blast nozzle (not seen in this view) that is secured to the end of whip hose  76 . In this manner, operator  86  may direct high pressure abrasive stream  84  against the surface being worked. 
     Further safety elements to the overall system of the present invention are shown in  FIG.  5    and include operator whip hose support belt/harness  85  in addition to the aforementioned operator protection suit. This harness  85 , which is preferably removably connected to an appropriate point on whip hose  76 , allows the operator to manipulate the device of the present invention without bearing the entire weight of the whip hose using his or her arms. This harness (which may be a belt or a combination of a belt and shoulder straps) provides additional safety to the operator and helps reduce fatigue. 
     Reference is finally made to  FIG.  6    which is a cross-sectional view of a second preferred embodiment of the nozzle shroud and safety device of the present invention showing the interior layers of noise reduction materials and structures, in much the same manner as in  FIG.  2   . Most of the components of this second preferred embodiment are the same as or are similar to corresponding components shown in the first preferred embodiment. In  FIG.  6   , nozzle shroud assembly  10  is again shown connected to whip hose  12  through hose nozzle coupler  14  which connects to shroud nozzle attachment collar  20  by way of shroud collar hose threaded attachment  22 . In this second preferred embodiment, blasting nozzle  16 , which terminates nozzle coupler  14 , is again secured to the shroud using threaded attachment  22  which rotates captively on attachment collar  20 . Once again, shroud cone collar  24  is fixed on attachment collar  20  and supports outer cone shell  92  which forms the overall enclosure for the noise dampening structures. As in the first preferred embodiment, blasting nozzle  16  presents its nozzle outlet port  18  in the axial center of metal mesh blast column  26 . Mesh blast column  26  is again the forward extension of shroud nozzle attachment collar  20  and is preferably constructed of a rigid metal cylinder perforated with an array of apertures as shown. Surrounding mesh blast column  26  is inner acoustic dampener material  36  preferably constructed from open cell dimensional acoustic foam. Intermediate air gap  38  separates inner acoustic dampener material  36  from outer acoustic dampener material  90 . In this second preferred embodiment, outer acoustic dampener material  90  is again constructed from a layer of dense acoustic panel, but in this embodiment extends further forward towards the open end of the device as shown. This outer acoustic material is still generally confined and shaped by outer cone shell  92 , but in the second embodiment shown, extends outward (forward) to terminate in a chevron shaped acoustic material edge  94 . Outer cone shell  92  likewise extends outward (forward) to terminate in a chevron shaped cone shell edge  96 . These distinct chevron shaped peripheral edges to the outer acoustic material layer and the outer cone shell have the effect of further disrupting the partially attenuated acoustic waves emanating from the device. Depending on the operational parameters of the system (the type of abrasive, the air pressure, the work surface, etc.) the partially closed end of the first preferred embodiment of the present invention may be seen to contribute to a back pressure on the system that could affect efficiency. Although this back pressure has not been seen to be significant in most abrasive blasting operations, the structures of the second preferred embodiment provide an alternative that still achieves a significant noise reduction. 
     It should be noted that the multiple levels or layers of noise reduction elements in the above described preferred embodiments may be applied together or in groups to provide an optimized noise reduction shroud and nozzle safety assembly. For example, the chevron shaped edges described in the second preferred embodiment may be used with the baffle and front end cap structures of the first preferred embodiments. The air curtain system described and shown with each of the preferred embodiments may or may not be utilized depending on the availability of the ancillary air flow and/or the requirements for a specific surface being worked. 
     The device of the present invention may also be constructed so as to be capable of replacing or renewing the acoustic material components after a period of use. While the abrasive particles entrained in the blasting air stream generally exit the device, turbulent flow around the nozzle will inevitably result in particulates becoming trapped in the acoustic material which will, over time, reduce its ability to absorb and attenuate acoustic waves. Mechanisms for separating and replacing the shroud cone components from the rigid (typically metal) hose connection coupling components are anticipated. 
     Apart from the acoustic materials whose preferred compositions have been generally described above, the rigid components of the shroud may be made from metal (preferably light weight) or from rigid composites that can hold up under the high forces and rough handling typically associated with abrasive blasting systems and operation. Because the mesh blast column described with each embodiment is the first acoustic dampening layer to encounter the abrasive air flow, albeit indirectly, it is preferred that this component be made from a strong metal such as steel. The relatively thin wall of the structure and the array of perforations in that cylindrical wall generally offset the weight associated with the denser metal. The outer cone shell, on the other hand, lends itself to weight reduction by being made of a lighter weight composite material even though a thin walled metal cone enclosure could provide a more durable enclosure without being overly heavy for the operator to handle. In the end, operator fatigue with abrasive blasting using the device of the present invention will primarily come from the very strong forces associated with the blast stream itself rather than the weight of the device of the present invention. The typical backwards force exerted on one hand (prior art blasting methods typically involve manipulating the nozzle with one hand while the other hand secures and manipulates the whip hose) for a blasting nozzle without the shroud of the present invention can average twenty to twenty-one pounds. With the shroud in place, such forces can average eleven to twelve pounds which, when distributed between the two hands holding the shrouded nozzle of the present invention, can be in the range of five and a half to six pounds of force on each hand. In other words, there is evidence to show that use of the device of the present invention actually reduces operator fatigue rather than increasing it. 
     It will be apparent that the safety aspects of the present invention are in part provided by extending the shroud forward of the nozzle such that inadvertent placement of a hand, arm, leg or other part of the body of the operator in front of the nozzle is made less likely. The preferred two handed operation of the device also improves safety by providing much greater control of the direction of the abrasive blast stream as well as reduction in vibration. Although not itself a novel feature, the dead man switch incorporated into the rear handle further improves the safe operation of the device. In particular, however, it is the noise reduction (for both the operator and those nearby) that provides improved safety by reducing the likelihood of short term or long term hearing loss that has become ubiquitous of abrasive blasting operations, even with ancillary ear protection in place. 
     Although the present invention has been described in terms of the foregoing preferred embodiments, this description has been provided by way of explanation only, and is not intended to be construed as a limitation of the invention. Those skilled in the art will recognize modifications of the present invention that might accommodate specific abrasive blasting systems and specific surfaces to be worked. Those skilled in the art will further recognize additional methods for modifying the geometry and size of the components of the system to facilitate optimal use of particular abrasives and/or operational air pressures. Such modifications, as to structure, orientation, geometry, and even composition and construction techniques, where such modifications are coincidental to the type of abrasive blasting system being utilized, do not necessarily depart from the spirit and scope of the invention.