Patent Publication Number: US-8523088-B2

Title: Particle spraying

Description:
TECHNICAL FIELD 
     This invention relates to particle spraying, and more particularly to spraying discrete fastening bits towards a support surface to which the sprayed bits adhere. 
     BACKGROUND 
     Mechanical touch fasteners are traditionally formed by weaving methods, or by molding discrete fastener elements on a substrate. Applying such touch fasteners to larger surfaces, such as a wall or floor, can involve positioning and adhering a section of touch fastener to the surface, often positioning several small sections of touch fastener to cover a large area. Non-planar surfaces in particular can be difficult to cover, even with large (e.g., stretched) webs of touch fastener material. Other means of providing surfaces with touch fastening properties are sought, particularly to releasably engage such surfaces with fibrous loop fasteners. 
     SUMMARY 
     One aspect of the invention features a particle sprayer including a particle source, a spray outlet coupled to the particle source, and a conduit extending from a pressurized fluid inlet to the spray outlet and configured to constrain a flow of carrier fluid to flow along the conduit toward the spray outlet to propel particles from the particle source away from the spray outlet, the particles including discrete fastening bits having one or more projections, with each projection having an overhanging head for snagging fibers. 
     In some cases, the particle source is releasably coupled to the spray outlet. 
     In some examples, the particle source is provided in the form of a reservoir in which a quantity of particles is contained. In some applications, the reservoir may be an enclosed and/or hermetically sealed container. Examples of a suitable container may include, but are not limited to, a can, a bottle, a jug, or a bag. In some embodiments, the container is of an appropriate size to be hand held by a user. 
     In some instances, the reservoir defines an opening for replenishing sprayed particles. 
     In some cases, the reservoir contains a carrier fluid. The reservoir may contain a selected ratio of particles or bits to carrier fluid. In some instances, the carrier fluid is motivated by a propellant. Examples of a suitable propellant may include, but are not limited to, an inert gas, compressed air, or a liquefied gas (e.g., compressed butane). In some embodiments, the carrier fluid is provided in the form of a foam, a liquefied gas, or a low viscosity liquid. In some applications, the carrier fluid includes an adhesive (such as a solvent based adhesive). In some cases, the particles are distributed substantially uniformly in the carrier fluid at rest. In some instances, the viscosity of the carrier fluid is sufficient to hold the particles in suspension when the carrier fluid is at rest. The carrier fluid may include one or more suspending agents (such as a thixotropic agent). In some cases, the density of the carrier fluid is approximately equal to the density of the particles, such that the particles have neutral buoyancy in the carrier fluid. 
     In some implementations, the particle sprayer is provided with a loose mixing element (such as a stainless steel ball) for dispersing the particles in the carrier fluid. 
     In some applications, the particle sprayer further includes a venturi constriction in hydraulic communication with the reservoir for siphoning particles from the reservoir. Preferably, the venturi constriction causes a low pressure region (such as a vacuum region) to form proximate an opening in the reservoir when a fluid flows through the constriction. 
     In some examples, the particle sprayer further includes a pump for injecting a propellant into the reservoir. The pump may be provided in the form of a hand operated pump or a pump driven by an electric motor. 
     In some embodiments, the particle sprayer further includes a fluid source coupled to the pressurized fluid inlet. The fluid source may be externally located with respect to the other components of the particle sprayer. 
     In some applications, the fluid source is placed in fluid communication with the pressurized fluid inlet. 
     In some instances, the fluid source is provided in the form of a reservoir containing a quantity of fluid. 
     In some cases, the fluid source includes a pump (such as a hand operated pump or a pump driven by an electric motor) for injecting fluid into the conduit. The fluid may be a carrier fluid or a propellant. 
     In some embodiments, the particle sprayer further includes a longitudinally continuous ribbon and a cutter for cutting through the ribbon at discrete intervals to form the discrete fastening bits. The ribbon may define a longitudinal axis and the cutter may be configured to cut completely through the ribbon along the longitudinal axis of the ribbon. In some cases, the cutter is mounted to an outer edge of a wheel. The cutter preferably includes a solid cutting edge. The cutting edge may form an acute cutting angle. In some examples, the ribbon includes a polymeric resin containing a thermoplastic. 
     In some implementations, the particle sprayer further includes a support surface coupled to the cutter for supporting a portion of the ribbon during use. The support surface may be provided in the form of a bed knife. 
     In some embodiments, the particle sprayer further includes a conveyor coupled to the cutter for feeding the ribbon towards the cutter. The conveyor may include a single feed roll or a pair of counter rotating feed rolls. 
     In some examples, the particle sprayer further includes a valve in hydraulic communication with the particle source for dispensing particles. The valve may be provided in the form of an aerosol valve or a metering game. In some cases, the valve includes a plunger. In some applications, the valve includes an opening of sufficient size to dispense particles (such as discrete fastening bits). 
     In some implementations, the particle sprayer further includes a suitable actuator coupled to the valve for adjusting the valve between opened and closed positions. Examples of a suitable actuator include, but are not limited to, a spring biased trigger, a rotatable knob, or a spring biased plunger. 
     In some cases, the spray outlet includes an opening of sufficient size to eject discrete fastening bits. Preferably, the opening or orifice includes an open area of at least about 1.1 square millimeters. 
     In some embodiments, the spray outlet includes a nozzle. The nozzle may be placed in hydraulic communication with a fluid source. In some cases, the nozzle includes an opening of sufficient size to eject or propel particles (such as discrete fastening bits). In some examples, the nozzle defines a first orifice and a second orifice, the first orifice being configured to eject bits and the second orifice being configured to eject fluid. Preferably, the first orifice includes an open area of at least about 1.1 square millimeters and the second nozzle includes an open area of at least about 0.1 square millimeter. 
     In some cases, a multiplicity of the bits are highly hydrophilic. 
     In some applications, a multiplicity of the bits are statically charged. 
     In some embodiments, a multiplicity of the bits include one or more compressible portions. 
     In some examples, a multiplicity of the bits include one or more pliable portions. 
     In some implementations, a multiplicity of the bits include one or more porous portions. 
     In some instances, a multiplicity of the bits include one or more elastically deformable portions. 
     In some embodiments, a multiplicity of the bits are aerodynamically included to land on a support surface in a selected orientation when sprayed. The selected orientation is characterized by the bit having at least one projection head extending away from the support surface. 
     In some examples, each bit includes a quantity of adhesive, the bits being configured to release the adhesive upon impact with a support surface. 
     In some cases, each bit includes opposite side surfaces defining the projections. One, or both, of the opposite side surfaces of each bit may be non-planar. 
     In various touch fastening applications, each projection head defines a crook for releasably snagging fibers. 
     In some instances, each bit has an overall thickness, measured between side surfaces, that is less than the maximum overall linear dimension of the bit. 
     In some embodiments, all linear dimensions of each bit are less than about 1.2 millimeters. 
     In many cases, a multiplicity of the bits are of an average bit size less than about three millimeters across. 
     In some examples, all or substantially all of the particles are discrete fastening bits. 
     Yet another aspect of the invention features a particle sprayer including a reservoir containing a multiplicity of particles, a valve in hydraulic communication with the reservoir for dispensing particles from the reservoir, and a nozzle coupled to the reservoir for spraying particles dispensed by the valve, the particles including discrete fastening bits, each bit having one or more projections, with each projection having an overhanging head for snagging fibers. 
     Yet another aspect of the invention features a particle sprayer including a source of particles, means for displacing the particles from the source, and means for propelling the particles away from the source towards a support surface in a spray, the particles including discrete fastening bits, each bit having one or more projections, with each projection having an overhanging head for snagging fibers. 
     Yet another aspect of the invention features a method of spraying particles. The method includes providing a particle sprayer, the particle sprayer including a particle source, a spray outlet coupled to the particle source, a conduit extending from a pressurized fluid inlet to the spray outlet and configured to constrain a flow of carrier fluid to flow along the conduit toward the spray outlet to propel particles from the particle source away from the spray outlet, and an actuator coupled to the conduit and configured to initiate spraying of the particles, the particles including discrete fastening bits having one or more projections, with each projection having an overhanging head for snagging fibers. The method further includes operating the actuator to initiate particle spraying. 
     Various embodiments can provide a very flexible means of adding fastening bits to a pre-formed surface, either to produce a touch fastening material that is later applied to another surface, or to impart touch fastening properties directly to an otherwise functional surface, such as a surface of a building, or to a curved surface. Some examples of the methods described herein will be considered appropriate for implementation by contractors or other skilled users, while others may be performed by untrained operators, such as with sprayers purchased at retail stores. In some cases the supply of bits may be replenished, such as by replacement reservoirs or from bulk bags. In some other cases, the sprayer will be designed for disposal when the quantity of bits is exhausted. In some examples, the sprayer may be a part of a fastener manufacturing line; in some other cases it may be portable for carrying to a worksite. 
     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic representation of a particle sprayer. 
         FIGS. 2A and 2B  are cross-sectional views of a first particle sprayer. 
         FIGS. 3A and 3B  are cross-sectional views of a second particle sprayer. 
         FIG. 4A  is a side view of a third particle sprayer. 
         FIG. 4B  is a side view of a reservoir that is suitable for use in the particle sprayer shown in  FIG. 4A . 
         FIG. 5  is a side view of a fourth particle sprayer. 
         FIGS. 6A and 6B  are cross-sectional views of a fifth particle sprayer. 
         FIG. 7  is a cross-sectional view of a sixth particle sprayer. 
         FIG. 8  is a schematic representation of a seventh particle sprayer. 
         FIGS. 9A and 9B  are a perspective and side views of a distal end of a cutter. 
         FIG. 10  is an enlarged photograph showing a perspective view of a surface of a touch fastener product to which a number of fastening bits are adhered. 
         FIG. 11  is an even more enlarged view of a portion of the surface shown in  FIG. 10 . 
         FIG. 12  is an enlarged photograph showing a few fastening bits of the surface of  FIG. 10  engaging loop fibers of a mating fastener material. 
         FIG. 13  is a front view of a fastening bit. 
         FIG. 14  shows 27 different ribbon cross-sectional shapes, from which bits may be cut, the shapes labeled A through AA. 
         FIGS. 15A-15E  show, in side view, five different stable bit orientations upon a surface. 
         FIG. 16  shows a bit partially submerged in an adhesive coating. 
         FIG. 17  shows a bit floating on an adhesive coating. 
         FIG. 18A  illustrates a bit being righted by adhesive surface tension forces. 
         FIG. 18B  shows an adhesive coating being thinned through evaporation. 
         FIG. 19  shows a plurality of bits applied to a support surface. 
         FIGS. 20A through 20C  illustrate three different modes of discharging bits from an orifice smaller than the bit. 
         FIGS. 21A through 21C  illustrate three different modes of discharging a bit with discrete quantities of adhesive from an orifice of a particle sprayer onto a support surface. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a schematic view of a particle sprayer  100  that may be used to form a touch fastener product (e.g., touch fastener product  204 , see  FIG. 10 ), or to otherwise spray fastening particles onto a support surface or substrate. As shown, particle sprayer  100  includes a particle source  102  coupled to a spray outlet  104 , and a conduit  106  extending from a pressurized fluid inlet  108  to the spray outlet. Conduit  106  is configured to constrain a flow of carrier fluid  110  to flow along the conduit toward spray outlet  104  to propel particles  112  provided by particle source  102  away from the spray outlet. As used herein, the term “carrier fluid” refers to any fluid (e.g., a gas, liquid, or a combination of both) carrying and/or motivating particles  112  as the particles are sprayed. The particles  112  include discrete fastening bits (e.g., bits  180 , see  FIG. 10 ). In some examples, all or substantially all of particles  112  are discrete fastening bits. 
       FIGS. 2A and 2B  show a first example of a particle sprayer  100  in use. In this example, particle sprayer  100  is provided with a particle source  102  in the form of a reservoir  114  containing a quantity of particles  112 , which may either be dry, loosely packed particles or particles mixed in a liquid or semiliquid binder (e.g., a hardenable liquid such as adhesive  224 , see  FIG. 10 ). If mixed in a liquid binder that is to form a coating on a surface onto which the particles and binder are sprayed, the mixture should contain a selected ratio of particles  112  to binder in order to achieve a desired surface coating. Reservoir  114  is placed in hydraulic communication with a spray outlet  104  by operation of a valve, as discussed below. Spray outlet  104  features a cap  116  housing a frustoconical nozzle  118  having an orifice  120  for discharging particles  112  and carrier fluid  110 . Orifice  120  should be of a size suitable to discharge particles  112  at sufficient velocity to propel the particles away from the sprayer. In this example, orifice  120  is circular. For some particle shapes and sizes discussed below, orifice  120  has an open area of at least about 1.1 square millimeters. Reservoir  114  and nozzle  118  are each releasably coupled to a sprayer body  122 . In this example, the sprayer body  122  includes a barrel  121  and a handle  123 . 
     Reservoir  114  is funnel-shaped, with its smaller opening  124  in hydraulic communication with a hollow portion  125  of sprayer body  122 . Reservoir  114  may be formed of any material suitable to hold particles  112  and any associated fluid (e.g., a liquid binder). Reservoir  114  is positioned above sprayer body  122  such that the particles are urged by gravity toward opening  124 . If containing dry particles, the reservoir shape should be selected in accordance with dry packing properties of the particles, to keep the particles from packing in the reservoir and starving the sprayer. Dry flow additives may be included. 
     Particle sprayer  100  also includes a rigid conduit tube  126  that forms the downstream end of a conduit  106  which is coupled to an external pressurized fluid source (not shown). Conduit tube  126  extends through hollow portions  125  of sprayer body  122  from a pressurized fluid inlet of the sprayer body (in this example, a standard pneumatic quick-connect fitting, not shown, for attaching the sprayer to an air compressor or compressed air tank). Conduit tube  126  has a rigid tubular body terminating in a frustoconical outlet  128  that seats against an inner surface of nozzle  118 . Any communication between reservoir  114  and nozzle orifice  120  is blocked when conduit outlet  128  is pressed against the inner surface of nozzle  118 . During use, conduit tube  126  delivers a flow of carrier fluid  110  from the pressurized fluid source to outlet  128 . 
     As shown, outlet  128  and nozzle  118  cooperate to form a needle valve  113  in hydraulic communication with reservoir  114  for dispensing particles  112  into a stream of carrier fluid  110  such as air. A biasing member (in this example, a helical compression spring, not shown, disposed between a portion of sprayer body  122  and conduit tube  126 ) is used to urge outlet  128  towards nozzle  118 . An actuator  130  (in this example, a trigger) for adjusting the needle valve between opened and closed positions is pivotally coupled to sprayer body  122  by a pin  132  and to tube  126  by another pin  134 . As used herein, the term “opened position” refers to any valve position resulting in flow through the valve. Likewise, as used herein, the term “closed position” refers to the valve position in which flow through the valve is mostly blocked. 
       FIG. 2A  shows particle sprayer  100  with the needle valve in a closed position.  FIG. 2B  shows particle sprayer  100  with the needle valve is in an opened position. As shown, when actuator  130  is pulled towards sprayer handle  123 , the backwards pivoting motion of the actuator causes conduit outlet  128  to be refracted from nozzle  118 , thereby opening the valve by providing an annular opening  136  through which particles  112  are dispensed. Once particles  112  are dispensed by the needle valve, they are carried through nozzle orifice  120  and towards a support surface (not shown) by carrier fluid  110  discharged from conduit outlet  128 . 
     While in the illustrated example the carrier fluid continues to flow even with the trigger released, in a similar example actuator  130  also operates a pneumatic valve that opens in concert with needle valve  113 , such that when the trigger is released no carrier fluid is flowing along conduit  106 . 
       FIGS. 3A and 3B  show another particle sprayer  100  similar to the particle sprayer shown in  FIGS. 2A and 2B . In this example, particle sprayer  100   a  has a particle source  102  in the form of a first reservoir  114 ′ containing a quantity of dry particles  112 . The particle sprayer also includes a fluid source  137  in the form of a second reservoir  114 ″ containing a liquid binder  139 . First reservoir  114 ′ and second reservoir  114 ″ are placed in hydraulic communication with a spray outlet  104  by operation of a metering gate and a valve, respectively, as discussed below. Spray outlet  104  features a cap  116  housing a frustoconical nozzle  118  defining an orifice  120  for discharging liquid binder  139  into the flow of carrier fluid  110 . In this example, first reservoir  114 ′, second reservoir  114 ″, and nozzle  118  are each releasably coupled to a sprayer body  122 . As in the previous example, the sprayer body includes a barrel  121  and a handle  123 . 
     As shown, first reservoir  114 ′ is a cylindrical capsule having an opening  124 ′ at the bottom end of a size suitable for releasing particles  112 . Second reservoir  114 ″ is funnel-shaped, with its smaller opening  124 ″ in hydraulic communication with a hollow portion  125  of sprayer body  122 . As in the previous example, particle sprayer  100  also includes a conduit  106  having a rigid conduit tube  126 . A distal end  128  of conduit tube  126  is pressed against an inner surface of the nozzle to form a needle valve for dispensing liquid binder  139  from second reservoir  114 ″. An actuator  130  coupled to sprayer body  122  and tube  126  is used for adjusting the needle valve and a metering gate (discussed below) between opened and closed positions. Metering gate  138  is aligned with opening  124 ′ for dispensing particles  112  from second reservoir  114 ″. A trailing end of metering gate  138  is fixedly coupled to actuator  130  and a leading end of the metering gate traverses reservoir opening  124 ′. 
       FIG. 3A  shows particle sprayer  100   a  with both the needle valve and metering gate  138  in closed positions.  FIG. 3B  shows the particle sprayer with both the needle valve and metering gate  138  in opened positions. As shown, when actuator  130  is pulled towards sprayer handle  123 , the backward pivoting motion of the actuator causes conduit tube  126  to be retracted from nozzle  118 , thereby providing an annular opening  136  through which liquid binder  139  is dispensed. The pivoting motion of actuator  130  also causes metering gate  138  to be drawn back across opening  124 ′, thereby providing an orifice  140  through which particles  112  are dispensed by gravity. In this example, orifice  140  is provided with an open area of sufficient size to dispense discrete fastening bits. Once dispensed, liquid binder  139  is propelled through nozzle orifice  120  by carrier fluid  110  discharged from the conduit tube. As shown, particles  112  are released into a spray of liquid binder  139  and carrier fluid  110  and propelled away from the sprayer. In some examples, bits or particles  112  are configured (e.g., provided having the correct geometry and/or size) such that they are only partially wetted by the liquid binder in the spray. For instance, only one portion of each of the bits may be wetted by the liquid binder, leaving the other portions of the bits dry as fixed to a support surface of a touch fastener product. 
     In yet another example, the conduit tube  126  of the above example is replaced with a solid rod and reservoir  114 ″ contains a pressurized carrier fluid, such that retracting actuator  130  retracts the solid rod to release a spray of carrier fluid that entrains the dispensed bits falling from opening  124 ′. 
       FIG. 4A  shows yet another particle sprayer  100   b  in use. In this example, particle sprayer  100   b  is provided having a particle source  102  in the form of a reservoir  114   a  containing a quantity of particles  112  dispersed in a carrier fluid  110  (in this example, the carrier fluid includes a liquid binder or adhesive). Reservoir  114   a  is placed in hydraulic communication with a spray outlet  104  by a flexible conduit  126  in the form of a hose that forms the main body of a conduit  106 . Conduit  106  also includes a pressurized fluid inlet  108  coupled to reservoir  114   a . As shown, conduit  126  extends from pressurized fluid inlet  108  to spray outlet  104 , where a downstream portion of the conduit tube is coupled to an operable valve  141  disposed in a sprayer body  122 . Spray outlet  104  is provided in the form of a nozzle  118  having an orifice  120  configured to spray particles  112  carried by carrier fluid  110 , and a rigid conduit  142  extending from sprayer body  122  to the nozzle. As in previous examples, sprayer body  122  includes a barrel  121 , a handle  123 , and an actuator  130 . 
     As shown, reservoir  114   a  is a jug or other container including a handle  143  to facilitate transport of the reservoir by a user, an inlet  144  coupled to an external pressurized fluid source  150  (e.g., a propellant source) by way of a conduit  145 , and an outlet at conduit inlet  108  for releasing a mixture of particles  112  and carrier fluid  110  to conduit  126 . Propellant source  150  should be a suitable mechanical or pneumatic device for providing a pressurized flow of propellant  151  to reservoir  114   a . In this example, propellant source  150  is a positive displacement, motor driven air pump. As used herein, the term “propellant” refers to any fluid motivating another fluid (e.g., a fluid imparting a motive force on another fluid). For instance, in this example, propellant  151  is pressurized air (e.g., provided by a pressurized fluid source). A fluid may be considered “pressurized” when a pressure greater than atmospheric pressure is exerted on the fluid. Once provided to reservoir  114   a , propellant  151  bears down on carrier fluid  110  in which particles  112  are dispersed, thereby pushing the carrier fluid from the reservoir and through conduit  126 . Particles  112  are carried from reservoir  114   a  by the flowing carrier fluid. The pressure exerted on carrier fluid  110  by propellant  151  should be sufficient to drive the carrier fluid from reservoir  114   a  and through nozzle orifice  120  at sufficient velocity to propel the carrier fluid and particles  112  away from the sprayer. Carrier fluid  110  and particles  112  are provided in a constrained flow by the conduit  126  to valve  141  which is coupled to actuator  130 . Valve  141  is configured to dispense the mixture of carrier fluid  110  and particles  112  to spray outlet  104  in response to manual manipulation of actuator  130 . For instance, in this example, pulling actuator  130  adjusts valve  141  to an opened position, thereby allowing the mixture of carrier fluid and particles to pass through the valve. Valve  141  is in hydraulic communication with spray outlet  104 , such that when the valve is adjusted to an opened position, the mixture of carrier fluid  110  and particles  110  passes through rigid conduit  142  and is discharged through nozzle orifice  120  away from the sprayer. 
       FIG. 4B  shows an alternate reservoir  114   b  suitable for use in the particle sprayer  100   b  shown in  FIG. 4A . In this example, reservoir  114   b  is provided in the form of a jug or other closed container having an integral pump assembly  152 . Pump assembly  152  includes a pump casing (not shown) and a piston  154  mounted to the pump casing. The pump casing is configured to support reciprocating linear movement of piston  154 . Piston  154  features a piston rod  156  and a handle  158 . Handle  158  may be gripped by a user to displace piston rod  156  linearly inward and outward of the pump casing to inject a propellant (in this case ambient air) into reservoir  114   b . In this manner a sufficient amount of propellant to drive the mixture of carrier fluid and particles from the reservoir to the spray outlet can be provided by repeated manual operation of pump assembly  152 . 
       FIG. 5  shows a particle sprayer  100   c  having a particle source  102  in the form of a reservoir  114   c  containing a quantity of loosely packed, dry particles  112 . Reservoir  114   c  is coupled to a sprayer body  122 , the sprayer body including a handle  123 , a barrel  121 , and an actuator  130 . In this example, the reservoir  114   c  is a flexible sack or a bag having an opening  124  and a coupling member  157  (e.g., in this example, a standard male or female quick coupling member cooperating with a counterpart member of sprayer body  122 ) securing the reservoir to the sprayer body. Particle sprayer  122  also includes a spray outlet  104  having an orifice  120  for discharging particles  112  in a flow of air as a carrier fluid  110 . Spray outlet  104  is placed in fluid communication with reservoir  114  by a hose  126  which forms the main body of a conduit  106 . The conduit  106  also includes a pressurized fluid inlet  108  which is coupled to the barrel of sprayer body  122 . 
     As shown, particle sprayer  100   c  also includes a blower assembly  160  (depicted schematically) disposed within a hollow portion  125  of sprayer body  122 . Blower assembly  160  should be configured to provide a flow of carrier fluid  110  for motivating particles  112  from reservoir  114   c  to spray outlet  104 . In this example, blower assembly  160  features a motor driven, rotatable impeller mounted to sprayer body  122 . The impeller includes a multiplicity of vanes configured to create a pressure differential on opposite sides of the impeller when the impeller is revolved rapidly by the motor. The pressure differential generates a flow of carrier fluid  110  (in this example, air) passing through sprayer barrel  121 . Barrel  121  includes a venturi constriction  162  for syphoning particles  112  from reservoir  114   c . Venturi constriction  162  is in hydraulic communication with the reservoir opening  124  and creates a low pressure region  164  (e.g., a vacuum region) formed proximate reservoir opening  124 . The differential between low pressure region  164  and the ambient pressure of reservoir  114   c  is sufficient to siphon particles  112  from the reservoir and up into the flow of carrier fluid. The flowing carrier fluid  110  then carries the particles through conduit  126  and through orifice  120 . The bag of reservoir  114   c  may be sufficiently porous to admit ambient air into the bag, or may be sealed but sufficiently flexible to collapse during use. 
       FIGS. 6A and 6B  show a particle sprayer  100   d  in the form of an aerosol can. The can itself forms a reservoir  114   d  containing a quantity of particles  112 , a carrier fluid  110  in which the particles are dispersed, and a pressurized propellant  151  (in this example, an inert gas) bearing down on the carrier fluid. Particles  112  should be dispersed evenly in carrier fluid  110  prior to spraying. In some examples, particles  112  are suspended in carrier fluid  110  when the carrier fluid is at rest. For instance, the viscosity of carrier fluid  110  is sufficient to hold particles  112  in suspension when the carrier fluid is at rest. In this example, the carrier fluid  110  may include one or more suspending agents for attaining a sufficient viscosity to suspend particles  112  in the carrier fluid. In particular, carrier fluid  110  may be formed of a liquid binder to which a thixotropic agent is added (e.g., about 0.3% and 5% by volume of fused silica). In some examples, the density of particles  112  and the density of carrier fluid  110  are matched so that the particles have neutral buoyancy in the carrier fluid, thereby allowing the particles to remain dispersed when the carrier fluid is at rest. In some examples, particles  112  are suspended in carrier fluid  110  by surface energy. For instance, particles  112  may be highly hydrophilic, causing them to disperse in carrier fluid  110  due to their interactions with the ions in the carrier fluid solution. In some examples, particles  112  are electrostatically suspended in carrier fluid  110 . For instance, particles  112  may be statically charged such that they are motivated apart from one another, thereby creating a uniform semi-stable suspension of particles  112  in carrier fluid  110 . In some examples, particles  112  are dispersed and/or suspended in a viscous foam or gel carrier fluid  110 . In some examples, a liquid binder or hardenable fluid may be used as a carrier fluid (e.g., when creating a touch fastener product). For instance, in this example, carrier fluid  110  includes a quantity of V-Block PRIMER-SEALER, manufactured by APAC of 2424 Lakeland Road, Dalton, Ga. 30721 (www.apacadhesives.com). 
     In some cases, the fluid contents of the reservoir (e.g., a carrier fluid and/or a propellant) are not configured to hold the particles in a dispersed suspension. In such cases, the reservoir can be provided with a mixing element (such as a loose stainless steel ball) for dispersing the particles in the carrier fluid. For example, a user can shake the reservoir to agitate the mixing element and disperse the particles in the carrier fluid prior to spraying. 
     Reservoir  114   d  is a hermetically sealed can or bottle configured to contain one or more pressurized fluids. For instance, in this example, reservoir  114   d  is formed of a material with good tensile properties. As shown, reservoir  114   d  is an integral part of a sprayer body  122 , the sprayer body also including an opening  165  in which a spray outlet  104  is disposed, and a valve cup  166 . Spray outlet  104  features a nozzle  118  having an actuator  130 , an outlet orifice  120 , an inlet orifice  167 , and a stem  168  hydraulically coupling the inlet orifice to the outlet orifice. Spray outlet  104  and reservoir  114  are placed in hydraulic communication by a conduit  106  cooperating with a valve  141 , as discussed below. 
     A flexible conduit tube  126  forms the main body of conduit  106 , the conduit also including a pressurized fluid inlet  108  and an outlet  170  coupled to valve  141 . In this example, valve  141  features a housing  169  supported by a lower portion of valve cup  166 , a sealing member  171  (in this example, an o-ring gasket) positioned between an upper portion of the valve housing and the valve cup, a biasing member  172  (in this example, a helical compression spring), and a plunger  173  coupled to nozzle  118 . As shown, biasing member  172  and plunger  173  are disposed in valve housing  169 . 
       FIG. 6A  shows particle sprayer  100   d  with valve  141  in a closed position. As shown, when the valve is in a closed position, the force provided by biasing member  172  urges nozzle  118  upward (via plunger  173 ), such that inlet orifice  167  is pressed against sealing member  171 .  FIG. 6B  shows valve  141  in an opened position. As shown, when a user presses on actuator  130  (and therefore plunger  173 ) with sufficient force, the upwards force provided by biasing member  172  is overcome, thereby allowing nozzle  118  to be urged downwards. As the nozzle is pressed downwards, inlet orifice  167  traverses sealing member  171  and is placed in hydraulic communication with conduit tube  126 . At this point, there exists a passage from the pressurized reservoir to the ambient pressure (i.e., atmospheric pressure) environment. As such, propellant  151  is allowed to drive carrier fluid  110  from reservoir  114  through conduit house  126  and nozzle orifice  120 . Particles  112  are carried from the reservoir by the motivated carrier fluid and subsequently sprayed from the nozzle orifice away from the sprayer. 
     As shown in  FIGS. 6A and 6B , propellant  151  may be provided in the form of a pressurized inert gas. In some other examples, however, propellant  151  is provided in the form of a liquid or a liquefied gas (e.g., compressed butane). The liquefied gas may exist as a liquid when reservoir  114  is kept under high pressure (for example when valve  141  is closed). When the pressure on the liquefied gas is relieved (for example, when valve  141  is opened), some of the liquefied gas should begin to boil, thereby forming a layer of gas near the top of the reservoir bearing down on carrier fluid  110  and driving the carrier fluid as well as some of the liquefied gas through conduit tube  126  toward nozzle orifice  120 . In some cases, liquefied gas driven from the reservoir can be used to increase the flowability of the particles. For example, a liquefied gas propellant having a lower viscosity than the carrier fluid can be provided to the particle sprayer. Additionally, in some examples, the evaporating liquefied gas propellant forms bubbles in the carrier fluid, creating a foam. By using a propellant in the form of a liquid or liquefied gas, the mixture may be further diluted as it is sprayed towards the support surface. The propellant may evaporate upon release to the atmosphere, thereby increasing the ratio of bits to liquid binder on the support surface. 
       FIG. 7  shows a particle sprayer  100   e  similar to the particle sprayer shown in  FIGS. 6A and 6B . In this example, particle sprayer  100   e  has a particle source  102  in the form of a first reservoir  114   e  containing a quantity of particles  112  dispersed in a carrier fluid  110 . The particle sprayer  100   e  also includes a fluid source  137  in the form of a second reservoir  114   f  containing a liquid binder  139 . As shown, the reservoirs include flexible bags (in this example, hermetically sealed, multi-layered laminated pouches) disposed in a hollow cavity  125  of a sprayer body  122 . A propellant  151  occupies the remaining space in the hollow cavity. Sprayer body  122  is hermetically sealed, such that propellant  151  pressurizes hollow cavity  125  and presses in on the first and second reservoirs. The reservoirs are placed in hydraulic communication with a spray outlet  104  by first a first conduit  106 ′ and a second conduit  106 ″ cooperating with a valve (not shown) for dispensing the particles and carrier fluid to the spray outlet. Spray outlet  104  features a nozzle  118  having an actuator  130  as well as a first orifice  120 ′ and a second orifice  120 ″ hydraulically coupled to first conduit  106 ′ and second conduit  106 ″, respectively. For some particle shapes and sizes discussed below, first orifice  120 ′ should be provided having an open area of at least about 1.1 square millimeters. In this example, second orifice  120 ″ is provided having a smaller open area than the first orifice. In some examples, second orifice  120 ″ is provided having an open area of at least about 0.1 square millimeter. 
       FIG. 8  shows a schematic view of yet another particle sprayer  100   f . In this example, the particle source  102  coupled to a spray outlet  104 , a conduit  106  extending from a pressurized fluid inlet  108  to the spray outlet, and a reservoir  114   g  containing a liquid binder  139 . 
     Particle source  102  includes a flexible ribbon of stock material  174  having a longitudinal axis, and a wheel  176  on which a multiplicity of cutters  178  are mounted for cutting through the ribbon at discrete intervals to form discrete fastening bits  180 . Cutters  178  are mounted to the outer edge of wheel  176  and are configured to cut completely through the ribbon along the longitudinal axis. Ribbon  174  should be formed of a suitable material (e.g., thermoplastic) for forming discrete fastening bits, and may be of a cross-sectional shape chosen to provide overhanging projections on each severed bit. 
     Particle sprayer  100   f  further includes a support surface  182  (in this example, a bed knife) for supporting a distal end of ribbon  174  as discrete fastening bits  180  are severed. Support surface  182  may be formed of a much harder, wear-resistant material than cutters  178 . For instance, in this example, the support surface is formed of carbide, and the cutters are formed of 303 stainless steel. Rotation of the cutting wheel may be sufficient to pull ribbon  174  from spool  184  to advance the ribbon during cutting. Alternatively, other ribbon feeding means may be provided, such as a feed nip between counter-rotating rollers or a feed belt (not shown). 
       FIGS. 9A and 9B  show the detail of one of cutters  178 , which is formed to have a pointed projection  186  that engages and severs the ribbon. The trailing portion of projection  186  has a wedge-shaped relief  190 , and the leading edge  192  of the projection defines a rake angle β with a radius R of wheel  176 , such that the point  196  defined at the intersection of the radially distal edge  198  of the projection and leading edge  192  of the projection leads cutter  178  in its rotation. Distal edge  198  is shown essentially perpendicular to the cutting wheel radius from point  196  to the beginning of relief  190 . Rake angles of about 20 to 25 degrees have been found to be appropriate with polyester ribbons. While this cutter  178  is shaped with an outwardly-directed projection for forming concave cuts in the ribbon, cutting may also be performed by a cutter defining a recess, such that the ribbon is first engaged on either lateral side by the advancing edges of the walls defining the recess. Such a cutter shape may help to trap the ribbon end as it is severed, forming convex surfaces on the exposed ribbon end. 
     When forming a touch fastener product, it may be required to provide a support surface with a mixture of particles (e.g., discrete fastening bits  180 ) and liquid binder having a high volumetric ratio of particles to binder. In some examples, having a high volumetric ratio of bits to binder ensures that a sufficient number of bit fiber snagging components (e.g., projection heads  210 , see  FIG. 11 ) are exposed for loop engagement. The proper coating ratio can be achieved by governing the density of the liquid binder. For example, when the bits are suspended in a foam carrier fluid, the volume taken up by the liquid binder in the carrier fluid is greatly enhanced for a given mass of the mixture. As the foam carrying the particles flows from of the orifice of a particle sprayer, the cell structure of the foam may be destroyed (i.e., the foam collapses, releasing its gas and leaving behind the liquid binder), such that the final coating on the support surface has the original density of the liquid binder in the carrier fluid. As such, many more bits per volume of carrier fluid can be deposited on the support surface when compared with an un-foamed carrier fluid. Likewise, in some examples, the carrier fluid is provided in the form of a liquid having a low volume of liquid binder (in some applications, a water based acrylic adhesive mixed with about 66.67% by volume of water). In such examples, when the coating is allowed to set on the support surface, the majority of the liquid in the carrier fluid evaporates and the final coating of the support surface has the original density of the liquid binder in the carrier fluid. 
     As mentioned above, the particles  112  include discrete fastening bits. The discrete fastening bits  180  may be applied to a support surface to form a touch fastening product.  FIG. 10  shows a touch fastener product  204  having a broad support surface  206 , with a multiplicity of discrete fastening bits  180  dispersed across and fixed to the support surface  206  in various orientations. The bits  180  are dispersed in a random pattern, each bit being supported by surface  206  and generally separated from the other bits by varying distances. To give some sense of proportion, the bits  180  shown in  FIG. 10  are each only about one millimeter across, from tip to tip. 
       FIG. 11  shows an even more greatly enlarged view of surface  206  and a few of the bits  180 . Each bit  180  has multiple projections  208  extending in different directions, with at least one projection  208  of each bit extending away from surface  206 . Each projection has a head  210  that overhangs the bit beyond the neck  212  of the projection, to define crooks  214  for the releasable engagement of fibers. Each bit  180  has two opposite side surfaces  216  and  218  that form boundaries of surfaces  220  that define the projections. Surfaces  220  form the perimeter or profile of each projection, and the opposite side surfaces  216  and  218  form the broad faces of the bits and their projections. Each of the bits has a thickness, measured between its opposite side surfaces  216  and  218 , that is less than a maximum overall linear dimension of the bit. In the example shown, the thickness of each bit is only about 0.3 millimeter, while the maximum overall linear bit dimension, in this case measured between opposite projections, is about 1.0 millimeter, such that the ratio of thickness to maximum linear bit dimension is only about 0.3. 
     Each of the bits  180  shown in  FIGS. 10 and 11  has four projections  208  extending in perpendicular directions, such that the bit has an overall shape similar to a ‘+’ symbol, with rounded arrowheads on each projection. In this example, both of the opposite side surfaces  216  and  218  are non-planar, and are of complementary topography. The shape of the bits is such that, at rest on a planar horizontal surface, they will self-orient with at least one projection  208  extending away from the surface  206 , to be available for loop engagement. The bits  180  shown in  FIG. 11  each have a thickness, measured between their side surfaces  216  and  218 , of about 0.102 millimeter. Bits of a similar profile but of about 0.3 millimeter in thickness, have been found to exhibit higher peel performance when mated with some loop materials. 
     Thus, as fixed to surface  206  and as shown in  FIG. 12 , each bit  180  is oriented with at least one of the projections  208  extending away from the support surface  206  for engaging loop fibers  222 . In many cases, the projections themselves project at acute angles from the support surface  206 , such that fibers may be snagged under the projection and/or in the crooks formed on either side of the projection. Furthermore, because the bits  180  are distributed randomly, the fastening properties of the overall touch fastener product are generally independent of engagement direction. For many touch fastener applications, the bits will be distributed with an average bit density of at least one bit per square centimeter, with all linear dimensions of the bit being less than about 1.2 millimeters (in some cases, 0.25 millimeter or less across). For some applications, bit densities between about 8 and 15 bits per square centimeter are preferable, with bits of such small size. For some other applications, bits as large as, for example, three millimeters across, are useful. While it may be, due to the random distribution of the bits, that some bits become fixed to the surface in contact with other bits, in most cases it is preferable that the bits be spaced from other bits so that the presence of other bits does not impede the engagement of fibers by the exposed projections. 
     As can be seen in  FIGS. 11 and 12 , each bit is permanently fixed to support surface  206  by an adhesive  224  into which lower portions of each bit are embedded. While the degree of wetting on the surfaces of the bits, and the amount of each bit that remains exposed will vary, in this example most bits have three out of four projections directly adhered to surface  206 , leaving only one projection  208  of each bit exposed for engagement. With some other bit shapes (to be discussed further below), more than one projection of each bit will, on average, remain exposed for engagement. 
     The projected profile of each bit, as seen from one of its opposite side surfaces, is shown in  FIG. 13 . Each projection  208  ends at a head  210  that has an overall width ‘w’ of about 0.4 millimeter and a curved outer surface of radius ‘r’ of about 0.2 millimeter, overhanging a projection neck of a width ‘d’ of about 0.15 millimeter. The underside of each head forms two opposite loop-retaining crooks, the edges of each head extending back toward the bit a distance ‘u’ of about 0.033 millimeter. The maximum lateral dimension ‘z’ of the bit, measured from outer head surfaces, is about 1.02 millimeter. 
     Bits of non-planar opposite side surfaces of complementary topography may be formed by cutting the bits from a shaped ribbon (e.g., ribbon  174  of  FIG. 8 ) with a series of identical cuts, each cut simultaneously forming an opposite side surface  216  of one bit and an opposite side surface  218  of another bit. The ribbon shape and material resiliency may be chosen such that the process of cutting bits from the rail imparts further geometric properties. For example, as a cutter (e.g., cutter  178  of  FIGS. 9A and 9B ) enters the material, force from the cutter compresses the material of the ribbon, which remains compressed during cutting. Because the ribbon material is resilient, after a bit is severed from the rail its severed surface obtains a curvature perpendicular to the path of the cut, due to relaxing of the compressed bit material. Thus, curvature in one plane can be provided by cutter shape, while curvature in a perpendicular plane can be provided by compression during cutting, and curvature in yet another perpendicular plane can be provided by ribbon shape. In this manner, bit geometry may be altered in essentially any orthogonal direction. 
     Furthermore, the resulting geometry of each cut can be modified by adjusting the unsupported length of ribbon extending between the end of its support surface and the cutter. For example, spacing the cutter wheel so as to engage the ribbon beyond the end of its support will cause the unsupported length of rail to be resiliently deflected during cutting by bending forces induced by the cutting, such that, after the cutting, the unsupported length of ribbon returns to a position, prior to a subsequent cut, in which an edge of the ribbon corresponding to an exit point of the cutting extends farther in a longitudinal direction than an edge of the ribbon corresponding to an entrance point of the cutting. However, for many applications it may be preferable to reduce or eliminate any unsupported length of ribbon during cutting. 
     While the cutting patterns described above may be performed by linear reciprocation of a cutter blade, they may also be formed by a rotating cutter wheel (e.g., wheel  176 ). The methods of bit severing described herein may be employed to produce discrete bits that are then assembled into, or fed to, the various sprayers discussed above. 
       FIG. 14  shows several examples of cross-sections that may be continuously extruded to form ribbons from which bits may be severed. Each cross-section shown in  FIG. 14  represents a constant ribbon cross-section, with the outline of the profile representing the projection-defining surfaces that extend continuously along the length of the ribbon and maintain their as-extruded nature in the severed bits. Many shapes, like those labeled B-I, K, L, N and R, have four projections, each extending from a common hub generally perpendicular to two adjacent projections. In many of those, the projections are all identical. Shape L shows an example in which the projections are not all identical. Many, such as shapes B-F, I, L and R-Z, are symmetric about each of two axes (one vertical and the other horizontal as illustrated). Shape L, for example, is stiffer with respect to compression in the vertical direction, so as to withstand cutter load without buckling. Some, such as shapes M, O, P, S-W and Y, have both a major axis and a minor axis perpendicular to their longitudinal axis, with the cross-section longest along its major axis. With such shapes it is preferred that the cutting occur along the direction of their minor axis. Many of the shapes with major and minor axes of different dimensions have projection extending in only two opposite directions, such as in shapes M, O, P, T, U and W. Shapes S and Z each have six projections, each extending in a different direction, and shape AA has eight projections each extending in a different direction. Shape V is similar to shape W, but with the addition of projections extending from either end along the major axis. Shape Y has six primary projections extending in the direction of its minor axis, the neck of each primary projection carrying a pair of secondary projections extending in the direction of its major axis. Shape J has four primary projection groups, each group including several branches that form discrete projections, such that the outer periphery of the bit has 16 separate heads for engaging loop fibers, while additional features on the sides of the projection stems form even more engagement points. Many of the shapes have projections with heads that overhang their stems on both sides of the projection, such as those in shapes B-F, H-L, Q-W, Y and Z, and some of the projections of shapes X and AA. Other projections, such as those of shapes A, G and M-P, and some of those of shapes X and AA, have heads that overhang to engage fibers on only one side of their stem. In some shapes, such as shapes H and K, the projections each overhang in two directions, but at different distances along the projection, such that each projection defines two fiber-retaining crooks, one nearer the central hub of the bit than the other. In shape Z the heads overhang both sides of the projection stems to form crooks, but with no return of the tips of the head toward the hub of the bit, such that the underside surfaces of the heads are essentially flat and perpendicular to the adjacent projection stems surfaces. In shape Q projections extend at acute angles up and down from a central web (shown horizontal in the figure), the ends of which are also equipped with overhanging heads for loop engagement, such that the overall cross-section of the ribbon has the general appearance of a letter ‘N’ or ‘Z’. This shape also provides for some vertical collapse during cutting, the upper and lower arms of the shape elastically compressing against the central web to support the arms during cutting. In most of the illustrated shapes the outer surfaces of the projection heads are rounded, while the heads of shapes D and F are generally pointed. The various projections shown in these shapes are designed to have particular engagement and disengagement properties. For example, the heads of the projections of shape Z are designed to snag very low-loft fibers, such as those of non-woven materials, while the heads of the projections of shape N are designed to engage with high-loft loops and to aggressively retain the loop fibers once engaged, without distending. Of course, many other ribbon shapes, and corresponding bit shapes, are useful. 
     Referring next to  FIGS. 15A and 15E , when bits  180  are randomly distributed over a horizontal support surface  206 , and rest on that surface only under their own weight, they may assume any one of the orientations shown in these figures. All of these orientations have in common that at least one projection head  210  of the bit is raised from surface  206  for loop fiber engagement. In the orientation shown in  FIG. 15A , the bit is resting on a portion of its convex side surface, with one projection flat against surface  206  and the heads of two other projections in contact with surface  206 . One projection extends away from surface  206 , its head  210  fully raised or spaced from surface  206  for loop fiber engagement. Because the convex side surface of bit  180  defines essentially a 90-degree angle, the upwardly extending projection extends essentially perpendicular to surface  206 . In the orientation of  FIG. 15B , bit  180  is resting on three of its projection heads, with the fourth projection head  210  extending away from, and raised from, surface  206  for fiber engagement. Due to the shape of the bit, the upper projection extends at an acute angle to the surface. As seen from  FIGS. 10-12 , when broadcast over a surface many of the bits assume this particular orientation. In general, the shape and structure of the bits are stable as cut, prior to being distributed onto the surface. The bits are not applied to the surface in liquid form, nor do they obtain their individual shape by influence of gravity or the surface itself. In this sense they may be considered rigid bodies in comparison to the adhesive bonding them to the surface. 
       FIGS. 15C-15E  illustrate three other potential orientations that may be assumed by a bit  180  at rest on a horizontal surface  206 . The incidence of the orientation shown in  FIG. 15C , in which two heads  210  are raised at the distal ends of two projections extending at acute angles relative to surface  206 , is a function of the thickness of the bit, relative to other geometric properties and linear dimensions, with a thicker bit (e.g., one resulting from a higher rail advance rate between successive cuts) more frequently assuming this orientation than a thinner bit cut from the same rail. The orientations of  FIGS. 15D and 15E  may be considered stable orientations only in the presence of an adhesive mechanism. In these two orientations, three engageable heads  210  are raised, one on a vertically-extending projection and two on horizontally-extending projections. Even in these three orientations, at least one projection head  210  is raised from surface  206  for loop fiber engagement. 
     The dashed lines shown in  FIGS. 15A-15E  represent an upper surface of an adhesive  224  fixing the bits  180  in these orientations. The dashed lines are also labeled as  206   a  to illustrate that “surface” over which the bits  180  are sprayed may be a surface  206   a  of a layer of adhesive disposed on a substrate  206 . The bits  180  may be partially embedded in adhesive  224  as shown in these illustrations and in  FIG. 16 , or float on the adhesive surface as in  FIG. 17 . The adhesive  224  may be in place before the bits are sprayed, or may be delivered to the surface with the bits. 
     Even with relatively thin bits  180 , the orientations shown in  FIGS. 15D and 154E  have been observed occurring as a result of surface tension or capillary forces at the surface of a liquid adhesive. This phenomenon is illustrated in  FIG. 18A , which shows bit  180 , which initially is oriented as shown by dashed outline, righting itself due to forces at the interface between the adhesive  224  and the projection head  210  in contact with the adhesive. This phenomenon appears more frequently with very light/small bits  180  and high wetting properties between the adhesive and bit materials. 
     Once applied to the surface, the thickness of the adhesive  224  may be reduced by drying. In this manner, low solids water-based adhesives may be applied as coatings thicker than would otherwise be tolerable in the finished product.  FIG. 18B  illustrates water or solvent evaporating from the adhesive, leaving an adhesive with a higher proportion of solids fixing the bit to the surface. 
     Similarly, the bits may be fixed to a surface, such as to a film or other solidified resin layer, by at least partially melting the surface after the bits are sprayed onto the surface. For example, bits may at first rest on the surface of a solidified adhesive  224  (or film surface) as in  FIG. 17 , and then become partially embedded in the adhesive  224  as the adhesive is melted, such as to either be suspended within the adhesive (as in  FIG. 16 , for example), or to come to rest on an underlying substrate (as, for example, in  FIG. 15A ). In such cases it will generally be the case that the resin from which the bits are formed is chosen to not melt under the conditions required to melt the surface onto which the bits are sprayed. Such conditions could be elevated temperature, or energy supplied by radiation or other means, such as sonic vibration. 
     In some embodiments, a component of the bits  180  (e.g., a projection head  210 ) is provided with either a much higher or much lower affinity to the adhesive  224  than the rest of the bits  180 . In the case of high affinity, that component may then serve as the anchor for a coating of the adhesive  224  that would otherwise not wet onto the bit. Conversely, in the case of low affinity, that same component may serve as an exposed, fiber snagging portion for a coating of the adhesive  224  that would otherwise completely cover the bit. 
     In some embodiments, the bits  180  have either positive or negative buoyancy in a coating of adhesive  224 . When the bits  180  are provided having a positive buoyancy, they may be completely encapsulated in the adhesive coating when sprayed on the support surface  206  (e.g., a floor surface) but float upwards to expose one or more of the fiber engaging projection heads  210 . When the bits  180  are provided having a negative buoyancy, they may be completely encapsulated in the adhesive coating when sprayed on the support surface  206  (e.g., a ceiling surface) but sink downwards to expose one or more of the fiber engaging projection heads  210 . 
       FIG. 19  shows an additional illustration of a plurality of bits  180  applied to a support surface  206 . As was mentioned above, the bits are adhered to the support surface  206  by adhesive  224  and are oriented having at least one projection head  210  available for loop fiber engagement. 
     As discussed above referring to  FIGS. 10-19 , discrete fastening bits  180  may be configured for loop fiber engagement. The bits should also be configured for ejection from an orifice  120  of a particle sprayer  100 . In some examples, discrete fastening bits  180  are configured for ejection from an orifice  120  having a relatively small diameter.  FIG. 20A  shows a compressible bit  180  being discharged from an orifice  120  of a spray outlet  104 . The bit is formed of a material including a compressible substance (in this example, expanded polystyrene, however, melamine and urethane foam materials may also be suitable) such that the internal pressure of the reservoir in which the bit  180  is contained (e.g., reservoir  114   d , see  FIGS. 6A and 6B ) compresses the bit to a suitable size for being ejected from orifice  120 . Once bit  180  is free of orifice  120 , it expands in the lesser atmospheric pressure to a larger size for snagging fibers. 
       FIG. 20B  shows a highly elastic bit  180  being discharged from an orifice  120  of a spray outlet  104 . The bit is formed of a material including a highly elastic substance (e.g., the bit may have very little central mass and high aspect ratio projections). As shown, the undistorted dimensions of bit  180  would not allow it to be ejected from orifice  120 . Due to its highly elastic composition, however, the bit may be contorted and deformed to fit through orifice  120  under force of the flow of carrier fluid, and will elastically rebound to its original shape after ejection. 
       FIG. 20C  shows a plastically deformable bit  180  being discharged from an orifice  120  of a spray outlet  104 . Again, as shown, the undistorted dimensions of the bit would not allow it to be discharged from orifice  120 . Bit  180 , however, may be plastically contorted and deformed to fit through orifice  120 . The formable bit may retain at least some of its deformation after ejection, allowing curvature developed during ejection to assist in its orientation on the support surface. Additionally, bit  180  as deformed may be aerodynamically aligned for self-orientation onto a support surface  206  when sprayed in a carrier fluid. For example, the deformation of bit  180  may provide an aerodynamic leading end  226  for adhesion to the support surface and an aerodynamic trailing end  228  having projection heads  210  for engaging fibers. 
       FIGS. 21A-21C  show a bit  180  being discharged from an orifice  120  of a spray outlet  104  with discrete quantities of adhesive  224 . Spraying the bits such that the adhesive is only provided where the bits land can allow the support surface to which the bits are adhered to maintain its permeability, stretchability, or other similar properties. 
       FIG. 21A  shows a bit  180  having voids or pockets in which a quantity of adhesive  224  is disposed. In this example, adhesive  224  includes a foaming agent such that the adhesive filing the pockets of the bit is an unstable foam (e.g., a water based acrylic). After bits  180  have impacted support surface  206 , the foam collapses to allow adhesive  224  to vacate the pockets of the bit and flow onto the surface to fix the bit to the support surface. In some cases, the impact against surface  206  collapses the foam or otherwise ejects the adhesive from the bit. 
       FIG. 21B  shows a bit  180  encased in an adhesive  224 . After the encased bit impacts surface  206 , adhesive  224  is made to flow from the bit onto the surface to expose at least some of the projection heads  210  for engagement and to fix the bit to the surface, such as by melting of the adhesive. 
       FIG. 21C  shows a bit  180  with adhesive  224  collecting or clumping on its surface such that the bit is propelled toward a support surface  206  with little or no loose liquid (i.e., liquid not attached to the bits) in the spray. More specifically, as shown, adhesive  224  has accumulated in crooks  214  defined by projection heads  210 . In some other examples, one or more portions of the bit are provided having a higher affinity for the adhesive (e.g., wettability) than other portions of the bit, thereby causing the adhesive to wet only those portions of the bit having the high affinity. Or in some cases the entire surface of the bit is formed to have a high affinity to the adhesive, such that the adhesive tends to wet, and stick to, the surface of the bit. In still some other examples, the nozzle of spray outlet  104  is configured to release relatively large droplets of adhesive  224  with bits  180  in order to avoid having loose liquid in the spray. The resulting spray pattern may be particularly useful when spraying bits onto a permeable fabric, for example, so as to not impair the permeability of the overall fabric by flooding with the adhesive. Similarly, a stretchable material may retain its overall stretch properties even when adhering bits in small amounts of even a non-stretchable adhesive. 
     While a number of examples have been described for illustration purposes, the foregoing description is not intended to limit the scope of the invention, which is defined by the scope of the appended claims. There are and will be other examples and modifications within the scope of the following claims.