Abstract:
A dispenser for mixing together multiple fluids, such as foam components and dispensing the mixed fluids includes a body portion of the dispenser with fluid entrances and an exit. A handle extends from the body portion to facilitate grasping and operation by a user. A flow control valve is positioned in the body portion for controlling flow of foam components entering the dispenser mixing chamber. The trigger is movably mounted to the body portion in opposition to and spaced apart from the handle. A safety for preventing unintended operation of the dispenser is movably mounted to and extends lengthwise of the trigger that is always biased into a safety position. The safety has an arm for preventing movement of the trigger sufficient to cause unintended operation of the flow control valve, and the safety may be disengaged by the same single-handed action used to actuate the dispenser to dispense the mixed fluids.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to dispensers and gun-like dispensing devices used in the foam industry, and more particularly, to a dispenser which is adapted for easy, low-cost mass production manufacture capable of simple, selective actuation to prevent inadvertent or unintended discharge of chemical products. 
     Over the last couple of decades, there has been an ever-increasing use of polyurethane and like plastic foams for a number of applications. Urethane and related products, including isocyanurates, silicones, phenolics and epoxies, are well known as having a number of desirable characteristics. These include the potential for excellent insulation, compatibility with blowing or foaming agents, reproducibility of chemical characteristics, and excellent chemical and physical properties in the finished product. 
     Many urethane foams are resistant to degradation by many common solvents, moisture and atmospheric oxidation. Urethanes provide the best combination of heat insulation and physical strength for a given cost. The foam is naturally an adhesive material and bonds well to any number of substrates. In this connection, it can add structural strength to many articles where such strength is an important element. Fire retardance may be achieved easily with available formulations. 
     Urethane foams, being the reaction product of two individual components, may be varied in chemical composition for a number of purposes. Thus, urethane foams may be formulated so as to provide a finished product which is quite rigid, which is semi-rigid, or which is somewhat flexible and/or elastomeric. Foams of the kind in question may be made with almost exclusively closed cells, or with a desired proportion of open cells. 
     The types of products with which the instant invention may be used are primarily the two-component and single component closed cell foam types of product used for insulation purposes in building structures as well as open-celled foam types that are commonly used for packaging applications. The components of the foam are passed at high pressures above 40-250 p.s.i. through a hand-held dispenser which serves to meter and mix the components thoroughly in a nozzle from which they are discharged. Chemical components are taken directly to a job site in pre-pressurized cylinders, or shipped in bulk tanks that utilize external pumps or other methods of pressurization. Here, the amount of product required to be dispensed is not so large as to require permanent, expensive equipment, as would be used in a factory. However, the amount of product used is significantly larger than could be accommodated by using small, individual aerosol cans, for example. The individual containers of the components carry from several pounds up to 25 to 50 pounds or more of each component. These tanks are sufficiently portable to be moved about on the job site by one worker, but yet are able to provide sufficient foam to provide several hundred or thousand board feet of coverage. 
     Hand-held dispensers are used with these smaller chemical supply tanks and such dispensers provide the advantages and characteristics of low cost, reliability, and safety in use. 
     U.S. Pat. No. 4,676,437, issued Jun. 30, 1997, and assigned to assignee of the present invention discloses a representative construction in such a hand-held dispenser. This dispenser takes the form of a gun with a trigger and a safety for preventing inadvertent discharge of the chemical components from the dispensing gun. Such discharges are unwanted and may be unsafe. 
     The operating pressures, reactive components and other characteristics of the foam are such that unintended discharge is unwanted. These discharges create waste that clutters up the working area. Often these discharges result from careless or improper handling when users forget or disregard resetting the safety. One disadvantage of the dispenser of the &#39;437 patent is that manipulating the safety from an “on” position to an “off” position is and difficult and sometimes requires the use of two hands to move it. Another disadvantage is that resetting the trigger safety after use of the dispensing gun is not an automatic, or natural step taken in actuating the dispenser. The structure of this safety also makes manipulation from an “off” position to an “on” position easy to forget. Consequently, after the initial use the trigger safety is usually not moved back to an “on” position. In such situations if the gun or dispenser is inadvertently dropped during use, the trigger may be activated by the fall of the gun and foam is inadvertently discharged. 
     Therefore, there is a demand for a simple-to-use, automatically resetting safety on a foam dispenser which would provide the advantages and characteristics of low cost, safety and reliability in use. 
     The present invention is therefore directed to a safety mechanism for hand-held foam dispensers that overcomes the aforementioned disadvantages. 
     SUMMARY OF THE INVENTION 
     It is therefore a general object of the present invention to provide a foam dispenser which is adapted for easy, low-cost mass production manufacture and which includes an improved safety mechanism that is easy to use and which prevents inadvertent operation of the dispenser. 
     Another object of the present invention is to provide a safety for a foam dispenser which automatically resets to an “on” position after each use. 
     Yet another object of the present invention is to provide a safety incorporated into the trigger of a foam dispenser, which may be manipulated to an “off” position simultaneously with the trigger being grasped for effecting the discharge of foam from the dispenser. 
     Still yet another object of the present invention is to provide a foam dispenser having a safety extending from a grasping surface of a trigger of the dispenser such that a user may manipulate the safety and trigger with one hand in a natural grasping motion in order to actuate the discharge of foam components. 
     A further object of the present invention is to provide a trigger lock for a fluid dispensing apparatus, wherein apparatus has a handle, a trigger moveably mounted to the apparatus and capable of depression toward the handle to open a passage in the dispenser to permit fluid to pass through, the trigger having a lock member integrated therewith, the lock member having an actuating portion extending lengthwise of the trigger and depressible by a user, whereby depression of the lock member moves the lock member out of interference with a stop surface of the handle, so that the trigger may be fully depressed and the dispenser actuated, and the apparatus including a means for biasing the trigger into an open, non-depressed position. 
     The present invention accomplishes these and other objects by way of its novel and unique structure. A preferred embodiment of the present invention is characterized by a dispenser for mixing together two reactive foam components to form an expandable foam and dispensing the expandable foam, including a body portion having foam component entrances and a foam mixing chamber. A handle extends from the body portion to facilitate grasping and operation by a user. The flow control valve is located in the body portion for controlling flow of foam components entering the dispenser mixing chamber. A trigger is movably mounted to the body portion in opposition to and spaced apart from the handle. A safety latch, or trigger lock, is provided that prevents unintended operation of the dispenser. The safety is incorporated into the body of the trigger and it extends length wise of the trigger and has a projecting portion that projects past the grasping surface of the trigger. The safety is placed on the trigger so that it may be easily depressed when the trigger is grasped by a user, thereby permitting operation of the trigger. Likewise, when the user is not grasping the trigger, the safety is biased into a safety position so that even if the dispenser were to be dropped, the safety will prevent operation of the dispenser and discharge of the foam components. 
     An arm member is provided on the safety that extends rearwardly from the safety. The handle of the dispenser includes a stop surface and a cavity arranged adjacent to each other. When the safety is not depressed and a force is applied to the trigger, the arm member will interfere with the stop surface and prevent actuating movement of the trigger. When the trigger is grasped, the safety is automatically depressed and the arm member is moved out of opposition with the stop surface and into alignment with the handle cavity, which receives the arm member, thereby allowing full depression of the trigger by the operator. 
     These and other objects, features and advantages of the present invention will be clearly understood through consideration of the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the course of the following detailed description, reference will be made to the attached drawings wherein line reference numerals identify like parts and in which: 
     FIG. 1 is a perspective view of a dispenser having a safety mechanism incorporating the principles of the present invention; 
     FIG. 2 is an exploded perspective view of the dispenser of FIG. 1, showing the various components thereof; 
     FIG. 3 is a sectional view of the dispenser of FIG. 1, showing the safety in an “on” position; 
     FIG. 4 is the same sectional view as FIG. 3, but showing the safety in an “off” position with the trigger fully depressed; 
     FIG. 5 is a sectional view similar to that of FIGS. 3 and 4, showing the safety or trigger lock in an “on” with the trigger stopped from full movement; 
     FIG. 6 is a sectional view of an alternate embodiment for dispenser constructed in accordance with the principles of the present invention and showing the safety in an “on” position; 
     FIG. 7 is a vertical sectional view similar to that of FIG. 6, showing the safety in an “off” position and the trigger being partially depressed in its initial movement; 
     FIG. 8 is a vertical sectional view similar to that of FIGS. 6 and 7, showing the safety in an “off” position, and the trigger being fully depressed; 
     FIG. 9 is an elevational view of the trigger and safety removed from the foam dispenser; and, 
     FIG. 10 is a side sectional view of a prior art safety mechanism incorporated into a foam dispensing gun. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to FIG. 10, a prior art foam dispenser is shown generally at  200  and is representative of that disclosed and claimed in U.S. Pat. No. 4,676,437. In this known structure, the dispenser has a gun-like configuration with a gun body portion  202 , a handle  203  extending down from the gun body  202  and a trigger  204  movably mounted to the gun body  202 . The trigger is used to actuate a spool valve  205  by rotating the spool valve  205  so that internal passages  206  formed in the valve  205  are moved into alignment with passages  207  formed in two inlets  208  of the gun body  202 . When so aligned, these valve passages  206  also communicate with two inlets of a mixing and dispensing nozzle portion  210  of the gun  200 . 
     A spring  212  is provided that extends between the handle  203  and the trigger  204  and provides an outward bias to the trigger  204  so that the trigger always (in the absence of pressure exerted thereupon) stays in a ready position where the spool valve passages are not aligned with the two inlets so that foam components are unable to flow through the valve  205  and into the nozzle portion  210 . 
     In order to provide protection against unintended operation of the gun  200  and inadvertent discharge of the foam components, this known gun  200  incorporates a safety  220  in the form of a lever  221  that is movably mounted to the handle by way of a pin  222  or other similar member. 
     In operation, the safety  220  is rotated manually counterclockwise along the arrow S until the free end  224  of the lever lies in opposition to the trigger  204 . Movement of the safety lever  221  is limited by a stop edge  225  that bears against the inner surface  226  of the handle  203 . In this position, the safety  220  prevents movement of the trigger  204  by resisting forces applied to the trigger along the arrow F. To operate the gun  200 , the safety lever  221  is moved up clockwise into a recess  230  in the handle so that the lever&#39;s interference with the complete movement of the trigger is removed. 
     Although effective, this safety construction has certain disadvantages. For one, the safety lever is not biased into any particular position. For two, when the safety lever  221  is moved up, it remains in an “off” position so that if the gun is accidentally dropped, the trigger  204  can fully displace to move the valve  205  to a discharge position. This accidental discharge will create a mess and waste foam. 
     The present invention is directed to a safety or trigger lock, mechanism for use on such a foam dispenser or other fluid dispensers that has an improved structure that avoids these shortcomings. Referring now to FIG. 1, a dispenser constructed in accordance with the principles of the present invention is shown generally at  10 . The dispenser  10  takes the form of a gun as illustrated and includes a number of principal components, including a body portion  12  having a handle  14 , a flow control valve housing  16 , a nozzle recess  18 , a combined nozzle latch and ejector element  20 , a trigger  24 , a safety  26 , a biasing mechanism  28 , and a pair of inlet fittings  30 . 
     In FIG. 2, the dispenser body portion  12  has its handle  14  extending away therefrom and preferably in a direction to facilitate grasping by a user. The handle  14  includes a front face  32 , a rear face  34 , and a pair of sides  36 ,  38  that interconnect the front and rear faces  32 ,  34 . A cavity  40  located in the front face  32  of the handle  14  and is dimensioned to receive a catch  54 , or arm, that extends from the safety  26  when the safety is in an “off” position (FIG. 4) for the dispensing of foam. The handle  14  also includes a stop  42  formed on its front face  32  preferably adjacent the cavity  40  either below (FIGS. 3-4) or above (FIGS.  6 - 8 ). This stop  42  is located in opposition to the safety catch  54  when the safety  26  is an “on” position, such as shown in FIGS. 3,  5  and  6 . The stop  42  may be formed flush with the handle front face or as a projection on the front face. As illustrated, the stop  42  may be disposed between the cavity  40  and a cavity  44  of the handle that is formed to facilitate the molding of the handle  14 . The free end  58  of the catch arm  54  has a contoured surface  59  for engaging with the stop  42  and preventing operation of the dispenser  10  irrespective of the force a user may apply to the trigger  24 . A tip  56  on the free end  58  of the catch  54  locks-out the trigger  24  from inadvertent or improper operation. 
     When the safety  26  is in its “on” position and a user attempts to move the trigger  24  toward the handle  14  in order to operate the dispenser  10 , the catch  54  will contact the stop  42 , and if provided with a tip  56 , the tip  56  may partially engage the receptacle  44 . This engagement prevents further movement of the trigger  24  as shown in FIG.  5 . This locking engagement occurs when a force is applied to the lower part  130  of the trigger  24 , as would occur when the gun is dropped. Preferably, the cavity  40  is disposed above the stop  44 , with the receptacle  44  below the stop  42 . However, the cavity  40  may also be disposed in other embodiments below the stop  42  and the receptacle  44  is not necessary. (FIGS. 6-8.) 
     The handle  14  further includes a cavity  46  that receives a portion of the trigger biasing  28  shown as a return spring  60  and having a “clothespin” or hairpin configuration, operating in response to torsional forces generated in its central coil  62 . Other types of springs may also be used to accomplish the function described hereinafter. 
     The rear face  34  of the handle  14  may be characterized by an ergonomically-shaped curvilinear surface  48  that extends from a butt end  50  to an outwardly projecting stop  51 . The handle  14  is designed to be comfortable and non-fatiguing for the user, and also facilitates balance, grasping and actuation of the dispenser  10  by the user. 
     The upper portion of the dispenser body  12  includes a cylindrical control valve housing  16  with circular sidewalls  64  that define a cylindrical bore  66  extending transversely to the principal longitudinal axis of the housing  16 . The valve housing  16  also accommodates foam component fittings  30  each of which preferably includes a locking groove  68 . Each fitting  30  is secured in place against axial movement by an associated fitting lock in the preferred form of a spring clip  70 . A seal member is provided in the form of an O-ring  72  and is disposed in a sealing groove  69  for establishing a fluid tight seal between the fitting  30  and the gun housing  16 . 
     Surmounting the housing  16  is a mount  74  that includes generally parallel and slightly tapered side walls  76 ,  78  that hold the nozzle ejector latch member  20  when in a locking position. These sidewalls  76 ,  78  include an opening  80  for receiving the pivot ears  82  which attach the nozzle latch and ejector element  20  to the housing  16 . This element  20  has a rocker-style lever with a finger tab  84  on one side of the pivot ears  82 . Horizontal and vertical legs  86 ,  88  lie on the other side of the pivot ears  82 . The end portion of the latching leg  86  terminates in a hook  90 , while the front face  92  of the leg  88  acts to engage the rear face of a disposable nozzle. The side walls  76 ,  78  are spaced apart so that they snugly engage the legs  86 ,  88  of the latching and ejector element  20 , preventing it from moving freely except under pressure exerted on the finger lever  84 . 
     As shown best in FIGS. 3 and 4, the nozzle receiver assembly  18  is disposed at the forward end of the housing  16  and includes a radially inwardly facing cylindrical nozzle guide surface  94  terminating at its inner end in a front wall portion  96  which defines a mixing chamber  99 . Alignment slots  98 ,  100  may be provided in the nozzle guide surface  94  in order to align and guide the nozzle (not shown) into a position where it is ready to accept the fluid components for mixing and dispensing. 
     The spool valve  104  is shown to include identical outboard ears or tabs  106 ,  108 , each of which may be drilled. with holes, as shown at  107 ,  109 , to receive self-tapping threaded fasteners  111 ,  113  that connect the trigger  24  to the gun body  12  by way of the spool valve  104 . The spool valve  104  is subdivided into a pair of valve elements  110 ,  112  each including its own component flow passage  114 ,  116 . 
     A sealing means in the form of O-rings (not shown) are disposed in grooves that extend circumferentially about the spool valve  104  to subdivide it into the valve elements  110 ,  112 . The spool  104  is rotated by movement of the trigger assembly  24 . FIG. 3 illustrates the trigger  24  in a first operative position where the valve passages  114 ,  116  are not aligned with the inlets of the body portion  12  and foam components cannot pass through the dispenser. FIG. 4 illustrates the trigger  24  in a second operative position where valve passages  114 ,  116  are aligned with the inlets so that the flow components can flow directly through the dispenser and into the nozzle. 
     The trigger  24  includes a hand piece  120  in the form of a yoke having at its upper end, leg portions  122 ,  124 , each of which is slotted at  126 ,  128  so as to receive the spool valve ears  106 ,  108  which are fastened thereto by fasteners  111 ,  113 . The trigger  24  includes a contoured front grasping surface  130  that facilitates a user&#39;s gripping. A safety, or trigger lock,  26  is provided to prevent unintended operation of the trigger  24  and the dispenser  10 . As shown best in FIG. 3, a slot  132  is formed in the trigger and particularly in the front surface  130  and is adapted to receive the safety  26 . This slot  132  preferably extends through to the rear face  134  of the trigger. Preferably the slot  132  extends to a location of about two-thirds the longitudinal extent of the trigger  24 . A user may grasp both the safety  26  and the trigger  24  with the fingers of one hand in such a configuration, so that at least two of the user&#39;s fingers may grasp and actuate the safety  26 , while at least two of the user&#39;s fingers may grasp and actuate the trigger  24 . In this manner, a user can easily grasp and actuate the dispenser  10  with only one hand. 
     The safety  26  has a contoured outer surface  138  located on its leading face, a catch  54 , a pair of pivot ears  140 , a groove  142  and an arm  144 . The catch arm  54  extends away from the safety body in the direction of the handle  14 . The free end  58  of the catch  54  is disposed in opposition to the stop  42  when the safety  26  and trigger  24  are each in their respective first operative positions. (FIG. 3.) 
     A pair of pins, or pivot members  140 , are formed on opposing sides  150 ,  152  of the body of the safety and are received within a slot  154  is disposed in the rear face  134  of the trigger  24  within to facilitate movement of the safety  26  within the trigger  24 . This association locates the safety actuating surface  138  a predetermined distance away from the front face  130  of the trigger  24  (under urging of the spring  28 ) while permitting movement of the safety  26  either clockwise or counterclockwise. (FIGS. 3-4 or  6 - 8 ). 
     The use of the directional terms “clockwise” or “counterclockwise” herein pertain to the rotational movement of the safety  26  around its pivot point when the dispenser is facing the direction illustrated in FIGS. 1-8 and grasped in the right hand of the user. Were the user to hold the dispenser  10  in his left hand and point the dispenser in the opposite direction, it will be understood that these directions will be reversed. 
     A tab arm  144  extends at the bottom  156  of the safety  26  in opposition to an endwall  136  formed as part of the slot  132  and it limits movement of the safety  24  (as shown in FIG. 3) and possible disengagement of the safety  26  from the trigger  24 . A groove  142  in the safety may also be provided so as to receive a portion of the biasing spring  60 . 
     The return spring  60  includes a central coil  62  and a pair of opposite extending arms  63 , each of which terminates in a free end  61 . The free ends  61  of the spring  60  interconnect the slot  46  formed in the handle  14  and the groove  142  formed in the safety  26 , and thereby biases the safety and trigger into their positions shown in FIG.  3 . This biasing force is transferred to the trigger  24 , by way of the safety and particularly, via the pivot ears  140  and arm  144 . Thus, the trigger  24  and safety  26  are normally biased away from the handle  14 . The biasing means  28  also automatically resets the safety  26  and trigger  24  to this position after a user releases his pressure on the trigger and safety. 
     FIG. 3 illustrates the dispenser  10  in a “locked” condition where the safety  26  is in an “on” position, meaning it and the trigger  24  are biased away from the trigger so that the spool valve  104  is in a closed position. A clip  70  (FIG. 2) removably holds the inlet fittings  30  in place in a counterbore  158  of the dispenser housing  16 . The fitting  30  includes an O-ring  72  set in a groove  69  that facilitates sealing of the fitting  30  within the counterbore  130  in of fluid-tight relation (FIGS.  3  and  4 ). 
     The spool valve  104  is positioned that foam components cannot flow therethrough when the trigger  24  takes its first position of FIG.  3 . In this position the spool valve flow passages  114 ,  116  do not align with either of the adjacent inlet passages, and are blocked against foam component flow because they face interior portions of the valve bore that define the spool receiving opening  64 . 
     FIG. 4 shows the elements referred to in connection with a description of FIG. 3 in the same relation, except that the safety  26  has been actuated, or moved to its “off” position, and the trigger  24  has been displaced toward the handle  14  against the pressure at the biasing spring  60 . This movement aligns the passages of the spool valve  104  with the inlets so that the flow components can flow through the dispenser  10 . Grasping of both the safety  26  and hand piece portion  120  of the trigger  24  may be accomplished by the natural articulation of the fingers on one hand of the user. Preferably, the safety  26  extends over no more than two thirds the length of the hand piece portion  120  so that the user may grasp both. When the safety  26  is moved to an “off” position, the arm member  54  no longer opposes the stop  42 , but opposes the cavity  40 . As the trigger  24  is moved from its first operative position (FIG. 3) to its second operative position (FIG.  4 ), with the safety  26  depressed and in its “off” position, the arm member  54  will be received within the handle cavity  40  so that the spool valve  104  can be moved to align the flow passages of the dispenser to dispense foam. 
     After a user has finished using the dispenser  10  and releases the trigger  24 , the safety  26  also releases under urging of the biasing force of the return spring  60 . Both the handle  14  and the safety  26  are thus returned to their first operative positions. Thus, the trigger lock mechanism of the present invention has an automatic reset feature that requires no action on the part of the user and thus has a “deadman” reset feature. It should also be noted that the movement that operates the safety is a natural “grasping” or “squeezing” movement of the user which can be done in the single motion of depressing the trigger  24 , as contrasted to the complex movements required dispensers of the prior art. 
     As shown in FIG. 5, if a user attempts to actuate the valve  104  as described above without moving the safety  26  into its “off” position, the free end  58  of the catch  54  contacts the stop  42  and prevents further movement of the trigger. Preferably, the contoured surface  59  and tip  56  cooperate to capture the stop  42  therebetween so that no amount of additional force on the hand piece portion  120  will actuate the valve  104  without destroying the safety and/or trigger. 
     FIGS. 6-8 shows the elements referred to in connection with a description of FIGS. 3-5 in the generally same relation, except the mounting of the safety  26  in the trigger has been modified to reverse its rotational movement. The pivot ears  140  of the safety  26  are near the lower free end  160  of the trigger  24 . The actuating surface  138  of the safety  26  still extends along and projects out from the grasping surface  130  as described above. 
     In this embodiment, the activating movement of the safety is reversed, i.e., it moves clockwise about its pivot members, rather than counterclockwise as in the first embodiment, when the dispenser  10  is held in the user&#39;s right hand and the dispenser is oriented in the direction shown in FIGS. 7 and 8. The orientation of the spring  60  will remain the same, having its center coil  62  disposed beneath and between the two free ends  61  of the spring  60 . The spring  60  biases the safety  26  and trigger  24  away from the handle  14  where the flow passages  114 ,  116  of the spool valve  104  are not aligned with the inlets and wherein the safety catch arm  54  is positioned in opposition to the stop surface  42  of the handle  14 . The leading edge  130  of the safety  26  protrudes past the front contour of the handle  14  so that a user may depress it. When depressed, the safety moves in the manner shown in FIG. 7 so that its arm member  54  moves out of opposition to the handle stop surface  42  and into the handle cavity  40  so that the trigger may be fully depressed to the position shown in FIG. 8, where the spool valve flow passages are aligned with the inlet passages so that foam components can flow through the dispenser. 
     In its preferred form, the entire dispenser just described may be made from plastic materials, with the exception of the spool, the fasteners, the trigger spring, and the fittings. A major advantage of the invention is that the safety provides a simple impediment to inadvertent or accidental operation of the spool valve and automatically resets the safety to its “on” position without additional effort from the user. This greatly simplifies operation and servicing of the gun. Additional benefits include ease of manufacture, reduction of component waste, reduction of costs, and improved worker safety. 
     The nozzle itself may be of a type known to those skilled in the art, that includes a series of baffles or the like to permit mixing of the foam components prior to discharge. 
     The spool may be manufactured in an automatic screw machine or the like, being a cylindrical spool with end tabs, transverse fluid passages and circumferential O-ring grooves. It is located in a position of registry by the yoke-type trigger, which also prevents spool end play by having its inner surfaces lying closely adjacent the outer surface of the housing  16 . 
     In use, the remote ends of the hoses are hooked to supply tanks in a know manner. Then, it is merely necessary to insert a nozzle assembly in the dispenser. When the nozzle is fully seated, it is held in place by engagement with the latch. Thereupon, merely actuating the safety  26  while grasping the trigger  24  and moving both toward the handle performs the steps necessary to discharge a foaming plastic product through the nozzle outlet. The safety automatically resets to an “on” position after a user releases the trigger  24 . Attempted further operation of the dispenser without actuation of the safety  26  will fail. The dispenser is sufficiently economical that it may be thrown away after the contents of the tanks are emptied; however, the gun may be easily cleaned and rebuilt, if desired, at low cost without the use of skilled labor. 
     In use, the dispenser provides the advantages of simplicity, low cost of manufacture, reduction of component waste, increased safe operation, and ease of serviceability, consequently, it provides features not found in considerably more expensive dispensers. 
     While the preferred embodiments of the invention have been shown and described in the context of a foam component dispenser, it will be understood that the present invention also has utility and application to other fluid dispensers, and thus, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the spirit of the invention, the scope of which is defined by the appended claims.