Abstract:
A glue gun has a base adapted to receive electrical power in either cordless or corded operation, a barrel, a feed roller, a selectively removable glue stick holder in axial alignment with and disposed between a nozzle assembly and the feed roller and extending through an electric heater for containing a glue stick to be melted by the heater, a pinch roller adapted to press the glue stick against the feed roller so that rotation of the feed roller causes the glue stick to be urged toward the nozzle assembly in order to extrude melted glue therethrough, the nozzle assembly having a longitudinal passageway which is normally closed by a pair of valves serially disposed at opposite ends of the passageway and which are operable to open in response to pressure from melted glue produced by rotation of the feed roller and to close to trap melted glue in the passageway when feed roller rotation is terminated, and a trigger assembly to manually control the application of electric power to a drive motor to rotate the feed roller.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to hand tools, and more particularly to hand-held cordless or corded adhesive dispensers using electrically generated heat to melt the adhesive, which is in stick form. Such tools are commonly referred to as “glue guns.” 
     Glue guns are well known in the art, and various configurations for corded glue guns are illustrated in the following U. S. Pat. Nos.: 3,604,597, issued Sep. 14, 1971 to Harold E. Pohl et al.; U.S. Pat. No. 4,523,705, issued Jun. 18, 1985 to Richard W. Belanger et al., and U.S. Pat. No. 5,215,230, issued Jun. 1, 1993 to Grace Lee. In all of these patents, an electrical supply cord is permanently attached to the handle of the glue gun to provide, on demand, electrical current to a heater in the gun to melt a portion of an adhesive which is then expelled through a nozzle at the outer end of the “barrel” of the glue gun. Such corded guns for direct connection to an electrical power outlet by an electrical cord are well known in the art and are widely sold throughout the world at present in many different configurations. 
     A variation of this type of electrical current supply is shown in U. S. Pat. No. 4,826,049, issued May 2, 1989 to Howard D. Speer, in which the gun is placed in a base containing the electrical current source, and the melting of the adhesive occurs while the gun remains in the base. Removal of the gun from the base terminates the flow of the current through the heating element utilized to melt the adhesive. 
     Cordless type glue guns differ from the preceding types in that the gun contains a power source, a rechargeable battery, which is used to supply the current, on demand, to melt the adhesive. Such guns normally include a stand which contains a battery recharging circuit connected to a source of electrical power, so that when the gun is replaced in the stand after use, the battery is recharged. Such cordless guns and recharging systems are well known in the art and are widely sold throughout the world at present in many different configurations. 
     Whether corded or cordless, all glue guns have certain characteristics in common. They have a hand gun-like shape with a pistol grip which is grasped by the user when the gun is in use. The gun contains an electrical heater element, typically located in the gun “barrel.” The adhesive is in a solid stick form which extends through the barrel adjacent the heater element and is “melted” by the selective application of electrical power to the heater element. Application of the electrical power is controlled by a trigger mechanism. The gun barrel terminates in a nozzle, through which the molten adhesive is extruded by pressure applied to the adhesive stick by one or more of a variety of linkages actuated by actuation of the gun trigger. The nozzle typically includes a spring-loaded ball check valve in an effort to terminate the flow of molten adhesive as soon as pressure on the trigger is released, in an attempt to avoid molten adhesive dripping from the nozzle thereafter. 
     Corded and cordless glue guns each have their own advantages with respect to one another. For example, cordless guns provide portability for use on sites remote from an electrical outlet, while corded guns provide for continuous use without the necessity of recharging or changing the battery. Consequently, a user may utilize one of each type of gun to provide for maximum flexibility in performing work. 
     SUMMARY OF THE INVENTION 
     According to the present invention, a glue gun, suited for either cordless or corded operation, has a gun casing with a base and a barrel, the base being adapted to receive electrical power from a power source which is either a battery or an ac to dc converter; a heater element housing containing a heater element; a drive motor; electrical circuit means for applying electrical power to the heater element and to the drive motor; a feed roller disposed within the casing so as to be transverse to and in longitudinal alignment with the barrel and operable, in response to the selective application of electrical power to the drive motor, to be rotated thereby in a preselected direction, the barrel terminating in a nozzle remote from the feed roller; a removable glue stick holder disposed within the barrel in axial alignment with and between the nozzle and the feed roller so that a glue stick, when disposed within the glue stick holder, extends from the nozzle through the glue stick holder onto and beyond the feed roller; and a pinch roller for pressing the glue stick, when so disposed, against the feed roller when electrical power is applied to the drive motor, to assist in the urging the glue stick toward the nozzle in response to rotation of the feed roller in the preselected direction. In the presently preferred embodiment, the glue stick holder, which extends through the heater element, includes a peripheral stop ring to prevent the glue stick, as it is being fed toward the nozzle, from moving the glue stick holder through the heater. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more readily understood by referring to the accompanying drawings, in which: 
     FIG. 1 is a left side elevational view, in section, of a glue gun according to the present invention, in which the gun is shown as including a battery and battery charger for cordless operation of the glue gun; 
     FIG. 2 is a left side elevational view of the gun shown in FIG. 1, but with the barrel opened to illustrate the positioning of a glue stick in the gun; 
     FIG. 3 is a left side elevational view of an ac adapter and stand for use with the gun of FIG. 1 to replace the battery and battery charger so as to provide for corded operation of the gun; 
     FIG. 4 is a partial sectional view of the gun of FIG. 1 illustrating the gun trigger mechanism in its actuated disposition; 
     FIG. 5 is a view, similar to FIG. 4, but illustrating the trigger mechanism in its released disposition; 
     FIG. 6 is a partial sectional view of the glue dispensing nozzle of the gun of FIG. 1 when glue is being dispensed; 
     FIG. 7 is a view, in section, taken along lines  7 — 7  of FIG. 6; 
     FIG. 8 is a partial sectional view, similar to FIG. 6, but showing the glue dispensing nozzle when glue is not being dispensed; 
     FIG. 9 is a left side elevational view of a trigger fork for use with the glue gun of FIG. 1; 
     FIG. 10 is a top plan view of the trigger fork shown in FIG. 13; 
     FIG. 11 is a partial plan view, in section, of the glue gun of FIG. 1, taken along lines  11 — 11  of FIG. 4; 
     FIG. 12 is a partial plan view, in section, of the glue gun of FIG. 1, taken along lines  12 — 12  of FIG. 5; 
     FIG. 13 is a partial front elevational view, partially in section of a pinch roller assembly for use with the glue gun of FIG. 1, with the hinged barrel portion of the glue gun in its opened disposition for receiving a glue stick; 
     FIG. 14 is a partial sectional view of one of the pinch rollers shown in FIG. 13, illustrating its attachment to its mounting axle; 
     FIG. 15 is a schematic diagram of the presently preferred embodiment of the electrical circuit of the glue gun as illustrated in FIG. 1; 
     FIG. 16 is a schematic diagram of an alternate embodiment of the electrical circuit of a glue gun according to the present invention; 
     FIG. 17 is a schematic diagram of another alternate embodiment of the electrical circuit of a glue gun according to the present invention; and 
     FIG. 18 is a partial view, in section, of a glue gun utilizing the embodiment of electrical circuitry of FIG. 17, illustrating its implementation in the glue gun of FIG. 1 by providing a switch on the barrel adjacent the glue gun&#39;s heater element assembly. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring first to FIGS. 1,  2 ,  4  and  5 , a glue gun  100  includes a conventional rechargeable battery  102  and, in FIG.1, is shown as stored in a stand  104  (shown for illustrative purposes only in section in FIG.  1 ). The stand  104  includes an electrical power lead  106  connected to a conventional ac to dc converter  252  to supply dc power to the battery  102 , for recharging. The electrical circuitry for such converters is well known in the art, and so is not shown in FIG.  1 . The stand  104  has output terminals  110  through which the dc output of the charger  104  is applied to the battery  102  to recharge it. The battery  102  has a plug-in element  102 A with a pair of output terminals  112 ,  114 , shown schematically in FIG. 1, which plug into the gun  100  in a suitable recess so as to be in electrical contact with electrical leads  116 ,  118 , also shown schematically, to provide electrical power to the gun  100 . It will be understood that a third lead (not shown) may normally be utilized, when desired or required, as the case may be, in conventional fashion to meet electrical codes as to grounding. 
     The lead  116  has two branches,  116 A and  116 B. Lead branch  116 A is connected to an input terminal  120  of a miniature switch  122  of conventional design, whose output terminal  124  is connected to a lead  126 . The gun  100  has an outer casing  128 , shown in section, to which the switch is fixed in conventional fashion. The lead  126  is shown in FIG. 1, schematically, as connected to an input terminal  130  of a drive motor  132 . Lead branch  116 B is shown as connected to an input terminal  134  of an electrical heater element  136 A, which is contained in a heater element housing  136 . The lead  118  has a branch  118 A, which is shown, schematically, as connected to an output terminal  138  of the drive motor  132 , and a branch  118 B, which is shown as connected to an output terminal  140  of the heater element  136 A. FIG. 15 is a schematic diagram of this circuitry. 
     A worm gear  142  is fixed to a drive shaft  144  which is driven by the drive motor  132 . A feed roller  146 , mounted on an axle  146 A, engages the worm gear  142  in conventional fashion, so that rotation of the worm gear  142  in a predetermined direction rotates the feed roller  146  in a counterclockwise direction, thereby causing a glue stick  148 , which is engaged by the feed roller  146 , to be urged through the heater element housing  136  toward a nozzle assembly  150  in which a barrel portion  152  of the outer casing  128  terminates. In the preferred embodiment, a pinch roller assembly  154  urges the glue stick  148  against the feed roller  146  (see FIG.  4 ), so as to assist in urging the glue stick  148  toward the nozzle assembly  150  upon the counterclockwise rotation of the feed roller  146 , as will be described hereinafter specifically with respect to FIGS. 4 and 5. The motor  132 , drive gear  142  and worm gear  146  are attached to a motor and gear housing  156 , which is fixed to the casing  128  by any conventional means so as to be supported therein. 
     As is best seen in FIGS. 4 and 5, a trigger fork  158  (shown in detail in FIGS. 9 and 10) has a trigger  160  which extends through a trigger aperture  162  in the casing  128 . The trigger fork  158  has a pair of trigger arms  164  (see FIG. 10) between which a cross-arm  166  extends and is attached thereto by four bolts  168  in conventional fashion, as is shown in FIGS. 9 and 10, so as to straddle the worm gear  142 , see FIGS. 11 and 12. The switch  122  has an actuator element  170  which, when contacted by an actuator boss  172  formed on the rear surface of the cross-arm  166  by reason of pressure applied to the trigger  160  as shown in FIG. 4 overcoming the biasing of a trigger bias spring  174 , closes the switch  122  to complete the electrical circuit between the leads  116 ,  126 , applying electrical power to the motor  132 , which rotates the feed roller  146  in a counterclockwise direction to urge the glue stick  148  toward the heater element housing  136  (FIG.  1 ). 
     When the pressure on the trigger  160  is released, the cross-arm  166  moves away from the switch  122 , opening the electrical circuit to remove power from the motor  132 . The feed roller  146  no longer urges the glue stick  148  toward the nozzle assembly  150 . The switch  122  is fixed to the casing  128  by a pair of bolts  176  in conventional fashion. 
     Referring back to FIG. 1, a removable cylindrical glue stick holder  196  is positioned within a complementary passageway in the heater assembly  136  so as to extend through the heater assembly  136  at the forward end of the barrel portion  152  and engages the nozzle portion  150 . The glue stick  148  extends through the length of the glue stick holder  196 . A peripheral stop ring  196 A formed on the glue stick holder  196  prevents the glue stick  148 , as it is urged forward toward the nozzle portion  150  by the feed roller  146  upon actuation of the glue gun  100 , from carrying the glue stick holder  196  into the heater element assembly  136 . When it is necessary or the user desires to replace or change the glue stick  148 , the gun  100  is opened to the disposition shown in FIG. 2, and the glue stick holder  196  manually moved axially away from the nozzle assembly  150  and withdrawn from the heater assembly  136 , and either a different glue stick holder  196  and glue stick  148  is inserted in its place, or the existing glue stick  148  is withdrawn from the existing glue stick holder  196 , and replaced by a new glue stick of the desired characteristics, and the existing glue stick holder  196  reinserted into the heater assembly  136 , as shown in FIG.  1 . 
     Referring now to FIGS. 6,  7  and  8 , which are detail drawings of the nozzle assembly  150  in its opened (glue dispensing) disposition (FIG. 6) and in its closed disposition (FIG.  8 ), the nozzle assembly  150  includes a nozzle proper  198 , which abuts the glue stick holder  196 . The nozzle proper  198  has a longitudinal passageway  200  extending therethrough, within which a valve assembly  202 , including a valve stem  204 , is disposed within a valve insert  206 . The valve stem  204  terminates at its upstream end in a parti-spherical first valve head  208 . Formed in the valve insert  206  adjacent the upstream end of the valve stem  204  is an annular first valve seat  210 . The first valve head  208  seats against the first valve seat  210  when the valve assembly  202  is in its closed disposition (FIG.  8 ), so as to form a first closure of the longitudinal passageway  200 . 
     The opposite (downstream) end of the valve stem  204  is chamfered into a reduced cross-section valve stem portion  204 A, which terminates in a second valve head  212 , parti-spherical and parti-conical in its longitudinal configuration. When the valve assembly  202  is in its closed disposition (FIG.  8 ), the second valve head  212  seats against an annular second valve seat  210 A, which is formed in the nozzle proper  198 , so as to form a second (downstream) closure of the longitudinal passageway  200 . The valve assembly  202  is normally biased to its closed disposition (FIG. 8) by a valve bias spring  214 , through which the valve stem  204  extends. 
     The valve insert  206  has four guide elements  206 A,  206 B,  206 C,  206 D (FIG.  7 ), formed downstream of the first valve seat  210 , which serve to engage the periphery of the first valve head  208  so as to maintain the axial alignment of the valve stem  204  and so the valve heads  208 ,  212  with respect to the axis of the longitudinal passageway  200 . 
     A glue passageway  216  (FIGS. 6,  8 ) is formed within the valve insert  206  downstream of the first valve head  208 . When the first valve head  208  is unseated from the first valve seat  210  (FIG.  6 ), melted glue from the glue stick  148 , which has filled a glue inlet space  218  formed immediately upstream of the first valve seat  210  in the valve insert  206 , passes into the glue passageway  216  around the first valve head  208  through glue passages  216 AC,  216 CB,  216 BD,  216 DA formed between the guide elements  206 A,  206 B,  206 C,  206 D, as is shown in FIG.  7 . After passing into the glue passageway  216 , the melted glue passes out of the nozzle proper  198  through the second valve seat  210 A and an outlet passage  220  formed at the downstream end of the nozzle proper  198  by an outlet insert element  222 . 
     As is shown in FIGS. 1,  2 ,  9 , and  10 , the glue gun barrel  152  has a hinge  240  extending along the barrel top (the hinge  240  being omitted in FIGS. 4 and 5 for purposes of clarity). A hinged barrel portion  152 A (FIGS. 2,  13 ), comprising the upper left hand portion of the barrel  152 , is attached to the hinge  240 , so as to be selectively rotated away from a position adjacent the remainder of the barrel  152 , as is best seen in FIG. 13, so as to permit access to the glue stick holder  196 . The hinged barrel portion  152 A has a glue stick pressure pad  242  at the rear thereof to engage the glue stick  148  when the hinged barrel portion  152 A is in its closed disposition (see FIG. 13) so as to close the opening  186  in a longitudinal passageway  188  extending through the motor gear housing  156  to hold the glue stick  148  in place during operation of the glue gun  100 . A similar glue stick holder pressure pad  244  (FIG. 2) on the hinged barrel portion  152 A performs the same function with respect to the glue stick holder  196  adjacent the nozzle portion  150 . A clip  190 FIG. 13) extends substantially the length of the hinged barrel portion  152 A and is press-fitted onto a lip  192  formed thereon so as to frictionally engage a lip  194  formed on the casing when the hinged portion  152 A is rotated clockwise so as to close the passageway  188  and apply pressure to the glue stick holder  196  during operation of the glue gun  100 . 
     The pinch roller assembly  154  is shown in detail in FIG. 13, which is a partial rear elevational view, partially in section, taken along lines  13 — 13  of FIG.  4 . The pinch roller assembly  154  consists of a pair of oppositely disposed bell-shaped rollers  178 A,  178 B, mounted on an axle  180 . The axle  180  consists of a pair of axle members  180 A,  180 B, to which the rollers  178 A,  178 B are attached by means of a pair of bolts  182  in conventional fashion. FIG. 14 is a partial sectional view of one of the pairs of rollers  178 A,  178 B and axles  180 A,  180 B, which as assembled are mirror images of one another, illustrating the attachment of the rollers and axles through the use of the bolts  182  and washers  184 , to provide for the rotatability of the rollers. 
     As will be apparent from the foregoing the operation of the glue gun is as follows: 
     When the trigger  160  is pulled, trigger arms  164  move the cross-arm actuator boss  172  toward and into contact with the switch actuator element  170 , overcoming the bias of the trigger bias spring  174 , and closing the electrical circuit through the switch  122  to apply electrical power to the drive motor  132 , whose drive shaft  144  drives the worm gear  142  which in turn, rotates the feed roller  146  to urge the glue stick  148  toward the nozzle assembly  150  as shown by the arrow in FIG.  4 . Melted glue from the glue stick  148 , which has filled the glue inlet space  218 , is then forced against the first valve head  208 , overcoming the valve closing bias of the valve bias spring  214  so as to open the first valve seat  210 . Melted glue then flows into the passageway  220  in response to the urging by the rotation of the feed roller  146  of the glue stick  148  toward the nozzle assembly  150  The melted glue in the passageway  200  then flows through the second valve seat  210 A, which has been opened by the action of the valve stem moving the second valve head  212  in response to the movement of the first valve head  208  away from the first valve seat  210 . The melted glue then flows into the outlet passage  220  around the second valve head  212  and out of the nozzle assembly  150 . 
     In conventional glue guns, one of the problems often encountered is the continued passage of melted glue out of the dispensing nozzle after the trigger is released. The glue gun  100  solves this problem in the following manner: 
     When the trigger  160  is released, the trigger bias spring  174  immediately urges the cross arm  166  away from the switch  122 , thereby opening the switch  122  and terminating the application of electrical power to the drive motor  132 , to terminate the urging of the glue stick  148  toward the nozzle assembly  150 , so as to immediately terminate the pressure applied to the first valve head  210  by the melted glue, whereupon the urging of the valve bias spring  214  causes the first valve head  208  to close the first valve seat  210  and the valve stem  204  to move the second valve head  212  so as to close the second valve seat  210 A, trapping substantially all of the melted glue in the nozzle assembly within the passageway  200  until the trigger  160  is pulled again. 
     While the operation of the glue gun  100  has been described with respect to the utilization of the battery  102  as the source of electrical power for the motor  132  and heater element  136 A, the cordless glue gun of the present invention is equally adapted for use as a corded glue gun. To this end, FIG. 3 illustrates an ac to dc converter  252 , a power cord  254 , an adapter base  256  to supply dc electrical power to the glue gun  100  through a plug-in element  256 A, similar to the plug-in element  102 A of FIG.  1 . The adapter base  256  includes output terminals  112 ,  114  to make electrical contact between the power conversion circuitry and the electrical circuitry of the glue gun  100 , as is shown in FIG. 1, with the battery  102  and stand  104  being replaced by the corded adapter  250  (FIG.  3 ). Operation of the corded version of the glue gun  100  is otherwise identical to the operation of the cordless version described above. 
     FIG. 15 is an electrical schematic diagram of the glue gun  100  as shown in FIG.  1 . In this embodiment, electrical power is supplied to the heater element  136 A continuously, so long as the battery  102  retains an electrical charge. When the glue gun  100  is placed in the battery charger  104 , the battery  102  is recharged, and remains fully charged even though the heater element  136 A remains heated. 
     FIG. 16 is a schematic diagram of an alternate embodiment of electrical circuitry for the glue gun of the present invention, in which the electrical power is only applied to the heater element when the glue gun is placed in the charger stand  104  or when the trigger is pulled when in cordless operation, but continuously from output terminals  110  when the corded adapter  250  is utilized (not shown in FIG. 3, see FIG.  1 ). In FIG. 16, like reference numbers refer to like elements with respect to FIGS. 1 and 15. A branch lead  116 C connects the lead  116  to a branch lead  116 D and a branch lead  116 E. The branch lead  116 D is connected to an appropriate terminal of the output terminals  110 . The branch lead  116 E is connected to the heater element input terminal  134 . A branch lead  118 C connects the lead  118  to a branch lead  118 D and a branch lead  118 E. Diodes  116 F and  118 F are included in the branch leads  116 C and  118 C to prevent reverse flow of electrical current from the output terminals  110  through the branch leads  116 C,  118 C to the output terminals  112 ,  114  when the glue gun is in its stand. As will be apparent, so long as the glue gun is in the battery charger  104  (FIG. 1) in the corded adapter  250  (FIG.  3 ), and electrical current is being supplied by the converters  252 , electrical current will be applied to the heater element  136 A. However, when the gun is removed from the charger  104  in cordless operation, current flow through the heater element  136 A is terminated until either the trigger is pulled so as to close the switch  122  or the gun is returned to the charger  104 , so as to avoid discharging the battery  102  unnecessarily. 
     Both the embodiments of FIG.  15  and FIG. 16 provide for the continuous heating of the heater element  136 A in either cordless or corded operation, so long as the glue gun is placed in the battery charger  104  or the adapter stand  250  with dc power applied thereto. 
     FIG. 17, in which like reference numbers refer to like components with respect to FIGS. 15 and 16, is a schematic diagram of another alternate embodiment of electrical circuitry for the glue gun of the present invention. In the embodiment of FIG. 17, electrical current is selectively applied to the heater element  136 A, whether in cordless or corded operation, by means of a switch. As illustrated in FIG. 17, a switch  260  is connected by a branch lead  118 G to the heater element output terminal  140  and by a branch lead  118 H to the lead  118 . 
     While the switch  260  is shown in FIG. 17 as being placed between the output terminal  140  and the lead  118 , alternatively, it could equally well be placed in the lead  116 B so as to be located between the heater input terminal  134  and the lead  116 . In either embodiment, the switch  260  is manually operated by the user as desired to apply electrical current to the heater element  134  or remove the application of such power. This embodiment is particularly useful when the glue gun of the present invention, whether being used either in cordless or corded operation, will only be used intermittently, with long periods of inactivity, so that there is no necessity for maintaining the glue adjacent the glue stick constantly in a molten condition. The user can turn off the application of electrical power to the heater element  136 A by opening the switch  260 . At such time as the user desires to operate the glue gun, the switch  260  is closed to melt the glue stick, and the trigger pulled to close the switch  122  to initiate the extrusion of melted glue from the gun. 
     FIG. 18 is a partial view, in section, of a glue gun utilizing the embodiment of electrical circuitry of FIG. 17, illustrating its implementation in the glue gun of FIG. 1, in which like reference numbers refer to like parts with respect to FIGS. 1 and 17. As illustrated in FIG. 18, the switch  260  is located on the exterior of the barrel  152  below the heater element  136 A, although this location is for illustrative purposes only. Obviously, the switch could be placed at any location on the glue gun deemed convenient for the user. The switch  260  may be any of the wide variety of conventional commercially available switches designed for handling the voltage and wattage involved. While the switch  260  is shown in FIG. 23 as a push-button type switch, such is for illustrative purposes only and not by way of limitation. For example a slide type switch, which can also change the amount of power, for reducing the temperature (rheostat), could equally well be utilized, as is well known in the art as the equivalent thereof. 
     Although the presently preferred embodiments of the invention have been set forth herein in detail for illustrative purposes only, it will be apparent to those skilled in the art that variations and modifications thereof, including the rearrangement of parts, lie within the scope of the present invention, which is not limited to the specific structures of the embodiments shown or described herein, but only by the scope of the following claims.