Hot melt gun

Hot melt guns comprising a melt body having a melt chamber and a mechanism for feeding a rod of solid hot melt material to the chamber for melting and dispensing. The feeding mechanism comprises a carriage mounted for movement towards and away from the melt body, a clamp member pivotally mounted on the carriage and a trigger to cause the clamp member to grip the rod and feed it into the melt chamber. The clamp member has two pivot pins projecting from opposite sides, each pin having an arcuate coaxial bearing portion and at least one flat face. The pins are received in bearing openings defined by circular bearing surfaces in the carriage, Assembly openings are provided in each bearing surface extending around a minor arc and sufficiently wide for the pins to pass through when the flat faces are suitably oriented relative to the openings. However, when the gun is fully assembled, the arc of movement of the clamp member is restricted so that the pins cannot reach an orientation where the faces are sufficiently aligned with the assembly openings to permit the pins to be withdrawn.

BACKGROUND OF THE INVENTION 
This invention relates to a hot melt gun comprising a melt body having a 
melt chamber and feeding means for feeding a rod of hot melt material in 
solid form, under the control of an operator, into the melt chamber. The 
feeding means comprises a carriage mounted for movement towards and away 
from the melt body, a clamp member pivotally mounted on the carriage and a 
trigger connected to the clamp member by connecting means. As pressure is 
applied to the trigger by the operator the clamp member pivots into 
engagement with the rod of hot melt material supported by the carriage to 
grip the rod and, on further pressure on the trigger by the operator, to 
feed the rod into the melt chamber. 
Hot melt guns as described above are known. Such guns are described in 
German patent specifications Nos. 2249033 and 2265644. Suitable hot melt 
materials include glues, for sticking together various articles, and 
sealants. Rods of hot melt material for this purpose are commercially 
available, for example from the Assignee of the present Application. While 
such guns have proved reasonably satisfactory in operation, feeding means 
of the guns described in said specifications have a multiplicity of parts 
making rapid assembly inconvenient. 
SUMMARY OF THE INVENTION 
The hot melt gun of the present invention comprises a carriage, clamp 
member, connecting means, trigger, and a spring biasing the clamp member 
away from the rod of hot melt and the carriage away from the melt body, 
all constructed so that they can be conveniently and rapidly assembled to 
one another and into the gun body without additional equipment or 
fastening means. 
According to the present invention, assembly is also facilitated by the 
arrangement by which the clamp member engages the carriage. The clamp 
member has two coaxial pivot pins integral with and projecting outwardly 
from opposite sides of the clamp member. Each pivot pin has an arcuate 
coaxial bearing portion and at least one chordal flat face. The pivot pins 
are received in coaxial bearing openings at opposite sides of the 
carriage, the bearing openings being defined by substantially circular 
bearing surfaces against which the bearing portions of the pins are 
supported. Each bearing surface has an assembly opening extending around a 
minor arc in the surface remote from a rod of hot-melt supported by the 
carriage. The assembly openings are sufficiently wide for the pivot pins 
to easily pass through the assembly openings when the flat faces of the 
pins are suitably oriented relative to the assembly openings, i.e. with 
the flat faces generally parallel to a radius of the bearing openings 
bisecting the assembly openings. However, when assembled in the gun the 
arc of pivotal movement of the clamp member is restricted so that the 
pivot pins cannot reach an orientation where the flat faces are 
sufficiently aligned with the assembly openings to permit the pins to be 
withdrawn through the openings. 
Details relating to the hot melt guns of this invention as well as the 
advantages derived from such hot melt guns will be more fully appreciated 
from the Detailed Description of the Preferred Embodiments taken in 
connection with the Drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The illustrative hot melt gun shown in FIG. 1 comprises a body having two 
parts, 10 and 12. Part 12 of the body is broken away to show feeding means 
14, and other parts (described below) of the gun. As well as the feeding 
means the gun includes a melt body 16 in which is formed a melt chamber 
(not shown) of suitable configuration, for example having a conically 
tapering passage extending from an inlet end to nozzle 18 through which 
molten hot melt is expelled from the melt chamber. Melt body 16 further 
includes a heater chamber (not shown) normally substantially parallel with 
the melt chamber and having therein a suitable heating element, for 
example a so-called positive temperature coefficient heating element 
(PTC), in good thermal contact with melt body 16. Nozzle 18 may be cast 
integrally with melt body 16 or provided as a separate, detachable nozzle. 
Nozzle 18 may contain a valve, e.g. a ball valve, to prevent leakage of 
melt from the melt chamber when the gun is not in use. Heat insulating 
washer 20 surrounds the outlet end portion of the melt chamber adjacent 
the nozzle. Inlet sleeve 22, having flange 24 in contact with melt body 
16, may be received on an inlet tube (not shown) projecting rearwardly 
from melt body 16 and maintained in place on the tube by clip 26. Washer 
20 and flange 24 are received in positioning recesses provided by moldings 
on parts 10 and 12 of the gun body so that the body is spaced from and 
insulated from melt body 16. Inlet sleeve 22 has an inlet passage, coaxial 
with the melt chamber, through which rod 54 of hot melt material, for 
example, an adhesive or sealant, is introduced into the inlet end of the 
melt chamber. Guide collar 30, mounted in the body of the gun at the rear, 
provides a guide opening therethrough coaxial with the melt chamber to 
guide rod 54 of hot melt material and maintain the rod properly aligned 
with the melt chamber. Inlet sleeve 22 and guide collar 30 are preferably 
made of silicone rubber. Inlet sleeve 22, in addition to guiding the rod 
of hot melt material into the melt chamber, forms a seal with the rod, 
guarding against escape of molten hot melt material from the chamber. 
Parts 10 and 12 of the gun body are preferably molded of a tough plastic 
material. Parts 10 and 12 of the body maybe clipped together by clip means 
positioned so that access to the interior of the gun body is prevented and 
so that parts 10 and 12 of the body cannot be separated after assembly 
without damaging the body. The clip means of the illustrative gun 
comprises a plurality of cooperating pairs of clip members 32 and 34, one 
member on either body part 10 and 12, as shown in FIG. 4. Each clip member 
32 or 34 includes a hooked end portion 36 adapted to be received, when 
parts 10 and 12 of the gun body are assembled, in recess 38 of associated 
clip member 34 or 32. Recesses 38 of clip members 32 are in the exterior 
of body part 10 and recesses 38 of clip members 34 are in the interior of 
body part 12. Each hooked end portion 36 of clip members 32 and 34 
includes inclined face 40 which, as the body parts 10 and 12 are pressed 
together during assembly to engage the clip members, slide over one 
another to cam clip members 32 and 34 respectively inwardly and outwardly 
so that hooked end portions 36 slide past one another and snap into 
recesses 38. Recesses 38 are sufficiently deep and hooked end portions 36 
engage sufficiently deeply therein so that prying apart of clip members 32 
and 34 is effectively prevented. 
Feeding means 14 feeds rod 54 of hot melt material in solid form, under the 
control of an operator, into the melt chamber. Feeding means 14 (FIG. 1) 
of the illustrative gun includes carriage 42 (FIGS. 1 and 2) mounted for 
sliding movement toward and away from melt body 16. Flanges 44 of the 
carriage engage in slideways 46 (FIG. 1) molded in gun body parts 10 and 
12 and parallel with the axis of the melt chamber. Feeding means 14 
further includes a clamp member such as knife member 48 (FIGS. 1 and 3) 
mounted on carriage 42, and trigger 50 (FIG. 1) connected to knife member 
48 by connecting means including link 52. Trigger 50 is arranged to be 
operated by the operator to pivot knife member 48 into engagement with rod 
54 of solid hot melt material supported by carriage 42, inlet sleeve 22, 
and guide collar 30. Knife member 48 grips rod 54 and, on further pressure 
on trigger 50 by the operator, feeds rod 54 into the melt chamber. Feeding 
means 14 also includes a spring such as coil spring 56 by which knife 
member 48 is biased in a counter-clockwise direction (viewing FIG. 1) and 
by which carriage 42 is biased away from melt body 16. Feeding means 14 
comprising carriage 42, knife member 48, link 52, trigger 50, and spring 
56 are constructed in such a way that the parts can all be assembled to 
one another and into parts 10 and 12 of the gun body without additional 
equipment or fastening means. Feeding means 14 has been designed to have 
as few parts as possible, compared for example with the above-mentioned 
patent specifications, and to be assembled reliably and simply in such a 
way that when parts 10 and 12 of the gun body are snapped together the 
feeding means remains securely assembled, as will become apparent from the 
description following. 
Carriage 42 and knife member 48 may both be cast from a suitable metal. 
Part 110 of carriage 42 (FIGS. 1 and 2) includes guide aperture 58 through 
which rod 54 passes with a small clearance. The rod is thus supported by 
part 110. Knife member 48 is pivoted on carriage 42 by means of two 
coaxial pivot pins 60 (FIGS. 1 and 3) integral with knife member 48 and 
projecting outwardly from opposite sides of the knife member. 
Each pin 60 has an arcuate bearing portion and at least one chordal flat 
face. Preferably each pin 60 has two parallel flat faces 64 at opposite 
sides of the pin, the arcuate bearing portion being in two parts separated 
by the flat faces. Pivot pins 60 are arranged to be received in coaxial 
bearing openings 66 at opposite sides of carriage 42. Bearing openings 66 
are defined by substantially circular bearing surfaces 68 against which 
bearing portions 62 of pins 60 are supported. Each bearing surface 68 has 
assembly opening 70 extending around a minor arc in the surface remote 
from rod 54 of hot melt supported by carriage 42. Assembly openings 70 are 
sufficiently wide for pivot pins 60 to pass through the assembly openings 
when flat faces 64 of the pins are suitably oriented relative to the 
assembly opening (i.e. with the flat faces generally parallel to a radius 
of bearing openings 66 bisecting the assembly openings). However, when 
assembled in the gun, the arc of pivotal movement of knife member 48 is 
restricted so that pivot pins 60 cannot reach an orientation where flat 
faces 64 are sufficiently aligned with assembly opening 70 to permit the 
pins to be withdrawn, or escape, through the assembly opening. 
As mentioned above, feeding means 14 includes coil spring 56 arranged to 
bias knife 72 of knife member 48 away from rod 54 and to bias carriage 42 
away from melt body 16. Knife member 48 includes projecting portion 74 
projecting downwardly below a plane in which knife 72 of knife member 48 
and the axis of pivot pins 60 lies. Curved end portion 76 of the spring 56 
is received in pocket 78 at the rear of projecting portion 74. End portion 
80 of coil spring 56, remote from curved end portion 76, bears on face 82 
provided on one part, e.g. part 10 of the gun body. Part 10 of the body 
further comprises peg 84 around which spring 56 is coiled. When parts 10 
and 12 of the gun body are assembled, spring 56 is retained on peg 84 by 
engagement of peg 84 in a socket (not shown) molded integrally with part 
12 of the gun body. 
Projecting portion 74 of knife member 48 has a channel between two parts 86 
and 88 of projecting portions 74. The channel between parts 86 and 88 is 
substantially parallel with the path of travel of carriage 42. Link 52 is 
disposed in the channel between the parts 86 and 88, lying generally 
parallel with the path of travel of carriage 42. The link has one end 
portion 90 pivoted in boss 92 of part 86. Part 88 has assembly opening 94 
oriented so that link 52 can be introduced through assembly opening 94 to 
pivot end portion 90 in boss 92. However, when the gun is fully assembled, 
movement of link 52 is restricted, as will be described below, so that 
link 52 cannot escape through assembly opening 94. Link 52 of the 
illustrative gun is preferably in the form of a rigid wire, with end 
portion 90 bent at right-angles to the main part of the link so that end 
portion 90 is substantially parallel with the axis of pivot pins 60. The 
hole in boss 92 in which the end portion 90 is received is also 
substantially parallel with the axis of pivot pins 60, so that end portion 
90 pivots in the boss. Trigger 50 preferably is molded of a suitable 
plastic material and is pivotally mounted on the body of the gun by means 
of integrally molded pegs 96 (only one of which is visible in the 
drawings), which are received in opposed holes in parts 10 and 12 of the 
gun body to be parallel with the axis of pivot pins 60. Trigger 50 
includes pressure plate 98 arranged to be contacted by the finger of an 
operator to operate trigger 50. The arc of movement of the trigger is 
restricted by engagement of pressure plate 98 with the gun body and by 
engagement of stop member 100 (also molded integrally with trigger 50) 
with parts 10 and 12 of the gun body. Pivot portion 102 of link 52, remote 
from and parallel with end portion 90, is received in hole 104 in trigger 
50 parallel with the hole in boss 90. End part 106 of link 52 extends 
beyond pivot portion 102, end part 106 lying generally perpendicular to 
pivot portion 102 to retain the pivot portion in hole 104 in trigger 50. 
Power is supplied to the heater element in known manner by cable 108 
entering the gun through a handle portion. 
Feeding means 14 can be assembled simply: knife member 48 is first 
assembled with carriage 42 by introduction of pivot pins 60 into bearing 
openings 66. Link 52 is also assembled with knife member 48, with end 
portion 90 received in the hole in boss 92, the link being introduced 
through assembly opening 94 as described above. The assembly including 
carriage 42, knife member 48 and link 52 is assembled with spring 56 and 
positioned in part 10 of the body portion with lower (viewing FIG. 1) 
flange 44 of carriage 42 received in slideway 46 in part 10 and with the 
spring positioned around peg 84, as shown in FIG. 1. End part 106 of link 
52 is then introduced through hole 104 in the trigger and the appropriate 
peg of the trigger introduced into the hole (not shown) in part 10. When 
feeding means 14 is assembled, carriage 42 is urged by spring 56 away from 
the melt body (toward the right, viewing FIG. 1) along slideway 46 and the 
knife member is urged in a counter-clockwise direction (viewing FIG. 1), 
so that knife 72 is clear of rod 54. The link is in a position generally 
parallel with slideway 46. Stop member 100 engages part 10 of the body, 
preventing further clock-wise movement of the trigger (viewing FIG. 1). 
The orientation of knife member 48 relative to carriage 42 is such that 
pins 60 are unable to escape from bearing opening 66 through assembly 
opening 70 and likewise link 52 is unable to reach an orientation which 
would allow it to escape from the channel between parts 86 and 88 through 
assembly opening 94. After feeding means 14 and the other parts of the 
gun, including melt body 16, inlet sleeve 22, guide collar 30, electric 
leads and heater element, are properly assembled in part 10 of the gun 
body, part 12 of the body is aligned with part 10 and the two parts are 
pressed together so that clip members 32 and 34 snap together to lock body 
parts 10 and 12 to each other. When part 12 is assembled with part 10, peg 
96 of trigger 50 enters a cooperating hole in part 12 and peg 84 of body 
part 10 is received in the corresponding socket in part 12. Trigger 50 is 
thus held in place by the two pegs in body parts 10 and 12, and spring 56 
is held in position about peg 84 by the socket of body part 12. Upper 
(viewing FIG. 1) flange 44 is engaged in a slideway (parallel with the 
slideway of body part 10) in body part 12. 
When the trigger is moved in a counter-clockwise (viewing FIG. 1) direction 
by pressure on pressure plate 98, the knife member is pivoted by link 52 
in a clockwise direction to move knife 72 through an opening in carriage 
42 into engagement with rod 54. Further pressure on the trigger causes 
carriage 42 to move towards melt body 16 (toward the left, viewing FIG. 
1), engagement of knife 72 with rod 54 causing the rod to be gripped 
between knife 72 and carriage 42 and moved with the carriage towards the 
melt chamber. (The feeding means is shown in an intermediate position in 
FIG. 1.) Continued pressure on pressure plate 98 will rotate trigger 50 in 
a counter-clockwise direction to a maximum extent governed by contact of 
pressure plate 98 with body parts 10 and 12. With the trigger in this 
position, part 110 of the carriage 42 is adjacent the inlet end of inlet 
sleeve 22. In this most extreme, forward position of feeding means 14, 
knife member 48 is likewise at an orientation in which pins 60 are unable 
to escape from bearing openings 66 and link 52 is retained in the channel 
between parts 86 and 88. 
When trigger 50 is released, spring 56 urges knife member 48 in a 
counter-clockwise direction (viewing FIG. 1) so that knife 72 is moved out 
of contact with rod 54--which is held against movement rearwardly by 
collar 30 and inlet sleeve 32. Carriage 42 slides away from the melt body 
under the pressure of spring 56 to an extent determined by engagement of 
stop member 100 with body parts 10 and 12, the carriage sliding relative 
to rod 54 so that, on subsequent operation of the trigger 50, a fresh 
portion of rod 54 is gripped by knife 72 and part 110 of carriage 42. The 
illustrated hot melt gun completes the melting operation in known manner: 
as rod 54 is urged into the melt chamber by feeding means 14, heat 
supplied to melt body 16 by the heating element melts the material of rod 
54, and the molten material is dispensed through nozzle 18 under pressure 
applied by feeding means 14 to rod 54. Relaxation of pressure on trigger 
50 stops feed of rod 54 into the melt chamber and thus molten material 
ceases to be dispensed through nozzle 18. 
The illustrated hot melt gun is, as has been described, simple and quick to 
assemble and cannot be disassembled without breaking body parts 10 and 12, 
thus preventing unauthorized access to the inside of the gun, which could 
prove dangerous. Novel feeding means 14 is especially advantageous in that 
it consists of few moving parts and is extremely simple to assemble 
rapidly. Furthermore, body parts 10 and 12, preferably cooperate to retain 
feeding means 14 in its assembled condition so that because of the 
ingenious construction of the feeding means, there is no possibility of 
feeding means 14 becoming disassembled inside the gun body, a problem 
which has sometimes arisen in previously known designs of trigger-operated 
hot melt guns. 
The hot melt gun shown in FIGS. 1-4 and described above is intended as a 
non-limiting, illustrative example of the novel hot melt guns of the 
invention; other embodiments are possible within the scope of the 
invention. Hot melt guns according to the invention may be adapted for use 
in the melting and application of various hot melt materials commercially 
available in the form of solid rods, such as glues and sealants.