Note: Descriptions are shown in the official language in which they were submitted.
_ITLE_OF_THE_INVE2~TION:
MORTAR GUN
BACKGROUND OF THE; INVENTION-
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Field of the invention:
This invention relates to a mortar gun and more
particularly to mortar gun specifically adapted to dispense feed
mortar having a thick and viscous consistancy.
Prior art:
A search amongst prior art has re~ealed a pertinent
patent, namely U.S. patent 2,694,509 which discl.oses a mortar gun
somewhat similar to the present invention.
The previously patented mortar gun is provided with an
horizontally projecting circular nozzle ~referred to by numeral 16
and a worm feed screw referred to by numeral 17. The worm feed
screw 17 is adapted to push the mortar out through the front
section of the nozzle 16. The screw has a forward tapered end
which projects into the tapered front extension 20 of the front
wall l4, terminating just short oE the nozzle 16. The shaft 22
of the screw 16 has a t~apered section 21 which tapers down.
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It is stated in column l, lines 80 and 81, and column
2, lines 1-3, of U.S. patent 2,694,509, that this construction ;:~
insures the even feeding of the stiff mortar eliminating air `:~
spaces which ehe stiff mortar:would otherwise l.eave in giving the
mortar its final solid push.
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from the construction of the forward end of the worm feed screw.
Firstly, the shaft 22 of the worm screw 17 is very
dif~icult to manufacture according to the specifications disclo-
sed in the patent. Indeed, a shaft which tapers down almost to a
point having a screw also tapering down mounted on it requires a
lengthy and costly manufacturing process.
Secondly, since the tapered end 21 of the screw 17
terminates just short of the nozzle, a portion of the last thread
o~ the screw is always obstructing a section of the d;scharge
aperture. Although this constraint might seem trivial when
relatively flu;d mortar ;s used, the obstruct;on of a portion of
the nozzle as proven to be d;sastrous when relat;vely th;ck and
viscous fluid is used.
Thicker mortar ;s used pr;ncipally ;n Northern reg;ons
where the regulations frequently require that the mortar, to be
applied, be able to ma;ntain a ball-shape configuration without
sagging.
When such a firm and dense mortar ;s used to feed
sect;on of the discharge aperture obstructed by a worm feed
screw, as is the case with the mortar gun disclosed in U.S.
patent No. 2,694,509 the mortar is temporarily compressed,
squaezing out the water and causing a segregation wh;ch seperates
the sand particles. The segregated sand part;cles have a
tendency to get squeezed by the thread of the screw and lock the
9crew, thus d;sturbing the operat;on of the gun and possibly
causing damages to the structure of the gun.
Thirdly, when th;cker mortar is used, ;t has a
tendency to dry up along the peripheral wall of the tapered
section 20 of the nozzle 16 since the flow is slower around the
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per;phery than in the middle of the discharge sect;on. The
drying up of the mortar along the wall causes an obstruction
which tends to compress and thus segregate the mortar again
possibly causing damages to the gun.
SUMMARY OF THE INVENTION
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According~y, the present invention relates to mortar
gun which will circumvent the above mentioned d;sadvantages. The
improved mortar gun comprises a substantially vertical hopper
adapted to contain mortar and having a front wall, a rear wall
and a substantially horizontal bottom wall. A cylinder projects
~rwflrdly from the front wall of the hopper adjacent the bottom
of the front wall. A conically tapering nozzle extends inte-
grally and forwardly on the cylinder. A feed screw rotatably
lies along the bottom wall of the hopper from the back wall of
the hopper and projects within the cylinder until it reaches the
tapered nozzle. The screw has a central shaft and a thread
integrally mounted on the central shaft.
An helicoidally twisted and relatively flat plate of
~ti~f materisl extends integrally from the thread of the screw
into the nozzle. The helicoidally twisted flat plate rotatably
lies adjacent the corresponding inner wall of the conical nozzle.
~he helicoidal flat plate thus defines an unobstructed conical
sx;al passageway leading to a discharge aperture of the front end
of the conical tapered nozzle. Upon rotation of the screw, the
mortar in the hopper is pushed through the cylinder towards the
discharge nozzle by the feed screw. The mortar in the nozzle is
pushed through the passageway by the mortar leaving the cylinder
and by the helicoidal flat plate which frictionally transmits a
forward thrust to the mortar. The plste also scrapes the inner
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wall of the nozzle to prevent the mortar from sticking to it.
The helicoidal flat plate thus adapted to give the
mortar its fina] push towards the discharge open;ng without
obstructing the latter. It also prevents the mortar in the less
rapid flow adjacent the inner wall of the conical nozzle from
stick;ng to it. This particular construction is also relatively
inexpensive to manufacture since the helicoidal f]at plate is
manufactured independently and then simply welded to the existing
thread on the feeder screw.
BRIEF DESCRIPTION OF THE DRAWINGS: -
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Figure 1 is an elevation view of a mortar gun embodying
tbe invent;on;
Figure 2 is a partial frontal view of the mortar gun
taken along arrow 2 of figure 1;
Figure 2a is a frontal view of the conical screw
according to the invention;
Figure 3 is a longitudinal cross-sectional view of the
frontal end of the mortar gun taken along arrows 3-3 of figure 2;
Figure 4 is a partial view of a wall of brlck with
mortar of the type dispensed by the invention linking the bricks;
Figure 5 is a transversal cross-sectional view taken
along arrows 5-5 of Eigure l;
Figure 6 is a frontal view of the discharge nozzle;
Figure 7 is a side view of the discharge nozzle;
Figure 8 is a longitudinal cross-sectional view taken
along arrows 8-8 of figure 5 and illustrating the vibrating
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mechanism; and
Figure 9 i.s a top cross-sectional view taken along
arFows 9-9 of figure 5 also illustrating the vibrating mechanism.
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DETAILED DESCl~IPTION OF THE PREFERl~ED EMBODIMENT:
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Re~erring to figure 1, there is shown a mortar gun lO
embodying the invention. The mortar gun 10 has a rearwardly
inclined upper body 12. As illustrated more specifically in
f;gure 9, the upper body 12 has a pair of side walls 14, a front
wall 16 and a back wall 18. The walls 12, 14, 16 and 18 define a
substantially rectangular opened top referred to in figure 1 by
numeral 20.
The side walls 14 taper inwardly and integrally into a
trough like bottom wall 22. The bottom wall 22 and the front
wflll 16 extend integrally into a substantially circular forwardly
projecting cylinder 24.
As il]ustrated more specifically in figure 3, the
forwardly projecting cylinder 24 is provided with a set of
peripheral annular recess 26. The annular recess 26 are adapted
to receive a set of corresponding retaining rings 28.
A conically tapering adaptor 30 is slidably positioned
over the forwardly projecting cylinder 24. The adaptor 30 is
frictionally held in place by the retaining rings 28 which are
preferably made of material having elastomeric properties.
A discharge noæzle 32 is abuttingly and slidingly
positioned inside the adpator 30. The discharge nozzle 32 has a
substantially conical back section 34 adapted to fittingly abut
against a corresponding conically tapering inner wall 36 of the
adapter 30 and; a substantially truncated front section 38
characterized by two substantially oblique walls 40 defining a
substantially oval dlscharge aperture 42.
The oval dlscharge apert:ure 42 is particularly suited
for the application of mortar to link structural elements such as
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the bricks 78 of figure 4 which are linked together by a set of
mortar joints 80. The oval aperture 42 has preferably flat sides
to sl;de between rows of bricks.
A worm feed screw 44 rotatably extends along the
trough like bottom 22. The worm feed screw 44 has a shaft 46 on
which i9 integra]ly mounted a thread 48. As illustrated more
specifically in figure 8, the worm feed screw 44 extends
integrally at its rear end in~o an annular journal plate 50. The
annular plate 50 is rotatably mounted inside a corresponding race
52 provided in the back wall 18 of the hopper body 12. The
annular plate 50 is provided with a recess 54 adapted to receive
the frontal end of a driving shaft 56. A retaining screw 58
releasably keeps the driving shaft 56 linked to the annular plate
50.
The driving shaft 56 is connected to a motor (not
shown) protectively enclosed inside a motor casing 60. The motor
is controlled by a trigger switch 62.
One of the main features of the present invention
resides in the use of a vibrating rod 64 illustrated more
specifically in figures 5, 8 and 9. The vibrating rod 64 is
Rdapted to prevent the mortar from:segregating inside the hopper
body 12 and jamming the worm feed screw 44. The vibrating rod 64
is mounted inside a sleeve 66 which extends through the back wall
18 of the hopper body 12. : ~ : :
The v;brating rod 64 projects at its rear end over a .:
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v;brating wheel 68 mounted on the drivlng shaft 56. The : :~
vibrating wheel 68 has an external contour provided with protube~
rances 70~
When the drlving shaft 56 rotates, an abutting sleeve
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72 mounted on the vibrating rod 64 follows the contour of the
wheel 68 thus transforming the rotat;onal. movement of the driving
sha~t 56 into a pivotal oscillating movement of the vibrating rod
64 illustrated by the dotted lines and the arrows of figure 8.
The vibrating rod 64 is adapted to pivot about the
.sleeve 66 which is made of material having resilient el.astomeric
properties. As illustrated more specifically in figure 9, the
vibrating rod 64 when seen from the top has a zig-zag configura-
tion which allows it to cover a greater area.
As stated previously, the main feature of the present
invention res;des in the structure of the frontal end of the worm
feed screw 44 which is modified in order to perform more
efficiently and prevent the segregation of thicker mortar.
As illustrated more specifically in figure 3, the inner
wall 36 of the adapter 30 tapers down conically. The diameter of
the inner wall 36 is reduced from approximately one inch at the
junction 74 between the forwardly projecting cylinder 74 and the
adapter 32 to an approximate average diameter of 3/8 of an inch
at the narrow cross-section of the discharge aperture 42.
To prevent the mortar from beiog compressed by this
reduction in the flow diameter, the shaft 46 of the worm -Eeed
screw 44 terminates adjacent the junction 74. The thread 48 of
the worm feed screw 44 is prolonged integrally into a flat
helicoidal conical screw thread 76 having no central shaft. The
conical screw thread 76 ~is made of a re].atively thin~flat plate
of metal rotatably positioned adjacent the inner wal]. 36 of the
adapt~or 30.
The helicoidal plate 76 defines a conical passageway
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having a central axis colinear with the shaft 46 and leading to ~ .
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the discharge aperture 42.
The thread 48 oF the screw 44 is adapted to push the
mortar from the hopper 12 to the junct;on 74 between the cylinder
24 and the adaptor 30. Once the mortar reaches the adaptor 30, it
is pushed both by the mortar leaving the cylinder 24 and by a
frictionally transmitted helicoidal forward thrust imparted on
the mortar by the plate 76.
The width represented by the letter "W" in figure 3 of
the helicoidal plate 76 is thus much greater than the width "w"
of the thread 48 since the surface of contact with the mortar
must be opt;mized to frict:ionaly transmit the helicoidal forward
trust.
The section of the passageway defined by the conical
screw thread 76 being greater than the annu].ar peripheral section
defined between the periphery of the shaft 46 and an inner wa].l
47 of the cylinder, the section available for the mortar to flow
through is thus increased, compensating for the tapering inner
wall 36 and preventing compression of the mortar.
The conical screw thread 76 elegantly circumvents the
three previously mentionned disadvantages inherent to the worm
feed screw described in U.S. patent 2,694,509.
F;rstly, as mentionned earlier, the shaft of the mortar
gun described in the U.S. patent 2,694,509 which tapers down to a
point in order to compensate for the tapering down of the nozzle
is expensive to manufacture. The con~cal screw thread of the
present invention is manufactured independent].y and then simply
welded to the thread 48 of the screw 44. This greatly simplifies
the manufacturing proces~s thus representing a ma]or economical
advantage.
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Secondly, as illu.~trated clearly in figure 2a, since
the conical thread is made of a flat helicoidal .section of
material which rotatably lie.s adjacent the periphery of the inner
wall 36 of the adapter 30, the discharge aperture 4Z is never
obstructed by any structure. With the mortar gun described in
U.S. patent 2,694,509, since a conventional thread mounted on a
shaft was used all the way to the locat;.on of the discharge
aperture, a section of the last thread always obstructs the
di~charged aperture.
Thirdly, as indicated in figure 2a, during its rotation
the conical thread 76 defines a zone of friction with the inner
wall 36. In this zone of friction, the mortar which has a
tendency to dry up along the inner wall. is scraped from the wall
and pushed into the flow of mortar. This zone of friction
angularly rotates with the rotation of the helicoidal pl.ate 76.
The conical thread 76 is thus adapted to give the
mortar its final push towards the discharge opening 42 without
obstructing the latter and to prevent the mortar in the less ~:
rapid flow adjacent the inner WAll 36 from sticking to the wall.
To further improve the quality of the flow eæcaping
through the discharge opening 42, the width W of the conical
thread 76 i9 wider than the width W' of thread 48 of the worm
feed ~crew 44. The wider thread thus accelerates the flow of
mortar just prior to its discharge through the discharge aperture
42. ~ .
In order to maintain the rate of flowing of mortar
throughout the cylindrical ;nner wall 47 and the conical inner
wall 36, the volume of mortar located over the shaft 46 in one
pitch of the thread 44 should be equal or greater thfln the volume
through one pitch of the he].icoidal plate 76. Considering that ~:
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the helico;dal piate 76 may have more than one pitch, and is
rotating in a con;cal sleeve 30, the length of successive pitches
in the d;rection of the discharge nozzle increases proportionally
to the tapering angle of the sleeve 30 for maintaining a constant
flow throughout.
One preferred embodiment of the discharge nozzle 32 is
;llustrated in figures 6 and 7. The discharge aperture 42 is
oblong with flattened sides 43 obta;ned from the tapered straight
walls 40. This oblong shape allows the projected mortar to
follow the jo;nts ~0 between the bricks.
Considering that the joints 80 are vertical and hori-
zontal, the adaptor 30 is rotatably mounted on the cylinder 24
for selectively orienting the flattened sidewalls in the direc-
tion of the vertical or horizontal joints. With the oblong
discharge, the forward tip 41 of the plate 76 which is narrower
and thinner, is accordingly flexible for scraping the inner wall
of the front section 38 of the discharge nozz]e 32. Such a
scraping operation causes the tip 4] of the plate 76 to have a
zone of friction and a zone of clearance as identified in figure
2b. ~
Although described in this patent as being used in
conjunction with a mortar gun, the construction of the forward
end o~ the feed screw whlch comprises a flat helicoidaL thread
extending integrally from the thread of a shafted worm feed screw
could be used in a number of other applications. In fact, it
could be used~ whenever the materisl is extruded through an
aperture provided at the end of a conical nozzle. Examples of
such mechan-sms includes plastic extrusion machines and dry
feeders,
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