[0001] The present invention relates to a device for the continuous delivery of uniform
quantities of dense and viscous fluid substances, in particular adhesives and similar
paste-like substances.
[0002] As is known, in many sectors of the manufacturing industry and in particular in the
shoe-manufacturing sector, use is made of various types of adhesives which are delivered
continuously in the form of uniform strands, in order to perform bonding, for example,
of the soles to the peripheral edge of the uppers, bonding of the heels and arch supports
and also application of leather and plastic profiles for external finishing of the
shoes.
[0003] In order to deliver a continuous strand of adhesive with a uniform cross-section,
normally of the polymerizable type, use is currently made of delivery/metering devices
which substantially consist of a tubular delivery body which has arranged inside it
a coaxial rod displaceable in either direction by means of an actuating group in the
form of a double-acting piston; an annular cavity is provided between said rod and
the cylindrical internal surface of the tubular body, via which the adhesive, introduced
under pressure, reaches the free end of the tubular body. The end of said displaceable
rod also comprises an obturator with an enlarged, substantially frusto-conical head
which alternately closes and opens the end of the tubular body.
[0004] These devices for delivering a continuous strand of adhesive have in practice some
serious drawbacks which limit the possibilities and proper use thereof, especially
as regards replacement of the type of adhesive and hermetic closure of the obturator
each time delivery is stopped.
[0005] In fact, it has been possible to note that the sealing means of the end obturator
are not always able to prevent dripping of the glue, when the delivery device is closed,
owing to glue dust and/or particles which may collect between the obturator and its
seat or also owing to wear of the contact surfaces, due to prolonged use of the delivery
device. Furthermore, the sealing means between the line of the duct feeding glue into
the cavity and the sealing member integral with the sliding rod which effects closure
thereof, are not always able to prevent the glue, under pressure, from rising up along
the rod itself and along the stem of the piston, stopping against the skirt of the
double-acting cylinder, and from hardening with the passing of time.
[0006] Furthermore, the lack of an effective sealing action between the obturator and its
closing seat may result, in addition to the dripping of glue when the delivery device
is at rest, also in the infiltration of air into the annular cavity, thus causing
hardening of the glue present in the said cavity and adversely affecting subsequent
operation of the delivery device.
[0007] The technical problem which is posed, therefore, is that of providing a device for
the continuous delivery of uniform quantities of dense fluid substances with a constant
cross-section, in particular adhesives of the polymerizable type, designed to eliminate
the drawbacks and the limitations of use of known delivery devices, without substantial
variations in the overall dimensions nor substantial additional costs compared to
those of known delivery devices.
[0008] Within the scope of this problem, the main aim is that of providing a device for
the delivery of adhesives and similar dense and/or viscous substances, structured
so as to prevent both the dripping of glue through the obturator and the seat of the
end of the end of the tubular supply body, and the infiltration of air into the cavity
when the obturator is closed.
[0009] Another aim of the invention is to provide a delivery device of the type specified
above, designed to allow easy and rapid replacement of the type of adhesive to be
supplied under pressure and ensure efficient and regular operation with any type of
adhesive or similar substance.
[0010] This technical problem is solved according to the present invention by a device for
the continuous delivery of dense and/or viscous substances, in particular adhesives
of the polymerizable type, comprising a tubular delivery body with a cylindrical rod
coaxially sliding, alternately, inside it by means of a double-acting piston so as
to create an annular cavity connected to a source supplying adhesive under pressure,
said rod being provided with substantially conical obturator means at its free end,
said device comprising, coaxially with said conical obturator and in the vicinity
thereof, at least two sealing members consisting of enlarged parts, integral with
said rod and sliding inside chambers or countersunk zones formed on the internal surface
of the tubular body, so as to seal off the end of the cavity only when the delivery
device is closed and prevent the entry of air into the cavity itself, there also being
provided at the opposite end of said annular cavity at least another sealing member,
consisting of a cylindrical body, coaxial with said rod and sliding inside a chamber
of larger diameter formed in the cylindrical body, below the aperture for introducing
the supply of adhesive inside said cavity, so as to seal off said supply aperture
and prevent the supply of adhesive to the cavity. According to a preferred embodiment
of the delivery device according to the invention, said two sealing members, integral
with the conical obturator, consist respectively of a frusto-conical body or enlarged
part coaxial with said rod and displaceable inside a chamber so as to ensure sealing
by means of contact against a toroidal ring coaxially integral with the external surface
of the conical body, and of a cylindrical enlarged part, coaxial with the rod displaceable
inside a chamber, designed to ensure sealing by insertion inside a cylindrical annular
shoulder projecting coaxially from said cylindrical body, immediately above the displacement
chamber of said enlarged part.
[0011] Further characteristic features and advantages of the present invention will emerge
more clearly from the following detailed description, with reference to the accompanying
drawings provided solely by way of example, in which:
Figure 1 is a cross-section along the diametral axis of the delivery device realized
according to the present invention and shown in the rest position (with the obturator
closed), and
Figure 2 is a cross-section of the same device according to Figure 1, shown instead
in the delivery position.
[0012] With reference to the aforementioned figures, the delivery device forming the subject
of the present invention substantially consists of a hollow cylindrical body 1 closed
at the top by an end-piece 1a and, at the bottom, by a similar end-piece 1b. It has
slidably mounted inside it a piston 2 of the double-acting type, which is displaceable
with a predetermined and adjustable travel by means of air introduced under pressure,
alternately, through the ducts 3 and 3a.
[0013] The stem 2a, passing through the bottom end-piece 1b, has axially connected to it,
by means of screwing, a cylindrical rod 4 sliding inside a straight tubular body 5
connected to the bottom end-piece 1b of the cylinder 1.
[0014] Said rod 4 has a constant diameter less than the internal diameter of the tubular
housing body 5, so as to create between rod and tubular body a cylindrical cavity
6 intended to convey the adhesive supplied to the top of said cavity by means of a
duct 7 which in turn is connected to a source supplying the adhesive under a suitable
pressure, said source being of the known type and not shown in the figures.
[0015] The bottom end of said rod 4, emerging partially from the end of the tubular body
5, is shaped substantially in the form of a truncated cone 8 and more precisely with
the conical surface 8a towards the inside, so as to form a member closing off the
end of the cavity 6 by sealingly fitting against the end of the mouth 5a of the tubular
body 5, the annular edge of which is correspondingly countersunk.
[0016] Therefore, with each displacement of the rod 4 towards the piston body 1, the obturator
8 closes the cavity 6, stopping adhesive introduced inside the cavity itself from
emerging, while with each displacement of the obturator 8 towards the outside of the
tubular body 5, the adhesive is able to emerge (in the direction of the arrows F in
Figure 2) in the form of a cylindrical layer which then, after flowing round the external
surface of the obturator, is united in the form of a continuous thread or strand.
[0017] Finally the bottom end of the obturator 8 has inserted inside it a freely rotating
ball 9 designed to facilitate sliding of the end of the tubular body 5 on the surface
onto which the strand of adhesive is to be applied.
[0018] In a delivery device of the type described above, the present invention envisages
the application of a plurality of sealing members to prevent any dripping of glue
in the event of a poor sealing action of the obturator 8 and the entry of air inside
the cavity 6 when the obturator is closed, as well as additional sealing members inside
the delivery device, designed to shut off securely the aperture of the duct 7 which
introduces the adhesive into the cavity 6.
[0019] Said bottom sealing members substantially consist of a first frusto-conical enlarged
part 10, coaxially integral with the rod 4 and sliding inside a chamber 11 formed
by means of a countersunk zone in the cylindrical wall of the tubular body 5; the
seal preventing adhesive and air entering the cavity is provided by means of insertion
of the larger-diameter zone of the conical enlarged part 10 within a toroidal ring
12, integral with the external surface of the conical body 10. Therefore, with each
opening travel movement of the obturator 8, the enlarged part 10 is also displaced,
returning inside the chamber 11 and thus allowing the adhesive to continue towards
the exit point.
[0020] An additional sealing member, consisting of a small cylinder 13 coaxially integral
with the rod 4, is provided above and coaxial with said frusto-conical seal 10, said
sealing member also being displaceable inside a cylindrical chamber 14 and forming
the seal by means of insertion inside an annular shoulder 15 emerging radially from
the internal cylindrical surface of the tubular body 5.
[0021] The simultaneous displacement of the three sealing members, i.e. the obturator 8,
the frusto-conical enlarged part 10 and the cylindrical body 14, ensures a sealing
action preventing any dripping of adhesive when the obturator is closed and infiltration
of air into the cavity 6; consequently, the cavity of the delivery device may be kept
filled with adhesive without the danger of hardening and/or alteration.
[0022] Still according to the invention, the inlet aperture of the supply pipe 7 into the
cavity 6 is provided with an additional cylindrical chamber 16 formed in the internal
surface of the cylindrical body 5 and having a greater diameter than the cavity 6,
inside which a small cylinder 17 is displaceable, said cylinder being intended to
shut off the aperture of the duct 7 (Figure 1) at the same time as closure of the
bottom sealing members 8a, 10 and 14. Furthermore, the stem 2a of the piston is provided
with a toroidal seal 18 designed to prevent the adhesive under pressure from rising
up along the stem, as well as a toroidal seal 19 providing a sealing action preventing
the air actuating the piston from escaping.
[0023] The improved delivery device according to the invention comprises moreover a tubular
block 20 associated with the supply duct 7, which block comprises conventional unidirectional
valve means consisting of a ball 20a biased by a spring 20b against a seat 20c for
rapid engagement with the tube 21 connected to the source supplying adhesive under
pressure, so as to allow easy and rapid changing of the type of adhesive, whenever
required.
[0024] In practice, it has been possible to establish that all of said sealing members associated
with the rod actuating the end obturator ensure, in all conditions of use and with
every type of adhesive or other dense and/or viscous substance, a perfect sealing
action preventing dripping of glue through the obturator and infiltration of air inside
the cavity.
[0025] Obviously, in its practical realization, the invention as described in accordance
with any one of its possible embodiments may be subject to modifications as regards
the materials used, the number of additional sealing members, the dimensions of the
various constructional parts and its dimensions, without departing from the protective
scope of the said invention.
1. Device for the continuous delivery of dense and/or viscous substances, in particular
adhesives of the polymerizable type, comprising a tubular delivery body (5) with a
cylindrical rod (4) coaxially sliding, alternately, inside it by means of a double-acting
piston (2) so as to create an annular cavity connected to a source supplying adhesive
under pressure, said rod being provided with substantially conical obturator means
(8a) at its free end, characterized in that it comprises, coaxially with said conical
obturator (8a) and in the vicinity thereof, at least two sealing members consisting
of enlarged parts (10, 13), integral with said rod (4) and sliding inside chambers
or countersunk zones (11, 14) formed on the internal surface of the tubular body (5),
so as to seal off the end of the cavity only when the delivery device is closed and
prevent the entry of air into the cavity itself, there also being provided at the
opposite end of said annular cavity (6) at least another sealing member, consisting
of a cylindrical body (17), coaxial with said rod (4) and sliding inside a chamber
(16) of larger diameter (16) formed in the cylindrical body, below the aperture (7)
for introducing the supply of adhesive inside said cavity, so as to seal off said
supply aperture (7) and prevent the supply of adhesive to the cavity (6).
2. Delivery device according to Claim 1, characterized in that said two sealing members,
integral with the conical obturator, consist respectively of a frusto-conical body
or enlarged part (10) coaxial with said rod (4) and displaceable inside a chamber
(11) so as to ensure sealing by means of contact against a toroidal ring (12) coaxially
integral with the external surface of the conical body (12), and of a cylindrical
enlarged part (13), coaxial with the rod (4), displaceable inside a chamber (14),
designed to ensure sealing by means of insertion inside a cylindrical annular shoulder
(15) projecting coaxially from said cylindrical body (5), immediately above the displacement
chamber (14) of said enlarged part (13).
3. Delivery device according to Claim 1, characterized in that at least one toroidal
seal (18) is positioned at the end of said cylindrical rod, opposite to the metering
end, being designed to cooperate with the rod (2a) in order to prevent adhesive rising
up along the rod itself.
4. Delivery device according to Claim 1, characterized in that can be removably connected
to a source supplying adhesive under pressure via rapid-engagement connecting means
(20, 21) for facilitating a change in the type of adhesive.