WO1999062766A1 - Pasty material volumetric doser apparatus for filling purposes in a thermoform packaging line - Google Patents

Abstract

The doser apparatus comprises a dosing chamber (4) provided with a piston (5) which can be displaced by a pasty material (M) introduced from a first extremity (4a) of said chamber (4), from a first position (5A) to a second position (5B) and to be actuated by a pressure fluid (F) introduced through a second extremity (4b) to return to said first position (5A) thereby displacing a certain volume of pasty material (M) delimited between the positions (5A and 5B), said volume being ejected through the first extremity (4a) which is associated, with sealed closing means (3, 17), to a first opening (6a) of a housing (6) which contains a valve body (7) with means (19) for its actuation, the housing communicating through an inlet (1) with said chamber (4), and alternatively, said chamber (4) communicating with the outlet (2), in a direct face-to-face relationship; a pusher (20) is provided with means (21-26) to empty the body (7).

Description

 VOLUMETRIC MEASURING EQUIPMENT OF PASTRY MATTER FOR FILLING A PACKAGING LINE BY THERMOFORMATION

Field of the Invention

The present invention concerns a volumetric dosing apparatus of pasty material, especially for minced meat and the like, for filling a thermoforming packaging line, of the type comprising at least one dosing chamber, of known, adjustable capacity, capable of be filled and emptied cyclically, automatically, to form portions of identical volume and deposit them in thermoformed cavities that move in a conveyor belt below said chamber.

Background of the Invention

Some apparatus for volumetric dosing of this type are known in the state of the art, mention may be made of Patent WO 9014578, in which a machine is described which includes a dosing chamber with an inlet and an outlet at one of its ends. Said dosing chamber is provided inside a distributor to alternately communicate said chamber with said inlet and with said outlet, and of a plunger capable of being freely displaced by the effect of the pressure exerted by a pasty matter introduced to the chamber of dosing by means of a feeder, a pump or the like, through said inlet and said distributor in the inlet position. The aforementioned free travel of the piston goes from a first position to a second position, preset by a stop, precisely adjustable using a spindle system, which defines the volume to be dosed. Then said piston is driven in the opposite direction, by means of compressed air, being forced to return to said first position by displacing the dosed volume of pasty matter through said distributor in a position of communication with said outlet, from where it is capable of being collected in a container, or sausage. Said apparatus has pneumatic means that lift the entire dosing chamber in order to allow access to the alternative distributor for periodic extraction, cleaning and / or inspection.

The apparatus described above is fully effective in terms of formation of portions of the same volume, but, nevertheless, has the disadvantage of performing the expulsion of the portions in a horizontal direction, inappropriate for filling thermoformed cavities arranged on a continuous conveyor belt. Another drawback lies in the low production capacity of said apparatus due to the existence of a single dosing chamber, especially considering that the conveyor belt admits, thanks to its width, multiple longitudinal rows of thermoformed cavities.

Finally, it should be noted that the system of accessing the alternative distributor, lifting large parts and supporting them in an elevated position, has several drawbacks; first, relatively powerful fluidomechanical means are required to perform said operation; and secondly, any failure in said fluidomechanical means while accessing the distributor can cause the supported parts to descend, which directly implies an accident risk for the manipulator operator.

Brief exposition of the invention

Therefore, it is an objective of the present invention to provide a volumetric dosing apparatus of pasty material for filling a thermoforming packaging line, provided with multiple outlet openings for the dosed portions positioned vertically downwards, mounted on a support liable to be placed above a conveyor belt, so that said outlet openings are facing and close to thermoformed cavities arranged thereon.

Another object of the invention is to provide an apparatus of the type referred to with means for accessing the distributor mechanism that are simple, easy to handle and safe for the operator.

These objectives are achieved, in an apparatus according to the present invention, by vertically arranging one or more dosing chambers provided with a pusher and a piston inside, served by an alternative distributor provided with a single rotating valve body, actuated by means own, in an independent accommodation of the dosing chambers and located orthogonally below them. Said valve body, in cooperation with corresponding conduits communicated with said housing, is capable of conducting a pasty material introduced by an external feeder through an inlet arranged in an axial position towards the inside of the dosing chambers and, successively and alternately , driving the pasty matter inside the dosing chambers, pushed by pneumatic means, to as many outlets located in the lower part of said housing of the valve body, aligned with said chambers.

Because the extraction of the volume of dosed pasty matter is carried out through the ducts formed by the valve body, the apparatus of the invention has a combined system formed by pistons for the extraction of the volume portions of the interior of the chambers. , which correspond to the doses themselves, and of some pushers to completely empty the sections inside the valve body. To this end, said pushers are provided with stems that protrude through the upper end of the dosing chambers while the plungers are provided with central holes through which they can freely slide along a portion of said stems. The upper ends of all said rods are fixed to a plate provided with a sliding slide inserted in a second rod topped by both ends by two stops. A pneumatic cylinder moves a pneumatic clamp capable of grasping said plate to force, through their respective rods, the pushers to individually carry out the said path through the interior of the valve body, and to release said plate to allow said pushers, together with their corresponding plungers, make their joint route through the inside of their corresponding dosing chambers, displaced by the pressure of the pasty matter during filling, and impelled by compressed air injected by the upper end of said chambers during emptying.

When the pushers, together with the corresponding pistons, initiate the travel portion through the inside of the dosing chambers, the said plate, released from said clamp, makes contact with the upper stop of the second rod by dragging it in its path until the said one bottom stop makes contact with a block located in a predetermined position, precisely adjustable by means of a spindle driven by an electric motor. The distance corresponding to the path between the two stops, in combination with the inner diameter of the chambers of dosage, it determines the volume of the portions of pasty matter formed, therefore being able to regulate and predetermine with precision said volume regulating the position of said block.

The materialization of the housing of the valve body and its corresponding ducts and openings is carried out by means of a block fixed in a cantilever to a side cabinet, adjustable in height and provided with rolling feet, on which block a carrier base plate is hinged on a hinge. said dosing chambers with all their corresponding mechanisms, covered by a housing. Said block incorporates airtight fixing means for said plate in the working position, as well as a cover on one end also hinged and provided with sealing means. Said side cabinet incorporates a pneumatic cylinder for actuating the valve body, as well as electrical and pneumatic circuits with their corresponding control devices.

With this arrangement, the apparatus of the present invention is capable of being positioned so that its dosing head is above a conveyor belt, with said outlet openings facing and close to thermoformed cavities arranged thereon, for filling, the Dosed portion formation cycles synchronized with stop and advance cycles of said conveyor belt. These and other features of an apparatus according to the present invention, as well as its operation, will be more apparent from the detailed exposition thereof with references to the attached drawings, which are provided solely for the purpose of illustrating a possible embodiment. of the present invention, so they should not be construed as limiting. In the attached drawings:

Brief exposition of the invention

Fig. 1 is a general perspective view of an apparatus according to the invention; Fig. 2 is a cross-section, according to a conventional 90 ° plane of Fig. 3, of an apparatus according to the present invention; Fig. 3 is a cross-section, according to a conventional 90 ° plane of Fig. 2, of an apparatus according to the present invention; Figs. 4 and 5 are enlarged detail views of the assembly of the valve body and the dosing chambers in an apparatus according to the invention; Y Figs. 6 to 9 are schematic cross sections illustrating a sequence of the different phases of the operation of the present apparatus. For greater clarity in the drawing some elements have been represented with their most separate positions, and even some have been removed.

Detailed explanation of some execution examples

Referring, in the first place, to Fig. 1, a block linked to dosing chambers 4 (see also the remaining figures) can be seen, provided with connection means 47 to be fixed in cantilever to a side housing 41 mounted on a pair of feet 42, provided with wheels 43, capable of keeping the assembly in stable balance leaving ample space between said feet 42 and the outlet mouths of the outlet ducts 2, said housing incorporating said cylinder 19 for actuating the valve body 7, electrical circuitry and dynamic fluid elements (not shown) with corresponding control elements thereof and means 44, 45 for regulating the position of said block 9 in height so that it can be positioned above and next to containers A formed in a self-transported band B, which is an integral part of a packaging line, for example, by thermoforming. Said means for regulating the position of said block 9 in height consist of fixing elements 44 fixed to a first portion 41a, associated with said at least one foot 42, of the housing 41, in cooperation with elongated holes 45 formed in a second portion 41b, carrier of said block 9, of the housing 41, and because it includes a cover 46 for protecting the dosing chambers 4 and mechanisms associated therewith 21-35.

In Figs. 2 to 5 there is shown a part of said apparatus that includes a pair of dosing chambers 4, of axial development, each provided inside of a piston 5 that can move between a first position 5 A (see also the sequence illustrated in Figs. 6 to 9) and a second position 5B, said chambers 4 being associated, by a first end 4a, with sealing means 17, 36, to a passage duct 3 leading to a first opening 6a of a housing 6 that houses a valve body 7, whose housing 6 has a second opening 6b connected to an inlet duct 1 of pasty matter M, and a third opening 6c, directly facing the first opening 6a, connected to an outlet duct 2 of pasty material M. A fluid dynamic cylinder 19 is arranged to move said valve body 7 into said housing 6 so that said second opening 6b is communicated therethrough with said dosing chamber 4, and successive and in turn, said dosing chambers 4 with said first 6a and third 6c openings.

The dosing chambers 4 each include a pusher 20 that moves together with the plunger 5 in the path, in both directions, between its first 5A and second 5B positions. Said pusher 20 is further provided with means 21-26 for individually displacing it between a first position 20 A, adjacent to the first position 5 A of the plunger 5, and a second position 20B, flush with the mouth of the outlet duct 2 , crossing in said path the passages 3 and outlet 2 and the valve body 7.

Said housing 6 is embodied in a block 9, which includes said passageways 3 and outlet 2 and second opening 6b communicated with said housing 6, an articulation 16, such as a hinge, for a base plate 18 of said dosing chambers 4 , provided with appendages 35 to cooperate with a closure 17 to immobilize said chamber 4 in a working position, pressing elastic sealing joints 36 between said base plate 18 of the chambers 4 and said block 9. A hinge 37 is also provided. for a cover 38 of said second opening 6b, provided with a hole 38a for said inlet conduit 1, and a closure 39 to immobilize said cover 38 in a closed position, pressing an elastic sealing gasket 40 between said cover 38 and said block 9.

Said valve body 7 is cylindrical and is provided on its periphery with a recess 10 that communicates through a passage 11 with an opening 12 located at one of its bases, also including, for each dosing chamber 4, a transverse orifice 13 , through, which does not interfere with said recessed 10, so that said valve body 7 is capable of rotating alternately inside its housing 6 driven by said dynamic fluid cylinder 19, with the opening 12 continuously facing the inlet opening 6b, between a first position 7A, in which the recess 11 is facing the first end 4a of the dosing chambers 4, and a second position 7B in which the transverse orifices 13, are aligned on one side, with said chambers of dosing 4 through said passages 3, and on the other with said outlet ducts 2, forming some sections, straight and uniform, of evacuation ducts through which the pushers 20 move to complete the transfer of a volume of pasty matter M, dosed, to each of said cavities A, thermoformed in a transverse row of a band B which moves below and near the mouth of said outlet duct 2.

Said means for actuating said pusher 20 include a first rod 22, coaxial to the axis of chamber 4, bearer at one end of pusher 20 and joined at its other end, protruding from the second end 4b of chamber 4, at a plate 24 that includes a slide 25 that slides freely along a first portion 23a of a second rod 23, parallel to the first rod 22, the length of said first portion 23a being equal to the distance between the first 20A and second positions 20B of said pusher 20 in its path within the valve body 7, a dynamic fluid cylinder 21 provided with a rod 21a, with a stroke equivalent to said first portion 23a, bearing at its end of a dynamic dynamic clamp 26 capable of holding the plate is provided. 24 to force the pusher 20 to travel between its first 20A and second 20B positions, and vice versa, through the valve body 7 in its second position 7B under the action ón of said cylinder 21, and of releasing said plate 24 to allow the pusher 20 together with the plunger 5 to make its joint travel between the first position 5 A and the second position 5B, pushed by the effect of said pressure of the pasty matter M entering through the inlet duct 1, with the valve body 7 in its first position 7A, and the said reverse path driven by a pressurized fluid F introduced by the second end 4b of the chamber 4 and with the valve body 7 in its second position 7B. The piston 5 (see enlarged detail of Fig. 3) has a central hole

5c through which said first rod 22 slides freely inserted, said piston 5, both on its periphery and inside the central hole 5c, having elastic seals 27 of dynamic sealing with the inner wall of the chamber 4 and with the first stem 22 respectively. In order to delimit the volume to be dosed, said second rod 23 includes a second sliding portion 23b capable of sliding inserted inside a hole of a block 29 fixed in a predetermined position, adjustable, by means of a spindle 30, parallel to the second rod 23, driven by a motor 31, and because said first portions 23a and second 23b incorporate respective first 32 and second 33 stops at their respective free ends, so that the slide 25, in its displacement due to the filling of the chamber 4, interferes with the first stop 32 by dragging to the second rod 23, which travels until the second stop 33 contacts said block 29 delimiting the second position 5B of the piston 5 accompanied by the pusher 20, a third rod, fixed, parallel to the spindle 30, may be provided on which You can slide inserted block 29 to cooperate in your guidance.

The first position 5A of the piston 5 is delimited by a shoulder 28 formed by the slightly smaller diameter of the passageway 3 communicated with the housing 6.

The apparatus includes an end-of-stroke detector 48 of said plunger joint travel 5 with the pusher 20, which sends a signal to stop the entry of pasty matter M through the inlet conduit 1, to move the valve body 7 of the first position 7 A to the second position 7B, and activate the entrance of the pressurized fluid F through the second end 4b of the dosing chamber 4.

The phases that make up a cycle of dosing and filling of containers are the following: Fig. 6 illustrates a phase in which the piston 5, together with the pusher 20 moves inside the chamber 4 under the effect of pressure exerted by a pasty matter introduced from the inlet conduit 1 through the valve body 7 in position 7A. Said pasty matter is in direct contact with the pusher 20, which carries with it the piston 5 and the first rod 22, which is integral with the plate 24 carrying the slide 25 which contacts the stop 32 by dragging the second rod 23. The second rod 23 slides inside a hole of a block 29, fixed in a predetermined position by means of a spindle 30 driven by a motor 31, until the stop 33 of said rod 23 makes contact with said block 29 (Fig. 7 ), delimiting the second position 5B of the piston 5. At this time the entry of pasty matter is stopped by the inlet conduit 1 and the valve body 7 rotates inside its housing 6 to adopt the second position 7A.

The injection of a pressurized fluid, preferably air, is then started at the second end 4b of the chamber 4, so that the piston 5 is moves towards the first end 4a by dragging the pusher 20 and the rods first 22 and second 23, until said piston 5 abuts the shoulder 28 at the first end 4a of the chamber 4, which delimits the first position 5A of the piston 5 (Fig. 8). The volume delimited by the inner diameter of the chamber 4 and the distance between said first 5A and second 5B positions constitutes the exact dose of the portions to be packaged. Said distance is determined by the position of the block 29, and coincides with a second portion 23b of the second rod 23 that slides inside a hole of said block. Next, a pneumatic cylinder 21, whose rod 21a is a carrier of a pneumatic clamp 26 that closes by gripping the plate 24, forces the rod 22, carrier of the pusher 20, to move inside the valve body 7 and through the ducts of step 3 and outlet 2, from a first position 20A adjacent to the first position 5 A of the plunger 5, to a second position 20 B flush with the mouth of the outlet duct 2 (Fig. 9), completing the transfer of the material paste M to the container A of the conveyor belt B located below and next to said mouth of the outlet duct 2. In this path, the slide 25, integral with the plate 24, slides over the first portion 23a of the second rod 23.

Then, said cylinder 21 returns the pusher 20 to its first position 20A and the clamp 26 releases the plate 24, the apparatus being arranged to start a new cycle.

Claims

CLAIMS 1.- Volumetric dosing device of pasty material for filling a thermoforming packaging line, which includes a dosing chamber (4), axially developed, provided inside a piston (5) capable of being freely displaced by a pasty matter (M), introduced by a first end (4a) of said chamber (4), from a first position (5 A) to a second position (5B) and then be operated in the opposite direction, by a fluid under pressure (F) introduced from a second end (4b) of the chamber (4), to return to said first position (5A), displacing a metered volume of pasty matter (M) delimited between positions (5A) and (5B ) to expel it through said first end (4a), characterized in that said chamber (4) is associated by said first end (4a), with hermetic closing means (17, 36), to a passageway (3) leading to a first opening (6a) d and a housing (6) housing a valve body (7), whose housing (6) has a second opening (6b) connected to an inlet duct (1) of pasty material (M), and a third opening ( 6c), directly facing the first opening (6a), connected to an outlet duct (2) of pasty material (M), means (19) being provided for moving said valve body (7) into said housing ( 6) so that said second opening (6b) is communicated therethrough with said dosing chamber (4), and successively and in turn, said dosing chamber (4) with said first (6a) and third (6c) openings, and because said dosing chamber (4) includes a pusher (20) that moves together with the plunger (5) in the path between the first (5A) and second (5B) positions thereof, and vice versa, provided with means (21-26) to move it further, individually, between a first position (20 A), adjacent to the first position (5 A) of the piston (5), and a second position (20B) flush with the mouth of the outlet duct (2), passing through said passage (3) and outlet ducts (2) and the valve body (7 ). 2. Volumetric dosing apparatus according to claim 1, characterized in that said chamber (4) is hinged with respect to the housing (6), being capable of tilting to give access to said housing (6), valve body (7 ) and dosing chamber (4) for cleaning and / or extraction. 3. Volumetric dosing apparatus according to claim 1, characterized in that it includes a block (9), which defines said housing (6); said ducts of step (3) and exit (2) and second opening (6b) communicated with said housing (6); a joint (16), such as a hinge, for a base plate (18) that extends the mouth of said dosing chamber (4), provided with appendages (35) and / or openings to cooperate with closures (17) to immobilize said chamber (4) in a working position, by pressing an elastic sealing gasket (36) between said base plate (18) of the chamber (4) and said block (9); a hinge (37) for a cover (38) of said second opening (6b), provided with a hole (38a) for said inlet conduit (1); and a closure (39) to immobilize said cover (38) in a closed position, by pressing an elastic sealing gasket (40) between said cover (38) and said block (9). 4. Volumetric dosing apparatus according to claim 3, characterized in that said valve body (7) is cylindrical and is provided on its periphery with a recess (10) that communicates through a passage (11) with an opening (12 ) located in one of its bases, also including a transverse orifice (13), which does not interfere with said recessed (10), so that said valve body (7) is capable of rotating alternately inside its housing ( 6) actuated by said means (19), such as a fluid dynamic cylinder, with the opening (12) continuously facing the inlet opening (6b), between a first position (7A), in which the recess (11) is facing the first end (4a) of the dosing chamber (4), and a second position (7B) in which the transverse, through hole (13) is aligned on one side, with said dosing chamber (4) a through said passage duct (3) and on the other with said duct of exit (2), forming a straight and uniform section of evacuation duct through which the pusher (20) moves to complete the transfer of a volume of pasty matter (M), dosed, to a thermoformed cavity (A) in a band (B) that moves below and near the mouth of said outlet duct (2). 5. Volumetric dosing apparatus according to claim 4, characterized in that said means for actuating said pusher (20) include a first rod (22), coaxial to the axis of the chamber (4), carrier at one end of the pusher (20) and joined by its other end, which protrudes from the second end (4b) of the chamber (4), to a plate (24) that includes a slide (25) that slides freely along a first portion (23a) of a second rod (23), parallel to the first rod (22), the length of said first portion (23a) being equal to the distance between the first (20A) and second (20B) positions of said pusher (20) in its travel inside the valve body (7), a dynamic fluid cylinder (21) provided with a rod (21a), with at least equivalent stroke being provided to said first portion (23a), carrier at its end of a dynamic fluid clamp (26) capable of holding the plate (24) to force the pusher (20) to travel between its first (20A) and second (20B) positions , and vice versa, through the valve body (7), being in its second position (7B), and releasing said plate (24) to allow the pusher (20) together with the plunger (5) to make its joint travel between the first position (5 A) and the second position (5B), pushed by the effect of said pressure of the pasty matter (M) entering through the inlet duct (1) with the valve body (7) in its first position (7A), and the aforementioned reverse path driven by a pressurized fluid (F) introduced by e The second end (4b) of the chamber (4) and with the valve body (7) in its second position (7B). 6. Volumetric dosing apparatus according to claim 5, characterized in that the piston (5) has a central hole (5c) through which said first rod (22) freely slides, said piston (5), both in its periphery as inside the central hole (5c) of elastic seals (27) of dynamic sealing with the inner wall of the chamber (4) and with the first rod (22) respectively. 7. Volumetric dosing apparatus according to claim 6, characterized in that said second rod (23) includes a second portion (23b) capable of sliding inserted inside a hole of a block (29) fixed in a predetermined position, adjustable , by means of a spindle (30), parallel to the second rod (23), actuated by an actuator (31), and because said first (23a) and second (23b) portions incorporate respective first (32) and second (33) stops at their respective free ends, so that the slide (25), in its displacement due to the filling of the chamber (4), interferes with the first stop (32) by dragging, once the plate (24) is released, to the second rod (23), which travels until the second stop (33) contacts said block (29) delimiting the second position (5B) of the piston (5) accompanied by the pusher (20), a third rod being optionally provided, fixed, parallel to the spindle (30), on which you can slide inserted the block (29) to cooperate in its guidance. 8. Volumetric dosing apparatus according to claim 7, characterized because the first position (5A) of the piston (5) is delimited by a shoulder (28) formed by the slightly smaller diameter of the passageway (3) communicated with the housing (6). 9. Volumetric dosing apparatus according to any one of claims 3 to 8, characterized in that it includes a limit switch (48) of said plunger joint travel (5) with the pusher (20) that sends a signal to stop the entry of pasty matter (M) through the inlet duct (1), to move the valve body (7) from the first position (7 A) to the second position (7B), and activate the fluid inlet to pressure (F) at the second end (4b) of the dosing chamber (4). 10. Volumetric dosing apparatus according to any one of claims 3 to 9, characterized in that it integrates at least two dosing chambers (4) with their respective mechanisms operated in unison, associated with a single housing (6) provided with a single second opening (6b) communicated with a single inlet duct (1) and with so many first (6a) and third (6c) openings, communicated with as many respective passageways (3) and outlet (2) as dosing chambers (4 ) are willing. 11. Volumetric dosing apparatus according to claim 10, characterized in that said at least two chambers (4) are connected to a single base plate (18) articulated to a single block (9), which defines a single housing (6) which includes a single second opening (6b) communicated with said housing (6), and as many passage passages (3) and exit ducts (2) as dosing chambers (4) are arranged, also including; an articulation (16), such as a hinge, for said base plate (18) of said dosing chamber (4), provided with appendages (35) and / or openings to cooperate with closures (17) to immobilize said chambers (4) in a working position, by pressing, between said base plate (18) and said block (9), an elastic seal (36) for each chamber (4) arranged; a hinge (37) for a cover (38) of said second opening (6b), provided with a hole (38a) for said inlet conduit (1); and a closure (39) to immobilize said cover (38) in a closed position, by pressing an elastic sealing gasket (40) between said cover (38) and said block (9). 12. Volumetric dosing apparatus according to claim 11, characterized in that it includes a single valve body (7) with a single recessed (10) communicated through a passage (11) with a single opening (12) located at one of its bases, the only one being recessed (10) capable of covering the first ends (4a) of all the cameras (4) arranged, including also so many transverse holes (13), through, as dosing chambers (4) are arranged, said valve body (10) being operated by a single dynamic fluid cylinder (19). 13. Volumetric dosing apparatus according to claim 12, characterized in that each of the pusher stems (22) corresponding to said at least two dosing chambers (4) are connected to a single plate (24) with a single slide (25) linked to a single second rod (23), a single dynamic fluid cylinder (21) bearing a single dynamic fluid clamp (26) capable of holding the plate (24), and a single block (29) regulated by a single spindle (30) driven by a single actuator (31) and guided by a single fixed third rod (34). 14. Volumetric dosing apparatus according to any one of claims 3 to 13, characterized in that said block (9), linked to one or more dosing chambers (4), is provided with joining means (47) to be fixed in cantilever to a lateral housing (41) mounted on at least one foot (42) provided with wheels (43) capable of keeping the assembly in stable balance leaving ample space between said at least one foot (42) and the mouth or mouths of output of the one or more outlet ducts (2), said housing incorporating said cylinder (19) for actuating the valve body (7), electric circuitry and dynamic fluid elements with corresponding control elements thereof and means for regulating the position of said block (9) in height so that it can be positioned above and next to containers (A) formed in a self-transported band (B), which is an integral part of a line of packaging for example by thermoforming. 15. Volumetric dosing apparatus according to claim 14, characterized in that said means for regulating the position of said block (9) in height consist of fixing elements (44) integral with a first portion (41a), associated with said minus one foot (42), of the housing (41), in cooperation with elongated holes (45) formed in a second portion (41b), carrier of said block (9), of the housing (41), and because it includes a protective cover (46) for the dosing chambers (4) and mechanisms associated therewith (21-35).