WO2007015284A2

WO2007015284A2 - Salt spreader

Info

Publication number: WO2007015284A2
Application number: PCT/IT2006/000571
Authority: WO
Inventors: Roberto Piazzi
Original assignee: Studio Tecnico Piazzi Di Piazzi Geometra Roberto E C. S.A.S.
Priority date: 2005-08-04
Filing date: 2006-07-26
Publication date: 2007-02-08
Also published as: EP1913200A2; WO2007015284A3; ITBO20050522A1

Abstract

The salt spreader comprises a chassis (10) suited to be drawn by a towing vehicle, on which are fitted a reservoir (12) suited to contain a liquid solvent and a dump cistern (13), provided at the bottom with conveying means (17) for feeding the salt to spread. The cistern (13) is locked by a hatch (14) shaping a container (15) suited to contain leak-proof a further substance to spread and carries a distribution assembly (30) for the salt. A motor unit (34) with hydraulic operation controls the functioning of the conveying means (17) and of the distribution assembly (30) for distributing the salt. With the motor unit (34) is associated a proportionality device (35) suited to control the distribution of the substances to spread depending on the speed of the spreader.

Description

SALT SPREADER Technical field

[0001] The present invention relates to a salt spreader for spreading salt on the roads.

Background art

[0002] It is known that in winter dangerous ice layers may form on the roadbed as a consequence of snowfalls and sudden temperature reductions. In order to prevent the formation of such ice layers it is a common practice to have resort to road vehicles suited to spread on the roadbed suitable amounts of sodium chloride which, as it is well-known, lowers the water melting temperature so as to prevent any ice formation.

[0003] Such vehicles, commonly called salt spreaders, are substantially constituted by a lorry provided with a tank containing the salt to spread and presenting at the bottom of the tank a salt feeding device, for example of conveyor belt type. The tank is usually fitted on the body of a tractor of traditional type. At a rear portion the vehicle carries overhanging a salt distribution assembly provided with sensors suited to detect the feed speed of the vehicle in process of working. These sensors control the operation of hydraulic actuators comprising one hydraulic pump at least, suited to operate the distribution assembly in order to regulate the amount of salt to spread in relation to the speed of the lorry. The cited sensors usually comprise electronic components which however prove scarcely reliable at the very temperature and humidity conditions at which the salt spreaders are usually used.

[0004] In order to prevent effectively any ice formation, it is a known practice as well to distribute cyclically suitable amounts of humidified salt, that is mixed with calcium chloride at the liquid state. Furthermore calcium chloride at the liquid state is distributed in case of abundant snowfalls by means of machines provided with proper sprayers. In order to do so, specially equipped salt spreaders are needed.

[0005] Besides preventing the formation of ice layers through sodium chloride, in case of abundant snowfalls it is sometimes necessary to intervene urgently for dissolving already formed sheet ice which may prove very dangerous. Such emergency treatments consist in the localized distribution of a mixture suited to dissolve ice immediately, containing salt and calcium chloride at the solid state which is mixed with salt at a percentage of nearly 15-20%. Such mixture of salt and calcium chloride can' t be stored on the salt spreader because humidity would rapidly cause the formation of unserviceable compact blocks which could compromise the function of the distribution assembly. Therefore, when needed, the salt spreader has to be taken to the place where the calcium chloride is stored and supplied, the mixture has to be prepared, loaded on the spreader and shortly distributed on the interested areas.

[0006] This drawback proves particularly sensible because the roadbed, mostly in the motorway stretches, is preferably made of open-cell asphalt of draining type. This type of asphalt proves advantageous in case of rainfalls, because it helps the water draining, but on the contrary proves disadvantageous in case of abundant snowfalls. In fact the conformation itself of the draining asphalt allows the penetration of the snow inside the open cells, thus risking the immediate ice formation when the temperature lowers. This is also due to the contributory effect of the dragging and compression action exerted by the blades of the common snowploughs used as first intervention to remove the surface ice layer.

[0007] After the distribution of the mixture of salt and calcium chloride which is necessary to dissolve the formed sheet ice, salt is spread anew by another salt spreader so as to prevent any further formation of sheet ice.

[0008] After all that, it is evident that for preventing and contrasting effectively the ice formation on the roads a wide fleet of road vehicles is presently needed, differently equipped depending on the specific task, at notable managing charges. It is obvious that such vehicles often represent a tied up capital because they are usually used now and then, substantially only at the climatic conditions which require their use.

Disclosure of the invention

[0009] The aim of the present invention is to overcome the cited drawbacks, by devising a salt spreader which enables to perform all the different actions required for the prevention and the treatment of any ice formations on the roadbed.

[0010] Within this aim it is a further scope of the claimed invention to devise a salt spreader of simple conception, reliable function and versatile use, as well as provided with an easy and effective quantitative control of the supplied substances. [0011] The cited aims are achieved according to the claimed invention by a salt spreader comprising a chassis provided with a couple of independent wheels at least and suited to be drawn by a towing vehicle, which is characterized in that it comprises a reservoir fitted on said chassis and suited to contain a liquid solvent, for example calcium chloride at the liquid state; a dump cistern fitted on said chassis behind said reservoir, and provided at the bottom with conveying means for supplying the salt to spread; a hatch for the rear locking of said cistern, suitable for defining an opening for the discharge of the salt to spread at said conveying means and shaping a container suited to contain leak-proof a further substance to spread, for example calcium chloride in the solid state; a distribution assembly for the salt supplied by said cistern, carried by said hatch; a motor unit with hydraulic operation suited to drive the functioning of said conveying means, of said salt distribution assembly and of suppliers for said further substance to spread and for said liquid solvent; a proportionality device associated with said motor unit, suitable for controlling the distribution of the substances to supply depending on the velocity of said independent wheels.

Brief description of the drawings

[0012] Description details of the invention shall be further evident in the illustrations of a preferred embodiment of the salt spreader illustrated in the guideline drawings attached, wherein:

[0013] fig. 1 illustrates a side view of a the salt spreader according to the claimed invention;

[0014] fig. 2 illustrates the same side view of the machine in a different operational phase;

[0015] fig. 3 illustrates an enlarged side view of a rear portion of the same spreader;

[0016] fig. 4 illustrates a rear view of the cited dump cistern used in the same spreader;

[0017] fig. 5 illustrates a functional diagram of the same spreader;

[0018] fig. 6 and 7 respectively illustrate an axial cut-away view of a spraying device in different operational phases;

[0019] fig. 8 illustrates a schematic cross-section of said spraying device;

[0020] fig. 9 illustrates a functional diagram of a sprayer installation provided with a plurality of spraying devices according to the claimed invention.

Best mode for carrying out the invention [0021] With reference to such figures 1 refers to the salt spreader. The salt spreader 1 is substantially constituted by a semitrailer suited to be drawn on the road by a conventional towing vehicle or tractor, which for simplicity is not illustrated.

[0022] The salt spreader 1 provides for a chassis 10 provided with a couple of independent wheels 11 at a rear axle. The chassis 10 defines a platform suited to be articulated to the tractor, as illustrated in detail later on. On the platform 10 is fitted frontally a reservoir 12 suited to contain a suitable liquid solvent, for example liquid calcium chloride. At the back of the reservoir 12 on the platform 10 is fitted a dump cistern 13, open on the upper part, suited to contain a solid substance to spread, in particular a salt of the type of the sodium chloride. The cistern 13 is pivoted to the chassis 10 at its rear end and is suited to be lifted by suitably driven actuators 66. The cistern 13 is closed at the back by a hatch 14 suited to define internally a leak-proof container 15 suitable for the containment of a further substance, for example solid calcium chloride, which has to be protected against the outer atmospheric agents, mainly against humidity.

[0023] The substances contained inside the reservoir 12, the cistern 13 and the leak- proof container 15 are suited to be suitably distributed on the roadbed while the towing vehicle drawing the spreader 1 goes forward.

[0024] In particular the reservoir 12 supplies the liquid solvent which is suited to be sprayed on the roadbed by sprayer devices 100 fed by a displacement pump 33 provided on the spreader 1 , described in detail later on.

[0025] The cistern 13 is provided at its lower part with conveying means 17 of the conveyor belt type, whose control is described later on. The conveyor belt 17 is wound around a couple of drums 16 suited to be suitably operated in order to convey the salt through a discharge opening 18 defined at the lower part of the hatch 14 at an end portion of the conveyor belt 17. The opening 18 so defined is provided with a transversal slit 60 for the homogeneous distribution of the salt (see fig. 3). The height of the opening 18 is mechanically adjustable by means of a doser 61 constituted by a transversal roller 62 carried revolving by an oscillating frame 63 fixed at the hatch 14. Owing to the oscillation of the oscillating frame 63 the roller 62 can be suitably positioned between a lifted position at which it does not interfere with the opening 18 and a lowered position of complete blockage of the same opening 18.

[0026] On-stream the conveyor belt 17 is tensioned by a tensioner 70 acting suitably on the drums 16. In the same on-stream condition the belt 17 is fixed at the lower part of the cistern 13 by means of a supporting frame 67 (see fig. 4). To be more precise, the supporting frame 67 is pivoted on one side to the cistern 13 on a longitudinal pin 68, on the opposite side is fastened to it by means of releasable fixing pins 69. Actuators 71 are connected to the cistern 13 and to the supporting frame 67 in order to operate suitably the oscillation of the frame 67 between a horizontal working position and a position rotated externally to the cistern 13, suited to allow the substitution of the belt 17 (see fig. 4) upon release of the fixing pins 69.

[0027] The leak-proof container 15 shapes at its lower part a discharge tube 19 suited to be suitably locked by a gate 20 operated by actuators 21. To be more precise, in the working phase the discharge tube 19 is positioned above the end portion of the belt 17 downstream to the described opening 18.

[0028] Furthermore, upstream to the discharge tube 19, the container 15 shapes a reduction 22 of its cross-section, where is preferably positioned a feeding unit 23 of the rotating auger type, suited to convey the solid calcium chloride centrally towards the discharge tube 19. This feeding unit 23 is suited to be suitably operated by control means 24 which are described in detail later on. At its top the container 15 provides an opening for the supply of calcium chloride, provided with a leak-proof closing device 25, for example of the manhole type.

[0029] The hatch 14 provides at its top for a horizontal pin 26 for the articulation to the cistern 13. Upon control of actuators 27 the hatch 14 is suited to be carried oscillating between a vertical closing position (visible in fig. 1) against a frontal portion 29 of the cistern 13 and a rotated position at which such frontal portion 29 of the cistern 13 appears open (fig. 2). Sealing elements 28 are opportunely provided, which are positioned along a perimetrical area of the hatch 14, suitable for coming in contact with the frontal portion 29 at the cited closing position.

[0030] The solid calcium chloride contained inside the container 15 and the salt coming from the cistern 13 are suited to be distributed on the roadbed, in a separate or disjoint way, by a distribution assembly 30 carried by the hatch 14 itself. The distribution assembly 30 comprises a rotor 31 suited to exert a centrifugal action on the substances falling from the opening 18 and/ or from the discharge tube 19. Such centrifugal action is suited to cause the sprinkling of the substances depending on the angular rotational velocity of the rotor 31. The vertical positioning of the rotor 31 is adjustable by means of a specially provided actuator 64, so as to vary its distance from the roadbed.

[0031] In addition, in order to help the inflow of the salt and/or of the calcium chloride among the blades of the rotor 31 , the distribution assembly 30 comprises specially provided fixed conveyors 65 usually provided in combination with cleaning means acting on the conveyor belt 17. The distribution assembly 30 is operated, as described later on in detail, by driving means 32 of hydraulic type.

[0032] The operation of the conveyor belt 17 which supplies the salt, of the control means 24 for the supply of solid calcium chloride and of the distribution assembly 30, as well as of the displacement pump 33 intended for the distribution of liquid calcium chloride is performed by a motor unit 34 of hydraulic type suited to be advantageously driven by the feed motion of the independent wheels 11 (fig. 5).

[0033] The motor unit 34 is suitably associated with a proportionality device 35 intended to adjust the distribution parameters of the different substances. As described later on in detail, the proportionality device 35 provides for a control unit to which a plurality of operating items are associated.

[0034] The motor unit 34 is directly associated with the rotational motion of the independent wheels 11 , in case by the interposition of multipliers of the angular velocity. The motor unit 34 comprises a first pump 36 and a second pump 37 of the variable-displacement type, preferably of the type known under the commercial name " load sensing" , having a constant hydraulic flow regardless of the rotational velocity of the wheels 11.

[0035] In practice the pumps 36, 37 are respectively provided with a plate-shaped impeller 38 with adjustable inclination upon control of the proportionality device 35. Such adjustment is effected by specially provided valves 6, 7 for example of the proportioning type, upon control of proper electrical signals coming from the proportionality device 35.

[0036] The first pump 36, which preferably has a displacement greater than the second pump 37 has, is suited to drive the conveyor belt 17, the displacement pump 33 and a second displacement pump 40 for the salt humidification. Such operations are effected by the interposition of a suitable speed changer 41 and drive means 42. [0037] The speed changer 41 comprises a couple of input shafts driven suitably by respective motor drives 43 of hydraulic type suited to transmit the motion to an output shaft 44 according to preset gear ratios, determined by the rotational direction to which are selectively driven the motor drives 43 themselves. The motor drives 43 are supplied by a distributor 45 of electrical type directly supplied by the first pump 36 and connected to the proportionality device 35.

[0038] The drive means 42 comprise a first pulley 46 suited to be suitably put into gear with the output shaft 44 upon control of a pneumatic drive. Through flexible drive means, for example of belt type, the first pulley 46 is suited to transmit the rotational motion of the shaft 44 to a respective pulley connected with the displacement pump 33.

[0039] Furthermore the output shaft 44 is connected with a second pulley 47 which can be put into gear pneumatically for the connection with the second displacement pump 40 intended for the salt humidification.

[0040] The shaft 44 is connected to a third pulley 48 which can be put into gear pneumatically for the motion transmission to the drum 16 of the conveyor belt 17 by means of belt drive means. A reduction gear 49 is preferably interposed.

[0041] The drum 16 is fitted on a shaft 50 carrying at one end a wheel 51 suited to transmit the rotational motion to the feeding unit 23 of the solid calcium chloride contained in the container 15. The wheel 51 is suited to be engaged by a mating wheel 52 carried oscillating by an arm 53 pivoted on an axis 54 to which the rotating auger-type feeding unit 23 is coupled. The mating wheel 52 results connected to the axis 54 by means of belt means 55 wound suitably around pulleys 56 keyed on the axis 54.

[0042] The arm 53 is carried oscillating by the hatch 14 and operated by drive means 57 of pneumatic type between a lowered position at which the mating wheel 52 engages the wheel 51 (as visible in fig. 5) and a lifted position at which the wheels 51, 52 are disengaged. The drive means 57 further provide for driving that the pulleys 56 put into gear.

[0043] On the contrary the second pump 37 is suited to drive the driving means 32 of the rotor 31 for the distribution of the dry or humidified substances on the roadbed.

[0044] The control unit of the proportionality device 35 comprises a plurality of operating items acting on respective switches for the selection of the distribution parameters of the substances to supply.

[0045] A first operating item 58 of the control unit is intended for the selection of a value for the distribution width of the jet produced by the supplied substances. In particular, the first operating item 58 is suited to act on a double switch with two electric lines, so as to enable the transmission of two suitable electrical signals to the valves 6, 7 of the pumps 36, 37. These electrical signals are intended for presetting the impellers 38 of the pumps 36, 37 so as to cause a given proportionality ratio between the velocity of the wheels 11 and the angular velocity of the rotor 31 and of the output shaft 44, such as to assure the preset jet width. A first electrical signal of the double switch acts on the feeding circuit of the first pump 36 operating the driving means 32, while a second electrical signal intervenes on the circuit of the second pump 37 and on the distributor 45. In particular the electrical signal sent to the latter is suitable for setting the gear ratio between the input shafts and the output shaft 44 of the speed changer 41 , in order to cause the rotation of the output shaft 44, at a fixed velocity of the pump 36, for the distribution of the minimum quantity of product, for example 5 g/ m², depending on the spreading length.

[0046] In practice the first operating item 58 allows to select a value for the width of the jet supplied among a plurality of possible values, for example regularly distributed from 3 and 12 metres, to each of which corresponds a given electrical signal calculated quantitatively through the calibration of the switch. For example, if is known the value of the angular velocity of the rotor 31 necessary to produce a given distribution width, for a given quantity of supplied substance per road surface unit and for a given feed speed of the tractor, the values of the electrical signals to send for each possible selection to the valve 7 can be determined through the functioning curve of the valve 7 itself.

[0047] The manual entry of the electrical values determining the different velocities respectively of the driving means 32 and of the output shaft 44 for the minimum distribution of product, for example equal to 5 g/m², can be made on respective potentiometers corresponding to the different spreading width. Being known the rotation speed of the driving means 32 and of the output shaft 44, the electrical values are calculated mathematically through the proportionality curve of the valves 6, 7.

[0048] On the contrary, a second operating item 59 of the proportionality device 35 is suited to act on a respective switch in order to set the proportionality coefficient which determines the weight of product to spread per road surface unit. For example, the switch can have an interval scale regularly subdivided in values comprised from 5 to 40 g/m². in practice, this switch acts through the valve 6 on the first pump 36 in order to cause such inclinations of the respective impeller 38 to determine the selected distribution value for any feed speed of the tractor.

[0049] The calibration of the switch is made in a similar way as to what described for the first operating item 58. But in this case multipliers instead of electrical signals are entered for the switch potentiometers, which determine electrical values, for each product quantity, depending on the electrical values tested for the minimum product quantity (entered through the potentiometers of the first operating item 58) and for each spreading width. Being known the rotation velocities of the output shaft 44 at a fixed velocity of the pump 36, the multipliers are calculated mathematically through the proportionality curve of the valve 36.

[0050] Furthermore the proportionality device 35 comprises a third operating item 73 acting on a respective switch to select the type of product to supply. In practice, this operating item is suited to send suitable electrical signals so as to selectively activate the operation of the units intended for the distribution of the different substances. In particular this operating item sends proper signals to the pneumatic drives of the drive means 42, suitable for causing their selective activation. In addition, the switch is able to activate the distribution assembly 30 depending on the demand, if any, to supply substances contained in the container 15 and/or in the cistern 13.

[0051] The spreader 1 is suited to be connected frontally with the tractor through the articulation of a vertical pin 76.

[0052] The functioning of the salt spreader according to the claimed invention is described as follows.

[0053] On demand, the salt spreader is paired with the tractor and so suitably loaded with the substances needed for the different treatments to perform, for example with salt in the cistern 13, solid calcium chloride in the container 15 and liquid calcium chloride in the reservoir 12.

[0054] Before starting the supply phase, the distribution parameters of the different substances are set, acting on the operating items 58, 59 and 73 of the proportionality device 35. The distribution width is set up through the first operating items 58, the weight per road surface unit through the second operating item 59, and the type of substances to supply through the third operating item 73.

[0055] For example, by selecting the salt treatment the motion of the wheels 11 exclusively operates the conveyor belt 17 and the distribution assembly 30, while the displacement pumps 33, 40 and the feeding unit 23 remain inactive. On the contrary, by selecting the treatment with salt and solid calcium chloride are operated the feeding unit 23 conveying the solid calcium chloride towards the discharge tube 19 upon opening of the gate 20 by means of the actuators 21, as well as the conveyor belt 17 which receives the motion by the activation of the third pulley 48 of the drive means 42. If the treatment with solvent is selected instead, that is with the liquid calcium chloride, the first pulley 46 is activated, thus operating the displacement pump 33 suited to feed the variable flow sprayers. In this case the conveyor belt 17, the feeding unit 23 and the distribution assembly 30 are not operated.

[0056] Furthermore, it is possible to select the treatment with humidified salt which causes the operation of the conveyor belt 17, the distribution assembly 30 and the second displacement pump 40 by the activation of the second pulley 47 of the drive means 42.

[0057] When these parameters are set up, the tractor can start to move forward on the road for performing the required treatments in the desired ways. In particular, for each feed speed of the tractor and so for each angular velocity of the wheels 11 which operate the motor unit 34, the proportionality coefficients set by the proportionality device 35 secure proportional variations of the operation of the distribution assembly 30, the conveyor belt 17, the feeding unit 23 and the suppliers of the liquid substances, in particular the displacement pumps 33 and 40 suited to keep the distribution parameters constantly to the selected values.

[0058] When it is necessary to substitute the conveyor belt 17, for example because of wear, the road vehicle has to be stopped and the cistern 13 has to be lifted by means of the actuators 66. At the same time the actuators 27 have to be operated to take the hatch 14 to the opening position as to the frontal portion 29 of the cistern 13. After releasing the supporting frame 67 from the cistern 13 by acting on the fixing pins 69, the actuators 71 have to be operated to cause the rotation of the conveyor belt 17 outwards as to the cistern 13. In this configuration it is possible to easily remove the conveyor belt 17 for an immediate substitution.

[0059] At the end of the treatments it is possible to disconnect the semitrailer from the tractor. In case, the substances inside the reservoir 12, the cistern 13 and the leak-proof container 15 can be preserved without deterioration on the spreader until the subsequent use.

[0060] So the salt spreader reaches the aim to allow the performance of all different operations necessary to the prevention and the treatment of ice formations on the roadbed. In fact the different necessary substances, solid as well as liquid, can be loaded on the salt spreader and distributed on the roadbed on demand. Thanks to the leak-proof container 15 made by the rear hatch 14 even substances sensitive to outer agents, such as the solid calcium chloride, can be preserved on the salt spreader. Consequently it is possible to carry out the combined distribution of salt and solid calcium chloride with no need of premixing the two substances.

[0061] A prerogative of the salt spreader according to the claimed invention is represented by the effective control carried out by the proportionality device 35 on the distribution parameters. The proportionality device 35 enables to set up such operational conditions for the supplying devices downstream to the motor unit 34 as to secure constant distribution parameters in any condition of the road vehicle moving forward.

[0062] In practice, when are set up the proportionality coefficients processed by the initial calibration of the switches, the variations of the feed speed of the road vehicle are automatically transmitted proportionally to the operations downstream, so as to assure the preservation of the selected parameters. IN this connection it is worth pointing out that in the claimed salt spreader the cited speed variations are not detected by sensors put outside the spreader, but are directly transmitted by the independent wheels 11 to the motor unit 34. Moreover it is not necessary to use electronic components which can be easily damaged by adverse climatic conditions.

[0063] A further advantage of the claimed salt spreader consists in the ease with which the components most subject to wear can be substituted. This is the case of the conveyor belt 17 constantly in contact with salt, which can be rapidly substituted as previously described.

[0064] In the fig. 6 - 9 is illustrated a preferred embodiment of the sprayer 100 intended for the supply of a liquid substance fed at constant pressure. The sprayer 100 substantially comprises a body 102 inside which is positioned a cut-off 103 suitable for performing the variable flow supply of the liquid substance upon operation of suitable drive means.

[0065] The body 102 has preferably cylindrical shape and is closed at its opposite ends by respective heads 105, 106 indicated respectively as lower and upper one for reasons of clarity. The heads 105, 106 are made steadily integral with the body 102 by means of suitable screw elements 104. The upper head 106 contributes to define inside the body 102 an upper chamber 101 which is in connection with a threaded inlet hole 107 made coaxial to the upper head 106, and is closed on its lower part by the cut-off 103. The threaded hole 107 enables the connection to a suitable circuit feeding pressure air intended for the adjustment of the variable flow or simply for the closure of the sprayer.

[0066] The cut-off 103 is constituted by a cylindrical sleeve 113 sliding tight thanks to a suitable annular gasket 114 inside the body 102. The sleeve 113 presents an upper portion 123 with restricted diameter, in its turn sliding tight thanks to a suitable gasket 115 inside the upper head 106. Between the outer surface of the upper portion 123 of the sleeve 113 and the body 102 is defined a secondary chamber 110 with annular shape.

[0067] On the lower head 105 is axially made a threaded hole 109 for the feed of the liquid substance to supply. The liquid substance can pass through radial holes 116 made in the lower head 105 inside a lower chamber 108 defined between the lower head 105 itself and the bottom of the cut-off 103. From this chamber 108 the liquid substance can pass into the secondary chamber 110 through the holes 112 made in the cut-off 103.

[0068] During the active phase of the sprayer the lower chamber 108 is in connection with a slot 111 made on the body 102 for the supply of the liquid substance. The slot 111 has uniform height and involves substantially an arc of a circle coaxial to the body 102 (see fig. 8) so as to supply a substantially cone-shaped jet.

[0069] The slot 111 of the body 102 is suited to be intercepted progressively by the cut-off 103 for the adjustment of the flow of the liquid substance flowing from the slot 111 itself. In practice the cut-off 103 is movable between a lowered position closing completely the slot 111 (fig. 6) and a lifted position of complete opening.

[0070] Between the complete closure- and the complete opening positions defined by the cut-off 103 the slot 111 offers a light progressively bigger fro the outflow of the liquid substance. In particular the liquid substance is suited to be supplied in a cone of constant amplitude and with a flow determined exclusively by the axial position of the sleeve 113.

[0071] The functioning of the sprayer 100 is described as follows.

[0072] When the liquid substance is not supplied, the pressure air is fed to the upper chamber 101 to assure the closing of the slot 111. In particular the pressure air comes from the feeding circuit 125 through a specially provided pressure adjustment device 124 suited to modulate the axial contrasting thrust exerted by the air (fig. 9). In the cited condition the contrasting thrust exerted by the air is not balanced by any axial thrust in the contrary direction and so causes the sliding of the cut-off 103 to the position closing the slot 111.

[0073] When the liquid substance is supplied through the hole 109 inside the lower chamber 108, the same liquid substance flows out into the secondary chamber 110 through the holes 112 of the cut-off 103. Therefore the axial thrust exerted on the lower side of the cut-off 103 by the liquid substance entered into the lower chamber 108 is contrasted by the contrasting thrust exerted by the pressure air supplied inside the upper chamber 101 and by the liquid substance entered into the secondary chamber 110.

[0074] If the difference between the axial thrusts generated by the pressure of the liquid substance respectively in the lower chamber 108 and in the secondary chamber 110 is smaller than the axial thrust exerted by the pressure air in the upper chamber 101 , the cut-off 103 is maintained in the position closing the slot 111.

[0075] On the contrary if the above-mentioned difference between the axial thrusts generated by the liquid subastance is bigger than the axial thrust exerted by the pressure air in the upper chamber 101, the cut-off 103 slides inside the body 102, thus progressively uncovering the slot 111 till the balancing of the dynamic actions on the same cut-off 103. In this condition the spraying supply of the liquid substance takes place through the slot 111. It is worth noting that the flow supplied is univocally determined by the portion of the slot 111 which remains uncovered by the sleeve 113 of the cut-off 103. This opening portion depends on the balance between the thrusts which are exerted on the cut-off 103.

[0076] Therefore by suitably adjusting the contrasting thrust generated by the pressure air it is possible to modify the relative positioning of the cut-off 103 as to the body 102 and consequently the interception rate of the slot 111.

[0077] Alternatively the drive means can be of hydraulic type instead of pneumatic type. Furthermore it is possible to provide for mechanical drive means, for example by using spring elements suited to contrast the axial thrust exerted by the liquid substance inside the secondary chamber 110 through an elastic force, that is through an action which is directly proportional to the relative displacement of the cut-off 103.

[0078] Therefore the sprayer 100 is able to effectively carry out the spraying of liquid substances having variable flow and constant pressure, in a gradual and continuous way. This result is essentially due to the possibility of determining the interception rate of the slot 111 and consequently the flow supplied through the relative sliding between the body 102 and the cut-off 103. This sliding is modulated in an effective way by drive means which act to counterbalance the hydraulic thurst exerted by the liquid substance in the secondary chamber 110 in order to stop opportunely the relative sliding of the cut-off 103. Therefore each flow required downstream to the sprayer is realizable in an easy and reliable way.

[0079] The use of drive means of pneumatic or hydraulic type allows the realization of sprayer installations provided with a plurality of selectively excludable sprayers.

[0080] By way of example fig. 9 illustrates an installation provided with a plurality of sprayers 100 fed in a parallel way by a pressure air feeding circuit 125 provided with a single adjustment device 124. Each feeding branch 128 is intercepted by a valve 126, for example by an electronically controlled valve, in order to exclude selectively the adjustment device 124. By closing the electronically controlled valve 126 the air is directly supplied from the reservoir at the maximum pressure, thus generating such a contrasting thrust to close the slot 111 of the respective sprayer 100.

[0081] A prerogative of the sprayer 100 consists in the fact that the amplitude and the depth of the supplied jet result constant, and in particular ar not influenced by the flow variations. In fact the sliding of the sleeve 113 of the cut-off 103 as to the body 102 takes place orthogonally to the width of the slot 111, thus assuring the supply of a jet with constant width. Even the depth of the supplied jet is constant, as the flow variation is not realized by intervening on the pressure of the liquid pressure which, on the contrary, is maintained constant.

[0082] Materials adopted for the actual realization of the invention, as well as their shapes and sizes, can be various, depending on the requirements.

[0083] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the scope of each element identified by way of example by such reference signs.

Claims

1. Salt spreader, comprising a chassis (10) provided with a couple of independent wheels (11) at least and suited to be drawn by a towing vehicle, characterized in that it comprises a reservoir (12) fitted on said chassis (10) and suited to contain a liquid solvent, for example calcium chloride at the liquid state; a dump cistern (13) fitted on said chassis (10) behind said reservoir (12), and provided at the bottom with conveying means (17) for supplying the salt to spread; a hatch (14) for the rear locking of said cistern (13), suitable for defining an opening (18) for the discharge of the salt to spread at said conveying means (17) and shaping a container (15) suited to contain leak-proof a further substance to spread, for example calcium chloride in the solid state; a distribution assembly (30) for distributing the salt supplied by said cistern (13), carried by said hatch (14); a motor unit (34) with hydraulic operation suited to drive the functioning of said conveying means (17), of said salt distribution assembly (30) and of suppliers (24, 33, 100) of said further substance to spread and of said liquid solvent; a proportionality device (35) associated with said motor unit (34), suitable for controlling the distribution of the substances to supply depending on the velocity of said independent wheels (11).

2. Salt spreader according to claim 1 , characterized in that said proportionality device (35) comprises a control unit provided with a plurality of operational items (58, 59, 73) acting on respective switches suited to send corresponding electrical signals to said motor unit (34) for the selection of preset distribution parameters relating to said substances to supply.

3. Salt spreader according to claim 2, characterized in that said proportionality device (35) comprises a first operating item (58) suitable for the selection of a value for the distribution width of the produced jet, a second operating item (59) to set up a preset weight value per road surface unit for the substance to distribute, and a third operating item (73) to select the substances to supply by means of the selective operation of the units intended for the distribution of the said substances.

4. Salt spreader according to claim 1 , characterized in that said motor unit (34) comprises a first variable-displacement pump (36) and a second variable-displacement pump (37), preferably of the " load-sensing" type, respectively provided with a plate- shaped impeller (38) with adjustable inclination upon control of said proportionality device (35).

5. Salt spreader according to claim 4, characterized in that said impeller (38) is suited to be adjusted by valves (6, 7) upon operation of electrical signals coming from said proportionality device (35), in order to set up corresponding proportionality coefficients in the functioning of said motor unit (34) for controlling preset distribution parameters of said substances to supply.

6. Salt spreader according to claim 4, characterized in that said first pump (36) is suited to operate a displacement pump (33) for the supply of said solvent, a second displacement pump (40) intended for the salt humidification and said conveying means (17), by the interposition of a speed changer (41) with hydraulic operation controlled by said proportionality device (35).

7. Salt spreader according to claim 6, characterized in that said speed changer (41) is fed by said first pump (36) by the interposition of an electrically controlled distributor (45) connected to said proportionality device (35).

8. Salt spreader according to claim 6, characterized in that said speed changer (41) comprises an output shaft (44) with which are suited to be put into gear pulleys (46, 47, 48) upon pneumatic operation in order to selectively transmit the motion through flexible drive means (42).

9. Salt spreader according to claim 4, characterized in that said second pump (37) is suited to operate driving means (32) of said distribution assembly (30) for the distribution of said dry or humidified substances.

10. Salt spreader according to claim 1 , characterized in that said leak-proof container (15) shapes at its top an opening closed by a leak-proof closing device (25) and at its lower part a discharge tube (19) suited to be suitably locked by a gate (20) operated by actuators (21), wherein said further substance is suited to be conveyed by a rotating auger-type feeding unit (23) operated by said motor unit (34) at suitable phase and motion relation.

11. Salt spreader according to claim 10 characterized in that said feeding unit (23) is suitably operated by the motion of a wheel (51) integral with the motion of said conveying means (17), suited to be engaged by a mating wheel (52) carried oscillating by an arm (53) pivoted on an axis (54) to which said feeding unit (23) is coupled, being said mating wheel (52) connected to said axis (54) by means of belt means (55) wound around respective pulleys (56).

12. Salt spreader according to claim 1 , characterized in that said hatch (14) is articulated at its top to said cistern (13) by means of a horizontal articulation pin (26) for the opening of a frontal portion (29) of said cistern (13) upon control of respective actuators (27) and is provided with sealing elements (28) positioned peripherally, suited to come in contact with said frontal portion (29).

13. Salt spreader according to claim 1 , characterized in that said conveying means (17) shape a conveyor belt wound around respective drums (16), fastened to a supporting frame (67) on one side pivoted to said cistern (13) on a longitudinal pin (68) and on the opposite side fastened by means of fixing pins (69), being said supporting frame (67) operated oscillating on said longitudinal pin (68) by actuators (71) in order to carry out the substitution of said conveyor belt (17).

14. Salt spreader according to claim 1 , characterized in that said distribution assembly (30) provides for a rotor (31) rotating around a vertical axis, adjustable vertically by means of an actuator (64), associated with conveyors (65), in order to exert a centrifugal action on said substances to spread.

15. Salt spreader according to claim 1 , characterized in that said sprayer (100) for the supply of a liquid substance fed at constant pressure comprises a body (102) which internally defines a chamber (108) suited to be fed with the liquid substance to spread and which is provided with a slot (111) connected to the outside in connection with said chamber (108) for the discharge of said liquid substance; a cut-off (103) fitted sliding relatively to said body (102) so as to intercept progressively said slot (111) between a complete opening configuration and a closing configuration, and suited to be stressed by the pressure exerted by the liquid substance fed into said chamber (108); drive means suited to act on said cut-off (103) to contrast the thrust exerted on said cut-off (103) by the liquid substance fed in pressure into said chamber (108), so as to control the interception of said slot (111) in order to vary the outflow of said liquid substance.

16. Sprayer according to claim 15, characterized in that it comprises a secondary chamber (110) defined between said body (102) and said cut-off (103), in connection with said chamber (108) for receiving said substance suited to stress by pressure the same cut-off (103).

17. Sprayer according to claim 16, characterized in that said cut-off (103) is constituted by a sleeve (113) with substantially cylindrical shape, axially sliding tight inside said body (102) and shaping a portion (123) having reduced diameter, suited to define said secondary chamber (110) with annular shape as regards to said body (102) itself.

18. Sprayer according to claim 16, characterized in that said drive means are constituted by fluid-dynamic means comprising an auxiliary chamber (101) defined between said cut-off (103) and a head (106) of said body (102) for the inflow of a control fluid suited to act on the same cut-off (103) to contrast the resultant of the axial thrusts generated by said liquid substance fed in pressure inside said chamber (108) and said secondary chamber (110).

19. Sprayer according to claim 16, characterized in that said secondary chamber (110) presents a couple of walls positioned orthogonally to the axis of said cut-off (103), respectively defined by a head (106) of said body (102) and by said cut-off (103), on which said liquid substance is suited to act for stressing by pressure said cut-off (103), to contrast the thrust exerted by the same liquid substance fed in pressure inside said chamber (108).

20. Sprayer according to claim 18, characterized in that said drive means comprise an adjustment device (124) for the controlled inflow of said control fluid suited to act on said cut-off (103).

21. Sprayer according to claim 15, characterized in that said slot (111) has uniform height and substantially involves and arc of a circle coaxial to said body (102).

22. Sprayer installation comprising a plurality of sprayers according to claims 15, characterized in that it comprises fluid-dynamic drive means fed in parallel way by a feeding circuit (125) adjusted by a single pressure adjustment device (124), being each sprayer (100) selectively excludable from said adjustment device (124) by means of a respective valve (126).