MXPA99011432A - Paper forming activity control with lifting variable angle inertial stimulation blades - Google Patents

Abstract

A papermaking apparatus such as a Fourdrinier table which includes a long blade (10) and a trail blade (14). In the first aspect of the invention, the long blade (10) includes an upper undulated surface (12) with vents (18) passing from the upper undulated surface (12) to the lower surface of the long blade (10) which is at substantially atmospheric pressure. In the second aspect of the invention, the trail blade (14) includes an elevator-type device (22) for adjusting the vertical position of the trail blade. In a third aspect of the invention, a single elevator (38) is used to adjust the angle of the blade, the blade is provided as a modular or multiple-piece design, mounting buttons (52) are used to engage slots of T-shaped cross section in the blade and/or ceramic inserts (62) are included at wear points.

Description

CONTROL OF TRAINING ACTIVITY OF PAPER WITH BLADES OF INERTIAL STIMULATION OF ANGLE OF VARIABLE ELEVATION BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The first and second aspects of this invention relate to the creation of pulp activity and to the control of drainage in a Fourdrinier table, particularly by the use of variable elevation inertial stimulation blades which may also include meshed ventilation surfaces. limited. Furthermore, a third aspect of this invention refers to the variable inclination of the inertial stimulation blades, the inertial stimulation blades being provided in component parts, the use of ceramic inserts in the wear points of the inertial stimulation blades, and the use of the button or disc-based mounting apparatus for the inertial stimulation blades.

DESCRIPTION OF THE PREVIOUS TECHNIQUE The activity of the pulp in the first part of a Fourdrinier table is critical for the production of a good sheet of paper. In general, pulp activity can be defined as turbulence in the fiber-water suspension in the network or texture in formation. This turbulence takes place in all three dimensions. The activity plays a major role in the development of good formation by preventing the stratification of the leaf as it is formed, by breaking the fiber flocs, and by causing the orientation of the fibers to be random. Typically, the pulp activity quality is inversely proportional to the removal of water from the sheet. That is, activity is typically improved if dehydration is delayed. As the water is removed, the activity becomes more difficult because the leaf becomes hardened, and because water, which is the main medium in which the activity takes place, becomes more scarce. The good operation of the paper machine is therefore a balance between activity and drainage.

There are a number of additional methods to promote activity and drainage. A table roller causes a large positive pressure pulse to be applied to the sheet resulting from the water under the network or network in formation that is forced towards the entry point formed by the roller and the network in formation. This positive pulse has a positive effect on the activity of the pulp by causing the flow perpendicular to the surface of the sheet. Similarly, on the exit side of the roller, large negative pressures are generated, which greatly increase drainage. Table rollers are generally limited to relatively slow machines because at high speeds, the positive and negative pulse amplitudes become excessively large. Mechanical belts are used to promote and control activity and drainage. A vacuum pulse is generated by the clamping point formed by the network or texture in formation and the conventional metal strip or sheet, as the network passes over the metal sheet. Activity is generated through the use of a number of metallic sheets consecutively placed, promoting a positively reinforced activity in the pulp. Another type of metal sheet, sometimes referred to as * posi-blade ", incorporates a positive entry point to generate a positive and negative pressure pulse.The amplitude of the pressure pulse is determined in a large part by the angle formed This type of metal sheet simulates a table roll, but with pulses of positive and negative pressure of much smaller amplitude.The amplitudes are determined by the speed of the machine and the angles of the sheets of metal sheets Frequently, Fourdrinier tables are mechanically agitated to promote the activity of the pulp, especially in slower, narrower machines. While agitation may be a good way to improve training, it is undesirable because it is difficult and expensive to control and maintain, and in general very punishing for the team on and around the Fourdrinier table. For papermaking in general, most activity induction systems have the negative feature of excessive drainage. In the patent application no. No. 08 / 600,833, entitled "Velocity Induced Drain Method and Unit" filed on February 12, 1996, describes an alternative form for creating activity and draining The apparatus described therein, and illustrated herein as Figure 1, uncoupling activity and draining therefore provides independent control and optimization of activity and drainage.The device typically uses a long blade with a controlled surface at least partially non-flat or undulating, to induce initial activity in the leaf, and It limits the downstream flow of the blade through the placement of a rear blade to control drainage.The drainage is improved if the area between the long blade, the net in formation and the rear or drag blade remains bathed and surface tension is maintained between the water above and below the network, however, the implementation of this device has revealed previous phenomena not fully appreciated. The first occurs in the "backflow zone" on the long blade, particularly in the undulating portion, where the incompressible fluid is pumped through the forming network This was expected, however, the second activity is much more vigorous and As the forming net encompasses the relatively large distance between the leading edge of the long blade and the rear blade, the latter is deflected downwards due to the forces acting on it, these forces are gravitational and also They result from the induction of vacuum as the network travels along the long blade.With much, the latter predominates.The wire takes the form of an oblique chain since the forces are asymmetric along the cable between the supporting points If the long blade is high enough or the deflection of the net is severe enough, the cable will make contact with the long blade and the catenary shape will be Also distorted. The activity is induced when the net reaches the rear blade. The network path must make a rapid transition from the flexed state to the horizontal state very quickly at the leading edge of the drive blade due to the high voltages acting on the path of the network. The trajectory of the net therefore changes sharply as the net travels around the sharp leading edge of the trailing or rear blade. Inertial forces prevent the fluid suspension of the paper sheet from following the network, and inertial activity is induced as the sheet rises vertically. In addition, since the metal sheets are typically made of HDPE (or any other suitable material as would be known to a person skilled in the art), any introduction of wear points on the metal sheet can reduce the life of the metal sheet. Similarly, since metal sheets may require periodic replacement, particularly in high-speed operation, it is important to have a mounting system to enable rapid replacement of metal sheets. The drained submerged in a Fourdrinier network is described by US Pat. No. 5,522,969 to Corbellini et al. Entitled "Submerged Drain Method for the Formation and Dehydration of a Network on a Fourdrinier Texture" and US Pat. No. 5,242,547 to Corbellini et al., Entitled 'Submerged Drainage System for the Formation and Dehydration of a Network on a Fourdrinier Texture ". The positional control of the elements in the papermaking apparatus is described in US Pat. No. 5, 486,270 to Schiel titled 'Angularly Adjustable Drain Metal Sheet for Paper Machines'; U.S. Patent No. 5,421,961 to Miller entitled "Formation Board Position Control System", US Patent No. 5,262,010 to Bubik et al, entitled "Dehydration Device with Adjustable Force Elements for the Network Forming Section of a Processing Machine" of paper"; and U.S. Patent No. 5,221,438 to Takeuchi et al., entitled "Dehydration Device Support Device." U.S. Patent No. 3,595,747 to als entitled "Suction Box Coverages with Lines of Drain Hollows for Uniform Dehydration" and U.S. Patent No. 5,562, 807 to Baluha entitled "Fiber Movement in Transverse Direction and Dehydration Device." Another prior art includes the Patent North American No. 4,687,549 to Kallmes entitled "Hidroaleta Blade"; US Patent No. 4,838,896 to Kallmes entitled "Hydroallet Blade to Produce Turbulence"; and US Patent No. 3,573,159 to Sepall entitled 'Desflocculation of Pulp Pulp Suspension with Pressure Pulses'.

OBJECTIVES AND BRIEF DESCRIPTION OF THE INVENTION It is therefore an object of this invention to provide controlled pulp activity in the papermaking process, particularly on a Fourdrinier table. It is therefore a further object of this invention to provide controlled drainage in the papermaking process, particularly a Fourdrinier table. A further objective of this invention is therefore to provide controlled pulp activity, decoupled from controlled draining in the papermaking process, particularly in a Fourdrinier table. A further object of this invention is therefore to reduce the amount of fluid that is pumped through the forming network as the fluid passes over the corrugated portion of a long blade in the papermaking process, particularly at a table. Fourdrinier It is therefore a further object of this invention to provide a blade with a variable angle and a fixed relative front edge, particularly on a Fourdrinier table. A further object of this invention is therefore to provide a blade that can be manufactured into elements and mounted together, and which can be easily mounted in a papermaking apparatus, particularly a Fourdrinier table. A further object of this invention is therefore to provide increased resistance against wear at the points of wear of a metal foil in the papermaking process, particularly on a Fourdrinier table. Therefore, a final objective of this invention is to control the sharpness of the trajectory change as the network passes over the rear or trailing blade in the papermaking process, particularly in a Fourdrinier table. A first aspect of this invention provides the downward inclined atmospheric vents that extend from the corrugated portions of the long blade of the Fourdrinier table. This ventilation of the backflow zone to the atmosphere equals the pressure above and below the net and therefore controls the downward force on the net, thereby controlling the bending with respect to the rear or trailing blade. , controlled the inertial activity and thus eliminates the vacuum or bending of the network over the backflow zone. Only the gravitational force flexes the net and it has been shown that the gravitational bending is negligible except for very long stretches. In addition, if the ventilation is limited or strangulated, then the flexion can be controlled in an analogous manner and the activity can be "tuned" for optimal sheet formation.The ventilation control can be uniform or non-uniform through the surface of the long blade for the control of the profile transverse to the machine or the variable drain in the machine direction.The surface of the long blade may be toothed locally or in the direction transverse to the machine to provide the vents. The second aspect of the invention uses a lift-type configuration for raising or lowering the rear or trailing blade This controls the activity of the pulp by controlling the sharpness of the path change as the network in formation travels on the rear blade, with which controls the inertial activity.When a rear or drag blade is raised the angle formed by go and the surface of the rear blade is maximized. This maximizes the fast directional change of the network, and therefore maximizes inertial activity. Conversely, when the rear or trailing blade is lowered, the angle is minimized, and the inertial activity is decreased or eliminated. If the rear part of the long front blade is sufficiently high such that the net rests on it as the rear blade is lowered, the effect is improved. Furthermore, in the second aspect of the invention, successive blades can be cut in cascade so that the rear or trailing blade of the first pair becomes the leading blade of the second pair, etc. As the elevations of the successive blades are changed, the activity generated on the entire apparatus is affected. The activity can therefore be finally adjusted to desired levels. Since the path of the network determines the effectiveness of the device, it can be used with any length of blade, and can be used in conjunction with other control devices, such as the ventilated blades of the first aspect of this invention. A third aspect of this invention inclines the blade or metal belt at a variable angle. This variable angle can be achieved by a simple lift on the front or back of the blade either in combination with a hinge or a fixed support. Alternatively, the variable angle can be achieved with a first elevator on the front and a second elevator on the back of the blade. In addition, the variable angle can be achieved by taking advantage of the inherent weight and flexibility of the blade. In addition, the blade may also include ceramic inserts at the corners of its corrugated portions, in order to reduce wear. In addition, the blade is provided in two or more pieces (with the joint or weld in a downward inclined portion of the corrugation) and the blade is assembled using a "button-type" accessory that engages a groove in the section. T-shaped cross-section in the blade The surfaces of the traditional metal sheet for paper machines are short in the machine direction, compared to the special designs of the VID-type blades.The length of these blades varies depending on the design Specificity of the curvature of the upper surface, which may be comprised of symmetrical undulations, or more likely, oblique profiles to provide desired results.According to the fact that most machines operate with unique conditions, each blade can be designed to maximize operation and training for particular operating intervals for your environment.An important variable in design of the blades is the specific profile of the upper surface. The length of the blade in the machine direction is dependent on the preferred hydrodynamic profile desired. The hydrodynamic profiles are designed to produce a varying pressure profile over the entire length of the blade. This profile includes the positive and negative pressure pulses that effectively cause backflow of the fluid through the network in formation. These counterflows create a mixing action that best forms the sheet of paper. The pressure pattern is designed to create a net vacuum pulse, resulting in fluid drainage after significant mixing has been induced. Varying blade lengths that are considerably longer in the machine direction than standard metal drainage blades presents a manufacturing challenge in material procurement and physical profiling in a production environment. The attached design offers a simple and more economical way to produce long machined blades. In many cases, the availability of the material is limited to shorter lengths than what is required for the manufacture of customary design profiles. This creates the need for a sectional design. An additional benefit of the sectional design is that it simplifies manufacturing, by allowing smaller sections to be sculpted independently, making handling and machining less problematic. The joint securing of the knife sections one to the other is designed to create a sealed assurance, so as not to affect the operating pressure and the vacuum pulses created by the upper surface profile. In addition, the location of the joint is selected to be within a lower portion of the corrugations, to maintain its integrity of joint and structural integrity so that they are not affected by the wear induced by the network in formation. The ceramic design incorporating laterally beams that secure the ceramic components, and spaced by polyethylene sections, creates several advantages over traditional ceramic assemblies both in operation and in manufacture. In manufacturing, the size of the individual sections is significantly reduced, making the critical machining steps less difficult, and increasing the choice of material available for use in the application. The sectional assembly also allows the customary adjustment of the parts to each other. The ceramic portions of the profile are preferably located only at the critical wear points, and therefore are not a larger portion of the special profile of the blade. The polyethylene spacers make up most of the shape of the blade and because of this, several different blade profiles can be used simply by changing the polyethylene spacer designs. These spacer bushings are removable and can therefore be replaced with new spacers of any shape variation. The length of the blades in the direction of the machine, since it is relatively long, requires the safe assembly of the same. Typically, a retention slot is used for shorter, typical sheet metal blades. The blades of the present invention are typically much larger, due to their forced operation involved with their design, it is desirable to secure the mounting structure with at least two or more slots, one at each end of the metal sheet. Note that due to the overall size and weight of the metal sheets, it is relatively more difficult to install and secure them to the structure in the traditional way (T bars). The 'cylindrical' 'button' design allows for simple installation by creating significantly less frictional resistance between the blade and the securing mechanism, this is realized by the fact that the buttons are spaced on the structure, and therefore not They create a point of continuous contact between the blade and the retainer.

These also have diametral clearance, allowing them to follow the slot of the retainer on the blade as it is installed on the structure, thereby minimizing the need for strict tolerances of the slots during manufacture. These types of retainers can be used with any type of metal sheet that has significant rigidity in the cross machine direction.

BRIEF DESCRIPTION OF THE DRAWINGS The additional objects and advantages of the invention will become apparent from the following description and from the claims, and from the accompanying drawings, wherein: Figure 1 is a cross-sectional view of a prior art blade arrangement; Figure 2 is a cross-sectional view of the vents of a first aspect of the present invention; Figure 3 is a cross-sectional view of the elevator-type configuration of a second aspect of the present invention; Figure 4A is a cross-sectional view of the effect on the inertial zone by lifting the trailing or rear blade in the second aspect of the invention; Figure 4B is a cross-sectional view of the effect on the inertial zone when lowering the rear or drive blade in the second aspect of the invention; Figure 5 is a cross-sectional view of a third aspect of the invention using a simple riser and a hinged section to achieve a variable angle of the blade; Figure 6 is a cross-sectional view of the third aspect of the invention using an elevator and a support (which could be a second elevator) to reach a variable angle of the blade.

Figure 7A is a cross-sectional view of the third aspect of the invention illustrating a two-piece design and the mounting slots of a 'T' cross section.

Figure 7B is a cross-sectional view of an alternative embodiment of the third aspect of the invention, illustrating the use of ceramic inserts at the corners of the corrugations; Figure 8 is a perspective view of the mounting button used for the mounting system in combination with the mounting slots of Figure 7A; Figure 9A is a top view of the third aspect of the invention, showing the modular design for use with the ceramic inserts at the wear points; Figure 9B is a front view of the third aspect of the invention showing the modular design for use with the ceramic inserts at wear points; Figure 9C is a side, cross-sectional view of the third aspect of the invention, showing the modular design for use with the ceramic inserts at the wear points.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY Referring now to the drawings in detail where similar reference numerals indicate similar elements throughout the various views, it is noted that Figure 2 is a cross-sectional view of a first aspect of the invention. The long blade 10 has corrugations 12 which generally decline in the machine direction. The forming net 100 traverses a path or path immediately above and is supported by the long blade 10 and then immediately above and supported by the rear or drag blade 14. A counterflow zone 102 is formed above the long blade 10 and an inertial zone 104 is formed above the rear blade 14. The water is above and below the forming net 100 and is drained through a passageway 6 immediately between the long blade 10 and the blade. rear 14. In the area of the corrugations 12 of the long blade 10, vents 18 are formed which extend generally in a downward direction. The vents 18 allow the flow of liquid therethrough and equalize the pressure between the backflow zone 102 and the atmosphere. This ventilation of the backflow zone 102 to the atmosphere equals the pressure above and below the forming network 100 and therefore controls the downward force on the forming network 100., whereby the deflection or bending with respect to the rear blade 14 is controlled, controlling the inertial activity and eliminating the vacuum or deflection of the network on the counterflow zone 102. Only the gravitational force flexes the net, and has shown that deflection or gravitational bending is negligible except for very long stretches. In addition, if the ventilation is limited or strangulated, as illustrated by the valve or throttle 20, then the bending can be controlled in an analogous manner and the activity can be 'adjusted' for optimal sheet formation. the ventilation may be uniform or non-uniform across the surface of the long blade 10 for control of the transverse profile to the machine or variable drainage in the machine direction The vents 18 may be throttled independently or in groups of any size. The surface of the long blade may be indented locally or through the direction transverse to the machine to provide the vents 18. Alternatively, the vents 18 may be connected to a cavity in which the vacuum level is controlled. mode, the level of pressure between the cable and the blade can be independently controlled. 3, a cross-sectional view of a second aspect of the invention is observed. In Figure 2, the long blade 10 has corrugations 12 that generally decline in the machine direction. The forming net 100 traverses a path immediately above and supported by the long blade 10 and then immediately upwards and supported by the rear blade 14. A counterflow zone 102 is formed above the long blade 10 and an inertial zone 104 is formed. form above the rear blade 14. The water is above and below the forming network 100 and is drained through the passageway 16 immediately between the long blade 10 and the rear blade 14. The rear blade 14 further includes the knife elevator 22 which raises and lowers the rear knife 14. The vertical raising and lowering of the rear or drive blade 14, varies the angle? (see Figure 4A). That is, the descent of the rear blade 14 by means of the blade elevator 22 reduces the angle? as shown in Figure 4B, while the elevation of the rear blade 14 by means of the knife elevator increases the? as shown in Figure 4A. This controls the activity of the pulp by controlling the sharpness of the trajectory change as the forming net 100 travels on the rear blade 14 whereby the inertial activity is controlled. When a rear blade 14 is raised, the angle? formed by the net to come and the surface of the rear blade is maximized. This maximizes the rapid directional change of the network in formation 100 and therefore maximizes inertial activity. Conversely, when the rear blade 14 is lowered by the knife elevator 22, the angle? it is mized, and the inertial activity is diminished or eliminated. If the tail of the long front blade is sufficiently high, such that the forming net 100 lies on it as the rear blade 14 is lowered, the effect is improved. Furthermore, in the second aspect of the invention, successive blades may be cascaded so that the rear or trailing blade of the first pair becomes the leading blade of the second pair, etc. As the elevations of the successive blades change, the activity generated on the entire apparatus is affected. The activity can therefore be finally adjusted to desired levels. Since the path of the network determines the effectiveness of the device, it can be used with any blade, and can be used in conjunction with other control devices, such as the ventilated blades of the first aspect of this invention. With reference now to Figures 5-9C, the third aspect of the invention is observed. In particular, Figure 5 illustrates the blade or metal sheet 30 with a fixed leading edge 32. The trailing or trailing edge portion 34 is coupled to the fixed leading edge 32 by the hinge 36. The angle of the back or trailing wavy portion 34 is adjusted by the vertical elevator 38.

The design of Figure 5 has the advantage that the position of the leading edge 32 is fixed, and the variation of the angle of the back or trailing wavy portion 34 does not raise or lower the fixed leading edge 32. Figure 6 illustrates a design similar to Figure 5. The blade or metal blade 30 is a one-piece design. The portion of the blade 30 proximate the leading edge 32 'is coupled to the support 36 (which could be fixed or a vertical lifter) while the trailing or trailing edge 40 of the metal sheet 30 is supported by the vertical lifter 38. Alternatively, the support 36 could be a vertical elevator and the support 38 could be fixed. Typically, the blade 30 rests on the fixed support 36 to allow a change in the angle of the blade 30 with respect to the fixed support 36, as the trailing or trailing edge is raised and lowered by the vertical elevator 38. However, a variation of this aspect could include the integral flexible blade 30 with the fixed support 36. The variation of the angle of the blade 30 in response to the movement of the vertical lifter could be accommodated by the inherent flexibility of the blade.

Figure 7A illustrates the two-piece (or multiple) blade design. The blade 30 is composed of a front section 42 and a rear section 44. The joint or weld 46 between the front section 42 and the rear section 44 is formed from an angled portion 46 extending from a portion extending with direction downwards, of a waviness (with respect to the machine direction, so that the felt or liquid "not shown" does not push the front section 42 and the rear section 44 to separate them) and a toothed portion 48. The toothed portion 48 is shown with a male portion in the rear section 44 and a female portion in the front section 42. The front section 42 and the rear section 44 are held together by the pins 51 (in dashed lines) or similar fastening devices. The lower portion of the front section 42 and the rear section 44 include mounting slots 50 of a T-shaped cross section. The mounting slots 50 are used to attach the mounting buttons 52 as shown in Figure 8. In addition, the lower portion of the front section 42 and the rear section 44 include ventilation slots 53 of a T-shaped cross section. The ventilation slots 53 are in communication with the vents 55 which are in communication with the grooves of the undulations of the upper surface of the front section 42 and of the rear section 44. The ventilation slots 53 are attached to the variable plug strips 57 that can be vertically adjusted to either align the openings 65 of the variable plug strips 57 with the vents 55 or to block the vents 55 with the solid portions of the variable plug strips 57. Figure 7B shows insert ceramic tiles 62 at the corners of the corrugations of the blade 30 in a design otherwise similar to that shown in Figure 7A. Figure 8 illustrates the mounting button 52. The mounting button 52 includes a cylindrical rod 54 with a lower threaded portion 56. The upper circular lid 58 is integral with the intermediate circular portion 59 and the cylindrical rod 54. The washer 60 of a hollow cylindrical shape loosely engages the intermediate circular portion 59 immediately below the upper circular cap 58. As can be seen from the dashed lines in Figure 8, the inner wall 62 of the washer 60 is outwardly the intermediate circular portion 59, thereby allowing the 'play' between the washer 60 and the intermediate circular portion 59. Likewise, the cylindrical rod 54 passes through the central opening 61 of the cylindrical spacer bushing 63 which is adjacent with address downwardly of the washer 60. The mounting buttons 59 are secured to a frame or frame (not shown) by lower threaded portions 56. The upper cylindrical cap 58 and the washer 60 are then attached to the mounting slots 50 in the form of T (see Figure 7A). Figures 9A-9C illustrate a modular design with ceramic inserts 62 at the corners of the corrugations of the blade 30. The ceramic inserts 62 are supported by laterally biased beams 64. The beams 64 include side notches 66 which guide the portions grooves 68 in place to form the modular composite blade 30. In this way, the various objectives and advantages mentioned above are achieved more effectively. Although the preferred embodiments of the invention have been described in detail herein, it should be understood that this invention is not in any sense limited by these and its scope should be determined by that of the appended claims.

Claims (11)

1. An apparatus for making paper, characterized in that it comprises: a blade with a fixed front end and a rear end with a variable vertical position, an upper surface of the blade includes corrugations; and means for varying the vertical position of at least one of the leading end and the trailing end thereby varying a blade angle.

2. The invention according to claim 1, characterized in that the rear end is hinged with respect to the front end and the means for variation comprises an elevator supporting the rear end.

3. The invention according to claim 1, characterized in that the front end rests on a fixed support, and the means for variation comprises an elevator.

4. The invention according to claim 1, characterized in that the front end is fixed on a fixed support, the means for variation comprises an elevator, and the blade flexes in response to the vertical movement of the elevator.

5. A papermaking apparatus, characterized in that it comprises a blade with a front section and a rear section, the front and rear sections have coupling elements by means of which the front section and the rear section form a single blade.

6. The invention according to claim 5, characterized in that the blade includes corrugations on an upper surface thereof and a joint or weld is formed between the front and rear sections on a downwardly directed surface of a corrugation with respect to the direction of the machine of the apparatus for making paper.

7. An apparatus for the production of paper, characterized in that it comprises a corrugated blade with symmetrical corrugations, where the corners of the corrugated blade are formed of ceramic components and the channels of the corrugated blade are formed of plastic components.

8. The invention according to claim 7, characterized in that it also includes laterally biased beams, the ceramic components being formed above the laterally biased beams, and the glass fiber components are coupled to the lateral notches of the laterally biased beams.

9. A papermaking apparatus comprising a blade with at least two grooves on a lower side thereof, the grooves include a lower portion of cross section produced and an upper portion of increased cross section, which further includes the mounting elements corresponding to the slot for coupling to said slots.

10. The invention according to claim 9, characterized in that the mounting elements and include a cylindrical rod or rod with a threaded portion, a top lid portion, an intermediate circular portion between the cylindrical rod and the top lid portion and integral with this, a washer that engages the intermediate circular portion, wherein the upper cap portion and the washer correspond to the upper portion of the increased cross section and the stem corresponds to the lower portion of reduced cross section, and a cylindrical bushing with downward direction adjacent from the washer.

11. The invention according to claim 10, characterized in that the washer has an internal diameter greater than a diameter of the intermediate circular portion, thereby allowing the play between them.