Patent Publication Number: US-2013241157-A1

Title: Screw-bearing gasket

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of screw retainers. In addition, the present invention relates to systems attached by screws that are transported using the screw retainers of the invention, such as vehicles comprising said systems. 
     BACKGROUND 
     Several techniques are known for retaining screws coupled to elements to be screwed. As the transport of screws separately from the element to be screwed generally results in the loss of the screws, solutions have been developed whereby the screws can be transported loosely attached to the element to be screwed. This simplifies the assembly of the elements, as the screws are already arranged correctly. In addition, the loss of said elements during transport is prevented. 
     However, existing solutions generally maintain the union in a permanent manner. When attempting to couple these screws to fluid connection systems, such as pipes or automobile engines, the screws of the prior art are not appropriate, for the reasons described below. 
     A fluid connection is established by coupling two elements, where one of them is a subsystem of the vehicle (such as an engine, turbocharger, volumetric compressor, cooling system, etc.) and the other is a pipe subunit that carries fluids from one part of the vehicle to another. A person skilled in the art will understand that although in order to aid the understanding of the disclosure of the invention, a vehicle is mentioned and the subsystems generally present therein, the teachings of the invention are equally applicable to any other union of subsystems in which fluids pass, and where a tight union is therefore needed to ensure the sealing provided by a sealing gasket. 
     As the union between these two elements must be tight, the presence of a sealing gasket between them is necessary. These gaskets are made of metal in couplings where the ambient temperature or that of the fluid which is transported is high (above 200° C.), or when the outside medium or the fluid has aggressive properties (such as acids, oils, alcohols, fuels and the like) which can affect the chemical characteristics of the gaskets, causing them to degrade. 
     Also known are gaskets made of superimposed layers of ‘fibrous’ materials of ceramic nature (glass fiber, aramide and the like) and optional metallic layers that do not require specific sealing protrusions due to their low compression resistance. However, gaskets of this type are generally more expensive and recycling them entails greater difficulty than for gaskets that are 100% metallic. 
     A metallic gasket has at least one protrusion above its plane, such as a continuous projection rib that surrounds or delimits the area through which the fluid will pass from the pipe to the subsystem, or vice versa, to ensure tightness. This protrusion must exert a contact pressure on the interfaces that compress it which is substantially greater than the internal pressure of the fluid it is delimiting. Ideally, the contact pressure is elastic in nature. 
     To obtain this contact pressure, compression loads provided by screwed unions are generally used. It is common for the female thread of the screwed union to belong to the subsystem related to the vehicle. In specific cases, the gasket may include attachment elements so that it is integrally joined to the pipe subsystem by a folding of said elements. 
     In the vast majority of architectures of the pipe subsystem, this ends in a flange, banjo or elbow shape with a significant stiffness level, able to convert very efficiently the axial loads of the screws to compression loads of the sealing rib. 
     This efficient conversion is related to a high bending inertia module about the axis defined by the centres of the screwed areas, in the end element (banjo, flange, elbow etc.) of the pipe subsystem. The inertial module is proportional to the distance (thickness) of the end element. On the other hand, the weight and cost of the end component is also proportional to it, so that this is a limiting design parameter. 
     Similarly, maximum efficiency is achieved by reducing the friction torque opposing the rotation of the screw in the screwing process, so that the nominal torque is maximally converted into a compression axial load. These fiction torques are affected by both the contact cross-section and the coefficients of friction between materials. 
       FIG. 1  shows a cross-sectional view of a sealing joint  100  of the state of the art, where a sealing member  101  is mounted on a subsystem related to the vehicle  102 . The sealing joint is used to connect a pipe  103  in which flows a liquid  104 . The sealing member  101  comprises a flange as its main body  105  and a sealing gasket  106 . In the area  107  where liquid flows, the sealing gasket presents a protrusion  108  that delimits said area  107 . The sealing member  101  is assembled using a screw  109  threaded in a female thread  110  of the subsystem  102  related to the vehicle. Members of this type have the common drawback that they cannot retain screws. 
     In the case of these sealing members, the friction torques appear mainly in two places. The friction torque associated to the contact  111  of the threads of the screw and female, and the friction torque associated to the contact  112  between a stopping means such as a flange, which is a type of lip, or a washer of the screw head and the outer plane of the flange. This friction torque appears in the final stage of tightening and is directly proportional to the desired tightening force, being particularly high in case of lack of flatness of the contact area or lack of perpendicularity of the screw axis and the outer plane of the flange, as in these cases local contacts occur between the screw and the flange that can dramatically increase the friction torque. This effect is generally undesirable, as it considerably reduces the force transmitted to the sealing rib. The greater force needed to compensate for this loss results either in a less comfortable assembly or an undesired arrangement of the assembly tools. Therefore, there is a need to provide a system that facilitates the assembly of the screw while providing maximum tightness. 
     On another hand, if the transmission force to the sealing rib is not sufficient, liquid leaks can occur leading to engine malfunction. Moreover, as the sealing gasket is generally located in a hard to reach area with poor visibility for the worker who must assemble it, it is not possible to check whether the position of the screw and therefore the resulting seal is correct. Therefore, there is also a need to provide a system that allows the operator to assembly a sealing member in a simple manner that fulfills the necessary quality requirements. 
     An additional drawback of current systems is the limitation resulting from having to first place in position the sealing gasket with the flange and then place and mount the screws. This two-stage assembly is a slow process. Furthermore, as stated above, the pipe subsystem is generally located in an area that is hard to reach and has poor visibility. It is sometimes even in a position that cannot be reached with the hand, but only with a screwdriver or other assembly tool. Consequently, there is also a need to provide a system that facilitates the assembly of the sealing member, making it quicker, easier, and more reliable, even if the worker cannot check it. 
     SUMMARY OF THE INVENTION 
     All of the aforementioned drawbacks are solved by means of an optimised sealing member. In one embodiment of the invention, a sealing member is disclosed of the type coupled to another member through which liquids flow. The sealing member comprises a main body and a sealing gasket coupled to the main body. This sealing gasket is configured to retain screws. 
     In another embodiment of the invention, a system is disclosed for liquid circulation that comprises the sealing member, wherein said system is selected from the group consisting of an engine, a turbocharger, a volumetric compressor, a cooling system or a heating system. A person skilled in the art will understand that the sealing member of the invention can be coupled and used also with other systems not explicitly mentioned, provided that these systems involve the flow of fluids and require assembly by screws and a gasket to prevent fluid leakage. 
     Another embodiment of the invention discloses the use of the sealing member in the manufacture of a system for liquid flow and a vehicle comprising said system for liquid flow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a sealing member belonging to the state of the art by way of example. 
         FIG. 2  shows a sealing gasket by way of example. 
         FIG. 3  shows a sealing member according to one aspect of the invention. 
         FIGS. 4A-4F  show different arrangements of the retention hole in the sealing gasket according to another aspect of the invention. 
         FIG. 5  shows a retention hole according to one aspect of the invention by way of example, configured to be embedded in the hole of the flange. 
         FIGS. 6A-6D  show a sealing member according to an aspect of the invention that comprises a sealing gasket with lateral flaps. 
         FIG. 7  shows a retention hole according to an aspect of the invention in a flap that is open towards the end of the flap. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The sealing member disclosed by the present invention solves the drawbacks of the prior art. The member is configured such that it retains the screws needed for its subsequent assembly in a manner that makes them be properly arranged, thereby facilitating the assembly, as well as in the correct position to provide maximum tightness. 
     The sealing member is of the type screwed onto another element. This sealing member is used in systems in which liquids flow, such as water, oil, gasoline or others. The sealing member comprises a main body and a sealing gasket mounted on the main body, wherein the gasket is configured to retain the screws needed to assemble said sealing member. The main body can be any object comprising openings for screws to pass and openings for fluids to pass, which can be coupled by screws to another body to establish a union between pipe subsystems. Preferably, the main body is a flange, although as stated it can also be another element through which fluids pass and needs to be screwed to ensure the union between the two elements. 
     Metal gaskets are preferred for the sealing gaskets due to their lower cost and better recycling compared to gaskets made of superimposed fibrous materials. In addition, metal gaskets have the advantage of withstanding high temperatures, such as above 200° C., or external mediums or internal fluids with aggressive properties, such as acids or alcohols, thereby preventing the degradation of the gasket. 
     Metallic gaskets can be of the plasticising type, such as made from copper/aluminum or soft materials, or gaskets with spring-effect. These latter metal gaskets are preferably made of steel with a high elastic limit or stainless steel, with a thickness of less than 1 mm, preferably 0.4 mm, and can have coatings of organic materials such as acrylics, neoprene, fluorides or others with a thickness of tenths of micron. 
     The gasket has at least one protrusion above its plane, such as continuous projection or rib that surrounds or delimits the surrounding area through which the fluid will pass from the pipe to the subsystem, or vice versa. This rib is responsible for the tightness, and must exert a contact pressure, ideally elastic, on the interfaces that compress it which is substantially greater than the internal pressure of the fluid it is delimiting. 
     A sealing gasket is shown by way of example in  FIG. 2 . This gasket  200  has two openings  210  through which the liquid flows and two openings  220  through which the screws pass for the subsequent assembly. Around the flow openings  210  are one or more ribs  230  that delimit or surround the flow area and provide tightness. In one aspect of the invention, the gasket  200  has some attachment elements  240  that are arranged perpendicular to the central axis of the gasket  200 . In another aspect of the invention, there are also gaskets  200  with attachment elements  240  in the lateral positions, that is, in the direction of the central axis of the gasket  200 . The most common method used to manufacture the metal gaskets is a gradual stamping process with a matrix. The final cost of the gasket is proportional to the size of its cutting length, that is, proportional to the size of the blank needed to make it. 
     Because the sealing gaskets of the present invention are configured to retain the screws needed for subsequent assembly in a manner that they are already in place, thereby facilitating the assembly, as well as in the correct position to provide maximum tightness, the following drawbacks are solved. 
     The time invested by the final customer (assembler of the pipe subassembly to the car or engine) is reduced as the screws are already in their final assembly position, eliminating the stage requiring gathering and positioning the screws. They only need to be tightened to the appropriate torque. This is particularly advantageous because normally the pipe assembly is in a position that is hard to reach and has poor visibility, and sometimes cannot even be reached by the hand. 
     In this way, the risk is reduced of a screw falling and being lost during the assembly operation while the operator handles it. It also eliminates the risk of forgetting a screw. This is particularly advantageous in couplings with more than one screw. 
     In addition, it is possible to eliminate purchasing references by the customer and the need for logistic adjustment between the number of screws and the number of pipe subsystems, which results in fewer administrative tasks and the corresponding reduction in logistics human errors. The presence of the screws guarantees uniquely the presence of the sealing gasket in the system, so that it is impossible to assemble a pipe subsystem without a gasket. The positioning of the sealing rib is more accurate, as it is referenced with respect to the axis (axes) of the screw(s). 
     In an embodiment of the invention, to retain the screws in the sealing system the concept uses the holes through which the attachment screws pass to adjust the screw thread, so that the screws are locked in a subtle manner. These holes are called retention holes. This allows delivering said screws pre-mounted to a system, such as a flange-gasket, facilitating the assembly by the customer and improving the positioning of the screws to obtain maximum tightness. 
     In several embodiments and aspects of the invention, various methods for retaining the screw in the sealing system, specifically in the gasket, have been developed. All of these methods have in common that every screw is retained in a specific hole of the gasket provided for the screw to pass. 
       FIG. 3  is a cross-sectional view of an embodiment of the invention showing a sealing member  300  during its transportation (left) and once assembled (right). The sealing member  300  comprises a main body  301 , preferably a flange, and at least one gasket  302  configured to retain screws  303 . The gasket  302  is based on the gasket  200  of  FIG. 2  and it is mainly flat and located entirely under the contact surface of the main body  301  with attachment elements  340  that allow assembling the gasket  302  on the main body  301 . 
     The gasket  302  presents a retention hole  305  that is configured so that the screw  303  is retained in the hole  305  by its thread  304  and cannot pass freely through it. Preferably, the retainer hole  305  has a diameter that corresponds to the diameter of the screw  303 . 
     In an aspect of the invention, the attachment elements  340  are clipping tabs that protrude laterally and retain the gasket  302  on the main body  301 . More specifically, said clipping tabs are in a position perpendicular to the main axis of the gasket  302 , which can penalise the final cost of manufacturing the gasket  302  as the cutting progress is greater. However, this position is typically the only possible one to prevent contact of the clipping tabs with the base of the screw, as it could hinder or interfere with a correct screwing. Therefore, in this aspect an improved screwing is obtained at the expense of a higher production cost. 
     In another aspect of the invention, the attachment system can be lateral flaps that can be folded to rest above the main body  301 , either directly or with a separation between the folded flap and the main body  301 . The attachment of the gasket  302  to the main body is achieved by the flap alone and/or in combination with the screw. In addition, the flaps can also have a hole for an attachment screw to pass. 
     According to another aspect of the invention, the retention holes  305  in the gasket  302  through which pass the screws  303  can use the current geometry of the hole  305  through which pass the screws, as shown in  FIG. 3  or  FIG. 4A  which show a retention hole  305  by way of example. This improves the diametric accuracy, so that the screw  303  is threaded in the hole  305  using the small thickness of the gasket  302 , normally about 0.4 mm, as a threading. 
     However, this method can have the drawback of the constant contact of the (helical) threading of the screw  303  and the plane of the gasket  302 , which induces a torsion as the gasket  302  must adapt to the profile of the threading  304 . Depending on the distance between the hole  305  and the sealing rib  330  this parasitic torsion can affect the flatness of the rib  330 , compromising the effectiveness and uniformity of the contact pressure. 
     Therefore, in another aspect of the invention it is possible to minimise this effect by introducing threading openings in the retention hole  305  which are conveniently located in the direction towards the sealing rib  330 . A retention hole  305  of this configuration is shown by way of example in  FIG. 4B . These openings minimise the effect of the parasitic torsion on the flatness of the rib  330 . As can be seen, the retention hole  305  presents a circular geometry that is interrupted by a small opening  401 . 
     In another aspect, a modification is made of the perfectly circular geometry of the hole  305  of the gasket  302 , as can be seen in  FIGS. 4C to 4F . The hole  305  can be improved by using said modified geometry with lobes, helical arcs, crenellations by way of a washer or others. In these cases it is possible to reduce the screwing friction, resulting in a simpler assembly of the screws  303  in the gasket  302  as well as an improved positioning of the screw  303  to achieve maximum tightness. 
     A substantially circular geometry of the hole  305  provided with lobes  402  is shown by way of example in  FIGS. 4C and 4D .  FIGS. 4C and 4D  show a retention hole  305  with three lobes  402 . The maximum diameter of the hole  305  is greater than the diameter of the screw  303 , but there are still three contact points  403  corresponding to the diameter of the screw  303 . This is shown in detail in  FIG. 4D . 
     The lobes  402  reduce the points of contact  403  of the gasket and the screw. A geometry with three lobes has been shown to be ideal. A small number of contact points  403  leads to a lower screwing friction. This lower screwing friction facilitates the entrance of the initial thread of the screw  303 . 
     In another aspect a substantially circular geometry is used with an interruption compatible with the stamping process, to generate two opposing arcs at the bottom of the thread, which also reduce the number of contact points. This configuration of the retention hole  305  is shown in  FIG. 4E . The position of the arcs  404  is not limited, so that they can be located anywhere around the retention hole  305 . 
     These arcs  404  can be helically shaped or have a minimum stiffness so that they adapt during the screwing to the helix of the screw  303 . As in the shape with lobes  402 , the screwing friction is reduced and the insertion of the initial thread of the screw  303  is facilitated. 
     Yet another aspect uses a geometry in which the hole  305  can have crenellations by way of a retaining washer. The configuration of this retention hole  305  is shown in  FIG. 4F . As can be seen, there are multiple openings  405  (not all shown) in the retention hole  305 . This also reduces the contact points  406  (not all shown) of the gasket  302  and the screw  303 . 
     In this way, the screws  303  can be retained by a slight interference and friction. In addition, the result is a simpler insertion of the screw  303  in the initial thread  304  of the screw  303  and an improved positioning of said screw  303  for the subsequent assembly. In this case the crenellated area  405  can be flat or embedded in the hole for the screws to pass in the main body  301 . 
       FIG. 5  shows a configuration for the retention hole  305  according to another aspect of the invention. In this aspect the substantially circular modified geometry is changed, using instead a retention hole  305  configured so that it allows embedding  501  part of the gasket  200  in the hole of the main body  302 . In this way, more threadings are provided to attach the screw  304 , thereby improving its immobilisation. Although the embedding  501  is shown from the bottom, an embedding from the top is equally applicable in another aspect of the invention. The embedding  501  can range from some microns to a few millimeters. In one aspect of the invention, the embedding  501  in the holes of the main body  302  has at least 1 mm. 
     The sole requirement for the retention holes  305  described above is that their position match that of the hole for passage of the screws in the main body  301 . Therefore, the retention hole  305  can be provided either under the main body  301 , that is in the sealing plane, or above the main body  301 , parallel to the sealing plane. In the latter case the holes  305  are provided in lateral flaps that can be folded to rest above the main body  301 , either directly or with a separation between the folded flap and the main body  301 . 
     If the retention holes  305  are under the main body, there is a risk of detachment of metal particles or of the coating of the gasket  302  when screwing the screw  303 . These particles can interfere with the functioning of the fluid system, or contaminate this fluid. This particle detachment can be minimised by using the modified circular geometries, that is, when the hole  305  has lobes  402 , arcs  404  or crenellations  405 . 
     Another risk related to a retention hole  305  located under the main body is an insufficient preassembly of the screw  303 , as can be seen in  FIG. 3 . Only a short length of the screw  303  can be screwed so that it does not protrude excessively from the sealing plane, which would hinder the final assembly by the customer. This minimum screwing therefore lacks robustness, as there is the added risk that the typical vibrations of moving vehicles will make the screw  303  come loose during transport, making it fall and losing the screw  303  during transport or handling. 
     Therefore, in another aspect of the invention the retention hole  305  is placed above the main body  301  to minimise said risks. In this way, the screw  303  can be screwed at least by the thickness of the main body  301 , which is normally from 4 to 10 mm, so that it is retained in a more central and thus more robust manner, solving the problem of falling and preventing logistical problems. 
     In yet another aspect of the invention, it is possible to place a retention hole both above and under the main body. This requires the gasket  302  to have at least four openings for a screw to pass, configured to retain said screw. The retention holes in this aspect of the invention can be combined with all the aspects described above in relation to  FIGS. 4A-4F  and with the aspect of the embedding of  FIG. 5 . In addition, the retention holes in this aspect can consist of any combination of these aspects, that is, there can be an embedding on the top and on the bottom, or an embedding on the top and a modified hole on the bottom. 
     To provide a retention screw above the main body  301 , a gasket is used with lateral flaps that is configured to house said flaps after they are folded above the main body  301 . The flap can be directly above the main body  301 , that is, touching the main body  301 , or there can be a separation between the main body  301  and the flap. In any case, the folded flap is parallel to the sealing plane of the gasket. 
     A sealing gasket  602  according to this configuration is shown by way of example in  FIG. 6A . The gasket  602  is also based on the gasket  200  of  FIG. 2 . In addition to the flow openings  610 , protrusions  630  and the openings  620  for the screws to pass, it shows two flaps  650  in lateral position, that is, in the direction of the main axis of the gasket. These flaps  650  each have a hole  605  for a screw  303  to pass before passing to the main body  301  (not shown). In this example of gasket  602 , there is also a gap  660  in the connection between the flaps  650  and the gasket  602  that provides greater flexibility to the folded flap  650 . This gap  660  is shown in greater detail in  FIG. 6B . Optionally, there can be some clipping tabs  640  (not shown) in case the separation between the sealing plane and the flap plane is greater than the width of the main body  301 . 
     In this configuration the screw  303  goes through two holes  620 ,  605  in the gasket  602 . The bottom hole  620 , placed in the sealing plane, is clearly larger than the outer diameter of the screw  303 , preventing any contact with it. In this way it cannot interfere with the screw  303  and its positioning. In addition, no particles can be detached from the gasket  602  or its coating if applicable. The top holes  605  represent the retention holes in which the screw  303  is threaded. In addition, these retention holes  605  can have all the features described above and illustrated in the  FIGS. 4B-4F  or  FIG. 5  to reduce the screwing friction, such as the lobes  402 , the arcs  404 , the crenellations  405  or the embedding  501  or to improve the retention. 
     In another aspect of the invention a separation  670  is provided between the flap  650  and the main body  301  such that the fold is higher than the width of the main body  301 . An example of this configuration is shown in  FIG. 6C . In any case the configuration in which the folded flap  650  is located under the head of the screw  303  is maintained. However, to attach the gasket  602  to the main body  301  it is necessary to provide it with attachment elements  640  in the form of clipping tabs, since the flap  650  cannot be used for this. 
     According to  FIG. 6C  there are several ways to retain the screw  303 . The screw  605  of the flap  650  can have any of the aspects described above in relation to the  FIGS. 4A-4F  or  FIG. 5 , such as the geometry of the hole corresponding to the geometry of the screw, or its improvements regarding a small number of contact points, such as a hole with lobes  402 , with helical arcs  404  or crenellations  405  in the form of washers. 
     Therefore, the screw  303  is threaded in the flap  650  until it reaches the through hole in the main body  301 . In addition, the retention hole  605  in the flap  650  can have one or more clips  680  that are located on the lower plane of the flap  650 . Said clips  680  can retain the screw  303  by its head, preferably using a stopping means such as a flange or washer. In this way, said flange or washer of the screw  303  is retained between its two faces by the gasket  602 . 
     Using said one or more clips  680 , it is even possible to use a retention hole  605  having a diameter considerably greater than the thread  304  of the screw but smaller than the stopping means of the screw. This establishes a stop contact that allows blocking in the removal direction of the screw  303 . However, the assembly direction is not affected in any way, as shown in  FIG. 6C . 
     In another aspect of the invention, the flap  650  can comprise a retention flap  790  having an open end towards the flap  650  as shown in  FIG. 7 . This specific example shows the flap  650  with the retention hole  605  that is substantially larger than the thread diameter of the screw  303  and a clip  680  under the plane of the flap  650  for retaining said screw  303 . 
     In addition, the attachment area will be suitably weakened to aid the bending and the unclipping process of the screw  303 , as also shown in  FIG. 6B . The advantage is found here that no friction torque opposes the screw tightening torque, as the screw  303  is unclipped (disarranged) in the initial moments of the screwing. 
     However, this configuration of the flap  650  with a fold that is wider than the main body  301  has a series of drawbacks. On one hand, the gasket  602  requires some attachment elements  640 , preferably in the form of clipping tabs  240 , to assemble it on the main body  301 . This implies a greater cutting progress and a higher cost of manufacture of the gasket. In addition, the flap  650  remains after the assembly in a position above the screw  303 , which hinders the unscrewing process. A further drawback of this top position of the flap  650  is that contacts and noises of the flap  650  with its surroundings may occur due to the vibrations of the engine. 
     Therefore, it can be desirable to place the flap  650  directly above the main body  301  as shown in  FIG. 6D . This figure shows that the bottom hole  620  is greater than the diameter of the thread of the screw  303 , while the diameter of the retention hole  605 , the top hole, is the same as the diameter of the thread of the screw  303 . It can also be seen that the flap  650  is located directly above the main body  301 . 
     In addition, the configuration of  FIG. 6D  allows reducing the friction torque due to the reduction of the coefficient of friction between the interfaces, thereby improving the transmission efficiency of the axial loads of the screws  303  on the sealing rib  630 . This reduction in friction is particularly apparent when the flap  650  of the sealing gasket  602  is interposed between the stopping means of the head of the screw  303  and the outer plane of the main body  301 , that is, when the flap  650  is between the main body  301  and the head of the screw  303 . 
     In addition, in the case that the flaps  650  are between the main body  301  and the head of the screw  304 , these flaps  650  are also employed to attach the gasket  602  to the main body  301 . In this aspect, attachment elements  640  such as the clipping tabs  240  are not essential for achieving the retention, allowing the cutting progress and the cutting remains to be lower, improving the cost. 
     Thus, when the flaps  650  are between the main body  301  and the head of the screw  303 , a new contact surface is generated between the gasket  602  and the head of the screw  303 . An advantageous use can thus be made of the coefficient of friction of the material of the gasket  602  and the intrinsic flatness of the flap, reducing the friction torque against the tightening torque, in order to optimise the efficiency of the tightening torque on the sealing rib  630 . 
     However, when the tightening torque is applied during screwing due to the friction  112  between the head of the screw  303  and the flap  650  of the gasket  602 , a torsional torque is introduced on the flap  650  that must be compensated by the resistance of the gasket  602 , possibly affecting the sealing plane and twisting it. In another aspect of the invention, in order to reduce this transmission, the connection area between the top and bottom parts of the gasket  602 , that is between the folded flap  650  and the sealing plane, has a minimised cross-section as shown in  FIG. 6B . 
     In this way the deformation is concentrated on the connection sections, when necessary presenting at least one additional notch  660  by which the flap  650  would break due to the torsional torque, in these cases making independent the two areas of the gasket  602  by a certain force of tightening torque. However, this will not affect the secure retention of the screw  303 . 
     All aspects of the specific configurations of the retention hole  305 ,  605 , specifically as described with reference to  FIGS. 4A-4F  and  FIG. 5  can be used in any of the gaskets  200 ,  302  or  602 . All of these aspects can be used in a retention hole  305 ,  605  located under, above or on both sides of a main body  301 . In the latter case, all combinations of the aspects described with reference to  FIGS. 4A-4F  and  FIG. 5  are possible. 
     The description comprises several embodiments by way of example. As it is neither possible nor practical to describe in detail the full variety of combinations and permutations of the inventive concept, which would lead to a large number of embodiments and redundant paragraphs, the author understands that a person skilled in the art, after a direct and objective examination of this specification, would arrive at the different possible permutations and combinations of the various embodiments and aspects described. Consequently, the main embodiments and aspects have been described, in the understanding that they include the remaining combinations, variations and modifications, provided they fall within the scope of protection as defined by the claims. Therefore, a person skilled in the art would understand that the description of the embodiments provided does not limit the invention, nor do the drawings.