FIELD OF THE INVENTION

The present invention generally relates to a drilling component to form part of a drill string. More specifically, the present invention relates to a drilling component configured to interconnect various sections of a drill string.

BACKGROUND OF THE INVENTION

Percussion drilling is used to create a long borehole via a plurality of elongate drill string rods coupled together end-to-end by interconnected externally and internally threaded ends. The well-established technique breaks rock by hammering impacts transferred from the rock drill bit, mounted at one end of the drill string, to the rock at the bottom of the borehole. Typically, the energy required to break the rock is generated by a hydraulically driven piston that contacts the end of the drill string (via a shank adaptor) to create a stress (or shock) wave that propagates through the drill string and ultimately to the base rock level. Conventional externally and internally threaded couplings are described in EP 2845993, EP2845991 Al, EP 1259703, EP 1232321 and US 4,968,068.

When the externally and internally threaded ends of neighboring drill rods are coupled to create the drill string, the joint is typically subjected to bending forces during drilling. These bending moments fatigue the coupling and lead to breakage within the threaded portion of the joint. The drilling efficiency is also affected by the bending moments experienced by the coupling. Typically, it is the internally threaded end that is damaged and determines the operational lifetime of the coupling. In particular, stresses in the threaded section of the externally threaded end are typically considerable and transferred to the internally threaded end causing increased wearing of the internally threaded end leading to failure of the coupling.

Hence, it is an object of the present invention to try to overcome at least some of the deficiencies of present drill string couplings regarding service life of components and the drilling efficiency of the drill string. SUMMARY OF THE INVENTION

It is an objective of the present invention to provide a drilling component configured to interconnect sections of a drill string and capable of withstanding loading forces acting on the drill string in order to minimize the risk of failure of the drill string. It is a further objective to provide a drilling component having an improved resistance to bending moments in the drill string resultant for example from hole deviation or noncentral strikes by the drive piston at the lowermost drill rod or at the shank adaptor. It is a further objective to provide a drilling component for shoulder contact interconnection systems and for bottom contact interconnection systems all the while forming an integral and secure unit within the assembled drill string. The present invention further stems from the idea of increasing the service life the interconnecting component consequently resulting in longer intervals between required maintenances. The present invention is further directed to the improvement of drilling efficiency through the development of a more robust drilling component.

At least some of these and other objects are achieved by providing a drilling component having the features in the independent claims. Preferred embodiments are defined in the dependent claims.

Therefore, according to a first aspect of the present invention, there is provided a drilling component configured to interconnect a first section and a second section of a drill string. The drilling component comprises a first end portion configured to be arranged to face the first section of the drill string, wherein the first end portion comprises a first interconnecting portion configured to engage a corresponding interconnecting portion of the first section of the drill string. The drilling component of the first aspect further comprises a hollow interior configured to extend along a length direction of the drill string and to form a part of a passage through the drill string. Still further, the drilling component comprises a wall defining the hollow interior, wherein an area of a first cross-section of the wall is smaller than an area of a second cross-section of the wall and wherein the first cross-section is arranged between the second cross-section and the first end portion. The drilling component fulfils the function of coupling or interconnecting a first section of a drill string and a second section of a drill string. Within this specification the reference to the first and second sections of a drill string may encompass any component forming the assembled drill string which require interconnection by the drilling component such as, but not limited to, drill rods, a shank adaptor, drill tubes, a percussive hammer, a drill bit, a shaft or adaptor mounted at the driving end of the drill string or at the bit end of the drill string, etc. For instance, along the length of the drill string, the first section and the second section interconnected by the drilling component may both be drill rods or drill tubes. At the lowermost part of the drill string, i.e. closest to the bottom of the borehole, the first section may be a percussive hammer and the second section may be a drill rod or a drill tube. At the uppermost part of the drill string, i.e. closest to the mouth of the borehole, the first section may be a drill rod and the second section may be a shank adaptor. The drilling component is therefore advantageous in that it can interconnect any combination of the above exemplified first section and second section to form a drill string.

The drilling component further fulfils the function of transferring mechanical movements and impact forces through the sections of the drill string it interconnects. Accordingly, mechanical movements, such as the rotational movement exercised on the drill string by a hydraulically driven piston, and impact forces, such as the shock waves generated by a percussive hammer, may be transferred with minimal energy loss from one section of the drill string to the neighboring section of the drill string via the drilling component. The transferring of mechanical movement and impact forces enabled by the drilling component therefore results in a high drilling efficiency.

The interconnection is enabled by the first interconnecting portion comprised at the first end portion of the drilling component and by the corresponding interconnecting portion it engages. For example, the first interconnecting portion may comprise an externally threaded section and the corresponding interconnecting portion may comprise an internally threaded section together ensuring a secure coupling of the first section and second section of the drill string, having an improved resistance to bending moments in the drill string. Further embodiments of the first interconnecting portion will be discussed later within this specification.

The hollow interior of the drilling component enables the continuity of a passage along the length of the drill string, through each sections of the drill string. The part of this passage formed by the hollow interior of the drilling component therefore enables flushing medium, e.g. air or water, to travel through the length of the drill string without obstruction. Accordingly, the hollow interior of the drilling component permits high drilling efficiency.

The wall defining the hollow interior may be construed as the material enveloping the hollow interior and therefore enveloping the part of the passage formed by said hollow interior. Accordingly, the wall of the drilling component experiences stresses and strains induced by the bending moment and impact forces generated along the drill string during operation. Parameters of the wall, such as the type of material and the thickness of the material, i.e. the amount of material of the wall, along the drilling component permit a distribution of stresses along the wall in order to avoid or at least minimize stress concentrations in certain portions of the wall generally contributing to quicker wear and to a higher fatigue rate of the drilling component.

Accordingly, the present invention embodies a drilling component in which the area of a first cross-section of the wall is smaller than the area of a second cross-section of the wall, wherein the first cross-section is arranged between the second cross section and the first end portion of the drilling component. Within this specification, an area of a cross-section of the wall relates to the amount of material enveloping the hollow interior of the drilling component at a specific position along the length direction of the drill string. Therefore, the present invention embodies a reduction or removal of the material forming the wall towards the first end portion of the drilling component facing the first section of the drill string. The reduction or removal of material of the wall towards the first end portion of the drilling component consequently decreases the stiffness of the wall towards the first end portion, enabling a greater distribution of stress along the first interconnecting portion in the length direction of the drill string. For example, when considering the drilling component representing a male threaded spigot comprising an internal bore, the present invention embodies a greater removal of material of the wall surrounding the internal bore of the spigot towards its end facing the neighboring drill rod to which the spigot is coupled. Reducing the amount of material forming the wall of the spigot towards its end weakens the end portion of the spigot thus making it more susceptible to higher stress, consequently relieving some of the stress induced at opposite end of the spigot by bending moments and impact forces in the drill string. Accordingly, the stress distribution along the drilling component enabled by any removal of material towards the first end portion, i.e. smaller area of a cross-section of the wall, results in a greater resistance to wear and failure during operation, consequently resulting in a longer service life of the drilling component and in a greater drilling efficiency. Decreasing the stiffness of the wall towards the first end portion further decreases the stresses transferred to the corresponding interconnection portion engaged by the first interconnecting portion, which may decrease the wear induced on said corresponding interconnecting portion. As a result, this may increase the service life of the drilling component and drill string. Alternatively, the removal of material toward the first end portion of the drilling component may be defined in terms of the cross-sectional area of the hollow interior, expressing a larger hollowing out of the drilling component towards the first end portion. For instance, the present invention may embody a drilling component wherein a first cross-sectional area of the hollow interior is larger than a second cross-sectional area of the hollow interior, wherein the first cross-section is arranged between the second cross-section and the first end portion of the drilling component. The cross-sectional area of the hollow interior towards the first end portion may also be defined in terms inner diameter of the hollow interior of the drilling component, in the case of a cylindrical internal bore. For example, the present invention may embody a drilling component wherein a first inner diameter of the hollow interior is larger than a second inner diameter of the hollow interior, wherein the first inner diameter is arranged between the second inner diameter and the first end portion of the drilling component. The present invention is further advantageous in that it increases the resistance to bending moments and it is configured to better withstand the stresses resultant from transmission of the percussive shock wave both when the components of the drill string are perfectly aligned axially and also when deflected, i.e. being aligned slightly transverse to one another. It will further be appreciated that the drilling component according to the first aspect of the present invention is compatible with various applications of percussion drilling such as rotary drilling, top hammer drilling, down-the-hole drilling, etc.

According to an embodiment of the present invention, the first interconnecting portion may comprise an externally threaded section configured to engage the corresponding interconnecting portion of the first section of the drill string. The externally threaded section enables a secure coupling of a first section and second section of a drill string. The externally threaded section further permits efficient transfer of mechanical movement and impact forces to the corresponding interconnection portion it engages, resulting in greater drilling efficiency. For example, the first interconnecting portion may correspond to the threaded section of a male threaded spigot arranged at the lower end of a drill rod, i.e. second section of a drill string, and configured to securely engage a corresponding female threaded section arranged at the upper end of a neighboring drill rod, i.e. first section of the drill string, together forming an integral and secure unit within the assembled drill string. Alternatively to an externally threaded section, the first interconnecting portion may comprise a conical or polygonal interface, e.g. tapered drill rod, configured to engage a corresponding conical or polygonal interface of the first section of the drill string. The engagement of such conical interfaces yields a similar secure coupling and greater drilling efficiency as aforementioned in relation to the externally threaded section.

According to an embodiment of the present invention, the drilling component may comprise a second interconnecting portion configured to engage a corresponding interconnecting portion of a second section of the drill string. The second interconnecting portion may further comprise an internally threaded section configured to engage the corresponding interconnecting portion of the second section of the drill string. The internally threaded section enables a secure coupling of a second section and first section of a drill string. The internally threaded section further permits efficient transfer of mechanical movement and impact forces to the corresponding interconnection portion it engages, resulting in greater drilling efficiency. For example, the second interconnecting portion may correspond to the female threaded section arranged at the upper end of a drill rod, i.e. first section of the drill string, and configured to securely engage a corresponding threaded section of a male threaded spigot arranged at the lower end of a neighboring drill rod, i.e. second section of a drill string, together forming an integral and secure unit within the assembled drill string. Alternatively to an internally threaded section, the second interconnecting portion may comprise a conical or polygonal interface, e.g. tapered drill rod, as described in the previous embodiment.

According to an embodiment of the present invention, the drilling component may comprise a second interconnecting portion configured to be connected to a rock-drill piston interface. Within this specification, a rock-drill piston interface corresponds to a mechanical component enabling the joining of a first drill rod with the hydraulically driven piston inducing rotational movement of the drill string during drilling operations. For example, a rock-drill interface may correspond to a shank adaptor. The second interconnecting portion of the present embodiment is advantageous in that it enables the transfer of mechanical movement from the shank adaptor to the drill rod with minimal energy loss. In the case of top hammer drilling applications, the second interconnecting portion of the present embodiment also enables the transfer of impact forces from the shank adaptor to the drill rod with minimal energy loss. The present embodiment therefore enables great drilling efficiency of the drill string.

According to an embodiment of the present invention, the drilling component may comprise a shank positioned adjacent to the first interconnecting portion such that said first interconnecting portion may be arranged between the shank and the first end portion. The shank may be construed as a traditional region positioned adjacent the first interconnecting portion wherein a cross sectional profile at the transition region in a plane extending in a length direction of the drill string is curved such that a cross sectional area of the shank decreases axially towards the first interconnecting portion. The present embodiment is therefore advantageous in that the shank reinforces the drilling component against bending moments by reducing stress concentrations thus decreasing the risk of failure of the drilling component under load. According to an embodiment of the present invention, the drilling component may comprise a radially outward protruding shoulder configured to transfer a force to the first section of the drill string along the length direction of said drill string. The present embodiment is advantageous in that the shoulder provides a contact surface between the first and second sections of the drill string increasing the transfer efficiency of impact forces from the second section of the drill string to the first section of the drill string. For example, in the case of a male threaded spigot, the shoulder may be construed as protruding radially outwards from the length direction of the drill string such that the outside diameter of the shoulder is greater than an outside diameter of the threaded section of the male threaded spigot. Accordingly, the present embodiment enables a shoulder contact interconnecting system.

According to an embodiment of the present invention, the first end portion may comprise an end surface configured to transfer a force to the first section of the drill string along the length direction of said drill string. The present embodiment is advantageous in that the end surface provides a contact surface between the first and second sections of the drill string, increasing the transfer efficiency of impact forces from the second section of the drill string to the first section of the drill string. Accordingly, the present embodiment enables a bottom contact interconnecting system.

According to an embodiment of the present invention, the part of the passage formed by the hollow interior of the drilling component may be formed by a first region and a second region, wherein the first region is arranged at the first end portion and extends at least partially along the first interconnecting portion and wherein the second region extends between the first region and a second end portion of the drilling component. Moreover, a cross-sectional area of the first region may be larger than a cross-sectional area of the second region. The present embodiment enables a transition in dimensions of the hollow interior of the drilling component between the second region and the first region. The present embodiment therefore encompasses a transition in stiffness of the wall forming the hollow interior along the length direction of the drill string. Accordingly, the first region may represent a weakened region of the first interconnecting portion enabling a stress distribution along the first interconnecting portion therefore reducing the stresses transferred to the corresponding interconnecting portion it engages. Consequently, the first region has the effect of decreasing the wear induced on said corresponding interconnecting portion thereby increasing the service life of the drilling component and the drill string. Furthermore, the first region preferably extends from the first end portion along 20% to 80% of the first interconnecting portion, more preferably along 30% to 60% of the first interconnecting portion and most preferably along 50% of the first interconnecting portion.

According to an embodiment of the present invention, the second region of the part of the passage may comprise a cylindrical bore. Furthermore, the first region of the part of the passage may comprise a cross-sectional shape conforming to a circle, an oval or a polygon. The present embodiment provides the possibility of having differently shaped sections of the part of the passage of the drill string formed by the hollow interior of the drilling component. For example, the hollow interior along the second region may encompass a circular cross-sectional profile, e.g. a cylindrical part of the passage in the length direction of the drill string, whereas the hollow interior along the first region may encompass an oval cross-sectional profile, e.g. an elliptical part of the passage in the length direction of the drill string. The provision of varying the shape of the part of the passage formed by the hollow interior of the drilling component enables the optimization of the stress distribution along the first interconnecting portion depending on the drilling application, material of wall defining the hollow interior, flushing requirement, etc.

According to a second aspect of the present invention, there is provided a percussion drill string comprising at least one of the drilling components defined according to the first aspect of the present invention. For example, several drill rods may be coupled together by drilling components according to the first aspect to from an integral, secure and long-lasting drill string.

Further objectives of, features of, and advantages with, the present invention will become apparent when studying the following detailed disclosure, the drawings and the appended claims. Those skilled in the art will realize that different features of the present invention can be combined to create embodiments other than those described in the following.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

Fig. la- Id schematically show possible portions of an assembled drill string comprising a drilling component according to an exemplifying embodiment of the present invention,

Fig. 2 schematically shows the composition of a drilling component according to an exemplifying embodiment of the present invention,

Fig. 3 schematically shows the composition of a drilling component according to an exemplifying embodiment of the present invention,

Fig. 4 schematically show alternative composition of the drilling component according to an exemplifying embodiment of the present invention.

DETAILED DESCRIPTION

Fig. la - Fig. Id illustrate possible portions of an assembled drill string for percussion drilling in which at least one drilling component 110 according to the present invention is depicted in use. Referring to Fig. la, there is shown a portion 100 of an assembled drill string formed by a first section 120 and a second section 130 interconnected to one another by the drilling component 110. In Fig. la, the first section 120 and the second section 130 represent drill rods. The drilling component 110 comprises a first end portion facing the first section 120 and a first interconnecting portion 160 shown having an externally threaded section. The drilling component 110 further comprises a second interconnecting portion 170 shown having an internally threaded section enabling the interconnection with the externally threaded section of the first interconnecting portion 160. The drilling component 110 is further shown comprising a hollow interior 150 defined by the material enveloping it, i.e. wall, extending along the length direction 140 of the drill string and forming a part of the passage which extends throughout the drill string. Accordingly, the transfer of mechanical movement and impact forces from the second section 130 to the first section 120 is permitted by the secure engagement of the first interconnecting portion 160 and the second interconnecting portion 170 to which it corresponds. Referring now to Fig. lb, there is shown a portion 101 of an assembled drill string formed by a first section 121 and a second section 131 interconnected to one another by a drilling component 110. In Fig. lb, the first section 121 represents a drill rod, and the second section 131 represents a shank adapter, i.e. a rock-drill piston interface. The drilling component 110 illustrated in Fig. lb encompasses the same characteristics as defined in reference to the drilling component 110 depicted in Fig. la. Accordingly, the drilling component 110 of Fig. lb comprises a second interconnecting portion 170 interconnected to the shank adaptor 131 by engagement of a first interconnecting portion 160 of the shank adaptor 131. Referring now to Fig. 1c, there is shown a portion 102 of an assembled drill string formed by a first section 122 and a second section 132 interconnected to one another by the drilling component 110. In Fig. 1c, the first section 122 represents a percussive hammer at the end of which is connected a drill bit 125, and the second section 132 represents a drill rod. The drilling component 110 illustrated in Fig. 1c encompasses the same characteristics as defined in reference to the drilling component 110 depicted in Fig. la. Accordingly, the drilling component 110 of Fig. 1c comprises a first interconnecting portion 160 interconnected to the percussive hammer 122 by engagement of a second interconnecting portion 170 of the percussive hammer 122. Referring now to Fig. Id, there is shown a portion 103 of an assembled drill string formed by three consecutive drill rods 181, 182, 183 interconnected by a first drilling component 111 and a second drilling component 110 in the length direction 140 of the drill string. Fig. Id illustrates the first drilling component 111 interconnecting the first drill rod 181 to the second drill rod 182 by engagement of a first interconnecting portion 161 and a second interconnecting portion 171. The first interconnecting portion 161 is shown comprising a conical interface engaging the corresponding conical interface of the second interconnecting portion 171. Fig. Id further illustrates the second drilling component 110 interconnecting the second drill rod 182 and the third drill rod 183 wherein the second drilling component 110 encompasses the same characteristics as defined in reference to the drilling component 110 depicted in Fig. la. Referring now to Fig. 2, there is shown the composition of a drilling component 200 according to an exemplifying embodiment of the present invention. The drilling component 200 comprises a first end portion 260 in turn comprising a first interconnecting portion 210 configured to engage a corresponding interconnecting portion not shown in Fig. 2. The corresponding interconnecting portion may represent the second interconnecting portion described in the previous Fig. la- Id. In the embodiment illustrated in Fig. 2, the first interconnecting portion 210 extends along the length of the drilling component 200 and into a second end portion 270 of the drilling component 200. The first interconnecting portion 210 further comprises an externally threaded section 221 along its length. Moreover, there is shown in Fig. 2a hollow interior 230 extending throughout the drilling component 200 in the length direction 140 of the drill string and forming a part of the internal passage of the drill string when assembled. The hollow interior 230 is defined by the wall 220 corresponding to the material of the drilling component 200 surrounding the hollow interior 230. The part of the passage formed by the hollow interior 230 encompasses a transition in thickness of the wall 220 exemplified in Fig. 2 by a reduction of material in the first end portion 260, weakening said first end portion 260 such that the stiffness of the wall 220 along the first end portion 260 is reduced in comparison to the stiffness of the wall 220 along the rest of the drilling component 200. In other words, the portion of the wall 220 defining the hollow interior 230 at the first end portion 260 is formed with less material than the portion of the wall 220 defining the hollow interior 230 at the second end portion 270 of the drilling component 200. Accordingly, an area of a first cross-section 240 of the wall 220, is smaller than an area of a second cross-section 250 of the wall 220 when both cross-sections 240, 250 are positioned on either side of the dimensional transition of the hollow interior 230. In other words, the area of the first cross-section 240 of the wall 220 taken between the second cross-section 250 and the first end portion 260 is smaller than the area of the second cross-section 250 of the wall 220. For example, the area of the first cross-section 240 of the wall 220 may preferably be 20% smaller than the area of the second cross-section 250 of the wall 200, most preferably 30% smaller. It will be appreciated that both cross-sections 240, 250 shown in Fig. 2 are taken perpendicularly to the length direction 140 of the drill string. Furthermore, the drilling component 200 comprises a shank 280 positioned adjacent to the first interconnecting portion 210 such that the first interconnecting portion 210 is arranged between the shank 280 and the first end portion 260 along the length direction 140 of the drill string. The shank 280 is depicted in Fig. 2 as a transitional portion of the wall 220 between a radially outward protruding shoulder 290 and the first interconnecting portion 210. The radially protruding shoulder 290 illustrated in Fig. 2 comprises a contact surface 295 configured to abut a corresponding surface of a neighboring section of the drill string, increasing the transfer efficiency of impact forces along the drill string. Furthermore, it will be appreciated that the reduction of the area of the wall 220 of the drilling component 200 permits the distribution of stress generated by bending moments and impact forces towards the first end portion 260 thus reducing stress concentrations at the shank 280 and at the start of the externally threaded section 221 of the first interconnecting portion 210 in the length direction 140 of the drill string. It will further be appreciated that the drilling component 200 of the embodiment of Fig. 2 is integrally formed with the drill rod at the end of which it is positioned. Alternative connection methods are also embodied between the drilling component 200 and the drill rod at the end of which it is positioned such as welding.

Referring now to Fig. 3, there is shown the composition of a drilling component 300 according to an exemplifying embodiment of the present invention. As similarly characterized as the drilling component of Fig. 2, the drilling component 300 of Fig. 3 comprises a first interconnecting portion 310 depicted in Fig. 3 having an externally threaded section 321 and a wall 320 defining a hollow interior 330 extending throughout the drilling component 300 in the length direction 140 of the drill string and forming a part of the internal passage of the drill string when assembled. The part of the passage formed by the hollow interior 330 is formed by a first region 365 and a second region 375 wherein the first region 365 is arranged at the first end portion 360 of the drilling component 300 and extends to the middle of the first interconnecting portion 310. The second region 375 is shown in Fig. 3 extending between the first region 365 and the second end portion 370 of the drilling component 300. Moreover, the part of the passage formed by the hollow interior 330 encompasses a transition in dimension exemplified in Fig. 3 by an increased area of the hollow interior 330 of the first region 365 compared to the area of the hollow interior 330 of the second region 375. This increase in area has the effect of weakening the portion of the wall 320 enveloping the first region 365 such that the stiffness of said portion of the wall 320 is reduced in comparison to the stiffness of the portion of the wall 330 enveloping the second region 375. Accordingly, the cross-sectional area of a first cross-section 340 of the first region 365 of the hollow interior 330 is larger than the cross-sectional area of a second cross-section 350 of the second region 375. It will be appreciated that both cross-sections 340, 350 shown in Fig. 3 are taken perpendicularly to the length direction 140 of the drill string. It will therefore be appreciated that the increase of the area of the hollow interior 330 of the drilling component 300 from the second region 370 to the first region 360 permits the distribution of stress generated by bending moments and impact forces towards the portion of the wall 330 enveloping the first region 365 thus reducing stress concentrations in the portion of the wall enveloping the second region 375. In general, the preset invention, herein embodied by the drilling component 300, may be defined as a coupling comprising a cylindrical internal bore and an externally threaded section wherein the diameter of the cylindrical internal bore increases towards the end of the externally threaded section.

The wall 320 in the first region 365 has a cylindrical profile. In other words, the first region 365 comprises a cylindrical bore. The wall 320 in the first region 365 is parallel to the wall 320 in the second region 375. The wall 320 in the first region is parallel to the length direction 140. The wall 320 is the second region is parallel to the length direction 140.

Referring now to Fig. 4, there is shown an alternative composition of the drilling component according to an exemplifying embodiment of the present invention. Fig. 4 illustrates the drilling component 400 characterized similarly as the drilling component 200 of Fig. 2 and additionally comprising an area of a third cross-section 445 of the wall 420 being smaller than the area of the first cross-section 450 of the wall 420 and larger than the area of the second cross-section 440 of the wall 420. Fig. 4 therefore illustrates a second transition in thickness of the wall 420 in the first end portion 460 of the drilling component 400. Accordingly, the area of the first cross-section 440 of the wall 420 is arranged between two larger cross-sectional areas of the wall 420, i.e. the area of the second cross-section 450 of the wall 420 and the area of the third crosssection 445 of the wall 420. Furthermore, the drilling component 400 comprises an end surface 415 enabled by the increase in thickness of the wall 420 towards the end of the first interconnecting portion 410. The end surface 415 depicted in Fig. 4 is configured to abut a corresponding surface of a neighboring section of the drill string, increasing the transfer efficiency of impact forces along the drill string. The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.