MXPA98003450A - Threaded fastener system - Google Patents

Abstract

A fastener system capable of clamping a workpiece that provides for enhanced distribution of the internal forces that are generated in the components as a result of the assembly of the system. The fastener system includes an externally threaded member having a thread formed thereon with a substantially non-triangular profile, and an internally threaded member having a thread formed therein which also includes a substantially non-triangular profile. In assembled form, the substantially non-triangular thread faces of the internally and externally threaded members mate along a contact face and, by virtue of their unique thread forms, and able to withstand axial loads of greater magnitude than comparable systems employing threads having substantially triangular profiles.

Description

"THREADED FASTENING SYSTEM" BACKGROUND OF THE INVENTION 1) FIELD OF THE INVENTION This application is directed towards a novel concept in the construction of an external or internal matched thread device that provides improved distribution of internal forces that are generated in the components containing the external and internal threads. More specifically, the internal forces to which this invention relates are generated as a result of the applied axial tension, for example, developed by contact face clamping forces in a structure containing two or more separate parts that are join together using the technology of the threaded fastener. These internal forces, however, can also develop as a result of axial compression. The system that is the object of the novelty nature and the invention of the matching external and internal threads device is particularly suitable for, but not restricted by, a system that generates the internal thread, using material displacement technology, inserting the fastener external threading in a simple drilling pilot hole and applying a counter-rotation between the externally threaded component and the one containing the simple drilling hole towards which the internal thread will be formed. This monimal axial force is in a direction where the external clamp will move relative to the pilot simple drilling hole towards which the internal thread will be generated. 2) CURRENT STATE OF THE PREVIOUS TECHNIQUE Speaking the general terms, the purpose of having an external and internal threaded fastening device is to use the helical thread to generate a tension load during the counter rotation of the external and internal threaded elements that can be transmitted in a force that can be used to hold two or more component parts together, to form a structure. These external and internal clamping systems which are of known known proportions follow the normalization processes which allow either the external threaded part or the internal threaded part to be replaced by a component that has been manufactured to equal dimensions and within the predetermined limits of so that the characteristics of the system do not deserve them from the original intention, when replacements or changes of the component are made (Joseph Whitworth-id., 1800). These same systems, which satisfy the need for interchangeability of component parts, are still used today for structural and critical safety assemblies. Although variations in size and form have been introduced since the concept of initial normalization was developed and documented, basic understandings have remained since they relate to the matching / matching of external and internal fastener systems. It is important to note that the external and internal fastener systems that are in common use today are based on a thread profile geometry that is essentially equal to a triangle, where the flanks of the adjacent threads are straight-sided and a predetermined angle with respect to the axis of the thread. The included angle of the thread that has differences in magnitude, depends on the selected ratio to make the angular changes. External or internal fastener systems in common use additional development ratios above and below an imaginary line which is called the tilt line or, for threaded pieces of circular cross-section, the simple effective diameter. This imaginary line is in a radial position from the axis of the thread where the firmness of the material in the thread is equal to the air space distance between the adjacent threads. From these constructions have developed understandings that have been based on empirical studies and the use of vector diagrams to show and calculate the resistance of the external and internal coinciding threads under the effects of axially induced forces applied. In most of the cases, the developments and distribution of the induced loads and the resulting matched thread resistances are based on threads of essentially triangular section, and a predetermined included thread angle. It should also be noted, however, that thread profile designs that deviate from the essentially triangular shape, even when rare, have been developed to achieve certain objects. For example, my prior US Patent Number 5,061,135 discloses and claims the fastener which includes a thread profile geometry having a rear flank at an angle to the diameter of the fastener and a front angle with a rounded concave profile. A main object of this thread-forming fastener is to develop forces that will stimulate the flow of the material in a nut member, such as a flexible plastic or light alloy, in order to increase the amount of the nut material in contact with the rear flank in angle of the thread shape. Since this fastener is driven towards the thread material, the force engages and the impetuses generated between the rear flank at an angle and the rounded front flank in an adjacent thread form cause the desired material flow in the thread material. It should be noted that the flow of the thread material in the manner indicated would not be achieved if the geometry of the thread profile were symmetrical when it is related to a line that is perpendicular to the axis of the externally threaded fastener.

OBJECTS AND COMPENDIUM OF THE INVENTION Accordingly, a general object of this invention is to provide a threaded fastener system comprising matching external and internal threads and having a novel thread profile geometry which will improve the strength of the matched threads under an axially applied tension or compression force, above that of the matching threads having known profile shapes, such as those which are essentially triangular. In summary, the invention comprises a fastener system that includes an externally threaded member having a thread with an essentially non-triangular profile formed therein and an internally threaded member having a thread with an essentially non-triangular thread formed therein to match with the essentially non-triangular thread of the threaded member externally along a matched thread contact face, wherein in assembled form, an axial load develops on the externally threaded member, whose load is resisted along the face of the threaded member. matched thread contact and wherein the matching threads of the fastener system are capable of withstanding an axial, tension or compression load of greater magnitude than the matching threads of a system employing threads having an essentially triangular profile.

BRIEF { DESCRIPTION OF THE DRAWINGS The features of the present invention that are believed to be novel will be pointed out with particularity in the appended claims.

The organization and manner of operation of the invention, together with additional objects and advantages thereof, may be better understood by reference to the following detailed description in relation to the accompanying drawings, in which the like reference numbers identify elements same and in which: Figure 1 is a schematic view of a basic profile and design for the internal thread encompassed by the present invention. Figure 2 is a schematic view of the basic profile and design for the external thread encompassed by the present invention. Figure 3 is a schematic view of a finished assembly incorporating the fastener system of the present invention. Figure 3A is a schematic view showing the matching external and internal thread conditions encompassing the present invention. Figure 4 is a schematic view showing the conditions of the internal and external thread coincident in which the internal thread is formed by an external screw threaded author.

DETAILED DESCRIPTION OF THE PREFERRED MODALITY While the invention may be susceptible to a modality in different forms, the specific embodiments will be described in detail in the drawings and in the present with the understanding that the present disclosure should be considered an example of the principles of the invention and is not intended to limit the invention to that which is created and described herein. Referring to Figure 1, the basic and design profile of an internal screw thread 121 that is constructed in accordance with the teachings of the invention is shown. The profile of the internal thread 121 develops from the spokes 10 that exit from the centers such as the profile 121 which is symmetrical around the imaginary central line 11. The magnitude of the spokes 10 and the placement of the centers 14 are developed with reference to the relationship between current maximum known metal conditions of an external screw thread and the minimum metal conditions of an internal screw thread. For the purpose of an understanding, the relationship is related to a metric thread system that represents a simple effective diameter of an external screw thread in the position that is equal to the maximum value associated with the position of 6 g and tolerance as defined in ISO 965/1. The height represents the theoretical tip height of an external screw thread as it is placed above diameter 15 effective maximum theoretical maximum, as represented. The width of the theoretical tip of the metric screw thread is as shown by 19. The contour 22 being the profile 20 of the external thread that develops correspondingly. The theoretical relationship between this external thread profile 22 and the profile of the matching internal thread in accordance with the metric screw thread system and having a position and tolerance in accordance with 6 H, as defined in I.S.O. 965/1, is represented by the contour 23. The shape of this contour 23 is based on a simple effective diameter 16 having a magnitude 25 in accordance with which it lies between the medium of 6 H and the maximum of 6 H, as is defined in ISO 965/1. The system creates a theoretical space 24 between the angled profiles of the external thread 2'2 and the internal thread 23. When measuring the simple effective diameter 16 of the internal thread 23 or the simple effective diameter 15 of the external thread 22, the firmness of the profile of the internal thread and the profile of the external thread, which is presented by 20, is constant and is equal to half the magnitude of the axial inclination of the thread.

From this relationship, data positions 25 are developed in relation to the external thread 22 and 26 in relation to the internal thread 23. The spokes 10 are developed to pass through the data 25 and 26 in such a manner that each face 22 of the angled profile forms a length 18 of string at a height from the periphery equal to 24. The spokes 10 being considered as a minimum value in relation to the present invention The main (internal) thread diameter may be truncated as shown at 27 provided that this truncated condition is not less than or within the height 17. The centers 14 are placed in relation to the radii 10 and the data points 25 and 26 together with the angle described in the case of the screw thread metric system of proportions known with the past, is equal to 304.80 centimeters. As mentioned above, the profile of the internal thread according to the present invention is 1: S contained within the contour 121. Maintaining the proportions of the internal thread as described, the internal thread is allowed to use devices of Measurement of existing styles and types. Referring to Figure 2 the basic and design profile of the external screw thread 12E which is constructed in accordance with the teachings of the invention is shown. Also shown in Figure 2 is the basic profile of the internal thread 121 such that the preferred condition can be visualized where the contact face 32 between the internal thread profiles 121 and external 12E provide the largest proportion of the spokes 10. to remain in contact when an axially induced load 33 is applied through the member containing the external thread. The imaginary data line '31 illustrating the position of the simple effective diameter of the profile 12E of the external thread which is, in accordance with the present invention theoretically displaced by an amount represented by 34 within the theoretical simple effective diameter 16 of the thread 23 internal The value of the height 34 is essentially equal to half the distance between the simple effective diameter 16 of the internal thread of the simple effective diameter 15 of the external thread 22 as shown in Figure 1. The spokes 10 as shown in FIG. relates to the external thread 12E are essentially the same as those of the internal thread 121. The center point 14 of the radius is in the same relative position for both external and internal threads.

However, the displacement 34 between the simple effective diameter 16 and the simple effective diameter 31 requires that the angle alpha be increased (as indicated by beta) to the radius 10 and the displacement 34 in order to maintain the largest proportion of the spokes 10. to remain in contact on contact face 32. This necessary difference in the proportions of the external thread relative to the internal thread provides means for contact conditions of the thread along the pressure face 32 which is to be maintained within acceptable limits that fall within those occurring with the coincident thread profile of the current known proportions. This provides distinct advantages where the external thread of the fastener occurs independently of the internal thread where both external and internal threads and the components provide a fastening system. Figure 3 illustrates a fastener system employing the present invention wherein a workpiece 42 is retained in compression. Referring to Figure 3A an amplified schematic view of the matched thread condition present in Figure 3 is shown. Under the effect of the axial force 33 a resistance to this force develops along the contact face 32 of the matching thread.

One of the benefits that make sure that the contact face 32 is of a rounded profile which is that of increasing the contact area represented by 35 in relation to that which would occur from a matched thread profile which is essentially triangular, which is repressed by 36. This increase in surface area reduces the pressure, in unit area strength, which needs to be effectively restrained to offer resistance to axial force. The profile of the spokes of the matching threads under pressure will be more effective to prevent thread separation failure of a profile that is essentially triangular. The construction of the profile of the external thread is seen to keep the spokes 10 equal in magnitude. However, from the novel construction method, it will be seen that the center of the radius that develops an opposite face of the profile, semueve from 14 to 14a. Refng to Figure 4, a matching internal and external thread is shown in which the internal thread 10 is produced by self-tapping principles and the basic properties follow the dimensions of the externally threaded member.

In essence, the proportions of the external thread are made according to the dimensions that conform to those of the internal thread that would be in accordance with the teachings of the invention. Under these conditions, the coupling length of the radii remaining in contact 40 is increased through that represented by 35 in Figure 3 and therefore further reduces the pressure that needs to be restricted within the matched thread structure. The construction of the external threaded fastener having the thread profile in accordance with the teachings of the invention may have a lobular cross section or any other device that is seen to be applicable to efficiently form the internal thread during assembly Screw or bolt externally threaded. The utility of the teachings in accordance with the invention is to relate the respective forms of the internal and external proportions to elements that are defined in common terminology such as a nut and bolt respectively. Any of assembly processes that utilize the concepts will benefit from the ability of the fastener system of the invention to withstand higher forces applied axial than those of a more conventional system that is constructed with a thread profile that is substantially triangular all other factors being equal. Even though the specific embodiments of the invention have been shown and described in detail, it will be apparent to those skilled in the art that changes and modifications of the present invention and its various aspects can be made without departing from the invention in its broader aspects, Some of the changes and modifications are matters of routine engineering or design being other evident only after study. As such, the scope of the invention should not be limited by the specific embodiment and specific construction defined herein but should be defined by the appended claims and equivalents thereof. Accordingly, the aim of the appended claims is to cover all those changes and modifications that fall within the true spirit and scope of the invention.

Claims (20)

- CLAIMS:

1. An internal and external threaded fastener system coincident wherein a thread profile of the internal thread is symbolic of having curved surfaces that are concave, and wherein the thread profile of the external thread is symbolic of having matching curved surfaces that are convex, the magnitude of the curve of the inner concave thread and the curve of the external convex thread being essentially equal, the concave curvature of the internal thread being of a radius shape where the radius develops to lie between a profile face straight with an external thread of currently known proportions, wherein the external thread is at its known maximum metal condition, and a straight profile face of the internal thread of known known proportions, wherein the internal thread is in its condition of minimum known metal, and where the thread is allowed to be truncated from both the external and internal threads, but this truncation has to ensure that the Internal truncation does not allow interference from a tip of the outer thread profile when assembling the system.

A threaded fastening system according to claim 1, wherein a center of curvature of a load-bearing profile face of the external thread is in the same position, and has a radius of the same magnitude as that which develops for the profile of the concave internal thread, and wherein a face of opposite non-loaded convex thread profile has a radius of magnitude to the load bearing face, but has a center of curvature that is axially offset to accommodate a difference in the simple effective diameter of the internal thread and the simple effective diameter of the internal thread, while maintaining a constant thread width in an axial plane in the simple effective diameter position of the external thread equal to half an axial thread inclination , benefiting the system characteristics since it allows axially applied tension forces and axially applied compression forces to be applied to the threads of the matching system.

A threaded fastening system according to claim 1 or 2, wherein a thread tightness in the simple effective inclination diameter of the internal thread is equal to a thread firmness in the simple effective tilt diameter of the external thread; the firmness of both the external and internal threads being equal to the axial inclination of the external and internal threads to the selected simple effective inclination diameters.

4. A threaded fastener system according to claim 1, wherein the internal thread is generated from a simple pilot hole of appropriate size, assembling the external threaded fastener by counter-rotating the parts in such a way that the internal thread is formed by displacement methods of material .

A threaded fastening system according to claim 1 or 4, whereby the characteristics of the matched thread provide areas of basic matching thread shear that will be increased through a system of essentially equal proportions, only where The profile of a system is essentially triangular, in such a way that the resistances of the coincident thread will sustain the highest axially applied forces at the point of failure.

A matched threaded fastening system according to claim 2 or 4, wherein a surface contact area of the concave and convex threads is increased above products of similar size of essentially tringular profiles in such a manner that the stresses induced under the axially identical applied loads are decreased.

7. A fastener system comprising: an externally threaded member having a thread with an essentially non-triangular profile formed therein; and an internally threaded member having a thread with an essentially non-triangular thread profile formed therein to coincide with the essentially non-triangular thread of the threaded member externally along a contact face of the matched thread, wherein the assembled form, an axial load is developed on the externally threaded member that is resisted along the contact face of the matched thread, and wherein the matching threads of the fastener system are able to withstand the axial load of greater magnitude of the matching threads of a system, using threads that have an essentially triangular profile.

A threaded fastener system according to claim 7, wherein both the thread formed in the externally threaded member and the thread formed in the internally threaded member include front and rear thread faces and at least one of the faces of the thread on the externally threaded member includes a convex rounded profile, and at least one of the threaded faces on the internally threaded member includes a concave rounded profile, and where there is a matched thread contact face that resists the axial load between the rounded screw faces of the externally and internally threaded members.

A fastener system of claim 8, wherein a tangent to the convex or rounded thread profile of the external thread, wherein this tangent is in the radial position of a simple effective diameter of the external thread subtends an angle which is greater than an included angle subtended by a normal to a tangent of the rounded concave thread profile of the internal thread, to a simple effective diameter related to the internal thread, thus ensuring a maximum contact area on the faces of matching profiles and reducing the load per unit area developed in an axially applied force.

A fastener system of claim 9, wherein the front and rear faces of the thread formed in the externally threaded member are symmetrical with respect to each other, and the front and rear faces of the thread formed in the internally threaded member they are symmetrical with respect to each other, thus allowing the system to resist both tension and compression axial loads equally.

11. A fastener system of claim 7, wherein the externally threaded member has a circular cross-sectional area.

12. A fastener system of claim 7, wherein the externally threaded member has a non-circular lobular cross-sectional area.

A fastener system of claim 8, wherein both the thread formed in the externally threaded member and the thread formed in the internally threaded member include a profile that is truncated on the crest thereof, such that the truncation of the internal thread does not interfere with external truncation when the fastener system is in assembled form.

A fastener system of claim 7, wherein the thread formed in the internally threaded member is formed during the assembly of the fastener system by the thread formed in the externally threaded member.

15. An assembly that includes one or more work pieces subject to a clamping force by means of externally threaded fastening means and an internally threaded nut means, wherein the clamping force develops a tension load on the fastening means that is resisted to along one face of the thread contact formed between the matching rounded thread profiles generated both on the externally threaded fastener means and the internally threaded nut means.

16. An assembly according to claim 15, wherein the rounded thread profile effected in the externally threaded fastener means is substantially convex, and the rounded thread profile formed in the internally threaded nut means is essentially concave.

17. An assembly according to claim 15, wherein the externally threaded fastener means has a lobular cross-sectional area.

18. An assembly that includes one or more work pieces subjected to a separating force by an externally threaded separating means and an internally threaded nut means, wherein the separating force develops a compression charge on the holding means that is resisted a * along a thread contact face formed between the matching rounded thread profiles generated both in the externally threaded fastener means and in the internally threaded nut means.

19. An assembly according to claim 18, wherein the rounded thread profile formed in the externally threaded fastener means is essentially concave, and the rounded thread profile formed in the internally threaded nut means is substantially concave.

20. An assembly according to claim 18, wherein the externally threaded fastener means has a circular cross-sectional area.