BACKGROUND OF THE INVENTION Field of the Invention This invention relates generally to a method and means for locking the elements of a screw threaded joint, and more particularly precision torque locking such a joint.

Description of the Prior Art In my prior patent No. 4,901,426 I have disclosed and claimed the methods and equipment for forming threads or thread segments by pressing and without rotation.

In my prior patent issuing on co-pending allowed application Serial Number 07/833,665, Now U.S.P.

5,230,134 issued July 27, 1993. I have disclosed how the respective threaded portions of a mechanical joint may be formed in such a manner as to be matched or intentionally mismatched to afford a selective locking effect as two threadedly related parts are joined together.

In my parent application, of which the present disclosure is a continuation-in-part, Serial Number 08/045,654 filed April 9, 1993, Now U.S.P. 5,429,014 issed July 4, 1995 it was contemplated that there be provided an adjustable, preset, threaded and torqued pedal rod assembled to a mean dimension supplied by the customer and then securely locked into firm assembly for utilization without further adjustment in the assembly line of the customer.

SUMMARY OF THE INVENTION In accordance with the principles of the invention recognized in broad concept, a screw threaded joint affords improved precision torque locking action whether incorporated in a pedal rod, or whether incorporated in any other form of threaded joint, wherever two mechanical component parts are required to be locked together.

While a metallic work piece is one medium in which the inventive principles can be embodied, it should be understood that the principles of the present invention can also be practiced by using material made of plastic.

Thus, the present invention contemplates that there be pressure formed, without rotation, external threads or thread segments, on a first part in two distinctly discernible sections, namely, a first section in which the threads, or thread segments, have a predetermined pitch diameter of complementary dimensional size with the internal threads of a second part, thereby permitting the

threads of the first section to function as lead threads, and a second section wherein one or more external threads or thread segments pressure formed simultaneously with the threads or thread segments of the first section are formed with a pitch diameter at a second predetermined dimensional size larger than the pitch diameter of the first section. The preelection of the larger pitch diameter is very carefully chosen so that precision torque locking can be achieved.

By virtue of such provision, one or more of the threads or thread segments of the second section will engage the internal threads of the second part with a predetermined rotational resistance, thereby permitting the second section threads to function as locking threads and tending to lock the two parts against inadvertent separation.

This concept can be effectively utilized by making the respective sections of external threads or thread segments at two closely related pitch diameters, or by selectively increasing the pitch diameter of the threads or thread segments of the second section, thereby permitting the user to relatively rotatably advance the two threaded together parts selectively to achieve a precision torque locking of from about zero (0) to forty (40) inch pounds, or more, within close tolerance limits such as plus or minus two (2) inch pounds.

Thus, if the second threads are of a uniformly

sized pitch diameter, precision torque locking can be selectively achieved by engaging a selected number of threads. If the second threads are progressively and incrementally increasing in pitch diameter, precision torque locking can be selectively achieved by engaging threads of increased pitch diameter. The joinder may be repeated if desired. Moreover, at the option of the user, if desired, after such threaded joinder, the parts may be permanently bonded into firm assembly by pressure crimping.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded somewhat schematic view of the separable elements of a threaded joint wherein there is depicted in greatly exaggerated form for purposes of illustration, an externally threaded work piece wherein the pitch diameter of the threads, or thread segments, is incrementally increasing, and is intended to mate with an internally threaded work piece having threads of a uniform pitch diameter; Figure 2 is a view similar to Figure 1 but shows in exaggerated schematic form a set of threads or threaded segments formed externally on the work piece at a uniformly sized pitch diameter, which is somewhat larger than the pitch diameter of the internally threaded portion of its mating work piece; Figure 3 is a view similar to Figures 1 and 2, but showing the external threads in exaggerated schematic

form, disposed at two distinctively discernible adjoining portions, or sections, with the threads or thread segments, at two different pitch diameters, one larger than the other; Figure 4 is a view similar to Figures 1-3, but showing the threads on the externally threaded work piece in exaggerated schematic form, in two distinctively discernible adjoining portions, or sections, with the threads, or thread segments of the second section incrementally increasing in size of pitch diameter; Figure 5 is an exploded view showing the thread scheme of Figure 3 incorporated in a pedal rod assembly for a motor vehicle, parts being shown broken away, and parts being shown in section; Figure 6 is an exploded view showing the thread scheme of Figure 4 incorporated in a pedal rod assembly for a motor vehicle, parts being shown broken away, and parts being shown in sect ion; Figure 7 is a view similar to Figure 5, but showing the principles of the present invention applied to an offset form of vehicular pedal rod; Figure 8 is a view similar to Figure 6, but showing the principles of the present invention applied to an offset form of vehicular pedal rod; Figure 9 is a fragmentary elevational view of a joined together assembly in accordance with the present invention wherein the parts are pressure crimped into

firm assembly with one another; Figure 10 is an end elevational view of a so-called isolator mount widely used in the automotive industry, but modified to incorporate the locking joint of the present invention therein; Figure 11 is a fragmentary cross-sectional view showing in exaggerated detail and therefore somewhat schematic form the two-tiered multiple section external threads or thread segments of the present invention as incorporated in the isolator mount of Figure 10; Figure 12 is a cross-sectional view of the isolator mount taken on line XII-XII of Figure 10; Figure 13 is a cross-sectional view of an isolator mount taken on the plane of line XIII-XIII of Figure 10, but showing the principles of the present invention applied to an externally threaded element made of two pieces, instead of only one.

DESCRIPTION OF THE PREFERRED EMBODIMENT This application is a continuation-in-part of my co-pending application Serial Number 08/045,654 filed April 9, 1993 entitled "Adjustable Pedal Rod and method of Making Same," Now U.S.P. 5,429,014 issued July 4, 1995.

The principles of the present invention are more broadly applicable to mechanical joints of many different varieties as utilized in the mechanical arts, and accordingly, are not specifically limited to pedal rods.

Further, while the principles of the present invention are particularly applicable to a metal working medium, it should be understood that it is contemplated that the present invention can be advantageously applied to a plastic working medium as well.

With a typical metal work piece, by way of illustrative example, but not by way of limitation, a metal bar stock can be employed to provide two components, or two elements, of a mechanical joint that is intended to be threaded together. Thus, while any suitable ductile metal material can be selected, one exemplary form of material that has been successfully employed in the practice of the present invention could be steel exhibiting the characteristics 1010 to 1020, or 8620 steel, for parts intended to function as head parts in an automotive power actuation chain, or for rod elements in a comparable performance environment, material of Rockwell "B" 95-105 12L14 steel.

So far as plastic material is concerned, the compound must be formable and must retain its formed shape and exhibit the requisite resistance to forces anticipated in the operating environment in which the threaded together joint components or elements will be subjected.

Referring to the drawings, it will be understood that for purposes of clarity in understanding, an exaggerated form of illustration has been employed,

wherein small, but important, differences in pitch diameter of adjoining threads or thread segments have been greatly enlarged.

In each of the figures, Figures 1 through 4, inclusive, there is illustrated a first component or element of a mechanical joint 20. The part 20 is cross- hatched to depict a metal material, but as explained above, it contemplated by the present invention that it could also be made of plastic.

The part 20 has an opening which is formed with internal threads 21 having a predetermined pitch diameter 22.

In accordance with the principles of the present invention, a second component of element of the mechanical joint is provided at 23, and as explained above, may be made of any suitable material such as metal or plastic, providing it can be worked as a work piece to form on the external surface thereof, threads or thread segments, without rotation.

With a ductile metal, such threads or thread segments may be conveniently pressure formed without rotation and with great accuracy. For example, the work piece may be formed and shaped in a progressive die press machine which can be completely automated and computer controlled so as to conduct as many sequential operations successively as may be selectively programmed. the thread forming step would merely be one of the steps in

the program.

With a formable plastic material, it is conceivable that the second part 23 would be formed as a pressure die cast part, so that the threads, or thread segments, would be produced automatically as part of the basic forming operation.

In any event, a second part 23 is provided and is formed with external threads, or thread segments, 24 which are formed without rotation. The threads 24 are formed at a pitch diameter suitably matched and mated with the pitch diameter 22 of the first part so that the parts 20 and 23 can be mechanically joined simply by joining the two parts and rotating the parts relative to one another, whereupon the two parts will advance axially and will be threaded together in a mated threaded together relationship. In this regard, it will be understood that the threads, or thread segments, 21 and 24 are formed in the usual helical thread pattern for the purposes set forth.

In the form of the invention illustrated in Figure 1, one or more first threads are identified at 24a and are disposed in a lead position and formed with a pitch diameter 22a the same as pitch diameter 22 of the first part. Thus, the threads 24a readily function as a mating lead thread, or threads, when the two parts 20 and 23 are joined together.

However, each successive thread in a second section

of threads externally formed on the part 23 is incrementally increased in pitch diameter size to exhibit a slightly larger pitch diameter than the initial pitch diameter 22. As shown in Figure 1, the thread 24b has a pitch diameter 22b, thread 24c is at 22c, etc., with each thread increasing incrementally.

It has been determined as a practical matter that the pitch diameter of the larger diameter threads, or thread segments, on the external surface of the second part 23 should not exceed a pitch diameter in the order of approximately 0.001 to 0.003 inches larger than the standard pitch diameter of the internal threads 21 of the first part, i.e., sufficiently larger to achieve precision torque locking.

It will be appreciated that the first and second parts may be axially advanced selectively to successively engage the threads 24a through 24e sequentially, thereby achieving precision torque locking of the joint between the two parts 20 and 23.

In the form of the invention illustrated in Figure 2, the second part is identified at 33 and it will be noted that the threads or thread segments 34 are formed without rotation at a pitch diameter 32 which is larger than the pitch diameter 22, but all of the threads 34 are of same pitch diameter.

Thus, in operation, precision torque locking can be achieved by selectively engaging as many of the

threads, or thread segments, 34 as necessary to reach the level of torquing desired.

In the form of the invention illustrated in Figure 3, the second part is shown at 43 and has two tiers of external threads formed simultaneously without rotation in two distinctly identifiable sections axially adjacent one another, namely, a first section of threads, or thread segments, 44a formed with a pitch diameter 42a, the same as the pitch diameter 22, and a second section of threads, or thread segments, 44b formed with a pitch diameter 42b which, as disclosed above, is proportionally larger than the pitch diameter 22.

Thus, in operation the threads 44a will function as lead threads and will thread into the internal threads 21 in the normal manner, but the threads 44b will encounter resistance and will allow the user to achieve precision torque locking on a selective basis.

In the form of the invention illustrated in Figure 4, the second part is shown at 53 and has a firs section of threads or thread segments 54a formed with a pitch diameter 52a, identical to the pitch diameter 22, and successive threads or thread segments formed in a second section are depicted schematically at 54b, 54c and 54d with incrementally increased pitch diameters 52b through 52d, respectively.

In each of the various permutations of the inventive concept, it will be understood that the user

can achieve precision torque locking by exerting the desired amount of locking torque between the two parts.

To reverse the torque lock, the user may release the locked joint by applying a suitably increased torque in an opposite rotational direction. Further, repeatability is available since the assembly or disassembly of the components or elements 20 and 23 and no chemicals or adhesives or nylon patches are required in practicing the present invention.

Referring now to Figures 5-8 of the drawings, and as disclosed in my parent application, pedal rods are operatively connected in the actuating train of a motion mechanism actuated by the operator of a vehicle. Such pedal rods may include a rod 60 formed with a ball 61 at one end and may further include an internally threaded recess 5\62 which is adapted to receive the externally threaded shaft portion of a head member supplied in several different shapes.

Thus, in Figures 5 and 6, the head is shown at 70 and is illustrated in a single bar form, although those versed in the art will readily recognize that the head 70 could also take the form of a clevis. In Figures 7 and 8 the head is shown at 80 and constitutes a so-called offset head, which some OEM automobile manufacturers prefer for space accommodation reasons, inter alia.

In Figure 5, the thread scheme of Figure 3 is employed, i.e., a thread section 74a is formed without

rotation at a first pitch diameter 72a corresponding to the pitch diameter of the internal threads 62 and a second thread section 74b is simultaneously formed without rotation with a pitch diameter 72b which is proportionally larger.

Figure 6 illustrates a thread scheme similar to that of Figure 4 wherein a first section of threads, or thread segments, 74a having a pitch diameter of 72a provides a lead thread section for a second section of locking threads or thread segments 74b, 74c, 74d each formed to exhibit a progressively incrementally increas- ing pitch diameter 72b, 72c, 72d.

Figure 7 shows the thread scheme of Figure 3 applied to an offset style pedal rod, to wit, with first and second thread portions 84a and 84b, while Figure 8 shows the thread scheme of Figure 4 applied to an offset style pedal rod, namely, with a first thread section 84a and a second thread section including progressively increasing threads 84b, 84c and 84d having pitch diameters of 82a-82d respectively.

As will be evident from an inspection of Figure 9, in any and all forms of the invention, the threaded together first and second parts may be permanently bonded and assembled together by pressure crimping. Thus in Figure 9, four circumferentially spaced crimps are shown at 90 each of which constitutes an axially extending elongated slot which displaces material inwardly from the

outer part into a bonding relation with the inwardly adjacent part.

If desired, spaced end crimps as shown at 91 may also be employed to further insure the firm assembly, of the parts.

Referring now to Figures 10-13, the principles of the present invention are applied to an isolator mount shown generally at 100 and which includes a bracket 101 formed with a circumferentially extending peripheral groove 102 and a centrally disposed axial through opening 103 through which is extended an isolator mount shaft 104.

The shaft 104 may be constructed in at least two different manners, i.e., as a one-part member, or as a two-part sub-assembly. In both instances, the end product is the same and like reference numerals will be used to identify like parts. In Figure 11, the one piece design is shown wherein a single sheet form member is shaped and formed and reversely bent back upon itself at a fold line 105 to form a main body shaft 106 terminating at one end in a radially outwardly extending flange 107.

At its opposite end, there is formed a reduced diameter externally threaded shaft extension portion 108 having helical screw threads so that it can be threadedly engaged and locked in the internally threaded opening or recess 109 of a wall part 110.

A two piece permutation is shown in Figure 13.

Instead of a one piece sheet form part, two separate sheet form parts are shaped and formed to form complementary halves of a single unitary article having a planar interface identified at 105a. Together, the two interfaced parts form the main body shaft 106 terminating at one end in a radially outwardly extending flange 107.

At its opposite end, there is formed a reduced diameter externally threaded shaft extension portion 108 having helical screw threads so that it can be threadedly engaged and locked in the internally threaded opening or recess 109 of the wall part 110.

In order to lock the two parts firmly together, one of the parts has a pair of recesses 111 and 112 formed therein while the other part has a corresponding pair of projecting lugs 113 and 114 pressed out to accomplish a press fit which retains the parts in assembly.

In either event, the principles of the present invention may be very advantageously practiced with the isolator mount by forming the external threads on the reduced diameter shaft extension 108 as illustrated in Figure 11. Thus, the external threads are formed without rotation in two distinctly discernible sections to provide a first section of lead threads shown at 116 and having a pitch diameter the same as the pitch diameter as that of the internally threaded recess 109.

A second locking thread section is formed at 117 with a larger pitch diameter of approximately three

thousandths (0.003) of an inch greater pitch diameter than those of the first section of threads. the number of threads in the locking thread section can vary to achieve the objectives of precision torque locking and the resulting structure is ideally suited for applications wherein it is necessary to cope with violent shaking or heavy vibration.

to lock the isolator mount into the bracket, the necessary amount of torque is applied. To reverse the torque lock feature and release the bracket, it is merely necessary to apply a reverse torque of an appropriate quantum amount. The device can be effectively used without the necessity of employing any supplemental chemical adhesives or nylon patches or sealers.

If desired, a dimple lock crimp 118 may be formed in an axially extending flange 119 formed on the wall part 110, thereby locking the two parts together.

Although various minor modifications might be suggested by those skilled in the art, it should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.