US2421181A - Stud bolt - Google Patents

Description

May 27, 1947. J. w-. 'BATCHELDER STUD BOLT Filed Jan. 23, 1945 9544; aim

atented ay 7, l4?

STUD BOLT James William Batchelder, Alstead, N. 1!.

Application January 23, 1943, Serial No. 173,291

4 Claims. l

The present invention relates to an improveu form of stud bolt and to an assembly unit embodying the improved stud bolt.

It is a principal object of my invention to provide a stud bolt designed to be readily applied to a stud receiving element and which may likewise be easily and quickly removed from the stud receiving element without mutilation or damage to the threads.

Previous forms of stud bolts were provided with threads on both their stud and nut ends. These conventional forms of studs were not provided, however, with a stud extricating means. In applying the conventional form of stud, a wrench having a threaded blind hole of less depth than the length of the cooperating threaded nut end of the stud was used. The nut end of the stud was screwed into the hole in the wrench until it bottomed therein. Thereafter, further rotation of the wrench would cause the threaded stud end of the stud to screw into the stud receiving element. After the stud had been tightly secured to the receiving element, the rotation of the wrench was reversed, thus withdrawing and unthreading the wrench from the cooperating threads on the nut end of the stud. Obviously the torque required in rotating the wrench to remove the wrench from the stud could not be as great as the torque required to remove the stud from the stud receiving element since the stud would then be removed instead of the wrench. Therefore, it is apparent that the same wrench used in applying the stud could not be used to remove the stud. In conventional practice a Stillson or pipe wrench was used to remove the stud, and since the effectiveness of the pipe wrench depends on the serrations, or teeth, in the wrench jaws, it will be seen that the exposed thread surfaces on the stud would be mutilated, thus rendering the stud bolt unfit for further use.

It is, therefore, an important object of my invention to provide an improved form of stud bolt which may be applied and removed with the same wrench and which thus avoids the probability of any damage or mutilation to the exposed thread surfaces of the stud.

It is also an object of my invention to provide a form of stud bolt having specially shaped surfaces other than its thread surfaces, the shaped surfaces being selected to cooperate with similarly shaped jaws n the stud applying means, such as a wrench or the like.

Recent developments have made it advisable to use a stud bolt which may be threaded into a stud receiving recess of an element where it is desired that the threaded joint between the stud and the recess be absolutely liquid tight. It is, therefore, a further object of my invention to provide a stud bolt wherein a novel shape or form of thread is provided on the stud end to cooperate with a similarly shaped threaded recess in the stud receiving element to thereby effect a liquid tight joint.

A still further object of my invention is to provide a novel form of stud bolt having a socket extending inward from its nut end and adapted. to cooperate with a socket wrench which may be used to apply or remove the stud. Such socket formation within the nut end of the stud of my invention may also be provided with means exterior of the socket walls to reinforce the socket while the wrench is being used to apply or remove the stud.

It is also an object of my invention to provide an improved form of stud bolt having tape: threads on its stud'end, which, if properly applied, requires a back-off torque greater than or equal to the set-up torque as distinguished from the conventional stud in which the back-off torque is substantially less than the set-up torque.

Further objects and advantages will be readily apparent by reference to the following specification and drawing in which:

Figure 1 is a side elevation showing the preferred form of the stud bolt of my invention.

Figure 2 is a side elevation of a modified form of the stud bolt of my invention.

Figure 3 is an elevation of the nut end of the stud shown in Figure 2 and showing the socket walls shaped to cooperate with a socket wrench.

Figure 4 is a side elevation of a further modified form of stud bolt.

Figure 5 is a view of the nut end of the stud shown in Figure 4.

Figure 6 is a fragmentary elevation, partly in section, showing the stud form of Figure 2 together with its cooperating socket wrench and having a temporary means to reinforce the socket.

Figure 7 is a view similar to Figure 6 but showing the stud form of Figure 4 together with a suitable stud applying or removing socket wrench.

Figure 8 is a sectional view of an assembly unit of elements embodying the preferred form of stud bolt shown in Figure 1 with the stud bolt shown partly in elevation.

Referring to the drawing, the numeral 20 denotes generally the body of the preferred form of stud bolt of my invention. The body 20 is provided with a tapered and threaded stud end 21 which is to be received by a similarly shaped and threaded recess in a stud receiving element. The nut end of the body 20 is provided with threads 22 in the same hand as the end 2| to cooperate with a locking nut as will be further described. A cotter hole 23 may also be drilled through the nut end of the stud if desired. The body 20 has a non-threaded portion intermediate its ends which may be hexagonally shaped as at 24 to cooperate with the jaws of suitable types of conventional wrenches as will be readily understood.

The above described stud form as shown in Figure 1 may be readily applied to or removed from a stud receiving element merely by applying a conventional end wrench to the surfaces 24. Thus it will be seen that no damage or multilation of the threads on either the stud or nut ends of the bolt can occur when removing the stud with an end wrench or the like.

In Figures 2 and 3 of the drawing a modified form of stud bolt is shown having a socket 25 extendin inward from the threaded nut end 26 of the stud 21. The inside surfaces of the walls of the socket 25 are shaped to form splines 28 which may cooperate with a similarly shaped socket wrench such as will be referred to later in connection with Figure 6 of the drawing.

Figures 4 and of the drawing show a further modified form of stud bolt similar to the form shown in Figures 2 and 3. In this form the socket 29, extending inward from the nut end 30 of the stud 3! is hexagonally shaped as shown at 32 to cooperate with a similarly shaped socket wrench such as will be later referred to in connection with Figure 7. It should be pointed out that the exterior surfaces 3 3 opposite the walls of the socket 29 are non-threaded and may be cylindrical in shape or provided with any desired shape as long as they cooperate with similarly shaped jaws shown on the socket wrench of Figure '7.

It should be understood that a stud bolt formed as shown in either Figure 2 or 4 may be readily applied or removed from a stud receiving element by means of a socket wrench inserted within the socket provided in the nut end of the stud. I have found by experimentation, however, that it is sometimes advisable to provide means to reinforce the walls of the socket against radially expanding forces developed while the socket wrench is inserted and in applying or removing the stud. Such reinforcing means may take various forms but I have shown in Figures 6 and 7 two suitable variations of means to reinforce the socket walls. With reinforcing means exterior of the socket walls it is possible to use a larger socket having thinner socket walls and consequently a stronger wrench may be used to apply or remove the stud.

Referring to Figure 6, the threaded nut end 34 of the stud bolt is provided with a nut 35 temporarily positioned to surround the walls of the socket 36 while the socket wrench 31 is inserted and is applying or removing the stud. Thus the nut 35 temporarily reinforces the walls of the socket 36 while the stud is being applied or removed.

In Figure 7, a stud bolt such as previously described with reference to Figure 4 is shown in connection with a socket wrench designed to be used in applying or removing the stud. The threaded nut end 38 provided with the nonthreaded portion 39 is shown with a special shaped socket wrench having the hexagonal shaped portion 48 inserted within the similarly shaped socket M of the stud. The socket wrench is also provided with the member 42 shaped to enclose the surfaces 39 exterior of the walls of the socket 4|. Thus the socket wrench 43 comprising the members 40 and 42 effectively reinforces the walls of the socket 4| while it is inserted and is being used to apply or remove the stud.

Thus far I have described several improved forms of stud bolt, all of which are provided with specially shaped surfaces, exclusive of their thread surfaces, to facilitate the application and removal of the stud without damage to any of the exposed thread surfaces. It should be understood that any of the forms of stud bolt previously described may be provided with tapered or straight threads on either their stud or nut ends without departing from the invention. The improved form of stud bolt of my invention finds ready application for use where heavy rusting or painting renders it extremely diflicult to remove the stud. The specially shaped surfaces, with particular reference to the preferred form shown in Figure 1, provide adequate and efficient means to cooperate with the jaws of a wrench or the like when applying the tremendous torque often necessary to remove a rusted stud.

By actual experimentation I have found that the torque necessary to back off a stud equipped with straight threads is substantially less than the set-up torque. I have also found that the back-off torque of a stud equipped with a tapered thread on the stud end may be equal to, or greater than, the set-up torque. Therefore, when using a tapered thread on the stud end of the stud bolt it will be found that there is no tendency for the stud to back out when the straight threaded nut on the nut end is backed off, after first setting the stud up tight.

To illustrate the above statement, assume that a stud with a taper threaded stud end is initially set up with 300 inch pounds torque. Then assume a straight threaded nut on the nut end of the stud set up with 400 inch pounds torque, disregarding the friction between the bottom of the nut and its seat. In setting the nut up to 400 inch pounds, since the 400 inch pounds exceeds the initialset-up torque applied to the stud, the stud would move deeper into its associated taper threaded hole an amount equal to the distance that it would enter if a torque of 400 inch pounds were applied directly, instead of indirectly through the nut. Now assume that the back-off torque for the nut is of the set-up torque, as is usual with straight threaded nuts and bolts. The back-off torqu will then be in this instance 320 inch pounds which is less than the 400 inch pounds required to move the stud end equipped with taper threads. Therefore, such a stud form, having taper threads on its stud end only, is advantageous since it assures that the stud will not back off when backing off the nut for any reason.

Any of the forms of studs previously described may be applied to an assembly unit such as is shown in Figure 8 of the drawing. However, I

have selected the preferred form of stud as shown and described in connection with Figure 1 to illustrate a complete assembly unit embodying the stud bolt of my invention. The assembly unit shown in Figure 8 comprises the elements 44 and 45. The element 44 which might conceivably be an engine crankcase is provided with a tapered and threaded recess 46. Passing through the element 45 is a bore 41 adapted to register or be aligned with the threaded recess 4G. The stud bolt 48 having the tapered and threaded stud end 49 is threaded into the recess 46 by means of the hexagonally shaped body portion 50 cooperating with a suitably shaped stud applying wrench (not shown). After the stud is tightly applied into the recess 46, the element 45 may be positioned with the body of the stud 48 passing through the bore 41. Thereafter a nut 5| may be tightly threaded to the nut end 52 of the stud 48 to thereby detachably join elements 44 and 45. If a cotter pin 53 is inserted in the cotter hole 54 the assembled unit will have self-locking features as will be readily understood.

It should be mentioned that the taper threaded portion on the stud end of the bolt should have more than a slight amount of taper. the taper is very slight, the parts into which the tapered threaded end of the studs are received must possess high physical properties in order to resist expansion of the metal surrounding the internal threaded hole. With a slight taper and the use of ordinary metal I have found that the tapered threaded stud end will not lock in the tapered threaded recess, but will continue to rotate and enter the recess by deforming the metal surrounding the recess. However, if the angle or degree of taper is made sufficiently great, the taper threaded stud end will lock against more than a certain amount of rotation with the taper threaded recess, since the angle of taper is large enough to require considerable deformation of the metal surrounding the recess. In other words, the stresses in the material surrounding the recess lie below the elastic limit of the material. The angle of taper for a taper threaded stud where the deformation forces equal the elastic limit of the material is called the elastic deformation critical angle. Studs having tapered threads of a degree of taper below this critical angle will continue to screw into matching threaded recesses by expanding them from the minimum to maximum diameter of the taper threaded portion of the stud. It is, therefore, important that the above angle be made large enough so that the taper thread can be used without any tapping action with relatively soft materials such as aluminum, bronze, etc. I have found it undesirable to employ taper threaded sections having an included angle of less than about one degree. Standard pipe threads having an included angle of about three degrees thirty minutes have been found to be entirely satisfactory.

Since the form of stud employed in assembling the unit shown in Figure 8 is provided with the shaped surfaces to cooperate with stud applying means it will be apparent that the stud in this assembly may be readily applied to and removed from the element 44 without damage to the exposed thread surfaces. It is also of importance to point out that the tapered threads used in connection with the stud end of the preferred form of stud bolt are of distinct advantage when used in connection with the assembly unit of Figure 8 wherein the element 44 may be an engine crankcase or the like. The tapered threads are adapted to give an exceedingly tight fit between the stud 48 and the element 44 and such fit has been found to be absolutely liquid tight, if the stud is properly applied.

It should be understood that my invention is not limited to the specific embodiments shown but is capable of being modified within the scope of the appended claims without departing from the spirit of the invention.

I claim:

1. A stud bolt having a threaded end portion the entering thread pitch diameter of which is smaller than the pitch diameter of the thread further in from said entering thread for engagement in a threaded hole in a stud-receiving element, and a threaded portion in the same hand as said end portion for engagement with a threaded nut, the degree of taper between the entering pitch diameter and the pitch diameter of the thread further in being sufficiently large so that the deformation forces produced by tightening the taper threaded portion are less than the elastic limit of the material of the bolt and of the work into which the tapered portion is screwed without any tapping action so that when the stud is set up in the element under a torque at least substantially equal to that employed to set up the nut, the reverse direction torque necessary to be exerted on the stud to remove it from the element is greater than the reverse direction torque necessary to back off the nut, whereby the stud remains tight in the element when the nut is backed off.

2. A stud bolt having a threaded tapered end for engagement with a mating tapered hole in a stud-receiving element and a threaded portion in the same hand as said end for engagement with a threaded nut, the taper of said tapered threaded end being sufficiently large so that no deformation forces beyond the elastic limit of the stud or the material into which it is threaded without any tapping action are produced so that when the stud is set up in the element under a torque at least substantially equal to that employed to set up the nut, the reverse direction torque necessary to be exerted on the stud to remove it from the element is greater than the reverse direction torque necessary to back off the nut, whereby the stud remains tight in the element when the nut is backed off.

3. A stud bolt having a threaded end portion the entering thread pitch diameter of which is smaller than the pitch diameter of the thread further in from said entering thread for engagement in a threaded hole in a stud-receiving element, and a threaded portion in the same hand as said end portion for engagement with a threaded nut, the degree of taper between the entering pitch diameter and the pitch diameter of the thread further in being sufficiently large so that the deformation forces produced by tightening the taper threaded portion are less than the elastic limit of the material of the bolt and of the work into which the tapered portion is screwed without any tapping action so that when the stud is set up in the element under a torque at least substantially equal to that employed to set up the nut, the reverse direction torque necessary to be exerted on the stud to remove it from the element is greater than the reverse dirction torque necessary to back off the nut, whereby the stud remains tight in the element when the nut is backed off, said stud having an unthreaded face portion of non-circular cross section for engagement by a tool by manipulation of which said stud bolt may be turned to set it up or remove it from the element.

4. A stud bolt having a threaded tapered end for engagement with a mating tapered hole in a studreceiving element and a threaded portion in the same hand as said end for engagement with a threaded nut, the taper of said tapered threaded end being sufilciently large so that no deformation forces beyond the elastic limit of the stud or the material into which it is threaded without any tapping action are produced so that when the, stud is set up in the element under a torque at least substantially equal to that employed to set up the nut, the reverse direction torque necessary to be exerted on the stud to remove it from the element is greater than the reverse direction torque necessary to back off the nut, whereby the stud remains tight in the element when the nut is backed 011, said stud having an unthreaded face portion of non-circular cross section for engagement by a tool by manipulation of which said stud bolt may be turned to set it up or remove it from the element.

JAMES WILLIAM BATCHELDER.

REFERENCES CITED The following references are of record in the file of this patent:

Number Number UNITED STATES PATENTS Name Date Upson July 25, 1939 McCormick Jan. 24, 1893 dHallor Jan. 31, 1933 Zeidler Feb. 7, 1933 Hochberger July 30, 1918 Minnis May 8, 1917 Broluska, Dec. 1, 1914 Hunt et a1 June 14, 1927 Hunt Aug. 2, 1927 Key June 15, 1937 FOREIGN PATENTS Country Date Great Britain Sept, 24, 1931

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