GB2339255A

GB2339255A - Locking nut and fastener assembly

Info

Publication number: GB2339255A
Application number: GB9814421A
Authority: GB
Inventors: Andrew Middleton Mclaren
Original assignee: MCLAREN ALISON STEWART
Current assignee: MCLAREN ALISON STEWART
Priority date: 1998-07-04
Filing date: 1998-07-04
Publication date: 2000-01-19
Also published as: GB9814421D0

Description

1 2339255 Nut and fastener assembl This invention relates to a nut and in

particular a locking nut and fastener assembly. 5 At present there are several types of locking nut available on the market for example nuts with nylon inserts which have a limited locking capability and are not really re-usable, particularly in applications where high temperature is a factor these nuts with nylon inserts cannot be used. Furthermore, very often the nylon "tears" as the nut is tightened.

A number of nut types are also available where additional friction is attained by malformation. However, this is not technically advisable as it can cause damage to the mating component. For example some types are malformed by pressing the nut into a dished form and therefore the thread form is affected and no longer conforms to the thread of the fastener used. Others have a malformed spigot and because this is a permanent situation it causes damage to the fastener to which it is applied.

Other known locking elements of screw fastenings such as spring lock washers of various shapes, safety tab washers, cotter pins, friction elements in the nut, self locking frictional threads, the use of check nuts and check screws, are insufficient for machines operating with large impact forces and vibrations.

GB-A-2041139 discloses a nut assembly. However, in that invention a split nut is used which has no landing face to torque the nut against the subject to be bolted.

The aim of the present invention is to provide a nut and fastener assembly which obviates or mitigates these disadvantages.

2 According to one aspect of the invention there is provided a nut comprising a body with external surfaces for receiving a driving tool and an aperture passing through the body and having an internal thread for cooperation with a separate but corresponding threaded element, the said body having a integral spigot portion extending co-axially as a collar from around the aperture and having at least one slit therein to enable the spigot portion to function as a collet.

According to a second aspect of the invention there is provided a fastener assembly comprising a nut having a body with external surfaces for receiving a driving tool and an aperture passing through the body and having an internal thread for cooperation with a separate but corresponding threaded fastener element, the said body having an integral spigot portion extending co- axially as a collar from around the aperture and having at least one slit therein to enable the spigot portion to function as a collet; a threaded fastener element, and a locking element adapted to cooperate with the nut by being locatable in proximity to the nut upon the fastener element so that when the nut is run up against the locking element the spigot portion may be compressed against the fastener element.

The locking element may be another nut or washer or a combination thereof, or an apertured part of a larger component e.g. a wheel hub, provided that in each instance part of the locking element is adapted to mechanically engage the spigot by an interference fit so as to allow compression thereof.

It will be understood the locking element is conveniently a tapped component enabling it to be selectively run up the length of a threaded fastener e.g.

a bolt to a particular chosen point whereupon the nut of 3 this invention may be run up to bring the spigotted portion into interference fit with the correspondingly adapted washer using a suitable driving tool to cause locking of the nut at that chosen position. 5 The fastener element may be a bolt of any description provided that at least part of the length thereof is suitably threaded to receive at least one nut of this invention and a locking element or elements.

The invention will now be described herein below by way of illustration with reference to the accompanying drawings and examples.

Figure la a side view of the nut according to one embodiment of the invention b an end view of the nut of Figure la C an axial section of a mating washer showing the tapered aperture Figure 2 a longitudinal sectional view of the fastener assembly without a mating washer.

Figure 3 a longitudinal view of a longer length nut according to a further embodiment of the invention.

Figure 4 a longitudinal, sectional view of a double lock application according to a yet further embodiment of the invention.

A nut as shown in Figure 1 is provided which has a body 1 of substantially hexagonal circumference and a flat top 2 and bottom 3 surface each with a central aperture which extends into the centre of the body of the nut I thus connecting to form a through bore 4 in the body of the nut 1. Integrally connected to the bottom surface 3 of the nut is a spigot 5 which extends 4 coaxially from the body of the nut 1 to form a collar 6 around the aperture 4 in the base 3 of the nut 1. The outer surface of the spigot 5 is tapered. The end of the spigot 5 remote from the body of the nut I has a lesser diameter than the end of the spigot 5 adjacent the nut 1.

The collar 6 has longitudinal slots 7 positioned at equidistant intervals around its circumference. The slots 7 extend longitudinally towards the junction between the body of the nut I and the spigot 5 thereby allowing the spigot 5 to function as a collet.

Both the body of the nut 1 and the spigot 5 have an internal screw thread for cooperation with a fastener element 8.

The fastener element 8 is generally a bolt, at least part of the length of which is suitably threaded for cooperation with the body of the nut I and spigot 5 as described above. The bolt 8 can be of any suitable type such as a carriage bolt. Such a bolt 8 may have for example an allan head or a socket head which is adapted to receive a pin key or driving tool such as a wrench.

A fastener assembly 9 is also provided which comprises a nut 1 as described above, a fastener element 8 as previously described and a locking element 10. The locking element 10 is adapted to cooperate with the nut 1 by being locatable in proximity to the nut I upon the fastener element 8. The locking element 10 may be any suitable mating washer or nut which has a bore tapered to slightly greater dimensions of those of the spigot 5 (as shown in Figure 1c) to allow an interference fit between the nut 1 of the present invention and the mating washer 10 when the nut 1 is run up against the mating washer 10 so that the spigot portion 5 of the nut 1 is compressed against the bolt 8 or any other suitable fastener element Example 1

The nut is a standard 12.7mm (%I') BSW size with an additional spigot 4.32mm (0.17011) long, tapered at 70 the spigot is slit with six 1.02mm (0.04011) slits to facilitate closure with a collect action.

The mating washer which is 4.76mm (0.187511) thick will not allow the spigot to land. The taper of the washer bore is 8' which allows the spigot taper to increase on closure. The two diameters are of an interference fit and when the two parts are put together before assembly there will be a 1.27mm (0.05011) gap between the faces and when the nut is fully torqued the nut face will land on the washer face.

Example 2

The tapered spigot has a taper of 7340 at each side (150 included angle). The length of the spigot is 3911 of the nut length except in the case of the thin lock nut where the spigot is still 390-. of the standard nut length.

The mating washer has a taper of 80 in the bore so that when the collet closes it will conform to the taper in the washer bore. The washer thickness is 100i greater than the spigot length so that the spigot cannot contact the component to be fastened. It is important that the taper on the two components is exact and there will be a gap between the undersurface of the nut and the washer face of 25% of spigot length.

It should be noted that the size and form of thread used as an example is immaterial and the dimensions are proportional for any thread size or form.

Herein below are the results of tests carried out to compare the nut of the present invention with those of the prior art.

G Test 1 Firstly a fastener such as a standard carriage bolt was used and a standard nut was run down the thread followed by a mating washer and nut according to this invention, the nut herein after described as a lock nut. The lock nut was tightened against these components with a torque wrench, to several different torques. After each tightening the loosening torque was recorded. The test itself was carried out when having loosened off the standard nut the "drag" or friction was measured by torque wrench. The "drag" is defined as the Torque in Lbs/Ft induced to unscrew the lock nut after the nut has been loosened from the face to which it was tightened and the mating washer remains on the spigot. The results show that by using the lock nut of the present invention the "drag" or friction was found to be considerable thereby proving that a heavy "drag" had been attained by the closure of the tapered spigot. In addition, when the mating washer was released the lock nut was again free on the male thread. It was found that the results revealed that the lock nut of the present invention gave more advantageous results than the standard nut. The results of this test are as outlined in Table 1.

Test 2 The second test involved a special test rig being built to test the lock nut in severe vibration conditions. The test rig comprised two plates oscillating on two pillars and a main shaft which was driven by an electric motor. On the main shaft itself was located a cam which was used to drive the oscillating plates in a reciprocating movement, travelling on the vertical pillars against a shoulder. It was spring loaded for a fast downward movement and the reciprocating speed was 1400 times per minute thus making this particular test much more severe than a standard vibration test.

7 The test itself was carried out using one standard bolt and nut on one side of the test plate and a standard bolt with lock nut and mating washer of the present invention on the other side. various torques were applied and it was found that the standard bolt and nut loosened and indeed fell out whilst the lock nut and mating washer of the present invention were still tight and required the expected torque to be loosened. Table 2 illustrates the results of this test.

In another embodiment the lock nut 1 can also be applied without a mating washer 10 where the component to be secured has a bore of similar tapered dimensions as the spigot portion 5 of the nut 1 to enable retention of the spigot collar 6. In this case the component is drilled with either a clearance hole or a fitted tolerance and is counter bored by a tool preferably with a pilot to ensure an accurate tapered recess. There should be a gap of a quarter spigot length between the nut face and the component (as shown in Figure 2).

In a further embodiment the nut 1 and fastener assembly 9 can be applied to a wheel of automotive vehicles such as motor cars, lorries, track vehicles etc. In the case of road vehicles the stud holes 11 in the wheel would have to be adapted to mechanically engage the spigot portion of the nut 5 by interference fit to allow compression of same. It should be noted also that the lock nut 12 to be used in this particular application would generally be of longer length than a lock nut 1 to be used in other applications (as shown in Figure 3).

In a yet further embodiment the nut can also be used in double lock applications. A lock nut 1 according to the present invention is provided. A further lockable element 13 e.g. a nut adapted to cooperate with the lock nut of this invention is provided, which is a 8 substantially annular body 14 with a central bore 15 which includes a tapered recess 16 to receive the collar 6 of the spigot portion 5 of the lock nut 1. The rest of the bore 15 in the standard nut is threaded to receive the correspondingly threaded bolt 8 or fastener element B. The result is a double locking effect for such cases as engine big-ends (as shown in Figure 4).

It will be understood by those in the art that a manufacturer will have to establish a scale of tolerance to suit his method of manufacture whether by cold forming or machining but whichever method is adopted it is important to adhere to the aformentioned geometry.

is It will also be understood that the width of the slits in the spigot collar will vary according to the amount of closure for example an M12 nut will be approximately 1.0 mm whereas an M48 nut will be 6.0 mm ensuring that there is not interference between the closing faces.

In use of the lock nut 1 of the present invention a bolt 8 with a screw thread is provided and a washer 10 is selectively run up the length of the bolt 8 to a chosen point whereupon the lock nut 1 is also run up the bolt 8 to bring the spigotted portion 5 of the lock nut 1 into interference fit with the correspondingly adapted washer or nut 10 using a suitable driving tool such as a wrench etc to cause locking of the nut I at that chosen position.

The lock nut 1 of the present invention can be applied normally along with a suitably tapered washer or nut 10 to any assembly 9 but when the nut 1 is tightened to the correct torque the spigotted portion 5 of the lock nut 1 is closed onto the male thread of the bolt 8, screw or any other type of fastener, thereby gripping the thread and creating a greater friction.

9 The advantages of the present invention are that the screw thread of the lock nut or the fastener element such as the bolt are not malformed or damaged in any way.

Furthermore as can be seen from the test results the loosening torque for the nut of the present invention was found to be advantageous over a normal standard nut thus making it advantageous to use the nut and fastener assembly of the present invention in applications where safety is of paramount importance. Moreover the nut of this invention can be reused on many occasions It is envisaged that the nut and fastener assembly can be used in all types of applications for example n the oil industry, earth moving equipment, engines, shipbuilding, winches, cranes, aircrafts, washing machines or any other product where vibration occurs.

TABLE 1

TABLE OF SUGGESTED SPIGOT DIAMETERS AT POINT METRIC IMPERIAL Nut Size Spigot Nut Size Spigot Diameter (inches) Diameter (mm) (inches) M4 4.76 3/16 0.2193 M6 7.07 1/4 0.2925 M8 9.22 5/16 0.3605 M10 11.60 3/8 0.4380 M12 14.10 1/2 0.5850 M16 18.41 1/2 0.720 M20 22.50 3/4 0.850 M22 24.66 7/8 0.980 M24 27.17 1 1.125 M30 33.68 li4 1.395 M36 40.20 im 1.665 M48 S2.76 2 2.1875 M60 65.27 24 2.7075 M72 77.50 3 3.220 11 TABLE 2 RESULTS OF TORQUE TESTS TEST ON 1/211 BSW GRIP LOCK-NUT WITH WASHER Nut & Washer Hardened and Tempered to 32/34 Rc.

Test Torque Torque to Drag After Torque to No. Applied Loosen Loosening Loosen in Lbs/Foot Standard Nut Test A Test B Test A Test B 1 40 Lbs/Ft 38 34 14 20 28 2 50 Lbs/Ft 42 38 30 38 34 3 60 Lbs/Ft 45 41 41 39 40 4 70 Lbs/Ft 60 50 44 44 47 80 Lbs/FT 64 55 44 42 50 TEST ON 1/21' UNC GRIP LOCK-NUT WITH WASHER Nut & Washer Hardened and Tempered to 32/34 Rc.

Test Torque Torque to Drag After Torque to No. Applied Loosen Loosening Loosen in Lbs/Foot Standard Nut Test A Test B Test A Test B 1 40 Lbs/Ft 32 27 30 20 31 2 50 Lbs/Ft 31 32 32 36 34 3 60 Lbs/Ft 32 40 34 37 38 4 70 Lbs/Ft 41 43 38 36 40 80 Lbs/FT 42 46 38 37 42 12

Claims

1. A nut comprising a body with external surfaces for receiving a driving tool and an aperture passing through the body and having an internal thread for cooperation with a separate but corresponding threaded element, the said body having an integral spigot portion extending co-axially as a collar from azound the aperture and having at least one slit therein to enable the spigot portion to function as a collet.

2. A fastener assembly comprising a nut having a body with external surfaces for receiving a driving tool and an aperture passing through the body and having an internal thread for cooperation with a separate but corresponding threaded fastener element, the said body having an integral spigot portion extending co-axially as a collar from around the aperture and having at least one slit therein to enable the spigot portion to function as collet, a threaded fastener element, and a locking element adapted to cooperate with the nut by being locatable in proximity to the nut upon the fastener element so that when the nut is run up against the locking element the spigot portion may be compressed against the fastener element.

3. A fastener assembly according to claim 2 wherein at least part of the locking element is adapted to mechanically engage the spigot by an interference fit so as to allow compression thereof.

4. A fastener assembly according to Claims 2 or 3 wherein the locking element is another nut or washer or a combination thereof.

S. A fastener assembly according to Claims 3 or 4 wherein the locking element is a tapped component enabling it to be selectively run up the length of the threaded fastener to a particular chosen point.