GB1579355A

GB1579355A - Applying locking patches of resilient resin to articles

Info

Publication number: GB1579355A
Application number: GB28964/77A
Authority: GB
Original assignee: USM Corp
Current assignee: USM Corp
Priority date: 1976-07-12
Filing date: 1977-07-11
Publication date: 1980-11-19
Also published as: CA1071806A; JPS538640A; DE2731018A1; DE2731018C2; JPS6034428B2

Description

(54) IMPROVEMENTS IN OR RELATING TO APPLYING LOCKING PATCHES OF RESILIENT RESIN TO ARTICLES (71) We, USM CORPORATION, of Flemington, New Jersey, United States of America, a corporation duly organised and existing under the laws of said State of New Jersey, U.S.A., having a principal place of business at 140 Federal Street, Boston, Commonwealth of Massachusetts, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention is concerned with improvements in or relating to applying locking patches of resilient resin to articles in particular with applying such locking patches to articles which have an internally threaded portion and openings at both ends of the threaded portion.

In U.K. Patent Specification No. 1,475,750, there is described an apparatus by which an article may be provided with a locking patch on an internally threaded portion thereof. By the use of that apparatus, a locking patch can be obtained that is adequate for many purposes but for certain uses it is desired to provide greater locking torque. An increase in the amount of resin applied to form a thicker locking patch gives some increase in the locking torque but the increase obtainable is limited since an excessively thick patch causes difficulty in assembly and the generation of chips due to shearing off of portions of the patch.

It is an object of the present invention to provide an improved apparatus and method for applying locking patches of resilient resin to articles which have an internally threaded portion wherein locking patches with improved locking torque are obtained.

There is hereinafter described in detail an apparatus and a method of operation of the apparatus which are illustrative of the invention. The illustrative apparatus is suitable for use in applying locking patches of resilient resin to articles which have an internally threaded portion and openings at both ends of the threaded portion, the particular example of such an article in relation to which the illustrative apparatus is described being a nut. The illustrative apparatus comprises a turntable which forms conveying means arranged to receive nuts in notches therein and convey them along an arcuate treatment path by rotation of the turntable. The nuts are supported on the turntable with the longitudinal axes of their threaded portions extending upwardly and the openings at the ends of their threaded portions substantially uncovered.

The nuts are fed to the turntable down a loading chute of the illustrative apparatus and, while on the loading chute, they pass through a heating coil which forms heating means arranged to heat the threaded portions of the nuts received by the turntable to a temperature above the softening point of resin to be applied to the nuts. When a nut is on the turntable, a tube extends through its lower opening through which an air stream containing particles of resin can pass into the nut. The tube and openings through which particles are supplied to the air stream form directing means arranged to direct particles of the resin through the opening at the lower end of the threaded portion of the nut as the nut is conveyed over a first portion of the treatment path so that the particles impinge against a first area of the threaded portion. The particles are then softened by heat from the threaded portion and adhere building up a deposit on the first area.

The illustrative apparatus also comprises turning means comprising a resilient finger arranged to turn each nut on the turntable through a predetermined angle about the longitudinal axis of its threaded portion. The turning takes place after the nut has been conveyed over the first portion of the treatment path and before it is conveyed over a second portion of the treatment path. As the nut is conveyed over the second portion of the treatment path, continued operation of the directing means causes a deposit of resin to build up on a second area of the threaded portion. Thus, the locking patch is formed on two areas of the threaded portion.

The present invention provides, in one of its aspects an apparatus suitable for use in applying locking patches of resilient resin to articles which have an internally threaded portion and openings at both ends of the threaded portion, the apparatus comprising conveying means arranged to receive such threaded articles and convey them along a treatment path with the longitudinal axes of their threaded portions extending upwardly and the openings at the ends of their threaded portions substantially uncovered, heating means arranged to heat the threaded portions of articles received by the conveying means to a temperature above the softening point of resin to be applied to the articles, directing means arranged to direct particles of the resin through the openings at the lower ends of the threaded portions of the articles as the articles are conveyed over a first portion of the treatment path so that the particles impinge against a first area of each of the threaded portions, are softened by heat from the threaded portions, and build up a deposit on each of said first areas, and turning means arranged to turn each of the articles on the conveying means through a predetermined angle about the longitudinal axis of its threaded portion after the article has been conveyed over the first portion of the treatment path so that operation of the directing means as the articles are conveyed over a second portion of the treatment path causes a deposit of resin to build up on a second area of each of the threaded portions.

The present invention provides, in another of its aspects, a method of applying locking patches of resilient resin to articles which have an internally threaded portion and openings at both ends of the threaded portion, the method comprising conveying the articles along a treatment path with the longitudinal axes of their threaded portions extending upwardly and the openings at the ends of the their threaded portions substantially uncovered, heating the threaded portions of the articles to a temperature above the softening point of resin to be applied to the articles, directing particles of the resin through the openings at the lower ends of the threaded portions of the articles as the articles are conveyed over a first portion of the treatment path so that the particles impinge against a first area of each of the threaded portions, are softened by heat from the threaded portions, and build up a deposit on each of said first areas, and turning each of the articles through a predetermined angle about the longitudinal axis of its threaded portion to expose a second area of its threaded portion to the particles of resin so that a deposit is built up on the second area.

There now follows a detailed description, to be read with reference to the accompanying drawings, of the illustrative apparatus aforementioned. It is to be understood that the illustrative apparatus has been selected for description by way of example and not of limitation of the invention.

In the drawings: Figure 1 is a perspective view of the illustrative apparatus with parts broken away; Figure 2 is a plan view with parts broken away of the illustrative appartaus; Figure 3 is a sectional view taken on the line 111-111 in Figure 2; Figure 4 is a sectional view taken on the line IV-IV in Figure 2; Figure 5 is a sectional view taken on the line V-V in Figure 4; Figure 6 is a plan view, on an enlarged scale, of a loading chute of the illustrative apparatus; Figure 7 is an elevational view of the loading chute shown in Figure 6; Figure 8 is a plan view, on an enlarged scale, of an unloading chute of the illustrative apparatus; Figure 9 is an elevational view of the unloading chute shown in Figure 8; Figure 10 is a perspective view of the illustrative apparatus, with parts broken away, showing turning means of the apparatus; Figure 11 is a plan view, on an enlarged scale, of the turning means shown in Figure 10; Figure 12 is a view similar to Figure 11 of an alternative turning means of a modification of the illustrative apparatus; Figure 13 is a view similar to Figure 12 but showing the alternative turning means at a subsequent stage of its operation; and Figure 14 is a view taken in the direction of the arrow XIV in Figure 13.

The illustrative apparatus is suitable for use in applying locking patches of resilient resin to articles which have an internally threaded portion and openings at both ends of the threaded portion. An example of such an article is a nut N in relation to which the illustrative apparatus will be described.

The illustrative apparatus comprises conveying means arranged to receive nuts N and convey them along a treatment-path with the longitudinal axes of their threaded portions extending upwardly and the openings at the ends of their threaded portions substantially uncovered. The conveying means comprises a circular table 10 which is rotatable about a central axis thereof, in the direction shown by the arrows in Figures 1 and 2. In the operation of the illustrative apparatus, the table 10 is rotated continuously about a fixed housing 11 by means of a V-belt 19 received in a groove 18 of a hub 16 of the table 10 and driven by a motor (not shown). The upper surface of the table 10 is provided by a plate 17 fixed to the hub 16. The hub 16 is rotatable on a pair of bearings 20 and 21.

The illustrative apparatus also comprises a loading chute 12 (Figures 1, 2, 6 and 7) which is inclined downwardly towards the table 10 and is effective to deposit the nuts N on to the table 10. The rotation of the table 10 causes the nuts N to be carried under a vacuum hood 13 (Figures 1 and 2) to an unloading chute 14. The unloading chute 14 is inclined upwardly away from the table 10 and is effective to unload the nuts N from the table 10 (see Figures 8 and 9). The fixed housing 11 is provided with a hopper 15 (Figure 1) into which resin to be applied to the nuts N is introduced in particle form. Resin introduced into the hopper 15 passes down a central bore 28 of the housing 11 (Figure 10). The bore 28 communicates with a slotted opening 29 which. extends through 1800 except for a central section which is blocked by a member 29a. The slotted opening leads to the exterior of the housing 11 where it communicates with a plurality of apertures 22 in the table 10. A conical divider 30 is located in the bore 28 adjacent the opening 29 to assist in guiding particles to the opening 29.

The apertures 22 are in the hub 16 of the table 10 and are arranged around the entire circumference of the hub 16 (Figures 2 and 10). Thus as the table 10 rotates, at any one time, some of the apertures 22 communicate with the opening 29 while others are closed by either the housing or the member 29a. Each of the apertures 22 communicates with a tube 23 which is mounted on the table 10 beneath the plate 17 and extends radially of the table 10. Each of the tubes 23 provides a conduit movable with the table 10 through which a stream of resin particles can pass.

The outer periphery of the plate 17 is formed into a plurality of V-shaped notches 24. The shape of each notch 24 (see Figure 2) is substantially complementary to two adjacent flat areas of the exterior of a nut N. Thus, with hexagonal nuts N as shown in the drawings, the notches 24 form angles of 1200. The notches 24 are formed around the entire periphery of the plate 17 and each has a tongue 25 associated with it which forms a base for supporting a nut N with two of its flat areas in engagement with the notch 24. Each tongue 25 is secured to the plate 17 by means of a fastener 27 which also secures a bracket 26 to the plate 17.

The brackets 26 support the outer ends of the tubes 23. Each of the tongues 25 has a circular opening therethrough through which the outer end of the associated tube 23 passes (Figure 3). The outer end of the tubes are bent upwards at an angle of approximately 450 so that they extend through the lower openings of nuts N located in the notches 24. An inlet opening 31 (Figure 2) extends into the bore 28 at- its lowermost extremity and is connected to a source of air under pressure (not shown).

The portion of the housing 11 which is diametrically opposed to the opening 29 contains four vertically-extending cylindrical cavities 32 (Figures 2 and 3). Each cavity 32 communicates at its lower end with a chamber 33 and at its upper end with a slotted opening 34. The opening 34 extends over 1500 of the hub 16 being bounded by an inner wall 35. The opening 34 communicates with the apertures 22 while the apertures 22 are opposite the opening 34 and the chamber 33 is connected to a vacuum source (not shown) so that air can be sucked from the tubes 23.

The plate 17 is secured to the hub 16 by a removable retaining plate 36 held by four screws 37. Removal of the screws 37 and the plate 36 allows replacement of the plate 17 with a plate having notches 24 appropriate to nuts of a different size and/or shape. Because of the clearance between the table 10 and the housing 11, there is a possibility of particles, being transferred between the tubes 23 and the opening 29 or the opening 34 and the tubes 23, escaping between the outer surface of the housing 11 and the inner surface of the hub 16. To reduce this possibility, the housing 11 has two grooves 38 and 39 extending around it (Figure 4), the groove 38 being above the openings 29 and 34 and the groove 39 being below the openings A vertical bore 40 in the housing 11 communicates with the grooves 38 and 39 and is connected to a source of air under pressure (not shown) by a duct 43 so that air will flow from the grooves 38 and 39.

The vacuum hood 13 is divided into two portions for ease of construction and embraces the area around the opening 29. These portions are identical and therefore only one will be described in detail. This portion contains a chamber 44 connected to a vacuum source (not shown). A cover plate 45 extends outwardly from the hood portion so that it covers nuts N on the table 10 (Figure 1). The hood portion is divided by a plurality of partitions 46 which serve to equalise the pressure in the hood portion.

The aforementioned loading chute 12 comprises an outer rail 47 and an inner rail 48 (Figures 6 and 7). The distance between the rails 47 and 48 is substantially the width between opposite points of one of the nuts N. The nuts N travel down the chute 12 in a flat-to-flat orientation (Figure 2) and are therefore aligned for engagement with the notches 24. A segment 49 of the chute 12 is made of noninductive and heat-resistant material and is surrounded by an induction coil S0 (Figure 1) arranged to heat nuts N travelling along the segment 49. The coil 50 forms heating means arranged to heat the threaded portions of nuts N received by the table 10 to a temperature above the softening point of resin to be applied to the nuts N. The nuts N may be fed to the chute 12 by any suitable feeder for example a feeder of the vibrating type. The nuts N may be visualised as forming a chain which meshes with the notches 24 which may be visualised as forming a sprocket.

However, considering an individual nut N in a notch 24, the flat areas of the adjacent nuts define, with the walls of the notch 24 containing the nut N, a deep slot of which the side walls diverge (Figure 2). The clearance between the nut N and the diverging walls of the nut N provide limited freedom of rotation to the nut N which it will be seen is necessary.

As the table 10 is rotated, nuts N from the chute 12 drop on to the table 10 over the ends of the tubes 23 and into the notches 24. It is found that up to 600 nuts per minute can be fed to the table 10. Rotation of the table 10 then causes the nuts N to be conveyed along the aforementioned treatment path which is thus arcuate. The treatment path is opposite the vacuum hood 13 and comprises a first portion opposite the first portion of the opening 29, an intermediate portion opposite the member 29a, and a second portion opposite the second portion of the opening 29.

Once the nuts N have been conveyed along the treatment path, they come to the unloading chute 14 which is effective to remove the nuts from the table 10 (see Figures 1,8 and 9). The chute 14 comprises an outer rail 51 and an inner rail 52 and is generally similar to the loading chute 12 except that it provides-a ramp up which the nuts N travel away from the table 10. While on the table 10, the nuts N are retained in the notches 24 by a resilient pressure member 60 of the table 10 which abuts the rails 47 and 51.

Located adjacent the intermediate portion of the treatment path is turning means of the illustrative apparatus. The turning means is arranged to turn each of the nuts N on the table 10 through a predetermined angle about the longitudinal axis of its threaded portion after the nut N has been conveyed over the first portion of the treatment path. The turning means is arranged to displace the nuts N from the notches 24, turn them, and return them to the notches 24 in a new orientation relative to the notches 24. The nuts N will thus, if they are hexagonal, be turned through 60 or a multiple of 60".

In the illustrative apparatus, the turning means comprises a resilient finger 62 (Figures 10 and 11) which is mounted to engage outer flat areas 64 adjacent the outermost corner 66 of successive nuts N as they are conveyed along the intermediate portion of the treatment path. The finger 62 thus exerts a force on each nut N in the opposite direction to the direction of movement of the nuts N thereby creating a turning moment on each nut N. The clearance between the diverging flat areas of adjacent nuts allows turning of each nut N and the movement created by the finger 62 is sufficient to turn each nut N somewhat more than half of the 60 necessary to bring a corner 68 of the nut into alignment with the angle of the notch 24. This movement brings opposed flat areas 70 and 72 of the nut N into engagement with flat areas 74 and 76 of the adjacent nuts N spreading them against the action of the resilient pressure member 60. The pressure of the flats 74 and 76 against corners 78 and 80 of the nut N and the action of the resilient member 60 against a corner 82 of the nut N completes the turning of the nut N and returns it to the notch 24.

Before operating the illustrative apparatus, the hopper 15 is loaded with particles of thermoplastic resin. The resin may be a powder which is a mixture comprising a major proportion of powdered polyamide resin (suitably nylon 11) and a minor proportion of epoxy resin, the powder having a particle size distribution such that less than 2% is retained on a No. 70 Sieve, about 90 /" is retained on a No. 140 Sieve, and about 5% passes a No. 325 Sieve (U.S. sieve sizes).

With the resin introduced into the apparatus, the vacuum is applied to the chamber 33 and the duct 43 and air under pressure is applied to the inlet opening 31. Vacuum is also applied to the hood 13 and the induction coil 50 is energised. When these steps have been taken, the apparatus is started by activation of the motor which drives the belt 19 and the feeder of the chute 12 is activated.

An illustrative method of operation of the illustrative apparatus will now be described, in this method the nuts N are heated as they pass through the coil 50 to a temperature above the softening point of the resin thereby ensuring that the threaded portion of each nut N is above that temperature. As it approaches the table 10, each nut N is retained on the chute 12 by the outer rail 47 until it is received in a notch 24 with the longitudinal axis of its threaded portion extending upwardly, the openings at the ends of its threaded portion substantially uncovered, and the end of one of the tubes 23 extending through the lower opening of its threaded portion.

As the table 10 rotates, each nut N is carried along the treatment path. As it is carried along the first portion of the treatment path, the aperture 22 associated with the tube 23 which extends into the nut N comes into registry with the first portion of the opening 29 and air flows through the opening 31, the lower portion of the bore 28, the opening 29, the aperture 22, and the tube 23 into the nut N. As the air flows through the bore 28 it picks up particles of powder. The opening 31, the bore 28, the opening 29, the aperture 22 and the tube 23 thus form directing means which direct particles of the resin through the opening at the lower end,Qf the threaded portion of each nut N as the nuts N are carried over the first portion of the treatment path. The particles impinge against a first area of the threaded portion of the nut N, are softened by heat from the threaded portion, and adhere building up a deposit on the first area. The particles of resin are fed at a uniform rate and the air passing from the bore 28 into the opening 29 produces a slight suction or "Venturi effect" which draws the particles into the air stream.

When each nut N reaches the intermediate portion of the treatment path, the directing means ceases to direct the particles on to it because the opening 22 is blocked by the member 29a. Thus, the directing means operates while the nut N is conveyed along the first and second portions of the treatment path only. As it is conveyed along the intermediate-portion of the treatment path, each nut N is turned by the turning means exposing a second area of its threaded portion to the directing means and subsequently, as the nut N is conveyed over the second portion of the treatment path, continued operation of the directing means causes a deposit of resin to build up on the second area of its threaded portion.

As the particles are directed on to the nuts N, the vacuum hood 13 is drawing off excess particles through the upper opening of the threaded portion of each nut N. This prevents particles from adhering to the nuts except where they impinge directly on the threaded portions.

After passing under the hood 13, the nuts N arrive at the unloading chute 14, where the rail 51 forces them into a flat area to flat area orientation, and are removed from the table 10. Over the remaining portion of the rotation of the table 10, between the unloading chute 14 and the loading chute 12, which is approximately 150 , the apertures 22 register with the opening 34 and air is sucked through the tubes 23 to remove any excess particles therefrom. This serves to prevent particles collecting in the orifices of the tubes 23 at a position where they may be deposited in an undesirable position on a nut N.

A modified form of the illustrative apparatus otherwise identical to the illustrative apparatus has an alternative turning means (see Figures 12, 13 and 14).

The alternative turning means comprises a wedge 84 supported by an arm 85 above the table 10 in the intermediate portion of the treatment path. The wedge 84 is engaged by successive nuts N as they are conveyed, the wedge 84 thus displaces the nuts N from the notches 24, outwardly of the table 10, so that they can be more readily turned. The wedge 84 is disposed at an angle such that it is approximately parallel to the leading inner flat area of a nut N conveyed past it by the table 10. Once the nuts N have been displaced from the notches 24, a device 86 of the turning means turns them. The device 86 comprises a surface member in the form of a wheel 88 having a surface 90 which slopes upwardly in a direction away from the table 10 and is arranged to be engaged by successive nuts N displaced by the wedge 84. The slope of the surface 90 may be, for example, 40 upwardly from the horizontal. The wheel 88 is positioned opposite the wedge 84 less than a nut length further along in the direction of movement of the table 10 so that as a nut N is pushed from its notch 24 by the wedge 84, the outermost corner of the nut N rides up the surface 90. The device 86 also comprises means for rotating the wheel 88 about a shaft 89 so that the surface 90 moves in the same direction as the table 10 at a speed greater than that of the table 10. Thus, when the outermost corner of a nut N rides up the surface 90, a turning moment is applied to the nut N. Suitably the speed of the surface 90 is 1.5 times that of the table 10.

A ramp 92 is arranged to engage the undersurfaces of the nuts N before they reach the wedge 84. This ramp 92 slopes upwardly and is arranged to raise the nuts away from the tongues 25 before the nuts N are turned by the turning means.

The operation of the device 86 is illustrated by Figure 12. The retarding action of the wedge 84 on a nut N' moved against it by rotation of the table 10 packs together two or three nuts preceding the wedge 84 so that their adjacent flat areas are in all over contact and the two or three nuts move in a straight line tangentially outwardly from the notches 24. The packing together of the nuts and the tangential movement ensure adequate turning space for the nut N' as it is carried past the wedge 84 and the wheel 88. To aid in following the turning of the nuts, the corners of the nuts opposite the corners initially in the notches 24 have been marked in Figures 12 and 13 with small circles. As shown in Figures 13 and 14, when nut N' reaches the wedge 84 and is pushed out by the wedge, the corner of the nut N' marked with a circle rides up the sloping surface 90 and, since the speed of the surface 90 is greater than the speed of the notches 24, that corner is urged forwardly while the corner adjacent the notch 24 is retarded. Thus, a turning moment is created rotating the nut N' in the direction indicated by the arrow in Figure 13 so that the next corner of the nut N' is brought into registry with the angle of the notch 24.

After the nut N' has been turned, the return of the nut N' to a position with its faces in contact with the sides of its notch 24 is assisted by the slope of the surface 90 forward of a line between the centres of the table 10 and the wheel 88 and by a secondary ramp 96 which follows the wheel 88 to prevent the nut N' from tipping as it leaves the surface 90. The sloping upper surfaces of the tubes 23 may also assist in bringing the nut N' to a position with its faces in contact with the sides of the notch 24.

EXAMPLE A continuous succession of 3/8"-16 hex nuts was supplied in flat-to-flat relation to the loading chute 12 of an apparatus as shown in Figures 1 to 11, with the table 10 rotating at about 4.3 revolutions per minute and a resin feed of about 23 grams per minute of a mixture of powdered polyamide resin (nylon 11) and a minor proportion of epoxy resin. The mixture had a particle size distribution such that less than 2% was retained on a No. 70 Sieve, about 90 /" was retained on a No.

140 Sieve and about 5% passed a No. 325 Sieve. In passing down the chute 12, the -nuts were heated by the high frequency induction coil 50 to a temperature of about 575"F and then moved into registry with the V-shaped notches 24 of the support table 10 with their lower faces resting on the tongues 25 of the table and with the lower openings of the nuts generally aligned with the openings in the tongues so that the discharge ends of the particle directing conduits or tubes 23 extend within the open lower ends of the nuts for directing resin particles against the threaded surfaces of the nuts. As the table rotated, air and entrained resin particles flowed from the slotted opening 29 through the tubes 23 and against the hot threaded surfaces to build up deposits on the first areas of the threaded surfaces of the nuts.

Approximately halfway along the arcuate treatment path of the nuts from the loading chute 12 to the unloading chute 14, the supply of resin powder to the tubes 23 associated with the nuts reaching this location was blocked by the member 29a and the nuts were turned through 60 by the finger 62. After the nuts had been turned, supply of resin to the tubes 23 associated with the nuts was resumed to build up a deposit on a further area of the threaded surface. Nuts carried to the unloading chute were lifted by the chute 14 away from the support table 10 and pushed up the chute 14 by successive nuts reaching the chute.

After cooling, the nuts were tested for locking torque using Grade 5 zinc phosphate an oil finished hex head screws. The nuts were seated to 3,200 pounds before prevailing torque was measured.

Also for comparison, a succession of identical nuts was treated using the same conditions and the same machine except that the blocking segment and turning device had been removed so that all resin was deposited in a single area.

The results of the torque tests of the nuts prepared using the process and apparatus of the present application with

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

After cooling, the nuts were tested for locking torque using Grade 5 zinc phosphate an oil finished hex head screws. The nuts were seated to 3,200 pounds before prevailing torque was measured.

Also for comparison, a succession of identical nuts was treated using the same conditions and the same machine except that the blocking segment and turning device had been removed so that all resin was deposited in a single area.

The results of the torque tests of the nuts prepared using the process and apparatus of the present application with the nuts prepared without the improvements of the present application are given in the following table: 1st Removal 5th Removal

4 Installation max/min max/min Standard nuts* 69 36/25 28/17 Nuts rotated 60 * 61 50/37 39/27 Specification 80 max 12/5 8.5/4 *Values average of 5 tests in Ibs-inch.

In using the illustrative apparatus, resin is deposited on two areas and each deposit forms part of the locking patch. The first applied resin particles soften and adhere to the hot threaded surface and this softened resin is particularly effective for catching later applied particles progressively to build up the deposit of resin in the desired thickness and contour and to transfer softening heat from the hot threaded surface to melt the later applied particles so that the applied particles coalesce to a continuous body.

The thickness and to some extent the lateral dimensions of the resin deposits on the areas may be controlled by the temperatures of the nuts, the rate of supply of the resin particles and air, and the length of time during which resin particles are applied to the areas, i.e. the time required for a nut to be conveyed along one of the portions of the treatment path. The resin deposits are thicker at their centres and taper uniformly towards their edges. If desired, the deposits may be controlled such that the first and the second areas overlap so that the edges of the deposits overlap to an extent that the combined thickness of the overlapping edge portions approximate the thickness of the centres to form in effect a unitary patch over the combined area of the deposits to give a maximum locking effect for the locking patch area. The deposition may of course, be controlled to provide substantially separate locking patches or any condition between separate patches and a unitary patch.

In the illustrative apparatus, the table 10 is provided with sixty tubes 23, each tube projecting slightly into the nut N at approximately 450. The powder is thus guided through the tube 23 to strike the internal threads of the fastener at a point slightly above the lower most thread and the air powder flow is adjusted such that very little powder impinges upon the uppermost thread. As the tube 23 and the associated nut N rotate together over the 1800 segment, a steady, rather uniform flow of powder is projected into the nut except at the intermediate portion where the nut is turned and flow of powder is cut off by the member 29a.

By the use of the illustrative apparatus and illustrative method aforementioned, locking patches with improved locking tongue can be obtained since an increased quantity of resin can be applied without excessive thickness.

WHAT WE CLAIM IS: 1. An apparatus suitable for use in applying locking patches of resilient resin to articles which have an internally threaded portion and openings at both ends of the threaded portion, the apparatus comprising conveying means arranged to receive such threaded articles and convey them along a treatment path with the longitudinal axes of their threaded portions extending upwardly and the openings at the ends of their threaded portions substantially uncovered, heating means arranged to heat the threaded portions of articles received by the conveying means to a temperature above the softening point of resin to be applied to the articles, directing means arranged to direct particles of the resin through the openings at the lower ends of the threaded portions of the articles as the articles are conveyed over a first portion of the treatment path so that the particles impinge against a first area of each of the threaded portions, are softened by heat from the threaded portions, and build up a deposit on each of said first areas, and turning means arranged to turn each of the articles on the conveying means through a predetermined angle

about the longitudinal axis of its threaded portion after the article has been conveyed over the first portion of the treatment path so that operation of the directing means as the articles are conveyed over a second portion of the treatment path causes a deposit of resin to build up on a second area of each of the threaded portions.
2. An apparatus according to Claim I wherein the directing means comprises conduits movable with the conveying means each conduit being arranged to extend through the lower opening of one of the articles on the conveying means.
3.Apparatus according to Claim 2 wherein the conduit associated with each article is arranged to direct particles on to the article as aforesaid as the article is conveyed over the first and second portions of the treatment path but to cease to direct the particles on to it while the article is conveyed over an intermediate portion of the treatment path where the turning means is located.
4. An apparatus according to any one of Claims 1,2 and 3 wherein the articles are in the form of nuts having external flat areas, the conveying means comprising notches substantially complementary to two adjacent flat areas of the nut and a base associated with each notch for supporting the nuts with two of the flat areas of each nut in engagement with each notch, and the turning means being arranged to displace the nuts from the notches, turn them, and return them to the notches in a new orientation relative to the notches.
5. An apparatus according to Claim 4 wherein the conveying means comprises a circular table around the periphery of which the notches are formed, the table being rotatable to carry the nuts along the treatment path which is arcuate.
6. An apparatus according to either one of Claims 4 and 5 wherein the conveying means also comprises a resilient pressure member arranged to retain the nuts in the notches over the first and the second portions of the treatment path.
7. An apparatus according to any one of Claims 4, 5 and 6 wherein the turning means comprises a finger mounted to engage successive nuts as they are conveyed along the treatment path and exert a force thereon in the opposite direction to the direction of movement of the nuts thereby creating a turning moment on each nut.
8. An apparatus according to any one of Claims 4, 5 and 6 wherein the turning means comprises a wedge mounted adjacent the treatment path, the arrangement being such that successive nuts engage the wedge as they are conveyed and are displaced from their notches so that they can be more readily turned.
9. An apparatus according to Claim 8 wherein the turning means comprises a surface member having a surface which slopes upwardly in a direction away from the conveying means and is arranged to be engaged by successive nuts displaced by the wedge, and means to move the surface in the same direction as the conyeying means moves at a speed greater than that of the conveying means so that a turning moment is applied to the nuts.
10. An apparatus according to Claim 9 wherein the surface member is in the form of a wheel the rim of which provides said surface.
11. An apparatus according to any one of Claims 8,9 and 10 comprising a ramp arranged to raise the nuts relative to the conveying means before they are turned by the turning means.
12. An apparatus suitable for use in applying locking patches of resilient resin to articles which have an internally threaded portion and openings at both ends of the threaded portion constructed and arranged to operate substantially as hereinbefore described with reference to Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11 of the accompanying drawings.
13. An apparatus suitable for use in applying locking patches of resilient resin to articles which have an internally threaded portion and openings at both ends of the threaded portion constructed and arranged to operate substantially as hereinbefore described with reference to Figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 13 and 14 of the accompanying drawings.
14. A method of applying locking patches of resilient resin to articles which have an internally threaded portion and openings at both ends of the threaded portion, the method comprising conveying the articles along a treatment path with the longitudinal axes of their threaded portions extending upwardly and the openings at the ends of their threaded portions substantially uncovered, heating-the threaded portions of the articles to a temperature above the softening point of resin to be applied to the articles, directing particles of the resin through the openings at the lower ends of the threaded portions of the articles as the articles are conveyed over a first portion of the treatment path so that the particles impinge against a first area of each of the threaded portions, are softened by heat from the threaded portions, and build up a deposit on each of said first areas, and turning each of the articles through a predetermined angle about the longitudinal axis of its threaded portion to expose a second area of its threaded portion to the particles of resin so that a deposit is built up on the second area.
15. A method according to Claim 14 wherein the articles are turned through an angle such that the first and the second areas of each article overlap one another.
16. A method of applying locking patches of resilient resin to articles which have an internally threaded portion and openings at both ends of the threaded portion carried out substantially as hereinbefore described.