GB1583299A

GB1583299A - Screw-threaded fasteners

Info

Publication number: GB1583299A
Application number: GB2338978A
Authority: GB
Original assignee: PSM Fasteners Ltd
Current assignee: PSM Fasteners Ltd
Priority date: 1978-05-26
Filing date: 1978-05-26
Publication date: 1981-01-21

Description

(54) IMPROVEMENTS RELATING TO SCREW-THREADED FASTENERS (71) We, P.S.M. FASTENERS LIMITED, of Longacres Industrial Estate, Willenhall, West Midlands WV13 2JS, a British Company, 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 relates to the application ob a sealing/locking compound to the threads of a fastener in order to provide a seal or lock between the fastener and a complementary fastener when the two are assembled together The invention is particularly concerned with the application of sealing and/or locking compound, in the form of an anaerobic adhesive to a female fastener and seeks to overcome the problems that have been encountered in the past in applying a suitable film of adhesive to female fasteners.

The usual practice hitherto has been to apply the adhesive by means of the finger which inevitably means that either too little or too much adhesive is applied. If too little is applied then the seal and/or lock will be unsatisfactory if made at all whereas if too much is applied, there is difficulty in engaging the fasteners and screwing them up.

According to one aspect of the invention we provide a method of applying a sealing and/or locking compound (in liquid or semiliquid or paste form) to a screw threaded fastener wherein the fastener is placed in mating relationship with an applicator device which has a truncated formation or formations generally complementary to the fastener thread form and has a dispensing orifice which is arranged to discharge into the space between the truncated face of said formation (or at least one of the formations) of said fastener, wherein the fastener and applicator device are rotated relative to one another in one sense to thread the fastener onto the applicator device and wherein the fastener and applicator device are thereafter rotated relative to one another in the opposite sense to unscrew the fastener from an applicator device, the compound being disposed during one of said operations of relative rotation (preferably the screwing-on operation).

In practice, said formation on the applicator device will comprise a thread form complementary to the fastener thread form but having its crests truncated. Thus, when the fastener is unscrewed from the applicator device the truncated crests of its thread will perform a wiping action on the adhesive dispensed into the roots of rthe fastener thread form.

According to another aspect of the invention we provide an applicator device comprising a hollow body forming a reservoir for containing sealing and/or locking compound, a thread form On the body, the crests of the thread form being truncated, and at least one orifice extending from the reservoir to a truncated face of said thread form.

In practice, the applicator device will include means for effecting dispensing of the adhesive contained in the reservoir. The applicator device may be in the form of a simple hand-held tool wherein the piston is intended to be operated by thumb-pressure or it may be embodied in a machine.

According to a further aspect of the invention we provide apparatus for applying sealing and/or locking compound to screwthreaded fasteners comprising an applicator device as defined hereinabove, a carrier for mounting a fastener in registry with the applicator device, means for effecting relative rotation between the carrier and the applicator device to enable the fastener to be screwed onto or off the applicator device, and means for effecting dispensing of sealing and/or locking compound from the reservoir through said orifice.

Also according to the invention we provide a fastener whose threads have been coated with adhesive by means of the method and apparatus of Ithe invention.

In the presently preferred embodiment, the applicator device comprises an elongate body having a central blind bore which forms the reservoir, a piston received slidably in the central bore, a truncated, male thread form around the outer periphery of the body and a single radial passage constituting said orifice.

Preferably the sealing and/or locking compound is in the form of an anaerobic adhesive of the commercially available type wherein the adhesive is enclosed within a mass of tiny crushable capsules in a viscous liquid carrier. With this form of adhesive the coated fasteners can be left on the shelf for extended periods without affecting the adhesive properties of the compound. When the coated fastener, e.g. a nut, is assembled to a bolt or the like the capsules are crushed to release the adhesive and because the seal excludes air, the adhesive is then able to cure.

One example of the invention is illustrated in the accompanying drawings to which reference is now made.

As shown in Figure 1, a manually-operable applicator for coating nuts is in the form of a hypodermic-like construction comprising a body 10 having a central blind bore 12 receiving a piston 14. The body 10 has finger grips 16 to enable the operator to apply thumb pressure to the piston to press it inwardly along the bore 12. Adjacent its closed end, the body is provided with a truncated thread form 18 and a radial bore 20 of circular cross-section extends from the central bore 12 and opens at the truncated face of one convolution of the thread form.

In practice, the bore 12 is filled with an anaerobic adhesive, as described above, by removing the piston 14 and thereafter replacing it. Clearly, inward movement of the piston 14 will be effective to dispense the viscous slurry of carrier and adhesive capsules through the bore 20.

In use, a nut 30 (see Figure 2) is screwed onto the body 10 and during this operation the adhesive is dispensed uniformly so as to fill the gap between the roots of the nut thread form and the truncated faces of the applicator thread form. In Figure 2, the dispensed adhesive is indicated by reference numeral 32. After the nut thread form has been coated over its entire length or whatever part is desired to be coated, the nut is unscrewed. During this operation, it will be appreciated that the applicator thread form will perform a wiping action on the adhesive thus distributing the adhesive uniformly and removing any excess.

The applicator thread form will, in practice, complement that of the nuts to be coated and thus a range of applicators may be used for different sized nuts. Because the applicator and nut thread forms are generally com plementary and also because of the viscous nature of the adhesive slurry, in general a seal will be produced between the flanks of the applicator and nut threads which will prevent dispensing of too much adhesive.

Although the invention has been specifically described herein with reference to coating of nuts, it is envisaged that it may also be applied to the coating of male threaded components by suitable design of the applicator.

WHAT WE CLAIM IS : - 1. A method of applying a sealing and/or locking compound (in liquid or semi-liquid or paste form) to a screw-threaded fastener wherein the fastener is placed in mating relationship with an applicator device which has a truncated formation or formations generally complementary to the fastener thread form and has a dispensing orifice which is arranged to discharge into the space between the truncated face of said formation (or at least one of the formations) and the screwthread of said fastener, wherein the fastener and applicator device are rotated relative to one another in one sense to thread the fastener onto the applicator device and wherein the fastener and applicator device are thereafter rotated relative to one another in the opposite sense to unscrew the fastener from the applicator device, the compound being dispensed during one of the said operations of relative rotation.

2. A method as claimed in Claim 1 in which the component is dispensed during screwing the fastener onto the applicator.

3. A method as claimed in Claim 1 or 2 in which the relative rotation is performed with the applicator fixed, by rotating the fastener.

4. An applicator device comprising a hollow body forming a reservoir for containing sealing and/or locking compound, a thread form on the body, the crests of the thread form being truncated, and at least one orifice extending from the reservoir to a truncated face of said thread form.

5. An applicator device as claimed in Claim 4 in which the body slidably receives a piston, displacement of which is effective to dispense compound through said orifice.

6. An applicator device as claimed in Claim 4 which comprises an elongate body having a central blind bore which forms the reservoir, a piston received slidably in the central bore, a truncated male thread form around the outer periphery of the body and a single radial passage constituting said orifice.

7. Apparatus for applying sealing and /or locking compound to screw-threaded fasteners comprising an applicator device as claimed in Claim 4, 5 or 6, a carrier for mounting a fastener in registry with the applicator device, means for effecting relative rotation between the carrier and the applicator device to enable the fastener to be screwed onto

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. having a central blind bore which forms the reservoir, a piston received slidably in the central bore, a truncated, male thread form around the outer periphery of the body and a single radial passage constituting said orifice. Preferably the sealing and/or locking compound is in the form of an anaerobic adhesive of the commercially available type wherein the adhesive is enclosed within a mass of tiny crushable capsules in a viscous liquid carrier. With this form of adhesive the coated fasteners can be left on the shelf for extended periods without affecting the adhesive properties of the compound. When the coated fastener, e.g. a nut, is assembled to a bolt or the like the capsules are crushed to release the adhesive and because the seal excludes air, the adhesive is then able to cure. One example of the invention is illustrated in the accompanying drawings to which reference is now made. As shown in Figure 1, a manually-operable applicator for coating nuts is in the form of a hypodermic-like construction comprising a body 10 having a central blind bore 12 receiving a piston 14. The body 10 has finger grips 16 to enable the operator to apply thumb pressure to the piston to press it inwardly along the bore 12. Adjacent its closed end, the body is provided with a truncated thread form 18 and a radial bore 20 of circular cross-section extends from the central bore 12 and opens at the truncated face of one convolution of the thread form. In practice, the bore 12 is filled with an anaerobic adhesive, as described above, by removing the piston 14 and thereafter replacing it. Clearly, inward movement of the piston 14 will be effective to dispense the viscous slurry of carrier and adhesive capsules through the bore 20. In use, a nut 30 (see Figure 2) is screwed onto the body 10 and during this operation the adhesive is dispensed uniformly so as to fill the gap between the roots of the nut thread form and the truncated faces of the applicator thread form. In Figure 2, the dispensed adhesive is indicated by reference numeral 32. After the nut thread form has been coated over its entire length or whatever part is desired to be coated, the nut is unscrewed. During this operation, it will be appreciated that the applicator thread form will perform a wiping action on the adhesive thus distributing the adhesive uniformly and removing any excess. The applicator thread form will, in practice, complement that of the nuts to be coated and thus a range of applicators may be used for different sized nuts. Because the applicator and nut thread forms are generally com plementary and also because of the viscous nature of the adhesive slurry, in general a seal will be produced between the flanks of the applicator and nut threads which will prevent dispensing of too much adhesive. Although the invention has been specifically described herein with reference to coating of nuts, it is envisaged that it may also be applied to the coating of male threaded components by suitable design of the applicator. WHAT WE CLAIM IS : -

1. A method of applying a sealing and/or locking compound (in liquid or semi-liquid or paste form) to a screw-threaded fastener wherein the fastener is placed in mating relationship with an applicator device which has a truncated formation or formations generally complementary to the fastener thread form and has a dispensing orifice which is arranged to discharge into the space between the truncated face of said formation (or at least one of the formations) and the screwthread of said fastener, wherein the fastener and applicator device are rotated relative to one another in one sense to thread the fastener onto the applicator device and wherein the fastener and applicator device are thereafter rotated relative to one another in the opposite sense to unscrew the fastener from the applicator device, the compound being dispensed during one of the said operations of relative rotation.

or off the applicator device, and means for effecting dispensing of sealing and/or locking compound from the reservoir through said orifice.

8. A fastener when coated with sealing and/or locking compound by means of the method of Claim 1, the applicator device of Claim 4 or the apparatus of Claim 7.

9. An applicator device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.