[0001] This invention relates generally to a technique for applying a sealant to the threads
of a fastener for providing a fluid-tight seal when threadedly engaged with a mating
threaded element, as well as a device for carrying out such technique. More particularly,
this invention relates to such a method and device wherein the sealant is pressed
into the thread roots of the element, and differently sized elements are capable of
being coated without changing applicators.
[0002] Prior known techniques in the application of sealant, especially of the anaerobic
adhesive type, to the threads of female threaded fasteners are beset with problems
in failing to meet quality control standards such as the avoidance of air bubbles
during the application process. Otherwise, it has been difficult to control the requisite
quantity of sealant to be coated without giving a sloppy appearance and without applying
more than needed. On the other hand, known sealant applying and coating devices for
threaded fasteners, while better suited for controlling the desired amount of sealant
applied to the threads, are not without their shortcomings. Air bubbles quite often
remain entrapped in the applied sealant, resulting in a weakened seal and/or lock
between the coated fastener and its mating part. Besides, the nozzle or sealant applicator
used in the application process must be replaced with an appropriately sized applicator
each time a differently sized threaded element is to be coated.
[0003] Examples of these prior art devices are disclosed in U.S. Patent No, 3,956,533 to
Weber et al, Gebrauchsmuster 7930867.1, and in U.S. Patent No. 3,416,492 to Greenleaf.
In the Weber et al and German patents the applicator is in the form of a threaded
plug which engages the thteads of a female threaded element to be coated. With such
a screw threading coating operation, however, the threads are either incompletely
covered with sealant and/or formation of air bubbles is difficult to avoid because
of the inability to press the sealant in place. Moreover, differently sized female
threaded elements having differently sized threads require complementarily sized threaded
applicators, and repeated use of the same threaded applicator for the same sized elements
oftentimes results in an undue buildup of sealant on the applicator threads.
[0004] In the aforementioned Greenleaf patent, use of such a coating nozzler renders it
impossible to precisely control the amount of product to be coated or to effect a
pressing of the coating in place against the threads. And, other problems mentioned
above are not avoided by this coating approach.
[0005] The invention is concerned more particularly with a device for applying a sealant
to the threads of an element having a circular threaded opening, and a method employing
such a device, of a kind comprising a hollow sealant applicator having a central axis
and a sealant discharge orifice through a side wall thereof, the discharge orifice
lying at a predetermined radial distance from that axis, and a base for holding the
element, and in which the base and applicator are arranged for relative movement towards
and away from one another along that axis and transversely relative to one another
until an operative sealant applying position is reached where the side wall of the
applicator touches the threads of the fastener.
[0006] Such a kind of device is disclosed in FR-A-2,201,741. In the arrangement described
in this specification, the applicator is, during the sealant applying operation, rotated
inside the opening of the element, which is stationary, about an axis coaxial with
the element's axis and is provided with threads on its outer surface which engage
threadingly the threads of the element. Accordingly, the arrangmeent of the specification
suffers from disadvantages similar to those of the aforementioned prior art devices.
[0007] It is an object of this invention to provide a method for coating the internal threads
of a fastener, and a device generally of the kind referred to above for carrying out
the method, in such a manner as to precisely control the amount of applied sealant
while being pressed intimately into the fastener threads to substantially avoid air
bubble formation.
[0008] Another object of the invention is to provide such a method and device which requires
but a single applicator for the coating of differently sized threads of differently
sized threaded elements;
[0009] A further object of the present invention is to provide such a method and device
wherein the internally threaded element is held on a rotatable base against relative
transverse movement therewith, and a side force is induced during rotation to allow
sealant to be pressed into the thread roots of the element while any excess sealant
is wiped from the threads by the edge of a discharge orifice opening through a side
wall of a sealant applicator;
[0010] A still further object of the invention is to provide such a method and device wherein
the applicator has a smooth outer wall through which the discharge orifice opens,
the applicator being so positioned that its central axis lies parallel to and offset
in one direction from the rotational axis with the side wall contacting the crests
of the threads, such force thereby being induced in such one direction;
[0011] A still further object of the invention is to provide such a method and device wherein
the discharge orifice of the sealant applicator is elongated in the direction of the
applicator axis for spanning a plurality of threads for the simultaneous coating of
same during a single revolution;
[0012] A still further object of the present invention is to provide such a method and device
wherein the base may be made of magnetic material for holding a ferromagnetic threaded
element by magnetic attraction, or the base may be formed as a chuck element for holding
the threaded element in place.
[0013] According to the invention there is provided a device for applying a sealant to the
threads of an element having a circular threaded opening, comprising a hollow sealant
aplicator having a central axis and a sealant discharge orifice through a side wall
thereof, the discharge orifice lying at a predetermined radial distance from said
axis, and a base for holding the element, the base and the applicator being arranged
for relative movement toward and away from one another along said axis and transversely
relative to one another until an operative sealant applying position is reached in
which the side wall of the applicator touches the threads of the element, characterised
in that the side wall of the applicator, which in the operative sealant applying position
touches the threads of the element, has a smooth and unthreaded exterior, and in that
the base is rotatable in the operative sealant applying position about an axis which
is parallel to and offset from the applicator axis.
[0014] In this way a side force is induced in the direction of said discharge orifice during
rotation of said base to effect a forced discharge of sealant from said orifice into
the threads of the element.
[0015] According to the invention there is also provided a process for applying a sealant
to the threads of an element having a circular threaded opening, comprising holding
the element on a base for movement therewith, providing a hollow sealant applicator
having a central axis and a sealant discharge orifice opening through a side wall
thereof which orifice lies at a predetermined radial distance from said axis, relatively
moving the base with respect to the applicator along said axis and transversely relative
to one another until an operative sealant applying position is reached in which the
side wall of the applicator touches the threads of the element, and discharging the
sealant through said orifice into the threads, characterised by providing the side
wall of the applicator, which in the operative sealant applying position touches the
threads of the element, with a smooth and unthreaded exterior, and by rotating the
base during discharge of the sealant about a rotational axis which is parallel to
and offset from the applicator axis.
[0016] With such a process, a side force directed toward the orifice is induced during rotation
about said rotational axis for facilitating the pressing of sealant into the thread
roots of the element while any excess sealant is wiped from the threads by an edge
of said side wall.
[0017] The invention will now be described, by way of example with reference to the accompanying
drawings, in which:
Figure 1 is a side elevational view, partly in section, of the sealant applying device
according to the invention;
Figure 2 is a sectional view of the sealant applicator and the threaded element to
be coatd, taken substantially along line 2-2 of Figure 1;
Figure 3 is an elevational view of part of the sealant applicator and its discharge
orifice, taken substantially along line 3-3 of Figure 1;
Figure 4 is a schematic representation showing the eccentric path traced, during rotation
of the base, by the point of tangency between the orifice wall of the applicator and
the threads of the element to be coated; and
Figure 5 is a view similar to Figure 1, but without the applicator, of another holder
base which may be provided for the threaded element.
[0018] Turning now to the drawing wherein like reference characters refer to like and corresponding
parts throughout the several views, the sealant applying device is generally designated
10 in Figure 1 and comprises a rotatable base 11 mounted in some suitable manner for
rotation about its central axis 12 in a clockwise direction shown by the arrows of
Figures 1 and 2. Conventional means (not shown) are provided by rotating the base
in the illustrated direction, or in a counterclockwise direction without departing
from the invention.
[0019] A pilot 13 extends outwardly from the upper surface of the base over which an internally
threaded element E, such as a nut fastener, is seated. The pilot is shaped so that
it snugly embraces the lowermost thread portion of element E so as to prevent any
relative transverse shifting of the threaded element during the sealant applying process.
For a given inner diameter of element E, axis 14 of the pilot will be offset relative
to rotational axis 12 in either direction or will be coincident thereto. And, the
base may be made of magnetic material for holding elements of ferromagnetic material
thereto by magnetic attraction.
[0020] A hollow sealant applicator 15 is mounted in any normal manner for movement along
its central axis 16 in the directions illustrated by the double arrows in Figure 1.
The applicator is connected to a supply (not shown) of sealant S via a supply tube
17 having a discharge shut-off valve 18 associated therewith for opening and closing
the flow of sealant from the supply. A hollow passageway 19 of the applicator communicates
with supply tube 17 via valve 18 and terminates in a discharge orifice 21 (Fig. 3)
located in a side wall 22 of the applicator which lies at a predetermined transverse
distance from central axis 16. Side wall 22 has a smooth and unthreaded exterior as
shown.
[0021] The sealant applicator is positioned relative to the rotatable base such that its
central axis 16 lies to and offset in one direction from central axis 12 with side
wall 22 of the applicator in light contact engagement with the crests of the internal
threads T of the element to be coated (Figs. 1 and 2).
[0022] The applicator is mounted in place for axial movement, as aforedescribed, in the
direction of the double arrows of Figure 1, but is otherwise incapable of rotary movement
about its central axis 16. Base 11, on the other hand, is mounted in place for rotation
about its central axis 12, and may be further mounted for axial movement toward and
away from the applicator as an alternative to the mounting of the applicator for axial
movement, so long as relative axial movement between the applicator and the base is
facilitated. And, either the applicator or the base is mounted for transverse movement
so as to assure the necessary relative transverse positioning between these parts.
[0023] In carrying out the sealant applying operation, the applicator will be spaced axially
relative to the base a distance greater than the thickness of a threaded element E
to be coated. A base 11 will be selected having an appropriately sized pilot 13 substantially
equal to the outer diameter pf an element E to be coated. In other words, if the outer
diameter of the element to be coated is 2.5 cms (one inch), a base 11 having a 2.5
cm (one inch) pilot diameter will be selected. The applicator and base will then be
shifted transversely relative to one another until side wall 22 is'vertically aligned
with the crests of threads T at a point of tangency 23 (Fig. 4).
[0024] As will be described in more detail hereinafter, differently sized internally threaded
elements are capable of being coated using the same applicator 15, so long as the
offsetting relationship between axes 12 and 16 is maintained while side wall 22 touches
the crests of the threads. Obviously, if this offsetting and side wall contacting
relationship cannot be maintained for a particular internally threaded element, then
a smaller sized applicator must be chosen.
[0025] While the applicator and base are relatively spaced in a axial direction, an element
E is transferred by some suitable means and is seated on the rotatable base. If element
E is of ferromagnetic meterial, it will be seated over pilot 13 of a magentic base
11 so as to be held firmly in place by magnetic attraction. Otherwise, if the element
to be coated is of non-ferromagnetic material it will be seated within the jaws of
a chuck 29 (Fig. 5), which will be described in more detail hereinafter.
[0026] Valve 18 remains in a closed position, and the applicator is operatively connected
with an advance mechanism 24 so that, upon command, the applicator will be advanced
into the threaded opening of element E seated on the base. When the applicator reaches
its predetermined position of Fig. 1, sealant cut-off valve 18 is opened and sealant
under pressure in line 17 flows through passage 19 and out of the elongated discharge
orifice.
[0027] When valve 18 is opened, the means (not shown) provided for rotating the base is
actuated for effecting clockwise movement relative to the stationary applicator. At
the point of tangency 23, the discharged sealant under pressure is resisted by an
induced force F (Fig. 4) acting in a direction aligned with the direction in which
axis 16 is offet from axis 12. The snug engagement between the pilot and element E
and the sufficiently strong magnetic attraction between the base and E, facilitates
this induced force. The dischrage sealant is therefore pressed into the roots of threads
T during rotation of the base, and an edge 25 of the discharge orifice (Figs. 2 and
3) functions as a doctor blade wiping any excees sealant from the threads.
[0028] Valve 18 is operatively connected with an adjustable timing device (not shown) which
is set for maintaining the valve open for an interval permitting the sealant to flow
into the threads for at least one revolution of element E. When a sufficient amount
of sealant has been applied to the threads, shut-off valve 18 will close and the applicator
will be retracted from element E upon relative movement of the applicator and base
away from one another. However, before retracting the applicator, after valve 18 is
closed, the base may continue to be rotated if it is desired to smoothen the applied
sealant as edge 265 of the discharge orifice wipes the threads.
[0029] With the arrangement and operation as aforesaid, point of tengency 23 between side
wall 22 and threads T traces a circular path 26 about axis 12 of the base which is
eccentric relative to a circle 27 which is defined by the radial extent of side wall
22 from axis 16 of the applicator. Thus, it can be seen from the . schematic illustration
of Figure 4 that a single point of tangency 23 is defined by the offetting relationship
of axes 12 and 16 so that force F is induced at only this point for effecting the
pressing of discharged sealant in place without binding or interference between wall
22 and the threads which could otherwise occur if circles 26 and 27 were concentric.
[0030] Figures 1 and 4 illustrate pilot 13 as having its central axis lying between axes
12 and 16 so as to define an eccentric circle 28 relative to 26 and 27. Such is for
the purpose of illustration since the pilot, depending on its diameter, can lie with
its axis 14 aligned with axis 16, between axes 12 and 16, or to the left of axis 12
(when viewing Figs. 1 and 4). However, the pilot diameter cannot be smaller than circle
27.
[0031] Thus, in order to accommodate internally threaded elements of sizes larger than that
shown in the drawings relative to the size of the illustrated applicator, a base 11
having an appropriately sized pilot will be selected and mounted in place prior to
the coating operation. It can be therefore seen that, for pilot diameters larger than
circle 27, point 23 of tangency will be maintained for the same relatively sized applicator
with a force F induced for the purpose and in the manner aforedescribed.
[0032] For the coating of internally threaded elements which are non-ferromagnetic, the
base may be formed as a chuck 29 for snugly embracing element E, shown in Figure 5.
Thus, pilot 13 is eliminated, although axes 12 and 16 are offet for inducing a side
load force F at a point of tangency 23 similarly as described with reference to Figures
1 to 4. And, rather than a pilot, the chuck jaws holding element E vary in size for
different chucks to accommodate differently sized elements to be coated.
[0033] From the foregoing, it can be seen that a simple and economical yet highly effective
technique has been developed for the coating of internal threads of an element by
pressing sealant firmly into the thread roots as a side force is induced at a point
of trangency with the discharge orifice of an applicator, during rotation of that
point of tangency eccentrically relative to the rotational axis of the base. The outer
wall of the applicator through which the discharge orifice opens is smooth so as to
avoid any undue buildup of sealant during repeated sealant applications. Also, this
smooth exterior can accommodate differently sized internal threads of elements to
be coated, without having to substitute applicators as required by the prior art.
Another advantage in the use of an applicator of the present type is that it better
accommodates the preferred type of sealant which is in the form of an anaeorbic adhesive
enclosed with a mass of tiny crushable capsules in a viscous liquid carrier. With
the provision of a smooth-walled applicator according to the invention, it is less
likely that these capsules will prematurely crush during sealant discharge, rather
than at the time the mating threaded element engages the coated threads. At such time,
the capsules are crushed to release the adhesive after which it is able to cure in
the absence of air.
1. A device for applying a sealant to the threads of an element having a circular
threaded opening, comprising a hollow sealant applicator (15) having a central axis
and a sealant discharge orifice (21) through a side wall (22) thereof, the discharge
orifice (21) lying at a predetermined radial distance from said axis, and a base (11)
for holding the element, the base (11) and the applicator (15) being arranged for
relative movement toward and away from one another alongisaid axis and transversely
relative to one another until an operative sealant applying position is reached in
which the side wall of the applicator (15) touches the threads of the element, characterised
in that the side wall of the applicator, which in the operative sealant applying position
touches the threads of the element, has a smooth and unthreaded exterior, and in that
the base is rotatable in the operative sealant applying position about an axis which
is parallel to and offset from the applicator axis.
2. The device according to Claim 1, characterised in that said base is of magnetic
material and has a pilot piece on an upper surface thereof for holding and positioning
the element, of ferromagnetic material, by magnetic attraction or said base comprises
a chuck for holding and positioning said element.
3. The device according to Claim 1 or 2, characterised in that said orifice is elongated
in the direction of said applicator axis for spanning a plurality of element threads.
4. The device according to Claim 1, 2 or 3, characterised in that the orifice (21)
has a side edge (25) defining a doctor blade for smoothing the sealant applied to
the threads.
5. A process for applying a sealant to the threads of an element having a circular
threaded opening, comprising holding the element on a base (11) for movement therewith,
providing a hollow sealant applicator (15) having a central axis and a sealant discharge
orifice (21) opening through a side wall (22) thereof which orifice lies at a predetermined
radial distance from said axis, relatively moving the base with respect to the applicator
along said axis and transversely relative to one another until an operative sealant
applying poistion is reached in which the side wall of the applicator touches the
threads of the element, and discharging the sealant through said orifice into the
threads, characterised by providing the side wall of the applicator, which in the
operative sealant applying position touches the threads of the element, with a smooth
and unthreaded exterior, and by rotating the base during discharge of the sealant
about a rotational axis which is parallel to and offset from the applicator axis.
6. The process according to Claim 5, characterised in that excess sealant is wiped
from the threads by an edge (25) of the orifice defining a doctor blade during said
rotation.
7. The process according to Claim 5 or 6, characterised in that the discharging of
sealant spans a plurality of the threads for simultaneously applying sealant thereto.
8. The process according to Claims 5, 6 or 7, characterised in that the element is
magnetically held on said base.
9. The process according to Claims 5, 6, 7 or 8, characterised in that said base if
formed as a chuck for holding the element.
1. Vorrichtung zum Aufbringen eines überzuges auf das Gewinde eines Elementes, das
eine kreisförmige Gewindebohrung aufweist, umfassend einen hohlen Überzugs-Applikator
(15) mit einer zentralen Achse sowie einer in einer Seitenwand (22) befindlichen überzugs-Abgabe-Düse
(21), die in einem vorgegebenen radialen Abstand zur Achse liegt sowie einer Basis
(11) zum Halten des Elementes, wobei die Basis (11) und der Applikator (15) derart
relativ zueinander in Achsrichtung und quer hierzu bewegbar sind, bis eine wirksame
Überzugs-Auftrags-Position erreicht ist, in welcher die Seitenwand des Applikators
(15) das Gewinde des Elementes berührt, dadurch gekennzeichnet, daß die Seitenwand
des Applikators, die in wirksamer Auftragsposition das Gewinde des Elementes berührt,
eine glatte und gewindefreie Außenfläche aufweist, und daß die Basis in der wirksamen
Überzugs-Auftrags-Position um eine Achse verdrehbar ist, die parallel zur Applikatorachse,
aber gegen diese versetzt angeordnet ist.
2. Vorrichtung nach Anspruch 1, dadurch gekennzeichnet, daß die Bais aus magnetischem
Werkstoff besteht und auf ihrer oberen Seite ein Führungsstück zum Halten und Positionieren
des aus ferromagnetischem Material bestehenden Elementes durch Magnetkraft aufweist,
oder daß die Basis ein Futter zum Halten und Positionieren des Elementes umfaßt.
3. Vorrichtung nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Düse in Richtung
der Applikatorachse langgestreckt ist, um eine Mehrzahl von Geweindegängen zu umfassen.
4. Vorrichtung nach einem der Ansprüche 1-3, dadurch gekennzeichnet, daß die Düse
(21) eine. Seitenkante (25) aufweist, die eine Schaberklinge zum Glätten von auf das
Gewinde aufgetragenem Überzug aufweist.
5. Verfahren zum Auftragen eines Überzugs auf das Gewinde eines Elementes mit einer
kreisförmigen Gewindebohrung, umfassend das Halten des Elementes auf einer Basis (1)
zwecks Bewegung mit dieser, Vorsehen eines hohlen Auftragsapplikators (15), der eine
zentrale Achse hat, ferner eine Seitenwand (22), durch welche sich eine Auftrags-Abgabe-Düse
(21) hindruch erstreckt, die in einem vorbestimmten radialen Abstand zur Achse liegt,
durch Bewegen von Basis und Applikator relativ zueinander entlang der Achse und quer
hierzu, bis eine wirksame Überzugs-Auftrags-Position erreicht ist, in welcher die
Seitenwand des Applikators das Gewinde des Elementes berührt, und durch Abgeben des
Überzugs durch die Düse auf das Gewinde, dadurch gekennzeichnet, daß die Seitenwand
des Applikators, die in wirksamer Uberzugs-Auftrags-Position des Gewinde des Elementes
berührt, mit einer glatten und gewindefreien Außenfläche ausgestattet wird sowie durch
Verdrehen der Basis während des Auftragens des Überzuges um eine Drehachse, die zur
Applikatorachse parallel, aber gegen diese versetzt verläuft.
6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, daß überschüssiger überzug von
den Gewindegängen durch eine Kante (25) der Düse abgewischt wird, die während der
Verdrehung eine Schaberklinge bildet.
7. Verfahren nach Anspurch 5 oder 6, dadurch gekennzeichnet, daß das Abgeben des Überzugs
eine Mehrzahl von Gewindegängen zwecks gleichzeitigen Aufbringens von überzug auf
diese umfaßt.
8. Verfahren nach einem der Ansprüche 5-7, dadurch gekennzeichnet, daß das Element
auf der Basis magnetisch gehalten wird.
9. Verfahren nach einem der Ansprüche 5-8, dadurch gekennzeichnet, daß die Basis als
Futter zum Halten des Elementes ausgebildet ist.
1. Dispositif pour appliquer un enduit sur le filetage d'un élément pourvu d'une ouverture
circulaire filetée, comprenant un applicateur d'enduit évidé (15) pourvu d'un axe
central et d'un orifice de sortie d'enduit (21) à travers une paroi latérale (22),
cet orifice de sortie (21) étant situé à une distance radial prédéterminée dudit axe,
et une embase (11) pour maintenir l'élément l'embase (11) et l'applicateur (15) étant
agencés en vue d'un mouvement relatif l'un vers l'autre et inversement suivant ledit
axe et transversalement l'un par rapport à l'autre jusqu'à une position active d'application
de l'enduit dans laquelle le paroi latérale de l'applicateur (15) touche le filetage
de l'élément, caractérisé en ce que la paroi latérale de l'appicateur qui touche le
filetage de l'élément dans la position active d'application de l'enduit comporte une
surface extérieure lisse et non filetée, et en ce que l'embase est rotative dans la
position active d'application de l'enduit, autour d'un axe qui est parallèle et décalé
par rapport à l'axe de l'applicateur.
2. Dispositif selon la revendication 1, caractérisé en ce que ladite embase est -faite
d'une matière magnétique et comporte sur sa surface supérieure un guide pour maintenir
et positionner l'élément, en manière ferromagnétique, par attraction magnétique, ou
en ce que ladite embase comporte un mandrin pour maintenir et positionner ledit élément.
3. Dispositif selon la revendication 1 ou 2, caractérisé en ce que ledit orifice est
allongé dans la direction dudit axe de l'applicateur pour couvrir plusieurs filets
de l'élément.
4. Dispositif selon la revendication 1, 2 ou 3, caractérisé en ce que l'orifice (21)
comporte une arête latérale (25) servant de lame de raclage pour lisser l'enduit appliué
sur le filetage.
5. Procédé pour appliquer un enduit sur le filetage d'un élément pourvu d'une ouverture
circulaire filtée, dans lequel on maintient l'élément sur une embase (11) pour le
déplacer avec celle-ci, on utilise un applicateur d'enduit évidé (15) pourvu d'un
axe central et d'un orifice de sortie d'enduit (21) à travers une paroi latérale (22),
cet orifice de sortie étant situé à une distance radiale prédéterminée dudit axe,
on déplace l'embase par rapport à l'applicateur suivant ledit axe et transversalement
l'un par rapport à l'autre jusqu'à atteindre une position active d'application de
l'enduit dans laquelle la paroi latérale de l'applicateur touche le filetage de l'élément,
et l'on délivre l'enduit dans le filetage à travers ledit orifice, caractérisé en
ce que l'on ménage une surface extérieure lisse et non filtée sur la paroi extérieure
de l'applicateur qui touche le filetage de d'élément dans la position active d'application
de l'enduit, et l'on fait tourner l'embase, pendant qu'on délivre l'enduit, autour
d'un axe de rotation qui est parallèle et décalé par rapport à l'axe de l'applicateur.
6. Procédé selon la revendication 5, caractérisé en ce que l'on enlève l'enduit excédentaire
du filetage au moyen d'une arête (25) de l'orifice, servant de lame de raclage, pendant
ladite rotation.
7. Procédé selon la revendication 5 ou 6, caractérisé en ce que la sortie de l'enduit
couvre plusieurs des filets, pour leur appliquer l'enduit simultanément.
8. Procédé selon la revendication 5, 6 ou 7, caractérisé en ce que l'élément est maintenu
magnétiquement sur ladite embase.
9. Procédé selon la revendication 5, 6, 7 ou 8, caractérisé en ce que ladite embase
est formée d'un mandrin pour maintenir l'élément.