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EP 0 011 219 B1 |
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EUROPEAN PATENT SPECIFICATION |
(45) |
Mention of the grant of the patent: |
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25.05.1983 Bulletin 1983/21 |
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Date of filing: 06.11.1979 |
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(54) |
Connection of fluid flow path-defining components in down-the-hole hammer drills
Verbindung der flüssigkeitsaufnehmenden Teile von Tieflochbohrhämmern
Jonction d'éléments définissant un passage d'écoulement de fluid pour marteau perforateur
mis en oeuvre au fond d'un trou de forage
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Designated Contracting States: |
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AT BE CH DE FR GB IT SE |
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Priority: |
10.11.1978 GB 4412878
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Date of publication of application: |
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28.05.1980 Bulletin 1980/11 |
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Applicant: HALIFAX TOOL COMPANY LIMITED |
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Halifax
West Yorkshire HX3 9TW (GB) |
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Inventors: |
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- Cox, Nigel Bruce
Southowram
Halifax
Yorkshire (GB)
- Green, Christopher
Halifax
Yorkshire (GB)
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Representative: Jack, Bruce James et al |
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FORRESTER & BOEHMERT
Franz-Joseph-Strasse 38 D-80801 München D-80801 München (DE) |
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Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
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[0001] This invention concerns the connection of fluid flow path-defining components in
fluid-powered, free piston, down-the-hole hammer drills.
[0002] The invention is especially concerned with the establishment of reliable fluid-tight
connections between such components, notwithstanding the high stress and vibration
levels to which the components are subject in operation of the drill.
[0003] In a down-the-hole rock drill hammer unit, a piston is caused to reciprocate within
a cylinder and to deliver blows to an anvil surface on a bit shank. The reciprocation
of the piston is accomplished by alternately admitting pressure fluid such as compressed
air to working chambers at opposite ends of the cylinder, this admission of pressure
fluid to the working chambers, and the exhaust of fluid from these chambers, being
controlled at least partly by the motion of the piston within the cylinder and relative
to ports formed in the cylinder wall and/or in the piston or in a tube extending therein
or therethrough. There may be further control of the fluid flows by a valve system
or the arrangement may be "valveless" and rely entirely on the motion of the piston
relative to other components to accomplish the necessary control of fluid flows into
and out of the working chambers.
[0004] In many such hammer drills and similar fluid-powered free-piston devices, certain
of the fluid flow paths involve tubes that extend within the device and that are connected
to or closely associated with components subject to high levels of stress and/or vibration.
For instance, the piston may carry a tube that extends from one or other end thereof
so as to reciprocate with the piston and enter passages in a related component to
accomplish a fluid control function during parts of the travel of the piston within
the cylinder. In other cases the piston reciprocates relatively to a central tube
that is fixed at one or other of its ends and has ports that communicate with the
working chambers in accordance with the position of the piston relatively to the tube.
In yet other cases a tube is fixed within one or other of the working chambers to
enter a passage in the piston for part of the cycle of motion of the latter: a typical
instance of this latter arrangement is the so- called foot valve that comprises a
tube fixed to a central exhaust passage in the bit shank of a hammer drill and that
co-operates with the piston to control the exhaust of pressure fluid from the working
chambers.
[0005] It is a common experience in the operation of such hammer drills that such fluid-conveying
tubes as above discussed are prone to failure at their connections to the components
to which they are fixed. It is therefore common to adopt connection arrangements that
involve the interposition of resilient material to damp the transmission of vibration
energy between the respective parts and to effect fluid-tight sealing of the connection.
However, the arrangements hitherto used or proposed have in general been rather complex
and difficult to manufacture and/or involve problems of assembly in manufacture, so
leading to difficulties in servicing in the field, or have shown a lack of reliability
in service.
[0006] An object of the present invention is therefore to provide an interconnection system
that avoids the difficulties experienced hitherto in the above discussed situations
and that is simple and economical to manufacture.
[0007] In accordance with the invention, a fluid-powered free piston down-the-hole hammer
drill comprising fluid flow path-defining components including inner and outer components
having adjacent overlapping surfaces is characterised in that each of said overlapping
surfaces is formed with at least one circumferential recess, the recesses in the respective
components being opposed and together defining an annular space within which an elastomeric
sealing/retaining ring is accommodated.
[0008] In preferred embodiments of the invention, the overlapping surfaces of the two components
are a close fit one within the other and the or each said recess in one such surface
is of greater depth than the corresponding recess in the other surface, whereby the
or each sealing/ retaining ring is accommodated mainly in the deeper recess so as
to facilitate assembly of the connection by telescopic movement of the components
relative to one another. The over- lappping surfaces may be dimensioned to have an
interference fit, but in preferred embodiments they are dimensioned to have a sliding
fit.
[0009] Preferably the overlapping surface of each component is formed with a plurality of
said recesses so that there are a plurality of spaced-apart annular spaces each accommodating
an elastomeric sealing/retaining ring, the plurality of sealing/retaining rings thus
providing both a plural seal structure for preventing flow of fluid between the overlapping
surfaces, and spaced-apart resilient connections that distribute stresses between
the components and also serve to maintain alignment thereof.
[0010] In preferred embodiments of the invention the elastomeric sealing/retaining rings
are 0- rings, but rings of other configuration may be employed: in particular, rings
of non-circular section may be employed in recesses shaped to co-operate with such
rings to provide enhanced sealing performance.
[0011] The or each elastomeric sealing/retaining ring may be a free element fixed to neither
of the components. However in some embodiments such a ring may be fixed, e.g. by adhesive
bonding, in the accommodating recess of one of om the components prior to assembly
of the interconnection.
[0012] The components may be formed of any desired materials and may be of the same or of
different materials. One or the other or both of the components may be of composite
construction to provide required properties of structural strength and flexibility
or resilience.
[0013] To facilitate assembly of the interconnection, the inner component may have a tapered
lead-in to its surface formed with the or each said recess therein. That surface may
itself initially be tapered, or the component may be formed to permit such surface
to distort to tapered form in the course of assembly, provision being made to distort
or restore the shape of the surface after assembly, to a configuration matching the
complementary overlapping surface of the outer component.
[0014] Thus, for instance, in one embodiment of the invention, the inner component comprises
a tube one extremity of which is formed with circumferential recesses and a tapered
lead-in, the wall thickness of the tube in the region of this end being such as to
enable the tube to distort upon assembly to permit the tube end satisfactorily to
enter the outer component having its recesses fitted with elastomeric sealing/ retaining
rings. Introduction of a plug, for instance, a screw-threaded plug, into the tube
end following assembly may then serve to restore the tube end to its initial configuration
so that its external surface matches that of the outer component into which is has
been so fitted.
[0015] By such expedients, the sealing/retaining ring or rings may be placed under substantial
radial compression in the fully assembled interconnection, to achieve a required sealing
and/or retaining performance.
[0016] Some embodiments of the invention are illustrated by way of example in the accompanying
drawings in which:
FIGURES 1 A and 1B together constitute a part-sectional elevation of a down-the-hole
hammer drill unit embodying the invention;
FIGURE 2 is an enlargement of part of Figure 1A;
FIGURE 3 is an axial section of the valve part constituting the outer component of
the interconnection embodied in the drill unit;
FIGURE 4 is an axial section of the exhaust tube constituting the inner component
of the interconnection embodied in the drill unit:
FIGURE 5 is a partly schematic axial section of part of another down-the-hole hammer
drill unit embodying the invention;
FIGURE 6 shows in axial section one construction of the foot valve, embodying the
invention, in the drill unit of Figure 5; and
FIGURE 7 illustrates another construction of the foot valve, embodying the invention,
of the drill unit of Figure 5.
[0017] The hammer drill unit illustrated in Figures 1A and 1B comprises a casing 1 fitted
with a line 1 a within which a piston 2 is reciprocable to deliver blows on the anvil
surface at the end of a bit shank, the reciprocation of the piston 2 being effected
by the admission of compressed air alternately to working chambers 3, 3a at opposite
ends of the liner 1 a under the control of a valve mechanism including a valve element
4. The valve element 4 reciprocates within a valve structure including a valve bottom
5 that fits partly within the adjacent end of the liner 1 a and has through-flow passages
6 and a central bore.
[0018] An exhaust tube 7 is fitted to the bore of the valve bottom 5 by an interconnection
embodying the present invention and consisting of circumferential recesses in the
overlapping surfaces of the bore of the valve bottom 5 and of the exhaust tube 7,
respectively, the recesses in these components together defining a series of five
annular spaces that accommodate elastomeric sealing/retaining rings 8.
[0019] The configuration of the valve bottom 5 is best seen in Figures 2 and 3 that show
the bore to be of untapered cylindrical configuration formed with recesses 9 of rectangular
cross-section. The internal corners of the recess cross-section are radiussed and
the edges at the bore surface are relieved to avoid sharp corners and edges. This
valve bottom 5 is formed of steel, case-hardened after all machining operations have
been completed.
[0020] Figure 4 shows the form of the exhaust tube 7 prior to assembly. This tube is formed
of a high strength plastics material such as carbon fibre or glass fibre reinforced
plastic, or of a material such as the acetal plastics material sold by DuPont under
the Trade Mark "Delrin". As shown the tube has an end portion 10 formed with five
part-circular section circumferential recesses 11 at intervals corresponding with
the spacing of the recesses 9 in the bore of the valve bottom 5.
[0021] It will be observed that the recesses 9 in the bore of the valve bottom 5 are of
substantially greater depth than the recesses 11 on the exhaust tube 7. Thus the elastomeric
sealing/ retaining rings 8 are mainly accommodated in the recesses 9 and will be reliably
retained in their respective recesses during assembly of the interconnection by endwise
introduction of the exhaust tube 7 into the bore of the valve bottom. The different
shapes of the cross- sections of the respective recesses also ensure retention of
the sealing/retaining rings 8 during assembly, and ease the assembly operation.
[0022] The extremity of the exhaust tube 7 has a tapered lead-in 12 and the end portion
10 of the tube has a central bore that is formed with a tapered screw thread 13 for
part of its length.
[0023] As initially formed, the end portion 10 of the tube 7, apart from the lead-in 12,
is of untapered cylindrical form with an overall diameter such as to provide a sliding
fit with the bore of the valve bottom 5. In assembling the interconnection between
the exhaust tube and the valve bottom, the elastomeric sealing/ retaining rings 8,
suitably O-rings, are fitted to the recesses 9 of the valve bottom bore whereafter
the exhaust tube 7 is forced endwise into position in the bore. To assist the introduction
of the tube 7 into the bore a suitable lubricant is applied to the tube and to the
sealing ring-fitted valve bottom bore: the lubricant may be a light oil or a soap
or like solution.
[0024] Under the compressive loads imposed upon the tube end portion 10 by the sealing/
retaining rings 8 as the tube is forced into position and the rings 8 ride over the
lands between the recesses 11, the tube end portion 10 tends to distort and take a
slight taper "set". Accordingly, when the tube 7 has been forced fully into place
with its recesses 11 aligned with the corresponding recesses 9 of the valve bottom
bore, a screw-threaded plug 14 is screwed into the bore of the end portion 10 and
because of the taper of the screw thread 13 in that bore, causes progressive expansion
of the tube end portion 10 into close conformity with the bore of the valve bottom.
[0025] The sealing/retaining rings 8 in the assembled condition of the parts as illustrated
in Figures 1 and 2 provide multiple stress paths between the inner component constituted
by the exhaust tube 7 and the outer component constituted by the valve bottom 5. These
rings also provide multiple seals against leakage between these components and thus
reliably hold the tube 7 in place in the valve bottom, notwithstanding high levels
of vibration to which the components are subjected during operation, while preventing
leakage of pressure fluid from the region of the valve 4 along the outer wall of the
tube 7.
[0026] Figure 5 illustrates schematically and in axial section part of the leading end of
a down-the-hole hammer drill unit of the valveless type and having a foot valve arrangement
involving an interconnection embodying the invention.
[0027] The drill unit illustrated in this Figure 5 comprises a casing 20 defining a cylinder
within which a piston 21 is reciprocable to deliver blows on the anvil surface at
the end of a bit shank 22 so secured in the end of the casing 20 by means of a chuck
23 and a retaining and sealing ring 24 as to have limited freedom for axial movement
relatively to the casing 20. The bit shank 22 is formed with an exhaust passage 25
that extends to outlets in the bit head (not shown) and that is fitted with a foot
valve tube 26 that enters a bore in the piston 21 as this approaches its illustrated
power stroke-end position, so as to cut off the exhaust flow path for air in the adjacent
working chamber of the cylinder whilst providing a flow path for exhaust of air through
the piston from the working chamber at the other end of the cylinder defined by the
casing 20.
[0028] The foot valve 26, because it is fixed to the bit shank and protrudes from the anvil
surface thereof, experiences intense shock and vibration loading in the region of
its connection to the bit shank. The interconnection arrangement of the invention
is therefore well suited to securing the foot valve tube 26 in the bit shank.
[0029] Figure 6 illustrates one constructional form of this interconnection and it will
be seen that in this case the foot valve tube 26 is formed with rectangular cross-section
circumferential recesses that oppose part-circular section circumferential recesses
in an enlarged portion of the bore 25 of the bit shank, the opposed recesses together
defining a series of spaced-apart annular spaces each accommodating an elastomeric
sealing/retaining ring 27. The tube 26 may be made of any suitable material and if
desired may be fitted, after assembly, with a pressed-in sleeve to remove any inwards
distortion of the tube caused during assembly and to ensure a required fit between
the tube and the bore of the bit shank.
[0030] Figure 7 illustrates another construction in which the foot valve tube is of composite
configuration, having an end portion 26a formed of one material, for instance metal,
and constituting the inner component of the interconnection, and an extension portion
26b formed of a different material (e.g. a plastics material) and suitably attached
to the end portion 26a, before or after fitment of the latter to the bit shank 22.
The composite construction of the foot valve tube in Figure 7 enables the respective
portions thereof to be formed of materials chosen to provide the required properties
in those portions of the tube. Thus the end portion 26a may be formed of metal to
provide appropriate rigidity to withstand stresses transmitted through the sealing/retaining
rings 27, whereas the portion 26b may be of a material chosen to provide appropriate
resilience to seal within the piston bore and to tolerate slight misalignments between
the bit and the piston, and/or to be of low mass. Alternatively, the portion 26a might
be made of a plastics material and the portion 26b of metal, to provide appropriate
properties to meet certain performance requirements: for instance to enable the components
to withstand the erosion effects that result from water injection.
1. A fluid-powered free-piston down-the- hold hammer drill comprising fluid flow path-defining
components including inner and outer components (7, 5; 26, 22) having adjacent overlapping
surfaces, characterised in that each said overlapping surface is formed with at least
one circumferential recess (9, 11), the recesses in the respective components being
opposed and together defining an annular space within which an elastomeric sealing/retaining
ring (8, 27) is accommodated.
2. A hammer drill according to claim 1, further characterised in that said overlapping
surfaces are a close fit one within the other and the or each said recess in one such
surface is of greater depth than the corresponding recess in the other surface.
3. A hammer drill according to claim 1 or 2, further characterised in that each said
inner and outer component is formed with a plurality of said recesses (9, 11) providing
a plurality of spaced-apart annular spaces each accommodating an elastomeric sealing/retaining
ring (8).
4. A hammer drill according to claim 1, 2 or 3, further characterised in that the
or each said sealing/retaining ring (8) is an O-ring.
5. A hammer drill according to any preceding claim, further characterised in that
the or each said sealing/retaining ring (8) is a free element fixed to neither of
said components.
6. A hammer drill according to any preceding claim, further characterised in that
the said inner and outer components are formed of different materials.
7. A hammer drill according to any preceding claim, further characterised in that
the inner component (7) has a tapered lead-in (12) to its surface formed with the
or each said recess (11).
8. A hammer drill according to claim 7, further characterised in that the inner component
is a tube (7) having a recessed surface formed at one end (10) thereof behind said
tapered lead-in (12), the wall thickness of the tube in the region of said end (10)
being selected to distort on assembly of the inner component into the outer component
(5), and in that a plug is adapted to be introduced into said tube end, after assembly
thereof in said outer component, to restore the tube end, after assembly thereof in
said outer component, to restore the tube end to a configuration matching the outer
component recessed surface.
9. A hammer drill according to any preceding claim, in which the outer component is
a valve bottom (5) and the inner component is a central exhaust tube (7) extending
through the piston (2) of the hammer drill.
10. A hammer drill according to any one of claims 1 to 8, in which the outer component
is a drill bit shank (22) and the inner component is a foot valve tube (26).
1. Marteau perforateur fond du trou à pistons libres, actionné par un fluide, comprenant
des composants définissant un chemin d'écoulement pour le fluide incluant des composants
internes et externes (7, 5; 26, 22) possédant des surfaces adjacentes se recouvrant,
caractérisé en ce que chaque surface se recouvrant est formée avec au moins un évidement
périphérique (9, 11), les évidements, dans les composants respectifs, étant opposés
et définissant ensemble un espace annulaire à l'intérieur duquel est logée une bague
d'étanchéité/de retenu (8, 27) en élastomère.
2. Marteau perforateur selon la revendication 1, caractérisé en ce que les surfaces
ser recouvrant sont à adjustement serré l'une dans l'autre, l'évidement, ou chaque
évidement de l'une de ces surfaces ayant une profondeur plus grande que l'évidement
correspondant de l'autre surface.
3. Marteau perforateur selon l'une quelconque des revendications 1 ou 2, caractérisé
en ce que chaque composant interne et externe est formé avec une pluralité d'évidements
(9, 1 1 ), créant une pluralité d'espaces annulaires espacés, chacun recevant une
bague d'étan- chéite/de retenue (8) et élastomère.
4. Marteau perforateur selon l'une quelconque des revendication 1 à 3, caractérisé
en ce que chaque bague d'étanchéité/de retenue (8) est und joint torique.
5. Marteau perforateur selon l'une quelconque des revendications précédentes, caractérisé
en ce que la ou chaque bague d'étan- chéité/de retenue (8) est en élément libre qui
n'est fixé à aucun des composants.
6. Marteau perforateur selon l'une quelconque des revendications précédentes, caractérisé
en ce que le composant interne et le composant externe sont formés en des matériaux
différents.
7. Marteau perforateur selon l'une quelconque des revendications précédentes, caractérisé
en ce que le composant interne (7) possède une entrée conique (12) à sa surface formée
avec l'évidement ou chaque évidement (11).
8. Marteau perforateur selon la revendication 7, caractérisé en ce que le composant
interne est une tube (7) possédant une surface évidée formée à l'une de ses extrémités,
en arrière de l'entrée conique (12), l'épaisseur de la paroi du tube dans la zone
de ladite extrémité (10) étant choisie de façon à se déformer lors du montage du composant
interne dans le composant externe (5), et en ce qu'un bouchon est adapté pour être
introduit dans ladite extrémité du tube, après son montage dans le composant externe,
de façon à redonner à l'extrémité du tube une configuration, adaptée à la surface
.évidée du composant externe.
9. Marteau perforateur selon l'une quelconque des revendications précédentes, caractérisé
en ce que le composant externe est un fond de soupape (5) et le composant interne
est un tube d'échappement central (7) s'étendant à travers le piston (2) du marteau
perforateur.
10. Marteau perforateur selon l'une quelconque des revendications 1 à 8, caractérisé
en ce que le composant externe est une queue de trépan de perforateur (22), et le
composant interne est un tube (26) de clapet de pied.
1. Fließmitteibetätigter Flugkolben-Tieflochbohrhammer mit Fließmittelströmungsweg
definierenden Komponenten, welche innere und äußere Komponenten (7, 5; 26, 22) mit
einander benachbarten überlappenden Flächen umfassen, dadurch gekennzeichnet, daß
jede überlappende Fläche wenigstens eine Umfangsausnehmung (9, 11) aufweist, wobei
die Ausnehmungen in den jeweiligen Komponenten einander gegenüberliegen und gemeinsam
einen Ringraum bilden, in dem eine gummiartiger Dicht- und Rückhaltering (8, 27) sitzt.
2. Bohrhammer nach Anspruch 1, dadurch gekennzeichnet, daß die überlappenden Flächen
dadurch gebildet sind, daß jeweils eine Fläche mit Edelpassung in der anderen Fläche
sitzt, wobei die oder jede Ausnehmung in einer derartigen Fläche eine größere Tiefe
hat als die entsprechende Ausnehmung in der anderen Fläche.
3. Bohrhammer nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß jede innere und
äußere Komponente mit einer Vielzahl von Ausnehmungen (9, 11) versehen ist, wodurch
eine Vielzahl von mit Abstand angeordneten Ringräumen gebildet ist, von denen jeder
einen gummiartigen Dicht- und Rückhaltering (8) enthält.
4. Bohrhammer nach Anspruch 1, 2 oder 3, dadurch gekennzeichnet, daß der oder jeder
Dicht- und Rückhaltering (8) ein 0-ring ist.
5. Bohrhammer nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß
der oder jeder Dicht- und Rückhaltering (8) eine freies Element, welches an keiner
der Komponenten befestigt ist, ist.
6. Bohrhammer nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß
die inneren und äußeren Komponenten aus unterschiedlichen Materialien gebildet sind.
7. Bohrhammer nach einem der vorangehenden Ansprüche, dadurch gekennzeichnet, daß
die innere Komponente (7) eine angeschrägte Durchführung (12) zu ihrer mit der Ausnehmung
oder den Ausnehmungen (11) versehenen Oberfläche aufweist.
8. Bohrhammer nach Anspruch 7, dadurch gekennzeichnet, daß die innere Komponente ein
Rohr (7) ist, welches an einem Ende (10) hinter der angeschrägten Durchführung (12)
eine abgesetzte Fläche aufweist, wobei die Wandstärke des Rohres im Bereich des Endes
(10) so gewählt ist, daß die Wand sich beim Einbau der inneren Komponente in die äußere
Komponente (5) verformt, und daß nach dem Einbau in die äußere Komponente ein Stopfen
in das Rohrende einführbar ist, wodurch das Rohrende wieder in eine Konfiguration
gebracht wird, die der abgesetzten Fläche der äußeren Komponente entspricht.
9. Bohrhammer nach einem der vorangehenden Ansprüche, bei dem die äußere Komponente
ein Ventilboden (5) und die innere Komponente ein zentrales Auslaßrohr (7) ist, welches
sich durch den Kolben (2) des Bohrhammers erstreckt.
10. Bohrhammer nach einem der Ansprüche 1 bis 8, bei dem die äußere Komponente ein
Bohrmeißelschaft (22) und die innere Komponente ein Fußventilrohr (26) ist.