BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION

THIS INVENTION relates to automatic fastening machines

or tools, and, in particular, to the fastener delivery head for such

automatic fastening machines or tools.

2. PRIOR ART

Prior patent specifications, PCT/AU92/00621 (WO 93/09918)

and PCT/AU94/00013(WO 94/15736) by the present applicant both

disclose automatic fastening machines or tools wherein the fastening

head thereof operates with rivets and other types of fasteners, fed thereto

in alignment with a punch or engagement tool therefor, and supporting the

rivets or other fastener as the punch or engagement tool advances the

rivet or other fastener towards a workpiece (and typically an upsetting die

in the case of rivets).

While the fastening machines or tools disclosed in the above

documents have found commercial acceptance, customers continue to

propose new applications for fasteners, fastening diverse ranges of

workpieces together, and particularly where access for the fastening

operation is restricted, and sometimes extremely limited. The need to

provide fastener aligning, centralising, and anti-tumbling features in the

fastening head or nose pieces, particularly leading up to, and at the exit

point thereof for a fastener, by reduced dimension of the parts, introduces

fragility if the old techniques for control are retained. Short rivets in

particular need to be controlled and the prior art has proposed steel balls

or jaws for this purpose. If these are to be used they must be provided up

to, and very close to, the front face or nose of the fastening apparatus to

prevent tumbling, for example. A staggered sequence of such balls, or

like type devices, over the length of a delivery tube requires a fairly

elaborate construction, which restricts the capacity to reduce the front end

dimensions of the fastener feeding head.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a fastening head which addresses the aforementioned disadvantage in front end

dimension. Other objects and various advantages will hereinafter become

apparent.

DISCLOSURE OF THE INVENTION

The invention achieves its object in provision of a fastener

feeding head for a fastening machine or tool by which to apply fasteners

to a workpiece, said fastening head including:

a guide means with a fastener passage there through;

a drive means mounted for advance and retraction in the

fastener passage; a fastener engagement means disposed in the fastener

passage at or on a leading end of the drive means; and

a fastener feed means feeding fasteners to the fastener

passage, operative to align fasteners in the fastener passage with the

drive means;

characterised in that:

a gas control means is operative to effect or establish a gas

pressure in the fastener passage which is operative to maintain a fastener

therein in contact with, or in proper alignment or orientation to, the drive

means as the drive means is advanced in the fastener guide passage. In

order to effect the desired outcome the cross sectional dimension of the

fastener passage is ideally closely fitted to the radial dimension of the

fastener, its head in the case of a rivet. Alternately the foregoing might be

achieved by careful dimensioning of the fastener engagement means

such that it adequately fits to the fastener passage such that a suitable

degree of pressurisation is developed and maintained in the fastener

passage. A similar level of seal is required between the front end of the

fastener passage and the work pieces as is will be more clearly developed

herein below.

Preferably a fastener feeding head has a fastener feed

means which includes a delivery passage for fasteners, fitted with a

compressed gas source, operative to propel fasteners there through to

the fastener passage, there being a gate means associated with the guide

means to selectively isolate the fastener passage from the delivery

passage. The fastener feeding head is ideally associated with a gas flow

means in or associated with the guide means selectively directs gas from

the delivery passage to the front or nose end of the fastener passage,

forwardly spaced from the drive means, to cause compressed gas to

maintain fasteners in contact with the drive means as the drive means is

advanced in the fastener passage. Preferably a fastener feeding head in

accordance with the invention is one wherein the gas flow means includes

a piston driven gate means to switch gas in the delivery passage to flow

passages leading to the front or nose end of the fastener passage.

Preferably a fastener feeding head in accordance with the invention is one wherein one or more balls or the like are retractably

mounted in the guide means to retractably extend into the fastener

passage, on the opposite side thereof to the junction between the delivery

passage and the fastener passage, to assist alignment or centralising of

the fasteners with the punch. Ideally a fastener feeding head is one

wherein fasteners are supplied to the delivery passage by a supply tube

which may have an internal profile complementary to the shape of the

fasteners, the fasteners being propelled by compressed air blown down

the supply tube. Ideally there is provided a gate means which is

pneumatically controlled and the flow passages include one or more ports

directed into the fastener passage adjacent the nose end, the gas

directed thereto being sufficient to maintain contact of a fastener with the

fastener engagement means when the nose of the guide bush or feeder

block engages with a workpiece.

Preferably a fastener feeding head in accordance with the

invention is one wherein when the nose end of the guide means is in

contact with a workpiece, a vacuum means selectively at least partially

evacuates the fastener passage to maintain the fasteners in contact with

the punch as the punch is advanced in the fastener guide passage.

Ideally there is a compressed gas source to propel a fastener through the

delivery passage to the fastener passage, a gate means to selectively

isolate the fastener delivery passage from the fastener guide passage

after delivery thereto of a fastener, and, when the nose end of the

fastener passage is in contact with a workpiece, and a vacuum means to

selectively, at least partially, evacuate the fastener passage to maintain

the fastener in contact with the fastener engagement means as it is

advanced in the fastener guide passage. Ideally there is at least one slot

or groove provided in the nose end of the guide means to allow air to be

drawn into the fastener passage when the nose end is in contact with a

workpiece or at least one slot or groove is provided in the wall of the

fastener passage, connected to at least one port, in turn connected to a

vacuum source, wherein the vacuum source is operative to draw air into

the fastener guide passage through one or more grooves or ports in the

nose end of the guide means, air creating the means by which a fastener

is maintained in contact with the fastener engagement means as it drives

the fastener through the fastener passage into engagement with a

workpiece.

Preferably the invention provides a fastener feeding head

wherein the guide means is a guide bush, the drive means is a plunger

mounted for coaxial advance and retraction through the guide bush, the

fastener engagement means is a punch located at or on a leading end of

the plunger, and a carrier tape means transports rivets to the fastener

passage, and a gas passage or port means in the guide means operable

to connect a supply of compressed gas to the nose end of the fastener

passage to cause the compressed gas to be directed into the fastener

guide passage, spaced from the punch, the compressed gas being

operative, in use, to maintain the rivets in contact with the punch as the

punch is advanced in the fastener passage. Ideally the gas control

means includes means in the guide means operable to connect a supply

of compressed gas to the nose end of the fastener passage the

compressed gas being switchable to maintain the fasteners in contact

with the fastener engagement means as needed. The compressed gas

means and vacuum means may be selectively controlled by switchable or

computer controlled valves.

Throughout the specification, the term "fastener" shall

include rivets, screws, and like type fastening devices, nuts, washers and

similar type products with a ratio of radius to axial length calls for the

handling capacity of the invention herein set forth. The preferred

embodiments are in respect of rivets but the extension to other fasteners

only requires a variation of the fastener engagement means used in the apparatus. Thus the punch of the preferred embodiments may be readily

replaced by a driver for screws, in the case of screw fasteners as will be

readily apparent to the man skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

To enable the invention to be fully understood, preferred

embodiments will now be described with reference to the accompanying

drawings in which:

FIGS. 1 , 2 and 3 are sectional side views of a first

embodiment of a fastener feeder head in accordance with the invention

showing the apparatus at different steps in its operation;

FIG. 4 is a sectional side view of a second embodiment of

the invention in accordance with the invention;

FIG 5. is a sectional plan view taken on line 1-1 of FIG 4;

and

FIG. 6 is a side view of a third embodiment of the invention.

PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 3, a fastener feeding head 10 for a

fastening machine 100 may have a guide means which, in this

embodiment, includes bush 11 with a fastener passage or bore 12

(hereinafter referred to as a bore for convenience) in which may be

coaxially mounted a drive means such as plunger 13 (which will vary in

character depending on what style of fastener is used, which, in turn,

decides what action is to be performed by the drive means, hereinafter

referred to as a plunger for convenience) which can be associated, as

shown, with a fastener engagement means such as punch 14 (which will

vary depending on what style of fastener it is to engage with but is

conveniently referred to as a punch hereinafter) located or fitted at its

forward end. The plunger is mounted for reciprocal advance and

retractive movement in the bush 11. A fastener passage 15 is provided in

the bush leading to a front end or nose portion 16 of the guide bush 11

and up to the front face or nose 17. The fastener passage 15 is

preferably axially aligned with the punch 14 and it is open to the front face

17 to deliver fasteners thereto out of the fastener passage of the guide

bush. A delivery passage 18 for feeding fasteners to the fastener

passage can be provided in a side extension (or feeder block) 19 fitted to

or mounted on the guide bush 11. It is operably connected to the fastener

passage 15 with the junction of the two passages being below the forward

end of the punch 14 when the punch is fully retracted. A supply tube 20

may be connected to a source of fasteners such as rivets (not shown) and

the fastener being a rivet 21 in this case may be propelled through the

supply tube 20 and the delivery passage 18 ideally by means of a

compressed gas, such as compressed air.

When the rivets 21 enter the fastener passage 15, they may

be aligned and centred with the forward end of the punch 14 by a suitable

means or mechanism, including any of the mechanisms for this purpose

seen in the prior art, such as via a plurality of spring mounted balls 22. A

gate 23 may be provided, preferably with a pneumatic cylinder 24 which is

ideally operable to advance or retract a blade 25 whose end may form the

gate 23 so as to selectively isolate the delivery passage 18 from the

fastener passage 15. This may also serve to divert compressed air from

the delivery passage 18 to the nose end 16 and the front end of the

fastener passage 15. This may be effected by means of flow via air

passages 26, 27 and respective ports such as port 28. When the front

face 17 of the guide bush 11 engages workpieces such as work pieces

30, 31 , which in this embodiment are to be rivetted together, the front face

17 of the guide bush effectively seals the fastener passage to create

therein a pneumatic cylinder where the rivet 21 acts as a free floating

piston which is forced against the nose of the punch 14. Any air leakage

is to be at a rate which is smaller than the rate at which the compressed

air is supplied to the fastener passage 15. The punch 14 is then able to

advance the rivet 21 past the balls 22, which centre the rivet to the punch

axis. The force of the compressed air maintains the rivet in contact with

the punch as it is advanced through the fastener passage 15 and up to

the workpieces to then pierce the workpieces 30, 31 , and be upset by an

upsetting die (not shown) so as to complete the process. On retraction of

the punch 14, the compressed air supply may be switched off, the blade

25 may be retracted, with the apparatus being then ready for the next

cycle. In an alternative embodiment (not shown), the guide bush 11 can

be substituted by a feeder block mounted on the plunger of the fastening

machine 100.

Referring to the embodiment of FIGS. 4 and 5, the guide

bush 111 is substantially as hereinbefore described except that radial

grooves 128 are provided at the front face 117 of the guide bush 111 and

diametrically opposed slots 129 may extend up the wall of the fastener

passage 115 to be interconnected to vacuum passages 130 which may

be connected to a means of establishing a vacuum 131. In operation,

fasteners such as the rivets 121 may be delivered to the fastener passage

115, ideally propelled thereto by compressed air, through the delivery

passage 118, to be associated with, located against or engaged to the

forward end of the punch 114 generally as hereinbefore described with

reference to the first embodiment. The blade 125 may be advanced, as

shown in FIG. 4, to isolate the fastener passage 115 from the delivery

passage 118, and at this point the supply of compressed air may be shut

off. The vacuum supply 131 is then operative to draw air into the fastener

passage 115, past the rivet 121 and punch 114 (through slots 129). By

this means there is created the pressure differential which is needed to

develop the pressure which maintains the fastener in contact with the

nose of the punch. When the front face 117 of the guide bush 111

engages the workpieces 130, 131 , air can flow through the radial grooves

128 in the front face 117. The foregoing construction ensures that the

desired association or contact is maintained between the rivet 121 and

the punch 114 during operation of the fastener head.

When the punch 114 has advanced the rivet to and through

the workpieces 130, 131 (and the rivet has been upset by the upsetting

die, not shown), the vacuum source 131 may be rendered inoperative or

switched off, the blade 125 is retracted, the punch 114 is also retracted,

and the apparatus is ready to enable the next cycle to commence.

Referring now to FIG. 6, the guide bush 211 has a delivery

passage 218 through which fasteners such as the rivets 221 may be

transported via a carrier tape 229 into alignment with the punch 214 and

fastener passage 215. The advance of the carrier tape 229 can be

controlled by a suitable means such as finger 241 on a limit switch 240, in

turn connected to a suitable drive (not shown) for the carrier tape 229. Air

passage 226 may connect an air port 228 at the front face 217 of the

guide bush 211 to a supply of compressed air (not shown). When the

rivet 221 is aligned with the punch 214, and the front face 217 of the

guide bush 211 contacts the upper workpiece 230, a charge of

compressed air is allowed to be passed through the air passage 226 and

port 228 to cause the rivet 221 to be maintained in contact with the nose

end of the punch 214 as the latter is advanced in the fastener passage

215 towards the workpieces 230, 231. It will be noted that the

centralising balls (122 of FIG. 4) may be omitted in this embodiment.

Concentricity tolerances may permit the rivets 221 to float within the

fastener passage 215.

Both of compressed air, or the vacuum of the earlier

embodiments, may be used in any of the embodiments so as to maintain

the fastener or rivet 21 , 121 , 221 on the nose of the respective fastener

engagement means or punch 14, 114, 214. The need for balls or other

like devices (ie., similar to the balls 22, 122) along the fastener passage

and adjacent the front face 17, 117, 217 of the guide bush 11 , 111 , 21 1 is

obviated. The front end or nose of the guide bush can have greater

structural strength (while having dimensions which enable rivets or other

fasteners to be driven into, or carried to, the workpieces in confined

spaces).

Various changes and modifications may be made to the

embodiments described and illustrated without departing from the present

invention.