Fastener installation apparatus

Fastener installation apparatus for operating cyclically so as to instal successively a plurality of fasteners includes a fastener installation head (11) having an aperture (35) in which part of a fastener is inserted, and a vacuum generator (20) for creating an airflow in through the aperture (35), along a pipe (31) and into a receptacle (15) for broken-off fastener parts. The presence of a fastener in the aperture (35) causes a change in the level of vacuum in the pipe (31) and receptacle (15). The level of vacuum is sensed by vacuum level detection means (45), which gives an electrical signal to the apparatus control unit (14a, 14b). The control unit allows the installation apparatus to continue its cyclical operation only upon the presence or absence of fastener in the aperture (35) at the appropriate points in the cycle of operation of the apparatus.

BACKGROUND OF THE INVENTION 
The invention relates to fastener installation apparatus. More particularly 
it relates to such apparatus which includes an aperture into which part of 
a fastener to be installed thereby is inserted. 
Whereas in the past such fastener installation apparatus (e.g. for 
installing breakstem rivets) has normally been hand-held by an operator 
who actuated it and inserted new fasteners one at a time into the 
apparatus, there is now a requirement for such apparatus to operate 
cyclically and without direct supervision by an operator, so as to instal 
a plurality of fasteners successively and automatically. Such apparatus is 
usually arranged to feed new fasteners succesively to the fastener 
installation head, and to remove broken-off portions of fasteners 
therefrom. In order to enable the apparatus to work automatically without 
jamming, because of e.g. the misfeed of a new fastener to the installation 
head, or a broken-off portion not being completely and properly removed 
therefrom, it is necessary that the correct operation of various parts of 
the apparatus is monitored and checked automatically. 
SUMMARY OF THE INVENTION 
The present invention seeks to facilitate such functions. 
Accordingly, the invention also provides fastener installation apparatus 
for installing fasteners, which apparatus comprises:--fastener 
installation means including an aperture into which part of a fastener to 
be installed thereby is inserted; vacuum means, connected to the aperture, 
for drawing air in through the aperture; and vacuum level detection means 
for detecting whether the level of vacuum corresponds to the presence of a 
fastener in the aperture of the installation means. 
Preferably the flow of air drawn in through the aperture by the vacuum 
means is used to remove from the fastener installation means portions of 
fasteners which are broken off at the installation of the fastener. 
Preferably the apparatus includes a receptacle in which broken-off 
fastener portions are deposited by the airflow. Preferably the vacuum 
means draws air out of the receptacle and thus in through the aperture as 
aforesaid. Preferably the vacuum level detection means is connected to the 
receptacle to detect the level of vacuum therein. Preferably the vacuum 
level detection means is connected to the receptacle via the vacuum means. 
Alternatively, where the apparatus includes a passage connecting the 
aperture to the vacuum means, preferably the vacuum level detection means 
is connected to the passage adjacent the aperture the aperture, to detect 
the level of vacuum in the passage adjacent the apparatus. Where the 
apparatus is arranged to operate cyclically so as to instal a plurality of 
fasteners successively, prefereably it includes control means operative to 
allow the cyclical operation of the apparatus to continue, so as to instal 
a fastener, only upon the vacuum level detection means detecting a level 
of vacuum corresponding to the presence of the fastener in the aperture of 
the fastener installation means. Preferably the apparatus includes 
resetting means for resetting the vacuum level detection means, after the 
latter has detected the presence of a fastener in the aperture, to a state 
in which it is ready to detect the presence of a further fastener in the 
aperture, the resetting means being actuated to reset the vacuum level 
detection means by a signal indicating that the fastener which was in the 
aperture is no longer there. 
Where the apparatus also includes conveying means for conveying away from 
the fastener installation means a portion of a fastener which is broken 
off at the installation of the fastener, and portion detection means for 
detecting when a broken-off portion has reached a pre-determined position 
on its formerly along the conveying means, preferably the resetting means 
is actuated to reset the vacuum level detection means only upon, at least, 
the aforesaid broken-off portion detection means detecting the presence at 
the aforesaid pre-determined position of the broken-off portion of the 
previously installed fastener. 
The invention also provides fastener installation apparatus adapted to 
operate cyclically so as to instal successively a plurality of fasteners 
each having a portion which is broken-off at installation, which apparatus 
comprises:--fastener installation means for installing a fastener and 
thereby producing a broken-off portion, the fastener installation means 
including an aperture into which part of the fastener is inserted; 
conveying means for conveying the broken-off portion away from the 
installation means; portion detection means for detecting when the 
broken-off portion has reached a pre-determined position on its journey 
along the conveying means; vacuum means, connected to the aperture, for 
drawing air in through the aperture; vacuum level detection means for 
detecting whether the level of vacuum corresponds to the presence of a 
fastener in the aperture; control means operative to allow the cyclical 
operation of the apparatus to continue, so as to instal a fastener, only 
upon the vacuum level detection means detecting a level of vacuum 
corresponding to the presence of the fastener in the aperture of the 
fastener installation means; and resetting means for resetting the vacuum 
level detecting means after the latter has detected the presence of a 
fastener in the aperture, to a state in which it is ready to detect the 
presence of a further fastener in the aperture, the resetting means being 
actuated to reset the vacuum level detection means only upon, at least, 
the broken-off portion detection means detecting the presence at the 
aforesaid pre-determined position of the broken-off portion of the 
previously installed fastener.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring first to FIG. 1, a system for automatically and repetitively 
installing blind breakstem rivets comprises installation apparatus 11 
which is built within a rigid frame 12. The system is powered and operated 
by pneumatic and pneumatic/hydraulic means. To this end it comprises a 
pneumatic pressure source 13, electronic/pneumatic sequence controller 14, 
vacuum generator 20 and rivet stem receptacle 15, pneumatic/hydraulic 
intensifier 16 to power the hydraulically operated rivet installation 
head, rivet bowl feeder 17 and single rivet feeder 18. The units 11, 16 
and 18 and 20 are connected to and controlled by the sequence controller 
14 so as to feed new rivets one at a time to the installation apparatus 11 
and to control its operation in the way which will be described later. The 
controller 14 comprises a programmable electronic logic unit 14a and a 
pneumatic valve unit 14b. (FIG. 4). 
The installation apparatus 11 includes a reciprocable rivet installation 
head 19. New rivets are fed in front of it, one at a time, when it is in 
its rearward position, by means of rivet feeding means comprising rivet 
supporting means 21 which is movable transversely on a slide 22 actuated 
through a bell-crank 23 by a double-acting pneumatic actuator 24, 
controlled by the sequencer 14. New rivets from the single feeder 18 are 
blown one at a time into a feed tube 25, from the front end of which the 
rivet supporting means 21 transfers one rivet at a time to a pick-up 
position in front of the installation head 19. The installation head 19 is 
reciprocated axially by a double-acting pneumatic actuator 26, controlled 
by the sequencer 14. The installation head 19 includes within it a 
hydraulic actuator, fed by a hydraulic pipe 27 from the intensifier 16 
which is controlled by the sequencer 14. When the pneumatic actuator 24 is 
operated, it causes jaws 38 (FIG. 2) within the installation head 19 to 
grip a rivet stem 36 and pull it, thus deforming the rivet body. After 
each rivet 32 has been installed in a hole such as 28 in a workpiece 29, 
the part of the stem 36 which has been gripped and pulled by the jaws 38 
is broken off from the remainder of the rivet 32, and is then released by 
the jaws, from where it travels rearwardly down a stem extractor pipe 31, 
into the stem receptacle 15, due to the suction created by the vacuum 
generator 20. 
The front part of the rivet installation head 19 is shown in FIGS. 2 and 3 
and comprises a cylindrical barrel 33 having at its front end an annular 
steel anvil 34 formed with a central aperture 35. Into this aperture 35 is 
inserted the stem 36 of each rivet 32. The stem 36 is a fairly close fit 
in the aperture 35, and the vacuum applied to the aperture 35, through the 
stem receptacle 15, stem extractor pipe 31 and an axial passage 37 through 
the installation head 19, assists in retaining the rivet 32 on the anvil 
34 until it is installed. After each rivet 32 has been installed, a 
further rivet 32 is fed to the installation head 19 by the rivet feeding 
means. 
The use of an electronic/pneumatic sequencer such as 14 for automatically 
controlling the various elements of the system is well understood and will 
not be described further. In the following description it will be assumed 
that the operation of various elements of the system, and the various 
elements of the installation apparatus 11 in particular, are operated at 
the appropriate times by the sequencer 14. 
The installation system is intended to operate cyclically, to instal rivets 
successively. Each cycle may be initiated by a suitable signal fed to the 
sequence controller 14. 
As previously explained, it is necessary for the safe and proper operation 
of the system that operation is allowed to continue to the next stage only 
if the previous stage is complete. If it is not, operation of the system 
should stop immediately. Thus, the installation head 19 should be actuated 
to instal a rivet only if a rivet 32 is present in the aperture 35. The 
present applicants have appreciated that the presence of a rivet 32 in 
this position effectively seals the aperture 35 against air entering it. 
Since the vacuum generator 20 runs continuously, when a rivet 32 is in 
position in the aperture 35, the level of vacuum increases within the stem 
receptacle 15. Consequently, detecting the level of vacuum in the 
receptacle 15 detects whether or not there is a rivet 32 in the aperture 
35. 
Since, when the installation of each rivet 32 is complete, the stem breaks 
36 off and is conveyed away from the installation head 19, along the pipe 
31 towards and into the receptacle 15, detection of the presence of a 
broken off stem at a position along the pipe 31 will indicate that the 
rivet 32 has been installed. 
The means for detecting such vacuum level and stem presence will now be 
described with reference to FIGS. 4, 5 and 6. 
The stem receptacle 15 comprises a metal box 39 with a removable side wall 
41 for emptying stems 36 out of the box 39. The side wall 41 seals the box 
39 against air entry. The stem extractor pipe 31 (which consists of a 
flexible synthetic plastics hose) enters the opposite side of the box 
through a coupling sleeve 42. 
The vacuum generator 20 is of the venturi type which is fed with compressed 
air through a supply pipe 43. The vacuum side of the generator 20 is 
connected into the receptacle 15 through a rigid connection 44. The vacuum 
generator 20 runs continuously and exhausts the receptacle 15 and the stem 
extractor pipe 31. The other end of the pipe 31 is connected to the 
passage 37 through the installation head 19, and thus to the aperture 35. 
The level of vacuum in the receptacle 15 is detected by a vacuum-sensitive 
switch 45. This is connected via an air tube 46, through the vacuum 
generator 20, to respond to the level of vacuum. The level of vacuum in 
the vacuum generator 20 which is thus sensed is substantially the same as 
the level of vacuum in the receptacle 15. Alternatively the vacuum 
sensitive switch could be connected to the receptacle 15 itself, or to a 
convenient position on the stem extractor pipe 31. In this example 
apparatus, the vacuum switch 45 is of the movable-diaphragm type, in which 
the position of the diaphragm controls the opening or closing of two 
electrical contracts. When the level of vacuum within the receptacle 15 is 
sufficiently high (i.e., the air pressure is sufficiently low), the 
diaphragm moves to close the switch contacts, which are connected via an 
electrical lead 47 to the sequence controller 14. It is arranged that the 
vacuum switch 45 will close only at a vacuum level which corresponds to 
the presence of a rivet 32 on the anvil 34 sealing the aperture 35, as 
previously described. When the presence of a rivet 32 is thus detected at 
the correct stage, the sequence controller 14 allows the installation 
apparatus to proceed to the next stage of operation. In practice, moving 
thus to the next stage may well also require the detection of other parts 
of the apparatus to be in the correct states or positions. 
Detection of the progress of a broken off stem 36a along the extraction 
pipe 31, to a predetermined position 58 which is near the receptacle 15, 
is achieved by means of a proximity sensor 48. In this example apparatus, 
the sensor is an inductive sensor, which senses the presence of a metal 
stem 36 by a change in the electromagnetic inductance. The sensor 48 is 
mounted immediately against the pipe 31 at the position 58, which is near 
the receptacle 15. The sensor is held in a bracket 49, through which the 
pipe 31 also passes, to position the sensor against the pipe 31. The 
bracket 49 is mounted on the coupling sleeve 42. The presence of a broken 
off stem 36a at the position 58 opposite the sensor 48, as the stem 36a 
passes along the pipe 31, causes the sensor to emit an electrical output. 
Since the stem is moving along the pipe 31 at high speed, it actuates the 
sensor for only a very short time. An electrical output of such short 
duration is insufficient to actuate the electronic/pneumatic sequence 
controller 14, so there is provided a solid-state latching relay 51 (FIG. 
4) in an electrical lead 52 between the proximity sensor 48 and the 
controller 14. When the sensor 48 detects the passage of a stem 36 and 
gives an electrical output, this output latches the solid state relay 51 
to give an electrical output continuously to the controller 14 until the 
relay 51 is later reset by a reset pulse applied to it, at an appropriate 
time, by the controller 14. The reset pulse is applied along a connection 
indicated by 53 in FIG. 4. 
One problem which occurs in practice is that the vacuum-sensitive switch 45 
may suffer from hysteresis. That is to say, when it has been closed by the 
application of a sufficient level of vacuum, and the vacuum level is then 
reduced again, the switch 45 does not revert to the open position until 
the vacuum level has fallen to a value substantially below that at which 
it closes. When a rivet 32 has been installed, the relatively low rate at 
which atmospheric air can enter the small anvil aperture 35 means that the 
vacuum level in the receptacle 15 falls relatively slowly. In practice it 
is found that the vacuum-sensitive switch 45 may not reset to the open 
position in time for the next cycle of operation of the system. 
Consequently it is necessary to reset the vacuum-sensitive switch 45 
artificially. This is achieved by means of a reset valve 54, which is 
illustrated schematically in FIG. 6. 
The reset valve 54 is arranged in the air tube 46 between the receptacle 15 
and the vacuum-sensitive switch 45. It is a three-port valve which is 
spring-biassed so that it normally connects the air tube 46 directly to 
the switch 45. The valve 54 is actuated by a solenoid 55 (FIG. 6) to move 
so as to seal the air tube 46 and connect the vacuum-sensitive switch 45 
to atmosphere (i.e., to destroy the vacuum in the switch 45 and 
immediately reset it to the open condition). The solenoid 55 is connected 
to the electronic controller 14a by an electrical lead 56. When the 
solenoid 55 is de-actuated, the valve 54 reverts to its normal position, 
in which the switch 45 is connected to the air tube 46 to detect the level 
of vacuum in the receptacle 15. The solenoid 55 is actuated by the 
programmable electronic controller 14a so as to reset the vacuum switch 45 
only after the proximity sensor 48 has detected the presence of a broken 
off rivet stem 36a at the position 58 that is to say, when a rivet 32 has 
been installed so that there is no rivet 32 inserted in the anvil aperture 
35. 
In practice, resetting of the vacuum-sensitive switch 45 may also require 
the detection of other parts of the apparatus to be in the correct states 
or positions. The controller 14 is programmed so that the solenoid 55 is 
not de-actuated until a suitable later stage of the operation of the 
system when the vacuum level in the receptacle 15 will have fallen below 
that value which the vacuum-sensitive switch 45 will detect. 
FIG. 7 is similar to FIG. 4 but shows a slightly modified system. The 
vacuum switch 45 used in this modification does not suffer from the 
hysteresis problem mentioned above, so that it does not need any reset 
valve 54. Furthermore, the vacuum-level sensing air tube 46 is connected 
to the stem extracter pipe 31 at a position 57 adjacent the installation 
apparatus 11 and the aperture 35. It is believed that connection to detect 
the vacuum level adjacent the aperture 35, at which the presence or 
absence of a rivet 32 is to be detected, provides a faster and more 
reliable response of the vacuum switch 45. 
The invention is not restricted to the details of the foregoing example. 
Attention is drawn to our co-pending application Ser. No. 07/035188 which 
includes part of the foregoing description, but claims a different 
invention.