Note: Descriptions are shown in the official language in which they were submitted.
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FEED MECHANISM FOR GRAVITY FEED TACRERS
BACKGROUND OF THE INVENTION
This invention relates to a feeding
mechanism for fastener driving devices and more
particularly to fastening devices used in -
continuous production lines having a feeding
mechanism for feeding successive fasteners into
the drive track of the device.
Conventional staple feeding mechanisms
must perform the task of feeding and holding the
staples in the drive track. In certain devices,
sticks of staples are loaded onto a magazine that
is angled downward so that the force of gravity
aids in pulling the staples down to the nose of
the device and into the drive track. However, the
force of gravity alone is insufficient to feed and
hold the staples in the drive track.
To increase the force on the staples at
the nose of the device, a mechanism has been used
including a friction clutch and a wheel connected
to an electric motor. Thus, as the motor turns,
the clutch maintains a certain torque on the wheel
which in turn keeps a constant forward force on ~-
the staples. When a staple is driven, the
remaining staples are fed and held forward toward
the drive track. Other conventional feed
mechanisms use a ratchet to hold and feed staples
to the drive track. The feed is made under spring
pressure and the cycling action for the feed
stroke comes during the power stroke of the
device. It is common to connect the return piston
to a source of air under pressure which is
communicated in response to the actuation of the ~
device. Consequently, instead of feeding during ~ ~-
the drive stroke, the conventional ratchet is ;
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recycling or retracting during the drive stroke
and the fastener which has already been fed into
the drive track is held therein by a holding pawl.
Although these type of feed mechanisms work well
for their intended purpose, they typically require
an extra power source to be connected to the
device, and are inefficient and expensive.
Other conventional feed mechanisms employ
a spring biased pusher which contacts the rearmost
staple of the staple stick urging the staples
forward along a guide to the drive track. The
devices are effective in feeding and holding the
staples in the drive track of the device, however,
when a staple stick has been exhausted, the pusher
must be retracted to allow another staple stick to --
be placed on the guide. In a continuous
production line such interruptions can be
disruptive and costly due to lost productivity.
SUMMARY OF THE INVENTION
An object of the present invention is to
provide a fastener feeding mechanism for a
fastener driving device which requires no ~--
additional power source to hold the staples in the
drive track and which permits a supply of
fasteners to be fed to the drive track
continuously, limited only by the supply of
fasteners provided.
It is further object of the present
invention to provide a feed mechanism which uses
spring bias to hold the leading fastener in the
drive track during the fastener driving stroke and
to provide pneumatic cycling to operate the feed
mechanism during a portion of the operating cycle
of the drive element when it is not necessary to
hold a leading fastener in the drive track. Thus,
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the feeding mechanism may be advantageously
signalled by the device's plenum air and is
automatically timed to the device's engine cycle.
In accordance with the principles of the
present invention, these objectives are obtained
by providing in a fastener driving apparatus
including a nose piece assembly defining an
elongated drive track receiving a fastener driving
element therein movable through an operating cycle
including a drive stroke and return stroke, and a
fastener feeding track communicating laterally
with the drive track, an improved mechanism for
feeding fasteners from a fastener package into a
position to be driven by the fastener driving
element during the drive stroke thereof is
provided. The feeding mechanism includes an
actuating mechanism mounted for movement through
an operating cycle including (1) an operative
stroke in a direction along the fastener feeding :
track toward the drive track for feeding fasteners
to the drive track and (2) a return stroke. A
fastener holding mechanism is also provided and is
operatively coupled to the actuating mechanism for
movement therewith through the operating cycle :~
thereof, whereby during the operative stroke of :
the actuating mechanism the fastener holding
mechanism holds the fasteners in position biased ~ -~
toward the drive track during at least a portion :~ -~
of the drive stroke so that a leading fastener
from the fastener package is disposed in the drive
track in position to be contacted by the driving
element. The fastener holding mechanism is
. released~from the fasteners during the return
stroke of the actuating mechanism, during a
portion of operating cycle of the driving element
when a fastener need not be held in the drive
track.
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.
Another object of the present invention
is the provision of a device of the type
described, which is simple in construction,
effective in operation and economical to
manufacture and maintain. `
These and other objects of the present
invention will become apparent during the course
of the following detailed description and appended
claims.
The invention may be best understood with
reference to the accompanying drawings wherein an
illustrative embodiment is shown.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation view, with
parts in section, of a pneumatically operated
fastener driving device including a feeding
mechanism provided in accordance with the ~-
principles of the present invention; and
FIG. 2 is a plan view of the fastener
feeding mechanism provided in accordance with the
principles of the present invention.
Referring now more particularly to FIGS.
1 and 2 of the drawings, a fastener driving
device, generally indicated at 10 is shown having
a fastener feeding mechanism, generally indicated
at 12, embodying the principle of the present
invention. The device 10 includes the usual
fastener driving element 14 which is moved through
an operating cycle including a drive stroke and a
return s~roke preferably by a conventional
pneumatic system (not shown). `~;
The device 10 includes a rigid housing 16
- including a nose piece 18 having internal surfaces -
defining an elongated drive track 20. A staple
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magazine assembly 22 is secured to the nose piece
18 and extends rearwardly therefrom. The magazine
assembly 22 may be of any conventional design, is
adapted to receive a supply of staples in the form
of a staple stick and support and guide the
staples forwardly along a feed track 23 into the
drive track to be driven outwardly thereof by the
staple driving element 14. As shown in FIG. 1, a
portion of the staple stick is exposed, the
function of which will become apparent below.
The feeding mechanism 12 includes an
actuating mechanism generally indicated at 24 and ~-
a fastener holding mechanism, generally indicated
at 26. As best shown in FIG. 2, the actuating
mechanism includes a cylinder 28 coupled to the
device 10 at one end thereof. A piston 30 is
slidably mounted within the cylinder and has a
piston actuating rod 32 formed thereon extending
outwardly of the cylinder. The outer end of the
actuating rod 32 is coupled to the holding -
mechanism. The piston-cylinder arrangement may be
of any conventional design, for example, Model No. r~.
OlDX manufactured by BIMBA. The actuating
mechanism also includes an air inlet portion 34
which communicates with the plenum chamber 36 of
the device 10 via tube 38 and connector 39, the
function of which will ~ecome apparent below. The
actuating mechanism 24 further includes a spring
40 coupled to the holding mechanism 26 at one end
thereof, with the other end being in contact with
a surface of the inlet portion 34. The spring 40
normally biases the holding mechanism in a
direction toward the drive track.
As shown in FIG. 2, the fastener holding
mechanism 26 includes a feed block 41 supporting a
pair of holding pawls 42 disposed on opposing
sides of the staple stick 45. Each holding pawl
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42 is pivotally coupled to the feed block 41 by a
pin 44 at one end thereof. A compression spring
46 is coupled to an opposite end of each holding
pawl 42 at a position offset from an axis of the
pin 44. The other end of the compression spring
46 is coupled to the feed block 41. Each holding
pawl 42 includes an angled surface 43 terminating
at engaging edge 48. Edge 48 contacts a point
between staples of the exposed side portion of the
staple stick due to the bias of spring 40.
The operation of the mechanism 12 will be
appreciated with reference to FIGS. 1 and 2.
Spring 40 normally biases the holding mechanism in
a position toward the drive track during an
operating stroke of the actuating mechanism. The
forward motion of the holding mechanism 26 caus~s
the holding pawls 42 to contact the staple stick
so as to hold the staple stick, due to a moment
created by the compression springs 46 being offset
from the pins 44. Thus, during an initial part of
the drive stroke, the spring 40 ensures that a
leading staple of the staple stick is disposed in
the drive track. The driving element then moves
downward within the drive track and contacts the
leading staple. When the driving element has ~-
sheared off the leading staple and is part-way
through its drive stroke, the driving element
passes plenum feed holes 52 in cylinder sleeve 54.
Pressurized air then flows into plenum chamber 36
which is fed through tube 38 and into the
pneumatic cylinder 28. The pressurized air moves
the piston 30 in a direction away from the drive
track cQ~pressing the spring 40, thus permitting
the holding mechanism 26 to move away from the
drive track during a return stroke of the
actuating mechanism. When the holding mechanism
is pulled-back in a direction away from the
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feeding direction by the pneumatic cylinder 30,
the holding pawls 42 ratchet-off the staple stick
while maintaining contact therewith, due to the
force of inertia of the remaining staples acting
on angled surface 43 of the holding pawls 42.
The angle of surface 43 and the spring
force of springs 46 are such that the holding
pawls ratchet-off successive staples, thus, not
pulling the staples back along the feed track
toward the cylinder 30. Thus, the holding pawls
move from their holding position during the return ;~
stroke of the actuating mechanism, during a
portion of the operating cycle of the device 10
when it is not critical to hold the staples -~
securely in the nose piece 18.
After the return stroke of the driving
element 14 is complete, the plenum air is
exhausted through the nose piece 18 and removed
from the cylinder 30 which causes spring 40 to
expand and again push the holding mechanism 26
toward the drive track which moves the holding
pawls into their holding position to move the
fasteners forward along the feed track and to hold
a leading staple of the fastener package in the
drive track.
From the foregoing, it can be appreciated
that the fastener feeding mechanism offers
numerous advantages over prior art devices. Since
feeding and holding of the staples is not
performed from behind the staple stick, feeding is
only limited by the length of the staple stick and
need not be interrupted, for example, to retract a
pusher. _
Further, the mechanism requires no e~tra
power source to be connected to the device. The
mechanism is signaled by the device's plenum air
and is automatically timed to the operating cycle.
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In addition, since the plenum air is used agalnst
a spring, the mechanism is efficient.
It thus will be appreciated that the - -
objects of the invention have been fully and
effectively accomplished. It will be realized,
however, that the foregoing preferred embodiment
of the present invention has been shown and
described for the purpose of illustrating the
structural and functional principles of the
present invention and is subject to change without
departure from such principles. For example,
although the present invention was described with
reference to staple fasteners, it is contemplated
that the mechanism of the present invention may be
employed for feeding other fasteners, such as
nails. Thus, the invention includes all the
modifications encompassed within the spirit of the
following claims.
