Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
Field of the Invention
The present invention generally relates to pot broach-
ing machines and particularly to helical pot broaching machines
having an in-line driving means and rotating means to rotatably
translate a part through a pot broach.
Description of the Prior Art
Machines for broaching the teeth on a gear as a conse-
quence of a single passage of a work blank through a broach are
known. The teeth of the broach are located in a pot broach f`or
internal broaching and are usually arranged in longitudinal
alignment and are appropriately stepped to perform the required
tooth cutting operation. If the gear is a spur gear the teeth
are arranged in series extending parallel to the axis of the
broach. If the gear is a helical gear the teeth are arranged
in helically extending series.
A single passage of the gear blank upwardly through
the broach results in a complete cutting operation forming the
required teeth on the periphery of the gear. The gear is moved
upwardly above the upper open end of the broach into a clearance
position relative to the broach. It is at this time moved from
the work support to a chute which may be downwardly directed.
If the gear is to be a helical gear the gear blank must also be
rotated relative to the broach while it is being pushed through
the broach.
Prior art helical broaching has been accomplished by
rotating mechanisms of various sorts offset mounted from the
broach and being driven by similarly offset driving means. Off-
setting the rotating and driving means from the broach intro-
duces unsymmetr;c loadingj error, and backlash in the system.
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SUMMARY OF THE INYENTION
The present invention solves the forementioned problemsassociated with the prior art devices as well as others by pro-
viding an in-line helical pot broaching machine in which the pot
broach is mounted in-line with the rotating means and the
driving means.
In a specific embodiment the present invention has a
support base having a horizontal face on which the pot broach is
vertically mounted with the inlet side of the pot broach being
affixed to the horizontal face of the support base. This mount-
ing yields a symmetrical loading around the center line of the
work and tool axis and provides more rigidity than the usual
vertical surface mounted pot broaches. A helical nut housing
having a helical nut is mounted to the support base in-line with
the pot broach. A helical lead bar is connected to a hydraulic
drive piston through a swivel joint to allow the lead bar to ro-
tate in the helical nut in response to the translational motion
. of the drive piston. The lead bar has an expanding collet at the
end to grasp the part. Thus the part is rotated while it is
being pushed through the stationary pot broach by a drive assem-
bly which is in-line with the pot broach eliminating slop and
backlash found in known prior art offset drive mechanisms.
From the foregoing it will be seen that one aspect of
the present invention is to provide a helical pot broaching
machine.
Another aspect of the present invention is to provide a
helical pot broach having a drive assembly mounted in-line with
the pot broach.
These and other aspects of the present invention will
be more fully understood after a review of the following
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description of the preferred embodiments and the drawings.
RIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side view of the present pot broach
machine in the down pos1tion.
6 Fig. 2 is an expanded view of the helical nut and lead
bar of the machine of Fig. 1 in the up position.
Fig. 3 is a top view of the machine of Fig. 1.
DESCRIPTION OF THE PREFER~ED EMBODIMENT
Referring now to the drawings, Fig. 1 discloses a pot
broaching machine 10 which has a known pot broach 12 vertically
mounted along its horizontal base 74 to a support structure 16.
The horizontal base 14 has the pot broach 12 rigidly
affixed thereto by well known means such as nuts and bolts 18.
The pot broach 12 has an opening 20 through which a blank work-
plece 22 is inserted into the pot broach 12 by known loading
mechanisms (not shown~, The support structure 16 affixed to a
floor 24 which supports a known piston and cylinder device 26 in
which a piston (not shown) is vertically movable in-line with the
pot broach 12. The vertical mounting of the pot broach 12 along
a horizontal end to the support structure 16 provides a symmetri-
cal loading around the center line of the machine 10 yielding
added rigidity to the entire structure.
The machine 10 in operation loads the blank workpiece
22 to one end of the pot broach 12 and unloads the finished work-
piece 22 from the top of the pot broach 12. To accomplish this
loading-unloading, a known work transfer mechanism (not shown)
is provided which operates between a loading chute and an un-
loading chute. An example of such a mechanism is shown in
U.S. Patent No. 4,027,574, issued to The Babcock & Wilcox
Company; John Xavier Russell, inventor; title, POT BROACHING
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MACHINE, and the reader is referred thereto for a more detailed
description.
Since the broaching operation requires liquid cooling
and results in the formation of metal chips, a liquid and chip
collector 28 is sealably mounted around the base of the support
structure 16. The collector 28 directs the metal chips and
cooling liquid along an outlet to a reservoir where the chips
are filtered from the coolant and the coolant is recycled back
to the machine 10.
As can be seen from Figs. 1 through 3, the driving
means for pushing and simultaneously rotating the blank work-
piece 22 through the pot broach 12 is such that all required mo-
tion is performed in a straight line along the vertical axis of
the pot broach 12. This eliminates the necessity of utilizing
an offset hydraulic cylinder or other means of supplying linear
motion or an offset location for the pot broach as is prevalent
in known prior art devices. As a result of this in-line arrange-
ment, the machine 10 requires minimum floor space and produces
less downtime and maintenance cost due to the reduction of the
number of components required and the simpler constructional
nature of the few remaining components necessary for the opera-
tion of the in-line arrangement. The in-line arrangement also
makes possible the taking advantage of high speed broaching.
Linear vertical motion of the blank workpiece 22
through the pot broach 12 is provided by the piston and cylinder
assembly 26 being mounted directly under the pot broach 12 to
allow the piston 32 to be extended up and down in response to
fluid pressure provided to the piston assembly 26 through hy-
draulic connecting lines 34~ The piston 32 is connected to a
shaft 36 which terminates in an expandable collet 38 used to
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~igidly hold the blank workpiece 22 to the shaft 36 by way of
the collet 38. The shaft 36 is connected to the piston 32
through a collet actuating device 42 well known to those skilled
in the art. From the foregoing it will be understood that as
the blank workpiece 22 is slid into the pot broach 12 through
the passageway 20, it is aligned with the expandable collet 38.
An actuating signal to the hydraulic cylinder 26 causes the
piston 32 to move up actuating the collet actuating device 42
and causing the expandable collet 38 to slide into a hole 46 of
the blank workpiece 22 and expand therein causing the blank
workpiece 22 to be securely and nonrotatably fixed onto the
shaft 36. Without any further mechanisms the blank workpiece 22
would now be pushed up through the pot broach 12 to provide a
finished workpiece 22. However, since the workpiece 22 must be
rotated while it is being pushed through the pot broach 12, a
helical nut housing 48 having a helical nut 50 and a helical lead
bar 52 are provided.
The helical nut housing 48 is mounted in-line below
the pot broach 12 to be rigidly secured to the frame 16. The
helical lead bar 52 is fixed to the shaft 36 and the collet
actuating device by known means such as a pin 54 to require the
helical lead bar 52, the collet actuating device 42 and the
shaft 36 to move and rotate as a single unit. The helical lead
bar 52 is coupled to the piston 32 through a swivel ioint 56
which allows the piston 32 to exhibit purely linear motion to
push the collet actuating device 42 to the shaft 36 and the lead
bar 52 in a vertical direction while allowing the lead bar 52
along with the shaft 36 and the collet actuating device 42 to
rotate around the piston 32. The helical lead bar 52 is made of
hardened and ground high speed steel that has ground helical
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guide grooves 58 ground on the lower portion of the lead bar 52
where these grooves 58 engage the helical nut 50 which has
complimentary grooves.
In the down position shown in Fig. 1, the grooves 58
5 are engaged with the complimentary grooves of the helical nut 50.
Thus, when the blank workpiece 22 is aligned with the expandable
collet 38 and a upward stroke is initiated, the upward movement
of the piston 32 will cause the helical lead bar 52 to rotate as
it is laterally pushed through the stationary helical nut housing
48. Since the shaft 36 is rigidly connected to the helical iead
bar 52, the workpiece 22 rigidly afflxed to the expandable collet
38 will also be rotated as it is pushed through the pot broach
12. Towards the end of the upward stroke as the broached work-
piece 22 approaches the exit 60 of the pot broach 12, the work-
piece 22 encounters a series of spring-loaded stripper fingers
62. Further motion of the workpiece 22 causes the stripper
finger 62 to be pushed out by cam action unt.l the workpiece is
raised above the stripper finger 62 at which time they will
spring back and provide a rest for the finished workpiece 22.
Release of pressure from the shaft 32 on the collet actuating
device 42 will cause the expandable collet 38 to release its grip
on the finished workpiece 22 allowing the drive assembly 30 to
be lowered with the finished workpiece 22 remaining on the pot
broach outlet 60 in its resting position on the stripper finger
62. The finished workpiece 22 may now be moved out by a work
transfer mechanism with another unfin;shed blank workpiece 22
being inserted into the pot broach 12.
To prevent any contaminants such as chips and chip and
coolant mixture from entering the helical grooves of either the
lead bar or the helical nut 50, a guide and wiper assembly 64 is
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mounted between the inlet of the pot broach 12 and the helical
nut housing 48. This guide and wiper assembly 64 includes a
flexible member 66 which allows the shaft 36 to move through it
while preventing any chips and coolant from by-passing the
flexible member 66 to reach the helical grooves 58. Although
the foregoing discussion has dealt with a bottom-loading push-up
broaching machine, it will be understood that the described in-
line broaching principle equally applies to push-down, pull-up,
or pull-down broaching arrangements which may be further accom-
plished either horizontally or vertically. Since such modifica-
tions would be well within the expertise of people skilled in
the art, these various embodiments are not shown for the sake of
conciseness and readability but are intended to be covered by
the scope of the following claims.
