IMPROVEMENT TO A SURFACE BURRING TOOL

AMELIORATION APPORTEE A UN OUTIL D'EBARBAGE DE SURFACE

English Abstract

An improvement to a surface burring tool comprising the use of drive pins each with flat surfaces, the first flat surface to bear on the flat surfaces of the angled ramps of the tool body so as to reduce pressure and to thereby reduce wear, and the second flat surface to locate against an edge of the slot in the retaining clip of the blade assembly to prevent rotation of the pin. This will ensure that the first flat will be parallel to its ramp on insertion of the replaceable blade assembly into the tool body. Pin rotation might result in the first flat not remaining parallel the tool ramp on which the pin slides during tool operation.

French Abstract

Une amélioration est apportée à un outil débarbage de surface comprenant lutilisation dergots dentraînement avec des surfaces planes, la première surface plane reposant sur les surfaces planes des rampes inclinées du corps de loutil de manière à réduire la pression et, par conséquent, à réduire lusure. La deuxième surface plane repose contre un bord de la fente dans lélément de retenue de lensemble de lame afin déviter la rotation de lergot. Cela permettra de sassurer que la première surface plane sera parallèle à sa rampe au moment de linsertion de lensemble de lame remplaçable dans le corps de loutil. Une rotation de lergot pourrait faire en sorte que la première surface plane ne demeure pas parallèle à la rampe de loutil sur laquelle glisse lergot durant le fonctionnement de loutil.

Claims

Claims
1. In a surface burring tool, said tool having:
a tool body having inwardly angled ramps;
opposing rows of blades and aligned drive holes through each said rows of
blades;
a clip for holding said rows of blades in a side by side relationship and
having longitudinal drive
slots in alignment with said drive holes;
drive pins traversing said slots and said holes and having end portions to
engage said ramps;
the improvement comprising a first flat formed on at least each said end
portions of said pins
where said flats engage said ramps to thereby reduce pressure and wear between
said drive
pins and said ramps.
2. The surface burring tool of Claim 1 further including a second flat
operatively angled to said
first flat, said second flat formed on at least said end portions of said
drive pins, where said
second flat ensures that said drive pins can only be inserted through said
slots by aligning
said second flat with an edge of said slot to thereby prevent said pin's
rotation and to thereby
ensure said first flat is held parallel to said ramp.
7

Description

CA 02588431 2007-04-30
FIELD OF THE INVENTION
The present improvement invention relates to a tool such as that described in
US Patent
7,200,940 by the present applicant, used to burr a surface in preparation for
adhesive
bonding.
BACKGROUND OF THE INVENTION
Such a tool is pressed vertically against a surface whereby opposing rows of
toothed blades
are made to move a short distance towards each other so as to bite into the
surface and plow
multiple shallow grooves while peeling up burrs from the grooves which remain
attached to
the end of the groove. The burrs then serve to increase, for example,
adhesively bonded
structures. In that invention, round pins slide on flat, angled ramps to move
the blades.
Friction resists movement between two objects. The greater the force of
contact the greater
the friction. Force applied over and area, or pressure, is a function of force
per unit area, such
as pounds per square inch. For a given force, then, pressure rises as the
contact area decreases
and vice versa.
In the current tool design two round drive pin (a cylinder) passes through and
rides
horizontally on drive slots on a U-shaped, blade retaining clip. The pin also
passes through
aligned holes in the blades. The pins are longer that the clip and blades.
When this blade-clip-
pin assembly (the blade assembly) is inserted into the open bottom of the tool
body, the pin
ends contact their respective tool body ramps and where they can slide along
the ramps. Pin
rotation along the ramp may possibly occur but not necessarily. The contact
area between a
cylinder and a flat surface is tangential and extremely small and increasing
only with plastic
deformation in the region of contact. Thus if the operating force on the tool
is high as is the
1

CA 02588431 2007-04-30
case for many blades and teeth cutting deep in hard material, the pressure is
very high which
is undesirable since it leads to unwanted rapid wear of the ramp-pin or both.
SUMMARY OF THE INVENTION
The line-of-contact between a round pin and a ramp results in a extremely
small area of
contact therebetween. By way of background, a ball and a flat surface has a
point of contact
while a cylinder (pin) and a flat surface has a line of contact. Two flat
surfaces have a much
greater area in contact.
Given a downward operating force on the tool, the small contact area in the
existing tool
results in enormous pressure at that line of contact which, after repeated
use, is sufficient to
deform the ramps and/or pins. The deforming results in flaring (smearing by
plastic
deformation) of the ramp's sides which can cause the blades to jam. The tool
then requires
repair or replacement. How long such a tool failure takes to occur greatly
influences the value
of the tool and the surface burring process it performs.
The instant invention uses pins that have a flat surface formed along the
pin's length to
replace the line of contact with a much greater area of contact. The result is
greatly reduced
contact pressure and longer tool life which, in turns, lowers the cost of
adhesively bonded
products.
In one embodiment of the instant invention, the rod has a flat portion ('D"
shaped in cross
section) in contact with the ramp. Such a "D" shaped pin can nevertheless
operate in
convenient circular holes in the blades since the point of contact with the
blades is
diametrically opposite the ramp contact flat.
2

CA 02588431 2007-04-30
As a valuable side effect, reducing friction also makes for more of the force
applied to the
tool to be productively used to drive the teeth in the workpiece instead of
generating
unneeded friction and heat if the tool is operated rapidly).
A significant disadvantage of the above described contact flat is that the pin
must be
correctly oriented on insertion of the blade assembly into the tool. That is,
it is possible for
the pin to roll on insertion and cause the flat to thereby move out of contact
with its ramp. It
will then be necessary to rotate the pin and visually ensure the flat contacts
the ramp.
To overcome this disadvantage, a second embodiment of the instant invention
has a second
flat formed on the pin such that the pin diameter across from this second flat
is less that the
original pin diameter. By angling the first and second flats properly, the
first flat will be
parallel to the ramp surface so as to engage the ramp properly when the blade
assembly is
inserted in the tool since the pin is prevented from rotating in its slot
during insertion.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 Shows a side view of a complete tool comprising a tool body with
ramps and a
blade assembly having drive pins with flats or non-round areas for bearing on
the
ramps;
Figure 2 shows an end view of the blade assembly having two rows of opposing
blades
contained in their retaining clip and with the drive pins traversing the holes
and
slots of the clip and the pin ends exposed for engaging the tool body ramps;
Figure 3 shows a side view of the rows of blades without their retainer
showing the "D"
shaped pin in place through the aligned holes of the left row of blades which
will
move to the right when activated by a downwards force on the tool body;
3

CA 02588431 2007-04-30
Figure 4 shows a row of blades without their retainer showing how a
rectangular shaped
pin can be used and how the blades can have rectangular, open-ended holes for
pins such that the blades can be slid onto the pin rather than the pin
inserted
through the blades;
Figure 5 shows a perspective of a round drive pin with the flat area to bear
on the ramp
surface;
Figure 6 shows an end view of a drive pin with two flats, the first on the
right and at 45
degrees for engaging the tool ramp and the second on top at 0 degrees to
locate
against the upper edge of the slot of the retaining clip to ensure that the
first flat
remains properly oriented parallel to the tool body ramp when the blade
assembly is inserted into the tool body;
Figure 7 shows a side view of a retaining clip with longitudinal slots for the
drive pins to
ride in and where the left drive pin has a single flat while the right side
drive pin
has two flats, the top (or bottom) flat riding along the upper (or lower) edge
of
the slot.
DETAILED DESCRIPTION OF THE INVENTION
In Fig 1 tool 100 has a body 13 with left and right angled ramps 2. Body 13
receives
retainer clip 11 with its enclosed rows of opposing-travel blades 10 and IOa
and two drive
pins 4. An internal compression spring (not shown) urges the rows of blades
10, l0a apart
and also urges the pins 4 to the outer ends of the slots 12 such that upon
insertion the pins
initially engage notches 3 located at the begining of ramps 2.
4

CA 02588431 2007-04-30
In Fig 2 these assembled components (blades 10, 10a, pins 4 and clip 11 and
spring) are
defined as blade assembly 101.
Pins 4 (only one pin is shown in Figs 2, 3 and 4) fit through the aligned
holes 20 in blades
10, 10a and through slots 12 in clip 11. Notch 3 in tool body 13 at start of
ramps 2 prevents
the blade assembly 101 from accidently falling out.
By applying a downwards force 50, pins 4 are caused to travel up their
respective ramps,
i.e., the left ramp 2 causes its pin 4 to travel in direction 5. In this way
the left and right rows
of opposing blades thereby travel oppositely towards the tool center.
In the present invention Pins 4, 4a have a first flat 1 to slide on its ramp,
and a second flat
la to locate in slot 12. These flats may be formed (i.e., machined or ground)
along the length
of a round shaft from which pins are to be cut.
In Fig 2 the end view of rows of blades 10, 10a and retainer clip 11 showing
pin 4 to have
ends that extend beyond clip 11 and flat 1 to engage ramps 2.
Fig 3 shows the left row of blades 10 and right row of blades l Oa (partially
dashed) and pin
4 with flat 1 through the left holes, the right blades l0a show that the holes
20 are round. Fig
4 shows another embodiment of blades and pin where the blades have a slotted
opening 20a
to receive a rectangular pin 4a with flat surface 1 a to contact its
respective blades and whose
opposite flat surface will contact its respective ramp 2 on tool 13. This
embodiment will
allow a final gang-grind of the blades so that blade assembly 101 blades teeth
tips are all in
the same plane on the workpiece to be surface burred, and the pins are both
contacting all of
their respective rows of blades. This will ensure each tooth digs in equally
for even,
consistent burring.
Fig 5 shows a perspective of a drive pin 4 showing its formed flat 1 to ride
on its ramp 2 in
tool 13.

CA 02588431 2007-04-30
Fig 6 shows an end view of a preferred embodiment where round pin has two
flats: an
angled first flat 1 for engaging angled tool ramp and a second upper flat lb
to locate against
the upper edge of slot 12 in clip 11. (The lower edge of slot 11 may also be
used with flat lb
towards the bottom). The flat lb prevents pin 4 from rotating in slot 12
because the effective
diameter y (from flat lb across to pin's round surface) is less that the
original round pin's
diameter x. In use, slot 12 is formed in clip 11 to the lesser dimension y as
shown in Fig 7.
The pin therefore cannot fit through the slots 12 unless flat lb is aligned
with slot 12. This
prevents the pin from rotating when the blade assembly 101 is inserted into
tool body 13. If
pin 4 did rotate, the flat 1 may well no longer be parallel with its ramp
thereby canceling the
purpose of the flat which is to reduce pressure and wear on pin 4 and ramp 2
as the tool is
operated. Flat lb ensures that flats 1 on pins 4 do remain parallel to their
respective ramp
surfaces during insertion and replacement of blade assembly 101.
6

Representative Drawing