CA2588431C - Improvement to a surface burring tool - Google Patents

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.

Description

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 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 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 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 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.

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.

Claims (2)

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.