Metal tools and implements – making – Blank or process – Saws
Reexamination Certificate
2000-03-09
2001-09-18
Watts, Douglas D. (Department: 3724)
Metal tools and implements, making
Blank or process
Saws
C083S039000, C083S076400, C083S209000, C083S371000
Reexamination Certificate
active
06289767
ABSTRACT:
This invention relates to a method of cutting a band saw blade to length and to apparatus for cutting a band saw blade to length.
FIG. 3
shows an example of a saw blade which has a variable tooth pitch. The tooth pitch is the distance between the tips of adjacent teeth. In a variable tooth pitch saw blade the vertical distance between the tip of a tooth and the base of the intervening dip (known as the gullet) also varies. When manufacturing a continuous band saw blade having a variable tooth pitch, it is desirable to have matching teeth on the ends of the blade which are welded together to form the band saw blade.
A previous system for cutting a blade to length involves counting the number of teeth using an optical sensor, the number of teeth being used to approximate the length of saw which has passed by the optical sensor. Problems arise with this type of arrangement because with a variable tooth pitch blade the number of teeth detected does not correspond exactly to the total blade length because there is a varying distance between teeth. Consequently, significant disadvantages arise with this system because of its inability to detect a particular length of blade.
Another known system which was developed to address the disadvantages of the system mentioned above, uses an optical sensor to match the pitch of teeth for the ends which are to be welded together. This results in the amount of blade wasted being equal to at least the toothing interval, which is the length of blade over which the pattern of variable tooth pitch repeats. The amount wasted is frequently more than the toothing interval because the photocell used to detect the reference edge is located away from the point of cut. Consequently, because the pitch varies, the system has no means of knowing which part of the blade is in front of the cut point and the electronics must scan the pitches and pick the first pitch match, which could result in a wastage of blade equal to just less than twice the toothing interval.
It is an object of the present invention to address the above mentioned disadvantages.
According to one aspect of the present invention a method of cutting toothed blades from a length of blade material comprises:
a) locating the position of a first end of a first blade section and cutting the blade material at said position;
b) locating the position of a second end of the first blade section relative to a tooth of the blade material using sensing means and storing said position in a memory means;
c) advancing the blade material relative to the sensing means;
d) locating the position of a first end of a second blade section relative to a tooth of the blade material using said sensing means and storing said position in the memory means;
e) advancing said blade material to a cutting means and cutting the second end of the first blade section at the position stored in the memory means in step b) and cutting the first end of the second blade section at the position stored in the memory means in step d); and
f) advancing the blade material to locate, store and then cut first and second ends of subsequent blade sections by repeating steps b) to e).
The method may include steps a) to f) being performed consecutively.
The tooth in step (b) may be adjacent to the tooth in step (d). Alternatively, the tooth in step (b) and the tooth in step (d) may be separated by at least substantially the amount of blade material lost during the cutting operation. The latter case may occur when the tooth pitch of the blade material is substantially equal to or less than the amount of blade material lost during the cutting operation.
Step a) may be undertaken manually or may be undertaken in the same manner as steps b) and d).
The second end in step b) may be located by activating the sensing means after a predetermined length of blade material has passed said sensing means. The blade material may be metered by metering means, which may be metered rollers. The predetermined length may be substantially the desired length of the first blade section.
The position of said second end in either of steps b) and f) may be a predetermined distance from said tooth face, which distance may be determined taking into account the amount of material lost during cutting.
Preferably, the predetermined distance is substantially equal to the sum of the distance from the tooth face to the desired end position and an amount of blade material lost during cutting.
The position of said first end in either of steps d) and f) may be a predetermined distance from said tooth face, which distance may be determined taking into account the amount of material lost during cutting.
Preferably, the predetermined distance is substantially equal to the difference between the distance from the tooth face to the desired end position and an amount of blade material lost during cutting.
Preferably, the first and second end positions coincide with a gullet section of the blade material.
The method may be used with blade material having variable pitch teeth. Preferably, the position of said first and second ends coincide with substantially the same position in the pitch of the blade material.
When used with blade material having variable pitch teeth, an average value of the distance from the tooth face to a desired position in a gullet section of the tooth may be used as a standard value for determining the position of the first and second ends of the blade sections. The method may include subsequent joining of the two ends of the blade sections, preferably by welding.
After joining the joint may be ground to reduce any irregularities therein. The grinding may include grinding any mismatch between adjacent teeth in the join.
According to another aspect of the present invention apparatus for cutting toothed blades from a length of blade material comprises sensing means, memory means, blade advancing means and cutting means, in which, after location of a first end of a first blade section;
the sensing means is actuable to locate the position of a second end of the first blade section relative to a tooth of the blade material and store said position in the memory means;
the blade advancing means is actuable to advance said blade;
the sensing means is actuable to locate the position of a first end of a second blade section relative to a tooth of the blade material and store said position in the memory means; and
the blade advancing means is actuable to advance the blade material to the cutting means, which are actuable to cut the blade material at both the position of the second end of the first blade section stored in the memory means and the position of the first end of the second blade section stored in the memory means.
The tooth for the second end of the first blade section may be adjacent to the tooth for the first end of the second blade section. Alternatively those teeth may be separated by at least substantially the amount of blade material lost during operation of the cutting means.
The sensing means may include an edge detector, which may be an optical sensor.
The memory means may be electronic. The memory means may be computing means.
The blade advancing means may be metered, to determine the length of blade material passed therethrough. The blade advancing means may be rollers, which may be powered. The rollers may grip the blade material.
Any of the features disclosed herein may be combined with any aspect of the invention, in any combination.
REFERENCES:
patent: 361536 (1887-04-01), Miller
patent: 1503310 (1924-07-01), Ericson
patent: 1718746 (1929-06-01), Lougheed
patent: 4023448 (1977-05-01), Bertini
patent: 5101551 (1992-04-01), Rademacher et al.
Harrison Saw & Tool Limited
Michael & Best & Friedrich LLP
Watts Douglas D.
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