Apparatus for spanning a center-opening saw blade

A center-opening saw blade having an inner sawing edge is spanned or tensioned to provide an accurate, high quality cut by apparatus including inner and outer clamping collars between which an outer peripheral edge region of the saw blade is clamped, a spanner ring having an inner edge and an outer centering heel, the clamping collars being tightly affixed to the spanner ring with the clamping rings positioned in the centering heel with the inner edge of the spanner ring engaging an inner region of the saw blade to impart an initial stress thereto. A form ring is axially slidably mounted within the clamping collars and is slidable to engage an intermediate portion of the saw blade between the outer peripheral edge region clamped between the clamping collars and the inner region engaged by the inner edge of the spanner ring to impart a fine adjustment stress to the saw blade.

BACKGROUND OF THE INVENTION 
This invention relates generally to apparatus for use in material cutting 
operations and, more particularly, to apparatus for use with 
center-opening saw blades having an inner sawing edge for improving the 
accuracy and quality of the saw cut. 
Center-opening saw blades are used in the cutting of hard, brittle 
materials of the type used in the manufacture of electrical components, 
such, for example, as silicon, germanium, quartz, sapphire, garnet and the 
like. Such center-opening saw blades are formed of thin, high-strength 
sheet metal and have an inner circular edge provided with a fine coating 
of natural diamond embedded in a galvanized bonding material. The outer 
diameter of the saw blade is obtained using an appropriate ring. In 
manufacture, the saw blade is stretched on a drum kiln to provide a high 
modulus for the saw blade which resists lateral forces. 
The width or span of the saw blade is of great importance to the accuracy 
and quality of the cut obtained by the saw blade. The out-of-roundness 
error of the center opening about which the cutting edge is provided must 
be maintained at a minimum. It is also important to keep the sizes of the 
clamping collars and spanning edge rings which are used in the spanning or 
tensioning of the saw blade to a minimum. This is difficult to achieve, 
however, in saw blades having large diameters, such as about 21 inches or 
larger. 
Apparatus for spanning or applying tension to centeropening saw blades 
having inner cutting edges are known. In this connection, reference is 
made to U.S. Pat. No. 3,955,551 and to German patent application No. DE 28 
41 653. In particular, apparatus is disclosed in No. DE 28 41 653 wherein 
the spanning or tensioning of the blade is not produced through the use of 
a spanning edge. Rather, the saw blade is stretched by the provision, 
between a ring groove within the clamping collar and a correspondingly 
profiled spanning ring, of means whose position is axially adjustable 
through a large number of set screws for engaging a region of the saw 
blade close to its outer edge at the ring groove. When it is desired to 
apply a greater tension to the saw blade, such as where larger diameter 
saw blades are used, it is necessary that the blades project deeply into 
the ring groove to provide sufficient strength. 
A highly accurate and true circular track for the inner cutter edge of the 
saw blade is achieved by spanning the saw blade. Deviations in the 
roundness of the center opening in the saw blade are obtained in the case 
where the radius of the center-opening is too small by stretching the saw 
blade outwardly and through a partial axial bending of the saw blade by 
means of the spanning ring provided at the groove of the restraining 
collar. Depending upon the degree of true roundness of the saw blade 
opening and the heterogeneity of the saw blade material, the spanning ring 
will deform axially to a greater or lesser extent and will also obtain a 
slanted or oblique position with respect to the axis of rotation of the 
saw blade, thereby affecting the alignment of the machine to the detriment 
of the quality of the cut obtained. Such conventional techniques are also 
disadvantageous in that it is not possible to disassemble the saw blade to 
rotate the same outside of the machine in order to reduce set-up time. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide new and 
improved apparatus for spanning or tensioning center-opening saw blades 
and, in particular, saw blades having large diameters of about 21 inches 
or more. 
Another object of the present invention is to provide new and improved 
apparatus for tensioning or spanning center-opening saw blades with 
minimum inefficiency with planar and out-of-round errors being minimized 
while reducing preparation time on the center-opening saw machine. 
Briefly, in accordance with the present invention, these and other objects 
are attained by providing apparatus for tensioning or spanning a 
center-opening saw blade in a three-step procedure including saw blade 
changing, spanning, and centering. 
In accordance with the invention, the saw blade is initially tightly 
clamped between two clamping collars outside of the machine. Secondly, the 
assembled unit comprising the saw blade and clamping collars is mounted on 
a receiving flange of the saw axle or spindle. Thus, the pair of clamping 
collars and the saw blade fixed between them is tightly affixed, such as 
by screwing the same in an axial direction on the centering 
flange,whereupon the center-opening saw blade is pulled and stretched by 
tightening it against the receiving flange of the saw spindle. Thirdly, a 
fine adjustment of the previously tightened center-opening saw blade is 
obtained by a form ring which is axially slidably guided along the inner 
diameter of one of the clamping collars, supported outwardly and axially 
over a threaded rim. 
An important advantage of the spanning aparatus in accordance with the 
invention is that all of the mounting operations take place outside the 
machine and that all of the heavy components of the apparatus which are 
spaced a large radial distance from the center of rotation extend in a 
direction perpendicular to the axis of rotation and therefore do not 
detract from the alignment of the machine. Any deformation of the saw 
blade due to the spanning apparatus is essentially limited to a specified 
edge curvature. 
In accordance with one feature of the invention, one of the clamping 
collars is designed to promote an efficient flow of debris and cooling 
liquid onto the saw head.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings wherein like reference characters designate 
identical or corresponding parts throughout the several views, the 
apparatus of the invention will be described in conjunction with a 
description of its use. 
In a first step which is accomplished outside of the saw machine, a 
center-opening saw blade 2 is clamped at its outer peripheral edge region 
between outer and inner clamping collars 5 and 6 by means of screws 8. 
Thus, the outer and inner clamping collars 5 and 6 have clamping surfaces 
between which the saw blade is clamped to form a saw blade-clamping collar 
assembly which is adapted to be mounted over a spindle flange of the saw 
machine. 
The outer clamping collar 5 is provided with a substantially conical inner 
portion 12 which terminates at a bearing member 7. A form ring 3 is 
axially slidably mounted within the clamping collar 5 so as to be axially 
guided by the inner surface of collar 5. A plurality of set screws 4 are 
provided around the outer clamping collar 5 and through suitable 
adjustment of set screws 4, the form ring 3 can be axially moved to engage 
a portion of the saw blade. As seen in FIG. 1, the set screws 4 are 
adjusted to be in their outermost positions so that form ring 3 does not 
engage the saw blade 2. 
In a second operational step, the saw blade-clamping collar assembly of 
FIG. 1 is tightly affixed to a spanner ring 1 adapted to be mounted onto 
the spindle flange of the saw machine. The spanner ring 1 has an inner 
circular edge 10 and a centering heel 11 extending around a peripheral 
region thereof. The centering heel 11 comprises a shoulder that opens both 
axially and radially outwardly and when the saw-blade clamping collar 
assembly is affixed to spanner ring 1, the inner clamping collar 6 is 
tightly affixed on the centering heel shoulders. The saw-blade clamping 
collar assembly is affixed to the spanner ring 1 by means of screws 9. 
When the saw blade-clamping collar assembly is affixed to the spanner ring 
1, an inner region of the saw blade engages the inner edge 10 of the 
spanner ring 1 so that the saw blade 2 is diagonally drawn or stretched 
over the edge 10 to impart an initial stress to the saw blade. 
In a third operational step, a fine adjustment stress is imparted to the 
saw blade 2 through the adjustment of set screws 4 to engage the outer 
surface of the form ring 3 to axially slide the latter into engagement 
with an intermediate portion of the saw blade between the outer peripheral 
edge region clamped between the clamping collars 5 and 6 and the inner 
region which engages the inner edge 10 of spanner ring 1. In this manner, 
errors or deviations in roundness of the center opening of the saw blade, 
undulations and rolling tolerances in the saw blade can be corrected. 
The conically shaped inner portion 12 of the outer clamping collar 5 
preferably engages the saw blade 2 at bearing member 7 as seen in FIG. 2 
to divert cooling water and cutting debrisaround the saw in an 
advantageous manner. 
Obviously, numerous modications and variations of the present invention are 
possible in the light of the above teachings. It is therefore to be 
understood that within the scope of the claims appended hereto, the 
invention may be practiced otherewise than as specifically disclosed 
herein.