Tire tread cutting machine

A tire cutting machine can rotatably support a wheel mounted and inflated tire with the tread thereof facing one or the other, or both, of a groove cutter, and a rotatable siping blade assembled with a lead screw. The tire can be driven by a spiked roller for cutting circumferential grooves, or can be driven by the siping cutter and a lead screw when siping. The siping cutter can be shifted axially of the tire by a motor-driven feed screw with adjustable automatic shut-off.

The present improvements are concerned with a machine for cutting the tread 
of tires, as by circumferential grooving and/or siping. 
OBJECTS OF THE INVENTION 
A first object of the present invention is to provide an improved groove 
cutter for cutting a circumferential groove in a tire by relative rotary 
movement between the tire and a groove cutter. 
A second object of the invention is to provide an improved means for 
driving a wheel mounted and inflated tire by means of a feed screw, during 
siping. 
A third object of the invention is to provide an improvement in axial 
shifting of a siping cutter assembly relative to the tire, whereby there 
is obtained electric motor driven traversing of the siping cutter, with 
adjustable automatic stop. 
SUMMARY OF THE INVENTION 
According to a first aspect of these improvements, a machine, for cutting 
circumferential grooves in a tire tread, comprises: 
(i) a support including 
(a) means for carrying a tire rotatable about an axis, and 
(b) a member positioned radially beyond the tire 
(ii) a mounting carried by said support member and adjustable on said 
support member in the axial direction relative to the tire axis 
(iii) a grooving cutter carried by said mounting and adjustable thereon 
radially with respect to the tire axis, and 
(iv) drive means to act between said support and the tire for rotating the 
tire relative to the grooving cutter. 
The support member may include an elongated slotted opening extending 
parallel to the tire axis, said mounting being secured to said support 
member by a fastener engaged through said slotted opening, and in a 
preferred form said grooving cutter is mounted on a stem which is slidable 
in said mounting radially of the tire axis, a portion of said stem being 
screw-threaded and having engaged thereon an internally threaded knob for 
manual adjustment of the grooving cutter radially of the tire axis. 
According to a second aspect, a machine, for cutting sipes in a tire tread, 
comprises: 
(i) a support including means for carrying a tire rotatable about an axis, 
(ii) bearing means on said support for a shaft rotatable about an axis 
substantially tangential to said tire axis, said bearing means being 
adjustable radially with respect to the tire axis, 
(iii) a helical siping cutter and a helical lead screw on said shaft, and 
(iv) driving means to act between said support and said shaft for rotating 
said cutter and feed screw. 
The bearing means may be movable on said support parallel to said tire 
axis, and in a preferred form said support includes slide means extending 
parallel to said tire axis, a lead screw extending parallel to said slide 
means, a slider slidable on said slide means and engaged as a follower 
with said lead screw, said slider carrying said bearing means, an electric 
motor drive on said support coupled to said lead screw for rotating it, a 
switch on said slider in a current feed circuit for said motor drive, and 
stop means adjustable along said slide means and securable thereon in any 
selected position of adjustment to coact with said switch means to break 
the current feed circuit. 
The machine may serve for cutting both circumferential grooves and sipes in 
a tire tread, and may comprise: 
(i) a support including means for carrying a tire rotatable about an axis 
and a member positioned radially beyond the tire, 
(ii) a mounting carried by said support member and adjustable on said 
support member in the axial direction relative to the tire axis, 
(iii) a grooving cutter carried by said mounting and adjustable thereon 
radially with respect to the tire axis, 
(iv) bearing means on said support for a shaft rotatable about an axis 
substantially tangential to said tire axis, said bearing means being 
adjustable radially with respect to the tire axis, 
(v) a helical siping cutter and a helical lead screw on said shaft, and 
(vi) driving means to act between said support and said shaft for rotating 
said cutter and feed screw. 
Further objects of the invention will be partly pointed out in and partly 
obvious from the following detailed description with respect to the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The machine comprises a stationary support 1 having opposed spaced parallel 
side walls 2, 3, and a front wall 4, the rear end being open. Carried by 
the side walls 2, 3, adjacent the open end and at the upper part of the 
support there is provided a transverse shaft 5 which sits on blocks 6 so 
as to be readily removable and replaceable. The shaft 5 carries a 
frusto-conical sleeve 7 which serves to receive and center a mandrel 8 
bolted to the hub 9 of a vehicle wheel 10 having a tire 11. The mandrel is 
adjustable along the shaft 5 so that the wheel 10 may be positioned with 
its axial plane of symmetry X--X' substantially centrally in the support. 
For siping purposes only, the wheel and tire are freely rotatable. On the 
side walls 2, 3, there are provided flanges 12, 13, which are inclined so 
as to act as guide for facilitating insertion of the wheel into the 
support. 
On the support, adjacent the upper end of the front wall 4, there is 
provided on each side wall 2, 3, a pivot 14 carrying a mounting indicated 
generally by reference numeral 15. A spring 16 is connected at one end to 
the side wall 2 and at the other end to the mounting 15 to urge the 
mounting in the direction of the arrow "A" in FIG. 2. The mounting may be 
releasably latched in a non-operative position, seen in FIG. 2, by means 
of a latching lever 17, pivoted on the side wall 2 at 18 and protruding 
through an opening 19 in the mounting 15, the lever 17 having a notch 20 
in which the wall of the mounting 15 can be retained. When the lever 17 is 
raised manually, the wall of the mounting is disengaged from the notch 20 
and the mounting 15 is then moved by the spring 16 in the direction of the 
arrow "A." 
On the mounting 15 there is carried a guide frame assembly denoted 
generally by reference numeral 21. The guide frame assembly comprises a 
pair of side plates 22, 23, which are rigidly connected in spaced parallel 
relationship by an upper slide tube 24 and a lower slide tube 25 which are 
secured to the side plates by bolts 26. The frame assembly as a whole is 
mounted on the mounting 15 by a respective pivot 27 at each side engaged 
through the side plate and a side wall portion of the mounting 15, and can 
be moved with the aid of a handle 15a. 
On the upper and lower slide tubes 24, 25, there is carried an assembly of 
a rotary lead screw 28, a rotary siping cutter 29, and an electrical 
driving motor 30 for the cutter coupled by dog clutch elements 31, 32. 
Referring to FIG. 4, this assembly includes a bracket 33 on which are 
welded sleeves 34, 35 which respectively slide on the upper and lower 
slide tubes 24, and 25. For shifting the assembly along the slide tubes 
there is provided a block 36 which is secured to the bracket 33 and which 
is internally threaded and is engaged on a threaded lead screw 37 
journalled in the side plates 22, 23, of the mounting 15. The lead screw 
37 is rotated manually by means of a reduced-speed electric motor 38 
mounted at one end of the lead screw and coupled thereto by a ratchet 
drive device (not shown). 
The electric motor 38 is under the control of a snap switch 38a which is 
adapted to be put into "off" position when it contacts an adjustable 
end-stop 38b which can be slid along the upper slide tube 24 and then 
locked in a selected position of adjustment. 
On the upper part of the bracket 33 there is welded a sleeve 39 having ball 
races 40, 41, for a cutter shaft 42 carrying the cutter 29 which will be 
described hereinbelow in greater detail with reference to FIG. 5. The 
lower part of the bracket 33 has secured thereon the electric motor 30 
coupled through the dog clutch 31, 32, to a shaft 46 secured in the cutter 
shaft 42. 
Referring now to FIG. 5, the rotatable cutter has the cutter shaft 42, a 
lower clamping block 59 to seat on the shaft 42, the helical cutter blade 
29, an upper clamping block 61, a washer 62, a centering sleeve 63 to seat 
within the two blocks and the blade, and the helical feed screw 28, the 
whole being held in assembly by a screw (not shown) engaged into a 
threaded bore 65 in the shaft 42. The blade is helical and accordingly one 
end 29a is axially offset from the other end 29b, the two blocks 59 and 61 
being appropriately cut away to conform to the shaping of the blade. 
The operation of the machine when used for tire siping is as follows: 
A vehicle wheel with its tire is mounted on the shaft 5 and is adjusted so 
that its center line X--X' is substantially central in the support 1. With 
the mounting 15 in the non-operative position of FIG. 2, the cutter 
assembly is adjusted laterally until the axis of the cutter blade 29 is 
aligned with a first one of the usual several sections of tread which 
occur taken across the tire in order. 
Then the latching lever 17 is released to permit the lead screw 28 and 
cutter 29 to rest stationarily against the tire tread. The handwheel 43 is 
then rotated to rotate threaded shaft 44 in nut 45 (see FIG. 2) to adjust 
the position of the guide frame assembly 21 so as to place the axis of 
rotation of the cutter blade 29 at a true tangential position in relation 
to the circumference of the tire thread section. The motor 30 is then 
switched on to cause the cutter blade to rotate and cut the tread section. 
Due to the helical nature of the lead screw 28 and of the cutter blade, at 
each time of rotation the tire is pulled around by a circumferential 
increment of movement corresponding to the degree of axial offset of the 
two edges of the cutter blade. Accordingly, as cutting proceeds, the tire 
rotates until the entire tread section has been cut. The motor is then 
switched off, and the cutter assembly is adjusted laterally until the 
cutter is aligned with the next tread section, again with adjustment of 
the tangential position. The motor 30 is again energised to rotate the 
cutter and cut the section of tread. These operations are repeated until 
all the sections of tread have been cut. When the last section of tread 
has been cut, the motor is switched off, and the mounting 15 is pulled 
manually back to the non-operative position and is latched therein by the 
lever 17. The wheel and tire are removed, and a fresh wheel and tire can 
be inserted. 
A pipe 68 is mounted on the bracket 33 and has a jet nozzle 69 adjacent the 
cutter blade for supplying a lubricating liquid to the cutter. An inlet 
conduit union 70 for the liquid supply is provided on the support. 
Referring now to FIG. 6, there are shown details of a means for direct 
drive of the tire when the grooving cutter is to be used. 
At an end of the support 1, on each of the side walls 2, 3, there is 
mounted a slide block 85 in which is vertically slidable a rod 86, the two 
rods carrying at their upper end an inverted U-shaped frame 87. In the 
frame 87 there is journalled a transverse drive shaft 88 which has an 
integral roller portion 89 with radial spikes 90 adapted to bite into the 
tread of the tire 11 and give position drive engagement. The shaft 88 is 
connected through a speed reduction gear box 91 to an electrical drive 
motor 92. On each side wall 2, 3, there is mounted a bracket 93 on which 
is coupled a cylinder 94 of a hydraulic or pneumatic ram, the piston rod 
95 of the ram being connected to a lug 96 on the frame 87. The cylinders 
94 of the rams at each side of the machine are coupled by common piping 
(not shown) to a conventional hand-operable pump, with release valving. 
Coiled springs 97 are provided on the rod 86, above and below the block 85 
to reduce shock when the rams reach the ends of their stroke. When the 
machine is being used for siping, the rams are actuated to maintain the 
frame 87 at an increased height such that the spikes 90 are clear of the 
tire tread. When the machine is to be used for cutting of circumferential 
grooves, using the U-shaped cutter described below, the rams are actuated 
to permit lowering of the frame 87 to give positive drive between the 
spiked roller 89 and the tread of the tire. 
Referring now to FIGS. 6 and 7, there is shown a U-shaped or V-shaped 
groove cutter 98 carried on a stem 99 which can be adjusted vertically, 
i.e. radially with respect to the tire, by means of a knurled knob 100 
threaded onto a threaded portion of the stem 99, the latter being slidable 
in a mounting 101 which is secured to the cross-piece of the frame 87 by a 
bolt 102 passed through an elongated slot 103 in the frame 87. By 
releasing the bolt 102, the entire assembly 98, 99, 100, 101, can be 
adjusted axially of the tire, and then the bolt is tightened again. The 
depth of cut of a groove in the tire is controlled by adjustment of the 
knob 100. 
The term "siping" as used herein is to indicate the formation of a shallow 
cut or slash laterally of the tread and a satisfactory siping of a tire is 
accomplished by forming about eight shallow slashes to the running inch, 
for example, in a tread section completely across the tread, but at a 
depth in the tread so that the cuts are almost invisible unless said tread 
is flexed. 
When siped tires are used on a vehicle running on a dry road, the narrow 
rubber ribs of the tread between the siper slashes therein easily buckle 
and flex over sharp bumps and pits with less strain on the tire sidewalls 
so that the tire carcass life is extended. When the siped tires are used 
on ice or rain-slick roads, the tread bends at each tiny slash formed by 
the siping, forming a saw-toothed surface or squeegee-edged rubber ribs, 
which gives enhanced traction. 
Also a siped tire resists skidding and jack-knifing on fast stops of the 
vehicle as each rubber rib of the cross-cut tread bends back and its 
squeegee-shaped edge grabs the road.