Quick release mechanism for the tool of a concrete/asphalt abrader

A quick release mechanism for disengaging the cutting blade of a masonry saw is disclosed. Rotation of a threaded shaft to achieve axial movement through a closed partially threaded split collar lowers the cutting tool onto the work surface via a counterpivot mechanism which simultaneously compresses a gas spring. Only one half of the collar has threads complementary to those of the threaded shaft and pivots away from an opposing fixed unthreaded collar portion. Upon actuation of a release device, the threaded portion of the split collar pivots to an open position to disengage the threaded shaft whereby reverse axial movement of the threaded shaft and resultant upward disengagement of the cutting tool occur as the gas spring decompresses.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
Generally this invention relates to cutting tools and more particularly to 
a quick release mechanism for disengaging the cutting tool of a 
concrete/asphalt abrader used in construction and maintenance of road 
surfaces, parking lots, industrial plant floors and like surfaces made 
from stone aggregate. 
2. Description of the Prior Art 
The prior art for disengaging a cutting tool of a concrete/asphalt abrader 
from the workpiece has consisted simply of reverse operation of the 
engagement means. The prior art has not provided a quick release tool 
disengagement assembly, which is simple, safe and easy-to-use. 
Furthermore, the prior art for abraders useable for the above purposes and 
readily moveable from one location to another has relied on the mass of 
the abrader assembly to hold the tool on or in the workpiece. It has not 
provided means to otherwise maintain the tool under tension during 
operation and prevent workpiece irregularities from causing the cutting 
tool to unintentionally disengage from the workpiece. 
SUMMARY OF THE INVENTION 
The main object of the present invention is the provision of a relatively 
easy to operate release mechanism for quickly disengaging the cutting tool 
of a concrete/asphalt abrader, such as a cutter, grinder or planer. 
Another object is to provide a quick release mechanism which decreases the 
time and physical effort required for disengaging a tool from a workpiece 
such that the abrader operator can more efficiently accomplish the 
complete work task to be performed. 
Another object is to provide a quick release mechanism for disengaging the 
tool from a workpiece when emergency, safety or quality control 
circumstances so dictate. 
Yet another object is to provide a quick release mechanism for disengaging 
and retracting a tool from a workpiece upon operator actuation but which 
exerts, during engagement of the tool, a tension force to retain the tool 
in engagement upon the workpiece. 
Briefly, the invention is directed to a quick release mechanism for a 
cutting tool including gas spring means which is compressed upon the 
engagement of the tool by the manual rotation of a threaded shaft, the 
resilient means being permitted to decompress and disengage the cutting 
tool upon operation of a lever to disengage a screw threaded holding 
surface from the threaded shaft. 
Other objects and further scope of applicability of the present invention 
will become apparent from the detailed description given hereinafter. It 
should be understood, however, that the detailed description and specific 
examples, while indicating preferred embodiments of the invention, are 
given by way of illustration only, since various changes and modifications 
within the spirit and scope of the invention will become apparent to those 
skilled in the art from this detailed description.

DETAILED DESCRIPTION OF THE INVENTION 
Generally, in a conventional concrete/asphalt abrader, the cutting tool is 
supported by wheels affixed to the rearward end of the main frame and by 
wheels affixed to the forward end of a fork assembly, with the main frame 
and the fork assembly being pivotally connected at a mid region between 
the supporting wheels. In the case of a concrete masonry saw, a circular 
cutting blade or disk is attached to the forward end of the main frame. To 
use the cutting blade, the main frame and the fork assembly are pivoted 
relative to each other until the blade lowers and engages the workpiece 
such as a road surface or a floor of a building to the depth of cut 
desired. 
To pivot the main frame and the fork assembly and thereby engage the 
cutting blade, the saw operator moves the cut control linkage downward 
which in turn relatively pivots the wheeled end of the fork assembly 
upward and the cutting blade end of the main frame downward. The downward 
movement of the cutting blade can thus be continued until the desired 
depth of blade cut is attained whereupon the downward movement of the cut 
control linkage is terminated. Disengagement of the blade occurs by moving 
the cut control linkage upward. 
FIG. 1 shows a concrete/asphalt abrader, specifically a rotary circular saw 
assembly, supported for use by wheels 2 and 4 which are mounted on the 
rear portion of a main frame 6 and the front portion of a fork assembly 8, 
respectively. The main frame 6 and fork assembly 8 are pivotally connected 
at pivot 7 between wheels 2 and 4. Mounted on the control platform 10 
affixed to the handle bar assembly 12 is a bushing 14. A crank assembly 16 
is mounted on the bushing 14. The assembly 16 consists of a manually 
rotable handwheel 18 from which a shaft 20 is supported for rotation 
within bushing 14, shaft 20 extending through bushing 14 to engage the cut 
control linkage 22 at the collar assembly 24. The handwheel 18 is rotated 
by lifting ball knob handle 26 to extract it from a safety hole 28 in 
platform 10 and rotating it about the longitudinal axis of shaft 20. 
The upper portion of the shaft 20 has a threaded portion 30, the threads of 
which engage complementary threads in the collar assembly 24, which is 
described in greater detail hereinbelow. The cut control linkage 22 upon 
which the collar assembly 24 is mounted, extends downward to be pivotally 
attached at its lower end to the rear portion of the fork assembly 8. At 
the front end of the fork assembly 8, a cylindrical gas spring 32 is 
pivotally attached via the lower end of the cylinder piston rod 34. The 
gas spring 32 extends upward from the front end of the fork assembly 8 and 
is connected via its outer cylinder wall to a support structure 36 mounted 
on the front portion of the main frame 6, as shown in greater detail in 
FIG. 4. Additionally, mounted on the front portion of the main frame 6 is 
a cutting tool comprising a circular cutting blade 38. 
FIG. 2 shows in greater detail the interrelationship of the collar assembly 
24 with the threaded portion 30 of the shaft 20. To axially move the shaft 
20, the ball knob 18 is lifted upward to remove the ball knob handle 26 
from a safety hole 28 in the platform 10 and the handwheel 18 is then 
rotated. As the shaft 20 rotates, the threaded portion 30 engages the 
complementary threads on one half of the collar assembly 24 to axially 
move the cut control linkage 22 as shown in FIGS. 3A and 3B. 
Respectively, FIGS. 3A and 3B show the collar assembly 24 in a closed 
position wherein the threaded portion 30 of the shaft 20 are engaged with 
the complementary threads of the collar assembly24 and in an open position 
wherein the threaded portion 30 of the shaft 20 are disengaged from the 
complementary threads of the collar assembly 24. 
The collar assembly 24 has a perimeter support wall 40. Within the support 
wall 40 is a multi-jawed collar 42 consisting of a fixed jaw 44 and a 
pivotable jaw 46, the fixed jaw 44 being secured to the support wall 40 by 
fixed tab 48 which is rigidly affixed at opposite ends to the fixed jaw 44 
and the support wall 40, respectively. The pivotable jaw 46 is attached by 
a pivot pin 50 to an extension of the support wall 40. Generally, on the 
opposite side of the pivotable jaw 46 from the pivot pin 50, a pivot tab 
52 is rigidly affixed thereto. The fixed jaw 44 has a smooth inner arcuate 
surface 54 which communicates with the threaded portion 30 of the shaft 
20, while the pivotable jaw 46 has a threaded inner arcuate surface 56 
which has threads 58 complementary to those of the threaded portion 30 of 
the shaft 20. In addition to the multi-jawed collar 42, the collar 
assembly 24 has a release plunger 60, consisting of a plunger shaft 62, a 
knob 64, a spring 66, a fixed collar bushing 68, a nut bushing 70 rigidly 
affixed to the plunger shaft 62, and an end cap 72. The plunger shaft 62 
extends from the knob 64 through the support wall 40 and through the fixed 
tab 48 and the pivot tab 52, with the spring 66 being biased in an 
uncompressed state between the support wall 40 and the knob 64 to push the 
knob 64 away from the support wall 40 thereby maintaining the multi-jawed 
collar 42 in a closed position. 
To open the jaws of the multi-jawed collar 42, the knob 64 is depressed as 
shown in FIG. 3B causing the plunger shaft 62 to move through the fixed 
tab 48 until the nut bushing 70 engages and moves the pivot tab 52 and 
pivots the pivotable jaw 46 about the pivot pin 50 to disengage the 
threads 58 of the threaded inner arcuate surface 56 from the threaded 
portion 30 of the shaft 20. When the complementary threads 58 are 
disengaged from the threaded portion 30, the cut control linkage 22 is 
free to move upward and will do so under influence of the compressed gas 
spring 32. 
In operation, the operator of the saw shown in FIG. 1 rotates the handwheel 
18 which rotates the shaft 20, the threaded portion 30 of which, in 
engaging the complementary threads of the pivotable jaw 46 of the 
multi-jawed collar 42 moves the cut control linkage 22 axially downward. 
The downward movement moves the rear portion of the fork assembly 8 
downward, such movement being transmitted via the pivot connection 7 with 
the main frame 6 to move the front portion thereof downward. Consonant 
with this movement the cutting blade 38 is lowered onto and into the 
workpiece e.g. the surface of a concrete slab on roadway and the piston 
rod 34 moves upward to compress the gas spring 32, the cutting blade 38 
being held in engagement with the work surface by the tension force 
arising from the compression of the gas spring 32. To quickly disengage 
the cutting blade 38 from the workpiece, the release plunger 60 is 
actuated to pivot the pivotable jaw 46 of the multi-jawed collar 42 until 
threads 58 and threaded portion 30 are disengaged thereby permitting the 
cut control linkage 22 to move upward as the decompressive force of the 
gas cylinder spring 32 is transmitted through the linkage. 
The invention being thus described, it will be obvious that the same may be 
varied in many ways. Such variations are not to be regarded as a departure 
from the spirit and scope of the invention, and all such modifications are 
intended to be included within the scope of the following claims. For 
instance, it is to be appreciated that the quick release assembly, while 
illustrated with respect to a masonry saw, is adaptable to any 
concrete/asphalt surfaces, planer, scarifier, or similar apparatus.