Note: Descriptions are shown in the official language in which they were submitted.
~ 3~`3t'~2~
SOFT CONCRETE SAW
Back~round of the Invention
This invention relates ~o concrete, ~hich is a
combination of a hydraulic cementing substance, a~gregate,
water, ~nd, often other substances to fmpart specific
properties to the c~ncrete.
When concrete ls poured it is ~ypically in a wa~ery or
flowing fitate which allows ~he concrete to be spread
evenly over floor~. After a perio~ of time, varying with
the mixture of the concrete, the temperature, and the
moisture ~vailability, the concrete attains a workable
plasticity which permi~s the ~urface of the concrete to be
formed and to ret~in ~ finish. Typical finishing ~eans
include troweling, rubbing, or brushing. Applying the
desired ~urface texture ~s called "finishing" the
concrete, and ~ay ~nvolve repea~ed 6teps to 6equentially
refine the surface fini~h.
After the concreee i~ finished, it i~ allowed to ~tand
; for a period of time during which the concreee cures to
obtain i~s well-known, rock-like hardness. The curing or
~e~ing time depends on the mois~ure available, the
tem~era~ure, and ~he ~pecific addi~ves added to ~he
concrete to a~fect the curing time. AB ~he concrete cures
; ~t undergoes the~al stre~es cau~in~ the concrete to
expand and contract ln variou& manners depending on the
: shape and thickness of the concrete, and the type of
concrete. The~e ther~al stres~es can cause cracking. The
fully cure~ and hardened concrete ~lso exyands and
contracts due to te~perature changes with ~he result that
cracks form in the concrete.
It 16 common practice to provide 810t6 or grooves at
prede~ermined intervals in the concrete. If the grooves
extend all ehe way through éhe concrete, they can act as
an expansion or contraction joint to help prevent cracking
o the concret~. If the grooves are only on the ~urface
o~ the concrete, then the grooves cause the cracks to ~or~
1 3('o~2~
810ng the grooves 60 that they occur at regular intervals
and are not visible. The grooves, but not the cracks, are
visible.
One advantage to placing the grooves ln ~he ~oft,
concrete i8 that a weakened plane is provided by the
groove and that weakened plane is now installed before the
concrete start~ to cure and ~hrink. ~he concrete slab
will typically seek out the weakened plane to crack in, if
the plane i8 prem~turely there.
Pre~ently, these grooves are provided by forming or
grooving a 810t ~n the concrete with a grooving trowel,
while the concrete i~ still wet, iust after pouring. This
grooving i6 done while the concrete is very wet, and
before the concrete is sufficiently hard ~o 6upport a
persons weight. Thus this grooving ~ypically requires a
~upport ~tructure which would enable the person doing the
groovin~ to reach the lnteriors of concrete slabs withou~
placing ~he per~on'~ ~elght on the concreteO When the
concrete ~labs become ~ufficiently large, this method of
2~ providlng grooves proves imprace1cal and expensive~
Thi~ ~ype of grooving mu~t be done when ehe eoncrete
i~ ~ufficiently wet, otherwise the grooving ~rowel cannot
shove entrained rock~ OUt 0~ the way without it di~rupting
~he surface finish on the concrete. Essentially, ehe
concrete must be grooved ~USt after it is has ju~t been
poured, ~t which t~me the concrete ~s B0 wet that the
concrete sometLmes tends to 6ag back together and close
the groove, thu~ sequiring repeated grooving to maintain a
desired groove depth or shape.
For very l~rge ~labs of concrete, manually grooving
the freshly poured concrete is impractlcal or very
inconvenient ~nd expensive. For such large slab~, the
concrete is tgpically allowed to h~rden or 6etO Grooves
: are then cut in the suriace of the concrete by use of a
high-powered, rotating, abrasive saw blad~, often
lubricated with water. The blade iB typically made of
1 3C362~
diamond abrasive material and is provided with ~ liquid
coolant and lubricant to facilitate cutting ehe haraened
concrete .
Since these concre~e cutting machines tend to be
5 heavy, the concrete must be fairly hard in order to
support the weigh~ of the machine and operator. Further,
lf the concrete i~ not su~ficiently hard when cut, these
machines produce sn unaccepcably rough cut with a chipped
or cracked ~urface along the groove. ~lowever, ~he harder
the concrete, the more difficult it i6 to cut.
It is possible to use a hand held rotary saw as is
often used in cutting lumber, but using ~ blade designed
to cut concrete. Such ~aw~ are lighter ~eight, but still
require hard concrete to support the operator and to
provid~ cut grooves with acceptable smooth edges.
On an extremely hot and dry day, the concrete may be
sufficiently hard to 6upport a person's weight and not
leave a permanent indentation, about twelve hours after
~he concrete ha6 been poured. Typically, the concrete is
2~ not ~alked upon or cut un~il a~ lea~ ~he next day, or
about eighteen hours af~er ~he concrete has been finished.
If the concrete i5 CUt by a conveneional water
lubricated with wa~er diamond-~bra~ive ~aw, the earliest
it can be cut i8 the next day after finiæhing (about 1
a5 hour6), and even then a unacceptable cut is typically
produced a~ the edges of the concrete by the groove tend
to chip, ~pall and crack.
One major problem with cutting after the concrete
cures and hardens is that between the time of the initial
: 30 finish and the time it becomes praceical for a
conventional concrete 6aw to be used, the concrete slab
will have started it'~ normal characteristic ta ~hrink as
it dries, thus cau~ing contraction stress ~nd invariably
cracklng before the 6awing of contraction ~oints can be
periormed. This characteri~t$c shrinking usually takes
place somewhere between the time the initial finish is
- 1 ~C i628
co~pleted and before it becomes practical to pUt
conventional 6aw-cu~eing machine on the ~lab~ Th~ result
is cracking of the 61ab before ~aw cuttlng can be
initia~ed.
Further, cutting the hard concrete i~ a slow process,
which is slowed ~till further to ~eriodica].ly replace the
cutting blades as ehey abrade sway. Finally, these types
o~ machines tend to be not only bulky, but al80 expensive
and time consuming to operate and maintain. The noise of
the ~aw abrading the hardened concre~e i8 also very loud
and unpleasant.
There thus exists a need to provide an essier and
fa~ter apparatus and method for ~utting ~rooves in
concrete before the concrete cracks.
t5 5~ o~ L:_LC:L~9~
An apparatus is provided for cutting a groove in 60~t
concrete. The appara~us can cut the concrete any time
after the concrete is finished and bef~re the concrete
attains its rock like hardness, ~nd preferably before the
:20 concrete ha~ shrunk ~ufficien~ly ~o cause cracklng along
;planes other ~han tho~e planes defined by the cut grooves.
The æoft concr~te saw has a base plate on which are
mounted ~wo wheels and a ~kid plate, each of which
contact6 the concreee to provide a three point ~upport on
the concrete~ A mo~or i8 pivotally mounted on the base
plate. ~he motor drives a circular ~aw blade with an up
cut rotat~on. The saw blade extends throu~h a slot in the
platform, and ~ through a corresponding ~lot in the ~kid
plate, in order to project into and cut the concrete below
the ~kid plate.
The dimension~ of the slot in the skid plate are
~elected to support the concrete immediately adjacent the
~aw blade ~o as to prevent cracking of the concre~e as it
i8 cut. The dimension6 of the slot in the plat~orm are
al~o selected to lnhibit excessive build-up of concrete on
1 ~(`"62~
the platfor~ as the ~aw blade cu~ a groove in the
concrete.
The mot~r is moveably mounted ~n the plat~orm ~o that
the motor and saw blade can ri~e u~ when the saw blade
S hits a rock entrained in the concrete. A spring connected
between a ~upport on the base plate and the motor,
resiliently urges the . BW blade into the concrete and
allows adjust~ent of the force exerted by the ~aw blade on
the concrete wh$Ch i6 being cut. Thi8 ~pring controls the
ea~e with which the saw blade moves a6 the 6aw blade hits
a rock or other ob6trllct$0n in the concrete and helps
prevent concu~ion cracks a~ the blade hit6 ~uch rock~ or
obstructions in the concrete.
A handle is pivotally attached to the base plate ~o
æhove the base plate and ~aw across a large slab of
concrete wi~hout hindering the pivoting mo~ion of the ~aw
blade. Depending upon ~he size of the concrete slabs
which must be cu~, a varying number of handle e~tensions
can be added to ~ove the 6aw acros~ the concrete.
If the ~aw is to be retracted after being extended
~crosC 8 81ab, then a 801enold can ~ise the ~aw blade out
of the concre~eO A second 601enoid locks the handl~ into
a rlgid orlentation ~i h respec~ to the base place.
Shoving downward on the handle then rotates the base pla~e
; 25 onto two wheel~ while 8i~ultaneously rai~ing the ekid
plate off of the concrete 80 as to allow the saw to be
pulled back ~cross the concrete o~ two wheels with minimu~
impact on the fin~h of the concrete from the ~liding of
the skid plate.
3~ To help start the 6aw on the ed~es of ~he concrete, an
extra wheel can be added to the base plate, oppo~ite the
saw blade, in order to provide a stsble support ~ the ~aw
blade begins cutting lnto the edge of the concrete. This
extra wheel c~n be G~fset ~lightly above the other wheels
on the ba6e plate 80 that once the normal wheel6 are on
the concrete, the extra wheel is rai~ed above the concrete
1 3C3~2~
--6--
and no longer contacts the concrete~ Thus, the skid plate
and two of ~he ~heels provide a three point ~upport and
minimize rocking of ehe base plate.
There is thus provided a light weight 6aw for cutting
60ft concrete without the need for extensive alignment or
support apparatus. Further, ~ince the 6aw i6 cutting 60ft
concrete, the blade need not be replaced as often, nor
need the 6aw be as oomplex and expensive as previ~us saws.
Description of the Drawi~
The present invention will be better understood from
the description of the preferred embodiment which is given
below, taken in con~unction with ~he drawings (like
referenee charac~er~ or n~mber~ refer to like parts
throughout the description), ~nd in which:
FIG. 1 i~ a perspeceive view of the invention being
operated in the middle of a slab of concrete;
FIG. 2 iB an elevated perspective view of the front of
ehe saw of thi~ invention ~howing the motor and blade in a
lowered po~ition~
FlG. 3 is a lower perspective view of the ~aw of this
invention, ~howi~g the motor and blade in a raised
po itlon;
FIG~ 4 is an elevated perspeetive view of the back ot
the saw of thi~ ~nvention;
FIG. 5 ls a top elevational view o~ the ~aw of this
invention;
FIG. 6 i8 a side elevation of the ~aw of this
invention in ~peration;
FIG. 7 is an elevational view of the saw blade and
~lot in the skid plaee;
~IG. 8 i6 a perspective view o~ ~n alternate
embodiment of this invention;
FIG. g i~ a 6ectional view taken along A-A of FIG. 8,
showing an alternate embodiment of thi6 inven~ion.
FIG. 10 is a æectional view taken along A-A of ~lG. ~,
~howing an alternate embodiment of thi6 invention; and
I 3(~.,628
FlG. 11, is a ~ectional view Laken al~n~ A-A ~f ~IG. 8
~h~wing an alternate embodiment of this inven~ion7
FIG. 12, shows how the quali~y of the cut groove is
affected by ~he spacing be~ween the cu~ing blade and ~h~
side~ of the aperture in the base pla~e.
Description oi the Preferred Embodiment
As is shown in FIG. 2, by way of illustration, and not
by limit~tion, a soft concrete 6aw 10 comprises a base
plste 12 h~ving a generally rectangular ~hape. The base
plate 12 hes a lower sursce generally facing a slab of
concrete 13, wieh an upper ~urface of the base plate
f~cing away from ehe concrete 13.
Along one of the longer 6ide~ of the rectangular plate
12 there are a~ached ~wo front wheelR 14 and 16, and a
rear wheel 18. On the other long ~ide of the rectangular
base plate 12, generally oppo~ite the rear wheel 18, it is
located rear ~heel 20. The rear wheel 20 ~ets in a recess
22 ~FIG. 4) in the base plate 12 such thal the edge of the
re~r wheel 20 does not project beyond the edge of the
~enerally rectangular base pl~e 12, ~5 described in more
de~ail hereinafter~
A ~upport surface or plate l8 in movable contact with
the surf~ce of the concrete 13 in order ~o ~upport the
surface ~f the concrete immediately ~djacent the groove
being cut i~ the ~onerete 13. In ~he illustrated
e~bodiment, thl~ ~urface takes the form of a skid plate 24
which depends from the ba6e plate 12 in the direction of
the concrete 13, The skid plate 24 ~6 on the ~a~e side of
the base plate 12 a6 i~ the reces~ 22 and the rear wheel
20, ~nd l~ ~dj acent the longer ed~e of the ~ase plate
12. The 5kid plate 24 i6 oppo6ite the front wheel~ 14 and
~6.
In normal use, the 6aw 10 i~ ~upported on the concrete
~3 a~ ~hree point6, the ~kid plate 24, the front wheel 14,
~nd the rear wheel 18~ It i6 believed that the three
points o~ contact provide ~ more stable suppor~ and cause
1 3C~6~
less wobble of æaw 10 ~han would other support methods.
The wheels 16 and 20 are ~paced approxi~ately one eighth
to one-fourth of an inch from the plane defined by the
skid plate 24 and wheels 14 and 18, co th~t ehe wheels 16
and 20 do not nor~ally contact the concrete 13 as the sof t
concrete ~aw 10 i6 operated. The purpose of wheels 1b and
20 will be described later.
The wheels 14, 16, 18> and 20 can be the same wheels
as used on roller ~kates or skateboards. The wheels are
approximately 2.5 inches in diame~er, and 2~5 $nches
wide. The wheels are mounted to the base plate 12 ~o as
to rotate freely as the base plate 12 and ~aw 10 move
along the concrete 13.
Referring to FIGS. 2 ~nd 3, the skid plate 24 is a
generally rectangular ~trip of metal havin~ rounded ends
26 and 28 between which is a flat piece 30. The flat
piece 30 is generally parallel to the ba~e plate 12. The
fla~ piece 30 contact6 the concre~e 13 in order eo help
~upport the weigh~ of ~he ~aw 10. The rounded ends 26 and
28 prevent gougin~ the surface of the 80ft concre~e 13 as
the saw 10 CUtB the concrete 13.
The area of the ~kid plate 24 in contact with ~he
concrete 13, ~nd the area of ~he wheels 14 and 1~ which
al~o help Ruppor~ the weight of ~he ~aw 10, are all si2ed
~5 to provide a large enough area to distribute the weight o~
the caw 10 without detri~entally marking or 6ubstantially
damaging the surface finish on the soft concre~e 13 which
i~ being cut.
Referring to FIGS. ~ and 4, on the upper ~urface of
plate 12 is mounted a motor 32. The moeor 32 drives a
rotating cutting means such a6 circular æaw blade 34 (~'IG.
4) which in turn CUtB the concrete 13 (FIG. 2) to ~or~ a
groove.
Referring to ~IG. 2, saw blade 34 i5 typically
circular and ~ade of carborundumI or dia~ond coated
P~eel. The blade 34 has two generally flat sides, a
1 3C'',~2~
leading, or cutting edge, and 8 trailing edge. Th 6aw
blade 34 typically has lit~le or no kerf, or tooth
offset. Slots in the ~aw blade 34 carry the cut concrete
out o~ the concrete 13 to leave 8 groove or 610t in the
concrete. In the illustr~ted embodimen~, a 4.25 inch
dia~eter saw blade is used. Such blades are commercially
available.
The ~aw blade 34 rotates abou~ an axis subs~antially
parallel to the ~ase plate 12, and ~ubstantially
perpendicular to the direction of tr~vel of the 6aw 10.
The saw blade 34 thus rotates in a plane which is
~ubstantially parallel to the longer edges of the
rectangular base plate 12, and substantially parallel to
the direction of travel of the 6aw 10.
t5 Referring to ~IGS. 2 and 3, the saw blade 34 extends
through an aperture such a~ 810t 36 (FIG. 2) in the base
plate 12, and also through an ~p~rture ~uch as 610t 38
~FIG. 3) in the skid plate 24, in order to cut the
concrete 13 ~FIG~ 2). Thu6 ~he 810t 36 iæ a generally
receangular 810t located sub~tan~ially parallel to and
alon~ the length of the longer 6ide~ of the base plate
12~
Spaced below, and ~n ~ub6tantial alignment with ~lot
36, i8 810t 38. The ~lot 38 is ~lso generally rectangular
in shape, and iR placed in the flat piece 30 of ~kid plate
24. The width and length of 810t8 36 and 38 are
suificiently large ~o that the ~aw blade 34 does no~ bind
and size on the edges of tho~e slot~.
Referring to FIG. 2, the saw blade 34 rotates with an
up-cut motion such that the rotation of the cutting edge
of the ~aw blade 34 i5 out of the concrete ~3 which is
being cut, rather than being into the ~oncrete 13.
Alternately phra6ed, the rotation of the circular blade 34
i~ such as to ~mpede the forward motion of the saw 1~,
rather helping pull the ~aw 10 in the direction of travel.
1 ~n~,62~
- 10-
This up-cut saw rotation is u~ed to remove the soft
concrete from the groove cut by the 6aw blade 34. If ~he
~aw blade 34 had a down cut rotation, ~hen the 60ft
concrete cleared by the blade 34 could fill in the groove
S immediately behind ehe blade 34, effectively filling in
the groove with 60f~ concre~e. The up~cut rotation
removes ~he concrete 13 from the cut groove and helps
prevent the return of that removed concreLe ~rom filling
in and hardening in the slot.
This up-cut rotation of the blade 34 i8 con~rary to
conventional wi~dom and u~age which essentially 88y6 that
the blade 34 should cut into the ~urface on which the
quality of the surface fini~h adjacent the cut groove i~
important. Slnce ~he ~urface fini~h i~ importan~ only on
~he visible surface of the concrete 13, conventional
praceice would require a down-cu~ rotationO
The reason for conventional prac~ice i~ believed to be
that the down~cut rotation relies on the mass of the
concrete, into which the blade is cutting, ~o ~upport the
concrete adjacent the blade and to provide an acceptable
: quality of cut. Concre~e has much better compressive
capabili~cy than tens~le capability. The down-cut rotation
keeps ~he concrete ~djacent ~he 3roove in c~mpression,
which wlnimize~ chipping and cracking- The Up-CUt
25 rotation place~ the concrete ad; acent the groove in
tension, which with a conventlonal concrete cu~in~
dev~ ce, would re~ult ln unacceptable chipping and cracking
of the concrete adjacent the ~urface of the cut groove.
A æafety 6hield 40 i8 connected to the motor 32 ~o as
to ~urround and ~hield the portion of the cuttlng blade 34
which does not project through the slot 36 ln base plate
1~. The ~otor 32, shleld 40, and blade 34 ~hus for~ an
integral unit in the illustr~ted embodiment. In fact, i~
iB believed po6sible to use a commercially available wo~d
3S Baw, aometime~ called ~ circular hand saw, as the basic
mctor 3~ and shield 40 of thi6 invention. References to
1 3~.,623
these part6 as an in~egral uni~ does not meanr however,
that they could not be ~para~e compone~ts perf~rming the
same function.
~or reasons described later, it is desirable to have
the blade 34 moveably mounted ~o that the blade 34 can
yieldingly move in response to contact with obs~acles in
the concrete 13. In the illustrat~d embodimen~, as shown
in FIGS. 4 and 5, the motor 32, and thus ~he blade 34, is
pivotally mounted t~ base pla~e t2 80 as to rotate about
an axis which i6 substantially parallel to the rotational
axis of blade 34 (FIG. 5). There i~ thus a pivot sha~t 42
which, has one end connected to moe~r 32 via a bracket 44,
with the other end of the shafe 42 being connected to the
shield 40. The pi~ot ~haft 42 is rotatably conne~ted to
the base plate 12 by trunni~ns 46. The longitudinal axis
of pivot ~haft 42 ls ~ubstantially parallel to the
rotational axis ~f motor 32 and is substan~ially
perpendicular to the direction in which the concrete 13
~IG. 2) iæ to be cu~, grooved, or ~lot~ed.
In the illustrated embodiment there i6 a means for
resiliently urging the blade 34 ~gainst the concrete 13
~i~h a predetermined foree. Thls re~ilient means
preferably ~ake6 the form of re6ilien~ spring means, as
follows.
Referring ~o FIGS. 2 and 5, att~ched to the ~hield 40
~ ~he end of the ~hield which 1~ opposite the connection
with plvot ~haft 42, is a projection 4~. Referring now
to FIGS. 2 and 6, pro; ection 48 is on the exterior of ~he
shield 40, Auay from the blade 34, ~nd contains ~ notch
or engaging sperture ~uch ~ aperture 50. A tension
6pring 52 has one end engaging or connected to the
~per~ure 50, wlth the other end of ~prlng 52 connected to
~ post 54. The post 54 ~s connected eO base plate 12
adjacent the motor 32, and i6 sub~tantially perpendicular
to the surface of the ba~e plate 12.
1 3 C ", ~
-12-
ln the ~l~u~trated embodimen~, the spring 52 ~upp~rts
a portion of the weight o~ the ~otor 32, blade 34, and
shield 40 so as to ~djust or regulate ehe a~o~nt of forc~
with which the blade 34 is forced again~t the concrete
13. Several factor~ can be varied to control the amount
o~ force which the blade 34 exert~ on ~he concrete 13
during cutting. Such factors would include the distance
between the pivot shaft 42 and the motor 32, the ~istance
between the pivot ~haft 42 and the 6pring 52, the type,
size, and method of mounting of the cpring 5~, snd the
weight of the motor 32.
In the illu~trated embodiment, ~ 7.5 amp, 11,000
r.p.~. mstor 32 weighin~ about 6.2 pounds, i5 connected to
a spring 52 having ~ diameter of 3/8 of an inch, and an
uncompresse~ length of 1.75 iDche~ . The 6pacing between
-he sprin~ 52 and the pivo~ ~haft 42 is approxi~ately 7.5
inche~. The distance between the center line of the motor
32 (and the rotat10nal axi~ of blade 34) and the pivot
hsft 42 i~ appr~ximately 3.5 lnche~.
Referr~ng to FIG. 6, the force exerted by spring 52,
and the re~ul~ing force exerted by blade 34 on ~he
concrete 13, ~ffect6 the quali~y of the slot or groove
which is cu~ in the concrete 13. The concrete 13 i8 an
aBgregate of rock, ~and, and cement, with the rock being
of variable ~ize depending upon the requirements for ~he
strength of the concrete 13. When ehe blade 34 hits a
rock or o~her obs~ruction buried in the concrete 13,
problem~ can arise. The tension on the spring 52 can be
ad~usted eo reduce these problems ~nd to accommodate
varying ~ize~ of aggregate in the concrete 13.
If the motor 32 and blade 34 are rigidly mounted to
ehe base plate 12, then the entire concrete ~aw 10 can
conceivably come to a ~olting halt until the bl~de 34 can
cut through the entrained rock. Alternaeively, if the
concrete 13 i6 60ft enough, the rock may be ~lightly
pushed out ~f the way which can cause surface damage, an
1 3 ~ 2 ~
13
unacceptable saw cut, or resadual cracking before the rock
c~n be cut through. S~ill furth~r, the ~aw 10 co~ld
bounce up so as to disengage the blade 34 or. the skid
plate 34 from contact with the concrete 13. ln each o~
the~e casçs, the ~udden halt or change in ~he motion of
concrete ~aw 10 can mar the ~urface fini~h of the concrete
13. Perhaps more lmportantly, the ~udden i~pact of the
blade 34 with the rock can jar the rock 6ufficiently to
cause Fesidual cracking Qf the roncrete around the rock.
~o Similar re~ult6 csn occur i~ the blade 34 i6 moun~ed
~o that a predetermined force can cau~e the blade to move
~eparate from the base plate 12, but an exce~sive force is
exerted by the blade 34 on the concre~e 13. The eoncrete
can crack, a rough cut i~ made, and the ~urface fini6h of
the concrete can be impaired.
The goal of the ~prin~ 52 and the pivoting of the
motor 32 and blade 34 is to allow adjustment of ~he force
between ehe blade 34 snd the concrete 13, and to allow
movement of the blade 34, ~o ~hat the eontac~ between the
blade 34 and an entrained ob~tacle, ~uch as a rock, does
not damage the ~urace of the concrete 13 or cause
residual cr~cking of the concrete 13.
For the lllu~trated e~bDdiment, ehe weight or force
exerted by the motor 32, shield 40 an blade 34 i~ about
-5-5 pounds, which iB greater than de6ired. In the
illu~trated embodlment the ~pr~ng 5Z offloads a portion of
the weigh~ 80 that only about 2.5 - 3.0 pounds of ~orce
are exerted by ~he blade 34 on the concrete 13. Thus the
blade 334 i8 re~iliently urged into contact with ~he
concrete with a force of about 3.0 pounds. If needed, the
extension Gpring S2 could be readju6ted or replaced with
an appropri~tely 6ized spr;ng ln order to provide the
de6ired predetermined iorce between the bl~de 34 ~nd the
concrete 13.
One re~ult o~ ~djusting the force between the blade 34
and the concrete 13 i8 that the depth o~ the ~roove cut by
1 3(:i",h~8
-14-
the blade 34 can vary depending on how fast ~he ~aw 10 is
moved~ ~urther, ~he depth of the groove may be less when
the blade 34 hits rocks entrained in the concre~e 13. For
example, it is believed preferable for the depth o~ th~
grooves cut by ~aw 10 to be about 0.5 inehe~ deep, with a
minimum depth of .125 inches being marginally
acceptable. As the force of the spring 52 offloads more
and more of the ~orce exerted by blade 34, the blade 34
will cut a shallower and ~hallower gro~ve for a cons~ant
travel of saw 10. If a ~ull depth cut groove is required,
the fiaw 10 must move slower ~s the force between the blade
34 and the concrete 13 increases with the depth of the
groove. If ~he 6aw 10 is moving fase enough, ehen when
the blade 34 hit~ an entrained rock, ehe blade 34 bounces
up, only partially cutting the rock, and cutting a
shallower groove at that poin~.
Al~ernately phrased, the greater the tension ap~lied
eo the spring 52, the les~ ehe weight or force applied to
the saw blade 34, which in turn provides a faster forward
cut but al~o a 6hallower cut. The less the tension
applied to ~he 6pring 52, the ~rea~er the weight applied
~9 the 6aw blade 34 ~h$ch in ~urn deepen~ ~he overall
groove depth and 810ws the forward travel. If ~oo much
weight i~ applied to the blade 34, the 0kid plate 24 will
2s riBe off of ~he surface of c~ncrete 13 and ~he groove
quality will become unacceptable.
The exact mechani~m by which the offloaded an~ pivoted
blade 34 optimally cut~ through entrained rocks is
uncertain. It ia believed that a correct ~election of
the force exerted by the blade 34 on the concrete 13 will
allow the blsde 34 to ri~e up over an entr~ined rock so
80 aB to circumvent the rock. It i8 believed ~h~t rising
up to ehe rock allows the blade 34 to cut down in~o the
rock and does not cause a eevere jolt to either the
entrained rock or the concrete saw 10. This force
~ele~tion must consider the individual concrete mix
1 3(,~,62~
design, and e6pecially the size of the Aggregate (rock) in
the concrete. Alternately phrased, it i6 believed that if
the force with which ~he blade 34 ~s urged into ~he
concrete 13 is too great, then the operator must Rhove the
5 58W 1O in order to cut sideways through the rock. The
result is residual cracking around the rock, either from
the initial impact of the ~aw 10 with the entrained rock,
or from the ~ideways orce of ~he operator cutting
sideways through the rock.
It is ~elieved that if the force i8 correctly
adjusted, ~he blade 34 can resiliently accommodate the
impact with the entrained rock to minimize or prevent
damage to the concrete finish. A trade off be~ween the
desired depth o~ the rut groove, and the permi~sible
lS varlations in that depth o~ the cut groove exists. The
illu~trated embodiment is one combination that has been
judged preferable when working with aggregate up to one
(1) lnch in ~ize.
Thi problem with obstruction5, ~uch as entrained
i~ rock6, le not encountered with conventional cutting
~ach~ne6 ~ince ~he concrete 13 is su~ficiently hardened,
and the progress of the ~aw ~ufficiently 810w, 80 that the
entrained rocks ~re cut without the re~idual cracking
concern. For ehe grooving trowel~, the en~rained rocks
2~ ~re no problem since the concrete ~s grooved 3u~t after
pouring, while the rocks can be slowly urged ou~ of che
w~y of the grooving ~rowel without causing cracking.
While the amount of force between the blade 34 and the
concrete 13 ma~ Yary ~omewhat depending upon the 6ize of
the blade 34 ~nd ehe ~ize o~ the rocks entrained in the
concrete 13, it i6 believed that this force should be
about 2.5 - 3.0 pounds for the illustr~ted e~bodiment.
Thi6 force has been found ~uitable for cutting ~ 1/2 inch
deep groove in a 4 inch th$ck ~lab of concrete 13, with
3~ rock or aggregate up to 1 ~nch in ~ize.
1 3C"`62~
-16~
The quality of the groove cut in the concrete 13 is
also affected by the ~ize of the slot 38 (~IG. ~) with
re~pect to the portion of the blade 34 extendin~ through
tha~ slot. The force exerted on the concrete 13 by the
~kid plate 24 helps to suppor~ the ~urface vf ~he concrete
13 immediately adj~cent the groove which lb being cut in
the concrete 13. If the spacing between the ~ides of the
blade 34 ~nd the 610t 38 i8 too great, then the edges of
the cut groove will beco~e rough and uneven. It i~ also
possible that ~palling, chipping, or 6ur~ace cracking
~mmediately adjacent the edges of the groove will occur.
It is pre~erred to have the ~kid plate 24 ~upport the
concrete 13 immediately adjacene ~he groove being cut by
blade 340
~eferrlng to FIG. 7, it ~æ preferred ehat the
spacing b and c be~ween the side6 of ~he blade 34 and ~he
6ides of the clot 38 ~n the ~kid plate 24 be controlled.
~e~ting indicaees ~hat a spacing a~ clo~e as possible to
zero, without b~nding, provides ~he best surace ~inish
20 adjacent the cut groove. A spacing of less than 1/16 inch
(0.0625 inch) produces a cut groove of acceptable quality
with no readily perceived crack6 or chip~ or ~gged edges
~ sp~cing of 1/16 inch or 3lightly greater, of b and c,
provideæ a surface ~ini~h adjacent ehe groove tha~ is
2~ ~udged to be of questionable accep~ bility, having chips
and crackE thst are not perceptible at a distance, but
noticeable close up. A ~pacing of 3/32 of an inch
provides a groove that is usually unacceptable in terms of
chipping and cracking, and overall f inish. A spacing of
30 over 3/16 of ~n $nch provides a groove deemed unacceptable
ln terms of cracking, spalling, or co6~etic appearance at
~he edge of the groove.
These results are derived from test d~ta which
indicates that the relationship between the slot ~pacing
and the qu~lity of cut i~ not linear. ~ 12 below,
illustrates the ~e~t data and ~hows the manner in which
1 3C'`'~2~
- 17-
the 6pacin~, is believed ~co affect the quality of the
sur~ace f ini~h o~ the concrete 13 adj acent the cut groove .
It i~ believed that the effec~ of ~he ~pacing b and c
on each ~ide of the 6aw blade 34 is independent of the
5 quality oi the cut or groove formed on the o~her ~ide of
the blade 34. Thu6, i~ is possible to have tJ~e 6urface
finish on one ~ide of the groove acceptable, with the
opp~site side of the groove producing an unacceptable
finish ~djacent ~he cut groove because of too wide a
~pacing.
It iB believed pos~ible that the ~pac~ng may be
critical only at the CUttiTlg edge of the blade 34 since
that location i~ where the concrete 13 i~ being removed by
the up-cutting m~tion of the blade 34, ~nd the only place
where the concrete 13 l~ being theoret ically placed in
tension by the blade 34 80 as to cause cracking and
chipping. In practice, however, the ~aw 10 may wiggle and
wobble ~o that ehe blaae 34 actually contact~ the concrete
13 at point~ other th~n the cuteing edge o~ the blade
34. Thu6 the 810t 38 prefersbly has side~ ~hich
corre~pond ~o the ~hape of the side~ of the blade 347 and
are ~p~ced aR clo6ely a~ possible to ~he blade 34 without
~inding ehe ro~ation of the blade 34.
Referring ~o ~IGS. 3 and 7, the s~acing between the
up-cutting or cutting edge of the rotating blade 34 and
the adj~cent end of the 810t 38 i6 ~lso controlled in the
lllustrated embodiment. ~f the front edge of the ~lot 38
extend~ into the rounded end 26 o~ the skid plate 24, ~hen
placlng the cutting edge of the blade 34 sdjacent this end
30 of the ~lot 38 can cause ~ build up of the cut concrete
which c~n squeeze out of the ~lot 38 and under the rounded
end 26 80 a6 to mar the surfsce fini6h of the concrete 13
or cau6e tllting of the 3aw 10.
It i~ preferred that the front or leading edge of the
35 6lot 38 ~hich i~ ~djacent ehe leadlng or cu~ting edge of
the blade 34 not extend into the rounded end 26, but
1 3 ~, u 6 2 ~
-18-
r~ther termlnates in the flat piece 300 Further, it is
preferred that the space d between the cutting edge of the
blade 34 and the adjacent end of ~lot 38 be li~ited ~o as
not to greatly exceed 1/4 of an inch. Ideally, there is
5 zero ~pacing between the cutting edge of bl~de 34 and ehe
end o~ the ~lot 38. However, as the blade 34 wears, a
~pace will naturally develop, and a maximum ~paced of
about l /4 inch i6 preferred.
The spacing be~ween the back or trailing edge of the
blade 34 and the end of the ~lot 38 also aftects the
quality of the cut groove7 It i~ preferred that ~he slot
38 be extended into the rounded end 2~, or alternately
that a tunnel or other open piec~ be providedO The
preBence of a flat piece of metal on the concrete 13,
immediately following the groove cut by the blade 34,
would ~ct aR a trowel ~erving eo close over or otherwise
compromise the q~aliey of the groove which had previou~ly
been made~ E~tending the 810~ 38 all the way to the
rounded end 28 prevent~ closure of the previou6ly CUt
groGve and also prcv~des a sturdy attachment for the ~kid
plate 24 which prevent6 undue vibration during operation
of t~e concrete saw 10 (FIG. 3).
Referring to FIG. 2, thi~ deslre to prevent closing of
the groove immediately after it has ~een cut, also sffects
the placement of the rear wheel 20. The outer edge of
wheel 20 i~ preferably placed close to the rotational
plane of the bladè 34 and the ~roove cut by that blade,
but not ~o close th~t the wheel 20 would cause clo6ure o f
the groove cut in the concrete 13 by the blade 34.
3~ The ~ize of the alot 36 with re~pect to the blade 34
1~ al80 controlled in order to help prevent the fre~hly
cut concrete from accumulating on the blade 34 and tO
prevent the fre~hly cut concrete from being returned to
the groove which had just been eut. Thus, ~he width o~
~he slot 36 i8 preferably as close to the wid~h of the
blade 34 as possible. Limitations on the length of the
1 3~,6~
- 19-
slot 38 must also consider acco~moda~ing motion of the
blade 34 as it pivots around the ~haft 42 tFlG. 4) when
the blade 34 ~trikes rocks which are entrained in the
concrete 13.
5As the concrete 13 i6 removed from the groove by the
lots in the blade 34, ~he concrete dislodges from the
blade 34 and is depositPd between the lower surface of the
plate 12 facing the concrete 13, and the interior ~urface
of the skid plate 24 which faces the plate 12. ~bout 80%
of ehe concrete removed by the blade 34 iæ deposited on
the interior of ~kid plate 24. As more ~nd more concrete
di~lodges and accumulate6, the concrete i6 urge~ off of
the skid plaee 24 onto the adjoining eurface of oncrete
13. By ~he time the dislodged concrete exits the 6kid
1~ plate 24, it has hardened ~uificiently 80 that i~ is non-
adhesive and does not readily adhere or mold itself ~o the
concrete 13. The heat ~rom ehe cu~ting ~c~ion of blade 34
may contribute to thi~ hardening,
I~ iR not believed th~t the rotational ~peed of the
blade 34 haR any aignifican~ ~ffect on ~he ~pacing between
the blade 34 and ~he ~lot 380 The rotational ~peed of the
blade 34 does ~ave ao~e affec~ the ~peed and ease with
~hich ~he concrete ~aw 19 can cut ~cro6s the ~urface of
the concrete 13. Generally, ~ higher rotational speed of
the blade 34 allows faster cut~ln~ and thus fsster
~ovement of the concrete ~aw 10.
Referring to ~IG. 3, the width of the ~kid plate 24 is
such ~hat it not only support~ a portion of the weight of
the saw 10, but ~l~o allows harden$ng of the concrete
3~ after it ha~ been removed from the groove cut by the blade
34. A minimum width s~f 0.5 lnches has been found
sufficient to AllOW the dislodged concrete to harden
~nd/or air dry before lt slides off ~f the ~kid plate 24
onto the adjoining concrete 13 (FIG. 2), yee 6u~ficiently
large to prevent the ~ides of the skid pl~te 24 from
slicing like wire, or ~inking, rather than providing a
', . :
1 3~362~
-20-
support ~urface with minimal marring on the surface of the
concrete 13.
Referring to FIGS. ~ and 4, there 18 a handle 55
attached to the motor 32. The handle 55 c~n be grabbed by
a person i~ order to carry the concrete 6aw 10.
Referring to ~lG. 1, in order to enable operation of
the fi~W 1 0 on large slabs of conerete 13, without the use
of æcaffolding to ~upport the weigh~ of the opera~or,
extendable handle6 58 can be ~tached to the ba~e pla~e
12. The extendable handle6 58 function like ex~endable
broom handle~ to enable the ~aw 10 to be pushed OUt onto,
and withdrawn from, a lar~e slab of c~ncrete 13. In
sh~rt, ~he handle 48 provldes a means o~ moving or
propelling the saw 10 to cut grooves in the concrete 13.
A more detailed deserlption follows.
Referring to ~IG. 2, ~he concre~e ~aw 10 preferably
has three point~ o~ ~uppor~ at all ~imes ~he blade 34 is
cutting the concrete 13. The6e three point~ typically
comprise the ~kid plate 34, and two of the wheel~ 14, 16,
18, or 20, as de~cribed hereinafter. When ehe concrete
caw 10 i~ flr~t ~earted on the edge of a concrete sl~b,
the three point ~f contac~ compri~e the s~id plate 24 and
the front wheels 14 ~nd 16. The wheels 14 and 16 are
approx~ma~ely equal distance ~rom, but on opposite sides
2~ of, the rotation~l axi~ of the blade 34. Thus, ~here is a
stable ~hree point support among the wheel~ 14 and 16 and
the skid plate 24.
The front wheel 16 i8 located approximately 118 to 1/4
of an inch further aw~y ~rom the concrete 13 than is the
front wheel 14. Thus, when the BaW 1 0 has cut
~ufficiently far out lnto the concrete 13 BO tha~ the rear
wheel 18 rideB onto the surface of the concre~e 13, the
wheel 16 iB lifted out of contact with the concrete 13,
and the three point cupport then comprises the 6kid plate
24, the front wheel 14, and the rear wheel 1~. The of~set
wheel 16 ehus ~erves a~ a ~uide and support for the
1 3')362~
-21-
concrete saw 10 as the 6aw 1 0 begins cutting lnto the edgP
of a concrete slab, but not thereafter.
The use of an offse~ wheel 16 during the initial
por~ion of ~he cut made by the ~aw 10 does cause ~he blade
34 to cut at an angle wi~h respect to the ~urface of ~he
concrete 13, rather than cutting perpendicular to the
eoncrete 13. The ~aller the of~set of the wheel 16 with
respec~ ~o the other wheels, the less this angle will beO
During thi6 initial cut on the edge of ~he concrete
slab, ~he saw 10 could be operated by the handle 56
attached to the motor 32. After the saw 10 ie extended to
the edge of the operator'~ physical reach, the ~aw 10 can
be operated by an extendable handle 58.
Referring tO FIGS. 2 and 6, the handle 58 is pivotally
connected to the base plate 12 at pivo~ ~lock 60D The
pivot block 60 allows the extendable handle 58 tO pivot
about an axis substantially parallel ~o the rotational
axis of blade 34. As the c~ncre~e ~aw 10 moves onto the
concrete 13 and further away from ehe operator, addi~ional
extension~ can be attached to the extendable handle 58 at
~oints 59 ~FIG. 1) in order to acco~modate the necessary
reach. The connec~ion of extendable handles 58 at joints
59 can be by diverse mean~ ~uch as ~crew ehreads or
~ayonet mounts which are well known in the art and not
described ln detail herein.
The connection of the handle 58 to the base plate 12
provides a meanR for propelling the saw 1~ without
restrict$ng the movement or pivot action of the blade 34
about the pivot axi~ 42. The u8e 0~ the h~ndle 5~
a~tached directly to the motor 32 res~rictfi plvoting of
the blade 34, and can cause inadvertent damage to the
f inish of the concrete surface when the blade 34 hits a
rock entrained in the concrete a~ previously de6cribed.
During operat$on of the 6aw 10, the greatest drag
occurs at the blade 34 and skid plate 24. The pivot block
60 is preferably placed adjacent the blade 34 so as to
1 30~62~
move the concrete saw 10 wikhout skewing the blade 34 and saw
10. If the blade 34 skews so that the blade 34 is not parallel
to the line of travel of saw 10, then not only is-the resulting
groove in the concrete 13 wider than normal, but the skewing of
blade 34 can cause immediate or residual cracking, spalling, or
chipping in the surface of the concrete 13 immediately adjacent
the groove. Thus, it is desirable to have the force pushing
the concrete saw 10 applied so as to cause as little skewing of
the blade 34 as possible.
Referring to FIG. 5, for the illustrated embodiment,
applicant has found that the center line of the extendable
handle 58 can be along a line substantially parallel to the
cutting blade 34, and spaced approximately 1.5 inches
therefrom, toward the motor 32.
Referring again to FIGS. 2 and 6, the concrete saw 10 has
completed its cut, it may be desirable to retract the concrete
saw 10, rather than retrieve the saw 10 from the other side of
the slab of concrste. As described below, mechanisms are
provided to retract the blade 34 from the concrete 13, and to
.0 pivot the concreke saw 10 so as to disengage the skid plate 24
from sliding contact with the surface of the concrete 13.
The pivot block 60 is spaced apart from the base plate 12
by a boss 62 so that the pivot block 60 is above the surface of
the base plate 12. On the boss 62 is mounted a selector
bracket 64 which comprises a piece of metal rQughly resembling
a sector gear in shape. The selector bracket 64 has a narrow
edge extending in the direction of the extendable handle 58.
Into this edge are cut recesses or notches 66. These notches
66 are shaped and located so that they can mate with a tip 68
of a plunger 70 of a solenoid 72. The solenoid 72 is mounted
on, and is substantially parallel to, the extendable handle 58.
In operation, the angle between the extendable handle 58
and the base plate 12 will vary depending upon the
1 3r`362~
-23-
length of the handle 58 and the dis~ance of the 6aw 10
from the operator. The sngle i5 greater ~s the saw 1
comes nearer tO the operator.
A remotely actuatable means is provided to allow
S removal of the 6aw 10 ~rom a slab o~ concre~e without
dragging the skid plate 34 on the ~urface of ~he c~ncrete
13. When it is desired to retract the ~aw 10 from ~he
middle of a slab of concrete 13, the 60lenoid 72 is
energized so that the plunger 70 extend~ to cause tip 68
to engage with an adjacent notch 66. Depending upon the
angle of the extended handle 58, the tip 68 will engage
differing notche~ 66. The engage~ent o~ the tip 68 with
the notch 66 provides a linkage connection ~hereby ~he
handle 58 may be 6hoved down eowards the ground ~o exert a
torque or moment on~o the base plate 12. In e6sence, the
notche~ 66 and plunger 70 serve eo lock the handle 58 into
a fixed po~ition wlch re~pect to the ~aw 10. The result
i8 that the Raw 10 ~ilts onto the e~o rear wheels 1~ and
- 20 as the handle 58 i~ pu~hed to~ard the ground, thus
enabling the saw 10 ~o be rolled sff of ehe concrete 13
~lab without the ~kid plate 24 dr~gg~ng on the concrete
13.
As seen from ~ig. 6, the rear wheel 20 i8 also located
approximately lt8 ~o 1/4 of an lnch further away from the
2~ concrete 13 than ~ 8 the rear wheel 18 or the fron~ wheel
14, ~o that the wheel 20 doe~ not normally contact ~he
surface of the concrete 13. The off~eteing of the wheel
20 eauses a tilt to the base plate 12 when the saw 10 is
pivoted BO that it can roll on the wheels 13 ~nd 20. The
base plate 1~ mu~t not overhang the of~se~ ~heel 20 so
that the off~et of the wheel 20 cau~es a corner of the
ba~e plate 12 to dig into the concrete 13 when the base
plate 12 is tilted onto tbe rear wheel~ 18 and 20, To
provide as wide a ~upport as pos6ible in order to help
.35 minimize this tilting, the rear wheel 20 i8 preferably
: ~placed a8 close to the plane of the ~aw blade 34 as
I 3C,S~
-24-
possible, without cau~ing ~he groove cut by the blade 34
to close.
C~nceivably, the wheel 20 could be placed ~n the
opposite side of the groove than ~he other wheel6. It is
5 also believed possible that the three points of support
for normal operatlon could compri8e the two rear wheels 18
and 20 and the skid plate 24, with the two offset wheels
being the front wheels 14 and 16. In this ca6e, the
tilting of the base plate 12 would not occur during
retrieval of the ~aw 1~ since there would be no o~fset
between the rear wheel~ 18 and 20, ~ith both of those
wheels being on ~ub~tantially coplanar axis, if not the
~ame axis.
Another remo~ely actuatable meanG is al80 provided to
di6engage the blade 34 from cont&ct with ~he concrete
13. Referring to ~IGS. 2 and 3, a second solenoid 74 can
be u6ed to pivo~ the blade 34 ~ut of sontact wi~h ~he
conorete 13 (FIG. 2) befor2 the retraceion of the ~aw 10,
or ~t ary ti3e desired. This ~econd solenoid 74 is
2~ preferably located adJ~c~n~c tlhe spr1ng 52 80 as ~co provide
a force between the ba~e place 9 2 and the ~hie1d 40 which
causes the blade 34 to pivo~ out of i~ normal pv ition
~hich i6 ~n cont~ct ~ith t~e concrete 13~
More ~peclfically, there i8 ~hown ehe solenoid 74
conneceed to ~he ~o~or 32~ The solenoid 74 has a plunger
76 extending downw~rd ~owards the base plate 12. When the
~olenoid 74 i8 energized, the plunger 76 extends to
coneact and pu6h against the base plate 12 with the result
that the sh1eld b,o, motor 32, and saw blade 34 pivot about
the ~haft 4~ ~o as to rot~e the blade 34 a predetermined
di~tance, preferably out of cont~ct with the concrete
13. Pleferably, the ~olenoid 74 i~ connected adjacent the
~lade 34, perhaps ~ttached to the shield 40, ~o as to
place the force exerted by the ~olenoid 74 adjacent the
greate6t re0istance to di~engaging the blade 34 from the
concrete 13.
1 30~62~
-25-
Re~erring to FIG. 2, ~olen~ids 72 and 74, ~nd the
m~tor 3 are c~nnected to el~ctricsl wires 76 wh~ch r~n
along extenduble handle 58 ~o a con~rol dev~ce 78 on the
end o~ ~he handle 58 where ehey are controlled by rhe
operator. Thus the Roleno~ds 72 and 74 and ~he ~tor 3
can be re~o~ely sctuated by che operator of the ~aw 10.
If the wi~e8 76 ~re not suf~lciently long, then
connectors known in the art and n~t de6cribed in de~ail
herein, allow the u~e of ~xtens~on ~o the wires 7~ as
more and more handle~ 58 are added.
A mounting br3cket 80 ~ 8 plvotally connected to the
pivot shaft 4~. The ~ounting brscket 80 i8 shown as
connect~ng to the pivot ~haft 42 ~t two loc~tions on
generally opposit~ ~ides of ~he base pLate 12, ln order tO
provide a stable connection ~o the 6aw 1 0 . Connected to
the mouncing b~acke~ &0 læ ~ tubular cylinder ~2 which is
loca~ed ~o that i~ ~xtends along 8 line parallel to the
orlentatlon of the saw blade 34. ~ne end of the handle 58
extend6 ~hrough the cyl~ndrical ~ube 82 such that the
handle 58 can ~otate wlthln ~he ~ube 82. An end of the
ha~dle 58 pro~ect~ beyond the tube 82. V2riou6 devlces,
~uch ~ ~nap rlngs 84, ~llow the handle 58 ~o rotate
wlthln the cylindrical ~ube ~2, but ~e~train motion of the
handle 58 alsn~ the long~tudinal axls o~ the handle 5~ ~nd
cylindrlcal tube 82.
Thu~, the handle 58 can gu1de and propel the saw l o
through the connectlon w$th ~he bracket 80 and pivot shaft
42. The pivot~l conn~ction between the bracke~ 80 and the
p~vot sha~c 42 allows ehe h~ndle 58 eo ~ove up and down ln
~o ~ vertlcally orlentatlo~ wlth respect ~o the concrete 13.
In thl~ slternate embodlment, a U-~haped br~cket 88
has one slde connec~ed top, and preferably lntegrally
~or~ed ~ith 3afety ~h~eld 40. The open ends o~ the ~-
shaped bracket 88 are ~180 pivo~ally connected to ~he
p~vot shaf~ 42 such that the b~acke~ 88, 6a~e~y ~h~eld 4U,
motor 32, and ~aw blade 34 ~re all connect2d so as ~o
,~
I 3C302~
- 2 6 -
pivot ~bouc p~voe ~haf~ 42. Thus, the IJ-~haped bracket
88, and the mountlng bracket 80, both plvo~ about th~
common shaft, pivot 6haft 42.
A ~lexlble member Euch a~ wire cord go ha~ a f irst end
connected to the l~-~haped bracket ~8. and a ~econd ena
connected ~o that portion of ~he handle 58 extending
through the cylindrical tube 82. A6 the handle 5~ ls
rotated in the tube 82, ~he cord 90 wraps around the end
of the handle 58 B0 that the leng~h of ~he cord 90 is
~hortened, Shortenlng the length of cord 90 pulls on ~he
bracket 88 and pivot~ the ~aw blade 34 about the ~ivot
shaft 42 80 ~h~t ~he saw blade 34 can be wle~drawn fro~
contact with the concrete 13, as ~llus~rated ln ~IG.
10 . Controlled sho~tenin~ of the cord 90 can also be
u~ed to vsry the depth of the groove cut in the concrete
13 by the saw blade 34.
The ~otor 32 ~8 ~180 connect~d to ehe base plate 12 by
~eans of ~ ~econd flexible me~ber ~uch as che ~econd wlre
cord 92. Preferable, the ~econd cord 92 has a first end
connected to the front of the b~e pla~e 12, on the ~a~e
end as the wheel 1~ l~ 10C8~ed~ The sscond end o~ the
~econd co~d 92 1B pre~erable csnnected to ~ pro~ecein~
bracket 94 whlch ~roml and l~ connected to, the moto~ 32
~s shown ~n FIG. 8.
The second cord 92 i~ normally 61ack when the ~aw
klade 34 i~ at its desired cuttlng depth in the concre~e
13, as lllustr&ted in FIG. 9. Pre~erable, the ~econd cord
~2 ~ al80 slack when ehe f~rst cord 90 i8 shortened 80 as
to cause the ~aw blade 34 to pivot OUt of contac~ wlth the
concrete 13, a~ lllustrated in FlG. 10 . Fur~her pivoting
of ehe ~aw blade 34 and connected ~otor 32, c~u~e~ the
~econd cord 92 to become taut and exert a ~orce on the
front of the bas2 plate 12. If the force exerted by the
~econd cord 92 18 suf~lclent, the 8~W 10 wlll plvot on
the rear wheels 18 and 20 (~IG. 7), ~o that the skid plate
24 l8 moved out o~ co~tact with the surf~ce of the
r~
1 3C~,62~
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c~ncrete 13, ~s sh~wn ln FIG. 11.
Thus, the handle ~8 c~n be u6ed eo not only propel ~na
~,uide the 6aw 1~, but also to disenga~,e the 6aw blade 34
~rom the concrete 13, and furt~ler ~o di~eny,age the ~kid
plate 24 fr~m contact with the sur~sce of the concre~e 13,
80 that the ~aw 10 can be w~thdrawn fr~m the ~urface of
the concrete 13 with minimum danger o dama8ing the
surface of the concrete 13 by inadver~ent ~craping vf che
skid plate 24.
The saw 10 in preferably used to cut ~oft concrete,
not hardened concrete. The saw 10 can be used ~ust ~fter
the concre~e 13 has been fin~shed. At the tlme of
f~i6hlng, the concrete 13 has ~ttalned a workable
plast~clty that allows the concre~e 13 ~o be worked and
~S retain a 6urface t~nlsh, but the eonc~ete 13 ~8 n~t
~uf~ciently ha~d ~o ~llow acceptable cutting by
conv~ntional ~w8 or ~ethod~. The ~aw 10 can also cut
co~crete 13 wh~ch h~s ~et ~or ~everal hour~, and is
bel~eved ~o work wlth any concrete that i8 ~oo ~oft, or
2~ n~t sufficie~ly hard, ~o be cut sat~s~torily by
conv~tio~al ~bra~ve cu~ting ~chineR.
/ A~ previously ~en~loned, ~uch eonventlonsl cut~lng
.~ma~h~nes can p~oduce cut~ o~ unacceptable or dublous
/ ~cceptabiliey fro~ as ll~tle as 12 hour~ sfter $inl~hing
25~ $f the dsy i5 extremely hot, ~ay over 100 degree~
~ahrenheit. The~e conven~ional cutt~ng machine~ typically
are not used unt~l the nex~ d~y, ~abou~ 18 hours lates)
~nd ~ven then typieally produce unaccept~ble cut6. The
saw 10 wlll typically be used be ore ~he~e 12 hour and 18
hour ~igures. The 8~W 10 8110w~ "~ame day" cuttin~ of
gY~oves wlth acceptable 6urface finl~hes ad~acent the cue
groove~ i6 belleved that the saw 10 could be used at
or beyond the 12 and 18 hour figure~ and produce a cut
groove h~vlng a superlor ~inlsh ad~cent the sur~ace o~
the groove when co~pased to the groove quality of
conv~ntlonal ~br~sive ~schines. H~wever, the wear on the
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blade 34 would be great~r than nor~al.
Ideally, ehe 6aw 10 would be u6~d to cut ~rooves in
the concrete 13 before the concrete 13 has incurred its
characteri6tic ~hrink that occurs durin~ ~ettin~, to an
extent that cracks begin ~orming in the concrete 13.
More specifically, the finishing of concrete typically
proceeds through eversl stages. The first ~tage is to
pour the concre~e, tamp it and "bull float" the 8urface to
level the surface. At thi~ 6tage, the concreee is wet, and
cannot be walk~d upon without 8inking into the concrete.
If the ~oncrete i6 grooved with ~n edger or grooving
trowl, lt i8 fir~t done at thi~ ~tage, but mu~t be
repeated la~er. The concrete is typically not left with
this coarse of a finish, although such 8 rough fini~h may
be adequate for road ~urfaces and such.
At ehis first stage the concrete has a hardness of
which can not be ~easured by the conventional Swiss Hammer
eests u~ed for concrete. The Swiss Hammer relies on the
rebsund of a shaft from ~he hardened surface of the
29 concrete to measure hardness in pound~ per square inch, or
psi. At ~hi6 bull float ~tage, ~he concrete is ~o soft
that the plunger on the Swiss H~mmer ~ink~ lnto the
concrete and rebounds.
The saw 10 i~ believed to be able to cut the concrete
~t this b~ll float stage and form an acceptable groove,
alehough the weight of the ~aw 10 will cau~e the ~kid
plate 24 and wheels 14-20 to leave indentatlons in the
surface of the wet concrete 13. If cut at this 8t2ge, the
concrete 13 i6 preferably allowed to have its surface air
dry 80 that the lndentations from the weight of the 6aw 10
~re minimal or non-exi~tent.
The ~econd Btage o~ fin1~hing is called the "fresno"
gtage. Here the concrete has hardened, but still cannot
be walked on without sinking into the concrete. Th~
3~ fini~hing during this 6tage i8 done by long handled tools
since the concrete will not support a person's weight.
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The 6equential working of the concrete ~urface wlth tools
repeatedly brings moisture and cement to the ~ur~ace and
allows 8 ~moother finish to be applied to the concrete
13. If grooves are formed in the concrete by use o~ ~
grooving ~rowl, the grooves must be regrooved ~t ~his
~ta~e, and after each successive fini~hin~ 6tep.
The concrete during thi6 fre~no stage is still too
~oft to ~bta~n an accurate ham~er hardne6s. The ~urface
of the concrete 13 i8 ~moother than that of the fir6t
6tage. The saw 10 will cut ~atisfactory grooves in the
surface of concrete 13 fini~hed to this stage.
Preferably, the ~urface of the concrete 13 will be allowed
to air dry 80 ns to ~inimize the marks for~ed in the
surface of the concrete 13 by the weight of the ~aw 10.
lS Conventional concrete saws will not work
~ati6factorily at this fresno seage of finishing. The
grooYe6 ~ill be jagged at the edges. The concrete will be
~till be wa6hed away by the water lubricant of the
~brasive cutt~ng ~achines. Further, ~he welgh~ of
conventional cutting ~achines will leave unaccep~able
indentation~ ln the surface of the concrete.
The third seage of fini~hing u&e~ power ~rowl~ or
~inishlng m~chine~ to repea~edly ~ooth the surface of ~he
concrete 13. At this stsge the concre~e 73 i6 hard enough
25 80 a per~on will no~ sink in d~eply, but the ~urface of
the concrete 13 ~ill form indentations from the per~on's
weight. The operator of the finishing ~achines ~u~t walks
80 that the ~achine ~mooths out the lndentations. This
~achine fin~hing iB done 6everal times, with the concrete
~urface being allowed to air dry between each flnishing
operatlon. With each flnishing, moisture ~nd cement is
redrawn to the surface o~ the concrete 13. The concrete
13 becomes harder with every f inishing.
The saw 10 can cut the concrete 13 at this time and
~orm good grooves. Preferably, the 6urface of the
concrete ~8 allowed eo air dry B0 the last layer of
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moisture fro~ the flnl~hing oper~ion c~n ev~por~te. This
air dryin~ insures tha~ the weight o~ ~he saw 10 will no~
cau~e ~he ~kld plate 24 and the wheel~ 14-20, ~o mark the
~urface o~ ~he concre~e 13. Thi~ air d~yin~ ~ypically
takes ~rom 15 ~inutes on a warm dsy, to one hour on a cold
day.
It ~s belleved that a conventional saw could not cu~
concrete Bt this ~tage and produce ~n ~ccepta~le ~urface
adjacent the cut groove because of exce~lve ~palling and
10 cracking. Further, the weig,ht of an ~brasive cutting
achine would cause the wheel~ of ~he ID~chlrle to mark the
surf~ce of ~he concrete 13. A conYention~l h~nd ~aw with
a concre~e blade would not h~ve ~h~s signlflcant weight
problem, but such a 8aw would leave an un~ccept~ble ~gged
edge adjaeent the eut groove, and its sk~d plate would
mark the ~urface o~ the concre~e 13.
The ~aw 10 in the illu~ated embodlment allows the
~8e of e~uip~ent ~nd ~9to~ tha~ are co~lde~ably llghter
and 1~B~ powerful ehan previously u8ed. The saw 10 allows
cut~ng o~ grooves ~ a tl1De ~hlCh wa6 no~ p~eviou~ly
cons~dered pr~et~cal or feaslble or cu~tlng g,rooves in
concre~e, and wi~h ~ groove quality that i8 unexpec~d gsr
~he softness of the ~oneret~.
The saw 10 in the illu~trated e~bodlm@nt ~llows the
25 use of equip~en~ ~nd ~Dotor~ that are co~iderable lighter
~nd ~e~s power~ul than p~ev~ou~ly used. The ~sw 1
allows cuttlng of grooves at ~ Eime which wa~ no~
p~eviousl~ considered pract~cal ~r ieasible ~or cutting
g,roove~ ln concreee, ~nd wlth ~ groove quallty that i s
30 url2xpected f~r ~he ~tne3~ of the concrete.
Several t~ts were conduceed ~n sn stt~mpt ~o more
precisely define ~he hardnes~ ~ the concrete 13 which can
be cut by ehe saw 10 . A seeel rod weightin~, 5,75 pounds,
and havlng a d~ameter o~ 1.125 lnche~, was dropped from a
35 helg,ht of ~bout 23.75 lnches from the surtace of the
. oncrete 13. The rod had ~ flat end with the 23.75
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-31-
dimensi~n beln~ from the sur~sre of th~ con~rele 13 to the
~lat ~nd o~ ~he ~eel rod~ ~he depth v~ the ~ndent~tion
f~rmed by rod ln the concrete 13 was then measured.
Fo~ an lndentati~n of about .4 to .5 lnches, che ~aw
10 produced a good cut with no rough edges ad~acent the
cut groove. ~hl~ ~est was conduçted with the concrete 13
somewhere in the fre&no stage. The wheels 14 through 20,
and the skid pl~te 24 dld le~ve vislble ~racks on the
sur~ace of ~he concrete 13. Conven~ional 6~ws would not
10 produce acceptable cuts at thl~ stage. T~e water
lubrlc~n~ on ~n ~br3sive water Raw washes away the
concre~e and al80 the ~8Bregate; If the water i8 not used,
the cut groove ~ up wlth conorete. A conventional
rotary hsnd s~w with ~ blade deslgned for cutting concrete
produce6 ~ ~8gged cut with partial blockage of ~he cut, as
well a~ leaving gou~es ~rom the plate con~aotlng the
concrete 139
For ~ ~ot indentat~on of aboue .3 ~o .4 inches, the
~aw 19 ~lll prod~ces a good ~ut, and ehe wheel 14
20 thsough 20 and the s'kld plate 24 l~ave very sl~gh~ ~arks
or ~ndentatlon~ ln the æurfac@ o~ the conerete 13~
Convent~ onal ~aws do not work at thl~ hardnes~ . The water
lubrlcant f~o~ the abraslve saw ~ashes ~way ~che concrete
and the smalles ~ggre~te, bu~ does cu~ throu~h th2 larger
~gr~gate which i~ bound by the cemene. A conventicnal
ro~a~y hsnd saw with a ~lade des~ned ~or cutting concrete
still produces a ~ag8ed cut with partlal blockage of the
cut, ~nd al~o leaves ~arks fro~ the pla~e contactlng the
concrete 13.
When the rod ~akes ~n indentation of about 1/8 o~ an
~nch, the saw 10 still ~ak~s a good cu~, with 8
percep~ble, but small ~ndent~tion in the concrete ~rom
the wheels 14 through 20 ~nd the ~k~d plate 24.
Convent~onsl ~aws do not work ~lnce the water lubr$cated
~brsslve saw Dtill washe~ y the concrete adjaeent ~he
cu~ groove, and lts wheels leave not~ceable ~ndentations
1 30~62~
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~n the ~urface of the concrete 13. The mid ~o large 6ized
ag~rega~e ~djacent the surface of the cut groove is
~hipped out of ~he way leaving cavieiesO If the wa~er is
not used, the cut groove ills up with concrete. The
conventional rotary hand saw 8~ eaYes a ~ag8ed edge to
the cut groove.
When the rod makes a perceptlble round indentation of
abou~ 1l32 to 1/16 of an ~neh, the ~aw 10 produces a good
quality cut with ~mooth ~dges, snd ~lmo6~ no perceptlble
marks f~om the wheels 14 through 20 and ~kid plate 24.
Even at this stage, ehe ha~dness of the concre~e ls not
sufficient to allow ~easure~ent by the Swi~8 Ham~er.
Conventlonal saws ~tlll do no~ work at thi5 concrete
hardness. The water lubric~ted abrasive 6aw leaves a cut
wieh rounded edge~, and cavltle~ where the aRgregaee and
80~e ~urroundlng cement are chipped away. If the water ls
no~ used, the edges are ~ot 80 rounded, but ~he cavlties
rema~n. The convent~onal rotary ~aw wit~ a blade des$gned
~or cutt~ng concrete al80 ha~ chlpped and rough edges,
wl~h ~esidu~l cracking ~rsund ~he a~gregate ad~acent the
edge of the cue groove.
Convention~L conc~e~e ~aws, wi~h a blade rot~tlng a~
about 1700 rpm, produce a ~1n$mally ~ccep~able cut ~roove
when the concrete 13 has reached a hardness well in excess
o 1200 pound6 p~r square inch tpsi), as ~easured by a
Swl~s Hammer. Thls hardne~s typ~cally does not occur
until the next day, a~ prev~ously ~entioned. At this
hardness, there i6 ~ome ohlpplng and roughness a~ the
edges o~ the cut groove, but the re~ulting cavities,
cr~ck~, and roughness are relatively ~all, ranging fro~
the ~l~e of the ~nd used ln the concrete to sbout 1/8 of
an l~ch and lar~er~
A convent~onal ~otary saw with a blade designed to cut
concrete, ~d with a rotational speed of about 11,000 rpm,
does not beg~n ~o produce a cut groove with a quality th~t
I~ appro~ching an acceptable quallty, until ehe concrete
1 3C',~2~
-33-
has reached a hardness o~ about 1200 p8i or higher,
Again, there is some eracking, chipping and roughness at
the edges o:E the cut groove, bu~ the ~ize of the cavities
and roughness are relatively small as described above.
~S
