CA1308628C - Soft concrete saw - Google Patents

Abstract

SOFT CONCRETE SAW
ABSTRACT
In order to cut soft concrete before it has completely hardened, or about 12 to 18 hours after finishing, a rotating cutting blade and its drive motor are mounted on a wheeled support platform. The blade extends through a slot in the platform, and also through a skid plate depending from the platform, in order to cut the concrete below the skid plate. The slot and the skid plate are sized to support the concrete as it is being cut and to inhibit cracking and chipping of the concrete during cutting. The slot preferably has as little space as possible between the sides of the slot and the adjacent sides of the cutting blade. An extendable handle allows the device to be used beyond the physical reach of the operator.

Description

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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~

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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.
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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~

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.

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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.

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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 ~

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 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.

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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~

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 ~

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~

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~

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~

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~

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~

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~

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~

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~

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 1 3C",62~
-2~-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.

-"` 1 3C3~2~

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 -` 1 3~,62~

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 1 3C~2~

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~

~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~

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

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
1. A skid plate for use with a saw, comprising:
a skid plate having a slot therein through which a cutting blade extends to cut a surface, the slot having a leading end which contacts said surface during cutting a length extending beyond the cutting edge of the cutting blade, and a trailing end which is not in contact with said surface during cutting, when the entire skid plate is resting on the surface being cut.
2. A skid plate for use with a saw for cutting grooves in a surface, by means of a rotating cutting blade which extends through a slot in the skid plate to cut said surface, compris-ing:
a skid plate configured so that the skid plate contacts said surface concrete being cut beyond the cutting edge of the cutting blade, but configured so that the skid plate does not contact the surface immediately adjacent the groove cut in the surface by the rotating cutting blade after the cutting blade has completed the cut.
3. A skid plate for use with a saw for cutting grooves in a surface by means of a rotating cutting blade which extends through a slot in the skid plate to cut surface, the cutting blade having a leading cutting edge. and a trailing edge, comprising:
a skid plate having a first edge curved away from the surface on which the skid plate rests during cutting, and a second edge located opposite the first edge, and also curved away from the surface on which the skid plate rests during cutting, the skid plate having a slot therein extending beyond the cutting edge of the cutting blade from adjacent the first edge toward the second edge, the slot extending into the curved portion of the second edge of the skid plate so the skid plate does not contact the surface beyond the trailing edge of the cutting blade in the area immediately adjacent the cut in the surface.
4. A skid plate for use with a saw for cutting a concrete surface by means of a rotating cutting blade which extends through a slot in the skid plate to cut the surface, the cutting blade having a leading cutting edge, and a trailing edge, comprising:
a substantially rectangular sheet of material having a leading end and a trailing end opposite thereto, with the leading end being adjacent the cutting edge of the cutting blade during cutting, the skid plate having a slot therein through which the cutting blade extends to cut the surface, the slot extending to at least that portion of the trailing end which contacts the surface so the trailing edge does not contact the surface beyond the trailing edge of the cutting blade in the area immediately adjacent the cut in the surface when the entire skid plate is resting on the surface being cut.
5. A skid plate as described in Claim 4, wherein the skid plate has a width adjacent the length of the slot suffi-cient to allow any cut concrete removed by the cutting blade and falling on to the adjacent width of the skid plate, to harden sufficiently so that it will not stick to the concrete surface being cut.
6. An apparatus for use with a saw for cutting concrete, comprising:
a skid plate for use with a concrete saw, the skid plate having a slot therein through which a concrete cutting blade can extend, the concrete cutting blade having a leading cutting edge and sides, the slot having a correspondingly located leading end and sides, the slot being so dimensioned that the spacing between the sides of the concrete cutting blade and the immediately adjacent sides of the slot are less than 3/32 of an inch.
7. The apparatus of Claim 6, wherein the slot is so dimensioned that the spacing between the sides of the concrete cutting blade and the immediately adjacent sides of the slot are less than 1/16 of an inch.
8. The apparatus of Claim 6, wherein the slot is so dimensioned that the spacing between the sides of the concrete cutting blade and the immediately adjacent sides of the slot are less than 1/32 of an inch.

9. An apparatus for use with a saw for cutting concrete, comprising:
a skid plate for use with a concrete saw, the skid plate having a slot therein through which a concrete cutting blade can extend, the concrete cutting blade having a leading cutting edge and sides, the slot having a correspondingly located leading end and sides, the slot being so dimensioned that the spacing between the sides of the concrete cutting blade and the immediately adjacent sides of the slot are less than 3/32 of an inch along at least a substantial length of the slot, beginning at the cutting edge.
10. The apparatus of Claim 9, wherein the slot is so dimensioned that the spacing between the sides of the concrete cutting blade and the immediately adjacent sides of the slot are less than 1/16 of an inch.
11. The apparatus of Claim 9, wherein the slot is so dimensioned that the spacing between the sides of the concrete cutting blade and the immediately adjacent sides of the slot are less than 1/32 of an inch.
12. An apparatus for use with a saw for cutting concrete, comprising:
a skid plate for use with a concrete saw, the skid plate having a slot therein through which a concrete cutting blade can extend, the concrete cutting blade having a leading cutting edge and sides, the slot having a correspondingly located leading end and sides, the slot being so dimensioned that the spacing between the sides of the concrete cutting blade at the cutting edge of the blade and the immediately adjacent sides of the slot are less than 3/32 of an inch.
13. The apparatus of Claim 12, wherein the slot is so dimensioned that the spacing between the sides of the concrete cutting blade at the cutting edge of the blade and the im-mediately adjacent sides of the slot are less than 1/16 of an inch.
14. The apparatus of Claim 12, wherein the slot is so dimensioned that the spacing between the sides of the concrete cutting blade at the cutting edge of the blade and the im-mediately adjacent sides of the slot are less than l/32 of an inch.
15. The apparatus according to any one of Claims 6, 7, or 8, wherein the slot has a leading end adjacent the cutting edge. and a trailing end opposite the leading end, and wherein the leading end of the slot is in contact with the surface of the concrete during cutting, and a trailing end of the slot is not in contact with the surface of the concrete during cutting.
16. The apparatus of Claims 12, 13 or 14, wherein the slot has a leading end adjacent the cutting edge, and a trailing end opposite the leading end, and wherein the leading end of the slot is in contact with the surface of the concrete during cutting, and a trailing end of the slot is not in contact with the surface of the concrete during cutting.
17. The apparatus of Claims 12, 13, or 14, wherein the slot has a leading end adjacent the cutting edge, and a trailing end opposite the leading end, and wherein the leading end of the slot is in contact with the surface of the concrete during cutting, and a trailing end of the slot is not in contact with the surface of the concrete during cutting.
18. A saw as defined in Claim 13, wherein the distance between the leading edge of the cutting blade and the leading end of the slot is about 1/4 inch.
19. A depending skid plate for use with a wheeled saw having an upcutting rotating cutting blade for cutting concrete, and having a base rollably supported on wheels a predetermined distance above the surface of the concrete, comprising:
two mounting portions configured to secure the skid plate to the base so that the skid plate does not move relative to the saw during use;
a support plate having a flat portion with a lon-gitudinal slot therein, said slot positioned relative to the mounting portions so that the cutting blade extends through the slot to permit cutting of the concrete surface, the support plate being so dimensioned that it depends from the two mounting portions a distance sufficient to place substantially all of the flat portion of the support plate in contact with the concrete surface when the skid plate is mounted on the saw so that the flat portion of the skid plate is substantially parallel to the concrete surface being cut, with the slot being so dimensioned as to in inhibit chipping, spalling, and cracking of the concrete during cutting, the slot and the support plate having corresponding leading and trailing ends, with the leading end of the support plate curving toward the adjacent mounting portion, and with the leading end of the slot ending in the flat portion of the support plate.
20. A depending skid plate as defined in Claim 19, further comprising:
a tunnel in the skid plate extending from the trailing end of the slot into the trailing end of the support plate, the tunnel being configured to prevent the support plate from significantly trowelling the groove which is cut into the surface by the trailing end of the support plate.
21. A depending skid plate as defined in Claim 19, wherein the trailing end of the support plate curves toward the adjacent mounting portion, and wherein the trailing end of the slot extends into the curved portion at the trailing end, with the slot being configured to prevent substantial trowelling by the trailing end of the support plate whereby the skid plate does not compromise the quality of the groove which is cut into the surface by the rotating cutting blade.
22. A depending skid plate as defined in any one of Claims 19, 20 or 21 wherein the width of the slot is dimensioned such that there is a space of less than 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.
23. A depending skid plate as defined in any one of Claims 19, 20 or 21 wherein the width of the slot is dimensioned such that there is a space of between 1/64 and 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.
24. A skid plate for use with a wheeled saw with an upcutting rotating cutting blade for cutting unhardened concrete and having a base rollably supported on wheels a predetermined distance above the surface of the concrete, comprising:

two mounting portions configured to secure the skid plate to the base so that the skid plate does not move relative to the saw during use;
a support plate having a flat portion with a lon-gitudinal slot therein, said slot positioned relative to the mounting portions so that the cutting blade extends through the slot to permit cutting of the concrete surface, the support plate being so dimensioned that (i) it depends from the two mounting portions a distance sufficient to place substantially all of the flat portion of the support plate in substantially uniform contact with the concrete surface during cutting when the skid plate is mounted on the saw, and (ii) the flat portion supports a portion of the weight of the saw on the concrete surface during cutting without marring the surface of the concrete, the slot and the support plate having corresponding leading and trailing ends, with the leading end of the support plate curving toward the adjacent mounting portion, and with the leading end of the slot ending in the flat portion of the support plate.
25. A skid plate as defined in Claim 24, further comprising:
a tunnel in the skid plate extending from the trailing end of the slot into the trailing end of the support plate, the tunnel being configured to prevent the support plate from significantly trowelling the groove which is cut into the surface by the rotating cutting blade whereby the skid plate does not compromise the quality of that groove.
26. A depending skid plate as defined in Claim 24, wherein the trailing end of the support plate curves toward the adjacent mounting portion, and wherein the trailing end of the slot extends into the curved portion at the trailing end, with the slot being configured to prevent substantial trowelling by the trailing end of the support plate whereby the skid plate does not compromise the quality of the groove which is cut into the surface by the rotating cutting blade.
27. A depending skid plate as defined in any one of Claims 24, 25 or 26 wherein the width of the slot is dimensioned such that there is a space of less than 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.
28. A depending skid plate as defined in any one of Claims 24, 25 or 26 wherein the width of the slot is dimensioned such that there is a space of between 1/64 and 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.
29. A depending skid plate for use with a portable concrete cutting saw, comprising:
a substantially flat support portion having a slot therein through which a concrete cutting blade can extend to cut a concrete surface when substantially all of the flat portion is resting on the concrete surface being cut, the slot having a leading end and a trailing end, the flat portion having a corresponding leading end and trailing end;
a first connecting portion substantially parallel to the flat support portion but offset from the support portion to enable one end of the skid plate to be connected to the saw, the first connecting portion being structurally connected to the flat support portion by a curved surface at the leading end of the flat support portion;
a second connecting portion substantially parallel to the flat support portion but offset from the support portion to enable one end of the skid plate to be connected to the saw, the second connecting portion being structurally connected to the flat support portion adjacent the trailing end of the flat support.
30. A skid plate as defined in Claim 29, wherein the second connecting portion is structurally connected to the flat support portion by a curved surface at the trailing end of the flat support.
31. A skid plate as defined in Claim 30, wherein the slot extends into the curved portion of the trailing end of the flat support, the slot being dimensioned so that the trailing end of the support does not compromise the quality of the groove previously cut into the surface by the cutting blade.
32. A skid plate as defined in Claim 29, wherein the support portion contains a tunnel extending from the trailing end of the slot into the curved surface at the trailing end of the flat support, the tunnel being dimensioned so that the trailing end of the support does not compromise the quality of the groove previously cut into the surface by the cutting blade.
33. An offset skid plate for use with a portable concrete cutting saw, comprising:
a generally rectangular strip of metal having two rounded ends between which is a flat piece, the flat piece having a slot therein through which a concrete cutting blade can extend to cut a concrete surface when substantially all of the flat piece is resting on the concrete surface being cut, the slot and flat piece having corresponding leading ends and trailing ends, the rounded ends being connected to two generally flat connecting ends which are substantially parallel to the flat piece but offset from the flat piece to enable the skid plate to be connected to the saw.
34. An offset skid plate as defined in Claim 33, further comprising:
a tunnel in the skid plate adjacent the trailing end of the flat piece, the tunnel being configured so that the strip of metal does not contact the groove cut into the surface by the rotating cutting blade.
35. An offset skid plate as defined in Claim 33, wherein the trailing end of the slot extends into the adjacent rounded end, so that the trailing end of the slot does not contact the groove cut into the surface by the cutting blade.
36. An offset skid plate as defined in any one of Claims 33, 34 or 35 wherein the width of the slot is dimensioned such that there is a space of less than 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.
37. An offset skid plate as defined in any one of Claims 33, 34 or 35 wherein the width of the slot is dimensioned such that there is a space of between 1/64 and 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.

38. A depending skid plate for use with a portable concrete cutting saw, comprising:
two substantially flat connecting plates lying in a first plane and joined to opposite ends of a flat support plate which depends from the two connecting plates to lie in a second plane substantially parallel to the first plane, the support plate having a slot therein with the support plate and the slot having corresponding leading and trailing ends, the support plate curving toward the connecting portion to which it is joined adjacent the leading end of the support plate.
39. A depending skid plate as defined in Claim 38, further comprising:
a tunnel in the support plate disposed adjacent the trailing end of the slot and extending into the trailing end of the support plate so that the skid plate does not contact the groove cut into the surface by the rotating cutting blade.
40. A depending skid plate as defined in Claim 38, wherein trailing end of the slot extends to the trailing end of the support plate so that the trailing end of the support plate does not contact the groove cut into the surface by the cutting blade.
41. A depending skid plate as defined in Claim 40, wherein the trailing end of the support plate has a curved portion which curves toward the connecting portion to which it is joined, with the slot extending into that curved portion.
42. A depending skid plate as defined in any one of Claims 38, 39 or 40, wherein the width of the slot is dimensioned such that there is a space of less than 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.
43. A depending skid plate as defined in any one of Claims 38, 39 or 40, wherein the width of the slot is dimensioned such that there is a space of between 1/64 and 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.
44. An offset skid plate for use with a portable concrete cutting saw, comprising:

a flat support portion for supporting the saw on the surface being cut, the flat portion having a slot therein with a first and second end, the flat portion having corresponding first and second ends which curve away from the surface being cut and also curve in the opposite direction to form first and second co-planer connecting portions which are offset from, but substantially parallel to the support portion.
45. An offset skid plate as defined in Claim 44, wherein the slot extends into the curve at one end of the flat portion so that the skid plate does not trowel over the groove cut into the surface by the cutting blade.
46. An offset skid plate as defined in Claim 44, further comprising:
a tunnel at one end of the flat portion, the tunnel being configured so that the skid plate does not trowel over the groove cut into the surface by the cutting blade.
47. A depending skid plate as defined in any one of Claims 44, 45 or 46, wherein the width of the slot is so dimensioned that there is a space of less than 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.
48. A depending skid plate as defined in any one of Claims 44, 45 or 46, wherein the width of the slot is so dimensioned that there is a space of between 1/32 and 3/32 of an inch between the edges of the slot and the adjacent cutting edge of the blade when the blade is positioned in the slot for cutting.