AU631946B2 - A saw for cutting unhardened concrete - Google Patents

Description

UI MU La [i or UAV1LS UULLISON CAVE for and on behalf of thle Applicants).

92l008,q:\opcr\kay,67013.res,5 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION (Original) FOR OFFICE USE Class Int. Class Application Number: Lodged: Complete Specification Lodged: Accepted: Published: Priority: Related Art: It I'

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00 CO o 0 o 0 0*0000 0 0004 40*0 444 Name of Applicant: Address of Applicant: Actual Inventor(s):.

Address for Service: Edward Chiurninatta and Alan Ray Chiurninatta 16405 Evrett, Riverside, California 92504; 3855 Skofstad, Apartment No. 33, Riverside, California 92504, both of the United States respectively.

Edward Chiurninatta and Alan Ray Chiuminatta DAVIES COLLISON, Patent Attorneys, 1 Little Collins Street, Melbourne, 3000.

4 0 0000 4 0 t I 0*0 0 0 4*00 0000 0 0 0 00 0 0000 Complete Specification for the invention entitled: 'A saw for cutting unhardened concrete" *0 0*0 0 0 0 0 00 The following statement is a full description of this invention, including the best method of performing it known to us: -1 901122,gjndat.014 4 ky15l62.div,l ii t A SAW FOR CUTTING UNHARDENED CONCRETE This invention relates to a saw for cutting concrete, which is a combination of a hydraulic cementing substance, aggregate, water and, often, other substances to impart specific properties to the concrete.

When concrete is poured, it is typically in a watery or flowing state which allows the concrete to be spread evenly over floors. After a period of time, varying with the mixture of the concrete, the temperature, and the moisture availability, the concrete attains a workable plasticity which permits the surface of the concrete to be toformed and to retain a finish. Typical finishing means include troweling, rubbing, or brushing. Applying the desired surface texture is called "finishing"k the concrete, and may involve repeated steps to sequentially refine the surface finish.

4 After the concrete is finished, it is allowed to stand for a period of time during which the concrete cures to obtain its well-known, rock-like hardness. The curing or setting time depends on the moisture available, the o temperature, and the specific additives added to the~ do concrete to affect the curing time. As the concrete cures, it undergoes thermal stresses causing the concrete to expand and contract in various manners depending on the shape and thickness of the concrete and the type of concrete. These thermal stresses can cause cracking. The Sfully cured and hardened concrete also expands and 0.:contracts due to temperature changes with the result that cracks form in the concrete.

It is common practice to provide slots or grooves at predetermined intervals in the concrete. If the grooves extend all the way through the concrete, they can act as an expansion or contraction joint to help prevent cracking of the concrete. If the grooves are only on the surface of the concrete, then the grooves cause the cracks to form I -2along the grooves so that they occur at regular intervals and are not visible. The grooves, but not the cracks, are ;ing visible.

:es One advantage to placing the grooves in the soft concrete is that a weakened plane is provided by the groove and that weakened plane is now installed before the latery concrete starts to cure and shrink. The concrete slab will pread typically seek out the weakened plane to crack in if the with p plane is prematurely there.

Sthe 10 Presently, these grooves are provided by forming or kable 10 c grooving a slot in the concrete with a grooving trowel, to be while the concrete is still wet, just after pouring. This omeans o grooving is done while the concrete is very wet and before thethe concrete is sufficiently hard to support a person's rete, i 15 weight. Thus, this grooving typically requires a support s the structure which would enable the person doing the grooving to reach the interiors of concrete slabs without placing stand o o the person's weight on the concrete. When the concrete .olt s to slabs become sufficiently large, this method of providing rg or 20 grooves proves impractical and expensive.

the This type of grooving must be done when the concrete is sufficiently wet, otherwise, the grooving trowel cannot ures, 0000 ures, shove entrained rocks out of the way without it disrupting 0 e to the surface finish on the concrete. Essentially, the Sthe .1 25 concrete must be grooved just after it is has just been e of ofpoured, at which time the concrete is so wet that the The Tne concrete sometimes tends to sag back together and close the and l groove, thus requiring repeated grooving to maintain a that B desired groove depth or shape. o For very large slabs of concrete, manually grooving e s at the freshly poured concrete is impractical or very ooves inconvenient and expensive. For such large slabs, the as an concrete is typically allowed to harden or set. Grooves rig of are then cut in the surface of the concrete by use of a ,e of 35 high-powered, rotating, abrasive saw blade, often form lubricated with water. The blade is typically made of itI macl rva is bef are diamond abrasive material and is provided with a liquid coolant and lubricant to facilitate cutting the hardened 5 pro concrete. rep soft ~oveSince these concrete cutting machines tend to be the heavy, the concrete must be fairly hard in order to support al s tthe will weight of the machine and operator. Further, if the mai concrete is not sufficiently hard when cut, these machines 10 con the produce an unacceptably rough cut with a chipped or g rcracked surface along the groove. However, the harder the fas wl or 10 concrete, the more difficult it is to cut. con This It is possible to use a hand held rotary saw as is ~foe 00 0often used in cutting lumber, but using a blade designed to 15 the 3on' l0 cut concrete. Su_-h saws are lighter weight, but still Icon ~por 0 0require hard concrete to support the operator and to wving .0.1~15 provide cut grooves with acceptable smooth edges. des 00 On an extremely hot and dry day, the concrete may be icing ree:sufficiently hard to support a person's weight and not 20 bla dngleave a permanent indentation about twelve hours after thean concrete has been poured. Typically, the concrete is not fin 20 walked upon or, cut until at least the next day, or about suc ,,rete 001 iihd n 8hours after the concrete has been 0iise.0n ~~nnot If the concrete is cut by a conventional water025m tiglubricated, diamond-abrasive saw, the earliest it can be 4.of the been cut is the next day after finishing (about 18 hours), and 0 b been0 the 0:00even then, an unacceptable cut is typically produced as the0 Sthe edges of the concrete by the groove tend to chip, spall, 00and crack. 30 suf in ba 0 One major problem with cutting after thle concrete l cures and hardens is that between the time of the initial a >ving 00 finish and the time it becomes practical for a conventional b the ~concrete saw to be used, the concrete slab will have 3 c )ovesstarted its normal characteristic to shrink as it dries, of a thus causing contraction stress and invariably cracking ,ftenbefore the sawing of contraction joints can be performed.

e f35 This characteristic shrinking usually takes place somewhere between the time the initial finish is completed and before lowi40000 -4it becomes practical to put a conventional saw-cutting machine on the slab. The result is cracking of the slab before the saw cutting can be initiated.

Further, cutting the hard concrete is a slow process, which is slowed still further to periodically replace the cutting blades as they abrade away. Finally, these types of machines tend to be not only bulky, but also expensive and time consuming to operate and maintain. The noise of the saw abrading the hardened concrete is also very loud and unpleasant.

There thus exists a need to provide an easier and faster apparatus and method for putting grooves in concrete before the concrete cracks.

According to a first aspect of the present invention there is provided a method of cutting grooves in concrete, comprising the steps of: finishing an exterior surface of the concrete to a desired finishing stage; cutting a groove in said surface with a rotating ~20 blade having an up-cut rotation and having a cutting edge and sides, said cutting step occurring after said finishing step, but before said concrete has a hardness such that a 1.125 inch diameter steel rod with a flat end and weighing about 5.75 pounds, would cause an indentation in the surface of the concrete of about 1/32 of an inch when said rod is dropped from a height of o about 24 inches above the surface of the concrete; and supporting said surface immediately adjacent said sides of said rotating blade by means of support means 30 sufficiently close and along a portion of said rotating blade sufficient to prevent damage to said surface as said groove is cut.

Embodiments of the invention will now be described by way of example only, with reference to the accompanying drawings in which:- Figure 1 is a perspective view of an embodiment of 921007,gjnspe.os,1516Z4iv, 4 ~1 the invention being operated in the middle of a slab of concrete; Figure 2 is an elevated perspective view of the front of the saw showing the motor and blade in a lowered position; Figure 3 is a lower perspective view of the saw showing the motor and blade in a raised position; Figure 4 is an elevated perspective view of the back of the saw; Figure 5 is a top elevational view of the saw; Figure 6 is a side elevational view of the saw in operation; Figure 7 is an elevational view of the saw blade and slot in the skid plate; Figure 8 is a perspective view of an alternate embodiment of this invention; Figure 9 is a sectional view taken along A-A of Figure 8, showing an alternate embodiment of this invention; Figure 10 is a sectional view taken along A-A of Figure 8, showing an alternate embodiment of this 0a°. invention; Figure 11 is a sectional view taken along A-A of I Figure 8 showing an alternate embodiment of this Sa a 25 invention; and Figure 12 shows how the quality of the cut groove is 92007,gnspe.0051516div5 *0 o I. a oo ao a a v 921007,gjnspe.005,15162.div,5 i 1SXlii~3~~m H -6affected by the spacing between the cutting blade and the sides of the aperture in the base plate.

As is shown in Figure 1, by way of illustration and not by limitation, a soft concrete saw 10 comprises a i 5 base plate 12 having a generally rectangular shape. The i base plate 12 has a lower surface generally facing a slab of o q t s 9a 9 01120,jns .5,1516.div,6 ^00 j I O 0 t 0 .j Q *i *I f e i s 912,jseo sl12i, 44415 254 -7concrete 13, with an upper surface of the base plate facing away from the concrete 13.

Along one of the longer sides of the rectangular plate 12 there are attached two front wheels 14 and 16 and a rear wheel 18. On the other long side of the rectangular base plate 12, generally opposite the rear wheel 18, is located a rear wheel 20. The rear wheel 20 sits in a recess 22 (Figure 4) in the base plate 12 such that the edge of the rear wheel 20 does not project beyond the edge of the generally rectangular base plate 12, as described in more detail hereinafter.

A support surface or plate is in movable contact with the surface of the concrete 13 in order to support the surface of the concrete immediately adjacent the groove being cut in the concrete 13. In the illustrated embodiment, this surface takes the form of a skid plate 24 which depends from the base plate 12 in the direction of the concrete 13. The skid plate 24 is on the same side of the base plate 12 as is the recess 22 and the rear wheel 20, and is adjacent the longer edge of the base plate 12.

The skid plate is opposite the front wheels 14 and 16.

In normal use, the saw 10 is supported on the concrete 13 at three points, the skid plate 24, the front wheel 14, and the rear wheel 18. It is believed that the three points of contact provide a more stable support and cause less wobble of the saw 10 than would other support methods.

The wheels 16 and 20 are spaced approxim~ately .125 to of an inch from the plane defined by the skid plate 24 and wheels 14 and 18, so that the wheels 16 and 20 do not normally contact the concrete 13 as the soft concrete saw is operated. The purpose of the wheels 16 and 20 will be described later.

The wheels 14, 16, 18 and 20 can be the same wheels as used on roller skates or skateboards. The wheels are approximately 2.5 inches in diameter and 2.5 inches wide.

The wheels are mounted to the base plate 12 so as to rotate -8freely as the base plate 12 and saw 10 move along the concrete 13.

Referring to Figures 2 and 3, the skid plate 24 is a generally rectangular strip of metal having rounded ends 26 and 28 between which is a flat piece 30. The flat piece is generally parallel to the base plate 12. The flat piece contacts the concrete 13 in order to help support the weight of the saw 10. The rounded ends 26 and 28 prevent gouging the surface of the soft concrete 13 as the saw cuts the concrete 13.

The area of the skid plate 24 in contact with the concrete 13 and the area of the wheels 14 and 18 which p falso help support the weight of the saw 10, are all sized to provide a large enough area to distribute the weight of 0 Q the saw 10 without detrimentally marking or substantially damaging the surface finish on the soft concrete 13 which os is being cut.

o t o Referring to Figures 2 and 4, on the upper surface of plate 12 is mounted a motor 32. The motor 32 drives a rotating cutting means such as circular saw blade 34 (Figure 4) which in turn cuts the concrete 13 (Figure 2) to 0 0 form a groove.

oK. Referring to Figure 2, saw blade 34 is typically circular and made or carborundum, or diamond coated steel.

25 The blade 34 has two generally flat sides, a leading or 0 -K cutting edge, and a trailing edge. The saw blade 34 typically has little or no kerf or tooth offset. Slots in the saw blade 34 carry the cut concrete out of the 0 concrete 13 to leave a groove or slot in the concrete. In the illustrated embodiment, a 4.25-inch diameter saw blade is used. Such blades are commercially available.

The saw blade 34 rotates about an axis substantially parallel to the base plate 12, and substantially perpendicular to the direction of travel of the saw The saw blade 34 thus rotates in a plane which is substantially parallel to the longer edges of the i- z~~pl e 0 r 0 40 0 0 j 0 0 -9rectangular base plate 12, and substantially parallel to the direction of travel of the saw Referring to Figures 2 and 3, the saw blade 34 extends through an aperture such as a slot 36 (Figure 2) in the base plate 12 and also through an aperture such as a slot 38 (Figure 3) in the skid plate 24, in order to cut the concrete 13 (Figure Thus, the slot 36 is a generally rectangular slot located substantially parallel to and along the length of the longer sides of the base plate 12.

Spaced below, and in substantial alignment with slot 36, is slot 38. The slot 38 is also generally rectangular in shape, and is placed in the flat piece 30 of skid plate 24. The width and length of slots 36 and 38 are sufficiently large so that the saw blade 34 does not bind and seize on the edges of those slots.

Referring to Figure 2, the saw blade 34 rotates with an up-cut motion such that the rotation of the cutting edge of the saw blade 34 is out of the concrete 13 which is being cut, rather than being into the concrete 13.

Alternately phrased, the rotation of the circular blade 34 is such as to impede the forward motion of the saw rather helping pull the saw 10 in the direction of travel.

This up-cut saw rotation is used to remove the soft concrete from the groove cut by the saw blade 34. If the saw blade 34 had a down cut rotation, then the soft concrete cleared by the blade 34 could fill in the groove immediately behind the blade 34, effectively filling in the groove with soft concrete. The up-cut rotation removes the concrete 13 from the cut groove and helps prevent the return of that removed concrete from filling in and hardening in the slot.

This up-cut rotation of the blade 34 is contrary to conventional wisdom and usage which essentially says that the blade 34 should cut into the surface on which the quality of the surface finish adjacent the cut groove is important. Since the surface finish is important only on C 0 4 z0 2.9 64 00 Fc;c;ith dge is 13.

34 1.

oft the oft ove the the the and to :hat the Sis on -,Do o Do the visible surface of the concrete 13, conventional practice would require a down-cut rotation.

The reason for conventional practice is believed to be that the down-cut rotation relies on the mass of the concrete, into which the blade is cutting, to support the concrete adjacent the blade and to provide an acceptable quality of cut. Concrete has much better compressive capability than tensile capability. The down-cut rotation keeps the concrete adjacent the groove in compression, which minimizes chipping and cracking. The up-cut rotation places the concrete adjacent the groove in tension, which with a conventional concrete cutting device, would result in unacceptable chipping and cracking of the concrete adjacent the surface of the cut groove.

A safety shield 40 is connected to the motor 32 so as to surround and shield the portion of the cutting blade 34 which does not project through the slot 36 in base plate 12. The motor 32, shield 40, and blade 34 thus form an integral unit in the illustrated embodiment. In fact, it is believed possible to use a commercially available wood saw, sometimes called a circular hand saw, as the basic motor 32 and shield 40 of this invention. References to these parts as an integral unit does not mean, however, that they could not be separate components performing the same function.

For reasons described later, it is desirable to have the blade 34 movably mounted so that the blade 34 can yieldingly move in response to contact with obstacles in the concrete 13. In the illustrated embodiment, as shown in Figures 4 and 5, the motor 32, and thus the blade 34, is pivotally mounted to base plate 12 so as to rotate about an axis which is substantially parallel to the rotational axis of blade 34 (Figure There is thus a pivot shaft 42 which has one end connected to motor 32 via a bracket 44, with the other end of the shaft 42 being connected to the shield 40. The pivot shaft 42 is rotatably connected to ii I a 77p tj 4 .1 lIll 4 60 .6 '3 6 300 14

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ft -24- I- c~..~-.lnr.r.nlpi~-nZ~m jnal 2 be the the able 3ive :ion ion, -ion ich ;ult -ete as 34 ate an it rood Sic to 'er, the ave can in own is an xis 42 44, the to

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44r Ii 0 t rP -11the base plate 12 by trunnions 46. The longitudinal axis of pivot shaft 42 is substantially parallel to the rotational axis of motor 32 and is substantially perpendicular to the direction in which the concrete 13 (Figure 2) is to be cut, grooved, or slotted.

In the illustrated embodiment there is a means for resiliently urging the blade 34 against the concrete 13 with a predetermined force. This resilient means preferably takes the form of resilient spring means as follows.

Referring to Figures 2 and 5, attached to the shield at the end of the shield which is opposite the connection with pivot shaft 42 is a projection 48.

Referring now to Figures 2 and 6, projection 48 is on the exterior of the shield 40, away from the blade 34, and contains a notch or engaging aperture such as aperture 50.

A tension spring 52 has one end engaging or connected to the aperture 50, with the other end of spring 52 connected to a post 54. The post 54 is connected to base plate 12 adjacent the motor 32 and is substantially perpendicular to the surface of the base plate 12.

In the illustrated embodiment, the spring 52 supports a portion of the weight of the motor 32, blade 34, and shield 40 so as to adjust or regulate the amount of force with which the blai 34 is forced against the concrete 13.

Several factors can be varied to control the amount of force which the blade 34 exerts on the concrete 13 during cutting. Such factors would include the distance between the pivot shaft 42 and the motor 32, the distance between the pivot shaft 42 and the spring 52, the type, size and method of mounting of the spring 52, and the weight of the motor 32.

In the illustrated embodiment, a 7.5 amp, 11,000 rpm motor 32 weighing about 6.2 pounds is connected to a spring 52 having a diameter of 3/8 of an inch and an uncompressed length of 1.75 inches. The spacing between the spring 52 i f 0 0 0 0I 44 00"0 4440 444 4401 4 44 *4 4 0*40 (000 2nO 00: 0 0 00d 00404 000* 84d\ 8 48 00 0 4 4 4.

1 1 I 0 L i p00,; ~rl~nr IIs~la~- -12and the pivot shaft 42 is approximately 7.5 inches. The distance between the center line of the motor 32 (and the rotational axis of blade 34) and the pivot shaft 42 is approximately 3.5 inches.

Referring to Figure 6, the force exerted by spring 52, and the resulting force exerted by blade 34 on the concrete 13, affects the quality of the slot or groove which is cut in the concrete 13. The concrete 13 is an aggregate of rock and cement with the rock being of variable size depending upon the requirements for the strength of the concrete 13. When the blade 34 hits a rock or other obstruction buried in the concrete 13 problems can arise.

The tension on the spring 52 can be adjusted to reduce these problems and to accommodate varying sizes of aggregate in the concrete 13.

If the motor 32 and blade 34 are rigidly mounted to the base plate 12 then the entire concrete saw 10 can conceivably come to a jolting halt until the blade 34 can cut through the entrained rock. Alternatively, if the 0 .4..20concrete 13 is soft enough, the rock may be slightly pushed out of the way which can cause surface damage, an unacceptable saw cut, or residual cracking before the rock can be cut through. Still further, the saw 10 could bounce up so as to disengage the blade 34 or the skid plate 34 from contact with the concrete 13. In each of these cases, the sudden halt or change in the motion of concrete .44can mar the surface finish of the concrete 13. Perhaps more importantly, the sudden impact of the blade 34 with the rock can jar the rock sufficiently to cause residual cracking of the concrete around the rock.

Similar results can occur if the blade 34 is mounted so that a predetermined force can cause the blade to move separate from the base plate 1-1, but an excessive force is exerted by the blade 34 on the concrete 13. The concrete can crack, a rough cut is made, and the surface finish of the concrete can be impaired.

0 0 00 3 0 13- The goal of the spring 52 and the pivoting of the motor 32 and blade 34 is to allow adjustment of the force between the. blade 34 and the concrete 13, and to alow movement of the blade 34, so that the contact between the blade 34 and an entrained obstacle, such as a rock, does not damage the surface of the concrete 13 or cause residual cracking of the concrete 13.

For the illustrated embodiment, the weight or force exerted by the motor 32, shield 40 and blade 34 is about pounds, which is greater than desired. In the illustrated embodiment, the spring 52 off-loads a portion of the weight so that only about 2.5-3.0 pounds of force are exerted by the blade 34 on the concrete 13. Thus, the blade 34 is resiliently urged into contact with the concrete with a force of about three pounds. If needed, the extension spring 52 could be readjusted or replaced with an appropriately sized spring in order to provide the desired predetermined force between the blade 34 and the concrete 13.

one result of adjusting the force between the blade 34 and the concrete 13 is that the depth of the groove cut by the blade 34 can vary depending on how fast the saw 10 is moved. Further, the depth of the groove may be less when the blade 34 hits rocks entrained in the concrete 13. For example, it is believed preferable for the depth of the grooves cut by saw 10 to be about .5 inch deep, with a -minimum depth of .125 inch being marginally acceptable.

As the force of the spring 52 off-loads more and more of the force exerted by blade 34, the blade 34 will cut a shallower and shallower groove for a constant travel of saw If a full depth cut groove is required, the saw must -move slower as the force between the blade 34 and the concrete 13 increases with the depth of the groove. If the saw 10 is -moving fast enough, then when the blade 344 hits an entrained rock, the blade 34 bounces up, only partially -14- Scutting the rock, and cutting a shallower groove at that point.

Alternately phrased, the greater the tension applied to the spring 52, the less the weight or force applied to the saw blade 34, which in turn provides a faster forward Scut but also a shallower cut. The less the tension applied to the spring 52, the greater the weight applied to the saw blade 34 which in turn deepens the overall groove depth and slows the forward travel. If too much weight is applied to the blade 34, the skid plate 24 will rise off of the surface of concrete 13 and the groove quality will oo become unacceptable.

The exact mechanism by which the off-loaded and o004 pivoted blade 34 optimally cuts through entrained rocks is uncertain. It is believed that a correct selection of the force exerted by the blade 34 on the concrete 13 will allow the blade 34 to rise up over an entrained rock so as to circumvent the rock. It is believed that rising up to the rock allows the blade 34 to cut down into the rock and does 20 not cause a severe jolt to either the entrained rock or the oo corncrete saw 10. This force selection must consider the ind~.vidual concrete mix design and especially the size of q the aggregate (rock) in the concrete. Alternately phrased, it is believed that if the force with which the blade 34 is urged into the concrete 13 is too great, then the operator must shove the saw 10 in order to cut sideways through the 0 rock. The result is residual cracking around the rock, either from the initial impact of the saw 10 with the entrained rock or from the sideways force of the operator cutting sideways through the rock.

It is believed that if the force is correctly adjusted, the blade 34 can resiliently accommodate the impact with the entrained rock to minimize or prevent damage to the concrete finish. A trade-off between the desired depth of the cut groove and the permissible variations in that depth of the cut groove exists. The

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illustrated embodiment is one combination that has been i judged preferably when working with aggregate up to one i inch in size.

i SThis problem with obstructions, such as entrained rocks, is not encountered with conventional cutting machines since the concrete 13 is sufficiently hardened and the progress of the saw sufficiently slow so that the entrained rocks are cut without the residual cracking concrete. For the grooving trowels, the entrained rocks are no problem since the concrete is grooved just after o pouring, while the rocks can be slowly urged out of the way of the grooving trowel without causing cracking.

While the amount of force between the blade 34 and the 4440 concrete 13 may vary somewhat depending upon the size of the blade 34 and the size of the rocks entrained in the concrete 13, it is believed that this force should be about 2.5-3.0 pounds for the illustrated embodiment. This force has a been found suitable for cutting a .5 inch deep groove in a 4-inch thick slab of concrete 13, with rock or ._420 aggregate up to 1 inch in size.

0 o The quality of the groove cut in the concrete 13 is also affected by the size of the slot 38 (Figure 3) with 0 respect to the portion of the blade 34 extending through :00) .that slot. The force exerted on the concrete 13 by the skid plate 24 helps to support the surface of the concrete 13 immediately adjacent the groove which is being cut in o o the concrete 13. If the spacing between the sides of the blade 34 and the slot 38 is too great, then the edges of the cut groove will become rough and uneven. It is also possible that spalling, chipping or surface cracking immediately adjacent the edges of the groove will occur.

It is preferred to have the skid plate 24 support the concrete 134 immediately adjacent the groove being cut by the blade 34.

Referring to Figure 7, it is preferred that the spacing b and c between the sides of the blade 34 and the form I& A. %J r AS .JVWt Lu A.W tA r %JL ql h4 lubricated with water. The blade is typically made of I wmwmm -1-I~ ii-..-lilP -sr~*I -16been one ined ting lened the -king rocks ifter the d the e of the about force deep ck or 13 is with irough y the )crete ut in )f the jes of also acking occur.

t the :ut by it the nd the 4 4 4 444*Q Ioe.

'"l5 sides of the slot 38 in the skid plate 24 be controlled.

Testing indicates that a spacing as close as possible to zero, without binding, provides the best surface finish adjacent the cut groove. A spacing of less than .0625 (1/16) inch produces a cut groove of acceptable quality with no readily perceived cracks or chips or jagged edges.

A spacing of 1/16 inch, or slightly greater than b and c, provides a surface finish adjacent the groove that is judged to be of questionable acceptability, having chips and cracks that are not perceptible at a distance, but noticeable close up. A spacing of 3/32 of an inch provides a groove that is usually unacceptable in terms of chipping and cracking, and overall finish. A spacing of over 3/16 of an inch provides a groove deemed acceptable in terms of cracking, spalling or cosmetic appearance at the edge of the groove.

These results are derived from test data which indicate that the relationship between the slot spacing and the quality of cut is not linear. Figure 12 below illustrates the test data and shows the manner in which the spacing is believed to affect the quality of the surface finish of the concrete 13 adjacent the cut groove.

It is believed that the effect of the spacing b and c on each side of the saw blade 34 is independent of the quality of the cut or groove formed on the other side of the blade 34. Thus, it is possible to have the surface finish on one side of the groove acceptable, with the opposite side of the groove producing an unacceptable finish adjacent the cut groove because of too wide a spacing.

It is believed possible that the spacing may be critical only at the cutting edge of the blade 34 since that location is where the concrete 13 is being removed by the up-cutting motion of the blade 34, and the only place where the concrete 13 is being theoretically placed in tension by the blade 34 so as to cause cracking and I I) a Q 44 44 4 4 4 4 I 4II 4444 4, 4 20 a 4 4 0 4 0 94 4 411 444444B 4 4 4 4 0 4 6 4 44 aof 35 This characteristic shrinking usually takes place somewhere between the time the initial finish is completed and before -17- :)lled.

chipping. In practice, however, the saw 10 may wiggle and )le towobble so that the blade 34 actually contacts the concrete .0625h 13 at points other than the cutting edge of the blade 34.

iality Thus, the slot 38 preferably has sides which correspond the shape of the sides of the blade 34, and are spaced as ad ;e~s.

closely as possible to the blade 34 without binding the ~nd crotation of the blade 34.

at is Referring to Figures 3 and 7, the spacing between the chips up-cutting or cutting edge of the rotating blade 34 and the but 10 adjacent end of the slot 38 is also controlled in the ~viesillustrated embodiment. If the front edge of the slot 38 ipping 3/16 extends into the rounded end 26 of the skid plate 24 then .ms of4 placing the cutting edge of the blade 34 adjacent this end 44 of the slot 38 can cause a build up of the cut concrete [ge'of which can squeeze out of the slot 38 and under the rounded 1 whic 444end 26 so as to mar the surface finish of the concrete 13 or cause tilting of the saw ?acingIt is preferred that the front or leading edge of the belowslot 38 which is adjacent the leading or cutting edge of which 4 1a20 t o20the blade 34 not extend into the rounded end 26, but rather fenne the th fla piece 30. Further, it is preferred )ove. that the space d between the cutting edge of the blade 34 and c 44 theand the adjacent end of slot 38 be limited so as not to spcn bewethhutngegefbae34adteedo ofgreatly exceed .25 of an inch. Ideally, there is zero 6 6 4 Q irface 4 2 pcn ewe h utn deo ld 4adteedo a.the slot 38. However, as the blade 34 wears, a space will V.44 4i th 4 646 1~ thQ naturally develop, and a maximum space of about .25 inch is table preferred.

Lde aThe spacing between the back or trailing edge of the blade 34 and the end of the slot 38 also affects the 3 Ly bequality of the cut groove. It is preferred that the slot sne38 be extended into the rounded end 28 or, alternatively, ed by that a tunnel or other open piece be provided. The placepresence of a flat piece of metal on the concrete 13, immediately following the groove cut by the blade 34, would 3 and act as a trowel serving to close over or otherwise Eore 921007,gjnspe.005,15162.div,4

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-18compromise the quality of the groove which had previously and been made. Extending the slot 38 all the way to the :rete I 34 rounded end 28 prevents closure of the previously cut a 34. St groove and also provides a sturdy attachment for the skid id to d5 plate 24 which prevents undue vibration during operation of Sd as i Sthe the concrete saw 10 (Figure 3).

I the Referring to Figure 2, this desire to prevent closing St of the groove immediately after it has been cut, also n the d t affects the placement of the rear wheel 20. The outer edge I d the 10 of wheel 20 is preferably placed close to the rotational i the plane of the blade 34 and the groove cut by that blade, but :t 38 Sh not so close that the wheel 20 would cause closure of the then d groove cut in the concrete 13 by the blade 34.

s end crt 15 The size of the slot 36 with respect to the blade 34 crete unded 15 is also controlled in order to help prevent the freshlyi unded S1 cut concrete from accumulating on the blade 34 and to te 13 te 3prevent the freshly cut concrete from being returned to the groove which had just been cut. Thus, the width of the f the slot 36 is preferably as close to the width of the blade 34 ge of ther 20 as possible. Limitations on the length of the slot 38 must ather...

also consider accommodating motion of the blade 34 as it erred o 2 d pivots around the shaft 42 (Figure 4) when the blade 34 de 34 strikes rocks which are entrained in the concrete 13.

ot to As the concrete 13 is removed from the groove by the 1 zero 25 slots in the blade 34, the concrete dislodges from the a 6.

nd of .l blade 34 and is deposited between the lower surface of the will I So" plate 12 facing the concrete 13 and the interior surface ich is 4i 9 of the skid plate 24 which faces the plate 12. About -f the of the concrete removed by the blade 34 is deposited on f the 30 the interior of skid plate 24. As more and more concrete s the slot dislodges and accumulates, the concrete is urged off the vely, skid plate 24 onto the adjoining surface of concrete 13.

.vely, The By the time the dislodged concrete exits the skid plate 24, The it has hardened sufficiently so that it is nonadhesive and a 13, would 35 does not readily adhere or mold itself to the concrete 13.

would !rwise

I-

r, 921007,gjnspe.005,15162-div,5t )u sly -19the The heat from the cutting action of the blade 34 may cut

C

skidtrbt t hs adnig skdIt is not believed that the rotational speed of the of blade 34 has any significant effect on the spacing between the blade 34 and the slot 38. The rotational speed of :)singblade 34 does not have some affect the speed and ease with also which the concrete saw 10 can cut across the surface of the edge concrete 13. Generally, a higher rotational speed of the4 ionalblade 34 allows faster cutting and thus faster movement of but 10 the concrete saw E the Referring to Figure 3, the width of the skid plate 24 1 r~ 0040:is such that it not only supports a portion of the weight Je 34 of the saw 10, but also allows hardening of the concrete eshly I:after it has been removed from the groove cut by the blade I 4 d to 15 34. A minimum width of .5 inch has been found sufficient 1 o, the to allow the dislodged concrete to harden and/or air dry C the before it slides off the skid plate 24 onto the adjoining de 34 1'concrete 13 (Figure yet sufficiently large to prevent must Iithe sides of the skid plate 24 from slicing like wire, or it 0 0 20 sinking, rather than providing a support surface with ~~1-11,0 le 34 minimal marring on the surface of the concrete 13.

Referring to Figures 2 and 4, there is a handle y the 4attached to the motor 32. The handle 55 can be grabbed by a the a person in order to carry the concrete saw Referring to Figure 1, in order to enable operation of 2 rface Ithe saw 10 on large slabs of concrete 13, without the use t 80% 4 of scaffolding to support the weight of the operator, ad on extendable handles 58 can be attached to the base plate 12.

crete The extendable handles 58 function like extendable broom f the 30 handles to enable the saw 10 to be pushed out onto, and e 13. withdrawn from, a large slab of concrete 13. In short, the .e 24, handle 48 provides a means of moving or propelling the saw e and 10 to cut grooves in the concrete 13. A more detailed e 13. description follows.

Referring to Figure 2, the concrete saw 10 preferably has three points of support at all times the blade 34 is 901120,gjnspe.005,15162-div,6 4e FCI bi-' I i t 44 4 may f the tween >f the with )f the )f the ?nt of Lte 24 Jeight icrete blade Lcient r dry )ining -event 7e, or with le 55 'ed by on of e use ator, e 12.

broom and the a saw ailed (4P 8 8 ''4 44 44e15 4 40o 84 0 cutting the concrete 13. These three points typically comprise the skid plate 34 and two of the wheels 14, 16, 18 or 20, as described hereinafter. When the concrete saw is first started on the edge of a concrete slab, the three points of contact comprise the skid plate 24 and the front wheels 14 and 16. The wheels 14 and 16 are approximately equidistant from, but on opposite sides of, the rotational axis of the blade 34. Thus, there is a stable three point support among the wheels 14 and 16 and the skid plate 24.

The front wheel 16 is located approximately .125 to of an inch further away from the concrete 13 than is the front wheel 14. Thus, when the saw 10 has cut sufficiently far out into the concrete 13 so that the rear wheel 18 rides onto the surface of the concrete 13 the wheel 16 is lifted out of contact with the concrete 13, and the three point support then comprises the skid plate 24, the front wheel 14, and the rear wheel 18. The offset wheel 16 thus serves as a guide and support for the concrete saw 10 as the saw 10 begins cutting into the edge of a concrete slab, but not thereafter.

The use of an offset wheel 16 during the initial portion of the cut made by the saw 10 does cause the blade 34 to cut at an angle with respect to the surface of the concrete 13, rather than cutting perpendicular to the concrete 13. The smaller the offset of the wheel 16 with respect to the other wheels, the less this angle will be.

During this initial cut on the edge of the concrete slab, the saw 10 could be operated by the handle 56 attached to the motor 32. After the saw 10 is extended to the edge of the operator's physical reach, the saw 10 can be operated by an extendable handle 58.

Referring to Figures 2 and 6, the handle 58 is pivotally connected to the base plate 12 at pivot block The pivot block 60 allows the extendable handle 58 to pivot about an axis substantially parallel to the rotational axis 4 44 0 8 O 4.

Oo' 8 20 08* 0* 4 4 4I 4 40~ 04 ,4 0u 8P 8 84~ 4 P t2 0 4448 4 4 4 4 44I 4 4444 44400, 44 4 1 i 4 O 4 1 a c3 3 d 0 p t b c c, dl rably 14 is ha, -33- THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: The wheels are mounted to the base plate 12 so as to rotate I I -21ally j of blade 34. As the concrete saw 10 moves onto the r 16, I concrete 13 and further away from the operator, additional

I

saw extensions can be attached to the extendable handle 58 at

I

the joints 59 (Figure 1) in order to accommodate the necessary b S+the 5 reach. The connection of extendable handles 58 at joints are 59 can be by diverse means such as screw threads or bayonet C c of, mounts which are well known in the art and not described in is a |detail herein.

and I The connection of the handle 58 to the base plate 12 provides a means for propelling the saw 10 without to 9 j restricting the movement or pivot action of the blade 34

.J

an is about the pivot axis 42. The use of the handle 56 attached J cut directly to the motor 32 restricts pivoting of the blade rear i 34 and can cause inadvertent damage to the finish of the 3 15 concrete surface when the blade 34 hits a rock entrained 3 the and in the concrete as previously described. .e 24, During operation of the saw 10, the greatest drag ffset I occurs at the blade 34 and skid plate 24'. The pivot block r the 60 is preferably placed adjacent the blade 34 so as to move edge 'i 20 the concrete saw 10 without skewing the blade 34 and saw o edge 10. If the blade 34 skews so that the blade 34 is not 020 nitial I parallel to the line of travel of saw 10, then not only is blade 4 .4 the resulting groove in the concrete 13 wider than normal, ,f the H I abut the skewing of blade 34 can cause immediate or residual o the I 25 cracking, spalling, or chipping in the surface of the 6 with L" v concrete 13 immediately adjacent the groove. Thus, it is be. B 1 desirable to have the force pushing the concrete saw 10 00 be.

napplied so as to cause as little skewing of the blade 34 as lie 56 possible.

ded to 30 Referring to Figure 5, for the illustrated embodiment, can applicant has found that the center line of the extendable handle 58 can be along a line substantially parallel to the 58 is cutting blade 34, and spaced approximately 1.5 inches )ck 60. therefrom, toward the motor 32.

pivot 35 Referring again to Figures 2 and 6, when the concrete pivot ki axis saw 10 has completed its cut, it may be desirable to 34 hardness of 1200 psi. w1 0 -22retract the concrete saw 10, rather than retrieve the saw from the other side of the slab of concrete. As described below, mechanisms are provided to retract the blade 34 from the concrete 13 and to pivot the concrete 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 roughly 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 length of the handle 58 and the distance of the saw 10 from the operator. The angle is greater as the saw 10 comes nearer to the operator.

A remotely actuatable means is provided to allow removal of the saw 10 from a slab of concrete without dragging the skid plate 34 on the surface of the concrete 13. When it is desired to retract the saw 10 from the middle of a slab of concrete 13, the solenoid 72 is energized so that the plunger 70 extends 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 notches 66. The engagement of the tip 68 with the notch 66 provides a linkage connection whereby the handle 58 may be shoved down towards the ground to exert a torque or moment onto the base plate 12. In essence, the notches 66 and plunger 70 serve to lock the handle 58 into a fixed position with respect to the saw 10. The result is that 4000 ~0 0 4000 0 00 4 0 O 00 0 0 0 0 0 00 -23the saw 10 tilts onto the two rear wheels 18 and 20 as the handle 58 is pushed toward the ground, thus enabling the saw 10 to be rolled off of the concrete 13 slab without the H skid plate 24 dragging on the concrete 13.

As seen from Figure 6, the rear wheel 20 is also located approximately .125 to .25 of an inch further away from the concrete 13 than is the rear wheel 18 or the front wheel 14 so that the wheel 20 does not normally contact the surface of the concrete 13. The offsetting of the wheel 20 causes a tile to the base plate 12 when the saw is pivoted so that it can roll on the wheels 18 and The base plate 12 must not overhang the offset wheel 20 so that the offset of the wheel 20 causes a corner of the base plate 12 to dig into the concrete 13 when the base plate 12 is tilted onto the rear wheels 18 and 20. To provide as ~2 4 wide a support as possible in order to help minimize this tilting, the rear wheel 20 is preferably placed as close to the plane of the saw blade 34 as possible, without causing the groove cut by the blade 34 to close.

-2 0 Conceivably, the wheel 20 could be placed on the '4opposite side of the groove than the other wheels. It is also believed possible that the three points of support for normal operation could comprise the two rear wheels 18 and and the skid plate 24 with the two offset wheels being the front wheels 14 and 16. In this case, the tilting of the base plate 12 would not occur during retrieval *of the 2 saw 10 since there would be no offset between the rear' wheels 18 and 20 with both of those wheels being on substantially coplanar axis, if not the same axis.

Another remotely actuatable means is also provided to disengage the blade 34 from contact with the concrete 13.

Referring to Figures 2 and 3, a second solenoid 74 can be used to pivot the blade 34 out of contact with the concrete 13 (Figure 2) before the retraction of the saw 10, or at any time desired. This second solenoid 74 is preferably located adjacent the spring 52 so as to provide a force -24between the base plate 12 and the shield 40 which causes the blade 34 to pivot out of its normal position which is in contact with the concrete 13.

More specif ically, there is shown the solenoid 74 connected to the motor 32. The solenoid 74 has a plunger 76 extending downward towards the base plate 12. When the solenoid 74 is energized, the plunger 76 extends to contact and push against the base plate 12 with the result that the shield 40, motor 32, and saw blade 34 pivot about the shaft 42 so as to rotate the blade 34 a predetermined 0 distance, preferably out of contact with the concrete 13.

Preferably, the solenoid 74 is connected adjacent the blade 34, perhaps attached to the shield 40, so as to place the V 4 force exerted by the solenoid 74 adjacent the greatest resistance to disengaging the blade .34 from the concrete 13.

Referring to Figure 2, solenoids 72 and 74, and the motor 32 tare connected to electrical wires 76 which run along extendable handle 58 to a control device (not shown) 00..*20 on the end of the handle 58 where they are controlled by 444 the operator. Thus, the solenoids 72 and 74 and the motor 4 0 32 can be remotely actuated by the operator of the saw If the wires 76 are not sufficiently long, then connectors known in the art and not described in detail herein, allow the use of extensions to the wires 76 as more and more handles 58 are added.

04 A mounting bracket 80 is pivotally connected to the.

pivot shaft 42. The mounting bracket 80 is shown as connecting to the pivot shaft 42 at two locations on generally opposite sides of the base plate 12, in order to provide a stable connection to the saw 10. Connected to the mounting bracket 80 is a tubular cylinder 82 which is( located so that it extends along a line parallel to the orientation of the saw blade 34. One end of the handle 58 extends through the cylindrical tube 82 such that the handle 58 can rotate within the tube 82. Various devices, such as snap rings 84, allow the handle 58 to rotate within the cylindrical tube 82, but restrain motion of the handle 58 along the longitudinal axis of the handle 58 and cylindrical tube 82.

Thus, the handle 58 can guide and propel the saw I' through the connection with the bracket 80 and pivot shaft 42. The pivotal connection between the bracket 80 and the pivot shaft 42 allows the handle 58 to move up and down in a vertical orientation with respect to the concrete 13.

In this alternate embodiment, a U-shaped bracket 88 has one side connected top and preferably integrally lo-,formed with safety shield 40. The open ends of the a U-shaped bracket 88 are also pivotally connected to the pivot shaft 42 such that the bracket 88, safety shield motor 32, and saw blade 34 are all connected so as to pivot about pivot shaft 42. Thus, the U-shaped bracket 88, and the mounting bracket 80, both pivot about the commoil shaft, pivot shaft 42.

A flexible member, such as wire cord 90, has a first end connected to the U-shaped bracket 88 and a second end I, connected to that portion of the handle 58 extending through the cylindrical tube 82. As the handle 58 is rotated in the tube 82, the cord 90 wraps around the end of 0 4# the handle 58 so that the length of the cord 90 is shortened. Shortening the length of cord 90 pulls on the .~.bracket 88 and pivots the saw -blade 34 about the pivot '~~:shaft 42 so that the saw blade 34 can be withdrawn from' contact with the concrete 13, as illustrated in Figure Controlled shortening of the cord 90 can also be used to vary the depth of the groove cut in the concrete 13 by the saw blade 34.

The motor 32 is also connected to the base plate 12 by means of a second flexible member such as the second wire cord 92. Preferably, the second cord 92 has a first end connected to the front of the base plate 12, on the same end as the wheel 14 is located. The second end of the

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-26- ,ithin second cord 92 is preferably connected to a projecting iandle andbracket 94 which from, and is connected to, the motor 32 as SandI shown in Figure 8.

~I The second cord 92 is normally slack when the saw aw f0 5 blade 34 is its desired cutting depth in the concrete 13, shaft i i (I as illustrated in Figure 9. Preferably, the second cord 92 di is also slack when the first cord 90 is shortened so as to )wn in cause the saw blade 34 to pivot out of contact with the concrete 13, as illustrated in Figure 10. Further pivoting ;et 88 of the saw blade 34 and connected motor 32 causes the grally groly 'osecond cord 92 to become taut and exert a force on the f the front of the base plate 12. If the force exerted by the .o the Ssecond cord 92 is sufficient, the saw 10 will pivot on the Id 40, rear wheels 18 and 20 (Figure 7) so that the skid plate 24 pivot is moved out of contact with the surface of the concrete 13 8, and o s8 ,ao as shown in Figure 11.

shaft, Thus, the handle 58 can be used to not only propel and guide the saw 10, but also to disengage the saw blade 34 first from the concrete 13, and further to disengage the skid nd end o 20 plate 24 from contact with the surface of the concrete 13 ending so that the saw 10 can be withdrawn from the surface of the 58 is I concrete 13 with minimum danger of damaging the surface of end of the concrete 13 by inadvertent scraping of the skid is plate 24.

The saw 10 is preferably used to cut soft concrete, pivot pivot not hardened concrete., The saw 10 can be used just after n from' the concrete 13 has been finished. At the time of Lre 0. finishing, the concrete 13 has attained a workable sed to ed to plasticity that allows the concrete 13 to be worked and by the retain a surface finish, but the concrete 13 is not sufficiently hard to allow acceptable cutting by s 12 by Sconventional saws or methods. The saw 10 can also cut Id wire concrete 13 which has set for several hours, and is st end believed to work with any concrete that is too soft, or not xe same 35 sufficiently hard, to be cut satisfactorily by conventional of the abrasive cutting machines.

>/N

-27- As pr'eviously mentioned, such conventional cutting machines can produce cuts of unacceptable or dubious quality from as little as 12 hours after finishing if the day is extremely hot, say over 100 degrees Fahrenheit.

These conventional cutting machines typically are not used until the next day (about 18 hours later), and even then, typically produce unacceptable cuts. The saw 10 will typically be used before these 12 hour and 18 hour figures.

The saw 10 allows "same day" cutting of grooves with acceptable surface finishes adjacent the cut grooves. it o ois believed that the saw 10 could be used at or beyond the 12 and 18 hour f igures and produce a cut groove having a superior finish adjacent the surface of the groov,- when compared to the groove quality of conventional abrasive machines. However, the wear on the blade 34 would be 44greater than normal.

Ideally, the saw 10 would be used to cut grooves in the concrete 13 before the concrete 13 has incurred its characteristic shrink that occurs during setting, to an extent that cracks begin forming in the concrete 13.

More specifically, the finishing of concrete typically proceeds through sever-al stages. The f irst stage is to Opour the concrete, tamp it and "bull float" the surface to :'~:level the surface. At this stage, the concrete is wet and *4 25 cannot be walked upon without sinking into the concrete.

If the concrete is grooved with an edger or grooving 44 44 trowel, it is f irst done at this stage but must be repeated later. The concrete is typically not left with such a coarse finish, although a rough finish may be adequate for road rurfaces and such.

At this first stage the concrete has a hardness which cannot be measured by the conventional Swiss Hammer tests used for concrete. The Swiss Hammer relies on the rebound of a shaft from the hardened surface of the concrete to measure hardness in pounds per square inch, or psi. At this bull float stage, the concrete is so soft that the -28plunger on the Swiss Hammer sinks into the concrete and does not rebound properly.

The saw 10 is believed to be able to cut the concrete at this bull float stage and form an acceptable groove, although the weight of the saw 10 will cause the skid plate 24 and wheels 14-20 to leave indentations in the surface of the wet concrete 13. If cut at this stage, the concrete 13 is preferably allowed to have its surface air dry so that the indentations from the weight of the saw 10 are minimal or non-existent.

The second stage of finishing is called the "fresno" stage. Here the concrete has hardened, but still cannot be walked on without sinking into the concrete. The finishing during this stage is done by long handled tools since the concrete will not support a person's weight. The sequential working of the concrete surface with tools repeatedly brings moisture and cement to the surface and allows a smoother finish to be applied to the concrete 13.

If grooves are formed in the concrete by use of a grooving trowel, the grooves must be re-grooved at this stage, and after each successive finishing step.

The concrete during this fresno stage is still too soft to obtain an accurate hammer hardness. The surface of the concrete 13 is smoother than that of the first stage.

2 The saw 10 will cut satisfactory grooves in the surface of 44 the -concrete 13 finished to this stage. Prfaby th surface of the concrete 13 will be allowed to air dry so as to minimize the marks formed in the surface of the concrete 13 by the weight of the saw Conventional concrete saws will not work satisfactorily at this fresno stage of finishing. The grooves will be jagged at the edges. The concrete will be washed away by the water lubricant of the abrasive cutting machines. Further, the weight of conventional cutting machines will leave unacceptable indentations in the surface of the concrete.

-29- The third stage of f inishing uses power trowels or finishing machines to repeatedly smooth the surface of the concrete 13. At this stage the concrete 13 is hard enough so a person will not sink in deeply, but the surface of the concrete 13 will form indentations from the person's weight. The operator of the finishing machines just walks so that the machine smooths out the indentations. This machine finishing is done several times, with the concrete surface being allowed to air dry between each finishing operation. With each finishing, moisture and cement is a ~.redrawn to the surface of the concrete 13. The concrete 13 49 becomes harder with every finishing.

a The saw 10 can cut the concrete 13 at this time and 4.aform good grooves. Preferably, the surface of the concrete is allowed to air dry so the last layer of moisture from the finishing operation can evaporate. This air drying insures that the weight of the saw 10 will not cause the skid plate 24 and the wheels 14-20, to mark the surface of the concrete 13. This air drying typically takes from 12 0 minutes on a warm day to one hour on a cold day.

It is believed that a conventional, saw could not cut concrete at this stage and produce an acceptable surface adjacent the cut groove because of excessive spalling and *04cracking. Further, the weight of an abrasive cutting machine would cause the wheels of the machine to mark the 444surface of the concrete 13. A conventional hand saw with a 4, 4 concrete blade would not have this significant weight problem, but such a saw would leave an unacceptable jagged edge adjacent the cut groove, and its skid plate would mark the surface of the concrete 13.

The saw 10 in the illustrated embodiment allows the use of equipment and motors that are considerably lighter and less powerful than previously used. The saw 10 allows cutting of grooves at a time which was not previously considered practical or feasible for cutting grooves in -t- ItI ftI i concrete, and with a groove quality that is unexpected for i the softness of the concrete.

I Several tests were conducted in an attempt to more precisely define the hardness of the concrete 13 which can be cut by the saw 10. A steel rod weighing about 5.75 pounds having a diameter of 1.125 inches was dropped from a height of about 23.75 or 24 inches from the surface of the concrete 13. The rod had a flat end with the 23.75 dimension being from the surface of the concrete 13 to the flat end of the steel rod. The depth of the indentation formed by rod in the concrete 13 was then measured.

For an indentation of about .4 to .5 inch, the saw produced a good cut with no rough edges adjacent the cut groove. This test was conducted with the concrete 13 somewhere in the fresno stage. The wheels 14 through and the skid plate 24 did leave visible tracks on the surface of the concrete 13. Conventional saws would not produce acceptable cuts at this stage. The water lubricant on an abrasive water saw washes away the concrete and also o0 the aggregate; if the water is not used, the cut groove fills up with concrete. A conventional rotary hand saw with a blade designed for cutting concrete produces a jagged cut with partial blockage of the cut, as well as o° leaving gouges from the plate contacting the concrete 13.

The saw 10 is believed to be able to cut the concrete 13 when the rod makes an indentation greater than .5 inch when dropped from the 23.75-inch height.

For a rod indentation of about .3 to .4 inch, the saw still produces a good cut and the wheels 14 through and the skid plate 24 leave very slight marks or indentations in the surface of the concrete 13.

Conventional saws do not work at this hardness. The water lubricant from the abrasive saw washes away the concrete and the smaller aggregate, but does cut through the larger aggregate which is bound by the cement. A conventional rotary hand saw with a blade designed for cutting concrete act as a trowel serving to close over or otherwise -31for still produces a jagged cut with partial blockage of the more cut, and also leaves marks from the plate contacting the can concrete 13.

5.75 When the rod makes an indentation of about .125 inch, the saw 10 still makes a good cut with a perceptible, but of small, indentation in the concrete from the wheels !4 3 through 20 and the skid plate 24. Conventional saws do not the work since the water lubricated abrasive saw still washes ionaway the concrete adjacent the cut groove and its wheels leave noticeable indentations in the surface of the w 10 concrete 13. The mid to large sized aggregate adjacent cut the surface of the cut groove is chipped out of the way leaving cavities. If the water is not used, the cut groove 3 13 up with concrete. The conventional rotary hand saw still leaves a jagged edge to the cut groove. LiWhen the rod makes a perceptible round indentation of not Lcant 1]about 1/32 to 1/16 of an inch, the saw 10 produces a good also quality cut with smooth edges, and almost no perceptible ~ovemarks from the wheels 14 through 20 and skid plate 24.

sa '20 Even at this stage, the hardness of the concrete is not ~s a '.a<sufficient to allow measurement by the Swiss Hammer. 2 las Conventional saws still do not work at this concrete 13. hardness. The water lubricated abrasive saw leaves a cut V with rounded edges and cavities where the aggregate and :e 13 some surrounding cement are chipped away. If the water is when not used, the edges are not so rounded, but the cavities saw 4a remain. The conventional rotary saw with a blade designed 4 fh 20for cutting concrete also has chipped and rough edges with or 2 residual cracking around the aggregate adjacent the edge of 1.30 the cut groove.

qaterConventional concrete saws, with a blade rotating at -rete about 1700 rpm, produce a minimally acceptable cut groove when the concrete 13 has reached a hardness well in excess irger of 1200 pounds per square inch (psi) as measured by a Lonal -rete 35 Swiss Hamm~er. This hardness typically does not occur until the next day, as previously mentioned. At this ~I i

I"UF~

-32hardness, there is some chipping and roughness at the edges of the cut groove, but the resulting cavities, cracks and roughness are relatively small, ranging from the size of the sand used in the concrete to about .125 inch and larger.

SA conventional rotary saw with a blade designed to cut concrete and with a rotational speed of about 11,000 rpm also does not begin to produce a cut groove with a quality that can be acceptable until the concrete has reached a hardness of about 1200 psi or higher. When cut at this 0hardness using a conventional rotary saw with a concrete S0 cutting balde, there is some cracking, chipping, and roughness at the edges of the cut groove, but the size of the cavities and roughness are relatively small as S 15 described above.

i::

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i!i 1 61

Claims (14)

1. 2. A method of cutting grooves in concrete, as defined in Claim i, wherein the concrete is finished to the bull 1 float stage.
2. 3. A method of cutting grooves in concrete, as defined i a: in Claim 1, wherein the concrete is finished to the fresno stage.
3. 4. A method of cutting grooves in concrete, as defined in Claim i, wherein the concrete is finished to the trowel stage. A method of cutting grooves in concrete, as defined in any one of Claims 1 to 4, wherein said cutting step occurs before the hardness of said concrete reaches a 921007,gjnspe-005,15162div,33 -34- hardness of 1200 psi.
4. 6. A method of cutting grooves in concrete, as defined in any one of Claims 1 to 5, wherein said support means supports said surface immediately adjacent said sides of said rotating blade within 1/8 of an inch of the sides of said rotating blade.
5. 7. A method of cutting grooves in concrete, as defined in Claim 6, wherein said support means supports said surface immediately adjacent said sides of said rotating blade within 3/32 of an inch of the sides of said rotating blade. B8. A method of cutting grooves in concrete, as defined in Claim 7, wherein said support means supports said surface immediately adjacent said sides of said rotating blade within 1/16 of an inch of the sides of said rotating blade.
6. 9. A method as defined in any one of Claims 1 to 8, 0 wherein said cutting step occurs before the concrete has 0° a hardness such that said steel rod causes an indentation of about 1/8 of an inch. A method as defined in any one of Claims 1 to 8, °o wherein said cutting step occurs before the concrete has 0 a hardness such that said steel rod causes and indentation of about 1/2 of an inch. 000000 o
7. 11. A method as defined in any one of Claims 1 to 8, wherein said cutting step occurs before the concrete has a hardness such that said steel rod causes an indentation of between 1/32 to 1/2 of an inch.
8. 12. A method as defined in any one of Claims 1 to 8, 921007,gjnspe.005, 51624iv,34 i iii I I 1~Y-w wherein said cutting step occurs before the concrete has a hardness such that said steel rod causes an indentation of between 1/32 to 1/3 of an inch.
9. 13. A method as defined in any one of Claims 1 to 12, further comprising the step of pivoting the rotating blade away from the exterior surface of the concrete when the rotating blade contacts an obstruction in the concrete, so that the rotating blade does not apply sufficient force to the obstruction to crack the concrete immediately adjacent the obstruction.
10. 14. A method as defined in any one of Claims 1 to 13, further comprising the step of rollably supporting the rotating blade on the concrete surface. A method as defined in any one of Claims 1 to 14, further comprising the step of remotely disengaging said rotating blade from said concrete.
11. 16. A finished concrete surface having at least one °groove cut therein in accordance with any one of Claims 1 to
12. 17. A method defined in any one of Claims 1 to 13, a .wherein a said rotating blade has cutting segments about its periphery, the cutting segments having an edge with 0sides, and said supporting step supports said surface along a length of the concrete which extends beyond the sides of the cutting segment as they exit the concrete surface.
13. 18. A method as defined in any one of Claims 1 to 13, wherein said supporting step supports said surface adjacent said cut groove beyond a trailing edge of said cutting blade. 921007,gjnspe.005,15162div,35 i _iill; B -i; :I ii -i; -36-
14. 19. A method of cutting grooves in concrete according to claim 1 and as substantially hereinbefore described with reference to the accompanying drawings. DATED this 8th day of October 1992 Edward Chiuminatta and Alan Ray Chiuminatta By Their Patent Attorneys DAVIES COLLISON CAVE Kj 6 921GG8,gjnspe.005,15162div,36 v i