US3537340A - Method and apparatus for grooving rolls - Google Patents

Description

Q 70 c. M. WESTBROOK I METHOD AND APPARATUS FOR GROOVING ROLLS 4 Sheets-Sheet 1 FiledAug. 23, 1968 INVENTOR. v CARL M. WESTBROOK.

Nov. 31-1970 c. M. WESTBROOK 3,537,340

METHOD AND APPARATUS FOR GROOVING ROLLS 4 I Sheets-Shet 2 Filed Aug; 23, 1968 'INVENTOR. CARL M. WESTBROOK.

Nov. 3, 1970 c. M. WESTBROOK Y 3,537,340

METHOD AND- APPARATUS FOR GROOVING ROLLS Filed Aug. 23, 1968 4 Shets-Sheet :5

:2 l8 s j 55 Jr 1h avg 1 r4 )0 on 1 H n* 68 69/ as b -55 55 J -s4 Q FIG 4 L54 ijf WWQ? v INVENTOR. CARL M. WESTBROOK.

United States Patent O1 fice 3,537,340 Patented Nov. 3, 1970 METHOD AND APPlAgfiISUS FOR GROOVING Carl M. Westbrook, Beloit, Wis., assignor to Beloit Corporation, Beloit, Wis., a corporation of Delaware Filed Aug. 23, 1968, Ser. No. 754,782 Int. Cl. B23b 3/36 U.S. Cl. 82-2 13 Claims ABSTRACT OF THE DISCLOSURE A method and apparatus for cutting relatively deep and narrow helical or annular grooves in a roll for a papermachine or the like employs a saw, preferably a bandsaw, which is fed into the cylindriial surface of a rotating roll under controlled pressure while supported laterally and rearwardly along the portion of the blade engaged with the roll.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to a method and apparatus for machining a continuous series of relatively narrow and deep annular or helical grooves in the cylindrical surface of a roll for a papermachine or the like; and, more particularly, for machining such grooves in large metal rolls made of an alloy which cannot be so machined economically by conventional means.

Description of the prior art Within the past few years, a significant development in the papermachine art has been the invention and utilization of grooved rolls of the type disclosed in commonly assigned U.S. Pat. No. 3,198,697 and in other related U.S. patent disclosures referred to therein. In accordance with that invention, a papermachine roll, e.g. a press roll, is adapted to dewater a web at a roll nip by means of a continuous pattern of relatively narrow axially spaced grooves in the roll surface which carry water away from the web at the nip area while preserving sufiicient cylindrical land surface at the roll periphery to prevent production of undesirable irregularities in the web. As disclosed in the above-identified U.S. patent, a typical press roll of this type may be provided with a grooved surface comprising a continuous helical groove about .020 inch wide and .100 inch deep, with a pitch of about eight turns per inch of roll axis.

To provide a roll with a grooved surface of the type just described, it would appear obvious first to grind the roll to the required cylindrical shape and then to cut the continuous helical groove by means of a narrow cutting tool carried by the lathe carriage and advanced by a lead screw in the same manner by which screw threads are conventionally cut on an engine lathe. In practice, though, the narrowness of the groove, as compared to its depth, substantially precludes cutting the groove with a single point tool in one operation, due not only to the required thinness and resulting weakness of the tool itself but also to the corresponding difiiculty in cooling the cutting edge and providing effective chip removal. Accordingly, multiple cuts are required to bring the groove to its full depth. Since a typical roll might easily be three feet in diameter and thirty feet long, the total groove length of something over 5 /2 miles obviously detracts from making repeated cuts with a single point tool; suggesting rather the use of a progressive gang tool with successive cutting points taking progressively deeper cuts in adjacent groove kerfs. Alternatively, it would probably also be apparent to cut the groove to its full depth in a single opration by means of a milling cutter or slitting saw carried by the lathe carriage, in which case the cutter conventionally would be rotated in the opposite direction to the roll rotation to provide optimum chip removal from the deep and narrow saw kerf.

In the case of rolls made of an easily machinable material such as bronze or even cast iron, or in the case of rolls provided with a resilient shell of rubber or other similar material, one of these two techniques generally can be adapted to produce the required groove pattern without exceeding machining costs which are commercially acceptable at the present state of the art. However, the less favorable machinability characteristics of typical cast stainless ferrous alloys otherwise highly desirable for such rolls, reduces the life expectancy of either of the above types of tooling to the extent that such techniques simply cannot be utilized within the limits of economical feasability.

Since one of the contributing factors to the difficulty in machining such alloys is their pronounced tendency to work harden at an abrasion or shear surface, I have discovered that a significant improvement in tool life can be achieved in the employment of a grooving saw by retating both the saw and the roll in the same direction so that each successive saw tooth first penetrates the unhardened ground periphery of the roll and cuts beneath the hardened surface produced by the preceding tooth. This of course implies that each tooth must perform properly its cutting operation so that the next tooth does not encounter more metal than it can remove effectively or does not encounter the work hardened surface produced by the preceding cut. Either of such situations will rapidly dull or even break the particular tooth in question and thereby similarly overload the succeeding one; thus progressively destroying the effectiveness of the saw in a relatively short time. Due to the inherent resiliency of a circular saw any significant interruption in the proper cutting action of successive teeth, as occasioned by the almost inevitable jamming of a chip in a tooth gullet will cause the blade to flex sufliciently to initiate the above-described malfunctioning, resulting in progressively increasing chattering and deterioration of the blade. This problem is further complicated by the fact that the power required to drive the blade with each tooth taking its proportional cut is so relatively great in the case of these alloys as to impart additional substantial distortive influences to the blade itself. While it is possible to stiffen the blade to some extent by sandwiching it between rigid annular support Washers, the resulting decrease in the flexibility and chattering potential of the blade is at best only partially effective inasmuch as an overloaded tooth is then incapable of resiliently yielding and must either cut or be dulled or be broken.

The foregoing is not intended to imply that circular saws employed as described above cannot survie for more than a few feet of out before coming completely useless, but my experiments have shown that even very carefully controlled applications beyond the capabilities of most high production processes, the maximum effective life even of very high quality carbide faced circular saw blades is far too short to be economically acceptable due to the many blades required to groove a typical papermachine roll and the corresponding loss of time involved in replacing such blades and reestablishing the cutting process. Additionally, it should also be recognized that the employment of circular grooving saws presents a very grave risk of damaging the cylindrical roll surface in the not unlikely event of blade breakage, in which case the broken circular blade is very apt to twist beyond the groove kerf and to gouge the adjacent cylindrical land surface.

3 SUMMARY OF THE INVENTION The present invention is directed to providing techniques and equipment for decreasing the expense involved in grooving rolls of the type described above by such a substantial factor as to make practicable even the heretofore economically unfeasible grooving of stainless ferrous al- 10y rolls.

Briefly, the invention contemplates accomplishing such grooving operations by means of a sawing technique and apparatus whereby the above-described method of grooving utilizing a saw blade running in the same direction as the roll surface is employed in conjunction with saw support and cutting pressure control means by which the cutting portion of the saw is stabilized very positively but is able nevertheless to yield momentarily to relieve excessive pressure occasioned by chip jamming or the like. Additionally, the pressure maintaining the saw blade at the desired kerf depth is not constant but rather is controlled automatically so that a new sharp blade is urged into the saw kerf with less pressure than a duller but still satisfactory blade; thus prolonging blade life by avoiding blade pressures greater than those necessary in accordance with blade sharpness.

In the preferred embodiment of the invention, these means are employed in connection with a radical departure from conventional sawing practice comprising the substitution of a band saw blade for a circular grooving saw. It is readily evident that the substantially lower cost per tooth of a band saw blade as compared to a circular slitting saw blade, combined with corresponding longer life of the blade, would be significant factors favoring such a band sawing technique. However, the present invention does not contemplate simply substituting a conventional bandsaw for a circular saw, which experimentation has indicated to be completely unfeasible. In a conventional band saw, the portion of the blade engaged with the work is unsupported except by its own tension, which cannot be increased sufiiciently to provide the required blade stability for the instant application, without exceeding the tensile strength limitations of the blade. Also, if such rigidity could be achieved by extreme blade tensioning, the concomitant inability of the blade to yield rearwardly leads to the same problems of tooth breakage previously discussed. Accordingly, the present invention utilizes a band saw blade in a completely unorthodox manner whereby the path of the blade adjacent the saw kerf is substantially independent of blade tension; that portion of the blade being positively supported with laterally and rearwardly in a guide member which in turn is yieldable rearwardly and exerts controlled cutting pressure on the blade. Accordingly, the advantages of the yieldable pressure control system and those inherent in a bandsaw blade per se are combined to achieve maximum tool cost economy and to minimize production interruptions to a much greater extent that heretofore possible. Additionally, since the blade is sufiicient flexible to yield rearwardly with the guide member independently of the blade support wheels, those wheels can be made relatively massive to minimize longitudinal chattering of the blade, without thereby increasing the inertia of the rearwardly movable elements of the pressure control system.

Various means for practicing the invention and other advantages and novel features thereof will be apparent from the following detailed description of an illustrative preferred embodiment, reference being made to the accompanying drawings in which like reference numerals denote like elements.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a broken partial front elevational view of a band saw roll grooving apparatus according to a preferred embodiment of the invention, such apparatus being depicted in the process of grooving a roll mounted between centers on an engine lathe;

FIG. 2 is a partial top plan view trated in FIG. 1;

FIG. 3 is a cross-sectional end elevational view of the structure shown in FIG. 2, taken from the tailstock end of the illustrated engine lathe;

FIG. 4 is a perspective rear view of the pressure control assembly of the subject apparatus;

FIG. 5 is an end elevational view of the pressure control assembly shown in FIG. 4 taken from the headstock end of the engine lathe;

FIG. 6 coresponds generally to FIG. 5 and illustrates the pressure control assembly with its guide roller frame removed;

FIG. 7 is a cross-sectional end view corresponding to a greatly enlarged portion of FIG. 3, showing a portion of the band saw blade supported in engagement with the roll being grooved;

FIG. 8 is a perspective rear view of the blade support structure of the pressure control assembly, with portions of that structure depicted broken away; and

FIG. 9 is a schematic diagram of the pneumatic circuit employed to regulate automatically the force with which the band saw blade is urged into cutting engagement with the roll by the pressure control assembly.

DESCRIPTION OF THE ILLUSTRATIVE PREFERRED EMBODIMENTS As will be readily apparent by reference to FIGS. 1 through 3, the illustrated band saw roll grooving device is employed in conjunction with a large conventional screw cutting engine lathe comprising a headstock 11, a chuck or faceplate 12, a bed 13, and a tailstock 14. The roll being grooved, shown at 15, is mounted between centers 16 and 17 in parallel relation to the lathe bed, and is driven in a clockwise direction as viewed from the headstock by chuck 12 or other equivalent means. The grooving device, per se, is identified generally by numeral 18 and comprises a frame 19 including a base portion 21 attached to the lathe carriage 22 by a transverse dovetail slide 23, so that the entire grooving device can be advanced toward and away from the roll by means of crossfeed screw 24. The lathe carriage is, of course, movable along the lathe bed by disengageable engagement with a lead screw, 25 which is driven at a rotational speed in predetermined relation to the rotational speed of the roll so that the carriage advances uniformly along the roll by a given distance during each revolution thereof. For example, to groove a roll of the type previously described, having a lead of about eight grooves per inch, the carriage is advanced uniformly by about .125 inch during each revolution of the roll.

A vertical support member 26 extends upwardly from the base portion of frame 19 at an acute angle to the centerline of the lathe, and is buttressed by a rigid web 27. At the lower end of this vertical support member, a relatively massive lower band wheel 28 is carried by horizontal shaft 29 journaled in stationary journal bearing 31 so that the wheel is likewise in a vertical plane intercepting the centerline of the lathe at an acute angle, e.g. an angle of about 20. Shaft 29, in turn, is connected to drive motor 32 through a right angle reduction gearbox 33. Accordingly, wheel 28 can be driven in a clockwise direction as viewed from its rear face at a predetermined speed by the drive motor, the speed of which is adjustable by means of a conventional variable speed control unit shown at 34.

The upper band wheel 35 is substantially similar to and located directly above the lower wheel 28. However, its central shaft 36 is not journaled rigidly in the vertical support member 26 but rather in a journal slide member 37 supported for vertical sliding movement on bars 38 of a trarnming frame 39, which, in turn, is carried by horizontal trunnions 41. Below the journal slide, an air cylinder 42 is rockably attached thereto and to the vertical frame member and is pressurized by compressed air of the structure illusthrough a suitable pressure control valve as shown at 43 in FIG. 9, thereby urging the upper band wheel upwardly with a predetermined force. Additionally, by means of adjustable tramming screws 44, the horizontal attitude of the upper wheel shaft 36 can be adjusted slightly as explained below.

The band saw blade 45 is supported about the upper and lower band wheels against the respective annular rims 46 and 47 thereof and can be maintained at any desired tension by corresponding regulation of the air pressure supplied to cylinder 42. To maintain the blade on the wheels in rearward contact with annular rims 46 and 47, tramming screws 44 are adjusted so that the face of the upper wheel is slanted slightly toward the roll regardless of its position along bars 38. Also, if desired, the peripheral blade support surfaces 48 and 49 of the respective upper and lower wheels can be crowned or tapered slightly to further maintain the blade in predetermined axial relation to the wheels, as is known in the band saw art.

Between the upper and lower wheels 35 and 28, the teeth 51 along the portion of the blade nearest the roll travel downwardly as shown in FIG. 7, and are adapted to engage the periphery of the roll; whereas the other side of the blade is spaced well beyond the roll. Actually, the horizontal angle defined between the roll and the two vertical portions of the blade need be only large enough to keep the upwardly moving blade teeth out of contact with the roll. However, the relatively larger angle of approximately 20 provided in the illustrated embodiment enables the inoperative portion of the saw blade to clear end flanges or the like that may be encountered in grooving different types of rolls.

The pressure control assembly 52, shown in detail by FIGS. 4 through 8, comprises a substantially vertical base plate .53 mounted transversely to the axis of the roll on a heavy support member 54 of frame 19 by means of tramming screws 55. A slide frame 56 is bolted rigidly to base plate 53 and is provided with a horizontal dovetail slot 57 which receives a mating dovetail tongue 58 on slide plate 59, thereby supporting the latter plate for horizontal sliding movement relative to frame 19. An abutment member 60 provided with an adjustable abutment screw 61 is rigidly attached to slide plate 56 and overlaps the forward end of the dovetail tongue 58, thereby limiting the rearward movement of the slide plate relative to frame 19 by the abutment of screw 61 against the corresponding forwardly facing edge surface of slide frame 56. Forwardly of the slide plate, and in alignment therewith an air cylinder or bellows unit 62 is mounted to the slide frame with its piston rod 63 or the equivalent in abutment with the slide plate. Cylinder 62 thus urges plate 56 rearwardly to the position defined by abutment member 61 under a variable predetermined force, as hereinafter explained, in opposition to the forward force exerted on the slide plate by a spring 64 compressed between block 65 attached to that plate and block 66 on slide frame 56.

As previously mentioned, the portion of the band saw blade adjacent the roll and the slide plate is supported both laterally and along its smooth edge surface opposite its teeth by a support unit 67 mounted to the slide plate for movement therewith. As best illustrated in FIG. 8, this support unit comprises a pair of heavy guide blocks 68 and 69 sandwiched together and mounted to the slide plate by bolts 71. Between the two blocks, a very hard guide insert 72 made of tungsten carbide or the like is received vertically in rearwardly facing channel 73 of block 68 and is held rigidly in place by screws 71. The face of the guide insert adjacent block 68 is recessed as shown at 75 to provide lateral support for the corresponding side surface of the blade behind the band teeth; with the smooth back edge of the blade 76 opposite the teeth being similarly engaged by channel surface 77. The opposite side surface of the blade adjacent block 69 is engaged by the flat end surfaces of a plurality of hard guide pistons 78 received in respective bores 79 in block 69. These bores which communicate through hole 80 with a source of compressed air regulated by pressure regulator 81 shown in FIG. 9, thus maintaining the blade in firm supported contact with insert recess surface 75. The blade teeth, of course, must project beyond the guide block, but only by a distance corresponding to the depth of the required cut, which is substantially less than the overall width of the blade. Thus, it will be apparent that the path of the blade in engagement with the roll is maintained laterally in a predetermined plane established by the guide unit and is urged into the saw kerf by cylinder 62 to a depth established by abutment member 61 in accordance with the adjustment of lead screw 25.

Since the cutting portion of the saw blade engages the roll perpendicularly, whereas the band wheels are disposed at an angle to the roll, a corresponding twist must be imparted to the downwardly moving segment of the blade. Therefore, in order that this twisting will not interfere with free movement of the blade through the support unit, a pair of ball bearing twisting rollers 82 and 83 are mounted at opposite sides of the blade directly above the guide blocks to align the blade with the guide insert. In order to accommodate slight variations in the thickness of the blade, or a chip or the like adhering thereto, roller 82 is mounted directly to a support block 84 rigidly attached to base plate 53, whereas roller 83 is mounted to a yieldable support member 85 pivotally attached to block 84 by a pin 86 and biased by a strong spring 87 to urge roller 83 into firm but yieldable engagement with the blade.

In addition to twisting the blade in a horizontal plane, as just described it is also necessary to adjust the vertical path of the cutting portion of the blade slightly out of a vertical plane in accordance with the helix angle of the groove being generated. By means of the previously identified tramming screws 55, however, both this adjustment and any adjustment required of the support unit in a horizontal plane can be readily accomplished without disturbing the position of frame member 19v relative to the lathe.

As illustrated in FIGS. 4 and 5, a heavy arch member 88 straddles the pressure control assembly and is bolted rigidly to support member 54 of frame 19 by bolts 89. This arch member serves to support roller bar 91, which is received in channel 92 of the arch member and adjust able relative thereto in transverse relation to the roll by means of adjusting screw 93 and lock bolt 94. The roller bar, in turn, rotatably supports a ball bearing roller member 95, which is adapted to be in firm rolling contact with the roll when frame 19 is adjusted to provide the required penetration of the saw blade into the roll surface. Consequently, once the roller is adjusted relative to the saw frame in accordance with a given kerf depth, it pro vides a convenient means for subsequently resetting the saw frame to the same position and discourages accidental adjustment of the saw to cut deeper than desired. Additionally, the firm rolling contact between the roll and the guide roller tends to dampen relatively high frequency oscillations that may otherwise develop in the saw frame or the roll or both if the periphery of the roll were engaged with the saw frame only through the cutting blade.

Referring now to FIG. 7, which shows the saw blade in the process of cutting a roll groove, it will be seen that the saw teeth and the portion of the roll being sawed are both moving in the same direction, i.e. downwardly. Therefore, each saw tooth initially engages a cylindrical roll surface rather than the work hardened bottom surface of the kerf established by the preceding tooth. Consequently, the saw teeth need not penetrate through work hardened surfaces, thereby substantially prolonging the sharpness of the teeth. Although not illustrated in the drawings, a conventional coolant supply system is preferably employed to supply a cooling and lubricating fluid to the blade in the sawing region, as is well known in the machining art.

The system employed to regulate the air pressure supplied to cylinder unit 62 in order to control the cutting pressure exerted on the saw blade includes a pneumatic saw position gauging device comprising a tubular orifice member 96 supported on slide frame 56 by bracket member 97, as best illustrated in FIGS. 4 through 6. Rearwardly of the orifice member, a gauging block 98 is attached to slide plate 59 and extends over the slide frame so that the fiat face 99 of a hardened gauging dowel 101 is in direct alignment with the rearward open orifice end of member 96. By mears of adjusting nuts 102, which position the orifice member axially in relation to bracket 96, the orifice member can be adjusted to vary the dis tance between its rearward orifice end and the opposed flat face of the gauging dowel. As the slide plate moves forwardly, the face of the gauging dowel therefore ap' proaches the rearward end of the orifice member. Accordingly, as is well known in the air gauging art, the psition of the slide member, and thereby of the saw blade, modulates the rate at which air under predetermined pres sure can exhaust through the orifice member and thereby produces in the air supply system corresponding pressure changes functionally related to the depth of penetration of the saw into the roll.

As illustrated schematically in FIG. 9, the air supply system of the subject apparatus includes an air compressor 103 adapted to deliver compressed air to two pressure regulator valves 104 and 105, which are arranged in parallel relation to one another along air lines 106 and 107 between the air compressor and respective variable flow restricting valves 108 and 109 and pressure indicating gauges 111 and 112. By means of these two pressure regulating valves, the air pressure in air line 107 is adjusted to a pressure typically several times greater than that in line 106. Beyond gauge 111, the low pressure air line 106 is connected to orifice member 96 by line 113 and also to the control pressure input of a commercially available pressure amplifier valve 114 by line 115. The flow amplifier valve, in turn, is adapted to vary the pressure delivered from air line 107 to cylinder member 62 through line 116 in response to pressure changes in air line 115 connected to the orifice member, whereby the pressure delivered to the bellows is at all times greater than that in the orifice air line by a given factor determined by the particular characteristics of the amplifier valve. Thus, a newly sharpened blade which is particularly susceptible to tooth damage under excessive cutting pressure, is maintained at the full kerf depth under relatively light pressure. As the blade gradually becomes duller, however, it refuses to cut to the full kerf depth under that relatively light pressure and therefore produces a kerf of correspondingly reduced depth. As this occurs, the resulting decrease in the effective size of the air exhaust orifice produces a corresponding amplified increase in the cutting pressure exerted on the blade. Con sequently, the depth of the kerf gradually diminishes within acceptable tolerance limitations as the saw becomes duller and more resistant to increased cutting pressure, but at a rate much slower than if only the relatively light cutting pressure were maintained constantly on the blade. Due to the compressability of the air in the air lines between the flow restrictor valves 108 and 109 and the corresponding orifice and cylinder members, the response of the bellow members to changes in the position of the saw blade is somewhat delayed. This important factor allows the saw blade to move momentarily in a forward direction before being subjected to a correspondingly greater restorative influence, thereby allowing it to yield momentarily to a localized irregularity in the saw kerf caused by a jammed chip or the like. In a typical application of the invention, in which a ten pitch band saw blade with little or no set was employed to cut a groove .020 inch wide in a stainless ferrous alloy roll 36 inches in diameter, the cutting pressure required to maintain a newly sharpened saw blade at the required kerf depth was in the neighborhood of 45 lbs. In other words, disregarding the counteracting force of spring 64, this blade cutting pressure was equivalent to air pressure of 15 p.s.i. in airline 116, acting on a piston or bellows of three square inches effective area within unit 62. As the saw blade became increasingly dull, the cutting pressure required to maintain the minimum acceptable kerf depth of .070 rose to around lbs. before the blade became too dull to continue cutting effectively without further increasing the cutting pressure to a point at which tooth breakage would be very likely to occur.

When the saw blade ultimately becomes too dull to cut to the minimum acceptable kerf depth without endangering tooth breakage, the subject apparatus automatically retracts the blade from the roll to prevent ruining an otherwise resharpenable blade or possibly damaging the roll. For this purpose, an electric switch 117 is supported on support member 54 by bracket 118, as shown in FIGS. 4 through 6, and is adapted to be closed by abutment member 119 adjustably supported on slide plate 59 by threaded bracket 121. Thus, the axial position of the abutment member, which is adjustable by threading it through bracket member 121 and locking it in place by means of jam nut 122, establishes the forward position of the slide plate at which switch 117 is closed. This switch, in turn, is connected by wires 123 to a power source, not shown, and to a solenoid operated dump valve 123 in air line 125. Accordingly, the air pressure to the bellows member is released automatically whenever the saw blade is displaced beyond the minimum acceptable kerf depth. To prevent recycling of the bellows member after the pressure is released in air line 125, the commercially available dumping value 124 is adapted to remain open after its solenoid is energized, until it is manually reset to again establish pressure in air line 125. Additionally, a warning light or other signal means as shown at 126 can also be energized in response to the closing of switch 117, to alert the machine operator to the fact that the saw has ceased to perform in its intended manner.

While the illustrated preferred embodiment of the in vention relates specifically to a grooving device employing a band saw, it should be apparent that the pressure control assembly could also be adapted to support and regulate the pressure with which a circular saw blade or the like is engaged with a revolving roll to perform the same type of grooving operation. Also, while the invention is particularly suitable for machining stainless ferrous alloys which could not heretofore be grooved at commercially acceptable cost by conventional means, it will be recognized that the subject method and apparatus are equally applicable to grooving more easily machinable materials at higher speeds and lower costs than have previously been achieved.

Although the foregoing description relates to particular embodiments of the invention, variations and modifica tions thereof obviously can be made without departing from the spirit and scope of the invention. Accordingly, the foregoing disclosure is to be considered only as illustrative and not as limiting the scope of the invention which is defined by the following claims.

I claim:

1. An apparatus for sawing a circumferential groove in the periphery of a cylindrical roll rotating in a predetermined direction about its axis, said apparatus including:

(a) an elongate bed structure,

(b) a carriage movable along said bed structure in parallel relation to the axis of said roll,

(c) a frame carried by said carriage and adjustably movable relative thereto in transverse relation to the axis of said roll,

(d) a plurality of band wheels carried by said frame member,

(e) a toothed band saw blade supported by said band 'Wheels such that the central cutting portion of a segment of said blade spanned tangentially between two of said band wheels is tangential to and adjacent the periphery of said roll,

(f) drive means for moving said band saw blade longitudinally to impart cutting movement to the saw teeth comprising said cutting portion of said blade,

(g) a blade guide member supported on said frame member for movement relative thereto toward and away from said roll in substantially perpendicular relation to the axis thereof, said blade guide member including blade supporting surfaces engaged with opposite sides of said cutting portion of said blade beyond the teeth thereof and with the smooth edge of said cutting portion of said blade opposite those teeth to position said blade laterally in fixed relation to said frame and to move said cutting portion of said blade relative to said frame and said band wheels toward and away from said roll upon corresponding movement of said blade guide member.

2. An apparatus according to claim 1 including:

(a) stop means for limiting the movement of said blade guide member relative to said frame toward said roll to establish a predetermined extended position of said cutting portion of said blade at which said teeth thereof penetrate said roll to a predetermined depth established by the position of said frame member on said carriage in relation to said roll,

(b) blade retracting means for moving said blade guide member relative to said frame away from said roll,

() blade feeding means for urging said blade guide member relative to said frame toward said extended position to thereby engage said teeth of said cutting portion of said blade with said roll, and

(d) a pressure control system for modulating the pressure with which said blade guide member is so urged toward said extended position as a function of the depth of penetration into said roll of said teeth along said cutting portion of said blade.

3. An apparatus according to claim 1 including means for moving said carriage along said bed in parallel rela tion to the axis of said roll at a speed bearing a positive predetermined ratio to the rotational speed of said roll.

4. An apparatus according to claim 1 in which said cutting portion of said saw blade is moved by said drive means in the same direction as but at a greater speed than the peripheral region of said roll engaged and penetrated thereby.

5. Apparatus according to claim 1 including means for yieldably biasing one of said blade support surfaces engaged with one side of said cutting portion of said blade toward the corresponding opposite surface engaged with the other side of said cutting portion of said blade, said opmsite surface being immovable relative to said blade guide member.

6. An apparatus according to claim 2 in which said pres sure control system modulates said pressure in response to movement of said blade guide member in inverse pro portion to the depth of penetration of the teeth of said cutting portion of said blade into said roll.

7. An apparatus according to claim 6 in which said pressure control system includes time delay means for delaying the response of said pressure control system to movement of said blade guide member as a predetermined function of the rate at which such movement occurs.

8. An apparatus according to claim 6 in which said blade feeding means comprises:

(a) a pneumatic transducer adapted to urge said blade guide member toward said extended position under a force proportional to the pressure of compressed air supplied to said transducer,

(b) a source of compressed air,

(c) first air line means for supplying compressed air from said source of compressed air to said transducer at a pressure determined by said control system as a function of the depth of penetration of the teeth of said cutting portion of said blade into said roll.

9. An apparatus according to claim 8 in which said pressure control system comprises:

(a) a pneumatic position sensing device including an orifice member and an orifice restricting member, such members being mounted respectively to relatively movable elements of said blade guide member and said frame so that the orifice opening of said orifice member is increasingly restricted by said orifice restricting member as said blade guide member moves progressively relative to said frame away from said roll,

(b) second air line means connecting said sensing device to said source of compressed air,

(0) a pressure regulating valve adapted to admit air to said second air line means from said source of compressed air at a predetermined fixed pressure, and

(d) a pressure amplifying valve adapted to respond to the pressure in said second air line means beyond said pressure regulating valve to adjust the pressure in said first air line means so that the latter pressure is higher than the former by a predetermined factor established by the pressure amplification characteristics of said pressure amplifying valve.

10. An apparatus according to claim 9 including a variable flow restrictor valve in said second air line means remote from said orifice member for varying the rate at which said amplifying valve responds to variations in the restriction of said orifice of said orifice member by said resistor member.

11. An apparatus for regulating the cutting pressure exerted on a surface being sawed by a cutting portion of a toothed band saw blade centrally located along a segment of said blade spanned tangentially between two band wheels, said apparatus comprising:

(a) a blade guide member including guide surfaces supporting in fixed relation to said guide member the opposite sides of said cutting portion of said blade and the smooth edge of said portion of said blade opposite the corresponding saw teeth,

(b) support means supporting said guide member for movement relative to said band wheels toward said work piece along the plane of said cutting portion of said blade, and

(c) blade feeding means for urging said blade guide member toward said work piece with a force functionally related to the depth of penetration of said blade into said work piece.

12. An apparatus for sawing a circumferential groove in the periphery of a cylindrical roll rotating in a predetermined direction about its axis, said apparatus in cluding:

(a) a power driven saw blade having a series of cutting teeth along one edge thereof,

(b) a frame member supporting said saw blade with a cutting portion of the toothed edge thereof adjacent said periphery of said roll,

(0) a blade guide structure movably carried by said frame member and engageable with both sides of said cutting portion of said blade beyond the teeth thereof for substantially preventing lateral movement of said cutting portion of said blade relative to said frame member and for maintaining that portion of said blade in a plane substantially perpendicular to said roll axis,

(d) blade feeding means bidirectionally movable relative to said frame member between the retracted location and an extended location to effect corresponding movement of said cutting portion of said blade in said plane between a retracted position be- 11 yond the periphery of said roll and an extended position at which the toothed edge of said cutting portion of said blade penetrates said roll to a pre determined depth,

(e) fluid pressure means for so moving said blade feeding means toward said extended location to thereby effect corresponding movement of said blade toward said extended position thereof,

(f) pressure regulating means responsive to the movement of said blade feeding means between said retracted and extended locations thereof to modulate the force with which said cutting portion of said blade is urged toward said extended location in inverse proportion to the depth of penetration of said cutting portion of said blade into said roll, and

(g) time delay means incorporated in said pressure regulating means for delaying the response to said pressure regulating means to movement of said blade feeding means as a predetermined function of the rate of such movement.

13. A method of sawing a groove in a work piece by means of a toothed band saw blade in cutting engagement with said work piece along a segment of said blade spanned tangentially between two band wheels, said method comprising; applying only to the portion of said blade engaged with said work piece a force tending to move that portion of said blade relative to said band wheels toward said work piece, measuring the depth of penetration of said blade into said work piece; and modulating the magnitude of said force as a function of the measured depth of penetration of said cutting portion of said blade into said work piece.

References Cited UNITED STATES PATENTS 2,033,946 3/1936 Lippincott 83201.02 2,934,106 4/1960 Chapman et al. 143-160 3,059,516 10/1962 Cleland et a1. 143160 XR LEONIDAS VLACHOS, Primary Examiner US. Cl. X.R.

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