US2686460A - Paper machinery - Google Patents

Description

Aug. 17, 1954 A. E. BRIDGE ETAL PAPER MACHINERY 2 Sheets-Sheet 1 Filed Feb. 23, 1950 DRAW AIR BLAST 6 m N 0E0. M65 5mm WRG T mm m A Y B 0 w 0 9 O 8 0 m 7 E O m 6 E 0 P 5 m 0 m w w 0 R 2 m m m AT TOR NEYS Aug. 17, 1954 A. E. BRIDGE ET AL PAPER MACHINERY Filed Feb. 25,1950

2 Sheets-Sheet 2 INVENTORS ADAM E. BRIDGE e; BY ma mas/550w co WYMMQQM VITrI FWIWQMI' ATTORNE Ys Patented Aug. 17, 1954 PAPER MACHINERY Adam E. Bridge, Franklin, and Albert G. Gibson,

Midd-Ietown, Ohio, assignorsto The Black- Clawson- Company, Hamilton, Ohio, a corporation of Ohio- Application February 23, 1950, Serial No. 145,838

8 Claims. 1

This invention relates to cutter bars or knives for refining apparatus of the type utilized for the treatment of cellulose fibers and the like in the preparation of paper making stock.

The invention has particular application to cutter bars for refiners such as Jordans and beaters wherein a plurality of bars are carried by a plug or other rotating member in such manner that they are arranged generally axially of the axis of the plug with their outer edges exposed for working on the fibers in the stock, the invention being applicable to both the bars carried by the rotating member and also to. the cooperating stationary bars such as in; the shell of a Jordan.

These outer edges of the bars accordingly constitute their working edges which are subjected to a major portion of the wear in operation, and it is desirable that they possess adequate hardness to withstand continued use over long periods and that the degree of hardness. along these working edges be properly correlated with the degree of toughness required in the remainder of the bar, including the portion secured. to the plug or other rotating member.

For example, in a common construction of bars for the plug of a Jordan, the cutter bars are retained on the plug by means of: a series of rings interfitting with hook portions of the: bars which are formed along theirinner edges and are subjected to substantial stresses, including centrifugal force, during operation. These working stresses are accordingly of importance in determining the degree of hardness which can be imparted to the bar as-a whole without havingthe hook portions become so brittle as to be in danger of breaking in. use. If the bar is of optimum hardness for the working edge, it would be too brittle along the hook portions of the bar. On the other hand, if the bar is of optimum toughness for the hook portions, the working edge would not be hard enough and. would tend to erode too rapidly and to burr, forming sharp edges which would cause cutting of the. fibers instead of the desired rubbing action, and if it is.

attempted to overcome these disadvantages and to obtain diiierent degrees of hardness and toughness along the edges of the bar by means of a surface or edge coating or by welding or otherwise securing a harder working edgeportion to a backing of tougher metal, the cost of production tends to become too high to compensate for such improved results as may be obtained.

The usual result for bars which are uniformly heat treated in a furnace is accordingly a compromise, with a resultant shorter useful life than if. the bar were differentially hardened to give the desired hardness or toughness at each point. A further factor affecting the useful life of such uniformly heat treated bars is that with the hook: portions formed therein by punching before the heat treatment, scratch lines are formed transversely of the bar which constitute stress points at which cracks tend to develop during the subquent heat treatment, thus materially weakening the bar and increasing the possibility of breakage of these hook portions. Similar disadvantages exist in the case of. such bars which. do not have hook or lug. portions in that the back edge portion of the bar must be tough enough to prevent premature failure.

It is accordingly one of the principal objects of the present inventionto provide a cutter bar of the above character which is integrally formed, as distinguished from a welded or other composite structure, and which possesses properties of differential hardness and toughness across the width thereof such. that. a minor portion of the bar extending lengthwise of and including its working edge is hardened to a. predetermined high degree of hardness while the remainder of the bar including its opposite edge portion is substantially less hard and forms a tough supporting portion for the hardened working edge.

Bars having these desired characteristics are produced in accordance with the-invention by a controlled method of heat treatment in which the heat is applied successively to different localized portions of the bar to obtain the desired properties of differential hardness and toughness. Thus in the first heating step, the heat is applied only to the minor portion of the bar along its working edge where maximum hardness is desired in the finished bar, this step being readily carried out by passing the bar through a high frequency induction field of high intensity which is limited in its effective cross-sectional dimensions to receive only the desired limited portion of the bar therethrough. This portion of the bar is thus heated very rapidly to a predetermined high temperature, and it is then immediately quenched with a suitable fluid such as oil in order to limit the cross-sectional area of the bar in which the hardening takes place.

Following quenching, heat is again applied to the bar but only to the portion thereof along its back edge which was not directly heated during the first heating step, and this second heating step may similarly be carried out by means of a high frequency induction field, with the intensity of this field and hence the heating effect bein lower than that of the first step to limit the temperature reached in the bar durin this second heating step to a lower ran e such that the tem- 7 per is drawn from the back ed e portion of the bar. This second heating step is read ly carried out before the bar has coo ed com etely from the first heating step. and in fact while another portion of the same bar is under o n the first heating step. and it has been found desirable to cool the bar slowly in air at room temperature after drawing rather than to ouench it. Durin this Slow coolin he t will flow hv condu tion to the working e e portion of the bar to a sufiieie'ot extent to effe t r u tion in the hardness therein as comp red with the hardness im arted the eto durin the first heatin step. and thus in the finished bar the portion of the bar here wear takes place in use is hardened as desired. while the balance of the bar i phst t lv le s a d. It is also found that with the dr win he thus anplied to the h k p rt on of the, her frfllnwod hv slow cool n su h werpin r as m v tend to t ke place along the bar a a re ult of the fi t he tinc step in s hct ntiallv com n ated for without remi rir addit on l corre ti e tre tment.

This method not on y is ca ab e of C hti'nflouslv producin cutter bars havin the pr ert es of d fferential hardness and tou hness referred to. but it lso offers t e advanta e of re dy control of the de ree of h rdness and tou hness in the Several portions of the bars by su t ble adiustrnent of the draw temperature. Th s is p ticularly advanta eous in v ew of the fa t that different de rees of hardne s are desire in utter b r for Jnrrlans and other re ners depend n upon th p rticular st k to be w rked on an the arti ular time of paper for whi h the stock is intended. With the met od of the pre ent invention adiustment of the intens ty of one or both of the induction fields em loyed in the he t ng steps, and of the te perature and res ure of the quenchin fluid. will control the hardness properties of the finished bars. and after the proper set of conditions is determined each of a pluralitv of suc essive bars treated under these conditions will be found to osse s uniforml the desired properties of differential hardness and tou hness.

It is accordingly another object of the invention to provide a simple, economical and practical method of heat treating cutter bars of the above character under controlled conditions such that the degree of hardness of the finished bar is readily predetermined and controlled and a desired high degree of hardness is obtained along the working edge of the bar while the portion of the bar along its back edge in which the retaining hook portions are formed is of a substantially lower degree of hardness and substantially greater degree of toughness for withstanding the centrifugal force and other stresses on the bar incident to use thereof.

It is also an object of the invention to provide simple apparatus for continually heat treating successive cutter bars of the above character by induction heating under controlled conditions such that the working edge portion of each bar is hardened to a predetermined extent while the opposite edge portion of the bar is caused to be come substantially less hard and substantially tougher than the working edge, and wherein provision is made for ready adjustment and control of the heating conditions in accordance with the particular degree of hardness or toughness desired in different portions of each bar.

Other objects and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.

In the drawings:

Fig. 1 is a view in side elevation of a Jordan bar constructed in accordance with the invention;

Fig. 2 is a diagrammatic perspective view illustrating successive steps of the heat treating method for producing the bar of Fig. 1;

Fig. 3 is a side elevation of the Jordan plug;

Fig. 4 is an enlarged detail view in section showing one of the bars mounted in the Jordan pl Fig. 5 is a fragmentary side elevation of the mounting or back edge portion of the bar of Fig. 4 and including one of the hook portions there- Fig. 6 is a graph aligned with Figs. 4 and 5 to show respectively the typical hardness of the bar from edge to edge before heat treatment, after hardening but before drawing, and in the finished bar after both hardening and drawing;

Fig. 7 is a diagrammatic plan view of apparatus in accordance with the invention for carrying out the heat treating method;

Fig. 8 is a fragmentary side elevation of the apparatus of Fig. '7;

Fig. 9 is an enlarged detail view in section on the line 9-9 of Fig. 8; and

Fig. 10 is an enlarged detail view in section on the line IG|0 of Fig. 8.

Referring to the drawings, which illustrate a preferred embodiment of the invention, Fig. 1 shows a Jordan bar 15 on which the working edge is identified as 20, and which has hook portions 22 formed along its edge 23 opposite working edge 20 for engaging the usual retaining rings of the J ordan plug, the complete plug being shown at 25 in Fig. 3. A lug 26 is formed at one end of the bar to receive the usual keeper ring 2'! at the smaller end of the plug, and bar 15 also has a bead 28 which runs along each side thereof approximately midway between the working edge 29 and back edge 23. The bar l5 as shown is one of many designs of cutter bars, both rotating and stationary, adaptable and responsive to differential heat treatment in accordance with the invention to give it properties of difierential hardness and toughness such that a minor portion thereof running along the working edge 20 is hardened to a comparatively high degree in order to give the desired resistance to abrasion in this portion of the bar, while the portion of the bar extending along its back edge 23 and including the hooks 22 is substantially less hard and substantially tougher than the working edge to support the bar on the plug during operation of the Jordan.

A controlled method of heat treatment for imparting thes properties to successive cutter bars is illustrated diagrammatically in Fig. 2, which shows a plurality of bars 3% arranged in end-to-cnd relation for travel in the direction indicated by the arrow 3| through a. pair of high frequency induction heating fixtures 33 and 3t. As shown, the fixture 33 includes a portion of generally saddle shape arranged to straddle the limited portion of the bar which is intended to form the working edge in the finished bar, shown s its upper edge, and fixture 33 is proportioned to receive only about one-quarter of the width of the bar. This fixture includes an induction coil which is supplied with current at. a. predetermined high wattage to create the desired high intensity field across the portion of the fixture through which the upper edge of each bar 30 passes.

The drawing fixture 34 is of channel shape and of such proportions as to receive approximately th entire lower portion of. each. bar 30? which was excluded from the hardening coil fixture 33, i'. e., the lower approximately three-quarters of the bar, and fixture 34 is shown as spaced from. fixture 33 but sufficiently close thereto to receive the leading end of each bar before its trailing end has left fixture 33. This fixture 34' also includes a high frequency induction coil, and in carrying out the above method, it is supplied with current at a predetermined wattage lower than the hardening coil of the fixture 33 to eiTect heating of the portion of the bar passing therethrough to a predetermined lower temperature than is reached in the portion of the bar heated by the fixtur 33.

A fixture indicated generally at 35 is provided for applying quenching fluid to the edgeportion of the bar heated in the fixture 33, this quenching fixture 35 being preferably arranged as shown to discharge a stream of oil against each side of the heated edge portion of the bar. It has been found desirable to apply the quench ing oil at substantial pressure and constant temperature in order to produce rapid cooling of the heated working edge portion of the bar before the corresponding point on the opposite edge of the bar reaches the drawing fixture 34, and the quenching fixture 35 is accordingly positioned closely adjacent the hardening fixture 33, this immediate and rapid quenching being also desirable in minimizing distortion of the bar as a result of th edge hardening step. The application of the drawing heat at the fixture 34 only along the back edge portion of the bar is also of material importance in controlling and preventing distortion of the bar and thus substantially eliminating the necessity for further corrective treatment.

Further control over the temperatures reached in the bar and thus increased accuracy of control over the hardness properties in the finished bars is obtained by regulating the temperatures of the fixtures 33 and 34- themselves, as by circulating a cooling fluid through the fixtures as indicated at 36 and 31. This may be readily and satisfactorily done by connecting the two fixtures with the same source of quenching fluid used to supply th quenching fixture 35. Also, in order to reduce burning of the quenching oil as the bars pass through the drawing. fixture 33, an air blast 38 may be located as shown between fixtures 3t and 35 to strip excess oil from each bar before it reaches fixture 34.

The power input to each of the coil fixtures 33 and 34, and hence the temperature reached in the bar during the heating and drawing steps, is readily predetermined and controlled in accordance with the initial composition of the bar and the desired final properties of differential hardness and toughness, and these properties are further afiected by the rate of travel of the bars through the fixtures and also by the temperature and pressure of the quenching fluid. For example, Figs. 4 to 6 illustrate these properties of a section of a bar I5 treated as described in connection with Fig. 2 and having subs-tantially the following initial percentage composition :1

Fig. 6 illustrates the changes in the hardness properties of atypical bar It of this composition resulting from treatment by the method as i1- lustrated in Fig. 2 under the following conditions:

Bar width 2% inches. Bar thickness inch. Rate of. bar travel 24 inches per minute. Power input to hardening fixture 23 kw.

Distance between hardening and quenching fixtures 1; inch. Distance between hardening and drawing fixtures 12 inches. Quenching fluid temperature 98 F. Quenching fluid pressure 10 pounds Power input to drawing per sq. inch.

fixture 17 kw.

Under these conditions, with the dimensions of the hardening fixture 33 such as to give an effective length of approximately 4 inches for the field therein, the upper edge portion of the bar reaches a temperature of the order of 1575 F. With the quenching flu-id applied to the bar substantially immediately at the temperature and pressure indicated, the temperature of the upper portion of the bar will drop to a range of the order of 400 to 500 F. before the bar reaches the drawing fixture 3d, and with the dimensions of this fixture 34 such as to give an effective length of approximately 9 inches for the field therein; the drawing temperature in the lower portion of the bar will reach approximately 1200 F. Also, although the heat is applied in this fixture only to the previous unheated portion of the bar, there will be a flow of heat by conduction to the upper edge 20 of the bar to raise its temperature materially, to a range of the order of I000 R, and similarly during the subsequent cooling period, the temperature throughout the entire bar willbe substantially equalized by conduction.

In Fig. 4, the bar i5 is shown fragmentarilfy as mounted in the Jordan plug 25' with its hard working edge 20" outermost, and the graphs in Fig. 6 are aligned with Figs. 4 and 5 to illustrate the changes in the hardness of the bar from edge to edge resulting from heat treatment under the above operating conditions. The continuousline 40 represents the initial hardness of the bar before treatment as measured on the Rockwell C scale, and it will be noted that this hardness is uniform across the entire width of the bar at a value of approximately '28 Rockwell C. The long and short dash curve 42 shows the hardness of the bar following hardening in the fixture 33 and. quenching but before drawing. As shown, the hardness of the bar along and adjacent'its working edge 20 is increased to between 60- and 7 62 Rockwell C, but the hardened area covers only a little over a quarter of the width of the bar, with the hardness dropping sharply to a range not materially different from that of the untreated bar over the remaining portion of its width.

Th curve 44 comprising short dashes shows the hardness of the bar following completion of the drawing step in the fixture 34 and subsequent air cooling at room temperature. it will be noted that the hardness at the working edge 20 has been reduced to approximately 39 Rockwell C, and this hardness is relatively uniform near the edge 20 and over approximately one-quarter of the width of the bar, at which point it drops sharply to about 2'7 Rockwell C. The hardness remains in this range across the adjacent intermediate portion of the bar, which is approxi mately equal in extent to the hard portion, and then it again drops comparatively rapidly at about the middle of the bar to a range between approximately 20 and 22 Rockwell C across the remaining approximately 50% of the width of the bar.

In other words, following completion of the heat treatment under the above conditions, the bar comprises a minor portion, amounting to about one-quarter of its width, extending along and including the working edge which has a hardness substantially greater than the initial hardness of the untreated bar. At the same time, approximately one-half the width of the bar, including its back edge 23 and the hook portion 22, has a hardness which not only is sub stantially lower than that along the working edge but is materially lower than the initial hardness of the untreated bar. The intermediate portion of the bar which connects the hard and soft portions is of an intermediate range of hardness not materially different from that of the untreated bar.

These properties of differential hardness and toughness can be obtained with a high degree of uniformity in a plurality of successive bars of the same composition which are heat treated as described under the same conditions. A full set of bars of substantially identical hardness prop erties for the plug or shell of a refiner or beater can thus be produced by this method, as contrasted with sets of bars heat treated as a batch according to the usual practice, since when a set of bars is batch treated in a furnace, it is commonly found that all bars in the set are not heated to the same extent and that the quenching conditions ar not uniform for all bars in the set. These non-uniform results are avoided in the method of the present invention, which provides for treatment of each successive bar of a set under identical conditions.

Different degrees of hardness in the bars can also be obtained by adjustment of the operating conditions in accordance with the desired results in the finished bar. Thus in. the above example, the hardness of the bar along its working edge can be changed as desired by appropriate adjustment of the power input to the drawing coil 34. For example, if the power input is reduced from 17 kw. to kw., the hardness along the working edge of the bar will measure in the neighborhood of 42 Rockwell C, and if the power input is increased to 19 kw., the hardness of the working edge will be reduced to the neighborhood of 33 Rockwell C. Also, the rate of travel of the bars through the heating fixtures is of importance in determining the temperatures to which the several portions of the bars are heated. For example, in order to obtain the same properties as shown in Fig. 6 in bars of or inch in thickness, the rate of travel should be reduced to from 20 to 22 feet per minute if the other operating conditions remain the same, and similarly for a bar of inch thickness, the rate of travel should be increased to from 28 to 30 feet per minute.

It will thus be apparent that the properties desired in each portion of the bar can be efiectively determined in advance and produced in successive bars as desired. As a result, it is possible and practical in accordance with the invention to obtain bars for the plug or shell of a Jordan or other refiner which are harder along their working edges than the bars previously obtainable by methods of heat treatment in which the hardness along the working edge required compromise with the degree of toughness necessary along the supporting edge of the bars. Also, since as noted the method of the operation makes possible the reduction of the degree of hardness along the back edge of the bar as compared with the initial hardness of the untreated bar, when mounting hooks or lugs such as the hooks 22 are desired, they can be formed therein by punching after heat treatment, thus eliminating the development of cracks at the hook portions such as tend to be caused when the hooks are punched prior to heat treatment of the bars.

Figs. 7 to 10 illustrate more or less diagrammatically a machine for continuously performing the heat treating method described in connection with Fig. 2. The main body 50 of the machine is shown as an elongated channel arranged on one edge and having a plate 5! secured within its open side and a front cover 52, and the base of the machine is indicated generally at 53. The induction coil fixture 33 is shown as supported on a housing 55 containing its associated electrical equipment, and the drawing coil fixture 34 is similarly supported by a housing 56 for its associated electrical apparatus.

The quenching fixture 35 is shown as supported by a bracket 6! adjacent the hardening coil, and this fixture is shown as a quench ring 69 adapted to receive the upper portion of the bar 30 as shown fragmentarily in Fig. 10. The quenching oil is supplied to the ring 60 by a pair of pipes 62 which are connected by a hose E3 and valve 64 with a main oil supply pipe 65 running along the front of the machine. This pipe is in turn supplied with oil under pressure by means of the pump 65 and reservoir 61, and the oil is maintained at constant temperature by circulation through a cooling chamber 58 supplied with a suitable cooling medium such as water as indicated at 59.

The channel 58 supports a series of driven conveyor units 70 for continuously conveying the bars 36 through the coils 55 and 51 and the quenching ring 60. Referring to Fig. 9, each of these conveyor units includes a quill H supported by the channel at and plate 5! and having a spindle I2 rotatably mounted therein by means of bearings 13 and 14. At its inner end, each spindle carries a friction wheel 75 counterbored on one side to receive a smaller friction wheel 15 having a serrated or otherwise roughened periphery. A wheel Tl is positioned between the friction wheel 15 and a shoulder 18 on the spindle, and a coil spring is held in engagement with the outer face of friction wheel 15 by a nut 8| threaded on the end of the spindle. These parts are proportioned to form a groove between the wheels I and I! for receiving the lower edge portion of the bar 30, with the spring 86 serving to maintain axial pressure on the bar between wheels I5 and TI.

The outer or forward end of each spindle I2 carries a sprocket wheel 83, and a chain 8 engages each sprocket 83 and the two end sprockets 85 and 86. The end sprocket 85 is shown as on the same shaft with a sprocket 81 driven through chain 88 and sprocket 89 by a motor 90 provided with a variable transmission such as a Reeves drive 9| for adjusting the speed of sprocket 89. The end sprocket 86 has a tensioned mounting comprising a fork 92 extending through the end plate 93 and carrying a spring '94 held under compression against plate 93 by nut 95. A guard 96 extends along the channel 50 above the sprockets 83 to insure proper driving engagement of the chain 84 with each sprocket.

With this arrangement, the spindles ll are all positively driven and thus cause rotation of the wheels l5, l6 and TI to convey the successive bars 33 lengthwise of the machine and through the hardening and drawing coils and the quenching fixture. Since the bars are heated to high temperatures as described, it is desirable to prevent undue heating of the parts of this conveyor mechanism which come into contact with them, and accordingly provision is made for cooling the conveyor. As shown in Fig. 9, each of the spindles II is provided with a central bore $19 which extends from its outer end to approximately the mid-plane of the small friction wheel I6, and a tube Iliii of smaller outer diameter than bore 99 is inserted therein to a position near the inner end thereof. The other end of each of these tubes is connected with the oil supply pipe 65 through a petco'ck IOI, and thus oil from the same source as the quenching oil for fiixture 34 is supplied under pressure to the inner end of each bore 99, whence it flows to the outer end and discharges as indicated by the arrows I02 into a trough I03 connected with reservoir 67, from which it is withdrawn by pump 66 at I04 and returned to the system through the cooling chamber 68.

Pressure rolls are provided abov certain of the conveyor rollers for maintaining the bars 30 in proper vertical'alignment as they travel through the machine and also for assuring frictional contact between the lower edges of the bars and the friction wheels I6. Referring to Fig. 10, each pressur roll HE] is grooved to receive the upper edge of the bars 39 and is rotatably mounted on one end of a crank arm III having its opposite end journaled in a bearing block I I 2 mounted on channel 50. A coil spring H5 is mounted between a lug H6 on the block H2 and a lug II! on the crank III in position to bias the arm in clockwise direction as viewed in Fig. 8, and a bolt H8 carried by arm III serves as an adjustable stop limiting downward movement of the pressure rolls.

In operation as the successive bars travel through the machine, they pass under the rolls H0 and cause the latter to rise against the springs H5, the springs thus serving to exert downward pressure on the bars to maintain them in driven contact with the friction wheels 76. Furthermore, with the rolls I I0 grooved as shown, the bars are held in proper lateral and vertical relation with the coil fixtures 33 and 34 to assure that only the desired portion of each bar passes through these fixtures as described. It should in 10 this connect-ion be noted that each of th rolls I ID in Fig. 8 is provided with the biased crank mounting described, the showing of this mechanism being eliminated for most of rolls III] in Figs. 7 and 8 for simplicity of illustration.

This machine is accordingly well suited for performing the heat treating method described in connection with Fig. 2, and it has been successfully operated to produce Jordan bars having the properties of differential hardness illustrated by Fig. 6. The machine is readily adjustable as desired in accordance with the temperatures at the heating fixtures, the temperature and pressure of the quenching oil and the rate of travel of the bars required to produce a predetermined condition of differential hardness in the finished bars, and thus it provides for accurate repetition of the same conditions for each of a plurality of successive bars to assure uniform properties in all the bars of a set.

Reference is made to our copending application Serial No. 426,532,, filed April 29, 1954, as a division of the present case.

While the article and method herein described, and the form of apparatus for carrying this method into effect, constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to this precise article, method and form of apparatus, and that changes may be made in either Without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

l. A cutter bar for a refiner of the character described comprising an integrally formed and initially homogeneous elongated bar having one edge thereof constiuting a working edge, said bar having a portion thereof including said working edge and a zone of substantial cross-section adjacent said working edge hardened to a predetermined relatively high degree of hardness, and the remainder of said bar including the opposite edge thereof being substantially less hard than said working edge portion to provide a tough supporting portion for said bar.

2. A cutter bar for a refiner of the character described comprising an integrally formed and initially homogeneous elongated bar having one edge thereof constituting a working edge, said bar being differentially hardened by induction heating to provide a predetermined relatively 'high degree of hardness along said working edge and a zone of substantial cross-section adjacent said working edge with the remainder of said bar including the opposite edge thereof being substantially less hard to provide a tough supporting portion for said bar.

3. A cutter bar for a refiner of the character described comprising an integrally formed and initially homogeneous elongated bar having one edge thereof constituting a working edge, said bar having a portion thereof of substantial crosssection less than one-half the width of said bar extending along and including said working edge hardened to a predetermined relatively high degree of hardness, another portion of said bar of substantial cross-section less than one-half the width of said bar extending along and including the opposite edge thereof being substantially less hard to provide a tough supporting portion for said hardened working edge, and the remainder of said bar intermediate said hardened and tough portions being of a hardness intermediate the degrees of hardness of said edge portions.

4. A cutter bar for a refiner of the character described comprising an integrally formed and initially homogeneous elongated bar having one edge thereof constituting a working edge, said bar having a portion thereof extending along said Working edge and across approximately oneiourth of the width thereof hardened to a predetermined relatively high degree of hardness, the portion of said bar extending along the opposite edge thereof and across approximately one-half the width thereof being substantially less hard to provide a tough supporting portion for said bar, and the remainder of said bar intermediate said edge portions being of a hardness intermediate the degrees of hardness of said edge portions.

5. A cutter bar for a refiner of the character described comprising an integrally formed and initially homogeneous elongated bar of a predetermined substantially uniform initial degree of hardness, one edge of said bar constituting a working edge, said bar having a portion thereof of substantial cross-section less than one-half the width of said bar extending along said working edge hardened to a predetermined degree of hardness substantially greater than said initial degree of hardness, and another portion of said bar of substantial cross-section less than onehalf the Width of said bar extending along and including the opposite edge thereof being substantially less hard than said initial degree of hardness to provide a tough supporting portion for said hardened working edge.

6. A cutter bar for a refiner of the character described comprising an integrally formed and initially homogeneous elongated bar of a predetermined substantially uniform initial degree of hardness, one edge of said bar constituting a working edge, said bar having a portion thereof of substantial cross-section less than one-half the width of said bar extending along said working edge hardened to a predetermined degree of hardness substantially greater than said initial degree of hardness, another portion of said bar of substantial cross-section less than one-half the width of said bar extending along and including the opposite edge thereof being substantially less hard than said initial degree of hardness, and the remainder of said bar intermediate and connecting said edge portions being of a degree of hardness not materially different from said initial degree of hardness.

7. A cutter bar for the plug of a Jordan engine comprising an integrally formed and initially homogeneous elongated bar having one working edge, a portion of said bar of substantial crosssection less than one-half the width of said bar extending along and including said working edge being of a predetermined relatively high degree of hardness, the remainder of said bar including the opposite edge thereof being substantially less hard than said working edge, and said bar having hooked portions formed in said less hard portion adjacent said opposite edge for securing said bar to said plug.

8. A cutter bar for the plug of a Jordan engine comprising an integrally formed and initially homogeneous elongated bar having one working edge, a portion of said bar of substantial crosssection less than one-half the width of said bar extending along and including said working edge being of a predetermined relatively high degree of hardness, another portion of said bar of substantial cross-section less than one-half the width of said bar extending along the opposite edge thereof being substantially less hard to provide a tough supporting portion for said bar, said bar having hooked portions formed in said tough portion for securing said bar to said plug, and said bar also including a portion intermediate said edge portions of a degree of hardness intermediate the degrees of hardness of said edge portions.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 550,253 Cross et a1 Nov. 26, 1895 1,248,814 Craig Dec. 4, 1917 1,396,600 Simpson Nov. 8, 1921 1,538,028 Davis May 19, 1925 1,560,743 Van Buskirk Nov. 10, 1925 2,008,228 Riehm July 16, 1935 2,067,549 Sykes Jan. 12, 1937 2,103,716 Frickey Dec. 28, 1937 2,138,811 Abe Dec. 6, 1938 2,144,377 Kennedy Jan. 17, 1939 2,146,791 Bridge Feb. 14, 1939 2,146,830 Martindale Feb. 14, 1939 2,254,307 Mott et al. Sept. 2, 1941 2,310,384 Arnoldy Feb. 9, 1943 2,371,459 Mittelmann Mar. 13, 1945 2,514,547 Jones July 11, 1950

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