This invention relates to band saw machines of the com¬ mercial type in which an endless saw blade band is looped abou a pair of wheels, one of which is driven. The wheels are usually mounted in the saw head or housing, and in some of these machines the housing is hinged, while in other types it is mounted on vertical posts or guides. In some installations the blade is moved through the work, while in other types of machines the work is fed through the blade. Approximately mid¬ way between the wheels of all band saws, a pair of saw guides are located, which are spaced apart a distance greater than the cross-sectional size of work pieces to be cut by the machines. These saw guides hold the blade at a fixed angle, apply uniform pressure to the back edge of the band saw blade and define the cutting span of the blade. As the teeth of the blade cut through the work piece, all teeth in contact with the work have an equal, albeit, minimum force applied thereto. This causes the blade to bow outwardly from the kerf of the work and each tooth does not cut as full a chip as it is inherently capable of cutting. When cutting very hard or large work pieces, the cutting efficiency of conventional band saws is thus relatively low and this is manifested by relatively long cutting times and short blade life per unit cross-sectional diameter of the work piece.

A number of solutions have been suggested in the prior art to overcome these drawbacks. Generally, these proposed

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solutions have involved variations in the configuration of the band saw blade. One such proposal is disclosed in my prior patent application, Serial No. 434,712, filed October 15, 1982 now Patent No. 4,425,653 granted on January 3, 1984. My prior application discusses a number of earlier patents, including Patent Nos. 4,195,543, 4,160,397, 4,205,571, 1,850,478, 817,361, 286,706 and Canadian Patent No. 883,602. In all these prior patents, improved cutting action is claimed to be related to variations in the blade confi ^• g-su"-ration.

The present invention involves a basically different approach, being one in which a conventional band saw blade is used, but the blade holder or machine is rocked or oscillated so that the cutting angle of the blade, relative to the work piece, is continually and automatically varied in the cutting plane of the blade. The oscillation is such that the length of the kerf in contact with the blade at any one time is reduced in com¬ parison with that of a parallel edged band saw blade when used in a conventional band saw machine.

The Rathert Patent No. 2,549,236 discloses a Log Bucking Chain Saw in which a chain saw is mounted at its outer end on a vertical motor driven chain drive whereby the outer end of the chain saw may be raised or lowered under the control of an operating switch on the handle of the chain saw. In effect, this arrangement provides a power means for lifting or lowering the outer end of the chain saw in much the same manner as might be used by woodsman or carpenter in manually rocking a chain saw

or hand saw in cutting through a work piece. Despite th existence of such prior art, application is not aware of an band saw machines in which means has been provided for automati cally and continuously oscillating a band saw relative to a wor piece.

The principal object of this invention is to provide band, saw machine which imparts a continuous rocking action t the cutting span of the blade so that the teeth of the blade cu the work along a convex curve whereby the total pressure on th blade is reduced to enable the teeth to cut a larger chip wit resultant faster cutting action and improved blade wear.

Also, an important object of this invention is to pro¬ vide an oscillating band saw machine in which the cutting angle of the saw blade is automatically and continuously varied rela¬ tive to the work for improved cutting efficiency.

Another object of this invention is to provide a band saw of the above type in which the blade of the band saw per se is oscillated relative to the work piece.

A further object of this invention is to provide a band saw of the above type in which the band saw and its drive means are oscillated relative to the work piece.

The above and other objects and advantages of this invention will be more readily appreciated by a reading of the following description with reference to the accompanying drawings in which:

Fig. 1 is a side elevational view of the band saw illustrative of its oscillating mechanism.

Fig. 2 is a rear elevational view of the band saw illustrative of its oscillating mechanism.

Fig. 3 is a section on an enlarged scale taken along line 3-3 of Fig. 2;

Fig. 4 is a section on an enlarged scale taken along line 4-4 of Fig. 2;

Fig. 5 is a partial elevational view showing saw guides of a band saw illustrative of an alternative embodiment of this invention, and

Fig. 6 is a cross-sectional view on an enlarged scale showing a blade oscillating means of the alternative embodiment of this invention.

Referring in detail to the drawings, in Fig. 1 is shown a band saw machine 8 of the type embodying this invention. The machine includes a base 10 and a head or band saw housing 12. A work piece w is shown mounted on the upper surface of the base is held in fixed relation thereon by vise or clamping members 14

The band saw head 12 comprises a hinged or pivotable housing in which a band saw 16 in the form of an endless loop is disposed around an idler wheel or pulley (not shown) disposed within one end of the housing and a drive wheel (not shown) disposed in the opposite end of the housing. As illustrated,

the band saw housing is supported at its outer end by an hydraulic or pneumatic cyliner 17 and connecting rod 19 and at its other end by an eccentric drive mechanism 18 by which the entire housing is rocked or oscillated continually during a sawing operation. The cylinder 17 is pivotably mounted so that the housing can be rocked in a circular path which lies in the plane of the saw blade.

The lower span of the band saw 16 is disposed between a pair of spaced saw guide arms 20 and 22 which include guide blocks or rolls at their lower ends to hold the moving blade in a plane perpendicular to the work w and urge the blade against the work piece.

The drive mechanism includes an electric drive motor 24 coupled to a reduction gear box 26. The output shaft 28 of the gear box is rotatably supported by bearings in laterally spaced fixed mounting brackets 30 and 32, the lower edges of which are affixed to the upper surface of base 10.

Disposed between the brackets 30 and 32 is a cam or eccentric shaft 34 which has its outer ends supported by ball bearings 35 fitted into circular cutouts in mounting plates 36 and 38 which are caused to oscillate in a response to rotation by the eccentric shaft 34, the eccentric being driven by rota¬ tion of shaft 28. As best shown in Fig. 3 the inner edges of the plates 36 and 38 are affixed to a cylindrical tubular member 40 which itself is attached to the edges of a pair of laterally spaced plates 42 and 44 which fixedly extend from the

end of the housing 12. The center of rotation of cam shaft 34 has sufficient offset or eccentricity from the axis of shaft 28 to impart a predetermined oscillation or rocking action to the saw blade 16. The result is that the blade 16 is presented to the work in a cycle of constantly changing angular orientation. Thus, any point on each of the plates 36 and 38 and on cutting span of the blade 16 is caused to rotate about a circular path in response to the rotation of the drive shaft 28 and cam shaft 34. It has been found that a cam throw or offset of about 1/2 inch and a drive shaft speed of about 20 rpm provides a suitable oscillating cycle or periodicity for the angular variation of the saw blade. A cycle time of about 1-10 seconds is deemed suitable for purposes of this invention, while a 2-4 second cycle is considered preferable.

To evaluate the cutting efficiency of a band saw machine embodying this invention, a number of actual cutting tests were conducted using the same band saw machine for the tests of Examples I and II. For Example I, the machine was used in a conventional manner and for Example II, it was oscillated.

EXAMPLE I

A H.E.M. Band Saw machine was fitted with a standard type bimetal welded edge with M-42 steel cutting edge band saw 1" x .035" x 3/4 vari-tooth and was run at 90 feet/minute with coolant PB-10, 3:1. A work piece of 304 stainless steel, 8 ^M diameter bar stock was sawed in a series of through cuts and the time recorded for each slice as follows:

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CUT NO. TIME/MIN. CUT NO. TIME/MIN.

1. 16.20 6. 26.43

2. 16.00 7. 29.54

3. 18.86 8. 29.90

4. 21.08 9. 32.82

5. 25.28 10. 39.74

Avg. 25.59

EXAMPLE II

A H.E.M. Band Saw machine of the above type was modi¬ fied so that an identical band saw blade was oscillated at a constantly changing angle relative to the work as described above. Again, a 304 stainless steel 8" diameter bar was sawed through in a sequence of cuts and the following data recorded:

CUT NO. TIME/MIN. CUT NO. TIME/MIN.

1. 11.29 6. 11.42

2. 10.72 7. 11.44

3. 10.92 8. 11.90

4. 11.04 9. 12.50

5. 11.27 10. 13.29

Avg. 11.44

Comparison of these two tests shows a remarkable improvement in all cutting times and it will also be noted that by cut No. 10, the saw blade in Example 1 was badly worn since its cutting time had increased by more than 100%. In contrast for the blade in Example II, cut No. 10 shows only about a 15%

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increase in cutting time. In addition, the rocking band saw in Example II was used to make a total of thirty (30) separate cuts and the time recorded for the last cut was 15.75 min. for a loss in cutting efficiency of only about 40%.

An alternate embodiment of this invention is illus¬ trated in Figs. 5 and 6 and comprises of a band saw machine which may be of the conventional type, such as a "H.E.M." Band Saw or a "DO ALL" Band Saw wherein the cutting head of the machine is hinded at one end thereof. In this embodiment, the head of the band saw machine is not rocked or oscillated but is maintained at essentially the same angle relative to the work while the cutting span of the saw blade 50 between saw guides 46 and 48 is itself deflected or rocked relative to the work w.

The effect of varying the cutting angle of the blade per se has been found to be generally similar to that achieved by rocking the band saw head as described above in conjunction with Figs. 1-4.

There are, of course, a number of different types of mechanisms which could be used for changing the cutting angle of the blade and one such means is illustrated in Figs. 5 and 6.

As best shown in Fig. 6, a cylinder 56 is bored into the lower end of the saw guide arm 46 and a tubular conduit 52 is connected to a pressurized fluid source, such as for a pneumatic or hydraulic system. Disposed within the cylinder is a small piston 54 equipped with a sealing ring 58. to form a

fluid tight seal with the cylinder wall. A connecting pin 6 having its upper shank portion slidably fitted into a bore i the lower end of the piston 54 is adapted to transmit downwar motion of the piston 54 to saw guide block 60 engaged with the upper edge portion of the band saw blade 50. The lower end of the connecting pin 62 is affixed as at 63 to the block 60 so that downward movement of the piston 54 is transmitted by the guide block 60 to the band saw 50.

A cross pin 64 extends transversely through the connec¬ tor pin 62, piston 54 and a vertically elongated slot 65 in the wall of cylinder 46. This construction serves to retain the several movable components in assembled relation while per¬ mitting reciprocable movement of piston 54. Means is provided to apply fluid high pressure intermittently to piston 54 and to release such pressure. As the piston 54 moves downward in the saw guide arm 46, the leading end portion of the blade 50 in relation to its direction of movement, as indicated by the arrow in Fig. 5, is deflected downward by the guide block 60 as it advances past the arm 46. This causes the span of blade 50 moving between the saw guides 46 and 48 to be angularly tilted. The blade is held in this angular orientation for a predeter¬ mined period of time and this is retracted when high pressure in the cylinder 56 is released. Tension of the blade and pressure against the work will cause the blade 50 to resume to its undeflected condition, that is both the leading and trailing end portions of the blade are again disposed normal to the saw guides 46 and 48. In this embodiment, the cutting span of the

blade per se is alternatively tilted and released in an inter¬ mittent or cyclical rocking action.

EXAMPLE III

To evaluate the performance of this embodiment, a series of cutting tests were conducted using a standard "DO ALL" C-80 type Band Saw. The machine was fitted with a standard type bimetal, welded edge band saw having an M-42 steel cutting edge 1" x .035" x 3/4 vari-tooth. The saw was run at a speed of 120 feet per minute using a Houghton 3:1 coolant and the machine was operated in a conventional manner. A series of through cuts were made on 304 stainless steel bar stock of 4 inch diameter. The time for each complete cut-off was recorded as follows:

CUT NO. TIME/MIN. CUT NO. ^' TIME/MIN.

1. 7.82 11. 9.38

3. 7.61 13. 9.90

5. 5.75 15. 10.20

7. 6.64 17. 10.98

9. 9.19 19. 11.41

Avg. 8 . 89

EXAMPLE IV

For this Example all the conditions of Example III wer duplicated, except that the fluid pressure operated piston 54, as shown in Fig. 6, was operated on a 2 second cycle i.e., 1 seconds "on" and 1/2 seconds "off". It is considered that an suitable time cycle could be used as long as the blade angle is intermittently varied by a 2-4 second cycle is preferred. With the angle of the cutting span portion of the blade being inter¬ mittently varied, the following results were obtained:

CUT NO. TIME/MIN. CUT NO. TIME/MIN.

1. 3.91 11. 3.78

3. 3.49 13. 3.95

5. 3.03 15. 4.12

7. 3.37 17. 4.26

9. 3.86 19. 4.21

Avg. 3.80

With this blade, the tests were continued for 35 cuts and the final cutting time was 5.22 minutes.

A comparison of these two tests again showed a most surprising and dramatic improvement in cutting efficiency and blade wear.

Both embodiments of this invention disclosed herein manifest a remarkable improvement in cutting speed and blade wear for a band saw in which the blade angle, as presented to the work, is varied as it cuts through the work and not main-

tained at a constant angle for any substantial period of time as is invariably done in conventional band saws.

While cutting efficiencies were achieved by either rocking the band saw machine or the cutting span of the blade, it will be apparent to those skilled in the art that means could also be provided, whereby the work itself could be manipulated relative to the saw blade with equivalent results in faster cutting speed and longer blade wear.

Having thus disclosed this invention what is claimed is: