US3128806A

US3128806A - shields

Info

Publication number: US3128806A
Authority: US
Priority date: 1963-11-20
Publication date: 1964-04-14
Anticipated expiration: 1981-04-14
Also published as: GB976326A

Description

April 14, 1964 D. w. SHIELDS ARM BIASING CONSTRUCTION FOR RING TYPE DEBARKERS Filed Sept. 24, 1962 5 Sheets-Sheet l INVENTOR. .Dea-n LL}. Shields BY 2, 2 I fl x-Q H'b'tor-neys A ril 14, 1964 D. w. SHIELDS ARM BIASING CONSTRUCTION FOR RING TYPE DEBARKERS Filed Sept. 24, 1962 INVENTOR. Dean S/lieIc/S BY 3 Sheets-Sheet 2 5.42 zf/YWM Hzzarn e 5 United States Patent Ofiice Patented Apr. 14., 1964 3,128,805 ARM BIASING CGNSTRUCTION FOR RING TYPE DEBARKERS Dean W. Shields, Birmingham, A121,, assignor to Budow Manufacturing Company, Inc., a corporation of Alabama Filed Sept. 24, 1962, Ser. No. 225,634 Claims. (Cl. 144-408) This invention relates generally to ring type debarkers and specifically to means for urging the tool carrying arms toward the log to be debarked.

In this art it is now known that it is desirable to urge the debarking tools against the log with substantially constant pressure regardless of the size log being debarked. That is, during a given season of the year and when debarking logs of a given species harvested in any given season of the year, such constant tool pressure is desirable. Since logs to be debarked in a particular machine may vary in diameter from say 5 inches to 30 inches, some means must be provided to compensate for such size variations, especially when the arms are loaded by springs. Generally speaking, spring systems exert varying forces depending upon the degree of compression or tension thereof and this of course varies with each log diameter. In fact, the distance of the tools from the center of the ring varies during the debarking of each log since logs are generally larger at the butt ends than at the top ends. Further, it is imperative that such arm loading mechanisms be simple, rugged and trouble-free and most desirable that the system involve as few lubrication points and pivots as is possible.

In view of the foregoing the prime object of my invention is to provide a tool arm loading system which accomplishes the objects and has the advantages above mentioned.

Another object is to provide a spring system for each arm and to transmit the force of each spring system to its associated arm through a flexible member such as a cable, the cable passing over the outer end or nose of the arm which is so contoured that in all inner and outer positions of the tool end of the arm, the effective force of the spring urging the tool into contact with the log remains substantially constant throughout the range of log sizes for which the debarker is designed.

A further object is to provide apparatus of the character designated in which the force of the spring system is transmitted directly to the outer end of the tool arm, eliminating various intermediate arms, links and the like, and providing apparatus in which the force transmitting system itself is substantially unaffected by centrifugal force on the parts thereof as the debarker ring rotates.

A still further object is to so design the nose or outer end of the arm around which the flexible member passes as to compensate for the adverse effect on constant tool force of the spring travel, the change in eifective moment arm due to rotation of the arm about its pivot, and centrifugal force on the tool arm itself.

Apparatus illustrating features of my invention is shown in the accompanying drawings forming a part hereof in which:

FIG. 1 is a front elevational view of the ring of a debarker having my improved arm biasing means applied thereto, removed from the remainder of the debarker, partly broken away and in section;

FIG. 2 is an enlarged detail fragmental front elevational view with certain parts broken away and in section;

FIG. 3 (sheet 1) is a slightly enlarged detail sectional view taken generally along line 33 of FIG. 2;

FIG. 4 is a fragmental end elevational view of one of the debarking arms looking generally in the direction of the arrows 44 of FIG. 2;

FIG. 5 is a fragmental plan view of the end of one of the spring housings and the cross head for the ends of the flexible member that extend around and under the outer ends of the debarker arms;

FIG. 6 is a graph plotting the relation between given angular positions of one of the tool arms and centrifugal force on said arm;

FIG. 7 is a graph plotting the relation between the spring travel in inches and the force exerted by the spring in pounds;

FIG. 8 is a graph plotting the effective lever arm in inches against the rotation of the arm in degrees starting at full open position; and,

FIG. 9 is a graph showing the relation between the tool movement in inches against the loading force on the tool in pounds, with the ring rotating at its designed speed.

Referring now to the drawings for a better understanding of my invention I show at 10 the ring of a debarker which as Will be understood has an opening 11 therethrough through which the log to be debarked passes. It will be understood that the ring is mounted on suitable supports, bearings, trunnions or the like, not shown, for rotation in the direction of arrow 12.

Mounted on one face, namely the front face, or in other words, the side of the ring from which the log approaches, are a plurality of debarker arms indicated generally by the numeral '13. Since each of the arms and its associated spring mechanism are identical, a description of one will suffice for all. It will be understood that the debarker may be equipped with three, five, or more arms.

Each of the arms 13 may be fabricated of plate members welded together and each may embody a hub 14. The hub 14 is mounted on the outer race 16 of an antifriction bearing 17 (FIG. 3). The inner race 18 of the bearing is mounted on a pin 19 which may have a threaded outer end 21 receiving a lock nut 21*. The bearing may be sealed in the hub 14 by an oil seal 22. The pin 19 may have an intermediate shoulder 24 and a rearward end section 19 threaded to receive a lock nut 26. The pin 1? is supported in a suitable bushing 27 passing through the periphery of the ring which will be understood is made up of the

plates

10 and 18 The entire ring may be mounted for rotation on large diameter journal 10.

The arms are slightly spaced, on the order of, say, 20 thousandths inch, from wear plates 28 (FIG. 1) welded to the side of the ring. In normal operation the wear plates are not contacted by the arms; however, should a log hit the ends of the arms head-on and deflect them toward the ring, the wear plates are contacted by the sides of the arms to prevent damage to the bearings and pins already described.

Mounted adjacent each arm, as by being welded to a bracket 29 outstanding from the ring, is a spring housing in the form of a tubular member 31. As best shown in FIG. 2, the spring housing is closed at its forward end by a closure 32 and is open at its rear end 33. Also, the closure 32 is provided with a vertically elongated opening 34.

Mounted in each of the housings 31 is a double coil compression spring 36. The spring abuts at its upper end against an extension 32 spaced inwardly from the closure 32 and its outer end abuts a disc 37 having a threaded opening at its center.

Passing through the elongated opening 34 is a rod 38. The rod 38 is provided with a threaded inner end 39 onto which the disc 37 is screwed. A lock nut 41 serves to hold the spring in adjusted position within its housing as determined by the position of threaded disc or nut 37.

On the forward end of rod 38 is a cross head 42. Firmly secured in suitable openings in the cross head are the

ends

43 and 44 of a cable 45. The cable 45 passes around the nose or cam surface 13* of the arm, which later will be described, and the bight thereof passes under a cleat 46 welded to the underside of the arm 13.

From what has been described it will be seen that the springs pulling through the cables 45 urge each of the arms inwardly so that the tools 13 thereof are urged into contact with the log L to be debarked. Suitable stop means in the form of brackets 47 are provided for each arm to limit inward movement of the tools.

lt is the shape or contour of the outer end or nose 13 of each arm, in combination with a flexible member such as the cables 45 to transmit the force of the springs 36 thereto with which this invention is particularly concerned.

Upon considering the position of the arms in FIG. 2 of the drawings, it will be seen that the effective force of the springs urging the tool 13' inwardly is the force of the spring times the lever arm indicated at 48. It will further be understood that when the ring is rotating, centrifugal force acting through the center of mass of the lower part of the arms, indicated diagrammatically at 49, tends to move the tool 13 away from the log. *Further, as the arms open outwardly, thereby to operate upon a log of larger diameter than the one shown in FIG. 2, the effective lever arm 48 decreases. Still further, as the tool ends of the arms move outwardly, further compressing the spring 36, the force exerted by such spring increases. It is these three variables that I have been enabled to design out by the particular shape and contour of the nose or end 13 of the arm against which the flexible member bears. In other words, by shaping the surface which contacts the cable in predetermined fashion, I can compensate for the increase in spring pressure, the effect of centrifugal force, and the change in the efiective lever arm 48.

Referring now particularly to FIG. 6 of the drawings, I will first discuss the effect of centrifugal force which tends to open the arms. In a typical 30 inch debarker equipped with my invention and having arms heavy enough to do the job, the centrifugal force on the arms will start at nothing at zero rpm. and may increase to as much as 1040 pounds at the design speed of, say, 75 rpm. of the ring. Therefore, one consideration of the shape or contour of the nose 13* is to make the lever arm 48 longer, in order to compensate for the opening effect on the arms of centrifugal force.

Referring now to FIG. 7 it will be understood that the springs here involved are considerably heavy springs, such for instance springs of a nature in which the force may increase, starting with the arms in fully closed position, by as much as 600 pounds per inch of travel of the rod 38 outwardly of the housing 31. Such springs may be compressed as much as six inches. Therefore, such springs may exert a force of 2400 pounds when the arms are fully closed, since they are pre-compressed for initial loading and as much as 4800 pounds when the arms are fully open.

Referring now to FIG. 8 it will be seen that the effective lever arm 48, namely, a line normal to the center line of the cable and passing through the center of the pivot point, also varies due to simple rotation of the arm about its pivot point. Thus, for instance, in a 30 inch debarker, and starting with the arms at fully open position and calling this zero degrees rotation, it may be desirable for the lever arm 48 to be on the order of, say, 3 inches, and at fully closed position on the order of, say, 4.4 inches.

In FIG. 9 I show the result which may be achieved by properly contouring the nose or cable engaging outer end of the arm 13. Thus, the loading force on the tool, at the innermost position for the smallest log to be debarked may be on the order of 320 pounds, depending upon the season of the year. It is desired that the tool loading force remain constant. In other words, FIG. 9 of the drawings represents the sum total of the design which this invention affords, taking into account the variables diagrammatically illustrated in FIGS. 6, 7 and 8. By increasing the initial tension on the springs, in the example given, I can increase this constant tool loading force to, say 600 pounds; by decreasing it, in the example given, I can maintain this constant force, at say 240 pounds.

The precise method of determining the shape of the cam or contoured portion 13 of the arms is as follows:

Having selected the spring 36 required to do the job and knowing the variation in its force per linear inch of compression, knowing the effective center of mass and the weight of the arm and the revolutions per minute of the ring, knowing by layout the change in the effective lever arm 48 for a tool arm of given length, having selected the length of the arm outwardly of the pivot point, by plotting the required forces for each degree of movement of the arm, I can arrive at the exact length of the effective lever arm 48 for each degree of rotation of the tool arm to maintain constant tool loading. Having arrived at these figures it is a simple matter then to plot the exact shape of the nose or cam portion 13.

It is to be especially noted that by so shaping the nose of the arm over which the cable passes, thus to keep the tool pressure force constant throughout the range of log sizes for which the debarker is designed, I have eliminated a large number of linkages, pivots and the like. My improved arm biasing apparatus thus is simple, rugged, and fully effective.

While I have stated herein that the line indicating the effective tool force in FIG. 9 is absolutely constant, it will be appreciated that the effective force of gravity on the arms, in their several positions, is also a variable. However, I have neglected taking this into account, first, because it is small, and second, because it does not affect the constancy of the tool pressure more than one or two percent, which is negligible.

In view of the foregoing it will be apparent that I have devised an improved means for urging or biasing debarker arms to their work, at substantially constant force throughout the entire range of log sizes for which the debarker is designed. By passing the rod 38 through a washer 38 which may be of felt or other fibrous material, and which is free to slide in the slot 38", and then by providing a closure for the end 33 of the housing 31, not shown, the springs are substantially sealed in their housings. Sufiicient air can leak around the washer 38 so that no part of the apparatus in the housing becomes a piston, thus to interfere with its movement.

It is to be noted that my improved arm urging or biasing system embodies a minimum number of parts which are subject to centrifugal force which would have undesirable inertia. Therefore, the tools of a debarker equipped with my improved system ride readily into and out of depressions, over knots and the like on the surfaces of the logs. By simply running in or out on the threaded washers or nuts 37, the tool loading force may be varied. In the illustration given it may be increased to exert as much as 600 pounds on the tools, or as little as around 200 pounds.

In actual practice debarkers equipped with my improved apparatus have proved to be extremely satisfactory, trouble-free and rugged in operation. As of the date of this application about fifteen debarkers thus equipped have been built and sold commercially. These have ranged in size from three arm, 24 inch debarkers, to five arm, 38 inch debarkers. By using a double tapered roller hearing as shown in FIG. 3, I am enabled to seal the bearings, maintaining them always well lubricated, thus to increase the trouble-free operation of the apparatus.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

What I claim is:

l. The combination with the ring of a ring type debarker,

(a) of a tool carrying arm pivotally mounted intermediate its ends on a side of the ring,

(b) a spring abutment for a compression spring mounted on the ring adjacent the pivot point of the arm,

() a compression spring having one end resting against the abutment,

(d) a cross head in contact with the opposite end of the spring,

(e) a flexible member operatively connected at one end to the cross head and with its other end passing loosely around at least a portion of the outer end of the arm and secured to the arm,

(1) and the surface of the outer end of the arm engaged by the flexible member being so contoured that the resultant force of the spring urging the tool toward the center of the ring remains substantially constant throughout the range of inner and outer movement of the tool carrying end of the arm.

2. The combination with the ring of a ring type debarker,

(a) of an arm pivoted intermediate its ends to a side of the ring and having a debarking tool on its inner end,

(b) an abutment for a compression spring mounted on said side of the ring adjacent said pivot point,

(0) a compression spring having one end resting against the abutment,

(d) a flexible member operatively connected at one end to the ends of the spring opposite the abutment and passing loosely over at least a portion of the end of the arm outwardly of the pivot point thereof,

(e) means securing the flexible member to the arm at a point thereon removed from the portion thereof over which the flexible member loosely passes, and

(f) the portion of the end of the arm loosely engaged by the flexible member being so contoured that as the arm moves from closed position to open position, thus to compress the spring, the effective lever arm through which the spring acts on the debarker arm decreases, thereby to load the tools substantially constantly throughout the range of log sizes for which the debarker is designed.

3. For use in a ring type debarker,

(a) a tool arm pivoted intermediate its inner and outer ends and disposed to carry a debarking tool on its inner end,

(b) a spring for the arm characterized in that the force delivered thereby varies with its travel,

(0) a flexible member operatively connected to transmit the force of said spring to the arm, and

(d) a contoured section on the arm outwardly of its pivot point over which the cable passes in unattached manner, the cable being secured to the arm at a point other than in said contoured section thereof, the configuration of said contoured section being such as to compensate for the change in force exerted by the spring and for the change in effective lever arm through which the force thereof is applied to said arm, whereby the tool is urged against logs of varying diameter with substantially constant force.

4. Apparatus as defined in claim 3 in which the configuration of said contoured part of the arm also is constructed and arranged to compensate at least in part for the opening effect on the arms of centrifugal force to which the arm is subjected when in place on the ring of a debarker.

5. Apparatus as defined in claim 3 in which,

(a) the spring is a compression spring,

(b) and in which the flexible member is a length of cable or the like doubled back upon itself with the bight thereof secured to the arm and the free ends thereof operatively connected to the spring in a fashion to transmit compressive force thereof to the arms through the flexible member.

References Cited in the file of this patent UNITED STATES PATENTS 2,786,499 Brundell et a1 Mar. 26, 1957 2,897,859 Annis Aug. 4, 1959 3,058,500 Smith Oct. 16, 1962

Claims

3. FOR USE IN A RING TYPE DEBARKER, (A) A TOOL ARM PIVOTED INTERMEDIATE ITS INNER AND OUTER ENDS AND DISPOSED TO CARRY A DEBARKING TOOL ON ITS INNER END, (B) A SPRING FOR THE ARM CHARACTERIZED IN THAT THE FORCE DELIVERED THEREBY VARIES WITH ITS TRAVEL, (C) A FLEXIBLE MEMBER OPERATIVELY CONNECTED TO TRANSMIT THE FORCE OF SAID SPRING TO THE ARM, AND (D) A CONTOURED SECTION ON THE ARM OUTWARDLY OF ITS PIVOT POINT OVER WHICH THE CABLE PASSES IN UNATTACHED MANNER, THE CABLE BEING SECURED TO THE ARM AT A POINT OTHER THAN IN SAID CONTOURED SECTION THEREOF, THE CONFIGURATION OF SAID CONTOURED SECTION BEING SUCH AS TO COMPENSATE FOR THE CHANGE IN FORCE EXERTED BY THE SPRING AND FOR THE CHANGE IN EFFECTIVE LEVER ARM THROUGH WHICH THE FORCE THEREOF IS APPLIED TO SAID ARM, WHEREBY THE TOOL IS URGED AGAINST LOGS OF VARYING DIAMETER WITH SUBSTANTIALLY CONSTANT FORCE.