US3550653A - Tree trunk slasher - Google Patents

Description

United States Patent lnventors Edward Gauthier Baraga; I Robert A. Larson, LAnse; Philip E.

LaTendresse, Baraga, Mich. No. 658,703 Filed Ktl' l'i'i'ii? Patented Dec. 29, 1970 Assignee Pettibone Corporation a corporation of Delaware TREE TRUNK SLASHER 6 Claims, 17 Drawing Figs. u.s.c|.....' 143/46, 143/48, 143/92, 144/3 lnt. 8271) 5/00, B27b 31/00, B27c 9/00 Field of Search 143/43,

[56] References Cited UNITED STATES PATENTS 2,889,858 6/1959 Roberts 43 4 3,229,733 1/1966 Albers..... 145/46 3,343,644 9/1967 Kljuchnikov etal.. 153/46X 3,414,027 12/1968 Larva et al 143/46 3,455,352 7/1969 Sanders etal 143/46 Primary Examiner-Harrison C. Hinson Anarney-Darbo, Robertson & Vandenburgh ABSTRACT: A self-loading vehicle saws tree trunks to pulpwood lengths and uses the same source of power for advancing the vehicle to new operating locations. It also may be hauled at higher speed by a tractor-truck. Nearly all of its operations are hydraulic, including self-propulsion. Among its special features are some hydraulic features, some features of folding for highway travel. some yieldability of projecting parts forming bins. provision of two bins to which cut lengths may be selectively ejected, and means for holding a second tree trunk in ready" position and dumping it onto a feed conveyor when the conveyor is clear.

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P 14' E ZaYZdrsS 2 ward Gazzffiz r E Ji PATENTED DEC29 l9 1 sum 07 OF M TREE TRUNK SLASHER INTRODUCTION This invention relates to mobile self-loading tree trunk slashers, machines which can move themselves from site to site in a forest and which pick up long tree trunks which have been felled and cut them intologs of predetermined length such as pulpwood length.

Machines of this character have been known before, but the present invention provides a number of advantages over prior machines of this type. Use of a single engine for all functions except major highway transport is made thoroughly practicable. All or nearly all functions are performed by hydraulic means. For highway transport, major portions of the structure fold so as to reduce the lengthof the structure and make it suitable for truck-tractor hauling. In use, the cut lengths of logs are received by a choice of two bins, each formed of parts yieldable in case a tree is struck during self-propulsion, and then self-retuming. A problem of proper traction, due to the fact that the weight on one set of wheels is approximately three times that on another, is overcome in a very simple manner by providing a hydraulic motor for each set, these motors being connected hydraulically in parallel but providing the proper ratio of torque for their wheels by virtue of one being connected to a set of wheels through a speed reducing chain drive. A bumper retards the tree trunk as it is fed to its final position for sawing off a length, but does not try to return to its original position prematurely. This is accomplished in a very simple manner by causing a cylinder associated with the saw feed arm to act as a pump as the return stroke of this arm is completed, thus pressing the bumper back in place hydraulically.

Additional objects and advantages of the invention will be apparent from the following description and from the drawings.

DESIGNATION OF FIGURES FIG. 1 is a side elevation of one form of mobile tree trunk slasher of the present invention, substantially this form having been successfully operated.

FIG. 2 is a top view of the structure shown in FIG. 1 with the loader and some other parts omitted for simplification.

FIG. 3 is a fragmentary side elevation on a greatly enlarged scale of approximately the left-hand one-third of the structure shown in FIG. 1.

FIG. 4 is a transverse sectional view taken approximately along the line 4-4 of FIG. 3.

FIG. 5 is a view looking down on one of the arms forming the log receiving bin or cradle showing the manner in which it may yield if it hits an obstruction.

FIG. 6 is a vertical sectional view, fragmentary, taken approximately along the line 6-6 of FIG. 4.

FIGS. 7 to 13 are detailed views of different parts of the structure.

FIG. 14 is a view of the machine folded and mounted on a truck-tractor for highway transportation.

FIG. 15 is a view showing a log in ready" position, awaiting a clear conveyor on which to be dropped.

FIG. 16 is a hydraulic diagram of the machine with omission of some conventional details.

FIG. 17 is a circuit diagram of the machine, omitting some conventional detailsf INTENT CLAUSE Although the following disclosure offered for public dissemination is detailed to ensure adequacy and aid understanding, this is not intended to prejudice that purpose of a patent which is to cover each new inventive concept therein no matter how others may later disguise it by variations in form or additions or further improvements. The claims at the end hereof are intended as the chief air toward this purpose, as it is these that meet the requirement of pointing out the parts, improvements. or combinations in which the inventive concepts are found.

GENERAL DESCRIPTION In the form of tree trunk slasher illustrated, a main frame or chassis 11 is carried by two sets of wheels 12 and 13, both drivable hydraulically as described further below. The wheel set 13 is mounted on a swing axle 14 which may be steered by hydraulic cylinder 16. A standard 17 extends upwardly from the chassis and has mounted at the top thereof a loader 18 which swings on standard 17 and includes articulated arms 19 and 21 the latter of which carries a grapple 22 by which tree trunks may be loaded onto a conveyor (rollers 24) which moves the trunks longitudinally of chassis 11. The rollers 241.

are hydraulically driven. One of them, 24A, is carried at the tip of extension 26 of the chassis 11. The others extend along the chassis 11 to a point adjacent to a saw 28. With the saw 28 in its withdrawn position, a tree trunk may be fed past it until the trunk strikes a bumper 29 which yieldingly stops the advance of the trunk, actuating a switch described below in the course of doing so. This switch causes the advance of the saw which is pivotably mounted as seen in FIG. 4. At the start of the advance of the saw 28, the hydraulic drive of rollers 24 is discontinued. As the saw completes its cut, this severed length of log drops or is lowered onto a V-shaped tilt table 31. Table 31 is then automatically tilted either to the right or left, as seen in FIG. 4 to dump the severed log into the selected one of the two bins 32 seen in FIG. 4. Both bins are formed by heavy U shaped bars 32. Saw 28 is now retracted, tilt table 31 returned to level position, bumper 29 returned to its initial position, and the drive of rollers 24 resumed. When either bin is filled, or when convenient, loader 18 is used to remove the logs from it, usually placing them on a truck for transportation.

Loader 18 includes an operators platform 34 which preferably swings with the loader. A second operator's platform 36 may be provided for exercising such occasional manual intervention of the sawing operation as is required. It is also possible to provide a full set of controls on the loader platform 34 so that a single operator may attend the entire machine.

The loader 18 is a conventional unit and need not be described in detail.

During operation, a set of outrigger feet 38 will be pressed hydraulically against the ground to resist the tilting action of lifting a tree trunk by the loader l8.

All of the operations of the illustrated equipment are hydraulic with the exception that if the saw is a circular saw, as distinguished from a chain saw, driving it by a drive shaft represented in FIGS. 1 and 2 by the broken line 41 is preferred. The driven end of drive shaft 41 will usually be connected to engine 42 by a set of V-belts. The engine 42 also drives a set of positive displacement pumps, capable of developing high pressures, for the hydraulic operations.

Additional features are or may be provided as described below.

CONVEYOR ROLLERS The conveyor rollers 24 are preferably of the form shown in FIG. 10. Due to their general contour, they may be defined as a log-centering shape, with reference to the fact that the diameter reduces toward the center from both ends. Each roller is made up of a core tube 46 to which a number of radial plates 47 are welded, the plates 47 being provided with teeth 48 to ensure adequate feeding bite on the undersurface of the trunk resting on them. Added strength is provided by end plates 49.

The tube 46 is pinned to a drive shaft 51, carried by bearings 52 and coupled by flexible coupling 53 to the output shaft of a rotary hydraulic motor 54. The various hydraulic motors 54 may all be connected for control by a single valve, although for reasons described below, the motor for end roller 24A is preferably provided with a separate valve for discontinuing its drive while the other rollers are driven.

TILT TABLE The tilt table 31 may be controlled by a pair of cylinders 56 and 57 as seen in FIG. 4. The cylinders are butted end to end, the cylinder 56 controlling a piston rod 58 and the cylinder 57 controlling a piston rod 59. When one of the piston rods is extended, the table is level, as seen in FIG. 4, full lines. The cylinder 56 is used for this purpose. It is apparent that if both piston rods are extended, the table will tilt to the left as seen in broken lines in FIG. 4. Likewise, it is apparent that if both piston rods are retracted, the table will tilt in the opposite direction.

Preferably a bin is located on each side. They may be used selectively in two ways. According to one method, all of the cut logs are placed in either selected bin until it is filled. Then, while the other bin is used, the loader operator can remove the cut lengths from the filled bin. According to another method, the selection of the bin to be used can depend upon the nature of the wood, thus permitting two kinds of wood to be sorted out.

FLEXIBLE AND TILTABLE BIN ARMS In the illustrated form of the invention, the arm 32 is doubly movable. One movement is illustrated in FIG. 5. If during the course of vehicle movement between working positions, a projecting arm 32 should strike a tree, it can yield as indicated in FIG. 5. After passing the tree, it returns to the full line position shown in FIG. which may be called the perpendicular or centered position. During operation the arms maintain themselves in this centered position. These features are accomplished in a very simple manner seen best a the right in FIG. 4. A cap 61 is welded to the end of bar 32 at an angle of approximately 30 and rests on a collar 62, the top of which is also at an angle of 30". It is apparent that the movement shown in FIG. 5 will cause the cap 61 to ride up on collar 62, pulling the arm up with it, so that gravity tends to recenter the arm 32.

The preferred welding construction is shown in FIG. 6 where it is seen'that cap 61 is formed in part by a ring which is welded along its inside to the bar 32. It may be aesthetically desirable to add a closure cap 63 especially if bars 32 are hollow, and in that event a closure cap 64 at their outer ends will also be desirable.

Another movement of bars 32 is provided by pivotally mounting the collars 62, as best seen in FIG. 6. The two pivotal movement allows the bars 32 to be swung up over or alongside of the tilt plate 31 during road transportation, as seen in FIG. 14. When the place of operation is reached, they are merely swung back downwardly until they come to rest in brackets 66 which are of approximately semicylindrical shape to receive the bars 32.

FOLDING OF FRAME Although the swinging in of arms 32, and the hydraulic retraction of Outriggers 38, will reduce the width of the machine to a width permissible for highway movement, longitudinal folding 32, also provided. Thus the extension 26 may be swung about the pivotal point 68 to the position shown in FIG. 14. This folding is greatly facilitated by the fact that the conveyor is a hydraulically driven live roller conveyor. The single drive motor 54A, for the feed roller 24A at the tip of the extension 26 can be connected by a pair of pipes, each with a sufficient length of hose connection 69 to bend around the pivotal axis 68.

By providing a very large brace 71 abutting the end of the main chassis 11, it is possible to provide sufficient strength so that when the extension is unfolded, the entire weight of tree trunks, even with some bumping, can be withstood.

As seen in FIG. 1, a so called fifth wheel" 72 is provided for coupling this vehicle to a truck-tractor, as seen in FIG. 14. FIG. 14 also illustrates the fact that when the tractor has been backed under the fifth wheel 72. the nearest wheels 12 are raised off of the ground. Upon disconnecting rear wheels 13 SAWlNG-AID Loo 'SUPPORTER FIGS. 7, 8 and 9 illustrate a devieegw hich my or may not be found to be needed. It is more likely, to be needed with a chain saw than with a circle saw. Also it is less likely to be needed if the last feed roller 24 is as close as possible to the saw. According to this device, the end of the length of the trunk to be cut off can be supported adjacent to the saw by a support plate 81 carried by a swinging bracket 82. This structure may swing on a shaft 83 and be controlled by a hydraulic cylinder 84. The upper end of plate 81 has a log-centering contour similar to the contour of the feed rollers 24.

Normally the plate 81 will be swung down to the position shown in dotted lines in FIG. 7. When need for it is encountered or expected, cylinder 84 will be operated to swing it up against the log after the log has been fed to cutting position, so that the trailing end of the length to" be cut will merely be supported in this position as the saw cuts through it. Then, or after the saw returns sufficiently to be safely free, the connections which actuated cylinder 84 are reversed to return support plate 81 to this dotted line position. The ejection of the cut length then follows as if the plate 81 had not been used. It is at present contemplated that this control of cylinder 84 will be manual. However, if frequent need should'be encountered, it could be made automatic.

Unless a customer especially requests it, it is expected to omit this feature, at least when a circle saw is used.

SAW MOUNTING AND ACT UATION The mounting and actuating of the saw is seen in FIG. 4. It is carried by an arm 86 of platelike nature except for suitable bearings or journaling on shaft 87. The arm 86 is advanced to make the cut and returned by cylinder 88. The saw of course will be rotatably carried by the arm 86 through a suitable bearing and driven by a drive shaft 41 provided with a telescopic portion and universal joints. The shaft 41 is preferably driven by a multibelt drive through engine 42. It is important that this engine be of the class known as stationary engines so that it will be provided with adequate cooling independently of movement of the vehicle. This same engine also drives all the hydraulic pumps.

BUMPER AND HYDRAULICS THEREOF The value of a tree trunk slasher obviously depends upon the amount of cut wood it can produce per day. This in turn not only depends on the speed of cut but on the shortness of time between cuts. To contribute to the shortness between cuts, relatively high speed of feed of the tree trunk is here provided. However, rapid movement of the tree trunk represents a problem of producing a quick stop of the heavy tree trunk as it reaches the desired point. It has been common to provide a bumper or target 29 to aid in this purpose and heretofore they have been stationary or spring mounted. A better mounting with better action is provided by the present invention, as seen in FIG. 3.

Bumper 29 is carried by a tube 91 which slides in a fixed sleeve 92. Preferably when the bumper has moved about 2% inches from its outermost position, it comes to rest against a resilient cushion or pad 93. It is preferred, however, that the log speed be greatly reduced before this cushion is reached. The retardation of the log is preferably accomplished mainly by a hydraulic cylinder 94.

Driving of the conveyor rollers is discontinued as a result of actuation of limit switch 96. This is actuated by a rod 97 on bumper 29 and which slides through fixed guide 98. This rod and guide have a further function of maintaining bumper 29 in proper orientation. It may be noted that the upper part of this bumper is preferably in the form of a grill to give the operator visibility through it.

The special hydraulics for cylinder 94 according to one aspect of the present invention are seen at the lower left of FIG. 16.'When the tree trunk hits the bumper 29, piston 97 of cylinder 94 ejects hydraulic fluid from the cylinder. At this time there is no place for the fluid to go except through restrictor valve 98 to common return line 99 leading to reservoir 101. In FIG. 6 the reservoir 101 is shown physically near the center of the FIG. but is also represented at numerous other points diagrammatically. At the speed of feed of the tree trunk, the valve 98 offers substantial resistance and rapidly retards the movement of the trunk.

After about an inch of movement of bumper 29, switch 96 is actuated. As represented by broken lines in FIG. 6, switch 96 will cause actuation of saw arm 86. A piston 102, linked to saw arm 86 as seen best in F IO. 12 is drawn out of a cylinder 103, which may be called a master cylinder. When this movement starts, oil from cylinder 94.may flow into cylinder 103 and the resistance to movement of the tree trunk is reduced. By this time, however, the tree trunk has been greatly retarded, and it may now push bumper 29 relatively gently against the cushion 93. However, because actuation of saw arm 86 also actuates switch 175 to stop the drive of the conveyor, the log may ideally stop sooner. Then bumper 29 is free to recede further and danger of binding is substantially eliminated.

It may be observed that the pressure which continues to be developed in cylinder 94 when switch 96 is actuated is exerted in cylinder 103 in a direction to aid in starting the saw arm 102, thus more quickly overcoming the inertia of this saw arm and the heavy saw blade so they more quickly attain the desired advancing speed. It may also be observed that except for the slight return movement of bumper 29 induced by cushion or pad 93, there is no force exerted rearwardly by bumper 29 on the tree trunk to cause any binding on the saw after the cut is complete.

During the cutting stroke of arm 86, piston 102 draws hydraulic fluid into cylinder 103 to fill this cylinder. The amount of oil required beyond that supplied by cylinder'94 is drawn from the common return line 99 through check valve 104, this flow being aided by the slight pressure always encountered in a common return line 99.

After the cut is complete, as the saw arm 86 is returned, movement of piston 102 into cylinder 103 ejects hydraulic fluid from the cylinder 103. This oil cannot flow back through check valve 104 and its flow through restrictor valve 98 is resisted. Accordingly, some of this oil flows into cylinder 94 to eject its piston 97 thereby returning bumper 29 to its outermost position. When this position of 'buinper 29 has been reached, all of the remaining oil ejectedfrom cylinder 103 flows out through restrictor valve 98.

Both of the cylinders 94 and 103 are connected, at the ends through which the pistons extend, to a return line leading to reservoir 101. This is merely to prevent the bleeding which would be encountered if air were admitted to the cylinders on the idle side of the piston.

It may be observed in FIG. 3 that cylinder 94 is readily removable for servicing, being pinned to a link 106 which in turn is pinned to lugs 107.

FEEDER HOLDDOWN There are times when it is desirable to press the tree trunk firmly down on the feed rollers 24. This is especially likely when small trunks are being sawed, perhaps several at a time, or when the remaining piece is only a little longer than the length to be cut. The need is preferably supplied by a heavy or weighted plate 108 pivoted at 109, at a point such that an advancing log can pass under the pivoted rear end of the plate 108 and cam the plate up, the front end of the plate then pressing the trunk onto the forward feed roller 24.

READY POSITION FOR NEXT TREE TRUNK In order to disclose the preferred from of the invention, it is noted that the machine is preferably provided with facilities for holding a second tree trunk in ready position and dumping this trunk onto the conveyor when space for it has been cleared. FIG. 15 shows a second tree trunk 111A in the ready position while the previous tree trunk 111 is still on the conveyor. Tree trunk 111A rests in part on roller 24A and in part on a pivoted cradle-shaped arm 112. When tree trunk 111 has advanced to clear the way for trunk 111A, cradlearm 112 will be hydraulically actuated to dump trunk 111A onto the conveyor. This is a valuable feature for saving time between cuts, and it also gives more flexibility in the use of loader 18.

While the tree trunk rests in ready position, the drive of hydraulic motor 54A for feed roller 24A is discontinued. It will be resumed at the same time that the trunk 111A is dumped onto the conveyor so that then all of the conveyor rollers by which this trunk is supported will be driven, when feeding is desired.

HYDRAULIC CIRCUIT Although most of the special features of the hydraulic circuitry will'already be apparent, they will be made more clear by FIG. 16 which also shows some features not already indicated.

Engine 42 drives a set of hydraulic pumps 116 each having its own filtered intake 117. One of the filtered intakes is shown as double the others because its associated section A of the pump has substantially larger capacity than sections B to D.

This section A of the pump is used for driving the hydraulic drive motor 54 for the feed rolls. It will be observed that these feed rolls are connected in interpositioned or intermingled sets of three connected in hydraulic series. The series connections prevent one motor from spinning freely if the log is not resting on its associated roller, and tending to consume the entire oil flow. The interpositioning of the sets substantially eliminates the possibility that all three rollers of any one set will be in a position to spin freely. A solenoid valve 119 controls the bypass 121 for the end motor 54A, in order to shut this motor off when it is supporting a log in the ready position as already indicated.

A solenoid valve 122 controls the supply of fluid to motors 54. It has been represented as a double solenoid valve springcentered and with an optional manual control lever. When in the center position to which it is returned by the springs, it will be in a power-through" condition making the hydraulic fluid from section A of pump 116 available through line 123 for driving the vehicle wheels as described below. When either solenoid 124 or solenoid 126 is operated, pressure fluid will be supplied to the corresponding side of the hydraulic motors 54 for driving the roller conveyor, the two solenoids providing for drive, in opposite directions. The forward drive is of course the direction which will be used except in rare occasions when the tree trunk hangs up and should be backed away. When power is connected to one side of the motors 54, the other side will be connected by valve 122 to return. Each of the connecting lines 127 and 128 is provided with a pressure relief valve 118, discharging to return so that no matter what pressure is available from the pump for other purposes, the pressure on motors 54 will be limited as desired.

The next two sections B and C of pump 116 are connected to valves 131 and 132, both of which merely give a choice between carrying the pressure fluid to the loader 18 for its various functions, or making it available for driving the vehicle wheels.

The last section D of pump 116 is connected to valve 133 which controls the steering cylinder 16 seen in FIG. 2. When valve 133 is in neutral position, it passes the power fluid through line 134 for the saw operating functions controlled by valve cluster 136. Line 134 may desirably include a pressure unloading or relief valve 137. A known advantage of an unloading valve is to save power by allowing discharge at low pressure so long as pressure is maintained in accumulator 138 without added flow to it.

While driving the vehicle by its own power, the hydraulic fluid will not be needed for the saw or feed roll functions and hence it may be devoted entirely to the driving and steering functions. The section D of pump 16 is used for nothing else than steering at this time and hence steering is reliably available..

The drive of the wheels 12 and 13 is controlled by valve complex 141. In neutral, the drive motors 142 and 143 are not driven and in fact are preferably hydraulically locked. Moving the spools of valve cluster 141 connects motors 142 and 143 for forward drive, and shifting the spool of valve of 141 in the opposite direction reverses the direction of drive.

Motors 142 and 143 are preferably identical as a matter of reducing the number of different parts. However, the torque which can be applied to wheels 12 without slipping is approximately three times that which-can be applied to wheels 13 without slipping, under like conditions because there is approximately three times as much of the vehicle weight on wheels 12 as on wheels 13. This differential torque is provided by connecting motor 143 in direct drive relationship to the differential driving wheel 13, while the motor 142 is connected to the differential for wheels 12 through a 3 to 1 ratio speed reducing chain drive l44.-The motors 142 and 143 are connected hydraulically in parallel so that both can be subjected to full fluid pressure.

Each of solenoids 146, 147, etc., controls a separate section of valve cluster 136. Each section is a reversing valve. Section A controls the feed or return of the saw, actuating cylinder 88. To limit the speed of flow in the cutting direction, an adjustable flow control valve 151 is provided. It is preferred that the full face of the piston be used for the return stroke, inasmuch as the only time when great force may be needed is for withdrawing the saw under wedging conditions. A manual onoff valve 152 locks the saw in an advanced position, so it will not project beyond the vehicle when-traveling.

Sections B and C control the cradle for the ready log and the support plate 81. Section D causes ejection of the cut log in the direction chosen by selector valve 153. When Section D connects fluid power to line 154, this applies power below both pistons, projecting the upper piston and retracting the lower piston. As seen in FIG. 4, this will hold the V-shaped tilt table 31 in a generally horizontal position so that the cut length of log will be properly held until the cut is complete. The spaces above the two pistons are connected to discharge through lines 156 and 157. When the saw has completed its cut and as the saw arm 86 reaches the limit of its movement, it actuates a limit switch to control solenoid 149 to reverse section B of the valve so that line 158 is connected to hydraulic pressure fluid and line 154 is connected to discharge. Depending upon the position of valve 153, controlled by a solenoid, fluid pressure from line 158 will be connected either to the upper end of the upper cylinder or to the upper end of the lower cylinder. in the latter case, the tilt table would be tilted to eject the log in one direction and in the other case, the tilt table would be swung in the opposite direction to eject the log in the opposite direction. In either event, the log falls into the appropriate bin.

When solenoid 149 is deenergized for returning tilt table 31 to horizontal, only the one-of lines 156, 157 which had been connected to pressure fluid for ejecting the log is connected to the return line, the other being blocked. In normal operation, this causes no trouble. If an abnormal situation causes failure of tilt table to restore to level, a momentary shifting of valve 153 will remedy this.

8 ELECTRICAL CIRCUIT Although circuits for the foregoing can be devised without trouble by those skilled in the art, FIG. 17 shows some special or less common features. It will be observed at the left-hand end of the FIG. one set of switches represents those accessible to the operator on platform 36. Preferably all of these switches are duplicated by switches accessible to an operator on the platform 34 of the loader so that one-man operation will be possible when desired. In general, these are all supplied with l2-volt electrical voltage from source wire 161 which, through key-operated switch 160, is connected to the electrical system of the stationary engine 42, this electrical system being shown at the lower right of FIG. 17, and needing no explanation.

When switch 86 is actuated by the target, it preferably actuates a counter as shown and also energizes line 162 leading through the saw shifted" switch 163. If the saw is in its out or returned position, switch 163 (having been tripped by one end of lost-motion tripper 165) connects wire 162 to wire 164, actuating solenoid 146 to reverse section A of valve 136 and cause cylinder 88 to feed the saw.

After the saw has passed through the cut, and as it reaches the limit of its movement, saw arm 86 trips switch 163 to disconnect wire 164 thereby deenergizing the saw feed solenoid. Thereupon, Section A of valve 136 returns by spring action and reverses the connections for cylinder 88 to return the saw. Solenoid 146 can be deenergized to convert saw feed to saw return in other ways. At each operator's position is a sawretum switch 166 which is a normally closed switch connected in series with wire 162. Either operator can open his switch 166 to back the saw out of the cut. When the open switch 166 is allowed to close, the feed of the saw is resumed, unless bumper 29 has returned.

In addition, a governor or speed-responsive switch 167 is connected in the grounding line 168 for solenoid 146. Governor 167 is mounted on the arbor of the saw, and if the speed of the saw falls below a predetermined speed satisfactory for sawing, governor switch 167 opens the ground circuit. As soon as the saw gets back to speed, governor switch 167 closes the ground circuit and feed will resume. It will be observed that with the connection illustrated, the governor switch 167 is even a safeguard against manual operation of feed switches 169, because if the saw is not up to speed their circuit will be broken at governor switch 167. Occasionally, however, it is desirable to advance the saw while it is stationary or rotating slowly, as in making adjustments, or as a step in locking the saw at its inner position for travel. To permit this, a normally open manual switch 171 is provided for overriding the governor switch 167.

When saw shifted switch 163 is tripped at the end of the feeding stroke of saw arm 186, it also connects line 162 to line 172 which causes ejection of the cut log, and disconnects line 164 to cause return of the saw. The ejection is caused by completion of the circuit through lines 172 and 173 and solenoid 149. The feeding of the tree trunk is initiated by completing a circuit through a switch 175 and line 174, a three-position switch 176 at both stations, connected in series, a solenoid 124, the forward solenoid for controlling valve means 122. Switch 175 is a safety conveyor feeding switch open at all times except when the saw is at its outermost position. If advancing trunk snags on something, either operator can reverse the drive by shifting his switch 176 to the reverse position. Also, either operator can stop the drive by shifting his switch 176 to the intermediate position. When either switch is in reverse position, and provided that switch 176 at the left in FIG. 17 is not in the off position, solenoid 126 will be energized instead of solenoid 127, causing the opposite actuation of valve means 122 to reverse the drive of the feed rollers. At the left there is also illustrated a manual handle 181 which is preferably provided for manual operation of the valve means 122 by the operate at that position in the event any power failure or the like sh uld prevent operation by the switches.

clearlyseen in FIG. '17, closing either switch 183 energizes solenoid 148 to actuate the section C of valve 136, reversing the hydraulic connections to cylinder 84 of FIG. 7.

The switches 186 by which either operator may choose between right-hand ejection and left-hand ejection may be of the three-pole type illustrated so-that either operator, re-

gardless of the position of the switch remotely positioned from him, can cause energization or deenergization of solenoid 187 to control valve 153. A different circuit can be used if it is preferred tohave a switch at one of the positions always in a certain position to indicate a corresponding direction of ejection.

Operating either of switches 188 will energize solenoid 189 to operate valve 119 to open or close the bypass. of drive motor 54A for the feed roller 24A at the tail of extension 26. Alternatively this solenoid can be connected in parallel with solenoid 147 to drive roller 24A whenever cylinder 113 is actuated to move its tree trunk onto the conveyor.

Preferably, the saw mill is made operable by manual operation of the essential valves, in the event of failure of the electrical valve-operating circuitry. This is accomplished by locating valves 136 and 153 at the supervisors position (above platfonn 36) and providing them, as well as more remote valve 122, with handles 190 accessible to him. Valves for the loader are conventionally manual. Valve 119 and its ready log" device are not essential; but a manual control for valve 119 above platfonn 36 could be added if desired.

ADDlTlONAL FEATURES OR DETAILS variations as compared to wheels 12. When wheels 12are.

lag. Because the conveyor cannot start feeding the log until the saw is safely out of the way, there is no danger in this.

We claim:

1. A sawmill including a log-feeding conveyor, a bumper toward which the conveyor feeds logs at substantial speed, means for severing the log at a given distance from the bumper, and energy dissipating means for resisting the movement of the bumper on impact by a log, said means being substantially free, initially after operation, of a resilient tendency to return the bumper, and means for subsequently causing return of the bumper after a cut complete.

2. A sawmill, according to the previous claim including a hydraulic cylinder piston combination connected to the bumper to eject hydraulic fluid when the bumper is moved by the impact of the log, and means to resist that discharge to dissipate energy and retard the log.

I 3. A saw mill, according to the previous claim, including a power saw, an arm for advancing the power saw to cut the log,

a cylinder and piston combination coupled to the arm to eject fluid when the arm returns after a saw cut, said cylinders being connected hydraulically so that the fluid ejected upon return of the arm returns the bumper.

4. A sawmill according to claim 1, including support means lying under the log portion to be severed, for supporting said portion near its level when fed to prevent its falling to a wedging angle during severing, said support means being constructed to dump the portion after a cut is complete.

5. A sawmill including a conveyor for feeding long heavy pieces to be cut, a bumper toward which the conveyor feeds pieces at substantial speed, means for severing the piece at a given distance from the bumper, and energy dissipating means for resisting, substantially by energy dissipation, the movement of the bumper on impact by a piece, said means being substantially free, initially after operation and regardless of the distance it is moved by impact of the piece, of a resilient tendency to return the bumper to cause binding, and means raised off the ground by the fifth wheel, that connection is not v rigid. Accordingly, the rocking action about pin 192 should be restrained. This is accomplished by connecting links 193.

The hydraulic drive motor 143 is carried by the housing structure of axle 191 and is unaffected by the rocking action. It is also unaffected by the steering action as axle 191 and in termediate bolster 194 jointly swing about the steering axis for steering.

Valve cluster 136 is a parallel type rather than a powerthrough type. The available pressure is applied through all of its sections at all times. The available flow from accumulator 138 is usually enough to operate more than one of the connected cylinders at once; but if not, the more resistant would for subsequently causing return of the bumper after a cut is complete.

6. A sawmill including a conveyor for feeding long heavy pieces to be cut, a drive for'the conveyor, a bumper toward which the conveyorfeeds pieces at substantial speed, means for severing the piece at a given distance from the bumper, a hydraulic cylinder piston combination connected to the bumper to eject hydraulic fluid when the bumper is moved by the impact of the piece, and means to resist that discharge to dissipate energy and retard the piece:

means actuated at least in part by the initial movement of the bumper by the piece to stop the drive of the conveyor;

said bumper then being free to recede further to substan tially eliminate the danger of binding; and a power saw, an arm for advancing the power saw to cut the piece, and means, inefi'ective until after the cut is complete, for returning the bumper.

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