US1847657A - Sawmill dog - Google Patents

Description

March `1, 1932. R LANGILL ET AL SAWMILL DOG original Filed April 28. 192'7 3 Sheets-Sheet 2 INVENTOR.

mi M 46V )umu-f ATTORNEY5.

March 1, 1932. R. LANGILL ET AL SAWMILL DOG f Original Filed April 28. 1927 3 Sheets-Sheet 3 www Wm MMM@ L m 4 Patented Mar. l, 1932 nNTED STATES 4PAralar OFFICE ROSS LAN GILL AND STANLEY B. LANG-ILL, MENOMINEE, MICHIGAN, ASSIGNORS T0 THE PRESCOTT COMPANY, OF MENOMINEE, MICHIGAN, A CORPORA'J?IONV OF MICHI- GAN SAWMILL Doe s Application `filed April 28, 1927, Serial No. 187,170 `Renewed January 9, 1931.

This invention relates in general to saw.

mill dogs, and more particularly to an im'- proved fluid pressure operated sawmill' dog of the type forming the subject matter of the eo-pending application of Adolph L. Haase, for sawmill dog, filed June (i, 1925, Serial No. eased l The object of the invention is to provide an improved type of sawmill dog of this character wherein a fluid pressure'motor operates through a chain or other similar flexible ele-v ment for the purpose not only of positively and powerfully urging both log engaging members into proper gripping engagement with the log or board, but also for positively retracting both of the log engaging members. In other words, both'log ei'igaging members are positively forced into gripping engage ment with the log or board, 'and both log engaging members are positively forced apart to disengage the log or board.

Another important object of the invention is to provide a'sawmill dog of this character 'which is' organized With'the knee 1n such H manner that the entire dog may shift back and forth with respect to the vface of the knee under the control of a liuid pressure motor whereby the log engaging members maybe positioned well out beyond the' face of the knee for the purpose ofengaging a log or heavy timber, and also may be positioned adjacent the face of the knee for the purpose of 'engaging a board of relatively th'inor'light timber. n

Another object is to'provide adeg of this character 'wherein vthe flexible element is'so organized 'with the fluid pressure motor, the frame of the dog and the log engaging mem` bers as to impart a straight line movement to the log engaging'members in such manner as not to tend to bind the same.

A further object is to provide a dog having the advantages and capacities referred to and which is of simple and durable construction, reliable and effective in operation, easily controllable, 'and comparatively inenpensive to manufacture.

Other objects and advantages reside in certain novel features of the ,construction, arrangement aud combination o fparts which will be hereinafter more fully described and' vention and organized AWith a knee plate whereby it is attached Yto the knee of the sawmill; and

Figure 2 is a View partly in side elevation looking toward .the opposite side ofthe air dog from that shown in Figure l and partly in vertical section, the dog being shown 'mounted on the knee of the sawmill; and

F igureB isa view 1n front elevation of the arrangement shown 1n Figure 2; and.

Figures 4 and 5 are views in horizontal sec- -tiontaken on line t`4of Figure 3, but showing the different positions of the dog relative to the face of theknee; and

Figure 46 is a fragmentary View in side elevation similarto Figure l but illustrating a different position of the dog relative to the knee face; and y 4'Figure 7 isafragmentary view in section von line (1-7 of Figure 6. Y v

- `Referring,to the drawings, it will be seen that thedog embodying the present invention includes a frame designated generally at l, the frame 1 having'a horizontalbase portion 2, a vertical side` portion 3 vwhich may be ribbed-`for ,strength and cut out to reduce :its weight, and a horizontal top portion 4.

Preferably, the frame is a one piece casting, the ibase port1on2 and-top portion 4L of the frame l fhavmg' aligned sockets 5 formed thereon, and in these aligned sockets the ends of a pair of front guiderods 6 and of a single rear guide rod 7 are lit-ted and secured as by means ofpins 8.

Gnltlie front guide rods 6 an upper logr engagmgniember designated generally at 9 and a lower log engaging member designa-ted generally at 10` are mounted for vertical slidving `movement toward and awayy from each other. The log engagingzmemberst) and 10 comprise slides 1l and l2 respectively, the slides ll and 12 having openings in which therods 6 are slidably fittedwhereby the a piston 23,

slides 11 and 12 may be freely adjusted up and down on the rods 6. A downwardly directed log engaging tooth 13 is fixed to and carried by the slide 11 and a similar but upwardly directed tooth 14 is fixed to and carried by an integral extension 12a of the slide 12. v

For the purpose of positively pulling the log engaging members toward each other and into engagement with the log,or the like, and also for positively pulling both of the log engaging members out of the log and away from each other a fluid pressure motor designated generally at F is mounted on the frame and is operatively connected to the `log engaging members in a manner which will be hereinafter more fully described.

rlhe'iiuid` pressuremotor F comprises a ,movable cylinder 15 having integral apertured guideV lugs 16 which slidably receive the guide rod7 whereby the 'cylinder 15 is .constrained to slide up and down on the guide rod 7 .closed by heads orl end members 17 equipped with stuiing boxes 18 through which the At its ends the cylinder 15 is upper and lower sections 19 and 2O of a pis- AVton rod designated generally at 22 are slidably eat-ended. As shown in Figure 2, the adjacent ends of the sections 19 and 2O of the piston rod 22 are threadedly connected with the piston 23 being a working fit in the cylinder 15. The lower end of the lower section of the piston rod 22 is fastened'in any suitable manner to the base portion v2 of the frame, a nut 24 being shown for this purpose inFigure 2. The upper section 19 of the piston rod 22 is similarly fastened to the top portion of the frame, and, in

the embodiment of the invention illustrated, a cap 25 is threadedly engaged with the upper section-19 of the piston rod and bears against the top portion of the frame toobtain the Yfastening action.

It will now be understood that with this assembly `of the movable cylinder 1,5 and the stationary piston 23 the lcylinder will be moved downwardly when pressure is supplied vbelow the piston` 23 and permitted to exhaust from above the piston 23, anden the other hand, the cylinder 15 will be moved upwardly when the pressure is supplied above the piston 23 and permitted to exhaust from below the piston 23.

lnA order to conveniently supply and exhaust the pressure above and below .the piston in the manner required for proper operation, the upper section 19 of the piston rod 22 is made up of' concentric tubes 26 and 27 the tube 26 being threaded into the piston 23 and having-ports 28 which communicate with the interior of the cylinder 15 above the piston 23. The upper end of this tube 26 is threaded into the cap 25 and communicates with a chamber 29 therein. The tube 27 is threaded into an axial passage 30 provided in the upper end and ofthe section 2O of the piston rod 22 and communicating at its lower end with a diametrical passage 31 which opens out into the interior of the cylinder 15 below the piston 23. The piston 23 is, of' course, formed with an axial opening into which the sections of the piston rod are threaded. The upper end of this inner tube 27 is suitably connected to the cap 25 and communicates with a chamber 32 formed in the cap 25 and entirely separated from and non-communicable with the chamber 29 of the cap. A pipe 33 which leads from any suitable source of supply of fluid pressure connects with the valve casing 34 of a conventional four-way valve 35. rl`he casing 34 has a vent 36 leading to the atmosphere and also has a suitably ported plug 37 which controls communication of the pressure supply pipe 33 and venty 36 with pipe lines 38 and 39 leading to the chambers 29 and 32 respectively.

By turnin T the valve to one position the fluid pressure supply pipe 33 is placed in communication with the pipe 39 and the pipe 38 is placed in communication with thevent 36, thereby 'causing fluid pressure to flow into the chamber 32, down through the tube 27 to the passage 30 and thence through the passage 31 into the cylinder 15 below the piston 23. This forces the cylinder 15 downwardly and the air in the cylinder 15 above. ythe piston 23 escapes through the ports 28,

tion of the valve, pressure is trapped on both sides of the piston and the cylinder is locked in position. p

rf'he downward Vmovement of the cylinder 15 is utilized to pull the log engaging meinbers together to cause them to powerfully and properly grip the log or the like, and in carrying out this purpose the lower lend of the cylinder l5 is provided with a pair of lugs 4() which-may be cast integral with the cylinder at one side of the center thereof. On these lugs 40, a sprocket wheel 41 is rotatably' mounted and meshes with an intermediatel portion of a sprocket chain 42.A The sprocket chain 42 has one end connected as at 43 with the upper rearward portion of the slide 11 of the logengaging member 9. This chain 42 is then extended downwardly to the sprocket s wheel 41 and after passing under and around the sprocket wheel 41 is extended upwardly to a sprocket wheel 44 rotatably mounted on a resiliently supported hanger bracket 45.

The bracket V45 has a stud 46 fixed theretoV and this stud passes through an opening in the top portion 4 of the frame and is yieldably supported on the frame against downward movement by means of thevcompression coil spring 47 encircling stud 46 above the frame and having its lower end engaging' the top of the 'frame and its upper' end enga gingan adj ustable abutment on the stud 46, which abutment may consist of a washer 48 and nuts 49. After passing over and around the sprocket wheel 44 the chain 42 extends downwardly between the guide rods 6 and passes through an opening 11 provided in the slide 11 (see Figs. 4 and 5) and on down to the slideY 12 ofthe log engaging member 10, the chain 42 being fixed to the slide 12 as indicated at 50 (see Fig. v3). The chain 42 connects with the top of slide 12 near its center and thus exerts an even and direct pull on the slide which moves the same without tending to bind iton its rod 6. The

saine effect is approximated inrespect of the connection .of the chain 42 to the slide 11. )Vith this arrangement, when the cylinder15 moves downwardly the sprocket wheel y 41 acts on the chain 42 to cause the chain to pull the log engaging member'9 downwardly and the log engagingmember 12 upwardly, thus causing the teeth and 14 of the log engagiii members to engage and bite into the log, as illustrated in dotted lines in Figure 2.

The spring 47 and bracket 45 and associated parts provide a tensioning device and shock absorber which takes up slack in' the chain 42, and also relieves the other elements of the dog of severe shocks and strains.

The upward movement of the cylinder 15 is .utilized to positively pull both log engaging members out of the log and away from each other, and .for effecting this operation, a sprocket wheel 51 is rotatably mounted on lugs 52 cast integral with the upper end of the cylinder 15 on the opposite side ofthe center from the lugs (see Fig. 3). A sprocket chain 53 is fixed as at 54 tothe lower rearward portion of the slidefll of the log engaging member 9 and -is then passed up and over the sprocket wheel51 and down to, around and under a sprocket. wheel 55 rotatably mounted on a bracket 56 fastened to` the base portion 2 of the frame 1. p After passing under and around the sprocket wheel 55 the chain 53 is fixed as at57 to the upper rear@ ward portion of the slide 12 of the log engaging member 10. When the cylinder 15 moves upwardly, the sprocket wheel 51 acts -onthe chain 53 to cause it to move the log engaging member 9 upwardly and the logengaging member 10 downwardly, a positive pull being exerted on both log engaging members for disengaging them from the logand moving them apart. However, when the cylinder'l is moved downwardly and the' log engaging lmembers 9 andL 10 move toward each other by the action of the chain 42, then the. chain 53 is slackened in proportionto permit the chain 42 to bring the log engaging members toward each other.

In the drawings (see Figs. 2, 4 and 5) the centers of the sprocket wheels 41 rand 51 are shown slightly oset from each other in a direction transversely ofthe vsawmill carriage, and ywhile this may be done it has been soshown merely to facilitate illustration and understanding of the arrangement of the chains 42 and 53. In building a dog the axes of the sprocket'wheels 41 and 51 will lie in the sameA vertical plane although -these sprocket wheelsv willbe oifsetslightly in this plane in the direction of. the length of the sawmill carriage.

` To enable the dog to engage either a-heavy ,log ortimbei' or a relatively light board -to best advantage it is proposed to mount the dog upon the knee in such a manner that it can be shifted in and out relative to the knee face.v In carrying'out this purpose a knee plate 60 is provided and-is rigidly and securely fastened tothe knee61 by suitable fas- -tening devices.` The fa ce of the knee is designated at 62. (')n this knee plate the frame 1 of the dog is'mounted for in and out movenient, this mounting being effected by means of headed studs 63 extending through slots 64 in the kneel plate 60 and threaded into the Yframe 1. Antifriction sleeves or collars 63a are provided on the Shanks of the studsf63 andengage the walls of the slots 64. This shiftable mounting of the vframe of the dog of the knee plate is also aided by the mechyanism employed for eifectingand controlling the in and out movement, as will hereinafter more fully appear.A

The mechanism for shifting frame 1 in and out comprises a power cylinder suitably fixed to the frame 1 and having a piston A71'1itted therein for sliding movement. Piston 71 has piston rod 72 which projects beyond both-ends of the cylinder, the rod 72 extending through stufling boxes 73 on the endplates of the cylinderTO. Theupper and lower portions of the piston rod 72 are formed with racks 74 which are slidablymounted in guides `75 on the frame 1 and which mesh with mutilated pinions 78 having bearing portions 79 journalled or rotatably mounted in bearings Y8O provided therefor in the frame 1 (see Figures 2,4 and 5). Each bearaing portion 7 9`of each pinion 7 8 has a disk 81 pnned or otherwise suitably fixed thereto. The discs 81 operate in elongated bearing l openings or slots 82 provided therefor in the knee plate 60 and these discs 81 have flanges 133 coacting with the frame 1 to hold the discs in; the slots 32 and yet leave them free to roll back and forth in these slots. Each disc 81 has Van eccentric pin or crank pin 84 threaded therein or otherwise suitably fixed thereto, each pin 84 being pivotally connected to one end of a link 85, the other end of theliiik S5 being pivotally mounted on a pin or stud 86 threaded into or otherwise suitably fixed to the knee plate 60. Pressure is supplied. to either end of the cylinder 70 and exhausted from the opposite end thereof of the `control of the conventional four way may be projected.

i nfl vvalve Si' having ports communicating with source of supply ot fluid pressure and with the atmosphere, and also connected with the pipe SSVleading to the opposite ends of the cylinder 0. s

Figure 1 shows' the dog positioned with the log` engaging members retracted or positioned as far inwardly as they may be with respect to the knee face; To project the dog and its log' engaging members, fluid under pressure is suppliedto the upper end of thecylinder 70 exhausted from the lower end thereof. This moves the piston 71 downwardly and consequently moves the rack 74: downwardly, thereby'rotating the mutilated pinion 78 and consequentlyv the discs 81. As the Ydiscs S1 have their crank pins pivoted tothe links 85, which are constrained to swing about allred axis, the discs 81, when rotated, roll along .theslots 82, and when they are rotated by downward movement of the rack 74, they roll from the position shown in Figure 1 to the position shown in Figure, thereby moving the dog forwardly with respect to the knee face to project the log engaging members outwardly beyond the knee face as far as they Reverse movement of the piston 71 causes reverse operation of these parts and shifts the .dog rearwardly on the -knee plate to lmove the log engaging members from the full line position of Figure 6 and the dotted line position of Figures 1 and 2 to the i'ull line positions of Figures 1 and 2.

As clearly shown in Figures 1 and 6, the elongated slots or bearing openings 82 are formed with enlargement 82. at their ends. This prevents the discs 81 from striking the ends ofthe slots7 the discs merely rolling along the guide portions 82h of the slots.

'lVhen the frame 1 and the mechanism carried thereby has been shifted to either of its extreme positions the links 85 are on dead center as will be understood from a comparison 1 of Figures 1 and 6. This makes the shifting means self-locking independently ofY the fluid pressure, although the fluid pressure in the cylinder .70 also tends to maintain the shifting mechanismY and the frame in the extreme position to which they are adjusted.

The discs 81 being constrained to roll back and forth in the slots S2 of the knee plate and being pinned to the pinions 78 which have bearing portions .79 rotatably mounted on the frame 1, aid in the support of the dog on the knee plate, and with the studs 63 and their slots (illv constrain the dog to in and out movement on the knee plate.

From the foregoing-'it will be understood that the log engaging members not only may be powerfully forced into gripping engagement with the log, but may also be positively withdrawn therefrom. This reverse actuation of the log engaging members may be Y.carried outirrespective of the position of the dog relative to the knee face; In other words, the log engaging members may be properly controlled and actuated with the dog shiftedout relative toi the knee face as shown Vin full lines inFigur-e and in dotted lines in Figure 2, and also when the dog is shifted in relative to the knee face as shown in full lines iii-Figures and Il, and in either of these positions the log engaging members may be positively movedin either direction. These advantages are had inan organization which utilizes lluid pressure/motors not only for actuating thevlogengaging members, but also for shiftingA the dog in and out. Therfluid pressure motor which actuates the logI engaging members 'isi so ouraganize'd.with the intermediate chain and sprocket-s, and the intermediate ohain isso connected up with the log engaging members that the log engaging members areA moved'under the action ofa direct pull exerted in the line of movement of these members, thereby insuring smooth and easymovement and avoiding tilting or binding. v Y i The invention claimed is:

1. A sawmill dog comprising a pair of log vengaging members mounted for sliding move- -ment toward and away from each other, a

fluid pressure motor, a flexiblel element, a guide member mounted on the frame and around which the -flexible element is trained 'and an actuating element lshifted by the fluid pressure motor and also engaged with the flexible element. the opposite ends of the flexible element being secured to the log holding members and 'moving in opposite directions,V

for causiiig-the flexible element to positively move both logengaging members away from eachother when the fluid pressure motor is operated for such purposes.

, 2. A sawmill dog comprising' a frame, a pair of 'log engaging' `members slidably mounted on Vthe frame for movement toward and away from eachother, a fluid pressure motor, a flexible element having its ends secured to the` log engaging members and eX- tended therefrom in substantially the line of movement of said members, said flexible element having-a portion freely passing through one of. said lofi en raging members, and rotatable elements mounted on the frame and .on the fluid pressure motor and coacting with vthe flexible element whereby to exert aidirect straight line pull on the log engaging meinbers'and cause them to be drawn toward each other without binding upon appropriate operation of the fluid pressure motor.

sawmill dog` comprising a frame, guides mount-ed on the frame, a pair of log engaging members incliuiling slides slidably interengaged with the-guides and also having teeth adapted for engaging the logl or the like, a fluid pressure. motor mounted on the frame, apair of flexible elements, each flexible' element being'connected to both log engaging me1nbers,

rotatable elements 130 mounted on the frame and around which-flexible elements are trained and movable actuatiiigelements shifted by the fluid pressure motor andalso engaged with the flexible elements whereby the fluid pressure motor serves to positivelj,7 urge the log engaging members toward each other and also to positively retract both log engaging members.

4.-. A sawmill dog comprising a frame,

guide nieai'isfniounted on thel frame, a pair on the frame,fiexible elements, and rotatableelementsl mounted on the frame and on the fluid pressure motor and around which the flexible element-s are trained, opposite ends ofthe flexible elements being connected to the log :engaging members kand moving in oppositev directions upon operation of ythe fluid pressure vmotor to positively move the log' engaging members toward each other when the fluid pressure motor is loperated A in one direction and lto positively moveboth log engaging members away from each other when the fluid pressure motor is moved in an opposite direction.

5. A sawmill dog comprising a frame, a

pair of log engaging members slidably mounted on the frame for movement toward and away from each other, a fluid pressure motor including a piston having a piston rod fixedto the frame and a movable cylin-- der in which thepiston operates, controllable means for supplying and exhausting fluid pressure to the cylinder above and below the piston whereby the cylinder may be moved in either direction, a flexible element having its ends secured to the log engaging members and extended vtherefrom in substantially the line of movement of said members, said flexible element having a portion freely passing through one of the `log engaging members, a rotatable element mounted on the lower portion of the cylinder and around which .an intermediate portion of said flexible element is trained, a resiliently supported rotatable element mounted on the frame and around which the flexible element is also passed, a second flexible element having its ends connected to the log engaging members and extending therefrom in directions opposite to those in which the ends of the first mentioned flexible element extend from the log engaging members, a rotatable element mounted on the frame and around which a portion of the second flexible element passes, and a rotatable eleinent mounted onthe upper portion of. the cylinder and around which another portion of the second flexible element passes.

6. In a device of the character described, a knee, a sawmill dog having a frame mounted on the knee for in and out movement, fluid pressure motor mounted on thev frame, ro-

tata'ble'elements mounted on the .frame and4 actuated from the fluidpressuremotor, discs connected to said rotatable elements for movement therewith, said knee having a member provided with elongated `bearing openings for 'the discs, and means coacting withfthe discs andV with said member for'cziusing the frame to move in and out relative to the knee when the rotatable elements are rotated.

1. In a device of the character described, a knee, a sawmill dog having a frame mounted on the knee for in and out movement, a fluidL pressure motor mounted on the frame, rotatable elements mounted on the frame and actuated vfrom the fluid pressure motor, discs connected to saidV rotatable elements for move-4 ment therewith, said knee having a member provided with elongated bearing openings for the discs, and links pivotally connected to saiddiscs and to said member for causing the frame to shift vrelative to the knee when-the. rotatable elements are rotated. Y

8. In `a device of the character described, a knee, a knee plate secured thereto, 'a sawmill dog having a frame, means for supporting the frame on the knee plate for in and out shifting movement, a'fluid pressure motor including a cylinder fixed to the frame and a piston having a piston rod projecting from the opposite ends of the cylinder and provided with racks, pinions' rotatably mounted on the frame and meshed with the racks, discs fixed to the pinions, said knee plate having elongated bear,-

ing lslots in which the discs are fitted, said" discs having flanges to lprevent their displacement from the bearing slots, and links ecceiitrically pivoted to the discs and also pivoted to the knee plate. 1 Y

9. In afdevice of the character described, 'a knee, a knee plate secured thereto, a sawmill dog having a frame, means for supporting the fraiiie'on the knee plate'for in and` out shifting movement, a fluid pressure motorincluding a cylinder xed to the frame and a piston having a piston rod projecting from the opposite ends of the cylinder and provided with racks, pinionsrotatably 'mounted' on the frame and meshed with the racks, discs fixed to the pinions, said knee plate having elongated-bearing slots in which the discs vare fitted, fand links ecceiitrically pivoted to the discs and also pivotedto the knee plate.

10. In a device of the character described, a knee, a sawmill doghavingav frame mounted j on the kneefor in and fout movement, a fluid between the pinions and the knee and operating to cause the dog 'to move in and out relative to the knee when the pinions kare rotated. n l1. A. sawmill dogcoinprising zi-frame, a

iio

iso

one of thelog engaging members, a rotatable element actuated by the fluid pressure motor and around which an intermediate portion of said fiexible element is trained, a rotatable element mounted on the frame ancla-round which the fiexible element is also passed, a second flexible element having` its ends coni nected to the log engaging members and eX- tendin'g therefrom in directions opposite to those in which the ends of the first mentioned flexible element extend from the log engaging members, a rotatable element mounted on the frame and around which a portion of the second flexible eleinentpasses, and a rotatek able element mounted on the fluid pressure motor and karound which another portion of' the second flexible element passes.

l2. A sawmill 'dog comprising a pair of log engaging members, a fluid pressure motor and a flexible element operated from the Huid pressure motor and having oppositely moving portions connected tothe log engaging members for positively moving both log engaging members away from each other upon appropriate actuation of theV fluid pressure motor.

k13. In a device of the character described, a. sawmill dog mount-ing, means supporting the sawmill dog mounting for in and out movement, a fluid pressure motor carried by said mounting, rotatable elements journaled on said mounting and geared to `and actuated from said fluid pressure motor, and a link for each rotatable element, each link being constrained to oscillate about a fixed axis and being eccentrically connected toits rotatable l element.

14. In a device of the-character described, a knee` a sawmill dog mount-ing supported on the knee for in and out movement, a fluid pressure motor carried by said mounting, ro-

tatable elements journaled on the mounting and geared to and actuated from the fluidA pressure motor, and links interposed between therotatable elements and the knee, each link having one end eccentrically pivoted to a rotatable element and having its other end constrained to oscillate about anv axis fixed with respect to the knee, said links being positioned on dead center on either eXtreme position of the dog mounting.

l5. A sawmill dog'coinprising upper andY lower opposed log engaging members, guide mea-ns constraining said log engaging members to movementtoward and away from each other in a vertical plane, areversely operable motor, means actuated from the motor when the saine is run in'one direction to positively urge the log engaging members toward each other, a Vflexible clement, guide and actuating members coopci'able with the flexible ele-l ment and deflecting the same to provide 0ppositely moving portions, said oppositely moving portions being connected to both log engaging members to positively move both log engaging members away from each other when said flexible element is positively actuated by said actuating member, and a driving connect-ion between said motor and said actuating member for so moving the actuating member as'to cause the same to positively actuate the flexible element when said motor is run in an opposite direction.

16. le; dog for use on the knee of a sawmill carriage. and comprising upper and lower opposed log engaging members, guide means constraining said log engaging inembers to movement toward and away from eachother in a vertical plane, two flexible elements, two sets of guide and actuating members,'said sets otguide and actuating l members engaging and deflecting said flexible elements to provide oppositely moving portions in each flexible element, one of said moving portions of each *element being connected to oneV of said log engaging members and the other'of said moving portions of each flexible element being connected to the otherv of said log engagingmembers, the connections of said oppositely moving portions of said fle/:ril le elements with said log engaging members being'such that when one of said flexible elements is positively actuated by its actuating member it moves the dogs toward each other and when the other is so actuatedv it moves the dogs away from each other, arevers'ely operable motor, and driving connection between said motor and said actuating members whereby when said motor is run in one direction the dogs are positively moved toward 'each other and when the motor is run in an opposite direction both dogs are positively pulled away from each other.

In witness whereof, we hereto aiiix oursignatures.

ROSS LANGILL. STANLEY B. LANGILL.

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