US2548067A - Hydraulically operated set mechanism for the head block kneees of a sawmill carriage - Google Patents

Description

April 10, 19N H. G. ROBERTS 2,543,067

HYDRAULICALLY-OPERATED SET MECHANISM FOR THE HEAD BLOCK KNEEs oF A sAwMILL ,CARRIAGE April 10, 19M

Filed July 29, 1947 H. G. ROBERTS 2,548,067 HYDRAuLIcALLY-OPERATED sET MECHANISM FOR THE HEAD BLOCK KNEEs oF A sAwMILL CARRIAGE 6 Sheets-Sheet 2 E INVENTOR. l Hen/"y G. Rober' zS i 'BY April l0, li951 H. G. ROBER HYDRAULICALLY-OPERATED SET MECHANISM FOR THE HEAD BLOCK KNEES 0E A sAwMILL CARRIAGE 6 Sheets-Sheet 3 Filed July 29, 1947 INVENTOR. Hen/"g 6. Robe/"fs 7/Z%2/azfmaavxmm pri 10, i951 H. G. RoBERTs 2,548,067

HYDRAULICALLY-OPERATED SET MECHANISM FOR THE HEAD BLocx xNEEs oF A sAwMILL cARRxAGE Filed July 29. 1947 6 Sheets-Sheet 4 April 10, 1951 H G.- ROBERTS 2,548,067

' HYDRAULICALLY-OPERATED SET MECHANISM FOR THE HEAD BLOCK KNEES 0F A SAWMILL CARRIAGE Filed July 29, 1947 e sheets-sheet 5 April 10, 1951 H. G. ROBERTS 2,548,067

HYDRAULICALLY-OPERATED SET MECHANISM FOR THE HEAD BLOCK KNEES 0F A SAWMILL CARRIAGE Filed July 29, 1947 6 Sheets-Sheet 6 VIT@ f ES

t N m Q INVENTOR. v #en/"g 6 Robers Patented Apr. 10, 1951 HYDRAULICALLYV OPERATED' SET MECHA- NISM FOR THE HEAD BLOCK KNEES OF A SAWMILL CARRIAGE Henry G. Roberts, Prattville, Ala..

Application July 29, 1947, Serial No. 764,310v

4 Claims.

This invention relates to hydraulically-oping movements of the knees will be elTected hydraulically.

It is among the objects of the invention to provide a construction of the type described which will set up the logs with great accuracy and thus eliminate variations in the thickness of the boards. It is well known that where the setting up of logs is effected through conventional rack and pinion construction, screw shafts, and equivalent mechanism, or where the setting up is effected pneumatically but controlled by such mechanism, substantial variations occur in the thickness of the boards cut, due to lost motion and back lash in the mechanical parts.

In order to obviate such difficulties, and eliminate variations in the thickness of the boards due to such causes, the present invention provides a construction in which there are no exposed parts which can develop lost motion in an endwise direction, and in which the setting is eiected with great accuracy.

It is a further object of the invention to provide set mechanism of the type described which will actuate all of the knees of a multi-block carriage simultaneously and with equal accuracy.

A further object of the invention resides in the provision, in a mechanism of the type described, of a construction permitting lsome lateral displacement of the knees, thus giving some exibility to the parts of the mechanism subjected to shock when a log is rolled when the carriage.

Further objects of the invention reside in the provision of means for quickly receding the head Vblock knees.

A further object of the invention resides in the provision of a mechanism of the type described in Which certain Wearing parts, such as the slides -for the'knees are readily removable and interchangeable.

'I'he foregoing and other objects and features of the invention will be made fully apparent to those skilled in the art from a consideration of the following detailed description, taken in conjunction with the accompanying drawings, in which:

Figure 1 shows a top plan View of a saw mill carriage having the hydraulically-operated set works of the present invention mounted thereon.

Figures 2, 3, and 4 are sectional views, with parts inelevation, of the hydraulic actuatinfg mechanism at the rear end, at an intermediate section, and at the front end thereof, respectively, and when arranged in alignment from left to right represent such a view of the complete actuating mechanism.

Figure 5 shows a section taken on the line 5-5 of Figure 2. l

Figure 6 shows a section taken on the line 6--6 of Figure 3.

Figure 7 shows a section taken on the line 1 ,1 of Figure 4.

Figure 8 shows a top plan view of the portion of the set works at thefront vend of the carriage.

Figure 9 shows the parts ofFgure 8 in side elevation.

Figure 10 shows a transverse section, taken on the line Ill-I8 of Figure 1, through one of 'the head blocks, and looking toward the knees. Y

Figure 11 shows a diagram of the hydraulic system.

Figure 12 is a side elevational View illustrating the application of a dust hood to protect certain parts of the mechanism, and showing a modied form of the set indicating means. v

In the drawings, numeral I6 indicates generally a saw mill carriage, which', it will be understood, is 'mounted to travel in the usual manner with reference to the saw of the mill. A plurality of head blocks l1, 18, and I 9 extend transversely of the carriage I6 in the usual manner. In this instance, three head blocks are shown. However, it will be understood that the invention is equally applicable to a saw mill carriage having any desired number of head blocks. On the head blocks, knees 2D, 2| and 22 are slidably supported in a manner which will hereinafter be made apparent. v v f The knees 20, 2|, and 22' are set and receded by piston rods 23, 24, and 25, which rods are simultaneously actuated by pistons 26, 21, and 28, reciprocable in cylinders 29, 30, and 3l of a unitary hydraulic setting and receding mecha nism indicated generally at 32.

The hydraulic setting and receding mechanism is shown in detail in Figures 2, 3, and 4, and includes a cylinder 35 (see Figure 4) having a the joint between the iianges 42 and 43 will be made uid tight, as will other similar joints, hereinafter to be described, throughout the system. It will be seen that that portion of the cylinder space of the cylinder 35 to the rear of the piston 36 is in full open communication with a chamber 4| formed in the header 44.

The inner end oi the cylinder '3| also opens into the chamber 45| of the header 44, the cylinder 3l being provided with flanged ends 45 for securing said cylinder to a side face of the header with the cylinder 3| extending .at a -right langle to the cylinder 35. The flanged end .46 of a .tubular member 41 is secured about a central opening in the face of the header 44 opposite that to which the cylinder 35 is secured. The tube 41 has an internal diameter which is -substantally larger than the external diameter of the rod 31, and the tube is substantially coaxial `with the rod so that a relatively large annular passage Yis provided therebetween.

The tubular member 41 -zextends longitudinally of the carriage I6 to a point adjacent the cylinder i30, where it is connected at 'the hanged end 48 thereof to a header 49,-see .Figure `3. `The :inner end lof the cylinder y3l) is connected at the anged end 56 thereof to an adjacent face of 'the header and is in Aopen :communication-with the interior thereof. The flanged end VI of a tubularmember 52 is secured :to .the face :of the header 49 opposite to that to which the .tubular Vmember 41 is secured, and extends in alignment therewith. The tubular member ,52 fis of the same diameter as the tubular member 41, providing asimilar annular passage with the rod 31 which extends therethrough. The Ytubular member 52 extends to a kheader 54 at the-inner end of the -cylinder 29 and 'is secured to one face of lthis header by a Yflange 53, see Figure `2. The inner `end of the cylinder 29 yis also secured to an adjacent face of this header through a flange 255,. The Iianged .end '56 of `a cylinder 51 secures this .cylinder on the -side of the `header 54 opposite to the side to which the tubular member 52 is .attached and in alignment with .f

-said tubular member. The rod 131 extends lthrough the header 154 land has a reduced kend portion secured through a piston 58 reciprocative -in the cylinder L51. The louter end of V.the :cylinder 51 isv provided with a flange 59 and :this endisclosedby a head `60 secured-tosaidflange.

A iiuid pressure supply Vand exhaust pipe `63 passes through the head 44l) of the cylinder 3.5 for connecting the 'cylinder space between the outer 'face of V`the piston 36 .and the cylinder head Y4l) alternatively .with the source kof uid pressure and a suitable exhaust tank in Valmanner hereinafter to be described. .Afsimilar passage -64 through the cylinder head l6l) 'connects `the .interior -of the cylinder 51 on the outer side of ythe piston 58 with said `'source of supply and with said exhaust tank alternatively vin a manner -to be described. The interior vof the hydraulic setting mechanism between the inner :faces ,of the pistons 3.6 and =58 .is lled with fluid,

,preferably -oil, maintained under a `substantially constant pressure, as will hereinafter be rdescribed. The connection 65 for supplying uid pressure .to this portion of the mechanism is .shownas being made to ithe header 54., see Fig- '.ures 2 and 5. Obviously, this connection can .be .made eat any `chnvenient point gin 'the system.

The ,pistons 26, .21., and 2'8 are connected :to ythe rod 3,1 y.through sprocket chains 66, 61. and 6.8., respectively. The lconnection between, the

sage '88, but not to both simultaneously.

sprocket chains and the pistons is made through piston bolts 69, 10, and 1I, and the chains, riding on idle sprockets 12, 13, and 14 in the headers 54, 49, and 44, respectively, extend along the shaft 31 in the direction of the piston 36 for .a distance at least equal to the stroke of said pistons when the same are at the inner ends of their respective cylinders. The chains are secured to the rod 31 by bolts 15 extending through said rod.

In ordeia to limit wear and resulting lost motion, the sprockets 12, 13, and 14 are preferably mounted in a manner shown in Figure 6. As shown :in this figure, the sprocket 13 is fixed on a tubular sleeve 16 extending vertically across the header 49. The sleeve 16 is rotatably mounted on a shaft 11 supported in the upper and lower walls of the header. The shaft 11 is removably mounted in the header 49, but is secured against rotation by means of a screw 18 having a-.tongue at the end thereof engaged in a groove :in the -upper end of the shaft 11. Rotation of the screw 18 is prevented by a lock nut 19. By this construction, a wide zbearing surface is provided for the rotating sprocket 13, and this surface is continuously lubricated by the oil in the interior of themechanism. It will be understood that the other sprockets 12 and ,14 are mounted in the same manner.

Inthe :construction described in the foregoing, lit will be observed that the piston 36 is much larger than .the pistons v26, 21, v28 and 58. The effective area of the inner face of the piston 36 is made equal to the sum of the effective areas of the inner faces of the pistons 26, 21, and 28 and 58. It will be seen that when the piston 35 moves inwardly, tending to decrease the volumetric capacity of the closed interior chamber of the mechanism, the pistons 26, Y21, 28, and 56 move outwardly from this closed chamber, tending to increase the volume thereof. Since the effective areas vof Ythe pistons moving outwardly are the same as the effective arealof the piston moving inwardly and the strokes rare the esame, the total volumetric capacity of the interior chamber of the mechanism is constant.

The mechanism described in the foregoing is ysupplied with a suitable motive fluid, such-as' oil under pressure, from a .hydraulic system, a ldiagram of which is shown in Figure 11. The system comprises Va pump 8l adapted to be driven .by a motor 82, or 4other vprime mover, to draw oil from a supply tank -83 through a suction pipe84 and discharge the same under ,pressure Vthrough a pipe '85 to a three-way valve -86. The valve 86 is adapted to be manually actuated to permit `the -oil to flow to either a passage 81 `or ra pas- The passage 81 is connected through a check valve k89 to one branch of a T 90. Another branch of fthe T v96 is connected to the inlet and exhaust pipe 63 of the cylinder 35, and the third branch of the T 90 is connected by a pipe '9| to a manually-controlled valve 92, and thence -by rway of `pipe 93 to the-supply tank 83.

The other passage 88 leading from the threeway valve 86 is connected through a check valve 94 and a pipe 95 to one branch of a T 96. A second branch of the T 96 is lconnected to the inlet and exhaust pipe 64 of the cylinder 51. The third branch of .the T 96 is connected to a manually-operable valve 98 and thence by way .of -a pipe 99 tonne branch of Aa T 100. A second branch lof the T .|09 is connected by a pipe IDI to a check valve '1.02, the opposite vside of which check valve is connected to the pipe 65 leading to the interior chamber of the mechanism through the header 54. The third branch of the T |00 is connected to a relief valve |03 opening in a direction to permit the flow of oil to a return pipe |04k when the pressure on the intake side of said valve |03 exceeds a predetermined pressure. The return pipe |04 leads back to the supply tank 83.

The valves 92 and 98 are connected for simultaneous actuation in such a manner that when one is opened the other will be closed. To this end (see Figures 1 and 1l) the stem of the valve 92 is provided with an arm |05, andthe stem ofV the valve 98 is provided with an arm |06, and

the two arms are connected by a rod I 01 for joint operation through a lever |08 adapted to `be manually actuated through a hand lever |09.

of its stroke, that is, adjacent the header 44,

and the piston 58 is at the outer end of its stroke, that is, adjacent the cylinder head 60. The three-way valve 86 is now operated so that the pipe 88 is in open communication with the discharge pipe 85 of the pump 8|, and communication between this discharge pipe 85 and the pipe 81 is closed. Simultaneously the rod |01 is actuated through the levers |09 and |08 to close the valve 98 and to open the valve 92. Oil under pressure is now supplied by the pipe 88, pipe 95, and pipe 64 to apply fluid pressure to the working face (left hand side) of the piston 58. This piston is now driven to the right, and the piston 36 being connected to the piston 58 by the rod 31 is likewise driven to the right, forcing the oil in the cylinder 35 out through the passage 63, the pipe 9|, and the open valve 92 to the supply tank 83. The pistons 26, 21, and 28 being connected to the rod 31 by the chains 66, 61, and 68, these pistons are drawn inwardly, that is toward the headers 54, 49, and 44, until the piston 58 has been forced to the inner end of its stroke, as shown in Figure 2, in which position the piston 36 will be at the outer end of its stroke, as shown in Figure 4, and the pistons 26, 21, and 28 will be adjacent the header ends of the cylinders I1,

position closely adjacent the open ends of the cylinders 29, 30, and 3|.

When the knees have reached their fully receded positions, the operator discontinues the supply of motive fluid to the cylinder 51, the parts remaining at rest while a log is rolled upon the carriage. In order to so discontinue the supply of motive iiuid to the cylinder 51 while the piston 36 of the cylinder 35 remains at rest, the

`operator has vonly to move the lever |09 back into the position shown in Figure 1, in which the valve 92 is closed and the valve 98 is opened. The

motive uid now flows back to 'the tank 83 through the relief valve |03.

Alternatively, the

anche? 6 operator may leave the valve 92 open and the valve 98 closed, but turn the three-Way valve 86 so that the fluid flows through the pipe 81. The iluid thus returns to the tank 83 without exerting material force upon the outer or Working face of the piston 36 as the pump 8| idles. In either case, after the log has been positioned on the carriage, the valve 92 will either be closed or will now be closed by the operator, and the valve 98 will be opened. LThe valve 86 is actuated to connect the pipe 81 to the discharge pipe 85 of the pump 8|, and, accordingly, motive fluid will be supplied to the interior of the cylinder 35 through the pipe 63, forcing the piston 36 inwardly. As the piston 38 moves to the left from the position shown in Figure 4, on its working stroke, the piston 58 moves to the left from the position shown in Figure 2, on its exhaust stroke, the oil being exhausted through the pipe 64, the open valve 98, and thence to the supply tank 83 through the relief valve |03. Simultaneously with the movement of the pistons 36 and 58 to A the left, the pistons 26, 21, and 28 must move outwardly in the cylinders 29, 30, and 3|, and, accordingly, force the rods 23, 24, and 25 outwardly. The outward movement of the pistons 26, 21, and 28 will correspond exactly to the distance through which the pistons 36 and 58 move, for since the pistons 26, 21, and 28 are connected to the rod 31 through the sprocket chains 66, 61, and 68, the pistons 26, 21, and 28 can move no further than the distance through which the rod 31 moves. However each of the pistons 26, 21, and 28 must move as far as permitted by the chains 66, 61, and 68, for should one of the pistons, say 26, meeting with a greater resistance than the other pistons, tend to stop, or lag behind th-e other pistons in its outward movement, this stopping or lagging of the piston 26 would decrease the volumetric capacity of the interior pressure chamber of the system. The inner face of the piston 26 constitutes a portion of the surrounding wall of this interior chamber. Since the interior chamberis filled with oil at a pressure determined by the setting of the relief valve |03, and since this oil cannot flow back out of the interior chamber due to the check valve |02, any decrease in the effective volumetric capacity of this interior chamber would build up a high pressure. It will thus be seen that each of the pistons 26, 21, and 28 must move outwardly at the same rate and for the same distance as the piston 36 moves to the left.

It will be understood, of course, that in the `ordinary setting-up operation, the piston 36 does not move continuously to the left in the manner .in which the piston 58 is moved to the right in receding the head blocks. The manner in which the knees, and accordingly the logs indicated at I I8, are set up will be apparent from a consideration of Figures 8 and 9. As shown in Figure 8, a scale or index I|I extends adjacent the cylin- `der 3| on the side thereof convenient to the loperator at the Valve 86 and hand lever |09. A

pointer |I2 adapted to overlie the scale III, is formed at one end of a rod H3, which extends to and is secured on the knee 22. As shown, the rod I3 is connected to the knee 22 by one of the nuts I|4 which secures the piston rod 25 to for moving the pointer |I2 relative to the scale at a rate proportionate to the movementV of 'the knee 22 may be adopted. The operator determines the setting of the-knee 22 attendant to the setting of the logs I l0 by observation of the posi- Obviously, any other suitable meansV tion lof ,the l`pointer .|.|.2 relative to the .scale .I Assuming, .'for example, .that lthe'log is to `be set upfor sawing .two-inch boards, the operator .observes .the movement .of the pointer I2 along the -index .for .an equivalent .distance and then Acuts oi the supply of .motive fluid through .the Apipe 81 Vby actuating the valve 86 to close this .pipe and open the pipe 88. At this timepthe operator does .not actuate the hand lever |09, leaving the valve 92 closed andthe valve98 open. The fluid thus :passes without great resistance through the pipe 188, the open valve 98, and the relief valve |03 to the tank 83, while the piston 36 is locked in set position, there being .no .escape of -luid from thecylinder-S through .the-check `valveil andthe closed valve 92. In this manner, the log is set up after each passage .through the mill, any tendency of the .log to roll in either direction is eliminated due to .the pressure of oil in the outer end of the cylinder 5l, or the Youter end of cylinder 35 until the log has been sawed, when the knees are again receded A`in the mannerdescribed.

It will be understood that variations may :be made in the operation of the hydraulic system -from vthat described. For example, Awhen Ythe valve 86 is actuated .to close the pipe 87, upon the completion of .a setting-up operation, .it is not Lessential that the -valve also open the passage 88 at .this time. Thus, if the entrance to .the pipe 8:1 is closed, and the 'entrance to the lpipe 88 remains closed, :a back pressure 'will be built up between the `three-way valve 86 and the pump 8| in the Ypipe A85 which .may be used to control Athe operation of the pump through .any knownpressure-control device.

It will be observed that in the construction described vin the foregoing, there are no exposed moving parts which4 are subject to wear in a 'direction which Iwould result in inaccuracies in the setting-up operation. As seen in Figures 9 and 10, the lslides of `.the head blocks are subjected to wear in a Vertical direction, and also to a lesser extent in a lateral direction. However, there are no parts which may 'wear in an .endwise direction. 'The sliding portions of the head block knees may be formed of two ycast iron plates HS, spaced by a plate IH 0f lesser width than the plates i6. The .plates lare bolted together, as indicated at I9, and `when said plates become worn, the same may be readily replaced. The bolts |'8 extend not only through the plates IIS and il, but also -throughthe'lower horizontal portion H9 of the head block knees. It will be understood that this horizontal portion is integral with the upright portion of the knee being either formed integrally therewith or secured thereto, as by Welding.

As stated in the foregoing, there may be some vertical and some lateral play between the head block knees 29, 2|, and 22, and their respective head blocks. Thus, although no endwise `play is permitted, a certain flexibility in lateral and vertical directions is permissible. In order to prevent vertical and lateral displacement of the knees, which may occur when a log is rolled upon the carriage, from being transmitted through the rods 23, 24, and 25, into a twisting action upon the pistons 26, 2l, and 28, the connection between the rods and pistons is formed with a balland-socket joint, as shown at IZB in Figure 4. This figure, which shows the ball-and-socket connection between the rod 25 and piston .28, will serve to illustrate a .similar .connection between each of the rods and their respective pistons.

.As statedin the foregoing, the ends ofthe cylin- Yders 2S and 30 and 3| are open. Thispermits slight swinging of the rods 23, 24, and in the manner described .in the foregoing. In order to prevent dust from entering the ends of the cylinders, these may be provided with flexible coverings at the ends thereof, or dust hoods covering the rods 23, 24, and 25 may be secured to theknees in a manner to ride over the cylinders 29, 30, and 3|. In Figure 12, such a hood |2| is .shownattached to the knees 22 in a position to ride over thecylinder 3| and cover the rod 25 throughout the length of the movement thereof. The .appli- .cation of such hoods to the other knees will be self-evident. In the .form of the invention shown in this figure, the indexing means is slightlymodied. The scale `is formed on the side of the hood |2| and .constitutes a movable-scale coacting with a xed pointer |2.

From the foregoing, it will be seen that the inventionprovides a complete hydraulic system for receding and setting the head block knees-of a saw mill carriage. It will be apparent that since .the invention provides a construction in which there are no exposed parts which .can develop lost motion in an-endwise direction, the invention attains its objective in eliminating variations in the thickness of boards due to lost-motion and backlash in this direction. It will be apparent that no inaccuracy can be introduced into the system due to any leakage of fluid from -the interior chamber formed in the mechanism 32, since any loss of iluid in this chamber is continuously replaced as a result of the action of therelief valve |63. Since the pistons 26, 2T, and 28 directly actuate the knees 29, 2|, and 22, they may be called knee-actuating pistons, and since the piston 36 is driven 'to effect the setting motion, and the piston 58 is vdriven to effect the receding motion, these pistons will be called the setting piston and the receding piston, respectively, in the following claims. y

While there has been herein described a preferred embodiment of the invention, other embodiments within the scope of the appended claims will be apparent to those skilled in the art from a consideration of the form shown and teachings hereof.

Having thus described the invention, I claim:

1. Fluid operated saw mill set works, comprising a longitudinal tube, a longitudinal rod mounted within the longitudinal tube and extending throughout the major portion of the length of the tube, the longitudinal tube having an inside diameter substantially greater than the diameter of the longitudinal rod, plungers secured to the longitudinal rod near its opposite ends and near the opposite ends of the longitudinal tube, the opposite ends of the longitudinal tube having openings outwardly of the plungers whereby uid under pressure may be introduced into and exhausted from the ends of the longitudinal tube for shifting the longitudinal rod, a plurality of substantially horizontal transverse tubes connected with the `longitudinal tube and having their bores in communication with the bore 'of the longitudinal tube, reciprocatory plungers mounted within the transverse tubes and having Vparts extending beyond the Aouter ends lof the transverse tubes, and iiexibleelements connected with the reciprocatory plungers of the transverse tubes and with the longitudinal rod for retracting the reciprocatory plungers when the longi- 9 tudinal rod is shifted in one direction, the nexible elements extending within the longitudinal tube between such tube and the longitudinal rod, the longitudinal. and transverse tubes being iilled with fluid inwardly of their plungers.

2. Fluid operated saw mill set works, comprising a longitudinal tube, a longitudinal rod mounted within the longitudinal tube for reciprocation and extending throughout the major portion of the length of the tube, the tube having an inside diameter substantially greater than the diameter of the rod, a longitudinal cylinder secured to one end of the longitudinal tube, the tube and cylinder having their bores in communication, the inside diameter of the cylinder being larger than the inside diameter of the tube, a large piston mounted within theV longitudinal cylinder for reciprocation and connected with the longitudinal rod, a small piston connected with the opposite end of the longitudinal rod for reciprocation within the longitudinal tube, the outer ends of the tube and cylinder having openings through which fluid under pressure may be introduced into and exhausted from the tube and cylinder outwardly of the large and small pistons, transverse cylinders connected with the longitudinal tube between its ends and having their bores in communication with the bore of the tube, I

the plungers when the longitudinal rod is shifted in one direction.

3. Fluid operated saw mill set works, comprising a longitudinal tube, a longitudinal rod mounted within the longitudinal tube for reciprocation and extending throughout the major portion of the length of the tube, the tube having an inside diameter substantially greater than the diameter of the rod, a longitudinal cylinder secured to one end of the longitudinal tube, the tube and cylinder having their bores in communication, the inside diameter of the cylinder being larger than the inside diameter of the tube, a large piston mounted within the longitudinal cylinder for reciprocation and connected with the longitudinal rod, a small piston connected with the opposite end `of the longitudinal rod for reciprocation within the longitudinal tube, the outer ends of the tube and cylinder having openings through which uid under pressure may be introduced into and exhausted from the tube and cylinder outwardly of the large and small pistons, transverse cylinders connected with the longitudinal tube between its ends and having their bores in communication with the bore of the tube, reciprocatory plungers mounted within the transverse cylinders and having operating parts extending beyond the outer ends of the transverse cylinders, the combined eiective areas of the plungers and small piston being substantially equal to the effective area of the large piston, the longitudinal tube and transverse cylinders being adapted to be filled with uid inwardly of the large and small pistons and plungers, sprocket wheels j ournaled within the longitudinal tube adjacent to the inner ends of the transverse cylinders, and sprocket chains engaging over the sprocket wheels and connected at their ends with the plungers and longitudinal rod, the sprocket chains extending between the longitudinal rod and tube and being completely enclosed by the tube and transverse cylinders, the sprocket chains serving to retract the plungers when the longitudinal rod is shifted in one direction.

4. Fluid operated saw mill set works, comprising longitudinally spaced sections of tubing, tubular headers connecting the ends of adjacent sections of tubing and forming therewith a continuous straight tubular chamber, one end section of tubing having a bore larger than the bores of the other sections of tubing, a longitudinal rod mounted within the tubular chamber for recipro-cation and extending throughout substantially the entire length thereof, a large piston secured to one end of the rod and disposed within the section of tubing having the large bore, a small piston secured to the opposite end of the rod and disposed within the opposite end section of tubing. the tubular chamber having ends provided with openings whereby iluid under pressure may be introduced into and exhausted from the chamber outwardly of the large and small pistons, transverse cylinders connected with the headers and having their outer ends open and their bores in communication with the chamber, plungers mounted within the transverse cylinders for reciprocation and including plunger rods which extend through the outer open ends of the transverse cylinders for connection with head block knees, the combined eiective areas of the plungers and small piston being equal to the effective area of the large piston, one header having an opening through which the chamber and transverse cylinders may be filled with iiuid and maintained lled, and flexible elements connected with the plungers and longitudinal rod and arranged between the rod and bore of the chamber and serving to retract the plungers when the rod is shifted in one direction.

HENRY G. ROBERTS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 275,468 Clark Apr. '10, 1883 301,472 Barnhurst July 8, 1884 303,747 Pelton Aug. 19, 1884 313,396 Wilkin Mar. 3, 1885 316,532 Forbes Apr. 28, 1885 370,413 Rinderknecht Sept. 27, 1887 702.200 Greene June 10, 1902 762,170 Hopper June 7, 1904 994,021 McElroy May 30, 1911 1,561,341 Martin Nov. 10, 1925 1,768,029 Bratlie June 24, 1930

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