US2270059A - Control mechanism for sawmill carriage steam feeds - Google Patents

Description

Jan. 13, 1942. f M. KAHR 2,270,059

CONTROL MECHANISM FOR SAWMILL CARRIAGE STEAM FEEDS Filed Nov. 7, 193B 2 Sheets-Sheet 1 "aQL Y INVENTOR. v Ward/n ffahr' ATTORNEY.

M. KAHR 2,270,059

CONTROL MECHANISM FOR SAWMILL CARRIAGE STEAM FEEDS Jan. 13, 1942.

Filed Nov. '7, 1938 2 Sheets-Sheet 2 WW QQ m ZLEJW ww R Iiiii INVENTOR. BY mam/n K357" b ATTORNEY.

Patented Jan. 13, 1942 CONTROL MECHANISM FOR SAWMI LL CARRIAGE STEAM FEEDS Martin Kahr, Milwaukee, Wis., assignor to The Filer & Stowell (10., Milwaukee, Wis., a corporation of Wisconsin Application November 7, 1938, Serial No. 239,204

3 Claims. (01. 121-41) This invention relates to an improvement in control mechanism for saw mill carriage steam feeds.

Saw mill carriages are commonly reciprocated by means of a reciprocating steam engine which usually has a fixed cylinder and a reciprocating piston, the latter being connected to the carriage. The distribution of the steam supply to the opposite ends of the cylinder is controlled by means of distributing valves which are necessarily rather large and heavy and this, together with the necessity for very rapid operation of the carriage, has led to the use of a servo-motor for operating the valve. The action. of the servomotor is controlled by means of the pilot valve, regulated in its action from a control lever which may be conveniently manipulated by the sawyer. The nature of the organization and particularly the inertia of the various parts renders it difiicult for the sawyer to readily and easily exert an exact control over the operation of the servo-motor. The piston of the servo-motor tends to overtravel and impair the intended operation of the pilot valve by which it is controlled.

The principal object of the present invention is to so interrelate and interconnect the piston of the servo-motor and its pilot valve as to dampen the action of these parts and overcome the disturbing actions of inertia with the result that the sawyer can very conveniently exercise just the control he desires over the action of the servomotor and the consequent actuation of the saw mill carriage.

Another object of the invention is to provide a control device of this character which is extremely simple and compact in its construction, reliable, smooth and eflicient in its operation, readily and easily controllable, and easy and comparatively inexpensive to manufacture and install. I

Other objects and advantages reside in certain novel features of the construction, arrangement and combination of parts which will be hereinafter more fully described and particularly pointed out in the appended claims, reference being had to the accompanying drawings forming a part of this specification, and in which:

Figure 1 is a diagrammatic view in elevation illustrating the general layout of a steam feed for saw mill carriages equipped with a steam valve controller embodying the present invention;

Figure 2 is a similar view in top plan of the structure shown in Figure 1;

tion looking toward the left hand end of-Figure 2, parts being shown in section for the sake of example and illustration; I

Figure 4 is a view in vertical section taken on line 44 of Figure 2, parts being shown in elevation for the sake of illustration;

Figure 5 is a view partly in section and partly in elevation showing the dampening device of the present invention on an enlarged scale; and

Figure 6 is a view in vertical cross section taken on line 66 of Figure 5.

Referring to the drawings, the numeral Ill designates the cylinder of a saw mill carriage steam feed which is of conventional construction and fixed in place in the usual manner. The piston reciprocable in the cylinder is not shown but it has a piston rod II which is connected in the usual way to the saw mill carriage.

Steam is supplied from a boiler (not shown) through a pipe l2 which has branches l3 and it connected to the inlet sides of steam feed valves I5 and I6 which control the passage of the steam through the inlet pipes I1 and I8 communicating with the opposite ends of the cylinder H3. The feed valves l5 and I6 are opened and closed by the usual valve gear, designated generally at 20, and have a main operating rod 2| suitably coupled as at 22 to the piston rod 23 of a servo-motor designated generally at 24.

The servo-motor 24 is of conventional construction' and has a fixed cylinder 25 suitably supported and a piston 26 reciprocable in the cylinder 25. The piston rod 23 is threadedly connected as at 21 to one end of the piston, the threaded connection being maintained by means of a lock nut 28. Steam is supplied to the cylinder 25 from the boiler to a steam pipe 29 which has branches 30 and 3| in open and constant communication with the opposite ends of the cylinder.

The piston 26 is formed with spaced heads 32 and 33 having piston rings 34 to establish a fluid tight sliding relation between the piston heads and the wall of the cylinder. The body portion of the piston in between its spaced heads is of less diameter than the cylinder to define an exhaust space 36 with which an exhaust pipe 31 is in constant communication. An axial opening or bore 38 extends through the heads and body of the piston from one end thereof to the other although the ends of this bore are eiiectively closed on by means of the piston rod 23 and a companion piston rod 23' and associated structure. At the center of the body portion of the Figure 3 is a fragmentary view in end elevapiston 26 a chamber 40 is provided and communicates with the exhaust space 36 at all times through a port 4|. On the opposite sides of the chamber 40 annular grooves 42 and 43 are provided and these grooves respectively communicate with the inner ends of steam passages 44 and 45. The passages 44 and 45 lead from their respective grooves cut through the ends of the piston and consequently are in communication at all times with the steam pressure always maintained at the opposite ends of the cylinder. .A piston type pilot valve designated generally at 46 is provided and has spaced piston heads 41 and 48 fitted in the axial opening or bore 38 of the.

piston of the servo-motor and respectively cooperable with the annular grooves 42 and 43 either to plug these grooves or else to selectively uncover them and allow steam to flow therethrough to the exhaust and consequently reduce the pressure on one side or the other of the piston and cause it to be moved toward one end or the other of the cylinder. Such motions of the piston moves the piston rod 23 in one direction or the other and consequently serves to open or close the steam feed valve depending, of course, on the direction of the motion. The companion piston rod 23 is in the form of a pipe or tube and works through a stufiing box 50 provided on one of the end heads of the cylinder 25. The pilot valve 46 has an elongated valve stem 5| which extends back through and beyond the-hollow piston rod 23. A cross head 52 has its hub threadedly connected with the outer end of the piston rod 23 and it is held in adjusted position thereon by means of a lock nut 53. The outer end of. the piston rod 23' is provided with a packing gland 54 through which the stem of the pilot valve extends. Just beyond the packing gland 54 a second cross head, designated at 55, is provided and has its hub threadedly interconnected with the threaded outer end 5| of the valve stem 5|. A look nut 56 maintains the adjustment of the cross head 55. A clevis 51 is interconnected with the outer end of the valve stem 5| just beyond the cross head and is connected through a system of links and levers designated generally at 58 with the manually operable control lever 59. Rods 60, preferably two in number, extend from the cross head 52 through openings 6| in the cross head 55 and beyond the same. Nuts 63 secure one end of each of the rods to the cross head 52. The intermediate portions of the rods are slidably interfitted with the opening 6| in the cross head 55. Compression coil springs 64 encircle the rods 65 between the cross heads 52 and 55 and abut these cross heads at theiropposite ends. Springs 65 encircle the portions of the rods projecting beyond the cross head 55 and their inner ends engage this cross head while their outer ends engage one of a pair of nuts 66 threaded on the outer ends of the rods 60. The springs are under compression which may, of course, be varied by suitably adjusting the cross heads relative to each other and the nuts 66.

In practice, the valve controllers embodying the present invention are tested before shipment and the springs 64 and 65 are so adjusted that the pilot valve 45 is centrally located in the piston of the servo-motor and the control lever moves with equal ease in either direction. When this is accomplished, the operation is then very smooth and the control lever 59 can then be moved very easily. This also has the effect, with the springs appropriately tightened, to dampen any vibration that might otherwise be set up by the pilot valve 46 and the piston 26 of the servo-motor.

When making the adjustment described the linkage to the right of part 51 is disconnected and the lock nut 56 is loosened. The whole assembly shown in Figure 5 can then be rotated on the piston rod 23'. The consequent shifting of the yoke 52 changes the tension of the springs 64. The tension of the springs 65 is adjusted by adjusting the nuts 66. Of course, after the appropriate adjustments are made the several lock nuts are tightened and the operating or control linkage reconnected. With a valve controller of this character, when the operating or control lever 59 is moved to shift the pilot valve 46 with respect to the piston 26 and thereby reduce the pressure on one side or the other of the piston and cause it to move correspondingly, it moves without the piston 26 tending to overtravel since the motion is dampened by the action of the springs 64 and 65 or interconnected in the manner described between the piston rod of the servomotor piston and the valve stem of the pilot valve.

While I have shown and described one construction in which the invention may be advantageously embodied, it is to be understood that the construction shown has been selected merely for the purpose of illustration or example and that various changes in the size, shape and arrangement of the parts may be made without departing from the spirit of the invention or the scope of the subjoined claims.

The invention claimed is:

1. A control mechanism comprising a servomotor having a piston rod, a pilot valve for said servo-motor, said valve having an operating stem shiftable axially of said rod, and means interconnecting said stem and rod and comprising spaced cross heads connected to said stem and to said rod, guide rods secured to one of said cross heads, the other of said cross heads having openings through which the guide rods slidably extend, the guide rods projecting beyond said lastnamed cross head, compression coil springs encircling the guide rods and abutting the cross heads at the opposite ends, and a second set of coil springs encircling the projecting portions of the guide rods and abutting one of the cross heads at their inner ends, and adjustable abutments for the outer ends of said springs mounted on the outer end portions of said guide rods.

2. A control mechanism for saw mill carriage steam feeds comprising a servo-motor having a cylinder, a piston in the cylinder having a piston rod extending beyond one end thereof and adapted for connection with the valve gear of the steam feed, a hollow piston rod extending through at one end of the cylinder, a pilot valve associated with. the piston of the servo-motor and shiftable axially thereof to control the motions of said piston, a stem connected to the pilot valve and extending through and beyond the hol- 10W piston rod, a control lever operatively interconnected with said stem, and means interconnecting the valve stem and the hollow piston rod and comprising spaced cross heads connected to said valve stem and to said hollow piston rod, rods secured to one of said cross heads, the other of said cross heads having openings through which the rods slidably extend, the rodsprojecting beyond said last named cross head, compression coil springs encircling the rods and abutting the cross heads at the opposite ends and 3/5861 ond set of coil springs encircling the projecting portions of the rods and abutting one of the cross heads at their inner ends, and adjustable abutments for the outer ends of said springs mounted on the outer end portions of said rods.

3. A control mechanism for saw mill carriage steam feeds comprising a servo-motor having a cylinder, a piston in the cylinder having a piston rod extending beyond one end thereof and adapted for connection with the valve gear of the steam feed, a hollow piston rod extending through at one end of the cylinder, a pilot valve associated with the piston of the servo-motor and shiftable axially thereof to control the motions of said piston, a stem connected to the pilot valve and extending through and beyond the hollow piston rod, a control lever operatively interconnected with said stem, and means interconnecting the valve stem and the hollow piston rod and comprising spaced cross heads connected to said valve stem and to said hollow piston rod, rods secured to one of said cross heads, the other of said cross heads having openings through which the rods slidably extend, the rods projecting beyond said last named cross head, compression coil springs encircling the rods and abutting the cross heads at the opposite ends, and a second set of coil springs encircling the projecting portions of the rods and abutting one of the cross heads at their inner ends, and adjustable abutments for the outer ends of said springs mounted on the outer end portions of said rods, the cross head connected to the hollow piston rod being adjustable therealong to vary the tension of the 15 springs engaged by it.

MARTIN KAHR.

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