THE FRICTION CLUTCH

The driving shaft of the machine is in two sections: The shaft proper, and the short shaft that carries the driving pinion. This pinion meshes with the driving gear, the two shafts being held together by a taper pin. The driving pinion makes eleven revolutions to one of the gear, the ratio being 11 to 1.

The outer end of the driving shaft is hollow. Inside of the hollow shaft is a clutch rod and a spring. The spring fits against a collar on this rod and draws the rod inward. The inner end of the clutch rod is fastened by means of a long screw pin extending through a hole in the rod to a collar which encircles the shaft, the hole in the shaft being slotted, so that when the collar is moved the rod moves also. On the outward end of the shaft is mounted the friction clutch, the levers being fastened to the end of the clutch rod. The friction clutch is keyed to the hollow shaft, so when the clutch is turned it also turns the shaft.

Pressure on a forked lever fulcrumed to the base of the machine, one end of which encircles the collar and the other end touching the lower stop lever, holds the clutch out of action. When the pressure of the forked lever against the collar is released, the clutch spring expands and the clutch rod moves the collar inward until the leather buffers are pushed against the inner surface of the driving pulley, causing the shaft to rotate.

After the machine has made a complete revolution, a pawl on cam No. 10 contacts the upper stopping lever and through the lower stopping lever forces the forked lever against the collar, throwing the friction out of action.

The Clutch Spring

The clutch spring is held in place by a small collar on the inside end of the clutch rod and a screw bushing on the outside, by which the tension of the spring is regulated. This tension should be sixteen to twenty pounds. A screw pin passes through a slot in the shaft, through the clutch rod, and into the opposite side of the collar. The outer end of the clutch rod is connected to the friction clutch by a screw which passes through the clutch rod. By taking off the clutch and hooking a balance spring in the screw hole in the rod and pulling out on the scale, the instant the rod moves the scale indicates the tension of the spring registered. One end of the clutch rod is connected to the collar on the shaft, and the other end is connected to the clutch. When the collar is moved the clutch rod also moves in the same direction.

When the clutch rod spring is adjusted to a tension of 16 to 20 pounds it gives about the right friction to carry the machine through all its operations where everything is working properly, but if anything sticks or makes the machine run hard, the clutch will slip.

Friction Clutch Adjustments

There are three positions of the starting and stopping lever: Starting, operation, and stopping. When pulled all of the way out the lever is in starting position. When the lever is in starting position, the eccentric screw in the starting and stopping lever pulls against the lug in the vertical lever and causes the upper lug to force the automatic stopping pawl off the upper stopping lever. This sets the machine in action. When the lever is half way out it is in operating position and allows the machine to start when a line is sent in. When the lever is pushed all the way in the clutch is thrown out of action and the machine is stopped.

When making any adjustments, have the lever in starting position (out as far as it will go). If the automatic stopping pawl is resting on the upper stopping lever, the adjustments could not be made, as the lower stopping lever would be forcing the forked lever against the collar, throwing the friction clutch out of action.

The friction clutch should be adjusted so as to have ¹⁵/₃₂ of an inch between the collar and the shaft bearing. Place a ¹⁵/₃₂ inch gage between the right-hand side of the collar and the left-hand side of the shaft bearing. If the distance is less than ¹⁵/₃₂ of an inch, dress the leather buffers with a file. If the distance is more, place cardboard under the buffers to increase the thickness. On old-style machines this adjustment was made by two nuts, one on each side of the clutch rod. Putting cardboard under the buffers will not satisfactorily drive the machine if something else is wrong. If there is too much packing under the leathers the starting and stopping lever will have no effect on the clutch and the machine will not stop properly.

The upper stopping lever and the lower stopping lever are fastened by pin pivots to a steel shaft which passes through the vertical lever. This allows a limited up and down movement of the stopping levers. The shaft is held in position by a set screw in the top of the vertical lever bracket. When the machine is in action the forked lever must be free of the collar. If it is not, the clutch does not get the proper pressure on the inside of the pulley, because the forked lever would push against the collar and force the rod and clutch outward. To be sure the forked lever is free of the collar, adjust so there is ¹/₃₂ of an inch between the lower stopping lever and the forked lever. This adjustment is made by the screw in the lower part of the upper stopping lever.

When the upper stopping pawl comes to rest on the upper stopping lever, it forces the adjusting screw in the lower part of the upper stopping lever against the lower stopping lever, and the bottom end of the lower stopping lever causes the forked lever to force the collar out, throwing the clutch out of action and stopping the machine. This gives a horizontal movement from a vertical action. The automatic stop pawl should rest on the upper stopping lever ¼ of an inch when the machine is at normal. This adjustment is made by loosening the set screw which holds the shaft in the vertical starting lever, and moving the lever sidewise. When the stopping pawl rests ¼ of an inch on the upper stopping lever, the automatic safety pawl will also rest on it exactly the same, as both pawls are adjusted the same.

Fastened to cam No. 10 are two pawls. One is the automatic stopping pawl and stops the machine after it has made one complete revolution. The other is the automatic safety pawl, and stops the machine when a line fails to transfer from the first to the second elevator. These two pawls are adjusted by screws that pass through the pawl and strike the lug of the cam, and are held against this lug with a spring. The distance from the left-hand side of the pawl to the left-hand side of the cam should be ¹⁵/₁₆ of an inch.

The vertical lever is fastened to the column, at the back of the machine above the forked lever, by a hexagon head machine screw at its upper end. The lower end is held in place by the shaft which passes through the lever into the machine frame. The only time the vertical lever is in action is when the machine is started by the starting and stopping lever. On the starting lever is an eccentric screw which stands behind the lower lug of the vertical lever. When the starting and stopping lever is pulled out, the eccentric screw engages the lower lug and pulls it forward, causing the upper lug to push the stopping or safety pawls clear of the upper stopping lever. There are three lugs on the vertical lever: The upper lug, the lower lug, and the lug inside of the bracket.

There is a headless screw in the vertical lever bracket, the front end encircled by a spring. This spring forces the vertical lever back to its normal position after the lever has been pulled forward by the starting and stopping lever. When pulled forward, the upper lug strikes against the automatic stopping pawl forcing it clear of the upper stopping lever. This adjustment is made by means of the headless screw in the lever bracket. The proper adjustment forces the stopping pawl ¹/₁₆ of an inch clear of the upper stopping lever. The lug inside the bracket should permit the upper lug to clear the stopping pawl ¹/₆₄ of an inch when the lug is at rest. This adjustment is made by turning the adjusting screw in the column opposite the headless screw. This screw regulates the stroke of the inner lug.

Unless the upper vertical lug, after pushing the stopping pawls off the upper stopping lever, returns clear of the pawls, it would prevent the pawls from seating properly on the upper stopping lever.

The adjustment of the lower lug of the vertical lever and the eccentric screw on the starting lever should be made by releasing the set nut on the eccentric screw and turning the screw until there is ¹/₃₂ of an inch between the screw and the lug. If this adjustment is not properly made it will interfere with the upper lug and throw it out of adjustment.

Friction Clutch Hints

To remove the friction clutch: Push in on the starting and stopping lever. Take out the fulcrum screw or remove the nut from the outer end of the clutch rod. Remove the clutch arm key screw. The clutch can now be removed. Be careful in replacing the friction to have the key with the bevel down and toward the back of the keyway.

The driving pulleys or gear can be removed only when the friction clutch is removed.

To remove the clutch rod spring: Remove the friction clutch. Unscrew the screw bushing from the end of the shaft, take out the screw extending through the collar, and pull out the clutch rod and the spring.

If the machine stops on the upper stopping lever with a jerk, the inner side of the driving pulley or the friction clutch leathers are gummy or the friction is out of adjustment.

The inner surface of the driving pulley must be kept clean.

If the machine slows up while casting or ejecting, the clutch is slipping.

The ¹⁵/₃₂ of an inch adjustment is made by the nut on the clutch rod on the old style, and by building up under the leathers on the new.

The ¹/₃₂ of an inch adjustment is made by the screw in the lower part of the upper stopping lever.

The machine will not stop when the key screw in the clutch arm works loose, allowing the friction clutch to work toward the outer end of the shaft.

A screw holding the clutch leather shoe in place, may extend above the shoe and cause the friction to slip.

The friction link collar, where it fastens on to the clutch rod, should be parallel with the driving pulley or gear when the machine is in operating position; if not, there is unequal pressure on the links and shoes, causing a slipping clutch.

Study the friction clutch adjustments, but do not change them every time something stops the machine. It is much easier to break an adjustment than to make one.

A piece of metal from a squirt lodged between the mold disk guide or back of the rim on the disk will cause it to bind, placing more pull on the clutch.