Shaper Mechanism Types
.

Crank, Rack or Geared, Friction Geared and Hydraulic 
        Crank Shapers generally use a bull gear which has an offset pin which can be adjusted to vary the radius of the throw and therefore alter the stroke. This pin, mounted in a sliding block which can reciprocate in a slot in a pivoted lever, induces a slow and fast cycle to the oscillation of the lever. As the free end of the lever is linked to the shaper ram, the slow motion is used for the cutting stroke and the fast motion to return the ram on the non-cutting stroke. In most shapers, the ram is slotted to receive a fastening stud to secure the link connected to the lever. The slot enables the ram to be positioned by adjustment to the work piece. 
A schematic drawing.
        The main advantage seen in this principle, was that an exact end of stroke determination could be made, to allow cutting to a line. 
        The main disadvantage in the early crank shapers was in setup, many required the operator to adjust the crankpin, i.e. the stroke adjustment, inside the machine. An additional factor is that crank shapers do not present a constant cutting speed to the tool due to the action of the operat-ing lever, velocity being less at either end of the stroke.
        However, the advantages of the system have recognized by the fact that the majority of shapers ever built, have been crank shapers.
        Another variant of the crank driven shaper, was the type that used the Whitworth Quick Return Motion. This worked in a similar way to the above system, the main different was that the pivot for the slotted lever or rocker was within the crankpin circle, whereas in the system above, it was outside that circle.
        The Whitworth Quick Motion was used on early pillar type shapers, but was found mainly on Traversing Head Shapers. Because the mechanism was con fined within the diameter of the bull gear, this made the construc- tion of Traversing Head Shapers quite simple, as it meant the mechanism could be above the bed.. Whitworth Quick Motion
        Rack or Geared Shapers can have either one or two racks on the underside of the ram, Two belts, one crossed, driving to idling pulleys either side of a pulley fixed to the rack pinion driving shaft. Adjustable dogs on the ram, engage the belt shifting linkage to move the forward belt onto the fixed pulley for the cutting stroke, replacing it with the reverse belt for the rearward stroke. 
        The shifting belt system did not allow for accuracy in length of cut so was not a popualr choice for those wishing to cut to a line.
        Uniformity of cutting speed and ease of setup being the only attributes of this actuating system. A Smith & Mills shaper of this type can been seen here.
        Friction Geared Shapers used a friction clutch to reduce the shortcomings of the belt shifting shapers. Hendey with their friction shaper with the mechanism patented by Eli J. Manville greatly improved  on  the rack or gear driven shaper. Manville's still used straight and crossed belts but they drove pulleys that were engaged to the rack driving pinion shaft when engaged by a friction (clutch). The clutch was tripped by dogs that could be set to determine the stroke of the shaper as well as the position of the ram. These dogs were alongside of the ram and could be set with the machine in motion. The front dog engaged the "friction" to lock the crossed belt driven pulley, to the pinion shaft, imparting rearward motion, the rear dog, engaging the forward motion pulley. The Hendey shapers had two diameters on the forward motion pulley to allow a variation in cutting speeds between iron and steel. The reverse motion was normally driven at a faster speed from the countershaft to reduce the idle time. 
        The advantages of friction gear driven shapers over crank was the uniform stroke speed and the ease of setup. 
        The main disadvantage being the less than finite end of stroke determination although superior to the geared style shaper, linkage lost motion and possible friction clutch wear, were factors that not to be ignored.
        Hydraulic Drive Shapers utilise a hydraulic ram to reciprocate the ram, the inherent bias of a double acting ram imparting a natural quick return stroke. Adjustable dogs determine both the length of stroke and the position of the ram. Simplicity of control over speed, stroke etc together with constant cutting speeds, had to be weighed against cost, the hydraulic shaper was the most expensive of all. Nice to work, though.. Schematic here:
Back
 
 
 
 
 
 
 
 
 
 
 
 

Site Meter