Spring Clutch Overview:
The basic wrap spring clutch consists of three parts: an input hub, an output hub, and a spring. The inside diameter of the spring is slightly smaller than the outside diameter of the two hubs. When the parts are assembled and one hub is rotated in the direction that the spring is wound, the spring wraps down tightly on both hubs causing the clutch to drive. The greater the force the tighter the spring grips the hubs. When the rotation is reversed, the spring loosens its grip and slips. In the free direction there is slight drag caused by the spring being slightly smaller than the drums. Tiny-Clutch spring clutches are very versitile & can provide many different functions.
Helander Products offers three lines of Spring Clutches:
SP-Series Spring Clutches are our most versitile line of spring clutches, providing the following five functions.
Overrunning Spring Clutch: In its simplest form the spring clutch functions as an overrunning clutch. It drives one way and slips upon reversal; the output is free to overrun the input. It can also be used as a backstopping clutch.
On-Off Spring Clutch: With the addition of a radial tang on the input end of the spring, the on-off clutch can be controlled. Normally the input hub rotates continuously and drives the output hub. When the tang is stopped*, the spring unwraps and uncouples the clutch. The output may coast to a stop depending upon the inertia of the driven load.
* The spring is surrounded & controlled by a release collar which has a protruding lug on its circumference. This collar is mechanically triggered or we can provide actuator brakets & solenoids if elctrical triggering is required.
Indexing Spring Clutch: The addition of a second spring tang anchored to the output assures the output always stops in the same angular position when the release collar is stopped. Different numbers of lugs can be added to the release collar to create single or fractional revolution clutches.
Adjustable Indexing Spring Clutch: In some applications it is desirable to precisely adjust the angular stopping position of the output hub after installation in a piece of equipment. This is accomplished by the use of our patented clamp type adjusting collar* which securely clamps the output end of the spring to the output hub. When the clamp screw is loosened, the output hub may be rotated relative to the lug on the release collar.
* U.S. Patent 3,835,972
Positive Stop Indexing Spring Clutch: A pin projecting from the release collar extends into a radial slot in the adjusting collar*. When the release collar is stopped, the output hub continues to rotate through a few degrees of arc until the radial slot face strikes the stop pin. This feature provides an adjustable, positive stop in applications involving higher inertia loads and where the output member tends to over-travel the stopped release collar possibly damaging the spring. Both the degrees of over-travel and the output stopping position can be adjusted simultaneously after installation in a piece of equipment.
* U.S. Patent 3,835,972
M-Series Magnetic Spring Clutches function similarly to the On-Off Spring Clutch, with the addition of an electromagnetic coil that actuates it. Normally the input hub rotates continuously and the output hub is free in both directions. When power is applied, the spring wraps down & couples the clutch. When power is removed, the spring unwraps and uncouples the clutch. The output may coast to a stop depending upon the inertia of the driven load.
AD-Series Autodisconnect Spring Clutches function similarly to the M-Series magnetic spring clutch, without the electromagnetic coil that actuates it. When no torque is applied to the input, the output is free in both directions. When torque is applied to the input, the spring wraps down & the clutch drives. These are purely mechanical automatically disconnecting clutches and require no external actuation. AD-Series clutches are ideal for applications such as tape take up reels when the output must be free in order to retrieve material off of the reel.