Variable step size impulse drive
AssigneeThe Singer Company
InventorGeorge Obermann
Life of this patent
Estimating the term…
Abstract
The impulse drive mechanism has a drive pawl which is periodically retracted sufficiently to engage a tooth at maximum tooth spacing to advance the sequence control cam a maximum step. If a lesser step is desired (can be used) the ratchet tooth spacing is decreased and the masking device which incorporates a follower engaging the cam on the inside of the ratchet is moved into position to prevent engagement of the pawl with a tooth at greater spacing. The cam drum can be advanced in small angular increments when only tolling time and the angular increment can be increased to accomodate sequential switching during the advance step if required.
Claims10
The combination with a timer of the type having a switching device rotated in a step-by-step manner, of
- a ratchet mounted for rotation about its axis and including ratchet teeth,
- a pivot,
- a lever mounted on the pivot and including a cam follower,
- a rotatable impulse cam having a slow-rise, fast-drop face,
- spring means biasing the follower against the cam face,
- a drive pawl pivoted on the lever,
- said pawl being biased into engagement with the ratchet,
- said cam actuating the pawl a fixed distance equivalent to a fixed angular relationship to said ratchet each time said follower drops down the fast-drop face,
- said ratchet teeth having various angular spacings up to said fixed angular relationship,
- means sensing the angular size of the step next to be taken and limiting engagement of the pawl with the ratchet accordingly.
The combination with a timer of the type having a switching device rotated in a step-by-step manner, of
- a ratchet mounted for rotation about its axis and including ratchet teeth,
- a pivot,
- a lever mounted on the pivot and including a cam follower,
- a rotatable impulse cam having a slow-rise, fast-drop face,
- spring means biasing the follower against the cam face,
- a drive pawl pivoted on the lever,
- said pawl being biased into engagement with the ratchet,
- the teeth on said ratchet having various angular spacings up to X.degree.
- and means preventing engagement of the pawl with any but the next tooth even though more than one tooth may be within X.degree. of the tooth last engaged.
The combination with a timer of the type having a switching device rotated in a step-by-step manner, of
- a ratchet mounted for rotation about its axis and including ratchet teeth,
- a pivot,
- a lever mounted on the pivot and including a cam follower,
- a rotatable impulse cam having a slow-rise, fast-drop face,
- spring means biasing the follower against the cam face, a drive pawl pivoted on the lever,
- said pawl being biased into engagement with the ratchet,
- the geomertry of the lever and cam rise being selected so the drive pawl is retracted a finite distance as the cam rotates so as to be capable of engagement with a ratchet tooth having an angular position relative to the previously engaged tooth of X.degree.,
- the teeth on said ratchet being spaced by various spacings up to X.degree.,
- a control cam fixed with respect to and rotatable with said ratchet,
- a control follower engageable with said control cam,
- a masking device controlled by the control follower and moveable into position limiting engagement of the pawl to the next tooth even though more than one tooth may be within X.degree. of the last tooth engaged so the ratchet is advanced only the number of degrees by which said last tooth and said next tooth are separated.
Dependencies are inferred from the claim text.