Patent Publication Number: US-6215079-B1

Title: Pressure controlled time switch

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention involves a time switch used for example for triggering off or terminating a procedure when relatively short switching times are preset, only mechanical energy sources are available, and so forth. A non-exclusive area of use lies in motion control for the transportation rollers of paper towel dispensers or the like. 
     2. Description of the Related Art 
     Examples in this respect are shown for example in U.S. Pat. No. 2 369 851, U.S. Pat. No. 2, 592,786. U.S. Pat. No. 2,930,664 or GB-A 2 043 592 and GB-A 2 096 099. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention concerns a time switch having a switching member on which a suction cup is arranged, a counterpart body against which the suction cup can be pressed forming a reduced-pressure space, with air contained in the suction cup being displaced, an air inlet opening into the reduced-pressure space, the cross-section of the opening preferably being adjustable to establish the release time of the suction cup from the counterpart body, and a resetting device whose resetting force is less than the suction force of the suction cup when pressed against the counterpart body. A needle valve or the like which is provided with an adjusting screw is arranged in the continuously open air inlet opening for fixing the switching time, that is to say that time until the reduced pressure has returned to normal due to the intake of air, to such an extent that the return force of the time switch exceeds the suction force. 
     The intake of air can be altered by means of the adjusting screw, but that is not an appropriate course of action whenever the switching cycle is to experience a one-off acceleration effect and is then to continue to move at the intended setting. 
     In accordance with the invention associated with the reduced-pressure space is a venting opening with a sealing closure element which is urged in the closed position, so that it is possible to implement any reduction in the duration of the switching time by lifting off the closure element. 
     The reduced-pressure space thus has two openings, namely the air inlet opening which determines the predetermined switching time and the venting opening which permits the switching time to be reduced and the closure element of which is for example actuated by hand. 
     A preferred embodiment provides that the counterpart body is a fixed plate and the venting opening provided with the closure element is disposed in the counterpart body. A plate which is fixed with respect to the housing and which is not flexible improves the sealing contact of the closure element which is arranged in particular on a lever which is engaged on the one hand by a return spring and on the other hand by an actuating element which operates against the return spring. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The invention will now be described in greater detail with reference to the Figures of the accompanying drawings without being limited thereto. 
     In the drawings: 
     FIG. 1 is a diagrammatic side view of a closed time switch, and 
     FIG. 2 is a diagrammatic side view of an opened time switch. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The time switch has a housing or a support frame  1  on which there is provided a plate or the like as a counterpart body  11  in relation to a suction cup  3  which is arranged on a switching member  5 . The switching member  5  is mounted displaceably in a guide  2  and has a bore  6  which terminates in an air inlet opening  9  of small cross-section, which is arranged within the suction cup  3 . The cross-section of the air inlet opening  9  is adjustable to control the release time of the suction cup  3  from the counterpart body  11 . The outer end of the bore  6  preferably carries a needle valve  7  with an adjusting screw  8 , the rotation of which changes the speed at which the air flows into the reduced-pressure space  10 . A return spring  4  urges the switching member  5  in opposite relationship to the suction force of the suction cup  3  so that the switching member  5  is transferred from the position shown in FIG. 1 after sufficient intake of air by way of the opening  9  into the position shown in FIG.  2 . 
     If the switching time is to be shortened once, this is not effected by turning the adjusting screw  8  which would then have to be re-set, but by venting the reduced-pressure space  10 . For that purpose the counterpart body  11  is provided which venting opening  12  associated with the reduced-pressure space  10  comprising a sealing closure element  13  which is urged in the closed position. 
     The closure element  13  is provided with a seal  14  and arranged on a lever  15  which is pivotable about an axis  16 . The lever  15  is engaged on the one hand by a return spring  17  which presses the closure element  13  against the venting opening  12  and on the other an actuating element  21 , by means of which the venting opening  12  can be opened and which acts in opposite relationship to the return spring  17 .