GB1596810A

GB1596810A - Electric interval timer

Info

Publication number: GB1596810A
Application number: GB13222/78A
Authority: GB
Original assignee: Crouzet SA
Current assignee: Thales Avionics SAS
Priority date: 1977-04-19
Filing date: 1978-04-05
Publication date: 1981-09-03
Also published as: DE2816166A1; IT1094375B; ES468813A1; DE2816166C3; FR2388332A1; IT7822349A0; DE2816166B2; FR2388332B1

Description

(54) ELECTRIC INTERVAL TIMER (71) We, CROUZET, a joint stock company organised and existing under the Laws of France, of 128 Avenue de la Republique, 75011 Paris, France, do hereby declare the invention, for which we pray that a patent may be granted to us, andthe method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an electromagnetic interval timer comprising a synchronous motor driving reduction gearing whose output wheel is mounted upon a shaft adapted to be tilted under the action of an armature of an electromagnet, said output wheel being thus able to engage a time wheel so as to drive it rotationally. Such a device will hereinafter be referred to as a device of the above mentioned type.

In conventional timing devices, a synchronous motor drives, through a reduction gear and a clutch, a time wheel having a recess or a cam surface adapted to vary the position of an electric contact. In general this time wheel, whose return to the zero position is permitted by an electromagnetic clutch, is subject to the action of a return spring. A recess without teeth is so arranged on the periphery of the time wheel that, at the end of a timed period, the output wheel of the reducing gear which drives the time wheel descends into this recess, and that the motor can continue to rotate between two timed periods without entraining the time wheel.This arrangement, however, presents the disadvantage that between two timed periods the wall of the recess, under the action of the return spring of thei time wheel, continues to run against the output wheel of the reducing gear, so that the last tooth of the time wheel, adjacent to the recess, wears the output wheel.

An object of the present invention is to obviate this disadvantage and the invention provides a device of the above mentioned type. characterised in that it comprises first and second cam wheels coaxial with the time wheel, the first cam wheel being driven rotationally by said time wheel, and the second cam wheel being moved between two angular positions by the armature of the electromagnet, the first cam wheel having a recess or notch adapted to receive, at the end of a preset time period, a follower mounted upon a lever which is thus permitted to tilt said shaft of said output wheel and also to actuate an electric contact,- the second cam wheel being provided with two cam surfaces adapted to coact with said follower and said shaft respectively to hold the follower out of engagement with the first cam wheel and the output wheel out of engagement with the time wheel, when said second cam wheel is in one of its said two angular positions.

With the arrangement of the invention, at the end of a timed period, i.e. at the instant when the follower drops into the recess in the first cam wheel, the lever disengages the output wheel of the reducing gear from the time wheel, and the shaft of the output wheel can continue rotating, rubbing against the lever but without the possibility of wearing the output wheel Moreover, play may be present between the time wheel and the first cam wheel, to enable the follower to drop rapidly into the recess of the time wheel at the termination of a timed period.

According to the arrangement of the cam surfaces of the second cam wheel, the interval timer of the invention may be conceived to provide for the timed period to occur either whilst the electromagnet is energised - this providing a device with normal clutch action - or while the electromagnet is deenergised --the latter case being that of a device with reversed clutch action.

The invention will be described further, by way-of example, with reference to the accompanying drawing in which the single figure is a diagrammatic perspective view, with parts cut away, illustrating a preferred embodiment of the interval timer of the invention, constructed to have normal clutch action.

The illustrated interval timer according to the invention comprises a conventional synchronous motor (which is not shown) driving a reduction gearing of which only output wheel la is illustrated in the figure. The wheel la is seated on a shaft 1 This shaft 1 is adapted to be tilted more particularly under the action of an electromagnet 3 provided with an armature 3a, as is explained below, so that the output wheel la can, as a result, engage a time wheel 2.

The device further comprises a first cam wheel 9 and a second cam wheel 5 both of which are coaxial with the time wheel 2. The first cam wheel 9 can be driven rotationally, with play, by the time wheel 2, by means of a tenan 2a which is integral with the wheel 2 and co-operates with a semi-cylindrical member 2c, integral with the first cam wheel 9. The second cam wheel 5 can be pivoted by the armature 3a of the electromagnet 3, through a connection rod 4.

The first cam wheel 9 has a notch or recess 9a intended for the reception of a follower 7a projecting from a lever 7 pivotably mounted upon a shaft (not shown) whose axis is parallel to that of the wheels 2, 9 and 5, and is adapted to actuate, by an arm 7b, a mobile blade 8a of an electric contact unit 8.

The second cam wheel 5 has two cam surfaces 5a and 5b located to coact with the follower 7a and the shaft 1 of the output wheel la respectively.

The time wheel 2 is driven rotationally, clockwise in the figure, by a spring indicated diagrammatically at 2b. The output wheel la is brought into engagement with the time wheel 2 by a spring 17 acting on end ib of the shaft 1 whose displacement is restricted by a slot 16a formed in a plate 16 of the apparatus. The second cam wheel 5 is caused to rotate, counter-clockwise in the figure, by a spring 6. The follower 7a and an arm 7c of the lever 7 are urged towards the first cam wheel 9 and the shaft 1 respectively by a spring 10 fixed to the arm 7b of the lever 7.

An indexing knob 11, provided on the plate 16, allows fine presetting of the timing, i.e. adjustment of the counterclockwise angle of rotation of the time wheel 2, by means of a tenon 12 integral with said knob 11 and disposed so that a bar 13, integral with shaft 2d of the time wheel 2, abuts against the tenon 12 under the action of the spring 2b, which biases the time wheel 2 to rotate in a clockwise motion, and thus the bar 13 when the apparatus is returned to zero. Thus, the tenon 12 and the bar 13 define the angular position of the time wheel 2 at the start of a timed period.

Once the indexing knob 11 has been reset to zero and the synchronous motor is running, the electromagnet 3 is energized and attracts the armature 3a, which in the case of an apparatus with normal clutch action causes the cam wheel 5 to rotate clockwise by means of the rod 4, pushed by the armature 3a, against the action of the spring 6. In this way the cam surfaces Sa and 5b act neither on the follower 7a, which abuts the edge of the first cam wheel 9, nor on the shaft 1. The end 1b of the shaft 1 being loaded by the spring 17, the output wheel la meshes with the time wheel 2, which is then driven rotationally by this wheel la. The timing cycle progresses.After the preset rotation of the time wheel 2, the notch or recess 9a comes into register with the follower 7a and this can drop into said notch 9a under the action of the spring 10, which causes the lever 7 to turn, this determining the end of the timed period. While the lever 7 is turning, its arm 7c shifts the shaft 1 against the action of the spring 17 so as to disengage the wheel la from the time wheel 2, and the arm 7b of the lever releases the blade 8a to change over the contact unit 8.

The shaft 1 of the wheel la can continue to turn, rubbing against the arm 7c of the lever 7, but without the teeth of wheel la suffering any wear.

As the electromagnet 3 is de-energised, the spring 6 is enabled to pivot the cam wheel 5 counterclockwise, the cam surface 5a repelling the follower 7a, which causes the lever 7 to turn against the action of its return spring 10. The arm 7c of the lever 7 disengages the shaft 1, but the cam face 5b takes the place of the arm 7c of the lever 7 to repel the shaft 1 and hold the output wheel la of the reduction gear declutched from the time wheel 2. The arm 7b repels the blade 8a so as to reverse once more the counter unit 8.

It must be emphasised that the invention is not restricted to a device with normal clutch action, and a device with reversed clutch action could have equally well been described instead, in which case the timed period would correspond to the electromagnet being de-energised.

The timing device of the invention is reliable, easy to assemble and to wire.

WHAT WE CLAIM IS: 1. An interval timer with electromagnetically controlled starting of a timed period comprising a synchronous motor driving reduction gearing whose output wheel is mounted upon a shaft adapted to tilt under the action of an armature of an electromagnet, said output wheel being thus able to engage a time wheel so as to drive it rotationally, the device being characterised in that it comprises first and second cam wheels coaxial with the time wheel, the first cam wheel being driven rotationally by said time wheel, and the second cam wheel being moved between two angular postions by the armature of the electromagnet. the first cam wheel having a recess or notch adapted to receive, at the end of a preset time period, a followed mounted upon a lever which is thus permitted to tilt said shaft of said output

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. wheel la is illustrated in the figure. The wheel la is seated on a shaft 1 This shaft 1 is adapted to be tilted more particularly under the action of an electromagnet 3 provided with an armature 3a, as is explained below, so that the output wheel la can, as a result, engage a time wheel 2. The device further comprises a first cam wheel 9 and a second cam wheel 5 both of which are coaxial with the time wheel 2. The first cam wheel 9 can be driven rotationally, with play, by the time wheel 2, by means of a tenan 2a which is integral with the wheel 2 and co-operates with a semi-cylindrical member 2c, integral with the first cam wheel 9. The second cam wheel 5 can be pivoted by the armature 3a of the electromagnet 3, through a connection rod 4. The first cam wheel 9 has a notch or recess 9a intended for the reception of a follower 7a projecting from a lever 7 pivotably mounted upon a shaft (not shown) whose axis is parallel to that of the wheels 2, 9 and 5, and is adapted to actuate, by an arm 7b, a mobile blade 8a of an electric contact unit 8. The second cam wheel 5 has two cam surfaces 5a and 5b located to coact with the follower 7a and the shaft 1 of the output wheel la respectively. The time wheel 2 is driven rotationally, clockwise in the figure, by a spring indicated diagrammatically at 2b. The output wheel la is brought into engagement with the time wheel 2 by a spring 17 acting on end ib of the shaft 1 whose displacement is restricted by a slot 16a formed in a plate 16 of the apparatus. The second cam wheel 5 is caused to rotate, counter-clockwise in the figure, by a spring 6. The follower 7a and an arm 7c of the lever 7 are urged towards the first cam wheel 9 and the shaft 1 respectively by a spring 10 fixed to the arm 7b of the lever 7. An indexing knob 11, provided on the plate 16, allows fine presetting of the timing, i.e. adjustment of the counterclockwise angle of rotation of the time wheel 2, by means of a tenon 12 integral with said knob 11 and disposed so that a bar 13, integral with shaft 2d of the time wheel 2, abuts against the tenon 12 under the action of the spring 2b, which biases the time wheel 2 to rotate in a clockwise motion, and thus the bar 13 when the apparatus is returned to zero. Thus, the tenon 12 and the bar 13 define the angular position of the time wheel 2 at the start of a timed period. Once the indexing knob 11 has been reset to zero and the synchronous motor is running, the electromagnet 3 is energized and attracts the armature 3a, which in the case of an apparatus with normal clutch action causes the cam wheel 5 to rotate clockwise by means of the rod 4, pushed by the armature 3a, against the action of the spring 6. In this way the cam surfaces Sa and 5b act neither on the follower 7a, which abuts the edge of the first cam wheel 9, nor on the shaft 1. The end 1b of the shaft 1 being loaded by the spring 17, the output wheel la meshes with the time wheel 2, which is then driven rotationally by this wheel la. The timing cycle progresses.After the preset rotation of the time wheel 2, the notch or recess 9a comes into register with the follower 7a and this can drop into said notch 9a under the action of the spring 10, which causes the lever 7 to turn, this determining the end of the timed period. While the lever 7 is turning, its arm 7c shifts the shaft 1 against the action of the spring 17 so as to disengage the wheel la from the time wheel 2, and the arm 7b of the lever releases the blade 8a to change over the contact unit 8. The shaft 1 of the wheel la can continue to turn, rubbing against the arm 7c of the lever 7, but without the teeth of wheel la suffering any wear. As the electromagnet 3 is de-energised, the spring 6 is enabled to pivot the cam wheel 5 counterclockwise, the cam surface 5a repelling the follower 7a, which causes the lever 7 to turn against the action of its return spring 10. The arm 7c of the lever 7 disengages the shaft 1, but the cam face 5b takes the place of the arm 7c of the lever 7 to repel the shaft 1 and hold the output wheel la of the reduction gear declutched from the time wheel 2. The arm 7b repels the blade 8a so as to reverse once more the counter unit 8. It must be emphasised that the invention is not restricted to a device with normal clutch action, and a device with reversed clutch action could have equally well been described instead, in which case the timed period would correspond to the electromagnet being de-energised. The timing device of the invention is reliable, easy to assemble and to wire. WHAT WE CLAIM IS:

1. An interval timer with electromagnetically controlled starting of a timed period comprising a synchronous motor driving reduction gearing whose output wheel is mounted upon a shaft adapted to tilt under the action of an armature of an electromagnet, said output wheel being thus able to engage a time wheel so as to drive it rotationally, the device being characterised in that it comprises first and second cam wheels coaxial with the time wheel, the first cam wheel being driven rotationally by said time wheel, and the second cam wheel being moved between two angular postions by the armature of the electromagnet. the first cam wheel having a recess or notch adapted to receive, at the end of a preset time period, a followed mounted upon a lever which is thus permitted to tilt said shaft of said output

wheel and also to actuate an electric contact, the second cam wheel being provided with two cam surfaces adapted to coact with said follower and said shaft respectively to hold the follower out of engagement with the first cam wheel and the output wheel out of engagement with the time wheel when said second cam wheel is in one of its said two angular positions.

2. An interval timer as claimed in claim 1 in which there is play between the time wheel and the first cam wheel.

3. An interval timer substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.