GB2064049A - A "slow rise" quick drop mechanism - Google Patents

Abstract

A slow rise quick drop mechanism comprises a rotary cam (1) having a recess (5) on its surface which departs from the circular surface of the remainder of the cam (1) and a cam follower member (3) which is movable longitudinally and pivotably and having within it a shaped aperture (7) for receiving a central hub (4) on the cam (1), the arrangement being such that the surfaces of the aperture (7) and of the cam (1) together with possible movements of the follower (3) cause the follower member (3) to be raised out of the recess (5) in the cam (1) during rotation of the cam (1) in the first direction thus enabling the follower (3) to drop back rapidly into the cam recess (5) on rotation of the cam (1) in the opposite direction. <IMAGE>

Description

SPECIFICATION Slow "rise" quick "drop" mechanism This invention relates to a slow "rise" quick "drop" mechanism. The function of such a device is to provide-for a mechanism in which a movement in a first direction provides initially a slow build up to a desired point but which, on a return movement, provides a quick drop at the end of this return movement.

Such a mechanism is used in setting a clock type timing mechanism in which a slow "rise" is required during manual setting which is achieved by rotation in a first sense up to a point indicating the time the mechanism will take to return to its original position. Thereafter it is desired to run the mechanism back at a very much slower speed so as to provide for a timing facility, the timing facility ending at a complete return with a quick "drop" at this point. As will be appreciated, with a timing mechanism of this sort, the setting movement is relatively fast and therefore unless the "rise" was of a slow nature, the mechanism would tend to lock. However, on the return timing movement, if the "drop" were again slow, due to the very much slower rate of the return, it would be impossible the "drop" to take place at the exact point in time at which it was intended.

One mechanism has already been proposed for achieving this function. Two rotary cams having an axial mounting, are provided the two cams having different profiles and being connected together by means of a spring so as to allow limited rotary motion between them. One cam (action cam) would be provided with a steep recess while the other cam (setting cam) would be provided with a recess which, on the side at which a follower would have to pass in setting the mechanism, has a more gentle slope. In this way, the follower at the start of a setting operation would be situated in the bottom of both of the recesses and would, during a setting action, be pushed against the walls of the recesses.Because of the gentler slope of the setting cam, the follower would tend to rise up this surface at the same time turning the action cam relative to the setting cam until the follower was raised by the setting cam out of the recesses. The spring would then return the action cam to its original position relative to the setting cam and maintain it in this position. During the return movement, the follower would follow the surface of the action cam and would thus pass above the slope of the setting cam and would drop off suddenly into the recess of the action cam.

However, this known device suffers from various disadvantages in manufacture, requiring as it does at least three moving parts. It is relatively difficult to manufacture cheaply and from relatively cheap material such as plastics.

According to the invention there is provided a slow "rise" quick "drop" mechanism comprising a rotary cam having a recess on its surface, departing from the circular surface of the remainder and a cam follower member which is movable longitudinally and pivotably and having within it a shaped aperture for receiving a central hub on the cam, the surfaces of the aperture and of the cam together with the possible movements of the follower causing the follower member to be raised out of the recess in the cam during rotation of the cam in a first direction but enabling the follower to drop back rapidly into the cam recess on rotation of the cam in the opposite direction.

In a preferred arrangement of the cam, the cam is of generally circular formation having a deep recess in one position around its surface and a second shallow recess adjacent thereto.

The cam follower may have a substantially right angle triangle aperture through which the cam hub protrudes. The hypotenuse of the triangle is preferably associated with the cam such that, during an initial movement of the cam, the cam follower will rise out of the main recess by virtue of the cam follower sliding with its hypotenuse slope in engagement with the cam hub.

In a further embodiment of the invention, the aperture in the cam follower may be of generally square shape with the deep recess in the cam having a shallow profile to one side. Thus the follower pin may lift out of the groove up the shallow slope during setting movement of the cam and during return movement of the cam, the positioning of the hub in the aperture being such that the follower pin will move rapidly back into the main recess of the cam.

The invention will now be described in greater detail, by way of example, with references to the drawings in which: Figure 1 is a perspective view of a cam and follower element in accordance with the first embodiment of the invention.

Figures 2 to 5 are side views of the cam and follower mechanism showing the relatively position of the two parts at rest, during hand sessing, during initial return and prior to taking up the rest position respectively.

Figure 6 is a view similar to Figure 2 but showing a different shape of cam follower aperture in the rest position and, Figure 7 is a view similar to Figure 6 but showing the parts approaching the end of the timing cycle.

Referring firstly to Figure 1, it will be seen that the mechanism consists basically of a generally circular cam 1 which is associated with a follower member 2 carrying a follower element in a form of a pin 3. As can be seen, the cam 1 itself has a central hub 4 and two recesses 5 and 6 one of which 5 is relatively deep and the other of which 6 is relatively shallow and is positioned adjacent to the deep recess 5 and clockwise thereof (as shown) where setting is performed anti-clockwise and vice versa. The cam follower member 2 is provided at its other end (not shown) with a slot arrangement whereby the follower member can move up and down relative to the cam shaft and can pivot to the right or left of this vertical position.As can be seen, in particular in Figure 2, the follower member 2 has an aperture 7 which is of generally right angle triangle form with rounded corners, the rounded corners being generally of a similar radius to a diameter of the hub 4 on the cam. This hub 4, is located inside the aperture. A spring (not shown) is provided which biases the cam follower member downwards tending to move the follower pin itself in a direction towards the axis of the cam.

Figure 2 shows the position of the mechanism at rest. In this position, the cam 1 is situated with its major recess 5 at the top and the cam follower member 2 is in its lowest position with the cam hub 4 situated in the apex 9 of the triangular aperture 7 so that the pin 3 of the cam follower member 2 lies in the bottom of the major recess 5.

The setting operation of the mechanism is carried out by rotation of the cam 1 in an anticlockwise direction, thus rotation of the cam 1 acting to wind up a clock mechanism attached thereto but not shown.

Initial anti-clockwise rotation of the cam 1 will push the cam follower member 2 to the left as a result of the engagement of the pin 3 with the side of the recess 5. Since, because of the slope of the hypotenuse 10 of the triangular aperture 7, the left-ward movement of the follower member 2 can only proceed accompanied by a rising of the cam follower member 2 which in turn moves the follower pin 3 upwards in the recess 5 until it reaches the lip of the recess. This is the position shown in Figure 3. Further rotation of the cam 1 anti-clockwise will cause the pin 3 to move relatively around the exterior surface of the cam 1.

The cam 1 is turned until the desired time for rerun is set. This is the position shown in Figure 4.

Immediately, the timing mechanism will start to rotate the cam 1 back in the clockwise direction and this will proceed without movement of the cam follower member 2 until, towards the end of the timing run, the follower pin 3 drops into the small recess or indent 6, adjacent the major recess 5. This engagement will, on further rotation of the cam 1 in the clockwise direction, cause the pin 3 together with the follower member 2 to be moved to the right until the hub 4 of the cam 1 comes to rest against the vertical wall 11 of the triangular aperture 7. At this point, the cam follower member 2 can move no further to the right and the pin 3 will thus be shifted out of the indent 6 and over the lip of the main recess 5 as shown in Figure 5.

As soon as the pin 3 clears the lip of the recess 5, it will drop rapidly to the bottom of the recess under the action of the bias spring of the cam follower member, thus indicating the completion of the timing run. This downward movement of the cam follower member can be used to create any action which was to be achieved at the end of the timing run.

The mechanism is now in the rest position as was shown in Figure 2 and the cycle can be repeated by resetting the mechanism.

In an alternative form of the invention, as shown in Figures 6 and 7, the cam element 21 has a shallow slope 28 to the right of its main recess 25 and the aperture 27 in the cam follower member 22 is of generally rectangular form instead of the triangular form of the first embodiment.

Starting from the position shown in Figure 6, which is the rest position, this mechanism is also set by rotating the cam 21 anti-clockwise. As the cam moves anti-clockwise, the pin 23 is prevented from being moved to the left by the engagement of the hub 24 in the right hand corner 32 of the follower member aperture. Thus the pin 23 will move along the shallow slope 28 causing it to lift out of the recess 25 onto the main surface of the cam 21. After this point, the cam 21 is further rotated until the required time setting has been achieved.

As previously, the cam 21 will then be rotated back again by the clock mechanism until it once again arrives with its detent 26 opposite to the pin 23 which will engage therein. This engagement will cause the cam follower member 22 to move to the right until the hub 24 of the cam 21 engages the vertical surface 33 on the left hand side of the follower aperture 27. Further clockwise rotation of the cam 21 will then unseat the pin 23 from the indent 26 and cause it to move over the lip of the main recess 25. The spring bias of the follower member 22 will then act to move the pin 23 rapidly to the left and down into the bottom of the main recess 25. This movement of the cam follower member will then cause the timed action to take place.

It will be appreciated that with both mechanisms, destruction of the clock mechanism by rotation in the wrong direction is not possible.

It will also be appreciated that, while the description of the mechanisms have related to arrangements with the cam follower members moving generally vertically, the spring bias will of course allow it to be orientated in any desired position. Nevertheless, in some circumstances, with the orientation as shown, the spring may be omitted and the operation of the cam follower member may take place under gravity.

The mechanism shown, while particularly suitable for use with a manually settable timing mechanism may be used for any other purposes having a need for the particular action which is provided by this mechanism. In its timing context, the clock mechanism can be constructed to provide any desired length of time delay between setting and action and this may stretch from under a minute to a large number of hours.

The timing mechanism as described is particularly suitable for application to a pet feeder where it is desired to provide quantitites of pet food at particular times without the necessity of the human operator being there at that time.

However, any other suitable timed arrangement may well use the mechanism of the invention.

It will be understood that various modifications may be made to the described embodiments. Thus the mechanism could provide for reversal of the sense of rotation, i.e. clockwise for setting and anti-clockwise for timing. The pin on the cam follower may be replaced by a roller for a reduction in friction.

Claims (9)

1. A slow rise quick drop mechanism comprising a rotary cam having a recess on its surface departing from generally circular surface of the remainder of the cam and a cam follower member which is movable longitudinally and pivotably, which has a follower engaging the cam surface, and has within it a shaped aperture for receiving a central hub on the cam, the surfaces of the aperture and of the cam, together with the allowable movements of the follower, enabling the follower to rise relatively slowly out of the recess in the cam during rotation of the cam in a first direction but enabling the follower to drop relatively rapidly back into the cam recess on rotation of the cam in the opposite direction.

2. A mechanism as claimed in claim 1, wherein the follower is a follower pin in engagement with the cam, and the following member is biased by a spring in a direction to bias the follower pin inwardly from the cam edge.

3. A mechanism as claimed in claim 2, wherein the cam is of generally circular formation having a deep recess in one position around its surface and a second shallower recess adjacent thereto.

4. A mechanism as claimed in claims 2 or 3, wherein the cam follower member has a substantially right angle triangle aperture through which the hub of the cam protrudes.

5. A mechanism as claimed in claim 4, wherein the hypotenuse of the triangle is associated with the cam hub in such a way that, during an initial movement of the cam, the cam follower will rise out of the main recess by virtue of the cam follower sliding with its hypotenuse slope in engagement with the cam hub.

6. A mechanism as claimed in claim 2 or 3, wherein the cam follower has an aperture of generally square shape and the deep recess in the cam has a shallow slope at the side leading to the second shallower recess.

7. A mechanism as claimed in claim 5, wherein, during setting movement of the cam, the follower pin on the follower will lift out of the groove up the shallow slope and during return movement of the cam, the positioning of the hub in the aperture is such that the follower pin will fall rapidly back into the main recess of the cam under the action of the biasing spring.

8. A mechanism as claimed in claim 3 and any claim appendent directly or indirectly thereto, wherein the shallower recess serves to retain the follower pin and cause the follower itself to move with the pin until the relative locations of the aperture and cam hub are such that there is no restriction to the movement of the pin into the deeper recess, the cam hub in this position engaging a wall of the aperture and forcing the pin out of the shallower recess on further rotation of the cam.

9. A slow rise quick drop mechanism substantially as described herein with reference to the drawings.