GB2294544A

GB2294544A - Sample collector

Info

Publication number: GB2294544A
Application number: GB9421410A
Authority: GB
Inventors: Brian Powell
Original assignee: Aquamatic Ltd
Current assignee: Aquamatic Ltd
Priority date: 1994-10-25
Filing date: 1994-10-25
Publication date: 1996-05-01
Anticipated expiration: 2014-10-25
Also published as: GB2294544B; GB9421410D0

Abstract

The sample collector has a holder for a plurality of sample collection containers and a delivery arrangement for delivering samples to containers in the holder and positioning means relatively positioning said holder and delivery arrangement for sample delivery to a selected one of said containers, said positioning means comprising a rotary cam with a drive motor and a plurality of cam followers corresponding to the number of positions provided for by the positioning means, the cam including a lost motion section in which it does not move the cam follower engaged for the time being, and motor switch-off means at the end of the lost motion section.

Description

SAMPLE COLLECTOR This invention relates to sample collectors, especially, but not exclusively for the automatic collection of liquid samples.

WO 93/04355 describes an automatic liquid sampler which is programmable to take samples, e.g. from a river, at timed intervals. The metred samples are collected in a sample collector which essentially comprises a bucket. Such a sampler is useful for monitoring wastewater and may be arranged, for example, to take a metred sample every hour. The total sample for the day is removed from the collector during a timed visit and the sampler left for another day's collecting.

The sampler described in WO 93/04355 is characterised by a remarkably simple and inexpensive design which is easy to dismantle and reassemble for cleaning.

Sample collectors are known which will permit the collection and holding, separately, of individual samples so, perhaps, that the diurual variation in the effluent content of a watercourse might be monitored. The present invention provides a sample collector for such a task which can work very well with the sampler of WO 93/043 55.

A problem with arrangements intended to locate, say, a delivery tube over a bottle is that unless very precise control and very precise engineering are combined in the design, there will be an accumulation of errors which will, in a more or less short time, lead to incorrect positioning, so that a sample will miss its target. Such precise control and engineering are expensive.

The sampler of this invention has a positioning arrangement that assures correct positioning without the need for such costly precision control and engineering.

The invention comprises a sample collector comprising a holder for a plurality of sample collection containers and a delivery arrangement for delivering samples to containers in the holder and positioning means relatively positioning said holder and delivery arrangement for sample delivery to a selected one of said containers, said positioning means comprising a rotary cam with a drive motor and a plurality of cam followers corresponding to the number ofpositions provided for by the positioning means, the cam including a lost motion section in which it does not move the cam follower engaged for the time being, and motor switch-off means at the end of the lost motion section.

The cam may be a helix cam, the lost motion selection being a flat extension to the helix.

The cam may make one revolution for a position change from one container to an adjacent container.

The motor switch-off means may comprise a microswitch.

The cam followers may be radial projections from a wheel, the cam being arranged for rotiation on an axis, substantially tangential to the wheel.

The sample collector may comprise a "home" position finder arrangement which may comprise a microswitch, and may comprise a programmable controller arranged to start the motor at predeterminable times.

As mentioned, the sample collector may be adapted for use with an automatic liquid sampler as described in WO 93/04355, when the programmable controller may be that of the said automatic liquid sampler when so used.

The sample collector may comprise a unit adapted to be mounted in place of the sample collector described in WO 93/04355 and to receive the delivery tube thereof in an upper inlet to a laterally extending distribution tube positioned by the positioning means. The distribution tube may extend radically outwardly of a wheel rotatable about the axis of the said delivery tube and have a spout positionable over sample collection containers in the holder. The spout may be flexible so as to locate over the rims of the sample collection containers in the holder.

One embodiment sample collector according to the invention will now be described with reference to the accompanying drawings, in which: Figure 1. is a perspective view of the automatic sample collector of WO 93/043 55; Figure 2. is a simplified side elevation of the sample collector of the present application; Figure 3. is a part cut-away plan view of the sample collector shown in Figure 2; Figure 4. is a diagrammatic plan view of the positioning means of the sample collector.

Figures 2, 3 and 4 of the drawings illustrate a sample collector designed to be used in place of the sample collector 21 of the automatic sampler of WO 93/04355 depicted in Figure 1, which is a self-contained unit adapted to be located in remote places to function automatically under its oun power and control to withdraw samples e.g. of river water through sample supply tube 27 to be metered in a chamber 11 for collection in the collector 21 via sample delivery tube 23.

The sampler of Figure 1 may be programmed via a keypad 31 inputting to a programmable controller to sample, say, every hour. Each sample is added to the samples in the container, which may be emptied, for example once a day, for analysis.

The present invention provides for the individual collection of samples in sample collection containers 111 loaded into a holder 112 via a delivery arrangement 113.

In this embodiment, the holder 112 is stationary and the delivery arrangement 113, comprising a distribution tube 114 which extends radially outwardly of a wheel 1 15, rotates about the axis of the delivery tube 23 of the automatic sampler of Figure 1, the tube 114 having a spout 11 4a (desirably flexible to be able to flip over the rims of the openings of badly positioned sample collection containers) positionable over the sample collection containers 111 mounted in the holder 112.

Devising a means of positioning the spout 1 14a accurately and reliably over the containers 111 is not, of course, a difficult problem, given the fruits of modern technology such as stepper motors, digitial controllers and the like. Devising a robust, inexpensive means of doing so without the need of precision engineering is not so straightfonvard.

The solution adopted herein lies in positioning means 116 comprising a rotary cam 117 with a drive motor 118 (with gearbox 119 to give an output speed of 60 rpm) and a plurality of cam followers 121 around the rim of the wheel 115 corresponding to the number ofpositions provided for - corresponding, of course, to the number of containers 111 the holder 112 accommodates.

Such an arrangement, were that all there be to it, would need extremely accurate engineering and control to prevent the accumulation of errors which would eventually have the spout 115 overruning and delivering samples away from the containers or even into the wrong containers.

To avoid this happening without the need for precision the invention provides that the cam 117 includes a lost motion section 122 in which it does not move the cam follower engaged for the time being, and the motor switch-off means 123 are provided activated by the end 122a ofthe lost motion section 122.

As seen in Figure 4, the cam 117 is a helix cam, the lost motion section 122 being a flat extension to the helix. The cam makes one revolution for a position change from one container 111 to the next adjacent one. The motor switch-off means 123 comprise a microswitch closed as the lost motion section 122 approaches it and released at the end of 122a of the section.

The cam 117 can this be designed and adjusted always to move a follower to a precise location and then stop before picking up the next-succeeding cam follower.

The cam followers 121 are simple peg-like radial projections from the rim of the wheel 115. For a 24 hour, once-per-hour sampling cycle, the holder 112 would have 24 container positions and there would be 24 followers 121 spaced at 15 intervals.

An additional feature is a "home" fmder arrangement comprising a fixed position microswitch 124 and a cam 125 on the wheel 115. Here, again, there is no need for great precision - the "home" position can be defined as the position attainted when the motor is switched off by the microswitch 123 after the microswitch 124 has been engaged by the cam 125.

The collector can conveniently be controlled from the same controller used for the automatic sampler of WO 93/04355 which can, of course, be a programmable micro processor and this facilitates synchronising the positioning with the delivering of sample.

It is not necessary to fill the holder 112 - the programmer can cause the motor to operate several times in succession to skip container locations. Even if once-a-day collection is all that is required, the use of two sample collection containers can allow service flexibility, the container to be emptied for analysis being available for 24 hous after it has been substituted by the alternate.

Claims

1. A sample collector comprising a holder for a plurality of sample collection containers and a delivery arrangement for delivering samples to containers in the holder and positioning means relatively positioning said holder and delivery arrangement for sample delivery to a selected one of said containers, said positioning means comprising a rotary cam with a drive motor and a plurality of cam followers corresponding to the number of positions provided for by the positioning means, the cam including a lost motion section in which it does not move the cam follower engaged for the time being, and motor switch-off means at the end of the lost motion section.

2. A sample collector according to claim 1, wherein the cam is a helix cam, the last motion section being a flat extension to the helix.

3. A sample collector according to claim 1 or claim 2, wherein the cam makes one revolution for a position change from one container to the adjacent container.

4. A sample collector according to any preceding claim wherein the motor switch-off means comprises a microswitch.

5. A sample collector according to any preceding claim wherein the cam followers are radial projections from a wheel, the cam being arranged for rotation on an axis substantially tangential to the wheel.

6. A sample collector according to any preceding claim wherein the sample collector may comprise a "home" position finder arrangement which comprises a microswitch and a programmable controller arranged to start the motor at predeterminable times.