GB2146094A

GB2146094A - Timing mechanism utilising porous plug

Info

Publication number: GB2146094A
Application number: GB08323592A
Authority: GB
Inventors: Robert Michael George Fielding
Original assignee: Dudley Industries Ltd
Current assignee: Dudley Industries Ltd
Priority date: 1983-09-02
Filing date: 1983-09-02
Publication date: 1985-04-11
Also published as: GB8323592D0

Abstract

In a timing mechanism for a towel dispenser comprising two suction cups 11,12 and a tubular member 13 for admitting air to the space between the cups, a porous plug member 18 is provided inside member 13 to control the rate at which air is admitted to break the suction between the cups. The support 20 for the cup 12 may be resiliently biased away from member 13. The flow characteristic of the porous plug member is preadjusted by compression and/or cutting thereof. The porous plug may be fibrous, ceramic or sintered powdered metal. <IMAGE>

Description

SPECIFICATION Valve for timing mechanism The present invention relates to a valve for a timing mechanism and more particularly for mechanisms which produce a time delay in roller towel dispensers and paper towel roll dispensers.

In dispensers such as roller towel dispensers it is often arranged that the towel can only be pulled out at spaced intervals in time.

This means prevents wasteful use of the towel.

One existing mechanism for introducing this time delay comprises two mutually-facing rubber vacuum cups which are compressed together as the towel is pulled. One of the cup supports is fixed and the other is movable and is attached to a towel release mechanism.

After the cups have been compressed together, further dispensing of the towel is prevented. When the cups part, the movable support actuates the towel release mechanism to permit more towel to be dispensed. The time delay introduced by the mechanism corresponds to the time that it takes the suction between the compressed cups to be broken.

One known arrangement for allowing air to bleed slowly into the compressed rubber vacuum cuts comprises a needle valve and an associated orifice. The time taken for the two cups to be separated can be increased by screwing the needle into the valve seating.

The present invention seeks to provide a convenient arrangement for determining the time delay.

According to a first aspect of the present invention there is provided a valve for a timing mechanism comprising two co-operating suction members, a passage for admitting air to the space formed between the two suction members, and a porous plug member within the passage.

The suction members are preferably in the form of cups of a flexible material e.g. rubber.

The porous plug member is preferably mounted in a passage inside a hollow support for one of the suction members. The other suction member may be mounted on a movable support which is associated with a timing mechanism and which may be resiliently biased away from the first suction member.

According to a second aspect of the present invention there is provided a method of adjusting the rate at which air will flow. in use, through a porous plug member in a valve for a timing mechanism, comprising the step of compressing the plug member to a predetermined extent.

A large number of similar standard plug members may be initially produced and then compressed individually or in smaller batches to obtain the desired flow characteristics. Instead of or in addition to compression part of the plug member may be cut off to adjust the delay time which it introduces.

A preferred embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawing which shows a valve for a timing mechanism.

The valve 10 comprises two mutually-facing vacuum rubber cups 11, 1 2. Cup 11 is firmly attached to a fixed tubular support member 1 3. A dust cap 14 is provided at the end of the tubular member 13, the dust cap having one or more openings 1 6 to permit the entry of air as indicated by arrow A. The end of tubular member adjacent the cup 11 is filled with a plug 1 8 of material of specific porasity.

Cup 1 2 is firmly attached to a movable shaft 20 which actuates further means, for example the towel release mechanism of a roller towel dispenser. Shaft 20 is resiliently biased, by spring means (not shown), in the direction B tending to pull the cups 11, 1 2 apart.

In use, when the towel is pulled, cup 1 2 is forced against cup 11 to create a partial vacuum therebetween, shaft 20 being in its upper position as shown in the Figure. Air enters through dust cap 1 4 into the tubular member 1 3 and its flow is restricted by the porous plug 1 8. When the suction is broken, shaft 20, which is resiliently biased downwards, and cup 1 2 move to actuate the timing mechanism.

The porous material of the plug 1 8 may be fibrous, ceramic on a sintered powdered metal of a non-corrosive type (e.g. bronze or stainless steel).

An advantage of the above arrangement is that a single plug of material replaces the valve, valve seating and any control members of the conventional arrangements. In addition, the delay can be readily pre-set to one of a range of values in the factory. The plugs for a batch of timing mechanisms are made with characteristics such that they produce a time delay of 1/2 to 1 second, which corresponds to the minimum time delay required in practice. For a particular timing mechanism, this delay can be increased and set in the factory by controlled compression of the plug. This compresses the air gaps within the material and restricts the air flow so as to increase the time taken for the required volume of air to pass through. Thus once set in the factory, the time delay cannot be altered subsequently by unauthorised interference.

Various modifications may be made to the above-described arrangement. For example the length of the plug 1 8 may be reduced by cutting to adjust the delay time introduced. In another modification shaft 20 is not resiliently-biased.

1. A timing mechanism comprising two

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Valve for timing mechanism The present invention relates to a valve for a timing mechanism and more particularly for mechanisms which produce a time delay in roller towel dispensers and paper towel roll dispensers. In dispensers such as roller towel dispensers it is often arranged that the towel can only be pulled out at spaced intervals in time. This means prevents wasteful use of the towel. One existing mechanism for introducing this time delay comprises two mutually-facing rubber vacuum cups which are compressed together as the towel is pulled. One of the cup supports is fixed and the other is movable and is attached to a towel release mechanism. After the cups have been compressed together, further dispensing of the towel is prevented. When the cups part, the movable support actuates the towel release mechanism to permit more towel to be dispensed. The time delay introduced by the mechanism corresponds to the time that it takes the suction between the compressed cups to be broken. One known arrangement for allowing air to bleed slowly into the compressed rubber vacuum cuts comprises a needle valve and an associated orifice. The time taken for the two cups to be separated can be increased by screwing the needle into the valve seating. The present invention seeks to provide a convenient arrangement for determining the time delay. According to a first aspect of the present invention there is provided a valve for a timing mechanism comprising two co-operating suction members, a passage for admitting air to the space formed between the two suction members, and a porous plug member within the passage. The suction members are preferably in the form of cups of a flexible material e.g. rubber. The porous plug member is preferably mounted in a passage inside a hollow support for one of the suction members. The other suction member may be mounted on a movable support which is associated with a timing mechanism and which may be resiliently biased away from the first suction member. According to a second aspect of the present invention there is provided a method of adjusting the rate at which air will flow. in use, through a porous plug member in a valve for a timing mechanism, comprising the step of compressing the plug member to a predetermined extent. A large number of similar standard plug members may be initially produced and then compressed individually or in smaller batches to obtain the desired flow characteristics. Instead of or in addition to compression part of the plug member may be cut off to adjust the delay time which it introduces. A preferred embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawing which shows a valve for a timing mechanism. The valve 10 comprises two mutually-facing vacuum rubber cups 11, 1 2. Cup 11 is firmly attached to a fixed tubular support member 1 3. A dust cap 14 is provided at the end of the tubular member 13, the dust cap having one or more openings 1 6 to permit the entry of air as indicated by arrow A. The end of tubular member adjacent the cup 11 is filled with a plug 1 8 of material of specific porasity. Cup 1 2 is firmly attached to a movable shaft 20 which actuates further means, for example the towel release mechanism of a roller towel dispenser. Shaft 20 is resiliently biased, by spring means (not shown), in the direction B tending to pull the cups 11, 1 2 apart. In use, when the towel is pulled, cup 1 2 is forced against cup 11 to create a partial vacuum therebetween, shaft 20 being in its upper position as shown in the Figure. Air enters through dust cap 1 4 into the tubular member 1 3 and its flow is restricted by the porous plug 1 8. When the suction is broken, shaft 20, which is resiliently biased downwards, and cup 1 2 move to actuate the timing mechanism. The porous material of the plug 1 8 may be fibrous, ceramic on a sintered powdered metal of a non-corrosive type (e.g. bronze or stainless steel). An advantage of the above arrangement is that a single plug of material replaces the valve, valve seating and any control members of the conventional arrangements. In addition, the delay can be readily pre-set to one of a range of values in the factory. The plugs for a batch of timing mechanisms are made with characteristics such that they produce a time delay of 1/2 to 1 second, which corresponds to the minimum time delay required in practice. For a particular timing mechanism, this delay can be increased and set in the factory by controlled compression of the plug. This compresses the air gaps within the material and restricts the air flow so as to increase the time taken for the required volume of air to pass through. Thus once set in the factory, the time delay cannot be altered subsequently by unauthorised interference. Various modifications may be made to the above-described arrangement. For example the length of the plug 1 8 may be reduced by cutting to adjust the delay time introduced. In another modification shaft 20 is not resiliently-biased. CLAIMS

1. A timing mechanism comprising two co-operating suction members, a passage for admitting air to the space formed between the two suction members, and a delay element for determining the rate at which air is admitted to said space. wherein said delay element is constituted by a porous plug member within the passage.

2. A timing mechanism according to claim 1, wherein the suction members are in the form of cups of a flexible material.

3. A timing mechanism according to claim 1 or 2, wherein said passage is inside a hollow support for one of the suction members.

4. A timing mechanism according to claim 3, wherein the other suction member is mounted on a movable support.

5. A timing mechanism according to claim 4, wherein said other suction member is resiiiently biased away from the first suction member.

6. A timing mechanism substantially as herein described with reference to the accompanying drawing.

7. A roller towel device incorporating a timing mechanism according to any preceding claim.

8. A method of controlling air flow in a timing mechanism comprising a porous plug member, comprising the step of modifying the flow characteristic of the plug member.

9. A method according to claim 8, wherein the modification comprises compressing the plug member.

10. A method according to claim 8 or 9, wherein the modification comprises cutting off part of the porous plug member.

11. A method of controlling air flow in a timing mechanism substantially as herein described with reference to the accompanying drawing.