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United States Patent [w]
US005937970A [ii] Patent Number:  Date of Patent:
 COMPRESSED AIR LUBRICATORS
 Inventor: Michael J Wates, Moreton-in-Marsh, United Kingdom
 Assignee: IMI Norgren Limited, Lichfield, United Kingdom
 Appl. No.: 08/923,539
 Filed: Sep. 4, 1997
 Foreign Application Priority Data
Sep. 4, 1996 [GB] United Kingdom 9618414
 Int. CI.6 F16N 7/30; G01F 1/22
 U.S. CI 184/55.2; 73/861.53
 Field of Search 73/861.42, 861.46,
73/861.47, 861.49, 861.53, 861.58, 861.61, 861.63, 861.82; 184/55.2, 57, 58, 59; 251/123, 124, 43; 137/843, 852, 854
 References Cited
U.S. PATENT DOCUMENTS
3,572,469 3/1971 Miller et al 184/55.2
3,680,661 8/1972 Dolegowski 184/55.2
3,696,889 10/1972 Brake 184/55.2
COMPRESSED AIR LUBRICATORS
FIELD OF THE INVENTION
This invention relates to compressed air lubricators and more particularly to the so-called "flow sensor" which is conventionally incorporated into them.
BACKGROUND OF THE INVENTION
It is well-known that many pneumatic devices, such as certain pneumatic tools, cylinders and control valves require the compressed air to contain a lubricant in the form of an 10 oil fog. For that purpose, compressed air lines frequently include a lubricator unit that introduces a fog of oil into the compressed air as it flows through it. The lubricator includes an adjustable oil metering device so that the user can adjust the amount of oil introduced into the compressed air depend- 15 ing on the lubrication requirements of the pneumatic devices in question. The oil is automatically introduced into the compressed air, via the metering device, by virtue of a small pressure drop, typically of the order of 100 mbar, established in the lubricator by the flow sensor which is located in the 20 lubricator's flow passage and which acts as a venturi type of device.
One requisite characteristic of the flow sensor is that, as the compressed air flow rate through the lubricator increases consequent on an increased demand for compressed air, the 25 pressure drop increases approximately proportionally whereby the amount of oil introduced into the compressed air increases, also approximately proportionally. In other words, at a given setting of the metering device, the flow sensor ensures that the oil-to-air concentration remains 30 substantially constant over a wide range of air flow rates through the lubricator. To that end, the flow sensor conventionally comprises a disc-like structure fixedly secured in the lubricator's flow passage, the air passing through an annular gap defined between the periphery of the disc and the 35 internal surface of the flow passage. As the compressed air flow rate through the lubricator increases, the disc progressively deforms in a downstream direction whereby the cross-sectional area of the annular gap increases. In one typical design, the flow sensor comprises a flexible, plain- 40 surfaced elastomeric disc secured in place at its centre which tends towards a conical configuration as the air flow rate through the lubricator increases. Accordingly, the circumference of the disc attempts to reduce, ie the rubber attempts to become circumferentially compressed, but the inherent 45 nature of the material resists this. In practice, therefore, we have found that the periphery of the disc actually hinges so as to form four small 'flaps'. In any event, because of the disc's inherent resistance to being deformed, the aforementioned design places a restriction on the maximum com- 50 pressed air flow rate through the lubricator.
In an alternative, known design, the flow sensor comprises a diametric support rib to which a pair of semi-circular flaps are hinged by thin membranes. Again, this design of flow sensor is usually made of an elastomer as an integral 55 moulding. Whilst, in that design, deformation of the sensor occurs more readily (by virtue of a hinging action of the flaps), the support rib occupies a relatively large proportion of the cross-sectional area of the lubricator's flow passage thereby limiting the flow capacity therethrough. 60
It is an object of the present invention to provide an improved flow sensor for a compressed air lubricator which, other things being equal, will permit of higher air flow rates.
SUMMARY OF THE INVENTION 65
According to one aspect of the present invention, therefore, there is provided a flow sensor for a compressed
air lubricator, the sensor comprising a resiliently flexible disc having mounting means for fixedly mounting it in the flow passageway of the lubricator, characterised in that one or both major surfaces of the disc have formed therein a plurality of substantially radially extending, elongate channels thereby affording radial lines of weakness.
We have discovered that the radial lines of weakness enable the disc readily and progressively to deform, with increasing compressed air flow rate, from a substantially planar configuration to a fluted cone-like configuration whereby the lubricator may cope with relatively higher air flow capacities.
In one preferred embodiment, the flow sensor comprises a thin disc of substantially uniform thickness, each surface of the disc having two radial channels formed in it arranged on one and the same diameter, the channels in one surface being offset by 90° to those in the other surface.
In another preferred embodiment, the flow sensor comprises a thin disc of substantially uniform thickness having three radially extending channels formed symmetrically in each of its surfaces (ie extending at about 120° to one another) with those in one surface being offset by about 60° to those in the other, reverse surface.
Each channel is, in cross-section, preferably arcuate.
The mounting means may correspond to one or other of those used for known flow sensors. For example, it may comprise a hole formed centrally in the disc surrounded by a short hollow cylindrical boss that projects from one surface of the disc and that is formed integrally therewith.
The disc and the mounting means are preferably moulded in one piece from an elastomer, for example a polyurethane or nitrile rubber.
According to a further aspect of the present invention, there is provided a compressed air lubricator including a flow sensor as defined above.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:
FIG. 1 is a sectional side elevation, on a reduced scale, of a compressed air lubricator including a flow sensor of the invention;
FIG. 2 is a detail of the circled part II of FIG. 1;
FIG. 3 is an end view of one form of flow sensor in the direction of arrow III in FIG. 2;
FIG. 4 is a side view of the flow sensor shown in FIG. 3 in the direction of arrow IV in FIG. 3;
FIG. 5 is a view similar to that of FIG. 3 showing an alternative form of flow sensor; and
FIG. 6 is an end view, downstream of the air flow, of the flow sensor shown in FIG. 5 when in a more or less fully deformed state, ie. when the flow rate through the lubricator is more or less at its maximum.
DESCRIPTION OF THE PREFERRED
Referring first to FIGS. 1 and 2, save for the particular design of the flow sensor, all of the components are conventional and will be familiar to those skilled in the art. Briefly, however, the lubricator comprises a body 1 having an inlet passageway 2 in communication with an outlet passageway 3 connected into a compressed air line (not shown).