GB1560657A

GB1560657A - Suction mounting

Info

Publication number: GB1560657A
Application number: GB4278576A
Authority: GB
Original assignee: EALING BECK Ltd
Current assignee: EALING BECK Ltd
Priority date: 1976-10-14
Filing date: 1976-10-14
Publication date: 1980-02-06
Also published as: FR2367935A1; DE2746119A1

Description

(54) IMPROVEMENTS IN OR RELATING TO SUCTION MOUNTING (71) We, EALING BECK LIMITED, a British Company, of Greycaine Road, Watford WD2 4PW, Hertfordshire, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement.

This invention relates to suction mounting arrangements. Such arrangements may be in the form of mounting bases to which articles can be attached, or may be integral parts of portable apparatus, for example domestic food mincers which are usually attached in use to kitchen worksurfaces, and small portable vices which can be attached to the smooth surface of say a laboratory workbench, which surface commonly have a surface layer of laminated plastics material.

Known suction mounting arrangements emply a resilient diaphragm, the rim of which is placed in contact with the mouting surface and the central region of the diaphragm is then raised by means of a lever to create a suction holding force.

According to the present invention there is provided a suction mounting arrangement for mounting to a smooth flat surface, and comprising a body having a substantially flat surface portion, a sealing member disposed in a channel extending around said surface portion, a piston arranged to fit sealingly within a blind bore in the body, a capillary bore coupling the blind end of the bore to the said surface portion of the body, and either means operative to urge the piston outwardly relative to the blind end of the bore, or means operative to retain releasably the piston at a predetermined position spaced from its fully inserted position.

Preferably the cross-sectional area of the bore is substantially less than the area encompassed by the sealing member, so that a desired holding force can be obtained by the application to the piston of a correspondingly smaller force.

In the case where the suction mounting arrangement includes the urging means, an operator will press the piston fully into the bore, against the action of the urging means, expelling air through the capillary bore, and the mounting arrangement can then be placed on the smooth surface and the piston released. However, if the mounting arrangement is already in position on the surface prior to this actuation of the piston, it is advisable momentarily to break the seal between the arrangement and the surface before the piston is released to ensure that the pressure in the enclosed volume is not greater than atomspheric pressure.

In the case where the mounting arrangement includes the retaining means, the operator will similarly press the piston fully into the bore, but instead of the piston being urged outwardly by the urging means upon release of the applied force, the operator will apply a withdrawal force to the piston (or to a member integral with or attached to the piston) to cause it to move outwardly to the predetermined position and thereby develop a reduced pressure under the face of the body. In order to maintain the resultant holding force, the piston must be prevented from moving inwardly under the effect of the differential air pressure on it, and this is effected by the retaining means which retains the piston at the predetermined position in the bore.

Preferably the inner end of the piston is substantially complementary to the blind end of bore. This assist in obtaining a small residual volume for the arrangement.

In use, the body is pressed against the mounting surface by means of the reduced pressure under the flat surface portion. If desired, the body may be shaped such that the flat surface portion lies in contact with the mounting surface.

Alternatively, there may be support means projecting from the body proud of the general plane of the flat surface portion, and in this case the flat surface portion will lie spaced from the mounting surface.

Thus there is imparted considerable stability to the mounting arrangements as compared with the known arrangements where the body itself makes no direct contact with the mounting surface but only indirectly via the resilient diaphragm, and renders the present mounting arrangements suitable for use in situations where mechanical stability is required. Thus a preferred use is as a mounting base for mounting optical components on an optical table, and for such a use, arrangements employing the aforementioned urging means are preferred since it is likely that their manner of operation will result in less disturbance to the base and thus enable a greater accuracy of positioning on the mounting table.

The present invention thus enables the provision of an optical system comprising an optical table having a smooth surface, optical components such as lens mounts, filters holders, illuminators, detectors and the like, and mounting bases for the optical components, which mounting bases include a suction mounting arrangement in accordance with the present invention.

The support means is preferably disposed outwardly relative to the sealing member and may be in the form of a continuous run with a flat annular contact land surrounding the sealing member. Alternatively, it may be in the form of at least three individual spaced-apart projections.

It will be appreciated that for good efficiency the support means, if present, should be proud of the flat surface portion such that in use there is a clearance gap not greater than 25 microns, and preferably of about 5 microns, between the surface portion and the smooth surface to which the arrangement is attached.

The urging means may be a compression spring.

Preferably the channel is dimensioned such that the sealing member is a sealing fit between opposite walls of the channel and the volume between the sealing member and the bottom of the channel is vented to the atmosphere.

Although optimum stability is obtained when there is actual contact between the mounting surface and the body (the flat surface portion or the support means), and the channel will be dimensioned to try to achieve such actual contact, it has been found that in manufacture the production tolerances of the dimensions of sealing members, conveniently O-rings, and of the channel can result in a "worst-case" condition in which there is no actual contact between the mounting surface and the body but the gap is so small, in the region of a few microns, that for practical purposes the stability is satisfactory.Furthermore, in most "worst-cases" this minute gap only exists when the mounting arrangement is in the form of a mounting base and is unloaded, i.e. has no object mounted on it, the preferred actual contact condition being obtained whilst a load, for example an optical component, is on the mounting base.

Reference will now be made to the following drawing in which : Figure 1 is a perspective view of a preferred embodiment of an optical component mounting base; Figure 2 is a vertical section through the optical component mounting base shown in Figure 1; Figure 3 is a similar section through a modified form of the base of Figure 1; and Figure 4 is a similar section through a part of another modified form of the base of Figure 1.

In Figures 1 and 2 there is shown a mounting base 10 having a cylindrical body portion 10a with a rectangular top portion 10b. The base 10 has a height of 42 mm and a side length of 100 mm, and is formed from a block of aluminium alloy.

The underside of the body portion 10a has a circular rim 11 with a flat annular land 12 to make contact with an underlying optical table 13. The rim 11 encircles a centrallydisposed circular land 14 being separated from it by a circular channel 15 containing an O-ring seal 16. The plane of the surface of land 14 is spaced from the plane of the contact land 12 by 25 microns to provide a volume bounded by table 13, land 14 and O-ring 16 which is as small as practicable without contact between land 14 and the table.

In the body portion 10a is a cylinder 17 constituted by a brass liner 18 fitting within a bore 19. A piston 20 fits within cylinder 17 and is sealed to the liner 18 by an O-ring seal 21. An operating plunger 22 is mounted on the free end of a reduced diameter portion extending outwardly from the outer end of the piston. The cylinder 17 is blind and the inner end of piston 20 has a complementary shape to permit surface-to-surface contact when the piston engages the blind end of the cylinder, thus to make the residual volume in the cylinder as small as possible.

A capillary bore 23, which couples the blind end of cylinder 17 with the surface of land 14, has a diameter of 1 mm. In actual practice it is desired to make the diameter of capillary bore 24 as small as practicable, and this will be determined by the technique used to form the capillary bore.

Disposed in bore 19 is a helical compression spring 25 which reacts against a limit stop 24 and the operating plunger 22 to return the piston 20 outwardly after it has been pushed into the cylinder by an operating force applied to the plunger.

The top portion 10b of the mounting base 10 is attached to the body portion 10a by four screws 26. The upper surface of the top portion 10b is formed with a threaded hole 27 in conventional manner to permit attachment of an optical system component, for example a lens mount. If desired, there may be a plurality of holes 27. For fine adjustment, the lens mount may include micrometer translations of conventional form.

To secure the mounting base 10 to the optical table 13, an operator applies finger pressure to the plunger 22 to move the piston inwardly, against the action of spring 25, and to maintain the piston abutting the blind end of the cylinder 17. The base can then be placed in a desired position on the table and the applied pressure on the plunger released whereupon the spring acts to push the piston outwardly so reducing the pressure under the land 14 and creating a suction holding force.

The channel 15 is formed with parallel side faces 28 and 29 and an angled bottom seating face 30 of such proportions that the O-ring seal 16, when inserted into the channel, is an interference fit on to both parallel side faces 28 and 29 and is also in contact with the angled face 30 all round its periphery. When in this position, the outer surface of the O-ring seal 16 is proud of the land 12 by a few tens of microns to ensure a sealing action between the table 13 and the mounting base 10 when the base is applied to the table surface.

The channel 15 has a small hole 31 which is positioned adjacent to the bottom of channel 15 and through the rim 11 to the outside surface of the body position 10a.

This allows for the release of trapped air to the atmosphere from channel 15 when the base 10 becomes pressed against the table 13, by virtue of the suction effect, thus facilitating deformation of the O-ring seal 16 coincident with the pressure against the four pressure faces at 13, 28, 29 and 30 to form the vacuum seal and also to allow the land 12 to make contact with the table surface 13.

It will be appreciated that under equilibrium conditions the spring force acting on the piston is equal to the force due to the differential air pressure on the piston. Thus spring 25 will be selected to have a spring constant sufficiently small that the spring can be fully compressed by a have-applied force, and to have a wide turn spacing so that there is obtained a large return movement of the piston before equilibrium is reached with corresponding large reduction in air pressure in the cylinder (and under the land 14).

Tests conducted on a mounting base as described above indicate that the base can withstand a pull-off force normal to the table of approximately 20 kgms/cm offset, and can maintain such a holding force for at least 48 hours. Also, this holding force can be reliably repeatable since it is determined by the force exerted on the piston by the spring, but to obtain such repetition an operator must take care to depress the plunger fully and to ensure that the pressure under land 14 is atmospheric before the plunger is released.

An advantage of the above base is that it will normally be positioned on the optical table while the plunger is depressed, and that the action of releasing the plunger to render the base operative is unlikely to cause any significant disturbance of the base.

An optical component mounting system employing suction, in particular the above suction-operated mounting base, has the versatility of magnetic mounting employing switchable magnets in that the base can be placed in any desired position on the optical table. Moreover, the use of suction enables the height of the base to be kept small, for example the above base has a height of 42 mm as compared with heights in the region of 70 mm for magnetically-operated bases; and in comparison with such known bases, suction-operated bases can be considerably lighter and this readily enables the optical table to be used vertically instead of horizontally. It will be appreciated that an optical table suitable for use with suctionoperated bases will be smooth in order to obtain a good seal at O-ring 16 between the table and the base.Thus great savings in cost can be achieved over magnetic-based systems since the special magnetic table (usually steel) employed can be replaced by one which is of simple construction and made of relatively cheap materials, suitably reinforced if desired.

Suction-operated bases can be used in conjunction with existing granite optical tables since these generally have a sufficiently smooth surface to permit satisfactory attachment.

Figure 3 shows part of a modified form of mounting base in which the spring 25, is not employed. Instead, the mounting is operated by application of a withdrawing force on an operating plunger 22' extending outwardly from the piston. Operating plunger 22' is longer than the operating plunger 22 in Figure 1 and has a head 32 at its end. The piston is thus pulled against the differential air pressure on the piston until the outer end part of the piston is withdrawn from the cylinder exposing an annular groove 33 and enabling a cooperating locking member 34 movably attached to body position 10a to engage in the groove 33. This modification has fewer parts than the Figure 1 base and can thus have a smaller initial volume; does not reply on spring characteristics for determining the amount of piston movement from the fully inserted position, and consequently can have a larger volume.

Figure 4 shows a modification in which the body portion is provided with three individual projections 35 uniformally spaced around the rim 11, instead of having a flat annular land 12 as in Figure 2 or Figure 3. If desired, there may be more than three projections 35. For explanatory purposes, the size of the projections 35 has been greatly exaggerated in Figure 4.

Instead of the operating plunger 22' being integral with the piston, it may be in the form of a rod or shaft pivotally attached to the piston so that it can be swung against the side of the body portion 10a and releasably held there by, for example a spring clip.

Whereas the above bases are formed from a block of aluminium alloy, if desired the block may be of a plastics material provided that the material is rigid and is substantially non-porous.

If a greater holding force is required, the base can have a larger side dimension enabling a greater area for land 14, or more strictly the area defined by the seal at the O-ring.

WHAT WE CLAIM IS: 1. A suction mounting arrangement for mounting to a smooth flat surface, and comprising a body having a substantially flat surface portion, a sealing member disposed in a channel extending around said surface portion, a piston arranged to fit sealingly within a blind bore in the body, a capillary bore coupling the blind end of the bore to said surface portion of the body, and either means operative to urge the piston outwardly relative to the blind end of the bore, or means operative to retain releasably the piston at a predetermined position spaced from its fully inserted position.

2. An arrangement as claimed in claim 1 wherein the cross-sectional area of the bore is substantially less than the area encompassed by the sealing member.

3. An arrangement as claimed in either claim 1 or claim 2 wherein the inner end of the piston is substantially complementary to the blind end of bore.

4. An arrangement as claimed in any one of claims 1 to 3 wherein the body is shaped such that the flat surface portion lies, in use, in contact with the mounting surface.

5. An arrangement as claimed in any one of claims 1 to 3 comprising support means projecting from the body proud of the general plane of the flat surface portion.

6. An arrangement as claimed in claim 5 wherein the support means is disposed outwardly relative to the sealing member.

7. An arrangement as claimed in claim 6 wherein the support means is in the form of a continuous rim with a flat annular contact land surrounding the sealing member.

8. An arrangement as claimed in either claim 5 or claim 6 wherein the support means is in the form of at least three individual spaced-apart projections.

9. An arrangement as claimed in any one of claims 5 to 8 wherein the support means is proud of the flat surface portion by a distance not greater than 25 microns.

10 An arrangement as claimed in claim 9 wherein the support means is about 5 microns proud of the flat surface portion.

11. An arrangement as claimed in any one of the preceding claims wherein the urging means, when present, is a compression spring.

12. An arrangement as claimed in any one of the preceding claims wherein the sealing member seals against side faces of the groove, and including means for venting the volume between the sealing member and the bottom of the groove.

13. An arrangement as claimed in claim 12 wherein the groove has an inclined bottom face and the sealing member, when disposed in the groove is in contact with the inclined bottom face along the periphery of the sealing member.

14. A suction mounting arrangement substantially as hereinbefore described with reference to and as shown in either Figures 1 and 2, or Figure 3, of the accompanying drawing.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. engage in the groove 33. This modification has fewer parts than the Figure 1 base and can thus have a smaller initial volume; does not reply on spring characteristics for determining the amount of piston movement from the fully inserted position, and consequently can have a larger volume. Figure 4 shows a modification in which the body portion is provided with three individual projections 35 uniformally spaced around the rim 11, instead of having a flat annular land 12 as in Figure 2 or Figure 3. If desired, there may be more than three projections 35. For explanatory purposes, the size of the projections 35 has been greatly exaggerated in Figure 4. Instead of the operating plunger 22' being integral with the piston, it may be in the form of a rod or shaft pivotally attached to the piston so that it can be swung against the side of the body portion 10a and releasably held there by, for example a spring clip. Whereas the above bases are formed from a block of aluminium alloy, if desired the block may be of a plastics material provided that the material is rigid and is substantially non-porous. If a greater holding force is required, the base can have a larger side dimension enabling a greater area for land 14, or more strictly the area defined by the seal at the O-ring. WHAT WE CLAIM IS:

1. A suction mounting arrangement for mounting to a smooth flat surface, and comprising a body having a substantially flat surface portion, a sealing member disposed in a channel extending around said surface portion, a piston arranged to fit sealingly within a blind bore in the body, a capillary bore coupling the blind end of the bore to said surface portion of the body, and either means operative to urge the piston outwardly relative to the blind end of the bore, or means operative to retain releasably the piston at a predetermined position spaced from its fully inserted position.