GB2082495A - Diaphragm manufacture - Google Patents

Abstract

Apparatus for semi-automatically producing shaped diaphragms particularly for use in gas meters comprises a stack holder (17) and a shell holder (18). For each operation a shell is placed in the shell holder (18) with its concave surface facing down above the convex surface of the topmost shell (24) of a stack of similar shells held by the stack holder. A sheet of uncured diaphragm fabric (25) is placed beneath the shell holder (18) and vacuum applied to pull it up into close comformity with the concave surface of the shell therein. The shell and shaped diaphragm are then transferred to the top of the stack and the process repeated. <IMAGE>

Description

SPECIFICATION Diaphragms This invention relates to the shaping of flexible diaphragms, particularly though not exclusively, for use in gas meters.

The invention provides a method of shaping a plurality of flexible diaphragms comprising the steps of locating a first shell member adjacent a similar shell member held by a stack holder so that the concave surface of one faces the convex surface of the other, placing a flat sheet of uncured or semi-cured diaphragm fabric between the two shell members and causing it to conform to the shape of either or both of the facing surfaces thereof, nesting the first shell member with the said similar shell member with the shaped diaphragm therebetween so that it is held together with the similar shell member by the stack holder, and repeating the above steps said first shell member taking up the previous location of the similar shell member, so that a stack of nested shell members and shaped diaphragms is formed.

The invention according to another aspect provides apparatus for carrying out the method set forth above, the apparatus comprising a shell holder and a stack holder and means for moving a first shell member held by the shell holder to nest with the end member of a stack of similar shell members held by said stack holder whereby said first shell member is transferred from the shell holder to the stack holder.

The invention also extends to a diaphragm formed by the method or apparatus set forth above.

Specific embodiments of the apparatus are shown in the accompanying diagrammatic drawings, in which:~ Figure 1 is a side section through an apparatus in a loading position for a first cycle, Figure 2 is a side section through the apparatus of Fig. 1 in a diaphragm forming position of the first cycle, Figure 3 is a side section through the appratus of Fig. 1 in a stacked position of the first cycle, Figure 4 is a side section through the apparatus of Fig. 1 in a loading position for the commencement of the next cycle, Figure 5 is a detail of a shell used in the apparatus of Fig. 1, and Figure 6 is a diagram illustrating another form of apparatus.

Referring first to Fig. 1, the apparatus comprises stationary platform (11) on which are mounted vertically acting hydraulic rams (12) supporting an annular blank holder (13). Hydraulically operated clamps (15) are movable radially outwardly from the position shown in Fig. 1 to that shown in Fig. 2 to release a lower shell (16) located radially within the blank holder, with its convex surface facing upwards.

Another hydraulically operated ram carries a movable stack holder comprising a platform (17) on which the lower shell (16) is located by pegs (not shown).

The upper part of the appratus comprises an upper shell holder (18)vertically above the platform (17) and movable up and down by a hydraulically operated ram (19). The upper shell holder has passageways (20) connected to a vacuum source, and another passageway (21) connected to the vacuum source independently of passageways (20). Pillars (22) connected to ram (19) may pass through openings in the upper shell holder (18).

As shown in Fig. 1, the apparatus is in the starting position with the upper shell holder (18) and the blank holder (13) and platform (17) in their uppermost positions. Loading of the apparatus can take place in this position by first inserting an upper shell (24) into the upper shell holder with its concave surface facing downwards towards the lower shell.

Vacuum is applied through passageways (20) to hold the upper shell in position.

A flat uncured sheet (25) of diaphragm fabric is then placed over the lower shell, the sheet being formed of a woven fabric coated with uncured or semi-cured synthetic rubber.

The ram (19) moves the upper shell holder (18) down into contact with blank holder (13).

With the sheet (25) held between shell holder (18) and blank holder (13), vacuum is then applied through passageway (21). A connecting opening (27) in the upper shell (24) conveys the vacuum to pull the sheet (25) into the concave opening in the upper shell into the position shown in Fig. 2. This shapes the diaphragm.

The ram (19)then moves the upper shell holder further down until the upper and lower shells are sandwiched together with the shaped diaphragm between them. The clamps (15) are then released, allowing the upper shell to continue its descent through the blank holder (1 3), overcoming the resistance of ram (29) holding up platform (17) so that the position in Fig. 3 is reached.

As shown, the sandwich of the two shells and the diaphragm is brought down so that the loose protruding edge of the diaphragm is below the stationary platform (11). This ensures that when moved up again, the loose edges turn downwards as shown at (28), and do not interfere with subsequent operations.

Finally, the rams are operated to take the upper shell holder and the blank holder back to their uppermost starting positions again.

Without removing the two shells and diaphragms now clamped by clamps (15) to the blank holder, a new upper shell and sheet of diaphragm fabric are placed in position as shown in Fig. 4. The same sequence of operations is followed to shape a diaphragm in the new upper shell and then stack the new diaphragm and shell on top of the two shells and diaphragm already held on the platform (17).

The sequence is followed until a plurality, e.g. ten diaphragms, is formed with the corresponding eleven shells, and is stacked on the lower platform (17).

The stack is then removed, held in clamps in an oven held at a predetermined curing temperature for the diaphragm, e.g. at 120 C -160 C, for a predetermined time, e.g. one hour.

The rams are arranged to operate automatically, once the diaphragm sheet and upper shell have been manually positioned.

The shells are identical in shape as shown in greater detail in Fig. 5, and nest into one another with the diaphragms therebetween.

The shells each comprise a rim (30), sloping sides (32) and a flat bottom (31). The thickness 'T' of the rim is considerably thicker than the thickness ''t'' of the sloping sides, so that the shells can nest. In order to aid the shaping of the diaphragm, the shells may be heated. e.g. to 140or. The heating may be carried out indirectly by heating the adjacent parts of the apparatus.

The supply of the flat uncured diaphragm fabric to the apparatus may be from a roll of fabric which is fed into the location and cut to shape by a knife (not shown) which descends before the position of Fig. 2 is reached.

While the above apparatus has been described using hydraulic rams, it is within the invention to use pneumatic power.

Another embodiment of the invention, shown in Fig. 6, does not use vacuum for pulling the sheets of diaphragm fabric into the upper shell, but uses a pressure method using one shell to push the fabric into the other shell, the fabric being press formed between the two shells. The apparatus of Fig. 6 is generally inverted with relation to the orientation of that of Figs. 1 to 5. The stack (40) of shells and shaped diaphragms is held in a stack carrier (not shown) in the upper part of the apparatus, new shells being loaded onto a shell carrier (not shown) in the lower part of the apparatus.

A continuous web of uncured diaphragm fabric is pulled onto a drum (41) in steps, each step placing a fresh area of fabric beneath the stack (40). A new lower shell (44) is positioned on the shell carrier (not shown) and is moved upwardly by the shell carrier. The edges of the fabric are thus trapped between surfaces on the shell carrier and stack carrier (not shown) and cut by a knife (42) to form a diaphragm blank. A location hole is burned into each corner of the blank by a hot filament (43). The stack (40) is then released from the stack carrier so that the lowest shell is pressed down into the shell (44), so forming the diaphragm blank to conform to the mating shapes of the two shells. The stack carrier is now reengaged with the stack at a - lower position so that shell (44) now forms the lowest member of the stack. The shell carrier then disengages from shell (44) and is lowered ready for the formation of the next diaphragm.

The stack of formed diaphragms may be removed from time to time in order to cure the diaphragms in an oven. However, the stack must always have at least one shell to mate with the new lower shell (44).

Claims (16)

1. A method of shaping a plurality of flexible diaphragms comprising the steps of locating a first shell member adjacent a similar shell member held by a stack holder so that the concave surface of one faces the convex surface of the other, placing a flat sheet of uncured or semi-cured diaphragm fabric between the two shell member and causing it to conform to the shape of either or both of the facing surfaces thereof, nesting the first shell member with the said similar shell member with the shaped diaphragm therebetween so that it is held together with the similar shell member by the stack holder and repeating the above steps said first shell member taking up the previous location of the similar shell member, so that a stack of nested shell members and shaped diaphragms is formed.

2. A method as claimed in claim 1, wherein said step of causing the flat sheet to conform comprises applying a vacuum to the interior of said first shell member so pulling the fabric into contact therewith.

3. A method as claimed in claim 1, wherein said step of causing the flat sheet to conform is combined with the step of nesting the shell members together, the fabric being trapped between the convex and concave surfaces of the shell members.

4. A method as claimed in any of claims 1 to 3, wherein said first shell member is located above the similar shell member, the stack being formed vertically below the first shell member.

5. A method as claimed-in any of claims 1 to 3, wherein said first shell member is io- cated below the similar shell member, the stack being formed vertically above the first shell member.

6. A method as claimed in any of claims 1 to 5, wherein said step of placing a flat sheet? of fabric between the shell members comprises feeding in a section from a continuous web of material, and an additional step of cutting out a diaphragm blank is included before the fabric is caused to conform to the shell shape

7. A method as claimed in any of claims 1 to 6, including a step of forming location holes around the edges of the blank by a burning method.

8. A method of shaping a plurality of flexible diaphragms, substantially as described hereinbefore with reference to Figs. 1 to 5 or to Fig. 6 of the accompanying drawings.

9. Apparatus for carrying out the method of claim 1 comprising a shell holder and a stack holder and means for moving a first shell member held by the shell to nest with the end member of a stack of similar shell members held by said stack holder, whereby said first shell member is transferred from the shell holder to the stack holder.

10. Apparatus as claimed in claim 9, including means for applying a vacuum to the interior of a first shell member held in said shell holder whereby to pull a sheet of fabric into conformity therewith before the first shell member is transferred to the stack.

11. Apparatus as claimed in claim 9 or 10, wherein said stack holder is adapted to readjust its position as each shell member is added thereto so that the end shell member of the stack always takes up the same location relative to the shell holder.

12. Apparatus as claimed in any of claims 9 to 11, including means for feeding a continuous web of fabric between the shell holder and the stack holder, and cutter means for cutting out a diaphragm blank from said fabric.

13. Apparatus as claimed in any of claims 9 to 12, including a means for burning location holes around the edges of the diaphragm.

14. Apparatus as claimed in any of claims 9 to 13, including hydraulic or pneumatic rams programmed to carry out at least part of the method automatically.

15. Apparatus for shaping a plurality of flexible diaphragms substantially as described hereinbefore with reference to Figs. 1 to 5 or to Fig. 6 of the accompanying drawings.

16. A flexible diaphragm produced by the method of any of claims 1 to 8 or made by the apparatus of any of claims 9 to 15.