DISKS ARRANGEMENT BETWEEN A SPINDLE AND A SHUTTER OF A VALVE

Technical field

[0001] The invention is directed to the field of tap or valves for gas, in particular for industrial compressed gas that is usually stored in containers such as cylinders.

Background art

[0002] Prior art patent document published GB 2 21 1 586 A discloses a tap or valve for gas cylinders. The tap comprises a body with an inlet portion to be screwed into the neck portion of a gas cylinder. The body comprises a passage for the gas with a first shut-off valve operated by the pressure of a gas and a second shut-off valve, downstream of the first shut-off valve and manually operated. The second shut-off valve comprises a shutter that cooperates with a seat formed in the passage. The shutter is operated by a spindle that is mounted on the body via a thread engagement. A hand-wheel is fixed to the spindle. A flexible membrane extends between the shutter and the spindle and forms a gas tight barrier between the gas passage, in the body and the spindle, and the exterior of the valve. A pressure disk is provided between the membrane and the head of the spindle. The membrane is pre-shaped so as to form a deepening in which the pressure disk is located. The spindle's head is generally curved and convex and contacts a generally flat face of the pressure disk. The opposed face of the pressure disk, resting on the flexible membrane is generally curved and conforms to the deepening in the membrane. The purpose of the pressure disk is to reduce the torque transmission from the spindle to the membrane. To that end, the pressure disk is "housed" in the deepening of the pre-shaped membrane. The pressure disk is thereby prevented from rotating, or at least is less free to rotate, relative to the membrane. The friction caused by the rotation of the spindle is therefore essentially between the generally curved spindle's head and the generally flat pressure disk. This design is interesting in that it avoids frictional wear at the membrane. It requires however that the membrane is pre-shaped with a deepening. This operation can however be difficult to carry out, in particular when the membrane comprises a stack of several disks. It can also weaken the membrane by the plastic deformation.

[0003] Prior art patent document published EP 0 246 584 A2 discloses a tap or valve for a gas cylinder. The tap comprises a shutter that is actuated by a rotating spindle. Similarly to the previous teaching, a flexible gas tight membrane is arranged between the spindle and the shutter. Also similarly to the previous teaching, the tap comprises a pressure element interposed between the head of the spindle and the membrane. A washer is arranged between the membrane and the pressure disk for assisting the deformation of the membrane at an annular portion. This increases the fatigue resistance of the membrane. The transmission of torque between the spindle and the membrane is still present despite the use of a pressure disk. The reason is essentially that the contact surface between the spindle's head and the pressure disk is large for providing stability to said disk. The frictional torque transmitted through the contact between the spindle and the pressure disk is substantial. An important operating torque is therefore transmitted to the membrane.

[0004] Prior art patent document published LU 86714 discloses a tap or valve for a gas cylinder similar to the one of the previous document.

Summary of invention

Technical Problem

[0005] The invention has for technical problem to overcome at least one drawback of the above mentioned prior art. More specifically, the invention has for technical problem to provide a tap for compressed gas, with a shutter, an actuating spindle and a flexible membrane between said shutter and spindle, that provides a reduced operating torque and a reduced wear to the membrane while remaining cheap to manufacture.

Technical solution

[0006] The invention is directed to a tap for gas, in particular for compressed gas, comprising: a body with a gas inlet, a gas outlet and a passage fluidly interconnecting said inlet and outlet; a shutter movable in translation in the body for cooperating with a seat for shutting-off the passage; a rotating and translating spindle configured for moving the shutter towards the seat; a disk-shaped membrane between the spindle and the shutter, said membrane having its periphery attached to the body in a gas tight manner so as to delimit the passage; a pressure disk between the spindle and the at least one membrane; wherein the membrane and the pressure disk are generally flat and the pressure disk has a constant thickness.

[0007] By generally flat it is meant that the membrane and the pressure disk are flat in the absence of external force and can be elastically deformed by movement of the spindle and/or the shutter so as to exhibit a general curved profile.

[0008] According to a preferred embodiment, the pressure disk is free of attachment at its periphery.

[0009] According to a preferred embodiment, the pressure disk is made of a metal plate, preferably a stainless steel plate.

[0010] According to a preferred embodiment, the pressure disk has a thickness of less than 0.3mm.

[001 1] According to a preferred embodiment, the pressure disk has a thickness of less than 0.2mm.

[0012] According to a preferred embodiment, the pressure disk has a thickness of less than 0.15mm.

[0013] According to a preferred embodiment, the spindle has a contact surface with the pressure disk, said surface being convex and symmetric around a longitudinal axis of said spindle. Advantageously, the contact surface of the spindle rotates with said spindle. The pressure disk can have a diameter that is equal to or less than the diameter of the contact surface of the spindle.

[0014] According to a preferred embodiment, the membrane is a stack of at least three superimposed disks.

[0015] According to a preferred embodiment, the membrane is made of at least one metal alloy plate, preferably with a thickness of less than 0.3mm, more preferably with a thickness of less than 0.2mm. [0016] According to a preferred embodiment, the pressure disk has a diameter that is less than the diameter of the membrane.

[0017] According to a preferred embodiment, the body comprises a cavity with a shoulder, and a gland engaging with the cavity and with an annular front portion pressing the periphery of the membrane against said shoulder. Advantageously, the gland comprises a bore receiving the contact surface of the spindle and the pressure disk. The bore is circular. The front portion can be flat and the bore can be directly adjacent to said front portion.

[0018] According to a preferred embodiment, the pressure disk is in direct contact with the membrane, and is located inside the annular front portion of the gland.

[0019] According to a preferred embodiment, the spindle has an outer thread engaging with an inner thread of the gland, the rotation of said spindle causing translation of said spindle and movement of the shutter.

[0020] According to a preferred embodiment, the shutter has an operation stroke from a closed position to a fully opened position, the membrane being configured for elastically deforming over said stroke.

[0021] According to a preferred embodiment, the stroke is less than 0.5 mm, preferably less than 0.4mm.

Advantages of the invention

[0022] The invention is particularly interesting in that it reduces the frictional torque between the rotating spindle and the non-rotating membrane in a simple and cheap manner. Indeed, the use of circular plate portions for the membrane and the pressure disk is particularly economic and efficient. Damages to the membrane are also avoided. In addition, the tap is rendered more compact in the longitudinal direction since the superimposition of the pressure disk and the membrane is very thin, e.g. less than 1 mm.

Brief description of the drawings

[0023] Figure 1 is perspective view of a tap for compressed gas in accordance with the invention.

[0024] Figure 2 is a cross-sectional view of the tap of figure 1.

[0025] Figure 3 is an exploded view of the tap of figures 1 and 2. Description of an embodiment

[0026] Figures 1 to 3 illustrate a tap for compressed gas, in accordance with the invention.

[0027] In figure 1 , the tap 2 is illustrated in perspective. It comprises a body 4 with an inlet 6, an outlet 8 and a hand-wheel for operating the tap in order to open or close a passage between the inlet 6 and the outlet 8.

[0028] With reference to figure 2, the body 4 of the tap 2 comprises a passage 12 for the gas, said passage 12 fluidly interconnecting the outlet 8 with the inlet 6. The body 4 comprises a seat 14 that is formed around the passage 12. The body 4 houses a shutter 16 that is movable in translation for cooperating the seat 14. More specifically, the shutter 16 can comprises a softer material 16 ¹ that contacts the seat 14 for closing the passage 12. The shutter 16 is urged away from the seat 14 by a spring 18. The shutter 16 comprises also a head portion 16 ² that is opposite to the softer material 16 ¹ .

[0029] The tap 2 comprises a membrane 20 that extends transversely to the longitudinal axis. The membrane 20 is in contact with the head portion 16 ² of the shutter 16. The periphery of the membrane 20 rests on a shoulder 4 ¹ of the cavity of the body housing the shutter 20. A gland 22 is engaged by means of a thread with the cavity. It comprises an annular front portion 22 ¹ that presses the periphery of the membrane 20 against the annular shaped shoulder 4 ¹ . The membrane 20 forms a gas tight barrier that delimits the passage 10. It forms a barrier between the shutter 20 and a spindle 24. The spindle 24 comprises a front surface 24 ¹ that contacts the membrane 20. It comprises also an outer thread 24 ² that mates with an inner thread 22 ² of the gland 22. Upon rotation of the spindle 24, this latter moves progressively up or down along the longitudinal axis of the tap 2, in addition to the rotational movement. The contact surface 24 ¹ of the spindle 24 with the membrane 20 is generally curved and convex. The spindle 24 comprises also a portion with fluting in the form of grooves 24 ³ that extend longitudinally. These grooves engage with corresponding rips of the hand- wheel 10. [0030] Figure 3 is an exploded view of the tap of figures 1 and 2. As apparent in figure 3, the membrane 20 is a stack of four disks 20 ¹ , 20 ² , 20 ³ and 20 ⁴ . The disks are preferably identical in shape and material. They are made of metallic material, more specifically of metal plate. The metal can for example stainless steel or a supper alloy, like Hastelloy® C276. They have a constant thickness that is advantageously less than 0.3mm, preferably less than 0.2mm.

[0031] Still with reference with figure 3, we can observe that the tap 2 comprises also a pressure disk 28 interposed between the spindle 24 and the membrane 20. This pressure disk also made of a metal plate, i.e. with a constant thickness. The thickness is less than 0.3mm, preferably less than 0.2mm. The diameter of the pressure disk 28 is less than the diameter of the membrane 20. The periphery of the membrane 20 is clamped between the annular shoulder 4 ¹ and the annular front portion 22 ¹ of the gland 22 (see figure 2), whereas the pressure disk 28 is freely interposed between the membrane 20 and the spindle 24. During assembly, the series of disks of the membrane 20 are put in place on the shoulder 4 ¹ and the pressure disk 28 is placed at the centre on the membrane 20 prior to screwing the gland 22 with the spindle 24. When engaging the gland 22, care is taken not to clamp the periphery of the pressure disk. To that end, the diameter of said disk 28 is advantageously less than the inner diameter of the annular front portion 22 ¹ of the gland 22. This provides some radial play that facilitates assembly.

[0032] As apparent in figure 3, the disks 20 ¹ , 20 ² , 20 ³ and 20 ⁴ of the membrane 20 are generally flat prior mounting in the tap body. With reference to figure 2, the membrane 20 is generally flat in at least one position of the shutter 16 relative to the seat 14. Depending on the position of the shutter, the membrane can take a slightly curved shape but remains generally flat. The flatness of the membrane can be characterized in that the membrane fails to exhibit local deformations, the membrane being either plane or taking a general curved shape over its entire extent, the curvature being essentially constant along a diameter over the entire extent of the membrane. Similarly, with reference to figure 3, the pressure disk 28 is also generally flat prior assembly.

[0033] The arrangement of the pressure disk 28 against the membrane 20 is particularly interesting because it minimizes the transmission of frictional torque during manipulation of the hand-wheel while keeping the construction quite simple and cheap. Indeed, the flat and direct contact between the pressure disk 28 and the proximate disk 20 ¹ of the membrane 20 generates low frictional forces that allow the pressure disk 28 to rotate relative to the membrane 20. This prevents frictional wear of the membrane 20. This latter remains therefore unaffected by the transmission of torque by the spindle. The convex curved shape of the spindle contact surface 24 ¹ minimizes the torque transmission to the pressure disk 28, thereby limiting the resistant torque on the spindle and wear on the pressure disk 28. Also the pressure disk can be made of different material since it does not contact the pressurized gas. Also the pressure disk 28, by being made of a plate and therefore by being flexible, follows the deformation of the membrane and keeps a tight contact with the membrane.

[0034] The above design provides also a compact construction in the longitudinal direction, essentially in view of the flat construction of the membrane and of the pressure disk.