GB2038282A

GB2038282A - Suction grippers

Info

Publication number: GB2038282A
Application number: GB7941725A
Authority: GB
Original assignee: Festo Maschinenfabrik Gottlieb Stoll Firma
Current assignee: Festo Maschinenfabrik Gottlieb Stoll Firma
Priority date: 1978-12-06
Filing date: 1979-12-04
Publication date: 1980-07-23
Also published as: FR2443417A1; SE7910014L; DE2852681A1; DE2852681C3; GB2038282B; DE2852681B2; ES485934A1; CH640482A5; FR2443417B1; SE442627B

Abstract

The invention relates to a vacuum bell carrier wherein negative pressure in an operating aperture (42) is provided by passing compressed air through a Venturi channel arrangement (22, 32). By expansion of the air between two jet bodies (18, 30), the flow rate is increased to create a vacuum. <IMAGE>

Description

SPECIFICATION Vacuum-bell carriers The invention relates to a vacuum-bell carrier.

Normally a bell carrier of the type comprising a housing having an operating opening under negative pressure has in addition to the operating opening, which is connectable with the vacuum-bell, a second opening which communicates with the latter. Vacuum-bells are today increasingly used for the transport of objects having a smooth surface such as sheet metal or glass plates, the system being applied to industrial establishments including small plants which are not necessarily equipped with their own vacuum supply. In these cases a separate vacuum pump has to be provided and the pipes required for its operation have to be installed. A compressed air connection will be available, however, in the majority of industrial establishments.

The object of the invention is to provide a vacuum bell carrier which is operable by compressed air.

According to the present invention there is provided a vacuum bell carrier comprising a housing wherein is defined a Venturi channel arrangement for providing a negative pressure in an operating aperture when compressed air is passed through the Venturi arrangement, the operating aperture being positioned in the housing laterally of the Venturi channel arrangement.

Preferably the Venturi channel arrangement comprises an ejector jet and a collector jet in alignment with an axial gap therebetween.

Preferably also the section of bore in the ejector jet having the smallest cross-section, is substantially equal to one sixth of the cross-section of the collector jet bore.

Embodiments of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which: Figure lisa longitudinal section through a vacuum bell carrier of a first embodiment; and Figure2 is a longitudinal section through a vacuum bell carrier of a second embodiment in which compressed air is automatically admitted into the bell so that it may release the component it carries.

Referring to Figure 1, a vacuum bell carrier has a housing 10 through which extends a longitudinal bore 12. One end of the bore 12, i.e. the left hand end in the drawing, has a thread 14 which serves for the connection with a compressed air supply line, a thread 16 on the other end serving for connection with a waste air hose.

An ejector jet body with an axial duct 20 is screwed into the left hand end of the bore 12. The front or inner end face of this ejector jet body 18 is provided with a jeb opening 22 which is of slight conical cross-section opening towards the front face.

A cylindrical external surface section 24 of the ejector jet body 18 is press-fitted into the bore 12 and glued on to the bore wall as an additional precaution. Adjacent to this cylindrical section is a concial surface section 26. A shoulder 28 of the ejector jet body 18 supports itself against a complementary shoulder in the bore 12.

Similarly, a collector jet body 30 is press-fitted into the bore 12 from the right hand end, and glued. The diameter of an axial duct 32 in this jet body is six times greater than the smallest diameter of the jet opening 22. A recess of the shape of a truncated cone 34, provided in the front or inner end face of the collector jet body 30, comprises a tubular member 36 which is integrally formed on to the collector jet body, projecting centrally therefrom. The front end face of the tubular member 36 ends adjacent to the front end face of the ejector jet body 18, leaving a narrow annular gap 38 which connects with a chamber defined by the bore 12, the surface section 26 of the ejector jet body 18, and the recess 34 in the collector jet body 30.A radial channel 40 at the inner ends of the two jet bodies provides a connection between the chamber and an operating outlet 42 into which a vacuum bell (not shown) may be screwed.

Continuous bores 44 are provided for the assem blyofthevacuum bell carrier with a lifting gear.

In operation, the line supplying compressed air, which is connected by means of the thread 14, admits compressed air to the jet opening 22. When leaving this opening 22, which opens into the channel 32 of enlarged diameter, the air expands and its rate of flow is correspondingly increased. In a similar fashion to a water jet pump, the annular gap 38 creates a vacuum at the operating outlet 42.

In a modified design of a vacuum bell carrier (Figure 2), the operating aperture of the ejector jet body 18 is automatically exposed to excess pressure when the pneumatic load is discontinued.

A housing 46 is for this purpose enlarged so that it may accommodate a cylindrical reservoir 48 which is closed by a cover 50. A cylindrical projection 52 extending from the cover internally into the reservoir 48 is sealed against the latter by means of a sealing ring 54.

A channel 56, extending transversely relative to the axis of the reservoir, is formed inside the cover 50 and closed on one end by means of a stopper 58, its other end being connected through a small axial duct 60 with an axial parallel channel 62 in the housing 46. A sealing ring 64 is provided at the joint.

There are provided in the lower section of the housing, an ejector jet body and a collector jet body press-fitted and glued into a bore. These components are very similar to those of the vacuum bell carrier according to Figure 1. For this reason the same reference numbers are used with corresponding parts which need not be described again.

However, the thread 14 is provided in an enlarged diameter head 66 of the jet body 18, and the latter comprises additionally a radial channel 68 which provides a connection between the channel 20 and the channel 62.

The cover 50 has a blind bore 70 intersecting the channel 56, into which a tube 72 with an axial channel 74 is pressure-tightly inserted. The channel 74 extends into a cylindrical valve chamber 76 of increased diameter which is integrally formed into a cup-shaped end section 78 of the tube 72. An inner end surface of this section 78 ends near a lower wall 80 of the pressure reservoir, leaving a short space so that the valve chamber 76 is connected with the reservoir 48 through an annular gap 82.

A coaxial projection 84 on the bottom wall 80 extends into the valve chamber 76 and has an axial channel 86 which is connected with the bore 12 at a position located adjacent to the inner ends of the two jet bodies 18 and 30.

Inside the valve chamber 76 is located a rotationally symmetrical valve body 88 which is formed of an elastomer material. Its plane-parallel surface areas 90,92 are capable of closing the channels 74 and 86 respectively. The valve body moreover comprises an integrally formed, concial, continuous sealing lip 94, the cross-section of which tapers towards the free end. The apex of a cone defined by the sealing lip 94 would be located in the channel 74.

Athreaded opening 96 in the reservoir 48 may be closed by means of a venting plug 98 which supports its head on the housing wall over a washer 100.

In operation, to create a vacuum in the vacuum bell, which is connected with the operating outlet 48, it is again necessary that compressed air should be conducted under expansion through the channel 20 into the channel 32. However, the compressed air passes at the same time through the channels 68,62, 56, and 74 and thence into the valve chamber 76 where it presses the resilient sealing lip 94 radially inwardly to reach the reservoir 48 through the annular gap 82. The valve body 88 is simultaneously forced into a position where it closes the channel 86; this action is assisted by the vacuum which is built up inside the channel 86.

When the pressure in the reservoir 48 is substantially equal to the pressure in the channel 20 the sealing lip 94 resumes its previous position in contact with the internal wall of the valve chamber 76 where it acts as a non-return valve and prevents the compressed air from returning from the reservoir 48 into the channel 74. Being loaded by the differential pressure (including the vacuum admitted to the annular section on the underside which covers the channel 86), the valve body remains in the position in which it closes the channel 86. This condition, in which the operating outlet 42 is permanently under a vacuum, remains unchanged as long as compressed air is admitted through the compressed air supply line. As a rule the pressure in the reservoir 48 will be approximately 8 atmospheres.

When the supply of compressed air to the channel 20 is cut off no pressure will be applied to the upper side of the valve body 80. The pressure loading the outermost annular section of the valve body 88, supplied from the reservoir 48, forces the valve body 88 to move rapidly upwards and the compressed air in the reservoir 48 rapidly streams into the vacuum bell through the channel 86 and the operating outlet 42. It follows that the vacuum bell is equally rapidly loaded by excess pressure and consequently immediately releases the component.

By press-fitting andlor glueing the jet bodies in position, isolation of the Venturi duct from the atmosphere is particularly efficient.

With the provision of the pressure reservoir, the removal of the vacuum bell from the component it carries is not limited to disconnecting the vacuum.

This effect is augmented by admitting compressed air into the bell, so that the component may be separated from the bell in a minimum of time. The carrier is particularly favourable in thai it comprises only one valve body which serves both as a nonreturn valve when filling the pressure reservoir, and as an automatic control valve between the pressure reservoir and the operating outlet. The valve chamber may be removed from the pressure reservoir as one complete unit together with the valve body. This facilitates assembly and maintenance considerably.

Claims

1. Avacuum bell carrier comprising a housing wherein is defined a Venturi channel arrangement for providing a negative pressure in an operating aperture when compressed air is passed through the Venturi arrangement, the operating aperture being positioned in the housing laterally of the Venturi channel arrangement.

2. A carrier according to claim 1, wherein the Venturi channel arrangement comprises an ejector jet and a collector jet in alignment with an axial gap therebetween.

3. A carrier according to claim 2, wherein the section of bore in the ejector jet having the smallest cross-section, is substantially equal to one sixth of the cross-section of the collector jet bore.

4. A carrier according to claim 2 or 3, wherein the ejector bore widens out in the direction of flow.

5. A carrier according to any of the claims 2 to 4, wherein the collector jet has a body defining a recess of truncated conical section, the recess being located in an end face adjacent to the ejector jet and a central tubular part extending into the recess.

6. A carrier according to claim 5, wherein the aperture angle of the recess is substantially 1 20"C.

7. A carrier according to any of the claims 2 to 6, wherein the ejector jet has a body which tapers towards an outlet in a conical configuration.

8. A carrier according to claim 7, wherein the aperture angle of the ejector jet outlet is substantial liy200.

9. A carrier according to any of the preceding claims, wherein the operating aperture communicates with an annular gap which is defined between adjacent surfaces of the ejector jet and the collector jet.

10. A carrier according to any of the preceding claims, wherein the ejector jet andlor the collector jet are press-fitted andior glued into a bore of the housing.

11. A carrier according to anyofthe preceding claims, wherein the operating aperture is connectible through a servo valve with a pressure reservoir which is arranged to be switched into an open position when the supply of pressure to the Venturi channel arrangement is disconnected.

12. A carrier according to claim 11, wherein the pressure reservoir is connected through a nonreturn valve with a pressure supply line communicating with the Venturi channel arrangement.

13. A carrier according to claim 12, wherein the non-return valve is formed by the flexible skirt of a valve body.

14. A carrier according to claim 13, wherein, with the servo valve in a closed position, the total cross-section of the valve body is pressure loaded on one side through the supply line, the pressure available in the operating aperture being effective on a small central area of the valve body cross-section, and pressure from the pressure reservoir being effective on a circumferential area of the valve body cross-section.

15. A carrier according to claim 14, wherein the valve body is located in a substantially cylindrical valve chamber, a line which connects with the supply line opening into one end wall of the chamber, and the opposite end wall defining an annular passage to the pressure reservoir and comprising a channel which communicates with the operating aperture.

16. A carrier according to claim 15, wherein the skirt of the valve body which constitutes a nonreturn valve is designed as a concial sealing lip which widens towards the opposite end wall of the valve chamber.

17. A carrier according to claim 16, wherein the cross-section of the sealing lip decreases towards its free end.

18. A carrier according to any of the claims 15 to 17, wherein the valve chamber is cup-shaped and is supported on a tube which is carried by a cover of the pressure reservoir, the latter being integrated into the housing.

19. A carrier according to claim 18, wherein the cover has a cylindrical projection which is pressuretightly inserted into the pressure chamber.

20. A carrier according to claim 18 or 19, wherein the line which connects with the supply line is so connected through a transverse channel in the cover and an axial channel in the housing.

21. A carrier according to any of claims 11 to 20, wherein the capacity of the pressure reservoir is arranged to exceed the effective volume of the vacuum bell which is connected with the operating aperture.

22. A vacuum bell carrier substantially as herein before described with reference to the accompanying drawings.

23. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.