Method for Operating a Vacuum Pump, as well as a Vacuum Pump Designed for this Purpose with Two Inlets and One Outlet, its Use and Vacuum Packaging Machines Equipped Therewith

Abstract

The present invention relates to a method for evacuating at least two external vacuum chambers i and j (20, 20) with a vacuum pump (10), in particular a rotary vane vacuum pump (10), whereby the vacuum chamber i (20) is evacuated from the initial pressure p.sub.02(i) to a final pressure p.sub.12(i) via the second inlet (2) during an evacuation time t.sub.p2(i) and at the same time the vacuum chamber j (20) is evacuated via the first inlet (1) from the initial pressure p.sub.01(j) to a final pressure p.sub.11(j) during an evacuation time t.sub.p1(j).

A rotary vane vacuum pump (10) designed for this purpose is characterized in that it has two inlets (1, 2) and one outlet (3), the two inlets (1, 2) being arranged offset at an angle to one another, and is also subject matter of the present invention, as is its use in the method according to the invention and a vacuum packaging machine which comprises a rotary vane vacuum pump (10) designed in this way.

Claims

1. A method for evacuating at least two vacuum chambers i and j with a vacuum pump (10), comprising: a cylinder having an outlet, as well as a first inlet and a second inlet, whereby both inlets are connectable to said vacuum chambers i and j independently from each other, and a rotor arranged eccentrically to a central axis of the cylinder and within the cylinder, said rotor forming a conveying chamber with an inner wall of the cylinder, and at least two vanes, received in a movable way in respective slots of the rotor and, with rotation of the rotor, are pressed against the inner wall of the cylinder thereby forming sealing points thus dividing the conveying space into individual conveying chambers, in which gas can be conveyed from the first inlet to the second inlet and from the second inlet to the outlet of the vacuum pump, the second inlet being arranged offset by an angle to the first inlet in a conveying direction, the method having the following steps: a) Providing the at least two vacuum chambers i and j with an initial pressure p.sub.02(i) and an initial pressure p.sub.01(j), where p.sub.02(i)p.sub.01(j); b) Connecting the second inlet to the vacuum chamber i and the first inlet to the vacuum chamber j; c) Evacuating the vacuum chamber i from the initial pressure p.sub.02(i) to a final pressure p.sub.12(i) via the second inlet during an evacuation time t.sub.p2(i) and simultaneously evacuating the vacuum chamber j via the first inlet from the initial pressure p.sub.01(j) to a final pressure p.sub.11(j) during an evacuation time t.sub.p1(j); d) Closing and separating the vacuum chamber i from the second inlet and the vacuum chamber j from the first inlet.

2. The method according to claim 1, whereby at least three vacuum chambers i, j and k are evacuated cyclically, which has the following steps: a) Providing said at least three vacuum chambers i, j, k with the initial pressures p.sub.02(i)=p.sub.02(k) and p.sub.01(j), where p.sub.02(i)>p.sub.01(j); b) Connecting the second inlet to the vacuum chamber i and the first inlet to the vacuum chamber j; c) Evacuating the vacuum chamber i from the initial pressure p.sub.02(i) to a final pressure p.sub.12(i) via the second inlet during an evacuation time t.sub.p2(i) and simultaneously evacuating the vacuum chamber j via the first inlet from the initial pressure p.sub.01(j) to a final pressure p.sub.11(j) during an evacuation time t.sub.p1(j), whereby p.sub.02(i)>p.sub.12(i) and p.sub.01(j)>p.sub.11(j); d) Closing and separating the vacuum chamber i from the second inlet and the vacuum chamber j from the first inlet; e) Connecting the second inlet to the vacuum chamber k and connecting the first inlet to the vacuum chamber i; f) Evacuating the vacuum chamber k from the initial pressure p.sub.02(k) to a final pressure p.sub.12(k) via the second inlet during an evacuation time t.sub.p2(k) and simultaneously evacuating the vacuum chamber i from the initial pressure p.sub.01(i) to a final pressure p.sub.11(i) during an evacuation time t.sub.p1(i), whereby p.sub.02(k)>p.sub.12(k) and p.sub.01(i)>p.sub.11(i); g) Closing and separating the vacuum chamber k from the second inlet and the vacuum chamber i from the first inlet; h) Optionally repeating steps b) to g).

3. The method according to claim 1, wherein the final pressure p.sub.12(i) of the vacuum chamber i connected to the second inlet and the initial pressure p.sub.01(j) of the vacuum chamber j connected to the first inlet in step c) deviate from each other by a maximum of 25%.

4. The method according to claim 1, whereby the initial pressure of the vacuum chamber j is p.sub.02(j)=p.sub.02(i), whereby the initial pressures p.sub.02(i) and p.sub.02(j), in particular both, correspond to atmospheric pressure, comprising the following steps which are carried out before step a): a.i) Connecting the second inlet to the vacuum chamber j; a.ii) Evacuating the vacuum chamber j from the initial pressure p.sub.02(j) to a final pressure p.sub.12(j) via the second inlet during an evacuation time t.sub.p2(j) with p.sub.12(j)=p.sub.01(j); a.iii) Closing and separating the vacuum chamber j from the second inlet.

5. The method according to claim 1, wherein the evacuation times t.sub.p2(i/j) via the second inlet and the evacuation times t.sub.p1(i/j) via the first inlet differ from one another by a maximum of 30%.

6. The method according to claim 1, wherein the vacuum chamber i and/or the vacuum chamber j is an external chamber which contains a package for a foodstuff.

7. A vacuum pump, designed for carrying out the method according to claim 1 comprising: a cylinder having an outlet, as well as a first inlet and a second inlet, both inlets being connectable to a vacuum chamber to be evacuated, and a rotor arranged for rotation in a rotary vane chamber and having at least two vanes which project radially beyond a body of the rotor and define with an inner wall of the rotary vane chamber a conveying volume which, by rotation of the rotor, can be conveyed from the second inlet to the first inlet and from the first inlet to the outlet of the vacuum pump, wherein the second inlet is arranged offset by an angle to the first inlet in a conveying direction.

8. The vacuum pump according to claim 7, wherein the angle between the first inlet and the second inlet is designed according to the desired volume flows {dot over (V)}.sub.1 und {dot over (V)}.sub.2.

9. The vacuum pump according to claim 7, wherein the first inlet and/or the second inlet is a radial inlet.

10. The vacuum pump according to claim 7, wherein the number of vanes is selected such that there is a sealing point between the first inlet and the second inlet.

11. The vacuum pump according to claim 7, wherein the number of vanes is in the range of 3 to 17.

12. A vacuum packaging machine comprising the vacuum pump according to claim 7.

13. The method according to claim 1, wherein the final pressure p.sub.12(i) of the vacuum chamber i connected to the second inlet and the initial pressure p.sub.01(j) of the vacuum chamber j connected to the first inlet in step c) deviate from each other by a maximum of 5%.

14. The method according to claim 2, wherein the final pressure p.sub.12(k) of the vacuum chamber k connected to the second inlet and the initial pressure p.sub.01(j) of the vacuum chamber j connected to the first inlet in step f) deviate from each other by a maximum of 25%.

15. The method according to claim 1, wherein the evacuation times t.sub.p2(i/j) via the second inlet and the evacuation times t.sub.p1(i/j) via the first inlet differ from one another by a maximum of 5%.

16. The method according to claim 2, wherein the evacuation times t.sub.p2(k) via the second inlet and the evacuation times t.sub.p1(k) via the first inlet differ from one another by a maximum of 30%.

17. The method according to claim 2, wherein the vacuum chamber i and/or the vacuum chamber j and/or the vacuum chamber k is an external chamber which contains a package for a foodstuff.

18. The method according to claim 1, said vacuum pump being a rotary vane vacuum pump.

19. The method according to claim 2, said vacuum pump being a rotary vane vacuum pump.

20. The vacuum pump according to claim 7, said vacuum pump being a rotary vane vacuum pump.

21. The vacuum packaging machine according to claim 12, said vacuum packaging machine being a rotary vacuum packaging machine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Shown are:

[0066] FIG. 1: a schematic representation of a state-of-the-art system in which two single-stage rotary vane vacuum pumps simultaneously evacuate two different vacuum chambers;

[0067] FIG. 2: a schematic representation of a further state of the art, in which the stages of a two-stage rotary vane vacuum pump evacuate two different vacuum chambers simultaneously;

[0068] FIG. 3: a schematic representation of the single-stage rotary vane vacuum pump according to the invention with two inlets, via which two different vacuum chambers are evacuated simultaneously;

[0069] FIG. 4: a cross section of a stage with six vanes of a rotary vane vacuum pump according to the invention, with the arrow at the top indicating inlet 1, the arrow at the bottom right indicating inlet 2 and the arrow at the bottom left indicating the outlet;

[0070] FIG. 5: a cross section of a stage with six vanes of a rotary vane vacuum pump according to the invention, with the arrow at the top indicating inlet 1, the arrow at the bottom right indicating inlet 2 and the arrow at the bottom left indicating the outlet.

DESCRIPTION OF THE STATE OF THE ART

[0071] From FIG. 1, an arrangement of the prior art can be seen in which two single-stage rotary vane vacuum pumps simultaneously evacuate two of three different vacuum chambers i/20, j/20 and k/20 in a cyclical process. At the same time, the third vacuum chamber, which is not connected to one of the two rotary vane vacuum pumps, is ventilated. The rotary vane vacuum pump 22 is the fore-pump here, while the rotary vane vacuum pump 21 is the high vacuum pump.

[0072] In valve position 41, the vacuum chamber i/20 with fore-pump 22 is evacuated from an initial pressure p.sub.02(i) to a final pressure p.sub.12(i) and the vacuum chamber j/20 with the high vacuum pump 21 is evacuated from an initial pressure p.sub.01(j) to a final pressure p.sub.11(j). The following applies: p.sub.02(i)>p.sub.12(i)p.sub.01(j)>p.sub.11(j). In parallel, the vacuum chamber k/20 is brought to an initial pressure p.sub.02(k).

[0073] When the valve is changed from position 41 to position 42, the vacuum chambers are disconnected from the pumps and reconnected as follows: At valve position 42, vacuum chamber k/20 is evacuated with fore-pump 22 from an initial pressure po2 (k) to a final pressure p12 (k) and vacuum chamber i/20 is evacuated with the high vacuum pump 21 from the initial pressure p.sub.12(i) to the final pressure p.sub.11(i). The following applies: p.sub.02(k)>p.sub.12(k)p.sub.12(i)>p.sub.11(i). In parallel, the vacuum chamber j/20 is brought to an initial pressure p.sub.02(j).

[0074] When the valve is changed from position 42 to position 43, the vacuum chambers are disconnected from the pumps and reconnected as follows: At valve position 43, vacuum chamber j/20 is evacuated with rotary vane vacuum pump 22 from an initial pressure p.sub.02(j) to a final pressure p.sub.12(j) and vacuum chamber k/20 is evacuated with rotary vane vacuum pump 21 from the initial pressure p.sub.12(k) to the final pressure p.sub.11(k). The following thereby applies: p.sub.02(j)>p.sub.12(j)p.sub.12(k)>p.sub.11(k). In parallel, the vacuum chamber i/20 is brought to an initial pressure p.sub.02(i).

[0075] The valve position is then changed from position 43 to position 41 and the cycle starts again from the beginning.

[0076] This arrangement is significantly more expensive than the rotary vane vacuum pump according to the invention in terms of its purchase and operating costs. In addition, its use in a packaging machine, in particular a rotary vacuum packaging machine, requires more installation space than the rotary vane vacuum pump according to the invention. Another disadvantage of this arrangement is the higher maintenance costs.

[0077] FIG. 2 shows a schematic representation of a two-stage rotary vane vacuum pump as is also known from the state of the art. In this case, the two stages evacuate two of three different vacuum chambers i/20, j/20 and k/20 simultaneously in a cyclical process. At the same time, the third vacuum chamber, which is not connected to one of the two stages, is ventilated. Stage 32 is the fore-vacuum stage, while stage 31 is the high-vacuum stage.

[0078] In valve position 41, the vacuum chamber i/20 is evacuated, with the fore-vacuum stage 32, from an initial pressure p.sub.02(i) to a final pressure p.sub.12(i), and the vacuum chamber j/20 is evacuated, with the high vacuum stage 31, from an initial pressure p.sub.01(j) to a final pressure p.sub.11(j). The following thereby applies: p.sub.02(i)>p.sub.12(i)p.sub.01(j)>p.sub.11(j). In parallel, the vacuum chamber k/20 is brought to an initial pressure p.sub.02(k).

[0079] When the valve is changed from position 41 to position 42, the vacuum chambers are disconnected from stages 31 and 32 of the pump and reconnected as follows: At valve position 42, the vacuum chamber k/20 with the fore-vacuum stage 32 is evacuated from an initial pressure p.sub.02(k) to a final pressure p.sub.12(k) and the vacuum chamber i/20 with the high vacuum stage 31 is evacuated from an initial pressure p.sub.01(i) to a final pressure p.sub.11(i). The following thereby applies: p.sub.02(k)>p.sub.12(k)p.sub.01(i)>p.sub.11(i). In parallel, the vacuum chamber j/20 is brought to an initial pressure p.sub.02(j).

[0080] When the valve is changed from position 42 to position 43, the vacuum chambers are disconnected from the pump stages and reconnected as follows: At valve position 43, the vacuum chamber j/20 with the fore-vacuum stage 32 is evacuated from an initial pressure p.sub.02(j) to a final pressure p.sub.12(j) and the vacuum chamber k/20 with the high vacuum stage 31 is evacuated from an initial pressure p.sub.01(k) to a final pressure p.sub.11(k). The following thereby applies: p.sub.02(j)>p.sub.12(j)p.sub.01(k)>p.sub.11(k). In parallel, the vacuum chamber i/20 is brought to an initial pressure p.sub.02(i).

[0081] The valve position is then changed from position 43 to position 41 and the cycle starts again from the beginning.

[0082] Here too the procurement costs are higher than with the rotary vane vacuum pump according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS ACCORDING TO THE INVENTION

[0083] FIG. 3 shows a schematic representation of the single-stage rotary vane vacuum pump 10 according to the invention with two inlets 1, 2, via whose two inlets 1, 2 two of three vacuum chambers i/20, j/20, k/20 are evacuated simultaneously. At the same time, the third vacuum chamber, which is not connected to one of the two inlets, is ventilated. Inlet 1 is the high vacuum inlet and inlet 2 is the fore-vacuum inlet: Inlets 1, 2 are each connected in turn to vacuum chambers i/20, j/20, k/20.

[0084] In the first valve position 41, the vacuum chamber i/20 is connected to the fore-vacuum inlet 2 and the vacuum chamber j/20 is connected to the high vacuum inlet 1. The vacuum chamber i/20 is evacuated there in an evacuation time t.sub.p2(i) from an initial pressure p.sub.02(i) to a final pressure p.sub.12(i), while, preferably simultaneously (t.sub.p2(i)=t.sub.p1(j)), the vacuum chamber j/20 is evacuated in an evacuation time t.sub.p1(j) from an initial pressure p.sub.01(j) to a final pressure p.sub.11(j). In this case, p.sub.02(i)>p.sub.12(i)p.sub.01(j)>p.sub.11(j) applies. Ideally, p.sub.12(i) and p.sub.01(j) are the same, i.e. their values preferably deviate from each other by a maximum of 25%, particularly preferably by a maximum of 15%, especially preferably by a maximum of 10%, most preferably by a maximum of 5%. The vacuum chamber k/20 is not connected to any of the inlets and is brought to an initial pressure p.sub.02(k) in parallel.

[0085] The valve position is then changed from valve position 41 to valve position 42. During the change, none of the vacuum chambers i/20, j/20 and k/20 is connected to an inlet of the pump.

[0086] In the second valve position 42, the vacuum chamber k/20 is connected to the fore-vacuum inlet 2 and the vacuum chamber i/20 is connected to the high vacuum inlet 1. The vacuum chamber k/20 is evacuated from an initial pressure p.sub.02(k) to a final pressure p.sub.12(k) in an evacuation time t.sub.p2(k), while, preferably simultaneously (t.sub.p2(k)=t.sub.p1(i)), the vacuum chamber i/20 is evacuated from the initial pressure p.sub.01(i) to the final pressure p.sub.11(i) in an evacuation time t.sub.p1(i). In this case, p.sub.02(k)>p.sub.12(k)p.sub.01(i)>p.sub.11(i) applies. Ideally, p.sub.12(k) and p.sub.12(i) are the same, i.e. their values preferably deviate from each other by a maximum of 25%, particularly preferably by a maximum of 15%, most preferably by a maximum of 10%, most preferably by a maximum of 5%. The vacuum chamber j/20 is not connected to any of the pump inlets and is brought to the initial pressure p.sub.02(j) in parallel.

[0087] The valve position is then changed from valve position 42 to valve position 43. During the change, none of the vacuum chambers i/20, j/20 and k/20 is connected to an inlet of the pump.

[0088] In the third valve position 43, the vacuum chamber j/20 is connected to the fore-vacuum inlet 2 and the vacuum chamber k/20 is connected to the high vacuum inlet 1. The vacuum chamber k/20 is evacuated from the initial pressure p.sub.01(k) to the final pressure p.sub.11(k) in an evacuation time t.sub.p1(k), while, preferably simultaneously (t.sub.p2(j)=t.sub.p1(k)), the vacuum chamber j/20 is evacuated from an initial pressure p.sub.02(j) to the final pressure p.sub.12(j) in an evacuation time t.sub.p2(j). In this case, p.sub.02(j)>p.sub.12(j)p.sub.01(k)>p.sub.11(k) applies. Ideally, p.sub.01(k) and p.sub.12(j) are the same, i.e. their values preferably deviate from each other by a maximum of 25%, particularly preferably by a maximum of 15%, most preferably by a maximum of 10%, most preferably by a maximum of 5%. The vacuum chamber i/20 is not connected to any of the inlets of the pump and is brought to an initial pressure p.sub.02(i) in parallel.

[0089] The valve position is then changed from valve position 43 to valve position 41 and the cycle starts again from the beginning.

[0090] FIG. 4 shows a cross section of an embodiment of the rotary vane vacuum pump 10 according to the invention with six vanes 7, 7, 7 etc. in the corresponding slots 8, 8, 8 etc., with the arrow at the top indicating inlet 1, the arrow at the bottom right indicating inlet 2 and the arrow at the bottom left indicating outlet 3

[0091] FIG. 5 also shows a cross section of an embodiment of the rotary vane vacuum pump 10 according to the invention with six vanes 7, 7, 7 etc. in the corresponding slots 8, 8, 8 etc., with the arrow at the top indicating inlet 1, the arrow at the bottom right indicating inlet 2 and the arrow at the bottom left indicating outlet 3. The rotary vane vacuum pump according to FIG. 5 differs from that according to FIG. 4 in the position of the first inlet 1.

[0092] In the embodiment according to FIG. 4 the two inlets 1 and 2 are separated by at least one vane. In the rotor position shown, the two inlets 1 and 2 are separated by exactly one vane 7. The conveying chambers 9 und 9 are connected to the inlet 1, while the conveying chamber 9 is connected to the inlet 2. In the state shown in FIG. 5, the conveying chamber 9 separates inlet 1 (connected to conveying chamber 9) from inlet 2 (connected to conveying chamber 9). This leads to increased internal tightness, since two vanes and thereby a complete conveying chamber 9 between the two inlets 1 and 2 serves as buffer between them. The return flow losses are thereby less, which leads to a better end pressure and suction capability. This means that the pump-down times are shorter than they would be without this buffer.

LIST OF REFERENCE NUMERALS

[0093] 10 vacuum pump, in particular rotary vane vacuum pump [0094] 1 first inlet/high-vacuum inlet [0095] 2 second inlet/fore-vacuum inlet [0096] 3 outlet [0097] 11 connection for the first inlet [0098] 12 connection for the second inlet [0099] 4 cylinder [0100] 5 rotor [0101] 6 conveying chamber [0102] 7, 7, 7 etc. vane [0103] 8, 8, 8 etc. slot(s) [0104] 9, 9, 9 etc. conveying chamber(s) [0105] 14 inner wall of the cylinder [0106] 17, 17, 17 etc. sealing point(s) [0107] 20, 20, 20 etc. vacuum chamber(s) [0108] 21 high-vacuum pump [0109] 22 fore-pump [0110] 31 high-vacuum stage [0111] 32 fore-vacuum stage [0112] 41, 42, 43 valve position