Cooled dry vacuum screw pump

Abstract

The present invention relates to rotary screw positive displacement machines used as a vacuum pump wherein additional intake air is provided allowing cooling to the invention which permits extended operation at extreme vacuum pressure. The rotary screw nature of the vacuum pump allows operation without additional lubrication with the additional intake air ensuring that thermal expansion will not disrupt the tight tolerances of the invention. The invention allows simultaneous operation as a vacuum pump and air compressor.

Claims

1. A rotary screw vacuum pump comprising: two or more rotors having meshed helical formations and being supported for rotation in respective bores inside a casing, wherein the operation of the said rotors introduces, compresses and discharges gas from the rotary screw vacuum pump, and the said rotors are driven by an external motive force; wherein the casing comprises: a gas inlet port for admitting gas to the casing; a gas outlet port for discharging gas from the casing; and at least one gas injection port located in a wall of the casing for the introduction of the gas at atmospheric pressure at an intermediate point between the gas inlet port and the gas outlet port, wherein the gas injection port is a single diagonal channel the direction of which is the same as the diagonal direction of the rotor adjacent to the said gas injection port.

2. The rotary screw vacuum pump of claim 1 wherein there are two rotors and one of the said rotors of which is a male rotor and the other of which is a female rotor.

3. The rotary screw vacuum pump of one of claims 1-2 wherein one of the rotors is driven directly by the external motive force and the remaining rotors are driven through gears connected to the external motive force.

4. The rotary screw vacuum pump of one of claims 1-2 wherein all of the rotors are driven through gears connected to the external motive force.

5. The rotary screw vacuum pump of claim 2 wherein the male rotor is driven directly by the external motive force and the female rotor is driven through gears connected to the external motive force.

6. The rotary screw vacuum pump of claim 2 wherein the female rotor is driven directly by the external motive force and the male rotor is driven through gears connected to the external motive force.

7. The rotary screw vacuum pump of claim 2 wherein the male rotor and the female rotor are both driven through gears connected to the external motive force.

8. The rotary screw vacuum pump of any of the preceding claims wherein the gas inlet port and the gas outlet port are connected through suitable ducting to a valve to provide for control of the vacuum and the gas being compressed and discharged.

9. The rotary screw vacuum pump of any of the preceding claims wherein the gas is air.

10. The rotary screw vacuum pump of any of claims 2 or 3-9 wherein the male rotor has three lobes and the female rotor has five lobes.

11. The rotary screw vacuum pump of any of claims 2 or 3-9 wherein the male rotor and the female rotor have meshed helical profiles.

12. A rotary screw vacuum pump for mobile operation comprising: a male rotor of three (3) lobes and a female rotor of five (5) lobes having meshed helical formation; the male rotor and the female rotor being supported for rotation in respective bores inside a casing, wherein the operation of the male rotor and female rotor are driven by an external motive force through gears which introduces, compresses and discharges air from the invention; wherein the casing comprises: an air inlet port for admitting air to the casing; an air outlet port for discharging air from the casing; and an air injection port located in a wall of the casing for the introduction of the air at an intermediate point between the air inlet port and the air outlet port, wherein the said air injection port is a single diagonal channel the direction of which is the same as the diagonal direction of the rotor adjacent to the said air injection port.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described by way of example with reference to the drawings, in which:

(2) FIG. 1 is a simplified cut-away view of the invention from the bottom.

(3) FIG. 2 is a simplified cut-away view of the invention from the side which shows the location of the air injection port.

(4) FIG. 3 is a simplified view of the invention seem from the air inlet.

(5) FIG. 4 is a cross-section of a preferred embodiment of the male or main rotor of the invention seen from the air outlet end.

(6) FIG. 5 is a hidden-line drawing of a side view of a preferred embodiment of the male or main rotor of the invention.

(7) FIG. 6 is a cross-section of a preferred embodiment of the female or gate rotor of the invention seen from the air outlet end.

(8) FIG. 7 is a hidden-line drawing of a side view of a preferred embodiment of the female or gate rotor of the invention.

(9) FIG. 8 is a detailed view of a preferred embodiment of the assembled invention.

(10) FIG. 9 is an exploded view of all of the parts of a preferred embodiment of the invention.

(11) FIG. 10 is a table of simulation results with the injection port closed.

(12) FIG. 11 is a table of simulation results with the injection port open.

DETAILED DESCRIPTION OF THE INVENTION

(13) In the following detailed description, only certain exemplary embodiments have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of this description.

(14) The same reference numerals indicate the same members in all of the drawings.

(15) FIG. 1 shows a simplified cross-sectional view of the invention from the bottom. The figure shows the casing 1, the air inlet end of the casing 65, and the air injection port 70 and the actual air injection opening in the casing 71. Not shown is the air outlet port which is on the opposite side of the casing. Rotational force is applied to the shaft 80 which is directly connected to the gate rotor 5 and which also drives the main rotor 4 through the gearbox 82, in a direction opposite to that of the gate rotor 5 as indicated in the drawing. The compression of the air between the rotors 4 and 5 causes air to be drawn in at the air inlet end of the casing 65 creating a vacuum.

(16) The lobes of the main rotor 4, the interaction of the lobes of the gate rotor 5 with the grooves of the main rotor 4 and the wall of the casing 1 create a number of moving chambers of air 90. Three such moving chambers of air are shown as 90a, 90b and 90c. Similar unlabeled moving chambers of air are created on the opposite side of the casing.

(17) As the main rotor 4 turns, the moving chamber of air 90b uncovers the air injection port opening 71 in the air injection port 70. Because the air in chamber 90b is under a vacuum, air at atmospheric pressure and temperature enters into the said air chamber in turn causing the air in the system to be cooled.

(18) FIG. 2 shows a simplified cut-away view of the invention from the side including the air injection port opening 71. The main rotor 4 is adjacent to the air injection port opening 71 in the casing 1. The main rotor 4 is driven through the gearbox 82 in the direction shown on the drawing.

(19) The driving of the main rotor 4 causes a vacuum to be created at the air inlet end of the casing 65 causing air to enter the device and create the previously described moving chambers of air. The moving chambers of air are under a vacuum. Accordingly, when the moving chamber of air 90b is cut off from outside air from the air inlet end of the casing 65 by the interaction of the rotor 4 and the casing 1 at the point labelled 92, and the air injection opening 71 is uncovered, air at atmospheric pressure and temperature enters into the said air chamber in turn causing the air in the system to be cooled.

(20) Through the operation of the rotors, when the moving chambers of air reach the outlet opening 92, compressed air is exhausted through the outlet port 66.

(21) FIG. 3 is a simplified view of the invention seem from the air inlet 65. The main rotor 4 and the gate rotor 5 are seen behind the end plate 2 which is in turn attached to the casing 1. The outlet port 66 and the air injection port 70 are also seen.

(22) As the rotors 4 and 5 rotate in the direction indicated in the drawing, the lobes of the rotors 4 and 5 begin to define one of the moving chambers of air 90. The end plate 2 acts as a wall of the moving chamber of air 90. The movement of air created by the rotation of the rotors creates a vacuum. The moving chamber of air 90 is initially compressed by the action of the rotors causing the air to be heated. The moving chamber of air 90 continues the length of the rotors until cooling air at atmospheric pressure is introduced at the air injection port 70. The air is finally exhausted at the air outlet 66.

(23) FIG. 4 shows a cross-section of a preferred embodiment of the main or male rotor 4 of the invention seen from the air outlet end of the rotor. The rotor comprises three (3) lobes about a central axis 95. Each lobe has a leading edge 96 and a groove 97. The actual shape of the rotor lobes is obtained as described above.

(24) FIG. 5 shows a hidden-line drawing of a side view of a preferred embodiment of the main or male rotor 4 of the invention. The drawing shows a leading edge 96 and a groove 97 in a right-handed thread.

(25) FIG. 6 shows a cross-section of a preferred embodiment of the gate or female rotor of the invention seen from the air outlet end of the rotor. The rotor comprises five (5) lobes about a central axis with each lobe having a leading edge 98 and a groove 99. The actual shape of the rotor lobes is obtained as described above.

(26) FIG. 7 is a hidden-line drawing of a side view of a preferred embodiment of the gate or female rotor 5 of the invention. The drawing shows a leading edge 98 and a groove 99 in a left-handed-thread.

(27) It should be clear from the description and the detailed description of the drawings herein that the main or male rotor and gate or female rotor must be established in a fashion by which they will work together. Because the rotors operate in different directions, the handedness of the threads of each of the rotors must be opposite in a two-rotor invention. In addition, the number and shaping of the lobes must be designed to work together.

(28) FIG. 8 shows a detailed view of a preferred embodiment of the invention. Rotational force is applied to the shaft 80 and translated through the gearbox 82 to the rotors which are not seen in the drawing. A four-way diverter valve 44 allows connection of vacuum and compressed air at two different points 45 on the valve. The diverter valve 44 is in turn connected to the air inlet 65 of the casing 1 through the intake elbow 41. Atmospheric air for cooling is applied to the air injection port through the air injection elbow 52 after the air injection port plug 53 is removed. The outlet port 66 is connected to the diverter valve 44 through the exhaust elbow 42.

(29) In operation, the invention produces both a vacuum at the air inlet 65 and compressed air at the outlet port 66. The use of the elbows 41 and 42 and the four-way diverter valve 44 allows for the use of both vacuum and compression at the same time and in a controllable fashion through the two ports 45. The four-way diverter valve 44 allows the ports 45 to be switched between vacuum and compressor operation. Additional piping connected to the ports 45 would be used in practice to apply the vacuum and compression as required.

(30) Although the preferred embodiment of the invention is shown in a vertical or upright position in the drawing, because the air injection elbow 52 is located on one side of the invention, the invention can also be mounted on the side opposite to the air injection elbow 52 in a horizontal configuration.

(31) FIG. 9 shows an exploded view of the parts of a preferred embodiment of the invention. The rotors 4 and 5 are mounted in the casing 1 using appropriate mounting hardware. The hardware allows gear 6 attached to the main or male rotor 4 and gear 8 attached to the gate or female rotor 5 to, in turn, be driven by gear 10. Gear 10 is extended outside of the housing gearbox cover 3 in order to be connected to external motive force. The air injection port 70 is covered with appropriate hardware 54 which allows the introduction of air at atmospheric pressure and temperature through the air injection elbow 52 when the air injection port plug 53 is removed. The hardware 54 and air injection elbow 52 prevent any interference or interaction with the main or male rotor 4 rotating adjacent to the air injection port 70. The air inlet port 2 and air outlet port are connected to elbows 41 and 42 respectively to the four-way valve 44. The use of the elbows 41 and 42 also prevent any interference or interaction with the rotors while in operation. Depending on the setting of the four-way valve 44, compressed air or vacuum is available at the two ports 45.

(32) FIG. 10 shows simulation results of the invention with the air injection port 70 closed. As can be noted in the results, output gas temperature are in the range of 574 to 668 degrees Celsius. Output temperatures in this range would require special handling in operational situations with personnel in the near vicinity of the device.

(33) FIG. 11 shows simulation results of the invention with the air injection port 70 open. Operational output air temperatures are between 200 and 210 degrees Celsius. Such temperatures can be handled easily in operational situations with personnel in the near vicinity of the device.

(34) The present application discloses a rotary screw vacuum pump having the ability to operate at a lower outlet air temperature. The invention disclosed reduces maintenance costs by reducing the size of the pump, that the pump may be operated without lubrication and in a mode that allows both vacuum and compressed air to be provided at the same time.

(35) The above description presents the best mode contemplated for carrying out the present invention, and of the manner and process of making and using it, in such full, clear, concise, and exact terms as to enable any person skilled in the art to which it pertains to make and use this invention. This invention is, however, susceptible to modifications and alternate constructions from that discussed above that are fully equivalent.

(36) Consequently, this invention is not limited to the particular embodiments disclosed. On the contrary, this invention covers all modifications and alternate constructions coming within the spirit and scope of the invention as generally expressed by the following claims, which particularly point out and distinctly claim the subject matter of the invention. While the disclosure has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive.

(37) All references cited are incorporated herein by reference in their entireties. To the extent publications and patents or patent applications incorporated by reference contradict the disclosure contained in the specification, the specification is intended to supersede and take precedence over any such contradictory material.

(38) Although the foregoing has been described in some detail by way of illustrations and examples for purposes of clarity and understanding, it is apparent to those skilled in the art that certain changes and modifications may be practiced. Therefore, the description and examples should not be construed as limiting the scope of the invention to the specific embodiments and examples described herein, but rather to also cover all modification and alternatives coming with the true scope and spirit of the invention.