Screw Vacuum Pump Unit

The present invention relates to a screw pump unit.

As disclosed in the official gazette of Japanese patent application Laid-open No. 60-216089 (the specification of U.S. Ser. No. 701,199), a prior-art screw vacuum pump is such that a pair of male and female rotors which rotate meshing with each other are received in the working chamber of a casing which has suction ports and discharge ports, and that the rotors are driven by a driver, whereby a gas is imbibed from a space to have its pressure lowered, into the interstice between both the rollers, and it has its pressure raised and is exhausted into the atmosphere.

In the prior-art unit, the axes of the male rotor and female rotor are arranged within a horizontal plane, and both the rotors are arrayed within the horizontal plane, so that a floor area required for installation enlarges. Moreover, on account of the structure in which the suction ports and discharge ports of the casing are arranged on both the sides of tne horizontal plane (in the upper surface of the casing and the lower surface thereof), either the suction ports or the discharge ports are lie in the lower surface of the casing. Therefore, the job of connecting pipes to the suction ports or the discharge ports lying in the lower surface of the casing must be carried out at the lower surface of the casing, and the job efficiency is very inferior. Further, in a case where reaction products have deposited in the vacuum pump as in use for the evacuation of a semiconductor manufacturing plant, it is not easy to eliminate the products or to routinely inspect the situation of deposition. In performing these operations, there are the problems that pipes need to be detached and that special tools are required.

An object of the present invention is to provide a screw vacuum pump unit which can facilitate maintenance.

Another object of the present invention is to provide a screw vacuum pump unit which can decrease a floor area for installation and can simultaneously faciliate maintenance.

The present invention for accomplishing the objects is characterized in that both a screw block and a motor are mounted on one side surface of the casing of a speed change gear, that the axes of both male and female rotors in the screw block are arranged in vertical adjacency within a plane substantially perpendicular to a horizontal plane, and that suction ports and discharge ports are arranged on both sides with the perpendicular plane intervening therebetween.

Since, as described above, the male rotor and the female rotor are arrayed in the perpendicular (vertical) direction, the floor area suffices with an extent for receiving a single rotor and can be made smaller than in the prior art. Simultaneously, since the suction ports and the discharge ports are respectively located on the right side and left side of both the rotors and are prevented from lying at the lower surface of the casing, a job for connecting pipes to the suction and discharge ports and jobs for maintenance, such as the clearing and inspection of deposits, can be readily conducted.

FIG. 1 is an exterior view of a screw vacuum pump showing an embodiment of the present invention;

FIG. 2 is a sectional view taken along line II--II in FIG. 1;

FIG. 3 is a sectional view taken along line III--III in FIG. 1;

FIG. 4 is a sectional view showing an embodiment of the present invention in which only one horizontal suction port is provided;

FIG. 5 is a sectional view showing an embodiment of the present invention in the case where the whole vacuum pump is enveloped in a sound-insulating cover;

FIG. 6 is a sectional view of the essential portions of an embodiment in which a silencer cartridge is arranged in a discharge port; and

FIG. 7 is a sectional view of the silencer cartridge.

FIG. 1 is an exterior view of a screw vacuum pump unit which has two suction ports, FIG. 2 is a sectional view taken along line II--II in FIG. 1, and FIG. 3 is a sectional view taken along line III--III in FIG. 1.

A male rotor 1 has a plurality of twisted lands and grooves, while a female rotor 2 has a plurality of twisted grooves and lands. The lands of the male rotor 1 are shaped so as to mesh with the grooves of the female rotor 2, and the grooves of the male rotor 1 so as to mesh with the lands of the female rotor 2. A screw casing is constructed of a main casing 3, and an end casing 4 which is coupled to one end face of the main casing 3 by bolts. The main casing 3 defines therein a working chamber 30, which is surrounded with a water jacket 27. A cover 5 is coupled to the end face of the end casing 4 remote from the main casing 3. The male rotor 1 and female rotor 2 mentioned above are received in the working chamber 30 of the main casing 3.

Bearings 7, 8 and shaft seals 23, 24 are arranged between both the rotors 1, 2 and the main casing 3. Likewise, bearings 9, 10 and shaft seals 25, 26 are arranged between both the rotors 1, 2 and the end casing 4. The two rotors 1 and 2 are rotatably supported by the bearings 7, 8, 9 and 10.

Gears 11 and 12 are coupled to one end side of both the rotors 1, 2, and they mesh with each other. The gear 12 meshes with a drive gear 13 which is coupled to the shaft of a motor 14. The gears 11, 12 and the drive gear 13 are received in the gear casing 6 of a speed change gear. Herein, the male rotor r1, female rotor 2 and motor 14 are arranged respectively one below the other in such a manner that the respective axes of both the rotors 1, 2 and the motor 14 are horizontal and are parallel to one another and that the axes as viewed from the gear side are aligned within a plane extending in the perpendicular (vertical) direction. That is, the axis centers of the rotors 1 and 2 and the motor 14 are arranged one below the other on a vertical line so as to decrease the width of the pump in the horizontal direction. The motor 14 and the screw casing, which receives the male rotor 1 and the female rotor 2 therein, are arranged on one side of the gear casing 6, and the flange 3f of the main casing 3 is coupled to the gear casing 6 by bolts. The main casing 3 is provided with suction ports 3a, 3b on one side thereof, and with discharge ports 3c, 3d, 3e on the other side thereof. The suction ports 3a and 3b are held in communication with the working chamber 30 by the suction port 3a, while the discharge ports 3c, 3d and 3e are held in communication with the same by the discharge port 3d. The suction port 3a extends in the horizontal direction, and the suction port 3b communicates therewith orthogonally from above. On the other hand, the discharge port 3d can discharge gases in the horizontal direction, the discharge port 3c communicates with the port 3d orthogonally from above, and the discharge port 3e communicates with the port 3d orthogonally from below. In other words, the suction port is composed of a suction port 3a capable of sucking in the horizontal direction and a suction port 3b capable of sucking in a direction orthogonal to suction port 3a. The discharge port 3d can discharge in the horizontal direction, whereas discharge port 3c can discharge in one direction orthogonal to port 3d and port 3e can discharge in another direction orthogonal to port 3d. As a result, the suction port has two possible directions and the discharge port has three possible directions to facilitate piping and maintenance. Numeral 16 designates a suction side stop collar, and symbols 17a and 17b denote discharge side stop collars.

The details of the structure of the screw block are substantially the same as described in the specification of U.S. Ser. No. 701,199, and the details of the shaft seals 23, 24, 25 and 26 as described in U.S. Pat. No. 4,487,563.

Besides, the embodiment comprises an oil pump (not shown) which feeds oil 29 to the meshing parts of the bearings 7, 8, 9 and 10 and the gears 11, 12 and 13.

When the motor 14 is driven, the rotors 1 and 2 are rotated through the drive gear 13 and the gears 11 and 12, and the fluid of a chamber to be evacuated is imbibed from the suction port 3b into the working chamber 30 (in FIG. 3, the suction port 3a is held closed by the stop collar 16) and is emitted from the discharge port 3c through discharge openings 15a and 15b (in FIG. 3, the discharge ports 3d and 3e are held closed by the respective stop collars 17a and 17b). In a case where the fluid is to be imbibed from the suction port 3a for the convenience of piping, it is easy that the suction side stop collar 16 is detached to open the suction port 3a and that the suction port 3b is closed. Likewise, on the discharge side, it is easy to select a necessary one from among the discharge ports 3c, 3d and 3e and to connect a pipe thereto. In addition, in such a case where deposits having adhered to the interior of the vacuum pump unit due to reaction gases are to be cleared, a vertically penetrating passage extending from the discharge port (a passage extending from the discharge port 3c in communication therewith) makes it possible to sweep away the deposits with a brush or the like from the upper discharge port 3c and to put them out from the lower discharge port 3e. Therefore, operations for maintenance can be readily performed.

According to the present embodiment, the rotors 1, 2 and the motor 14 are so arranged that their axes are horizontal and are parallel to one another and that the axes viewed from the axial end side are aligned on the perpendicular plane. Moreover, the screw casing which receives the male rotor 1 and female rotor 2 therein, and the motor 14 are arranged on one side of the gear casing 6. Therefore, the widthwise and lengthwise dimensions of the pump proper can be sharply reduced to make the installation area smaller, and suction and discharge pipes can be readily connected to facilitate operations for maintenance such as the clearing of deposits at the discharge ports.

FIG. 4 is a sectional view corresponding to FIG. 3, of a screw vacuum pump unit which shows an embodiment of the present invention and which is provided with a single horizontal suction port.

FIG. 5 is a sectional view showing an embodiment in which the present invention is applied to a case of enveloping the whole vacuum pump in a sound-insulating cover in order to reduce noise (this figure corresponds to a section III--III in the case of enveloping the whole vacuum pump of FIG. 1 in a sound-insulating cover). Referring to FIG. 5, symbols 18a and 18b denote suction pipes which connect the sound-insulating cover 21 and the suction ports of the pump proper, symbols 19a, 19b and 19c denote discharge pipes which connect the sound-insulating cover and the discharge ports of the pump proper, and numeral 20 denotes a sound-absorbing material which is stuck to the inner surface of the sound-insulating cover. As illustrated in the figure, a plurality of piping ports are provided in the upper parts and sideward parts of the sound-insulating cover. This brings forth the effect that piping is very easy. Moreover, the discharge ports 3c, 3d and 3e are provided in three directions, so that when reaction products have deposited at the discharge ports, the deposits can be readily cleared from the upper port 3c or the horizontal port 3d and put out from the lower port 3e. This brings forth the effect that the maintenance of the pump unit is very easy.

FIG. 6 shows an embodiment in which silencer cartridges 22 are inserted in the discharge ports 3c, 3d and 3e in order to facilitate the clearing and simultaneously to silence the pump unit. As shown in FIG. 7, the silencer cartridge 22 is constructed of an outer cylinder 22c, an inner cylinder 22b which is formed of a punching metal plate (porous steel plate), and a sound-absorbing material 22a which is packed between the inner and outer cylinders 22b, 22c.

When the silencer cartridges 22 are inserted in the discharge ports in this manner, reaction products deposit on the inner surfaces of these silencer cartridges. When a predetermined period of time has lapsed or when the pump unit is to be inspected, the stop collars 17a and 17b are detached, and the silencer cartridges 22 are replaced with new ones, whereby the reaction products having deposited at the discharge ports or in discharge regions can be eliminated.