SINGLE SCREW COMPRESSOR

Abstract

A single screw compressor comprises a main rotor and at least one gate rotor, a casing for the main rotor having a discharge port at a discharge end of the casing, and a slide slidable within a bore in the casing adjacent the main rotor. The slide has a cut-out (6) between first (2) and second (4) sealing parts of the slide, the slide is slidable between a high volume ratio position where the cut-out (6) is within the casing and provides a path to the discharge port, and a low volume ratio position where the slide is beyond the discharge end of the casing to provide a fixed discharge path in the bore of the casing.

Claims

1. A single screw compressor comprising a main rotor and at least one gate rotor, a casing for the main rotor having a discharge port at a discharge end of the casing, and a slide slidable within a bore in the casing adjacent the main rotor, the slide having a cut-out between first and second sealing parts of the slide, the slide being slidable between a high volume ratio position where the cut-out is within the casing and provides a path to the discharge port, and a low volume ratio position where the slide is beyond the discharge end of the casing to provide a fixed discharge path in the bore of the casing.

2. A compressor according to claim 1, wherein the first, i.e. upstream, sealing part of the rotor, has a surface facing away from the cut-out that is substantially in a plane transverse to the axes of the slide and the main rotor.

3. A compressor according to claim 1, wherein the first, i.e. upstream, sealing part of the rotor, has a surface facing away from the cut-out that is inclined to a plane transverse to the axes of the slide and the main rotor at an angle substantially the same as the main rotor pitch angle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which;

[0013] FIG. 1 shows the known capacity control slide discussed above;

[0014] FIG. 2 shows the known VR control slide discussed above;

[0015] FIGS. 3 and 4 are views showing the known VR control slide and its leakage paths;

[0016] FIG. 5 shows a slide according to an embodiment of the invention;

[0017] FIGS. 6 and 7 show the slide of FIG. 5 at different positions in the compressor;

[0018] FIG. 8 shown a slide according to an alternative embodiment; and

[0019] FIGS. 9 and 10 show the slide of FIG. 5 at different positions in the compressor.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0020] FIG. 5 shows a slide according to the invention having sealing parts 2, 4 and a cut-out 6.

[0021] FIG. 6 shows the slide of FIG. 5 positioned in towards the main casing alongside the main rotor. The cut-out 6 provides an accurate high VR discharge port.

[0022] FIG. 7 shows how a lower VR is achieved. The slide is pulled out from the casing so that it is beyond the main rotor and thus the VR is formed from the port 8 remaining in the casing.

[0023] The slide of FIGS. 5 to 7 is a simple slide. The higher VR slide discharge port provided by the cut-out 6 correctly aligns with the rotor flute, but when the slide is withdrawn beyond the rotor the remaining low VR fixed port does not match the true VR requirement.

[0024] FIGS. 8 to 10 show an alternative slide which has the same high VR cut-out as the slide of FIGS. 5 to 7. However this slide also has the correct low VR remaining in the casing when the slide is moved out of engagement beyond the rotor as shown in FIG. 10.

[0025] The simple slide of FIGS. 5 to 7 is easier to produce and the VR compromise is less detrimental at the Low VR operating conditions than at higher VR conditions. The true VR slide of FIGS. 8 to 10 will provide the highest efficiency.