Method of assembling a rotary apparatus

Abstract: A rotary apparatus (10), such as a pneumatic motor, comprises an end plate (20) having a race cavity (22), a main rotor (30) with a stub shaft (32) extending from one end, and a bearing (40), which includes an outer race (42) seated in the race cavity (22) and an inner race (44) having a central bore (50). The stub shaft (32) is fitted into the central bore (50) with a frictional fit. The threaded shank (62) of a screw (60) is threaded into a threaded socket (80) in the stub shaft (32) and is used to draw the stub shaft (32) into the central bore (50) with a washer (70) bearing against a head (64) of the screw, and against the inner race (44), whereby a controlled gap (g) can be provided between an outer surface (36) of the main rotor (30) and an inner surface (26) of the end plate (20).

Description: This invention pertains to a method of assembling a rotary apparatus of a type comprising a static structure; a rotary structure, and a bearing interposed between the static and rotary structures, as exemplified by a pneumatic motor. This invention provides a method for establishing a controlled gap between a main rotor and an end plate of such apparatus. Commonly, the static structure of a rotary apparatus of the type noted above includes an end plate, which has a cavity to accommodate a bearing race. It is convenient to refer to the cavity as a race cavity. Commonly, the rotary structure thereof includes a main rotor and a stub shaft extending from one end of the main rotor, and the bearing includes an outer race seated in the race cavity of the end plate and an inner race having a central bore to accommodate the stub shaft, which is sized so as to be fittable into the central bore with a frictional fit. Commonly, the bearing is a rolling contact bearing including plural rolling elements interposed between the outer and inner races, as exemplified by a ball bearing. Heretofore, it has been common for the outer race of the bearing to be press-fitted into the race cavity and for the stub shaft to be press-fitted into the central bore of the inner race, via a hydraulic or mechanical press. Generally, it is satisfactory to employ a hydraulic or mechanical press to press the outer race properly into the race cavity, as it can be easily ascertained when the outer race has been pressed fully into the race cavity. However, it is difficult to employ a hydraulic or mechanical press to press the stub shaft properly into the inner race, as it is necessary to provide a gap within a narrow range of tolerances ( e.g. 0.05 mm to 0.10 mm) between the main rotor and the end plate for proper operation of the rotary apparatus. It may be then necessary to employ gauges to assure a gap has been provided there-between which falls within such a range. According to this invention, a method of assembling a rotary apparatus having an axis and comprising a static structure, a rotary structure, and a rolling contact bearing interposed between the static and rotary structures, the static structure including an end plate having a race cavity, the rotary structure including a main rotor having a stub shaft extending from one end of the main rotor and including a distal end and a screw threaded socket open at the distal end, the rolling contact bearing including an outer race, an inner race, and plural rolling elements interposed between the outer and inner races, the outer race being seated in the race cavity of the end plate, the inner race having a central bore and having an outer end and an inner end, the stub shaft having a distal end and fitting into the central bore, from the inner end of the inner race, with a frictional fit, whereby to assemble the rotary apparatus a screw having a threaded shank and an integral head, is threaded into the threaded socket, a washer having an outer face and an inner face, is interposed between the screw head and the outer end of the inner race, the threaded shank being screwed into the threaded socket with the outer face of the washer bearing against the screw head and the inner face of the washer bearing against the outer end of the inner race thereby drawing the stub shaft into the central bore until the inner face of the washer bears against the distal end of the stub shaft, thereby providing a controlled gap (g) between the main rotor and the end plate, whereupon the screw and the washer may be optionally removed. Even if a hydraulic or mechanical press is employed to press the stub shaft partly into the central bore, the screw is still used to draw the stub shaft further into the central bore to define the required controlled gap. Although this invention has been applied initially to a pneumatic motor, it is contemplated that this invention may prove to be widely applicable to other rotary apparatus, whether pneumatic, hydraulic, mechanical, or electrical. A particular embodiment of the present invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a perspective view of a rotary apparatus, such as a pneumatic motor, of the type noted above; and, Figure 2, on a larger scale, is a fragmentary, partly cross-sectioned view of such a rotary apparatus constituting a preferred embodiment of this invention. As shown in Figure 1, a pneumatic motor 10 exemplifies a rotary apparatus of the type noted above. Thus, the pneumatic motor 10 defines an axis and comprises a static structure, a rotary structure, and a bearing interposed between the static and rotary structures. As shown in Figure 2 the static structure includes an end plate 20, which has a race cavity 22 with a chamfered edge 24 and which has an inner surface 26 normal to the axis defined by the pneumatic motor 10. The end plate 20 is mounted suitably within an outer housing 12, which is shown in Figure 1, with an 0-ring 28 surrounding and sealing the end plate 20. Further, the rotary structure includes a main rotor 30 and a stub shaft 32, which extends axially from one end of the main rotor 30 and which has a distal end 34. The main rotor 30 and the stub shaft 32 are integral, preferably being machined from a single piece of aluminum. At the same end, the main rotor 30 has an outer surface 36, which is normal to the axis defined by the pneumatic motor 10. As shown in Figure 1, the main rotor 30 has radial vanes 38, which are partially omitted in Figure 2. Moreover, a rolling contact bearing 40 is interposed between the static and rotary structures. The rolling contact bearing 40 includes an outer race 42, an inner race 44, and plural rolling elements 46 interposed between the outer race 42 and the inner race 44. Preferably, as shown, the outer race 42 is enclosed by an outer collar 48. As shown, the rolling contact bearing 40 is a conventional ball bearing, in which the rolling elements 46 are balls. The outer race 42, as enclosed by the outer collar 48, is seated in the race cavity 22 of the end plate 20. A hydraulic or mechanical press (not shown) is employed to press the outer race 42, as enclosed by the outer collar 48, fully into the race cavity 22 with an interference fit. The chamfered edge 24 facilitates initial entry of the outer race 42, as enclosed by the outer collar 48, into the race cavity 22. The inner race 44 has a central bore 50. The stub shaft 32 is sized so as to be fittable into the central bore 50, through an inner end 52 of the central bore 50, with an interference fit. The distal end 34 of the stub shaft 32 is chamfered, as shown, so as to facilitate initial entry of the stub shaft 32 into the central bore 50. It is contemplated to employ such a press to press the stub shaft 32 partly but not fully into the central bore 50 and to employ means having a threaded connection to the stub shaft 32 to draw the stub shaft 32 further into the central bore 50. It also is contemplated by this invention to employ means having a threaded connection to the stub shaft 32 to draw the stub shaft 32 initially and further into the central bore 50. In either instance, the stub shaft 32 is drawn into the central bore 50 for a sufficient distance to provide a controlled gap g within a narrow range of tolerances (e.g. 0.05 mm to 0.10 mm) between the outer surface 36 of the main rotor 30 and the inner surface 26 of the end plate 20. As shown in Figure 2, a screw 60 having a threaded shank 62 and having an integral head 64 with a driving socket 66 to accommodate a driving tool (not shown) and an annular washer 70 having an outer surface 72 and an inner surface 74 are employed to draw the stub shaft 32 into the central bore 50. The threaded shank 62 is threadable into a threaded socket 80 extending axially into the rotary structure, opening at the distal end 34 of the stub shaft 32. As shown in Figure 2, the threaded socket 80 extends through the stub shaft 32, into the main rotor 30. For assembly, a driving tool co-acting with the driving socket 66 in the screw head 64 is used to drive the screw 60 so that the threaded shank 62 is threaded into the threaded socket 80. The threaded shank 62 is threaded into the threaded socket 80 until the outer surface 72 of the washer bears against the screw head 64 and the inner surface 74 of the washer 70 bears against the distal end 34 of the stub shaft 32 and against an outer end 82 of the inner race 44, so as to draw the stub shaft 32 into the central bore 50 for a sufficient distance to provide the controlled gap g between the outer surface 36 of the main rotor 30 and the inner surface 26 of the end plate 20, whereupon the screw 60 and the washer 70 may be optionally removed. Advantageously, the assembling method described above enables the gap g to be precisely controlled without employing gauges when the rotary apparatus is assembled. As an example, threads designated M6 x 1.0 mm provide axial movement of one millimetre per 360° of rotation.

Claims: A method of assembling a rotary apparatus (10) having an axis and comprising a static structure (12), a rotary structure (30), and a rolling contact bearing (40) interposed between the static (12) and rotary (30) structures, the static structure (12) including an end plate (20) having a race cavity (22), the rotary structure including a main rotor (30) having a stub shaft (32) extending from one end of the main rotor (30) and including a distal end (34) and a screw threaded socket (80) open at the distal end (34), the rolling contact bearing (40) including an outer race (42), an inner race (44), and plural rolling elements (46) interposed between the outer (42) and inner (44) races, the outer race (42) being seated in the race cavity (22) of the end plate (20), the inner race (44) having a central bore (50) and having an outer end and an inner end, the stub shaft (32) having a distal end (34) and fitting into the central bore (50), from the inner end of the inner race (44), with a frictional fit, whereby to assemble the rotary apparatus a screw (60) having a threaded shank (62) and an integral head (64), is threaded into the threaded socket (80), a washer (70) having an outer face (72) and an inner face (74), is interposed between the screw head (64) and the outer end of the inner race (44), the threaded shank (62) being screwed into the threaded socket (80) with the outer face (72) of the washer (70) bearing against the screw head (64) and the inner face (74) of the washer (70) bearing against the outer end of the inner race (44) thereby drawing the stub shaft (32) into the central bore (50) until the inner face (74) of the washer (70) bears against the distal end (34) of the stub shaft (32), thereby providing a controlled gap (g) between the main rotor (30) and the end plate (20), whereupon the screw (60) and the washer (70) may be optionally removed. A method according to claim 1, wherein the end plate (20) has an inner surface (26) and the main rotor (30) has an outer surface (36) facing the inner surface (26) of the end plate (20), the controlled gap (g) being defined by these facing surfaces (26, 36). A method according to claim 2, wherein the facing surfaces (26, 36) are normal to the axis.

Inventors: CHEUNG NELSON, CHEUNG, NELSON
Applicants: ILLINOIS TOOL WORKS, ILLINOIS TOOL WORKS INC.
Application year: 1995
Main classification: F01C1
IPC codes: F03B17, F01C21, F16C35, F01C1, F16C19