TURBO-COMPRESSOR HAVING AIR COOLED BEARING

Abstract: A turbo-compressor air supply system for supplying air at relatively low pressure and high volume to a paint spray system or the like. The air supply system comprises a drive motor (30) including a casing (31), a drive shaft (32) projecting from the casing and air intake means (84) in fluid communication with the casing. A turbo-compressor (36) is provided which includes a housing (37), a drive shaft (38) having first and second projecting ends, a bearing housing (72) projecting from the compressor housing and disposed concentrically around and spaced from a projecting end of the drive shaft and a bearing (34) disposed concentrically around the projecting end. A drive train (42) couples the compressor drive shaft with the other projecting end of the drive motor shaft to enable the motor to drive the turbo-compressor. Means (74) are provided for placing the bearing housing in fluid communication with a drive motor casing and associated air intake means to provide cooling for the bearing.

Description: The invention relates to a turbo-compressor air supply system as described in the preamble of claim 1. This system, in which the drive motor and the turbo-compressor are mounted side by side upon a horizontal support is known from DE-B-1 265 011. In this known system the casing enclosing the motor is in communication with the housing which encloses the turbo-compressor so that during operation air flows from the casing to the housing, thus providing some kind of cooling for the turbo-compressor. In this known system both the first (upper) and the second (lower) bearing of the turbine shaft are enclosed in the turbo-compressor housing. The heat, developed in the immediate environment of the turbo shaft bearings cannot be dissipated and will build up to high levels. The upper bearing shaft being the hottest as warm air tends to rise. It has, for example, been found that the operating temperature in the vicinity of the upper turbine shaft bearing can reach 97°C or even higher levels. Such temperature often exceed the performance specifications of the bearing and lead to premature bearing failure. The invention aims to obviate this drawback and this aim is achieved by means of the measures as described in the characterizing clause of the main claim. By virtue of the positive pressure with which a stream of cooling air is supplied to the interior of the bearing housing a very efficient cooling of the bearing is obtained resulting in much lowering operating temperatures and thus in a much longer service life of the bearing and consequently of the entire turbo-compressor air supply system. Preferred embodiments of the invention are described in the subclaims. IN THE DRAWINGS Figure 1 is a side elevational view, with certain parts broken away or shown in section, of a turbo-compressor air supply system embodying the present invention; Figure 2 is a top plan view of the apparatus of Figure 1; Figure 3 is a detailed view, with certain parts broken away or shown in section, of upper portions of the turbo-compressor and motor of Figure 1; Figure 4 is a cross sectional view along lines 4-4 of Figure 3; Figure 5 is a detailed view, with certain parts broken away or shown in section, of the upper portion of the turbo-compressor of Figure 1; and Figure 6 is an exploded view of the structures shown in Figure 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Throughout the following description and drawing, identical reference numbers are used to refer to the same components shown in multiple figures of the drawing. Referring first to Figures 1 and 2 a portable air supply system embodying the present invention includes a hollow box-like housing designated generally 10 having cross frame members 12 fixedly secured to its opposite ends and projecting outwardly beyond the opposite sides of the box as best seen in Figure 2. From each end of each cross frame member 12, vertical legs project downwardly, one set of legs 14 having caster mounted wheels mounted at the lower end, while the other set of legs 14 rotatably carries a somewhat larger, non-steerable set of wheels 18. Housing 10 is a simple rectangular box formed with a top wall 20, opposed sidewalls 22, end walls 24 and a bottom wall 26. Bottom wall 26 is removable, being held to the side and end walls 22, 24 by bolts, not shown, to provide access to the chamber 28 within the housing. An electric drive motor 30 is mounted upon the top wall of the housing with its drive shaft 32 disposed vertically and projecting downwardly through an opening 34 in top wall 20. A multi-stage turbo-compressor 36 is also fixedly mounted upon top wall 20 with its drive shaft 38 projecting downwardly through an opening 40 in top wall 20, as best seen in Figure 1. Rotation of the shaft of drive motor 30 is transmitted to the shaft 38 of turbo-compressor 36 by a belt and pulley drive designated generally 42 located within chamber 28. Bottom wall 26 is formed with two reasonably large openings 46, 48. A pair of open ended vertically disposed tubular pipes 49 project vertically through housing 10 and are fixedly secured within tightly fitting openings, not shown, in top wall 20 and bottom wall 26 of the housing. A flexible wall tube 50 is clamped to the upper end of each pipe 49 to connect the pipe to extensions 52 of the air inlets to compressor 36. Drive motor 30 is mounted upon a plate 54 which is slidable relative to top wall 20 of the housing. An adjustment bolt 56 is operable to position the motor longitudinally of the housing to thereby regulate the tension of the drive belt of the belt and pulley drive 42. When the belt tension is adjusted, plate 54 is clamped in position to top wall 20 by bolts not shown. Referring now particularly to Figure 3, a detailed view of the upper end of compressor 36, there is provided a bearing housing 72 which projects from the compressor housing 37. Compressor housing 37 is formed with a sleeve 80 which encases bearing housing 72. As can be seen by referring to Figures 4 and 5, the bearing housing 72 is disposed concentrically around and spaced from an upper projecting portion of the drive shaft 38. The bearing 34 is mounted onto shaft 38 by means of a nut 41. An air space 78 is formed between at least part of the inside of sleeve 80 and the inside of bearing housing 72. Air space 78 is further defined by cap 92 and top plate 94 which, respectively, seal off the top and bottom of air space 78. A shaft seal 96 is disposed between the top of shaft 38 and cap 92. Sleeve 80 further comprises an air inlet 86 and air outlets 88 as can be seen in Figure 4. As is conventional, a plurality of air inlets 84 are formed in the top of the casing 31 which encloses drive motor 30. As can be seen from the arrows, which indicate air flow direction, ambient air enters first the plurality of air inlets 84 and the motor housing 31. An air outlet 90 adjacent the top of motor casing 31 is provided. A means of fluid communication in the form of a hollow tube 74 connects air outlet 90 and air inlets 86 formed in sleeve 80. By means of hollow tube 74, a portion of a stream of air introduced into motor casing 31 by means of the plurality of inlets 84 is diverted around bearing housing 72. It flows through air space 78 therein and then exits by means of air outlet 88. This flow of air is indicated by the arrows in Figures 3 and 4. By means of the portion of air which is diverted around the bearing housing 72, the environment in which the bearing 34 operates is made cooler. The operating temperature of the upper shaft bearing 34 of the turbo-compressor of the instant invention under actual operating conditions has been found to be approximately 82°C. This represents a temperature drop of approximately 15°C attributable to the design of the air cooled turbo-compressor of the instant invention. The temperature drop is largely due to two factors. First, by extending turbine shaft 38 so that it projects out of the upper end of compressor housing 36, the bearing is no longer subjected to much of the heat generated by the operation of the turbo-compressor. Secondly by diverting some of the air flowing through the motor casing 31 around the bearing housing 72, a further cooling effect is achieved. The herein invention may comprise additional structures, such as two piece sleeve 82 which, as depicted in Figure 5, is mounted over the end of the hollow tube 70 adjacent air outlet 90 disposed in motor casing 31. Sleeve 82 provides a means of adjusting the length of hollow pipe 74 to accommodate different length drive belts or different pulley sizes used in the operation of a turbo-compressor 37. While the herein invention has been described with respect to certain embodiments and exemplifications thereof, it is not intended to be so limited but solely by the claims appended hereto.

Claims: 1. A turbo-compressor air supply system for applying air at relatively low pressure and high volume to a paintspray system, said air supply system comprising: a drive motor (30) with: a casing (31) enclosing the motor (30), a drive shaft (32) projecting from said casing (31), air intake means (84) in fluid communication with that casing (31) and an air outlet (90) in the casing, a turbo-compressor (36) including: a housing (37), a drive shaft (38) having first and second ends projecting from said housing (37), first (34) and second bearings for the drive shaft (38); drive train means (42), coupling the drive motor drive shaft (32) with the projecting second end of the compressor drive shaft (38) to enable said motor to drive the turbo-compressor, characterized in that the first bearing (34) of the turbo-compressor drive shaft (38) is enclosed in a bearing housing (72) projecting from the compressor housing (37) and disposed concentrically around and spaced from the first projecting end of the drive shaft (38), said bearing housing having an interior surrounding the bearing, fluid communication means (74) being provided for supplying a stream of cooling air at a positive pressure to the bearing housing (72), and placing the interior of the bearing housing (72) in fluid communication with the air outlet (90) in the drive motor casing (31) for supplying at least a portion of the air entering during operation through the air intake means (84) to the bearing housing to cool the bearing. 2. A system of claim 1, characterized in that the fluid communication means (70) comprises means (74, 82) of adjusting the length thereof. 3. A system of claim 2, characterized in that the means of adjusting comprises an adjustable slide (82) disposed over an end (74) of a hollow tube (70), said adjustable slide including means of connection to one of said air inlet (86) and said air outlet (90). 4. A system of claim 1, characterized by an air space formed between at least part of the bearing (34) and at least part of the bearing housing (72). 5. A system of claim 1, further comprising air outlet means disposed in the bearing housing.

Inventors: TOTH, DENNIS W.
Applicants: CAN-AM ENGINEERED PRODUCTS, INC.
Application year: 1988
Main classification: F04D25
IPC codes: F04D29, F02C7, F04D25, B05B7, F04D17