EP1657440A1

EP1657440A1 - Fan guard having channel to direct cooling air to a piston cylinder

Info

Publication number: EP1657440A1
Application number: EP05023696A
Authority: EP
Inventors: Gary S. Hueppchen
Original assignee: Thomas Industries Inc
Current assignee: Thomas Industries Inc
Priority date: 2004-11-12
Filing date: 2005-10-28
Publication date: 2006-05-17
Also published as: CA2523995A1; US20060104833A1; CN1818380A

Abstract

A pump includes a housing, a shaft supported by the housing, a piston assembly, a fan blade, and a fan guard. The piston assembly includes a piston cylinder and is operably coupled to the shaft. The fan blade is operable to generate cooling flow. The fan guard is mounted to the housing and includes a channel configured to direct at least a first portion of the cooling flow to the piston cylinder.

Description

BACKGROUND OF THE INVENTION

The invention relates generally to the field of pumps, such as compressors and vacuum pumps, and more particularly, to a compressor having a fan guard with a channel to direct cooling air to a piston cylinder.
Reciprocating piston or diaphragm pumps typically have a metal housing, for example, a cast aluminum alloy, in which bearings are mounted which journal the shaft which drives the pump. A metal housing is needed, particularly for larger pumps, to withstand the forces of driving the piston or diaphragm and containing the pressure exerted in the compression chamber of the pump.
A rotary electric motor is usually used to drive these pumps and the motor requires cooling. In one such pump, the motor is provided between two housings, each of which is separate from the other and houses one compression chamber. The shaft of the motor is a through shaft so that each end of the shaft mounts one of the pistons or diaphragms that work to vary the volume of the compression chamber in the housing at the corresponding end of the shaft. Further out from where the piston or diaphragm is mounted, a rotary fan blade is mounted to each end of the shaft to draw a flow of cooling air into the housing at that end and blow it onto the rotor and stator coils of the motor.
For cooling efficiency, it is desirable to make the part of the housing in which the rotary fan blade is mounted circular and just slightly larger than the diameter of the fan blade. The clearance between the tips of the fan blades and the interior housing surface should be as small as possible because, if not, the air drawn into the housing by the fan blades will simply blow back out past the tips of the blade, and not be directed over the coils of the motor. For applications in which the pump is contained inside of a separate enclosure, it may be permissible to leave open the end of the housing at which the fan blade is mounted. However, if the pump is going to be exposed or sold as a stand-alone product, the end of the housing must be closed with a cover that permits air to be drawn into the housing, but prevents the insertion of larger objects or fingers. This cover, typically called a fan guard, should not deleteriously affect the operation of the fan nor add to the lateral size or detract from the appearance of the fan.
The effectiveness of the cooling system in reducing the stator temperature of the motor affects the range of applications in which the pump may be employed. The voltage at which the motor is driven and the output pressure of the pump affect the amount of heat that is generated in the motor. More effective cooling expands the range of applications suitable for a given pump and motor.
The motor is not the only temperature-sensitive component in a pump. Wobble pistons are sometimes used in oil-less air compressors and vacuum pumps. A wobble piston includes a peripheral seal on the piston head that engages the cylinder bore. The piston head and its connecting rod are fixed to each other, and the connecting rod is mounted on an eccentric on a shaft. As the eccentric is turned by the shaft, the wobble piston is moved in and out and "wobbles" from side to side. Wobble pistons typically employ a Teflon® or other similar material disc or cup which serves both as a guide for the wobble piston and as a pneumatic seal between the piston and the wall of the cylinder in which it moves. The working surface of the cylinder has a hardened polished surface, providing a smooth surface for cooperating with the Teflon® seal of the piston. The service life of the Teflon® material depends in part on the temperature of the cylinder with which the seal interfaces. A higher temperature typically corresponds to a shorter service life due to increased friction between the cup and the cylinder wall.
The bearings used to support the motor shaft also have a service life determined at least in part by temperature. Generally, a higher bearing temperature equates to a shorter bearing service life.
Hence, cooling efficiency not only affects the range of applications for a particular pump, but also the service life of temperature-sensitive components in the pump. The present invention addresses these problems.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed generally to a fan guard that directs cooling air flow to a piston cylinder.
One aspect of the invention is seen in a pump including a housing, a shaft supported by the housing, a piston assembly, a fan blade, and a fan guard. The piston assembly includes a piston cylinder and is operably coupled to the shaft. The fan blade is operable to generate cooling flow. The fan guard is mounted to the housing and includes a channel configured to direct at least a first portion of the cooling flow to the piston cylinder.
Another aspect of the present invention is seen in a fan guard. The fan guard includes a front surface defining a cooling flow opening and sidewalls defining a channel having a first end proximate the cooling flow opening. A baffle is positioned proximate a second end of the channel.
Other objects, advantages and features of the present invention will become apparent from the following specification when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements and in which:
Figure 1 is an isometric view of a pump in accordance with one embodiment of the present invention;
Figure 2 is a partial cross section view of the pump of Figure 1;
Figure 3 is an end view of the pump of Figure 1 with the fan guard removed; and
Figure 4 is an isometric back view of a fan guard employed in the pump of Figure 1.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention may be embodied in any of several different forms, the present invention is described here with the understanding that the present disclosure is to be considered as setting forth an exemplification of the present invention that is not intended to limit the invention to the specific embodiment(s) illustrated. Nothing in this application is considered critical or essential to the present invention unless explicitly indicated as being "critical" or "essential."
Figure 1 illustrates a pump 10 of the invention having a motor 12 with a housing 14 at one end and a housing 16 at the other. The housings 14, 16 are cast of aluminum alloy and are essentially identical. A head assembly 18, which includes head members 20, 22 and connecting tubes 24, 26, is bolted to the housings 14, 16 above respective compression chamber portions 28, 30 of the housings 14, 16 to help hold the housings 14, 16 together and maintain their angular position with respect to each other. The pump 10 also includes fan guards 32, one at each end, which are essentially identical to one another. The pump 10 of the present invention may be employed in a variety of applications, including but not limited to cable drying, sewage aeration, tire inflation, etc.
Referring to Figures 2 and 3, a partial cross section view of the pump 10 and an end view of the pump 10 with the fan guard 32 removed are shown, respectively. The motor 12 has a shaft 34 which extends through it and into both housings 14, 16, nearly to the end of each respective housing 14, 16. As both housings 14, 16 are essentially identical, only the housing 14 is shown in Figure 2. Each end of the shaft 34 mounts a rotary fan blade 36 which is rotated by the shaft 34 within a fan cavity 37 defined by the housing 14 in a direction so as to draw air into each respective housing 14, 16 and direct it over the coils of the motor 12 (i.e., an axial component of the cooling flow). In one embodiment, the rotary fan blade 36 is secured to the shaft 34 using a spring clip 38.
The housings 14, 16 are provided with ventilation slots 39 to allow the exhausting of cooling air. The housings 14, 16 mount bearings 40 which journal the shaft 34. The housings 14, 16 also have openings (not shown) in them which provide for the axial through-flow of air so that air moved by the fan blade 36 reaches the coils of the motor 12.
The pump 10 includes a piston assembly 42 including a piston cylinder 44 and a piston head 46 operating within the piston cylinder 44 to compress the operating fluid (e.g., air) to provide the pumping action. The piston head 46 is coupled by a connecting rod 48 to an eccentric 50 fixed to the shaft 34. In operation, the shaft 34 and attached eccentric 50 rotates causing the connecting rod 48 and piston head 46 to move within the piston cylinder 44. A flapper valve (not shown) mounted to the valve plate 52 allows the air to enter the piston cylinder 44 on the downstroke of the piston cycle and seals to prevent air passage on the upstroke. The piston head 46 also includes a piston cup 54 constructed of Teflon® or other similar material that provides a sliding seal between the piston head 46 and the piston cylinder 44. The piston cup 54 has a service life that may vary based on the temperature of the piston cylinder 44, with a higher cylinder temperature resulting in a shorter service life.
Besides allowing axial cooling air flow to dissipate heat that is transferred from the motor 12 to the housings 14, 16 to the bearings 40, the fan guard 32 also directs cooling flow over the piston cylinder 44 to dissipate heat generated during the compression process. The housings 14, 16 includes openings 56 (shown in Figure 1) to allow the exhaust of cooling air directed over the piston cylinder 44.
Turning now to Figure 4 an isometric back view of the fan guard 32 is provided. The front surface of the fan guard 32 is visible in Figure 1. The fan guard 32 defines a cooling flow opening 57 in its front surface to provide for the passage of cooling flow past the fan guard 32. The fan guard includes rib members 58 spanning the cooling flow opening 57 and support members 60 running perpendicular to the rib members 58. The spacing and arrangement of the rib and support members 58, 60 may vary depending on the particular implementation. In general, the rib and support members 58, 60 are arranged to allow the passage of cooling flow, but to prevent foreign objects from entering the area proximate the moving rotary fan blade 36. In the illustrated embodiment, the fan guard 32 is made of a resilient plastic resin, such as a polyester polymer. The fan guard 32 includes a tab 62 that interfaces with a corresponding notch 64 (shown in Figure 2) in the housing 14 to secure the bottom portion of the fan guard 32 to the housing 16. Mounting holes 66 are defined in the fan guard 32 to allow the passage of screws for securing the fan guard 32 to the housing 14 via corresponding holes 68 (shown in Figure 3) in the housing 14. Any means may be used to secure the fan guard 32 to the housing 14.
The fan guard 32 includes sidewalls 70 that define a channel 72. The channel 72 terminates in a baffle 74 that changes the direction of radial cooling flow generated by the rotary fan blade 36 to impinge on the piston cylinder 44, as indicated by the arrow 76 shown in Figure 2. The sidewalls 70 also define a flared portion 78 that collects the radial air flow and directs the flow into the channel 72.
Returning to Figure 2, the rotary fan blade 36 includes an extended hub 80 that abuts the eccentric 50 to positively locate the rotary fan blade 36 along the shaft 34 within the fan cavity 37. The rotary fan blade 36 is positioned to optimize the cooling provided to the piston cylinder 44 by the cooling flow redirected by the fan guard 32. The optimal shaft position may be determined empirically and may vary depending on the particular geometry of the pump 10. In the illustrated embodiment, the rotary fan blade 36 extends axially beyond the fan cavity 37 defined by the housing 14 into the space bounded by the fan guard 32. This position has been found to increase the effectiveness of the fan guard 32 in redirecting the radial air flow to cool the piston cylinder 44.
Redirecting cooling flow over the piston cylinder 44, as described herein, reduces the operating temperature of the piston assembly 42. The combination of the rotary fan blade 36 and fan guard 32 also reduces the temperature of the bearings 40 and the motor 12. Such temperature reductions increase the operating lives of the piston cup 54 and the bearings 40 for a given set of operating conditions. The improved heat dissipation characteristics may also be employed to extend the operating range of the pump 10 to allow operation at higher pressures, different voltages, and/or lower frequency voltage inputs.
The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the invention. Accordingly, the protection sought herein is as set forth in the claims below.

Claims

A pump, comprising:
a housing;

a shaft supported by the housing;

a piston assembly including a piston cylinder and being operably coupled to the shaft;

a fan blade operable to generate cooling flow; and

a fan guard mounted to the housing and including a channel configured to direct at least a first portion of the cooling flow to the piston cylinder.
The pump of claim 1, wherein the fan blade is mounted to the shaft.
The pump of claim 1, wherein the fan guard further comprises sidewalls defining the channel, the channel having a first end proximate the piston cylinder.
The pump of claim 3, wherein the fan guard further comprises a baffle defined at the first end of the channel and configured to direct the cooling flow to the piston cylinder.
The pump of claim 4, wherein the baffle is configured to direct the cooling flow to sidewalls of the piston cylinder.
The pump of claim 3, wherein the sidewalls further define a flared portion located proximate a second end of the channel.
The pump of claim 1, wherein the channel is closed on three sides.
The pump of claim 6, wherein the housing defines a fan cavity, the fan blade is located at least partially within the fan cavity, and the second end of the channel communicates with the fan cavity.
The pump of claim 1, wherein the housing defines a fan cavity and the fan blade is located at least partially within the fan cavity.
The pump of claim 9, wherein the fan blade extends beyond the fan cavity defined by the housing into a cavity defined by the fan guard.
The pump of claim 1, further comprising a stop surface mounted to the shaft, wherein the fan blade includes a hub abutting the stop surface.
The pump of claim 1, wherein the stop surface further comprises an eccentric mounted to the shaft and operably coupled to the piston assembly.
The pump of claim 1, wherein the channel is oriented perpendicularly with respect to an axis of the shaft.
The pump of claim 1, wherein the housing defines vent openings proximate the piston cylinder to allow exhaust of cooling flow directed by the fan guard to the piston cylinder.
The pump of claim 1, further comprising a motor operable to rotate the shaft, wherein the fan guard is configured to direct a second portion of the cooling flow to the motor.
The pump of claim 1, further comprising at least one bearing supporting the shaft, wherein the fan guard is configured to direct a second portion of the cooling flow to the bearing.
The pump of claim 15, wherein the first portion of the cooling flow comprises a radial component of the cooling flow, and the second portion of the cooling flow comprises an axial component of the cooling flow.
The pump of claim 1, wherein the first portion of the cooling flow comprises a radial component of the cooling flow.
A fan guard, comprising:
a front surface defining a cooling flow opening;

sidewalls defining a channel having a first end proximate the cooling flow opening;

a baffle positioned proximate a second end of the channel.
The fan guard of claim 19, further comprising a plurality of rib members spanning the cooling flow opening.
The fan guard of claim 19, wherein the sidewalls further define a flared portion located proximate the first end of the channel.
The fan guard of claim 19, wherein the channel is closed on three sides.
The fan guard of claim 19, wherein the baffle redirects a radial component of cooling air flow received by the fan guard by approximately 90 degrees towards a piston cylinder of an attached pump.