WO1983003640A1

WO1983003640A1 - Portable air compressor

Info

Publication number: WO1983003640A1
Application number: PCT/US1982/000480
Authority: WO
Inventors: Scott & Fetzer Company The
Original assignee: Pettyjohn, Austin, E.; Widman, Robert, K.
Priority date: 1982-04-19
Filing date: 1982-04-19
Publication date: 1983-10-27
Also published as: DE8237196U1

Abstract

A portable, expansible chamber air compressor includes a motor housing (11), a scotch yoke apparatus (50) driving pistons (52, 53) in compression chambers (45, 46) defined by cylinders (37, 38) and heads (35, 36), a fan (30) and a fan shroud (12). The heads separate the motor housing and fan shroud, and are disposed within the outer peripheries of the housing and shroud (when viewed in end view). The fan generates a cooling air stream which is divided by the heads to produce air streams (A) flowing over the heads and immediately away from the compressor, and air streams (B) flowing into the center area of the compressor, under the heads, around the cylinders and onto pressurized air ducts, all to provide cooling and enhance compressor output.

Description

PORTABLE AIR COMPRESSOR

This invention relates to fluid compres¬ sors and more particularly to portable air compres¬ sors suitable for general consumer use. 5 Portable air compressors present specific problems in terms of weight and output, generally measured in cubic feet per minute. Where^"compressed air is desired for use in general spraying, paint¬ ing, sandblasting, caulking, inflation and the like,_. τ_g sufficient output levels must be provided in order to accomplish the task. Large output levels can easily be provided in larger compressors for contin¬ uous heavy duty applications, but the large output , levels usually only come with the weight attendant __ large motors and heavy compressor castings. It is difficult to provide suitable air outputs for these general tasks from a truly portable compressor of the type which can easily be hand carried from job to job. o Moreover, while greater output capacity and better output characteristics are normally obtained from multiple cylinder compressors, the use of multiple cylinders and the advantages thereof m st be compared carefully to the problems of weight where truly portable compressors are required.

Known prior "portable" air compressors are of various configurations; most of the multiple 5 cylinder variety include cylinders and heads extend¬ ing significantly outwardly of the confines of any motor, fan or the like. When the compressor is operated, the cylinders and heads get hot, signifi¬ cantly reducing output capacity. Ducts for cooling 0 have been proposed, but these too extend outwardly of the unit, giving it a bulky, T-shaped appearance and reducing its portability.

Other known compressors have components within a single housing, but the operational heat of 5 the compressor and motor, and the greater difficulty of ventilation all combine to reduce output capa¬ city.

Accordingly, it has been one objective of the invention to provide an - improved protable air O -- compressor having improved output capacity.

A further objective of the invention has been to provide an improved multiple cylinder portable air compressor.

A further objective of the invention has 5 been to provide an improved twin cylinder, heavy duty, but portable air compressor for general consumer use.

To these ends, the invention contemplates an air compressor including a motor, motor housing

3 twin air compression chambers, cooling fan and shroud combined in a unique way to produce high output in a portable package substantially the same size in girth as the motor housing. More particu- larly, the invention contemplates the utilization of a scotch yoke driven compressor and a particular construction and disposition of components to significantly increase operational cooling and thereby obtain increased output. According to the invention, a scotch yoke drive is used to produce a short stroke, twin cylinder compressor wherein the compressor heads are disposed inwardly toward the drive shaft a substan¬ tial distance. In particular, the cylinder heads are disposed in an inward position which is general¬ ly no greater radial distance from the drive shaft axis than are the outer peripheries of the motor housing, fan blades and shroud. By separating the motor -housing from the fan shroud at the cylinder head area, the cooling air stream from the fan is divided by the heads into: (a) a first stream flowing over the heads, cooling them, and then carrying heat directly away from the compressor; and (b) into a second stream circulating under the heads and around the cylinders. No additional ducting is required.

Moreover, the cylinders are open-ended toward the center of the compressor and the second stream of air is used to cool the underside of the pistons.

Finally, the heads include compressed air passageways communicating with an outlet and con- nected with a slip tube also disposed in the direct cooling stream from the fan.

The enhanced cooling produced by the invention as noted above serves to increase the compressor's output, and lighter weight components can be utilized to provide a truly portable twin cylinder compressor having an output capable of fulfilling the general compressed air needs of the consumer.

These and other objectives and advantages will become readily apparent from the following description of a preferred embodiment of the inven¬ tion and from the drawings in which:

Fig. 1 is a perspective view of the invention; Fig. 2 is an elevational view of the invention;

Fig. 3 is a cross sectional view taken along lines 3-3 of Fig. 2;

Fig. 4 is a cross sectional view taken along lines 4-4 of Fig. 2; and

Fig. 5 is a cross sectional view taken along lines 5-5 of Fig. 2.

Turning now to Fig. 1 of the drawings, there is shown a portable air compressor 10 according to the invention. The air compressor 10 includes a motor (not shown), a motor housing 11, a fan shroud 12, a compressor means shown generally at

13, a pressure relief means 14 and a handle 15. It will be appreciated that the entire compressor is generally disposed within the same girth as that of the motor housing, the only exceptions being the pressure relief means 14, handle 15 and feet 16, 17 and 18 (Fig. 5) . This relationship is perhaps better seen in Fig. 2, which shows the additional features of the switch 19 and power cord 20 for the motor within housing 11.

In a preferred embodiment, the motor utilized in the compressor is any suitable form of electric motor as is well known in the industry and comprises in and of itself no particular portion of the invention.

The internal details of the invention are best seen in Figs. 3-5. In Fig. 3 a drive shaft 25 is shown extending along the drive shaft axis 26.

The drive shaft 25 extends through an end of the housing 11 from the motor (not shown) . A fan 30 is mounted at one end of the drive shaft and compressor means 13 are disposed in the unit inboard of the fan

30, as shown in Fig. 3. As best seen in Figs. 3 and

5, the compressor means includes compressor heads 35 and 36, supporting cylinders 37 and 38. Each of the heads is provided with a check valve respectively shown at 39 and 40, which selectively communicate between the compression chambers, defined by the respective cylinders and heads, and passageways for the compressed air, such passageways being seen at 5 41 and 42 in Fig. 5. The head 35 and cylinder 37 defines a compression chamber 45, while the head 36 and cylinder 38 define a compression chamber 46.

A single piston member, referred to as a scotch yoke piston, is disposed within the cylinders 0 37 and 38. The scotch yoke piston assembly 50 includes a connecting web 51 connected between two piston members 52 and 53 provided with suitable sealing rings, as shown, for sealing engagement with the respective cylinders.. As shown in Fig. 5, the 5 web 51 is provided with an aperture 54 to accommo¬ date the extension therethrough of the drive shaft 25. Accordingly, and as best seen in Fig. 5, the scotch yoke piston assembly 50 can reciprocate between the heads 35 and 36, with the aperture or ^*0 •' slot 54 simply accommodating the drive shaft 25.

In order to drive the scotch yoke piston assembly, a cam 60 is mounted on the drive shaft 25. The cam 60 comprises a roller bearing having an inner race 61 and an outer race 62, separated by 5 ball bearings 63. The bearing cam 60 is mounted on a drive shaft carried eccentric 65, such that as the drive shaft 25 is rotated, the bearing cam is moved in an oscillating path. The eccentric 65 is provided with a weight 66 for counterbalancing the drive.

As shown in Fig. 3, the bearing cam 60 engages L-shaped wear buttons 68 and 69, respective- ly, which are mounted on the bottoms of the respec¬ tive pistons 52 and 53. As shown in Fig. 3, the bearing cam 60 engages a depending portion of the wear button to retain the piston assembly 50 from rotation. The outer race of the bearing cam engages the major surface of the wear buttons in order to drive the pistons as the bearing cam is oscillated by its eccentric mounting on the drive shaft 25.

Further considering the construction of the compressor 10, it will be appreciated that an end plate 75 (Fig. 5) is secured to the housing 11 and includes integral finned portion 76 and lower integral non-finned portion 77 extending therefrom. These portions extend outwardly from the end plate 75 approximately the same distance as the width of the respective heads 35 and 36 and form flanges, as shown in Fig. 5, to which the heads 35 and 36 are secured.

Extending upwardly from portion 77 is a support bracket 78 supporting an oiled pad or wick 79. Oil pad 79 is disposed in a position to engage the bearing cam 60 and to lubricate the cam.

Returning now the consideration of the compressor means 13, it will be noted in Fig. 5 that the compressor head 35 is provided with a plug 43, while the compressor head 36 is provided with an outlet fitting 44. Nevertheless, each head includes the passages 41 and 42 which are commonly joined by a slip tube 85 inserted into bores in the respective heads as the compressor is assembled. Slip tube 85 is sealed to the head by means of the O-rings shown on each end thereof and serves to communicate passage 41 with passage 42.

Also, it will be appreciated that the pressure relief means 14 is provided with a fitting

86 which is threaded into the passageway 42. Fitting 86 communicates the passageway 42 with the pressure relief means which may be any suitable adjustable pressure relief device, as is well known in the industry and which does not in and of itself comprise a part of this invention. In particular, the pressure relief means 14 may be an adjustable, spring-loaded pressure relief means which can be set at various pressures to control relief of the compressor and thus the pressure produced at the outlet fitting 44 for use by the consumer.

In operation then, of the compressor, it will be appreciated that as the shaft 25 rotates, the bearing cam 60 oscillates to drive the piston assembly 50 in reciprocable directions within the cylinders 37 and 38. As the piston 52 begins its inward direction to its final inward position as shown in Fig. 5, it will be appreciated that the ball check 39 seats in the head to close off the passageway 41 from the compression chamber 45. At the same time, it will be appreciated that the flapper valves 90 which cover the ports 91 in the piston, unseat to permit air to flow into the 5 compression chamber 45. At the same time and during this motion, the flapper valves 92 covering the ports 93 of the piston 53 have closed, and as the piston 53 moves toward the head it serves to compress air in the compression chamber 46, 0 unseating the ball check 40 and compressing air into the passageway 42. Thereafter, as the shaft 25 continues to rotate, the bearing cam oscillates and reciprocates the pistons in the reverse direction, whereupon flapper 90 closes to close off ports 91 5 and compress the air in chamber 45. This unseats the ball check valve 39 and air is compressed into the passageway 41. Thus, air is compressed into the common passageways 41 and 42 which are joined by the slip tube 85. It will be noted that the outlet ^*0-' fitting 44 is open to the passageway 42, and thus compressed air in the common passageways is exhausted through the fitting 44.

The pressure relief means 14 can be operated to vent substantially all of the pressure 5 within the lines 41 and 42 (should the outlet fitting be connected to a tool, for example), or the pressure relief means can be closed down to close off any vent through the fitting 86 and cause the passageways 41 and 42 to be pressurized, thereby introducing controlled pressurized air at the outlet fitting 44.

Turning now to Fig. 4, it will be appre- ciated that the fan 30 includes four fan blades 30a, 30b, 30c and 30d. Each of the fan blades has an outer periphery 31 transcribing an arc as the blades rotate. This arc, although very slightly inwardly of the outer girth of the motor housing 11 and of the shroud 12, is nevertheless substantially dis- posed at a distance no further from the drive axis

26 outwardly in a radial direction than those members. The fan blades 30a through 30b are mounted via a fan hub 32 on the drive shaft 25.

Considering now the cooling aspects of the invention, it will be appreciated that the heads 35 and 36 and the slip tube 85 are disposed primarily within the arc which is proscribed by the periphery 31 of the rotating- fan blades 30a through 30d. Moreover, and perhaps as best appreciated from Fig. 4, it will be appreciated that the rotating fan blades, which move in a counterclockwise direction, serve to generate a stream of cooling air. This air is drawn through the air inlet 95 of the shroud 12 and through a foam or other type filter 96. As the air is drawn through the filter 96, it is directed rearwardly by means of the shroud peripheral wall portions 12a, 12b which extend parallel to the drive axis 26. At this point it will also be appreciated that the shroud peripheral portions 12a and 12b, as shown in Fig. 3, are slightly outward of the fan blades, but are no further outwardly, in a radial direction from the drive axis 26 than the outer periphery of the housing 11. 5 As the fan 30 is rotated to generate a cooling stream of air, it will be appreciated that the heads 35 and 36 lie substantially within the cooling air stream, as best seen in Fig. 4. As the air stream moves from the fan against the head, it 0 will also be appreciated that the heads serve to divide the cooling air stream into separate air streams. For example, the heads 35 and 36 divide the outer portions of the cooling air stream into a first stream which flows over the tops of the heads. 5 ' This is generally shown by the arrow A for each head. In addition, the heads separate an inner or second air stream which flows under the heads and around the chambers 45 and 46. This is shown by the arrows B in Fig. 3. ^*0 •' In this regard it will be appreciated that the first air stream, indicated by the arrows A, flows over the heads and then outwardly and immediately away from the compressor, carrying the heat of the heads therewith. The second air stream, 5 indicated by the arrows B, however, flows under the heads and around the chambers 45 and 46. In addition, it will be appreciated that the cooling air blows directly over the lower portions of the cylinders 37 and 38 and against the lower surfaces of the respective pistons, thereby cooling the cylinders and the pistons and providing fresh cool air for compression. Moreover, the second air stream indicated the arrows B flows over the bearing cam, its eccentric mounting in the drive shaft and then against the end plate 75, thereby serving to cool the entire apparatus.

It will also be appreciated that the air stream indicated by the arrows B flows over the slip tube 85 (Fig. 4) , thereby cooling that tube and further enhancing the cooling of the compressor and the compressed air therein.

Moreover, further structural details of the invention provide further and increased cooling advantages. For example, it will be appreciated that the shroud 12 is discontinuous from the motor housing 11 and is separated therefrom by the compression means, and in particular the compressor heads 35 and 36. In the preferred embodiment, the shroud is made from a plastic or suitable synthetic material and is mounted directly to the respective heads 35 and 36.

This separation, combined with the inward disposition of the heads from the general outer girth of both the shroud 12 and the housing 11, permits the heads to function as cooling air stream dividers, producing a cooling flow of air over the heads, and then immediately away from the compres¬ sor, to carry the heat away therefrom, all without any separate ducting being required to direct air over the heads, and without directing any cooling air, which has become heated as a result of flowing over the heads, into the motor area. . 5 It will be appreciated that the compressor according to the invention may be made of varying size and weighted components producing differing outputs, and yet still providing a portable compres¬ sor. By way of illustration only, a preferred 10 embodiment of the compressor according to the invention has the following approximate specifica¬ tions:

Range of pressure developed - 0+to 100 pounds per square inch 15 Number of cylinders - 2 opposed

Delivery - 2 cubic feet per minute § 40 pounds per square inch Weight - 20 pounds

^'2X3 ■^■ Size - 11-3/4" x 7-1/2" x

8-3/4" Power Requirement - 120 VAC @ 9 Amps

Nevertheless, other specifications can be provided in portable compressors according to the 25 invention without departing from the scope hereof.

Accordingly, the present invention pro¬ vides a substantially improved, portable twin cylinder air compressor. As a result of the unique combination and utilization of the scotch yoke drive and the disposition of the compressor heads and cylinders in relation to the motor housing, fan and fan shroud, enhanced cooling is provided all in a portable twin cylinder package which does not require cylinders, ducts or shrouds to extend beyond the general girth of the motor housing. Despite the compression of the compressor components into a relatively tight spacing, enhanced and improved cooling is provided -by the invention described herein in order to promote increased compressor output, as has been described.

It will be appreciated that these and other advantages and modifications ^" will become readily apparent to those of ordinary skill in the art, and the applicant intends to be bound only by the claims appended hereto.

I CLAIM:

Claims

( 1 ) A fluid compressor comprising : a motor and means housing said motor ; a drive shaft; a fan mounted on an end of said shaft, for blowing cooling air; compressor means disposed between said housing means and said fan; a shroud surrounding said fan and defining duct means for directing fan blown cooling air over said compressor means; said compressor means separating said housing means and said shroud.

(2) Apparatus as in claim 1, wherein said compressor means includes two expansible chambers defined by compressor head members; said fan circumscribing an arc of greater radial distance from said drive shaft than the distance of said head -members therefrom.

-Iβ-

tS) Apparatus as in claim 2, wherein said fan is operable to blow a stream of cooling air toward said compressor means, each of said head members disposed in said air stream and separating said air stream into two portions , one of which flows over said head member and then away from said apparatus, and another of which flows under said head member and around said chamber.

(4) Apparatus as in claim 3, wherein said chambers have open lower ends, and further including piston means in each chamber, said other air stream flowing past said open chamber ends and^' cooling said pistons.

(5) Apparatus as in claim 3, including compressed fluid passages in said head members and a slip tube means extending between said head members and operably connecting said passages in said respective head members, said slip tube member being disposed in a position such that it lies within a stream of cooling air blown by said fan.

(6) Apparatus as in claim 5, further including a compressed fluid outlet communicating with the passages in one of said head members and further including pressure relief means in operative communication with said fluid outlet.

(7) A fluid compressor comprising: a motor and motor housing means enclosing said motor; a motor drive shaft extending outwardly of said motor; compression means adjacent said drive shaft and operably connected thereto, said compression means including expansible chambers having chamber heads; a fan means secured to an end of said drive shaft for blowing cooling air over said chambers and said heads;

. shroud means for directing fan blown cooling air over said chambers and said heads, said shroud means having peripheral surfaces substantially parallel to said drive shaft and disposed therefrom approximately the same radial distance as the extension of said housing therefrom; and said shroud means and said motor housing being discontinuous, said heads extending there¬ between.

O

(8) A fluid compressor comprising: a motor; said motor having a drive shaft extending therefrom along an elongated drive axis; 5 a motor housing disposed about said motor and said drive axis; at least two opposed expansible chambers having opposed chamber heads; a double piston means disposed within said 0 chambers for respective reciprocation therein; means connecting said piston means to said drive shaft between said motor and one end of said drive shaf for reciprocating said piston means upon rotation of said drive shaft by said motor; 5 a fan means connected to said drive shaft proximate said one end thereof and disposed to blow air over said chambers;

. shroud means disposed around said fan and terminating proximate said chambers; ^'0 •- said shroud means having peripheral portions disposed about and outwardly of said drive axis approximately the same distance as said housing is disposed from said drive axis;

-said peripheral portions of the shroud 5 means and said chamber heads defining an exhaust guide means for directing air blown by said fan over said chambers and over said heads.

(9) Apparatus as in claim 20, wherein said opposed chamber heads define compressed fluid passageways,and further including a tube means extending between and . operably connecting the respective compressed fluid passageways, said tube means being disposed within said shroud and within a flow of air blown by said fan.

(10) Apparatus as in claim 21, wherein said heads include opposed aligned tube receiving bores communicating with said passageways and said tube means comprises a straight tube slip-fit into said bores respectively at respective ends of said tube.