Abstract:
A portable air compressor assembly includes a tubular frame having a pair of parallelogram shaped side sections. A support plate is connected between the side sections and horizontally positioned in a compressor normal operating position. A plurality of operating components connect to the support plate. A fluid pressure tank is supported perpendicular to the side sections and forward of the operating components. The frame envelopes the operating components&#39; outer perimeter and angularly extends to a stop point rearward of the operating components. When tipped rearward to the stop point, the compressor assembly returns by gravity to the compressor normal operating position. An instrument and connector panel including an engine on/off switch is mounted in a protected position. Wheels and structural feet are removable and a handle is retractable and removable for shipping.

Description:
This application is a continuation of U.S. patent application Ser. No. 10/392,567 filed on Mar. 20, 2003 and entitled “Support Structure for a Portable Air Compressor” which claimed priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 60/417,725 filed on Oct. 10, 2002. The disclosure of the above applications are incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The present invention relates in general to air compressors and more specifically to a support structure for a portable air compressor. 
   BACKGROUND OF THE INVENTION 
   Air compressors normally provide a source of pressurized air which is temporarily stored in a pressure tank. A motivating means, typically an electric motor or a combustion engine, is connected to a compressor unit. The compressor unit typically includes a piston assembly, or compressor pump, which compresses air from the atmosphere and forces it into the fluid pressure tank for temporary storage. To make air compressors portable for job site use, structural frames are provided. The frames normally provide at least one wheel for mobility of the air compressor assembly. 
   Several drawbacks exist for common portable air compressor assemblies. The first drawback is that the component parts of the air compressor assembly, typically items that include the muffler from a gasoline engine and the air filter for the engine, and the cooling head for the compressor, are often arranged outside of the structural envelope of the frame supporting the air compressor assembly. Other smaller items such as the bleed and drain valve for the fluid pressure tank, the individual gages used to determine the pressure of the system, and drain ports from the various operating components are also frequently exposed (i.e., extending outside of an envelope of the frame). Exposed components are susceptible to damage. 
   Another disadvantage of known portable air compressor assemblies is the tendency of the assembly to tip over when pushed or pulled by the handle. Wheels used to support and provide for movement of the frame also allow the entire assembly to rotate and flip over. When an air compressor assembly flips over, damage to those items which extend beyond the perimeter of the frame can occur and fuel spillage can also occur. 
   It is therefore desirable to provide a portable air compressor assembly which overcomes the drawbacks of known air compressor assemblies. 
   SUMMARY OF THE INVENTION 
   In one preferred embodiment of the present invention, a portable air compressor assembly includes a frame having a pair of parallel side sections. A support plate is horizontally connected between the side sections in a compressor normal operating position. A plurality of operating components connect to the support plate. A fluid pressure tank is supported perpendicular to the side sections and forward of the operating components. The frame side sections envelope an outer perimeter of the operating components and angularly extend to a frame rotation stop point rearward of the operating components. When tipped rearward to the frame rotation stop point, the compressor assembly returns by gravity to the compressor normal operating position. 
   In another preferred embodiment, a support structure for a portable air compressor includes a frame having a pair of approximately parallel side sections and a support plate horizontally disposed between the side sections. A plurality of components are connected to the support plate including an engine, a compressor and a fluid pressure tank. An axle is slidably disposed through a lower tubular portion of both side sections, the axle having distal ends operably forming opposed outer planar envelopes of the portable air compressor. An instrument support panel is connectably disposed on the frame and positioned adjacent to a select one of the outer planar envelopes. A plurality of instruments including an engine on/off switch, at least one pressure gage, at least one quick-disconnect fitting and at least one unloader valve are each mounted on the instrument support panel such that each of the instruments and the instrument support plate are completely disposed within one of the selected outer planar envelopes. 
   Wheels, rotatably supported on the axle, and structural feet are used to support the assembly and are each removable for shipping. A center-of-gravity for the assembly is positioned forward of the wheels such that when the assembly tips rearward, the center-of-gravity remains forward of a vertical axis taken through the axle, biasing the assembly to return to a normal operating position by gravity. In another preferred embodiment, the side sections provide dual lift handles for the assembly. In still another preferred embodiment, a centrally positioned handle is retractable or removable for shipping. 
   Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
       FIG. 1  is a perspective view of a preferred embodiment for an air compressor assembly of the present invention; 
       FIG. 2  is a plan view of the assembly of  FIG. 1  identifying the fluid storage tank orientation relative to the longitudinal axis of the assembly; 
       FIG. 3  is a side elevation view taken along Section  3  of  FIG. 2  showing a control panel mounted to the frame structure; 
       FIG. 4  is a side elevation view taken along Section  4  of  FIG. 2  identifying the relationship between the wheels and supporting feet of the present invention, and a center-of-gravity for the assembly; 
       FIG. 5  is the side elevation view of  FIG. 4  showing the compressor assembly rotated about the axis of the wheels to a stop position determined by an aft projecting portion of the frame; 
       FIG. 6  is a plan view showing an exemplary engine and compressor mounted on the support plate between the two side sections; 
       FIG. 7  is a side elevation view taken at Section  7  of  FIG. 6  identifying that all components of the engine and air compressor are fully enclosed within an envelope of the frame; 
       FIG. 8  is rear elevation view taken at Section  8  of  FIG. 7  showing the geometry of the supporting feet and the axle rotatably penetrating the tubular members of the frame; 
       FIG. 9  is a plan view from an underside of the compressor assembly, taken at Section  9  of  FIG. 7 , detailing the lower support plate and the mounting fasteners used to support the equipment to the support plate; 
       FIG. 10  is a perspective view of another preferred embodiment of the present invention having a frame structurally connected to the fluid pressure tank and a centrally positioned forward support handle; and 
       FIG. 11  is a diagrammatic flow chart of the method steps to bias a portable air compressor of the present invention toward a horizontal operating position. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     FIG. 1  shows an air compressor assembly  10  according to a preferred embodiment of the present invention. The air compressor assembly  10  includes a frame  12 , a component group  14 , and a fluid pressure tank  16 . A first wheel  18  and a second wheel  20  are rotatably supported from the frame  12  at an aft end of the air compressor assembly  10 . The frame  12  includes a first side  22  and a second side  24 . The first side  22  and the second side  24  are generally tubular shaped frame members generally formed in a parallelogram configuration having rounded corners. A support plate  26  is provided at a lower portion of the frame  12  and is mechanically joined to the first side  22  and the second side  24 , respectively. A pair of support feet  28  (only one is visible in this view) are mechanically joined to a forward end of the frame  12  at an under surface of the support plate  26  as described in better detail in reference to  FIG. 9 . 
   Each of the support feet  28  includes an elastomeric pad  30 . The purpose of the elastomeric pad  30  is to reduce the sliding motion of the air compressor assembly  10  when the engine is operating and to prevent the unit from sliding when placed on a relatively smooth surface. A control panel  32  is provided on either the first side  22  or the second side  24 . In the embodiment shown, the control panel  32  is supported by an upper horizontal and a lower horizontal member of the first side  22 . The control panel  32  is further described in reference to  FIG. 3 . A rear support member  34  is provided to structurally join the first side  22  to the second side  24 . The rear support member  34  also serves as a portion of a frame rotation stop point where the frame  12  contacts the ground surface as described in better detail in reference to  FIG. 5 . In a preferred embodiment, the rear support member  34  and the support plate  26  are each welded to the first side  22  and the second side  24 . 
   As shown in  FIG. 2 , the frame  12  is configured such that the component group  14  is totally enclosed within an envelope of the frame  12 . An assembly longitudinal axis A is shown bisecting the frame  12 . The fluid pressure tank  16  includes a tank longitudinal axis B positioned approximately perpendicular to the assembly longitudinal axis A. 
   As best seen in  FIG. 3 , the control panel  32  is supported at both an upper and lower extremity to the frame  12 . In a preferred embodiment, the control panel  32  is mechanically fastened (e.g., welded) at joints  33  to the frame  12 . The control panel  32  is shown in  FIG. 3  in a generally vertical orientation, however, the control panel  32  can also be supported along a major side using a mechanically fastened joint similar to joint  33  to either an upper horizontal or a lower horizontal portion of the frame  12 . A plurality of components are mounted on the control panel  32 . In particular, the control panel includes at least one pressure gage  36 , an air regulator adjustment knob  37 , an unloader valve  38 , an engine on/off switch  39 , and a pair of quick disconnect fittings  40 . The arrangement of components on the control panel  32  is exemplary of a plurality of configurations of the pressure gages  36 , the unloader valve  38 , the on/off switch  39 , and the quick disconnect fittings  40  that are possible. 
   As detailed in  FIG. 4 , a rear tubular member  41  joins an upper horizontal to a lower horizontal tube of the frame  12  for both the first side  22  (not shown) and the second side  24 . Each rear tubular member  41  forms a frame clearance angle θ from a ground surface C as shown. The frame clearance angle θ permits the air compressor assembly  10  to be rotated about an axis of rotation D formed at the center of each of the first wheel  18  (not shown) and the second wheel  20 . An axle vertical axis E extends from the axis of rotation D. A center-of-gravity  42  is disposed forward of the axle vertical axis E. The position shown for the air compressor assembly  10  in  FIG. 4  is the normal operating position having each of the first wheel  18  and the second wheel  20  and each of the support feet  28  contacting the ground surface C. It will be apparent to a person of skill that the ground surface C can vary in geometry from that shown such that the normal operating position can vary providing that each of the wheels and the support feet contact the ground surface C. Also as shown in  FIG. 4 , the second wheel  20  (as well as the first wheel  18 , not shown) are positioned at a rear-most portion of the lower horizontal tube of the frame  12 . The fluid pressure tank  16  is generally positioned over the support feet  28  as shown. The configuration of the frame  12  therefore provides the wheels ( 18 ,  20 ) and the support feet  28  adjacent to the heaviest components to adequately support the components of the air compressor assembly  10 . References herein to forward and rear (and rearward) directions are in relation to the forward direction arrow F. 
   As best seen in  FIG. 5 , the air compressor assembly  10  is rotated about the axis of rotation D in the lift rotation direction H, until the rear tubular member  41  and/or the rear support member  34  contact the ground surface C. A frame rotation stop point  44  is shown at the point of contact between the frame  12  and the ground surface C. At the rotated position shown in  FIG. 5 , the center-of-gravity  42  remains forward of the axle vertical axis E. The frame  12  in this position is rotated to an assembly rotation angle φ from the ground surface C. At the assembly rotation angle φ, gravity will bias the air compressor assembly  10  to rotate in the return rotation direction J about the axis of rotation D to return to the normal operating position shown in  FIG. 4 . For the condition shown in  FIG. 5  having a horizontal ground surface C, the maximum assembly rotation angle φ will depend on several variables including (with reference to  FIG. 4 ), the distance X between the axle vertical axis E and a rearward facing end of the frame  12 , a radius of the wheels Y, and the height Z from the ground surface C to the frame rotation stop point  44 . 
   Referring back to  FIG. 4 , a total height T and a total length V for the air compressor assembly  10  are shown. In a preferred embodiment, the total height T is approximately 51 cm (20″), and the total length V is approximately 119 cm (47″). It will be the obvious that the dimensions of the present invention can be varied without departing from the spirit and scope of the present invention. 
   As best detailed in  FIG. 6 , a gasoline powered reciprocating engine  50  and a compressor pump  52  are shown. The engine  50  includes a drive pulley  54  coupled by a V-belt (not shown) to a rotating pulley  56  of the compressor pump  52 . The arrangement of the engine  50 , the compressor pump  52 , and the fluid pressure tank  16  is selected to generally evenly distribute the weight of these components about the assembly longitudinal axis A. The first side  22  provides a pull/lift location  58  and the second side  24  provides a pull/lift location  60  to manually lift and move the air compressor assembly  10  from a forward end of the compressor assembly  10 . The air compressor assembly  10  can be lifted from either of the pull/lift locations  58  or  60 , respectively, however; to push the air compressor assembly  10  in a direction opposite to the forward direction F, it is preferable to hold both the pull/lift locations  58  and  60  simultaneously. In the embodiment shown, the fluid pressure tank  16  is partially supported from the frame  12  by a pair of brackets  61  which are mechanically connected to each of a pair of tabs  62  welded to the fluid pressure tank  16 . 
   The axle  46  has distal ends which form each of an outer planar envelope K and an outer planar envelope L shown. The end caps  48  are included within the outer planar envelopes K and L, respectively. The frame  12  and all of the components including those mounted to the control panel  32  and bounded by the control panel outer envelope M are within the region bounded by the outer planar envelopes K and L, respectively. 
   As shown in  FIG. 7 , rear facing components of the engine  50 , including a muffler  63 , are positioned within the envelope of the frame  12 . A compressor body  64  and a cooling head  66  of the compressor  52  also fit within the envelope of the frame  12 . This arrangement reduces the potential for damage occurring to these components by extending beyond the protected boundary of the frame  12 . 
   Referring now to  FIG. 8 , the brackets  61  and the tabs  62  supporting the fluid pressure tank  16  to the frame  12  are shown in greater detail. The axle  46  is rotatably positioned through apertures (not shown) formed in the lower horizontal members of the first side  22  and the second side  24  of the frame  12  approximate an aft end of the compressor assembly  10 . The geometry and structure of the support feet  28  are also shown. The structure of the support feet  28  is mechanically fastened to the support plate  26  as best described in reference to  FIG. 9 . The support feet  28  form a portion of a support structure  68  which includes arches  70  to separate each of the support feet  28 . The arches  70  allow the air compressor assembly  10  to remain stationery and each of the support feet  28  in contact with the ground surface C when the ground surface C varies from the horizontal plane shown. 
   As best shown in  FIG. 9 , an undersurface of the air compressor assembly  10  provides the support locations for the support plate  26  to each of the first side  22  and the second side  24 , respectively. A plurality of weld joints  72  join portions of the support plate  26  to each of the first side  22  and the second side  24 . A drain valve  74  for the fluid pressure tank  16  is accessible via an aperture  76  formed in the support structure  68 . A raised area  78  of the support structure  68  adjacent to the drain valve  74  provides additional protection for the portion of the drain valve  74  extending below the outer circumference of the fluid pressure tank  16 . The support structure  68  is mechanically connected to the fluid pressure tank  16  via a plurality of fasteners  80  and tabs (not shown). The compressor  52  (shown in  FIG. 7 ), is mounted to the support plate  26  via a plurality of fasteners  82 . A drain fitting (not shown) for the compressor  52  is aligned with a drain aperture  84  through the support plate  26  in order to drain the lubrication fluid contents of the compressor  52 . The engine  50 , similarly shown in  FIG. 7 , is mounted to the support plate  26  via a plurality of fasteners  86 . A drain fitting  88  for the engine  50  has a drain aperture  90  aligned therewith to permit the lubrication fluid of the engine  50  to be drained. 
   Referring to  FIG. 10 , an air compressor assembly  100  for another preferred embodiment of the present invention is shown. The air compressor assembly  100  includes a frame  102 , a component group  104 , and a fluid pressure tank  106  similar to the air compressor assembly  10 . Other components shown including the wheels and the control panel are similar to those shown for air compressor assembly  10  and are therefore not further discussed herein. The frame  102  includes a first side  108  and a second side  110 , generally formed of tubular material. Each of the first side  108  and the second side  110  have distal ends  109  and  111 , respectively positioned approximately in line with a longitudinal axis of the fluid pressure tank  106  as viewed from a plan view of the air compressor assembly  100 . A pair of tabs  112  are joined by each of a pair of fasteners  114  to the first side  108  and the second side  110  on a first end and are welded to the fluid pressure tank  106  on a second end. The frame  102  is therefore connected at both an upper surface and a lower surface of the fluid pressure tank  106  and partially relies on the rigidity of the fluid pressure tank  106  to stiffen the frame  102 . The frame  102  also includes a central lift section  116  which is aligned approximately with the assembly longitudinal axis (similar to the assembly longitudinal axis A of the air compressor assembly  10 ) at a forward end of the air compressor assembly  100 . The central lift section  116  permits the air compressor assembly  100  to be pushed or pulled along the air compressor assembly  100  longitudinal axis. Optionally, the central lift section  116  is extended in the forward direction F from a stowed position (shown) to an extended position (shown in phantom) and locked in the extended position. Additionally, the central lift section can be totally removed. Mechanical locking means to lock the central lift section  116  in either of the stowed or the extended positions such as spring loaded pins are known and are therefore not discussed further herein. To make the central lift section  116  extendable, a diameter of the central lift section  116  is made either smaller or larger than the diameter of both the first side  108  and the second side  110 . 
   Referring finally to  FIG. 11 , the method steps to bias a compressor assembly of the present invention are described. In an initial step  200 , a center-of-gravity for a compressor assembly is calculated. In a step  202 , a pair of wheels having a common axis of rotation and a vertical axis disposed through the common axis of rotation is positioned aft of the center-of-gravity. In a following step  204 , a frame contact surface is extended rearward of the common rotation axis of the wheels. In a next step  206 , a lifting handle is disposed forward of the center-of-gravity. In step  208 , a rotation path for the compressor assembly is defined which varies between a normal operating position and a rotated position, the rotated position having the frame contact surface contacting a ground surface when the lifting handle is used to rotate the compressor assembly about the common axis of rotation. In a final step  210 , the frame contact surface is prepositioned to retain the center-of-gravity forward of the vertical axis, throughout the compressor assembly rotation path, to bias the compressor assembly to return by gravity from the rotated position to the normal operating position for any position of the compressor assembly along the rotation path. 
   An air compressor assembly of the present invention offers several advantages. The rear frame geometry together with selected placement of the center-of-gravity of the unit reduces the likelihood that the air compressor assembly will tip over. A gravity bias returns the unit to the normal operating position. The frame of the air compressor assembly provides a totally enclosed volume to protect the equipment supported by the frame. The control panel of the present invention provides for all of the items mounted thereon to be contained within a planar envelope formed by the ends of the axle supporting the wheels. This reduces the potential to damage any of the components mounted on the control panel. Apertures are provided in the support plate to drain the fluids from the compressor and engine, as well as providing an access for operation of the drain and vent valve from the fluid pressure tank. Multiple support points are available for the different frame embodiments of the present invention to allow the units to be pushed or pulled without tipping over the unit. The small space envelope of the assembly of the present invention permits the entire unit to be placed within standard compartments of commercially available trucks used in the construction industry. The wheels, the support feet, and the forward handle of the air compressor assembly are removable to facilitate a shipping configuration and packaging of the unit. 
   The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.