Engine cooling system for skid steer loaders

A skid steer loader includes an engine compartment and a heat exchanger compartment located behind the operator's compartment. A fan shroud mounted between the heat exchanger compartment and the engine compartment has a first air intake aperture opening into the heat exchanger compartment, a second air intake aperture opening into the engine compartment, and an exhaust port. A double-bladed radial fan is mounted for rotation within the fan shroud between the first and second air intake apertures. A fan drive mechanism coupled to the engine rotates the fan. The fan simultaneously induces a heat exchanger airflow of ambient air through the heat exchanger compartment and into the fan shroud through the first air intake aperture, and an engine compartment evacuation airflow from within the engine compartment into the fan shroud through the second air intake aperture. The heat exchanger airflow and engine compartment evacuation airflows are mixed and jointly discharged from the loader through the exhaust port.

REFERENCE TO COPENDING APPLICATION 
Reference is hereby made to a copending application entitled "Skid Steer 
Loader and Method of Assembly", filed Oct. 13, 1987, assigned Ser. No. 
07/108,128, and assigned to the same assignee as the present invention. 
BACKGROUND OF THE INVENTION 
1. Field of the Invention. 
The present invention relates generally to engine cooling systems for skid 
steer loaders. In particular, the present invention is a flexible cooling 
system which can utilize a single fan to draw fresh air through the 
radiator, and to evacuate dust, debris and engine-heated air from the 
engine compartment. 
2. Description of the Prior Art. 
Skid steer loaders are compact, highly maneuverable vehicles which are 
commonly used in a variety of applications. Maneuverability of skid steer 
loaders is enhanced by a favorable weight ratio for the weight carried at 
the front and rear axles during loaded and unloaded conditions. It is 
desirable to provide as compact a vehicle structure as possible to 
maximize the efficiency of this weight ratio. Accordingly, known skid 
steer loaders have an engine compartment located at the rear of the 
vehicle immediately behind the operator's compartment. Approximately 70% 
of the vehicle weight thereby overlies the rear axle when the bucket at 
the front of the vehicle is unloaded. 
Due to the extremes in environments and operating conditions to which skid 
steer loaders are often subjected, durable and high capacity engine 
cooling systems are required. Skid steer loaders are frequently used in 
locations where considerable air borne debris, dust and other contaminants 
are present. Contaminant concentration is typically greatest near the 
surface on which the loader operates, and decreases at greater distances 
from the surface. However, the engine compartment in skid steer loaders is 
usually positioned relatively low on the vehicle, near the surface where 
contaminant concentration is greatest. 
The engine compartment of a skid steer loader is typically located 
immediately behind and sometimes extends underneath the operator's 
compartment. Unless provisions are made to evacuate engine-heated air from 
within the engine compartment, temperatures within the operator's 
compartment can become uncomfortable. However, if too much air is 
evacuated from the engine compartment, contaminants will be drawn in 
through various randomly located openings. This dust and debris will 
accumulate within the engine compartment, reduce cooling system 
efficiency, and result in other problems. 
A variety of engine cooling systems have been utilized in skid steer 
loaders, and are disclosed generally in the Henline et al. U.S. Pat. No. 
4,117,90 and the Mather et al. U.S. Pat. No. 4,535,868. In one prior art 
design, the radiator and oil cooler are mounted between a louvered rear 
closure and an engine fan. The engine fan draws air from outside the 
vehicle through the radiator and oil cooler. While cooling systems of this 
type can provide adequate cooling for the engine, no provision is made for 
evacuating heated air from within the engine compartment. As a result, the 
operator's compartment can get hot, providing an uncomfortable working 
environment for the operator. Furthermore, the large mass of air passing 
through the radiator and oil cooler is drawn from locations near the 
surface. Dust and debris therefore build up within the engine compartment 
and reduce cooling system efficiency. 
Another engine cooling system uses a fan driven by a hydraulic motor to 
pull ambient air through an intake radiator and oil cooler located near 
the top of the engine compartment. Although less debris is drawn into the 
engine compartment, this system does nothing to alleviate uncomfortably 
high temperatures which can develop in the operator's compartment. 
In still other known cooling systems, air is drawn through louvers into the 
engine compartment by a radial fan, and directed out of the engine 
compartment through the radiator and oil cooler. While this system has the 
advantage of evacuating heated air from the engine compartment thereby 
reducing the temperature in the operator's compartment, it is not without 
its drawbacks. Dust and dirt drawn into the engine compartment by the fan 
is blown into the radiator and oil cooler, thereby decreasing their 
efficiency. 
Another problem associated with the above-described cooling systems relates 
to the design constraints imposed upon designers. A relatively large mass 
of air must be drawn through the restrictions of the oil cooler and 
radiator. In general, the larger the engine used in the loader, the 
greater the air flow needed to adequately cool it. With a line of skid 
steer loaders having differently sized engines it can therefore be 
difficult to provide the optimum balance between fan size, blade 
configuration and fan speed in order to minimize fan horsepower 
consumption and noise while at the same time maximizing the mass of air 
transmitted. 
It is evident that there is a continuing need for improved cooling systems 
for skid steer loaders. A cooling system which draws ambient air through 
the radiator and oil cooler, and which evacuates heated air from within 
the engine compartment, is desired. The system should evacuate only 
sufficient air from the engine compartment to maintain a stable near 
ambient condition so as to minimize the amount of debris carried into the 
engine compartment. Air drawn through the radiator and oil cooler should 
be as free of contaminants as possible. The system must, of course, be 
efficient. It should also be flexible enough to be capable of being 
adapted to a variety of different loader models having differing system 
demands. 
SUMMARY OF THE INVENTION 
One embodiment of the present invention is a skid steer loader of the type 
including a heat exchanger and engine enclosure located behind an 
operator's compartment. An ambient air intake and an exhaust port extend 
through the enclosure. A fan shroud mounted within the enclosure has an 
enclosure evacuation air intake which opens into the enclosure, a heat 
exchanger air intake, and an exhaust port communicating with the exhaust 
port extending through the enclosure. An engine and radiator are mounted 
within the enclosure. The radiator is mounted between the ambient air 
intake of the enclosure and the heat exchanger air intake of the fan 
shroud. A radial fan is mounted for rotation within the fan shroud between 
the enclosure evacuation air intake and the heat exchanger air intake. Fan 
drive means coupled between the engine and the radial fan rotate the fan. 
The fan thereby induces a heat exchanger air flow from the ambient air 
intake through the radiator and into the fan shroud through the heat 
exchanger air intake, while simultaneously inducing an enclosure 
evacuation air flow from within the enclosure into the fan shroud through 
the enclosure evacuation air intake. The heat exchanger air flow and 
enclosure evacuation air flow are mixed and jointly discharged from the 
heat exchanger and engine enclosure through its exhaust port. 
In preferred embodiments the heat exchanger and engine enclosure includes 
both an engine compartment and a heat exchanger compartment. The engine is 
mounted within the engine compartment while the radiator is mounted within 
the heat exchanger compartment. The fan shroud is mounted with its heat 
exchanger air intake opening into the heat exchanger compartment, and the 
enclosure evacuation air intake opening into the engine compartment. The 
fan drive means includes a belt and pulley linkage which couples the 
engine to the radial fan. 
In one embodiment, the radial fan includes a base having first and second 
opposite sides with the first side oriented toward the heat exchanger air 
intake of the fan shroud, and the second side oriented toward the 
enclosure evacuation air intake. A plurality of heat exchanger airflow fan 
blades extend from the first side of the base, while a plurality of 
enclosure evacuation airflow fan blades extend from the second side of the 
base. The heat exchanger airflow fan blades are configured to draw a 
greater mass of air than the enclosure evacuation airflow fan blades. In 
other embodiments, the radial fan includes a base having a first side 
oriented toward the heat exchanger air intake of the fan shroud, and a 
plurality of apertures extending therethrough. A plurality of fan blades 
extend from the first side of the base. The enclosure evacuation air flow 
then flows into the fan shroud through the enclosure evacuation air intake 
and the apertures in the base of the fan, before being discharged. 
Skid steer loaders utilizing engine cooling systems in accordance with the 
present invention have considerable advantages over those of the prior 
art. A single fan can be utilized to draw ambient air through the radiator 
while simultaneously evacuating the engine compartment. The radiator can 
thereby efficiently perform its cooling functions, while heated air from 
within the engine compartment is discharged. Temperature within the 
operator's compartment can thereby be more easily regulated.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A skid steer loader 10 in accordance with the present invention is 
illustrated generally in FIGS. 1 and 2. As shown, loader 10, includes a 
main frame assembly 16, lift arm assembly 30 and operator's compartment 
40. An engine compartment 22 and heat exchanger compartment 24 are located 
at the rear of the vehicle. A pair of wheels 12 which are mounted to stub 
axles 14 extend from both sides of main frame 16. 
Lift arm assembly 30 is mounted to upright members 20 of main frame 
assembly 16. As shown, lift arm assembly 30 includes an upper portion 
formed by a pair of lift arms 32 which overlie wheels 12 and are pivotally 
mounted at a rearward end to upright members 20, and a lower portion 33. 
Pivotally mounted to lower portion 33 is an attachment such as bucket 34. 
Lift arm assembly 30 is raised and lowered with respect to main frame 
assembly 16 by means of a pair of boom lift cylinders 36, each of which 
has a first end pivotally mounted to one of upright members 20, and a 
second end pivotally mounted to one of lift arms 32. Bucket 34 is rotated 
with respect to lift arms 32 in a known manner by means of a bucket tilt 
cylinder (not visible). 
Operator's compartment 40 is partially enclosed by a cab 42 which is 
defined by side guard panels 44, overhead panel 46, rear guard panel 48, 
back panel 50 and seat pan 52. Cab 42 is an integral unit which is 
pivotally mounted at its rear to main frame 16. Cab 42, including seat 54 
which is mounted to pan 52, can thereby be rotated upwardly and toward the 
rear of loader 10 to permit access to engine compartment 22 and other 
mechanical and hydraulic systems yet to be described. 
All functions of loader 10 can be controlled by an operator from within 
operator's compartment 40. The hydraulic drive system described in 
subsequent portions of this specification is actuated and vehicle 10 
steered using a pair of levers 58, one on each side of seat 54, which can 
be moved independently in a forward and rearward direction. Motion of 
levers 58 causes wheels 12 on that side of the loader to rotate at a speed 
and in a direction corresponding to the extent and direction in which the 
respective lever is moved. Boom lift cylinder 36 and the bucket tilt 
cylinder are actuated by means of foot pedals (FIG. 15) mounted toward the 
front of operator's compartment 40. The general operation of skid steer 
loaders such as that illustrated and described above is well known. 
The assembly of loader 10 begins with the fabrication of a lower frame 
assembly 60 which is illustrated generally in FIG. 3. Lower frame assembly 
60 is fabricated around a transmission case 62 which can be of a 
conventional design, such as that described in the Bauer et al. U.S. Pat. 
No. 4,060,261. As perhaps best shown in FIG. 4, transmission case 62 is 
constructed from two elongated sections 59 and 61 which are welded 
together to form a top wall 64, side walls 66, (only one of which is 
visible), and bottom wall (not visible). Top wall 64 includes three 
openings 71 through which access to mechanical systems within transmission 
case 62 can be gained. Side walls 66 each include a motor opening 67. A 
pair of axle housings 74 are welded to and extend from each side wall 66 
of transmission case 62. 
A back lower frame end flange 80 encloses one end of transmission case 62, 
and a front lower frame end flange 82 encloses the opposite end. End 
flanges 80 and 82 will have been previously fabricated from metal, and can 
be welded to the ends of transmission case 62. In the embodiment shown, 
end flanges 80 and 82 extend from the sides of transmission case 62 and 
are generally parallel to axle housings 74. Back end flange 80 has a pair 
of opposite side edges 84 which are vertically oriented and parallel to 
transmission case side walls 66, a bottom edge 88 and top edge 92. A pair 
of integral mounting brackets 96 extend upward from opposite sides of top 
edge 92 of back end flange 80. Front end flange 82 also has a pair of 
opposite side edges 86, top edge 94 and bottom edge 90. 
Referring back to FIG. 3, lower frame assembly 60 is shown to include a 
pair of side flanges 100 which are fabricated from metal and have a motor 
aperture 102 and a pair of axle housing apertures 104. Side flanges 100 
are mounted to lower frame assembly 60 with axle housings 74 extending 
through apertures 104. Opposite edges 106 and 108 of side flanges 100 fit 
adjacent and are welded to edges 84 and 86 of end flanges 80 and 82, 
respectively. Flanges 100 are preferably welded to axle housings 74 as 
well. Bottom panels 101 (only one is visible in FIG. 3) extend between and 
are welded to back end flange bottom edge 88, front end flange bottom edge 
90, side flange lower edges 99, and the lower edges of transmission case 
side walls 66. The bottom of lower frame 60 is thereby enclosed by bottom 
panels 101. 
Lower frame assembly 60 also includes an engine mount platform or assembly 
110 which is mounted to back end flange 80 opposite transmission case 62. 
Engine mount assembly 110 can be fabricated from a single sheet of metal, 
and is illustrated in greater detail in FIG. 16. As shown, engine mount 
assembly 110 is fabricated to include a center belly pan panel 112, side 
belly pan panels 111, and vertically oriented side flanges 116. A pair of 
integral mounting flanges 114 extend laterally from a rear of side flanges 
116. Side flanges 116 and mounting flanges 114 have holes therein to 
facilitate the mounting of main frame assembly 16. Engine mount assembly 
110 is an integral element of lower frame assembly 60, being mounted to 
transmission case 62 by welding forward edges of panels 111, 112 and 
flanges 116 to back end flange 80 as shown in FIG. 3. A rear mounting 
bracket 118 is oriented in a laterally extending direction and welded to a 
rear edge of panels 111, 112 and flanges 114, at the rear of engine mount 
assembly 110. 
The assembly of lower frame assembly 60 is completed by mounting a 
hydraulic motor 78, which in some embodiments also includes a gear 
reduction mechanism, to each side wall 66 adjacent motor openings 67. An 
axle shaft (not visible) with a wheel mount 76 on one end thereof is 
rotatably fit within each axle housing 74. Hydraulic motors 78 are coupled 
within transmission case 62 to the axles on the side of the transmission 
case to which it is mounted by means of a sprocket and chain linkage (not 
visible) in a well known manner. Cover plates 70 are then secured to top 
wall 64 of transmission case 62, covering openings 71. 
While lower frame assembly 60 is being fabricated and assembled in the 
manner described above, engine and hydraulic pump assembly 140, which is 
perhaps best shown in FIGS. 5 and 6, can be simultaneously assembled. 
Engine and pump assembly 140 includes an engine 142 (only the case of 
which is shown in section in FIGS. 5 and 6 for purposes of clarity), a 
hydraulic pump assembly 144, and an engine/pump mounting bracket 146. 
Engine 142 can be of any commercially available type suited to the 
application, and has a drive shaft 148 which extends from its flywheel end 
face 150. Hydraulic pump assembly 144 includes a pair of variable 
displacement pumps 143 and 145, and an implement pump 147, all of which 
are driven by a common drive shaft 152. Drive shaft 152 extends from front 
face 154 of pump assembly 144. Engine 142 and pump assembly 144 are 
manufactured and/or subsequently machined in such a manner that their 
respective flywheel end face 150 and front face 154 are planar, and 
perpendicular to their drive shafts 148 and 152. 
Engine/pump mounting bracket 146 has a back face 156, a front face 158, and 
a guard rim 160 which extends in a generally perpendicular direction from 
the periphery of the front face. Mounting bracket 146 is manufactured 
and/or machined after manufacture so that an engine mounting portion 162A 
and a pump mounting portion 162B of back face 156 are planar and parallel 
to one another. Engine 142 is secured to mounting bracket 146 by bolts 
164, with its flywheel end face 150 fit adjacent engine mounting portion 
162A of back face 156. Since surfaces 150 and 156 are planar, and drive 
shaft 148 extends perpendicularly from engine flywheel end face 150, 
perpendicular alignment between shaft 148 and back face 156 of mounting 
bracket 146 is ensured. A drive pulley 198 is then mounted to the end of 
engine drive shaft 148. 
Engine/pump mounting bracket 146 also includes a starter motor mount 151 
fabricated integrally therewith on its periphery near engine mounting 
portion 162A. Starter motor 153 (FIG. 12) can be fastened directly to 
mount 151, and coupled to engine drive shaft 148 through a linkage (not 
shown) in a convention manner. 
Pump assembly 144 is adjustably secured to mounting bracket 146 by means of 
adjustable mounting bracket 168. Bracket 168 is fabricated and/or 
subsequently machined in such a manner as to include a hydraulic pump 
assembly mounting face 170 on one side thereof, and a mutually parallel 
mounting bracket face 172 on the opposite side. A pair of horizontally 
oriented slots 174 extend through bracket 168 near its upper edge, and are 
positioned in such a manner as to be vertically aligned with bores 176 
which extend through portion 162B of engine/pump mounting bracket 146. 
Adjustable mounting bracket 168 is sized to have a height greater than the 
height of aperture 178 in engine/pump mounting bracket 146. Upper and 
lower portions of mounting bracket face 172 will therefore extend beyond 
aperture 178 and fit against portion 162B of back face 156 of engine/pump 
mounting bracket 146. 
Hydraulic pump assembly 144 is mounted to bracket 168 by fasteners (not 
shown), with its front face 154 flush with pump mounting face 170. 
Adjustable bracket 168, in turn, is mounted to engine/pump mounting 
bracket 146 by means of bolts 180 which extend through slots 174 and bores 
176, and are secured by nuts (not shown). Mounting bracket face 172 of 
adjustable bracket 168 will be flush with surface portion 162B of 
engine/pump mounting bracket 146. Since pump shaft 152 is oriented 
perpendicular to front face 154, and front face 154, faces 170 and 172 of 
adjustable bracket 168, and pump mounting portion 162B of bracket 146 are 
all parallel to one another, pump shaft 152 will be parallel to engine 
shaft 148 when hydraulic pump assembly 144 and engine 142 are mounted to 
engine/pump mounting bracket 146 in the manner described. An integral pump 
and fan drive pulley unit 196 is mounted to the end of pump shaft 152. 
Pump pulley 197 of pump and fan drive pulley unit 196 is coupled by drive 
belts 194 to engine pulley 198 as shown. Unit 196 also includes a fan 
drive pulley 251. 
The position of hydraulic pump assembly 144 on engine/pump mounting bracket 
146 can be adjusted while at the same time maintaining shafts 152 and 148 
in their mutually parallel state. This is accomplished by means of 
brackets 182 and 184, and adjustment rod 186. Bracket 182 is fastened to 
engine/pump mounting bracket 146 by means of bolts 188 (FIG. 6) and 
extends from the engine/pump mounting bracket toward hydraulic pump 
assembly 144. Bracket 184 is secured to adjustable bracket 168 by means of 
bolt 190. A semicircularly bent end of rod 186 extends through a bore in 
bracket 184 and is secured thereto, while a threaded end of rod 186 
extends through a bore in bracket 182. When bolts 180 are loosened, 
adjustable bracket 168 and hydraulic pump assembly 144 can be moved 
horizontally toward or away from engine 142 by turning nuts 192 which are 
threaded onto rod 186 on opposite sides of bracket 182. 
Additional support between engine 142 and pump assembly 144 is provided by 
brackets 204 and 208. One end of bracket 204 is fastened by bolts 206 to 
the side of engine 142 which faces pump assembly 144. Bracket 208 includes 
an elongated slot 209, and is fastened to bracket 204 with slot 209 
opening toward pump assembly 144 and oriented parallel to surface 156 of 
engine/pump mounting bracket 146. Hydraulic pump 144 is then secured to 
bracket 208 by one or more bolts 211 which extend through slot 209. 
Following the assembly of engine and hydraulic pump assembly 140 in the 
above-described manner, the position of hydraulic pump assembly 144 on 
engine/pump mounting bracket 146 can be adjusted to properly tension belts 
194. Bolts 180 and 211 are loosened to permit movement of adjustable 
bracket 168 and pump assembly 144 with respect to engine/pump mounting 
bracket 146 and engine 142. Nuts 192 are then rotated to move pump 
assembly 144 toward or away from engine 142 until the proper tension is 
applied to belts 194. Pump assembly 144 is then securely fastened with 
respect to engine 142 by tightening bolts 180 and 211. In an alternative 
embodiment, a spring-loaded idler pulley (not shown) which is mounted to 
bracket 146 applies pressure to drive belts 194 at a location intermediate 
pump and fan drive pulley unit 196 and engine pulley 198, thereby properly 
tensioning the drive belts. 
After it has been assembled and trimmed in the manner described above, 
engine and hydraulic pump assembly 140 are mounted to engine mount 
assembly 110 at the rear of lower frame assembly 60, as shown in FIG. 7. 
Engine 142 is fastened to rear mounting bracket 118 of engine mount 
assembly 110 by means of brackets 200 and bolts 202 and 203. Engine/pump 
mounting bracket 146 and bracket 204 are secured to mounting brackets 96 
of lower frame assembly 60 by bolts 211 (FIGS. 6, 14 and 15). A fuel tank 
(not shown) can be located between belly pan panels 111, 112 and engine 
142. 
From the above description it can be seen that engine/pump mounting bracket 
146 permits engine 142 and pump assembly 144 to be assembled with respect 
to each other before engine and pump assembly 140 is mounted to lower 
frame 60. Tension on belts 194 can be easily adjusted while at the same 
time maintaining proper alignment of engine drive shaft 148 and pump drive 
shaft 152. Furthermore, all of these procedures can be performed before 
main frame 16 is mounted to lower frame 60, hindering access to these 
portions of loader 10. Maintenance procedures involving motor 142, pump 
assembly 144 and belts 194 are also facilitated. 
After engine and pump assembly 110 has been mounted to lower frame 60, 
hydraulic hoses or lines 350 which provide hydraulic fluid from variable 
displacement pump 143 to hydraulic motor 78 on the right side of the 
loader 10 can be connected. Similarly, hydraulic lines 352 which supply 
fluid between variable displacement pump 145 and hydraulic motor 78 on the 
left side of loader 10 can be added. These assembly procedures are 
illustrated in FIG. 15. Boom control pedal 282 and bucket control pedal 
284, as well as their respective linkages 286 and 288, can also be 
assembled on lower frame 60 at this time. All mechanical systems on lower 
frame assembly 60, including engine and pump assembly 140 and those within 
transmission case 62, can be fully tested and adjusted at this time 
without interference from main frame 16. These procedures increase 
manufacturing efficiency. 
Main frame assembly 16 is illustrated in greater detail FIG. 8. Main frame 
assembly 16 is fabricated from steel and includes a pair of longitudinally 
extending and laterally spaced side beams 18 having outwardly directed 
upper flanges 210 which will overlie wheels 12 (FIGS. 1 and 2) and serve 
as protective fenders for loader 10. Side beams 18 are joined at the front 
by front cross or wall member 212, and at the rear by upright fabrication 
214. The bottom side of main frame 16 is completely open. 
Upright fabrication 214 includes a pair of upright members 20. Each upright 
member 20 includes a pair of laterally spaced side portions 216 and 218 
joined by a vertically extending rear portion 220. Inner side portions 218 
abut side beams 18, while side portions 216 are spaced outwardly from 
portions 218 to provide a channel therebetween. Each side portion 218 has 
an exhaust port 254 (FIGS. 1, 2 and 9) located near its forward edge. 
Mounting brackets 221 (only one is visible in FIG. 8) extend between lower 
edges of side portions 216 and side beams 18. Front cross member 220 
extends between side portions 218 near the upper part of the front side of 
uprights 20. A generally vertically oriented rear cross member 222 and a 
generally horizontally oriented top cross member 224 extend between side 
portions 218 near the upper part of the rear of uprights 20. Boom pivot 
mounts 226 to which boom arms 32 of lift arm assembly 30 are pivotally 
connected are provided at the upper end of each upright 20. Cab pivot 
mounts 228 are located on the front side of front cross member 220. Main 
frame assembly 16 can be similar to that disclosed in the Bauer et al. 
U.S. Pat. No. 4,055,262, and is preferably fabricated from plates of steel 
which are welded together. 
As shown in FIG. 9, a fan assembly 230, radiator 232, oil cooler 234, 
muffler 236 and hydraulic control valve 231 can be mounted (by means of 
fasteners not shown) to main frame assembly 16 after its fabrication and 
prior to its positioning on lower frame 60. Hydraulic fluid hoses 233 
which couple control valve 231 to boom lift cylinders 36, pump assembly 
144, the bucket tilt cylinder, and other auxiliary attachments (not shown) 
can also be easily positioned and secured to main frame 16 at this time. 
Radiator 232 and oil cooler 234 are mounted adjacent one another between 
front cross member 220 and rear cross member 222. This relationship, with 
radiator 232 positioned below oil cooler 234, can also be seen in FIGS. 13 
and 14. Grill 28 (FIGS. 13 and 14), which includes a debris filtering 
screen (not separately shown), is mounted between uprights 20 and cross 
members 220 and 224 above oil cooler 234. Muffler 236 is mounted below top 
cross member 224 and to the rear of rear cross member 222. Exhaust pipe 
238 extends from muffler 236 through an aperture in top cross member 224. 
Fan assembly 230 includes a fan shroud 240, radial fan 242, and fan drive 
244. Fan shroud 240 can be manufactured from plastic material, and 
includes a central portion 246 with a first or upper air intake aperture 
248 in the top side thereof. A second or lower air intake aperture 241 
(FIGS. 13 and 14) is located on the bottom side of fan shroud 240, 
opposite aperture 248. A pair of duct sections 250 communicate with and 
extend from opposite sides of central portion 246 of shroud 240. Each duct 
section 250 terminates in an exhaust port 252. As perhaps best shown in 
FIGS. 13 and 14, fan assembly 230 is mounted immediately below front cross 
member 220 and rear cross member 222. Fan shroud exhaust ports 252 
communicate with exhaust ports 254 which open through members 218 of 
uprights 20. 
Radial fan 242 is mounted for rotation within central portion 246 of fan 
shroud 240, adjacent to and between air intake apertures 248 and 241. As 
is shown in greater detail in FIGS. 10 and 17, radial fan 242 is a 
double-bladed fan, having a concave base 272 with a first set of heat 
exchanger blades 274 extending from a first side thereof, and a second set 
of engine compartment blades 275 extending from a second side. As shown in 
FIG. 14, radial fan 242 is mounted within fan shroud 240 with heat 
exchanger blades 274 extending toward upper air intake aperture 248, and 
engine compartment blades 275 extending toward lower air intake aperture 
241. For reasons described in subsequent portions of this specification, 
engine compartment blades 275 are smaller than heat exchanger blades 274. 
Blades 274 and 275 are contoured and positioned with respect to base 272 
to optimize air flow requirements with power demands. Base 272 is concave 
so that the center of gravity of fan 242 is near the bearings of fan drive 
244. Radial fan 242 is cast from a magnesium-aluminum alloy in one 
embodiment. Other materials can be used as well. 
Referring again to FIGS. 9, 13 and 14, fan drive 244 is a right angle drive 
mechanism in the illustrated embodiment, and is mounted below central 
portion 246 of fan shroud 240. In other embodiments hydraulic or electric 
motor drives can be used. The embodiment shown in FIG. 18 includes a 
hydraulic motor 400 which drives fan 242. Hydraulic motor 400 is coupled 
to one of the hydraulic pumps by means of hydraulic hoses 402. An output 
driveshaft 245 of fan drive 244 is connected to base 272 of radial fan 
242. Fan drive 244 has an input drive shaft 243 which is coupled to 
hydraulic pump drive shaft 152 through pulleys 247, 249 and 251, and belt 
253. Radial fan 242 will thereby be rotated within fan shround 240 by 
engine 142. The tension on belt 253 is adjusted by means of idler pulley 
249. 
As illustrated in FIG. 12, main frame 16, to which fan assembly 230 (not 
visible in FIG. 12), oil cooler 234, radiator 232, muffler 236 and other 
mechanical and hydraulic components have been mounted, can next be dropped 
onto and fastened to lower frame assembly 60. This step is performed after 
engine and hydraulic pump assembly 140 has been mounted to lower frame 
assembly 60. Side beams 18 are fastened to side flanges 100 by bolts 290. 
Mounting brackets 221 of uprights 20 are secured to mounting flanges 114 
of engine mount assembly 110, while more forward portions of uprights 20 
are fastened to side flanges 116. Required interconnections between oil 
cooler 234, radiator 232, muffler 236, and engine 142 can then be easily 
and conveniently made. 
The assembly of remaining structural elements of loader 10 can then 
continue in a known manner. Hydraulic fluid hoses 233, which have already 
been positioned on main frame 16, can be connected to pump assembly 144. 
Control linkages such as linkage 286 which couples foot control pedal 282 
to hydraulic control valve 231 can be added. Front closure panels 283 
which extend between side beams 18 below seat pan 52 are fastened in 
place. Door 26 is hingedly connected to one of uprights 20 at the rear of 
the vehicle. Cab 42 is pivotally connected to pivot mounts 228. Lift arm 
assembly 30 is pivotally mounted to uprights 20 at pivot mounts 226. 
Instrumentation and controls such as levers 58 within operator compartment 
40 are also added, as are linkages 302 which couple these levers to 
variable displacement pumps 143 and 145. 
It can be seen from FIG. 13 that engine compartment 22 has a rearward 
portion defined at its rear by door 26, at its bottom by panels 111 and 
112 of engine mount assembly 110, at its sides by portions 218 of uprights 
20, at its front by the back wall 50 of cab 42, and on its top by cross 
members 220 and 224 and the side and lower surfaces of fan shroud 240. A 
forward portion of engine compartment 22 opens into lower frame assembly 
60 below cab 42. This forward portion of engine compartment 22 is defined 
by back panel 50 and seat pan 52 of cab 42, front closure panels 283, side 
beams 18 of main frame 16, and bottom panels 101 and transmission case 62 
of lower frame assembly 60. 
Heat exchanger compartment 24 is defined on its sides by portions 218 of 
uprights 20, at its rear by cross member 222, at its front by cross member 
220, at the top by grill 28, and at its bottom by the top surface of fan 
shroud 240. 
When loader 10 is being driven by an operator, radial fan 242 will be 
rotated at a high speed within fan shroud 240. Heat exchanger blades 274 
will thereby draw fresh ambient air through the screen of grill 28, oil 
cooler 234 and radiator 232, and into fan shroud 240 through its upper 
aperture 248. This air, which will have been heated through the transfer 
of heat when passing through oil cooler 234 and radiator 232, is 
discharged from loader 10 through fan shroud ducts 250 and exhaust ports 
254. Concurrently, engine compartment blades 275 of radial fan 242 will 
draw air and debris from within engine compartment 22. This air and debris 
will be mixed with the air drawn through heat exchanger compartment 24, 
and jointly discharged through exhaust ports 254. The mass of air drawn 
from engine compartment 22 will be relatively small (e.g. 600 CFM) 
compared to that drawn through grill 28 (e.g. 3600 CFM) since heat 
exchanger blades 274 are larger and configured to be more efficient than 
engine compartment blades 275. 
The double inlet fan shroud system of loader 10 has significant advantages 
over prior art designs. Heated air and debris from within engine 
compartment 22 are evacuated without being passed through oil cooler 234 
or radiator 232. Temperatures within operator's compartment 40 can then be 
maintained at a comfortable level. The relatively small mass of air drawn 
from engine compartment 22, with respect to that being drawn through heat 
exchanger compartment 24, also helps cool engine 142. Furthermore, by 
selecting proper fan speed and size of blades 275, the minimum air flow 
required to maintain a stable near ambient condition within engine 
compartment 22 can be selected. This minimizes the amount of dirt, dust 
and other debris carried into engine compartment 22 resulting in a more 
serviceable unit. The reduced temperatures within engine compartment 22 
also results in a more favorable environment for heat sensitive 
components. Useable life of seals and other components can thereby be 
extended. Fresh and therefore relatively cool ambient air (as opposed to 
heated air from within the engine compartment) is drawn through heat 
exchanger compartment 24. The heat transfer efficiency of oil cooler 234 
and radiator 232 are therefore better than if air from within the engine 
compartment were used. Since the ambient air drawn into heat exchanger 
compartment 24 is taken from the top of the vehicle and relatively high 
above the ground, it will have relatively little dust and debris which 
might otherwise clog the radiator and oil cooler. This fan system can also 
be efficiently manufactured. 
Yet other advantages of the disclosed double inlet fan system reside in its 
flexibility. The use of engine/pump mounting bracket 146 along with the 
pulley and drive belt linkage permits different engines having various 
speed and power outputs to be easily coupled to one of a variety of 
different pumps having various displacements and speed. Fan size, blade 
configuration and fan speed can also be selected to minimize horsepower 
consumption and fan noise while maximizing the volumes of air being 
transmitted. Air flow through the heat exchanger compartment and from the 
engine compartment can also be independently selected through the 
configurations of fan blade sizes and aperture openings. Since a variety 
of different types of fan drives can be used, and speed ratios can be 
adjusted using different sized pulleys, fan characteristics can be 
suitably selected to optimize operating characteristics without being 
limited by engine, pump or vehicle speed. This high degree of flexibility 
is very important in that it permits a line of differently sized skid 
steer loader models to be efficiently produced. 
An alternative radial fan 270 is illustrated in FIG. 11. Radial fan 270 
includes a circular base 256 with a plurality (five are shown) of air 
intake apertures 258 which extend therethrough. Mounted to base 256 and 
extending perpendicularly therefrom are a plurality of fan blades 260. As 
shown, all fan blades 260 are mounted at the same angle with respect to 
radial axes of base 256. A ring 262 is fastened to the ends of fan blade 
260 opposite base 256. In one embodiment, fan blades 260 are welded to 
plate 256 and ring 262. Fan 270 can be cast or molded from other materials 
as well. 
Fan 270 can be mounted to output drive shaft 245 of fan drive 244 in place 
of radial fan 242 previously described. When loader 10 is being driven by 
an operator, radial fan 270 will rotate within fan shroud 240, and draw 
fresh ambient air through the screen of grill 28, oil cooler 234 and 
radiator 232, and into fan shroud 240 through its upper intake aperture 
248. This air is then discharged from loader 10 through fan shroud ducts 
250 and exhaust ports 254 in a manner identical to that previously 
described. Concurrently, air and debris from within engine compartment 22 
will be drawn through apertures 258 of plate 256, mixed with the air drawn 
through heat exchanger compartment 24, and jointly discharged through 
exhaust ports 254. A mass of air draw through engine compartment 22 can be 
selected by varying the size and quantity of apertures 258. 
Although the present invention has been described with reference to 
preferred embodiments, workers skilled in the art will recognize that 
changes may be made in form and detail without departing from the spirit 
and scope of the invention.