SKID STEER LOADERS

Abstract: Hydraulic drive for a skid steer loader wherein the power plant (12) drives a continuously variable output pump (13) whose output is coupled by control valves (17) to hydraulic drive motors with speed control achieved by adjusting the pump output (13) and steering achieved by setting of the control valves (17).

Description: "SKID STEER LOADERS" TECHNICAL FIELD OF THE INVENTION THIS INVENTION relates to a skid steer loader and more particularly to a skid steer loader of the type driven by hydraulic motors. BACKGROUND ART The coirtmon skid steer loader is run on wheels with the front and back wheel pairs locked together using chains and sprockets. Steering is by separate forward and rearward movement of the left and right hand side wheel pairs such that with one side driving forward and the other rearward, the skid steer loader may be turned within its own length. The drive to these machines is commonly to each wheel pair through separate hydraulic motors which are controlled by two forward/reverse levers. The hydraulics of these machines are basic and motor control is sought by the degree of valve opening to control hydrauli.c fluid flow. But in operation, movement of the vehicle and its driver, precise control of the valve is difficult as any impulsive movement will move the driver and his positioning of the control lever. Driving becomes a continual tiresome process of correction. Control of speed is difficult because precise control of valve opening is not possible particularly for the novice and more particularly as the driver's body weight is thrown about to cause him to inadvertently change the lever setting. OUTLINE OF THE INVENTION An object of the invention is a skid steer loader enabling a more precise operation than is achieved with more conventional equipment which is prone to control problems on rough surfaces and surfaces presenting varying resistances to operation of digging equipment such as front buckets. A further O PI object is a skid steer loader with a more familiar steering mechanism than what is conventionally employed on like equipment. Another object of the invention is a skid steer loader offering reliable speed control in adverse conditions. Additionally, the skid steer loader of the invention may enable a more precise application of power in operations requiring the application of force in a controlled manner. The invention also aims at provision of a skid steer loader which may be provided with tracks rather than wheels for operation in water logged or other soft soil conditions. Also the invention aims to provide a skid steer loader having application in many general tractor type situations. Further objects and advantages of the present invention will hereinafter become apparent. The invention achieves its objects by the provision of a skid steer loader which comprises a power source coupled by suitable coupling means to at least one variable output hydraulic pressure means, which said pressure means is hydraulically coupled to separate steering/driving control valves, said control valves controlling the flow of hydraulic fluid to separate hydraulic motors which said motors are each coupled to a respective set of drive mechanisms of the skid steer loader, wherein steering/driving control levers are operatively coupled to said control valves and an accelerator control means is operatively coupled to said variable output hydraulic pressure means to control the output thereof. BRIEF DESCRIPTION OF THE DRAWINGS In order that the invention may be more readily understood and put into practical effect, reference will now be made to the accompanying drawings which illustrate a number of preferred embodiments O P thereof and wherein:- Fig. 1 shows a schematic of a skid steer loader according to the invention; Fig. 2 illustrates an hydraulic system suitable for driving a loader according to the invention; Fig. 3 illustrates an hydraulic system suitable for operating the bucket of a loader according to the invention; Fig. 4 shows schematically the connection of a hydraulic motor to the drive wheel; Fig. 5 illustrates an alternate hydraulic system to that shown by Fig. 2; Fig. 6 illustrates schematically an arrangement of hydraulic pumps for use with the alternate hydraulic system of Fig. 5. METHOD OF PERFORMANCE In Fig. 1 a skid steer loader is shown employing a track configuration with track 11 driven by drive wheel 10 and looped around rear idler wheel 28 with a number of intermediate rollers 29 to 31. Power to the skid steer loader is provided by motor 12 which drives a variable output pump 13 which is connected to accelerator 14 by a suitable linkage 15. The output of pump 13 is taken through flow divider 16 to two control valves, one being shown as 17 in Figure 1, and connected to control lever 18. Movement of lever 18 switches valve 17 into forward or reverse modes to appropriately power an hydraulic motor (not shown) which drives wheel 10. The skid steer loader of Fig. 1 is shown fitted with a bucket 19 which is tilted by ram 20 and is mounted for vertical movement on boom 21 powered by ram 22. Conveniently, the skid steer loader may be constructed upon a steel plate 32 with the framework of the loader being in square type boxing which is sectioned and sealed appropriately to provide suitable oil storage tanks for the various hydraulic systems. Thus, the vertical support 25 for the boom 21 can contain the oil for the drive motors. Cross beam 35 might store oil for the bucket. The various tanks may be fitted with suitable breathers. Fig. 2 shows the arrangement of the hydraulic system which can be used in the present skid steer loaders. A diesel motor 12 may be employed to drive variable pump 13 whose output is controlled through a driver operated accelerator and suitable linkages. The output of pump 13 is split by a flow divider into two separate drive/steering systems comprised of double acting valves 17a and 17b and hydraulic motors 58 and 59. Control valves 17a and 17b can be operated by the usual upstanding drive/steering levers 18a and 18b. Movement of lewrs 18a and 18b forward or backwards puts their corresponding hydraulic motors into reverse or forward motion respectively. By crossing the hydraulic lines 55,54 with 56,57 such that the left hand lever operates the right hand hydraulic motor, operation of the skid steer loader can be made more conventional. By pushing forward on the right hand lever, the skid steer loader may be made to veer right. Operation of the two levers 18a and 18b produces no effect until the accelerator is operated to feed the output of pump 13 into the hydraulic lines and by control of the pump, a continuously variable, reliably achieved, speed control is made possible. The double acting valves 17a, 17b need only be on or off. There is no lever juggling required in order to gain control of the skid steer loader. Should rough operating conditions jostle the driver his control of the vehicle is not impaired through unintentional movements of the drive/steering OMP ( T levers as occurs in the prior art devices. The present hydraulic system gives the operator a more complete control of the loader. In Fig. 3 there is shown an additional hydraulic system which might be employed to provide suitable pressurised fluid to the various rams of the loader. Pump 27 may be connected off the back of diesel motor 12 to feed fluid to say ram 22 of Fig. 1. Control of this fluid is achieved by a suitable extra leve control 61 mounted atop one of the levers 18a or 18b at an elbow joint 62. Movement of this lever controls via a suitable double acting valve 71 the movement of the bucket in the vertical direction. Similarly other rams and hydraulic systems may be run off pump 27. The skid steer loader might be equipped with various agricultural implements, fitted say on the rear of the loader, powered by pump 27 and a suitable hydraulic ram or motor. In this way the skid steer loader may do duty as a small farm tractor and perform a wide range of tasks. in Fig. 4 the connection of the hydraulic motor 59 to the drive sprocket wheel (not shown) is illustrated schematically with flange 76 for receiving a sprocket wheel having flange bolts 77. Flange 76 is mounted on the end of axle 71 turning within two bearings 72 and 73 held in case 74 which houses a reservoir of lubricating oil. Axle 71 may be fitted with a suitable braking mechanism such as a drum type brake system represented as 75. Motor 59 is mounted to the inward end of axle 71 of the skid steer loader. The skid steer loader of the present invention may be provided with a standard dimension, three point linkage at the rear for attachment to a range of add on extras providing a variety of functions such as that of a back hoe, chain digger, post hole digger, ripper, general earth moving and/or farm equipment such as rotary hoe, scrub cutters and misting spray machine. In this manner the equipment can be used in light earthmoving, industry, agriculture, mining, dam clearing, working of ship holds, etc. The three point linkage may be formed upon adjustable arms providing telescopic movement, as well as up and down movement, to enable depth control and horizontal attitude of equipment mounted to the linkage. The top linkage point of the three point linkage may be provided with a double acting ram to move the linkage fore and aft along a horizontal direction. The two lower linkage points may be mounted upon telescopic arms pivotally connected to the rear of the vehicle for vertical movement under the action of double acting rams. The double acting rams may be independently operable to enable equipment supported on the three point linkage to be held horizontal when the skid steer vehicle is on sloping surfaces. The various above described degrees of freedom enable a variety of adjustments to positioning of equipment mounted on the linkage with tilting being possible in all directions. The three point linkage may be provided with hydraulic control lines and hydraulic motors do away with the need for the conventional mechanical power take off points. Fig. 5 shows an alternate form which the hydraulic system may take. A diesel motor, or other suitable power source 130, drives two ganged, variable output pumps 131 and 132 and an auxilliary pump 133. The three pumps may be arranged as shown in Fig. 6, interconnected by a gear box to which the three pumps are mounted. Each of the variable output pumps are connected to respective hydraulic motors 134 and 137 which may connect to drive sprockets or other connection means 136 and 139 through reduction boxes 135 and 138, if required. Oil for the pumps is drawn from a reserve 148. Control of the hydraulic motors 134 and 137 is by suitable control levers switching pressurised fluid from the variable output pumps which are controlled by a suitable accelerator control means to produce a hydraulic system operating in similar advantageous manner as described above in respect of Fig. 2. The auxilliary pump 133 of Fig. 5 may supply one or more rams with its output suitably split and controlled by means such as double acting control valves 140 and 141 provided with control levers 142 and 143. The output of the double acting valve 140 may feed a number of rams, such as lifting rams 145 and 146, whilst double acting valve 141 might control a dump ram 147 in order to give full control over the skid steer loader bucket. Other combinations of pumps, valves, and rams may be added to enable operation of a range of additional equipment and their ' interconnectio will be obvious to a man skilled in the art. In Fig. 6 is indicated a mechanism by which the requisite plurality of pumps, for an hydraulic syste such as that shown in Fig. 5, may be interconnected and mounted to a power source such as a diesel or other like motor. In Fig. 6 the three pumps, variable output pumps 151 and 152, and auxilliary pump 156, are mounted to a gear box 157 providing power to the respective pumps off a drive shaft 150 from the power source. The gear box 157 may be simply mounted to the bell-housing at the rear of the power source and directly connected thereto. The above described mechanisms enable the production of a small skid type loader mounted on crawler tracks to enable a go anywhere performance, not obtained by prior vehicles of the type. The use of OM crawler tracks distributes weight and enables the machine to work in wet and boggy conditions, sand, etc. The crawler tracks additionally serve to reduce the pitching of the machine as it moves over rough terrain to levels below that experienced by wheeled vehicles to further reduce driver jostling and the onset of "pig rooting" common with more conventional types of skid steer loaders. The employment of a three point quick hitch linkage at the rear of the vehicle enables the front bucket to remain attached whilst additional mechanisms are mounted behind to extend the range of activities which may be performed by the vehicle. The bucket may be grounded to anchor the machine for greater stability during operation of the additional apparatus carried on the three point linkage. While the above has been given by way of illustrative example, many modifications and variations as would be apparent to persons skilled in. he art may be made thereto without departing from the broad scope and ambit of the invention as herein set forth and defined in the following claims. O P

Claims: CLAIMS 1. A skid steer loader which comprises a power source (12) coupled by suitable coupling means to at least one variable output hydraulic pressure means (13) , which said pressure means (13) is hydraulically coupled to separate steering/driving control valves (17) , said control valves (17) controlling the flow of hydraulic fluid to separate hydraulic motors which said motors are each coupled to a respective set of drive mechanisms (10) of the skid steer loader, wherein steering/driving control levers (18) are operatively coupled to said control valves (17) and an acceleration control means (14) is operatively coupled to said variable output hydraulic means (13) to control the output thereof. 2. A skid steer loader as claimed in Claim 1 wherein one variable output hydraulic pressure means (13) is provided hydraulically coupled via a flow divider (16) to said separate steering/driving control valves (17) . 3. A skid steer loader as claimed in Claim 1 wherein at least one auxilliary hydraulic pressure means (27) is coupled to said power source (12) to provide hydraulic pressure to various operating rams and/or hydraulic motors, connected to provide motive power to various work performing mechanisms attached to said skid steer loader. 4. A skid steer loader as claimed in Claim 1 wherein each said motor is coupled via a reduction gear box to a respective drive sprocket operatively engaged with a crawler track to provide motive power thereto. 5. A skid steer loader as claimed in Claim 1 wherein said power source is coupled to two variable output hydraulic pressure means (131,132), each being coupled by respective steering/driving control valves to respective hydraulic motors (134,137) powering said drive mechanisms, said accelerator control means being operatively coupled to both said variable pressure means (131,132). 6. A skid steer loader as claimed in Claim 5 wherein at least one auxilliary hydraulic pressure means (133) is coupled to said power source (130) to provide hydraulic pressure to various operating rams, and/or hydraulic motors, connected to provide motive power to various work performing mechanisms attached to said skid steer loader. 7. A skid steer loader as claimed in Claim 6 wherein said two variable output hydraulic pressure means (131,132) and said at least one auxilliary hydraulic pressure means (133) are ganged together for joint operation off a single output shaft of said power source (130) which may be run at constant speed. ^TRE Q &/?N

Inventors: EDGERTON EDGAR ROBERT CHARLES, EDGERTON, EDGAR, ROBERT, CHARLES
Applicants: EDGERTON EDGAR ROBERT CHARLES, EDGERTON, EDGAR, ROBERT, CHARLES
Application year: 1983
Main classification: B62D11
IPC codes: B62D11