US2931305A

US2931305A - Automatic throttle control

Info

Publication number: US2931305A
Authority: US
Inventors: Ronald R Stratton
Original assignee: STRATTON EQUIPMENT CO
Current assignee: STRATTON EQUIPMENT CO
Priority date: 1957-04-25
Filing date: 1957-04-25
Publication date: 1960-04-05
Anticipated expiration: 1977-04-05

Description

April 5, 1960 R. R. STRATTON AUTOMATIC THROTTLE CONTROL Filed April 25, 1957 sgli INVENTOR.

Paw/1w A. 5754770 BY flM, M

AT TOPNE Y5:

AUTOMATIC THROTTLE CONTROL Ronald R. Stratton, Cleveland, Ohio,

Equipment Company, of Ohio assignor to Stratton Cleveland, Ohio, a corporation This invention relates to an automatic speed control for internal combustion engines and more particularly to an automatic throttle control for the engines of motor trucks embodying hydraulically operated devices such as dump bodies, lift platforms and the like in which the hydraulic pressure for operation of the device is furnished by a pump driven by a power take off from the truck engine.

Large numbers of trucks having hydraulic devices operated by power take off means driven by the engine are in use at the present time. Such trucks customarily embody a hydraulic motor, usually in the form of a cylinder, arranged to actuate a dump body, lift platform and the like or to perform some other desired function; a valve for controlling the flow of fluid to the hydraulic cylinder, the valve ordinarily being disposed outside of the cab of the truck at a point where the operator can observe the motion of the body, platform or the like; a pump for supplying hydraulic fluid under pressure to the cylinder; appropriate fluid connections for the devices; and a power take off usually embodying auxiliary gearing so that the main truck engine can be employed to drive the pump,

The ordinary idling speed of the engine is not suflicient to furnish sufiicient fluid under pressure to operate the hydraulic cylinder at a reasonably rapid rate of speed. Accordingly, operators of such trucks frequently pull out the hand throttle in the cab of the truck sufliciently to race the engine under no load at the speed which the operator thinks is proper. Then the operator leaves the cab, goes to his station adjacent the hydraulic control valve and by suitable manipulation of the valve, controls the operation of the cylinder. The result is that the truck engine is raced at excessive speeds for considerable periods of time, fuel consumption of the engine is excessive and the engine is subject to injury and rapid wear because of racing under no load. Another mode of operation employed by some drivers is to move the control valve to operating position with the en ine idling, then to go back to the cab and manipulate the throttle while leaning out of the door of the cab in an effort to observe the position of the body, platform or the like. This mode of operation is dangerous because it requires the operator to be away from his proper position at the control valve during the dumping or lifting operation.

According to the present invention these difficulties are eliminated by means of a hydraulic actuator for the carburetor throttle of the truck engine that permits the engine to operate at idling speed whenever there is no lifting load on the pump, i.e., whenever the back pressure on the pump is at a comparatively low value, and opens the throttle to a predetermined amount to give the desired speed of engine operation whenever the hydraulic cylinder is operated to lift the body, platform or the like, i.e., whenever the back pressure on the outlet side of the pump exceeds a predetermined amount.

A general object of the present invention is the provision of a simple, substantially foolproof device for controlling the speed of operation of truck engines so as autonited States Patent O matically to increase the speed of the engine whenever it is desired to lift a load by the hydraulic cylinder and automatically to reduce the engine speed to the idling rate when the load is removed. Another object is the provision of a sturdy device of this character which can be manufactured at comparatively low cost and which can be readily installed on an existing truck engine and in connection with conventional hydraulic systems. A further object is the provision of such a device which is adapted to meet the requirements of various installations and operating conditions. Further objects and advantages of the invention will become apparent from the following description of a preferred form thereof, reference being made to the accompanying drawings. The essential characteristics are summarized in the claims.

Referring to the drawings,

Figure 1 shows the control apparatus of the present invention as it may be applied to a truck having a hydraulically actuated dump body;

Figure 2 is a diagram showing the hydraulic circuits of the apparatus of Figure l; and

Figure 3 is a longitudinal sectional view on an enlarged scale illustrating a preferred form of hydraulic device consisting of a cylinder and piston mechanism for operating the engine throttle.

As shown in Figure 1 of the drawing, the control device may be adapted to a conventional motor truck indicated in broken lines at T. Truck T has a chassis 10, a dump body 11 and a hydraulic lifting cylinder 12 embodying a piston 13 and piston rod 14. The cylinder and piston act between the chassis and the dump body 11 and operate so as to raise and lower the body to and from the dumping position as shown in the drawing when fluid under pressure is admitted to and withdrawn from cylinder 12.

Fluid under pressure is supplied to the cylinder 12 by the pump 15 which is driven from the conventional power take off unit 17 associated with the truck transmission 18. Thus, power for pump 15 may be furnished by the truck engine 19. The flow of hydraulic fluid to and from the cylinder 12 is controlled by the control valve 20 which preferably is mounted outside of the truck cab at a point where the operator can observe the motion and position of the dump body 11. Fluid returning from the cylinder 12 is discharged into a sump or tank 21 which is connected to the intake side of the pump 15 to complete the hydraulic circuit. The speed of the engine 19 is controlled by a conventional throttle or butterfly valve operated through lever 22 disposed adjacent the carburetor 23. All of these elements may be of conventional construction. The opening of the throttle is automatically controlled by a pressure responsive mechanism preferably comprising a hydraulic cylinder and piston assembly indicated in general at 25 in Figures 1 and 2 and which will be described in detail below, this mechanism preferably being connected to the lever 22 through a flexible tension element such as the non-kinking chain 26; the chain acts as a slip or lost motion connection so that there is no interference with ordinary control of the engine throttle in driving the truck.

Referring now to Figures 2 and 3 of the drawings, the

hydraulic circuits include a pump outlet conduit 30 extending from the outlet side of pump 15 to valve 20, a cylinder conduit 31 extending from the valve 20 to the lower end of the cylinder 12, a return conduit 32 ex: tending from the valve 20 to the tank or sump 21, and a pump intake conduit 33 extending from tank or sump 21 to the intake side of pump 15. The valve 20 may be of conventional construction, is operated by handle 34 and is arranged so that when the valve is in the central position shown in broken lines and indicated at a, the control is in neutral and the liquid is simply circulated by the thid'fighth conduit 30 to the valve 20, then thfdiigli coridnit" 32' to the sump 21 and through conduit 33 back to the pump. With the valve in this position the only back, pressure on-the pump is created by pressure dfopiintheflfluid'lines,and in a properly designed system thispressnredrepis'lo'was' compared to operating pressures;

whenfthe'handle' 3 4" is moved to the full line position 7 sh'oWn'at b the fluid supplied to the valve through the conduitf30' is pumped through conduit 31 to cylinder 12. Thus, a load is placed upon the pump 15 and the pressure in' conduit 3t) promptly increases substantially above the normal'idling or neutral pressure on the pump.

The valve is arranged so that pressure can be retained within'the'cylinder' 12 'nierely'by moving the handle 34 back'fto position a at which time the fluid within the cylinder" is' locked therein while the fluid displaced by the unters simply re-circulated as described above and the back pressure on the pump is reduced. The piston 13' tween the back pressure on pump 15 under the no load' conditions-of valve handle positions a and c and the backi'pres's'ure on the pump under the load condition'of position b is utilized to control the engine throttle so that the engine is idled' whenever the valve is in neutral position or in position to lower the load and is operated at apredete'rminedincreased speed whenever the valve ajssaeoa r '4' ing into bore 44 and'provided with a fluid coupling 55 for connecting chamber 44 of cylinder 40 to conduit 56. Conduit 56 is connected to conduit 32 at any convenient point as shown in Figure 2, and thus the pressure in sump 21 is reflected within chamber 44 of cylinder 40. The high pressure side of the fluid system is connected to cylinder 40 through an opening 61 that is provided with r a fluid coupling 62 for connecting -chamber'57 of cylinder is -'nioved to the position to raise the load. This is accomplished by theapparatus indicated in general at 25 in Figures 1 and 2 and shown in enlarged section in Figured. Referring particularly to Figure 3, the control apparatus 25 comprises a cylinder 40 supported by abracket' 41 which in turn may be mounted at any con venient location within the engine-compartment, for example, on the cylinder head of engine 19. Within cylinder'40 is a piston 42 mounted on a piston rod 43. It will. be noted that piston 42- is not provided with any fluid-tight packing or rings. 7

Piston 42 operates in bore 44 of the cylinder 40 which is threaded as at 49 to receive end cap, 50 which consti tutes' the head of cylinder 40. End cap Si) is provided with a central bore 51 beginning at its inside end and extending'into, but not through, the end cap and ending at end'wall- 52; the bore 51 acts as a guide and the end wall provides a stop for piston rod 43 to limit movement of the piston and rod-to the left as shown in Figure *3. There is sufficient clearance between bore 51 and the pis ton-rod to prevent trapping of fluid in the bore except that the action of the piston rod in the bore preferably gives a-slight cushioning effect. Piston rod 43 is connected to chain 26, which as noted above is connected to actuate the engine throttle. Movement of the piston to the left in the arrangement shown in the drawings opens the throttle; .movement' to the right permits the throttle to close. Cylinder 40 has a bore 57 of reduced diameter which is threaded as at 58 at'the end remote from cylinder head 50 to receive a centrally bored nut 59 which also, guides piston rod 43. Nut 59 embodies a u conventional fluid tight packing such asQ-ring packing 60 disposedin an appropriate groove in the central bore of nut 59; At the endremote from cylinder head 50 bore-44 terminates inan inwardly extending shoulder 53 provided by the reduced diameter bore 57.- Shoulder 53 acts as a'stop to limit the movement of piston '42 to the, right as viewed in" Figure 3. e

40 to conduit 63, Conduit 63 is connected to conduit 30 at anyconvenient point arid thus the discharge=pres sure of pump 15-is reflected within chamber-57 offcylinder 40. a

In order to return the piston 42 to the position shown in Figure 3 consequentrupon a reduction of pressure within'chamber 57, a spring'64 is disposed concentrically of piston rod 43 between piston 42 and cylinder head 59. When control apparatus 25 is assembled as shown in Figure 3, spring 64 is compressed-between cylinder head 50 and piston 42 so that under no load conditions with the valve control handle 34 in either of positions a or c, the spring 64 retains piston 42 in the position: shown'in Figure 3 against the comparatively low back: pressure upon the pump 15 existing in

lines

63 and 30;

However, when the valve handle 3 4-is moved to-position a and the pump 15 placed under load, the increased back pressure upon the pump moves the piston to the left in cylinder 40 against the action of the sprin'g andopens the engine throttle. As the fluid pressureinchamber 57 forces piston 42 to the left in Figure 3, a point is reached where the piston uncovers part of port 54 in the wall of cylinder- 40 connected to conduit 56. When the piston is in this position, therefore, the total net: pressure forcing the piston against the spring is reduced" as compared to the pump discharge pressure, becausefluid is permitted to bypass the piston 42 and flow to the return conduit 56. Thus the piston reaches a .point of substantial equilibrium where the pressure in'bore 57 is substantially balanced by the'spring 64 and the tension of the chain 26, connecting the piston rod to the engine throttle. Ordinary increases in pump pressure move-the, piston very slightly when thislcondition isreached be-' cause the piston uncovers more of the opening54ias it moves to the left. The result is that in normal opera tion the piston floats in a range in'which a small portion of the opening 54 is uncovered and unduemovement of. the piston and throttle is prevented without requiringaa verystifi spring. Thus, the throttle is opened promptly with a relatively low back pressure on. the pump, but the presence of the return opening 54 prevents excessive opening of the throttle and overspeeding of theengine: under all normal conditions; However, if for any reason" unusually high pressures'are developeduin bore'57', the wall 52 acts as a stop for the piston rod '43 to providers" fixed limit to the distance the-piston canmove'to the left and to the amount of opening of the engine throttle." Inasmuch as piston 53 is not provided with any packing or: rings, there is a small amount of leakage between piston 42 and the wall of bore 44. The leakage flowing backthrough return line 56, does not substantially affect'the operation'of the device, but the freedom of movement and small amount of friction between the piston andthe wall of bore 44 make it possible for the spring" 64 The :cylinder'40'is connected 1nto the low pressure side of fluid s'ystemby means of a por't-oropening 54extend-j to move the piston back to' its original positionimmediately upon reduction of the pump pressure;

7 The movement of the piston controls the'throttle and hence the speed of the engine 19 through suitable means such as the flexible chain 26. The proper length chain is such that the chain is slightly slack when piston- 42. isin the position shown in Figure 3 under no load con'-' ditions so that the conventional spring in the engine throttle mechanism can operate to move the throttle to idling position. However, when thepressure withi'n the cylinder 40 builds up by reason of a load on the pump 15, the piston moves to the left (Figure 3) and the-pistonrod 43 applies tension-to 'chain 26-, ,thereby openingithe;

throttle slightly and speeding up the engine and further building up the pressure within the system. Thus, the speed of the engine is increased until further opening of the throttle is prevented either by a balance of the net pressure on the piston and the force exerted by the spring in opposition thereto or, in some circumstances, by engagement of piston rod 43 with the end wall 52 of central bore 51 in cylinder head 50. By adjustment of the length of flexible chain 26 and, if desired, adjustment of the point of connection of the chain to lever 22, the speed to which the engine is accelerated under load may be set to a desired range. In operation and with the device properly adjusted the truck driver merely engages the power take ofi unit 17 to start operation of the pump. Thereafter, he leaves the truck cab with the throttle in idling position, goes to the proper station by the control valve 20 and operates the control valve handle 34 to raise and lower the truck body and load as desired. Whenever the pump is under load, the truck engine automatically accelerates to the desired speed to give ample power for lifting the load, but overspeeding of the engine is prevented by the floating action of the piston with respect to the port 54. Whenever the load on the pump 15 is removed, the engine immediately decelerates to idling speed, thus saving fuel and wear and tear on the engine. Because of the action of the piston in uncovering port 54, the strength of the spring is not critical so long as it has sufiicient strength to return the piston to its initial position promptly upon reduction in pump pressure. The elimination of packing for the piston not only reduces manufacturing costs, but also makes the device more quickly responsive to changes in pump pressure. The device is simple and foolproof, can be manufactured at low cost and can be adapted readily to various makes of trucks and different operating conditions. The device does not interfere with ordinary manual control of the throttle in driving the truck.

Those skilled in the art will appreciate that various changes and modifications can be made in the preferred form of apparatus described herein without departing from the spirit and scope of the invention.

I claim:

1. In combination with an engine having a throttle and a pump driven by said engine, an automatic control device for controlling the throttle of said engine, said automatic control device comprising a cylinder, means for fixedly supporting said cylinder relative to said engine, a piston in said cylinder, said piston having a non-fluid tight fit in said cylinder, a conduit connected to said cylinder on one side of said piston and communicating with the outlet side of said pump, whereby pressure on the outlet side of said pump tends to move said piston in one direction, a second conduit connected to said cylinder on the opposite side of said piston from the first said conduit and communicating with the inlet side of said pump, a piston rod secured to said piston and extending to the exterior of said cylinder on the same side on Which the conduit communicating with the outlet side of said pump is connected and extending on the other side of said piston within the interior of said cylinder, a spring engaging said piston and surrounding said piston rod for moving the piston in the opposite direction, a cylinder head on said cylinder at the opposite end from that through which said piston rod extends to exterior of said cylinder embodying a piston rod guide and stop to limit the movement of said piston rod toward said cylinder head and engaging the end of said spring, a flexible chain for operatively connecting said piston rod to the throttle of the engine to open the throttle upon movement of said piston in response to an increase in fluid pressure in said cylinder, and to permit the throttle to close upon movement of said piston in the opposite direction under the influence of said spring when the fluid pressure in the cylinder is reduced.

2. In combination with, an engine having a throttle and a pump driven by said engine, an automatic control device for controlling the throttle of said engine, said automatic control device comprising a cylinder, means for fixedly supporting said cylinder relative to said engine, a piston in said cylinder, said piston having a non-fluid tight fit in said cylinder, a conduit connected to said cylinder on one side of said piston and communicating with the outlet side of said pump, whereby pressure on the outlet side of said pump tends to move said piston in one direction, a second conduit connected to said cylinder on the opposite side of said piston from the first said conduit and communicating with the inlet side of said pump, whereby the pressure on the inlet side of said pump tends to exhaust the cylinder on that side of the piston to which said second conduit connects, a piston rod secured to said piston and extending to the exterior of said cylinder on the same side on which the conduit communicating with the outlet side of said pump is connected and extending on the other side of said piston within the interior of said cylinder, a spring engaging said piston and surrounding said piston rod for moving the piston in the opposite direction, an internal shoulder within said cylinder engageable with said piston for limiting the movement of said piston in response to pressure in said cylinder, a cylinder head on said cylinder at the opposite end from that through which said piston rod extends to exterior of said cylinder embodying a piston rod guide and engaging the end of said spring, a flexible chain for operatively connecting said piston rod to the throttle of the engine to open the throttle upon movement of said piston in response to an increase in fluid pressure in sald cylinder, and to permit the throttle to close upon movement of said piston in the opposite direction under the influence of said spring when the fluid pressure in the cylinder is reduced.

3. In combination with an engine having a throttle and a pump driven by said engine, an automatic control device for controlling the throttle of said engine, said automatic control device comprising a cylinder, a means for supporting said cylinder relative to said engine, a piston in said cylinder, said piston having a non-fluid tight fit in said cylinder, a conduit connected to said cylinder on one side of said piston and communicating with the outlet side of said pump whereby the discharge pressure of the pump tends to move said piston in one direction, said cylinder having a port and a second conduit connected to said port on the opposite side of said piston from the first said conduit and communicating with the inlet side of said pump, said port being in a positlon to be uncovered by said piston after a predetermined movement of said piston in response to pressure in said cylinder, a piston rod secured to said piston and extending to the exterior of said cylinder, a spring engaging said piston and tending to move said piston in the opposite direction and a lost motion connection for operatively connecting said piston rod to the throttle of the engine to open the throttle upon movement of said piston in said one direction in response to an increase in fluid pressure in said cylinder, and to permit the throttle to close upon movement of said piston in the opposite direction under the influence of said spring when the fluid pressure in the cylinder is reduced.

References Cited in the file of this patent UNITED STATES PATENTS 825,718 Grimes July 10, 1906 1,259,090 Ferris et al. Mar. 12, 1918 2,234,798 Craig Mar. 11, 1941 2,292,294 Rotter Aug. 4, 1942 2,364,812 Pierson Dec. 12, 1944 2,642,805 Nepper June 23, 1953 2,690,712 Foote Oct. 5, 1954 2,800,921 Wright July 30, 1957