US3426916A

US3426916A - Boom retracting machinery

Info

Publication number: US3426916A
Application number: US650032A
Authority: US
Inventors: Carl F Novotny
Original assignee: Bucyrus Erie Co
Current assignee: NORTHWEST ENGINEERING Co A CORP OF
Priority date: 1967-06-29
Filing date: 1967-06-29
Publication date: 1969-02-11
Anticipated expiration: 1986-02-11
Also published as: DE1531147B2; GB1174698A; DE1531147A1

Description

Feb 11, 1969 c. F. NoyoTNY `3,426,916

BOOM RETRACT ING MACHINERY Filed June 29, 1967 sheet of 2 LOAD-(1N loo,ooo INCH Les.)

0 20 4o 0. 'o 7.00 /2'0 4 lo [8o ROTATIONUN DEGREES) INVENTOR CARL E. NovoTNv ATTORNEY Feb-11, 1969 C F, .NOVOTNY 3,426,916

BOOM RETRACTING MACHINERY Filed Juneze, 1967 sheetv 2 om lNvENToR CARL F. NovoTNv AT TORNEY United States Patent 6 Claims ABSTRACT F THE DISCLOSURE The bifurcated foot of the boom of a truck mounted crane is pivotally attached to respective outer ends of parallel retracting arms, the inner ends of which are fulcrumed on the revolving frame and connected by a torque shaft. The arms a-re pivotal through 180 to lift and move the boom foot between a retracted position to the rear of the frame and a forward working position. An actuating lever for the arms has an inner end fulcnlmed on the fra-me below the fulcrum of the arms and an outer end which has a pin and slot connection with one arm. A hydraulic actuator cylinder is connected between the frame and a midpoint of the lever and is operable to reciprocally pivot the lever and, therefore, the arms.

Background of the invention It is desirable in a truck mounted crane or the like to be able to retract the boom to shorten the machine for travel purposes. The copending application of George W. Mork, Ser. No. 600,541, tiled Dec. 9, 1966, discloses an embodiment of a truck mounted crane with a retractable boom in which the boom foot is connected to the outer ends of actuating arms which are fulcrumed on the re- `volving frame. The arms are pivotal through 180 to lift and move the boom foot between a forward working position and a retracted position to the rear of the frame.

The general arrangement shown in the aforesaid Mork application is very satisfactory from the standpoint of simplicity and strength, but it is difficult to provide suitable lmeans for pivoting the arms. The primary problem in this regard is the variability of the torque load as the boom moves from one position to the other. During retraction, for example, the arms pivot between positions in which they extend horizontally forward and horizontally rearward. Since the boom foot is supported at the ends of the arms, the torque load begins at a maximum, goes to zero as the arms pass through vertical and then again becomes a maximum. Further, the torque load changes from positive to negative as the arms pass through vertical. Because of the dramatic changes in degree and character of the torque load, it is extremely ditiicult to provide an eicient actuating means to pivot the arms.

Summary of the invention The boom retracting machinery of this invention provides a turning block linkage for retracting and extending the boom. The retracting arms form one moving link, and an actuating lever forms the other moving link, the outer end of the actuating lever having a lost motion or sliding block connection with one of the arms. The fulcrum of the actuating lever is below the fulcrum of the retracting arms so that it is required to move through substantially less angular distance as the arms move through 180 As a result, it is possible to use a single conventionally mounted hydraulic cylinder as an actuator. Not only does the machinery of the invention allow for an extremely simple but strong apparatus, but its torque capability matches the torque load almost exactly.

3,426,916 Patented Feb. l1, 1969 ICC Brief description of the drawings FIG. 1 is a fragmentary schematic view of a truck mounted crane lwith the boom retracting machinery of this invention incorporated therein, the elements being shown in a working position with an intermediate retracting position being shown in broken lines,

FIG. 2 is an enlarged fragmentary side view of the apparatus of FIG. 1, but with the elements shown in a fully retracted position,

FIG. 3 is an enlarged fragmentary top view similar to FIG. 2 and further illustrating the elements shown therein, and

FIG. 4 is a graph showing torque capability and load curves for the machinery of FIGS. 1-3.

Description of the preferred embodiment The numeral 1 n t-he drawings designates the revolving frame of a truck mounted crane, only a portion thereof being shown, and the numeral 2 designates a generally conventional `boom lmounted thereon. As can be seen in FIG. 3, the foot portion of the boom 2 is bifurcated to define two spaced, rearwardly extending parts 3. The ends of the parts 3 are pivotally connected at 4 to the respective outer ends of parallel retracting arms 5, the points `l serving not only as points of connection, but also servin-g to dene the actual foot of the boom 2.

A pair of laterally spaced, upstanding supports 6 are provided on the frame 1, and -a transverse tubular torque shaft 7 is journaled therein. The inner ends of the retracting arms 5 are fixed to the respective ends of the tube 7 to pivotally mount them on the frame 1, with the center of the tube 7 deiining a fulcrum for the arms 5.

Obvious additional elements of the truck mounted crane such as the carrier vehicle, hoist machinery, etc. are not fully shown and described herein since they are well known to those skilled in the art and art not necessary per se to the invention herein. A specific illustrative showing of such a crane, and a showing of a retractable boom of the Igeneral type contemplated herein, can be found in the aforementioned copending application of George W. Mork, Ser. No. 600,541.

`One of the supports 6, the one to the front in FIGS. l and 2 and below in PIG. 3, also suitably pivotally mounts and denes a fulcrurn I8 for the inner end of an actuating lever 9, the fulcrurn l8 being outside, below and just slightly behind the fulcrum 7 of the arms 5. The actuating lever 9 is pivotal in a vertical plane adjacent and parallel to the plane of pivotal movement of the nearest arm 5. The outer end of the lever 9 is provided 'with a transverse pin 10 which is received and movable in a longitudinally extending slot 11 formed in the associated arm 5, the pin 1 0 and slot 11 defining a lost motion or sliding block connection between the outer end of the lever 9 and the associated arm 5, which connection is at any suitable midpoint, i.e., point between the ends, of the arm 5.

A conventional two-way hydraulic actuator cylinder 12 of suitable form is pivotally connected at one end 13 to the frame 1 and has its other end pivotally connected to the lever 9 at a suitable midpoint 14. Extension and retraction of the cylinder 12 will cause the lever 9 to pivot reciprocally in a vertical plane about its fulcrum 8, the transverse pivotal connections 13 and 14 allowing the cylinder 12 to move vertically as required. Because of the connection afforded by the pin 10 and slot 11, the lever 9 'will in turn cause the arms 5 to pivot .about their fulcrum 7 to move the boom foot `4. The lever 9' acts only on the nearest arm S of course, but the torque shaft 7 transmits its force substantially equally to the far arm 5.

As a result of having the shaft 7, it is unnecessary to provide two levers 9 and actuating cylinders 12.

The full line showing f FIG. 1 illustrates what is termed a working position in which the boom foot 4 is at the forward end of the frame 1 and the arms S are horizontal and extend forwardly from their fulcrums 7. In this position, the lever 9 extends upwardly and forwardly from its fulcrum 8 and the cylinder 12 is fully retracted. During working, the boom foot 4 will of course be suitably locked in place, and the boom 2 may be lulfed in the usual fashion.

When it is desired to retract the boom 2, it is first fully lowered to the horizontal position shown in FIG. 1 wherein a guiding and supporting wheel 15 provided on the tip of the boom 2 rests on the ground. The cylinder 12 is then extended to cause counterclockwise pivoting of the lever 9 and arms 5, the elements then moving through the intermediate position shown in broken lines in FIG. 1 to the position shown in FIG. 2 which is termed a retracted position. In retracted position, the boom foot 4 is at the rear of the frame 1 and the arms 5 are horizontal and extended rearwardly from their fulcrum 7, the lever 9 extends upwardly and rearwardly, and the cylinder 12 is fully extended. As the elements move from working to retracting position, the pin 10 moves from the outer end of the slot 11 to the inner end and then back again to the outer end, thus providing a lost motion connection which compensates for the difference in elevation of the fulcrums 7 and 8. Having the fulcrum 8 offset behind the fulcrum 7 insures against a dead spot when the arms 5 reach a vertical position. The same effect could of course be had by offsetting the fulcrum 8 forwardly.

As the boom 2 is retracted, the foot 4 moves in a semicircle, and as a result the initial and final phases of its movement are largely vertical with the major horizontal movement occurring between. During the first phase of movement, the boom foot 4 is lifted quickly, and this insures that the underside of the boom 2 will clear the `forward edge of the frame 1 during much of the retracting movement. As the boom 2 moves backward during this portion `of the process, much of its weight is carried -by the wheel 15 which rolls along the ground. As illustrated by the broken line showing in FIG. l, when the arms 5 are vertical the underside of the boom 2 is spaced substantially above the frame 1. At some point after the arms 5 pass vertical so that the foot 4 begins to move down, however, the underside of the boom 2 will be moved down far enough to come against the forward edge of the frame 1, and rollers 16 are provided on the frame 1 and are positioned to engage the underside of the boom 2 at this point. When the boom 2 is against the rollers 16, further rearward and downward pivotal movement of the arms 5 will cause the boom 2 to pivot about and roll rearwardly on the rollers 16, and the weight of the boom 2 will be shifted from the wheel 15 to the rollers 16, the wheel 15 then being lifted off the ground.

rlhe curve 17 shown in FIG. 4 reflects the torque load on the boom retracting machinery shown during a movement from working to retracted position, this load being of course primarily the result of the weight of the boom 2 which is approximately 4500 pounds in this embodiment. At the beginning of a retracting action, the load is maximum in degree and is positive -or clockwise in character. When the load is positive, pushing force by the cylinder 12 is required to effect movement. The positive torque load gradually decreases in degree as the arms 5 pivot upwardly toward a vertical position and reaches zero at the point 18 where they are fully vertical. As soon as the arms 5 pass through vertical, the torque load changes from positive or clockwise to negative or counterclockwise, and at this point the cylinder 12 assumes a holding function. (For the sake of clarity, the torque load curve after the zero point is passed is shown in FIG. 4 as being above the abscissa in FIG. 4, but it is drawn in broken lines to indicate that it is negative in character.) As the arms 5 move further, from vertical to fully retracted position, the load gradually increases again in degree. At a point marked 19, however, the boom 2 comes against the rollers 16, and at this point the load instantly goes back to positive, a pushing force by the cylinder 12 being required to pivot the boom 2 onto the rollers 16. This is shown by the phantom vertical line leading upwardly from the point 19, the continuation of the curve 17 from this line being shown as a full line to indicate its positive character.

The curve 20 in FIG. 4 defines and illustrates the torque capability of the boom retracting mechanism shown, assuming a ve inch cylinder with a two inch piston operated at 2000 p.s.i. The system capability, it will be seen, is also at a maximum when the elements are in working position, decreases to a minimum at a point 21 when the lever 9 is vertical and increases again to a maximum when the elements are in retracted position. The output capability of the system also changes from positive to negative at the point 21 and goes back to positive at a point 22 corresponding to the point 1-9, the cylinder 12 changing from pushing to pulling functions and back through suitable circuitry known to those skilled in the art. The minimum point 21 of the curve 20 and the zero point 18 of the curve 17 do not exactly coincide because of the slight rearward spacing of the fulcrurn 8 from the fulcrum 7, but they very closely approximate one another. All in all, it will be seen that the

curves

17 and 20 are very similar so that the capability of the system is very closely matched to the requirements put upon it, and the same will obviously be true for a movement back to working position. This close matching .provides obvious design advantages in that minimal elements can -be used and no substantial capability or work is wasted. The necessity of pivoting the boom 2 onto the rollers 16 affects the symmetry of the

curves

17 and 20 t-o some extent, but does not significantly change the close matching of capability to load, For movement from retracted to working position or vice versa both the load and capability, for all practical purposes, begin at a maximum, go through zero together and end at a maximum.

The

curves

17 and 20 assume certain sizes, weights, and other conditions. The general relationships shown, however, will obtain even if these conditions are varied.

It will also be noted from an examination of FIGS. 1 and 2 that whereas the arms 5 pivot through approximately during a retracting action or a return to working position, the lever 9 pivots through a substantially lesser angular distance. This allows for the use of the single xed cylinder 12 as an actuator. If a cylinder were to be attached directly to the arms 5 to move them through 180, some provision would have to -be made for moving its point of connection with the frame 1 to allow for the full 180 movement required.

Although a preferred embodiment of the invention has been shown herein, it will be obvious to those skilled in the art that variations in the structure shown can be made without departure from the concept of the invention. Further, the invention is not limited in possible use to truck mounted cranes and other applications are obviously feasible. In view of the .possible variations in both structure and use, the invention is not intended to be limited by the showing herein or in any other manner except insofar as limitations appear specically in the following claims.

I claim:

1. In a truck mounted crane or the like having a revolving frame, a retracting arm having an inner end fulcrumed on the frame and an outer end, and a boom having a foot pivotally connected to the outer end of the retracting arm, the combination therewith of: an actuating lever having an inner end fulcrumed on the frame at a point below the fulcrum of the actuating arm and an outer end connected to a mid-point of the actuating arm with a lost motion connection; and an actuator connected between the frame and a midpoint of the actuating lever, the actuator being operable to reciprocally pivot the actuating lever to in turn cause reciprocal pivotal movement of the actuating arm.

2. The combination of claim 1 wherein the actuator comprises a two-way hydraulic cylinder with transverse pivotal connections at its ends to the frame and actuating lever.

3. The combination of claim 1 wherein there are two parallel retracting arms and the boom foot is bifurcated with its two parts connected to the outer ends of respective arms; and wherein there is a transverse torque shaft connecting the inner ends of the arms; and wherein the actuating lever is connected to only one of the arms.

4. The combination of claim 1 wherein the lost motion connection between the outer end of the actuating lever and the arm comprises a longitudinal slot provided in the arm and a transverse pin at the outer end of the actuating lever this is received and movable in the slot.

5. The combination of claim 1 wherein the fulcrum of the lever is offset from the fulcrum of the arm to prevent a dead spot as the arms go through vertical.

6. The combination of claim 1 wherein the actuator comprises a two-way hydraulic cylinder with transverse pivotal connections at its ends to the frame and actuating lever; and wherein there are ltwo parallel retracting arms and the boom foot is bifurcated with its two parts connected to the outer ends of respective arms; and wherein there is a transverse torque shaft connecting the inner ends of the arms; and wherein the actuating lever is connected to only one of the arms; and wherein the lost motion connection between the outer end of the actuating lever and the arms comprises a longitudinal slot provided in the arm and a transverse pin at the outer end of the actuating lever that is received and movable in the slot; and wherein the fulcrum of the lever is otset from the fulcrum of the arm to prevent a dead spot as the arms go through vertical.

FOREIGN PATENTS 1,214,066 11/1959 France.

HUGO O. SCHULZ, Primary Examiner.

U.S. Cl. X.R. 2. l2-7O jgg@ UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 426, 916 Dated February 11, 1969 Inventor s) Carl F., Novotny It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 75, "actuatingH should be retractng Column 5, line l, "actuating" should be retractin Column 5, line 6, "actuating" Should be retracting Signed and sealed this 3rd day of April 1973.

(SEAL) Attest:

EDWARD'M.FLETCHER,JR. ROBERT GOTTSCHLK Attestlng Officer Commissioner of Patents