US3171545A - Three section telescoping crane boom - Google Patents

Description

2 Sheets-Sheet 1 S. G. KNIGHT ETAL THREE SECTION TELESCOPING CRANE BOOM March 2, 1965 Filed Deo. 5, 1962 /J-Z 'y 'IEIOII 1615 t JZ 55 1 56 )Ill l L', I "Y "I lll Il! Q s 10 jme/22%@ March 2, 1965 s. G. KNIGHT ETAL v THREE SECTION TELESCOPING CRANE BOOM 2 sheets-sheet 2 Filed Deo. 5, 1962 United States Patent Ohce artists Patented Mar. 2, 1965 3 171,545 THREE SECTIN TEJESCOPING CRANE BOOM Sidney G. Knight and F V. Swanson, Wausau, Wis.,

assignors to Drott Manufacturing Corporation, Milwaukee, Wis., a corporation of Wisconsin Filed Dec. 3, 1962, Ser. No. 241,632 4 Claims. (Cl. 212-144) This invention relates to mobile cranes and more particularly -to a mast and extension boom structure for use with mobile cranes.

Mobile cranes in general comprise a Vehicle which supports an upwardly extending mast having a boom pivoted thereto on a horizontal axis with means for swinging the boom vertically and a movable block at the end of the boom to pick up a load. The boom is preferably extensible to reach out and pick up loads at different distances from the vehicle.

One of the problems encountered with such cranes involves the construction of the mast and mounting of the boom and power operating means thereon to swing the boom vertically without unduly complicating the structure or requiring an extra large vand expensive motor to swing the boom. This problem also involves the matter of balancing the parts so that the maximum load can be raised by the crane without tilting the mast or the vehicle.

Another problem is construction of lthe telescoping boom to provide the desired strength in different extended positions thereof without making the boom structure unduly heavy. In this connection, it is noted that a boom of at least three sections is necessary to obtain the desired degree of extension and of the three sections the base section is always largest and strongest and the end section is always the smallest and weakest. It is also noted that the heaviest loads are picked upclose to the vehicle. It is therefore desirable in extending the boom to move the intermediate and end sections out together as far as possible before extending the end section from the intermediate section in order to obtain maximum strength.

It is one of the objects of the present invention to provide a mobile crane in which the mast and boom are so constructed and connected as to provide the best possible balance and to enable the boom to be pivoted vertically to raise the maximum weight by the use of a relatively small motor which is easily and simply mounted to produce minimum interference with operation of the boom.

According to a feature of the invention, the mast is formed with a horizontally elongated upper section to one end of which the boom is pivoted and angular intermediate and vertical lower sections with an extensible and contractible uid motor pivoted at one end to the boom and at its other end to the lower part of the mast to produce maximum lifting effect and minimum interference with the operating parts.

A further object is to provide an extensible boom for a mobile crane or the like in which the end intermediate sections are latched together until the intermediate sec`- tion is fully extended from the base sec-tion and are then automatically released for extension of the end section.

According to a feature of the invention the latch means comprises a pin projecting laterally from the inner end of the end section through an opening at the inner end of the intermediate section and a cam carried by the outer end of the base section to cam the pin out of the opening when the intermediate section approaches the limit of its outward movement in the base section.

The above and other objects and features of the invention will be more readily apparent from the following description when read in connection wit-h the accompanying drawings, in which:

FIG. 1 is a perspective view of a mobile crane embodying the invention;

FIG. 2 is a partial side view with parts broken away;

FIG. 3 is an enlarged side view of the extensible boom with parts broken away and in section;

FIG. 4 is a partial section on the line 4-4 of FIG. 3; and

FIG. 5 is a partial section on the line 5 5 of FIG. 3.

The mobile crane, as shown in FIG. l, includes a vehicle, indicated generally at 10, which may be of the wheel or track laying type, but which is shown as being supported on wheels 11. The vehicle contains its own source of motive power and may be driven from place to place by an operator housed in a cab 12. In addition to controlling the vehicle, the operator may also control operation of the crane structure.

The crane structure comprises a mast which is rotatably mounted in a rotatable support 13 on the vehicle for turning about a vertical axis. The mast as shown comprises a lower vertical portion 14 mounted on the support 13, an intermediate portion 15 lying at an acute angle to the vertical and an upper horizontal portion 16. The several portions of the mast may be fabricated of steel plates secured together in a substantially channel section structure, as best seen in FIG. l, for convenient mounting of t-he boom therein.

A boom, indicated generally at 17, is pivoted at one end to the free end of the horizontal mast portion 16 on an axis indicated at 1S. In its lowered position the boom may lie between the sides of the horizontal channel section 16 of the mast, as seen in FIG. l, and may be swung upwardly about the pivotal connection 18, as illustrated in FIG. 2. For controlling the mast an extensible and contractible hydraulic motor comprising a cylinder 19 and a piston having a piston rod 21 projecting from one end thereof is pivotally connected to the mast and to the boom. As shown, the end of the piston rod 21 is pivoted at 22 to a point on the mast spaced from the pivotal axis 18 and preferably lying adjacent the opposite end of the horizontal mast portion 16. The end of the cylinder is pivoted at 23 in the lower vertical portion of the mast so that the cylinder and piston mechanism lie substantially between the sides of the channel shaped intermediate mast portion I5. In this location, the cylinder and piston mechanism is protected by the mast and occupies a minimum amount of space. The motor is also positioned so that its angle of action on the boom is favorable in all pivoted positions of the boom so that a motor of minimum size may be used to control vertical swinging movement of the boom.

The boom, as best seen in FIGS. 3 to 5, is formed of three tubular sections which telescopically intert with each other and which are preferably, although not necessarily, rectangular in section. The three sections comprise a base section 24, an intermediate section 25 and an end section 26. The base section carries a bracket 2'7 at its inner end through which it is pivoted on the mast. Intermediate its ends the base section carries a winch mechanism comprising a rotatable drum 28 enclosed within a housing 29 secured to the base section. The drum 28 may be driven through any desired type of motor as, for example, a hydraulically operated motor 31 as shown in FIG. 2, which is supplied with operating liquid under pressure under the control of the crane operator.

The intermediate section is of a size to slide fully into or substantially out of the outer end of the base section, suitable sliding bearing members not shown being provided to facilitate this sliding movement. The end section 26 is similarly slidably tted into the intermediate section. The end section carries at its outer end a block and tackle mechanism for lifting a load, although it will be understood that any other desired type of load engaging Vthe boom. Since the base section is-the largest` and cor-v 70 and lifting means could be substituted.'v As shown, a head the sheave 33 and over a sheave in a blockY 35 which may carry a load engaging hook 36. The cable .thenV passes over the otherrsection of .thedouble sheave 33 andoack l Ito an anchor point on the block, as illustrated. With this construction when the drum 28 is rotated in one direction 'or the other the cable will be wound onto or unwound from `the drum to vcause the block 35"to be raised vand lowered, as will be understood. Y l

According to the present invention, the endand intermediate sections of the boom are latched together against relaitve movement during initial extension of boom and until .the intermediate section has reached substantially the full limit of its movement Voutward fromthe base section. As best seen in FlG. 4, the latch comprises a sleeve 37 secured to the inner end of the end section 26 and slidably carrying a pair of latching pins 38 which are adapted to project from opposite ends of the sleeve and which are urged apart by a `compression spring 39. When the end section is fully retracted into the intermediate section, the latch pins 38 will extend through latching openings 41 formed in the side Walls of the intermediate section. Preferably the openings 41 are ared at their ends, as shown, and the latch pins have tapered ends, as shown, so that -when the latch pins are moved to a position with their outer ends llush or substantially ush with the outer surface of the intermediate section, they will be cammed inwardly yto their full released position by exertion of longitudinal pressure thereon.

In order to release the latch pins so that the end section can be extended from the intermediate section, cam

means are provided as best seen in FIG. 5. Each ofthe' lcam means, as shown, comprises a wedge-shaped plate member 42 pivoted at one end,V as shown at 43, on a bracket extending outward from the base Section 24.

The other end of the cam member is adapted to .be adjustably secured to the base section by an adjusting screw `44. When the cam plate is properly adjusted its 'inner surface will taper inwardly of the base sectionfrom a point flush with the inner surface .o-f the base section adjacent to the pivot 43 to a Vpoint substantially flush with the inner `surfaces ofthe intermediate-section 25 adjacent to the adjusting screw 44. The cam plate may, if desired, be provided with a wear stripy at its rtip which can easily be replaced in the event of wear. The boom is adaptedto be extended and retracted vby power means controllable by the operator from the cab. 12 of the crane. In the preferred form shown, the power means comprises an extensible and rectractable fluid motor, including a cylinder 45 pivoted at oneV end to a bracket 46 carried by the inner end of the basesection. A piston in the cylinder has its piston rod extending from the opposite end thereof and connected to the outer end of the end section of the boom, as shown at 47. When the iluid motor is extended the boom will 'be extended correspondingly and when the fluid motor is retracted it will telescope the Vintermediate and end sections of the boom into the base section to provide the minimum lboom length. Y l

During extension of thel boom, the latch pins 38 will 'initially be engaged lin thel latching openings 41 to hold the intermediate and end section against movement relative to each other. Thus during the` initial extension, the'v intermediate and end'sections will move together and will reinforce each other to provide Afory maximum ystrength rof respondingly strongest of the several sections, this feaor substantially ush with the outer Surfaces .-of the intermediate section. Whena further extending force is exerted on the endsection bythe uid motor, .the latch pins willl be cammedinwardly due to the shapeof ,their ends and tothe lshape of the-openings 41 to slide against the inner surface of theV intermediate section.l At this time, -the boom can be'exended to its maximum reach with the end section telescoping out ,of'the intermediate section. Upon retraction of the boom, the latch pin will re-engage in the latching openings, the operation being entirely automaticand without any attention from the operator. i

While one embodiment of the invention has been shown and described herein, it will be understood that it is illustrative only and not to be taken as a definition of the scope of the invention, reference being had for .this purpose ot the appended claims. y

What is claimed is:

l. In a mobile crane, an extensible boom comprising a tubular base section, a tubular intermediate section telescopically slidable in the base section, an end section telescopically slidable lengthwise in the intermediate vsection, latch means releasable holding the intermediate and end sections against relative sliding movement, means Acarried by the base section to engage and release the latch means when the intermediate section has reached substantially the limit of `its outward movement in the base section, Vand power means engaging .the basev and end sections toV extend and retract the boom.

2. The construction of claim 1 in which the end section is tubular andthe power means is an extensible hydraulic kinner end toproject through said opening when theboom is retracted thereby to hold the end and` intermediate sections against relative sliding movement, cam meanswcarried by the base section adjacent to itsV outer end to cngage the latch pin and cam itvv radially inward out of said opening when thev intermediate section is at substantially the limit of its outward movement in the base section,

fand -power means connected to the base and end sections to expand vand retract theboom.

4. The construction of yclaim 3 in which the end section is tubular and the power means is an extensible and contractable uid motor Vlying in the'end section when the boom is retracted.

References Cited by the Examiner UNITED STATES PATENTS 1/57 Boysen et al 212-145 2,787,383 4/57 Antos et al 212-55 X 2,819,803 V`1/58r Obenchain 212-55 SAMUEL FLCOLEMAN, Acting Primary Examiner.

' J, ALBRECHT, Examiner.

Claims (1)

1. IN A MOBILE CRANE, AN EXTENSIBLE BOOM COMPRISING A TUBULAR BASE SECTION, A TUBULAR INTERMEDIATE SECTION TELESCOPICALLY SLIDABLE IN THE BASE SECTION, AN END SECTION TELESCOPICALL SLIDABLE LENGTHWISE IN THE INTERMEDIATE SECTION, LATCH MEANS RELEASABLE HOLDING THE INTERMEDIATE AND END SECTIONS AGAINST RELATIVE SLIDING MOVEMENT, MEANS CARRIED BY THE BASE SECTION TO ENGAGE AND RELEASE THE LATCH MEANS WHEN THE INTERMEDIATE SECTION HAS REACHED SUBSTANTIALLY THE LIMIT OF ITS OUTWARD MOVEMENT IN THE BASE SECTION, AND POWER MEANS ENGAGING THE BASE AND END SECTIONS TO EXTEND AND RETRACT THE BOOM.

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