Self propelled and extensible boom

Abstract

A self-propelled rotatable hydraulic lift having a body with an extensible boom pivotally attached to the upper rear portion of a counterweight and terminating in a self-leveling workman's platform. Remote lift controls are provided at the platform by means of control lines contained in flexible conduits within the boom. The center of gravity of the counterweight is located between the pivotal connection of the boom and the axis of rotation of the boom to provide both improved stability with respect to back tipping when the boom is extended vertically and a smaller rotational diameter for the lift body.

Description

BACKGROUND OF THE INVENTION

a. Field of the Invention

This invention relates to self-propelled hydraulic lifts of the type having an extensible boom terminating in a work platform.

b. Brief Description of the Prior Art

Self-propelled hydraulic lifts are well-known, as, for example, is shown in U.S. Pat. No. 3,319,739, issued May 16, 1967. Extensible and rotatable booms on devices of this general type are also well known as is shown, for example, in U.S. Pat. No. 2,786,723, issued Mar. 26, 1957. Extensible boom assemblies which provide for remote control of the boom at a workman's platform attached to the outer end of the boom are illustrated, for example, in U.S. Pat. No. 3,136,385, issued June 9, 1964 to J. M. Eitel and U.S. Pat. No. 3,379,279 issued Apr. 23, 1968 to E. G. Slusher.

However, such conventional lifts suffer from several disadvantages which limit their utility. For example, such lifts, conventionally, have either been mounted on a truck body, U.S. Pat. No. 3,136,385, for example, or have utilized a counterweight extending significantly beyond the point of attachment of the boom to the lift. In either event, the resulting structure is relatively large, limiting its access and/or rotation to comparatively wide passageways. Furthermore, when an extensible boom has been used, control cables necessarily included within the boom for remote control of the lift have been subject to wear and failure by reason of the repeated stresses applied thereto during boom extension and retraction.

SUMMARY OF THE INVENTION

A hydraulic lift, according to the present invention, includes a self-propelled frame including four wheels with a rotatable body mounted thereon. Counterweight means are mounted on said body at one side thereof, said counterweight means tapering downwardly inwardly to the center of the frame, said counterweight structure permit permits the lowering of the boom 12 to horizontal or below horizontal positions.

The turret plate 144 is rotatably attached to the frame 18 by any conventional means. Depending upon the particular equipment to be utilized, the various power sources required by the lift 10 may be mounted on the turret or base plate 144, the frame 18, and the counterweight assembly 140. In FIG. 1, the housing 20 has a bifurcated cover 143, which may be, for example, of heavy duty plastic material. The cover 143 is positioned along the sloping top 158 and front 152 of the counterweight assembly body 142 so as to permit the boom 12 to be lowered to a below-horizontal position, as previously described. As will be apparent from FIGS. 1 and 9 through 11, the counterweight 142 comprises a portion through 11, the counterweight body 142 comprises the peripheral portion of the body or housing 20 most remote from the axis of rotation, and the cover 143 extends forward from the counterweight body 142 to laterally enclose the axis of rotation. In the preferred embodiment, the housing 20 also includes fuel tanks for the lift 10, which are mounted on the sloping upper surface of the counterweight body 142 and are enclosed by the cover 143 of the housing 20.

The counterweight itself may, for example, consist of a steel casing which is loaded with ballast material to provide the desired weight and is then sealed. Because of the disposition of the boom mounting bracket 146 on the counterweight body 142, it will be apparent that the center of gravity of the counter-weight assembly 140 is always located between the point of pivotal connection of the boom 12 on the counterweight assembly 140 and the axis of rotation of the boom with respect to the lift 10.

Referring now to FIG. 11, the lift 10 of the present invention is shown with the boom in its most upright position, which is the condition which presents the greatest danger of back tipping of the lift when operated on an inclination. As is seen in FIG. 11, the lift 10 has a center of gravity location 160, which lies well within the track of the lit lift frame and is disposed between the axis of rotation of the housing 20 (and thus the boom 12) and the point of pivotal attachment 146A for the boom 12 Thus, the lift 10 will not back tip.

This stability against back tipping is to be contrasted with prior art lifts such as the lift 162 illustrates in FIG. 12. In such a prior art lift, a frame 164 has wheels 166 mounted thereon so as to be self-propelled by locomotion apparatus (not shown). The lift 162 has a an extensible boom 168 which is pivotally mounted to a housing 170 at a pivot point 172. The lift 162 has a counterweight assembly 174 attached to the housing to provide a center of gravity location 176 which is well outside the track formed by the wheels 166. Further, as will be seen from FIG. 12, the pivot point 172 for the boom 168, with respect to its axis of rotation in the lift 162, is located between the lift center of gravity 176 and the axis of rotation. Thus, the prior art lift 162, when in the upright position, and especially when operating on an inclination, is in danger of or will actually tip over, with the resultant damage to the lift and injury to the workman operating the lift from the workman's platform.

This danger of back tipping is avoided by the present invention in two respects. The center of gravity for the lift is always located between the pivot point of the boom and the axis of rotation of the boom. Additionally, in the preferred embodiment, further stability is provided by locating the center of gravity of the counterweight assembly within the track of the lift. When so located, the lift can not back tip under any normal conditions of operation. The angle of inclination required for such back tipping is so great as to give the workman adequate advance warning of the danger present, so that appropriate corrective positioning of the lift can be undertaken.

Additionally, by locating the center of gravity of the lift as provided by the present invention, the lift may operate in much more confined passageways than the prior art lifts, as will be evident from a comparison of FIGS. 11 and 12. Such operation provides for greatly increased warehouse capacity and the like, since the necessity for the wider access aisles in conventional warehouse operation is obviated. The aisles need be no wider than the lift itself, since rotation, in the preferred embodiment, of the housing 20 does not cause the housing 20 to extend beyond the track of the lift formed by the frame 18 and wheels 22, as contrasted to the great extension of the prior art lift 162 housing beyond the track of the lift when rotated for lateral positioning of the workman's platform.

By pivoting the boom from the upper rear surface of the counterweight body a longer boom reach results than for comparable prior art lifts, while the greater proximity of the counterweight body center of gravity to the lift axis of rotation simultaneously provides the ease of access in operation. In addition to the increased reach due to location on the upper surface of the counterweight body , a longer boom can be utilized as compared to prior art lifts. Thus, because the boom attaches directly to the top rear of the counterweight body, it is possible to design a longer boom to reach greater heights and place the counterweight assembly, and therefore the boom pivot pin, much closer to the axis of rotation as compared to the distance on a conventional lift of this type. Furthermore, since the workman's platform on the longer boom would be further away from the axis of rotation if the counterweight body remained in the same location as on a shorter boom lift, the counterweight body and boom pivot pin may be relocated to a slightly greater distance from the axis of rotation to compensate for the increased positive overturning moment imposed by a loaded platform with the boom in its horizontal position. This relocation of the boom pivot pin moves the workman's platform closer to the axis of rotation when the boom is in the elevated position, enabling the workman to work closer to the axis of rotation, and thereby simplifying the lift maneuvering required by the workman in that lift configuration when working.

Claims

1. In a lift, the combination of

a self propelled frame;

a boom; and

a body mounted on said frame so as to be selectively rotatable thereon about an axis of rotation; said body including

(a) a counterweight with a center of gravity, said counterweight being fixed to said body so as to form a portion thereof which is most remote from the axis of rotation, and

(b) means for pivotally attaching said boom to said body so that the counterweight center of gravity is always disposed between the boom pivotal attachment and the axis of rotation.

2. The lift of claim 1, and in which the frame has four wheels rotatably attached thereto, the lift having a track which is determined thereby, and in which the counterweight is disposed on the body with respect to the axis of rotation so that the rotation of the body rotates the counterweight within the track of the lift.

3. The lift of claim 1, and in which the frame has four wheels rotatably attached thereto, the lift having a track which is determined thereby, and in which the counterweight is so disposed on the body with respect to the axis of rotation so that the rotation of the body rotates the counterweight center of gravity within the track of the lift.

4. The lift of claims 1, 2 or 3, and in which the counterweight has a front side adjacent the axis of rotation, a back side remote from the axis of rotation, and a top side intersecting the front and back sides, and in which the boom is pivotally attached to the

counterweight adjacent the intersection of the top and back sides. 5. The lift of claim 4 16 and in which the top side slopes downwardly from the back side to the front side.

6. The lift of claim 4, and in which the boom is pivotally attached to the top side of the counterweight.

7. The lift of claim 5, and in which the boom is pivotally attached to the top side of the counterweight.

8. In a lift, the combination of

a self-propelled frame including four wheels defining a track for the lift;

a body mounted on said frame, said body being rotatable about an axis of rotation with respect to said frame;

said body including counterweight means mounted at one side thereof so as to be rotatable about said axis of rotation, said counterweight means being displaced from said axis of rotation and having a front side adjacent said axis of rotation, a back side remote from said axis of rotation, a top side intersecting said front and back sides, and a center of gravity located between the front and back sides;

a boom; and

means for pivotally attaching the boom to the body so that the center of gravity of the counterweight means is always disposed between the point of

pivotal attachment and said axis of rotation. 9. The combination of claim 8 19 and in which the boom is extensible, said extensible boom comprising:

an outer boom, said outer boom being pivotally attached to the counterweight means;

an inner boom terminating in a workman's platform, said inner boom being disposed within said outer boom;

means for selectively initiating relative movement between the inner boom and the outer boom so as to move the workman's platform away from or toward the frame including a hydraulic cylinder fixed to the inner boom interior remote from the pivotal connection and a cylinder rod fixed to the outer boom adjacent the pivotal connection, and means for selectively applying hydraulic fluid to said cylinder to initiate relative movement between the cylinder and cylinder rod;

remote lift control means located at the workman's platform; and

means for connecting said remote lift control means to the lift including

control lines extending to the workman's platform, said lines passing through the inner and outer booms,

flexible conduits having first ends fixed to the outer boom interior remote from the pivotal connection and second ends fixed to the inner boom interior adjacent the pivotal connection, said control lines passing through said conduits,

a carrier assembly mounted on and slidable along the cylinder rod,

a sheave from each flexible conduit and having an outer surface around a portion of which said flexible conduit passes,

means fixing each sheave to the carrier assembly, and carrier assembly retraction means for moving said carrier assembly along the cylinder rod in the direction of movement of the inner boom but at one-half the rate of movement thereof, comprising

(a) a retraction cable

(b) means for attaching one end of the retraction cable to the outer boom interior adjacent the pivotal connection

(c) a carriage idler pulley attached to the carrier assembly

(d) a rear outer boom idler pulley attached to the outer boom interior adjacent the pivotal connection

(e) a front outer boom idler pulley attached to the outer boom interior remote from the pivotal connection,

(f) means for attaching the second end of the retraction cable to the inner boom adjacent the pivotal connection, and

(g) a shield for each sheave, said shield being attached to the carrier assembly and disposed so as to cover a substantial portion of the sheave outer surface over which the flexible conduit passes so as to prevent the

flexible conduit, if slack, from sliding off the sheave.

10. In an extensible boom, the combination of: an outer boom;

an inner boom disposed within and extending outwardly from a first end of said outer boom;

means for selectively initiating relative movement between the inner boom and the outer boom so as to move the inner boom outwardly through said outer boom first end including a rod-fed hydraulic actuator having a cylinder fixed to the inner boom interior and a cylinder rod fixed to the outer boom;

control lines passing through the inner and outer booms;

flexible conduits having first ends fixed to the outer boom interior adjacent said outer boom first end and second ends fixed to the inner boom interior remote from said outer boom first end, said control lines passing through said conduits;

a carrier assembly mounted on and slidable along the cylinder rod;

a sheave for each flexible conduit and having an outer surface around a portion of which said flexible conduit passes;

means fixing each sheave to the carrier assembly; and carrier assembly retraction means for moving said carrier assembly along the cylinder rod in the direction of movement of the inner boom but at one-half the rate of movement thereof, comprising

(a) a retraction cable,

(b) means for attaching one end of the retraction cable to the outer boom interior remote from said outer boom first end,

(c) a carriage idler pulley attached to the carrier assembly,

(d) a rear outer boom idler pulley attached to the outer boom interior remote from said outer boom first end,

(e) a front outer boom idler pulley attached to the outer boom interior adjacent the outer boom first end,

(f) means for attaching the other end of the retraction cable to the inner boom remote from the outer boom first end, and

(g) a shield for each sheave, said shield being attached to the carrier assembly and disposed so as to cover a substantial portion of the sheave outer surface over which the flexible conduit passes so as to prevent the

flexible conduit, if slack, from sliding off the sheave. 11. In a lift of the type having a self-propelled four-wheeled frame defining a track for the lift, and a boom, the combination of:

a housing comprising

(a) a base mounted on said frame so as to be selectively rotatable about an axis of rotation and

(b) a counterweight having a center of gravity and being fixed to said base so as to be rotatable therewith, said counterweight

(i) being disposed on said base so as to be remote from said axis of rotation but with its center of gravity always within the lift track upon rotation of the base, and

(ii) having a rear side remote from said axis of rotation and a front side adjacent thereto, and a top side which intersects said front and rear sides, said housing having a back of which said counterweight rear side forms at least a portion, and

means for pivotally attaching said boom to said counterweight top side adjacent the rear side intersection and remote from the front side intersection, whereby the counterweight center of gravity is disposed

between the axis of rotation and the boom pivotal attachment. 12. A lift according to claim 11, and in which the rear side of the counterweight is

always within the lift track upon rotation. 13. A lift according to claims 11 or 12, and in which the top side slopes downwardly from the rear side intersection to the front side intersection to permit the boom to be lowered to a below-horizontal position.

14. In a lift, the combination of

a self propelled frame;

a boom; and

a body mounted on said frame so as to be selectively rotatable thereon about an axis of rotation;

said rotatable body including

(a) a counterweight body with a center of gravity, said counterweight body being fixed to said rotatable body so as to comprise the peripheral portion thereof which is most remote from the axis of rotation, and

(b) means for pivotally attaching said boom to said rotatable body adjacent to said counterweight body so that the counterweight body center of gravity is always disposed between the boom pivotal attachment and the axis of rotation,

and in which the frame has four wheels rotatably attached thereto, the lift having a track which is determined thereby, and in which the counterweight body is disposed on the rotatable body with respect to the axis of rotation so that the rotation of the rotatable body rotates the counterweight body center of gravity within the track of the lift.

15. The lift of claim 14, and in which the counterweight body is disposed on the rotatable body with respect to the axis of rotation so that the rotation of the rotatable body rotates the counterweight body within the track of the lift.

16. The lift of claims 14 or 15, and in which the counterweight body has a front side adjacent the axis of rotation, a back side remote from the axis of rotation, and a top side intersecting the front and back sides, and in which the boom is pivotally attached to the counterweight body adjacent the intersection of the top and back sides.

17. The lift of claim 16, and in which the boom is pivotally attached to the top side of the counterweight body.

18. The lift of claim 5, and in which the boom is pivotally attached to the top side of the counterweight body.

19. In a lift, the combination of a self-propelled frame including four wheels defining a track for the lift;

a body mounted on said frame, said body being rotatable about an axis of rotation with respect to said frame;

said rotatable body including counterweight means mounted at the side thereof which is most remote from said axis of rotation so as to be rotatable about said axis of rotation, said counterweight means being displaced from said axis of rotation and having a front side adjacent said axis of rotation, a back side remote from said axis of rotation, a top side intersecting said front and back sides, and a center of gravity located within the track between the front and back sides;

a boom; and

means for pivotally attaching the boom to the rotatable body adjacent to said counterweight means so that the center of gravity of the counterweight means is always disposed within the track between the point of pivotal attachment and said axis of rotation.