LIGHT WEIGHT BOOM CONSTRUCTION

• US 3,837,502 A
• Filed: 03/12/1973
• Issued: 09/24/1974
• Est. Priority Date: 03/12/1973
• Status: Expired due to Term

• Current Assignee: Northwest Engineering, Inc.
• Original Assignee: John T. Hornagold
• Inventors: Hornagold, John T.
• Primary Examiner(s): Schacher, Richard A.
• Assistant Examiner(s): Nase, Jeffrey
• Application Number:
  US05/340,018
• Time in Patent Office: 561 Days
• Field of Search: 212/55,144 52/115,118 308/3R
• US Class Current: 212/349
• CPC Class Codes: B66C 23/705 telescoped by hydraulic jacks
• CPC Class Codes: B66C 23/707 guiding devices for telescopic jibs

Abstract

A truck mounted crane has a three-part, extensible boom in which telescopic motion is accomplished by a pair of extension cylinders contained within the boom. Frictional forces between the slidably mounted boom sections are minimized by improved pad assemblies positioned at selected bearing points. Support members in the form of rollers are positioned within the boom immediately above the lower extension cylinder to not only prevent the extension cylinder from buckling under full load conditions, but to support the outer boom section when it is retracted inward. The result is a reduction in the size and weight of the extension cylinders and a consequent reduction in boom weight.

Claims

1. In a telescopic boom having an inner boom section containing an extension cylinder which is connected thereto and lies along a substantial part of its length, and having an outer boom section slidably connected to the inner boom section to telescope therewithin between a retracted and extended position, the improvement comprising:

a set of supports spaced along the length of the inner boom section and positioned between the extension cylinder contained therein and the outer boom section when in its retracted position, each support extending completely across the interior of said inner boom section to connect with opposing side walls thereof, wherein each support not only engages and carries said retracted outer boom section, but also engages and provides lateral support for said extension cylinder when it bends under heavy loads.

2. The telescopic boom as recited in claim 1 in which said supports are rollers which rotatably connect with the opposing side walls of said inner boom section.

3. The telescopic boom as recited in claim 2 in which each roller includes a sleeve made of a relatively soft material which will not damage said extension cylinder when it engages the roller.

4. The telescopic boom as recited in claim 2 in which a plate is fastened to the extension cylinder at a point intermediate its ends and said plate extends sideways in both directions from said cylinder to provide sideways support for said cylinder by engaging one of the sidewalls of said inner boom section when said cylinder bows in sideways direction under axial loading.

5. The telescopic boom as recited in claim 2 in which said outer boom section contains a second extension cylinder which is connected thereto and lies along a substantial part of its length, and there is a second set of supports spaced along the length of the outer boom section and positioned above said second extension cylinder to provide lateral support therefor under heavy loads.

6. The telescopic boom as recited in claim 1 in which the slidable connection of said outer boom section to said inner boom section is obtained by a pair of pad assemblies and each pad assembly includes:

a base having a top surface, said base being connected to one of said boom sections;

a frame member connected to said base and extending over said top surface, said frame member having an opening therethrough which forms a recess;

a pad disposed within said opening and having a bearing surface which extends above said frame member to slidably engage the other of said Boom sections; and

a retainer plate disposed between the base and frame member and connected to said pad, said retainer plate having outer dimensions larger than the opening in said frame member.

7. The telescopic boom as recited in claim 6 in which said frame member includes a flange which is fastened to said base to separate said frame member from the top surface of said base and said retainer plate is disposed within the space provided by this separation.

8. The telescopic boom as recited in claim 6 in which said retainer plate is bonded to the pad.