Title:
Self-centering stock support
Kind Code:
A1


Abstract:
A mounting stock support or support jig assembly is disclosed for use in the manufacture of large, symmetrical hollow welded metal vessels having openings in one end, particularly exemplified by conventional hollow concrete mixing drums for transit concrete mixing trucks. The device is fully mechanized and automatically centers a cradled drum or other vessel for turning or rotation in the cradle and completion of welding assembly and other tasks requiring accurate centered rotation of the vessel such as machining roller tracks.



Inventors:
Schrafel, Tracy L. (West Concord, MN, US)
Application Number:
11/595342
Publication Date:
05/15/2008
Filing Date:
11/10/2006
Assignee:
McNeilus Truck and Manufacturing, Inc. (Dodge Center, MN, US)
Primary Class:
International Classes:
B65H1/00
View Patent Images:
Related US Applications:



Primary Examiner:
WILSON, LEE D
Attorney, Agent or Firm:
DeWitt LLP (Minneapolis, MN, US)
Claims:
What is claimed is:

1. A self-centering stock support or support jig for use in processing large symmetrical hollow vessels that have a central opening at one end including drums for transit concrete mixing trucks comprising: (a) a central shaft assembly; (b) an expandable grabber assembly mounted on said central shaft including a substantially round head plate carrying an array of radially distributed, radially extendable vessel-grabbing fingers operable in unison to center and retain a vessel about said shaft using said opening; (c) a mounting system for retaining and enabling the rotation of said support jig assembly with rotation of said central shaft assembly; and (d) a mechanized finger operating system for extending and retracting said grabbing fingers.

2. An apparatus as in claim 1 wherein said finger operating system further comprises a centrally mounted tubular sleeve member and linkage connected between said tubular sleeve member and said vessel-grabbing fingers, said tubular sleeve member being reciprocally operable along said central shaft assembly.

3. An apparatus as in claim 2 wherein said central shaft assembly includes hollow shaft members and wherein said finger operating system further includes a draw bar member mounted within said hollow shaft members and connected to operate said tubular sleeve member reciprocally along said central shaft assembly, thereby extending and retracting said vessel-grabbing fingers.

4. An apparatus as in claim 3 wherein each of said vessel-grabbing fingers is mounted to operate along a radially disposed slot in said round head plate and including a radially disposed cam slot mounted on said round head plate next to each of said grabbing fingers, each of said grabbing fingers being further provided with a pair of attached follower members which ride in a corresponding cam slot as each said vessel-grabbing finger extends or retracts radially.

5. An apparatus as in claim 3 wherein said draw bar is operated by a pair of fluid-operated cylinders.

6. An apparatus as in claim 5 wherein said fluid-operated cylinders are hydraulic cylinders.

7. An apparatus as in claim 3 wherein said shaft assembly includes a bearing sleeve assembly which allows said hollow shaft members to rotate.

8. An apparatus as in claim 1 wherein said vessel-grabbing fingers are provided with a series of stepped notches to accommodate a plurality of vessel opening sizes.

9. An apparatus as in claim 1 wherein the number of extendable vessel-grabbing fingers is four.

10. An apparatus as in claim 4 wherein the number of extendable vessel-grabbing fingers is four.

11. An apparatus as in claim 4 wherein said vessel-grabbing fingers are provided with a series of stepped notches to accommodate a plurality of vessel opening sizes.

12. An mounting system as in claim 1 wherein said hollow vessel is a mixing drum for a transit concrete mixer truck.

Description:

BACKGROUND OF THE INVENTION

I. Field of the Invention

The present invention relates generally to the manufacture of rather large, hollow work pieces which require accurate rotation about a central axis during phases of the manufacture processing. These vessels are generally of a class having a varying round cross section and an access opening at one end thereof, for example, and include concrete mixing drums for transit concrete mixer trucks. More particularly, however, the invention is directed to an adjustable stock support device or support jig which carries, and automatically centers, the hollow vessel with respect to a central shaft which is used to rotate the vessel in a welding cradle in the manufacturing process for assembly and welding of vessel sections and to allow a machinist to machine bearing surfaces or a roller track surface in a safe and efficient manner.

II. Related Art

In the assembly process for steel concrete mixing drums, sections of the drum are seam-welded together during the assembly of the drum. During part of the process, the drum is carried by a heavy stock support device or support jig known as a tail stock in which the tail or aft section of the drum is centered on four manually adjustable extending grabbing devices or fingers using the access opening. The fingers must be manually adjusted, one at a time, by a worker from inside the drum to center the drum for further processing. All this must be done with the partially assembled vessel shell situated in an elevated position. As the grabbing fingers are adjusted, the partially fabricated drum must be turned or spun to achieve and check as to whether it is in a centered position with respect to the central turning shaft. This is a time-consuming and arduous task.

Thus, this assembly procedure requires a difficult and labor intensive process to properly mount and align the vessel for further processing. Accordingly, it would be desirable if a mechanized aligning and self-centering device could be developed that would eliminate the need for manual adjustment of the grabbing fingers by workers inside partially assembled vessels. This would not only save a great deal of labor, but time in aligning the vessel for further processing.

SUMMARY OF THE INVENTION

By means of the present invention, there is presented a mounting stock support or support jig assembly for use in the manufacture of large, symmetrical hollow welded metal vessels having openings in one end, particularly exemplified by conventional hollow steel concrete mixing drums, that is fully mechanized and centers and retains a cradled drum or other vessel for turning or rotation in the cradle and completion of welding assembly and other tasks requiring accurate centered rotation of the vessel such as machining roller tracks.

The stock support or support jig of the present invention includes an expandable grabber assembly carried at one end of a central shaft assembly. The central shaft is mounted for rotation and carried in a cradle support assembly. The support jig is designed to be turned as necessary by a connected prime mover such as an electric motor and gear reducer system which is conventional and not part of the present invention. The expandable grabber assembly includes a substantially round head plate carrying an array of radially distributed extendable vessel-grabbing or retaining fingers which operate radially in unison to center a vessel opening about the central shaft assembly.

The radially distributed extendable vessel-grabbing or retaining fingers are provided with a series of stepped notches which engage and retain the rim of a central access opening in a mixing drum or other vessel and enable the device to accommodate a variety of vessel opening sizes. The radially distributed extendable vessel-grabbing or retaining fingers are each mounted to move along a radially directed slot in the head plate attached by an intermediate link which is pivotally mounted between a hollow tubular member slidably mounted to reciprocate along the central shaft assembly. A cam slot is mounted next to each of the extendable vessel-grabbing fingers. Each of the grabbing fingers moves radially guided along an adjacent cam slot using a pair of attached followers. The reciprocal motion of the tubular member is controlled by a draw bar nested inside the central shaft assembly and pinned between the hollow tubular member and a draw bar operating collar assembly. The draw bar is designed for movement along a rectilinear path within the hollow central shaft assembly operated reciprocally using a pair of hydraulic cylinders mounted between the collar assembly and a shaft mounting collar fixed to members attached to the cradle frame.

In operation, the self-centering stock support or support jig is matched with the opening of a vessel mounted for rotation in a welding cradle until the appropriate notches for the particular size vessel opening of interest are advanced inside the rim of the opening. Thereafter, the hydraulic cylinders are operated to operate the draw bar which, in turn, operates the hollow tubular sleeve member along the hollow shaft assembly and extends the vessel-grabbing fingers equally in unison, thereby capturing the rim of the vessel to be assembled in centered alignment with the central shaft assembly. The assembly can thereafter be turned as desired and the vessel attached to the self-centering stock support will turn and remain in an aligned centered position in the welding cradle.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like numerals designate like parts throughout the same:

FIG. 1 is a perspective schematic view of a self-centering stock support or support jig in accordance with the invention mounted in a support frame;

FIG. 2 is a side view partially in section with parts removed for clarity of the device of FIG. 1;

FIG. 3 is an enlarged perspective view partially in section with parts removed for clarity similar to FIG. 2; and

FIGS. 4 and 5 are side views of work pieces mounted for processing using the device of the invention.

DETAILED DESCRIPTION

The detailed description that follows will illustrate the invention in conjunction with a number of drawing figures which depict an embodiment of the invention. The description is presented to show an example of the invention and is not intended to be limiting in any manner as it is believed that certain variations within the spirit and scope of the invention would occur to those skilled in the art.

FIG. 1 is a perspective representation of a self-centering stock support or support jig in accordance with the present invention. The device is shown generally at 10 as mounted on a heavy cradle support structure 12 which includes heavy mounting plates 14 fixed to cradle top member 16. The stock support or support jig structure includes a main hollow shaft assembly which has a main hollow shaft member 18 (FIGS. 2 and 3) and forward shaft member 20 which carry an internally mounted reciprocating draw bar member 22. The hollow shaft member 18 is journaled for rotation in a bearing sleeve assembly 24 mounted on the mounting plates 14 and including spaced heavy roller bearing collars 26, 28 fixed to shaft member 18 and roller bearings 30, 32 mounted in recess and sleeve member 34.

Forward shaft member 20 includes a shoulder 36 and carries an outer sleeve member 38 to which are fixed a plurality of radially distributed gusset members 40. The self-centering stock support or support jig further includes a large round head plate member 42 which has a plurality of radially distributed slots which carry radially movable vessel-grabbing or retaining fingers 44 which contain a series of stepped notches 46. Hollow slotted cam members 48 are fixed alongside and parallel to each of the grabbing fingers 44 which are also provided with a pair of spaced cam follower members 50 fixed thereto so that the followers ride in the cam slots as the grabbing fingers extend and retract radially. A pair of link members 52 connect each grabber finger 44 with a corresponding gusset member at pivot joints 54, 56. Whereas the number of fingers can be varied, the illustrative embodiment utilizes four fingers approximately 90 degrees about the periphery of the disk member 42. It should be understood that this number should be three or more in order to achieve the proper self-centering function.

One end of the draw bar 22 is fixed to the tubular sleeve member 38 by heavy pin member 58 which extends through a slot 76 in shaft member 20 and at the other end is fixed to a draw bar operating collar assembly 60 which, in turn, is fixed to slide along the hollow shaft member 18 and which includes a pair of heavy-duty plate members 62, 64. The draw bar member 22 is pinned at 66 to the operating collar assembly 60. A pair of double-acting hydraulic cylinders 68, 70 (FIG. 1) are mounted between the draw bar, operating collar assembly and a fixed mounting collar member 72 that is fixed to base plate members 14. A slot 74 is also provided in hollow shaft 18 to allow translation of the draw bar member 22 (FIGS. 4 and 5).

The system contains a further counterbalancing rear section 80 having a peripheral recess 82 designed to rotate on a block 84. This end attaches to a prime mover (not shown) which is used to turn the assembly as desired in a well-known manner.

FIGS. 4 and 5 show side views with parts cut away for clarity of transit concrete mixing drums 100 and 102, respectively, mounted in a welding cradle, a partial view of the frame of which is shown at 104, being addressed by a self-centering stock support or support jig 10 in accordance with the present invention. The drums 100, 102 are mounted for rotation at 106 on support pedestal 108. Drum 110 is shown with the internal fins in place at 110.

It should be noted that once the rear of the drum is mounted on a pedestal in a well-known manner for rotation and the opening as at 112 secured in the stock support or support jig, the entire drum can be rotated as desired while remaining in a centered position.

This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the example as required. However, it is to be understood that the invention can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself.