STRETCHER WITH REMOVABLE PRESSURE BLOCK

Abstract

A stretcher has two head housings, and a removable pressure block/clamp assembly which is located in the housings and positioned via hydraulic cylinders. The hydraulic cylinders raise the pressure block assembly, and the gripper hydraulic cylinders lower the pressure block assembly onto a removal fixture which moves into and out of the head housing.

Description

CLAIM OF PRIORITY

This application claims priority from provisional application Ser. No. 63/407,878 filed on Sep. 19, 2022, the entirety of which is incorporated by reference herein.

BACKGROUND OF THE DISCLOSURE

The present disclosure relates to rolled or extruded metal and sheet metal or metal plate processing. More particularly, the present disclosure relates to a method and apparatus for installing and removing a pressure block or clamp assembly from a stretcher leveler (stretcher).

A wide variety of manufactured goods contain processed sheet metal. For example, aircraft, automobiles, file cabinets and household appliances, to name only a few, contain sheet metal. The sheet metal is typically purchased directly from steel mills and/or steel service centers, but may be passed through intermediate processors (sometimes referred to as “toll” processors) before it is received by an original equipment manufacturer (OEM).

Various methods exist for flattening or stretching sheet metal. Flatness of sheet metal is important because virtually all stamping and blanking operations require a substantially flat sheet. Also, in certain applications, such as in the aerospace industry, residual stress free material is critical. Good surface conditions are also important, especially in applications where the top and/or bottom surfaces of the metal sheet will be painted.

There are a number of common defects that effect sheet metal flatness. For example, when sheet metal is rolled into coil form for convenient storage and transportation, the strip tends to take on a coiled shape. This curvature is commonly referred to as “coil set.” Coil set occurs because the sheet metal has been bent past its yield point. More specifically, when sheet metal is coiled, the metal fibers near the inside surface of the curved sheet are compressed past their yield point, and the metal fibers near the outside surface of the curved sheet are stretched past their yield point. Another type of shape defect known as “edge wave” occurs if the edge portions of the sheet are longer than the center portion of the sheet, resulting in undulations in one or both of the edge portions of the sheet. A similar type of shape defect known as “center buckle” results if the center portion of the sheet is longer than one or both of the edge portions, which results in bulging or undulating of the central portion of the sheet.

An existing method of flattening sheet metal is called “stretcher leveling.” Stretcher leveling is generally considered to be a superior flattening process because, unlike roller leveling, it rectifies the problem of internal residual stresses.

To prepare the stretchers for operation, a metal strip is withdrawn from a coil. Then with the pressure/clamping assemblies of the stretching machine in their raised positions, the strip is fed between upper and lower grippers through the space between the upper and lower grippers on the head frame. In other words, the strip is advanced along a path through the stretcher.

The stretcher can include a feeding mechanism, including a plurality of powered rollers for pulling and/or pushing the sheet metal strip through the stretcher assembly. The feeding mechanism can advance the sheet metal strip through the stretcher assembly at precise increments.

A typical stretch leveler includes a pair of grippers or jaws that securely grips the opposing ends of the sheet to be stretched. In a preferred embodiment of the disclosure, upper grippers are moved up and down, while lower grippers remain stationary. However, it is contemplated that the lower grippers could move while the upper grippers remain stationary, or both upper and lower grippers could move.

The surface portions of the grippers that engage or grip the sheet metal to hold the sheet against movement during stretching are typically textured steel with a hardened coating, or have a replaceable friction material to provide a secure grip. In operation, the grippers are hydraulically controlled to engage the opposed ends of the sheet and, once a firm contact is made, hydraulic actuators move the main housing away from the fixed main housing stretching the sheet. The entire cross section of the metal sheet is stretched past its yield point (i.e., beyond its elastic limit) such that all internal residual stresses are eliminated from top to bottom and from side to side.

For example, U.S. Pat. No. 4,751,838, issued to Kenneth Voges, discloses an “in-line stretcher leveler.” The teachings of this patent are incorporated herein by reference.

A problem with existing stretcher designs is that the pressure block/clamp assembly or plurality of cylinders are substantially or completely enclosed within a housing of the stretcher heads and is very difficult to access to remove or repair components.

For example, cylinders and grippers are not accessible and it requires a significant effort to access and remove or repair these components.

Thus, there is a need for an easily accessible and removable pressure block/clamp assembly which facilitates removal and repair of components, while saving time and expenditure, while providing better overall results.

SUMMARY OF THE DISCLOSURE

The disclosure relates to a stretching device. More particularly, it relates to a direct acting stretching device which has a removable pressure block/clamp assembly for easy access for removal and repair of components.

A stretching device has opposite ends, a moveable head assembly and a fixed head assembly connected with beams. These head assemblies are used to pull or stretch a sheet or plate between the stretcher heads, wherein the fixed head can have grippers which holds the sheet or plate in place and is stationary, while the movable head can have grippers which grips and clamps down on the sheet or plate and moves to stretch the sheet or plate.

In accordance with one aspect of the disclosure, the stretcher has a removable pressure block/clamp assembly which is removed via a frame on rollers which is moved with a winch or a hydraulic cylinder. The block is positioned externally with regard to the stretcher for easy installation and removal. Cylinders can either pull up or push up the pressure block positioning it into its raised operating position.

In accordance with another aspect of the disclosure, a stretcher with a removable pressure block has a housing and a pressure block which is located in the housing and is positioned by hydraulic cylinders. The hydraulic cylinders raise and lower the pressure block onto a removable fixture which allows the assembly to be removed from the head housing. Alternately, the pressure block assembly can be directly mounted to wheels to move the pressure block out of the housing.

In accordance with another aspect of the disclosure, the grippers are accessed through a window of the stretcher head housing for changing out or replacing. The grippers may have a cardboard or chipboard or metal configuration.

In accordance with another aspect of the disclosure, the pressure block/clamp assembly is easily removed from the stretcher head housing.

In accordance with still another aspect of the disclosure, the pressure block/clamp assembly is easily installed onto the stretcher head housing.

In accordance with still another aspect of the present disclosure, a stretching device has two head housings; a first gripper and second gripper attached to each head housing; wherein a movable head and fixed head used to stretch the sheet between the stretcher head housings.

Still other aspects of the disclosure will become apparent upon a reading and understanding of the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a stretcher head housing and removable pressure block/clamp assembly in accordance with a preferred embodiment of the disclosure.

FIG. 2 is a front elevational view of the stretcher head housing of FIG. 1 in accordance with another aspect of the disclosure.

FIG. 3 is a side elevational view of the stretcher head housing in accordance with another aspect of the disclosure.

FIG. 4 is a perspective view of the gripper plate removal stand.

FIG. 5 is a side elevational view of the stretcher head housing and the pressure block outside of the housing in accordance with another aspect of the disclosure.

FIG. 6 is a perspective view of a stretcher head housing and pressure block of FIG. 5.

FIG. 7 is a perspective view of a removed pressure block/clamp assembly of FIG. 6.

DETAILED DESCRIPTION OF THE DISCLOSURE

Reference numerals are used to describe the components of the disclosure:

• • 1 Main housing
  • 2 Pressure block/clamp assembly positioning cylinder
  • 3 Gripper change window
  • 4 Pressure block/clamp assembly
  • 5 Gripper plate
  • 6 Gripper plate removal stand
  • 7 Hydraulic piping
  • 8 Removal fixture
  • 9 Hydraulic hose carrier
  • 10 Removal winch
  • 11 Side blocks
  • 12 Rollers
  • 13 Side wall
  • 14 Piston
  • 15 Piston
  • 16 Piston
  • 17 opening
  • 18 opposite side
  • 19 opposite side
  • 21 upper gripper
  • 23 lower gripper

Referring now to FIGS. 1-7, a stretcher head housing 1 with a removable pressure block/clamp assembly 4 is shown, in accordance with a preferred embodiment of the disclosure. The pressure block 4 is pulled into an operating position by pressure block positioning hydraulic cylinders 2. The cylinders 2 extend through openings 17 formed in the top of housing 1 and pull up the pressure block 4 via blocks 11 located on opposite sides 18, 19 of the housing. The cylinders 2 lift and hold the pressure block in the raised operating position (with an air gap below the pressure block) as seen in FIGS. 1, 2 and 3. The cylinders 2 can also lower the pressure block onto a pressure block removal fixture 8 (seen in FIG. 5) which has rollers 12 which rolls into and out of the housing to receive the pressure block for installation and removal. Alternately, the pressure block can have wheels directly mounted to the pressure block for removal.

Referring to FIGS. 3 and 4, a gripper change window 3 is provided in a side wall 13 of the stretcher housing 1 to access the gripper plates 5 for removal and changing out using a gripper plate removal stand 6. The gripper plates 5 are of a metal construction and may include slots to add cardboard or chipboard may need to be changed out as needed (see Butech U.S. Pat. No. 9,327,334 incorporated by reference herein).

Metallic grippers typically get changed out every 6-12 months for maintenance or refurbishment, while cardboard or chipboard grippers get changed out after every three, four or five coils of sheet metal.

There are two upper grippers 21 and two lower grippers 23. In the preferred embodiment, the lower grippers remain fixed, while the upper grippers move up and down, to grip the material to be stretched. Alternatively, the lower grippers can move while the upper grippers remain fixed, or both the upper and lower grippers can move.

Referring now to FIG. 6, the pressure block/clamp assembly 4 has three (or more or less) pistons 14, 15 and 16 located at the upper wall of the pressure blocks which apply the gripping force straight down onto the gripper plates. Pressure block hydraulic piping 7 provides the hydraulic fluid to the pistons. A hydraulic hose carrier 9 is provided for the pressure block. A pressure block removal fixture 8 is provided for receiving the pressure block for removal from the stretcher housing 1.

Referring now to FIG. 5, rollers 12 on the fixture 8 enable the fixture 8 to be rolled into position under the elevated pressure block in the stretcher housing 1. The pressure block is then lowered via cylinders 2 onto the removal fixture. Referring to FIG. 7, for example a pressure block removal winch 10 (or hydraulic cylinder) is preferably used to pull the pressure block out of the stretcher housing 1.

The Figures illustrate a pressure block at the exit moving head of the stretcher. There is also a pressure block at the entry fixed head of the stretcher.

A detailed description of the removal and installation of the pressure block is now provided.

To install the pressure block 4 onto the stretcher, both upper and lower grippers and gripper retainers are removed. The pressure block positioning cylinders are fully extended. The stretcher is fully extended—only when installing the pressure block in the moving head. The pressure block is then placed on the removal fixture 8, with care being used to center it with the heads as close as possible. The winch assembly 10 is placed on the opposite side of the stretcher. A wire rope supplied with the winch is attached to an eyebolt on the removal fixture 8. The winch cable is then fed through the stretcher and hooked or attached to the wire rope. The pressure block is carefully pulled into the stretcher head. Once the pressure block is fully seated, the pressure block pull back cylinders 2 are retracted to pull the block into place.

To remove the pressure block from the stretcher, both upper and lower grippers and gripper retainers are removed. The stretcher is fully extended—only when removing the pressure block in the moving head. The removal fixture 8 is placed on a conveyor and it is pushed into the head until it stops under the pressure block. The pressure block positioning cylinders 2 are fully extended to lower the pressure block onto the removal fixture 8. The winch assembly 10 is placed on the same end of stretcher as the pressure block. The winch cable is attached to the (removal) eyebolt on the cart. The pressure block is carefully pulled out of the stretcher head.

The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment and the claims be construed as including all such modifications and alterations insofar as they come within the scope of the above disclosure and claims or the equivalents thereof.

Claims

1. A stretcher with a removable pressure block assembly comprising:

a head housing;

a pressure block assembly which is located in said housing and positioned within said housing via hydraulic cylinders; said hydraulic cylinders raise said pressure block assembly; and said hydraulic cylinders lower said pressure block assembly to move said pressure block out of said housing.

2. The stretcher of claim 1, further comprising a window formed in a wall of said housing for accessing gripper plates within said housing for removal.

3. The stretcher of claim 2, wherein said gripper plates comprises upper gripper plates and lower gripper plates.

4. The stretcher of claim 3, wherein said lower gripper plates remain fixed in said housing.

5. The stretcher of claim 3, wherein said upper gripper plates move up and down relative to said housing.

6. The stretcher of claim 3, wherein said pressure block assembly comprises at least one piston which applies gripping force onto said lower gripping plates.

7. The stretcher of claim 6, wherein said pressure block assembly further comprises hydraulic piping for providing hydraulic fluid to said at least one piston.

8. The stretcher of claim 1, further comprising a removal fixture wherein said removal fixture comprises rollers for moving said removal fixture into and out of said housing.

9. The stretcher of claim 1, wherein said hydraulic cylinders lower said pressure block assembly onto said removal fixture.

10. The stretcher of claim 9, further comprising a mechanism to pull said pressure block assembly out of said head housing.

11. A stretcher with a removable pressure block assembly comprising:

a head housing having a window in a side wall to access gripper plates;

a pressure block assembly which is located in said housing and positioned by hydraulic cylinders which raise the pressure block assembly and lower said pressure block assembly for removing said pressure block assembly from said head housing.

12. The stretcher of claim 11, wherein said gripper plates comprises upper gripper plates and lower gripper plates.

13. The stretcher of claim 12, wherein said lower gripper plates remain fixed relative to said head housing.

14. The stretcher of claim 12, wherein said upper gripper plates move up and down relative to said head housing.

15. The stretcher of claim 12, wherein said pressure block assembly comprises at least one piston which applies gripping force through said upper gripper plates onto said lower gripping plates.

16. The stretcher of claim 15, wherein said pressure block assembly further comprises hydraulic piping for providing hydraulic fluid to said at least one piston.

17. The stretcher of claim 11, further comprising a removal fixture for moving said pressure block assembly out of said head housing.

18. The stretcher of claim 17, wherein said hydraulic cylinders lower said pressure block assembly onto said removal fixture.

19. The stretcher of claim 18, further comprising a mechanism to pull or push said pressure block assembly out of said head housing.