Metal deforming – By use of non-deforming work-gripping clamp and relatively... – By individually non-deforming clamps
Reexamination Certificate
2000-04-06
2001-11-20
Crane, Daniel C. (Department: 3725)
Metal deforming
By use of non-deforming work-gripping clamp and relatively...
By individually non-deforming clamps
C072S371000, C269S037000
Reexamination Certificate
active
06318142
ABSTRACT:
The present invention relates to a spacer device for use with apparatus for forming from a plurality of metal bars secured together at each end a twisted and enlarged basket of bulbous shape, as illustrated in
FIG. 1
of the accompanying drawings. These basket-shaped articles are commonly used as decorative features in wrought iron designs.
It is known to form decorative baskets from a plurality of metal bars using both manually operated and electro-hydraulic machines. A manually operated apparatus for forming baskets from metal bars is disclosed in PCT/GB96/02817. In general terms the operating procedure for both machines is the same. Firstly, a group of straight, square section metal bars, typically four in number, with the ends secured together is secured at each end between a fixed gripper ring or clamp and a rotatable gripper ring or clamp of the machine. The bars are then twisted on the machine through 360 degrees in one direction causing the bars to assume the shape and configuration shown in
FIG. 2
of the accompanying drawings. The bars are then twisted in the reverse direction through 720 degrees whilst at the same time the distance between the fixed and the rotatable clamps is shortened to exert a compressive force on the bars. This is illustrated in
FIG. 3
of the accompanying drawings. The result is generally that each steel bar in the now formed basket has, by virtue of its initial twist, lost its ability to resist a compressive force and so when twisted in the reverse direction and compressed buckles outwardly to assume the required bulbous shape. Each of the bars in the group is subject to near destructive twisting, particularly in the regions (a) thereof where the bars enter the clamps. In metallurgical terms this weakens the bars at these points.
For ease of availability and for cost considerations general quality hot rolled mild steel is the material of choice for the metal bars from which decorative baskets are formed. However, the manufacturing tolerances of this material are so wide that even along a single length of 6 meter stock bar its size, cross-section and strength can vary greatly. These variations can give rise to inconsistencies in the shape of the formed baskets. In particular, the size of the gap between each adjacent pairs of bars can be irregular. This problem can be overcome by using metal bar of high quality and close dimensional tolerances. However, the cost of such bar makes the finished product prohibitively expensive.
It is an object of the present invention to provide a spacer device for use with a basket forming apparatus which ensures regular spacing between the metal bars forming the basket, thus obviating the need to employ quality close tolerance steel.
According to the present invention there is provided a spacer device for use with a basket forming apparatus, the spacer device comprising a plurality of angularly spaced, radially extending arms corresponding in number to the number of metal bars forming the basket, each of which arms is adapted in use to engage with a respective one of the metal bars forming the basket-shaped article as the said article is twisted into its finished shape.
In use the spacer device according to the present invention is placed in position on the unfinished basket-shaped article immediately prior to untwisting the article through the last few degrees of rotation. As the article is twisted through these last few degrees of rotation each of the metal bars engages with a respective one of the arms of the spacer device, thus ensuring that the gap between adjacent pairs of metal bars is limited to the angular distance between the arms against which they engage.
In a preferred embodiment of the present invention the bars forming the spacer device are equi-angularly spaced, thus ensuring that all of the metal bars forming the basket-shaped article are equi-distantly spaced.
To ensure that the spacer device is retained in position on the unfinished basket-shaped article at least one of the said radially extending arms may comprise a hook at its free end which hooks over one of the metal bars forming the basket-shaped article.
In one embodiment of the present invention each of the said arms extends radially outwardly from a central hub.
In an alternative embodiment of the present invention each of the said arms extends radially inwardly from an annular support or collar the internal diameter of which is greater than the maximum outer diameter of the basket-shaped article. In this alternative embodiment each of the said arms is at least partially retractable relative to the collar thereby facilitating placement of the spacer device on the article and engagement of the arms in the gaps between adjacent pairs of metal bars. The arms can also be retracted to facilitate removal of the spacer device from the finished article.
The retractable arms may be moved in and out of their working positions simultaneously by means of an automatic drive system. Alternatively, each arm may be moved manually between its extended and retracted positions. In this later case each arm is preferably connected to a spring which biases it towards its extended position and locking means for engaging the arm against the spring bias in its retracted position.
REFERENCES:
patent: 2855972 (1958-10-01), Greider
patent: 4007616 (1977-02-01), Aleck
patent: 4262515 (1981-04-01), Frei
patent: 4549423 (1985-10-01), Masui
patent: 5801336 (1998-09-01), Blanding
patent: 197 15 081 A1 (1998-01-01), None
patent: 3221736 (1983-12-01), None
patent: WO 97/18908 (1997-05-01), None
Crane Daniel C.
Fay Sharpe Fagan Minnich & McKee LLP
Wood Ian
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