BACKGROUND OF THE INVENTION

1) Field of the Invention

The present invention relates to a lock for an adjustable brace of the type used in the erection of precast concrete panels in building construction.

2) Description of the Prior Art

Adjustable braces are often used for the temporary bracing of concrete wall panels in their erected condition prior to coupling of the panels to form a self-supporting structure. Standard braces for this purpose typically comprise a telescopic leg retained in a selected extension by a pin inserted through aligned holes within two telescopic parts of the leg, the telescopic parts providing coarse adjustment of the overall length of the prop. Finer adjustment is achieved by a screw-threaded coupling between the lower end of the leg and the adjacent anchor plate by which the brace is anchored to a floor slab. The coupling typically comprises a threaded rod aligned with the axis of the leg and engaged into an internally-threaded fitting within the adjacent end of the leg, the outer end of the rod being pivotally coupled to the anchor plate by a pivot pin extending through a transverse bore at the end of the rod. Accordingly, rotation of the leg relative to the rod and anchor plate (or vice versa) will result in variation of the effective length of the rod extending between the end of the leg and the anchor plate. This fine adjustment usually takes place when the brace is in position in order to set the panel at a precise vertical orientation.

Braces of this type may need to be maintained in position on the building site for some weeks, sometimes some months. Unless precautions are taken, the braces can be tampered with during this period, for example as a result of vandalism when the building site is unattended or through deliberate action of persons working on the site either as a mischievous act or perhaps to shift the panel a little in order to make their job easier. However this happens and for whatever reason it happens, tampering with the brace so that it no longer securely retains the panel in a precisely vertical orientation can have serious, potentially fatal, consequences. For telescopic props, health and safety regulations may require the pin locking the two telescopic parts of the leg itself to be locked in position to prevent its removal without the use of a special tool or key. While this can be an effective deterrent against pin removal and hence reduces the risk of the brace being rendered completely ineffective, the prop can still be subjected to unauthorised adjustment by rotation of the leg relative to the anchor plate.

SUMMARY OF THE INVENTION

The present invention in its preferred embodiment provides a lock which can be applied between the anchor plate and end of the leg so as to prevent unauthorised adjustment rotation of the leg.

According to the present invention there is provided a latch for an adjustable brace to lock against rotation between a leg of the brace and an anchor plate so as to prevent adjustment in the effective length of the brace, the latch having an end (a first end) engageable with the anchor plate and an opposite end (a second end) selectively engageable with the adjacent end of the leg or with structure rigidly secured thereto to prevent relative rotation between the leg and plate. In a preferred embodiment of the invention, the latch at least at its second end portion is of a channel form in which the end of the leg or structure attached thereto is receivable whereby rotation is prevented by co-operation with the walls of the channel. Preferably, the latch is retained in its engaged, latching, position by means releasably locking the second end of the latch to the leg. Preferably the locking means consists of a removable locking pin extending across the open side of the channel.

The present invention also provides an adjustable brace having fitted thereto a latch as defined above. The present invention also provides a method of retro-fitting a latch as defined above to an existing brace of the type in which a leg of the brace is rotatable relative to an anchor plate at each end so as to adjust the effective length of the leg, the brace including a connecting rod between an end of the leg and the adjacent anchor plate and to which it is pivo tally coupled by means of a pin, the method comprising removing the pin, and pivotally mounting the said first end of the latch to the plate by means of a pin applied to reconnect the rod to the anchor plate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a perspective view from one side of the lower end portion of an adjustable telescopic brace having fitted thereto a latch forming an anti-rotation lock in accordance with the preferred embodiment of the invention;

Figure 2 is a perspective view similar to Figure 1 from the other side;

Figure 3 is a perspective view similar to Figure 1 from the front; and

Figure 4 is a perspective view to an enlarged scale showing the latch per se, the view showing the latch inverted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The accompanying drawings show the lower end portion of an adjustable brace which is itself substantially conventional apart from the addition of an anti-rotation lock in accordance with the preferred embodiment of the invention. The brace comprises a telescopic leg 2 formed by telescopic parts 2a, 2b of square section tubing, the two parts being held at their selected extension by means of a pin 4 retained against unauthorised removal by a lock 6. A threaded rod 8 (the thread is not shown in the drawings) engaged into an internally-threaded fitting in the lower end of the inner telescopic part 2b connects the leg to an anchor plate 10. The plate 10 is of a standard construction and comprises a pair of spaced upstanding flanges 12. The outer end of the rod 8 lies between these flanges and is pivotally connected to the plate by a pin 14 extending between the two flanges and through a transverse bore in the rod; in practice, the pin may be formed by a bolt. The anchor plate can thereby swing relative to the leg and threaded rod about the transverse axis defined by the pin 14. The base 16 of the anchor plate is configured for co-operation with an anchor bolt by which the plate is secured to a floor slab. A corresponding anchor plate is provided at the upper end of the leg and is connected to the end of the outer telescopic part 2a by a coupling which enables the upper anchor plate to swing relative to the leg and also to enable the leg to rotate relative to the upper plate.

The anti-rotation lock in accordance with the preferred embodiment of the invention is in the form of a simple pivotal latch 20 of channel shape. The latch 20 is pressed out of metal sheet and comprises at one end a pair of lugs 22 projecting longitudinally and at the other end a pair of lugs 24 projecting laterally. The spacing between the lugs 22 corresponds to the spacing between the external surfaces of the two flanges 12 on the anchor plate 10. The lugs 22 are apertured to receive the pin 14 by which the threaded rod 8 at the end of the leg is attached to the anchor plate so that the latch 20 is able to pivot on that pin. It is pivotal between an unlatched position in which it is swung outwardly so that its base rests on the ground behind the anchor plate, and a latched position, which is the position shown in the drawings, in which it has been swung upwardly so that its upper end cradles the lower end of the inner telescopic leg part 2b. The two laterally-projecting lugs 24 at that end project beyond the surface of the inner leg part 2b and are apertured to receive a removable pin 28 extending between the lugs in the manner shown whereby the latch is held in its operative position. For convenience the pin used to retain the latch may be of the same form as the pin 4, used to retain the telescopic leg parts and is itself locked against unauthorised removal by a similar type of lock shown at 30. The width of the internal channel of the latch is similar to the width of the inner leg part 2b and the lugs 24 which receive the pin 28 are so dimensioned that with the pin 28 resting on the upper side of the inner leg part 2b, the base of the latch is held close to the lower side of the inner leg part. It will be understood that with the latch thus in position, it will act to lock the leg against rotation relative to the anchor plate and hence against rotation that would otherwise result in adjustment in the length of the brace.

Although the invention has been described in relation to a prop with a telescopic leg it is equally applicable to props of similar form but with a single non-telescopic leg. Although in the embodiment shown the co-operation between the latch 20 and the leg 2 results from the square cross section of the tubing used to form the leg, braces are not always constructed with legs of that characteristic shape and many are constructed from tubing of round (circular) section tubing. However a brace leg formed from such tubing can be adapted for co-operation with the same latch by welding to the end of the leg a washer or plate having a square outer shape to fit into the interior of the channel of the latch so that co-operation between the walls of the channel and the sides of the washer will prevent rotation of the leg.

While the latch described can be incorporated during the production of the brace, it also has the significant advantage that it can be retro-fitted to existing braces. This is of some significance because there are many braces already in use. They are robustly made and have a long potential working life. All that is necessary to fit the latch to an existing brace is to remove the pin connection between the anchor plate and threaded rod and fit the latch using the pin to secure both the rod and latch.

Although in the embodiments described the latch is fitted to the anchor plate at the lower end of the brace, it may alternatively be fitted to the anchor plate at the upper end of the brace for co-operation with the upper end of the leg to thereby prevent rotation of the leg. In this respect, the connection between the upper end of the leg and the anchor plate at that end will be similar to that at the lower end, except that the connecting rod is not threaded. The embodiment has been described by way of example only and modifications are possible within the scope of the invention.