An improved drum for a lorry-based concrete mixer is described. The drum comprises a drum body having an edge defining an aperture for permitting access to a drum body interior and a manhole cover hingedly attached to the drum body, the manhole cover being movable from an aperture dosed position, in which the aperture is sealed, to an aperture open position, in which the aperture is open and the drum body interior may be accessed. The drum further comprises at least one locking mechanism adapted to lock the manhole cover In the aperture dosed position, an edge of the manhole cover being trapped between the/each locking mechanism and the drum edge in the aperture closed position. The at least one locking mechanism is adapted to support the manhole cover in a retained position between the aperture dosed position and the aperture open position.

PRIORITY APPLICATIONS

This application is a U.S. National Stage Filing under 35 U.S.C. §371 from International Application No. PCT/GB2013/000271, filed on 18 Jun. 2013, and published as WO2013/190256 A1 on 27 Dec. 2013, which claims the benefit under 35 U.S.C. §119 to United Kingdome Application No. GB 1210804.9, filed on 19 Jun. 2012; which applications and publication are incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to an improved drum for a concrete mixer and particularly, but not exclusively, to a drum with improved access.

BACKGROUND TO THE INVENTION

Mobile concrete mixers having a mixer drum mounted on a truck chassis are well-known in the building industry. Such concrete mixers are used to transport liquid concrete (comprising cement, sand and water) from a plant to a building site where the concrete is to be used. The concrete mixer drum is typically mounted at an angle on the truck chassis with the opening of the drum some height above the ground. The drum is rotated in the first direction to draw materials into the drum during transportation to the building site and it includes internal screws or ribs which expel concrete from the drum through the discharge chute when the drum is rotated in the opposite direction.

Access to the interior of the drum is required for cleaning and maintenance purposes. Accordingly, the drums are typically manufactured including a manhole which is closed by a manhole cover that is securely bolted to the drum using, typically, twelve separate bolts. To gain access to the drum interior, an operator must release each of these bolts and remove the manhole cover, before climbing to the manhole. This is a time-consuming process and the weight of the manhole cover is such that it can be a cumbersome operation to remove the manhole cover out of the way of the access into the drum, particularly if the user still holding the tools.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an improved drum for a lorry-based concrete mixer, the drum comprising:

a drum body having an edge defining an aperture for permitting access to a drum body interior;

a manhole cover hingedly attached to the drum body, the manhole cover being movable from an aperture closed position, in which the aperture is sealed, to an aperture open position, in which the aperture is open and the drum body interior may be accessed; and

at least one locking mechanism adapted to lock the manhole cover in the aperture closed position, an edge of the manhole cover being trapped between the/each locking mechanism and the drum edge in the aperture closed position;

wherein the at least one locking mechanism is adapted to support the manhole cover in a retained position between the aperture closed position and the aperture open position.

In at least one embodiment of the present invention, providing a drum for a lorry-based concrete mixer which incorporates a hinge and at least one locking mechanism allows for the manhole cover to be moved from the aperture closed position to the aperture open position without the possibility of the manhole cover being dropped and potentially damaged. Being able to retain the manhole cover in a position between the aperture closed and open positions allows the user to release the manhole cover and then swing it open in two separate operations.

The manhole cover may be biased to the aperture open position. Providing a manhole cover which is biased to the open position permits access to the interior of the drum more quickly.

The manhole cover may be biased under its own weight. Such an arrangement permits the manhole cover to swing open when it is released by the locking mechanism.

In the manhole cover closed position, the locking mechanisms may compress the manhole cover against the drum edge. Such an arrangement forms a tight seal.

In the retained position, the seal between the manhole cover and the drum edge is broken.

In an embodiment, in moving from the aperture closed position to the manhole cover retained position, the manhole cover moves away from the drum edge in a direction substantially perpendicular to the drum edge. In an embodiment, in moving from the manhole cover retained position to the aperture open position, at least part of the movement is a rotational movement. Particularly, the manhole cover may be rotated to move clear of the/each locking mechanism.

The manhole cover may comprise gripping means. Gripping means are provided to allow the manhole cover to be moved to the aperture open position. The gripping means may be handles.

The manhole cover may be hingedly attached to the drum by means of an arm. The arm may be attached at a first end to the drum body and at a second end to the manhole cover. The manhole cover may be rotationally movable with respect to the other. A rotational movement of the manhole cover, in some embodiments, is required to move the manhole cover from the retained position to the aperture open position.

In an embodiment, a tool is required to release the locking mechanism and allows the manhole cover to move from the aperture closed position to the retained position. In this arrangement, a tool can be used to release the manhole cover to the retained position allowing the operator to put down his tool and then use both hands to rotate the manhole cover such that it is no longer retained and can be swung about the hinge to the aperture open position.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring toFIG. 1, a side view of an improved drum, generally indicated by reference numeral10, for a lorry-based concrete mixer2, the drum10is shown mounted to the chassis4of the lorry-based concrete mixer2with an open end6elevated with respect to a closed end8. The present invention provides access to the closed end8without the need to enter the drum10through the elevated open end6.

Referring toFIG. 2, the drum10comprises a drum body12having an edge13defining an aperture16for permitting access to a drum body interior50. The drum10further includes a manhole cover14hingedly attached to the drum body12by means of a hinge15. The manhole cover14is movable from an aperture open position (shown inFIG. 2) to an aperture closed position (shown inFIG. 4).

Mounted to the drum body12, adjacent the aperture16, are six locking mechanisms20a-20f. Each locking mechanism20comprises a tag22welded to the drum body12, and a bolt26. As will be shown, in the aperture closed position, each bolt26is tightened against a lug18defined by the manhole cover14, each bolt26pressing a lug18against the drum body12to form a seal between the manhole cover14and the drum body edge13.

Referring toFIG. 3, the manhole cover14has been swung around the hinge15to engage with the drum body12. It will be seen from this drawing that the hinge15comprises an arm28connected at a first end30to the drum body12and at a second end32to the manhole cover14. The arm first end30, in the position shown inFIG. 3, is lower than the arm second end32so that the manhole cover14is biased to the open position shown inFIG. 2due to its weight. A first handle34and a second handle36are provided on the manhole cover14to allow the operator to maintain a firm grip on the manhole cover14as, in the position shown inFIG. 3, it will wish to open under its own weight.

From the position shown inFIG. 3, the manhole cover14is rotated around a bolt40which connects the arm second end32to the manhole cover14. The manhole cover14is rotated until the lugs18are behind the locking mechanisms20. This position can easily be found by the operator as, as shown inFIG. 4, all that is required is for the manhole cover14to be rotated until the first handle34engages the arm18. In moving from the position shown inFIG. 3to the position shown inFIG. 4, the manhole cover14has been rotated anticlockwise. A clockwise rotation would have engaged the second handle36with the arm28and similarly, in this position, the lugs18would be behind the locking mechanisms20, albeit a lug/locking mechanism combination be different to that shown inFIG. 4.

In the position shown inFIG. 4, the operator can safely release his grip on the handles34,36as the manhole cover14will rest against the locking mechanisms20. To seal the aperture16, each of the bolts26is tightened to sandwich the manhole cover lugs18between the locking mechanisms20and the drum body12. In this position a seal is formed between the drum body edge13and the manhole cover14.

To open the aperture16, the sequence of operations described is reversed. When the bolts26are released, the manhole cover14is retained by the locking mechanisms20permitting the operator to put the tool he has used to slacken the bolts26down before taking a grip on the handles34,36and take the weight of the manhole cover14before rotating the manhole cover14away from the locking mechanisms20and allowing it to swing open to the position shown inFIG. 2.