GB2113063A - Bakery oven - Google Patents

Abstract

A wheeled rack (22) has a chamfered guide block (28) at the top thereof (of Fig. 3) the guide block, as the rack enters the oven, co-operating with a tapered horizontal guide channel (34,32) in the roof of the oven. The block then enters a hollow box of the lifting member (40), comprising beam (49) side walls (44) and flanges (46) and is stopped by stop on bracket (52). The rack lifting and rotating unit (60) now is energised to vertically lift the rack via rotatable shaft (42). <IMAGE>

Description

SPECIFICATION Bakery oven This invention relates to a bakery oven. It has been common for a considerable time to cook bakery products while-they are disposed on horizontal trays arranged one above the other on a wheeled rack. Such racks are wheeled into and out of the oven one after another. Efforts have been made to mechanise and automate this procedure. In one system, described in British Patent Specification No. 1 191 369, a wheeled rack, referred to as a wheeled transport waggon, engages upwardly sloping (flared) rails and is lifted as it is pushed into the oven.This arrangement is liable to give rise to difficulties in ensuring that rollers on the rack and the flared rails are in proper alignment; also the smooth motion of the rack into the oven may be affected by dirt or burnt bakery products which may adhere to the rails, or may cause the rollers to stick rather than rotate freely.

It is an aim of the present invention to provide an improved bakery oven.

According to the present invention, there is provided a bakery oven incorporating a rack lifting and rotating unit located in its roof zone and a linear drive unit, connected to the lifting unit, and arranged upon energisation to lift a wheeled rack vertically once it is located centrally in the oven.

Also according to the invention, there is provided a wheeled rack for a bakery oven having a guide block at the top thereof, the guide block being dimensioned to co-operate with a horizontal guide channel in or near the roof of the oven which channel is parallel sided over a major portion of its length and has a laterally outwardly tapering entry portion, the guide block also being dimensioned to co-operate with an elongate lifting member.

In a preferred embodiment of the invention, the rack lifting unit includes a substantially vertical rotatable shaft extending upwardly from an elongate lifting member, and in operation the lifting member engages the underside of marginal portions of the guide block as the lifting member is moved upwardly by the linear drive unit, so lifting the rack.

The elongate lifting member may take the form of a hollow box having substantially vertical longitudinal walls and an inwardly-extending flange connected to the bottom edge of each longitudinal wall. These flanges serve as the marginal portions which engage under the guide block. A stop fixed to the oven roof is preferably included to limit the longitudinal movement of the guide block relative to the lifting member as the rack is moved into the oven.

Other advantageous fearues of the invention will be understood from the following non-limiting description of an example thereof given with reference to the accompanying drawings in which: Figure 1 is a longitudinal vertical cross-section through an oven according to the invention showing a rack resting on the oven floor; Figure 2 is a front view of the oven shown in Figure 1 showing a rack therein in its elevated position; and Figure 3 is a plan view showing the layout of the rack top frame and the linear drive unit on top of the oven.

The oven illustrated in Figures 1-3 has side walls 10, 12, a roof 14 and a rear wall 16.

Conventional means, not shown, are provided for heating air and circulating the hot air to cook the bakery items, e.g. biscuits, pies, rolls, buns, which are carried on trays (one shown at 18, Figure 2) which in turn are carried on side runners 20 forming part of a wheeled rack 22. This rack is of a conventional type and in accordance with a particular embodiment of the invention, has a support bracket or block 24 upon which is mounted a guide block or guide plate 26. This block 26 is elongated and has parallel substantially vertical side walls 28, end walls 30, and chamfered corners to provide tapering ends as seen best in Figure 3.

A horizontal guide channel is secured to the roof of the oven and is constituted by parallel vertical metal plates 32 connected to outwardlytapering metal plates 34 which are located nearer to the door opening 36 of the oven. In use, the outwardly tapering plates 34 serve as a funnel in a horizontal plane which receives and guides the block 26 on top of the rack and guides it between the plates 44 as the rack is pushed into the oven.

The plates 32, 34 are fixed to the over roof by support brackets 36.

An elongate lifting member 40 is fixed to a vertical rotatable shaft 42 mounted to pass through the roof 14 of the oven. The lifting member is of hollow box-like form with open ends.

It has longitudinal side walls 44 having inwardlyextending flanges 46 (Figure 2). The walls 44 are connected by a cross beam 48 which is fixed to the lower end of the rotary shaft 42. The side walls 44 are spaced apart by a distance slightly greater than the width of the guide block 26. In use, the horizontal flanges 46 engage under the longitudinal edge portions of the block 26 when the linear drive unit 60 is actuated, so lifting the rack ready for rotation.

A stop 50 is fixed to the roof of the oven by a bracket 52. It is positioned to engage a set screw 54 located in one end of the lifting member 40, as seen just about to occur in Figure 1. When the rack 22 is pushed into the oven, the guide block 26 is guided by plates 34, 32 to enter longitudinally into the hollow box lifting member 40, and its leading end strikes an end plate of the member 40. This end plate carries the set screw 54 which in conjunction with fixed stop 50 serves as a stop preventing the lifting member 40 from being substantially shifted by the force applied at the impact by the guide block 26, and so prevents bending of the shaft 42.

As an optional features, a limit switch or other position sensor may be included to sense when the guide block 26 is in its fully entered position, and the resulting signal may be used to initiate the lifting and then the rotation of the rack.

The oven has a rack lifting and rotating unit 60 located in its roof zone. This includes the vertical shaft 42 to which is attached the lifting member 40. The shaft passes through a gearbox 66 internally of a bored spindle in the gear box. A key and key-way between the shaft 42 and the bored spindle allow the shaft to be driven to rotate about its own axis while also being free to move bodily in an axial (i.e. vertical) direction. The spindle in the gearbox 66 is driven to rotate through gearing (not shown) in turn driven by an electric motor 68.

Thus the shaft 42 is rotated when desired. The top end of the shaft 42 extends into a swivel-overload rotational slipping mechanism 70 which connects the shaft to a chain 72 which passes over a sprocket 74 and is connected by levers 76 to a movable member 78 of a linear drive unit 80. For example the unit 80 may be a piston-cylinder assembly having a piston rod and powered pneumatically or hydraulically, or a leadscrew powered by an electric motor. Alternatively the linear drive unit may be a linear motor. Its function is to lift the rack 22 vertically once the rack is properly located within the oven.

The function of the mechanism 70 is two-fold.

Firstly while connecting the chain 52 and the shaft 42 it permits the latter to rotate freely relative to the former. Secondly it includes a rotational slipping clutch which slips if there is an obstruction to the rotation of the rack 22.

In an alternative embodiment of the invention, not illustrated, the lifting of the rack 22 could be achieved by driving the sprocket 72, or by a cable and winch arrangement, and any such equivalent arrangements are considered to be within the scope of the invention.

The rack may be pushed into the oven manually, or a pusher mechanism may be provided. The sequencing of operation of such a pusher mechanism, the oven door, and the rack lifting and rotating unit may be controlled by any suitable means, for example by limit switches and/or an electronic timer, in association with an appropriate control circuit. These are not described in detail as their general principles will be familiar to one skilled in the art.

It will be seen that the invention as particularly described and illustrated herein provides a virtually foolproof method of correctly locating a rack in a bakery oven, prior to lifting and rotating same, and considerable tolerance is permitted in the height of the oven floor since the vertical extent of the side guides 32, 34 and the side plates 44 is considerably greater than the height of the guide block 26. Moreover there is an automatic alignment function as the rack is pushed in, due to the mutual tapering on the block 26 and the plates 34, and this tends to prevent any sticking and binding and so avoids hold-ups in production.

Claims (6)

1. A bakery oven incorporating a rack lifting and rotating unit located in its roof zone and a linear drive unit, connected to the lifting unit, and arranged upon energisation to lift a wheeled rack vertically once it is located centrally in the oven.

2. A wheeled rack for a bakery oven according to Claim 1 and having a guide block at the top thereof, the guide block being dimensioned to cooperate with a horizontal guide channel in or near the roof of the oven which channel is parallel sided over a major portion of its length and has a laterally outwardly tapering entry portion, the guide block also being dimensioned to co-operate with an elongate lifting member.

3. An oven according to Claim 1 in which the rack lifting unit -includes a substantially vertical rotatable shaft extending upwardly from an elongate lifting member and is constructed so that in operation the lifting member engages the underside of marginal portions of the guide block as the lifting member is moved upwardly by the linear drive unit, so lifting the rack.

4. An oven according to Claim 1 or 3 in which the elongate lifting member is a hollow box having substantially vertical longitudinal walls and an inwardly-extending flange connected to the bottom edge of each longitudinal wall, whereby in use such flanges serve as the marginal portions which engage under the guide block.

5. An oven according to Claim 4 in which a stop fixed to the oven roof is included to limit the longitudinal movement of the guide block relative to the lifting member as the rack is moved into the oven.

6. A bakery oven substantially as herein described with reference to and as illustrated in the accompanying drawings.