OBJECT OF THE INVENTION
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The invention proposed herein relates to a novel mechanism for supporting a vertical lift door of an oven. The oven, of the type known as a grilling oven, is intended for cooking food by retaining the heat produced by wood or coal combustion.
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The vertical liftable door is characterised by having an opening and closing movement in a vertical plane, perpendicular to the floor and parallel to the front face of the oven. This type of oven opening is very advantageous, as it reduces the space required in front of the oven for handling and also protects the user when they start to open the oven.
BACKGROUND OF THE INVENTION
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The invention proposed in the present specification is based on the experience accumulated during years of manufacturing and marketing Utility Model U201730317. Although the holder of this Utility Model, Maria Rosa López Gómez, does not correspond to the holder of the present application, it should be pointed out that they are mother and son and that it was therefore the latter who in practice manufactured and marketed the previous Utility Model. This prior art to the proposed invention, the registration of which as a Utility Model was requested on 22-03-2017 and granted on 20-06-2017, has been in production and in use to date, providing the applicant with sufficient experience for the development of the solutions that are proposed in the present specification and which serve to correct the deficiencies that the use of the initial Utility Model has made apparent.
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The previous Utility Model covered the liftable door and its lifting mechanism, whereas the present application is only focused on the lifting mechanism, which has been redesigned. The liftable door has not undergone any substantial modification, except for the fact that it can now be opaque in addition to being made of glass, as its initial design was very successful and consistent.
DESCRIPTION OF THE INVENTION
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As the invention proposed in this specification is motivated by the improvement of a previous invention, we will begin by explaining the problems that the use of Utility Model U201730317 has brought to light and, using the same as a script, describe the features of the novel invention.
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The following shortcomings can be listed in the above invention:
- 1. Problems of breakage of the cable that transmits the weight of the door to the rear counterweight. In the above design, the weight of the door is transmitted by a steel cable, usually made of braided steel to improve its bending capacity and tensile strength, which passes through a pulley before being connected to the counterweight. The friction between said cable and the pulley, in addition to the continuous bending thereof, produces wear due to fatigue in the cable, which means that it has to be replaced frequently, generating continuous maintenance stoppages.
- 2. When running the cable through a pulley, all the tension on the cable is transmitted to the shaft of the pulley, which has required a lot of maintenance and in cases where this has been slightly deficient, friction with unpleasant noises and even seizure between the pulley and the shaft has occurred.
- 3. The liftable door is attached to the oven by four arms, one at the bottom and one at the top on each side of the oven. The two lower arms are connected to the supporting mechanism of the liftable door via a shaft. This shaft is under high stress as well as working in a high temperature environment as it is closer to the oven mouth, in addition to the heat that reaches the same due to thermal conduction through the surrounding materials. These two factors have led to friction problems in the shaft, resulting in unpleasant noises and an unsatisfactory movement of the liftable door.
- 4. As the weight of the door to be lifted is limited by the weight that the pulley shaft is capable of holding, as this is the weakest element of the assembly, the previous door design was only available with a glass pane that occupied most of the liftable door surface.
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The deficiencies described above have led the applicant to search for solutions that have materialised in the invention proposed in this specification.
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The proposed innovation retains the idea of supporting the weight of the liftable door (2) by placing a counterweight, but the supporting mechanism (1) has been redesigned so that the liftable door (2) is now supported using the Archimedean lever principle, where the shaft (1.4) between the secondary arm (1.8) and the primary arm (1.1) will be the fulcrum. The new supporting mechanism (1) joins the counterweight to the fulcrum on the shaft (1.4) by means of two articulated metal arms. The first of these, the primary arm (1.1), is connected to the secondary arm (1.8) via a shaft (1.4) with special features. One of the features of this shaft (1.4) is that the assembly is anchored to a rectangular metal template called support(1.4.1), with a hole in the centre of the exact diameter to insert and weld a circular metal part that will be the rotation shaft (1.4.2), which has undergone tempering to increase its hardness and also to have a better sliding, since the outer surface when hardened acquires a lower friction coefficient. Another feature is that a self-lubricating bronze friction bushing (1.4.3) is located on the rotation shaft (1.4.2). As bronze has a higher coefficient of expansion than iron, it will expand more with heat, thus preventing the possibility of seizure between the rotation shaft (1.4.2) and the friction bushing (1.4.3). Another feature is that on top of the friction bushing (1.4.3) there is a boss (1.4.4), a circular metal part, which is where the primary arm (1.1) is welded. This primary arm (1.1) is a metal template with a slightly convex curvature which has at one end a pivot point on the shaft (1.4) with the secondary arm (1.8), which is also coupled to the boss (1.4.4) by means of two milled slots (1.4.4.2) which prevent the same from rotating on the boss (1.4.4), the secondary arm (1.8) being fixed by means of a washer (1.4.5) and a nut (1.4.6). It is the secondary arm (1.8) that transmits the weight of the liftable door (2) to the fulcrum of the supporting mechanism (1) located on the shaft (1.4), the secondary arm (1.8) being a metal template with a slightly concave curved shape that is joined to the liftable door (2) by means of a hinged joint.
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The connecting rod (1.2) is connected to the primary arm (1.1) through a bolt, the upper bolt (1.6), so that there is a hinged joint therebetween that transmits the weight of the counterweight to the fulcrum on the shaft (1.4), but without this force generating any momentum. The connecting rod (1.2) is a straight metal template, having a fixed length, and with a hinged movement at both ends.
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The last of the elements of the supporting mechanism (1) is the counterweight (1.3), which is joined to one end of the connecting rod (1.2) by means of another bolt, the lower bolt (1.7), which allows a hinged joint between both elements. This counterweight can be of various sizes, depending on the weight of the liftable door (2) to be lifted. This establishes a swinging movement between the counterweight (1.3) and the liftable door (2) with a fulcrum on the shaft (1.4). If the weight of the liftable door (2) increases, the weight of the counterweight (1.3) must be increased to counterbalance and keep the swinging motion balanced.
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The novel design of the supporting mechanism (1) now allows the liftable door (2) to be either glass or opaque. While in the glass version, the inside of the oven is visible from the outside, this implies a high heat loss through the glass. In the opaque version the inside is not visible without opening the door, but the heat loss is much lower, considerably reducing the consumption of the element chosen as fuel, whether it is wood or coal. It will be up to the future customer to decide which features best suit their requirements, but now they are spoilt for choice.
BRIEF DESCRIPTION OF THE DRAWINGS
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To complement the mentioned descriptions, drawings in which the features of the object to be registered can be seen in an illustrative and non-limiting manner, are attached to better understand said features. The following is therefore presented:
- Figure 1 shows a perspective view of the rear and left side of the oven, taking the front as a reference. For a better view of the supporting mechanism(1), the oven has been stripped of its rear cover, its left and right side covers as well as its upper cover. With the covers on, the primary arm (1.1), the connecting rod (1.2) and the counterweight (1.3) would be hidden, with only the secondary arm (1.8) being visible.
- Figure 2 shows a left side elevation view where, for a better display of the supporting mechanism (1), the oven has been stripped of the rear cover and the side covers but not of the upper cover.
- Figure 3 shows a perspective image of the shaft (1.4) between the secondary arm (1.8) and the primary arm (1.1) where it can be seen how the assembly is anchored to the support (1.4.1) to reinforce its support.
- Figure 4 shows a perspective view of a cross section of the assembly of parts that are coupled on the shaft (1.4) between the primary arm (1.1) and the secondary arm (1.8).
- Figure 5 shows a perspective view of the support (1.4.1) where it can be seen that the rotation shaft (1.4.2) is coupled to the template by being inserted into a hole in the template and then welded together. This approach achieves enormous strength in this support.
- Figure 6 shows a perspective view of the friction bushing (1.4.3) made of bronze.
- Figure 7 shows a perspective view of the boss (1.4.4) showing one of the milled slots (1.4.4.2) for coupling the secondary arm (1.8), the recess (1.4.4.4) which acts as a stop for the primary arm (1.1) and the hole(1.4.4.1) for the lubrication of the friction bushing(1.4.3).
PREFERRED EMBODIMENT OF THE INVENTION
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The invention proposed in the present specification begins with the laser cutting of all the metal templates of the supporting mechanism (1), such as: the primary arm (1.1), the secondary arm (1.8), the connecting rod (1.2) and the support (1.4.1). These templates are drilled and punched at the ends.
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The supports(1.4.1) of the supporting mechanism (1) are placed on both sides of the already formed oven on its outer structure. The rotation shaft (1.4.2) is then inserted into the hole previously drilled in the support (1.4.1) and the joint is welded in place. The bushing (1.4.3), with the boss (1.4.4) already fitted, is inserted onto the rotation shaft (1.4.2). The connection between the friction bushing (1.4.3) and the boss (1.4.4) must be fixed, so that both are integrally rotated. To achieve this, the bronze bushing (1.4.3) is subjected to extreme quenching, which causes same to shrink, which allows the bushing (1.4.3) to be easily inserted into the boss (1.4.4). When it expands and is inserted into the boss, when it is brought up to room temperature it will be firmly bound together, ensuring that they rotate integrally. With the friction bushing (1.4.3) and boss (1.4.4) already assembled, a through hole is drilled in both parts to create a hole (1.4.4.1) through which the friction bushing (1.4.3) can be greased.
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On the boss (1.4.4) the primary arm (1.1) is inserted up to a recess (1.4.4.4) made in the boss (1.4.4) which acts as a stop, so that by inserting the bore at one end of the primary arm (1.1) up to the recess (1.4.4.4) made in the boss (1.4.4) and welding the joint, the joint will be permanently fixed. The secondary arm (1.8) is then inserted into the boss (1.4.4) by means of a quasi-rectangular punching at one end of the boss and up to the stop provided by the milled slots (1.4.4.2) in the boss (1.4.4). The dimensions of the quasi-rectangular punching are determined by making the two milled slots (1.4.4.2) parallel to each other on the boss (1.4.4), which is circular. The secondary arm shall be fixed to the boss (1.4.4) by means of a washer (1.4.5) and a nut (1.4.6) which is screwed onto a thread (1.4.4.3) at the end of the boss (1.4.4) furthest from the oven.
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Now the liftable door (2) could be fixed to the free end of the secondary arm(1.8), by means of a pin secured with a nut, leaving the assembly as a hinged joint.
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On the other side of the fulcrum which is the shaft (1.4), after the primary arm (1.1), the connecting rod (1.2) would be attached thereto by means of the upper bolt (1.6) allowing the rotation of both parts. By attaching the counterweight (1.3) to the connecting rod (1.2) at the free end by means of the lower bolt (1.7), the supporting mechanism (1) is already assembled.