with reference to the figures , fig1 shows diagramatically a food warmer indicated generally by reference number 10 and comprising a frame 11 with supporting legs 12 on which is supported a tank 13 . during use , on the tank 13 is placed a recipient ( not shown ) with the food , warmed by a hot water bath in the tank , as known in the field . to the frame is hinged laterally along a horizontal axis a cover 14 operated by means of a handle 15 for rotating it around the hinge axis and access to the underlying recipient . in accordance with the present invention the cover has two side brackets 18 , 19 which engage in respective supports and facing side pins 16 , 17 which identify the axis of rotation of the cover . at least one of the two side pins is connected to a reaction device for counterbalancing the rotation moment produced by the weight of the cover in its various positions between the closed position and the fully open position . as may be seen clearly in fig1 and 2 the reaction device consists of a gas spring advantageously inserted in a seat made in the left supporting leg 12 in fig1 . the air spring 20 is connected to one end of the frame and at the other end to the pin 16 by means of a kinematic transmission mechanism such as a crank 21 to convert the rotary movement of the pin into linear movement for the gas spring . as may be seen clearly in fig2 the engagement brackets 18 , 19 of the cover ( advantageously provided with a virtually cylindrical shape around the rotation axis ) have a forked conformation for engagement in the respective pins 16 , 17 upon vertical lowering of the cover . in fig3 and 4 is shown in greater detail the coupling between the fork and the left support with the other being virtually equivalent and thus not shown in detail . the pins 16 , 17 project axially from respective supports 22 , 23 integral with the frame and cylindrical in shape with their axes coinciding with the axes of the pins . each cylindrical support can be received in a complementary seat with cylindrical wall 24 , 25 made in the respective fork . as clearly seen in fig4 for the left coupling , to permit insertion of the cylindrical supports in the cylindrical seats each seat 24 , 25 has a peripheral opening 26 having a breadth less than its diameter and each support 22 , 23 has a lateral flattening 27 along two parallel chords to become narrower at the width of the opening . in this manner the cover can be lowered vertically ( in closed position ) onto the frame with the forks engaging with the hingeing supports 22 , 23 as shown in fig4 . upon rotation of the cover the flattened side walls 27 of the supports become misaligned with the opening 26 of the cylindrical seats of the forks and thus the cover can rotate but not detach itself accidentally from the frame 11 . each fork also has a groove or slot 28 , 29 parallel to the opening 26 and open in the same direction to receive the part of the pin 16 , 17 projecting from the respective supports 22 , 23 . as may be clearly seen in fig3 and 4 the pin 16 connected to the gas spring has a part projecting from the support 22 which is laterally flattened to identify flat parallel walls 30 which couple with minimum play in the grooves 28 provided with appropriate width so as to constitute a faceted gain to make rotation of the pin and the cover integral . if the opposite pin 17 is also equipped with a gas spring the pin 17 and the corresponding groove 29 can also be provided with integral coupling for rotation . as an alternative the pin 17 can be provided cylindrical without flattening and the groove 29 can have breadth sufficient to receive it freely or the pin 17 can be omitted entirely with the cover rotating on the support 23 . in use the cover is mounted easily by lowering it vertically in the closed position as may be clearly seen in fig1 and 2 so that the pins and supports couple with their respective seats in the forks . by rotating the cover towards the open position the crank 21 increasingly loads the spring or the gas springs and increases its arm to supply a force which balances instant by instant the rotation movement produced by the weight of the cover whose center of gravity draws away from the vertical plane containing the axes of the pins . as is readily imaginable to those skilled in the art , by selecting appropriately the thrust of the gas spring and the offset of the crank it is possible to perfectly balance the cover so that is has neutral behaviour in any open position . it is now clear that the set purposes have been achieved by supplying a food warmer which externally keeps its conventional form without visible mechanisms and which has however a perfectly balanced cover . at the same time the food warmer in accordance with the present invention remains easy to open for cleaning with the cover separating from the base by means of mere vertical lifting . in addition , the opening movement of the cover remains of considerable width , e . g approximately 170 degrees . naturally the above description of an embodiment applying the innovative principles of the present invention is given merely by way of example and therefore is not to be taken as a limitation of the patent right claimed here . for example , the spring or the gas springs can be positioned in positions alternative to that shown in the drawings , for example a horizontal position inside the ring of the frame surrounding the tank . in addition , the kinematic transmission mechanism for the motion between the pin and the gas spring can be different from that of the crank and can be - provided e . g by means of a cam or a geared coupling . lastly , the reaction means can be different from a gas spring .
a food warmer has a cover hinged on a frame by means of opposing side hinges for rotating it around an axis of rotation between a closed position and a fully open position . at least one of the s hinges comprises coupling means between the cover and the frame which rotate integrally with the cover against the action of reaction means mounted on the frame . in this manner the action of the reaction means supplies virtual balancing of the moment produced by the weight of the cover .