Patent GB-1137192-A (GB)
Title: Oven door bolting and locking arrangement
IPC: F24C15/02
Filed: 1967-03-06
Abstract: 1,137,192. Remotely controlled fastenings. WESTINGHOUSE ELECTRIC CORP. 6 March, 1967 [28 April, 1966 (3)], No. 10437/67. Heading E2A. A bolting and locking arrangement for securing the door 18 of an oven cavity 16 adapted to be heated to high temeratures, comprises bolting means located generally at the front of said oven for bolting said door in a closed position, a lock effecting assembly 26 located at the rear of said oven, link means 28 including a drawbar 48 extending from said lock effecting assembly to said bolting means and being movable by said bolting means from a first position in which said bolting means are operable to a second position in which the forward end portion of said drawbar extends across the path of movement of said bolting means and biasing means 60 for biasing said link means towards said first position thereof, the lock effecting assembly including stop means 64 responsive to temperature is said oven cavity for preventing movement of said link means towards said first position thereof thereby to prevent release of said bolting means. In the arrangement shown the door 18 is a hinged drop door having a fixed handle 20 extending across the width of the door near its top edge; a pivotable handle 22 is mounted below the fixed handle and by rotating the handle 22 about a quarter of a turn a bolt 40 of the bolting means, is turned up to project out of the top edge of the door to engage an opening 38 in a keeper bracket 24 which is part of the bolting means and which is mounted in the oven framing structure 36. The bracket 24 comprises two nesting parts one being secured by screws 42 to the structure 36 and the other being adjustably secured to the first part. The forward edge 44 of the keeper opening is angled relative to the plane of rotation of the bolt 40 to provide a ramp surface to pull the oven door towards the sealed position. The link means 28, in addition to the draw bar 48, includes a bell crank 50 which is pivotally secured to the keeper bracket 24 and has one arm connected to the draw bar 48. The other arm of the bell crank is in the path of the bolt 40 and turning the bolt 40 into the keeper slot 38 turns the bell crank, pulls the drawbar 48 forwardly and places the extreme end portion 48a of the drawbar in a position to obstruct the releasing movement of the bolt; the drawbar is biased by the spring 60 away from the door so that unless its movement away from the door under the urge of the spring is obstructed releasing movement of the handle 22 is not prevented; however if the stop means prevents the drawbar moving under the bias of the spring, the handle 22 cannot be moved and the door remains in bolted condition. The link means also includes a rear link 56 having one end portion pivotally connected to the rear end portion of the drawbar 48, the link extending at a right angle from the drawbar into the lock effecting assembly 26 where it is mounted to pivot about a vertical. axis. The lock effecting assembly 26 comprises a base 76 secured to the rear wall 78 of the structure 36 for limited pivotal movement about a vertical axis passing through vertically aligned upper and lower fasteners 80; the fasteners extend through spacers which space the base 76 from the wall 78 to permit it to rock slightly upon the spacers. This arrangement is used to compensate for the thermal expansion and contraction of the structure 36 to prevent the forward end portion of the draw bar 48 from being pulled out of the releasing path of the bolt during the heat cleaning cycle. The compensating arrangement includes an arm 84 rigidly connected to two opposite corners of the base by fasteners 86 and a bar 88 connecting the arm 84 to the keeper bracket; the bar 88 is of the same material as the drawbar 48 and of the same dimensions and hence the base 76 rocks as required to keep the adjusted relationship between the rear link 56 and the operating parts in the lock affecting assembly and keep the forward end portion of the drawbar in the path of the bolt. In the locking condition rearward movement of the drawbar 48 is prevented by a pin which constitutes the stop means 64 and is connected to the armature of a solenoid 66 by a helical spring 68a, the spring 68a permitting lateral deflection of the free end portion of the pin 64. The armature and hence the pin 64 are biassed downwardly by the spring 68a. The link 56 pivots about a vertical axis defined by several notches 58 in rearwardly directed flanges on the base 76 and when the drawbar is pulled forwardly during bolting of the door the righthand end of the link 56 moves towards the rear (towards the viewer as shown in Fig. 7); normally the locking pin 64 rests on the righthand end part 62 of the link 56 and the movement of the link 56 during the bolting operation causes a shoulder 62a of the link to engage the end of the locking pin 64 and deflect the pin to the position 64b shown in Fig. 8; this causes the pin to come into engagement with a V shaped wire element 70 and results in closure of a switch 72 in series with the solenoid 66; the solenoid is then energised and is retracted against the bias of spring 68 and assumes a vertical position which again centres it with respect to the element 70, this permitting the switch 72 to again open and thus allows the biasing spring 68 to drive the pin 64 downwardly past the link part 62 to the position 64c shown in Fig. 8. If the handle 22 is then moved in the releasing direction the link part 62 engages the end of the pin 64 and carries it towards the 64d position, if the solenoid 66 is not then disabled in response to a high oven temperature, as explained later. The solenoid is again energised by the contact of the pin with the element 70 to retract and re-centre the pin which then moves down under its bias onto the link part 62 so that release of the oven door is not prevented. However if the solenoid is disabled the part 62 forces the pin end over to the 64d position against the edge of a flange 90 and prevents further movement of the link part 62 and hence of the handle 22 and bolt 40 so that the door remains bolted. When the locking pin 64 assumes the 64c position it also closes a normally open interlock switch 92 in series with other parts which function during the high temperature period. The lock effecting assembly also includes a timing arrangement for terminating the supply of heat to the oven; a timer motor 94, Fig. 9 is mounted on the base 76 and has its output shaft flexibly connected through a spring sleeve 98 to a drive shaft 96; the drive shaft is slidably supported at its left end, Fig. 7, in a horizontal slot 100 and a tension spring 102 urges the left end in the direction towards the door. The output shaft includes a worm thread drive section 104 adapted to be engaged by a wheel 106 carried by the rear link 56 for movement therewith and provided with teeth on its periphery adapted to mesh with the teeth of the worm drive section 104; the timing arrangement causes the opening of a normally closed switch 108 after a predetermined period of engagement of the drive shaft and wheel when the door is bolted shut. The wheel 106 is mounted for rotation about a bolt 110 which secures it to the link 56, a helical return spring between the wheel and the link 56 urging the wheel in a counter-clockwise direction to a start position. A U-shaped member 114 is carried by the bolt 110 for turning movement relative to the bolt and the wheel 106 has several lugs (not shown) disposed to engage the member 114 when the wheel rotates sufficiently in either direction. The bight of the member 114 is confined, for movement between a stop 118 and an actuating lever for the switch 108. When the link 56 is in the releasing position the wheel 106 is out of engagement with the section 104 and the helical return spring urges the wheel 106 in a counterclockwise direction until one of the lugs engages the member 114 which in turn engages the stop 118. When the link 56 is moved to the bolting position the wheel is carried into engagement with the worm drive section and with the timer motor 94 energised the wheel is slowly rotated in a clockwise direction until the adjacent lug engages the member 114 and moves it into engagement with the actuating lever of the normally closed switch 108; when the switch 108 opens heat cleaning energisation is terminated and the timer motor 94 is deenergised; subsequently after the oven has cooled sufficiently and after the bolting means is operated to releasing condition the wheel will be moved back away from the worm section 104 and the return spring resets the wheel to its initial position. The circuitry for controlling the oven is shown in Fig. 11 and includes a selector switch which in the clean position has its contacts 122 closed to energise the timer motor 94 and a transformer 120, provided the interlocked switch 92 has been closed by the locking pin 64, as described above. The secondary of the transformer 120 provides power through another set of contacts 123 of the selector switch in the clean position, to operate relay means 124 to a position energising a top heating element 30 in the oven; when the oven temperature rises above the normal cooking temperature, a normally open thermostat switch 74 closes and shorts out the solenoid 66 and the solenoid switch 72 thus disabling the solenoid so that the lock pin 64 cannot be retracted out of the way of the link part 62 so that the door cannot be opened. The switch 74 remains closed until the oven temperature falls into the normal cooking range. The timer-operated switch 108 opens after the period determined by the timer and this de-energises the transformer 120 so that the element 30 is switched off to allow the oven to cool.