Abstract:
A low cost toaster having a metal body and plastic end panels. The end panels have cooling inlet vents near their lower ends and the top wall of the metal body has air outlet vents. Ambient air admitted through the inlet vents flows upwardly through the toaster and outwardly through the outlet vents to provide a cooling effect sufficient to allow the use of inexpensive plastic material for molding the end panels. The toaster has a bread lifter made entirely from a wire rod, a bread lifter extension made entirely from a wire rod, and a toast color cam made entirely from a single piece of sheet metal.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a division of Application No. 09/354,824, filed Jul. 16, 1999, now U.S. Pat. No. 6,105,486 which is a division of application Ser. No. 08/944,150, filed Oct. 6, 1997, now U.S. Pat. No. 5,924,355, dated Jul. 20, 1999. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a household electric toaster but aspects of this invention can be used in other heating appliances, particularly toasters for commercial use. 
     BACKGROUND OF THE INVENTION 
     Household toasters commonly have a control chamber separated by a vertical front frame plate from a toasting chamber. A bread carriage plate, termed a “bread lifter plate” herein, is slidably received on a support post in the control chamber and carries a pair of bread supports, termed “bread lifters” herein, that extend into and at least partially through the toasting chamber between heating elements therein. The lifter plate and accordingly the bread lifters are vertically-movable between a lowered position for holding bread or other food items in position to be toasted and a raised position for permitting the bread or other food items to be placed on or removed from the bread lifters. 
     Some toasters have only one bread lifter and some have more than two bread lifters. For ease of discussion, this invention is disclosed for use in a toaster configuration which has two bread lifters, such presently being the most common configuration. However, as will become apparent, aspects of this invention described below can be used in other toaster configurations. 
     In many toasters, the bread supports are part of a vertically movable support carriage to which the bread supports are connected. Spring means biases the support carriage upwardly so that the bread supports are normally in their upper, non-toasting position. The support carriage can be lowered to the toasting position by manipulation of a control lever, termed a “lifter extension” herein, accessible from outside the housing. During a toasting cycle, a latch mechanism holds the support carriage with its bread supports in their lowered, toasting position. User-adjustable electric means controls the toasting cycle times during which the bread supports are latched in their lowered position in order to toast the food items to the desired toast color. 
     A latch comprising a pivotally mounted armature or latch plate biased away from the face of the solenoid coil hooks over an upwardly-facing surface on the bread carriage plate when the carriage plate is lowered to its toasting position. To terminate a toasting cycle, a solenoid switch is closed, causing the solenoid to be energized, whereupon the latch plate is pulled toward the solenoid coil and unhooked from the carriage plate. The bread lifter spring returns the bread lifter assembly to its raised position during which time the bread lifter that was holding the power switch closed moves upwardly away from the power switch and the power switch opens. 
     In order to energize the solenoid coil at the end of the toasting cycle, a bimetal heat sensing assembly in the toasting chamber drives a horizontally-movable switch operating shaft outwardly toward a movable switch contact located in the control chamber. The duration of the toasting cycle and, therefore, the resultant degree or “color” to which the toast is toasted, is adjusted by a toast color control cam that moves the switch contacts nearer to or farther from the end of the bimetal-driven switch operating shaft, so that the excursion of the shaft from the beginning of a toasting cycle to the end of a toasting cycle required to close the solenoid switch can be changed to obtain different toast colors. 
     Notwithstanding the several elements that comprise a household toaster, household toasters are usually remarkably inexpensive. The low cost partly results from the use of sophisticated manufacturing and assembling techniques. There is however, an ever-present need to reduce the costs of toasters in order to provide toasters to the public at low costs and meet the demands of a competitive industry. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide an improved household electric toaster. More particularly, an object of this invention is to provide a rugged, high quality household toaster which can be manufactured at relatively low cost. To accomplish these objects, this invention utilizes improvements in the following areas of toaster construction and operation: 
     1. The toaster has a metal body and plastic end panels. The end panels have cooling inlet vents near their lower ends that admit ambient air into the ends of the toaster. The flowing air flows outwardly through air outlet vents in the top wall of the metal body. The cooling is sufficient to enable the use of an inexpensive plastic material, preferably polypropylene, for molding the end panels. In contrast, plastic end panels are normally made from plastic materials that have a greater heat rating. 
     2. Each bread lifter is made entirely from a wire rod and is connected to the lifter plate without the use of fasteners, welding or soldering and, for ease of assembly, in a manner that prevents rotation of the lifter about a vertical axis. 
     3. The bread lifter extension is made entirely from a wire rod. 
     4. A toast color cam is made entirely from a single piece of sheet metal and is supported by the front frame plate of the toaster. 
     Other objects and advantages of this invention will become apparent in view of the following description taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a fragmentary perspective view of a toaster in accordance with this invention. 
     FIG. 2 is an exploded, perspective view of parts of the toaster of FIG.  1 . 
     FIG. 3 is an exploded perspective view of the frame and toaster mechanical operating parts shown assembled in FIG.  2 . 
     FIG. 4 is a highly simplified, diagrammatic and cross-sectional view of the toaster of FIG. 1, and illustrates the path of ambient air flowing upwardly inside the ends of the toaster. 
     FIG. 5 is a perspective view of a bread lifter assembly shown also in FIGS. 1 and 2. 
     FIG. 6 is an elevational view of the bread lifter assembly of FIG.  5 . 
     FIG. 7 is a fragmentary, plan view of a portion of the front of the toaster showing a toast color control assembly including a one-piece toast color control cam in accordance with this invention. 
     FIG. 8 is view similar to FIG. 7 but with the toast color control cam in a different position of adjustment. 
     FIG. 9 is a front elevational view of the control chamber of the toaster of FIG.  1 . 
     FIG. 10 is fragmentary, partly cross-sectional and partly plan view taken on line  10 — 10  of FIG. 9 of a portion of the toast color control assembly illustrating a carriage plate hooked by a latch plate or armature. 
     FIG. 11 is a view similar to FIG. 10 but showing the latch plate moved away from the carriage plate by the lifter extension. 
    
    
     DETAILED DESCRIPTION 
     With reference first to FIGS. 1 and 2, this invention is shown embodied in a household electric toaster  20  comprising a frame  22  and operating parts to be described below partly covered by a tubular metal body  24  having its opposite ends closed by plastic end panels, namely a front end panel  26  and a rear end panel  28 . The end panels  26  and  28  are connected to the metal body  24  by means of metal clips  30  on the end panels  26  and  28  that extend into cooperating apertures  32  in the upper ends of the metal body  24 . The end panels  26  and  28  are also connected to the metal body  24  by screws (not shown) that extend upwardly through screw-receiving apertures  34  in the bottom portions of the metal body  24  and into holes  36  in mounting flanges  38  adjacent the bottom edges of the end panels  26  and  28 . (only the holes  36  and the mounting flange  38  of the rear end panel  28  are illustrated in the drawings. These parts are essentially identical to the corresponding parts of the front end panel  26 .) 
     With reference also to FIGS. 3 and 4, the toaster frame  22  includes a base frame plate  40 , a top frame plate  42 , a front frame plate  44  and a rear frame plate  46 . The front frame plate  44  separates the toaster  20  into a control chamber  48  at its forward end and a toasting chamber  50 . Toasting chamber  50  is heated by plural heating elements  52  that extend substantially the length thereof. The rear frame plate  46  separates the toasting chamber  50  from a rear chamber  54 . Large openings  55  in the top wall of the metal body  24  open to the toasting chamber  50  enable bread or other food items to be toasted to be placed in and removed from the toasting chamber  50 . 
     FIG. 3 also shows wire grills  56 , a power switch assembly  58 , and a crumb tray  60 , all of which are conventional and form no part of the instant invention. 
     In order to use inexpensive plastic materials which do not have a high heat rating, a front heat shield  62  is located in the control chamber  48  and a rear heat shield  64  is located in the rear chamber  54 . The heat shields  62  and  64  preferably are integrally formed with and depend from the top frame plate  42 . Furthermore, the front end panel  26  has several inlet cooling vents  66  in the lower portion thereof that admit ambient air into the control chamber  48 . Similarly, the rear end panel  28  has several cooling vents  68  in the lower portion thereof that admit ambient air into the rear control chamber  54 . Ambient air will also enter the control chamber  48  and the rear chamber  54  through various openings in the base frame plate  40 . 
     Referring to FIG. 4, the ambient air entering the control and rear chambers  48  and  54  flows upwardly therethrough and outwardly through two pairs of air outlet vents  70  and  72  in the top wall of the metal body  24  which overlie and open to, respectively, the control chamber  48  and the rear chamber  54 . Provision of the heat shields  62  and  64  and the venting of ambient air through the control chamber  48  and the rear chamber  54 , inexpensive plastic materials can be used to mold the end panels  26  and  28 . End panels  26  and  28  made from polypropylene are presently preferred because polypropylene is relatively inexpensive and easy to use. 
     With reference to FIGS. 3,  5 ,  6  and  9 , a bread lifter assembly, generally designated  80  is mounted for vertical movement on a guide post  82  that extends vertically between the base frame plate  40  and the top frame plate  42 . The lifter assembly includes a generally vertical bread lifter carriage plate  84  formed from sheet metal and adapted to be supported for vertical movement in the control chamber  48 . The carriage plate  84  has a top margin  86 , a bottom margin  88 , and opposite side margins  90 . A pair of angled slots  92  open to respective ones of the side margins  90  and an L-shaped tab  96  extends forwardly and upwardly from the front face of the sheet material forming the carriage plate  84 , the tab being struck out of the sheet material. 
     The lifter assembly  80  further includes a pair of bread lifters  98  for holding food items to be toasted in the toasting chamber. Each bread lifter comprises a one-piece wire rod having a first, generally-horizontal, food-supporting section or arm  100  in which the wire rod extends along a zig-zag or tortuous path having excursions extended to both sides beyond a horizontal center axis of the path to provide an upwardly-facing, food-supporting surface  102 . Each bread lifter has a second, generally-vertical, connecting section  104  extending upwardly from an end of the first section  100 , the second section  104  having a lower end portion  106  extending along the rear face of the carriage plate  84 , a horizontal slot section  108  extending through one of the angled slots  92 , and an intermediate section  110  extending along the front face of the carriage plate  84 , and an upper end portion  112  extending at approximately 90° to the intermediate section  110  and confined between the L-shaped tab  96  and the front face of the carriage plate  84 . This construction enables one to easily insert the bread lifters  98 , after they are previously connected to the bread carriage plate  84  as illustrated, through slots  114  in the front frame plate  44  (FIGS.  3  and  9 ). Note that the bread lifters  98  would uncontrollably pivot about their horizontal slots section  108  if the upper end portion  112  was not confined by the L-shaped tab  96  and the front face of the carriage plate  84 . Small tabs  116  struck out from the carriage plate  84  assist in holding the bread lifters  98  in a horizontal orientation until the bread lifters  98  are inserted into the toasting chamber  50 . After assembly into the toasting chamber  50 , the bread lifters  98  are confined to their horizontal orientations by vertical slots  118  and  120  in the front and rear frame plates  44  and  46 , respectively. 
     With reference to FIGS. 5,  6  and  9  through  11 , the bread lifter assembly  80  further includes a bearing  130  at its right side lower corner margin adapted to be hooked by a pivotally-mounted latch plate or armature  132  that holds said lifter carriage plate  84  in its lower, toasting position during a toasting cycle. In accordance with this invention, the carriage plate  84  further has a pair of forwardly-extending support plates  134  adjacent its upper margin struck out of the sheet material that forms said lifter plate  84 . The support plates  134  have upper surfaces contoured to pivotally support a lifter extension, generally designated  136  which is also made from a one-piece wire rod. The lifter extension  136  has a horizontal, transversely-extending section  138  supported by said support plates  134  for pivotal movement about the major axis of the transversely-extending section  138 , and a vertical section  140  depending from the outer, side end of the transversely-extending horizontal section for engaging said latch and moving said latch out of engagement with the bearing  130  upon pivotal movement of the lifter extension  136 . 
     The lifter extension  136  further includes a horizontal, forwardly-extending front end portion  142  adapted to receive a lifter knob  144  (FIGS. 1 and 2) for lowering the lifter assembly  80  and for disengaging the latch plate  132  from the lifter plate  84  by pivotal movement of the lifter extension  136  about the horizontal axis of its transversely-extending section  138 . 
     In normal operation of the toaster  20 , a solenoid coil  146  is energized at the end of toasting cycle and draws the latch plate or armature away from the bearing  130 . This releases the bread lifter assembly  80  whereupon it moves upwardly under the bias of a lifter spring  148  (FIGS.  3  and  9 ). A toasting cycle can be interrupted by raising the lifter knob  144  whereupon a horizontal arm  150  at the bottom of the vertical section  140  of the lifter extension pushes the latch plate  132  away from the bearing  130  as illustrated in FIGS. 10 and 11. 
     Referring now to FIGS. 3,  7  and  8 , normal operation of the toaster is controlled by a bimetal assembly  152  that drives a switch operating shaft  154  outwardly as the temperature within the toasting chamber increases. Switch contacts (not shown) within a switch housing  156  are caused to close when the operating shaft pushes one contact into engagement with the other. Closure of the switch causes the solenoid coil to be energized and pull the latch  132  away from the bearing  130  whereupon the bread carriage is released and moves upwardly to open the power switch assembly  58  to terminate the toasting cycle. The spacing between the switch contacts and the near end of the operating shaft when the toaster is cold determines the excursion of the switch operating shaft  154  necessary to complete closure of the switch contacts. In accordance with this invention, the end of the switch housing  156  carrying the switch contacts for the solenoid coil  146  is pivoted against the bias of a switch-housing spring  158  by a color control cam  160  made from a single piece of sheet metal that extends through a slot  162  in the front plate  44  from which it derives support.