US 3823280 A
Description (OCR text may contain errors)
United States Patent [191 Obermann et al.
TIMER Inventors: George Obermann, Niles; Michael H. Enger, Schaumburg; Michael F. Misik, Jr., Norridge, all of ill.
Controls Company of America, Schiller Park, [11.
Filed: Oct. 26, 1973 Appl. No.: 409,961
 References Cited UNITED STATES PATENTS 9/ l 954 Morrison 335/73 5/l968 Laszlo t 335/73 3/1970 Rulseh et al. ZOO/I66 J 4/1973 Voland et al. 200/166 J Primary Examiner-Harold Broome Attorney, Agent, or Firm Michael, Best & Friedrich  ABSTRACT The motor subassembly is mounted in the housing with the motor leads dressed between the motor case and the housing and connected to the motor terminal m1 3,823,280 July 9,1974
' and to a switch blade terminal and does not require grounding. The gear case somewhat divides the motor case to retain the coil while the motor case cover cooperates with the gear case to enclose and journal the gearing with the drive pinion projecting therebetween to drive the gear on the perimeter of the timing cam. The timing cam is journaled on the bushing extruded from the motor cover and in the aperture in the housing cover with the gear cluster extension projecting into and visible in the cam hub'to afford visual verification of motor operation. The three switch blades are accurately located in the housing by tabs engaging locating cavities and the pivoted yoke has pads which space the two outside blades from each other. During the time between defrost cycles the No. 1 blade rides on the cam with the No. 2 blade engaging the No. 1 blade. When the No. 1 blade drops off the cam drop, the No. 3 blade engages the No. 2 blade and remains so engaged until the No. 2 blade drops off the cam. The tangential distance between the ends of blades No. l and No. 2 determines the duration of the cycle in combination with the rotational speed 'of the cam. All components are trapped by the assembly of the cover to the housing which is accomplished without fasteners. The great reduction in parts while completely enclosing the product results in a quiet, low cost, accurate timer which is easily serviced in the field by way of easy verification of operation.
6 Claims, 9 Drawing Figures K f 40 43 a5 T m f e? l 7 W \Q g- W 5 7 VT H '70 Z2 4% Q/ 7% ll @2 1 49:2 M
56/ :e, l I u a/ It I Q3 h. 4 I
I! I II! "lli I l I PATENTEUJUL 14 3.823280 SHEU 2 (1F 2 rrME-n BACKGROUND OF THE INVENTION This timer is designed for controlling refrigerator defrost cycles. Timers for such use have heretofore required more parts and space than the present design. The prior timers accomplished the desired end 'controlling defrost cycles but offered clear opportunity for improvement.
SUMMARY OF THE INVENTION output pinion gear 36 projecting through motor cover 38 and joumaled therein. Another gear cluster that is axially in line with cam 44 also includes shaft 40 which projects through the motor cover 36 into the hollow hub 42 of the molded timing cam and gear 44. The gear on the perimeter of this molding is driven by pinion 36 and the molding has a cam shape best seen in FIG. I. The cam is driven in the clockwise direction (FIG. 1) and has a slow rise portion extending from point R at the bottom of the fast drop portion S and running coun terclockwise around the gear to the drop position T. It
will be noted the top face of this molding 44 includes an annular boss 46 which functions as a bearing acting against the bottom of housing cover 14. The hub 42 projects through the housing cover for access from the exterior of the timer. The end of the hub has a one-way parts are accurately located in the molded housing and the cover functions to pin and/or retain all parts in assembled position while .the cover pins. are sonically welded to complete the assembly. The spacer/yoke member insures accurate switching at minimal cost with few parts.
DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view with the cover removed.
FIG. 2 is a vertical section taken through the center of the motor and the center of the timing cam.
FIG. 3 is a perspective view of the completed timer.
is formed from the terminal portion of the blade for lo cation purposes. I
F IG: 3 shows the pointed tabs which are formed from the terminal portion of the blades for the purpose of re taining the blades in the housing.
FIG. 9 is a perspective of the underside of the cover.
DESCRIPTION OF THE PREFERRED EMBODIMENT Timer housing I0 includes body 12 and cover 114. The body has a cavity M which receives motor and gear case assembly 16. This assembly includes motor case 18, the bottom of which is lanced to provide upwardly projecting stator poles 20 which lie inside coil 22. The coil is enclosed by the gear case 24 pressed inside the motor case 18 and having lanced poles 26 concentric with and lying between poles 20. The permanent magnet rotor 28 is mounted on shaft 30 joumaled in the motor case and in the cover 38 and carrying drive pinion 32 which drives the reduction gear clusters. One cluster includes an output shaft 34 carrying screwdriver slot arrangement generally denoted 48 permitting the serviceman to manually drive the cam in a clockwise direction (only) to check out the operation of the switching. It will be noted that the extension of shaft 40 isvisible through the center of the hub 42. The end of the shaft has a flat 49 cut therein so as to give a different visual impression when viewed head-on. The purpose of this is to permit observation of the shaft end to determine whether or not the motor is operating.
The timercam is generally operated at a speed of onetwelfth or one twenty-fourth revolution per hour and this, of course, would be very difficult to observe. The end of shaft 46, however, rotates at approximately 13 RPM and this speed of rotation can, of course, be observed. I
It will be noted that the motor and gear assembly constitutes a complete subassembly totally enclosed within the motor case Wand motor cover 38 with the coil leads 50,52 being brought out the bottom of the subassembly and led up the side of the subassembly between the subassembly and the housing body 12 for connection to terminal 54 and the terminal portion of the middle switch blade 56. The middle blade will also be referred to as the second blade. The shaft 40 projects through the opening in motor cover 38 and the perimeter of the opening is extruded outwardly at 54 to provide a bushing or bearing surface for hub 42 of the timing cam. The timing cam hub 42 is also joumaled in the aperture in housing cover 14. It will also be noted that motor cover 36 is provided with projecting mounting ears 58,66, each of which is provided with an aperture which aligns with an aperture in the housing body T2 for purposes which will appear more fully hereinafter.
Three switch blades are mounted in the housing. The first blade 62 has itsproximal portion mounted in a slot in the. housing body ll2 with the end projecting to the exterior of the housing for connection to external wiring. The distal end of the blade carries a contact 64 and is adapted to ride on the cam surface of the timing cam 44. The middle or second blade 56 is similarly mounted in the slot and is longer than the first blade 62 by an amount designated X in FIG. ll, the significance of this dimension being more fully explained hereinafter. The second blade carries a contact on each side of the blade at the distal portion, contact 66 being engageable with contact 64 on the first blade and contact 68 being engageable with contact 76 carried by the distal portion of blade 72 which is also mounted in a slot in the housing body with its end projecting to the exterior of the 3 housing for external electrical connection. All of the blades are biased towards the cam.
A yoke or spacer member 74 is pivotally mounted on post 76 molded in the housing underneath the blades. Cover 14 is provided with a depending finger 78 which rests on top of the hub portion 80 of the yoke 74 to retain the yoke in its assembled position. The yoke includes two upstanding arms 82,84 which straddle blade 56 while lying between the first and second blades in the case of arm 82 and between the second and third blades in the case of arm 84. The outer surface of arm 82 is engageable with the blade 62 while the outer surface of arm 84 is engageable with the third blade. Thus when the parts are in the position shown in either FIG. 4 or FIG. 5 (i.e., when only the first blade is in contact with the cam), the yoke functions to space the third blade a predetermined distance from the first blade and this, in turn, prevents the third blade from making contact with the second or middle blade. It will be noted the coil leads 50,52 are connected to the motor terminal 54 and to the middle blade terminal 56. Thus these two terminals are designed to be electrically hot.
When this timer is used for timing defrost cycles, at the conclusion of a defrost cycle theend of the middle or second blade 56 will have just dropped off the drop position T so that the second blade is now in contact with the first blade and the first blade is riding on the low portion of the rise of the cam. At this time the yoke or spacer 74 functions to prevent engagement of the third blade with the second blade. Thus the electrically hot blade 56 is connected to blade 62 as 'well as being connected to the coil. The compressor may be connected in series through this switching so that the compressor is free to operate under these conditions. After either 12 or 24 hours has elapsed, the far distal end of the first blade 62 will drop off the cam to the position shown in F IG. 1. Under these conditions the distal end of the second blade will rest on the maximum rise portion. Thus the connection between the first and second blades is broken but the movement of the first blade to the bottom of the drop S will permit the third blade to now move under self-bias into engagement with the second blade, thus making a circuit from the second blade to the third. This can control a heater, for example, while breaking the compressor circuit. The duration of the defrost cycle starts at this instant and lasts until the distal end of the second blade drops off point T. This, then, means that the dimension X (mentioned before) becomes determinative of the duration of the cycle in combination with the rotary speed of the timing cam.
Therefore, the distance X is one which must be controlled with precision and it is a simple matter to stamp a blade to a precise length. The next step in controlling this precision is to precisely mount the blade so that it lies exactly where it was designed to lie. Towards this end the proximal portion of each blade is provided with a shear-formed tab 86 (see FIG. 7) which is a simple thing to control with great precision. This tab is designed to be received in the cavity 87 adjacent each of the blades where they lie in the slots. This, then, precisely locates each blade and terminal relative to the body and relative to the cam. The cavity can be controlled with accuracy and its location, of course, is fixed. During assembly it is desirable to lock the blades into position so they cannot drop out and towards this end each blade is provided with sheared, pointed tabs 88 which project upwardly as the blade is inserted into the slot but which dig into the plastic body and prevent removal of the blades once they have been seated. F urthermore, the cover overlies all of these blades and retains them in position.
The cover itself is provided with integral depending plastic pins 91,93 which are received in the holes 90,92 and pins 95,97 are received in the holes 94,96 in the mounting ears 58,60 of the motor subassembly. These holes 94,96, of course, line up with holes in the housing. The enlarged portion of each of these pins overlies the ears 58 and 60 to firmly hold the ears in the desired position and the extending reduced diameter portion of the pins pass into the holes and are then sonically welded into the body to firmly lock the cover in place while at the same time functioning to hold all of the parts in position. No conventional fasteners are used in the assembly of the entire timer.
1. A timer comprising a housing,
a timing cam rotatably mounted in the housing having a slow rise-fast drop surface,
motor and gear means rotating the cam,
three switch blades mounted in the housing with their distal ends adjacent and biased towards the cam, the first of the blades being closest to the cam and always in engagement with the cam,
thesecond blade being longer than the first so it engages the rise after the first blade drops at the fast drop portion of the cam until the second blade drops at the fast drop,
a yoke member pivoted in the housing and having an arm projecting between the first and second blades and another arm projecting between the second and third blades with the second blade free to move freely between the arms and the arms serving to determine the minimum spacing between the first and third blades whereby the third blade is held out of contact with the second blade while the second blade is in contact with the first blade as the first blade engages the slow rise of the cam and the third blade is free to contact the second blade while the second blade is in contact with the cam.
2. A timer according to claim 1 .in which the cam has a hollow hub and the motor and gear means includes a shaft projecting into the hub and having an end configuration which readily indicates whether or not it is rotating,
said hub projecting through the housing whereby the hub and the shaft are clearly visible from the exterior of the housing.
3. A timer according to claim 2 in which the exposed end of the hub has a one-way driving configuration whereby the cam may be manually advanced.
4. A timer according to claim 2 in which the motor and cam means are enclosed in a casing mounted as a unit in the housing,
said housing including a body and a cover,
said cam being joumaled on the casing and the cover,
said cover including means for engaging and retaining the casing in position in the housing. 5. A timer according to claim 1 in which the proximal ends of the blades are mounted in slots in the housing wall,
, 6 6. A timer according to claim 5 in which the housing includes a cover which functions to retain the blades in said slots.