US 2725444 A
Description (OCR text may contain errors)
NOV. 29, A. O. GROOMS ELECTRICAL APPARATUS Filed Feb. 9, 1 952 8 Fig.3
IN VEN TOR.
United States Patent ELECTRICAL APPARATUS Albert 0. Grooms, Richwood, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application February 9, 1952, Serial No. 270,779
2 (Zlaims. (Cl. 200-140) This invention relates to electrical control means such as may be used in refrigerating apparatus and more particularly to the general type of control shown in my Patent 2,351,038.
This particular type of control has been outstanding in performance. It is an object of my invention to provide a periodic defrosting arrangement for the general type of control shown in my patent. such a device is to periodically alter the temperature and pressure relationships, for example, every twenty cycles of the control or refrigerating system so that the evaporator temperature will rise sufliciently high for a brief period to defrost the evaporator.
This object is attained by providing a rotatable ratchet wheel upon the positive connecting means which is rotated a tooth at a time during the reciprocation of the connecting means. a stopping surface cooperating with a stationary stop member. In one position of the stopping surface of the ratchet wheel, it is provided with a notch allowing an added amount of travel of the connecting mean-s in one direction providing an abnormally high switch closing temperature during one refrigeration cycle.
Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.
In the drawings:
Fig. 1 is a view in elevation of one form of my invention;
Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1;
Fig. 3 is a sectional view taken along the line 3-3 of Fig. l; and
Fig. 4 is a fragmentary view in elevation showing a modified form of temperature adjustment applied to Fig. 1.
Referring now more particularly to the drawings, there is shown a U-shaped metal frame member 20 having a terminal member 22 of electric insulating material connecting the two ends of the frame member 20. This terminal member 22 is provided with two terminal posts 24 and 26. The inner end of the terminal post 26 has connected thereto a bent leaf spring contact member 28 which carries the movable contact 30. The threaded adjustable terminal post 24 carries the stationary contact 32, which is electrically insulated from the movable contact 30 excepting when the contacts are in closed position.
At the bottom of the U-shaped member 20 there is provided a threaded adjustable supporting means 33 in the form of a threaded bushing, which is threaded through an aperture in the bottom of the frame 20. The threaded bushing 33 is provided with an inner bearing which is rotatably mounted upon the bottom of a mounting member 35. To the upper end of the mounting member 35 is connected the lower end of the bellows 34 while the lower end is connected to a capillary tube thermo-sen- The purpose of I The ratchet wheel is provided with.
sitive element 36 which may be charged with some suitable volatile liquid.
Fastened to the upper end of the bellows 34 is a metal follower member 58 provided at its lower end with feet which are soldered or welded to the upper closed end of the bellows 34. This follower member 58 has riveted to its upper end an insulated extension 659 provided with a slot adjacent to its upper end which receives an intermediate portion of the leaf spring member 28. On either side of the bellows follower 58 the follower member is provided with V-shaped notches which receive the inner knife edges of the toggle links 64 and 66. The outer end of the toggle link 64 is received in a notch provided in the bushing 65 which is rotatably mounted in a screw 63 threaded through the frame member as shown in Fig. 1 for adjusting the column loading upon the links 64 and 66. The outer end of the toggle link 66 has its knife edge held within a notch provided in the folded over leaf spring 70 having its vertical location adjustable by the adjusting screw 71 which extends through the frame 20 and threads into a threaded fitting fastened to the lower end of the leaf spring 70 as shown in Fig. 1.
The upper end of the bellows follower 58 is provided with a projecting foot 81 adapted to engage the adjacent end of the adjusting screw 83 which is threaded through the terminal member 22 for the purpose of providing an adjustable stop for the upward movement of the bellows follower 58. The bellows follower 58 is provided with an additional projecting foot 85 extending beneath the large flat head of a screw 87, likewise threaded into the terminal member 22. This foot 85 is adapted to engage the head 87 to stop the downward movement of the bellows follower 58 in the most extreme permissible limit of movement in that direction. Such a control will provide unvarying opening and closing points.
To provide a means for obtaining an abnormally high switch closing temperature at periodic intervals, I provide a ratchet wheel-89 which is rotatably mounted upon the bellows follower 58 as shown. The ratchet wheel 89 at the side of the ratchet teeth is provided with a stopping surface 91, the greater portion of which is cylindrical. In its downward movement, this stopping surface 91 normally engages the projecting portion of a stop member 93 which is fastened to and projects from the side of the frame 20 as shown in Fig. 1. This, therefore, provides the normal switch closing temperature and pressure since it normally limits the lower position of the follower 58, and by reason of the toggle links 64 and 66 this location determines the switch closing temperature.
To obtain a defrosting cycle periodically, the stopping surface 91 is provided with a notch 95 adapted to receive the projecting portion of the member 93 in the position of rotation shown in Fig. 2 to allow an augmented travel of the follower 58 in the downward direction to provide an abnormally high temperature cycle suitable for causing defrosting of a refrigerant evaporator.
The ratchet wheel 89 is rotated step-by-step by an anchor type of member 121 pivoted upon a pin 123 to the bellows follower member 58. The anchor member 121 has a projecting portion 125 which is adapted to engage a post 127 projecting from the terminal member 22 before the foot 81 engages the adjusting screw 83. A spring 129 which is coiled about the pivot pin 123 has one end 131 in engagement with a notch in the insulating member 60 and has its opposite end bearing against a portion of the projection 125 to normally hold the left-hand tooth of the anchor member in engagement with the ratchet wheel as shown in Fig. 2. When the projection 125 engages the post 127 the anchor member 121 will be pivoted in the clockwise direction to cause its right-hand tooth to engage near the tip of one of the teeth upon the periphery of the ratchet wheel 89 and cam it a short angular distance so that the ratchet wheel is rotated every time the post 127 is engaged by the projection 125.
Rotatably mounted upon the frame 20 is the knob shaft 133 which extends through the hollow center portion of the ratchet wheel 89 as shown in Fig. 2. This knob shaft 133 is provided with a knob 135 at its outer end and also with a shut-01f cam 137 which, in one position of the knob, is adapted to engage and move the projection 138 away from one of the feet of the bellows follower 58 for the purpose of preventing the upward movement of the bellows follower 58 so as to prevent the closing of the contacts 30 and 32.
In Fig. 4 there is shown an arrangement wherein a modified form of knob shaft and bar spring are used in place of the knob shaft 133 and the bar spring 70. In this Fig. 4 a knob shaft 233 and a bar spring 270 are provided which are similar to the knob shaft and leaf spring in my patent herein mentioned. The knob shaft 233 includes a threaded portion 234 threaded through the side wall of the frame 20 and extending into engagement with the leaf spring 270 to apply a force thereto. This applies column loading to the toggle links 64 and 66 in the same manner as does the leaf spring 70. The knob shaft 233 is also provided with a rotatable cam 235 which engages a projection 237 extending from the bar spring 270. This projection 237, which serves as a bellows follower, is kept in engagement with the periphery of the cam 235 by a small coil spring 239 seated upon the frame 20 and extending into en gagement with the lower portion of the bar spring 270. The cam 235 is provided with a projection 241 adapted to engage a projection 243 upon the bellows 34 to move to and hold the bellows follower 58 in its lowermost position to prevent the closing of the contacts 30 and 32. In this way, I have applied the periodic ratchet wheel type of defrosting mechanism to the two forms of switch disclosed herein. It is obvious that this mechanism may be used for various control devices incorporating this type-of snap-action mechanism whenever it is desired periodically to provide an abnormal temperature or pressure limit.
While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.
What is claimed is as follows:
1. A control including an actuating means movable along a predetermined line, a control means, a positive connecting means extending generally along and movable along said line positively connecting said actuating means and saidcontrol means for moving said control means substantially in direct proportion to the movement of said actuating means, a toggle means operably connected to one of said means for insuring a snap action movement of said control means, frame means for supporting said actuating means and said control means, a ratchet wheel rotatably mounted upon and bodily carried by said connecting means, said ratchet wheel being provided with an irregular stopping surface rotatable along with the ratchet wheel, a stop means mounted on said frame having a stopping surface cooperating with said stopping surface upon said ratchet wheel to stop the connecting means in different positions in one direction of movement, and a pawl means operated in response to the movement of the connecting means and cooperating with the ratchet wheel for rotating the ratchet wheel.
2. A control including frame means, an actuating means mounted upon the frame means near one end and having an actuating movement toward and away from said end, a control means mounted upon the frame means near the opposite end, a positive connecting means extending substantially in the direction of and movable substantially in the direction of the actuating movement of said actuating means, said connecting means substantially positively connecting said actuating means and said control means for moving said control means substantially in direct proportion to the movement of said actuating means, a ratchet wheel rotatably mounted upon and bodily carried by said positive connecting means, said ratchet wheel being provided with an irregular stopping surface, a stop means mounted upon said frame having a stopping surface cooperating with said stopping surface upon said ratchet wheel to stop the connecting means in different positions in one direction of movement, a pawl means movably mounted upon said connecting means so as to be bodily movable with the connecting means, a stationary means connected to the frame means located so as to be in the path of movement of said pawl means and to be engaged by the pawl means so that the pawl means is moved at each engagement, said pawl means having means for moving said ratchet wheel in a step by step movement to cause different portions of said irregular stopping surface to be successively presented, and a toggle means for controlling the movement of said connecting means.
References Cited in the file of this patent UNITED STATES PATENTS 1,833,544 Vold Nov. 24, 1931 1,933,580 Bauer Nov. 7, 1933 2,351,038 Grooms June 13, 1944 2,538,639 Ayers Jan. 16, 1951