US2715812A - Clock power maintaining spring device - Google Patents

Description

Aug, 23, 1955 M. GRETHER ET AL CLOCK POWER MAINTAINING SPRING DEVICE Filed Dec. 6, 1950 CLQ CK POWER MAINTAINING SPRING DEVICE Lester M. Grether and Peter Olson, Delavan, Wis, as-

signors to The George W. Borg Corporation, Chicago, 111., a corporation of Delaware Application December 6, 1950, Serial No. 199,495

3 Claims. (Cl. 58-7) The present invention relates in general to electric clocks, but more in particular to electric clocks which are provided with an automatic winding mechanism, such as are used in automobiles. The object of the invention is to provide a new and improved clock of this character.

A clock of the type to which the invention relates includes a ratchet wheel having a driving connection with the center wheel and center shaft of the clock movement. There is also a motor mechanism comprising an electromagnet, a rotatable armature, and a main spring. The .main spring rotates the armature, which has pawls cooperating with the ratchet wheel to rotate the same and thereby drive the clock movement. When the main spring has run down the armature actuates a switch mechanism which energizes the electromagnet to rotate the armature in the opposite direction and retension the main spring.

A special object of the invention is a new and improved motor mechanism for a clock of the foregoing character, which is mounted on an independent frame so that it is demountable and interchangeable with similar motor mechanisms. In so far as this feature is concerned the invention may be considered as an improvement on the clock shown in the pending application of Olson, Ser. No. 710,983, filed November 20, 1946, and now forfeited.

Another special object of the invention is a new and improved center shaft and ratchet wheel assembly for a clock of the foregoing character, designed to eliminate erratic errors in time keeping to which such clocks have been subject in the past. As regards this feature the invention may be considered as an improvement on the clock shown in the patent to Hobbs, No. 2,146,119, granted February 7, 1939.

The above and other features of the invention will be described more in detail in the specification which follows, reference being had to the accompanying drawing, in which Fig. 1 is a plan view of the clock movement, the motor mechanism being detached therefrom;

Fig. 2 is a plan view of the motor mechanism;

Fig. 3 is a side view of the complete clock, comprising the movement shown in Fig. 1 and the motor mechanism shown in Fig. 2;

Fig. 4 is a section through the center shaft and ratchet wheel assembly, on the axis of the center shaft;

Fig. 5 is a section through the electromagnet and frame plate of the motor mechanism, on the line 55, Fig. 2;

Fig. 6 is a side view of the center wheel and hub as sembly, as seen from the right in Fig. 4; and

Fig. 7 is a side view of the reserve spring and housing, as seen from the right in Fig. 4.

Referring to the drawing, the various parts of the clock movement are mounted in a frame which cornprises the front plate 10, the center plate 11, and the center shaft bearing plate 12. These plates are held together in spaced relation by means which includes the tubular posts or pillars 13, 14, and 15. The construction may be explained in connection with Fig. 3, Where the pillar 13 and associated parts are shown in section. At the left the pillar 13 has a short section of reduced diameter forming a shoulder against which the front plate 10 is secured by means of a screw 16. The pillar has a longer section of reduced diameter at the right on which the plates 11 and 12 are assembled, plate 11 resting against the shoulder on pillar 13 and plate 12 being separated from plate 11 by the tubular spacer 17. The plates 11 and 12 are held in position on pillar 13 by means of a pillar 20 having a section 18 of reduced diameter which is threaded into the end of pillar 13, opposite the screw 16. The plates 11 and 12 and spacer 17 are thus clamped between the shoulders on pillars 13 and 20.

The construction at the other two pillars 14 and 15 is the same. The pillars 21 and 22 are similar to pillar and are threaded into pillars 14 and 15, respectively, to secure the plates 11 and 12. The three pillars 20, 21, and 22 may therefore be regarded as part of the clock movement frame, and afford means for mounting the frame of the motor mechanism, as will be explained presently.

The clock movement is of known construction and only those parts which are concerned with the invention are shown. These parts include the center shaft 23, the center wheel 25, and the ratchet wheel 26, and along with other cooperating parts will be explained more fully in connection with Fig. 4.

Mention has been made heretofore of the center shaft and ratchet wheel assembly and while these parts are referred to as one assembly in accordance with prior practice, the invention actually provides two independent assemblies, one comprising the center shaft and center wheel and associated parts, while the other comprises the ratchet wheel, the reserve spring, and associated parts, the purpose being to isolate the ratchet wheel so far as possible from the center shaft and parts directly associated therewith.

The center shaft 23 has a bearing in the frame plate 10 and another bearing in the stud 41 This stud has internal and external bearing surfaces and is secured to the frame plate 12 by riveting or staking, as shown in the drawing. The center wheel 25, which drives the escapement mechanism through a gear train, is mounted on the hub which is supported on the center shaft 23. The center shaft has a collar 33 fixed thereto, which is disposed in a recess 32 in hub 30. The center shaft also has a pinion 24 fixed thereto, which drives the hour hand through the usual gear train. There is a flat washer 28 and a spring washer 29 interposed between the hub of pinion 24 and the center wheel 25. This spring washer is compressed somewhat to hold the hub 30 against the collar 33, thus providing a frictional coupling through which hub 30 drives the center shaft while permitting independent rotation of the center shaft to set the hands of the clock.

The ratchet wheel 26 is mounted on a hub 39, which is rotatable on the stud 41). The hub 39 is formed with a shoulder against which the ratchet wheel is clamped by staking the end of the hub, whereby the parts are firmly secured together. The reserve spring housing 34 is a shallow cup shaped stamping and is rotatably sup ported on the hub 39, where it is retained by a head formed at the end of the hub. The housing and the reserve spring are of course assembled on the hub prior to mounting the ratchet wheel thereon. The reserve spring, sometimes referred to as the power maintaining spring, is indicated at 37 and is disposed within the housing 34. One end of the spring, indicated at 38 in Fig. 4, is bent to the right and passes through a hole in the ratchet wheel 26. The other end of the spring,

not shown in Fig. 4 but shown in Fig. 7, is bent to the left and passes through a hole in the housing 34. Thus the reserve spring constitutes a flexible coupling through which the ratchet wheel rotates the housing.

While the ratchet wheel and housing are independently supported on the stud as described, they nevertheless have to drive the center wheel and center shaft. This is taken care of by means of a doubly forked member 31 mounted on the hub 30, and the two projecting members 35 and 36 which are struck from the base of the housing 34 and extend between the forks of member 31, as shown clearly in Fig. 4. The shape of the forked member 31 is best seen in Fig. 6.

The reference character 27, Fig. 3, indicates a holding pawl which functions to prevent backward rotation of the ratchet Wheel 26 during winding or retensioning of the main spring.

The motor mechanism is mounted on the back plate 60, this single plate and the core of the electromagnet constituting the motor mechanism frame.

The electromagnet core comprises a laminated soft iron bar 61 of rectangular cross section, having the curved pole pieces 62 and 63. The bar 61 is formed with shoulders at the ends, as indicated in Fig. 2, and the pole pieces rest against these shoulders where they are secured by riveting or upsetting the ends of the bar outside the pole pieces. The pole piece 63 has two integrally formed studs such as 64 which extend through holes in the back plate 68 and have their ends staked or riveted to secure the pole piece to the back plate. The pole piece 62 is similarly secured to the back plate by means of two studs such as 65.

The reference character 68 indicates a bearing comprising a tube which has a press fit in a hole in the core bar 61 and also in a hole in the back plate 60. The bearing tube is further supported by means of two heavy rectangular insulators 66 and 67 which are pressed onto the core bar before the pole pieces 62 and 63 are assembled thereto. These insulators have semicylindrical recesses which engage the tube 68 on opposite sides thereof.

The insulators 69 and 70 are threaded on the core bar 61 just inside the pole pieces. There is also a thin tube of paper or other suitable insulating material which covers the core bar 61 in the winding spaces. The winding is in two sections 71 and 72, as shown in Fig. 2.

The armature 73 has pole pieces 74 and 75 cooperating with the pole pieces 62 and 63, respectively, and is fixed to the centrally disposed shaft 76 which extends through the bearing tube 68. The armature and shaft are thus supported for rotation on the axis of shaft 76. The main spring is indicated at 77 and tends to rotate the armature 73 in a clockwise direction as seen in Fig. 2.

The two pawls 78 and 79 are rotatably mounted on the armature 73 and are adapted to cooperate with the ratchet wheel 26 of the clock movement when the motor mechanism is assembled thereto. In order to bring the pawls into the plane of the ratchet wheel, short brass studs are riveted to the armature at the proper points and the pivots for the pawls pass through holes drilled in the studs. The springs 80 and 81 are associated with pawls 78 and 79, respectively, and tend to rotate the pawls on their pivots to the positions in which they are shown in Fig. 2.

A suitable switch mechanism 85 is provided, for controlling the circuit of the electromagnet. The switch mechanism is mounted on the back plate 60 and may be similar to the one shown in Hobbs patent previously referred to. The switch mechanism is thus part of the motor mechanism, along with the electromagnet and armature, and can be operated by hand manipulation of the armature for the purpose of adjustment.

Before the motor mechanism is assembled to the clock movement the pawls 78 and 79 are rotated in a counterclockwise direction far enough so that the ends of the pawls are engaged by the down turned ends of the springs 80 and 81. The springs then hold the pawls in their rotated positions, in which the ends of the pawls are farther apart than the diameter of ratchet wheel 26. The pawls having been displaced, the two frames may be brought together with the armature side of the motor mechanism adjacent the ratchet wheel side of the clock movement. The motor mechanism is then so oriented that the ends of the pillars 20, 21, and 22, which are of reduced diameter, are aligned with the holes 87, 88 and 89, respectively, in the back plate 60, whereupon the back plate is pressed on to the pillars and against the shoulders thereon, the parts assuming the positions in which they are shown in Fig. 3. The frames are secured together by the screws 90, 91 and 92, which are threaded into the pillars 20, 21, and 22, respectively.

The pawls 78 and 79 are released into engagement with the ratchet wheel 26 by means of a small hook which can be used to compress the springs 80 and 81. In the case of pawl 78, for instance, the hook can be inserted behind the down turned end of the spring 80 to draw it forward far enough to clear the end of the pawl. The clock being held in the proper position, the pawl will then fall by gravity against the ratchet wheel where it is held by the spring when the latter is released.

Having been assembled as described, the clock may be operated by connecting it to a suitable source of current. In practice the live pole of the battery, assuming the clock is used in an automobile, is connected to the binding post 93. to which one end of the winding of the electrornagnet is connected. The other end of the winding is connected to the frame and thence to ground through the switch 85 when the switch is closed.

When the clock is connected up in this manner, the electromagnet is energized to rotate the armature 73, thereby tensioning the main spring 77 and opening the switch 85 to open the circuit of the electromagnet. The pin 86 has some play in the fork 95 so that the electromagnet circuit is not broken until the requisite movement of the armature has taken place. During the rotation of the armature the ratchet wheel 26 is held against rotation by the pawl 27. The pawls 78 and 79 slide over the teeth of the ratchet wheel and when the electromagnet becomes deencrgized they promptly engage the teeth to drive the ratchet wheel as the main spring 77 begins to rotate the armature 73 in a clockwise direction. The ratchet wheel and its hub 39 rotate on the stud 40 and the rotation of the former tensions the spring 37 which starts to rotate the housing 34 as soon as sufiicient tension is developed. The housing 34 rotates the hub 30 by means of the projecting members 35 and 36 and the forked member 31. In this way the main spring drives the hub 30 and center wheel 25, which drive the center shaft 23 and the escapement mechanism.

The armature 73 rotates slowly under control of the escapement mechanism as it drives the clock movement and shortly before it reaches the position in which it is shown in Fig. 2 the switch 85 is closed again to reenergize the electromagnet and repeat the winding operation. As soon as the armature 73 starts to rotate, the pawls 78 and 79 cease to apply power to the ratchet wheel 26 but this wheel is instantly held by the pawl 27 and the spring 37 is thus enabled to continue to supply power to drive the clock movement. The winding operation takes only a small fraction of a second and when it is completed the pawls 78 and 79 again take over the driving function. The operation continues in this manner, the clock being rewound at intervals of about 2 minutes, the exact interval depending on several factors and being regulated properly by adjustment of the switch.

It will be seen that the invention provides a self winding electric clock having a number of advantageous features. The demountable motor mechanism is simplified, all the parts being mounted on a single frame plate, which is the back plate 60. The novel arrangement of the magnet core and back plate to provide a support for the armature bearing 68 affords an accurate and wear proof mounting for the armature, which makes it possible to substantially reduce the air gaps between the poles of the armature and the poles of the electromagnei'. This increases the power supplied to the armature during winding, for a given number of ampere turns, and makes it possible to increase the resistance of the electromagnet winding substantially while developing the same power as heretofore. Using a smaller size of wire in the wind ing, the current consumption has been reduced by as much as thirty per cent while still providing ample winding power. The reduction in the current of course reduces arcing at the switch contacts and increases the life of the switch.

As regards the novel arrangement for the center shaft and ratchet wheel assembly, which involves supporting the ratchet wheel independent of the center shaft and center wheel, it is found that this arrangement completely eliminates the off time defect to which clock; such as shown in the Hobbs patent are subject.

Explaining this more in detail, in the clock shown by Hobbs the ratchet wheel is rotatably mounted on the same hub which supports the center wheel and accordingly is supported on the center shaft through the dium of this hub. The reserve spring is located between a flange on the hub and the ratchet wheel and provides a secondary drive for the clock movement which is effective only during winding, the main drive being effected by a pin on the ratchet wheel which projects in. J a slot in the hub flange. With this construction the center wheel hub is subjected to periodic shocks of varying intensity during winding of the clock, one occurring at the start of winding when the ratchet wheel is engaged by the holding pawl, another when the driving pawls take a fresh hold on the ratchet wheel at the completion of the winding operation, and another when the pin on the ratchet wheel engages the side of the slot in the hub flange after taking up the slack in the reserve sprmg.

Due apparently to the inertia of the center shaft and hour hand drive, these shocks tend to produce a relative rotation between the center wheel and the center shaft which causes the off time phenomena referred to. The error is not great but may amount to as much :13 2 or 3 minutes per day. The defect has been overcome by employing a friction washer between the center shaft pinion and center wheel which is rather stiff, thus providing considerable friction which opposes the tendency toward rotation of the center wheel on the center shaf This expedient is not altogether satisfactory because it makes the clock hard to set and with the maximum friction considered allowable the off time defect occasionally shows up.

The defect is overcome according to the invention b" providing an independent support 40 for the ratchet wheel 26 and by eliminating entirely the positive pin drive between the ratchet wheel and center wheel hub, this positive drive being replaced by a resilient drive through the reserve spring. This spring, it should b:

mentioned, is made somewhat stiffer than the spring formerly used. The invention has the further advantage that the friction washer 29 may be and is preferably made rather weak, providing only sufficient friction to drive the center shaft and the hands of the clock. This makes the clock very easy to set and without any danger of the off time error being encountered.

While a certain specific embodiment of the invention has been disclosed herein, it will be understood that modifications may be made, and we do not therefore wish to be restricted to the exact form of the invention as shown and described herein but desire to include and have protected by Letters Patent all forms and modifications thereof which come within the scope of the appended claims.

We claim:

1. In a clock movement, a frame including a frame plate, a ratchet wheel, means fixed to said frame plate providing a bearing for said ratchet wheel, said wheel having a hub fixed thereto, a housing rotatable on said hub, and a reserve spring in said housing, said spring having one end connected to said housing and the other end connected to said ratchet wheel.

2. In a clock movement, a frame including a frame plate, a support fixed to said frame plate, a ratchet wheel having a hub rotatably mounted on said support, a member rotatable on said hub and cooperating with said wheel to form a housing, and a reserve spring having its opposite ends connected to said wheel and said member, respectively, said spring being located in said housing and constituting the sole means through which said wheel rotates said member.

3. In a clock movement, a frame comprising two plates secured together in spaced relation, a center shaft rotatably supported on said plates, a center wheel having a hub rotatable on said center shaft, a friction coupling through which said center wheel rotates said center shaft, a ratchet wheel, a housing member, means including a support fixed to one frame plate supporting said ratchet wheel and member for rotation on the axis of said center shaft, means comprising a reserve spring through which said ratchet wheel rotates said member, and cooperating parts on said member and said center wheel hub whereby rotation of said member rotates said hub.

References Cited in the file of this patent UNlTED STATES PATENTS 1,735,105 Bethel Nov. 12, 1929 1,918,057 Putnam July 11, 1933 2,089,280 Loeffier Aug. 10, 1937 2,146,119 Hobbs Feb. 7, 1939 2,254,536 Loeffier Sept. 2, 1941 2,319,134 Johnson May 11, 1943 2,406,216 Goldberg Aug. 20, 1946 2,491,453 Knobel Dec. 13, 1949 2,519,713 Steinmann Aug. 22, 1950 2,545,835 Wilson et a1. Mar. 20, 1951

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