US3566238A

US3566238A - Motor governor

Info

Publication number: US3566238A
Application number: US735215A
Authority: US
Inventors: Hideaki Akiyama
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 1967-06-14
Filing date: 1968-06-07
Publication date: 1971-02-23
Anticipated expiration: 1988-02-23

Abstract

A cam rotates at a speed proportional to that of an electric motor and a projection thereon strikes and vibrates a springbiased contact arm having an electric contact on its outer end. When the impulses thus given to the arm are given at a frequency equal to the natural vibrational frequency of the contact arm, the contacts never close and the current to the motor drops, reducing its speed slightly.

Description

United States Patent Hideaki Akiyama Yokohama-shi, Japan 735,215

June 7, 1968 Feb. 23, 1971 Kabushiki Kaisha Ricoh Tokyo, Japan June 14, 1967 Japan lnventor App]. No. Filed Patented Assignee Priority MOTOR GOVERNOR 14 Claims, 6 Drawing Figs.

U.S. Cl

318/346, 318/349 lnt.Cl H02p 5/10 318/346,

Field of Search [56] References Cited UNITED STATES PATENTS 3,215,219 11/1965 l-lolzer 318/349 3,317,808 5/1967 Yott 318/346 Primary Examiner-Cris L. Rader Assistant Examiner-Thomas Langer AttorneyPBurgess, Ryan and Hicks ABSTRACT: A cam rotates at a speed proportional to that of an electric motor and a projection thereon strikes and vibrates a spring-Biased contact am having an electric contact on its outer end. When the impulses thus given to the arm are given at a frequency equal to the natural vibrational frequency of the contact arm, the contacts never close and the current to the motor drops; reducing its speed slightly.

PATENTED FEB23 l97l 9 54 FIG. 5

INVENTOR H/DEAK/ AK/ YAMA ATTORNI Y MOTOR GOVERNOR SUMMARY OF THE INVENTION According to the invention, the controlling of motor speed is performed by short-circuiting the resistor inserted in series with the motor-driving circuit. The series resistor is inserted into the motor-driving circuit or short-circuited by the opening or closing of the two contacts which are connected in parallel with the resistor. At least one of the two contacts is controlled by an elastically vibrating member which is driven by a cam plate fixed on the driving shaft of the motor. As the motor speed increases, the opening period of the two contacts is extended, which lengthens the time. when the resistor is being inserted in the motor-driving circuit. This causes the reduction of the current driving the motor, and the motor speed tends to drop. When the motor speed is decreased, on the other hand, the timewhen two contacts are closed increases, during which the series resistor being short-circuited. Thus, the motor-driving currentis increased and the motor speed is increased. As a result the motor speed is maintained substantially constant within certain specific limits.

The motor speed control is performed by varying the natural frequency of the vibrating member. The natural frequency may be varied either by changing the space between the two contacts, or changing the weight of the dead weight attached to the vibrating member, or by changing the strength of the spring which causes the restoration of the vibrating member always to the starting position.

One object of the present invention is to provide a motor governor of which speed can be adjusted during the rotation of motor.

Another object of the invention is to provide a motor governor of simple construction and less subject to troubles.

The invention may be more readily ascertained from the following detailed description of a preferred embodiment thereof shown, by way of example, in the accompanying drawings.

BRIEF EXPLANATION OF DRAWINGS be used in the invention respectively.

FIG. 4 shows a perspective view of still another embodiment of the invention.

FIG. shows a perspective view of a further different embodiment of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT FIG. I shows one embodiment of the invention. Referring to FIG. I, fixed contact arm 2 and a movable contact arm 3, which is made of elastic material, are fixed on a baseplate 1 and mutually insulated. The fixed contact arm 2 has a contact 4 on it, and movable contact arm 3 has a V-sliaped projection 30 at a suitable position close to its top end, and also a contact 5 anda dead weight 6 at a position in front of the contact 4. The distance between the

contacts

4 and 5 is adjustable by rotation of contact 5 which is pressed to contact 4 by the elastic force of the movable contact arm 3. The dead weight 6 is exchangeable with those of different weights, and may be integrated with the contact 5. On the opposite side of the base 1, a micromotor 7 is fixed, and the shaft 8 of the motor pierces the base I through a hole la and protrudes on to the same side as contact

arms

2 and 3. A cam disc 9 having a projection 9a is fixed at the protruding end of the shaft 8 and insulated from the shaft. The projection 34 of the movable contact arm 3 is pressed to the cam disc 9. The fixed contact arm 2, movable contact member 3, micromotor 7, fixed resistor 10 and capacitor 11 are connected as illustrated in FIGS. 1 and 2, and the

lead wires

12 and 13 are connected to the power supply (not shown).

. not always necessary.

The mechanism is so designed that, by adjusting the projection length of the contact 5 of the movable contact arm 3, the contact 5 becomes to contact with the other contact 4 when the V-shaped projection 3a of the movable contact arm 3 is sliding on the circumference of the cam disc 9, and the two contacts are separated only when the projection 9a of the cam isc 9 strikes the V-shaped projection 3a.

When the micromotor 7 rotates, the projection 9a contacts with the V-shaped projection 30 of the movable contact arm 3 at each rotation of the cam 9, and the contact arm 3 is pushed away from the fixed contact arm 2 against the elastic force of the former. Thereupon the

contacts

4 and 5 are separated.

When the speed of the micromotor 7 is relatively low, the movable contact arm 3 returns to its original position due to its elastic force before then the next contact takes place after the projection 9a passes through the point of V-shaped projection 3a, and the

contacts

4 and 5 close again. When the micromotor 7 is rotating with higher speed each next contact of the projection 9a with V-shaped projection 3a takes place before returning of the movableeontact arm 3 is completed, and the contact arm 3 is pushed away again. As it can be clearly understood from FIG. 2, since the resistor 10 circuited is short while the

contacts

4 and 5 are in contact, the speed of the micromotor 7 rises to cause a prolonged separation of the

contacts

4 and 5. On the other hand, when the

contacts

4 and 5 are kept separated, the resistor 10 is inserted in series with the driving circuit of the micromotor 7, and the micromotor speed is decreased. When it is lowered to a certain level, the movable contact arm 3 again comes to contact with the circumference of the cam 9, causing the closure of

contact points

4 and 5. Consequently, the micromotor speed again starts to increase. Thus the micromotor speed varies only within a limited range. Therefore, by suitably selecting the mechanical and electrical elements of this device, the micromotor speed can be maintained substantially constant.

The limit of speed of the micromotor 7 in which the movable contact arm 3 can maintain its pressurized contact with the circumference of the cam 9 is determined by the natural frequency of the moveable contact member 3. The natural frequency is determined by such factors as thickness, shape, weight and elasticity, of the movable contact arm 3, gap between the contacts 4 and S, and weight of the dead weight, etc. These physical properties of the movable contact arm 3 can not be easily changed, but the gap between the

contacts

4 and 5 and the weight of the dead weight can be varied easily as described in the foregoing. Thus the natural frequency of the movable contact arm 3 can be controlled by changing the above-mentioned variable factors. The capacitor 11 functions to prevent the occurence of discharge spark accompanying to the opening of the

contacts

4 and 5, whereby damage of both contacts is prevented.

Obviously, the same purpose of changing the weight of the dead weight can be accomplished by varying the position of the same. Furthermore, the cam disc 9 may have a plural number of projections as illustrated in FIG. 3A and FIG. 38. Also the V-sh'aped projection on the movable contact arm 3 is An improved embodiment over that of FIG. 1 is shown in FIG. 4, in which the movable contact arm 3 is not fixed on the baseplate l, but is rotatably mounted around a shaft 14 fixed on base 1. The contact arm 3, furthermore, is constantly urged to rotate in the direction of the cam 9 by a spring 15. In this design the elasticity of the movable contact arm 3 can be selected with relatively larger freedom.

Still another embodiment is shown in FIG. 5, in which a fixed contact member 52 and a movable contact arm 53 which is made of an elastic material are fixed on a baseplate 51 respectively, the bent ends of the contact members being mutually insulated. The fixed contact member 52 has a contact 54, and the movable contact arm 53 has a contact 55. Also the casing 56a of an oil damper 56 is provided on the base 51. A shaft 57 is rotatably mounted on the casing 560, and to the shaft a rotation resistance is given by the oil, for instance, silicon oil, contained in the casing 560. The shaft 57 has a groove 57a cut in the axial direction at its upper end, which engages with the projection 58a of a hole 58b provided at the base portion of a lever 58, the configuration of the hole 58b being identical with the cross section of the shaft 57. As the result of the engagement, the shaft 57 and the lever 58 rotate integrally. A piece 59 having a V-shaped projection 59a and made of an elastic material is fixed on the free end of the lever '58. A spring 61 extends between the piece 59 and an eccentric pin 60, via the shaft 57, the eccentric pin 60 being rotatably mounted on the bent portion 51a of the baseplate 51. By the spring 61, the piece 59is caused to constantly rotate in the direction of the movable contact arm 53. The strength of the spring 61 can be varied by rotating the eccentric pin 60. The end of the lever 58 presses the-movable contact arm 53 and causes the closure of the contacts 54 and 55 against the elastic force of the contact arm 53. A micromotor. 62 is fixed to the base 51, and its driving shaft 63 is fixed with a substantially disc-formed cam 64 which has a projection 64a. The position of the micromotor 62 is so selected that the projection 59a of the piece 59 can be pressed to the cam plate 64. While the V- shaped projection 59a of the piece 59 is contacting with the circumference of the cam 64, the lever 58 is rotated against the elastic force of the movable contact arm 53 to cause the closure of contacts 54 and 55 by spring 61. Whereas, when the projection 59a comes into contact with the projection 640, the piece 59 is clockwise rotated against the elastic force of spring 61 as illustrated in FlG. 5, and the movable contact arm 53 follows the movement of the lever 58 by its own elastic force. Thereupon the contact 55 is separated from contact 54. The electrical connection of the fixed constant member 52, movable contact arm 53, micromotor 62, fixed resistor 65 and capacitor 66 is identical to that in the embodiment of FIG. 2.

With the rotation of the micromotor 62, at each rotation of the cam 64, its projection 640 contacts with the V-shaped projection 59a of the piece 59, inducing clockwise rotation of the lever 58. While the micromotor speed is below a certain level,

the piece 59 comes into contact with the circumference of cam 64, and consequently the contacts 54 and 55 close. When the micromotor speed is increased, however, the lever 58 is rotated clockwise against the elastic force of the spring 61 and the resistance offered by the oil damper 56. Following the lever movement, the end of the movable contact arm 53 is pulled away from the fixed contact member 52 by its own elastic force. Consequently the contacts 54 and 55 are separated.

When the contacts 54 and 55 are in mutual contact, the resistor 65 is short-circuited by the two contacts as clearly indicated in the circuit diagram of FIG. 2, and the speed of the micromotor 62 increases. When 'the speed-exceeds a certain predetermined level, however, the contacts are kept separated. Whereupon the resistor 65 is inserted in series with the driving circuit of the micromotor 62, whereby decreasing the motor speed. When the speed of the micromotor is reduced below a certain level,- the clockwise rotation of the lever 58 is immediately put back, causing the closure of the contacts 54 and 55. Obviously this causes an increase in the motor speed. Thus the speed of the micromotor varies within only a limited range, andspecd of the motor can be maintained substantially constant similarly to the case of the device illustrated in FIG. 1. 7

In accordance with this embodiment, the speed of the micromotor 62 can be varied by changing the strength of the spring 61 with rotation of eccentric pin. Therefore operation of the device is very easy. Also the use of an oil damper smoothens the speed change of the motor.

lclaim:

l. A motor govemor comprising a motor fixed on a baseplate; a .cam plate fixed on the driving axis of said motor and having at least one projection; a member vibrated by said projection on said cam plate, with the rotation of the motor said member having a natural vibration frequency equal to the frequency with which it is struck by a cam plate projection when the motor is rotating at a desired speed; two contacts opened or closed in accordance with the vibration of said member; and a resistor inserted in series with thef'driving circuit of said motor and short-circuited while said contacts are closed.

2. The motor governor according to claim 1 characterized in that said member is rotatably supported on a shaft on the baseplate, and urged to rotate in a single direction by a spring.

3. The motor governor according to claim 1 characterized in that said member is made of elastic material, and its base portion is fixed to the baseplate.

4. The motor governor according to claims 1, characterized in that at least one of said contacts is supported by said member, and is adjustable.

5. The motor governor according to claim 3 characterized in that the strength of the spring is adjustable with an eccentric pm.

6. The motor governoraccording to claim 3 characterized in that said movable contact is supported by a separate elastic member from said elastically'vibrating member, and is opened or closed by said vibrating'member.

7. The motor governor according to claim 1 characterized in that said vibrating member is provided with a dead weight for changing the natural frequency of said member.

8. The motor governor according to claim 2 characterized in that an oil damper is provided around the rotative shaft of said elastically vibrating member.

9. The motor governor according to claim 2 characterized in that at least onev of said contacts is supported by said member, and is adjustable.

10. The motor governor according to claim 3 characterized in that at least one of said contacts is supported by said member, and is adjustable.

11. In a motor governor for maintaining a desired speed in an electric motor, a firstelectric contact, a second electric contact mounted on a vibratable support structure, vibration of said support structure moving the second electric contact toward and away from the first electric contact, said support structure having a natural frequency of vibration, resilient means urging the support structure into a position in which the contacts touch, a cam follower on the support structure, a rotatable cam connected to the motor for rotation at a speed proportional to the motor speed, and circuit means connected to the contacts for increasing the driving current flow to the motor while the contacts touch, wherein the improvement comprises a surface on the cam adapted to contact the cam follower and exert a periodic force thereon in a direction to open the contacts, said force being applied at the natural frequency of the support structure when the motor is at the desired speed. g k j 12. The device of claim 11 comprising means for varying the natural frequency of the support structure in order to vary the desired speed.

13. In a motor governor'for maintaining a desired speed in an electric motor, a first electric contact, a second electric contact mounted on a moveable support structure and moveable between a closed position in which the contacts touch and an open position in which the contacts are separated, circuit means connected to the contacts for increasing the driving current to the motor while the contacts are in the closed position, and separation means for periodically moving the second electrical contact to the open position, the frequency of such separation movements being proportional to the speed of the motor, wherein the improvement comprises a resilient element exerting a restoring force on the second electrical contact and its support structure urging said contact into the closed position, said resilient element being so matched to the mass of the second electrical contact and its moveable support structure that the time required for it to restore the second electrical contact to the closed position from the open position in the absence of an opposing force from the separation means is substantially equal to the time between successive separation movements when the motor is running at the desired speed.

mounted to strike the moveable suppor'fstructure of the moveable electrical contact at each revolution.

Patent No. 3566238 Inventor (9:) Hideaki Column 1, before line 1,

Column 2, line 22,

Column 2, line 23,

Column 4, linell,

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated February 23, 1971 Akiyama It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Insert the following: BACKGROUND OF THE DISCLOSURE:

The conventional mechanism emplo in micromotor governors used in cinecameJ etc. is such that the governor is fixed the driving shaft of the micromotor, and motor-driving circuit is opened or close: accordance with the centrifugal force cam by the rotation of the governor. In sucl mechanism, the motor must be stopped eacI time when the space between the contact 1 adjusted in order to vary the speed of t1 motor, since the contacts rotate togethe: with the body of the governor. Therefore the adjustment of speed can not be done v the motor being rotated. This needs ext: 1y complicated procedures. Furthermore, brushes are required for the supplying 01 electric current to the rotor. Brush mes are complex in structure, costly, and ter cause motor troubles. -7

after "resistor 10" insert is short delete "is short";

delete "claims" and insert claim Signed and sealed this (SEAL) Attest:

EDWARD M.FLETGHER, JR.

ttesting Officer 30th day of November 1971.

Claims

1. A motor governor comprising a motor fixed on a baseplate; a cam plate fixed on the driving axis of said motor and having at least one projection; a member vibrated by said projection on said cam plate, with the rotation of the motor said member having a natural vibration frequency equal to the frequency with which it is struck by a cam plate projection when the motor is rotating at a desired speed; two contacts opened or closed in accordance with the vibration of said member; and a resistor inserted in series with the driving circuit of said motor and short-circuited while said contacts are closed.

5. The motor governor according to claim 3 characterized in that the strength of the spring is adjustable with an eccentric pin.

6. The motor governor according to claim 3 characterized in that said movable contact is supported by a separate elastic member from said elastically vibrating member, and is opened or closed by said vibrating member.

9. The motor governor according to claim 2 characterized in that at least one of said contacts is supported by said member, and is adjustable.

11. In a motor governor for maintaining a desired speed in an electric motor, a first electric contact, a second electric contact mounted on a vibratable support structure, vibration of said support structure moving the second electric contact toward and away from the first electric contact, said support structure having a natural frequency of vibration, resilient means urging the support structure into a position in which the contacts touch, a cam follower on the support structure, a rotatable cam connected to the motor for rotation at a speed proportional to the motor speed, and circuit means connected to the contacts for increasing the driving current flow to the motor while the contacts touch, wherein the improvement comprises a surface on the cam adapted to contact the cam follower and exert a periodic force thereon in a direction to open the contacts, said Force being applied at the natural frequency of the support structure when the motor is at the desired speed.

12. The device of claim 11 comprising means for varying the natural frequency of the support structure in order to vary the desired speed.

13. In a motor governor for maintaining a desired speed in an electric motor, a first electric contact, a second electric contact mounted on a moveable support structure and moveable between a closed position in which the contacts touch and an open position in which the contacts are separated, circuit means connected to the contacts for increasing the driving current to the motor while the contacts are in the closed position, and separation means for periodically moving the second electrical contact to the open position, the frequency of such separation movements being proportional to the speed of the motor, wherein the improvement comprises a resilient element exerting a restoring force on the second electrical contact and its support structure urging said contact into the closed position, said resilient element being so matched to the mass of the second electrical contact and its moveable support structure that the time required for it to restore the second electrical contact to the closed position from the open position in the absence of an opposing force from the separation means is substantially equal to the time between successive separation movements when the motor is running at the desired speed.

14. The device of claim 13 wherein the separation means comprises a rotatable projection connected to the motor for rotation at a speed proportional to the motor speed and mounted to strike the moveable support structure of the moveable electrical contact at each revolution.