US3226621A - Sewing machine drive - Google Patents

Description

Dec. 28, 1965 Filed April 16, 1963 HQL R. HEINEMANN ETAL 3,226,621

SEWING MACHINE DRIVE 5 Sheets-Sheet 1 EU t5 i l 5 t// 9 \lM 1 4 'INVENTORJ ATTORNEY 2 1965 I R. HEINEMANN ETAL 3,226,621

SEWING MACHINE DRIVE Filed April 16, 1963 3 Sheets-Sheet 2 FIG. 6.

D i I- d Ua Va WQ, T i L W? W I I I HIGH LOW-V NUMBER OF POLES INVENTORS ROLF HEINEMANN HARRY REINECKE SIEGFRIED FREY BY ATTORNEY.

1965 R. HEINEMANN ETAL 3,226,621

SEWING MACHINE DRIVE Filed April 16, 1963 3 Sheets-Sheet 5 27 17v i E 5 l L -U 5 Y kw INVENTORS ATTORNEY United States Patent 3,226,621 SEWING MACHINE DRIVE Rolf Heinemann, Stuttgart-Zuifenhausen, Harry Reinecire,

Leinfelden, near Stuttgart, and Siegfried Frey, Heiligenstadt, Germany, assignors to Georgii-Kobold Elektro- Motoren-Apparatebau G.m.b.H., Stuttgart, Germany, a limited-liability company of Germany Filed Apr. 16, 1963, Ser. No. 273,403 Claims priority, application Germany, Apr. 28, 1962, G 34,844 8 Claims. (Cl. 31822 The present invention relates to a sewing machine drive consisting of an electric motor and a position indicator which is connected to the shaft of the sewing machine and is adapted to interrupt the drive in accordance with a certain angular position of this shaft which, in turn, corresponds to a selected needle position.

In sewing machine drives of this type it is conventional to employ a motor which rotates continuously during the operation of the sewing machine and may be connected to or disconnected from the sewing machine shaft. In order to stop the sewing machine shaft in response to a selected needle position, the brake element of a known sewing machine drive is positively driven by an auxiliary drive which slowly rotates the brake element and may be controlled by the position indicator. The known sewing machine drive has the disadvantage that it requires two separate drives, namely, the drive for the sewing machine shaft and the drive for the brake element.

It is an object of the present invention to provide a sewing machine drive which is less expensive than the sewing machine drive mentioned above, but fully attains the same purpose. According to the invention, this object is attained by providing the electric motor with a brake and with at least two separate windings with widely differing numbers of poles, by providing relays which are associated with these windings and the contacts of which are adapted to connect the different windings, and a main switch for operating these relays which has an off position and a number of on positions in accordance with the number of windings, and by connecting the relay which is associated with the motor winding with the highest number of poles in series with a contact which is held in the closed position during the operation of the motor and also in series with a contact of the position indicator.

By employing a motor with separate windings which have widely differing numbers of poles, it is possible te operate the motor at widely differing speeds. The ratio of the pole numbers should be as high as possible and amount at least to 1:2. During the normal operation of the sewing machine, the motor may then run at a high speed, while when the motor is being switched ofi, it may at first be controlled so as to run at a low speed which then permits the motor to be stopped accurately in any particular desired position by the brake of the motor. By employing the contacts of relays which are associated with the windings, it is possible to control the motor as desired. Since the main switch is provided with one off position and a number of on positions in accordance with the number of windings, it may be used for switching oil? the motor or for switching it on to run at different speeds. The main switch may then be designed so as to permit the different speeds to be switched on or off only in a certain order of succession, namely, so as progressively to increase the speed when the motor is being switched on and progressively to decrease the speed when the motor is being switched off. Since the relay which is associated with the winding with the highest number of poles and therefore controls the lowest speed of the motor is connected in series with a contact which remains closed dur- "ice ing the operation of the motor and with a contact of the position indicator, it is possible to stop the motor by means of its brake at any point which may be very accurately determined by opening the contact of the position indicator. The two contacts may then be either connected in parallel or in series to each other.

In order to prevent that when the motor is being switched off, the motor winding with the highest number of poles is switched oif before the speed of the motor shaft is decelerated to the speed which is in accordance with this winding, a time-delay circuit may be provided for delaying the release of the relay which is associated with this winding. If the time lag, which is produced by this delay circuit for the inductive deceleration of the motor shaft after the winding with the highest number of poles is switched on, is made of a sufficient size, it is possible to insure absolutely that the winding with the highest number of poles will be switched off by the position indicator only when the motor has been adjusted to the lowest possible speed. In this manner it is possible to stop the sewing machine shaft very accurately in any desired angular position thereof.

According to one preferred embodiment of the invention, the position indicator may be provided in the form of a pair of contacts which may be closed by the magnetic field of a permanent magnet which rotates together with the sewing machine shaft and by the magnetic field of one of two solenoids which amplify the field of the permanent magnet in opposite directions and may be selectively energized. By this surprisingly simple manner it is now possible to insure that the permanent magnet which rotates together with the sewing machine shaft will close the contacts only if one of the solenoids is energized. At the same time, the sewing machine shaft will hereby be fixed in the desired angular position in which the motor should be switched off entirely by the position indicator. By a suitable design of their supply circuit, the solenoids further insure that the position indicator will not be actuated until this is actually desired. One or the other of the two solenoids of the position indicator may for this purpose, for example, be selectively connected to a circuit by means of a preselection switch and be short-circuited by a make contact of an auxiliary relay and the make contact of the main switch which is associated with the motor winding with the highest number of poles and is connected in series with this contact of the auxiliary relay. This has the result that, when the pre-selection switch is in one position, the selected solenoid will be energized and the position indicator will thereby be active in the corresponding angular position of the sewing machine shaft. As long as the auxiliary relay and the closing contact of the main switch are switched on, however, the solenoids are shortcircuited so that the position indicator will not be active during the operation of the sewing machine. However, as soon as the auxiliary relay is deenergized, for example by the mentioned time-delay switch, the position indicator will become active and switch off the motor when the sewing machine shaft is in the desired position, which will then be stopped immediately by the brake with which this motor is provided.

Numerous tests have shown that the sewing machine may be stopped in any desired position with a surprising accuracy if suitable filtering means of a conventional type are provided for smoothing a rectified supply current for the relays so as to insure that especially the relay which is associated with the motor winding with the highest number of poles will be supplied with a very smooth direct current.

The sewing machine drive according to the invention may be constructed so as to require very little space if all of the control means for the operation of the motor are mounted in a common control box which, in turn, is mounted on the motor housing.

The various features and advantages of the present invention will become more clearly apparent from the following detailed description thereof which is to be read with reference to the accompanying drawings, in which- FIGURE 11 shows a side view of the electric motor, as seen in the direction of the arrow I in FIGURE 3 and of a control box from which the cover is removed and which is connected to the motor housing;

FIGURE 2 shows a vertical section through the upper part of the motor according to FIGURE 1;

FIGURE 3 shows a front view of the motor, as seen in the direction of the arrow III in FIGURE 1;

FIGURE 4 shows a front view of the position indicator;

FIGURE 5 shows, partly in section, a side view of the position indicator according to FIGURE 4; while FIGURE 6 shows a circuit diagram of the sewing machine drive according to FIGURES 1 to 5.

In the drawings, an electric motor which is indicated generally at 1 has a drive shaft 2 with a squirrel cage armature 3 thereon. Drive shaft 2 is rotatably mounted on bearings 4 in a housing 5 within which a set of stator plates 6. with stator windings 7 is mounted so as to surround the armature 3. A brake member 9 which carries a brake lining 8 and an electromagnetic winding L is rigidly secured to the housing 5. A control member 11 with a permanent magnet 12 thereon is mounted on one end portion 2 of drive shaft 2 so as to be slidable in the axial direction thereon, but nonrotatable relative thereto. The two poles of permanent magnet 12 are each provided with soft-iron parts 13 and 14, respectively, which are secured to the control member 11 and are facing soft-iron parts 16 and 17 of the brake member 9 which are connected to the core 15 of the electromagnetic winding L and thereby press the control member 11 against the brake lining 8. The electromagnetic winding L may be connected with a source of direct current in such a manner that the electric current will produce a magnetic field which opposes the magnetic field of the permanent magnet 12 and is adapted to eliminate the braking effect by lifting the control member 11 off the brake member 9. Up t this point, the electric motor is of a conventional construction.

For cooling the motor 1, an auxiliary motor 18 is pro vided which has a shaft 19 projecting into the housing of the motor 1, where it carries fan blades 19. The auxiliary motor 18 remains switched on during the entire operation of the sewing machine so that motor 1 will be cooled constantly.

Motor 1 together with the auxiliary motor 18 is pivotably connected by means of hinge members 21 to a sewing machine table 22 which is only indicated in part in FIG- URE 1. This piv-otable connection is necessary in order to permit the sewing machine to be driven by the same V-belt at different speeds, for which purpose a step pulley (not shown) with different pulley diameters may be mounted on the outer end 2" of the motor shaft 2.

The housing 5 of motor 1 carries a control box 23 for the control means of the sewing machine drive which will be mentioned in detail in the subsequent description of the circuit diagram as shown in FIGURE 6.

FIGURES 4 and 5 illustrate a position indicator which may be connected to the sewing machine shaft (not shown). This position indicator consists of a housing 24 in which a connecting socket 25 is rotatably mounted on a ball bearing 26. The connecting socket 25 is provided with a central bore 25' into which the end of the sewing machine shaft may be inserted to which the socket 25 may then be secured by a screw which is screwed into a tapped bore 27. On its inner end, the connecting socket 25 carries a rod-shaped permanent magnet 28 which extends at right angles to the axis of the sewing machine shaft and is magnetized in this direction. Adjacent to the permanent magnet 28 a conventional contactor E is provided which has two solenoids S1 and S2, as shown in FIGURE 6, and consists of two contact tongues or reeds, not shown in detail, which are disposed within a tube which is filled with an inert gas, and which are pressed against each other by the magnetic field of the permanent magnet 28 and the field of one of the solenoids S1 and S2 when the magnet is in a position in which it increases the strength of the magnetic field of the corresponding solenoid. The magnetic field of the permanent magnet 28 by itself does not, however, possess a sufiicicnt strength to press the two contact tongues of the contact-or E against each other. In order to screen the contactor from outer magnetic fields, it is protected by a cover 29 which consists of a material which conducts magnetic lines of force. In the circuit diagram according t FIGURE 6, the pair of electric contacts which are formed by the two contact tongues of the contactor E is indicated at e. For leading the conductors which are connected to the two contacts (2 out of the housing 24 of the position indicator, this housing is provided with an outlet tube 31. Housing 24 is adapted to be connected to the sewing machine table.

The electric motor 1 has two stator windings with widely differing numbers of poles. The ratio of the number of poles and thus the speed ratio of the motor shaft amounts at the time when the corresponding winding is being connected to at least 1:2, and preferably to 1:6 or 118. The connecting terminals for the three phases of the current which is supplied to the stator windings 7 of motor 1 are indicated in the diagram of FIGURE 6 at R, S, and T. These terminals R, S, and T may be selectively connected with the terminals Ua, Va, or Wa of the stator winding with the highest number of poles or with the terminals Ub, Vb, or Wb of the stator winding with a lower number of poles. The terminal R is for this purpose connected directly to the terminal Ua and Ub, while the terminals S and T are connected to the terminals Vb and Wb via the switch contacts b1 and b2, respectively, of a relay B when the latter is energized. When contacts b1 and b2 are in the neutral position, as shown, they connect the terminals S and T to the contacts a1 and 02 which, when closed, that is, when relay A is energized, are con nected with the terminals Va and Wu, respectively. Thus, when relay A is energized, the winding of the motor 1 with the highest number of poles will be connected and when in addition the relay B is also energized the winding with the lower number of poles will be connected.

For energizing the relays A and B, the phase terminal R is connected to a ground terminal Mp via a rectifier 32 so as to produce a direct current control voltage. The two poles of the rectifier 32 are first connected to a filter condenser 33 which is connected in parallel to a chain of control elements for energizing the relay B. This control chain is again connected in parallel through a filter resistor 34 to a filter condenser 35 which in turn is connected in parallel to a chain of control elements for energizing the relay A.

The chain of control elements for energizing the relay B comprises a contact t2 of a main switch C, a contact 113 of an auxiliary relay H, the winding of relay B, a resistor 36 and a condenser 37, and a winding H2 of the auxiliary relay H, all of which are connected in series. A condenser 37 is connected in parallel t the resistor 36 and the winding H2 of the auxiliary relay H. The condenser 37, the resistor 36 and the winding H2 form a resistancecapacity network, for short also called an R-C network. In FIGURE 6, all the mentioned elements are shown in the non-energized position.

The chain of control elements for actuating the relay A comprises a contact t1 of the main switch C, a throw-over switch contact I12 of the auxiliary relay H, and a thermal protective switch 38, all of which are connected in series. This series is connected in parallel to a holding contact 111 of the auxiliary relay H. This entire chain of control elements as described for actuating the relay A is connected in parallel to the contactor contacts e. The chain is finally completed by the windings of relay A and a relay D which are connected in series to the other elements as mentioned by-means of another winding H1 of the relay H, wound in the same sense as the winding H2. Relay D has a contact d which closes when this relay is energized and thereby connects the electromagnet coil L for releasing the brake of the brake motor.

' By means of a hand-operated preselection switch 39 either of the solenoids S1 or S2 of the position indicator may be connected via a resistor 41 to the supply circuit of the rectifier 32. By means of the throw-over contact h-2 of the auxiliary relay H and the contact t1 of the main switch C, the two solenoids S1 and S2 are short-circuited and therefore inoperative when the contacts h2 and t1 are in the closed position.

The two contacts t1 and t2 of the main switch C which in the embodiment of the invention as illustrated in FIG- URE l is provided in the form of a pull switch with a pull rod 42, are arranged in such manner that, when switch C 'by pulling the pull rod 42 is switched on in a first on position the contact t1 is closed and when it is switched on in a second on position the contact t2 is also closed. When the main switch C is switched ofl, this procedure occurs in the reverse order. The operation of the sewing machine drive according to the invention. as previously described is as follows: When the pull switch C is switched on, first the contact t1 is closed whereby the relay D is energized and the brake of the brake motor is released. At the same time the coil H1 of the relay Hand relay A are energized. By the energization of the auxiliary relay H the holding contact k1 is closed, the throw-over contact k2 is switched over, and the solenoids S1 and S2 are thereby deenergized and contact k3 is closed. At the same time, by the energization of relay A, the contacts a1 and a2 are closed, whereby the stator winding with the highest number of poles is switched on. The motor runs then at its low speed.

If thereafter by further operation of the pull rod 42 the contact t2 of the main switch C is closed, relay B and coil H2 of relay H will be energized and the condenser 37 be charged. Since the two coils H1 and H2 are wound in the same sense, the energization of winding H2 does not alfect the auxiliary relay H since the winding H1 is already energized. However, because of the energization of relay B, the contacts b1 and b2 are switched over so that the stator winding of the motor with the highest number of poles is switched off and the stator winding with a low number of poles is switched on. The motor then begins to run at its maximum speed.

If merely contact t2 of the main switch C is then switched off, relay B will be released so that the high-pole stator winding is again energized via the switch contacts b1 and b2. The motor shaft is then inductively decelerated to the lower speed. In the meantime, the condenser 37 discharges via the resistor 36 and the coil H2 of the auxiliary relay H. If thereafter also the contact 11 of the main switch C is switched off, the short circuit of solenoids S1 and S2 is interrupted s that before the angular position of the sewing machine shaft comes into the position as selected by the preselection switch 39, the contactor contact e will be closed and thereby coil H1 of the auxiliary relay H will be short-circuited. Coil H1 is thereby deenergized so that especially the holding contact hl is released whereby the supply line of the auxiliary relay H is interrupted. Relays A and D are then supplied merely through the pair of contacts 2. However, when the sewing machine shaft is in the desired angular position, the pair of contacts e will also be interrupted so that the high-pole stator winding will be switched off by the release of relay A and at the same time the brake will be engaged by the release of relay D.

If both contacts t2 and II of the main switch C are switched off in immediate succession, the auxiliary relay H will not be immediately deenergized when the contactor contacts 2 are being closed since coil H2 will still be supplied by the condenser 37 until the motor 1 is decelerated 6 to its lower speed. As soon as this occurs and the condenser 37 is discharged, the auxiliary relay H will be released and the proceedings will occur as described in the preceding paragraph.

The arrangement of the control elements have been described above, and especially of relays A, B, H, and D and the main switch C, of the filter means 33 to 35, the resistance- capacity unit 36, 37, and a terminal board 43 in the control box 23 which is connected to the motor housing, a very space-saving arrangement of the sewing machine drive is attained which may be easily inspected and permits repairs to be easily carried out.

Instead of attaining the time lag by a resistance-capacity unit, it is also possible to provide for this purpose a centrifugal switch (not shown) which is controlled by the speed of the motor shaft or sewing machine shaft. Such a centrifugal switch may be designed in such a manner that, when contact t2 of the main switch C is being switched off, the brake releasing coil L will be deenergized until the motor 1 is decelerated to the lower speed. When the motor 1 reaches this speed, the brake releasing coil L is again energized and will not again be deenergized until the relay A is released.

In place of two solenoids S1 and S2, it is also possible to employ a single solenoid in combination with a polereversing switch on the position indicator.

Although our invention has been illustrated and described with reference to the preferred embodiment thereof, we wish to have it understood that it is in no way limited to the details of such embodiment, but is capable of numerous modifications within the scope of the appended claims.

We claim:

1. A sewing machine drive, comprising an electric motor including a magnetically actuated brake for said electric motor and at least two separate windings with widely differing numbers of poles, a position indicator adapted to be connected to the shaft of a sewing machine and having a set of contacts for stopping the operation of said motor when said shaft is in a selected angular position, at least two relays including coils each operatively associated with one of said motor windings for energizing and disenergizing, respectively, the same, a main switch for rendering operative and inoperative, respectively, said relays, said main switch having one off position and at least two on positions, the number of on positions being identical with the number of said motor windings, a switch device having at least one set of contacts connected in series with said coil of one of said relays associated with one of said motor windings having the highest number of poles, said set of contacts of said switch device being actuable upon energizing any of said motor windings for actuating said one of said relays along a first supply path, said set of contacts of said position indicator being also connected in series with said relay associated with said winding with the highest number of poles for actuating said last mentioned relay along a second supply path, and means for energizing said magnetically actuated brake upon operation of said one of said relays in order to release said brake.

2. The sewing machine drive, as set forth in claim 1, which includes time-delay means for delaying the release of said one of said relays and holding it in the operative position for a predetermined time period upon disenergizing said switch device, said relay being associated with the motor winding with the highest number of poles.

3. The sewing machine drive, as set forth in claim 2, wherein said switch device comprises an auxiliary relay having two separate windings and a plurality of sets of contacts, including said at least one set of contacts, one of said windings of said auxiliary relay being connected in series with the coil of the other of said relays, associated with the other of said motor windings having the lower number of poles, said time-delay means comprises a resistance-capacity unit connected to said one Winding of said auxiliary relay, and the other of said windings of said auxiliary relay is connected in series with one of its own sets of contacts and in parallel with said set of contacts of said position indicator.

4. The sewing machine drive, as set forth in claim 3, in which said position indicator comprises a permanent magnet adapted to be connected to said sewing machine shaft, the magnetic axis of said permanent magnet extending at right angles relative to the longitudinal axis of said shaft, so that the magnetic field produced by said permanent magnet rotates about said axis of said shaft, upon rotation of the latter, and which includes at least two fixed solenoids, in which the magnetic fields of said solenoids have different directions relative to each other and are adapted to be magnified by said magnetic field of said permanent magnet when said shaft is in one of at least two angular positions related to one of said directions of said magnetic fields of said solenoids, means for selecting one of said solenoids for energization, and said sets of contacts of said position indicator comprising a pair of contact tongues adapted to be connected to each other when said magnetic field of the selected one of said solenoids is magnified by said magnetic field of said permanent magnet.

5. The sewing machine drive, as set forth in claim 4, in which said main switch has at least two sets of contacts, one set of said contacts is associated with said one of said motor windings and is connected in series with another of said sets of contacts of said auxiliary relay, said one set of said contacts of said main switch and said another set of said contacts of said auxiliary relay are connected in parallel with said solenoids.

6. The sewing machine drive, as set forth in claim 1, which includes control means for said electric motor constituted at least by said two relays and said auxiliary relay, and adapted to be supplied with and operated by a rectified current, and filtering means for smoothing said current.

7. The sewing machine drive, as set forth in claim 6, which includes a housing for said electric motor, a control housing connected to said housing for said electric motor, and said control means for said electric motor are mounted in said control housing.

8. The sewing machine drive, as set forth in claim 1, which includes an auxiliary motor and ventilating means connected to said auxiliary motor for cooling said main motor and said brake continuously during the operation of the sewing machine.

References Cited by the Examiner UNITED STATES PATENTS 1,751,424 3/1930 Rosenthal 310-62 2,604,864 7/1952 Merchant 1 12219 2,745,997 5/1956 Wessel ll22l9 2,847,956 8/1958 Hale ll22l9 3,061,696 10/1962 Peek 20087 3,149,593 9/1964 Johnson ll22l9 FOREIGN PATENTS 734,550 6/1953 Great Britain 892,823 3/ 1962 Great Britain.

ORIS L. RADER, Primary Examiner.

Claims (1)

1. A SEWING MACHINE DRIVE, COMPRISING AN ELECTRIC MOTOR INCLUDING A MAGNETICALLY ACTUATED BRAKE FOR SAID ELECTRIC MOTOR AND AT LEAST TWO SEPARATE WINDINGS WITH WIDELY DIFFERING NUMBERS OF POLES, A POSITION INDICATOR ADAPTED TO BE CONNECTED TO THE SHAFT OF A SEWING MACHINE AND HAVING A SET OF CONTACTS FOR STOPPING THE OPERATION OF SAID MOTOR WHEN SAID SHAFT IS IN A SELECTED ANGULAR POSITION, AT LEAST TWO RELAYS INCLUDING COILS EACH OPERATIVELY ASSOCIATED WITH ONE OF SAID MOTOR WINDINGS FOR ENERGIZING AND DISENERGIZING, RESPECTIVELY, THE SAME, A MAIN SWITCH FOR RENDERING OPERATIVE AND INOPERATIVE, RESPECTIVELY, SAID RELAYS, SAID MAIN SWITCH HAVING ONE OFF POSITION AND AT LEAST TWO ON POSITIONS, THE NUMBER OF ON POSITIONS BEING IDENTICAL WITH THE NUMBER OF SAID MOTOR WINDINGS, A SWITCH DEVICE HAVING AT LEAST ONE SET OF CONTACTS CONNECTED IN SERIES WITH SAID COIL OF ONE OF SAID RELAYS ASSOCIATED WITH ONE OF SAID MOTOR WINDINGS HAVING THE HIGHEST NUMBER OF POLES, SAID SET OF CONTACTS OF SAID SWITCH DEVICE BEING ACTUABLE UPON ENERGIZING ANY OF SAID MOTOR WINDINGS FOR ACTUATING SAID ONE OF SAID RELAYS ALONG A FIRST SUPPLY PATH, SAID SET OF CONTACTS OF SAID POSITION INDICATOR BEING ALSO CONNECTED IN SERIES WITH SAID RELAY ASSOCIATED WITH SAID WINDING WITH THE HIGHEST NUMBER OF POLES FOR ACTUATING SAID LAST MENTIONED RELAY ALONG A SECOND SUPPLY PATH, AND MEANS FOR ENERGIZING SAID MAGNETICALLY ACTUATED BRAKE UPON OPERATION OF SAID ONE OF SAID RELAYS IN ORDER TO RELEASE SAID BRAKE.

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