US2702016A

US2702016A - Sewing machine

Info

Publication number: US2702016A
Application number: US274145A
Authority: US
Inventors: Franklin A Reece
Original assignee: Reece Corp
Current assignee: Reece Corp
Priority date: 1952-02-29
Filing date: 1952-02-29
Publication date: 1955-02-15
Anticipated expiration: 1972-02-15

Description

Feb. 15, 1955 F. A. REECE 2,

SEWING MACHINE P iled Feb. 29, 1952 s Shdets-Sheet 1 FeB; 15, 1955 A. REECE 2,702,016

SEWING MACHINE Filed Feb. 29, 1952 5 Sheets-Sheet 2 Feb. 15, 1955 F. A. REECE'S 2,702,016

sums MACHINE.

Filed Feb. 29, 1952 5 Sheets-Sheet a Feb. 15, 1955 F. A. REECE 2,702,016

SEWING MACHINE Filed Feb. 29, 1952 5 Sheets-Sheet 4 Feb. 15, 1955 F. A. REECE 2,702,016

, SEWING MACHINE Filed Feb. 29, 1952- 5 Sheets-Sheet 5 United States Patent SEWING MACHINE Franklin A. Reece, Broolrline, Mass, a'sslgnor to The Reece Corporation, Boston, Mass, a corporation of Massachusetts This invention relates to sewing machines and more particularly to clutch and stop mechanism for such mac mes.

The present day power-operated commercial sewing machines operate at an extremely high rate of speed because of requirements for a high capacity of production. Such machines include buttonhole forming machines of various types, button sewing machines, overedgingmachines, label sewers, and the'like.. These machines are required to make a quick start, to sew at a high rate of speed, and then to come to a quick and positive stop at a. predetermined point, for instance, after sewing a predetermined number of stitches. A buttonhole machine sews at rates of 1800 to 3000 stitches per minute. The time element is so important in such repetitive continual operations, partly due to modern labor costs and other factors, that constant attempts are being made to obtain evenfaster cycles of operation,

i a matter of one or two second in each cycle having considerable effect on production capacity over an extended period of operation. While such a machine is being used, the power drive motor is in continuous operation. Therefore, in starting and automatically stopping the machine, a clutch mechanism isrequired to disconnect the driven parts from the driving elements, and a stop mechanism is required to operate in conjunction therewith to bring the driven parts to a positive stop automatically at a predetermined point at substantially the same time that the clutch is automatically disconnected. The stop mechanisms in previous machines have operated generally on the principle of a positive mechanical interruption of the rotation of the driven part, for instance, by the automatic interposing of a finger which abuts solidly, although cushioned, against a rotating part and brings it to an abrupt stop usually within a turn of the driving shaft. Cushioning devices such as heavy springs are used to absorb some of the shock of the sudden stop, but, nevertheless although such mechanisms operate well, the practical limit of speed at which they operate eificiently has been reached. Many such machines stop with such violence as to put a severe strain on the driven parts which add greatly to maintaining the parts in proper adjustment and timing one to the other. Therefore the stop motion is the limiting factor for speed.

Stop mechanisms using frictional stops would eliminate much of the shock and vibration referred to and provide a smoother stop, but they have not been satisfactory to date because of the inaccuracy of the stopping position-which must be established within close limits in this typeof machine. These machines vary in speed from time to time, one example being the first operations of the machine in the morning when the oil has not been warmed up, and there is more friction in the parts which removes more momentum from the machine than when running at full speed. It has heretofore been difficult to bring a machine to a positive stop by friction means under suchconditions of varying momentum.

This invention overcomes the .above difiiculties and limitations by providing a sewing machine, the driven parts of which can be operated at greater speeds than possible with previous machines having the usual clutch and stop mechanisms and in which at the same time the driven parts are engaged smoothly to the driving parts and are brought to a smooth and comparatively noiseless yet positive stop at a predetermined point as required.

ice

As will become apparent from the detailed description, the invention takes advantage of the benefits of smooth operation obtainable in friction type clutch and stop mechanisms. In operation, a preliminary braking action is exerted so as to remove most of the momentum of the moving parts before they arrive in the stop position. After this momentum has been removed and the machine has slowed down to 10% or 15% of its normal running speed, a large braking force is applied which stops the machine in a few degrees turn and as a result of this, the stopping position is established sufliciently accurately for practical purposes. Stated otherwise, the invention takes advantage of the fact that if a rotating part has small interia or momentum and a very heavy braking force is applied, it cannot deviate much from a continually consistent and closely located stop position. The smallness of the inertia or momentum when the heavy braking force is applied causes this result. On the other hand, if a rotating part has a large inertia or momentum and also a varying one, a constant braking force will cause a large variation in the stop position.

The invention is applicable in combination with any power' operated sewing machine where it is required to.

engage and disengage driven mechanism with driving mechanism and to bring the driven mechanism to a predetermined stop.

in the illustrative embodiment, the invention is shown in connection with the operation of the drive shaft for actuating the stitching mechanism in a machine of a general type adaptable for forming buttonholes.

In the drawings:

Fig. 1 shows a side elevation partly in section and partly broken away of a machine embodying the invention;

Fig. 2 is a detailed view partly in section taken along the lines 22 of Fig. 1;

Fig. 3 is a view similar to Fig. 2 with other parts taken in section showing the parts in stopped condition;

Fig. 4 is a view similar to Fig. 3 showing the parts in running condition; and

Figs. 5 to 10, inclusive, show a wiring diagram with the switches and circuits in various conditions of operation.

In the drawings in Fig. 1 the machine is shown assembled around a base 10 and it includes stitching mechanism comprising a needle 12 mounted on a needle bar 13 operating in an overhanging arm 14. The needle bar 13 is connected to be reciprocated vertically in the usual manner as by a rocker arm 16 and link 17 actuated by an eccentric 18 which is fast on a stitching mechanism drive shaft 20, as shown in Fig. 2. When engaged, as further described, the drive shaft 20 is driven through a belt 21 by suitable power means, such as an electric motor 22 mounted underneath the base 10.

Referring to Figs. 2-4, the belt 21 runs over a pulley 25 which is loose on the shaft 20 but connected fast to a drum shaped clutch driving element 26 which is rotatable within a fixed annular hollow shell 28 surrounding the clutch mechanism indicated at A. The driving element 26 includes a non-ferrous ring 27 preferably made of brass in order to avoid interference with the action of the magnetic field set up in the mechanism as will be described. The pulley 25 and driving element 26 are rotatable as a unit independently of the shell 28 and also of the shaft 20, being supported relative thereto in bearings 30 and 31, respectively. Keyed or otherwise made fast to the shaft 20 is a clutch driven element 35, the cylindrical peripheral surface 36, and the end surfaces 37 of which are in close proximity to corresponding

inner surfaces

40 and 41 of the driving element 26, thereby forming a gap or air space 45 between the driven element 26 and the driving element 35.

Disposed in the space 45 between the surfaces of the driving and driven elements is a quantity of finely divided magnetic material 50i. e. material which can be magnetized such as powdered iron and the like. The quantity of this material in' the space 45 is such that .the driving and driven

elements

26 and 35 can run substantially freely of each other for practical purposes when the finely divided magnetic material 50 is unmagnetized. Fixedly contained in the shell 28 is a magnetic coil 55,

' having a pair of connecting leads 56. When no electric current is introduced to the coil 55 through the leads 56, the belt 21, pulley and driving element 26 run free and the driven element and drive shaft 20 remain stationary. However. when the coil is energized by closing an electric circuit through the leads 56, the magnetic material 50 being within the magnetic field of the coil 55, becomes magnetized and assumes a structural pattern forming a bond which connects the driving element 26 to the driven element 35 so that the shaft 20 and therefore the needle bar 12 is operatively engaged to be driven by the drive motor 22.

Also keyed or otherwise made fast to the shaft 20 is a generally cylindrically shaped stop element which is housed within a fixed shell 62 surrounding stop mech anism indicated at B. The element 60 has a cylindrical peripheral surface 64 and end surfaces 65 in close proximity to corresponding inner surfaces 68 and 69 of the shell 62, thus forming a space of air gap 70 between the stop element 60 and the shell 62. The shell 62 has a non-ferrous, usually brass ring 63 to avoid interference with the action of the magnetic field to be described. Disposed throughout the space 70 is a quantity of finely divided magnetic material 50', similar to the material in the clutch assembly and in such quantity as to allow substantially free running of the stop element 60 when the material 50' is demagnetized. Fixedly mounted in the shell 62 and surrounding the stop element 60 and the magnetic materiai 50' is a magnetic coil having leads 76. When the coil 75 is die-energized, the shaft 20 and stop element 60 can run substantially free of the fixed shell 62, but when the coil 75 is energized by the closing of an electric circuit through the leads 76, the magnetic material 50' becomes magnetized assuming a structural pattern forming a bond between the surfaces of the stop element 60 and the inner surfaces of the shell 62. When the driven mechanism, including the drive shaft 20'is running, a comparatively small amount of current in the coil 75 causes the stop mechanism B to act as a braking device and a larger amount of current in the coil 75 stops and locks the stop element 60 and shaft 20 against rotation.

The clutch mechanism A and the stop' mechanism B operate in cooperation with each other. When the clutch is engaged to drive the shaft 20, the stop mechanism coil 75 is de-energized to allow free running of the shaft 20. However, when'it is desired to bring the driven mechanism to a stop, the clutch coil- 55 is de-energized to disengage the clutch, and the coil 75 is energized pref erably in increasing increments of current passing through the coil so as first to exert a braking action on I the driven mechanism and then to bring it to a positive stop. at a predetermined point. Fig. 3 is intended to illustrate'the parts with the driven mechanism in stopped position, the coil 55 being de-energized to disconnect the shaft 20 from the pulley 25 and the coil 75 being energized to stop and lock the shaft 20 at a predetermined point. Fig. 4 is intended to show the parts in running condition with the coil 75 de-energized and the coil 55 energized to connect the pulley 25 to the shaft 20. In these figures the energized magnetic material is shown as darker while the de-c'nergized material is lighter.

Referring to Fig. 2, mounted on the shaft 20 is a selector switch mechanism comprising two pairs of switch actuating eccentrics a, 80b and 81a, 81b, respectively, adapted to actuate two pairs of timing switches 85a, 85b, and 86a and 86b, only one switch 85a being shown in Fig. 2, the others being indicated in the wiring diagrams Figs. 5 to 10, since these switches are all of the same type. As will be further described, the switches 85a and 85b are in one timing circuit, and their actuating eccentrics 80a and 80b are adjusted so that both switches 85a and 85b are open only during fifteen degrees of one revolution of the drive shaft 20. Likewise the switches 86a-and 86b are in another timing circuit and their actuating eccentrics 81a and 81b are also adjusted so that both switches 86a and 86b are open only during fifteen degrees of the rotation of the drive shaft 20, the latte1 fifteen degree open position of the switches 86a and 86b being 180 degrees later than the fifteen degree open position for the switches 85a and 85!). These switches are used in pairs as a practical matter so that their respective circuits can be precisely adjusted to be open only during the desired number of degrees of rotation of the 4 shaft 20 and relative to each other and otherwise closed, all in timed relation with the rotation of the shaft 20.

Referring now to Fig. 5, a volt alternating current line 110 supplies current to the primary winding 111 of a transformer 112. When the machine is at rest and ready to start with the drive motor 22 running but with a starting switch 115 open and with all the other switches in the condition shown in Fig. 5, a ten volt current passes from the secondary winding 116 of the transformer 112 through a pair of

lines

117 and 118 to a current converter 120 for converting alternating current into direct current and from the converter 120 ten volts direct current passes in a closed circuit to energize the magnetic coil 75 in the stop mechanism B through

lines

123, 124 and 125 and a switch element of a relay 130 which is in the left hand position as shown with its coil 131 de-energized. The passage of the ten volt current through the coil 75 holds the drive shaft 20 in stationary position. In order to start the machine, the start switch 115 is closed manually or by other suitable means as shown in Fig. 6. Current now passes from the line 110 to energize the coil 141 of a relay by way of a line 142,

the switch 115, a line 143, and a line 144 back to the line 110. When the relay coil 141 is energized, a pair of

switches

145 and 146 are moved from left to right hand position as shown in Fig. 6, completing a five-volt circuit to energize the coil 151 of a relay by way of a five volt lead passing from the secondary winding 116 of the transformer 112, a current converter 161 for converting five-volt alternating currents into direct current, a wire 162. the switch 146 and a wire 163 to one side of the coil 151 and from the other side of the coil 151 through a wire 164 and back to the secondary coil 116 by way of the wire 123, the converter 120 and either of the wires 117 01:118. The closing of the switch 145 completes a circuit to energize the coil 131 by way of the wire 124 from .the converter 120 on one side and through a wire 132, the switch 145, and a wire 147 passing through the timing switches 86a and 861) which are in closed position and thence back to the other side of the converter 120 by way of the wire 123. When the relay coil 131 is thus energized, the

switches

135 and 136 of the relay 130 are moved from left to right-hand position and when the coil 151 of the relay 150 is energized, the relay switches 155, 156 and 157 are moved from left to right-hand position. These switches are shown in Fig. 6 in the process of moving from left to right-hand position.

In Fig. 7 the switches of the

relays

130 and 150 have completed their movement to right-hand position as shown. The circuit through the stop mechanism coil 75 is now broken and the coil is de-energized, thus releasing the shaft 20 from locked condition. The

switches

136 and 157 each forms a holding circuit from the wire 123 to the right-hand side of the relay coil 131, the current returning to the converter 120 from the coil 131 through the wire 124. The switch 156 forms a holding circuit to the left-hand end of the relay coil 151 from the wire 162 across the timing switches 85a and 85b and also across a stop switch through a wire 171 across the switch 156 and a wire 172, theright-hand side of the coil 151 being connected to the wire 123 and returning to the converter 120. The starting switch 115 may now be released to de-energize the relay coil 141 allowing the

switches

145 and 146 to return to left-hand position, but the relay coils 131 and 151 remain energized through their holding circuits maintaining their respective switches in right-hand position as shown in Fig. 7.

The magnetic coil 55 of the clutch A is now energized by passage of current to its right-hand side from the converter 120 through the wire 123 and to its left-hand side through a wire 152, the switch 155, a wire 153 from the switch 135 and thence from the wire 124 and the other side of the converter 120. This engages the clutch A and the shaft 20is now in motion for the sewing operation.

Sewing now continues until the normally closed stop switch 170 is opened by movement to the right as shown in Fig. 8, either manually or automatically as desired, for instance, after the sewing of a row of stitches of a predetermined length as determined by the movement of a work table or work clamp which movement may be adapted in any desired manner to open the switch 170. With the switch 170 open during the next rotation of the drive shaft 20, the switches 85a'and 85b are successively opened, thereby interrupting the holding circuit through the

wires

171 and 172 and switch 156 tothe relay coil 151, thus allowing the

switches

155, 156 and 157 to move to the.

Referring to Fig. 9, following the interval that the tim ing switches 85a and 85b are both open, one of these switches and then the other closes to form a five volt circuit to the magnetic coil 75 of the stop mechanism B through the wire 171, the switch 156 and the wire 125 on one side and the wire 123 on the other for the next 180 degrees of rotation of the shaft 20. The five volt current causes the stop mechanism B to act as a brake to slow the shaft 20 during 180 of rotation and to cushion the shock of a sudden stop. Following the half turn of the shaft 20 during which five volts pass through the magnetic coil 75, the switches 86a and 86b are both automatically held open for a brief part of the rotation of the shaft 20.

Referring to Fig. 10, this interrupts the holding circuit to the relay coil 131 through the wire 147 allowing the relay switches 135 and 136 to move to the left. This movement to the left of the switch 135 now establishes a l volt circuit through the magnetic coil 75 of the stop mechanism B directly from the converter 120 through the

wires

123, 124, 125 and the switch 135, bringing the shaft to an immediate stop. l

1 It will now be seen that by adjusting the timing switch operating eccentrics 80a, 80b, 81a and 81b angularly with respect to each' other on the shaft 20, the application of the smaller amount of current for exerting the braking action on the shaft 20 can be timed with respect to the application of the larger amount of current for bringing the shaft to rest so that not only can an adequate cushioning or braking action be applied as required but also the shaft may be brought to a stop at a desired predetermined point after operation of the stop switch 170.

in summary, when the machine is at rest with the drive motor opertaing to turn the belt 21 but with the driven parts including the drive shaft 20 inoperative, no current passes through the magnetic coil 55 of the 'clutch mechanism A, but a ten volt current is passing through the magnetic coil 75 of the stop mechanism B to hold the shaft 20 in locked position. Thereafter when the switch 115 is operated to start the machine, the current is cut off from the stop mechanism magnetic coil 75 and a ten volt current is introduced through the magnetic coil 55 of the clutch mechanism A to connect the drive shaft 20 to the belt 21 and the machine continues to operate as desired until operation of the stop switch 170 occurs. Upon operation of the stop switch 170, the current is cut out of the coil 55 to disconnect the belt 21 from the shaft 20 and simultaneously first a five volt current is introduced into the coil 75 to cause a braking action upon the shaft 20 for approximately one-half turn of the shaft and then a larger ten volt current is automatically introduced to the coil 75 to bring the shaft to a positive stop at a predetermined position as determined by the adjustment of the timing switches 85a, 85b and 86a, 86b and their actuating eccentrics 80a, 80b and 81a, 81b.

I claim':

1. Astop mechanism for a rotating driven shaft to bring said shaft to a stop at a predetermined point after a succession of continuous complete revolutions comprising in combination a rotatable element fast on said shaft, a fixed element in close proximity to said rotatable element, finely divided magnetic material disposed between said elements, a magnetic coil in proximity to said material, an electric circuit supplying selectively variable amounts of current to said coil, a stop switch operable to energize said circuit, and a, selector switch mechanism operating when said circuit is energized to connect progressively increasing amounts of current from said circuit to said coil, said selector switch mechanism being operated by said shaft and in accordance with its progressive rotational position thereby in progressive steps increasing the bond between said rotatable'and fixed elements to a degree sufficient to stop said shaft at the termination of a predetermined angular movement following the actuation of said stop switch.

2. A stop mechanism for a rotating driven shaft to bring said shaft 10 a stop at a predetermined point after a we cession of continuous compete revolutions comprising in combination a rotatable element fast on said shatt, a tilted eiement in close proximity to said rotatable element, finely divided magnetic material disposed between said elements, a magnetic coil in proximity to said material, an electric circuit supplying selectively variable amounts of current to said com, a stop switch operable to energize said circuit, a plurality of timing switches operating when said circuit is energized to connect progressively increasing amounts of current from said circuit to said can, and switch operating means rotated by said shaft and successively operating said switches in accordance with its progressive rotational position thereby in progressive steps increasing the bond between said rotatable and fixed elements to a degree suiticient to stop said shaft at the termination of a predetermined angular movement t'oliowmg the actuation of said stop switch.

3. A stop mechanism for a rotating driven shaft to bring said shaft to a stop at a predetermined point alter a succession of continuous complete revolutions comprising in combination a rotatable element fast on said shaft, a nxed element in close proximity to said rotatable element, finely divided magnetic material disposed between said elements,

amagneuc coil in proximity to said material, an electric circuit supplying selectively variable amounts of current to said coll, a stop switch operable to energiae said circuit, a plurality of timing switches operating when said circuit is energized to connect progressively increasing amounts or current from said Cll'CUll. i0 said coil, switch operating means rotated by said shaft and successively operatuig said switches in accordance with its progressive rotational position thereby in progressive steps increasing the bond between said rotatable and fixed elements to a degree sulficient to stop said shart at the termination of a predetermined angular movement IOllOWlllg the actuation of said stop switch, the said switch operating means being ad ustable in spaced relation with respect to each other and with respect to the rotational position or said shart thereby to ad ust the stop position or said shaft.

4. A sewing machine including stitching mechanism, power means to operate said stitching mechanism including a driven shart, means connecimg the driven shaft to the stitching mechanism operating the stitching mechanism in predetermined fixed relation to the rotation or the shaft and a mechanism to stop said driven shait and stitchingmechanism at a predetermined point after a succession of continuous complete ICVOlUtlOIlS or the shaft, saidmechanism comprising a' rotatable element fast on said shaft, a f xed element in close proximity to said rotatable element, finely divided magnetic material disposed between said elements, a magnetic coil in proximity to said material, an electric circuit supplying selectively variable amounts of current to said cou, a stop switch operable to energize said circuit, and a selector switch mechanism operating when said circuit is energized to connect progressively increasing amounts of current from said circuit to said coil, said selector switch mechanism being operated by said shaft and in accordance with its progressive rotational position thereby in progressive steps increasing the bond between said rotatable and fixed elements to a degree sufficient to stop said shaft and stitching mechanism at the termination of a predetermined angular movement of the shaft following the actuation of said stop switch.

References Cited in the file of this patent UNITED STATES PATENTS 2,259,574 Lillquist Oct. 21, 1941 2,546,393 Hale Mar. 27, 1951 2,573,065 Salemme Oct. 30, 1951 OTHER REFERENCES Technical Report 1213, National Bureau of Standards, Washington, D. C. Copy received in Div. 68 on March 30, 1948, l92-Magnetic Fluid Material.