Ultrasonic Sewing Machine

Abstract

An ultrasonic transducer assembly including a horn, is mounted in a sleeve bearing for axial movement by gravity to bring the horn toward an anvil. A spring actuated lever presses the transducer assembly toward the anvil with the final spring pressed position determined by an adjustable stop. The lever may be rotated by control means against the pressure of the spring to withdraw the assembly from the stop and to release it thereafter for spring movement back against the stop. The spring pressure is adjustable to determine the pressure required to accept the reaction to the ultrasonic vibrations of the horn, and the stop is adjustable to determine the positioning of the assembly relatively to the anvil.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an ultrasonic sewing or seaming machine of the type in which two or more sheets of plastic material are moved over an anvil and are welded together by the action of a resonating horn of an ultrasonic transducer assembly contacting the material.

2. Description of the Prior Art

Ultrasonic sewing machines are quite well known in the art, and much effort has been expended in the development of a truly effective machine which is efficient, will not damage the material being welded, and is relatively free of complexity. So far as is known, no truly simple and satisfactory machine has as yet been contributed.

In some prior art structures, an ultrasonic transducer assembly is held fixed in a particular position by adjustable means which will position the transducer assembly so that there exists a gap of predetermined size between the horn of the transducer assembly and the anvil over which the plastic material to be sewed is passed. The ultrasonic transducer assembly is so held in position as it must accept the reaction of the vibrating horn. However, because the transducer assembly is held fixed, it is obvious that the reaction to the horn is rigid, and that any overdue extension of the horn through resonance may damage the material being sewed.

As an alternative to a fixed ultrasonic transducer, it has been proposed that the ultrasonic assembly be completely or partially counterbalanced and that the vibrating horn be applied to the plastic sheet material to be sewed without a reaction accepting force. For this purpose, the ultrasonic assembly is held by a system of levers which counterbalance the weight of the assembly. Because of the use of the levers, the transducer is adapted to move with its horn relatively to the axis of movement of the horn. Further, there is no effective acceptance of the forces imposed by the horn.

In a still further construction, the ultrasonic transducer assembly is mounted on bearings so as to move freely toward the anvil over which the materials to be sewed are passed, but no means are provided for adjusting the positioning of the transducer and its horn, the pressure with which the horn vibrations are applied to the anvil, or even the limiting of the movement of the ultrasonic transducer relatively to the anvil.

The diversity of opinion of experts in the art is apparent from a study of this prior art, and is further demonstrated by the fact that in other structures which have been developed by the art, the ultrasonic assembly is urged by a spring away from operative position, the movement of the assembly by the spring bringing the horn away from the anvil. Through the application of adequate pneumatic pressure, the force of the spring is overcome and the ultrasonic transducer together with its horn are urged toward the anvil and the material to be passed over the anvil. Naturally, the pressure so exerted by the pneumatic pressure must be relatively great in order to overcome the force of the spring. So far as is known, the purpose of this construction is to move the transducer head away from the work, and then toward the work when such movement is desired and to hold it against the work, and no attempt is made to determine the reaction pressures to be applied against the ultrasonic assembly to effect the welding of the materials. The assembly is, to all intents and purposes, held in a rigid adjusted position against spring pressure.

SUMMARY OF THE INVENTION

The concept on which the invention of this application is based, is at considerable variance from the concepts of the prior art. Further, the concept includes a combination of elements in order to contribute the results sought, and it is this combination that is important. Thus, it has been found, in accordance with the concept of this invention, that while the ultrasonic transducer assembly should not be held rigidly in position relatively to the anvil, it should nevertheless be held with sufficient force, so as to be capable of accepting the reaction of the horn movement, but with this acceptance being in a non-rigid manner. Therefore, it is one feature of the invention that the ultrasonic transducer, rather than being counter-balanced by spring forces or nearly freely movable toward an anvil, be pressed by a spring toward the anvil over which the materials to be sewed is passed and against a limit position, and that the spring force be in addition to gravity urging the transducer assembly towards the anvil.

As a further feature of the invention, the pressure of the spring must be adjustable so as to determine the degree of force to be used in acceptance of the transducer vibrations, but that the movement of the entire transducer assembly toward the anvil be limited by an adjustable limiting mechanism. The spring pressure is so developed and adjusted relatively to a limit stop for the transducer assembly that it is sufficient to accept the ultrasonic forces. However, the reaction of those forces is accepted on a firm but yet non-rigid and adjusted basis.

As a further feature of the invention, the ultrasonic transducer assembly is mounted for movement in an axis that is parallel to the axis of vibration of its horn, with the bearing holding the assembly against any movement relatively to the said axis.

As a further particular feature of the assembly, the spring pressure is exerted against the transducer assembly in such a manner that there will be little if any tendency to bind it relatively to its mounting, thereby permitting the force of gravity and the force of the spring to urge the transducer assembly toward the anvil. More particularly, it is a feature of the invention as to this part thereof, that the transducer assembly be mounted in a sleeve secured rigidly to the main frame of the machine, and that a spring pressed lever protrude through an opening in the sleeve at a location between the ends of the sleeve, and applied to a surface of the transducer assembly intermediately of the ends thereof, all for the purpose of urging the transducer assembly toward the anvil.

As a still further feature of the invention, the transducer assembly per se may be moved bodily in its axis of movement whereby to move its horn away from the anvil. This movement is imparted merely by moving, against its spring pressure, a lever which is spring pressed normally to urge the transducer and its horn toward the anvil. In other words, the said spring pressed lever is adapted to pivot in either of opposed directions, in one direction by spring and another direction by means such as simple manual means. In this manner, the transducer assembly may itself, rather than through its mounting means, be moved relatively to its mounting means in an extremely simple manner and very effectively in either of opposed directions. Those skilled in the art will appreciate the fact that the movement of the transducer assembly may be effected in this manner without in any way disturbing the adjustable sewing position of the transducer assembly on its mounting, nor the spring forces that accept with gravity the reaction of the ultrasonic vibration of the horn.

It may be said therefore, in summary, that the invention of this application is based not only on a combination of concepts, but also on particular structural combination that will operate most effectively under the theory of the concepts of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are believed to be characteristic of this invention are set forth in the appended claims. The invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a perspective view of a machine incorporating the instant invention;

FIG. 2 is an elevational view of the machine of FIG. 1, illustrating the relationship of the ultrasonic transducer head and the anvil with which it coacts;

FIG. 3 is a section of part of the main frame of the machine, illustrating the mounting of the ultrasonic transducer assembly for sliding and spring forced movement;

FIG. 4 is a section taken along line 4--4 of FIG. 3;

FIG. 5 is a section and partial elevation taken along line 5--5 of FIG. 3;

FIG. 6 is a diagrammatic view illustrating the control of a level for lifting the transducer assembly and horn away from the anvil, and

FIG. 7 is a sectional view taken along line 7--7 of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now more particularly to the drawings, the machine of the invention is designated generally in FIG. 1 by reference numeral 10, and is shown mounted on a table assembly 11 as is customary in the art. The table has several controls such as a speed control treadle 12, an electronic power supply 13, and additional means which will be discussed in detail hereinafter. The main frame of the machine 10 is formed substantially as a hollow casting, designated by reference numeral 15, and at one end of the casting there is secured a sleeve bearing member 16. As seen in FIGS. 3 and 4, the sleeve bearing member 16 is fastened to the body of the casting 15 by a pair of screws 17. The sleeve bearing member 16 may be formed as an integral part of the casting 15 of the machine, but it is more economical to fabricate it separately and secure it in position on the casting 15 as illustrated. The transducer assembly is adapted for sliding motion within the sleeve bearing member 16 as will now be set forth.

The electro-acoustic transducer assembly operating at an ultrasonic frequency, typically 25 kHz, is designated generally by reference numeral 20 and may be of any standard construction. A transducer assembly suitable for the present purpose is shown, for instance, in U.S. Pat. No. 3,328,610 dated June 27, 1967, S. E. Jacke et al. In the form illustrated in this embodiment, the transducer assembly is fitted with a cylindrical shell surrounding the transducer assembly and the shell is secured to the transducer assembly at its upper end by screw 21 and at its lower end by screw 22. As far as this disclosure is concerned, it is merely important to know that the transducer assembly 20 is of cylindrical shape adapted to fit within the sleeve bearing member 16 and is adapted to slide along the axis of the sleeve bearing member 16, which axis is incidentally, parallel and coincidental with the longitudinal axis of the horn 23 coupled to the ultrasonic transducer assembly.

The transducer assembly 20 is controlled in its sliding motion within the sleeve bearing member 16 by a bracket 25 which is secured to the outer shell and the transducer assembly by a pair of screw studs 26. The bracket 25 is secured to an intermediate part of the transducer assembly, that is, between the two ends thereof to provide that any motion transmitted to the bracket 25 and thereby to the transducer assembly 20 will not cause a binding of the transducer assembly within the sleeve bearing 16.

In order to secure the bracket 25 to the transducer assembly, the transducer assembly 20 is first placed within the sleeve bearing member 16, after which, through an open portion of the casting 15, the screws 26 are secured in position as best illustrated in FIG. 3.

For imparting movement to the bracket 25, there is disposed in the machine a compound lever 30, best seen in FIG. 6, having a shaft portion 31 which is mounted for pivotal motion in bearings 32 and 33. The compound lever 30 has, extending from one end of its shaft portion 31, a lever arm 34, FIG. 3, which has an end portion adapted to rest within a slot 35 of the bracket 25. It will be apparent that rotation of the compound lever 30 about the axis of the shaft 31 on bearings 32 and 33 will act to move the arm 34 so as to impart motion to the bracket 25. The lever 30 has a further arm 36, which is best seen in FIG. 7. Attached to arm 36 at 37 is a tension spring 38, the other end of the spring 38 being secured at 39 to a sliding lug 40 which is in screw threaded engagement with a rotatable screw threaded shaft 41. One end of the screw threaded shaft 41 extends outwardly of the casting of the machine and has secured thereto a dial knob 42 which may be suitably calibrated relative to an index mark on the casting. It is obvious that upon rotation of the knob 42 the lug 40 is moved to adjust the tension of the spring 38, and therefore the force through which the spring 38 imparts rotation to the compound lever 30 in the direction of the arrow 43 in FIG. 7. Rotation of the compound lever 30 by spring 38 will urge the lever arm 34 in the direction of the arrow 44, FIG. 3, and impart a downward motion upon the transducer assembly 20 disposed in the sleeve bearing member 16.

The downward motion of the transducer assembly 20 is limited by an adjustable cam 50 best illustrated in FIGS. 4 and 5. Cam 50 is an integral part of a rotatably mounted shaft 51, having a screw threaded portion 52 fitting within a screw threaded opening 53 formed in a part of the casing 15. Shaft 51 is formed with a knob 54 and it is obvious that by rotating the knob 54, the shaft can be moved in opposite directions as is indicated by arrows 55. A part of bracket 25, designated by reference numeral 56, bears against the cam surface 50 and will act to limit the downward movement of the cam surface 56 and therefore the bracket 25. This will limit the downward movement of the transducer assembly 20 and of the horn 23.

The horn 23 coacts with any form of standard anvil, here designated by reference numeral 60, and it is obvious that both gravity and the pressure of spring 38 will urge the horn 23 toward the rotatable anvil 60 and that the cam surface 50 coacting with the cam surface 56 of bracket 25 will determine the gap desired between the horn 23 and the anvil 60. The gap adjustment will be determined largely by the thickness and stiffness of the material to be sealed.

It can now readily be seen that the ultrasonic transducer assembly is adapted for both spring pressure and gravity movement toward a rigid adjustable stop relatively to an anvil, and that the degree of pressure exerted by the spring may be adjusted to hold the transducer assembly as forcibly as is desired against the stop to accept the reaction of the ultrasonic vibrations of horn 23, and that the forces so accepted may be accepted in a non-rigid manner even though fairly firmly if desired.

It is also clear that the transducer assembly is mounted for movement in a particular axis which, in this invention, is coincidental with the axis of the horn, and that its movement will be confined to that axis. It is also apparent that the transmission of motion to the transducer assembly is arranged in a manner to prevent the application of angular forces to the transducer assembly, so that free motion under the influence of the spring 38 and the lever 30 and its arm 34 is possible.

It may be well at this point to indicate that the upper part of the sleeve bearing member 16 may be capped by a cover 16C in order to prevent the movement of dust into the bearing formed by the sleeve bearing member 16 and to conceal the electrical connection from the power supply to the transducer assembly.

In order to withdraw the ultrasonic transducer assembly 20 for lifting its horn 23 away from the anvil 60 without disturbing the setting of the spring pressures or the limit mechanism contributed by the cam 50, the compound lever 30 is formed with a further arm 65 (FIG. 7) which is connected at 66 to a link 67, which through suitable connection at 68 is coupled to a shaft 69 suitably mounted in bearings 70 and 71. The bearings are affixed to a part 72 which forms the base of the machine 10 and, preferably, is integral with the hollow casting 15 thereof as earlier set forth.

Shaft 69 may be moved through a connection, such as a ball and socket joint 75, by a knee operable lever 76, and this movement will effect movement of the link 67 and the lever portion 65 of compound lever 30, so as to rotate the compound lever 30 in the direction of the arrow 80 in FIG. 7, opposite to the direction of the arrow 43 in which the compound lever 30 is rotated by the spring 38. Therefore, movement of the link 67 in this manner will cause movement of the lever arm 34 of the compound lever 30 opposite to the direction of the arrow 44 seen in FIG. 3, and this action, in turn, will produce movement of the transducer assembly 20 away from the anvil 60. As soon as the lever 76 is released by the operator, the spring 38 will be allowed to act, and it will restore the transducer assembly to its downward position with the limit surface 56 resting against the cam 50, and with the transducer assembly now held downwardly in this position by the force of both the spring 38, and the action of gravity.

The speed of rotation of the anvil 60 is controlled by the foot treadle 12 acting upon a motor (not shown) which is coupled to the anvil 60. The speed of rotation of the anvil controls the feed rate at which the material to be sewn is fed underneath the frontal surface of the horn 23.

Another important feature of the present invention, greatly enhancing the convenience of the machine as far as the operator is concerned, resides in the fact that the casting 15, see FIG. 1, is made in the form of a horizontally disposed "L" comprising a horizontal body portion 15a disposed substantially parallel to the front edge 11a of the table assembly 11 and a shorter leg portion 15b disposed at right angle to the body portion 15a and extending in a direction toward the front edge 11a. The sleeve bearing member 16 supporting the transducer assembly 20 is fastened to the leg portion 15b as previously described. This configuration leaves the seaming station substantially unobstructed for visual inspection from all sides and permits, moreover, the material to be fed through the sewing station without the usual bunching of material experienced with conventional sewing machines. Also, the forward tilting of the transducer assembly 20 and tip of the horn 23 greatly improves the visibility of the seaming station.

It is believed that the very considerable advance in ultrasonic sewing found in both the concept and the apparatus set forth in this application, will now be apparent to those skilled in the art.

Claims

What is claimed is:

1. In a machine of the class described comprising:

a main frame;

an anvil over which material to be sewed is moved;

an ultrasonic transducer assembly including a horn adapted to resonate and contact material passed over said anvil for providing ultrasonic energy to the material;

bearing means supported by said main frame for mounting said assembly for gravitational sliding movement toward said anvil in an axis parallel to the axis of vibration of said horn while holding said assembly against movement except along said axis;

a spring supplementary to gravity urging said assembly along said axis toward sand anvil and said spring applying pressure to said transducer assembly through means of a pivoted lever which is urged by said pressure in a direction corresponding to the movement of said assembly toward the material to be sewed;

adjustable means disposed for limiting the motion of said assembly in said bearing means toward said anvil;

means for adjusting the force of said spring to cause the pressure of said spring against said assembly with gravity to oppose the reaction forces effective upon said ultrasonic transducer assembly as said horn contacts the material, and

means for moving said lever independently and against the pressure of said spring in a direction reverse to that in which it is urged by said spring, while not disturbing the adjustment of said spring.

2. In the combination of claim 1, said lever being pivoted on said main frame and having a pressure surface pressing against said transducer assembly to urge said assembly in the direction of its gravitational urge, said spring moving said lever on its pivot against said transducer assembly.

3. In the combination of claim 1, said bearing means being a sleeve bearing; an opening in said sleeve bearing through which said lever extends toward said transducer assembly, and said transducer assembly having a surface intermediate of its length engaged by said lever whereby said lever imparts movement to said assembly in either one of opposed directions.

4. In a machine of the class described comprising:

a main frame;

an anvil over which material to be sewed is moved;

an ultrasonic transducer assembly including a horn adapted to resonate and contact material passed over said anvil for providing ultrasonic energy to the material;

bearing means supported by said main frame for mounting said assembly for gravitational sliding movement toward said anvil in an axis parallel to the axis of vibration of said horn while holding said assembly against movement except along said axis;

a spring supplementary to gravity urging said assembly along said axis toward said anvil;

adjustable means disposed for limiting the motion of said assembly in said bearing means toward said anvil whereby to provide a stop;

means for adjusting the force of said spring to cause the pressure of said spring against said assembly with gravity to oppose the reaction forces effective upon said ultrasonic transducer assembly as said horn contacts the material, and

lever means coupled to said transducer assembly and operable for moving when actuated said assembly bodily within said bearing means relative to said anvil against the force exerted by said spring in a direction reverse to that in which said assembly is urged by said spring, while not disturbing the adjustment of said spring, and when not actuated and in the absence of said reaction forces causing said assembly to rest against said stop.