US 2289962 A
Description (OCR text may contain errors)
SR j N 73*668 SEAEEFJ QML SUBSTITUTE FOR MISSING XR y J. E. HANCOCK 2,289,962
VIBRATION DEVICE Original Filed May 6, 1939 yam-5'0? 2 252 22522222? /4 0 ufidig fasf'pvza 1% La g; 42 2 1 my;
Inventor.- John )3. Hancock,
H is Attorney.
UNITED STATES PATENT OFFICE VIBRATION DEVICE John E. Hancock, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Original application May 6, 1939-, Serial No.
272,179. Divided and this application Novemher 6, 1941, Serial No. 418,077
This is a division of my copending application Serial No. 272,179, filed May 6, 1939.
My invention relates to systems for the generating of mechanical vibration, or vibration motors or devices, of the moving coil type for the vibration testing of materials over wide ranges and implitudes of vibration.
It is the general object of the invention to provide an improved vibration device of the above type which is capable of converting large electric power into mechanical vibrations of relatively high frequency without damage to the moving system or other parts of the device.
It is a particular object to provide in the vibration device an improved pickup coil arrangement for generating a small voltage proportional to the velocity of motion of the moving system and in which substantially no undesired voltage, due to external magnetic fields, is generated in the pickup coil.
It is va further object to .provide an improved moving system for the vibration device.
It is another object to .provide an improved locking means [for the moving system to permit rigid mounting of test pieces on the device without danger of damage to the moving system.
The novel features which are considered to be characteristic of my invention are set forth with particularity in the appended claims. My 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 drawing wherein Fig. 1 is a perspective view of a vibration device embodying my invention, and Fig. 2 is a cross-sectional view of the embodiment illustrated in Fig. 1.
Referring to the perspective view, Fig. 1, of the Vibration device embodying my invention, it will be understood that the moving system within the vibration device is supported by the frame I comprising the top, bottom, and side elements or plates 2, 3 and 4 of an electromagnet. A dome-like structure 5, or structure in the form of the frustrum of a cone, mounted on the top plate 2 serves to protect the drive coil or moving coil portion of the moving system from injury and also provides a mounting means for an upper bearing 6 through which a sleeve 1 and a key 8, attached to the upper end of a drive rod 9 projecting upwardly of the vibration device and threaded for the attachment thereto of test pieces, are slidable. A front plate II) which is connected to the frame I carries terminals |2 and I3 for attachment of field, drive, and' pickup coils, enclosed Within the frame, to suitable power or other devices (not shown) associated with the vibration device. A pin I4 is provided adapted to lock the moving system while test pieces are being attached to drive rod 9.
Referring more particularly to the cross-sectional view of Fig. 2, the electromagnet having the top, .bottom and side plates 2, 3 and 4 com- .prises an annular pole piece |5 connected to the top plate 2, and a central .core |6 of cylindrical form projecting upwardly through the pole piece I5 and spaced therefrom to form an annular airgap H. A field coil l8 surrounds the core IS. The moving system comprises the above mentioned drive rod 9, a moving coil or driving coil structure IS, a bar magnet 20, a pole piece 2| for the magnet 20, the upper bearing sleeve 1 which also functions as a drive coil locking sleeve, the key 8 fastened to sleeve 1, a coil locking cone 22, and a lower bearing member 23. The latter bearing member 23 projects through and is slidable in a lower bearing 24 mounted on the lower end of core IS.
The driving coil structure |9 comprises a cylindrical lower portion 25, in which is embedded a driving coil 26 within the air gap l1, and a cone-shaped upper .portion 2! locked rigidly to drive rod 9 by clamping between locking sleeve 1 and locking cone 22. The sleeve '1 and cone 22 are screwed to the drive rod. Th upper end of core I6 is of concave or hollowed out form, and in the space 28 enclosed between the coneshaped upper portion 21 of driving coil structure l9 and the upper end of core I6 is mounted a helical centering spring 29 the upper end of which is fastened to locking cone 22 and the lower end to a spider 30 mounted on the core l6. Openings 3| are provided in dome structure 5, and openings 22 in bearing and locking sleeve 1 and rod 9, through which openings pin M is adapted to be inserted, these openings being in aligmnent when the moving system is centered by a spring 29.
The rod 9 extends partially through a central opening 33 formed through the core IS. The :bar magnet 20 is mounted in a recess 34 formed in the lower end of the rod 9 and the pole piece 2| is connected to the rod and in contact with the magnet. The lower end of the pole piece 2| is connected to the bearing member 23 which is of non-magnetic material. Adjacent to the pole piece 2| a pickup coil 35 is mounted on the wall of the central opening 33 of core Hi.
In operation of the vibration device, the pin M is inserted in the openings 3| of dome 5 of the fixed, structure and openings 32 of sleeve 1 and rod 9 of the moving system, in order to lock the moving system in place while a test piece (not shown) is being attached to the upper end of drive rod 9. The test piece may, therefore, be attached rigidly to rod 9 without unduly straining the key 8 which cooperates with bearing 6. The pin I4 is then removed, leaving the moving system, centered by spring 29, free to vibrate in linear motion. Field coil l8 and drive coil 26 are next energized respectively from suitable direct current and alternating current sources (not shown). The moving system then vibrates longitudinally at a desired frequency, being guided by the widely spaced bearings 6 and 24, mounted respectively at the top of the dome structure 5 and the lower end of core 1'6 of the magnet structure, and being prevented from rotational movement by the key 8 slidable in the bearing 6.
It will be noted that the moving system, comprising the driving coil structure having the cylindrical coil supporting portion and the coneshaped upper portion, is extremely rigid while being also extremely light. It has been found that with this construction of the moving system the vibration device operates on large power input with high efiiciency, and that test pieces attached to the drive rod may be vibrated at relatively high frequencies and with relatively large amplitudes of vibration. Further, while the form and construction of the driving coil structure ensures rigidity and lightness in the moving system, the arrangement is at the same time very compact, the centering spring being mounted in the space enclosed between the upper concaved face of the cone and the cone portion of the driving coil structure.
As the drive rod 9 vibrates longitudinally, the pole piece 2| of permanent magnet is vibrated relatively to fixed pickup coil 35, a small voltage being thus generated in the latter coil. This voltage is proportional to the velocity of motion of the drive rod, and due to the shielded position of the coil inside the massive iron structure of the electro-magnet assembly, only a very small or negligible voltage will be induced in coil due to any external magnetic fields. The small voltage generated in the pickup coil 35 by the vibration of magnet 20 may be used for any suitable purpose, for example, to operate a vibration velocity meter, or as the input to an amplifier which supplies driving coil 26, in order to obtain self-sustained oscillations of the moving system at resonant frequencies.
My invention has been described herein in a particular embodiment for purposes of illustration. It is to be understood, however, that the invention is susceptible ofvarious changes and modifications and that by the appended claims I intend to cover any such modifications as fall within the true spirit and scope of my invention.
What I claim as new and desire to secure by Letters Patent of the United States, is:
1. In a vibration device for vibration testing of test pieces, a frame structure, a drive rod adapted to vibrate longitudinally in said frame, a bearing for said rod mounted in said frame, a second bearing for said rod, a key connected to said rod and slidable in said second bearing to prevent rotational movement of said rod during vibration thereof, a centering spring for said rod connected at one end to said rod and at the other end to said frame structure, supporting means for said second bearing connected to said frame structure, said supporting means and said rod having apertures formed therein which are in alignment when said rod is centered by said spring, and a pin adapted to pass through said apertures to prevent torsional strain upon said key and said second bearing when said test pieces are being attached to said rod.
2. In a vibration device, the combination with a magnetic field structure including an annular pole piece and a central core arranged to provide an annular air gap, of a drive rod adapted to vibrate longitudinally of said core, a bearing for said rod, a hollow cone-shaped supporting member for said bearing mount-ed at its larger end on said field structure, a moving coil structure having a portion carrying a drive coil in said air gap and a cone-shaped portion without said air gap and within said hollow supporting member, the face of said central core adjacent to said hollow supporting member having a cavity of substantial depth formed therein, means to connect said cone-shaped portion at its smaller end to said rod, and a centering spring for said rod mounted in the space between the bottom of said cavity and said cone-shaped portion and connected at one end to said core and at the other end to said smaller end of said coneshaped portion.
JOHN E. HANCOCK.
See: Rayment, 2,118,862, Glass 172-126 (22575).