United States Patent Oihce 2,808,238 Patented Oct. 1, 1957 CONCRETE VIBRATOR Clem H. Spitler, Dayton, Ohio, assignor to Master Vibrator Company, Dayton, Ohio, a corporation of Ohio Application August 9, 1955, Serial No. 527,228

9 Claims. (Cl. 2591) struction as well as the means and mode of operation of concrete vibrators, whereby such vibrators may not only be economically manufactured, but will be more efficient and satisfactory in use, adaptable to a wide variety of applications, and be unlikely to get out of repair.

An object of the invention is to incorporate in a tool of the kind described a universal commutator type of motor, and thereby to obtain in a concrete vibrator or "like device the well known advantages of such a motor.

Another object of the invention is to provide in the tool a thermal overload control whereby operation of the motor automatically will be interrupted in the event of overheating.

Still another object of the invention is to construct the motor and associated parts in a unitary assembly in a manner substantially precluding damage thereto from the strenuous conditions of=use associated with concrete vibratingv tools.

A still further object of the invention is to provide a generally new mode of mounting and of actuating the commutator brushes.

A further object of the invention is to provide a concrete vibrator possessing the advantageous structural features, the inherent meritorious characteristics and the mode of operation herein mentioned.

With the above primary and other incidental objects in view as will more fully appear in the specification, the invention intended to'be protected by Letters Patent consists ofthe features of construction, the parts and combinations thereo'ffand the mode of operation as hereinafter described or illustrated in the accompany drawings, or their equivalents.

Referring to the accompanying drawing wherein is shown one but obviously not necessarily the only form of embodiment of the invention,

Fig. 1 is a view of a concrete vibrator constructed in accordance with the illustrative embodiment of the invention and including the cable and switch mechanism associated therewith;

Fig. 2 is a view at an enlarged scale and in longitudinal section of the vibrator tool of Fig. 1;

Fig. 3 is a top plan view in detail of the commutator brush holder; and

Fig. 4 is a diagram of the electrical circuit by which the motor is activated and controlled.

Like parts are indicated by similar characters of reference throughout the several views.

Referring to the drawings, a power actuating unit in accordance with the instant invention, may in accordance with the illustrated embodiment of the invention take a form as shown in Fig. 1 wherein a concrete vibrating tool 10 is suspended from cable means 11, the latter ineluding electrical conductors 12 extending from a plug 13. The latter is adapted to be connected to a source of electrical power, which may be a portable power generating unit. There is interposed in the cable 11 and electrical conductors 12 a manually operated switch mechanism 14 by which the supply of electrical power to the concrete vibrator 10 may be controlled. Powered by the electrical current so supplied, a motor in the device 10 rotates an eccentrically mounted weight, as will hereinafter more clearly appear, for a gyrating motion of the device 10, which motion is under control of a relatively remotely located operator who holds the control switch 14.

Considering the vibrating unit or device 10 in greater detail, it may be seen to include a cylindrical housing 15, one end of which is internally threaded to receive a reduced diameter externally threaded end of a housing 16 which is thus aligned with and forms a continuation or eX tension of the housing 15. The connection afiorded is a rigid yet releasable one. Installed in the other end of the housing extension 16 is a rounded closure member 17 which may be integrally united with the housing extension as by means of a weld 18. Within the closure member 17 is a bearing 19 and there is received in the first mentioned or inner end of the housing extension 16 a bearing 21. An eccentrically weighted member 22 has its ends rotatably mounted in the bearings 19 and 21. Thus, the part 22 has aligned ends coaxially disposed in the housings 15 and 16 and a laterally offset portion 23 which in response to rotary motion of the part in the bearings 19 and 21 produces an unbalanced condition resulting in a swinging, gyrating motion of the housings 15 and 16.

The housing 15 provides a mounting for the motor, which includes a field assembly 24 concentrically arranged in the housing 15 and an armature 26 coaxially disposed therein. Forming in elfect an integral part of the arrnature 26 is a central shaft 27 which at its lower or one end extends through and beyond a bearing 28 and is formed with an irregularly shaped extension 29 received in a similarly shaped socket 31 in the part 22. Rotation of the armature 26, and of the shaft 27 which is a part thereof, is eifective rotatively to drive the weighted part 22.

The connection between the housings 15 and 16 is a releasable one in order that the housing extension 16 may be readily removed and replaced with the same or a like driven tool. It may be noted, in this connection, that the connection between the shaft27 and the part 22 is disabled by the act of separating the housings 15 and 16 and is enabled by relative motion of the housings in an opposite or approaching or assembling sense.

The bearing 28 is mounted in a plate 32 having upstanding finger portions 33 in contacting supporting relation to one end of the field assembly 24. At the opposite end, the field assembly 24 is engaged by one end of a spacer sleeve 34 which at its other end is in contacting supporting relation to an upper bearing plate 35. Recessed in the under surface of the plate 35 is a bearing 36 receiving the other or opposite end of the shaft 27.

The bearing plates 32 and 35, spacer sleeve 34 and field assembly 24 occupy an interconnected relatively stationary relation to one another by virtue of longitudinal bolts 37 which extend from the bearing plate 25 downward through the sleeve 34 and field assembly 24 to the bearing plate 32. The armature shaft 27 is, as has been seen, mounted for relative rotary motion in the bearings 28 and 36, and is held against longitudinal motion by shoulders 38 and 39 thereon respectively abutting the bearings as described.

The bearing plate 35, together with the adjacent end of the motor assembly, defines a chamber 41 in the pe ripheral area of which are "the bolts '37 and in the center of which is the shaft 27. A commutator ring 42 is fast on the shaft 27 in the space 41,.and it in turn is surrounded'bya non-conductive disc 43 on-whic'h' are oppositely disposed brushholders 44 and 45. Brushes 'ldand 47 are in respective holders 44 and 45 and are urged by respective springs 48 and 49 toward the center-area of the disc where they engage and ride on the surface of the commutator 42. The springs '48 and '49 insure a continuous contact of the brushes with the commutator ring despite vibration and other causes which may tend momentarily to break such contact.

in the periphery of the disc '43 are semi-circular cutouts 51 through which pass power supply leads to 'the motor assembly. Also, bracket-line feet 52 are fastened to the underside of the disc and rest on the field assembly 24. The dis'c'43 and 'feet'52 are formedwith aligned openings '53 for passage of the bolts 37 therethrough. According .to the construction and arrangement of parts, it will be understood, the disc 43 is held against rotation with the commutator ring '42 and in effect becomes a part of the interconnected assembly of relatively stationary motor elements.

The upper end of the device 10, or that end receiving the cable 11, is closed by a member 54 welded to'the top of housing 15, as at "55. Projecting upwardly from the body of part 54 is a tubular projection 56, to which is connected one end of the cable 11 and over which a strain relief spring 57 is fitted. At the opposite or inner end of the part 54 is a reduced diameter cylindrical portion 58 received in the upper end of the housing 15 and substantially abutting the upper surface of the bearing plate 35. The part 54 is open throughout its length for entrance of the conductors 12 into a space '58 above the 1 plate 35. The conductors 12 are suitably connected to the electric motor, within the housing 15, and interposed in such connection is a thermal overload switch 59 mounted on the bearing plate 35 in position to be subjected to the heat generated in bearing 36 and in the chambers or spaces 41 and 58. 'In the event of overheating, or of a rise in temperature above a predetermined value the switch 59 operates to .open the circuit through the motor and thus to discontinue its operation until the temperature has decreased, whereupon the circuit is automatically reclosed.

The thermal overload switch '59 is, or may be, of a conventional kind as are the electrical connections to and from the motor, of which the switch 59 is .a part. Thus,

and as shown in Fig. 4, the conductors 12 may be considered to comprise electrical leads 61 and 62 extending from a source of electrical power. The switch 14 is represented therein as of the double pole single throw kind which when it is closed tends normally to establish a circuit through line 61 to field assembly 24, brush 44, commutator ring 42, brush 45 and thence to field assembly 24 and back by way of lead 62. The thermal switch 59 is interposed in lead -61 and when open .interrupts the flow of current as described irrespective of the position of switch 14.

Concentricity of the housing members 15 and 16 is insured by accurately machining the contacting threaded surfaces thereof. Such surfaces are machined in concentric relation with the bores of the housing. The threaded connection between the housing member 15 and 16 maintains mechanical connection of the two units and provides a seal against entrance of water or other foreign materials to the inside of the vibrating unit.

The present vibrator construction utilizes a universal type A. C.-D. C. motor. Being of the commutator type, the motor may be connected to either single phase A. C. current or to a source of direct current. The motor is of high speed characteristics operating at approximately 28,000 R. P. M. under no load conditions. With the weight 22 applied thereto, and the entire unit comprising the housings 15 and 16 assembled, the rotation of the motor is in the neighborhood of 15,000 R. P. M. or slightly over. When the assembled vibrator is placed within a mass of fresh concrete the unit has a speed of approximately 8,000 to more than 12,000 R. P. M. depending on the consistency of slump of the concrete being vibrated. With such high speed operation the vibratory impulsesdelivered to the mass-of freshly poured plastic concrete are of high frequency which provides for better-compaction and working of the concrete than vibrators heretofore known. While there have been vibrators heretofore used which produce high frequency vibration of the concrete, such vibrators required special power supply units which produced high frequency A. C. current. By this is meant the frequency of the A. C. current was in excess of the standard or conventional 60 cycle current normally employed. The ability to use the present vibrator unit connected to either a standard 60 cycle single phase A. C. power supply or .a source of D. C. current while still producing high frequency vibration of the plastic cement is of considerable advantage since it eliminates the need for the contractor to provide a special power supply and permits use of conventional power supplies normally obtainable on any construction job. Prior to development of the .present unit, use of conventional power supply (60 cycle single phase A. C.) produced speeds of less than 3600 R. P. .M., .the maximum synchronous speed at no-load of the induction or squirrel-cage motors which have heretofore been used as the driving means for prior art vibrators.

The construction of the vibrator shown herein is such that a minimum amount of vibration is produced in the region of the commutator 42. The minimum amount of vibration at this particular point is achieved through use of the tapered weight '22. The design of this weight is such that a crossover of vibration is provided in the region of the commutator and itsassociated brushes. In other words, the vibrator shown herein "becomes in a sense a pendulum swinging about a center approximately at the area occupied by the commutator and the brush ring. The vibration eifect at this point is substantially neutralized, thereby improving the operation of the commutator inasmuch as the brushes 46 and 47 are not subjected to excessive vibration. The brushes therefore do not bounce or vibrate on the commutator and excessive wear and arcing is consequently eliminated.

From the above description it will be apparent that there is thus provided a device of the character described possessing the particular features of advantage before enumerated as'desirable, but which obviously is susceptible of modification in its form, proportions, detail construction and arrangement of parts without departing from the principle involved or sacrificing any of its advantages.

While in order to comply with the statute the invention has been described in language more or less specific as to structural features, it is to be understood that the invention is not limited 'to the specific features shown, but that the means and construction herein disclosed comprise but one of several modes of putting the invention into effect, and the invention is therefore claimed in any of its forms or modifications within the legitimate and valid scope of the appended claims.

Having thus described my invention, I claim:

1. A concrete vibrator having a contained electric motor, including a housing section open at its opposite ends, bearing plates received in the respective opposite ends of said housing section, a field assembly disposed be tween said plates, bolts extending longitudinally between said bearing plates and defining a unitary assembly of said plates and said field assembly armature means coaxially disposed in said assembly including a shaft rotatably mounted in said bearing plates, a commutator ring on said shaft, a brush mounting ring having its periphery interengaged with said bolts, brushes onsaid disc engaged with said ring, a cable passing closure for one end of said housing section, a .housing extension on the other end of said housing section, and a weight mounted in said extension and rotatably driven by said shaft, said weight being so formed and connected to said shaft that vibration effects in the area of said commutator and brush ring are substantially neutralized in operation of said motor.

2. A concrete vibrator according to claim 1, characterized in that said cable passing closure has a cylindrical portion received in said one end of said housing and substantially abutting the adjacent one of said bearing plates.

3. A concrete vibrator having a contained electric motor, including a cylindrical housing section open at its opposite ends, a motor field assembly concentrically mounted in said housing between the ends thereof, armature means coaxially disposed relatively to said field assembly and including a shaft projecting through and beyond the opposite ends of said assembly, bearing plates receiving the opposite ends of said shaft, one of saidv shaft ends extending through and beyond its respective bearing plate, a housing extension detachably mounted on one end of said housing section receiving said one end of said shaft, an unbalanced rotary Weight in said extension fixed to and driven by said one end of said shaft, tie bolts extending longitudinally between and through said bearing plates, a commutator ring on said shaft, a brush mounting disc surrounding said shaft and peripherally interengaged with said bolts, brushes on said disc engaged with said bolts, brushes on said disc engaged with said ring, and a cable passing closure on the other end of said housing.

4. A concrete vibrator according to claim 3, wherein electrical connections admitted through said closure are arranged to close a circuit through said brushes, characterized by thermal sensitive means in said housing and connected to said motor for opening said circuit.

5. A concrete vibrator, including aligned tubular housing elements containing respectively an electric motor and an unbalanced rotary weight driven thereby, the adjacent ends of said housing elements being in rigid telescoping engagement with-one another, a tubular cable passing member installed in the other end of the housing containing said motor and defining with the motor a space in the said last mentioned housing between said cable passing member and said motor, electric current conductors entering said last mentioned housing by way of said member and passing through said space to electrical connection with said motor to close a circuit therethrough, and commutating means respectively connected to one of said housing elements and to said motor and spaced from said weight to lie in an area of substantially neutralized vibration.

6. A concrete vibrator according to claim 5 wherein said motor includes a shaft having one end projecting into said space, characterized by a bearing plate for said one end of said shaft, and a thermal overload switch mounted on said bearing plate and interposed in said conductors.

7. A concrete vibrator having therein a rotary eccentric 6 weight, including aligned tubular housing members, the adjacent ends of which are in rigid telescoping engagement with one another, a closure member in the opposite end of one of said housing members, the rotary eccentric weight being supported within said one housing member, a cable passing closure member in the opposite end of said other housing member, a universal A. C.D. C. motor concentrically supported in said other housing, electric current conductors entering said last mentioned housing by way of said cable passing closure member and connected to said motor, and a thermal overload interposed in said conductors between said cable passing closure member and said motor, the construction and arrangement being such that said thermal overload is responsive to excessive temperature within said housing to deenergize the motor until said temperature falls below a predetermined maximum and means mounting said eccentric weight in predetermined spaced relation to said motor to substantially neutralize vibration adjacent to said motor.

8. A concrete vibrator including a rotary eccentric weight at one end thereof, a high speed universal A. C.- D. C. motor at the other end thereof, the output shaft of said motor being connected to said rotary eccentric weight, said weight being spaced from said motor to provide vibration cross-over in the region of said motor, a source of single phase cycle A. C. current or D. C. current to which the motor is connected, the construction and arrangement being such that under load the weight is rotated at a speed in excess 3700 R. P. M. when said motor is energized by single phase A. C. power or D. C. power.

9. A concrete vibrator having a pair of aligned concentric housings, including a universal A. C.D. C. motor in one of said housings, an eccentric rotary weight in the other of said housings directly connected to the output shaft of said motor for unison rotation therewith, a commutator assembly adjacent one end of said motor including a brush mounting ring, the construction and arrangement being such that the commutator and brush mounting ring are located at a point of minimum vibration of said unit, said point being at the crossover of vibration developed by said rotary weight.

References Cited in the file of this patent UNITED STATES PATENTS 1,132,992 Wood Mar. 23, 1915 1,552,079 Prescott Sept. 1, 1925 1,624,423 Milton Aug. 12, 1927 2,085,998 Potter July 6, 1937 2,089,249 Bruns Aug. 10, 1937 2,176,118 Brinda Oct. 17, 1939 2,232,842 Douglass Feb. 25, 1941 2,531,120 Feaster Nov. 21, 1950 FOREIGN PATENTS 500,861 Great Britain Feb. 16, 1939 676,439 France Nov. 28, 1929 851,908 France Oct. 16, 1939