US 3559984 A
Description (OCR text may contain errors)
United States atent  lnventor Dan P. Westra Grand Haven, Mich. [2 l Appl. No. 736,856  Filed June 13, 1968  Patented Feb. 2, 1971  Assignee The Challenge Machinery Company Grand Haven, Mich.
a corporation of Michigan  JOGGING APPARATUS 19 Claims, 13 Drawing Figs.
 US. CL... 271/89  B65h31/34 50 Field of Search 271/89  References Cited UNITED STATES PATENTS 3,252,703 5/1966 Peugnet 271/89 Primary Examiner-Richard E. Aegerter Attorney-Price, Heneveld, Huizenga & Cooper ABSTRACT: An apparatus for vibrating stacks of paper stock or the like into aligned relationship with one another including a paper supporting table flexibly suspended above a suitable framework. The table has a shaft rotatably affixed thereto and the shaft is provided with adjustable offcenter weights at its extremity. Rotation of the shaft imparts vibration to the table, the degree of such vibration depending upon the adjustment of the weights. The apparatus is constructed such that the table may be tilted about the axis of the shaft and, thus, the dn've motor may be positioned on the support framework without necessitating readjustment of the driving mechanism each time the table angle is readjusted.
PATENTEU FEB 2 |97| SHEET 2 UF 4 INVENTOR. 044/ 1053724 SHEET '4 OF 4 PATENTEU FEB 2 IBYI INVENTOR. 004/ P. Mew/4 .IOGGING APPARATUS This invention relates to jogging apparatus and. more particularly. to such apparatus particularly adapted for vibrating stacks of paper stock or the like into aligned relationship so that it may be further processed.
In the paper-processing field it is often necessary to align a plurality of sheets. cards or the like into registry with one another in order that they may be further processed or packaged. Paper received from a cutter. press or the like. for example. must often be so aligned prior to further printing or cutting operations This alignment or registering is effected generally by positioning the stack of material in a vibrating table or tray with one or more of the edges thereof abutting an alignment guide. The table is then vibrated causing the individual sheets to come into alignment with the guide and. thus, into overlying registry with one another.
Devices for accomplishing the aligning function noted above are referred to in the art as joggersfj The prior an is replete with varying types of these apparatus. These prior art devices vary widely in both sophistication and complexity.
It has been proposed, for a example. to impart vibration to the paper supporting table or tray by means of a shaft rotatably affixed thereto having offcenter weights thereon. Means are provided for imparting rotation to the shaft and the offcenter characteristics of the weights causes it to vibrate and, thus, vibrate the table. The table or tray in such a situation, of course. is flexibly positioned above the framework of the apparatus by means of springs or the like. Joggers of this type usually include, additionally, some means for adjusting the offcenter weights such that the degree of vibration imparted to the table or tray may be altered depending upon the types of material being processed. Devices of this type are shown, for example, in US. Pat. No. 2,573,]64 to Scheinker and No. 3,062,539 to Obenshain.
Devices of the general type shown in these two patents suffer from a number of disadvantages. It is usually desirable, for a example, to make the paper supporting tray or table adjustable with respect to the horizontal so that differing weights or paper stock or the like may be jogged at differing angles. The necessity of providing a drive mechanism for the shaft, heretofore, required that the drive motor be tilted along with the table as a means of obviating the necessity of readjusting the drive mechanism each time the table tilt was readjusted. Difficulty has been experienced, additionally, in adjusting the degree of vibration of the table since the weights have been placed in relatively inaccessible positions within the joggers because of design considerations. Devices of this type, obviously, are somewhat awkward to utilize in the working environment.
Apparatus of the type described must include additionally, as noted, some type of structure for flexibly suspending the paper supporting table or tray with respect to the framework of the apparatus. Prior art proposals in this regard include primarily varying configurations of leaf springs, coil springs or the like. Suspension devices of this type have proved satisfactory with many types of joggers. They have contributed, however, to the problems of weight excessability and driving adjustments noted above in the weighted shaft type of jogger.
It is an object of this invention, therefore, to provide a jogging apparatus which is no not subject to the disadvantages outlined above.
It is an object of this invention, more particularly, to provide a jogging apparatus employing an offcenter weighted shaft to impart vibration to the table or tray wherein the offcenter weights and, thus, the degree of vibration of the apparatus, can be readily adjusted by the operator.
It is yet a further object of this invention to provide an apparatus of the type described having a paper supporting table or tray which can be tilted at any desired angle with respect to the horizontal without necessitating readjustment of the drive mechanism and, yet, wherein the drive motor is mounted on the nontilting portion of the apparatus. The apparatus which is the subject of this invention, thus, can be adjusted with relative ease.
It is yet another object of this invention to provide an apparatus of the type described embodying a flexible suspension structure between the paper-supporting table or tray and the frame of the apparatus which isolates effectively the base of the structure from tray vibration and which, additionally, structurally and functionally interrelates to other components of the apparatus in such a manner as to provide a highly efficient machine.
It is still another object of this invention to provide a weight adjustment mechanism on the apparatus which is easily accessible from the exterior of the machine; which may be positively adjusted to obtain the desired degree of vibration and, yet, which may be utilized effectively by persons having minimal familiarity with the apparatus.
It is also an object of this invention to provide an apparatus of the type described embodying a minimum number of components and, thus, an apparatus which may be fabricated and distributed at reasonable cost. In this regard, additionally, it is an object of this invention to provide such an apparatus wherein the simplicity of the components maximizes their life expectancy while minimizing the number of necessary repairs, replacements and the like.
These and other objects of this invention will be readily understood by those skilled in the art with reference to the following specification and accompanying FIGS. in which:
FIG. 1 is a front perspective view of the apparatus;
FIG. 2 is a fragmentary, side elevational view of the apparatus;
FIG. 3 is a plan view of the frame and table support assemblies;
FIG. 4 is a cross-sectional view taken along the plane lV-IV of FIG. 3;
FIG. 5 is a side elevational view of the structure illustrated in FIGS. 3 and 4;
FIG. 6 is an enlarged, fragmentary, front elevational view, partially in cross section, of the table support, adjustment and vibration assemblies;
FIG. 7 is an enlarged, fragmentary, plan view, partially in cross section, of the table support, adjustment and vibrating assemblies;
FIG. 8 is an exploded view of the table adjustment and support assemblies;
FIG. 9 is a front elevational view of one of the flexible mounts;
FIG. 10 is a side elevational view, partially in cross section, of one of the adjustable vibration assemblies;
FIG. 1 l is a front elevational view of the weight housing;
FIG. 12 is a cross-sectional view taken along plane XII-XII of FIG. 10; and
FIG. 13 is a cross-sectional view taken along plane XIII-XIII of FIG. 10.
Briefly, this invention comprises a jogging apparatus having a table upon which the stock to be jogged into alignment is positioned. A shaft having a series of offcenter weights is rotatably affixed to the table and means are provided for rotating the shaft. The table, of course, is supported in flexible fashion on a suitable support structure.
In accordance with one of the features of this invention, the angle of the table relative to the support structure is adjusted about an axis coinciding with the axis of the drive means for the offcenter weights, thus permitting adjustment of the table without readjustment of the driving mechanism for the shaft. According to another feature of this invention, the weight structure is adjusted by sliding one of the weights axially with respect to a mating weight to disengage a luglike locking arrangement and thereafter rotating the weight to the desired position and allowing it to reengage its mating weight.
Referring now to the FIGS. a preferred embodiment of this invention will be described in detail. FIGS. 1 and 2 illustrate the novel apparatus which includes a support structure 10 having a base 11 which, conveniently, can be mounted upon casters 12 for easy movement throughout the working facility. Base 11 has an upright pose 13 positioned thereon. Post 13 is retained by sleeve 14 and may be telescoped in and out thereof to raise and lower the height of the apparatus by ad justment assembly 15.
Mounted at the upper extremity of post 13 is the frame assembly which includes a Ibshapcd member 21 having a base 22 and upstanding side 23. The frame assembly 20 is affixed to post 13 by a post mount 24 in any suitable fashion.
Referring now additionally to FIGS. 3 through 7, the frame assembly 20 is provided with a suitable motor mount 25 on the upper side of the base 22 thereof. Apertures 26 are provided at the upper extremities of each of the sides 23. Each of the sides 23 is provided, additionally. with a curved slot 27 having a radius constant with respect to the aperture 26 on its respective side of the apparatus.
The table structure 70 is supported at each side of the apparatus by structures which are similar with the exception of their "left-handand right-hand" characteristics For purposes of clarity in the ensuing discussion, the structures on the left hand side of the machine (as viewed in FIGS. 1. 3 and 4) are denoted by the letter a and those on the right hand of the machine by the letter b. Similar reference numerals, of course, are utilized for similar components.
Referring now additionally to FIG. 8, each side of the apparatus is provided with a pivot arm assembly 30. Pivot arm 30a is positioned at the left side of the apparatus (as viewed in FIGS. 3 and 4) while pivot arm assembly 30b is positioned at the right side of the apparatus. Each of the pivot arm assemblies has a central portion 31 having an aperture 32 therein. From central portion 31 extend a pair of diverging arms 33, each of the arms having an aperture 34 in the extremity thereof. Also extending from central portion 31 is a depending adjustment leg 35 having an aperture 36 at its lower extremity.
The pivot arm assemblies 30a and 30b are affixed to upstanding sides 23 of U-shaped member 2]. by means of cylindrical arm mounts 37. Mounts 37, as shown best in FIGS. 6 and 7, are open at their interiors and are positioned in apertures 26 in side plates 23 and apertures 32 in pivot arms 30. The pivot arms 30 must be free to rotate with respect to side plates 23 of frame member 21 as will become apparent hereinafter and it may be necessary to secure the members 21, 37 and 30 together. Such securing, of course, can be readily accomplished by those skilled in the art.
The table angle adjustment assembly, indicated generally by the reference numeral 40, includes the depending legs 35 of each of the pivot arms 30 and the curved slots 27 in each of the upstanding sideplates 23 of U-shaped member 21. The adjustment assembly, conveniently, includes a shaft (not shown) passing between the upright sides 23 having a knobbed extremity 42 and a threaded opposite extremity upon which a suitable nut 41 is adapted to be affixed. The shaft passes through the apertures 36 in the pivot arms 30, through the slots 27 in upstanding sides 23 and into the nut 41. The curved slots 27 lie along the arc of a circle having the center of the cylinders 37 as its center and the distance between the midpoints of apertures 32 and 36 as its radius. By loosening knob 40, thus, the pivot arm assemblies 30 can be rotated to any desired position along slot 27 to tilt the paper-supporting table as will be discussed in detail hereinafter.
The vibration isolation assembly, indicated generally by the reference numeral 50, includes a series of four flexible mounts 51. Two of these mounts are provided at each side of the machine as will become clear from the following description. The mounts 51 are molded from any suitable flexible substance such as rubber or the like. During the molding process, shafts 52 and 53 (see FIG. 9) each having retainer caps 54 are integrally molded into the flexible mount member. The shafts 52 and 53, thus, are not interconnected but, rather, separated by the flexible rubber or rubberlike molded material forming the mount. It is possible, thus, to contort one of the shafts, for example 53, without causing a like contortion in shaft 52.
The table supports, indicated generally by the reference numerals 55a and 55b, each include a planar upper surface 56 having tapped apertures 57 suitably spaced thereon. The supports include, additionally, a pair of depending legs 58 each having slots 59 therein. That portion of the supports beneath a planar surface 56 adjacent the extremities of the support includes a mount shelf 60 against which the flexible mounts 51 are adapted to rest after assembly of the apparatus. The table support structures 55 also include two suitably tapped aper' tures in the bearing mounts 61, the purpose of which will become clear hereinafter.
The pivot arm 30flexible mount 5ltable support 55 mode of assembly for the left-hand side of the machine is illustrated best in FIG. 8. The right hand assembly. as noted previously, is identical with the exception of the mirror-imaged parts. The shafts 52 of two of the mounts 51 are received by apertures 34 in pivot arm 30. The shafts 53 pass through slots 59 in table support 55. The resultant configuration, as illustrated best in FIGS. 3 through 5, provides the planar surfaces 56 for reception of the paper support table or receptacle which is thus affixed to the base of the apparatus in angularly adjustable fashion. The table is flexible mounted with respect to the remainder of the apparatus, however, due to the presence of the flexible mounts 51 at the four extremities thereof.
The table or receptacle assembly, indicated generally by the reference numeral 70, comprises a flat rectangular member secured to the planar surfaces 56 of table supports 55 by means of suitable screws (not shown) threading into the apertures 57 on supports 55a and 55b. The rectangular plate 71 is positioned diagonally with respect to the table supports 55 in the manner indicated in FIGS. 1 and 2. The fastening of the table 70 to the supports fixes the spatial relationship of depending legs 58 and thus, will retain the pivot arm 30-mount S1-table support 55 in assembled configuration. If necessary, however, shafts 52 and 53 may be provided with additional locking means such as snap rings to retain the assembled components together.
A pair of upstanding side guides 73 are affixed to the edges of table 71 such that they converge at the lowermost extremity. of the paper-supporting table or receptacle when it is tilted downwardly by adjustment assembly 40. The paper to be jogged into registry, of course, is placed on the table 71 and, during the vibration thereof, the edges come into alignment with the side guides 73.
The drive assembly, indicated generally by the reference numeral 80, comprises an elongated shaft 81 rotatably secured to the lower surface of table supports 55a and 55b by means of suitable bearing caps 82. An electric motor 84 is suitably mounted upon the base 22 of the U-shaped member 21 and the shaft 81 rotated thereby through a pulley 83 and conventional V-belt 85. As shown best in FIGS. 6 and 7, the shaft 81 passes through the central portion of cylindrical mounts 37 at each extremity of the apparatus and into the bearings 82 on the table supports 55. The motor is activated by means of a switch 87 or, alternatively, a foot switch 86 suitably connected thereto.
The various components of the apparatus are sized such that shaft 81 passes through the proximate center of cylindrical mounts 37 during assembly of the apparatus. Since the pivotable members 30:: and 30b rotate about centers coinciding with the shaft 81, angular adjustment of the paper-supporting table by the movement of arms 35 does not affect the distance between the pulley on the motor 84 and the pulley on the shaft 83. The table, thus, may be adjusted to any desired angular position without necessitating the readjustment of the drive assembly 80.
Referring now additionally to FIGS. 10 through 13, the adjustment vibrating assemblies, indicated generally by the reference numerals 90a and 90b, each comprise a weight housing 91 suitably secured near each extremity of shaft 81. The weight housings 91 have circular recesses 92 therein and a series of apertures 93 are drilled into the body section 94 of the weight housing at the base of these recesses. The apertures 93, as shown best in FIGS. 11 and 13, are positioned onone side of the weight housing 91, the other side thereof being left solid. The material removed from the weight housing 91 during drilling or other forming of the apertures 93. of course. causes the aperture to be weighted heavier at one side thereof than at the other.
Weight housing 91 has. additionally. a tapped aperture 95 therein into which is threaded a capscrew 96 having a head 97 Diametrically opposite from aperture 95 is drilled and tapped a setscrew aperture 98 into which a suitable setscrew 99 is affixed. The setscrew 99 is provided merely as a means of counteracting and/or amplifying the weight differential resulting from the presence of capscrew 96. The necessity of providing this component. of course. will depend upon the design criterion utilized in the fabrication of the weight housing 91.
The adjustable weight assembly, indicated generally by the reference numerals 100a and comprises a body section 101 having a knob 102 protruding therefrom. Body section 101 is sized so as to fit rotatably into circular recess 92 in weight housing 91 and has a series of four apertures 103 drilled in one side thereof as shown best in FIGS. 10 and 12. The forming of the apertures 103 renders the adjustable weight assembly 100 heavier on one side than the other. The apertures 103 function, additionally, to receive the head 97 of capscrew 96 as will become apparent.
Knob section 102 of adjustable weight assembly 100 has a central cylindrical recess 104 bored or otherwise formed therein. After the assembly 100 has been placed around the extremity of shaft 81 with one of the apertures 103 engaging the head 97 of capscrew 96, a compression spring 105 is placed over the extremity of the shaft so as to lie within the cylindrical recess 104 in the manner shown in FIG. 10. A thrust bearing 106 is then positioned over the extremity of shaft 81 and a suitable screw 107 inserted through the thrust bearing into the extremity of the shaft. Screw 107, of course, functions to maintain spring 105 in compression and, thus, to maintain the adjustable weight assembly 100 in abutment with the weight housing 90 with one of the apertures 103 engaging the head 97 of the capscrew.
From an examination of FIGS. 10 through 13, it will be apparent that by rotating adjustably weight assembly 100 with respect to weight housing 91, the weight distribution surrounding each extremity of shaft 81 may be altered. Maximum offcenter weight distribution is achieved, of course. when the apertures 93 and 103 lie to the same side of shaft 81. Minimum offcenter weight distribution is achieved when the apertures 103 are rotated to a position on the side of shaft 81 opposite from the apertures 93.
The relative rotational positions of weight housings 91 and adjustable weight assemblies 100 are changed by grasping the knob section 102 and pulling it outwardly. This causes spring 105 to compress and, thus, the capscrew head 97 to pass out of engagement with the particular aperture 103 in which it has been positioned. The knob 102 and, thus, the adjustable weight assembly 100 is then rotated to the newly desired position and the knob 102 released. Compression spring 105 causes the adjustable weight assembly 100 to move back into abutment with the weight housing 91 with the capscrew head 97 positioned within another of the apertures 103. A dial or the like, conveniently, may be provided on the exterior of the assemblies to indicate visually the relative positions of the components 91 and 100.
When it is desired to utilize the apparatus which is the subject of this invention, the paper supporting table is first moved to the desired relative angular position with respect to the horizontal. This is accomplished by loosening knob 42 and pivoting pivot members 30 about mounting cylinders 37. When the desired point is reached, the knob 42 is retightened to secure the table at the desired position.
Subsequent to adjustment of the angular position of the table, the adjustable vibrating assemblies 90a and 90b are adjusted to the correct position by pulling the knobs 102 outwardly and rotating them with respect to the shaft in the manner discussed previously. With the weight assemblies 90 thus adjusted, the paper to be job jogged into alignment or registry is positioned into the paper-supporting table or receptacle assembly 70. The apparatus is then activated by either flipping switch 87 or depressing foot pedal 86.
Activation of the motor 84 causes shaft 81 to rotate. The rotation of shaft 81. in turn. is transferred to the adjustable weight assemblies at each of its extremities The offcenter weight distribution characteristics of the assemblies 90 cause the shaft 81 to vibrate in a manner which will be readily appreciated by those skilled in the art. This vibration. of course, is transferred directly to the paper-supporting assembly 70 since the shaft is rotatably mounted directly thereto by the bearing assemblies 82. The vibration is damped from the frame 20 and support structure 10. however, because of the presence of the flexible mounts 21 between the table supports 55 and the pivot arms 30. Vibration of the table causes the paper to align or come into registry against the sideplates 73. When registry has been completed, the apparatus is deactivated, readjusted if necessary, and utilized to align another batch of stock.
The instant apparatus may be utilized to receive and align stock issuing singly from a press or the like as well as to align preformed batches. In such a situation, of course, the table assembly 70 is positioned with respect to the particular output device such that the individual sheet pass directly thereonto. The aligned stacks of sheets may be removed from the apparatus intermittently as required by the output characteristics of the particular processing device with which it is operating in conjunction.
While a preferred embodiment of this invention has been described in detail, it will be readily apparent to those skilled in the art that other embodiments may be conceived and fabricated without departing from the spirit of this specification and the accompanying drawings. Such other embodiments are to be deemed as included within the scope of the following claims unless these claims, by their language, expressly state others otherwise.
1. In a jogging apparatus having a support structure; a drive motor mounted in nonflexible fashion upon said support structure; a receptacle within which the stock to be jogged into registry is positioned supported flexibly upon said structure in pivotable fashion with respect thereto; rotatable means ineluding offcenter weight means affixed to said receptacle for causing said receptacle to vibrate; and, drive means connected to said motor for driving said rotatable means, said drive means having an axis of rotation, the improvement comprising means for pivoting said receptacle with respect to said structure about an axis coinciding with the axis of said drive means.
2. The apparatus as set forth in claim 1 wherein said drive means comprises a shaft rotatably journaled on said receptacle.
3. The apparatus as set forth in claim 2 wherein said rotatable means are affixed to said shaft.
4. In a jogging apparatus having a support structure; a receptacle within which the stock to be jogged into registry is positioned supported flexibly upon said structure in pivotable fashion with respect thereto; rotatable means including 011'- center weight means affixed to said receptacle for causing said receptacle to vibrate; and, drive means having an axis of rotation for driving said rotatable said drive means including a shaft rotatably journaled on said receptacle, said rotatable means being affixed to said shaft, the improvement comprising means for pivoting said receptacle with respect to said structure about an axis coinciding with the axis of said drive means, said receptacle being pivotably affixed to said support structure by hollow tubular connection means having an interior measurement greater than the exterior measurement of said shaft, said shaft passing through said connecting means.
5. The apparatus as set forth in claim 4 wherein said support structure includes a pair of upstanding side members, said tubular connection means protruding outwardly in diverging fashion therefrom, and which further comprises: pivot members pivotably affixed to each of said connection means; and, means for selectively adjusting the angular position of each of said pivot members with respect to said side members.
6. The apparatus as set forth in claim wherein said adjustment means comprises an arm extending from each of said pnot members: a slot in each of said sidewalls. and means for securing selectively said arms at any predetermined position along a said slot 7 The apparatus as set forth in claim 6 wherein said slots are curved. the radius of cunature thereof equaling the distance between the axis of said tubular members and that point on said arms at which the are secured within said slots.
8. The apparatus as set forth in claim 5 which further comprises a receptacle support affixed to each of said pivot memhers by flexible coupling means. said receptacle being secured to said receptacle supports.
9. The apparatus as set forth in claim 8 wherein each of said pivot members has a pair of diverging support arms extending therefrom. said receptacle supports being affixed to said pivot members by said flexible coupling members at the extremities of each of said support arms.
10. The apparatus as set forth in claim 8 wherein said coupling means comprises a flexible resilient body section having a shaft extending outwardly from each side thereof, each of said shafts being independently supported within said body section and, thus, resiliently moveable with respect to the other of said shafts.
11. The apparatus as set forth in claim 8 wherein said shaft is rotatably journaled to said receptacle supports.
12. The apparatus as set forth in claim 11 wherein one of said rotatable means is mounted at each of the extremities of said shaft outside of said receptacle supports.
13. The apparatus as set forth in claim 12 wherein said rotatable means are adjustable.
14. In a jogging apparatus having a table supported in flexible fashion on a support upon which the stock to be jogged into alignment is positioned; a drive motor mounted in nonflexible fashion upon said support; a shaft rotatably affixed to said table; means rotatably interconnecting said motor and said shaft; and weighted members driven from said shaft to create an unbalanced vibration condition on said table as said shaft is rotated. the improvement comprising means for adjusting the angular position of said table with respect to the horizontal about an axis coinciding with the axis of said shaft.
15. In a jogging apparatus having a support structure; a receptacle within which the stock to be jogged into registry is positioned supported flexibly upon said structure in pivotable fashion with respect thereto; rotatable means including offcenter weight means affixed to said receptacle for causing said receptacle to vibrate; and. drive means having an axis of rotation for driving said rotatable means. the improvements comprising means for pivoting said receptacle with respect to said structure about an axis coinciding with the axis of said drive means. said rotatable means being affixed to a shaft rotatably affixed on said receptacle. said rotatable means including a first member affixed to said shaft. said first member being off balance with respect to the axis of said shaft; a second member mounted about said shaft and rotatable with respect thereto. said second member also being off balance with respect to said shaft; at least one lug member protruding from one of said members; a series of lug-engaging means on the other of said members adapted to engage said lug; and means for shifting said second member axially along said shaft to effect disengagement of said lug and the lug-engaging means then engaging it whereby said second member may be rotated to a different rotational position with respect to said first member and said lug brought into engagement with another of said lug-engaging means.
16. The apparatus as set forth in claim 15 which further comprises resilient means biasing said second member and said first member together so as to bring said lug and lug-engaging means into engagement.
17. The apparatus as set forth in claim 16 wherein said first and second members have facing surfaces urged into abutment by said biasing means, said lug member projecting from one of said surfaces toward the other thereof and wherein said lug-engaging means comprises a series of apertures in the other of said surfaces adapted to receive said lug member.
18. The apparatus as set forth in claim 17 which further comprises knob means integrally formed with said second member.
19. In a jogging apparatus having a support structure; a receptacle within which the stock to be jogged into registry is positioned supported flexibly upon said structure in pivotable fashion with respect thereto; rotatable means including offcenter weight means affixed to said receptacle for causing said receptacle to vibrate; and, drive means having an axis of rotation for driving said rotatable means, said drive means including a shaft rotatably journaled on said receptacle, the im provement comprising means for pivoting said receptacle with respect to said structure about an axis coinciding with the axis of said drive means; a motor fixedly mounted on said support structure; a pulley mounted on said shaft; and flexible endless drive means interconnecting said pulley and said motor.