Cam-like notched latch bars on the interior of the fly section automatically receive the manually extended spring-urged plunger on the cantilevered end of the extension cylinder for the boom inner mid-section. Binding of the plunger in the notched latch bar during retraction of the plunger is not detrimental to the proper operation of the plunger screw feed means and on subsequent minute movement of the boom outer mid-section during normal usage.
Other features and advantages of the invention will become apparent during the course of the following detailed description. I is a fragmentary vertical section taken through a telescopic crane boom equipped with the mechanism of the invention and showing particularly the cooperative action of a latch plunger and notched latch bar. The complete boom includes a base section While the boom is illustrated as being trapezoidal in cross section.
The illustrated telescopic boom has a first extension cylinder or ram 24 connected at 25 to the rear of inner mid-section 20 and being cantilevered forwardly from this point. The'rod of cylinder 24 is attached at 26 to base section A second cylinder or ram 27 beneath and parallel to the cylinder 24 has its rod end similarly attached as at 28 to the rear of outer mid-section 21 and has its rod attached at 29 to inner mid-section 20 of the telescopic boom.
The fragmentary parts of the two cylinders 24 and 27 appearing in FIG. A foot assembly 30 for the lower cylinder 27 consists ofa tubing section 31 having a rear end plate 32 bolted as at 33 to a mating plate or flange 34 on the leading end of lower cylinder A pair of spaced coupling sleeves 35, FIG.
This arrangement is for stability and distribution of stresses which may be quite high through the foot assembly At its forward end, the tubing section 31 carries a rigid welded triangular brace frame 39, provided on its lower corners with widely spaced retainers 40 for wear pads 41 which are in sliding contact with the bottom wall of manual fly section 22 near the side walls of the latter.
In FIG. Stabilizing and alignment means for the cantilevered end of the upper cylinder 24 relative to the lower cylinder 27 is also provided. This means includes abutting plates 42 and 43 on the forward end of cylinder 24 and on a rigid welded support structure ahead of the cylinder 24 which includes longitudinal bars 44 and 45, the latter being welded to the plate At their forward ends, the bars 44 and 45 carry another flange or plate 46 rigid therewith and parallel to the plate Interven- "ing block elements 47 are also included in the welded unit for strength, and beneath the blocks 47 a somewhat inclined plate or web 48 is welded to the blocks 47 and to the previously-described bars 44 and The two abutting plates 42 and 43 are firmly coupled together near their tops by tension bolts 51 which extend through the blocks 47 and also through a pair of stabilizing sleeves 52 on the top portion of cylinder The lower corners of plates 42 and 43 are coupled by additional bolts The welded structure including plates 43 and 46 and bars 44 and 45 and associated elements is therefore cantilevered ahead of the upper cylinder 24 and is disposed above the foot assembly To further support the leading end of cantilevered cylinder 24, a support and wear pad 54 is arranged in sliding contact with the top of cylinder 27 and is securely bolted as at 55 to the bottom of cylinder 24 through a welded bracket means For lateral support and alignability.
These side wear pads are retained on a pair of support arms 58 whose upper extensions 59 carry interfitting apertured knuckles 60, midway between the arms These apertured knuckles receive a pivot element or bolt 61 which is supported on and extends between the web 49 and bracket 50, FIG. Above the pivot element 61, arm extensions 59 straddle bar 45 and are equipped with opposed adjusting set screws 62 by means of which the wear pads 57 may be individually adjusted in relation to the lower cylinder A latch assembly 63 forming a key element of the invention is bodily mounted on the leading end of the welded structure which includes the plate This assembly includes a latch housing 64 which receives upper and lower pairs of mounting bolts 65 and The upper bolts 65 engage through plate 46 and blocks 47 and the lower bolts 66 engage through the plate 46, FIG.
Adjusting shims 67 for the latch assembly 63 are provided as required to locate it accurately in relation to the mounting plate The housing 64 has a bore 68 receiving an extensible and retractable latch plunger 69 therein. The plunger is sealed in the bore 68 by a suitable fluid seal 70, the internal chamber of the housing 64 being oil-filled.
The interior end of the latch plunger 69 carries a stepped flange 71 adapted to engage an annular shoulder 72 formed in the housing. A compression spring 73 surrounds latch plunger 69 in an enlarged bore chamber 74 of the housing and one end of this spring engages stepped flange 71 while its other end engages a shoulder 75 within the housing.
Spring 73 urges the latch plunger 69 inwardly or retracted relative to the housing The plunger 69 is restrained from rotation on its longitudinal axis by a pair of parallel plates 76 mounted on the top of housing 64, and cooperating with a pair of flats 77, FIG.
The latch plunger 69 is extended and retracted manually by an internal nut 78 driven axially by a screw shaft 79 whose outward movement is limited by a head 80 on the screw shaft. The latch plunger 69 is shown fully extended from the housing 64 in FIG. A second compression spring 81 inside of the plunger 69 is seated 4 on the nut 78 and urges the latch plunger outwardly toward its extended position.
The two springs 73 and '81 work in opposition in relation to the plunger The screw shaft 79 has a shank 87 swiveled and sealed within an opening of the cover plate 84, and the screw shaft is turned by a drive shaft 88 coupled through a first universal joint 89 with the screw shaft A bracket arm 90 welded to the cover plate 84 extends downwardly and to one side of tube section 31 and terminates near the bottom of brace frame 39, FIG.
This arm supports a sleeve 91 for a rotary shaft 92 coupled through a second universal joint 93 with the shaft The shaft 92 has a hex head 94 to permit turning by a manual crank wrench 95, FIGS. Wrench access openings 96 are formed in the bottom walls of boom sections 20, 21 and 22, as shown.
In cooperative relation with the latch plunger 69, a latch bar or plate 97 is fixedly secured to the top wall of manual fly section 22, FIGS.
This latch bar has sloping cam faces 98 on opposite sides of a centrally located receiver notch 99 for latch plunger The complete operational sequence is carried out with the telescopic boom in a horizontal position. To extend the manual fly section 22 from the fully retracted position of FIG.
The latch wrench 95 is now coupled to the turning head 94 and the screw shaft 79 is turned counter-clockwise to shift latch plunger 69 to the extended position. This manual operation is carried out from the bottom of the boom assembly as shown in FIG. As the outer mid-section nears full extension, the spring-loaded latch plunger 69 engages and rides over one of the sloping cam faces 98 and snaps into the notch 99 of the latch bar As the plunger 69 is pushed into the housing 64, the inner spring 81 is compressed.
As the outer midsection 21 continues to extend. At this point. The use of the shims 67 assures accuracy in the relationship of the plunger 69 to the latch bar notch The arrangement is such that the notch receives the plunger 69 at the same time that the extension cylinder 27 bottoms out and the fly section 22 is fully retracted in the outer mid-section In connection with the operation thus far described in FIGS.
If the fly section 22 happens to be extended a fraction of an inch in FIG. The fly section 22 will be moved back into the outer mid-section 21 until it engages its stops simultaneously with the bottoming out of lower cylinder A dipperstick 38 is vertically pivotally connected to an end of the boom 32, as at a pin 39 and a hydraulic dipperstick actuator 40 is connected between the boom 32 and dipperstick 38 for selectively effecting articulation therebetween.
A bucket, not shown, is vertically pivotally connected to the outer end of the dipperstick and provided for adjusting the bucket relative to the dipperstick is a powered linkage including a hydraulic bucket actuator Provided for selectively simultaneously locking the boom 32 in its raised transport position and the swing frame 28 in a centered position wherein it disposes the backhoe boom 32 centrally behind the tractor 12 is a lock mechanism The lock mechanism 44 is shown in detail in FIG.
The plate 48 extends forwardly beyond the pivot assembly 30 and has a rearwardly extending notch 50 formed in the forward end thereof. Fixed to the top surface of the plate 46 are right and left stop blocks 52 and 54 which define a channel 56 disposed in fore-and-aft alignment with the notch A pair of spaced lugs or ears 58 are fixed to the top of the plate 48 and received between the lugs 58 and vertically pivotally connected thereto by means of a pivot pin 60 is an elongate latch member The latch member 62 has a locking block 64 at its forward end received between the blocks 52 and 54 and in the notch 50 and has a cross pin 66 at its rear end received in downwardly opening notches 70 respectively formed in a pair of ears 72, fixed to laterally spaced members 74 and 76 of the boom such as to form a hook structure.
The locking block 64 is releasably secured to the remainder of the latch member 62 by a pair of vertical cap screws 78 while the cross pin 66 has a threaded rod 80 secured to the middle thereof and threaded into the rear of the remainder of the latch member 62 and held in place by a lock nut Thus the block 64 and cross pin 66 may each be replaced when worn and the length of the latch member 62 may be adjusted to ensure that the cross pin 66 enters the notches A control handle 84 includes a fore-and-aft extending section 86 having its rear end coupled to the latch member 62 by a ball and socket connector The handle 84 includes a section 90 which joins the forward end of the section 86 and projects upwardly through an L-shaped guide slot 92 located in a top wall of a control console The guide slot 92 is arranged to have a forward transverse leg in which the handle section 90 is held by a tension spring 94 when the handle 84 is holding the member 62 in a latched position, as shown.
The member 62 may be moved to an unlock position by moving the lever sideways to and then rearwardly in a fore-and-aft extending portion of the guide slot The operation of the lock mechanism 44 is as follows: Assuming the backhoe to be readied for transport by the tractor 12, the swing frame 28 will be centered, the boom 32 will be in its raised transport position and the latch member 62 will be in its latched position with the locking block 64 disposed between the stop blocks 52 and 54 and the notch 50 and with the cross pin 66 received in the notches 70 of the hook structure, all as illustrated in the drawing.
Should any side forces then occur which tend to rotate the swing frame 28 about the pivot assembly 30, these forces will be absorbed at the interface of the block 64 first with one or the other of the blocks 52 and 54 and then the forward end of the swing frame plate 48 when the member 62 has moved sideways, as permitted by the tolerance at the pivot pin The latch member 62 may be released once the tractor backhoe 10 has reached a desired work site by merely moving the handle 84 sideways in the guide slot 92 to the fore-and-aft extending portion thereof and then pushing rearwardly on the handle to effect rotation of the latch member 62 to thereby simultaneously disengage the cross pin 66 from the notches 70 and remove the locking block 64 from between the stop blocks 52 and This motion is primarily the result of the force generated by the movement of the piston rod 18 a during retraction of the locking and latching cylinder 18 , which as noted above is coupled directly to the bellcrank 22 via the hook-like projection As the bellcrank 22 pivots, the inwardly projecting cams 22 a, 22 b engage the adjacent surfaces of the lower flanges of the pin puller 46 a.
The locking pin 38 a then moves downwardly as a result of the connection established by bolt 44 and out of the opening O see action arrows I and J in FIGS. Consequently, the spring 42 a is compressed against the shelf-like structure 40 a see FIG. The retracted or unlocked position of the locking pin 38 a is maintained as long as the piston rod 18 a of the locking and latching cylinder 18 is held in the actuated retracted position, since the bellcrank 22 is prevented from pivoting back to the home position by the extended piston rod 18 a.
Once the locking pin 38 a is retracted, the extension cylinder 14 , which of course is now coupled to the boom section 12 a by the latching plates 30 in the latched position, may be further extended or retracted to effect the desired telescoping movement.
In the case of extension, the direct contact between the engagement surfaces 30 b of the latching plates 30 and the sidewalls of the selected boom section 12 a serves to transmit the motive force. Indeed, it should be appreciated that the latching plates 30 support the full weight of the selected boom section 12 a when unlocked and in the case of an outer section 12 b or 12 c, the weight of any previously extended sections as well , both during extension or retraction.
As should be further appreciated, this weight creates a rotational force on latching plates 30 in the opposite direction of action arrow Z FIG. This rotational force is balanced and counteracted by the projections 20 a, 20 b FIG. The frictional force between projections 20 a, 20 b and the camming surfaces 30 a prevent the movement of the frame 20 in the opposite direction of action arrow H in FIG.
Thus, as long as there is load on the latching plates 30 , they may not be withdrawn out of apertures A. Advantageously, this prevents the latching plates 30 from inadvertently moving to the unlatched positions until the corresponding locking pin 38 a - 38 c is returned to the locked position and the load is removed from the latching plates To relock and unlatch the selected boom section 12 a once the extended position is reached, the operation previously described is essentially reversed.
Generally referring to FIGS. This activation causes the engagement head of the projecting portions 20 a, 20 b of the support frame 20 to move along the inner camming surfaces 30 a on the latching plates 30 , but initially no camming action results due to the amount of frictional contact between projections 20 a, 20 b and the inner camming surfaces 30 a see FIG.
Of course, this ensures that the locking pin 38 a is returned to the home or locked position before the latching plates 30 are retracted. Note, however, that the position of the bellcrank 22 in the longitudinal direction does not change, since it is supported by the case 14 b of the extension cylinder The case 14 b of the extension cylinder 14 is retracted slightly to transfer load from the latching plates 30 to the locking pin 38 a. This reduces the frictional force between the projections 20 a, 20 b and the camming surfaces 30 a allowing the support frame 20 to slide axially along the case of the extension cylinder With specific reference to FIG.
Since the selected boom section 12 a is now locked and the weight of the now-extended section 12 a is fully assumed by the locking pin 38 a, this engagement causes the latching plates 30 to pivot from the latched position FIG.
Advantageously, moving the locking pin 38 a to the locked position prior to unlatching the plates 30 provides an extra level of protection against the accidental release of the selected boom section 12 a - 12 c. Also, once the plates 30 are in the home or unlatched positions as shown in. Hence, the latching and locking devices 28 , 36 are complementary, with the operation of one serving to either permit or prevent the operation of the other.
The operation of the locking and latching system 10 in which boom section 12 c is selected for movement, such as retraction from an extended position which presumes that any inner boom sections, such as sections 12 a and 12 b, have previously been extended is shown from a different perspective in FIGS.
In FIG. The case 14 b of the extension cylinder 14 is moved to the position where the latching plates 30 align with the apertures A in the sidewalls of boom section 12 c and the cams 22 a, 22 b projecting inwardly from the sidewalls of the bellcrank 22 are positioned in the opposed channels of the pin puller 46 c. The locking and latching cylinder 18 is then actuated retracted. Consequently, the engagement head of each projecting portion.
This moves bearings 32 away from the bellcrank 22 , which then begins to pivot note action arrow L. The frictional force between pin 38 c and opening O in the next adjacent boom section is reduced by extending the extension cylinder case 14 b away from its fixed rod end and to transfer load from pin 38 c to latching plates The movement of the bellcrank 22 continues as a result of the actuation of the locking and latching cylinder 18 until it is fully retracted and the spring 42 c is compressed such that locking pin 38 c is moved out of the opening O at the distal end of the next-adjacent, outermost boom section 12 d.
The extension cylinder 14 is then actuated to telescopingly move or retract the selected boom section 12 c into boom section 12 d, with any previously extended inner boom sections, such as sections 12 a, 12 b, being simultaneously moved toward the base of the crane or lifting device. When the selected section 12 c reaches the retracted position, as determined by comparing the known position of the opening O in the proximal end of the next-adjacent boom section 12 d with the distance traveled by the extension cylinder 14 , the locking and latching operations are reversed as previously described, such that the locking pin 38 c moves to the locked position and then the latching plates 30 are moved to the retracted or unlatched positions.
Advantageously, this requires only activating or extending the locking and latching cylinder As should now be appreciated, in the illustrated embodiment, both the operation of latching and unlocking a selected boom section 12 a - 12 c for extension or retraction is completed using a single motive device. Preferably, the single motive device uses only one locking and latching cylinder 18 to provide the locking and latching action.
This advantageously reduces the contribution of the locking and latching system 10 to the overall weight of the boom assembly 12 , the required maintenance, and the overall complexity. Also, since the single locking and latching cylinder 18 of the motive device is preferably axially aligned with the extension cylinder 14 , a more compact or low-profile locking and latching system 10 results.
For purposes of illustrating the operation of the system 10 , the locking and latching operation is described and illustrated as being performed on the boom section 12 a during extension, which is the innermost section just inside of the next-adjacent boom section 12 b, or on outer boom section 12 c during retraction. In the case where three or more nonextended boom sections 12 a - 12 d are present and extension is desired, it is desirable to start the telescoping operation by latching and then unlocking the innermost boom section 12 a, working inside out from that point.
In other words, the innermost section 12 a is first latched, unlocked, extended, locked and unlatched, and then the extension cylinder 14 is retracted to a position such that the latching plates 30 are aligned for insertion in the corresponding apertures A In the next-adjacent outer boom section 12 b.
The latching plates 30 are then moved to the latched position, the locking pin 38 b is pulled, the case 14 b of the extension cylinder 14 is moved a predetermined distance, and the locking pin 38 b is moved in a selected opening O in the next-adjacent boom section 12 c.
This operation is repeated as necessary until the boom assembly 12 is extended in the desired fashion. Reference to FIG. The locking pin 38 b of the next-adjacent boom section 12 b is illustrated, including the dual legs 39 a, 39 b, as is the shelf-like projection 40 b, the compression spring 42 b, and the pin puller 46 b having an I-shaped cross-section.
The spaced pairs of corresponding apertures A for receiving the outwardly directed portions of the latching plates 30 in the latched position are shown formed in the sidewall of each inner boom section, which in this case includes only sections 12 a and 12 b note that apertures A would not be provided in boom section 12 b if it were the outermost boom section in the boom assembly 12 , since it would be non-telescoping.
It is noted that in the embodiment of FIG. Regardless of the shape of the boom sections 12 a - 12 c, tribologically enhanced wear pads not shown are preferably interposed between the front and rear portions of adjacent sections to provide reduced friction contact. Although not shown in FIG.
A similar, but reversed, operation is performed when the inner boom section 12 a is retracted to the position shown in FIG. As should be appreciated, the same operation is completed on boom section 12 b when it is selected for telescoping movement relative to section 12 c, or section 12 c relative to section 12 d, or any combination of selected and next-adjacent boom sections.
With reference now to FIG. Specifically, at least one, and preferably a pair of wear pads 60 are provided along the inside surfaces of opposed sides of the frame 20 such as along the upper and lower surfaces, in the case where the frame 20 is oriented with the projections 20 a and 20 b extending in different horizontal planes.
Each wear pad 60 includes an engagement surface 62 contoured to match the generally cylindrical outer surface of the case 14 b of the extension cylinder Shims or spacers 64 may also be provided as necessary or desired to ensure that the reduced-friction, sliding contact is evenly achieved between the wear pad 60 and the outer surface of the case 14 b.
Each assembly including the wear pad 60 and the shim or spacer 64 may be secured in place by one or more fasteners F, such as threaded screws. These fasteners F project through apertures in the frame 20 and engage corresponding apertures in the material forming the wear pad Optional washers W may also be provided.
This trunnion mount is shown as comprising a pair of spaced supports 66 including U-shaped slots for receiving stub shafts projecting from the sides of the case 18 b of the cylinder 18 and aligned apertures for receiving fasteners riot shown.
Although not previously depicted, FIG. Turning now to FIG. Starting at the top of this figure, the U-shaped bellcrank 22 carries a pair of inwardly directed cams 22 a, 22 b. Each cam 22 a, 22 b includes a disc-shaped engagement head at one end and a projecting portion at the opposite end that is received in an aperture not labeled formed in the corresponding sidewall of the bellcrank A nut T may also be provided for securing the cams 22 a, 22 b to the bellcrank The yoke 24 includes spaced pivot structures 24 a, 24 b for pivotably supporting the bellcrank The pivot structures 24 a, 24 b are secured to a base 24 c of the yoke 24 and include oversized apertures 73 in which a bushing 68 and a spacer 70 are inserted.
A fastener, such as a capscrew 72 , is then inserted into the aperture 73 in each pivot structure 24 a, 24 b and through the second aperture in the sidewall of the bellcrank As a result of this arrangement of structures, the bellcrank 22 is capable of freely pivoting in response to the extension or retraction of the locking and latching cylinder Turning now to the bottom of FIG.
A thrust bearing 80 may be provided over the spacer 78 for engaging a first surface of each latching plate A bushing 82 is inserted in an aperture 30 d formed in each latching plate 30 at a strategic location to achieve the desired range of pivoting movement, with the inner surface of the bushing 82 engaging the outer surface of the spacer A second thrust bearing 84 may also be provided for engaging a second surface of each latching plate The yoke 24 is positioned over the second thrust bearing 84 , and a fastener, such as a capscrew 86 , is inserted into each aperture in the base 24 c, through each spacer 78 , and into the mounting block The result is that the yoke 24 is held securely in place against upward or side-to-side movement, while each latching plate 30 is capable of freely pivoting about the axis defined by the capscrew 86 as a result of being engaged by projections 20 a, 20 b.
A similar arrangement of structures may be provided for the other pair of latching plates 30 , if present, the only exception being that the yoke 24 may be replaced by a simple tie plate 87 see FIGS. This substitution is possible because no structures for pivotably supporting a bellcrank 22 are required on the opposite side of the extension cylinder Even with this modification, it should be appreciated that the same pivoting action may be reliably achieved as a result of the interaction between the engagement heads of the projecting portions 20 a, 20 b of the frame 20 and the inner camming surfaces 30 a of the latching plates It is also noted in FIG.
These pads 88 provide a low-friction wear surface for the projecting portions 20 a of the frame 20 as it moves to and fro as a result of the actuation of the locking and latching cylinder The wear pads 88 may be held in place by one or more fasteners, such as machine screws 90 , extending into apertures formed in the yoke 24 and mounting block 26 , respectively.
A similar wear pad 88 may be provided on the tie plate 87 which serves as a substitute for the yoke 24 along the opposite side of the extension cylinder 14 , as is shown in FIGS. An alternate embodiment of the locking and latching system 10 is shown in FIGS. The primary difference in the alternate embodiment is that the support bearings 32 are no longer provided for preventing the bellcrank 22 from pivoting when the latching plates 30 are in a latched position.
Instead, a bearing 92 which may be stationary or capable of rotating is positioned on and carried by a support 94 extending from the end of the projecting portion 20 a, which is shown as being positioned above the adjacent extension cylinder Hence, as the locking and latching cylinder 18 is retracted such that the frame 20 is moved towards the bellcrank 22 , the bearing 92 moves in the same direction note action arrow R. When the projecting portion 20 a reaches a position such that each latching plate 30 is cammed to the latched position, as in the first embodiment, the bearing 92 is positioned such that the bellcrank 22 is free to pivot and unlock the corresponding locking pin not shown by way of the engagement between the cams 22 a, 22 b and the corresponding pin puller As shown in FIG.
When the locking and latching cylinder 18 is then actuated extended , such as for moving the latching plates 30 to the unlatched position and returning the locking pin not shown to the locked position, the bearing 92 is returned to a position adjacent to or in contact with the bellcrank The bearing 92 in the home position thus prevents the bellcrank 22 from pivoting, which ensures that an adjacent locking pin 38 a - 38 c cannot be retracted as long as the locking and latching cylinder 18 is extended and hence the latching plates 30 are in the unlatched position.
In summary, an improved locking and latching system 10 for a boom assembly 12 is disclosed. The system 10 includes complementary locking and latching devices 28 , 36 that are preferably operated by a single motive device, including at least one locking and latching cylinder The locking and latching cylinder 18 is preferably axially aligned with the extension cylinder 14 used to telescopingly move a selected boom section 12 a - 12 c relative to a next-adjacent boom section 12 b - 12 d, and thus fits well within the confines of the boom assembly The latching device 26 includes at least one, and preferably two pairs of spaced latching plates These plates 30 are selectively moved between an unlatched position and a latched position in engagement with the selected boom section 12 a - 12 c by the engagement head of a projecting portion 20 a, 20 b of a support frame 20 coupled to and moved by the locking and latching cylinder Once the latching plates 30 are in place, the locking and latching cylinder 18 also assists in pivoting a bellcrank 22 such that a pin puller 46 a - 48 c is engaged and a corresponding locking pin 38 a - 38 c projecting through aligned openings formed in the selected and next-adjacent boom sections 12 a - 12 d is moved to an unlocked position.
Using the extension cylinder 14 , the selected boom section 12 a - 12 c is then telescopingly moved extended or retracted as desired, until the corresponding locking pin 38 a - 38 c is aligned with a corresponding opening O formed in the next-adjacent boom section such as at a predetermined extended or retracted position.
The locking and latching cylinder 18 is then actuated, such that the bellcrank 22 is first pivoted to return the corresponding locking pin 38 a - 38 c to the locked position and then the engagement heads of the projecting portions 20 a, 20 b of the support frame 20 return the latching plates 30 to the unlatched position. This ensures that the selected boom section 12 a - 12 c is locked in place before the latching plates 30 are retracted.
The locking and unlatching operation is then repeated for any other boom section 12 b - 12 c selected for telescoping movement. The foregoing description of the invention has been presented for purposes of illustration and description. The description is not intended to be exhaustive or to limit the invention to the precise form disclosed.
Obvious modifications or variations are possible in light of the above teachings. For example, the relative orientation of the components may be altered without substantially changing the overall principles of operation of the system
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