TROLLEY ASSEMBLY USING A SHOCK ABSORBER TROLLEY AND METHOD OF USE

TROLLEY ASSEMBLYUSING A SHOCKABSORBERTROLLEY AND METHOD OF

USE

FIELD OF THE INVENTION

The present invention is directed to a trolley assembly using a shock absorber trolley and a method of use and, in particular, to a trolley having a self-contained shock absorber mechanism that alleviates noise and load sway during bias banking of carriers supported by trolley assemblies.

BACKGROUND ART

In the prior art, power and free conveyors are well known systems made up of a power track, a free track, and a pair of trolleys capable of traveling along the free track, the trolleys supporting a carrier. The trolleys are usually divided into leading and trailing trolleys. Each leading trolley in a power and free system includes a driving dog portion which extends toward the power track and which is engageable by a pusher dog carried by a moving chain on the power track. When the pusher dog and the driving dog are engaged, the leading or drive trolley is pushed along the free track by the moving power chain. When the driving dog is retracted, or otherwise disengaged from the pusher dog, the trolley stops moving, thus halting the carrier.

In another system, a third trolley can be employed as the drive trolley. This third trolley is linked to the pair of trolleys by a structural member typically called a tow bar as disclosed in United States Patent No. 4,408,540 to Dehne. In these conveyors, the trolley assembly supporting the load travels from a single free track to split free tracks whereby the leading or drive trolley and the intermediate trolley travel on one track with the trailing trolley traveling on a second track. With this parallel track arrangement, the carriers are diagonally or biased banked, thus reducing the longitudinal spacing between successive carriers.

Trolleys and carriers are made of steel or similar alloys and consequently are quite heavy. The trolleys support a carrier which is also very massive and which may be supporting a heavy load or workpiece at any given time. Such carriers possess large kinetic energies when they roll along an accumulation section of a conveyor system, and this energy must be dissipated in order to stop the carrier. Because the carriers and trolleys are made from metal, a significant amount of energy from each collision between carriers and/or trolleys is dissipated as sound waves, and each impact produces a relatively loud noise. Since a given conveyor line may have multiple accumulation portions, and a plant may have multiple conveyor lines each equipped with multiple accumulators, the noise produced by the accumulation of carriers is substantial and frequent. This noise can be unpleasant to anyone in a plant where accumulators are used, and, to employees required to work in close proximity to these accumulators, the noise can have adverse health affects as well.

Noise can also be generated in power and free conveyors that employ bias banking. In these conveyors as noted above, the load is carried on a bias with respect to the conveyor travel direction to allow compact in-line storage. When the trolley assemblies accumulate in the biased configuration, they tend to generate noise when the leading trolley of one trolley assembly engages the trailing/intermediate trolley of the upstream trolley assembly.

Another problem with bias banking of trolley assemblies is load sway. Disengagement of the drive dog can be abrupt, thus generating a shock which can be transferred to the load carrier. When loads are biased banked, the abrupt disengagement can cause the load to swing into the downstream or previous load, causing further noise and possible load damage. One solution to this is the use of a telescopic element in the tow bar incorporating a piston and cylinder type damper to absorb shock during disengagement and prevent damage. Such a system is shown in United States Patent No. 3,720,172 to Dehne. Although the use of a shock absorber tow bar is preferred, it can be difficult and expensive to install in existing systems. Often times, limit switches, antibackups, and positioners have to be relocated to accommodate the difference in length between the shock absorber when fully open and when fully closed.

The high frequencies generated by this metal-to-metal contact can be particularly damaging to hearing. In addition, the trolleys are often not accumulated at regular intervals. Thus, the sound of each successive impact may come as something of a surprise to nearby employees. An employee who is startled by such sudden noises may have difficulty concentrating on his job. Attempts have been made, therefore, to reduce the noise created by these accumulations. One solution is to coat the metal surfaces normally making contact with rubber or a similar material which will absorb the impact of the collisions. However, such attempts have not been successful since such coatings are generally incapable of handling the impact loads, particularly when the loads are heavy.

In light of the disadvantages noted above, a need exists to control the noise generation for these types of conveyors as well as the load sway when the conveyors are biased with respect to the conveyor travel. The present invention overcomes the disadvantages in these types of conveyors by the utilization of a trolley having a shock absorbing mechanism linked with the trolley cam. The inventive trolley lessens the noise generated when a leading trolley contacts the cam of an intermediate trolley and, also, minimizes sway of trolley carriers when conveyed or stored in a biased banked configuration. The use of shock absorbing arrangements in the prior art for various applications is known. Shock absorbers are disposed in railway cars to absorb shocks imparted due to the stopping and starting of the cars. United States Patent No. 2,115,064 to Dwyer discloses a coupling arrangement in this regard. Similar arrangements are shown in United States Patent Nos. 3,178,035 and 3,223,049 to Peterson. United States Patent No. 3,216,590 to Bateson discloses another railway car shock absorbing device.

United States Patent No. 4,885,997 to Wakahayashi discloses a power and free conveyor having a free trolley with a main body and a slider mounted thereon, the slider being slidable longitudinally of the trolley. The slider has an engaging dog and an anti- coasting dog. The engaging dog of the slider is connected to the main body of the free trolley by a shock absorber. When the pusher of the power chain contacts the engaging dog, impact is diminished by the action of the shock absorber. However, Wakahayashi does not recognize the problem of noise generation and sway in bias banking of loads nor does it teach or suggest associating the shock absorber with the accumulation cam of a trolley.

SUMMARY OF THE INVENTION

Accordingly, a first object of the present invention is an improved trolley assembly for conveyor systems, particularly power and free conveyors.

Another object of the present invention is to reduce noise and load sway when accumulating bias banked trolley assemblies. A still further object of the present invention is a trolley having a shock absorbing mechanism linked to an accumulation cam of the trolley.

One other object of the present invention is a method of reducing noise and load sway during trolley assembly accumulation.

Other objects and advantages of the present invention will become apparent as a description thereof proceeds.

In satisfaction of the foregoing objects and advantages, the present invention provides an improvement in a trolley assembly adapted to be driven by a powered conveyor, the trolley assembly including a leading trolley having a forward operating link, an intermediate trolley having a rearward cam and a trailing trolley having a rearward cam. The trolleys are linked together and are adapted to travel in one or more tracks to collectively support a load using a carrier. The improvement comprises providing the intermediate trolley with a shock absorbing mechanism linked to the rearward cam thereof to absorb energy, reduce load sway, and alleviate noise during accumulation of a plurality of trolley assemblies. In one embodiment, the shock absorbing device is mounted between two side plates of the intermediate trolley and the shock absorbing mechanism uses a shock absorber body and a return spring arrangement. The shock absorbing mechanism can further comprise a tube containing a shock absorber body, one end of the tube secured to a rearward cam support, the rearward cam being attached to the rearward cam support. A tube guide is provided between the side plates, the tube guide having at least one opening permitting travel of the tube within the tube guide. A stop is arranged between the side plates and with a surface to resist a piston of the shock absorber body. Contact against the cam causes the tube to slide within the tube guide, the piston retracting to absorb the impact energy during trolley assembly contact with another trolley assembly. In one embodiment, the tube guide can include a bearing to allow for slidable movement of the tube within the guide. The intermediate trolley has a frame and the rearward cam shock extends from a portion of the frame at least a distance of travel of the shock absorbing mechanism. Once the load of the leading trolley is removed from the rearward cam, the return spring expands, returning the tube to a start position and extending the piston for a subsequent cycle.

The invention also includes a method of reducing noise and carrier sway when accumulating trolley assemblies by providing a plurality of trolley assemblies, each trolley assembly including a leading trolley having a forward operating link, an intermediate trolley having a rearward cam and a trailing trolley having a rearward cam. One of the trolley assemblies is moved along a pair of tracks whereby the assemblies are on a bias with respect to the direction of trolley assembly travel, the forward trolley and intermediate trolleys being on one track and the trailing trolley being on the other track. The operative link of the leading trolley of the moving trolley assembly engages the rearward cam of the intermediate trolley of a stationary and upstream trolley assembly to disengage the leading trolley of the moving assembly from the power chain. During impact between the leading trolley of the moving trolley assembly and the intermediate trolley of the upstream trolley assembly, noise and carrier sway caused by the impact between trolley assemblies is lessened by the shock absorber mechanism associated with the intermediate trolley. The shock absorber body piston compresses to absorb the impact energy when the assemblies contact each other. The shock-absorber-containing trolley can also be used as a trailing trolley when using only pairs of trolleys to absorb energy and dissipate noise during trolley assembly accumulation.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is now made to the drawings of the invention wherein: Figure 1 is a side view of an exemplary trolley assembly of the invention; Figure 2 is a schematic of an in-line trolley assembly configuration; Figure 3 is a schematic of a bias-banked configuration of the Figure 1 trolley assembly;

Figure 4 is a longitudinal sectional view of the intermediate trolley shown in Figure 1; Figure 5 shows a portion of the trolley of Figure 4;

Figures 6A and 6B are side views of an alternative tube and shock absorber body arrangement; Figures 7A, 7B, 7C, and 7D are side views of a guide block, tube cap, stop plate and bearing for the embodiment of Figures 6A and 6B; and

Figure 8 shows the embodiment of Figures 6A-7D as part of a trolley.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention overcomes the drawbacks in bias banked conveying systems by alleviating noise generation and load sway in a cost effective manner. By incorporating a shock absorber into the first load or intermediate trolley, the intermediate trolley is used to disengage the next carrier from the conveyor chain in bias banked situations. Since very few of the devices mentioned above, i.e., limit switches, positioners, antibackups, and the like, are used in sections of conveyor track employing bias banking, the time and cost of retrofitting an existing system is greatly reduced. Further, since possible load damage is the greatest during bias banking due to load swing or sway, reducing the abrupt disengagement in the diagonal banking area will minimize or eliminate load damage.

An exemplary embodiment of the invention is depicted in Figure 1 wherein a trolley assembly 10 includes a drive or leading trolley 1, an intermediate trolley 3 and a trailing trolley 5. Each trolley has pairs of trolley wheels 7 sized to travel on a conveyor or free track 9. A power track 11 is disposed above the free track 9, the power track guiding a pusher chain and pusher dog (not shown) to drive the trolley assembly 10. Since the interaction between the trolleys 1, 3, and 5 and the power track and chain are well known, a further description is not needed for understanding of the invention.

The trolley assembly 10 is designed to support a load 13 via a carrier assembly 15. The carrier assembly 15 is supported by a load bar 17 that connects the trailing trolley 5 and intermediate trolley 3, with a tow bar 19 connecting the leading trolley 1 and the intermediate trolley 3. The load bar 17 pivots about a point 21 so that the leading and intermediate trolleys 1 and 3 can travel on one track and the trolley 5 can travel on another track when the assembly is biased banked as described above. Bias banking is employed often times to consolidate the carrier load in a biased fashion for compactness of storage and/or accumulation. The tow bar 19 can also pivot with respect to each of the trolleys 1 and 3.

The leading trolley 1 is shown with an operating link 23 which is designed to interact with the accumulation cam 25 of a trailing trolley of an upstream trolley assembly as is well- known in the art. When the cam 25 engages the operating link 23, the link end 27 is moved to release a pusher dog of a drive chain (both not shown) so that the leading trolley 1 is no longer driven by the drive chain. Upstream trolleys are intended to mean those trolleys which contact a stopped or downstream trolley, the upstream trolley being accumulated by disengagement of its leading trolley with the power chain.

With reference to Figure 2, prior to the bias banking, the trolleys 1, 3, and 5 follow inline on a single track 9. In this configuration, the intermediate trolley 3 does not interact with the leading trolley of an upstream trolley assembly. Accumulation in this configuration could occur through interaction between trolleys 1 and 5 of successive assemblies.

Referring to Figure 3 and bias banking, the trolley assemblies 10 and 10' travel on two tracks 9 and 9'. The leading trolleys 1 and intermediate trolleys 3 follow on track 9 with the trailing trolleys 5 riding on track 9'. In this mode, the intermediate trolley 3 of the downstream assembly 10' becomes the trailing trolley so as to engage the leading trolley 1 of the upstream trolley assembly 10. The carrier 13 is shown on a bias defined by an angle π as measured from track 9 to the longitudinal axis of the carrier.

As noted above, the problem with bias banking is not only the noise generated by the leading trolley 1 of trolley assembly 10 banging into the intermediate/trailing trolley 3 of the upstream assembly 10', but swaying of the load 13 supported by the trolley assemblies. When the trolley assembly 10 is in an inline configuration, e.g., traveling on track 9 as shown in Figure 2, load sway is not a problem. However, in the bias banking mode of Figure 3, the loads tend to sway when the leading trolley of one trolley assembly contacts the intermediate and trailing trolley of the upstream trolley assembly. Load swaying can also cause contact between adjacent loads and/or carriers, thus causing damage to one or both loads.

The present invention solves the noise and sway problem by incorporating a shock absorbing mechanism in the intermediate trolley 3. With reference now to Figures 4 and 5, the intermediate trolley 3 is shown with a two-part trolley construction, a frame portion 41 supporting the pairs of trolley wheels 7 and roller guides 43. The frame portion 41 connects to a second frame portion 45 at 47. The frame portion 45 supports a portion of the load bar 17 via the member 49 as shown in Figure 1, the member 49 linked to the frame portion 45 at opening 50. The second frame portion 45 has two opposing side plates 51 , only one being shown in Figures 4 and 5. The side plates 51 are spaced apart to receive a shock absorber mechanism 61. The mechanism 61 includes a u-shaped cam clevis 63. The clevis 63 forms a channel sized to receive the cam 67. The cam 67 is connected to the clevis 63 via bolts 68 extending through the openings 70 in the clevis 63 and openings in the cam 67. Of course, other forms of attachment may be employed to connect the cam 67 and the clevis 63.

The clevis has a bight portion 73 which receives an internally threaded tube 75 via opening 76 in the bight portion 73. The outer surface of the tube is secured to the plate 73 using a set screw 78 but other conventional means can be used to secure the tube 75 to the clevis 63, e.g., welding, other mechanical fastenings or the like. The tube 75 rides in an opening in a tube guide or block 77. The opening in the guide block 77 has a bearing 79 therein to facilitate travel of the tube 75 within the opening in the tube 75. The bearing 79 is retained within a recess in the block 77 by clip 84. The block 77 is attached between the side plates 51 using fasteners (not shown), the fasteners extending through openings 80 in the plates 51 and guide block 77. The shock absorber mechanism 61 includes a shock absorber body 62 having a retractable piston 64 terminating in a stop 91. A stop plate 78 is secured at an end of the guide block 77 and between the plates 51 by any means, welding, fastening, or the like. The body 62 is externally threaded to be secured to the interior of the internally threaded tube 75. An externally threaded tube cap 81 is threaded to the threaded tube interior. The tube cap 81 has a bottom flange 83 extending inwardly toward the tube cap axis and a top ring portion 87, an outer peripheral portion 88 extending radially beyond the outer surface of the tube 75. The mechanism 61 also has a spring 89, one end abutting the stop 91, the opposite end 93 of the spring resting on the bottom flange 83 of the tube cap 81. During shock absorber operation, the tube 75 slides within the guide block 77 and the piston 64 retracts into the body 62 as a force is applied against the cam 67 from the operative link of a leading trolley as explained above. The spring 89 is compressed as the tube 77 slides within the guide block 77. The energy of impact when the trolley collides is absorbed by operation of the shock absorber body 62. When the trolleys are disengaged and the load is removed from the cam 67, the spring expands as shown in Figures 4 and 5 against the tube cap 81 to force the tube 75 in a direction away from the stop plate 78. At the same time, the piston extends so that the body

62 is ready for another energy absorption cycle. The tube 75 is secured within the tube guide 77 by the tube cap portion 88 extending beyond the tube outer surface, thus acting as a stop against the bearing 79.

The clevis 63 has protrusions 101, one shown in Figures 4 and 5, to guide the clevis

63 during its travel. Each protrusion 101 extends from the bight portion 73 to slide against a side surface of the plate 51 so that the clevis 63 does not rotate during travel. The plates 51 include an extension 103 to interface with the protrusions 101 for clevis protrusion guiding. The plates 51 also have openings 105 to link with the tow bar 19 as shown in Figure

1.

When the trolley assembly is used for bias banking as shown in Figure 3, the intermediate trolley 3 becomes the trailing trolley so as to engage the leading trolley of an upstream trolley assembly. During bias banking of adjacent trolley assemblies, the cam 67 of trolley 10' engages the operating link of the leading trolley 1 of the upstream trolley assembly 10, such engagement releasing the leading trolley from the pusher dog of the chain. When the cam 67 contacts the operative link of the leading trolley, the tube 75 slides within the guide block 77 and the piston 64 retracts into the body 62 against the stop plate 78 to absorb impact energy. As part of the contact between the cam 67 and the operative link, the tube 75 travels the distance X shown in Figure 5, preferably sized for about a 2 inch travel. Of course, other travel distances can be employed as can springs of varying spring constants. The spring 89 remains in the compressed condition as long as the leading trolley 1 of upstream trolley assembly 10 is bearing on the intermediate trolley 3 of the assembly 10'. Once the trolley assembly 10' containing the intermediate trolley 3 moves forward, i.e., leaves the bias banking area, the rearward cam 67 of intermediate trolley 3 is disengaged from the operative link of the leading trolley of assembly 10 and the spring 89 can expand so that the cam 67 and body 62 are again in position to dampen the load or impact energy applied when contacted by another leading trolley. Referring to Figures 6A-7D, an alternative shock absorber mechanism is depicted showing a tube 75' sized to slide within the guide block 77'. A shock absorber 62' has a piston 64', spring 89' and piston stop 91'. The body 62' seats against lip 108 in the guide block 77 and the damping force is adjustable by rotation of an adjustment knob 110. The stop plate 91 ' has a recess 112 to receive the end of the spring 89'.

Figure 8 shows the tube 75' and guide block 77' in the trolley frame portion 45. Figure 8 also shows the retracted and extended states of the piston 64'.

The shock absorber device provides a dual role in not only minimizing the noise generated when the cam 67 engages the leading trolley of an upstream trolley assembly but, also as importantly, minimizes the sway of the load supported by the trolley assembly. With the inventive trolley, additional noise generation that may be caused by load sway is also minimized.

It should be understood that although the intermediate trolley is shown as a trailing trolley in a biased banking arrangement, the intermediate trolley could also be used solely as a trailing trolley to minimize noise generation during trolley accumulation when using pairs of trolleys to support a carrier. Other shock absorbing devices could be used in place of the shock absorber as would be known in the art. The shock absorber can also be mounted in the tube in other ways than those depicted above.

Although the tube guide is shown as separate block, it could be made in a multi-piece construction, e.g., a plurality of bushed guide blocks with a collar interposed therebetween, the collar retaining the tube within the guides.

Although two side plates are shown, an alternative frame configuration could be used such as a unitary or one-piece design. Likewise, the cam 67 could be integrally linked to the cam clevis 63 as a one-piece construction. The frame portions 41 and 45 could also made as one-piece rather than a two piece assembly with a connection as shown in Figures 4 and 5.

As such, an invention has been disclosed in terms of preferred embodiments thereof which fulfills each and every one of the objects of the present invention as set forth above and provides new and improved trolley assembly including a shock-absorbing trolley to decelerate accumulating carriers and reduce carrier sway and noise generation. Of course, various changes, modifications and alterations from the teachings of the present invention may be contemplated by those skilled in the art without departing from the intended spirit and scope thereof. It is intended that the present invention only be limited by the terms of the appended claims.