Ledger mechanism for rod making machines

Ledger mechanism for rod making machines of tobacco industry comprising a first stationary ring gear (4), a first orbiting gear (5) staying in mesh with the first stationary ring gear (4), a second movable ring gear (6), a second orbiting gear (7) staying in mesh with the second movable ring gear (6). The ledger mechanism comprises a ledger (11) mechanically connected with the second movable ring gear (6) and the axis of the second orbiting gear (7) is coaxial with the axis of the first orbiting gear (5).

The object of the invention is a ledger mechanism for rod making machines in the tobacco industry.

In the tobacco industry rod making machines i.e. cigarette making machines and filter making machines (also combined filter making machines) are used. Continuous tobacco or filter rods are cut into discrete lengths (rods) by a cut-off device. Cutting off is realized by means of a rotary cutting head with knives positioned on its periphery, whereas the axis of rotation of the cutting head is arranged at an angle with relation to a horizontal plane. Inclining the cutting head provides a horizontal speed component of the knife parallel to the rod movement, the horizontal speed component of the knife should be equal to the speed of the rod being cut while cutting in order to enable proper cutting a continuous moving rod. Cutting a continuous rod requires that such a rod is supported whilst cutting which is usually realized by means of a ledger which has a round hole or holes to guide the rod and a slot through which knives of a cutting head move repeatedly. Typically the ledger is designed as a set of cutting tubes with a certain distance between them. In the art there are several mechanisms involving rotary motion for driving a ledger whereas the ledger itself makes linear reciprocating movement. British patent GB2108820 presents a ledger driven by a ledger mechanism comprising two gear arrangements consisting of an internal gear within which orbits an external gear which is half the diameter of the internal gear. The ledger is positioned on a connecting member the ends of which are pivotally joined with the external gears at points on the pitch diameter of the gears, due to which the ledger makes linear horizontal reciprocating movement.

American U.S. Pat. No. 6,478,031 presents a similar mechanism where a connecting member being a rod-supporting part between drive gears is made of two members connected to one another with a pivot pin. The two members are connected by an anti-backlash spring. Another American U.S. Pat. No. 4,444,210 presents a ledger mechanism in which there is used an elastic cushioning insert to manage with tensions in the connecting member.

All the above mentioned documents disclose mechanisms having two gear arrangements with a ledger situated on connecting members between the gear arrangements. Very important issue of the above mentioned inventions is the distance between the centre of the mass of the ledger and the line of movement of the pivotal joints of the gear arrangements. Due to this distance inertia forces are produced which cannot be balanced easily, the bigger the distance is the bigger inertia forces and vibrations are produced. The result is very noisy operation of the mechanisms.

The purpose of the present invention is developing a ledger mechanism having one gear arrangement which can be used at very high speed of a continuous rod up to about 600 m/min with improved realization of horizontal movement where a ledger is mounted on a non-rotary element of the gear arrangement.

The object of the invention is a ledger mechanism for rod making machines of tobacco industry comprising a first stationary ring gear, a first orbiting gear staying in mesh with the first stationary ring gear, a second movable ring gear, a second orbiting gear staying in mesh with the second movable ring gear, and a ledger mechanically connected with the second movable ring gear. The ledger is characterized in that the axis of the second orbiting gear is coaxial with the axis of the first orbiting gear.

Ledger mechanism is characterized in that the transmission ratio of the first stationary ring gear and the first orbiting gear is k=2.

Ledger mechanism is characterized in that the transmission ratio of the second movable ring gear6and the second orbiting gear7is k=2.

Ledger mechanism is characterized in that the pitch diameter of the first orbiting gear and the pitch diameter of the second orbiting gear are equal.

The advantage of applying the ledger mechanism according to the invention is achieving very low level of noise. Moreover the whole unit can be easily exchanged in case a new length of rods is needed in production. The ledger mechanism according to the invention comprises less parts than other known ledger mechanisms.

FIG. 1presents schematically a kinematics diagram of a gear arrangement1applied in the mechanism according to the invention. In the presented gear arrangement1there are two sets2and3of gears. The first set2of gears comprises a first stationary ring gear4and a first orbiting gear5. The first stationary ring gear4has internal teeth, the teeth of the first orbiting gear5are in mesh at point R2with the teeth of the first stationary ring gear4, whereas the transmission ratio k of the first stationary ring gear4and the orbiting gear5is 2:1 i.e. k=2. The first orbiting gear5orbits around the center C2of the stationary ring gear4and while orbiting the orbiting gear5rotates around its center M5. The second set3of gears (shown with dashed lines) comprises a second movable ring gear6and a second orbiting gear7. The second movable ring gear6has internal teeth, the teeth of the second orbiting gear7are in mesh at point R3with the teeth of the second movable ring gear6, whereas the transmission ratio k of the second movable ring gear and the second orbiting gear is 2:1 i.e. k=2. The second orbiting gear7orbits around the center C3of the second movable ring gear6and its centre M7overlaps the center M5of the first orbiting gear5. In the diagram shown inFIG. 1centers C2and C3coincide, also points R2and R3coincide.FIG. 2presents elements of the mechanism1according to the invention after the orbiting gears5and7have made some angular movement around the center C2due to the forced movement of the first orbiting gear5. The point R2of meshing has moved to the left and the point R3of meshing has moved to the right in the plane of the drawing. The center C3of the second movable ring gear6has moved to the left in the plane of the drawing. According to the invention a ledger is attached to the second movable ring gear6and makes reciprocal movement along a horizontal line, the stroke of the reciprocal movement is equal to the pitch diameter of the ring gear4. Thus the rotary movement of the orbiting gears5and7is transformed into reciprocal linear movement of the point C3.

FIG. 3presents a ledger mechanism according to the invention in a front view. The ledger11comprises two tubes12through which travels a continuous filter or tobacco rod CR. Knives of a cutting head (not shown) pass through a slot13between the tubes12and cut the rod CR into discrete lengths. The ledger11follows the movement of the center C3i.e. makes reciprocal movement to the left and right in the plane of the drawing.

FIG. 4shows a cross-section A-A through the ledger mechanism ofFIG. 3. The mechanism has a housing15in which there is a main shaft16having an axis X rotary assembled by means of bearings17and18. The axis X relates to the center C2inFIGS. 1 and 2. The main shaft16is driven by a known geared motor which is not shown in the drawing. In the main shaft there is a hollow shaft19rotary assembled by means of bearings21and22, on the shaft19there is fixed a first orbiting gear5which stays in mesh with a first stationary ring gear4. The axis Y of the first orbiting gear5relates to the center M5inFIGS. 1 and 2. On the shaft23mounted in the shaft16there is fixed a second orbiting gear7which stays in mesh with a movable ring gear6fixed in a gear mounting24rotary mounted on the hollow shaft19by means of a bearing25. The axis Z of the gear7relates to the center M7inFIGS. 1 and 2. The second movable ring gear6makes reciprocal movement in the direction perpendicular to the plane of the drawing with the gear mounting24on which is fixed a ledger11. A continuous tobacco or filter rod travels through the tubes12of the ledger11. In the presented embodiment the orbiting gears5and7have the same diameter.

Typical aspects of balancing the mechanism commonly known to specialists in mechanics are omitted in the description.

The advantage of the ledger mechanism according to the invention is a combination of small dimensions of the mechanism and low level of noise. The ledger mechanism is easily exchangeable so the time needed for setting a new length of cutting is very short. It can be realized by unscrewing the housing with a mechanism and replacing it with a housing comprising a mechanism for a new length of cutting.