1. A digital television (DTV) receiver for processing a DTV signal, the DTV receiver comprising:
a receiving unit for receiving a digital television signal including a plurality of extended text table (ETT) instances that appear in transport stream packets with common PID values, the ETT instances having common table ID values, each ETT instance comprising a section header and a message body, the section header containing a table identification (ID) field that serves to establish uniqueness of each ETT instance, the message body containing an extended text message (ETM) which provides detailed descriptions of a virtual channel or an event associated with each ETT instance,
wherein the header further contains a field indicating a protocol version which is set to 0 but is set to a different value later to indicate structurally different tables;
a demodulator for demodulating the digital television signal; and
an identifying unit for identifying at least one pertinent ETT instance from the plurality of ETT instances.
2. The DTV receiver of claim 1, wherein the protocol version field is a 8-bit field.
3. The DTV receiver of claim 1, wherein the table identification extension field defines a value indicating an event identifier (ID) associated with each event ETT instance.
4. The DTV receiver of claim 3, wherein the table identification extension field further defines a value indicating an ETM location.
5. The DTV receiver of claim 1, wherein the table identification extension field has a 16-bit integer value.
6. The DTV receiver of claim 1, wherein the plurality of event ETT instances are section-filtered based on a condition that the at least one pertinent event ETT instance has a specific PID value.
7. The DTV receiver of claim 1, wherein the plurality of event ETT instances are section-filtered based on a condition that the table ID extension field included in the at least one pertinent event ETT instance includes a specific value.
8. The DTV receiver of claim 7, wherein the specific value specifies a unique identification number of an event associated with the at least one pertinent event ETT instance.
9. The DTV receiver of claim 8, wherein the plurality of event ETT instances are section-filtered based on a condition that the table ID extension field included in the at least one pertinent event ETT instance includes a non-duplicative event identifier.
10. The DTV receiver of claim 1, further comprising:
a parser for parsing the identified at least one pertinent event ETT instance; and
a storage for storing an extended text message (ETM) included in the parsed event ETT instance.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A print head for use in a fused deposition modeling system, the print head comprising:
a liquefier pump assembly;
a housing body; and
a housing cover configured to attach to the housing body to define a cartridge assembly, wherein the liquefier pump assembly is retained by the cartridge assembly.
2. The print head of claim 1, wherein the liquefier pump assembly comprises:
a drive block retained within the cartridge assembly, and having a first opening and a second opposing opening, the first and second openings being offset by a channel that is configured to receive a filament of a material;
a rotatable shaft retained within the cartridge assembly, and having a toothed surface extending at least partially within the channel of the drive block, the toothed surface being configured to engage the received filament;
a filament tube having a first end and a second end, wherein the first end extends into the second opening of the drive block; and
a liquefier coupled to the second end of the filament tube.
3. The print head of claim 2, and further comprising:
a motor;
a rotatable gear axially connected to the motor, and having a threaded surface; and
a capstan gear having a rotational axis and perimeter teeth, the perimeter teeth being configured to engage the threaded surface of the rotatable gear, wherein the rotatable shaft extends from the rotational axis of the capstan gear.
4. The print head of claim 1, wherein the first opening of the drive block is configured to engage with a filament guide tube.
5. The print head of claim 1, wherein at least one of the housing body and the housing cover comprises a vent.
6. The print head of claim 1, and further comprising a circuit board secured to the housing cover, the circuit board being electrically connected to the liquefier pump assembly.
7. The print head of claim 1, and further comprising:
a motor operably connected to the liquefier pump assembly;
a rotatable gear axially connected to the motor; and
at least a portion of a rotary encoder configured to operably measure rotational angles of the rotatable gear.
8. A liquefier pump assembly for use in a print head of a fused deposition modeling system, the liquefier pump assembly comprising:
a structural component;
a drive block retained by the structural component, the drive block comprising a first opening configured to engage with a filament guide tube, a second opposing opening, and a third opening, the first and second openings being offset by a linear channel configured to receive a filament of a material, and the third opening intersecting the linear channel;
a liquefier assembly encased by the structural component, the liquefier assembly comprising an inlet coupled to the second opening of the drive block; and
a drive mechanism retained by the structural component and comprising a rotatable component extending into the channel of the drive block through the third opening, the rotatable component being configured to engage the received filament in the channel and drive the filament into the liquefier assembly.
9. The liquefier pump assembly of claim 8, wherein the rotatable component comprises a textured surface.
10. The liquefier pump assembly of claim 8, and further comprising a motor configured to provide rotational power to the drive mechanism.
11. The liquefier pump assembly of claim 10, wherein the drive mechanism further comprises a capstan gear configured to transfer the rotational power from the motor to the rotatable component.
12. The liquefier pump assembly of claim 11, wherein the rotatable component extends from a rotational axis of the capstan gear.
13. The liquefier pump assembly of claim 8, wherein the structural component has a bottom surface that includes a film comprising a fluorinated polymer.
14. The liquefier pump assembly of claim 8, wherein the liquefier assembly further comprises an extrusion tip, wherein the structural component defines an opening and has at least one radial tab extending into the opening, and wherein the extrusion tip is secured to the at least one radial tab.
15. A method for assembling a print head, the method comprising:
inserting a liquefier assembly into a structural component such that the structural component encases at least a portion of the liquefier assembly;
providing a rotatable component having a drive shaft extending from a rotational axis of a capstan gear, the drive shaft having a toothed surface;
inserting the toothed surface of the drive shaft into a drive block such that at least a portion of the toothed surface extends within a channel of the drive block;
engaging the liquefier assembly with a first opening in the drive block, the first opening being connected to the channel of the drive block; and
mounting the drive block to the structural component.
16. The method of claim 15, after further comprising inserting the drive shaft into an axial opening of the capstan gear.
17. The method of claim 15, wherein the liquefier assembly comprises an extrusion tip, and wherein the method further comprises spot welding the extrusion tip to the structural component.
18. The method of claim 15, and further comprising:
inserting the liquefier assembly and the structural component through a first housing component of the print head such that the rotatable component and the drive block are disposed at least partially within the first housing component; and
securing a second housing component to the first housing component.
19. The method of claim 18, and further comprising mounting a motor at least partially into the first housing component and engaging the motor with perimeter teeth of the capstan gear.
20. The method of claim 18, and further comprising electrically connecting the liquefier assembly to a circuit board retainable by at least one of the first housing component and the second housing component.