1. A top drive assembly for use on a drilling rig comprising:
a. a traveling block housing with an upper plate;
b. an airbag mounted to a lower airbag plate of the traveling block housing;
c. an upper airbag plate mounted to the airbag opposite the lower airbag plate of the traveling block housing;
d. a first link having a first link second end connected to the upper airbag plate, wherein the first link has a second slot;
e. a second link having a second link second end connected to the upper airbag plate, wherein the second link has a first slot;
f. a first sheave between a first outside plate and a first inside plate of the traveling block housing;
g. a third sheave between a second outside plate and a second inside plate of the traveling block housing;
h. a first pin serving as an axle and as a load transfer pin extending through the first sheave to a second load carrying plate of the traveling block housing;
i. a second pin serving as an axle and as a load transfer pin extending through the third sheave to a first load carrying plate of the traveling block housing;
j. a center housing plate between the first inside plate and the second inside plate;
k. a top drive for engaging a tubular, wherein the top drive is supported by the traveling block housing through a first link first end of the first link and through a second link first end of the second link, and wherein the top drive is independently movable with respect to the sheaves; and
l. an air valve secured to the airbag for injecting low pressure air at less than 300 psi from an air source into the airbag to expand the airbag, lift the links, or lower the links to provide thread compensation as the top drive makes up or breaks out a drill string of tubulars.
2. The top drive assembly of claim 1, further comprising: a second sheave parallel to the first sheave and rotating on the first pin between the first outside plate and the first inside plate, and a fourth sheave parallel to the third sheave and rotating on the second pin between the second outside plate and the second inside plate.
3. The top drive assembly of claim 1, wherein the airbag is toroidal in shape or double toroidal in shape.
4. The top drive assembly of claim 1, wherein the traveling block housing consists of the first lower plate, a first middle plate between and parallel to the first inside plate and the first outside plate, a second lower plate connected to the second outside plate opposite the upper plate, and a second middle plate between and parallel to the second inside plate and the second outside plate.
5. The top drive assembly of claim 1, wherein the traveling block housing is a one piece unit.
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 liquid crystal display device comprising a first substrate and a second substrate disposed to face each other so as to hold a liquid crystal layer between said first substrate and said second substrate, and a gate potential creating circuit for outputting a selection potential and a non-selection potential, scanning lines, signal lines, thin film transistors formed so as to correspond to intersection portions between said scanning lines and said signal lines, respectively, pixel electrodes electrically connected to said thin film transistors, respectively, and a gate control circuit for switching the selection potential and the non-selection potential supplied from said gate potential creating circuit over to each other, thereby supplying one of the selection potential and the non-selection potential to corresponding ones of said thin film transistors through corresponding one of said scanning lines being formed on said first substrate, and
a common electrode being formed either on said first substrate or said second substrate, wherein
a voltage control circuit for changing the non-selection potential to a potential in a rise area of said thin film transistor in accordance with a power source cut-off signal is connected between said gate potential creating circuit and said gate control circuit,
said voltage control circuit includes a diode connected between a supply terminal for the non-selection potential of said gate potential creating circuit and a ground potential, a first switching element connected between said supply terminal for the non-selection potential of said gate potential creating circuit and an input terminal for the non-selection potential of said gate control circuit, and a short-circuit element connected between an input terminal for the selection potential and said input terminal for the non-selection potential of said gate control circuit,
said first switching element cuts off between said supply terminal for the non-selection potential of said gate potential creating circuit and said input terminal for the non-selection potential of said gate control circuit in accordance with the power source cut-off signal, and
said short-circuit element substantially short-circuits between said input terminal for the selection potential and said input terminal for the non-selection potential of said gate control circuit in accordance with the power source cut-off signal.
2. The liquid crystal display device according to claim 1, wherein the power source cut-off signal is a signal which is held at an H level in a phase of a normal operation, and is held at an L level in a phase of a power source cut-off, and said first switching element is composed of an N-channel thin film transistor.
3. The liquid crystal display device according to claim 1, wherein stabilizing capacitors are connected between said supply terminal for the selection potential of said gate potential creating circuit and the ground potential, and between said supply terminal for the non-selection potential of said gate potential creating circuit and the ground potential, respectively.
4. The liquid crystal display device according to claim 3, wherein discharge resistors are connected in parallel with said stabilizing capacitors, respectively, and resistance values of said discharge resistors are identical to each other.
5. The liquid crystal display device according to claim 4, wherein a following relationship is established:
Cd\u2267C1
where Cd is a capacitance value of said stabilizing capacitor connected to said supply terminal for the selection potential of said gate potential creating circuit, and C1 is a capacitance value of said non-selection potential stabilizing capacitor.
6. The liquid crystal display device according to claim 3, wherein a non-selection potential stabilizing capacitor is connected between said input terminal for the non-selection potential of said gate control circuit, and the ground potential.
7. The liquid crystal display device according to claim 1, wherein said short-circuit element is composed of a resistor connected between said input terminal for the selection potential and said input terminal for the non-selection potential of said gate control circuit.
8. The liquid crystal display device according to claim 7, wherein a resistance value of said resistor is equal to or larger than 50 k\u03a9, and is equal to or smaller than 500 k\u03a9.
9. The liquid crystal display device according to claim 7, wherein said resistor is formed from the same film as that of a semiconductor layer of said thin film transistor.
10. The liquid crystal display device according to claim 1, wherein said short-circuit element is composed of a second switching element connected between said input terminal for the selection potential, and said input terminal for the non-selection potential of said gate control circuit, and said second switching element is adapted to be turned ON in accordance with the power source cut-off signal.
11. The liquid crystal display device according to claim 10, wherein the power source cut-off signal is a signal which is held at an H level in a phase of a normal operation, and is held at an L level in a phase of a power source cut-off, and said second switching element is composed of a P-channel thin film transistor.
12. The liquid crystal display device according to claim 1, wherein a potential of an input signal from said gate control circuit has inverse V letter-like characteristics in which the potential of the input signal from said gate control circuit temporarily rises up to the potential falling in the rise area after generation of the power source cut-off signal, and then converges to the ground potential.
13. The liquid crystal display device according to claim 1, wherein a period of time required for the potential of the input signal from said gate control circuit to reach the potential falling in the rise area is set as being equal to or shorter than one second.
14. The liquid crystal display device according to claim 1, wherein each of said gate potential creating circuit and said gate control circuit is formed in an outer peripheral portion of a display area of said first substrate, and a semiconductor layer includes a transistor made of polysilicon.