Oil well sucker rod safety block

A fail-safe knock-off block for use during the repair or servicing of oil well surface pumping equipment involving a longitudinally slotted pipe capped at each end by top and bottom pipe segments which are held in place concentric to the slotted pipe by a resilient handle. An inner handle on the slotted pipe allows the concentric caps to be rotated axially from an open position to a closed position, thus encircling the polish rod. The weight of the sucker rod string on the end caps during use compresses the end caps and resilient handle thus locking the safety block such that it can neither open nor come off the well head.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to an oil well sucker rod safety block. More 
specifically, the invention relates to a safety knock-off block that 
during operation completely encircles the sucker rod and will not open up 
or slip off the well head. 
2. Description of the Prior Art 
The basic concept of providing a device commonly called a knock-off block 
when servicing or repairing oil field pumping equipment is a well 
established practice. The so-called knock-off block is a spacer used to 
support the string of sucker rods in the oil well while work is being done 
on the engine or motor, gear box, pump jack, bridle or any other part of 
the aboveground pumping equipment. Ordinarily, the knock-off block is made 
from a two inch pipe or the like that has an approximately one and a half 
inch wide slot cut longitudinally along the length of the pipe. The 
slotted pipe than has two horseshoe shaped steel plates welded to the top 
and bottom with the open sides in alignment with the slot in the pipe. To 
use the knock-off block, the pump jack is stopped at the top of the 
stroke. The slot in the knock-off block is placed over the polish rod and 
the knock-off block is held in place by hand or is fastened in place, 
usually using wire or rope as the fastener. The pump jack is then lowered 
so that the polish rod liner head engages the knock-off block. The pump 
jack is lowered to the bottom of the stroke and stopped. Work can then be 
performed on the pump equipment. 
This type of knock-off block is well known for its dangerous behavior. It 
sometimes slips off the polish rod after weight is applied by lowering the 
rods, thus breaking the fastening devices and risking personal injury. 
Various attempts have been made to alleviate the above problem with limited 
commerical success. For example, in U.S. Pat. No. 1,196,647 spring biased 
jaws that surround the polish rod are provided to prevent the polish rod 
from exiting the slot. Such a solution is not fail-safe in that the device 
can still malfunction or be opened during use. Thus, a need for an 
inexpensive yet reliable safety block that cannot be removed or 
accidentally opened during use still exists. 
SUMMARY OF THE INVENTION 
In view of the previously known types of knock-off blocks and their 
associated deficiencies, I have discovered an improved fail-safe knock-off 
block. Thus, the present invention provides a safety block comprising: 
(a) a longitudinally slotted pipe wherein the slot is adapted to fit over 
the polish rod of an oil well pump in an axial orientation; 
(b) a slotted top plate perpendicularly attached to a longitudinally 
slotted pipe section wherein the slots are adapted to fit over the polish 
rod of the oil well pump in an axial orientation and wherein the 
longitudinally slotted pipe section of the top is further adapted to 
concentrically engage with the longitudinally slotted pipe; 
(c) a slotted bottom plate perpendicularly attached to another 
longitudinally slotted pipe section wherein the slots are adapted to fit 
over the polish rod of the oil well pump in an axial orientation and 
wherein the longitudinally slotted pipe section of the bottom is further 
adapted to concentrically engage to the other end of the longitudinally 
slotted pipe; and 
(d) a resilient attachment means connecting the top and bottom plates which 
are concentrically engaged to the longitudinal slotted pipe thus allowing 
the plates with slotted pipe segments to rotate axially relative to the 
longitudinally slotted pipe during no-load and to flex during compression 
thus interlocking the concentric pipe sections and pipe during use of the 
safety block. The present invention further provides that the resilient 
attachment means connecting the top and bottom plates also serves as a 
handle to aid in the axial rotation of the pipe segments and perpendicular 
plates and that the slotted pipe is also equipped with a handle to assist 
in this axial rotation. 
It is a primary object of the present invention to provide a safety block 
which can be readily and easily mounted or removed from the polish rod 
when no load is being applied. It is a further object that the safety 
block completely encircle the polish rod and be locked in place when 
compressed by the weight of the sucker rod string such that the safety 
block cannot fall off the well head. Fulfillment of these objects and the 
presence and fulfillment of other objects will be apparent upon reading of 
the specification and claims taken in conjunction with the attached 
drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The safety block according to the present invention, how it functions, and 
how it differs from the previously known knock-off blocks can perhaps be 
best explained and understood by reference to the drawings. 
FIG. 1 is a perspective view of the safety block, generally designated by 
the numeral 10. As illustrated, the safety block 10 is made up of a 
central or inner pipe 12 having a vertical (longitudinal) slot 14 
traversing the entire length of the inner pipe. A handle 16 is attached to 
the outer portion of the pipe 12 opposite the slot 14. On the top and 
bottom of the inner pipe 12 are two flat surfaces 18 and 20 equipped with 
slots 22 and 24. Welded to each flat surface 18 and 20 are slotted pipe 
segments 26 and 28. The slots of the pipe segments 26 and 28 are 
permanently aligned with the slots 22 and 24 of the flat surfaces. As 
further illustrated, the pipe segments 26 and 28 are concentrically 
positioned on the top and bottom of the pipe 12. A resilient handle 30 is 
welded to the flat surfaces 18 and 20, thus holding the pipe segments and 
flat surfaces suspended away from the ends of the inner pipe 12. In this 
manner, the inner pipe 12 is free to rotate axially within the safety 
block 10, by merely rotating handle 16 relative to handle 30. 
As illustrated in FIG. 2, when both handles 16 and 30 are rotated next to 
each other, all slots are aligned allowing the safety block to be easily 
and readily placed on or removed from the polish rod of the pumping unit. 
However, when the handles are rotated opposite to each other, see FIG. 3, 
the polish rod will be entirely encircled. As the polish rod is lowered, 
the weight of the sucker rod string will compress the upper flat surface 
18 against central pipe 12 with sufficient force that the safety block 10 
will be locked in position and absolutely cannot slip off the well head. 
The pump jack can then be detached from the sucker string and the 
necessary repair or service performed on the pumping equipment. Upon 
reassembly and attachment to the sucker rod string, the tension on the 
safety block is removed by lifting the string. The safety block can now be 
quickly opened and removed with minimum risk to the personnel. 
The safety block of the present invention can be made out of any high 
strength material generally employed in oil field equipment or the like. 
Various alternative designs to the overall unit are envisioned as being 
equivalent to the illustrated embodiment. For example, one or more of the 
handles can either be eliminated or incorporated into other elements of 
the device. The segmented pipes attached to the flat surfaces can readily 
be one continuous pipe with or without a discrete handle. In such an 
embodiment, the inner handle can readily be a pin or post extending 
through a circumferential slot or the like. Also, the resilience necessary 
to create the locking effect can be associated with the flexing of the 
sidewall rather than the bending of an external handle. 
Having thus described and exemplified the preferred embodiments with a 
certain degree of particularity, it is manifest that many changes can be 
made within the details of the safety block without departing from the 
spirit and scope of this invention. Therefore, it is to be understood that 
the invention is not limited to the embodiments set forth herein for 
purposes of exemplification, but is to be limited only by the scope of the 
attached claims, including the full range of equivalents to which each 
step thereof is entitled.