IMPROVEMENTS IN LATHE BACK HEADSTOCKS OR POPPETS
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Tom Birkett Barker and James
Alfred Ewins at the Office of the Commissioners of Patents on the 31st May
1883.
TOM BIRKETT BARKER of Birmingham in the County of Warwick Mechanical
Engineer and JAMES ALFRED EWINS also of Birmingham aforesaid Machinist
"IMPROVEMENTS IN LATHE BACK HEADSTOCKS OR POPPETS."
Screw and lever back centre or right hand lathe poppets are ordinarily con-
structed in two separate machines or apparatuses in combination with a lathe
headstock or poppet for the purposes of turning and boring substances placed
between the two centre points of the lathe, that is to say: the mechanism used in
combination with the lathe head appliances for the purposes of turning boring or
drilling holes, shaping and various other operations, each of which usually require
a separate or distinct poppet head or machine
The object of our invention is to combine in one back centre poppet or machine,
two machines or appliances admitting of exchange; in other words, a Screw Wheel
back centre poppet and a lever back centre poppet being used interchangeably or
in turns, the one following the other in alternate succession as the respective
operations or processes require them to be used, as hereinafter described
The lathe back centre combination poppet, has a cylindrical hole passing from
end to end of its head-A traversing slide or cylinder incapable of rotation
works as usual in the front part of the axial hole in the head of the said poppet―
The usual centre point is screwed and takes into the front end of the traversing
slide A forcing or advancing screw spindle, with a hand wheel or handle on
its end, works in the back part of the said cylindrical hole in the poppet head-
The terminal or front end of this forcing or advancing screw spindle, takes into
the back internal screwed end of the traversing cylindrical slide The forcing or
advancing screw spindle described has in front of and near the boss of the hand
wheel, an annular groove or depression formed from the said spindle; and within
this annular depression or groove, the stem of a detachable pin or peg takes (when
being used as a screw wheel back centre) and passing through the top of the solid
metal of the poppet head
Cut in the back boss of the hand wheel carrying the forcing screw spindle, is a

page_text: transverse or cross slot or opening the divided cheeks forming knuckles; and at
right angles to the said slot a cylindrical hole passes through the knuckles of a
proper size to receive the stem of the pin or peg described
At the back of the hand wheel and in a plane with the axis of the poppet
head, a link is jointed at one end to a bracket formed on the offside of the said
poppet head, the other end of the link is jointed to the end of a long lever for
working the slide
The said lever is also hinged vertically near its connection with the aforesaid
link for throwing the lever back, when out of use; and below the hinged part a
swell is formed with an eye or hole passing through it equal to the peg hole in the
knuckles described, which forms the connection of the lever with the forcing or
advancing screw spindle
The action of the mechanism when used as a back centre lathe poppet is as
follows-On the front face of the wheel boss abutting against the back open end of
the poppet head, the loose pin or peg is then passed vertically through the hole in
the said poppet head and terminating in the annular groove or depression in the
forcing or advancing screw spindle-The said pin or peg prevents the spindle from
moving longitudinally, but allows it to revolve or rotate within the poppet head-
so that by rotating the hand wheel the Screw on the end of its spindle advances
or traverses the cylindrical slide and centre point longitudinally, to and fro within
the poppet head.
Secondly when the apparatus is interchanged into a lever back centre poppet,
the modus operandi is as follows; the long lever connected to the attachment link
is turned down upon its hinged joint, and swung from the back of the poppet body,
the eye or hole in the face of the lever and the swell part carrying it is passed
between the knuckle joint on the back of the hand wheel; the pin or peg holding
the forcing spindle is then removed from the poppet head and spindle depression;
and passed through the hole in the knuckles described, and through the eye of the
lever; thereby connecting the said lever to the forcing or advancing screw spindle
By the removal of the pin or peg described the traversing cylindrical slide, and
the forcing screw spindle can now slide together freely within the axial hole in the
poppet head. The longitudinal advancing and retiring motion being effected for
boring drilling or other operations, by the lever attached to the knuckles on the
end of the forcing spindle, the lever taking its fulcrum from the end of the link
jointed to the lever, the link producing the desired parallelism consequent on the
cirvilinear motion of the lever.
There is thus produced a right hand or back centre poppet alternately performing
the same duty, both for a screw wheel back centre poppet and also a lever back
centre poppet; and acting interchangeably or in turns, as occasions require
The said poppet centre may be fixed or have a rising and falling motion.